cc(1) - man - phpMan

 

cc(1)
NAME SYNOPSIS DESCRIPTION
-c option says not to run the linker. Then the output consists of object files output by the -fmove-loop-invariants, -Wformat and so on. Most of these have both positive and negative
OPTIONS
Option Summary Options Controlling the Kind of Output -x language -x none -c Compile or assemble the source files, but do not link. The linking stage simply is not -S Stop after the stage of compilation proper; do not assemble. The output is in the form -E Stop after the preprocessing stage; do not run the compiler proper. The output is in the -o file -dumpbase dumpbase -dumpbase-ext auxdropsuf -dumpdir dumppfx -v Print (on standard error output) the commands executed to run the stages of compilation. --help --target-help --version -pass-exit-codes -pipe -specs=file -wrapper -ffile-prefix-map=old=new -fplugin=name.so -fplugin-arg-name-key=value -fdump-ada-spec[-slim] -fada-spec-parent=unit -fdump-go-spec=file Compiling C++ Programs Options Controlling C Dialect -ansi -std= -fgnu89-inline -fpermitted-flt-eval-methods=style -aux-info filename -fallow-parameterless-variadic-functions -fno-asm -fno-builtin -fno-builtin-function -fgimple -fhosted -ffreestanding -fopenacc -fopenacc-dim=geom -fopenmp -fopenmp-simd -fgnu-tm -fms-extensions -fplan9-extensions -fcond-mismatch -flax-vector-conversions -funsigned-char -fsigned-char -fsigned-bitfields -funsigned-bitfields -fno-signed-bitfields -fno-unsigned-bitfields -fsso-struct=endianness Options Controlling C++ Dialect -fabi-version=n -fabi-compat-version=n -fno-access-control -faligned-new -fchar8_t -fno-char8_t -fcheck-new -fconcepts -fconcepts-ts -fconstexpr-depth=n -fconstexpr-cache-depth=n -fconstexpr-loop-limit=n -fconstexpr-ops-limit=n -fcoroutines -fno-elide-constructors -fno-enforce-eh-specs -fextern-tls-init -fno-extern-tls-init -fno-gnu-keywords -fno-implicit-templates -fno-implicit-inline-templates -fno-implement-inlines -fmodules-ts -fno-modules-ts -fmodule-header -fmodule-header=user -fmodule-header=system -fmodule-implicit-inline -fno-module-lazy -fmodule-mapper=[hostname]:port[?ident] -fmodule-mapper=|program[?ident] args... -fmodule-mapper==socket[?ident] -fmodule-mapper=<>[inout][?ident] -fmodule-mapper=<in>out[?ident] -fmodule-mapper=file[?ident] -fmodule-only -fms-extensions -fnew-inheriting-ctors -fnew-ttp-matching -fno-nonansi-builtins -fnothrow-opt -fno-operator-names -fno-optional-diags -fpermissive -fno-pretty-templates -fno-rtti -fsized-deallocation -fstrict-enums -fstrong-eval-order -ftemplate-backtrace-limit=n -ftemplate-depth=n -fno-threadsafe-statics -fuse-cxa-atexit -fno-use-cxa-get-exception-ptr -fvisibility-inlines-hidden -fvisibility-ms-compat -fno-weak -fext-numeric-literals (C++ and Objective-C++ only) -nostdinc++ -flang-info-include-translate -flang-info-include-translate-not -flang-info-include-translate=header -flang-info-module-cmi -flang-info-module-cmi=module -stdlib=libstdc++,libc++ -Wabi-tag (C++ and Objective-C++ only) -Wcomma-subscript (C++ and Objective-C++ only) -Wctad-maybe-unsupported (C++ and Objective-C++ only) -Wctor-dtor-privacy (C++ and Objective-C++ only) -Wdelete-non-virtual-dtor (C++ and Objective-C++ only) -Wdeprecated-copy (C++ and Objective-C++ only) -Wno-deprecated-enum-enum-conversion (C++ and Objective-C++ only) -Wno-deprecated-enum-float-conversion (C++ and Objective-C++ only) -Wno-init-list-lifetime (C++ and Objective-C++ only) -Winvalid-imported-macros -Wno-literal-suffix (C++ and Objective-C++ only) -Wno-narrowing (C++ and Objective-C++ only) -Wnoexcept (C++ and Objective-C++ only) -Wnoexcept-type (C++ and Objective-C++ only) -Wclass-memaccess (C++ and Objective-C++ only) -Wnon-virtual-dtor (C++ and Objective-C++ only) -Wregister (C++ and Objective-C++ only) -Wreorder (C++ and Objective-C++ only) -Wno-pessimizing-move (C++ and Objective-C++ only) -Wno-redundant-move (C++ and Objective-C++ only) -Wrange-loop-construct (C++ and Objective-C++ only) -Wredundant-tags (C++ and Objective-C++ only) -Wno-subobject-linkage (C++ and Objective-C++ only) -Weffc++ (C++ and Objective-C++ only) -Wno-exceptions (C++ and Objective-C++ only) -Wstrict-null-sentinel (C++ and Objective-C++ only) -Wno-non-template-friend (C++ and Objective-C++ only) -Wold-style-cast (C++ and Objective-C++ only) -Woverloaded-virtual (C++ and Objective-C++ only) -Wno-pmf-conversions (C++ and Objective-C++ only) -Wsign-promo (C++ and Objective-C++ only) -Wtemplates (C++ and Objective-C++ only) -Wno-mismatched-new-delete (C++ and Objective-C++ only) -Wmismatched-tags (C++ and Objective-C++ only) -Wmultiple-inheritance (C++ and Objective-C++ only) -Wvirtual-inheritance -Wno-virtual-move-assign -Wnamespaces -Wno-terminate (C++ and Objective-C++ only) -Wno-vexing-parse (C++ and Objective-C++ only) -Wno-class-conversion (C++ and Objective-C++ only) -Wvolatile (C++ and Objective-C++ only) -Wzero-as-null-pointer-constant (C++ and Objective-C++ only) -Waligned-new -Wno-placement-new -Wplacement-new=n -Wcatch-value -Wcatch-value=n (C++ and Objective-C++ only) -Wconditionally-supported (C++ and Objective-C++ only) -Wno-delete-incomplete (C++ and Objective-C++ only) -Wextra-semi (C++, Objective-C++ only) -Wno-inaccessible-base (C++, Objective-C++ only) -Wno-inherited-variadic-ctor -Wno-invalid-offsetof (C++ and Objective-C++ only) -Wsized-deallocation (C++ and Objective-C++ only) -Wsuggest-final-types -Wsuggest-final-methods -Wsuggest-override -Wuseless-cast (C++ and Objective-C++ only) -Wno-conversion-null (C++ and Objective-C++ only) Options Controlling Objective-C and Objective-C++ Dialects -fconstant-string-class=class-name -fgnu-runtime -fnext-runtime -fno-nil-receivers -fobjc-abi-version=n -fobjc-call-cxx-cdtors -fobjc-direct-dispatch -fobjc-exceptions -fobjc-gc -fobjc-nilcheck -fobjc-std=objc1 -freplace-objc-classes -fzero-link -fno-local-ivars -fivar-visibility=[public|protected|private|package] -gen-decls -Wassign-intercept (Objective-C and Objective-C++ only) -Wno-property-assign-default (Objective-C and Objective-C++ only) -Wno-protocol (Objective-C and Objective-C++ only) -Wobjc-root-class (Objective-C and Objective-C++ only) -Wselector (Objective-C and Objective-C++ only) -Wstrict-selector-match (Objective-C and Objective-C++ only) -Wundeclared-selector (Objective-C and Objective-C++ only) -print-objc-runtime-info Options to Control Diagnostic Messages Formatting -fmessage-length=n -fdiagnostics-plain-output -fdiagnostics-show-location=once -fdiagnostics-show-location=every-line -fdiagnostics-color[=WHEN] -fno-diagnostics-color -fdiagnostics-urls[=WHEN] -fno-diagnostics-show-option -fno-diagnostics-show-caret -fno-diagnostics-show-labels -fno-diagnostics-show-cwe -fno-diagnostics-show-line-numbers -fdiagnostics-minimum-margin-width=width -fdiagnostics-parseable-fixits -fdiagnostics-generate-patch -fdiagnostics-show-template-tree -fno-elide-type -fdiagnostics-path-format=KIND -fdiagnostics-show-path-depths -fno-show-column -fdiagnostics-column-unit=UNIT -fdiagnostics-column-origin=ORIGIN -fdiagnostics-format=FORMAT Options to Request or Suppress Warnings -fsyntax-only -fmax-errors=n -w Inhibit all warning messages. -Werror -Werror= -Wfatal-errors -Wsuggest-final-types is more effective with link-time optimization and -Wmaybe-uninitialized -Wpedantic -pedantic -pedantic-errors -Wall -Wextra -Wabi (C, Objective-C, C++ and Objective-C++ only) -Wchar-subscripts -Wno-coverage-mismatch -Wno-cpp -Wdouble-promotion (C, C++, Objective-C and Objective-C++ only) -Wduplicate-decl-specifier (C and Objective-C only) -Wformat -Wformat=n -Wno-format-contains-nul -Wno-format-extra-args -Wformat-overflow -Wformat-overflow=level -Wno-format-zero-length -Wformat-nonliteral -Wformat-security -Wformat-signedness -Wformat-truncation -Wformat-truncation=level -Wformat-y2k -Wnonnull -Wnonnull-compare -Wnull-dereference -Winit-self (C, C++, Objective-C and Objective-C++ only) -Wno-implicit-int (C and Objective-C only) -Wno-implicit-function-declaration (C and Objective-C only) -Wimplicit (C and Objective-C only) -Wimplicit-fallthrough -Wimplicit-fallthrough=n -Wno-if-not-aligned (C, C++, Objective-C and Objective-C++ only) -Wignored-qualifiers (C and C++ only) -Wno-ignored-attributes (C and C++ only) -Wmain -Wmisleading-indentation (C and C++ only) -Wmissing-attributes -Wmissing-braces -Wmissing-include-dirs (C, C++, Objective-C and Objective-C++ only) -Wno-missing-profile -Wno-mismatched-dealloc -Wmultistatement-macros -Wparentheses -Wsequence-point -Wno-return-local-addr -Wreturn-type -Wno-shift-count-negative -Wno-shift-count-overflow -Wshift-negative-value -Wno-shift-overflow -Wshift-overflow=n -Wswitch -Wswitch-default -Wswitch-enum -Wno-switch-bool -Wno-switch-outside-range -Wno-switch-unreachable -Wsync-nand (C and C++ only) -Wunused-but-set-parameter -Wunused-but-set-variable -Wunused-function -Wunused-label -Wunused-local-typedefs (C, Objective-C, C++ and Objective-C++ only) -Wunused-parameter -Wno-unused-result -Wunused-variable -Wunused-const-variable -Wunused-const-variable=n -Wunused-value -Wunused -Wuninitialized -Wno-invalid-memory-model -Wmaybe-uninitialized -Wunknown-pragmas -Wno-pragmas -Wno-prio-ctor-dtor -Wstrict-aliasing -Wstrict-aliasing=n -Wstrict-overflow -Wstrict-overflow=n -Wstring-compare -Wno-stringop-overflow -Wstringop-overflow -Wstringop-overflow=type -Wno-stringop-overread -Wno-stringop-truncation -Wsuggest-attribute=[pure|const|noreturn|format|cold|malloc] -Walloc-zero -Walloc-size-larger-than=byte-size -Wno-alloc-size-larger-than -Walloca -Walloca-larger-than=byte-size -Wno-alloca-larger-than -Warith-conversion -Warray-bounds -Warray-bounds=n -Warray-parameter -Warray-parameter=n -Wattribute-alias=n -Wno-attribute-alias -Wbool-compare -Wbool-operation -Wduplicated-branches -Wduplicated-cond -Wframe-address -Wno-discarded-qualifiers (C and Objective-C only) -Wno-discarded-array-qualifiers (C and Objective-C only) -Wno-incompatible-pointer-types (C and Objective-C only) -Wno-int-conversion (C and Objective-C only) -Wzero-length-bounds -Wno-div-by-zero -Wsystem-headers -Wtautological-compare -Wtrampolines -Wfloat-equal -Wtraditional (C and Objective-C only) -Wtraditional-conversion (C and Objective-C only) -Wdeclaration-after-statement (C and Objective-C only) -Wshadow -Wno-shadow-ivar (Objective-C only) -Wshadow=global -Wshadow=local -Wshadow=compatible-local -Wlarger-than=byte-size -Wno-larger-than -Wframe-larger-than=byte-size -Wno-frame-larger-than -Wno-free-nonheap-object -Wstack-usage=byte-size -Wno-stack-usage -Wunsafe-loop-optimizations -Wno-pedantic-ms-format (MinGW targets only) -Wpointer-arith -Wno-pointer-compare -Wtsan -Wtype-limits -Wabsolute-value (C and Objective-C only) -Wcomment -Wcomments -Wtrigraphs -Wundef -Wexpansion-to-defined -Wunused-macros -Wno-endif-labels -Wbad-function-cast (C and Objective-C only) -Wc90-c99-compat (C and Objective-C only) -Wc99-c11-compat (C and Objective-C only) -Wc11-c2x-compat (C and Objective-C only) -Wc++-compat (C and Objective-C only) -Wc++11-compat (C++ and Objective-C++ only) -Wc++14-compat (C++ and Objective-C++ only) -Wc++17-compat (C++ and Objective-C++ only) -Wc++20-compat (C++ and Objective-C++ only) -Wcast-qual -Wcast-align -Wcast-align=strict -Wcast-function-type -Wwrite-strings -Wclobbered -Wconversion -Wdangling-else -Wdate-time -Wempty-body -Wno-endif-labels -Wenum-compare -Wenum-conversion -Wjump-misses-init (C, Objective-C only) -Wsign-compare -Wsign-conversion -Wfloat-conversion -Wno-scalar-storage-order -Wsizeof-array-div -Wsizeof-pointer-div -Wsizeof-pointer-memaccess -Wno-sizeof-array-argument -Wmemset-elt-size -Wmemset-transposed-args -Waddress -Wno-address-of-packed-member -Wlogical-op -Wlogical-not-parentheses -Waggregate-return -Wno-aggressive-loop-optimizations -Wno-attributes -Wno-builtin-declaration-mismatch -Wno-builtin-macro-redefined -Wstrict-prototypes (C and Objective-C only) -Wold-style-declaration (C and Objective-C only) -Wold-style-definition (C and Objective-C only) -Wmissing-parameter-type (C and Objective-C only) -Wmissing-prototypes (C and Objective-C only) -Wmissing-declarations -Wmissing-field-initializers -Wno-multichar -Wnormalized=[none|id|nfc|nfkc] -Wno-attribute-warning -Wno-deprecated -Wno-deprecated-declarations -Wno-overflow -Wno-odr -Wopenmp-simd -Woverride-init (C and Objective-C only) -Wno-override-init-side-effects (C and Objective-C only) -Wpacked -Wnopacked-bitfield-compat -Wpacked-not-aligned (C, C++, Objective-C and Objective-C++ only) -Wpadded -Wredundant-decls -Wrestrict -Wnested-externs (C and Objective-C only) -Winline -Wint-in-bool-context -Wno-int-to-pointer-cast -Wno-pointer-to-int-cast (C and Objective-C only) -Winvalid-pch -Wlong-long -Wvariadic-macros -Wno-varargs -Wvector-operation-performance -Wvla -Wvla-larger-than=byte-size -Wno-vla-larger-than -Wvla-parameter -Wvolatile-register-var -Wdisabled-optimization -Wpointer-sign (C and Objective-C only) -Wstack-protector -Woverlength-strings -Wunsuffixed-float-constants (C and Objective-C only) -Wno-lto-type-mismatch -Wno-designated-init (C and Objective-C only) Options That Control Static Analysis -fanalyzer -Wanalyzer-too-complex -Wno-analyzer-double-fclose -Wno-analyzer-double-free -Wno-analyzer-exposure-through-output-file -Wno-analyzer-file-leak -Wno-analyzer-free-of-non-heap -Wno-analyzer-malloc-leak -Wno-analyzer-mismatching-deallocation -Wno-analyzer-possible-null-argument -Wno-analyzer-possible-null-dereference -Wno-analyzer-null-argument -Wno-analyzer-null-dereference -Wno-analyzer-shift-count-negative -Wno-analyzer-shift-count-overflow -Wno-analyzer-stale-setjmp-buffer -Wno-analyzer-tainted-array-index -Wno-analyzer-unsafe-call-within-signal-handler -Wno-analyzer-use-after-free -Wno-analyzer-use-of-pointer-in-stale-stack-frame -Wno-analyzer-write-to-const -Wno-analyzer-write-to-string-literal -fanalyzer-call-summaries -fanalyzer-checker=name -fno-analyzer-feasibility -fanalyzer-fine-grained -fanalyzer-show-duplicate-count -fno-analyzer-state-merge -fno-analyzer-state-purge -fanalyzer-transitivity -fanalyzer-verbose-edges -fanalyzer-verbose-state-changes -fanalyzer-verbosity=level -fdump-analyzer -fdump-analyzer-stderr -fdump-analyzer-callgraph -fdump-analyzer-exploded-graph -fdump-analyzer-exploded-nodes -fdump-analyzer-exploded-nodes-2 -fdump-analyzer-exploded-nodes-3 -fdump-analyzer-feasibility -fdump-analyzer-json -fdump-analyzer-state-purge -fdump-analyzer-supergraph Options for Debugging Your Program -g Produce debugging information in the operating system's native format (stabs, COFF, -ggdb -gdwarf -gdwarf-version -gstabs -gstabs+ -gxcoff -gxcoff+ -gvms -glevel -ggdblevel -gstabslevel -gxcofflevel -gvmslevel -fno-eliminate-unused-debug-symbols -femit-class-debug-always -fno-merge-debug-strings -fdebug-prefix-map=old=new -fvar-tracking -fvar-tracking-assignments -gsplit-dwarf -gdwarf32 -gdwarf64 -gdescribe-dies -gpubnames -ggnu-pubnames -fdebug-types-section -grecord-gcc-switches -gno-record-gcc-switches -gstrict-dwarf -gno-strict-dwarf -gas-loc-support -gno-as-loc-support -gas-locview-support -gno-as-locview-support -gcolumn-info -gno-column-info -gstatement-frontiers -gno-statement-frontiers -gvariable-location-views -gvariable-location-views=incompat5 -gno-variable-location-views -ginternal-reset-location-views -gno-internal-reset-location-views -ginline-points -gno-inline-points -gz[=type] -femit-struct-debug-baseonly -femit-struct-debug-reduced -femit-struct-debug-detailed[=spec-list] -fno-dwarf2-cfi-asm -fno-eliminate-unused-debug-types Options That Control Optimization -O -O1 Optimize. Optimizing compilation takes somewhat more time, and a lot more memory for a -O2 Optimize even more. GCC performs nearly all supported optimizations that do not involve -O3 Optimize yet more. -O3 turns on all optimizations specified by -O2 and also turns on the -O0 Reduce compilation time and make debugging produce the expected results. This is the -Os Optimize for size. -Os enables all -O2 optimizations except those that often increase -Ofast -Og Optimize debugging experience. -Og should be the optimization level of choice for the -fno-defer-pop -fforward-propagate -ffp-contract=style -fomit-frame-pointer -foptimize-sibling-calls -foptimize-strlen -fno-inline -finline-small-functions -findirect-inlining -finline-functions -finline-functions-called-once -fearly-inlining -fipa-sra -finline-limit=n -fno-keep-inline-dllexport -fkeep-inline-functions -fkeep-static-functions -fkeep-static-consts -fmerge-constants -fmerge-all-constants -fmodulo-sched -fmodulo-sched-allow-regmoves -fno-branch-count-reg -fno-function-cse -fno-zero-initialized-in-bss -fthread-jumps -fsplit-wide-types -fsplit-wide-types-early -fcse-follow-jumps -fcse-skip-blocks -frerun-cse-after-loop -fgcse -fgcse-lm -fgcse-sm -fgcse-las -fgcse-after-reload -faggressive-loop-optimizations -funconstrained-commons -fcrossjumping -fauto-inc-dec -fdce -fdse -fif-conversion -fif-conversion2 -fdeclone-ctor-dtor -fdelete-null-pointer-checks -fdevirtualize -fdevirtualize-speculatively -fdevirtualize-at-ltrans -fexpensive-optimizations -free -fno-lifetime-dse -flive-range-shrinkage -fira-algorithm=algorithm -fira-region=region -fira-hoist-pressure -fira-loop-pressure -fno-ira-share-save-slots -fno-ira-share-spill-slots -flra-remat -fdelayed-branch -fschedule-insns -fschedule-insns2 -fno-sched-interblock -fno-sched-spec -fsched-pressure -fsched-spec-load -fsched-spec-load-dangerous -fsched-stalled-insns -fsched-stalled-insns=n -fsched-stalled-insns-dep -fsched-stalled-insns-dep=n -fsched2-use-superblocks -fsched-group-heuristic -fsched-critical-path-heuristic -fsched-spec-insn-heuristic -fsched-rank-heuristic -fsched-last-insn-heuristic -fsched-dep-count-heuristic -freschedule-modulo-scheduled-loops -fselective-scheduling -fselective-scheduling2 -fsel-sched-pipelining -fsel-sched-pipelining-outer-loops -fsemantic-interposition -fshrink-wrap -fshrink-wrap-separate -fcaller-saves -fcombine-stack-adjustments -fipa-ra -fconserve-stack -ftree-reassoc -fcode-hoisting -ftree-pre -ftree-partial-pre -ftree-forwprop -ftree-fre -ftree-phiprop -fhoist-adjacent-loads -ftree-copy-prop -fipa-pure-const -fipa-reference -fipa-reference-addressable -fipa-stack-alignment -fipa-pta -fipa-profile -fipa-modref -fipa-cp -fipa-cp-clone -fipa-bit-cp -fipa-vrp -fipa-icf -flive-patching=level -fisolate-erroneous-paths-dereference -fisolate-erroneous-paths-attribute -ftree-sink -ftree-bit-ccp -ftree-ccp -fssa-backprop -fssa-phiopt -ftree-switch-conversion -ftree-tail-merge -ftree-dce -ftree-builtin-call-dce -ffinite-loops -ftree-dominator-opts -ftree-dse -ftree-ch -ftree-loop-optimize -ftree-loop-linear -floop-strip-mine -floop-block -fgraphite-identity -floop-nest-optimize -floop-parallelize-all -ftree-coalesce-vars -ftree-loop-if-convert -ftree-loop-distribution -ftree-loop-distribute-patterns -floop-interchange -floop-unroll-and-jam -ftree-loop-im -ftree-loop-ivcanon -ftree-scev-cprop -fivopts -ftree-parallelize-loops=n -ftree-pta -ftree-sra -fstore-merging -ftree-ter -ftree-slsr -ftree-vectorize -ftree-loop-vectorize -ftree-slp-vectorize -fvect-cost-model=model -fsimd-cost-model=model -ftree-vrp -fsplit-paths -fsplit-ivs-in-unroller -fvariable-expansion-in-unroller -fpartial-inlining -fpredictive-commoning -fprefetch-loop-arrays -fno-printf-return-value -fno-peephole -fno-peephole2 -fno-guess-branch-probability -freorder-blocks -freorder-blocks-algorithm=algorithm -freorder-blocks-and-partition -freorder-functions -fstrict-aliasing -falign-functions -falign-functions=n -falign-functions=n:m -falign-functions=n:m:n2 -falign-functions=n:m:n2:m2 -flimit-function-alignment -falign-labels -falign-labels=n -falign-labels=n:m -falign-labels=n:m:n2 -falign-labels=n:m:n2:m2 -falign-loops -falign-loops=n -falign-loops=n:m -falign-loops=n:m:n2 -falign-loops=n:m:n2:m2 -falign-jumps -falign-jumps=n -falign-jumps=n:m -falign-jumps=n:m:n2 -falign-jumps=n:m:n2:m2 -fno-allocation-dce -fallow-store-data-races -funit-at-a-time -fno-toplevel-reorder -fweb -fwhole-program -flto[=n] -flto-partition=alg -flto-compression-level=n -fuse-linker-plugin -ffat-lto-objects -fcompare-elim -fcprop-registers -fprofile-correction -fprofile-partial-training -fprofile-use -fprofile-use=path -fauto-profile -fauto-profile=path -ffloat-store -fexcess-precision=style -ffast-math -fno-math-errno -funsafe-math-optimizations -fassociative-math -freciprocal-math -ffinite-math-only -fno-signed-zeros -fno-trapping-math -frounding-math -fsignaling-nans -fno-fp-int-builtin-inexact -fsingle-precision-constant -fcx-limited-range -fcx-fortran-rules -fbranch-probabilities -fprofile-values -fprofile-reorder-functions -fvpt -frename-registers -fschedule-fusion -ftracer -funroll-loops -funroll-all-loops -fpeel-loops -fmove-loop-invariants -fsplit-loops -funswitch-loops -fversion-loops-for-strides -ffunction-sections -fdata-sections -fstdarg-opt -fsection-anchors -fzero-call-used-regs=choice Program Instrumentation Options -p -pg Generate extra code to write profile information suitable for the analysis program prof -fprofile-arcs --coverage -ftest-coverage -fprofile-abs-path -fprofile-dir=path -fprofile-generate -fprofile-generate=path -fprofile-info-section -fprofile-info-section=name -fprofile-note=path -fprofile-prefix-path=path -fprofile-update=method -fprofile-filter-files=regex -fprofile-exclude-files=regex -fprofile-reproducible=[multithreaded|parallel-runs|serial] -fsanitize=address -fsanitize=kernel-address -fsanitize=hwaddress -fsanitize=kernel-hwaddress -fsanitize=pointer-compare -fsanitize=pointer-subtract -fsanitize=thread -fsanitize=leak -fsanitize=undefined -fno-sanitize=all -fasan-shadow-offset=number -fsanitize-sections=s1,s2,... -fsanitize-recover[=opts] -fsanitize-address-use-after-scope -fsanitize-undefined-trap-on-error -fsanitize-coverage=trace-pc -fsanitize-coverage=trace-cmp -fcf-protection=[full|branch|return|none|check] -fstack-protector -fstack-protector-all -fstack-protector-strong -fstack-protector-explicit -fstack-check -fstack-clash-protection -fstack-limit-register=reg -fstack-limit-symbol=sym -fno-stack-limit -fsplit-stack -fvtable-verify=[std|preinit|none] -fvtv-debug -fvtv-counts -finstrument-functions -finstrument-functions-exclude-file-list=file,file,... -finstrument-functions-exclude-function-list=sym,sym,... -fpatchable-function-entry=N[,M] Options Controlling the Preprocessor -D name -D name=definition -U name -include file -imacros file -undef -pthread -M Instead of outputting the result of preprocessing, output a rule suitable for make -MM Like -M but do not mention header files that are found in system header directories, nor -MF file -MG In conjunction with an option such as -M requesting dependency generation, -MG assumes -Mno-modules -MP This option instructs CPP to add a phony target for each dependency other than the main -MT target -MQ target -MD -MD is equivalent to -M -MF file, except that -E is not implied. The driver determines -MMD -fpreprocessed -fdirectives-only -fdollars-in-identifiers -fextended-identifiers -fno-canonical-system-headers -fmax-include-depth=depth -ftabstop=width -ftrack-macro-expansion[=level] -fmacro-prefix-map=old=new -fexec-charset=charset -fwide-exec-charset=charset -finput-charset=charset -fpch-deps -fpch-preprocess -fworking-directory -A predicate=answer -A -predicate=answer -C Do not discard comments. All comments are passed through to the output file, except for -CC Do not discard comments, including during macro expansion. This is like -C, except that -P Inhibit generation of linemarkers in the output from the preprocessor. This might be -traditional -traditional-cpp -trigraphs -remap -H Print the name of each header file used, in addition to other normal activities. Each -dletters -fdebug-cpp -Wp,option -Xpreprocessor option -no-integrated-cpp -flarge-source-files Passing Options to the Assembler -Wa,option -Xassembler option Options for Linking -c -S -E If any of these options is used, then the linker is not run, and object file names should -flinker-output=type -fuse-ld=bfd -fuse-ld=gold -fuse-ld=lld -fuse-ld=mold -llibrary -l library -lobjc -nostartfiles -nodefaultlibs -nolibc -nostdlib -e entry -pie -no-pie -static-pie -pthread -r Produce a relocatable object as output. This is also known as partial linking. -rdynamic -s Remove all symbol table and relocation information from the executable. -static -shared -shared-libgcc -static-libgcc -static-libasan -static-libtsan -static-liblsan -static-libubsan -static-libstdc++ -symbolic -T script -Xlinker option -Wl,option -u symbol -z keyword Options for Directory Search -I dir -iquote dir -isystem dir -idirafter dir -I- Split the include path. This option has been deprecated. Please use -iquote instead for -iprefix prefix -iwithprefix dir -iwithprefixbefore dir -isysroot dir -imultilib dir -nostdinc -nostdinc++ -iplugindir=dir -Ldir -Bprefix -no-canonical-prefixes --no-sysroot-suffix Options for Code Generation Conventions -fstack-reuse=reuse-level -ftrapv -fwrapv -fwrapv-pointer -fstrict-overflow -fexceptions -fnon-call-exceptions -fdelete-dead-exceptions -funwind-tables -fasynchronous-unwind-tables -fno-gnu-unique -fpcc-struct-return -freg-struct-return -fshort-enums -fshort-wchar -fcommon -fno-ident -finhibit-size-directive -fverbose-asm -frecord-gcc-switches -fpic -fPIC -fpie -fPIE -fno-plt -fno-jump-tables -fno-bit-tests -ffixed-reg -fcall-used-reg -fcall-saved-reg -fpack-struct[=n] -fleading-underscore -ftls-model=model -ftrampolines -fvisibility=[default|internal|hidden|protected] -fstrict-volatile-bitfields -fsync-libcalls GCC Developer Options -fcallgraph-info -fcallgraph-info=MARKERS -dletters -fdump-rtl-pass -fdump-rtl-pass=filename -fdump-debug -fdump-earlydebug -fdump-noaddr -freport-bug -fdump-unnumbered -fdump-unnumbered-links -fdump-ipa-switch -fdump-ipa-switch-options -fdump-lang -fdump-lang-all -fdump-lang-switch -fdump-lang-switch-options -fdump-lang-switch-options=filename vops (macros) may provide additional information. This option is applicable to C++ -fdump-passes -fdump-statistics-option -fdump-tree-all -fdump-tree-switch -fdump-tree-switch-options -fdump-tree-switch-options=filename -fopt-info -fopt-info-options -fopt-info-options=filename -fsave-optimization-record -fsched-verbose=n -fenable-kind-pass -fdisable-kind-pass=range-list -fchecking -fchecking=n -frandom-seed=string -save-temps -save-temps=cwd -save-temps=obj -time[=file] -fdump-final-insns[=file] -fcompare-debug[=opts] -fcompare-debug-second -gtoggle -fvar-tracking-assignments-toggle -Q Makes the compiler print out each function name as it is compiled, and print some -ftime-report -ftime-report-details -fira-verbose=n -flto-report -flto-report-wpa -fmem-report -fmem-report-wpa -fpre-ipa-mem-report -fpost-ipa-mem-report -fprofile-report -fstack-usage -fstats -fdbg-cnt-list -fdbg-cnt=counter-value-list -print-file-name=library -print-multi-directory -print-multi-lib -print-multi-os-directory -print-multiarch -print-prog-name=program -print-libgcc-file-name -print-search-dirs -print-sysroot -print-sysroot-headers-suffix -dumpmachine -dumpversion -dumpfullversion -dumpspecs Machine-Dependent Options -mabi=name -mbig-endian -mgeneral-regs-only -mlittle-endian -mcmodel=tiny -mcmodel=small -mcmodel=large -mstrict-align -mno-strict-align -momit-leaf-frame-pointer -mno-omit-leaf-frame-pointer -mstack-protector-guard=guard -mstack-protector-guard-reg=reg -mstack-protector-guard-offset=offset -mtls-dialect=desc -mtls-dialect=traditional -mtls-size=size -mfix-cortex-a53-835769 -mno-fix-cortex-a53-835769 -mfix-cortex-a53-843419 -mno-fix-cortex-a53-843419 -mlow-precision-recip-sqrt -mno-low-precision-recip-sqrt -mlow-precision-sqrt -mno-low-precision-sqrt -mlow-precision-div -mno-low-precision-div -mtrack-speculation -mno-track-speculation -moutline-atomics -mno-outline-atomics -march=name -mtune=name -mcpu=name -moverride=string -mverbose-cost-dump -mpc-relative-literal-loads -mno-pc-relative-literal-loads -msign-return-address=scope -mbranch-protection=none|standard|pac-ret[+leaf+b-key]|bti -mharden-sls=opts -msve-vector-bits=bits -march and -mcpu Feature Modifiers crypto simd rdma fp16 fp16fml rcpc dotprod sha2 sha3 profile memtag ssbs predres sve2 sve2-bitperm sve2-sm4 sve2-aes sve2-sha3 i8mm f32mm f64mm bf16 flagm pauth -mhalf-reg-file -mprefer-short-insn-regs -mbranch-cost=num -mcmove -mnops=num -mno-soft-cmpsf -mstack-offset=num -mno-round-nearest -mlong-calls -mshort-calls -msmall16 -mfp-mode=mode -mno-split-lohi -mno-postinc -mno-postmodify -mnovect-double -max-vect-align=num -msplit-vecmove-early -m1reg-reg -march=gpu -mtune=gpu -msram-ecc=on -msram-ecc=off -msram-ecc=any -mstack-size=bytes -mxnack -mbarrel-shifter -mjli-always -mcpu=cpu -mdpfp -mdpfp-compact -mdpfp-fast -mno-dpfp-lrsr -mea -mno-mpy -mmul32x16 -mmul64 -mnorm -mspfp -mspfp-compact -mspfp-fast -msimd -msoft-float -mswap -matomic -mdiv-rem -mcode-density -mll64 -mtp-regno=regno -mmpy-option=multo -mfpu=fpu -mirq-ctrl-saved=register-range, blink, lp_count -mrgf-banked-regs=number -mlpc-width=width -mrf16 -mbranch-index -mdsp-packa -mdvbf -mlock -mmac-d16 -mmac-24 -mrtsc -mswape -mtelephony -mxy -misize -mannotate-align -marclinux -marclinux_prof -mlong-calls -mmedium-calls -G num -mno-sdata -mvolatile-cache -mno-volatile-cache -malign-call -mauto-modify-reg -mbbit-peephole -mno-brcc -mcase-vector-pcrel -mcompact-casesi -mno-cond-exec -mearly-cbranchsi -mexpand-adddi -mindexed-loads -mlra -mlra-priority-none -mlra-priority-compact -mlra-priority-noncompact -mmillicode -mcode-density-frame -mmixed-code -mq-class -mRcq -mRcw -msize-level=level -mtune=cpu -mmultcost=num -munalign-prob-threshold=probability -margonaut -mbig-endian -EB Compile code for big-endian targets. Use of these options is now deprecated. Big-endian -mlittle-endian -EL Compile code for little-endian targets. Use of these options is now deprecated. Little- -mbarrel_shifter -mdpfp_compact -mdpfp_fast -mdsp_packa -mEA -mmac_24 -mmac_d16 -mspfp_compact -mspfp_fast -mtune=cpu -multcost=num -mabi=name -mapcs-frame -mapcs -mthumb-interwork -mno-sched-prolog -mfloat-abi=name -mgeneral-regs-only -mlittle-endian -mbig-endian -mbe8 -mbe32 -march=name[+extension...] -mtune=name -mcpu=name[+extension...] -mfpu=name -mfp16-format=name -mstructure-size-boundary=n -mabort-on-noreturn -mlong-calls -mno-long-calls -msingle-pic-base -mpic-register=reg -mpic-data-is-text-relative -mpoke-function-name -mthumb -marm -mflip-thumb -mtpcs-frame -mtpcs-leaf-frame -mcallee-super-interworking -mcaller-super-interworking -mtp=name -mtls-dialect=dialect -mword-relocations -mfix-cortex-m3-ldrd -munaligned-access -mno-unaligned-access -mneon-for-64bits -mslow-flash-data -masm-syntax-unified -mrestrict-it -mprint-tune-info -mverbose-cost-dump -mpure-code -mcmse -mfix-cmse-cve-2021-35465 -mfdpic -mno-fdpic -mmcu=mcu -mabsdata -maccumulate-args -mbranch-cost=cost -mcall-prologues -mdouble=bits -mlong-double=bits -mgas-isr-prologues -mint8 -mmain-is-OS_task -mn-flash=num -mno-interrupts -mrelax -mrmw -mshort-calls -msp8 -mstrict-X -mtiny-stack -mfract-convert-truncate -nodevicelib -nodevicespecs -Waddr-space-convert -Wmisspelled-isr -mcpu=cpu[-sirevision] -msim -momit-leaf-frame-pointer -mspecld-anomaly -mno-specld-anomaly -mcsync-anomaly -mno-csync-anomaly -mlow64k -mno-low64k -mstack-check-l1 -mid-shared-library -mno-id-shared-library -mleaf-id-shared-library -mno-leaf-id-shared-library -mshared-library-id=n -msep-data -mno-sep-data -mlong-calls -mno-long-calls -mfast-fp -minline-plt -mmulticore -mcorea -mcoreb -msdram -micplb -march=name -mbig-endian -mlittle-endian -msim -msdata=default -msdata=all -msdata=none -march=architecture-type -mcpu=architecture-type -mtune=architecture-type -mmax-stack-frame=n -metrax4 -metrax100 -mmul-bug-workaround -mno-mul-bug-workaround -mpdebug -mcc-init -mno-side-effects -mstack-align -mno-stack-align -mdata-align -mno-data-align -mconst-align -mno-const-align -m32-bit -m16-bit -m8-bit -mno-prologue-epilogue -mprologue-epilogue -melf -sim -sim2 -mmac -mcr16cplus -mcr16c -msim -mint32 -mbit-ops -mdata-model=model -march=arch -mcpu=cpu -mbig-endian -EB -mlittle-endian -EL Select big- or little-endian code. The default is little-endian. -mfloat-abi=name -mhard-float -msoft-float -mdouble-float -mno-double-float -mfdivdu -mno-fdivdu -mfpu=fpu -melrw -mno-elrw -mistack -mno-istack -mmp -mcp -mcache -msecurity -mtrust -mdsp -medsp -mvdsp -mdiv -mno-div -msmart -mno-smart -mhigh-registers -mno-high-registers -manchor -mno-anchor -mpushpop -mno-pushpop -mmultiple-stld -mstm -mno-multiple-stld -mno-stm -mconstpool -mno-constpool -mstack-size -mno-stack-size -mccrt -mno-ccrt -mbranch-cost=n -msched-prolog -mno-sched-prolog -msim -Fdir -iframeworkdir -gused -gfull -mmacosx-version-min=version -mkernel -mone-byte-bool -mfix-and-continue -ffix-and-continue -findirect-data -all_load -arch_errors_fatal -bind_at_load -bundle -bundle_loader executable -dynamiclib -force_cpusubtype_ALL -allowable_client client_name -client_name -compatibility_version -current_version -dead_strip -dependency-file -dylib_file -dylinker_install_name -dynamic -exported_symbols_list -filelist -flat_namespace -force_flat_namespace -headerpad_max_install_names -image_base -init -install_name -keep_private_externs -multi_module -multiply_defined -multiply_defined_unused -noall_load -no_dead_strip_inits_and_terms -nofixprebinding -nomultidefs -noprebind -noseglinkedit -pagezero_size -prebind -prebind_all_twolevel_modules -private_bundle -read_only_relocs -sectalign -sectobjectsymbols -whyload -seg1addr -sectcreate -sectobjectsymbols -sectorder -segaddr -segs_read_only_addr -segs_read_write_addr -seg_addr_table -seg_addr_table_filename -seglinkedit -segprot -segs_read_only_addr -segs_read_write_addr -single_module -static -sub_library -sub_umbrella -twolevel_namespace -umbrella -undefined -unexported_symbols_list -weak_reference_mismatches -whatsloaded -mno-soft-float -msoft-float -mfp-reg -mno-fp-regs -mieee -mieee-with-inexact -mfp-trap-mode=trap-mode -mfp-rounding-mode=rounding-mode -mtrap-precision=trap-precision -mieee-conformant -mbuild-constants -mbwx -mno-bwx -mcix -mno-cix -mfix -mno-fix -mmax -mno-max -mfloat-vax -mfloat-ieee -mexplicit-relocs -mno-explicit-relocs -msmall-data -mlarge-data -msmall-text -mlarge-text -mcpu=cpu_type -mtune=cpu_type -mmemory-latency=time -mframe-limit=bytes -mkernel=version -mbig-endian -mlittle-endian -mxbpf -msmall-model -mno-lsim -msim -mlra -mnodiv -mft32b -mcompress -mnopm -mgpr-32 -mgpr-64 -mfpr-32 -mfpr-64 -mhard-float -msoft-float -malloc-cc -mfixed-cc -mdword -mno-dword -mdouble -mno-double -mmedia -mno-media -mmuladd -mno-muladd -mfdpic -minline-plt -mTLS -mtls -mgprel-ro -multilib-library-pic -mlinked-fp -mlong-calls -malign-labels -mlibrary-pic -macc-4 -macc-8 -mpack -mno-pack -mno-eflags -mcond-move -mno-cond-move -mscc -mno-scc -mcond-exec -mno-cond-exec -mvliw-branch -mno-vliw-branch -mmulti-cond-exec -mno-multi-cond-exec -mnested-cond-exec -mno-nested-cond-exec -moptimize-membar -mno-optimize-membar -mtomcat-stats -mcpu=cpu -mglibc -muclibc -mmusl -mbionic -mandroid -tno-android-cc -tno-android-ld -mrelax -mh Generate code for the H8/300H. -ms Generate code for the H8S. -mn Generate code for the H8S and H8/300H in the normal mode. This switch must be used -ms2600 -mexr -mno-exr -mint32 -malign-300 -march=architecture-type -mpa-risc-1-0 -mpa-risc-1-1 -mpa-risc-2-0 -mcaller-copies -mjump-in-delay -mdisable-fpregs -mdisable-indexing -mno-space-regs -mfast-indirect-calls -mfixed-range=register-range -mlong-load-store -mportable-runtime -mgas -mschedule=cpu-type -mlinker-opt -msoft-float -msio -mgnu-ld -mhp-ld -mlong-calls -munix=unix-std -nolibdld -static -threads -mbig-endian -mlittle-endian -mgnu-as -mno-gnu-as -mgnu-ld -mno-gnu-ld -mno-pic -mvolatile-asm-stop -mno-volatile-asm-stop -mregister-names -mno-register-names -mno-sdata -msdata -mconstant-gp -mauto-pic -minline-float-divide-min-latency -minline-float-divide-max-throughput -mno-inline-float-divide -minline-int-divide-min-latency -minline-int-divide-max-throughput -mno-inline-int-divide -minline-sqrt-min-latency -minline-sqrt-max-throughput -mno-inline-sqrt -mfused-madd -mno-fused-madd -mno-dwarf2-asm -mdwarf2-asm -mearly-stop-bits -mno-early-stop-bits -mfixed-range=register-range -mtls-size=tls-size -mtune=cpu-type -milp32 -mlp64 -mno-sched-br-data-spec -msched-br-data-spec -msched-ar-data-spec -mno-sched-ar-data-spec -mno-sched-control-spec -msched-control-spec -msched-br-in-data-spec -mno-sched-br-in-data-spec -msched-ar-in-data-spec -mno-sched-ar-in-data-spec -msched-in-control-spec -mno-sched-in-control-spec -mno-sched-prefer-non-data-spec-insns -msched-prefer-non-data-spec-insns -mno-sched-prefer-non-control-spec-insns -msched-prefer-non-control-spec-insns -mno-sched-count-spec-in-critical-path -msched-count-spec-in-critical-path -msched-spec-ldc -msched-control-spec-ldc -msched-stop-bits-after-every-cycle -msched-fp-mem-deps-zero-cost -msel-sched-dont-check-control-spec -msched-max-memory-insns=max-insns -msched-max-memory-insns-hard-limit -mbarrel-shift-enabled -mdivide-enabled -mmultiply-enabled -msign-extend-enabled -muser-enabled -mcpu=name -msim -memregs=number -m32r2 -m32rx -m32r -mmodel=small -mmodel=medium -mmodel=large -msdata=none -msdata=sdata -msdata=use -G num -mdebug -malign-loops -mno-align-loops -missue-rate=number -mbranch-cost=number -mflush-trap=number -mno-flush-trap -mflush-func=name -mno-flush-func -march=arch -mcpu=cpu -mtune=tune -m68000 -mc68000 -m68010 -m68020 -mc68020 -m68030 -m68040 -m68060 -mcpu32 -m5200 -m5206e -m528x -m5307 -m5407 -mcfv4e -m68020-40 -m68020-60 -mhard-float -m68881 -msoft-float -mdiv -mno-div -mshort -mno-short -mnobitfield -mno-bitfield -mbitfield -mrtd -malign-int -mno-align-int -mno-strict-align -mstrict-align -msep-data -mno-sep-data -mid-shared-library -mno-id-shared-library -mshared-library-id=n -mxgot -mno-xgot -mlong-jump-table-offsets -mhardlit -mno-hardlit -mdiv -mno-div -mrelax-immediate -mno-relax-immediate -mwide-bitfields -mno-wide-bitfields -m4byte-functions -mno-4byte-functions -mcallgraph-data -mno-callgraph-data -mslow-bytes -mno-slow-bytes -mlittle-endian -mbig-endian -m210 -m340 -mno-lsim -mstack-increment=size -mabsdiff -mall-opts -maverage -mbased=n -mbitops -mc=name -mclip -mconfig=name -mcop -mcop32 -mcop64 -mivc2 -mdc -mdiv -meb -mel -mio-volatile -ml Causes variables to be assigned to the ".far" section by default. -mleadz -mm Causes variables to be assigned to the ".near" section by default. -mminmax -mmult -mno-opts -mrepeat -ms Causes all variables to default to the ".tiny" section. Note that there is a 65536-byte -msatur -msdram -msim -msimnovec -mtf -mtiny=n -msoft-float -mhard-float -mmemcpy -mno-clearbss -mcpu=cpu-type -mxl-soft-mul -mxl-soft-div -mxl-barrel-shift -mxl-pattern-compare -msmall-divides -mxl-stack-check -mxl-gp-opt -mxl-multiply-high -mxl-float-convert -mxl-float-sqrt -mbig-endian -mlittle-endian -mxl-reorder -mxl-mode-app-model -EB Generate big-endian code. -EL Generate little-endian code. This is the default for mips*el-*-* configurations. -march=arch -mtune=arch -mips1 -mips2 -mips3 -mips4 -mips32 -mips32r3 -mips32r5 -mips32r6 -mips64 -mips64r2 -mips64r3 -mips64r5 -mips64r6 -mips16 -mno-mips16 -mflip-mips16 -minterlink-compressed -mno-interlink-compressed -minterlink-mips16 -mno-interlink-mips16 -mabi=32 -mabi=o64 -mabi=n32 -mabi=64 -mabi=eabi -mabicalls -mno-abicalls -mshared -mno-shared -mplt -mno-plt -mxgot -mno-xgot -mgp32 -mgp64 -mfp32 -mfp64 -mfpxx -mhard-float -msoft-float -mno-float -msingle-float -mdouble-float -modd-spreg -mno-odd-spreg -mabs=2008 -mabs=legacy -mnan=2008 -mnan=legacy -mllsc -mno-llsc -mdsp -mno-dsp -mdspr2 -mno-dspr2 -msmartmips -mno-smartmips -mpaired-single -mno-paired-single -mdmx -mno-mdmx -mips3d -mno-mips3d -mmicromips -mno-micromips -mmt -mno-mt -mmcu -mno-mcu -meva -mno-eva -mvirt -mno-virt -mxpa -mno-xpa -mcrc -mno-crc -mginv -mno-ginv -mloongson-mmi -mno-loongson-mmi -mloongson-ext -mno-loongson-ext -mloongson-ext2 -mno-loongson-ext2 -mlong64 -mlong32 -msym32 -mno-sym32 -G num -mlocal-sdata -mno-local-sdata -mextern-sdata -mno-extern-sdata -mgpopt -mno-gpopt -membedded-data -mno-embedded-data -muninit-const-in-rodata -mno-uninit-const-in-rodata -mcode-readable=setting -msplit-addresses -mno-split-addresses -mexplicit-relocs -mno-explicit-relocs -mcheck-zero-division -mno-check-zero-division -mdivide-traps -mdivide-breaks -mload-store-pairs -mno-load-store-pairs -mmemcpy -mno-memcpy -mlong-calls -mno-long-calls -mmad -mno-mad -mimadd -mno-imadd -mfused-madd -mno-fused-madd -nocpp -mfix-24k -mno-fix-24k -mfix-r4000 -mno-fix-r4000 -mfix-r4400 -mno-fix-r4400 -mfix-r10000 -mno-fix-r10000 -mfix-r5900 -mno-fix-r5900 -mfix-rm7000 -mno-fix-rm7000 -mfix-vr4120 -mno-fix-vr4120 -mfix-vr4130 -mfix-sb1 -mno-fix-sb1 -mr10k-cache-barrier=setting -mflush-func=func -mno-flush-func -mbranch-likely -mno-branch-likely -mcompact-branches=never -mcompact-branches=optimal -mcompact-branches=always -mfp-exceptions -mno-fp-exceptions -mvr4130-align -mno-vr4130-align -msynci -mno-synci -mrelax-pic-calls -mno-relax-pic-calls -mmcount-ra-address -mno-mcount-ra-address -mframe-header-opt -mno-frame-header-opt -mlxc1-sxc1 -mno-lxc1-sxc1 -mmadd4 -mno-madd4 -mlibfuncs -mno-libfuncs -mepsilon -mno-epsilon -mabi=mmixware -mabi=gnu -mzero-extend -mno-zero-extend -mknuthdiv -mno-knuthdiv -mtoplevel-symbols -mno-toplevel-symbols -melf -mbranch-predict -mno-branch-predict -mbase-addresses -mno-base-addresses -msingle-exit -mno-single-exit -mmult-bug -mno-mult-bug -mam33 -mno-am33 -mam33-2 -mam34 -mtune=cpu-type -mreturn-pointer-on-d0 -mno-crt0 -mrelax -mliw -mno-liw -msetlb -mno-setlb -meb -mel -mmul.x -mno-crt0 -masm-hex -mmcu= -mwarn-mcu -mno-warn-mcu -mcpu= -msim -mlarge -msmall -mrelax mhwmult= -minrt -mtiny-printf -mmax-inline-shift= -mcode-region= -mdata-region= -msilicon-errata= -msilicon-errata-warn= -mwarn-devices-csv -mno-warn-devices-csv -mbig-endian -mlittle-endian -mreduced-regs -mfull-regs -mcmov -mno-cmov -mext-perf -mno-ext-perf -mext-perf2 -mno-ext-perf2 -mext-string -mno-ext-string -mv3push -mno-v3push -m16-bit -mno-16-bit -misr-vector-size=num -mcache-block-size=num -march=arch -mcmodel=code-model -mctor-dtor -mrelax -G num -mgpopt=option -mgpopt -mno-gpopt -mgprel-sec=regexp -mr0rel-sec=regexp -mel -meb -march=arch -mbypass-cache -mno-bypass-cache -mno-cache-volatile -mcache-volatile -mno-fast-sw-div -mfast-sw-div -mno-hw-mul -mhw-mul -mno-hw-mulx -mhw-mulx -mno-hw-div -mhw-div -mbmx -mno-bmx -mcdx -mno-cdx -mcustom-insn=N -mno-custom-insn -mcustom-fpu-cfg=name -mhal -msmallc -msys-crt0=startfile -msys-lib=systemlib -m64 -misa=ISA-string -mmainkernel -moptimize -msoft-stack -muniform-simt -mgomp -mboard=name -mnewlib -msoft-div -mhard-div -msoft-mul -mhard-mul -msoft-float -mhard-float -mdouble-float -munordered-float -mcmov -mror -mrori -msext -msfimm -mshftimm -mfpu -msoft-float -mac0 -mno-ac0 -m40 -m45 -m10 -mint16 -mno-int32 -mint32 -mno-int16 -msplit -munix-asm -mdec-asm -mgnu-asm -mlra -mae=ae_type -msymbol-as-address -mno-inefficient-warnings -minrt -mmcu=mcu -mno-relax -mloop -mabi=variant -mbranch-cost=n -mplt -mno-plt -mabi=ABI-string -mfdiv -mno-fdiv -mdiv -mno-div -march=ISA-string -mcpu=processor-string -mtune=processor-string -mpreferred-stack-boundary=num -msmall-data-limit=n -msave-restore -mno-save-restore -mshorten-memrefs -mno-shorten-memrefs -mstrict-align -mno-strict-align -mcmodel=medlow -mcmodel=medany -mexplicit-relocs -mno-exlicit-relocs -mrelax -mno-relax -memit-attribute -mno-emit-attribute -malign-data=type -mbig-endian -mlittle-endian -mstack-protector-guard=guard -mstack-protector-guard-reg=reg -mstack-protector-guard-offset=offset -msim -mmul=none -mmul=g10 -mmul=g13 -mmul=g14 -mmul=rl78 -mcpu=g10 -mcpu=g13 -mcpu=g14 -mcpu=rl78 -mg10 -mg13 -mg14 -mrl78 -mallregs -m64bit-doubles -m32bit-doubles -msave-mduc-in-interrupts -mno-save-mduc-in-interrupts -mpowerpc-gpopt -mno-powerpc-gpopt -mpowerpc-gfxopt -mno-powerpc-gfxopt -mpowerpc64 -mno-powerpc64 -mmfcrf -mno-mfcrf -mpopcntb -mno-popcntb -mpopcntd -mno-popcntd -mfprnd -mno-fprnd -mcmpb -mno-cmpb -mhard-dfp -mno-hard-dfp -mcpu=cpu_type -mtune=cpu_type -mcmodel=small -mcmodel=medium -mcmodel=large -maltivec -mno-altivec -mvrsave -mno-vrsave -msecure-plt -mbss-plt -misel -mno-isel -mvsx -mno-vsx -mcrypto -mno-crypto -mhtm -mno-htm -mpower8-fusion -mno-power8-fusion -mpower8-vector -mno-power8-vector -mquad-memory -mno-quad-memory -mquad-memory-atomic -mno-quad-memory-atomic -mfloat128 -mno-float128 -mfloat128-hardware -mno-float128-hardware -m32 -m64 -mfull-toc -mno-fp-in-toc -mno-sum-in-toc -mminimal-toc -maix64 -maix32 -mxl-compat -mno-xl-compat -mpe -malign-natural -malign-power -msoft-float -mhard-float -mmultiple -mno-multiple -mupdate -mno-update -mavoid-indexed-addresses -mno-avoid-indexed-addresses -mfused-madd -mno-fused-madd -mmulhw -mno-mulhw -mdlmzb -mno-dlmzb -mno-bit-align -mbit-align -mno-strict-align -mstrict-align -mrelocatable -mno-relocatable -mrelocatable-lib -mno-relocatable-lib -mno-toc -mtoc -mlittle -mlittle-endian -mbig -mbig-endian -mdynamic-no-pic -msingle-pic-base -mprioritize-restricted-insns=priority -msched-costly-dep=dependence_type -minsert-sched-nops=scheme -mcall-sysv -mcall-sysv-eabi -mcall-eabi -mcall-sysv-noeabi -mcall-aixdesc -mcall-linux -mcall-freebsd -mcall-netbsd -mcall-openbsd -mtraceback=traceback_type -maix-struct-return -msvr4-struct-return -mabi=abi-type -mabi=ibmlongdouble -mabi=ieeelongdouble -mabi=elfv1 -mabi=elfv2 -mgnu-attribute -mno-gnu-attribute -mprototype -mno-prototype -msim -mmvme -mads -myellowknife -mvxworks -memb -meabi -mno-eabi -msdata=eabi -msdata=sysv -msdata=default -msdata -msdata=data -msdata=none -mno-sdata -mreadonly-in-sdata -mblock-move-inline-limit=num -mblock-compare-inline-limit=num -mblock-compare-inline-loop-limit=num -mstring-compare-inline-limit=num -G num -mregnames -mno-regnames -mlongcall -mno-longcall -mpltseq -mno-pltseq -mtls-markers -mno-tls-markers -mrecip -mno-recip -mrecip=opt -mrecip-precision -mno-recip-precision -mveclibabi=type -mfriz -mno-friz -mpointers-to-nested-functions -mno-pointers-to-nested-functions -msave-toc-indirect -mno-save-toc-indirect -mcompat-align-parm -mno-compat-align-parm -mstack-protector-guard=guard -mstack-protector-guard-reg=reg -mstack-protector-guard-offset=offset -mstack-protector-guard-symbol=symbol -mpcrel -mno-pcrel -mprefixed -mno-prefixed -mmma -mno-mma -mrop-protect -mno-rop-protect -mprivileged -mno-privileged -mblock-ops-unaligned-vsx -mno-block-ops-unaligned-vsx -m64bit-doubles -m32bit-doubles -fpu -nofpu -mcpu=name -mbig-endian-data -mlittle-endian-data -msmall-data-limit=N -msim -mno-sim -mas100-syntax -mno-as100-syntax -mmax-constant-size=N -mrelax -mint-register=N -msave-acc-in-interrupts -mpid -mno-pid -mno-warn-multiple-fast-interrupts -mwarn-multiple-fast-interrupts -mallow-string-insns -mno-allow-string-insns -mjsr -mno-jsr -mhard-float -msoft-float -mhard-dfp -mno-hard-dfp -mlong-double-64 -mlong-double-128 -mbackchain -mno-backchain -mpacked-stack -mno-packed-stack -msmall-exec -mno-small-exec -m64 -m31 -mzarch -mesa -mhtm -mno-htm -mvx -mno-vx -mzvector -mno-zvector -mmvcle -mno-mvcle -mdebug -mno-debug -march=cpu-type -mtune=cpu-type -mtpf-trace -mno-tpf-trace -mtpf-trace-skip -mno-tpf-trace-skip -mfused-madd -mno-fused-madd -mwarn-framesize=framesize -mwarn-dynamicstack -mstack-guard=stack-guard -mstack-size=stack-size -mhotpatch=pre-halfwords,post-halfwords -meb -mel -mnhwloop -muls -mmac -mscore5 -mscore5u -mscore7 -mscore7d -m1 Generate code for the SH1. -m2 Generate code for the SH2. -m2e -m2a-nofpu -m2a-single-only -m2a-single -m2a -m3 Generate code for the SH3. -m3e -m4-nofpu -m4-single-only -m4-single -m4 Generate code for the SH4. -m4-100 -m4-100-nofpu -m4-100-single -m4-100-single-only -m4-200 -m4-200-nofpu -m4-200-single -m4-200-single-only -m4-300 -m4-300-nofpu -m4-300-single -m4-300-single-only -m4-340 -m4-500 -m4a-nofpu -m4a-single-only -m4a-single -m4a -m4al -mb Compile code for the processor in big-endian mode. -ml Compile code for the processor in little-endian mode. -mdalign -mrelax -mbigtable -mbitops -mfmovd -mrenesas -mno-renesas -mnomacsave -mieee -mno-ieee -minline-ic_invalidate -misize -mpadstruct -matomic-model=model -mtas -mprefergot -musermode -mno-usermode -multcost=number -mdiv=strategy -maccumulate-outgoing-args -mdivsi3_libfunc=name -mfixed-range=register-range -mbranch-cost=num -mzdcbranch -mno-zdcbranch -mcbranch-force-delay-slot -mfused-madd -mno-fused-madd -mfsca -mno-fsca -mfsrra -mno-fsrra -mpretend-cmove -mfdpic -mclear-hwcap -mimpure-text -pthreads -mno-app-regs -mapp-regs -mflat -mno-flat -mfpu -mhard-float -mno-fpu -msoft-float -mhard-quad-float -msoft-quad-float -mno-unaligned-doubles -munaligned-doubles -muser-mode -mno-user-mode -mfaster-structs -mno-faster-structs -mstd-struct-return -mno-std-struct-return -mlra -mno-lra -mcpu=cpu_type -mtune=cpu_type -mv8plus -mno-v8plus -mvis -mno-vis -mvis2 -mno-vis2 -mvis3 -mno-vis3 -mvis4 -mno-vis4 -mvis4b -mno-vis4b -mcbcond -mno-cbcond -mfmaf -mno-fmaf -mfsmuld -mno-fsmuld -mpopc -mno-popc -msubxc -mno-subxc -mfix-at697f -mfix-ut699 -mfix-ut700 -mfix-gr712rc -m32 -m64 -mcmodel=which -mmemory-model=mem-model -mstack-bias -mno-stack-bias -G Create a shared object. It is recommended that -symbolic or -shared be used instead. -Qy Identify the versions of each tool used by the compiler, in a ".ident" assembler -Qn Refrain from adding ".ident" directives to the output file (this is the default). -YP,dirs -Ym,dir -mcmodel=small -mcmodel=large -mcpu=name -m32 -m64 -mbig-endian -mlittle-endian -mcpu=name -m32 -mlong-calls -mno-long-calls -mno-ep -mep -mno-prolog-function -mprolog-function -mspace -mtda=n -msda=n -mzda=n -mv850 -mv850e3v5 -mv850e2v4 -mv850e2v3 -mv850e2 -mv850e1 -mv850es -mv850e -mdisable-callt -mno-disable-callt -mrelax -mno-relax -mlong-jumps -mno-long-jumps -msoft-float -mhard-float -mloop -mrh850-abi -mghs -mgcc-abi -m8byte-align -mno-8byte-align -mbig-switch -mapp-regs -mno-app-regs -munix -mgnu -mg Output code for G-format floating-point numbers instead of D-format. -mdebug -msim -mfpu -mhard-float -mno-fpu -msoft-float -mcpu=cpu_type -mtune=cpu_type -msv-mode -muser-mode -mvms-return-codes -mdebug-main=prefix -mmalloc64 -mpointer-size=size -mrtp -non-static -Bstatic -Bdynamic -Xbind-lazy -Xbind-now -march=cpu-type -mtune=cpu-type -mcpu=cpu-type -mfpmath=unit -masm=dialect -mieee-fp -mno-ieee-fp -m80387 -mhard-float -mno-80387 -msoft-float -mno-fp-ret-in-387 -mno-fancy-math-387 -malign-double -mno-align-double -m96bit-long-double -m128bit-long-double -mlong-double-64 -mlong-double-80 -mlong-double-128 -malign-data=type -mlarge-data-threshold=threshold -mrtd -mregparm=num -msseregparm -mvect8-ret-in-mem -mpc32 -mpc64 -mpc80 -mdaz-ftz -mstackrealign -mpreferred-stack-boundary=num -mincoming-stack-boundary=num -mmmx -msse -msse2 -msse3 -mssse3 -msse4 -msse4a -msse4.1 -msse4.2 -mavx -mavx2 -mavx512f -mavx512pf -mavx512er -mavx512cd -mavx512vl -mavx512bw -mavx512dq -mavx512ifma -mavx512vbmi -msha -maes -mpclmul -mclflushopt -mclwb -mfsgsbase -mptwrite -mrdrnd -mf16c -mfma -mpconfig -mwbnoinvd -mfma4 -mprfchw -mrdpid -mprefetchwt1 -mrdseed -msgx -mxop -mlwp -m3dnow -m3dnowa -mpopcnt -mabm -madx -mbmi -mbmi2 -mlzcnt -mfxsr -mxsave -mxsaveopt -mxsavec -mxsaves -mrtm -mhle -mtbm -mmwaitx -mclzero -mpku -mavx512vbmi2 -mavx512bf16 -mgfni -mvaes -mwaitpkg -mvpclmulqdq -mavx512bitalg -mmovdiri -mmovdir64b -menqcmd -muintr -mtsxldtrk -mavx512vpopcntdq -mavx512vp2intersect -mavx5124fmaps -mavx512vnni -mavxvnni -mavx5124vnniw -mcldemote -mserialize -mamx-tile -mamx-int8 -mamx-bf16 -mhreset -mkl -mwidekl -mdump-tune-features -mtune-ctrl=feature-list -mno-default -mcld -mvzeroupper -mprefer-avx128 -mprefer-vector-width=opt -mcx16 -msahf -mmovbe -mshstk -mcrc32 -mmwait -mrecip -mrecip=opt -mveclibabi=type -mabi=name -mforce-indirect-call -mmanual-endbr -mcall-ms2sysv-xlogues -mtls-dialect=type -mpush-args -mno-push-args -maccumulate-outgoing-args -mthreads -mms-bitfields -mno-ms-bitfields -mno-align-stringops -minline-all-stringops -minline-stringops-dynamically -mstringop-strategy=alg -mmemcpy-strategy=strategy -mmemset-strategy=strategy -momit-leaf-frame-pointer -mtls-direct-seg-refs -mno-tls-direct-seg-refs -msse2avx -mno-sse2avx -mfentry -mno-fentry -mrecord-mcount -mno-record-mcount -mnop-mcount -mno-nop-mcount -minstrument-return=type -mrecord-return -mno-record-return -mfentry-name=name -mfentry-section=name -mskip-rax-setup -mno-skip-rax-setup -m8bit-idiv -mno-8bit-idiv -mavx256-split-unaligned-load -mavx256-split-unaligned-store -mstack-protector-guard=guard -mstack-protector-guard-reg=reg -mstack-protector-guard-offset=offset -mgeneral-regs-only -mindirect-branch=choice -mfunction-return=choice -mindirect-branch-register -mharden-sls=choice -mindirect-branch-cs-prefix -m32 -m64 -mx32 -m16 -miamcu -mno-red-zone -mcmodel=small -mcmodel=kernel -mcmodel=medium -mcmodel=large -maddress-mode=long -maddress-mode=short -mneeded -mno-needed -mconsole -mdll -mnop-fun-dllimport -mthread -municode -mwin32 -mwindows -fno-set-stack-executable -fwritable-relocated-rdata -mpe-aligned-commons -msim -mconst16 -mno-const16 -mfused-madd -mno-fused-madd -mserialize-volatile -mno-serialize-volatile -mforce-no-pic -mtext-section-literals -mno-text-section-literals -mauto-litpools -mno-auto-litpools -mtarget-align -mno-target-align -mlongcalls -mno-longcalls -mabi=name -mabi=call0 -mabi=windowed
ENVIRONMENT BUGS FOOTNOTES SEE ALSO AUTHOR COPYRIGHT 
GCC(1)                                           GNU                                          GCC(1)



NAME
       gcc - GNU project C and C++ compiler

SYNOPSIS
       gcc [-c|-S|-E] [-std=standard]
           [-g] [-pg] [-Olevel]
           [-Wwarn...] [-Wpedantic]
           [-Idir...] [-Ldir...]
           [-Dmacro[=defn]...] [-Umacro]
           [-foption...] [-mmachine-option...]
           [-o outfile] [@file] infile...

       Only the most useful options are listed here; see below for the remainder.  g++ accepts
       mostly the same options as gcc.

DESCRIPTION
       When you invoke GCC, it normally does preprocessing, compilation, assembly and linking.  The
       "overall options" allow you to stop this process at an intermediate stage.  For example, the
       -c option says not to run the linker.  Then the output consists of object files output by the
       assembler.

       Other options are passed on to one or more stages of processing.  Some options control the
       preprocessor and others the compiler itself.  Yet other options control the assembler and
       linker; most of these are not documented here, since you rarely need to use any of them.

       Most of the command-line options that you can use with GCC are useful for C programs; when an
       option is only useful with another language (usually C++), the explanation says so
       explicitly.  If the description for a particular option does not mention a source language,
       you can use that option with all supported languages.

       The usual way to run GCC is to run the executable called gcc, or machine-gcc when cross-
       compiling, or machine-gcc-version to run a specific version of GCC.  When you compile C++
       programs, you should invoke GCC as g++ instead.

       The gcc program accepts options and file names as operands.  Many options have multi-letter
       names; therefore multiple single-letter options may not be grouped: -dv is very different
       from -d -v.

       You can mix options and other arguments.  For the most part, the order you use doesn't
       matter.  Order does matter when you use several options of the same kind; for example, if you
       specify -L more than once, the directories are searched in the order specified.  Also, the
       placement of the -l option is significant.

       Many options have long names starting with -f or with -W---for example,
       -fmove-loop-invariants, -Wformat and so on.  Most of these have both positive and negative
       forms; the negative form of -ffoo is -fno-foo.  This manual documents only one of these two
       forms, whichever one is not the default.

       Some options take one or more arguments typically separated either by a space or by the
       equals sign (=) from the option name.  Unless documented otherwise, an argument can be either
       numeric or a string.  Numeric arguments must typically be small unsigned decimal or
       hexadecimal integers.  Hexadecimal arguments must begin with the 0x prefix.  Arguments to
       options that specify a size threshold of some sort may be arbitrarily large decimal or
       hexadecimal integers followed by a byte size suffix designating a multiple of bytes such as
       "kB" and "KiB" for kilobyte and kibibyte, respectively, "MB" and "MiB" for megabyte and
       mebibyte, "GB" and "GiB" for gigabyte and gigibyte, and so on.  Such arguments are designated
       by byte-size in the following text.  Refer to the NIST, IEC, and other relevant national and
       international standards for the full listing and explanation of the binary and decimal byte
       size prefixes.

OPTIONS
   Option Summary
       Here is a summary of all the options, grouped by type.  Explanations are in the following
       sections.

       Overall Options
           -c  -S  -E  -o file -dumpbase dumpbase  -dumpbase-ext auxdropsuf -dumpdir dumppfx  -x
           language -v  -###  --help[=class[,...]]  --target-help  --version -pass-exit-codes  -pipe
           -specs=file  -wrapper @file  -ffile-prefix-map=old=new -fplugin=file
           -fplugin-arg-name=arg -fdump-ada-spec[-slim]  -fada-spec-parent=unit  -fdump-go-spec=file

       C Language Options
           -ansi  -std=standard  -fgnu89-inline -fpermitted-flt-eval-methods=standard -aux-info
           filename  -fallow-parameterless-variadic-functions -fno-asm  -fno-builtin
           -fno-builtin-function  -fgimple -fhosted  -ffreestanding -fopenacc  -fopenacc-dim=geom
           -fopenmp  -fopenmp-simd -fms-extensions  -fplan9-extensions  -fsso-struct=endianness
           -fallow-single-precision  -fcond-mismatch  -flax-vector-conversions -fsigned-bitfields
           -fsigned-char -funsigned-bitfields  -funsigned-char

       C++ Language Options
           -fabi-version=n  -fno-access-control -faligned-new=n  -fargs-in-order=n  -fchar8_t
           -fcheck-new -fconstexpr-depth=n  -fconstexpr-cache-depth=n -fconstexpr-loop-limit=n
           -fconstexpr-ops-limit=n -fno-elide-constructors -fno-enforce-eh-specs -fno-gnu-keywords
           -fno-implicit-templates -fno-implicit-inline-templates -fno-implement-inlines
           -fmodule-header[=kind] -fmodule-only -fmodules-ts -fmodule-implicit-inline
           -fno-module-lazy -fmodule-mapper=specification -fmodule-version-ignore -fms-extensions
           -fnew-inheriting-ctors -fnew-ttp-matching -fno-nonansi-builtins  -fnothrow-opt
           -fno-operator-names -fno-optional-diags  -fpermissive -fno-pretty-templates -fno-rtti
           -fsized-deallocation -ftemplate-backtrace-limit=n -ftemplate-depth=n
           -fno-threadsafe-statics  -fuse-cxa-atexit -fno-weak  -nostdinc++
           -fvisibility-inlines-hidden -fvisibility-ms-compat -fext-numeric-literals
           -flang-info-include-translate[=header] -flang-info-include-translate-not
           -flang-info-module-cmi[=module] -stdlib=libstdc++,libc++ -Wabi-tag  -Wcatch-value
           -Wcatch-value=n -Wno-class-conversion  -Wclass-memaccess -Wcomma-subscript
           -Wconditionally-supported -Wno-conversion-null  -Wctad-maybe-unsupported
           -Wctor-dtor-privacy  -Wno-delete-incomplete -Wdelete-non-virtual-dtor  -Wdeprecated-copy
           -Wdeprecated-copy-dtor -Wno-deprecated-enum-enum-conversion
           -Wno-deprecated-enum-float-conversion -Weffc++  -Wno-exceptions -Wextra-semi
           -Wno-inaccessible-base -Wno-inherited-variadic-ctor  -Wno-init-list-lifetime
           -Winvalid-imported-macros -Wno-invalid-offsetof  -Wno-literal-suffix
           -Wno-mismatched-new-delete -Wmismatched-tags -Wmultiple-inheritance  -Wnamespaces
           -Wnarrowing -Wnoexcept  -Wnoexcept-type  -Wnon-virtual-dtor -Wpessimizing-move
           -Wno-placement-new  -Wplacement-new=n -Wrange-loop-construct -Wredundant-move
           -Wredundant-tags -Wreorder  -Wregister -Wstrict-null-sentinel  -Wno-subobject-linkage
           -Wtemplates -Wno-non-template-friend  -Wold-style-cast -Woverloaded-virtual
           -Wno-pmf-conversions -Wsign-promo -Wsized-deallocation  -Wsuggest-final-methods
           -Wsuggest-final-types  -Wsuggest-override -Wno-terminate  -Wuseless-cast
           -Wno-vexing-parse -Wvirtual-inheritance -Wno-virtual-move-assign  -Wvolatile
           -Wzero-as-null-pointer-constant

       Objective-C and Objective-C++ Language Options
           -fconstant-string-class=class-name -fgnu-runtime  -fnext-runtime -fno-nil-receivers
           -fobjc-abi-version=n -fobjc-call-cxx-cdtors -fobjc-direct-dispatch -fobjc-exceptions
           -fobjc-gc -fobjc-nilcheck -fobjc-std=objc1 -fno-local-ivars
           -fivar-visibility=[public|protected|private|package] -freplace-objc-classes -fzero-link
           -gen-decls -Wassign-intercept  -Wno-property-assign-default -Wno-protocol
           -Wobjc-root-class -Wselector -Wstrict-selector-match -Wundeclared-selector

       Diagnostic Message Formatting Options
           -fmessage-length=n -fdiagnostics-plain-output -fdiagnostics-show-location=[once|every-
           line] -fdiagnostics-color=[auto|never|always] -fdiagnostics-urls=[auto|never|always]
           -fdiagnostics-format=[text|json] -fno-diagnostics-show-option
           -fno-diagnostics-show-caret -fno-diagnostics-show-labels
           -fno-diagnostics-show-line-numbers -fno-diagnostics-show-cwe
           -fdiagnostics-minimum-margin-width=width -fdiagnostics-parseable-fixits
           -fdiagnostics-generate-patch -fdiagnostics-show-template-tree  -fno-elide-type
           -fdiagnostics-path-format=[none|separate-events|inline-events]
           -fdiagnostics-show-path-depths -fno-show-column -fdiagnostics-column-unit=[display|byte]
           -fdiagnostics-column-origin=origin

       Warning Options
           -fsyntax-only  -fmax-errors=n  -Wpedantic -pedantic-errors -w  -Wextra  -Wall  -Wabi=n
           -Waddress  -Wno-address-of-packed-member  -Waggregate-return
           -Walloc-size-larger-than=byte-size  -Walloc-zero -Walloca  -Walloca-larger-than=byte-size
           -Wno-aggressive-loop-optimizations -Warith-conversion -Warray-bounds  -Warray-bounds=n
           -Wno-attributes  -Wattribute-alias=n -Wno-attribute-alias -Wno-attribute-warning
           -Wbool-compare  -Wbool-operation -Wno-builtin-declaration-mismatch
           -Wno-builtin-macro-redefined  -Wc90-c99-compat  -Wc99-c11-compat -Wc11-c2x-compat
           -Wc++-compat  -Wc++11-compat  -Wc++14-compat  -Wc++17-compat -Wc++20-compat -Wcast-align
           -Wcast-align=strict  -Wcast-function-type  -Wcast-qual -Wchar-subscripts -Wclobbered
           -Wcomment -Wconversion  -Wno-coverage-mismatch  -Wno-cpp -Wdangling-else  -Wdate-time
           -Wno-deprecated  -Wno-deprecated-declarations  -Wno-designated-init
           -Wdisabled-optimization -Wno-discarded-array-qualifiers  -Wno-discarded-qualifiers
           -Wno-div-by-zero  -Wdouble-promotion -Wduplicated-branches  -Wduplicated-cond
           -Wempty-body  -Wno-endif-labels  -Wenum-compare  -Wenum-conversion -Werror  -Werror=*
           -Wexpansion-to-defined  -Wfatal-errors -Wfloat-conversion  -Wfloat-equal  -Wformat
           -Wformat=2 -Wno-format-contains-nul  -Wno-format-extra-args -Wformat-nonliteral
           -Wformat-overflow=n -Wformat-security  -Wformat-signedness  -Wformat-truncation=n
           -Wformat-y2k  -Wframe-address -Wframe-larger-than=byte-size  -Wno-free-nonheap-object
           -Wno-if-not-aligned  -Wno-ignored-attributes -Wignored-qualifiers
           -Wno-incompatible-pointer-types -Wimplicit  -Wimplicit-fallthrough
           -Wimplicit-fallthrough=n -Wno-implicit-function-declaration  -Wno-implicit-int
           -Winit-self  -Winline  -Wno-int-conversion  -Wint-in-bool-context
           -Wno-int-to-pointer-cast  -Wno-invalid-memory-model -Winvalid-pch  -Wjump-misses-init
           -Wlarger-than=byte-size -Wlogical-not-parentheses  -Wlogical-op  -Wlong-long
           -Wno-lto-type-mismatch -Wmain  -Wmaybe-uninitialized -Wmemset-elt-size
           -Wmemset-transposed-args -Wmisleading-indentation  -Wmissing-attributes  -Wmissing-braces
           -Wmissing-field-initializers  -Wmissing-format-attribute -Wmissing-include-dirs
           -Wmissing-noreturn  -Wno-missing-profile -Wno-multichar  -Wmultistatement-macros
           -Wnonnull  -Wnonnull-compare -Wnormalized=[none|id|nfc|nfkc] -Wnull-dereference  -Wno-odr
           -Wopenmp-simd -Wno-overflow  -Woverlength-strings  -Wno-override-init-side-effects
           -Wpacked  -Wno-packed-bitfield-compat  -Wpacked-not-aligned  -Wpadded -Wparentheses
           -Wno-pedantic-ms-format -Wpointer-arith  -Wno-pointer-compare  -Wno-pointer-to-int-cast
           -Wno-pragmas  -Wno-prio-ctor-dtor  -Wredundant-decls -Wrestrict  -Wno-return-local-addr
           -Wreturn-type -Wno-scalar-storage-order  -Wsequence-point -Wshadow  -Wshadow=global
           -Wshadow=local  -Wshadow=compatible-local -Wno-shadow-ivar -Wno-shift-count-negative
           -Wno-shift-count-overflow  -Wshift-negative-value -Wno-shift-overflow  -Wshift-overflow=n
           -Wsign-compare  -Wsign-conversion -Wno-sizeof-array-argument -Wsizeof-array-div
           -Wsizeof-pointer-div  -Wsizeof-pointer-memaccess -Wstack-protector  -Wstack-usage=byte-
           size  -Wstrict-aliasing -Wstrict-aliasing=n  -Wstrict-overflow  -Wstrict-overflow=n
           -Wstring-compare -Wno-stringop-overflow -Wno-stringop-overread -Wno-stringop-truncation
           -Wsuggest-attribute=[pure|const|noreturn|format|malloc] -Wswitch  -Wno-switch-bool
           -Wswitch-default  -Wswitch-enum -Wno-switch-outside-range  -Wno-switch-unreachable
           -Wsync-nand -Wsystem-headers  -Wtautological-compare  -Wtrampolines  -Wtrigraphs -Wtsan
           -Wtype-limits  -Wundef -Wuninitialized  -Wunknown-pragmas -Wunsuffixed-float-constants
           -Wunused -Wunused-but-set-parameter  -Wunused-but-set-variable -Wunused-const-variable
           -Wunused-const-variable=n -Wunused-function  -Wunused-label  -Wunused-local-typedefs
           -Wunused-macros -Wunused-parameter  -Wno-unused-result -Wunused-value  -Wunused-variable
           -Wno-varargs  -Wvariadic-macros -Wvector-operation-performance -Wvla
           -Wvla-larger-than=byte-size  -Wno-vla-larger-than -Wvolatile-register-var
           -Wwrite-strings -Wzero-length-bounds

       Static Analyzer Options
           -fanalyzer -fanalyzer-call-summaries -fanalyzer-checker=name -fno-analyzer-feasibility
           -fanalyzer-fine-grained -fanalyzer-state-merge -fanalyzer-state-purge
           -fanalyzer-transitivity -fanalyzer-verbose-edges -fanalyzer-verbose-state-changes
           -fanalyzer-verbosity=level -fdump-analyzer -fdump-analyzer-stderr
           -fdump-analyzer-callgraph -fdump-analyzer-exploded-graph -fdump-analyzer-exploded-nodes
           -fdump-analyzer-exploded-nodes-2 -fdump-analyzer-exploded-nodes-3
           -fdump-analyzer-feasibility -fdump-analyzer-json -fdump-analyzer-state-purge
           -fdump-analyzer-supergraph -Wno-analyzer-double-fclose -Wno-analyzer-double-free
           -Wno-analyzer-exposure-through-output-file -Wno-analyzer-file-leak
           -Wno-analyzer-free-of-non-heap -Wno-analyzer-malloc-leak
           -Wno-analyzer-mismatching-deallocation -Wno-analyzer-null-argument
           -Wno-analyzer-null-dereference -Wno-analyzer-possible-null-argument
           -Wno-analyzer-possible-null-dereference -Wno-analyzer-shift-count-negative
           -Wno-analyzer-shift-count-overflow -Wno-analyzer-stale-setjmp-buffer
           -Wno-analyzer-tainted-array-index -Wanalyzer-too-complex
           -Wno-analyzer-unsafe-call-within-signal-handler -Wno-analyzer-use-after-free
           -Wno-analyzer-use-of-pointer-in-stale-stack-frame
           -Wno-analyzer-use-of-uninitialized-value -Wno-analyzer-write-to-const
           -Wno-analyzer-write-to-string-literal

       C and Objective-C-only Warning Options
           -Wbad-function-cast  -Wmissing-declarations -Wmissing-parameter-type
           -Wmissing-prototypes  -Wnested-externs -Wold-style-declaration  -Wold-style-definition
           -Wstrict-prototypes  -Wtraditional  -Wtraditional-conversion
           -Wdeclaration-after-statement  -Wpointer-sign

       Debugging Options
           -g  -glevel  -gdwarf  -gdwarf-version -ggdb  -grecord-gcc-switches
           -gno-record-gcc-switches -gstabs  -gstabs+  -gstrict-dwarf  -gno-strict-dwarf
           -gas-loc-support  -gno-as-loc-support -gas-locview-support  -gno-as-locview-support
           -gcolumn-info  -gno-column-info  -gdwarf32  -gdwarf64 -gstatement-frontiers
           -gno-statement-frontiers -gvariable-location-views  -gno-variable-location-views
           -ginternal-reset-location-views  -gno-internal-reset-location-views -ginline-points
           -gno-inline-points -gvms  -gxcoff  -gxcoff+  -gz[=type] -gsplit-dwarf  -gdescribe-dies
           -gno-describe-dies -fdebug-prefix-map=old=new  -fdebug-types-section
           -fno-eliminate-unused-debug-types -femit-struct-debug-baseonly
           -femit-struct-debug-reduced -femit-struct-debug-detailed[=spec-list]
           -fno-eliminate-unused-debug-symbols  -femit-class-debug-always -fno-merge-debug-strings
           -fno-dwarf2-cfi-asm -fvar-tracking  -fvar-tracking-assignments

       Optimization Options
           -faggressive-loop-optimizations -falign-functions[=n[:m:[n2[:m2]]]]
           -falign-jumps[=n[:m:[n2[:m2]]]] -falign-labels[=n[:m:[n2[:m2]]]]
           -falign-loops[=n[:m:[n2[:m2]]]] -fno-allocation-dce -fallow-store-data-races
           -fassociative-math  -fauto-profile  -fauto-profile[=path] -fauto-inc-dec
           -fbranch-probabilities -fcaller-saves -fcombine-stack-adjustments  -fconserve-stack
           -fcompare-elim  -fcprop-registers  -fcrossjumping -fcse-follow-jumps  -fcse-skip-blocks
           -fcx-fortran-rules -fcx-limited-range -fdata-sections  -fdce  -fdelayed-branch
           -fdelete-null-pointer-checks  -fdevirtualize  -fdevirtualize-speculatively
           -fdevirtualize-at-ltrans  -fdse -fearly-inlining  -fipa-sra  -fexpensive-optimizations
           -ffat-lto-objects -ffast-math  -ffinite-math-only  -ffloat-store
           -fexcess-precision=style -ffinite-loops -fforward-propagate  -ffp-contract=style
           -ffunction-sections -fgcse  -fgcse-after-reload  -fgcse-las  -fgcse-lm
           -fgraphite-identity -fgcse-sm  -fhoist-adjacent-loads  -fif-conversion -fif-conversion2
           -findirect-inlining -finline-functions  -finline-functions-called-once  -finline-limit=n
           -finline-small-functions -fipa-modref -fipa-cp  -fipa-cp-clone -fipa-bit-cp  -fipa-vrp
           -fipa-pta  -fipa-profile  -fipa-pure-const -fipa-reference  -fipa-reference-addressable
           -fipa-stack-alignment  -fipa-icf  -fira-algorithm=algorithm -flive-patching=level
           -fira-region=region  -fira-hoist-pressure -fira-loop-pressure  -fno-ira-share-save-slots
           -fno-ira-share-spill-slots -fisolate-erroneous-paths-dereference
           -fisolate-erroneous-paths-attribute -fivopts  -fkeep-inline-functions
           -fkeep-static-functions -fkeep-static-consts  -flimit-function-alignment
           -flive-range-shrinkage -floop-block  -floop-interchange  -floop-strip-mine
           -floop-unroll-and-jam  -floop-nest-optimize -floop-parallelize-all  -flra-remat  -flto
           -flto-compression-level -flto-partition=alg  -fmerge-all-constants -fmerge-constants
           -fmodulo-sched  -fmodulo-sched-allow-regmoves -fmove-loop-invariants
           -fno-branch-count-reg -fno-defer-pop  -fno-fp-int-builtin-inexact  -fno-function-cse
           -fno-guess-branch-probability  -fno-inline  -fno-math-errno  -fno-peephole -fno-peephole2
           -fno-printf-return-value  -fno-sched-interblock -fno-sched-spec  -fno-signed-zeros
           -fno-toplevel-reorder  -fno-trapping-math  -fno-zero-initialized-in-bss
           -fomit-frame-pointer  -foptimize-sibling-calls -fpartial-inlining  -fpeel-loops
           -fpredictive-commoning -fprefetch-loop-arrays -fprofile-correction -fprofile-use
           -fprofile-use=path -fprofile-partial-training -fprofile-values
           -fprofile-reorder-functions -freciprocal-math  -free  -frename-registers
           -freorder-blocks -freorder-blocks-algorithm=algorithm -freorder-blocks-and-partition
           -freorder-functions -frerun-cse-after-loop  -freschedule-modulo-scheduled-loops
           -frounding-math  -fsave-optimization-record -fsched2-use-superblocks  -fsched-pressure
           -fsched-spec-load  -fsched-spec-load-dangerous -fsched-stalled-insns-dep[=n]
           -fsched-stalled-insns[=n] -fsched-group-heuristic  -fsched-critical-path-heuristic
           -fsched-spec-insn-heuristic  -fsched-rank-heuristic -fsched-last-insn-heuristic
           -fsched-dep-count-heuristic -fschedule-fusion -fschedule-insns  -fschedule-insns2
           -fsection-anchors -fselective-scheduling  -fselective-scheduling2 -fsel-sched-pipelining
           -fsel-sched-pipelining-outer-loops -fsemantic-interposition  -fshrink-wrap
           -fshrink-wrap-separate -fsignaling-nans -fsingle-precision-constant
           -fsplit-ivs-in-unroller  -fsplit-loops -fsplit-paths -fsplit-wide-types
           -fsplit-wide-types-early  -fssa-backprop  -fssa-phiopt -fstdarg-opt  -fstore-merging
           -fstrict-aliasing -fthread-jumps  -ftracer  -ftree-bit-ccp -ftree-builtin-call-dce
           -ftree-ccp  -ftree-ch -ftree-coalesce-vars  -ftree-copy-prop  -ftree-dce
           -ftree-dominator-opts -ftree-dse  -ftree-forwprop  -ftree-fre  -fcode-hoisting
           -ftree-loop-if-convert  -ftree-loop-im -ftree-phiprop  -ftree-loop-distribution
           -ftree-loop-distribute-patterns -ftree-loop-ivcanon  -ftree-loop-linear
           -ftree-loop-optimize -ftree-loop-vectorize -ftree-parallelize-loops=n  -ftree-pre
           -ftree-partial-pre  -ftree-pta -ftree-reassoc  -ftree-scev-cprop  -ftree-sink
           -ftree-slsr  -ftree-sra -ftree-switch-conversion  -ftree-tail-merge -ftree-ter
           -ftree-vectorize  -ftree-vrp  -funconstrained-commons -funit-at-a-time
           -funroll-all-loops  -funroll-loops -funsafe-math-optimizations  -funswitch-loops -fipa-ra
           -fvariable-expansion-in-unroller  -fvect-cost-model  -fvpt -fweb  -fwhole-program  -fwpa
           -fuse-linker-plugin -fzero-call-used-regs --param name=value -O  -O0  -O1  -O2  -O3  -Os
           -Ofast  -Og

       Program Instrumentation Options
           -p  -pg  -fprofile-arcs  --coverage  -ftest-coverage -fprofile-abs-path
           -fprofile-dir=path  -fprofile-generate  -fprofile-generate=path -fprofile-info-section
           -fprofile-info-section=name -fprofile-note=path -fprofile-prefix-path=path
           -fprofile-update=method -fprofile-filter-files=regex -fprofile-exclude-files=regex
           -fprofile-reproducible=[multithreaded|parallel-runs|serial] -fsanitize=style
           -fsanitize-recover  -fsanitize-recover=style -fasan-shadow-offset=number
           -fsanitize-sections=s1,s2,...  -fsanitize-undefined-trap-on-error  -fbounds-check
           -fcf-protection=[full|branch|return|none|check] -fstack-protector  -fstack-protector-all
           -fstack-protector-strong -fstack-protector-explicit  -fstack-check
           -fstack-limit-register=reg  -fstack-limit-symbol=sym -fno-stack-limit  -fsplit-stack
           -fvtable-verify=[std|preinit|none] -fvtv-counts  -fvtv-debug -finstrument-functions
           -finstrument-functions-exclude-function-list=sym,sym,...
           -finstrument-functions-exclude-file-list=file,file,...

       Preprocessor Options
           -Aquestion=answer -A-question[=answer] -C  -CC  -Dmacro[=defn] -dD  -dI  -dM  -dN  -dU
           -fdebug-cpp  -fdirectives-only  -fdollars-in-identifiers -fexec-charset=charset
           -fextended-identifiers -finput-charset=charset  -flarge-source-files
           -fmacro-prefix-map=old=new -fmax-include-depth=depth -fno-canonical-system-headers
           -fpch-deps  -fpch-preprocess -fpreprocessed  -ftabstop=width  -ftrack-macro-expansion
           -fwide-exec-charset=charset  -fworking-directory -H  -imacros file  -include file -M  -MD
           -MF  -MG  -MM  -MMD  -MP  -MQ  -MT -Mno-modules -no-integrated-cpp  -P  -pthread  -remap
           -traditional  -traditional-cpp  -trigraphs -Umacro  -undef -Wp,option  -Xpreprocessor
           option

       Assembler Options
           -Wa,option  -Xassembler option

       Linker Options
           object-file-name  -fuse-ld=linker  -llibrary -nostartfiles  -nodefaultlibs  -nolibc
           -nostdlib -e entry  --entry=entry -pie  -pthread  -r  -rdynamic -s  -static  -static-pie
           -static-libgcc  -static-libstdc++ -static-libasan  -static-libtsan  -static-liblsan
           -static-libubsan -shared  -shared-libgcc  -symbolic -T script  -Wl,option  -Xlinker
           option -u symbol  -z keyword

       Directory Options
           -Bprefix  -Idir  -I- -idirafter dir -imacros file  -imultilib dir -iplugindir=dir
           -iprefix file -iquote dir  -isysroot dir  -isystem dir -iwithprefix dir
           -iwithprefixbefore dir -Ldir  -no-canonical-prefixes  --no-sysroot-suffix -nostdinc
           -nostdinc++  --sysroot=dir

       Code Generation Options
           -fcall-saved-reg  -fcall-used-reg -ffixed-reg  -fexceptions -fnon-call-exceptions
           -fdelete-dead-exceptions  -funwind-tables -fasynchronous-unwind-tables -fno-gnu-unique
           -finhibit-size-directive  -fcommon  -fno-ident -fpcc-struct-return  -fpic  -fPIC  -fpie
           -fPIE  -fno-plt -fno-jump-tables -fno-bit-tests -frecord-gcc-switches -freg-struct-return
           -fshort-enums  -fshort-wchar -fverbose-asm  -fpack-struct[=n] -fleading-underscore
           -ftls-model=model -fstack-reuse=reuse_level -ftrampolines  -ftrapv  -fwrapv
           -fvisibility=[default|internal|hidden|protected] -fstrict-volatile-bitfields
           -fsync-libcalls

       Developer Options
           -dletters  -dumpspecs  -dumpmachine  -dumpversion -dumpfullversion
           -fcallgraph-info[=su,da] -fchecking  -fchecking=n -fdbg-cnt-list   -fdbg-cnt=counter-
           value-list -fdisable-ipa-pass_name -fdisable-rtl-pass_name -fdisable-rtl-pass-name=range-
           list -fdisable-tree-pass_name -fdisable-tree-pass-name=range-list -fdump-debug
           -fdump-earlydebug -fdump-noaddr  -fdump-unnumbered  -fdump-unnumbered-links
           -fdump-final-insns[=file] -fdump-ipa-all  -fdump-ipa-cgraph  -fdump-ipa-inline
           -fdump-lang-all -fdump-lang-switch -fdump-lang-switch-options
           -fdump-lang-switch-options=filename -fdump-passes -fdump-rtl-pass
           -fdump-rtl-pass=filename -fdump-statistics -fdump-tree-all -fdump-tree-switch
           -fdump-tree-switch-options -fdump-tree-switch-options=filename -fcompare-debug[=opts]
           -fcompare-debug-second -fenable-kind-pass -fenable-kind-pass=range-list -fira-verbose=n
           -flto-report  -flto-report-wpa  -fmem-report-wpa -fmem-report  -fpre-ipa-mem-report
           -fpost-ipa-mem-report -fopt-info  -fopt-info-options[=file] -fprofile-report
           -frandom-seed=string  -fsched-verbose=n -fsel-sched-verbose  -fsel-sched-dump-cfg
           -fsel-sched-pipelining-verbose -fstats  -fstack-usage  -ftime-report
           -ftime-report-details -fvar-tracking-assignments-toggle  -gtoggle
           -print-file-name=library  -print-libgcc-file-name -print-multi-directory
           -print-multi-lib  -print-multi-os-directory -print-prog-name=program  -print-search-dirs
           -Q -print-sysroot  -print-sysroot-headers-suffix -save-temps  -save-temps=cwd
           -save-temps=obj  -time[=file]

       Machine-Dependent Options
           AArch64 Options -mabi=name  -mbig-endian  -mlittle-endian -mgeneral-regs-only
           -mcmodel=tiny  -mcmodel=small  -mcmodel=large -mstrict-align  -mno-strict-align
           -momit-leaf-frame-pointer -mtls-dialect=desc  -mtls-dialect=traditional -mtls-size=size
           -mfix-cortex-a53-835769  -mfix-cortex-a53-843419 -mlow-precision-recip-sqrt
           -mlow-precision-sqrt  -mlow-precision-div -mpc-relative-literal-loads
           -msign-return-address=scope -mbranch-protection=none|standard|pac-ret[+leaf +b-key]|bti
           -mharden-sls=opts -march=name  -mcpu=name  -mtune=name -moverride=string
           -mverbose-cost-dump -mstack-protector-guard=guard -mstack-protector-guard-reg=sysreg
           -mstack-protector-guard-offset=offset -mtrack-speculation -moutline-atomics

           Adapteva Epiphany Options -mhalf-reg-file  -mprefer-short-insn-regs -mbranch-cost=num
           -mcmove  -mnops=num  -msoft-cmpsf -msplit-lohi  -mpost-inc  -mpost-modify
           -mstack-offset=num -mround-nearest  -mlong-calls  -mshort-calls  -msmall16 -mfp-mode=mode
           -mvect-double  -max-vect-align=num -msplit-vecmove-early  -m1reg-reg

           AMD GCN Options -march=gpu -mtune=gpu -mstack-size=bytes

           ARC Options -mbarrel-shifter  -mjli-always -mcpu=cpu  -mA6  -mARC600  -mA7  -mARC700
           -mdpfp  -mdpfp-compact  -mdpfp-fast  -mno-dpfp-lrsr -mea  -mno-mpy  -mmul32x16  -mmul64
           -matomic -mnorm  -mspfp  -mspfp-compact  -mspfp-fast  -msimd  -msoft-float  -mswap -mcrc
           -mdsp-packa  -mdvbf  -mlock  -mmac-d16  -mmac-24  -mrtsc  -mswape -mtelephony  -mxy
           -misize  -mannotate-align  -marclinux  -marclinux_prof -mlong-calls  -mmedium-calls
           -msdata  -mirq-ctrl-saved -mrgf-banked-regs  -mlpc-width=width  -G num -mvolatile-cache
           -mtp-regno=regno -malign-call  -mauto-modify-reg  -mbbit-peephole  -mno-brcc
           -mcase-vector-pcrel  -mcompact-casesi  -mno-cond-exec  -mearly-cbranchsi -mexpand-adddi
           -mindexed-loads  -mlra  -mlra-priority-none -mlra-priority-compact mlra-priority-
           noncompact  -mmillicode -mmixed-code  -mq-class  -mRcq  -mRcw  -msize-level=level
           -mtune=cpu  -mmultcost=num  -mcode-density-frame -munalign-prob-threshold=probability
           -mmpy-option=multo -mdiv-rem  -mcode-density  -mll64  -mfpu=fpu  -mrf16  -mbranch-index

           ARM Options -mapcs-frame  -mno-apcs-frame -mabi=name -mapcs-stack-check
           -mno-apcs-stack-check -mapcs-reentrant  -mno-apcs-reentrant -mgeneral-regs-only
           -msched-prolog  -mno-sched-prolog -mlittle-endian  -mbig-endian -mbe8  -mbe32
           -mfloat-abi=name -mfp16-format=name -mthumb-interwork  -mno-thumb-interwork -mcpu=name
           -march=name  -mfpu=name -mtune=name  -mprint-tune-info -mstructure-size-boundary=n
           -mabort-on-noreturn -mlong-calls  -mno-long-calls -msingle-pic-base  -mno-single-pic-base
           -mpic-register=reg -mnop-fun-dllimport -mpoke-function-name -mthumb  -marm  -mflip-thumb
           -mtpcs-frame  -mtpcs-leaf-frame -mcaller-super-interworking  -mcallee-super-interworking
           -mtp=name  -mtls-dialect=dialect -mword-relocations -mfix-cortex-m3-ldrd
           -munaligned-access -mneon-for-64bits -mslow-flash-data -masm-syntax-unified -mrestrict-it
           -mverbose-cost-dump -mpure-code -mcmse -mfix-cmse-cve-2021-35465 -mfdpic

           AVR Options -mmcu=mcu  -mabsdata  -maccumulate-args -mbranch-cost=cost -mcall-prologues
           -mgas-isr-prologues  -mint8 -mdouble=bits -mlong-double=bits -mn_flash=size
           -mno-interrupts -mmain-is-OS_task  -mrelax  -mrmw  -mstrict-X  -mtiny-stack
           -mfract-convert-truncate -mshort-calls  -nodevicelib  -nodevicespecs -Waddr-space-convert
           -Wmisspelled-isr

           Blackfin Options -mcpu=cpu[-sirevision] -msim  -momit-leaf-frame-pointer
           -mno-omit-leaf-frame-pointer -mspecld-anomaly  -mno-specld-anomaly  -mcsync-anomaly
           -mno-csync-anomaly -mlow-64k  -mno-low64k  -mstack-check-l1  -mid-shared-library
           -mno-id-shared-library  -mshared-library-id=n -mleaf-id-shared-library
           -mno-leaf-id-shared-library -msep-data  -mno-sep-data  -mlong-calls  -mno-long-calls
           -mfast-fp  -minline-plt  -mmulticore  -mcorea  -mcoreb  -msdram -micplb

           C6X Options -mbig-endian  -mlittle-endian  -march=cpu -msim  -msdata=sdata-type

           CRIS Options -mcpu=cpu  -march=cpu -mtune=cpu -mmax-stack-frame=n -metrax4  -metrax100
           -mpdebug  -mcc-init  -mno-side-effects -mstack-align  -mdata-align  -mconst-align
           -m32-bit  -m16-bit  -m8-bit  -mno-prologue-epilogue -melf  -maout  -sim  -sim2
           -mmul-bug-workaround  -mno-mul-bug-workaround

           CR16 Options -mmac -mcr16cplus  -mcr16c -msim  -mint32  -mbit-ops -mdata-model=model

           C-SKY Options -march=arch  -mcpu=cpu -mbig-endian  -EB  -mlittle-endian  -EL -mhard-float
           -msoft-float  -mfpu=fpu  -mdouble-float  -mfdivdu -mfloat-abi=name -melrw  -mistack  -mmp
           -mcp  -mcache  -msecurity  -mtrust -mdsp  -medsp  -mvdsp -mdiv  -msmart  -mhigh-registers
           -manchor -mpushpop  -mmultiple-stld  -mconstpool  -mstack-size  -mccrt -mbranch-cost=n
           -mcse-cc  -msched-prolog -msim

           Darwin Options -all_load  -allowable_client  -arch  -arch_errors_fatal -arch_only
           -bind_at_load  -bundle  -bundle_loader -client_name  -compatibility_version
           -current_version -dead_strip -dependency-file  -dylib_file  -dylinker_install_name
           -dynamic  -dynamiclib  -exported_symbols_list -filelist  -flat_namespace
           -force_cpusubtype_ALL -force_flat_namespace  -headerpad_max_install_names -iframework
           -image_base  -init  -install_name  -keep_private_externs -multi_module  -multiply_defined
           -multiply_defined_unused -noall_load   -no_dead_strip_inits_and_terms -nofixprebinding
           -nomultidefs  -noprebind  -noseglinkedit -pagezero_size  -prebind
           -prebind_all_twolevel_modules -private_bundle  -read_only_relocs  -sectalign
           -sectobjectsymbols  -whyload  -seg1addr -sectcreate  -sectobjectsymbols  -sectorder
           -segaddr  -segs_read_only_addr  -segs_read_write_addr -seg_addr_table
           -seg_addr_table_filename  -seglinkedit -segprot  -segs_read_only_addr
           -segs_read_write_addr -single_module  -static  -sub_library  -sub_umbrella
           -twolevel_namespace  -umbrella  -undefined -unexported_symbols_list
           -weak_reference_mismatches -whatsloaded  -F  -gused  -gfull  -mmacosx-version-min=version
           -mkernel  -mone-byte-bool

           DEC Alpha Options -mno-fp-regs  -msoft-float -mieee  -mieee-with-inexact
           -mieee-conformant -mfp-trap-mode=mode  -mfp-rounding-mode=mode -mtrap-precision=mode
           -mbuild-constants -mcpu=cpu-type  -mtune=cpu-type -mbwx  -mmax  -mfix  -mcix -mfloat-vax
           -mfloat-ieee -mexplicit-relocs  -msmall-data  -mlarge-data -msmall-text  -mlarge-text
           -mmemory-latency=time

           eBPF Options -mbig-endian -mlittle-endian -mkernel=version -mframe-limit=bytes -mxbpf

           FR30 Options -msmall-model  -mno-lsim

           FT32 Options -msim  -mlra  -mnodiv  -mft32b  -mcompress  -mnopm

           FRV Options -mgpr-32  -mgpr-64  -mfpr-32  -mfpr-64 -mhard-float  -msoft-float -malloc-cc
           -mfixed-cc  -mdword  -mno-dword -mdouble  -mno-double -mmedia  -mno-media  -mmuladd
           -mno-muladd -mfdpic  -minline-plt  -mgprel-ro  -multilib-library-pic -mlinked-fp
           -mlong-calls  -malign-labels -mlibrary-pic  -macc-4  -macc-8 -mpack  -mno-pack
           -mno-eflags  -mcond-move  -mno-cond-move -moptimize-membar  -mno-optimize-membar -mscc
           -mno-scc  -mcond-exec  -mno-cond-exec -mvliw-branch  -mno-vliw-branch -mmulti-cond-exec
           -mno-multi-cond-exec  -mnested-cond-exec -mno-nested-cond-exec  -mtomcat-stats -mTLS
           -mtls -mcpu=cpu

           GNU/Linux Options -mglibc  -muclibc  -mmusl  -mbionic  -mandroid -tno-android-cc
           -tno-android-ld

           H8/300 Options -mrelax  -mh  -ms  -mn  -mexr  -mno-exr  -mint32  -malign-300

           HPPA Options -march=architecture-type -mcaller-copies  -mdisable-fpregs
           -mdisable-indexing -mfast-indirect-calls  -mgas  -mgnu-ld   -mhp-ld
           -mfixed-range=register-range -mjump-in-delay  -mlinker-opt  -mlong-calls
           -mlong-load-store  -mno-disable-fpregs -mno-disable-indexing  -mno-fast-indirect-calls
           -mno-gas -mno-jump-in-delay  -mno-long-load-store -mno-portable-runtime  -mno-soft-float
           -mno-space-regs  -msoft-float  -mpa-risc-1-0 -mpa-risc-1-1  -mpa-risc-2-0
           -mportable-runtime -mschedule=cpu-type  -mspace-regs  -msio  -mwsio -munix=unix-std
           -nolibdld  -static  -threads

           IA-64 Options -mbig-endian  -mlittle-endian  -mgnu-as  -mgnu-ld  -mno-pic
           -mvolatile-asm-stop  -mregister-names  -msdata  -mno-sdata -mconstant-gp  -mauto-pic
           -mfused-madd -minline-float-divide-min-latency -minline-float-divide-max-throughput
           -mno-inline-float-divide -minline-int-divide-min-latency
           -minline-int-divide-max-throughput -mno-inline-int-divide -minline-sqrt-min-latency
           -minline-sqrt-max-throughput -mno-inline-sqrt -mdwarf2-asm  -mearly-stop-bits
           -mfixed-range=register-range  -mtls-size=tls-size -mtune=cpu-type  -milp32  -mlp64
           -msched-br-data-spec  -msched-ar-data-spec  -msched-control-spec -msched-br-in-data-spec
           -msched-ar-in-data-spec  -msched-in-control-spec -msched-spec-ldc
           -msched-spec-control-ldc -msched-prefer-non-data-spec-insns
           -msched-prefer-non-control-spec-insns -msched-stop-bits-after-every-cycle
           -msched-count-spec-in-critical-path -msel-sched-dont-check-control-spec
           -msched-fp-mem-deps-zero-cost -msched-max-memory-insns-hard-limit
           -msched-max-memory-insns=max-insns

           LM32 Options -mbarrel-shift-enabled  -mdivide-enabled  -mmultiply-enabled
           -msign-extend-enabled  -muser-enabled

           M32R/D Options -m32r2  -m32rx  -m32r -mdebug -malign-loops  -mno-align-loops
           -missue-rate=number -mbranch-cost=number -mmodel=code-size-model-type -msdata=sdata-type
           -mno-flush-func  -mflush-func=name -mno-flush-trap  -mflush-trap=number -G num

           M32C Options -mcpu=cpu  -msim  -memregs=number

           M680x0 Options -march=arch  -mcpu=cpu  -mtune=tune -m68000  -m68020  -m68020-40
           -m68020-60  -m68030  -m68040 -m68060  -mcpu32  -m5200  -m5206e  -m528x  -m5307  -m5407
           -mcfv4e  -mbitfield  -mno-bitfield  -mc68000  -mc68020 -mnobitfield  -mrtd  -mno-rtd
           -mdiv  -mno-div  -mshort -mno-short  -mhard-float  -m68881  -msoft-float  -mpcrel
           -malign-int  -mstrict-align  -msep-data  -mno-sep-data -mshared-library-id=n
           -mid-shared-library  -mno-id-shared-library -mxgot  -mno-xgot  -mlong-jump-table-offsets

           MCore Options -mhardlit  -mno-hardlit  -mdiv  -mno-div  -mrelax-immediates
           -mno-relax-immediates  -mwide-bitfields  -mno-wide-bitfields -m4byte-functions
           -mno-4byte-functions  -mcallgraph-data -mno-callgraph-data  -mslow-bytes  -mno-slow-bytes
           -mno-lsim -mlittle-endian  -mbig-endian  -m210  -m340  -mstack-increment

           MeP Options -mabsdiff  -mall-opts  -maverage  -mbased=n  -mbitops -mc=n  -mclip
           -mconfig=name  -mcop  -mcop32  -mcop64  -mivc2 -mdc  -mdiv  -meb  -mel  -mio-volatile
           -ml  -mleadz  -mm  -mminmax -mmult  -mno-opts  -mrepeat  -ms  -msatur  -msdram  -msim
           -msimnovec  -mtf -mtiny=n

           MicroBlaze Options -msoft-float  -mhard-float  -msmall-divides  -mcpu=cpu -mmemcpy
           -mxl-soft-mul  -mxl-soft-div  -mxl-barrel-shift -mxl-pattern-compare  -mxl-stack-check
           -mxl-gp-opt  -mno-clearbss -mxl-multiply-high  -mxl-float-convert  -mxl-float-sqrt
           -mbig-endian  -mlittle-endian  -mxl-reorder  -mxl-mode-app-model
           -mpic-data-is-text-relative

           MIPS Options -EL  -EB  -march=arch  -mtune=arch -mips1  -mips2  -mips3  -mips4  -mips32
           -mips32r2  -mips32r3  -mips32r5 -mips32r6  -mips64  -mips64r2  -mips64r3  -mips64r5
           -mips64r6 -mips16  -mno-mips16  -mflip-mips16 -minterlink-compressed
           -mno-interlink-compressed -minterlink-mips16  -mno-interlink-mips16 -mabi=abi  -mabicalls
           -mno-abicalls -mshared  -mno-shared  -mplt  -mno-plt  -mxgot  -mno-xgot -mgp32  -mgp64
           -mfp32  -mfpxx  -mfp64  -mhard-float  -msoft-float -mno-float  -msingle-float
           -mdouble-float -modd-spreg  -mno-odd-spreg -mabs=mode  -mnan=encoding -mdsp  -mno-dsp
           -mdspr2  -mno-dspr2 -mmcu  -mmno-mcu -meva  -mno-eva -mvirt  -mno-virt -mxpa  -mno-xpa
           -mcrc  -mno-crc -mginv  -mno-ginv -mmicromips  -mno-micromips -mmsa  -mno-msa
           -mloongson-mmi  -mno-loongson-mmi -mloongson-ext  -mno-loongson-ext -mloongson-ext2
           -mno-loongson-ext2 -mfpu=fpu-type -msmartmips  -mno-smartmips -mpaired-single
           -mno-paired-single  -mdmx  -mno-mdmx -mips3d  -mno-mips3d  -mmt  -mno-mt  -mllsc
           -mno-llsc -mlong64  -mlong32  -msym32  -mno-sym32 -Gnum  -mlocal-sdata  -mno-local-sdata
           -mextern-sdata  -mno-extern-sdata  -mgpopt  -mno-gopt -membedded-data  -mno-embedded-data
           -muninit-const-in-rodata  -mno-uninit-const-in-rodata -mcode-readable=setting
           -msplit-addresses  -mno-split-addresses -mexplicit-relocs  -mno-explicit-relocs
           -mcheck-zero-division  -mno-check-zero-division -mdivide-traps  -mdivide-breaks
           -mload-store-pairs  -mno-load-store-pairs -mmemcpy  -mno-memcpy  -mlong-calls
           -mno-long-calls -mmad  -mno-mad  -mimadd  -mno-imadd  -mfused-madd  -mno-fused-madd
           -nocpp -mfix-24k  -mno-fix-24k -mfix-r4000  -mno-fix-r4000  -mfix-r4400  -mno-fix-r4400
           -mfix-r5900  -mno-fix-r5900 -mfix-r10000  -mno-fix-r10000  -mfix-rm7000  -mno-fix-rm7000
           -mfix-vr4120  -mno-fix-vr4120 -mfix-vr4130  -mno-fix-vr4130  -mfix-sb1  -mno-fix-sb1
           -mflush-func=func  -mno-flush-func -mbranch-cost=num  -mbranch-likely  -mno-branch-likely
           -mcompact-branches=policy -mfp-exceptions  -mno-fp-exceptions -mvr4130-align
           -mno-vr4130-align  -msynci  -mno-synci -mlxc1-sxc1  -mno-lxc1-sxc1  -mmadd4  -mno-madd4
           -mrelax-pic-calls  -mno-relax-pic-calls  -mmcount-ra-address -mframe-header-opt
           -mno-frame-header-opt

           MMIX Options -mlibfuncs  -mno-libfuncs  -mepsilon  -mno-epsilon  -mabi=gnu -mabi=mmixware
           -mzero-extend  -mknuthdiv  -mtoplevel-symbols -melf  -mbranch-predict
           -mno-branch-predict  -mbase-addresses -mno-base-addresses  -msingle-exit
           -mno-single-exit

           MN10300 Options -mmult-bug  -mno-mult-bug -mno-am33  -mam33  -mam33-2  -mam34 -mtune=cpu-
           type -mreturn-pointer-on-d0 -mno-crt0  -mrelax  -mliw  -msetlb

           Moxie Options -meb  -mel  -mmul.x  -mno-crt0

           MSP430 Options -msim  -masm-hex  -mmcu=  -mcpu=  -mlarge  -msmall  -mrelax -mwarn-mcu
           -mcode-region=  -mdata-region= -msilicon-errata=  -msilicon-errata-warn= -mhwmult=
           -minrt  -mtiny-printf  -mmax-inline-shift=

           NDS32 Options -mbig-endian  -mlittle-endian -mreduced-regs  -mfull-regs -mcmov  -mno-cmov
           -mext-perf  -mno-ext-perf -mext-perf2  -mno-ext-perf2 -mext-string  -mno-ext-string
           -mv3push  -mno-v3push -m16bit  -mno-16bit -misr-vector-size=num -mcache-block-size=num
           -march=arch -mcmodel=code-model -mctor-dtor  -mrelax

           Nios II Options -G num  -mgpopt=option  -mgpopt  -mno-gpopt -mgprel-sec=regexp
           -mr0rel-sec=regexp -mel  -meb -mno-bypass-cache  -mbypass-cache -mno-cache-volatile
           -mcache-volatile -mno-fast-sw-div  -mfast-sw-div -mhw-mul  -mno-hw-mul  -mhw-mulx
           -mno-hw-mulx  -mno-hw-div  -mhw-div -mcustom-insn=N  -mno-custom-insn
           -mcustom-fpu-cfg=name -mhal  -msmallc  -msys-crt0=name  -msys-lib=name -march=arch  -mbmx
           -mno-bmx  -mcdx  -mno-cdx

           Nvidia PTX Options -m64  -mmainkernel  -moptimize

           OpenRISC Options -mboard=name  -mnewlib  -mhard-mul  -mhard-div -msoft-mul  -msoft-div
           -msoft-float  -mhard-float  -mdouble-float -munordered-float -mcmov  -mror  -mrori
           -msext  -msfimm  -mshftimm

           PDP-11 Options -mfpu  -msoft-float  -mac0  -mno-ac0  -m40  -m45  -m10 -mint32  -mno-int16
           -mint16  -mno-int32 -msplit  -munix-asm  -mdec-asm  -mgnu-asm  -mlra

           picoChip Options -mae=ae_type  -mvliw-lookahead=N -msymbol-as-address
           -mno-inefficient-warnings

           PowerPC Options See RS/6000 and PowerPC Options.

           PRU Options -mmcu=mcu  -minrt  -mno-relax  -mloop -mabi=variant

           RISC-V Options -mbranch-cost=N-instruction -mplt  -mno-plt -mabi=ABI-string -mfdiv
           -mno-fdiv -mdiv  -mno-div -march=ISA-string -mtune=processor-string
           -mpreferred-stack-boundary=num -msmall-data-limit=N-bytes -msave-restore
           -mno-save-restore -mshorten-memrefs  -mno-shorten-memrefs -mstrict-align
           -mno-strict-align -mcmodel=medlow  -mcmodel=medany -mexplicit-relocs
           -mno-explicit-relocs -mrelax  -mno-relax -mriscv-attribute  -mmo-riscv-attribute
           -malign-data=type -mbig-endian  -mlittle-endian +-mstack-protector-guard=guard
           -mstack-protector-guard-reg=reg +-mstack-protector-guard-offset=offset

           RL78 Options -msim  -mmul=none  -mmul=g13  -mmul=g14  -mallregs -mcpu=g10  -mcpu=g13
           -mcpu=g14  -mg10  -mg13  -mg14 -m64bit-doubles  -m32bit-doubles
           -msave-mduc-in-interrupts

           RS/6000 and PowerPC Options -mcpu=cpu-type -mtune=cpu-type -mcmodel=code-model
           -mpowerpc64 -maltivec  -mno-altivec -mpowerpc-gpopt  -mno-powerpc-gpopt -mpowerpc-gfxopt
           -mno-powerpc-gfxopt -mmfcrf  -mno-mfcrf  -mpopcntb  -mno-popcntb  -mpopcntd  -mno-popcntd
           -mfprnd  -mno-fprnd -mcmpb  -mno-cmpb  -mhard-dfp  -mno-hard-dfp -mfull-toc
           -mminimal-toc  -mno-fp-in-toc  -mno-sum-in-toc -m64  -m32  -mxl-compat  -mno-xl-compat
           -mpe -malign-power  -malign-natural -msoft-float  -mhard-float  -mmultiple  -mno-multiple
           -mupdate  -mno-update -mavoid-indexed-addresses  -mno-avoid-indexed-addresses
           -mfused-madd  -mno-fused-madd  -mbit-align  -mno-bit-align -mstrict-align
           -mno-strict-align  -mrelocatable -mno-relocatable  -mrelocatable-lib
           -mno-relocatable-lib -mtoc  -mno-toc  -mlittle  -mlittle-endian  -mbig  -mbig-endian
           -mdynamic-no-pic  -mswdiv  -msingle-pic-base -mprioritize-restricted-insns=priority
           -msched-costly-dep=dependence_type -minsert-sched-nops=scheme -mcall-aixdesc  -mcall-eabi
           -mcall-freebsd -mcall-linux  -mcall-netbsd  -mcall-openbsd -mcall-sysv  -mcall-sysv-eabi
           -mcall-sysv-noeabi -mtraceback=traceback_type -maix-struct-return  -msvr4-struct-return
           -mabi=abi-type  -msecure-plt  -mbss-plt -mlongcall  -mno-longcall  -mpltseq  -mno-pltseq
           -mblock-move-inline-limit=num -mblock-compare-inline-limit=num
           -mblock-compare-inline-loop-limit=num -mno-block-ops-unaligned-vsx
           -mstring-compare-inline-limit=num -misel  -mno-isel -mvrsave  -mno-vrsave -mmulhw
           -mno-mulhw -mdlmzb  -mno-dlmzb -mprototype  -mno-prototype -msim  -mmvme  -mads
           -myellowknife  -memb  -msdata -msdata=opt  -mreadonly-in-sdata  -mvxworks  -G num -mrecip
           -mrecip=opt  -mno-recip  -mrecip-precision -mno-recip-precision -mveclibabi=type  -mfriz
           -mno-friz -mpointers-to-nested-functions  -mno-pointers-to-nested-functions
           -msave-toc-indirect  -mno-save-toc-indirect -mpower8-fusion  -mno-mpower8-fusion
           -mpower8-vector  -mno-power8-vector -mcrypto  -mno-crypto  -mhtm  -mno-htm -mquad-memory
           -mno-quad-memory -mquad-memory-atomic  -mno-quad-memory-atomic -mcompat-align-parm
           -mno-compat-align-parm -mfloat128  -mno-float128  -mfloat128-hardware
           -mno-float128-hardware -mgnu-attribute  -mno-gnu-attribute -mstack-protector-guard=guard
           -mstack-protector-guard-reg=reg -mstack-protector-guard-offset=offset -mprefixed
           -mno-prefixed -mpcrel -mno-pcrel -mmma -mno-mmma -mrop-protect -mno-rop-protect
           -mprivileged -mno-privileged

           RX Options -m64bit-doubles  -m32bit-doubles  -fpu  -nofpu -mcpu= -mbig-endian-data
           -mlittle-endian-data -msmall-data -msim  -mno-sim -mas100-syntax  -mno-as100-syntax
           -mrelax -mmax-constant-size= -mint-register= -mpid -mallow-string-insns
           -mno-allow-string-insns -mjsr -mno-warn-multiple-fast-interrupts -msave-acc-in-interrupts

           S/390 and zSeries Options -mtune=cpu-type  -march=cpu-type -mhard-float  -msoft-float
           -mhard-dfp  -mno-hard-dfp -mlong-double-64  -mlong-double-128 -mbackchain  -mno-backchain
           -mpacked-stack  -mno-packed-stack -msmall-exec  -mno-small-exec  -mmvcle  -mno-mvcle -m64
           -m31  -mdebug  -mno-debug  -mesa  -mzarch -mhtm  -mvx  -mzvector -mtpf-trace
           -mno-tpf-trace  -mtpf-trace-skip  -mno-tpf-trace-skip -mfused-madd  -mno-fused-madd
           -mwarn-framesize  -mwarn-dynamicstack  -mstack-size  -mstack-guard
           -mhotpatch=halfwords,halfwords

           Score Options -meb  -mel -mnhwloop -muls -mmac -mscore5  -mscore5u  -mscore7  -mscore7d

           SH Options -m1  -m2  -m2e -m2a-nofpu  -m2a-single-only  -m2a-single  -m2a -m3  -m3e
           -m4-nofpu  -m4-single-only  -m4-single  -m4 -m4a-nofpu  -m4a-single-only  -m4a-single
           -m4a  -m4al -mb  -ml  -mdalign  -mrelax -mbigtable  -mfmovd  -mrenesas  -mno-renesas
           -mnomacsave -mieee  -mno-ieee  -mbitops  -misize  -minline-ic_invalidate  -mpadstruct
           -mprefergot  -musermode  -multcost=number  -mdiv=strategy -mdivsi3_libfunc=name
           -mfixed-range=register-range -maccumulate-outgoing-args -matomic-model=atomic-model
           -mbranch-cost=num  -mzdcbranch  -mno-zdcbranch -mcbranch-force-delay-slot -mfused-madd
           -mno-fused-madd  -mfsca  -mno-fsca  -mfsrra  -mno-fsrra -mpretend-cmove  -mtas

           Solaris 2 Options -mclear-hwcap  -mno-clear-hwcap  -mimpure-text  -mno-impure-text
           -pthreads

           SPARC Options -mcpu=cpu-type -mtune=cpu-type -mcmodel=code-model -mmemory-model=mem-model
           -m32  -m64  -mapp-regs  -mno-app-regs -mfaster-structs  -mno-faster-structs  -mflat
           -mno-flat -mfpu  -mno-fpu  -mhard-float  -msoft-float -mhard-quad-float
           -msoft-quad-float -mstack-bias  -mno-stack-bias -mstd-struct-return
           -mno-std-struct-return -munaligned-doubles  -mno-unaligned-doubles -muser-mode
           -mno-user-mode -mv8plus  -mno-v8plus  -mvis  -mno-vis -mvis2  -mno-vis2  -mvis3
           -mno-vis3 -mvis4  -mno-vis4  -mvis4b  -mno-vis4b -mcbcond  -mno-cbcond  -mfmaf  -mno-fmaf
           -mfsmuld  -mno-fsmuld -mpopc  -mno-popc  -msubxc  -mno-subxc -mfix-at697f  -mfix-ut699
           -mfix-ut700  -mfix-gr712rc -mlra  -mno-lra

           System V Options -Qy  -Qn  -YP,paths  -Ym,dir

           TILE-Gx Options -mcpu=CPU  -m32  -m64  -mbig-endian  -mlittle-endian -mcmodel=code-model

           TILEPro Options -mcpu=cpu  -m32

           V850 Options -mlong-calls  -mno-long-calls  -mep  -mno-ep -mprolog-function
           -mno-prolog-function  -mspace -mtda=n  -msda=n  -mzda=n -mapp-regs  -mno-app-regs
           -mdisable-callt  -mno-disable-callt -mv850e2v3  -mv850e2  -mv850e1  -mv850es -mv850e
           -mv850  -mv850e3v5 -mloop -mrelax -mlong-jumps -msoft-float -mhard-float -mgcc-abi
           -mrh850-abi -mbig-switch

           VAX Options -mg  -mgnu  -munix

           Visium Options -mdebug  -msim  -mfpu  -mno-fpu  -mhard-float  -msoft-float -mcpu=cpu-type
           -mtune=cpu-type  -msv-mode  -muser-mode

           VMS Options -mvms-return-codes  -mdebug-main=prefix  -mmalloc64 -mpointer-size=size

           VxWorks Options -mrtp  -non-static  -Bstatic  -Bdynamic -Xbind-lazy  -Xbind-now

           x86 Options -mtune=cpu-type  -march=cpu-type -mtune-ctrl=feature-list
           -mdump-tune-features  -mno-default -mfpmath=unit -masm=dialect  -mno-fancy-math-387
           -mno-fp-ret-in-387  -m80387  -mhard-float  -msoft-float -mno-wide-multiply  -mrtd
           -malign-double -mpreferred-stack-boundary=num -mincoming-stack-boundary=num -mcld  -mcx16
           -msahf  -mmovbe  -mcrc32 -mmwait -mrecip  -mrecip=opt -mvzeroupper  -mprefer-avx128
           -mprefer-vector-width=opt -mmmx  -msse  -msse2  -msse3  -mssse3  -msse4.1  -msse4.2
           -msse4  -mavx -mavx2  -mavx512f  -mavx512pf  -mavx512er  -mavx512cd  -mavx512vl
           -mavx512bw  -mavx512dq  -mavx512ifma  -mavx512vbmi  -msha  -maes -mpclmul  -mfsgsbase
           -mrdrnd  -mf16c  -mfma  -mpconfig  -mwbnoinvd -mptwrite  -mprefetchwt1  -mclflushopt
           -mclwb  -mxsavec  -mxsaves -msse4a  -m3dnow  -m3dnowa  -mpopcnt  -mabm  -mbmi  -mtbm
           -mfma4  -mxop -madx  -mlzcnt  -mbmi2  -mfxsr  -mxsave  -mxsaveopt  -mrtm  -mhle  -mlwp
           -mmwaitx  -mclzero  -mpku  -mthreads  -mgfni  -mvaes  -mwaitpkg -mshstk -mmanual-endbr
           -mforce-indirect-call  -mavx512vbmi2 -mavx512bf16 -menqcmd -mvpclmulqdq  -mavx512bitalg
           -mmovdiri  -mmovdir64b  -mavx512vpopcntdq -mavx5124fmaps  -mavx512vnni  -mavx5124vnniw
           -mprfchw  -mrdpid -mrdseed  -msgx -mavx512vp2intersect -mserialize -mtsxldtrk -mamx-tile
           -mamx-int8  -mamx-bf16 -muintr -mhreset -mavxvnni -mcldemote  -mms-bitfields
           -mno-align-stringops  -minline-all-stringops -minline-stringops-dynamically
           -mstringop-strategy=alg -mkl -mwidekl -mmemcpy-strategy=strategy
           -mmemset-strategy=strategy -mpush-args  -maccumulate-outgoing-args  -m128bit-long-double
           -m96bit-long-double  -mlong-double-64  -mlong-double-80  -mlong-double-128 -mregparm=num
           -msseregparm -mveclibabi=type  -mvect8-ret-in-mem -mpc32  -mpc64  -mpc80 -mdaz-ftz
           -mstackrealign -momit-leaf-frame-pointer  -mno-red-zone  -mno-tls-direct-seg-refs
           -mcmodel=code-model  -mabi=name  -maddress-mode=mode -m32  -m64  -mx32  -m16  -miamcu
           -mlarge-data-threshold=num -msse2avx  -mfentry  -mrecord-mcount  -mnop-mcount
           -m8bit-idiv -minstrument-return=type -mfentry-name=name -mfentry-section=name
           -mavx256-split-unaligned-load  -mavx256-split-unaligned-store -malign-data=type
           -mstack-protector-guard=guard -mstack-protector-guard-reg=reg
           -mstack-protector-guard-offset=offset -mstack-protector-guard-symbol=symbol
           -mgeneral-regs-only  -mcall-ms2sysv-xlogues -mindirect-branch=choice
           -mfunction-return=choice -mindirect-branch-register -mharden-sls=choice
           -mindirect-branch-cs-prefix -mneeded

           x86 Windows Options -mconsole  -mcygwin  -mno-cygwin  -mdll -mnop-fun-dllimport  -mthread
           -municode  -mwin32  -mwindows  -fno-set-stack-executable

           Xstormy16 Options -msim

           Xtensa Options -mconst16  -mno-const16 -mfused-madd  -mno-fused-madd -mforce-no-pic
           -mserialize-volatile  -mno-serialize-volatile -mtext-section-literals
           -mno-text-section-literals -mauto-litpools  -mno-auto-litpools -mtarget-align
           -mno-target-align -mlongcalls  -mno-longcalls -mabi=abi-type

           zSeries Options See S/390 and zSeries Options.

   Options Controlling the Kind of Output
       Compilation can involve up to four stages: preprocessing, compilation proper, assembly and
       linking, always in that order.  GCC is capable of preprocessing and compiling several files
       either into several assembler input files, or into one assembler input file; then each
       assembler input file produces an object file, and linking combines all the object files
       (those newly compiled, and those specified as input) into an executable file.

       For any given input file, the file name suffix determines what kind of compilation is done:

       file.c
           C source code that must be preprocessed.

       file.i
           C source code that should not be preprocessed.

       file.ii
           C++ source code that should not be preprocessed.

       file.m
           Objective-C source code.  Note that you must link with the libobjc library to make an
           Objective-C program work.

       file.mi
           Objective-C source code that should not be preprocessed.

       file.mm
       file.M
           Objective-C++ source code.  Note that you must link with the libobjc library to make an
           Objective-C++ program work.  Note that .M refers to a literal capital M.

       file.mii
           Objective-C++ source code that should not be preprocessed.

       file.h
           C, C++, Objective-C or Objective-C++ header file to be turned into a precompiled header
           (default), or C, C++ header file to be turned into an Ada spec (via the -fdump-ada-spec
           switch).

       file.cc
       file.cp
       file.cxx
       file.cpp
       file.CPP
       file.c++
       file.C
           C++ source code that must be preprocessed.  Note that in .cxx, the last two letters must
           both be literally x.  Likewise, .C refers to a literal capital C.

       file.mm
       file.M
           Objective-C++ source code that must be preprocessed.

       file.mii
           Objective-C++ source code that should not be preprocessed.

       file.hh
       file.H
       file.hp
       file.hxx
       file.hpp
       file.HPP
       file.h++
       file.tcc
           C++ header file to be turned into a precompiled header or Ada spec.

       file.f
       file.for
       file.ftn
           Fixed form Fortran source code that should not be preprocessed.

       file.F
       file.FOR
       file.fpp
       file.FPP
       file.FTN
           Fixed form Fortran source code that must be preprocessed (with the traditional
           preprocessor).

       file.f90
       file.f95
       file.f03
       file.f08
           Free form Fortran source code that should not be preprocessed.

       file.F90
       file.F95
       file.F03
       file.F08
           Free form Fortran source code that must be preprocessed (with the traditional
           preprocessor).

       file.go
           Go source code.

       file.brig
           BRIG files (binary representation of HSAIL).

       file.d
           D source code.

       file.di
           D interface file.

       file.dd
           D documentation code (Ddoc).

       file.ads
           Ada source code file that contains a library unit declaration (a declaration of a
           package, subprogram, or generic, or a generic instantiation), or a library unit renaming
           declaration (a package, generic, or subprogram renaming declaration).  Such files are
           also called specs.

       file.adb
           Ada source code file containing a library unit body (a subprogram or package body).  Such
           files are also called bodies.

       file.s
           Assembler code.

       file.S
       file.sx
           Assembler code that must be preprocessed.

       other
           An object file to be fed straight into linking.  Any file name with no recognized suffix
           is treated this way.

       You can specify the input language explicitly with the -x option:

       -x language
           Specify explicitly the language for the following input files (rather than letting the
           compiler choose a default based on the file name suffix).  This option applies to all
           following input files until the next -x option.  Possible values for language are:

                   c  c-header  cpp-output
                   c++  c++-header  c++-system-header c++-user-header c++-cpp-output
                   objective-c  objective-c-header  objective-c-cpp-output
                   objective-c++ objective-c++-header objective-c++-cpp-output
                   assembler  assembler-with-cpp
                   ada
                   d
                   f77  f77-cpp-input f95  f95-cpp-input
                   go
                   brig

       -x none
           Turn off any specification of a language, so that subsequent files are handled according
           to their file name suffixes (as they are if -x has not been used at all).

       If you only want some of the stages of compilation, you can use -x (or filename suffixes) to
       tell gcc where to start, and one of the options -c, -S, or -E to say where gcc is to stop.
       Note that some combinations (for example, -x cpp-output -E) instruct gcc to do nothing at
       all.

       -c  Compile or assemble the source files, but do not link.  The linking stage simply is not
           done.  The ultimate output is in the form of an object file for each source file.

           By default, the object file name for a source file is made by replacing the suffix .c,
           .i, .s, etc., with .o.

           Unrecognized input files, not requiring compilation or assembly, are ignored.

       -S  Stop after the stage of compilation proper; do not assemble.  The output is in the form
           of an assembler code file for each non-assembler input file specified.

           By default, the assembler file name for a source file is made by replacing the suffix .c,
           .i, etc., with .s.

           Input files that don't require compilation are ignored.

       -E  Stop after the preprocessing stage; do not run the compiler proper.  The output is in the
           form of preprocessed source code, which is sent to the standard output.

           Input files that don't require preprocessing are ignored.

       -o file
           Place the primary output in file file.  This applies to whatever sort of output is being
           produced, whether it be an executable file, an object file, an assembler file or
           preprocessed C code.

           If -o is not specified, the default is to put an executable file in a.out, the object
           file for source.suffix in source.o, its assembler file in source.s, a precompiled header
           file in source.suffix.gch, and all preprocessed C source on standard output.

           Though -o names only the primary output, it also affects the naming of auxiliary and dump
           outputs.  See the examples below.  Unless overridden, both auxiliary outputs and dump
           outputs are placed in the same directory as the primary output.  In auxiliary outputs,
           the suffix of the input file is replaced with that of the auxiliary output file type; in
           dump outputs, the suffix of the dump file is appended to the input file suffix.  In
           compilation commands, the base name of both auxiliary and dump outputs is that of the
           primary output; in compile and link commands, the primary output name, minus the
           executable suffix, is combined with the input file name.  If both share the same base
           name, disregarding the suffix, the result of the combination is that base name,
           otherwise, they are concatenated, separated by a dash.

                   gcc -c foo.c ...

           will use foo.o as the primary output, and place aux outputs and dumps next to it, e.g.,
           aux file foo.dwo for -gsplit-dwarf, and dump file foo.c.???r.final for -fdump-rtl-final.

           If a non-linker output file is explicitly specified, aux and dump files by default take
           the same base name:

                   gcc -c foo.c -o dir/foobar.o ...

           will name aux outputs dir/foobar.* and dump outputs dir/foobar.c.*.

           A linker output will instead prefix aux and dump outputs:

                   gcc foo.c bar.c -o dir/foobar ...

           will generally name aux outputs dir/foobar-foo.* and dir/foobar-bar.*, and dump outputs
           dir/foobar-foo.c.* and dir/foobar-bar.c.*.

           The one exception to the above is when the executable shares the base name with the
           single input:

                   gcc foo.c -o dir/foo ...

           in which case aux outputs are named dir/foo.* and dump outputs named dir/foo.c.*.

           The location and the names of auxiliary and dump outputs can be adjusted by the options
           -dumpbase, -dumpbase-ext, -dumpdir, -save-temps=cwd, and -save-temps=obj.

       -dumpbase dumpbase
           This option sets the base name for auxiliary and dump output files.  It does not affect
           the name of the primary output file.  Intermediate outputs, when preserved, are not
           regarded as primary outputs, but as auxiliary outputs:

                   gcc -save-temps -S foo.c

           saves the (no longer) temporary preprocessed file in foo.i, and then compiles to the
           (implied) output file foo.s, whereas:

                   gcc -save-temps -dumpbase save-foo -c foo.c

           preprocesses to in save-foo.i, compiles to save-foo.s (now an intermediate, thus
           auxiliary output), and then assembles to the (implied) output file foo.o.

           Absent this option, dump and aux files take their names from the input file, or from the
           (non-linker) output file, if one is explicitly specified: dump output files (e.g. those
           requested by -fdump-* options) with the input name suffix, and aux output files (those
           requested by other non-dump options, e.g. "-save-temps", "-gsplit-dwarf",
           "-fcallgraph-info") without it.

           Similar suffix differentiation of dump and aux outputs can be attained for explicitly-
           given -dumpbase basename.suf by also specifying -dumpbase-ext .suf.

           If dumpbase is explicitly specified with any directory component, any dumppfx
           specification (e.g. -dumpdir or -save-temps=*) is ignored, and instead of appending to
           it, dumpbase fully overrides it:

                   gcc foo.c -c -o dir/foo.o -dumpbase alt/foo \
                     -dumpdir pfx- -save-temps=cwd ...

           creates auxiliary and dump outputs named alt/foo.*, disregarding dir/ in -o, the ./
           prefix implied by -save-temps=cwd, and pfx- in -dumpdir.

           When -dumpbase is specified in a command that compiles multiple inputs, or that compiles
           and then links, it may be combined with dumppfx, as specified under -dumpdir.  Then, each
           input file is compiled using the combined dumppfx, and default values for dumpbase and
           auxdropsuf are computed for each input file:

                   gcc foo.c bar.c -c -dumpbase main ...

           creates foo.o and bar.o as primary outputs, and avoids overwriting the auxiliary and dump
           outputs by using the dumpbase as a prefix, creating auxiliary and dump outputs named
           main-foo.*  and main-bar.*.

           An empty string specified as dumpbase avoids the influence of the output basename in the
           naming of auxiliary and dump outputs during compilation, computing default values :

                   gcc -c foo.c -o dir/foobar.o -dumpbase " ...

           will name aux outputs dir/foo.* and dump outputs dir/foo.c.*.  Note how their basenames
           are taken from the input name, but the directory still defaults to that of the output.

           The empty-string dumpbase does not prevent the use of the output basename for outputs
           during linking:

                   gcc foo.c bar.c -o dir/foobar -dumpbase " -flto ...

           The compilation of the source files will name auxiliary outputs dir/foo.* and dir/bar.*,
           and dump outputs dir/foo.c.* and dir/bar.c.*.  LTO recompilation during linking will use
           dir/foobar. as the prefix for dumps and auxiliary files.

       -dumpbase-ext auxdropsuf
           When forming the name of an auxiliary (but not a dump) output file, drop trailing
           auxdropsuf from dumpbase before appending any suffixes.  If not specified, this option
           defaults to the suffix of a default dumpbase, i.e., the suffix of the input file when
           -dumpbase is not present in the command line, or dumpbase is combined with dumppfx.

                   gcc foo.c -c -o dir/foo.o -dumpbase x-foo.c -dumpbase-ext .c ...

           creates dir/foo.o as the main output, and generates auxiliary outputs in dir/x-foo.*,
           taking the location of the primary output, and dropping the .c suffix from the dumpbase.
           Dump outputs retain the suffix: dir/x-foo.c.*.

           This option is disregarded if it does not match the suffix of a specified dumpbase,
           except as an alternative to the executable suffix when appending the linker output base
           name to dumppfx, as specified below:

                   gcc foo.c bar.c -o main.out -dumpbase-ext .out ...

           creates main.out as the primary output, and avoids overwriting the auxiliary and dump
           outputs by using the executable name minus auxdropsuf as a prefix, creating auxiliary
           outputs named main-foo.* and main-bar.* and dump outputs named main-foo.c.* and
           main-bar.c.*.

       -dumpdir dumppfx
           When forming the name of an auxiliary or dump output file, use dumppfx as a prefix:

                   gcc -dumpdir pfx- -c foo.c ...

           creates foo.o as the primary output, and auxiliary outputs named pfx-foo.*, combining the
           given dumppfx with the default dumpbase derived from the default primary output, derived
           in turn from the input name.  Dump outputs also take the input name suffix: pfx-foo.c.*.

           If dumppfx is to be used as a directory name, it must end with a directory separator:

                   gcc -dumpdir dir/ -c foo.c -o obj/bar.o ...

           creates obj/bar.o as the primary output, and auxiliary outputs named dir/bar.*, combining
           the given dumppfx with the default dumpbase derived from the primary output name.  Dump
           outputs also take the input name suffix: dir/bar.c.*.

           It defaults to the location of the output file, unless the output file is a special file
           like "/dev/null". Options -save-temps=cwd and -save-temps=obj override this default, just
           like an explicit -dumpdir option.  In case multiple such options are given, the last one
           prevails:

                   gcc -dumpdir pfx- -c foo.c -save-temps=obj ...

           outputs foo.o, with auxiliary outputs named foo.* because -save-temps=* overrides the
           dumppfx given by the earlier -dumpdir option.  It does not matter that =obj is the
           default for -save-temps, nor that the output directory is implicitly the current
           directory.  Dump outputs are named foo.c.*.

           When compiling from multiple input files, if -dumpbase is specified, dumpbase, minus a
           auxdropsuf suffix, and a dash are appended to (or override, if containing any directory
           components) an explicit or defaulted dumppfx, so that each of the multiple compilations
           gets differently-named aux and dump outputs.

                   gcc foo.c bar.c -c -dumpdir dir/pfx- -dumpbase main ...

           outputs auxiliary dumps to dir/pfx-main-foo.* and dir/pfx-main-bar.*, appending dumpbase-
           to dumppfx.  Dump outputs retain the input file suffix: dir/pfx-main-foo.c.*  and
           dir/pfx-main-bar.c.*, respectively.  Contrast with the single-input compilation:

                   gcc foo.c -c -dumpdir dir/pfx- -dumpbase main ...

           that, applying -dumpbase to a single source, does not compute and append a separate
           dumpbase per input file.  Its auxiliary and dump outputs go in dir/pfx-main.*.

           When compiling and then linking from multiple input files, a defaulted or explicitly
           specified dumppfx also undergoes the dumpbase- transformation above (e.g. the compilation
           of foo.c and bar.c above, but without -c).  If neither -dumpdir nor -dumpbase are given,
           the linker output base name, minus auxdropsuf, if specified, or the executable suffix
           otherwise, plus a dash is appended to the default dumppfx instead.  Note, however, that
           unlike earlier cases of linking:

                   gcc foo.c bar.c -dumpdir dir/pfx- -o main ...

           does not append the output name main to dumppfx, because -dumpdir is explicitly
           specified.  The goal is that the explicitly-specified dumppfx may contain the specified
           output name as part of the prefix, if desired; only an explicitly-specified -dumpbase
           would be combined with it, in order to avoid simply discarding a meaningful option.

           When compiling and then linking from a single input file, the linker output base name
           will only be appended to the default dumppfx as above if it does not share the base name
           with the single input file name.  This has been covered in single-input linking cases
           above, but not with an explicit -dumpdir that inhibits the combination, even if
           overridden by -save-temps=*:

                   gcc foo.c -dumpdir alt/pfx- -o dir/main.exe -save-temps=cwd ...

           Auxiliary outputs are named foo.*, and dump outputs foo.c.*, in the current working
           directory as ultimately requested by -save-temps=cwd.

           Summing it all up for an intuitive though slightly imprecise data flow: the primary
           output name is broken into a directory part and a basename part; dumppfx is set to the
           former, unless overridden by -dumpdir or -save-temps=*, and dumpbase is set to the
           latter, unless overriden by -dumpbase.  If there are multiple inputs or linking, this
           dumpbase may be combined with dumppfx and taken from each input file.  Auxiliary output
           names for each input are formed by combining dumppfx, dumpbase minus suffix, and the
           auxiliary output suffix; dump output names are only different in that the suffix from
           dumpbase is retained.

           When it comes to auxiliary and dump outputs created during LTO recompilation, a
           combination of dumppfx and dumpbase, as given or as derived from the linker output name
           but not from inputs, even in cases in which this combination would not otherwise be used
           as such, is passed down with a trailing period replacing the compiler-added dash, if any,
           as a -dumpdir option to lto-wrapper; being involved in linking, this program does not
           normally get any -dumpbase and -dumpbase-ext, and it ignores them.

           When running sub-compilers, lto-wrapper appends LTO stage names to the received dumppfx,
           ensures it contains a directory component so that it overrides any -dumpdir, and passes
           that as -dumpbase to sub-compilers.

       -v  Print (on standard error output) the commands executed to run the stages of compilation.
           Also print the version number of the compiler driver program and of the preprocessor and
           the compiler proper.

       -###
           Like -v except the commands are not executed and arguments are quoted unless they contain
           only alphanumeric characters or "./-_".  This is useful for shell scripts to capture the
           driver-generated command lines.

       --help
           Print (on the standard output) a description of the command-line options understood by
           gcc.  If the -v option is also specified then --help is also passed on to the various
           processes invoked by gcc, so that they can display the command-line options they accept.
           If the -Wextra option has also been specified (prior to the --help option), then command-
           line options that have no documentation associated with them are also displayed.

       --target-help
           Print (on the standard output) a description of target-specific command-line options for
           each tool.  For some targets extra target-specific information may also be printed.

       --help={class|[^]qualifier}[,...]
           Print (on the standard output) a description of the command-line options understood by
           the compiler that fit into all specified classes and qualifiers.  These are the supported
           classes:

           optimizers
               Display all of the optimization options supported by the compiler.

           warnings
               Display all of the options controlling warning messages produced by the compiler.

           target
               Display target-specific options.  Unlike the --target-help option however, target-
               specific options of the linker and assembler are not displayed.  This is because
               those tools do not currently support the extended --help= syntax.

           params
               Display the values recognized by the --param option.

           language
               Display the options supported for language, where language is the name of one of the
               languages supported in this version of GCC.  If an option is supported by all
               languages, one needs to select common class.

           common
               Display the options that are common to all languages.

           These are the supported qualifiers:

           undocumented
               Display only those options that are undocumented.

           joined
               Display options taking an argument that appears after an equal sign in the same
               continuous piece of text, such as: --help=target.

           separate
               Display options taking an argument that appears as a separate word following the
               original option, such as: -o output-file.

           Thus for example to display all the undocumented target-specific switches supported by
           the compiler, use:

                   --help=target,undocumented

           The sense of a qualifier can be inverted by prefixing it with the ^ character, so for
           example to display all binary warning options (i.e., ones that are either on or off and
           that do not take an argument) that have a description, use:

                   --help=warnings,^joined,^undocumented

           The argument to --help= should not consist solely of inverted qualifiers.

           Combining several classes is possible, although this usually restricts the output so much
           that there is nothing to display.  One case where it does work, however, is when one of
           the classes is target.  For example, to display all the target-specific optimization
           options, use:

                   --help=target,optimizers

           The --help= option can be repeated on the command line.  Each successive use displays its
           requested class of options, skipping those that have already been displayed.  If --help
           is also specified anywhere on the command line then this takes precedence over any
           --help= option.

           If the -Q option appears on the command line before the --help= option, then the
           descriptive text displayed by --help= is changed.  Instead of describing the displayed
           options, an indication is given as to whether the option is enabled, disabled or set to a
           specific value (assuming that the compiler knows this at the point where the --help=
           option is used).

           Here is a truncated example from the ARM port of gcc:

                     % gcc -Q -mabi=2 --help=target -c
                     The following options are target specific:
                     -mabi=                                2
                     -mabort-on-noreturn                   [disabled]
                     -mapcs                                [disabled]

           The output is sensitive to the effects of previous command-line options, so for example
           it is possible to find out which optimizations are enabled at -O2 by using:

                   -Q -O2 --help=optimizers

           Alternatively you can discover which binary optimizations are enabled by -O3 by using:

                   gcc -c -Q -O3 --help=optimizers > /tmp/O3-opts
                   gcc -c -Q -O2 --help=optimizers > /tmp/O2-opts
                   diff /tmp/O2-opts /tmp/O3-opts | grep enabled

       --version
           Display the version number and copyrights of the invoked GCC.

       -pass-exit-codes
           Normally the gcc program exits with the code of 1 if any phase of the compiler returns a
           non-success return code.  If you specify -pass-exit-codes, the gcc program instead
           returns with the numerically highest error produced by any phase returning an error
           indication.  The C, C++, and Fortran front ends return 4 if an internal compiler error is
           encountered.

       -pipe
           Use pipes rather than temporary files for communication between the various stages of
           compilation.  This fails to work on some systems where the assembler is unable to read
           from a pipe; but the GNU assembler has no trouble.

       -specs=file
           Process file after the compiler reads in the standard specs file, in order to override
           the defaults which the gcc driver program uses when determining what switches to pass to
           cc1, cc1plus, as, ld, etc.  More than one -specs=file can be specified on the command
           line, and they are processed in order, from left to right.

       -wrapper
           Invoke all subcommands under a wrapper program.  The name of the wrapper program and its
           parameters are passed as a comma separated list.

                   gcc -c t.c -wrapper gdb,--args

           This invokes all subprograms of gcc under gdb --args, thus the invocation of cc1 is gdb
           --args cc1 ....

       -ffile-prefix-map=old=new
           When compiling files residing in directory old, record any references to them in the
           result of the compilation as if the files resided in directory new instead.  Specifying
           this option is equivalent to specifying all the individual -f*-prefix-map options.  This
           can be used to make reproducible builds that are location independent.  See also
           -fmacro-prefix-map and -fdebug-prefix-map.

       -fplugin=name.so
           Load the plugin code in file name.so, assumed to be a shared object to be dlopen'd by the
           compiler.  The base name of the shared object file is used to identify the plugin for the
           purposes of argument parsing (See -fplugin-arg-name-key=value below).  Each plugin should
           define the callback functions specified in the Plugins API.

       -fplugin-arg-name-key=value
           Define an argument called key with a value of value for the plugin called name.

       -fdump-ada-spec[-slim]
           For C and C++ source and include files, generate corresponding Ada specs.

       -fada-spec-parent=unit
           In conjunction with -fdump-ada-spec[-slim] above, generate Ada specs as child units of
           parent unit.

       -fdump-go-spec=file
           For input files in any language, generate corresponding Go declarations in file.  This
           generates Go "const", "type", "var", and "func" declarations which may be a useful way to
           start writing a Go interface to code written in some other language.

       @file
           Read command-line options from file.  The options read are inserted in place of the
           original @file option.  If file does not exist, or cannot be read, then the option will
           be treated literally, and not removed.

           Options in file are separated by whitespace.  A whitespace character may be included in
           an option by surrounding the entire option in either single or double quotes.  Any
           character (including a backslash) may be included by prefixing the character to be
           included with a backslash.  The file may itself contain additional @file options; any
           such options will be processed recursively.

   Compiling C++ Programs
       C++ source files conventionally use one of the suffixes .C, .cc, .cpp, .CPP, .c++, .cp, or
       .cxx; C++ header files often use .hh, .hpp, .H, or (for shared template code) .tcc; and
       preprocessed C++ files use the suffix .ii.  GCC recognizes files with these names and
       compiles them as C++ programs even if you call the compiler the same way as for compiling C
       programs (usually with the name gcc).

       However, the use of gcc does not add the C++ library.  g++ is a program that calls GCC and
       automatically specifies linking against the C++ library.  It treats .c, .h and .i files as
       C++ source files instead of C source files unless -x is used.  This program is also useful
       when precompiling a C header file with a .h extension for use in C++ compilations.  On many
       systems, g++ is also installed with the name c++.

       When you compile C++ programs, you may specify many of the same command-line options that you
       use for compiling programs in any language; or command-line options meaningful for C and
       related languages; or options that are meaningful only for C++ programs.

   Options Controlling C Dialect
       The following options control the dialect of C (or languages derived from C, such as C++,
       Objective-C and Objective-C++) that the compiler accepts:

       -ansi
           In C mode, this is equivalent to -std=c90. In C++ mode, it is equivalent to -std=c++98.

           This turns off certain features of GCC that are incompatible with ISO C90 (when compiling
           C code), or of standard C++ (when compiling C++ code), such as the "asm" and "typeof"
           keywords, and predefined macros such as "unix" and "vax" that identify the type of system
           you are using.  It also enables the undesirable and rarely used ISO trigraph feature.
           For the C compiler, it disables recognition of C++ style // comments as well as the
           "inline" keyword.

           The alternate keywords "__asm__", "__extension__", "__inline__" and "__typeof__" continue
           to work despite -ansi.  You would not want to use them in an ISO C program, of course,
           but it is useful to put them in header files that might be included in compilations done
           with -ansi.  Alternate predefined macros such as "__unix__" and "__vax__" are also
           available, with or without -ansi.

           The -ansi option does not cause non-ISO programs to be rejected gratuitously.  For that,
           -Wpedantic is required in addition to -ansi.

           The macro "__STRICT_ANSI__" is predefined when the -ansi option is used.  Some header
           files may notice this macro and refrain from declaring certain functions or defining
           certain macros that the ISO standard doesn't call for; this is to avoid interfering with
           any programs that might use these names for other things.

           Functions that are normally built in but do not have semantics defined by ISO C (such as
           "alloca" and "ffs") are not built-in functions when -ansi is used.

       -std=
           Determine the language standard.   This option is currently only supported when compiling
           C or C++.

           The compiler can accept several base standards, such as c90 or c++98, and GNU dialects of
           those standards, such as gnu90 or gnu++98.  When a base standard is specified, the
           compiler accepts all programs following that standard plus those using GNU extensions
           that do not contradict it.  For example, -std=c90 turns off certain features of GCC that
           are incompatible with ISO C90, such as the "asm" and "typeof" keywords, but not other GNU
           extensions that do not have a meaning in ISO C90, such as omitting the middle term of a
           "?:" expression. On the other hand, when a GNU dialect of a standard is specified, all
           features supported by the compiler are enabled, even when those features change the
           meaning of the base standard.  As a result, some strict-conforming programs may be
           rejected.  The particular standard is used by -Wpedantic to identify which features are
           GNU extensions given that version of the standard. For example -std=gnu90 -Wpedantic
           warns about C++ style // comments, while -std=gnu99 -Wpedantic does not.

           A value for this option must be provided; possible values are

           c90
           c89
           iso9899:1990
               Support all ISO C90 programs (certain GNU extensions that conflict with ISO C90 are
               disabled). Same as -ansi for C code.

           iso9899:199409
               ISO C90 as modified in amendment 1.

           c99
           c9x
           iso9899:1999
           iso9899:199x
               ISO C99.  This standard is substantially completely supported, modulo bugs and
               floating-point issues (mainly but not entirely relating to optional C99 features from
               Annexes F and G).  See <http://gcc.gnu.org/c99status.html> for more information.  The
               names c9x and iso9899:199x are deprecated.

           c11
           c1x
           iso9899:2011
               ISO C11, the 2011 revision of the ISO C standard.  This standard is substantially
               completely supported, modulo bugs, floating-point issues (mainly but not entirely
               relating to optional C11 features from Annexes F and G) and the optional Annexes K
               (Bounds-checking interfaces) and L (Analyzability).  The name c1x is deprecated.

           c17
           c18
           iso9899:2017
           iso9899:2018
               ISO C17, the 2017 revision of the ISO C standard (published in 2018).  This standard
               is same as C11 except for corrections of defects (all of which are also applied with
               -std=c11) and a new value of "__STDC_VERSION__", and so is supported to the same
               extent as C11.

           c2x The next version of the ISO C standard, still under development.  The support for
               this version is experimental and incomplete.

           gnu90
           gnu89
               GNU dialect of ISO C90 (including some C99 features).

           gnu99
           gnu9x
               GNU dialect of ISO C99.  The name gnu9x is deprecated.

           gnu11
           gnu1x
               GNU dialect of ISO C11.  The name gnu1x is deprecated.

           gnu17
           gnu18
               GNU dialect of ISO C17.  This is the default for C code.

           gnu2x
               The next version of the ISO C standard, still under development, plus GNU extensions.
               The support for this version is experimental and incomplete.

           c++98
           c++03
               The 1998 ISO C++ standard plus the 2003 technical corrigendum and some additional
               defect reports. Same as -ansi for C++ code.

           gnu++98
           gnu++03
               GNU dialect of -std=c++98.

           c++11
           c++0x
               The 2011 ISO C++ standard plus amendments.  The name c++0x is deprecated.

           gnu++11
           gnu++0x
               GNU dialect of -std=c++11.  The name gnu++0x is deprecated.

           c++14
           c++1y
               The 2014 ISO C++ standard plus amendments.  The name c++1y is deprecated.

           gnu++14
           gnu++1y
               GNU dialect of -std=c++14.  The name gnu++1y is deprecated.

           c++17
           c++1z
               The 2017 ISO C++ standard plus amendments.  The name c++1z is deprecated.

           gnu++17
           gnu++1z
               GNU dialect of -std=c++17.  This is the default for C++ code.  The name gnu++1z is
               deprecated.

           c++20
           c++2a
               The 2020 ISO C++ standard plus amendments.  Support is experimental, and could change
               in incompatible ways in future releases.  The name c++2a is deprecated.

           gnu++20
           gnu++2a
               GNU dialect of -std=c++20.  Support is experimental, and could change in incompatible
               ways in future releases.  The name gnu++2a is deprecated.

           c++2b
           c++23
               The next revision of the ISO C++ standard, planned for 2023.  Support is highly
               experimental, and will almost certainly change in incompatible ways in future
               releases.

           gnu++2b
           gnu++23
               GNU dialect of -std=c++2b.  Support is highly experimental, and will almost certainly
               change in incompatible ways in future releases.

       -fgnu89-inline
           The option -fgnu89-inline tells GCC to use the traditional GNU semantics for "inline"
           functions when in C99 mode.

           Using this option is roughly equivalent to adding the "gnu_inline" function attribute to
           all inline functions.

           The option -fno-gnu89-inline explicitly tells GCC to use the C99 semantics for "inline"
           when in C99 or gnu99 mode (i.e., it specifies the default behavior).  This option is not
           supported in -std=c90 or -std=gnu90 mode.

           The preprocessor macros "__GNUC_GNU_INLINE__" and "__GNUC_STDC_INLINE__" may be used to
           check which semantics are in effect for "inline" functions.

       -fpermitted-flt-eval-methods=style
           ISO/IEC TS 18661-3 defines new permissible values for "FLT_EVAL_METHOD" that indicate
           that operations and constants with a semantic type that is an interchange or extended
           format should be evaluated to the precision and range of that type.  These new values are
           a superset of those permitted under C99/C11, which does not specify the meaning of other
           positive values of "FLT_EVAL_METHOD".  As such, code conforming to C11 may not have been
           written expecting the possibility of the new values.

           -fpermitted-flt-eval-methods specifies whether the compiler should allow only the values
           of "FLT_EVAL_METHOD" specified in C99/C11, or the extended set of values specified in
           ISO/IEC TS 18661-3.

           style is either "c11" or "ts-18661-3" as appropriate.

           The default when in a standards compliant mode (-std=c11 or similar) is
           -fpermitted-flt-eval-methods=c11.  The default when in a GNU dialect (-std=gnu11 or
           similar) is -fpermitted-flt-eval-methods=ts-18661-3.

       -aux-info filename
           Output to the given filename prototyped declarations for all functions declared and/or
           defined in a translation unit, including those in header files.  This option is silently
           ignored in any language other than C.

           Besides declarations, the file indicates, in comments, the origin of each declaration
           (source file and line), whether the declaration was implicit, prototyped or unprototyped
           (I, N for new or O for old, respectively, in the first character after the line number
           and the colon), and whether it came from a declaration or a definition (C or F,
           respectively, in the following character).  In the case of function definitions, a
           K&R-style list of arguments followed by their declarations is also provided, inside
           comments, after the declaration.

       -fallow-parameterless-variadic-functions
           Accept variadic functions without named parameters.

           Although it is possible to define such a function, this is not very useful as it is not
           possible to read the arguments.  This is only supported for C as this construct is
           allowed by C++.

       -fno-asm
           Do not recognize "asm", "inline" or "typeof" as a keyword, so that code can use these
           words as identifiers.  You can use the keywords "__asm__", "__inline__" and "__typeof__"
           instead.  -ansi implies -fno-asm.

           In C++, this switch only affects the "typeof" keyword, since "asm" and "inline" are
           standard keywords.  You may want to use the -fno-gnu-keywords flag instead, which has the
           same effect.  In C99 mode (-std=c99 or -std=gnu99), this switch only affects the "asm"
           and "typeof" keywords, since "inline" is a standard keyword in ISO C99.

       -fno-builtin
       -fno-builtin-function
           Don't recognize built-in functions that do not begin with __builtin_ as prefix.

           GCC normally generates special code to handle certain built-in functions more
           efficiently; for instance, calls to "alloca" may become single instructions which adjust
           the stack directly, and calls to "memcpy" may become inline copy loops.  The resulting
           code is often both smaller and faster, but since the function calls no longer appear as
           such, you cannot set a breakpoint on those calls, nor can you change the behavior of the
           functions by linking with a different library.  In addition, when a function is
           recognized as a built-in function, GCC may use information about that function to warn
           about problems with calls to that function, or to generate more efficient code, even if
           the resulting code still contains calls to that function.  For example, warnings are
           given with -Wformat for bad calls to "printf" when "printf" is built in and "strlen" is
           known not to modify global memory.

           With the -fno-builtin-function option only the built-in function function is disabled.
           function must not begin with __builtin_.  If a function is named that is not built-in in
           this version of GCC, this option is ignored.  There is no corresponding
           -fbuiltin-function option; if you wish to enable built-in functions selectively when
           using -fno-builtin or -ffreestanding, you may define macros such as:

                   #define abs(n)          __builtin_abs ((n))
                   #define strcpy(d, s)    __builtin_strcpy ((d), (s))

       -fgimple
           Enable parsing of function definitions marked with "__GIMPLE".  This is an experimental
           feature that allows unit testing of GIMPLE passes.

       -fhosted
           Assert that compilation targets a hosted environment.  This implies -fbuiltin.  A hosted
           environment is one in which the entire standard library is available, and in which "main"
           has a return type of "int".  Examples are nearly everything except a kernel.  This is
           equivalent to -fno-freestanding.

       -ffreestanding
           Assert that compilation targets a freestanding environment.  This implies -fno-builtin.
           A freestanding environment is one in which the standard library may not exist, and
           program startup may not necessarily be at "main".  The most obvious example is an OS
           kernel.  This is equivalent to -fno-hosted.

       -fopenacc
           Enable handling of OpenACC directives "#pragma acc" in C/C++ and "!$acc" in Fortran.
           When -fopenacc is specified, the compiler generates accelerated code according to the
           OpenACC Application Programming Interface v2.6 <https://www.openacc.org>.  This option
           implies -pthread, and thus is only supported on targets that have support for -pthread.

       -fopenacc-dim=geom
           Specify default compute dimensions for parallel offload regions that do not explicitly
           specify.  The geom value is a triple of ':'-separated sizes, in order 'gang', 'worker'
           and, 'vector'.  A size can be omitted, to use a target-specific default value.

       -fopenmp
           Enable handling of OpenMP directives "#pragma omp" in C/C++ and "!$omp" in Fortran.  When
           -fopenmp is specified, the compiler generates parallel code according to the OpenMP
           Application Program Interface v4.5 <https://www.openmp.org>.  This option implies
           -pthread, and thus is only supported on targets that have support for -pthread. -fopenmp
           implies -fopenmp-simd.

       -fopenmp-simd
           Enable handling of OpenMP's SIMD directives with "#pragma omp" in C/C++ and "!$omp" in
           Fortran. Other OpenMP directives are ignored.

       -fgnu-tm
           When the option -fgnu-tm is specified, the compiler generates code for the Linux variant
           of Intel's current Transactional Memory ABI specification document (Revision 1.1, May 6
           2009).  This is an experimental feature whose interface may change in future versions of
           GCC, as the official specification changes.  Please note that not all architectures are
           supported for this feature.

           For more information on GCC's support for transactional memory,

           Note that the transactional memory feature is not supported with non-call exceptions
           (-fnon-call-exceptions).

       -fms-extensions
           Accept some non-standard constructs used in Microsoft header files.

           In C++ code, this allows member names in structures to be similar to previous types
           declarations.

                   typedef int UOW;
                   struct ABC {
                     UOW UOW;
                   };

           Some cases of unnamed fields in structures and unions are only accepted with this option.

           Note that this option is off for all targets except for x86 targets using ms-abi.

       -fplan9-extensions
           Accept some non-standard constructs used in Plan 9 code.

           This enables -fms-extensions, permits passing pointers to structures with anonymous
           fields to functions that expect pointers to elements of the type of the field, and
           permits referring to anonymous fields declared using a typedef.    This is only supported
           for C, not C++.

       -fcond-mismatch
           Allow conditional expressions with mismatched types in the second and third arguments.
           The value of such an expression is void.  This option is not supported for C++.

       -flax-vector-conversions
           Allow implicit conversions between vectors with differing numbers of elements and/or
           incompatible element types.  This option should not be used for new code.

       -funsigned-char
           Let the type "char" be unsigned, like "unsigned char".

           Each kind of machine has a default for what "char" should be.  It is either like
           "unsigned char" by default or like "signed char" by default.

           Ideally, a portable program should always use "signed char" or "unsigned char" when it
           depends on the signedness of an object.  But many programs have been written to use plain
           "char" and expect it to be signed, or expect it to be unsigned, depending on the machines
           they were written for.  This option, and its inverse, let you make such a program work
           with the opposite default.

           The type "char" is always a distinct type from each of "signed char" or "unsigned char",
           even though its behavior is always just like one of those two.

       -fsigned-char
           Let the type "char" be signed, like "signed char".

           Note that this is equivalent to -fno-unsigned-char, which is the negative form of
           -funsigned-char.  Likewise, the option -fno-signed-char is equivalent to -funsigned-char.

       -fsigned-bitfields
       -funsigned-bitfields
       -fno-signed-bitfields
       -fno-unsigned-bitfields
           These options control whether a bit-field is signed or unsigned, when the declaration
           does not use either "signed" or "unsigned".  By default, such a bit-field is signed,
           because this is consistent: the basic integer types such as "int" are signed types.

       -fsso-struct=endianness
           Set the default scalar storage order of structures and unions to the specified
           endianness.  The accepted values are big-endian, little-endian and native for the native
           endianness of the target (the default).  This option is not supported for C++.

           Warning: the -fsso-struct switch causes GCC to generate code that is not binary
           compatible with code generated without it if the specified endianness is not the native
           endianness of the target.

   Options Controlling C++ Dialect
       This section describes the command-line options that are only meaningful for C++ programs.
       You can also use most of the GNU compiler options regardless of what language your program is
       in.  For example, you might compile a file firstClass.C like this:

               g++ -g -fstrict-enums -O -c firstClass.C

       In this example, only -fstrict-enums is an option meant only for C++ programs; you can use
       the other options with any language supported by GCC.

       Some options for compiling C programs, such as -std, are also relevant for C++ programs.

       Here is a list of options that are only for compiling C++ programs:

       -fabi-version=n
           Use version n of the C++ ABI.  The default is version 0.

           Version 0 refers to the version conforming most closely to the C++ ABI specification.
           Therefore, the ABI obtained using version 0 will change in different versions of G++ as
           ABI bugs are fixed.

           Version 1 is the version of the C++ ABI that first appeared in G++ 3.2.

           Version 2 is the version of the C++ ABI that first appeared in G++ 3.4, and was the
           default through G++ 4.9.

           Version 3 corrects an error in mangling a constant address as a template argument.

           Version 4, which first appeared in G++ 4.5, implements a standard mangling for vector
           types.

           Version 5, which first appeared in G++ 4.6, corrects the mangling of attribute
           const/volatile on function pointer types, decltype of a plain decl, and use of a function
           parameter in the declaration of another parameter.

           Version 6, which first appeared in G++ 4.7, corrects the promotion behavior of C++11
           scoped enums and the mangling of template argument packs, const/static_cast, prefix ++
           and --, and a class scope function used as a template argument.

           Version 7, which first appeared in G++ 4.8, that treats nullptr_t as a builtin type and
           corrects the mangling of lambdas in default argument scope.

           Version 8, which first appeared in G++ 4.9, corrects the substitution behavior of
           function types with function-cv-qualifiers.

           Version 9, which first appeared in G++ 5.2, corrects the alignment of "nullptr_t".

           Version 10, which first appeared in G++ 6.1, adds mangling of attributes that affect type
           identity, such as ia32 calling convention attributes (e.g. stdcall).

           Version 11, which first appeared in G++ 7, corrects the mangling of sizeof... expressions
           and operator names.  For multiple entities with the same name within a function, that are
           declared in different scopes, the mangling now changes starting with the twelfth
           occurrence.  It also implies -fnew-inheriting-ctors.

           Version 12, which first appeared in G++ 8, corrects the calling conventions for empty
           classes on the x86_64 target and for classes with only deleted copy/move constructors.
           It accidentally changes the calling convention for classes with a deleted copy
           constructor and a trivial move constructor.

           Version 13, which first appeared in G++ 8.2, fixes the accidental change in version 12.

           Version 14, which first appeared in G++ 10, corrects the mangling of the nullptr
           expression.

           Version 15, which first appeared in G++ 11, changes the mangling of "__alignof__" to be
           distinct from that of "alignof", and dependent operator names.

           See also -Wabi.

       -fabi-compat-version=n
           On targets that support strong aliases, G++ works around mangling changes by creating an
           alias with the correct mangled name when defining a symbol with an incorrect mangled
           name.  This switch specifies which ABI version to use for the alias.

           With -fabi-version=0 (the default), this defaults to 11 (GCC 7 compatibility).  If
           another ABI version is explicitly selected, this defaults to 0.  For compatibility with
           GCC versions 3.2 through 4.9, use -fabi-compat-version=2.

           If this option is not provided but -Wabi=n is, that version is used for compatibility
           aliases.  If this option is provided along with -Wabi (without the version), the version
           from this option is used for the warning.

       -fno-access-control
           Turn off all access checking.  This switch is mainly useful for working around bugs in
           the access control code.

       -faligned-new
           Enable support for C++17 "new" of types that require more alignment than "void*
           ::operator new(std::size_t)" provides.  A numeric argument such as "-faligned-new=32" can
           be used to specify how much alignment (in bytes) is provided by that function, but few
           users will need to override the default of "alignof(std::max_align_t)".

           This flag is enabled by default for -std=c++17.

       -fchar8_t
       -fno-char8_t
           Enable support for "char8_t" as adopted for C++20.  This includes the addition of a new
           "char8_t" fundamental type, changes to the types of UTF-8 string and character literals,
           new signatures for user-defined literals, associated standard library updates, and new
           "__cpp_char8_t" and "__cpp_lib_char8_t" feature test macros.

           This option enables functions to be overloaded for ordinary and UTF-8 strings:

                   int f(const char *);    // #1
                   int f(const char8_t *); // #2
                   int v1 = f("text");     // Calls #1
                   int v2 = f(u8"text");   // Calls #2

           and introduces new signatures for user-defined literals:

                   int operator""_udl1(char8_t);
                   int v3 = u8'x'_udl1;
                   int operator""_udl2(const char8_t*, std::size_t);
                   int v4 = u8"text"_udl2;
                   template<typename T, T...> int operator""_udl3();
                   int v5 = u8"text"_udl3;

           The change to the types of UTF-8 string and character literals introduces
           incompatibilities with ISO C++11 and later standards.  For example, the following code is
           well-formed under ISO C++11, but is ill-formed when -fchar8_t is specified.

                   char ca[] = u8"xx";     // error: char-array initialized from wide
                                           //        string
                   const char *cp = u8"xx";// error: invalid conversion from
                                           //        `const char8_t*' to `const char*'
                   int f(const char*);
                   auto v = f(u8"xx");     // error: invalid conversion from
                                           //        `const char8_t*' to `const char*'
                   std::string s{u8"xx"};  // error: no matching function for call to
                                           //        `std::basic_string<char>::basic_string()'
                   using namespace std::literals;
                   s = u8"xx"s;            // error: conversion from
                                           //        `basic_string<char8_t>' to non-scalar
                                           //        type `basic_string<char>' requested

       -fcheck-new
           Check that the pointer returned by "operator new" is non-null before attempting to modify
           the storage allocated.  This check is normally unnecessary because the C++ standard
           specifies that "operator new" only returns 0 if it is declared "throw()", in which case
           the compiler always checks the return value even without this option.  In all other
           cases, when "operator new" has a non-empty exception specification, memory exhaustion is
           signalled by throwing "std::bad_alloc".  See also new (nothrow).

       -fconcepts
       -fconcepts-ts
           Below -std=c++20, -fconcepts enables support for the C++ Extensions for Concepts
           Technical Specification, ISO 19217 (2015).

           With -std=c++20 and above, Concepts are part of the language standard, so -fconcepts
           defaults to on.  But the standard specification of Concepts differs significantly from
           the TS, so some constructs that were allowed in the TS but didn't make it into the
           standard can still be enabled by -fconcepts-ts.

       -fconstexpr-depth=n
           Set the maximum nested evaluation depth for C++11 constexpr functions to n.  A limit is
           needed to detect endless recursion during constant expression evaluation.  The minimum
           specified by the standard is 512.

       -fconstexpr-cache-depth=n
           Set the maximum level of nested evaluation depth for C++11 constexpr functions that will
           be cached to n.  This is a heuristic that trades off compilation speed (when the cache
           avoids repeated calculations) against memory consumption (when the cache grows very large
           from highly recursive evaluations).  The default is 8.  Very few users are likely to want
           to adjust it, but if your code does heavy constexpr calculations you might want to
           experiment to find which value works best for you.

       -fconstexpr-loop-limit=n
           Set the maximum number of iterations for a loop in C++14 constexpr functions to n.  A
           limit is needed to detect infinite loops during constant expression evaluation.  The
           default is 262144 (1<<18).

       -fconstexpr-ops-limit=n
           Set the maximum number of operations during a single constexpr evaluation.  Even when
           number of iterations of a single loop is limited with the above limit, if there are
           several nested loops and each of them has many iterations but still smaller than the
           above limit, or if in a body of some loop or even outside of a loop too many expressions
           need to be evaluated, the resulting constexpr evaluation might take too long.  The
           default is 33554432 (1<<25).

       -fcoroutines
           Enable support for the C++ coroutines extension (experimental).

       -fno-elide-constructors
           The C++ standard allows an implementation to omit creating a temporary that is only used
           to initialize another object of the same type.  Specifying this option disables that
           optimization, and forces G++ to call the copy constructor in all cases.  This option also
           causes G++ to call trivial member functions which otherwise would be expanded inline.

           In C++17, the compiler is required to omit these temporaries, but this option still
           affects trivial member functions.

       -fno-enforce-eh-specs
           Don't generate code to check for violation of exception specifications at run time.  This
           option violates the C++ standard, but may be useful for reducing code size in production
           builds, much like defining "NDEBUG".  This does not give user code permission to throw
           exceptions in violation of the exception specifications; the compiler still optimizes
           based on the specifications, so throwing an unexpected exception results in undefined
           behavior at run time.

       -fextern-tls-init
       -fno-extern-tls-init
           The C++11 and OpenMP standards allow "thread_local" and "threadprivate" variables to have
           dynamic (runtime) initialization.  To support this, any use of such a variable goes
           through a wrapper function that performs any necessary initialization.  When the use and
           definition of the variable are in the same translation unit, this overhead can be
           optimized away, but when the use is in a different translation unit there is significant
           overhead even if the variable doesn't actually need dynamic initialization.  If the
           programmer can be sure that no use of the variable in a non-defining TU needs to trigger
           dynamic initialization (either because the variable is statically initialized, or a use
           of the variable in the defining TU will be executed before any uses in another TU), they
           can avoid this overhead with the -fno-extern-tls-init option.

           On targets that support symbol aliases, the default is -fextern-tls-init.  On targets
           that do not support symbol aliases, the default is -fno-extern-tls-init.

       -fno-gnu-keywords
           Do not recognize "typeof" as a keyword, so that code can use this word as an identifier.
           You can use the keyword "__typeof__" instead.  This option is implied by the strict ISO
           C++ dialects: -ansi, -std=c++98, -std=c++11, etc.

       -fno-implicit-templates
           Never emit code for non-inline templates that are instantiated implicitly (i.e. by use);
           only emit code for explicit instantiations.  If you use this option, you must take care
           to structure your code to include all the necessary explicit instantiations to avoid
           getting undefined symbols at link time.

       -fno-implicit-inline-templates
           Don't emit code for implicit instantiations of inline templates, either.  The default is
           to handle inlines differently so that compiles with and without optimization need the
           same set of explicit instantiations.

       -fno-implement-inlines
           To save space, do not emit out-of-line copies of inline functions controlled by "#pragma
           implementation".  This causes linker errors if these functions are not inlined everywhere
           they are called.

       -fmodules-ts
       -fno-modules-ts
           Enable support for C++20 modules   The -fno-modules-ts is usually not needed, as that is
           the default.  Even though this is a C++20 feature, it is not currently implicitly enabled
           by selecting that standard version.

       -fmodule-header
       -fmodule-header=user
       -fmodule-header=system
           Compile a header file to create an importable header unit.

       -fmodule-implicit-inline
           Member functions defined in their class definitions are not implicitly inline for modular
           code.  This is different to traditional C++ behavior, for good reasons.  However, it may
           result in a difficulty during code porting.  This option makes such function definitions
           implicitly inline.  It does however generate an ABI incompatibility, so you must use it
           everywhere or nowhere.  (Such definitions outside of a named module remain implicitly
           inline, regardless.)

       -fno-module-lazy
           Disable lazy module importing and module mapper creation.

       -fmodule-mapper=[hostname]:port[?ident]
       -fmodule-mapper=|program[?ident] args...
       -fmodule-mapper==socket[?ident]
       -fmodule-mapper=<>[inout][?ident]
       -fmodule-mapper=<in>out[?ident]
       -fmodule-mapper=file[?ident]
           An oracle to query for module name to filename mappings.  If unspecified the
           CXX_MODULE_MAPPER environment variable is used, and if that is unset, an in-process
           default is provided.

       -fmodule-only
           Only emit the Compiled Module Interface, inhibiting any object file.

       -fms-extensions
           Disable Wpedantic warnings about constructs used in MFC, such as implicit int and getting
           a pointer to member function via non-standard syntax.

       -fnew-inheriting-ctors
           Enable the P0136 adjustment to the semantics of C++11 constructor inheritance.  This is
           part of C++17 but also considered to be a Defect Report against C++11 and C++14.  This
           flag is enabled by default unless -fabi-version=10 or lower is specified.

       -fnew-ttp-matching
           Enable the P0522 resolution to Core issue 150, template template parameters and default
           arguments: this allows a template with default template arguments as an argument for a
           template template parameter with fewer template parameters.  This flag is enabled by
           default for -std=c++17.

       -fno-nonansi-builtins
           Disable built-in declarations of functions that are not mandated by ANSI/ISO C.  These
           include "ffs", "alloca", "_exit", "index", "bzero", "conjf", and other related functions.

       -fnothrow-opt
           Treat a "throw()" exception specification as if it were a "noexcept" specification to
           reduce or eliminate the text size overhead relative to a function with no exception
           specification.  If the function has local variables of types with non-trivial
           destructors, the exception specification actually makes the function smaller because the
           EH cleanups for those variables can be optimized away.  The semantic effect is that an
           exception thrown out of a function with such an exception specification results in a call
           to "terminate" rather than "unexpected".

       -fno-operator-names
           Do not treat the operator name keywords "and", "bitand", "bitor", "compl", "not", "or"
           and "xor" as synonyms as keywords.

       -fno-optional-diags
           Disable diagnostics that the standard says a compiler does not need to issue.  Currently,
           the only such diagnostic issued by G++ is the one for a name having multiple meanings
           within a class.

       -fpermissive
           Downgrade some diagnostics about nonconformant code from errors to warnings.  Thus, using
           -fpermissive allows some nonconforming code to compile.

       -fno-pretty-templates
           When an error message refers to a specialization of a function template, the compiler
           normally prints the signature of the template followed by the template arguments and any
           typedefs or typenames in the signature (e.g. "void f(T) [with T = int]" rather than "void
           f(int)") so that it's clear which template is involved.  When an error message refers to
           a specialization of a class template, the compiler omits any template arguments that
           match the default template arguments for that template.  If either of these behaviors
           make it harder to understand the error message rather than easier, you can use
           -fno-pretty-templates to disable them.

       -fno-rtti
           Disable generation of information about every class with virtual functions for use by the
           C++ run-time type identification features ("dynamic_cast" and "typeid").  If you don't
           use those parts of the language, you can save some space by using this flag.  Note that
           exception handling uses the same information, but G++ generates it as needed. The
           "dynamic_cast" operator can still be used for casts that do not require run-time type
           information, i.e. casts to "void *" or to unambiguous base classes.

           Mixing code compiled with -frtti with that compiled with -fno-rtti may not work.  For
           example, programs may fail to link if a class compiled with -fno-rtti is used as a base
           for a class compiled with -frtti.

       -fsized-deallocation
           Enable the built-in global declarations

                   void operator delete (void *, std::size_t) noexcept;
                   void operator delete[] (void *, std::size_t) noexcept;

           as introduced in C++14.  This is useful for user-defined replacement deallocation
           functions that, for example, use the size of the object to make deallocation faster.
           Enabled by default under -std=c++14 and above.  The flag -Wsized-deallocation warns about
           places that might want to add a definition.

       -fstrict-enums
           Allow the compiler to optimize using the assumption that a value of enumerated type can
           only be one of the values of the enumeration (as defined in the C++ standard; basically,
           a value that can be represented in the minimum number of bits needed to represent all the
           enumerators).  This assumption may not be valid if the program uses a cast to convert an
           arbitrary integer value to the enumerated type.

       -fstrong-eval-order
           Evaluate member access, array subscripting, and shift expressions in left-to-right order,
           and evaluate assignment in right-to-left order, as adopted for C++17.  Enabled by default
           with -std=c++17.  -fstrong-eval-order=some enables just the ordering of member access and
           shift expressions, and is the default without -std=c++17.

       -ftemplate-backtrace-limit=n
           Set the maximum number of template instantiation notes for a single warning or error to
           n.  The default value is 10.

       -ftemplate-depth=n
           Set the maximum instantiation depth for template classes to n.  A limit on the template
           instantiation depth is needed to detect endless recursions during template class
           instantiation.  ANSI/ISO C++ conforming programs must not rely on a maximum depth greater
           than 17 (changed to 1024 in C++11).  The default value is 900, as the compiler can run
           out of stack space before hitting 1024 in some situations.

       -fno-threadsafe-statics
           Do not emit the extra code to use the routines specified in the C++ ABI for thread-safe
           initialization of local statics.  You can use this option to reduce code size slightly in
           code that doesn't need to be thread-safe.

       -fuse-cxa-atexit
           Register destructors for objects with static storage duration with the "__cxa_atexit"
           function rather than the "atexit" function.  This option is required for fully standards-
           compliant handling of static destructors, but only works if your C library supports
           "__cxa_atexit".

       -fno-use-cxa-get-exception-ptr
           Don't use the "__cxa_get_exception_ptr" runtime routine.  This causes
           "std::uncaught_exception" to be incorrect, but is necessary if the runtime routine is not
           available.

       -fvisibility-inlines-hidden
           This switch declares that the user does not attempt to compare pointers to inline
           functions or methods where the addresses of the two functions are taken in different
           shared objects.

           The effect of this is that GCC may, effectively, mark inline methods with "__attribute__
           ((visibility ("hidden")))" so that they do not appear in the export table of a DSO and do
           not require a PLT indirection when used within the DSO.  Enabling this option can have a
           dramatic effect on load and link times of a DSO as it massively reduces the size of the
           dynamic export table when the library makes heavy use of templates.

           The behavior of this switch is not quite the same as marking the methods as hidden
           directly, because it does not affect static variables local to the function or cause the
           compiler to deduce that the function is defined in only one shared object.

           You may mark a method as having a visibility explicitly to negate the effect of the
           switch for that method.  For example, if you do want to compare pointers to a particular
           inline method, you might mark it as having default visibility.  Marking the enclosing
           class with explicit visibility has no effect.

           Explicitly instantiated inline methods are unaffected by this option as their linkage
           might otherwise cross a shared library boundary.

       -fvisibility-ms-compat
           This flag attempts to use visibility settings to make GCC's C++ linkage model compatible
           with that of Microsoft Visual Studio.

           The flag makes these changes to GCC's linkage model:

           1.  It sets the default visibility to "hidden", like -fvisibility=hidden.

           2.  Types, but not their members, are not hidden by default.

           3.  The One Definition Rule is relaxed for types without explicit visibility
               specifications that are defined in more than one shared object: those declarations
               are permitted if they are permitted when this option is not used.

           In new code it is better to use -fvisibility=hidden and export those classes that are
           intended to be externally visible.  Unfortunately it is possible for code to rely,
           perhaps accidentally, on the Visual Studio behavior.

           Among the consequences of these changes are that static data members of the same type
           with the same name but defined in different shared objects are different, so changing one
           does not change the other; and that pointers to function members defined in different
           shared objects may not compare equal.  When this flag is given, it is a violation of the
           ODR to define types with the same name differently.

       -fno-weak
           Do not use weak symbol support, even if it is provided by the linker.  By default, G++
           uses weak symbols if they are available.  This option exists only for testing, and should
           not be used by end-users; it results in inferior code and has no benefits.  This option
           may be removed in a future release of G++.

       -fext-numeric-literals (C++ and Objective-C++ only)
           Accept imaginary, fixed-point, or machine-defined literal number suffixes as GNU
           extensions.  When this option is turned off these suffixes are treated as C++11 user-
           defined literal numeric suffixes.  This is on by default for all pre-C++11 dialects and
           all GNU dialects: -std=c++98, -std=gnu++98, -std=gnu++11, -std=gnu++14.  This option is
           off by default for ISO C++11 onwards (-std=c++11, ...).

       -nostdinc++
           Do not search for header files in the standard directories specific to C++, but do still
           search the other standard directories.  (This option is used when building the C++
           library.)

       -flang-info-include-translate
       -flang-info-include-translate-not
       -flang-info-include-translate=header
           Inform of include translation events.  The first will note accepted include translations,
           the second will note declined include translations.  The header form will inform of
           include translations relating to that specific header.  If header is of the form "user"
           or "<system>" it will be resolved to a specific user or system header using the include
           path.

       -flang-info-module-cmi
       -flang-info-module-cmi=module
           Inform of Compiled Module Interface pathnames.  The first will note all read CMI
           pathnames.  The module form will not reading a specific module's CMI.  module may be a
           named module or a header-unit (the latter indicated by either being a pathname containing
           directory separators or enclosed in "<>" or "").

       -stdlib=libstdc++,libc++
           When G++ is configured to support this option, it allows specification of alternate C++
           runtime libraries.  Two options are available: libstdc++ (the default, native C++ runtime
           for G++) and libc++ which is the C++ runtime installed on some operating systems (e.g.
           Darwin versions from Darwin11 onwards).  The option switches G++ to use the headers from
           the specified library and to emit "-lstdc++" or "-lc++" respectively, when a C++ runtime
           is required for linking.

       In addition, these warning options have meanings only for C++ programs:

       -Wabi-tag (C++ and Objective-C++ only)
           Warn when a type with an ABI tag is used in a context that does not have that ABI tag.
           See C++ Attributes for more information about ABI tags.

       -Wcomma-subscript (C++ and Objective-C++ only)
           Warn about uses of a comma expression within a subscripting expression.  This usage was
           deprecated in C++20.  However, a comma expression wrapped in "( )" is not deprecated.
           Example:

                   void f(int *a, int b, int c) {
                       a[b,c];     // deprecated
                       a[(b,c)];   // OK
                   }

           Enabled by default with -std=c++20.

       -Wctad-maybe-unsupported (C++ and Objective-C++ only)
           Warn when performing class template argument deduction (CTAD) on a type with no
           explicitly written deduction guides.  This warning will point out cases where CTAD
           succeeded only because the compiler synthesized the implicit deduction guides, which
           might not be what the programmer intended.  Certain style guides allow CTAD only on types
           that specifically "opt-in"; i.e., on types that are designed to support CTAD.  This
           warning can be suppressed with the following pattern:

                   struct allow_ctad_t; // any name works
                   template <typename T> struct S {
                     S(T) { }
                   };
                   S(allow_ctad_t) -> S<void>; // guide with incomplete parameter type will never be considered

       -Wctor-dtor-privacy (C++ and Objective-C++ only)
           Warn when a class seems unusable because all the constructors or destructors in that
           class are private, and it has neither friends nor public static member functions.  Also
           warn if there are no non-private methods, and there's at least one private member
           function that isn't a constructor or destructor.

       -Wdelete-non-virtual-dtor (C++ and Objective-C++ only)
           Warn when "delete" is used to destroy an instance of a class that has virtual functions
           and non-virtual destructor. It is unsafe to delete an instance of a derived class through
           a pointer to a base class if the base class does not have a virtual destructor.  This
           warning is enabled by -Wall.

       -Wdeprecated-copy (C++ and Objective-C++ only)
           Warn that the implicit declaration of a copy constructor or copy assignment operator is
           deprecated if the class has a user-provided copy constructor or copy assignment operator,
           in C++11 and up.  This warning is enabled by -Wextra.  With -Wdeprecated-copy-dtor, also
           deprecate if the class has a user-provided destructor.

       -Wno-deprecated-enum-enum-conversion (C++ and Objective-C++ only)
           Disable the warning about the case when the usual arithmetic conversions are applied on
           operands where one is of enumeration type and the other is of a different enumeration
           type.  This conversion was deprecated in C++20.  For example:

                   enum E1 { e };
                   enum E2 { f };
                   int k = f - e;

           -Wdeprecated-enum-enum-conversion is enabled by default with -std=c++20.  In pre-C++20
           dialects, this warning can be enabled by -Wenum-conversion.

       -Wno-deprecated-enum-float-conversion (C++ and Objective-C++ only)
           Disable the warning about the case when the usual arithmetic conversions are applied on
           operands where one is of enumeration type and the other is of a floating-point type.
           This conversion was deprecated in C++20.  For example:

                   enum E1 { e };
                   enum E2 { f };
                   bool b = e <= 3.7;

           -Wdeprecated-enum-float-conversion is enabled by default with -std=c++20.  In pre-C++20
           dialects, this warning can be enabled by -Wenum-conversion.

       -Wno-init-list-lifetime (C++ and Objective-C++ only)
           Do not warn about uses of "std::initializer_list" that are likely to result in dangling
           pointers.  Since the underlying array for an "initializer_list" is handled like a normal
           C++ temporary object, it is easy to inadvertently keep a pointer to the array past the
           end of the array's lifetime.  For example:

           *   If a function returns a temporary "initializer_list", or a local "initializer_list"
               variable, the array's lifetime ends at the end of the return statement, so the value
               returned has a dangling pointer.

           *   If a new-expression creates an "initializer_list", the array only lives until the end
               of the enclosing full-expression, so the "initializer_list" in the heap has a
               dangling pointer.

           *   When an "initializer_list" variable is assigned from a brace-enclosed initializer
               list, the temporary array created for the right side of the assignment only lives
               until the end of the full-expression, so at the next statement the "initializer_list"
               variable has a dangling pointer.

                       // li's initial underlying array lives as long as li
                       std::initializer_list<int> li = { 1,2,3 };
                       // assignment changes li to point to a temporary array
                       li = { 4, 5 };
                       // now the temporary is gone and li has a dangling pointer
                       int i = li.begin()[0] // undefined behavior

           *   When a list constructor stores the "begin" pointer from the "initializer_list"
               argument, this doesn't extend the lifetime of the array, so if a class variable is
               constructed from a temporary "initializer_list", the pointer is left dangling by the
               end of the variable declaration statement.

       -Winvalid-imported-macros
           Verify all imported macro definitions are valid at the end of compilation.  This is not
           enabled by default, as it requires additional processing to determine.  It may be useful
           when preparing sets of header-units to ensure consistent macros.

       -Wno-literal-suffix (C++ and Objective-C++ only)
           Do not warn when a string or character literal is followed by a ud-suffix which does not
           begin with an underscore.  As a conforming extension, GCC treats such suffixes as
           separate preprocessing tokens in order to maintain backwards compatibility with code that
           uses formatting macros from "<inttypes.h>".  For example:

                   #define __STDC_FORMAT_MACROS
                   #include <inttypes.h>
                   #include <stdio.h>

                   int main() {
                     int64_t i64 = 123;
                     printf("My int64: %" PRId64"\n", i64);
                   }

           In this case, "PRId64" is treated as a separate preprocessing token.

           This option also controls warnings when a user-defined literal operator is declared with
           a literal suffix identifier that doesn't begin with an underscore. Literal suffix
           identifiers that don't begin with an underscore are reserved for future standardization.

           These warnings are enabled by default.

       -Wno-narrowing (C++ and Objective-C++ only)
           For C++11 and later standards, narrowing conversions are diagnosed by default, as
           required by the standard.  A narrowing conversion from a constant produces an error, and
           a narrowing conversion from a non-constant produces a warning, but -Wno-narrowing
           suppresses the diagnostic.  Note that this does not affect the meaning of well-formed
           code; narrowing conversions are still considered ill-formed in SFINAE contexts.

           With -Wnarrowing in C++98, warn when a narrowing conversion prohibited by C++11 occurs
           within { }, e.g.

                   int i = { 2.2 }; // error: narrowing from double to int

           This flag is included in -Wall and -Wc++11-compat.

       -Wnoexcept (C++ and Objective-C++ only)
           Warn when a noexcept-expression evaluates to false because of a call to a function that
           does not have a non-throwing exception specification (i.e. "throw()" or "noexcept") but
           is known by the compiler to never throw an exception.

       -Wnoexcept-type (C++ and Objective-C++ only)
           Warn if the C++17 feature making "noexcept" part of a function type changes the mangled
           name of a symbol relative to C++14.  Enabled by -Wabi and -Wc++17-compat.

           As an example:

                   template <class T> void f(T t) { t(); };
                   void g() noexcept;
                   void h() { f(g); }

           In C++14, "f" calls "f<void(*)()>", but in C++17 it calls "f<void(*)()noexcept>".

       -Wclass-memaccess (C++ and Objective-C++ only)
           Warn when the destination of a call to a raw memory function such as "memset" or "memcpy"
           is an object of class type, and when writing into such an object might bypass the class
           non-trivial or deleted constructor or copy assignment, violate const-correctness or
           encapsulation, or corrupt virtual table pointers.  Modifying the representation of such
           objects may violate invariants maintained by member functions of the class.  For example,
           the call to "memset" below is undefined because it modifies a non-trivial class object
           and is, therefore, diagnosed.  The safe way to either initialize or clear the storage of
           objects of such types is by using the appropriate constructor or assignment operator, if
           one is available.

                   std::string str = "abc";
                   memset (&str, 0, sizeof str);

           The -Wclass-memaccess option is enabled by -Wall.  Explicitly casting the pointer to the
           class object to "void *" or to a type that can be safely accessed by the raw memory
           function suppresses the warning.

       -Wnon-virtual-dtor (C++ and Objective-C++ only)
           Warn when a class has virtual functions and an accessible non-virtual destructor itself
           or in an accessible polymorphic base class, in which case it is possible but unsafe to
           delete an instance of a derived class through a pointer to the class itself or base
           class.  This warning is automatically enabled if -Weffc++ is specified.

       -Wregister (C++ and Objective-C++ only)
           Warn on uses of the "register" storage class specifier, except when it is part of the GNU
           Explicit Register Variables extension.  The use of the "register" keyword as storage
           class specifier has been deprecated in C++11 and removed in C++17.  Enabled by default
           with -std=c++17.

       -Wreorder (C++ and Objective-C++ only)
           Warn when the order of member initializers given in the code does not match the order in
           which they must be executed.  For instance:

                   struct A {
                     int i;
                     int j;
                     A(): j (0), i (1) { }
                   };

           The compiler rearranges the member initializers for "i" and "j" to match the declaration
           order of the members, emitting a warning to that effect.  This warning is enabled by
           -Wall.

       -Wno-pessimizing-move (C++ and Objective-C++ only)
           This warning warns when a call to "std::move" prevents copy elision.  A typical scenario
           when copy elision can occur is when returning in a function with a class return type,
           when the expression being returned is the name of a non-volatile automatic object, and is
           not a function parameter, and has the same type as the function return type.

                   struct T {
                   ...
                   };
                   T fn()
                   {
                     T t;
                     ...
                     return std::move (t);
                   }

           But in this example, the "std::move" call prevents copy elision.

           This warning is enabled by -Wall.

       -Wno-redundant-move (C++ and Objective-C++ only)
           This warning warns about redundant calls to "std::move"; that is, when a move operation
           would have been performed even without the "std::move" call.  This happens because the
           compiler is forced to treat the object as if it were an rvalue in certain situations such
           as returning a local variable, where copy elision isn't applicable.  Consider:

                   struct T {
                   ...
                   };
                   T fn(T t)
                   {
                     ...
                     return std::move (t);
                   }

           Here, the "std::move" call is redundant.  Because G++ implements Core Issue 1579, another
           example is:

                   struct T { // convertible to U
                   ...
                   };
                   struct U {
                   ...
                   };
                   U fn()
                   {
                     T t;
                     ...
                     return std::move (t);
                   }

           In this example, copy elision isn't applicable because the type of the expression being
           returned and the function return type differ, yet G++ treats the return value as if it
           were designated by an rvalue.

           This warning is enabled by -Wextra.

       -Wrange-loop-construct (C++ and Objective-C++ only)
           This warning warns when a C++ range-based for-loop is creating an unnecessary copy.  This
           can happen when the range declaration is not a reference, but probably should be.  For
           example:

                   struct S { char arr[128]; };
                   void fn () {
                     S arr[5];
                     for (const auto x : arr) { ... }
                   }

           It does not warn when the type being copied is a trivially-copyable type whose size is
           less than 64 bytes.

           This warning also warns when a loop variable in a range-based for-loop is initialized
           with a value of a different type resulting in a copy.  For example:

                   void fn() {
                     int arr[10];
                     for (const double &x : arr) { ... }
                   }

           In the example above, in every iteration of the loop a temporary value of type "double"
           is created and destroyed, to which the reference "const double &" is bound.

           This warning is enabled by -Wall.

       -Wredundant-tags (C++ and Objective-C++ only)
           Warn about redundant class-key and enum-key in references to class types and enumerated
           types in contexts where the key can be eliminated without causing an ambiguity.  For
           example:

                   struct foo;
                   struct foo *p;   // warn that keyword struct can be eliminated

           On the other hand, in this example there is no warning:

                   struct foo;
                   void foo ();   // "hides" struct foo
                   void bar (struct foo&);  // no warning, keyword struct is necessary

       -Wno-subobject-linkage (C++ and Objective-C++ only)
           Do not warn if a class type has a base or a field whose type uses the anonymous namespace
           or depends on a type with no linkage.  If a type A depends on a type B with no or
           internal linkage, defining it in multiple translation units would be an ODR violation
           because the meaning of B is different in each translation unit.  If A only appears in a
           single translation unit, the best way to silence the warning is to give it internal
           linkage by putting it in an anonymous namespace as well.  The compiler doesn't give this
           warning for types defined in the main .C file, as those are unlikely to have multiple
           definitions.  -Wsubobject-linkage is enabled by default.

       -Weffc++ (C++ and Objective-C++ only)
           Warn about violations of the following style guidelines from Scott Meyers' Effective C++
           series of books:

           *   Define a copy constructor and an assignment operator for classes with dynamically-
               allocated memory.

           *   Prefer initialization to assignment in constructors.

           *   Have "operator=" return a reference to *this.

           *   Don't try to return a reference when you must return an object.

           *   Distinguish between prefix and postfix forms of increment and decrement operators.

           *   Never overload "&&", "||", or ",".

           This option also enables -Wnon-virtual-dtor, which is also one of the effective C++
           recommendations.  However, the check is extended to warn about the lack of virtual
           destructor in accessible non-polymorphic bases classes too.

           When selecting this option, be aware that the standard library headers do not obey all of
           these guidelines; use grep -v to filter out those warnings.

       -Wno-exceptions (C++ and Objective-C++ only)
           Disable the warning about the case when an exception handler is shadowed by another
           handler, which can point out a wrong ordering of exception handlers.

       -Wstrict-null-sentinel (C++ and Objective-C++ only)
           Warn about the use of an uncasted "NULL" as sentinel.  When compiling only with GCC this
           is a valid sentinel, as "NULL" is defined to "__null".  Although it is a null pointer
           constant rather than a null pointer, it is guaranteed to be of the same size as a
           pointer.  But this use is not portable across different compilers.

       -Wno-non-template-friend (C++ and Objective-C++ only)
           Disable warnings when non-template friend functions are declared within a template.  In
           very old versions of GCC that predate implementation of the ISO standard, declarations
           such as friend int foo(int), where the name of the friend is an unqualified-id, could be
           interpreted as a particular specialization of a template function; the warning exists to
           diagnose compatibility problems, and is enabled by default.

       -Wold-style-cast (C++ and Objective-C++ only)
           Warn if an old-style (C-style) cast to a non-void type is used within a C++ program.  The
           new-style casts ("dynamic_cast", "static_cast", "reinterpret_cast", and "const_cast") are
           less vulnerable to unintended effects and much easier to search for.

       -Woverloaded-virtual (C++ and Objective-C++ only)
           Warn when a function declaration hides virtual functions from a base class.  For example,
           in:

                   struct A {
                     virtual void f();
                   };

                   struct B: public A {
                     void f(int);
                   };

           the "A" class version of "f" is hidden in "B", and code like:

                   B* b;
                   b->f();

           fails to compile.

       -Wno-pmf-conversions (C++ and Objective-C++ only)
           Disable the diagnostic for converting a bound pointer to member function to a plain
           pointer.

       -Wsign-promo (C++ and Objective-C++ only)
           Warn when overload resolution chooses a promotion from unsigned or enumerated type to a
           signed type, over a conversion to an unsigned type of the same size.  Previous versions
           of G++ tried to preserve unsignedness, but the standard mandates the current behavior.

       -Wtemplates (C++ and Objective-C++ only)
           Warn when a primary template declaration is encountered.  Some coding rules disallow
           templates, and this may be used to enforce that rule.  The warning is inactive inside a
           system header file, such as the STL, so one can still use the STL.  One may also
           instantiate or specialize templates.

       -Wno-mismatched-new-delete (C++ and Objective-C++ only)
           Warn for mismatches between calls to "operator new" or "operator delete" and the
           corresponding call to the allocation or deallocation function.  This includes invocations
           of C++ "operator delete" with pointers returned from either mismatched forms of "operator
           new", or from other functions that allocate objects for which the "operator delete" isn't
           a suitable deallocator, as well as calls to other deallocation functions with pointers
           returned from "operator new" for which the deallocation function isn't suitable.

           For example, the "delete" expression in the function below is diagnosed because it
           doesn't match the array form of the "new" expression the pointer argument was returned
           from.  Similarly, the call to "free" is also diagnosed.

                   void f ()
                   {
                     int *a = new int[n];
                     delete a;   // warning: mismatch in array forms of expressions

                     char *p = new char[n];
                     free (p);   // warning: mismatch between new and free
                   }

           The related option -Wmismatched-dealloc diagnoses mismatches involving allocation and
           deallocation functions other than "operator new" and "operator delete".

           -Wmismatched-new-delete is enabled by default.

       -Wmismatched-tags (C++ and Objective-C++ only)
           Warn for declarations of structs, classes, and class templates and their specializations
           with a class-key that does not match either the definition or the first declaration if no
           definition is provided.

           For example, the declaration of "struct Object" in the argument list of "draw" triggers
           the warning.  To avoid it, either remove the redundant class-key "struct" or replace it
           with "class" to match its definition.

                   class Object {
                   public:
                     virtual ~Object () = 0;
                   };
                   void draw (struct Object*);

           It is not wrong to declare a class with the class-key "struct" as the example above
           shows.  The -Wmismatched-tags option is intended to help achieve a consistent style of
           class declarations.  In code that is intended to be portable to Windows-based compilers
           the warning helps prevent unresolved references due to the difference in the mangling of
           symbols declared with different class-keys.  The option can be used either on its own or
           in conjunction with -Wredundant-tags.

       -Wmultiple-inheritance (C++ and Objective-C++ only)
           Warn when a class is defined with multiple direct base classes.  Some coding rules
           disallow multiple inheritance, and this may be used to enforce that rule.  The warning is
           inactive inside a system header file, such as the STL, so one can still use the STL.  One
           may also define classes that indirectly use multiple inheritance.

       -Wvirtual-inheritance
           Warn when a class is defined with a virtual direct base class.  Some coding rules
           disallow multiple inheritance, and this may be used to enforce that rule.  The warning is
           inactive inside a system header file, such as the STL, so one can still use the STL.  One
           may also define classes that indirectly use virtual inheritance.

       -Wno-virtual-move-assign
           Suppress warnings about inheriting from a virtual base with a non-trivial C++11 move
           assignment operator.  This is dangerous because if the virtual base is reachable along
           more than one path, it is moved multiple times, which can mean both objects end up in the
           moved-from state.  If the move assignment operator is written to avoid moving from a
           moved-from object, this warning can be disabled.

       -Wnamespaces
           Warn when a namespace definition is opened.  Some coding rules disallow namespaces, and
           this may be used to enforce that rule.  The warning is inactive inside a system header
           file, such as the STL, so one can still use the STL.  One may also use using directives
           and qualified names.

       -Wno-terminate (C++ and Objective-C++ only)
           Disable the warning about a throw-expression that will immediately result in a call to
           "terminate".

       -Wno-vexing-parse (C++ and Objective-C++ only)
           Warn about the most vexing parse syntactic ambiguity.  This warns about the cases when a
           declaration looks like a variable definition, but the C++ language requires it to be
           interpreted as a function declaration.  For instance:

                   void f(double a) {
                     int i();        // extern int i (void);
                     int n(int(a));  // extern int n (int);
                   }

           Another example:

                   struct S { S(int); };
                   void f(double a) {
                     S x(int(a));   // extern struct S x (int);
                     S y(int());    // extern struct S y (int (*) (void));
                     S z();         // extern struct S z (void);
                   }

           The warning will suggest options how to deal with such an ambiguity; e.g., it can suggest
           removing the parentheses or using braces instead.

           This warning is enabled by default.

       -Wno-class-conversion (C++ and Objective-C++ only)
           Do not warn when a conversion function converts an object to the same type, to a base
           class of that type, or to void; such a conversion function will never be called.

       -Wvolatile (C++ and Objective-C++ only)
           Warn about deprecated uses of the "volatile" qualifier.  This includes postfix and prefix
           "++" and "--" expressions of "volatile"-qualified types, using simple assignments where
           the left operand is a "volatile"-qualified non-class type for their value, compound
           assignments where the left operand is a "volatile"-qualified non-class type,
           "volatile"-qualified function return type, "volatile"-qualified parameter type, and
           structured bindings of a "volatile"-qualified type.  This usage was deprecated in C++20.

           Enabled by default with -std=c++20.

       -Wzero-as-null-pointer-constant (C++ and Objective-C++ only)
           Warn when a literal 0 is used as null pointer constant.  This can be useful to facilitate
           the conversion to "nullptr" in C++11.

       -Waligned-new
           Warn about a new-expression of a type that requires greater alignment than the
           "alignof(std::max_align_t)" but uses an allocation function without an explicit alignment
           parameter. This option is enabled by -Wall.

           Normally this only warns about global allocation functions, but -Waligned-new=all also
           warns about class member allocation functions.

       -Wno-placement-new
       -Wplacement-new=n
           Warn about placement new expressions with undefined behavior, such as constructing an
           object in a buffer that is smaller than the type of the object.  For example, the
           placement new expression below is diagnosed because it attempts to construct an array of
           64 integers in a buffer only 64 bytes large.

                   char buf [64];
                   new (buf) int[64];

           This warning is enabled by default.

           -Wplacement-new=1
               This is the default warning level of -Wplacement-new.  At this level the warning is
               not issued for some strictly undefined constructs that GCC allows as extensions for
               compatibility with legacy code.  For example, the following "new" expression is not
               diagnosed at this level even though it has undefined behavior according to the C++
               standard because it writes past the end of the one-element array.

                       struct S { int n, a[1]; };
                       S *s = (S *)malloc (sizeof *s + 31 * sizeof s->a[0]);
                       new (s->a)int [32]();

           -Wplacement-new=2
               At this level, in addition to diagnosing all the same constructs as at level 1, a
               diagnostic is also issued for placement new expressions that construct an object in
               the last member of structure whose type is an array of a single element and whose
               size is less than the size of the object being constructed.  While the previous
               example would be diagnosed, the following construct makes use of the flexible member
               array extension to avoid the warning at level 2.

                       struct S { int n, a[]; };
                       S *s = (S *)malloc (sizeof *s + 32 * sizeof s->a[0]);
                       new (s->a)int [32]();

       -Wcatch-value
       -Wcatch-value=n (C++ and Objective-C++ only)
           Warn about catch handlers that do not catch via reference.  With -Wcatch-value=1 (or
           -Wcatch-value for short) warn about polymorphic class types that are caught by value.
           With -Wcatch-value=2 warn about all class types that are caught by value. With
           -Wcatch-value=3 warn about all types that are not caught by reference. -Wcatch-value is
           enabled by -Wall.

       -Wconditionally-supported (C++ and Objective-C++ only)
           Warn for conditionally-supported (C++11 [intro.defs]) constructs.

       -Wno-delete-incomplete (C++ and Objective-C++ only)
           Do not warn when deleting a pointer to incomplete type, which may cause undefined
           behavior at runtime.  This warning is enabled by default.

       -Wextra-semi (C++, Objective-C++ only)
           Warn about redundant semicolons after in-class function definitions.

       -Wno-inaccessible-base (C++, Objective-C++ only)
           This option controls warnings when a base class is inaccessible in a class derived from
           it due to ambiguity.  The warning is enabled by default.  Note that the warning for
           ambiguous virtual bases is enabled by the -Wextra option.

                   struct A { int a; };

                   struct B : A { };

                   struct C : B, A { };

       -Wno-inherited-variadic-ctor
           Suppress warnings about use of C++11 inheriting constructors when the base class
           inherited from has a C variadic constructor; the warning is on by default because the
           ellipsis is not inherited.

       -Wno-invalid-offsetof (C++ and Objective-C++ only)
           Suppress warnings from applying the "offsetof" macro to a non-POD type.  According to the
           2014 ISO C++ standard, applying "offsetof" to a non-standard-layout type is undefined.
           In existing C++ implementations, however, "offsetof" typically gives meaningful results.
           This flag is for users who are aware that they are writing nonportable code and who have
           deliberately chosen to ignore the warning about it.

           The restrictions on "offsetof" may be relaxed in a future version of the C++ standard.

       -Wsized-deallocation (C++ and Objective-C++ only)
           Warn about a definition of an unsized deallocation function

                   void operator delete (void *) noexcept;
                   void operator delete[] (void *) noexcept;

           without a definition of the corresponding sized deallocation function

                   void operator delete (void *, std::size_t) noexcept;
                   void operator delete[] (void *, std::size_t) noexcept;

           or vice versa.  Enabled by -Wextra along with -fsized-deallocation.

       -Wsuggest-final-types
           Warn about types with virtual methods where code quality would be improved if the type
           were declared with the C++11 "final" specifier, or, if possible, declared in an anonymous
           namespace. This allows GCC to more aggressively devirtualize the polymorphic calls. This
           warning is more effective with link-time optimization, where the information about the
           class hierarchy graph is more complete.

       -Wsuggest-final-methods
           Warn about virtual methods where code quality would be improved if the method were
           declared with the C++11 "final" specifier, or, if possible, its type were declared in an
           anonymous namespace or with the "final" specifier.  This warning is more effective with
           link-time optimization, where the information about the class hierarchy graph is more
           complete. It is recommended to first consider suggestions of -Wsuggest-final-types and
           then rebuild with new annotations.

       -Wsuggest-override
           Warn about overriding virtual functions that are not marked with the "override" keyword.

       -Wuseless-cast (C++ and Objective-C++ only)
           Warn when an expression is casted to its own type.

       -Wno-conversion-null (C++ and Objective-C++ only)
           Do not warn for conversions between "NULL" and non-pointer types. -Wconversion-null is
           enabled by default.

   Options Controlling Objective-C and Objective-C++ Dialects
       (NOTE: This manual does not describe the Objective-C and Objective-C++ languages themselves.

       This section describes the command-line options that are only meaningful for Objective-C and
       Objective-C++ programs.  You can also use most of the language-independent GNU compiler
       options.  For example, you might compile a file some_class.m like this:

               gcc -g -fgnu-runtime -O -c some_class.m

       In this example, -fgnu-runtime is an option meant only for Objective-C and Objective-C++
       programs; you can use the other options with any language supported by GCC.

       Note that since Objective-C is an extension of the C language, Objective-C compilations may
       also use options specific to the C front-end (e.g., -Wtraditional).  Similarly, Objective-C++
       compilations may use C++-specific options (e.g., -Wabi).

       Here is a list of options that are only for compiling Objective-C and Objective-C++ programs:

       -fconstant-string-class=class-name
           Use class-name as the name of the class to instantiate for each literal string specified
           with the syntax "@"..."".  The default class name is "NXConstantString" if the GNU
           runtime is being used, and "NSConstantString" if the NeXT runtime is being used (see
           below).  The -fconstant-cfstrings option, if also present, overrides the
           -fconstant-string-class setting and cause "@"..."" literals to be laid out as constant
           CoreFoundation strings.

       -fgnu-runtime
           Generate object code compatible with the standard GNU Objective-C runtime.  This is the
           default for most types of systems.

       -fnext-runtime
           Generate output compatible with the NeXT runtime.  This is the default for NeXT-based
           systems, including Darwin and Mac OS X.  The macro "__NEXT_RUNTIME__" is predefined if
           (and only if) this option is used.

       -fno-nil-receivers
           Assume that all Objective-C message dispatches ("[receiver message:arg]") in this
           translation unit ensure that the receiver is not "nil".  This allows for more efficient
           entry points in the runtime to be used.  This option is only available in conjunction
           with the NeXT runtime and ABI version 0 or 1.

       -fobjc-abi-version=n
           Use version n of the Objective-C ABI for the selected runtime.  This option is currently
           supported only for the NeXT runtime.  In that case, Version 0 is the traditional (32-bit)
           ABI without support for properties and other Objective-C 2.0 additions.  Version 1 is the
           traditional (32-bit) ABI with support for properties and other Objective-C 2.0 additions.
           Version 2 is the modern (64-bit) ABI.  If nothing is specified, the default is Version 0
           on 32-bit target machines, and Version 2 on 64-bit target machines.

       -fobjc-call-cxx-cdtors
           For each Objective-C class, check if any of its instance variables is a C++ object with a
           non-trivial default constructor.  If so, synthesize a special "- (id) .cxx_construct"
           instance method which runs non-trivial default constructors on any such instance
           variables, in order, and then return "self".  Similarly, check if any instance variable
           is a C++ object with a non-trivial destructor, and if so, synthesize a special "- (void)
           .cxx_destruct" method which runs all such default destructors, in reverse order.

           The "- (id) .cxx_construct" and "- (void) .cxx_destruct" methods thusly generated only
           operate on instance variables declared in the current Objective-C class, and not those
           inherited from superclasses.  It is the responsibility of the Objective-C runtime to
           invoke all such methods in an object's inheritance hierarchy.  The "- (id)
           .cxx_construct" methods are invoked by the runtime immediately after a new object
           instance is allocated; the "- (void) .cxx_destruct" methods are invoked immediately
           before the runtime deallocates an object instance.

           As of this writing, only the NeXT runtime on Mac OS X 10.4 and later has support for
           invoking the "- (id) .cxx_construct" and "- (void) .cxx_destruct" methods.

       -fobjc-direct-dispatch
           Allow fast jumps to the message dispatcher.  On Darwin this is accomplished via the comm
           page.

       -fobjc-exceptions
           Enable syntactic support for structured exception handling in Objective-C, similar to
           what is offered by C++.  This option is required to use the Objective-C keywords @try,
           @throw, @catch, @finally and @synchronized.  This option is available with both the GNU
           runtime and the NeXT runtime (but not available in conjunction with the NeXT runtime on
           Mac OS X 10.2 and earlier).

       -fobjc-gc
           Enable garbage collection (GC) in Objective-C and Objective-C++ programs.  This option is
           only available with the NeXT runtime; the GNU runtime has a different garbage collection
           implementation that does not require special compiler flags.

       -fobjc-nilcheck
           For the NeXT runtime with version 2 of the ABI, check for a nil receiver in method
           invocations before doing the actual method call.  This is the default and can be disabled
           using -fno-objc-nilcheck.  Class methods and super calls are never checked for nil in
           this way no matter what this flag is set to.  Currently this flag does nothing when the
           GNU runtime, or an older version of the NeXT runtime ABI, is used.

       -fobjc-std=objc1
           Conform to the language syntax of Objective-C 1.0, the language recognized by GCC 4.0.
           This only affects the Objective-C additions to the C/C++ language; it does not affect
           conformance to C/C++ standards, which is controlled by the separate C/C++ dialect option
           flags.  When this option is used with the Objective-C or Objective-C++ compiler, any
           Objective-C syntax that is not recognized by GCC 4.0 is rejected.  This is useful if you
           need to make sure that your Objective-C code can be compiled with older versions of GCC.

       -freplace-objc-classes
           Emit a special marker instructing ld(1) not to statically link in the resulting object
           file, and allow dyld(1) to load it in at run time instead.  This is used in conjunction
           with the Fix-and-Continue debugging mode, where the object file in question may be
           recompiled and dynamically reloaded in the course of program execution, without the need
           to restart the program itself.  Currently, Fix-and-Continue functionality is only
           available in conjunction with the NeXT runtime on Mac OS X 10.3 and later.

       -fzero-link
           When compiling for the NeXT runtime, the compiler ordinarily replaces calls to
           "objc_getClass("...")" (when the name of the class is known at compile time) with static
           class references that get initialized at load time, which improves run-time performance.
           Specifying the -fzero-link flag suppresses this behavior and causes calls to
           "objc_getClass("...")"  to be retained.  This is useful in Zero-Link debugging mode,
           since it allows for individual class implementations to be modified during program
           execution.  The GNU runtime currently always retains calls to "objc_get_class("...")"
           regardless of command-line options.

       -fno-local-ivars
           By default instance variables in Objective-C can be accessed as if they were local
           variables from within the methods of the class they're declared in.  This can lead to
           shadowing between instance variables and other variables declared either locally inside a
           class method or globally with the same name.  Specifying the -fno-local-ivars flag
           disables this behavior thus avoiding variable shadowing issues.

       -fivar-visibility=[public|protected|private|package]
           Set the default instance variable visibility to the specified option so that instance
           variables declared outside the scope of any access modifier directives default to the
           specified visibility.

       -gen-decls
           Dump interface declarations for all classes seen in the source file to a file named
           sourcename.decl.

       -Wassign-intercept (Objective-C and Objective-C++ only)
           Warn whenever an Objective-C assignment is being intercepted by the garbage collector.

       -Wno-property-assign-default (Objective-C and Objective-C++ only)
           Do not warn if a property for an Objective-C object has no assign semantics specified.

       -Wno-protocol (Objective-C and Objective-C++ only)
           If a class is declared to implement a protocol, a warning is issued for every method in
           the protocol that is not implemented by the class.  The default behavior is to issue a
           warning for every method not explicitly implemented in the class, even if a method
           implementation is inherited from the superclass.  If you use the -Wno-protocol option,
           then methods inherited from the superclass are considered to be implemented, and no
           warning is issued for them.

       -Wobjc-root-class (Objective-C and Objective-C++ only)
           Warn if a class interface lacks a superclass. Most classes will inherit from "NSObject"
           (or "Object") for example.  When declaring classes intended to be root classes, the
           warning can be suppressed by marking their interfaces with
           "__attribute__((objc_root_class))".

       -Wselector (Objective-C and Objective-C++ only)
           Warn if multiple methods of different types for the same selector are found during
           compilation.  The check is performed on the list of methods in the final stage of
           compilation.  Additionally, a check is performed for each selector appearing in a
           "@selector(...)"  expression, and a corresponding method for that selector has been found
           during compilation.  Because these checks scan the method table only at the end of
           compilation, these warnings are not produced if the final stage of compilation is not
           reached, for example because an error is found during compilation, or because the
           -fsyntax-only option is being used.

       -Wstrict-selector-match (Objective-C and Objective-C++ only)
           Warn if multiple methods with differing argument and/or return types are found for a
           given selector when attempting to send a message using this selector to a receiver of
           type "id" or "Class".  When this flag is off (which is the default behavior), the
           compiler omits such warnings if any differences found are confined to types that share
           the same size and alignment.

       -Wundeclared-selector (Objective-C and Objective-C++ only)
           Warn if a "@selector(...)" expression referring to an undeclared selector is found.  A
           selector is considered undeclared if no method with that name has been declared before
           the "@selector(...)" expression, either explicitly in an @interface or @protocol
           declaration, or implicitly in an @implementation section.  This option always performs
           its checks as soon as a "@selector(...)" expression is found, while -Wselector only
           performs its checks in the final stage of compilation.  This also enforces the coding
           style convention that methods and selectors must be declared before being used.

       -print-objc-runtime-info
           Generate C header describing the largest structure that is passed by value, if any.

   Options to Control Diagnostic Messages Formatting
       Traditionally, diagnostic messages have been formatted irrespective of the output device's
       aspect (e.g. its width, ...).  You can use the options described below to control the
       formatting algorithm for diagnostic messages, e.g. how many characters per line, how often
       source location information should be reported.  Note that some language front ends may not
       honor these options.

       -fmessage-length=n
           Try to format error messages so that they fit on lines of about n characters.  If n is
           zero, then no line-wrapping is done; each error message appears on a single line.  This
           is the default for all front ends.

           Note - this option also affects the display of the #error and #warning pre-processor
           directives, and the deprecated function/type/variable attribute.  It does not however
           affect the pragma GCC warning and pragma GCC error pragmas.

       -fdiagnostics-plain-output
           This option requests that diagnostic output look as plain as possible, which may be
           useful when running dejagnu or other utilities that need to parse diagnostics output and
           prefer that it remain more stable over time.  -fdiagnostics-plain-output is currently
           equivalent to the following options: -fno-diagnostics-show-caret
           -fno-diagnostics-show-line-numbers -fdiagnostics-color=never -fdiagnostics-urls=never
           -fdiagnostics-path-format=separate-events In the future, if GCC changes the default
           appearance of its diagnostics, the corresponding option to disable the new behavior will
           be added to this list.

       -fdiagnostics-show-location=once
           Only meaningful in line-wrapping mode.  Instructs the diagnostic messages reporter to
           emit source location information once; that is, in case the message is too long to fit on
           a single physical line and has to be wrapped, the source location won't be emitted (as
           prefix) again, over and over, in subsequent continuation lines.  This is the default
           behavior.

       -fdiagnostics-show-location=every-line
           Only meaningful in line-wrapping mode.  Instructs the diagnostic messages reporter to
           emit the same source location information (as prefix) for physical lines that result from
           the process of breaking a message which is too long to fit on a single line.

       -fdiagnostics-color[=WHEN]
       -fno-diagnostics-color
           Use color in diagnostics.  WHEN is never, always, or auto.  The default depends on how
           the compiler has been configured, it can be any of the above WHEN options or also never
           if GCC_COLORS environment variable isn't present in the environment, and auto otherwise.
           auto makes GCC use color only when the standard error is a terminal, and when not
           executing in an emacs shell.  The forms -fdiagnostics-color and -fno-diagnostics-color
           are aliases for -fdiagnostics-color=always and -fdiagnostics-color=never, respectively.

           The colors are defined by the environment variable GCC_COLORS.  Its value is a colon-
           separated list of capabilities and Select Graphic Rendition (SGR) substrings. SGR
           commands are interpreted by the terminal or terminal emulator.  (See the section in the
           documentation of your text terminal for permitted values and their meanings as character
           attributes.)  These substring values are integers in decimal representation and can be
           concatenated with semicolons.  Common values to concatenate include 1 for bold, 4 for
           underline, 5 for blink, 7 for inverse, 39 for default foreground color, 30 to 37 for
           foreground colors, 90 to 97 for 16-color mode foreground colors, 38;5;0 to 38;5;255 for
           88-color and 256-color modes foreground colors, 49 for default background color, 40 to 47
           for background colors, 100 to 107 for 16-color mode background colors, and 48;5;0 to
           48;5;255 for 88-color and 256-color modes background colors.

           The default GCC_COLORS is

                   error=01;31:warning=01;35:note=01;36:range1=32:range2=34:locus=01:\
                   quote=01:path=01;36:fixit-insert=32:fixit-delete=31:\
                   diff-filename=01:diff-hunk=32:diff-delete=31:diff-insert=32:\
                   type-diff=01;32

           where 01;31 is bold red, 01;35 is bold magenta, 01;36 is bold cyan, 32 is green, 34 is
           blue, 01 is bold, and 31 is red.  Setting GCC_COLORS to the empty string disables colors.
           Supported capabilities are as follows.

           "error="
               SGR substring for error: markers.

           "warning="
               SGR substring for warning: markers.

           "note="
               SGR substring for note: markers.

           "path="
               SGR substring for colorizing paths of control-flow events as printed via
               -fdiagnostics-path-format=, such as the identifiers of individual events and lines
               indicating interprocedural calls and returns.

           "range1="
               SGR substring for first additional range.

           "range2="
               SGR substring for second additional range.

           "locus="
               SGR substring for location information, file:line or file:line:column etc.

           "quote="
               SGR substring for information printed within quotes.

           "fixit-insert="
               SGR substring for fix-it hints suggesting text to be inserted or replaced.

           "fixit-delete="
               SGR substring for fix-it hints suggesting text to be deleted.

           "diff-filename="
               SGR substring for filename headers within generated patches.

           "diff-hunk="
               SGR substring for the starts of hunks within generated patches.

           "diff-delete="
               SGR substring for deleted lines within generated patches.

           "diff-insert="
               SGR substring for inserted lines within generated patches.

           "type-diff="
               SGR substring for highlighting mismatching types within template arguments in the C++
               frontend.

       -fdiagnostics-urls[=WHEN]
           Use escape sequences to embed URLs in diagnostics.  For example, when
           -fdiagnostics-show-option emits text showing the command-line option controlling a
           diagnostic, embed a URL for documentation of that option.

           WHEN is never, always, or auto.  auto makes GCC use URL escape sequences only when the
           standard error is a terminal, and when not executing in an emacs shell or any graphical
           terminal which is known to be incompatible with this feature, see below.

           The default depends on how the compiler has been configured.  It can be any of the above
           WHEN options.

           GCC can also be configured (via the --with-diagnostics-urls=auto-if-env configure-time
           option) so that the default is affected by environment variables.  Under such a
           configuration, GCC defaults to using auto if either GCC_URLS or TERM_URLS environment
           variables are present and non-empty in the environment of the compiler, or never if
           neither are.

           However, even with -fdiagnostics-urls=always the behavior is dependent on those
           environment variables: If GCC_URLS is set to empty or no, do not embed URLs in
           diagnostics.  If set to st, URLs use ST escape sequences.  If set to bel, the default,
           URLs use BEL escape sequences.  Any other non-empty value enables the feature.  If
           GCC_URLS is not set, use TERM_URLS as a fallback.  Note: ST is an ANSI escape sequence,
           string terminator ESC \, BEL is an ASCII character, CTRL-G that usually sounds like a
           beep.

           At this time GCC tries to detect also a few terminals that are known to not implement the
           URL feature, and have bugs or at least had bugs in some versions that are still in use,
           where the URL escapes are likely to misbehave, i.e. print garbage on the screen.  That
           list is currently xfce4-terminal, certain known to be buggy gnome-terminal versions, the
           linux console, and mingw.  This check can be skipped with the -fdiagnostics-urls=always.

       -fno-diagnostics-show-option
           By default, each diagnostic emitted includes text indicating the command-line option that
           directly controls the diagnostic (if such an option is known to the diagnostic
           machinery).  Specifying the -fno-diagnostics-show-option flag suppresses that behavior.

       -fno-diagnostics-show-caret
           By default, each diagnostic emitted includes the original source line and a caret ^
           indicating the column.  This option suppresses this information.  The source line is
           truncated to n characters, if the -fmessage-length=n option is given.  When the output is
           done to the terminal, the width is limited to the width given by the COLUMNS environment
           variable or, if not set, to the terminal width.

       -fno-diagnostics-show-labels
           By default, when printing source code (via -fdiagnostics-show-caret), diagnostics can
           label ranges of source code with pertinent information, such as the types of expressions:

                       printf ("foo %s bar", long_i + long_j);
                                    ~^       ~~~~~~~~~~~~~~~
                                     |              |
                                     char *         long int

           This option suppresses the printing of these labels (in the example above, the vertical
           bars and the "char *" and "long int" text).

       -fno-diagnostics-show-cwe
           Diagnostic messages can optionally have an associated
           @url{https://cwe.mitre.org/index.html, CWE} identifier.  GCC itself only provides such
           metadata for some of the -fanalyzer diagnostics.  GCC plugins may also provide
           diagnostics with such metadata.  By default, if this information is present, it will be
           printed with the diagnostic.  This option suppresses the printing of this metadata.

       -fno-diagnostics-show-line-numbers
           By default, when printing source code (via -fdiagnostics-show-caret), a left margin is
           printed, showing line numbers.  This option suppresses this left margin.

       -fdiagnostics-minimum-margin-width=width
           This option controls the minimum width of the left margin printed by
           -fdiagnostics-show-line-numbers.  It defaults to 6.

       -fdiagnostics-parseable-fixits
           Emit fix-it hints in a machine-parseable format, suitable for consumption by IDEs.  For
           each fix-it, a line will be printed after the relevant diagnostic, starting with the
           string "fix-it:".  For example:

                   fix-it:"test.c":{45:3-45:21}:"gtk_widget_show_all"

           The location is expressed as a half-open range, expressed as a count of bytes, starting
           at byte 1 for the initial column.  In the above example, bytes 3 through 20 of line 45 of
           "test.c" are to be replaced with the given string:

                   00000000011111111112222222222
                   12345678901234567890123456789
                     gtk_widget_showall (dlg);
                     ^^^^^^^^^^^^^^^^^^
                     gtk_widget_show_all

           The filename and replacement string escape backslash as "\\", tab as "\t", newline as
           "\n", double quotes as "\"", non-printable characters as octal (e.g. vertical tab as
           "\013").

           An empty replacement string indicates that the given range is to be removed.  An empty
           range (e.g. "45:3-45:3") indicates that the string is to be inserted at the given
           position.

       -fdiagnostics-generate-patch
           Print fix-it hints to stderr in unified diff format, after any diagnostics are printed.
           For example:

                   --- test.c
                   +++ test.c
                   @ -42,5 +42,5 @

                    void show_cb(GtkDialog *dlg)
                    {
                   -  gtk_widget_showall(dlg);
                   +  gtk_widget_show_all(dlg);
                    }

           The diff may or may not be colorized, following the same rules as for diagnostics (see
           -fdiagnostics-color).

       -fdiagnostics-show-template-tree
           In the C++ frontend, when printing diagnostics showing mismatching template types, such
           as:

                     could not convert 'std::map<int, std::vector<double> >()'
                       from 'map<[...],vector<double>>' to 'map<[...],vector<float>>

           the -fdiagnostics-show-template-tree flag enables printing a tree-like structure showing
           the common and differing parts of the types, such as:

                     map<
                       [...],
                       vector<
                         [double != float]>>

           The parts that differ are highlighted with color ("double" and "float" in this case).

       -fno-elide-type
           By default when the C++ frontend prints diagnostics showing mismatching template types,
           common parts of the types are printed as "[...]" to simplify the error message.  For
           example:

                     could not convert 'std::map<int, std::vector<double> >()'
                       from 'map<[...],vector<double>>' to 'map<[...],vector<float>>

           Specifying the -fno-elide-type flag suppresses that behavior.  This flag also affects the
           output of the -fdiagnostics-show-template-tree flag.

       -fdiagnostics-path-format=KIND
           Specify how to print paths of control-flow events for diagnostics that have such a path
           associated with them.

           KIND is none, separate-events, or inline-events, the default.

           none means to not print diagnostic paths.

           separate-events means to print a separate "note" diagnostic for each event within the
           diagnostic.  For example:

                   test.c:29:5: error: passing NULL as argument 1 to 'PyList_Append' which requires a non-NULL parameter
                   test.c:25:10: note: (1) when 'PyList_New' fails, returning NULL
                   test.c:27:3: note: (2) when 'i < count'
                   test.c:29:5: note: (3) when calling 'PyList_Append', passing NULL from (1) as argument 1

           inline-events means to print the events "inline" within the source code.  This view
           attempts to consolidate the events into runs of sufficiently-close events, printing them
           as labelled ranges within the source.

           For example, the same events as above might be printed as:

                     'test': events 1-3
                       |
                       |   25 |   list = PyList_New(0);
                       |      |          ^~~~~~~~~~~~~
                       |      |          |
                       |      |          (1) when 'PyList_New' fails, returning NULL
                       |   26 |
                       |   27 |   for (i = 0; i < count; i++) {
                       |      |   ~~~
                       |      |   |
                       |      |   (2) when 'i < count'
                       |   28 |     item = PyLong_FromLong(random());
                       |   29 |     PyList_Append(list, item);
                       |      |     ~~~~~~~~~~~~~~~~~~~~~~~~~
                       |      |     |
                       |      |     (3) when calling 'PyList_Append', passing NULL from (1) as argument 1
                       |

           Interprocedural control flow is shown by grouping the events by stack frame, and using
           indentation to show how stack frames are nested, pushed, and popped.

           For example:

                     'test': events 1-2
                       |
                       |  133 | {
                       |      | ^
                       |      | |
                       |      | (1) entering 'test'
                       |  134 |   boxed_int *obj = make_boxed_int (i);
                       |      |                    ~~~~~~~~~~~~~~~~~~
                       |      |                    |
                       |      |                    (2) calling 'make_boxed_int'
                       |
                       +--> 'make_boxed_int': events 3-4
                              |
                              |  120 | {
                              |      | ^
                              |      | |
                              |      | (3) entering 'make_boxed_int'
                              |  121 |   boxed_int *result = (boxed_int *)wrapped_malloc (sizeof (boxed_int));
                              |      |                                    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
                              |      |                                    |
                              |      |                                    (4) calling 'wrapped_malloc'
                              |
                              +--> 'wrapped_malloc': events 5-6
                                     |
                                     |    7 | {
                                     |      | ^
                                     |      | |
                                     |      | (5) entering 'wrapped_malloc'
                                     |    8 |   return malloc (size);
                                     |      |          ~~~~~~~~~~~~~
                                     |      |          |
                                     |      |          (6) calling 'malloc'
                                     |
                       <-------------+
                       |
                    'test': event 7
                       |
                       |  138 |   free_boxed_int (obj);
                       |      |   ^~~~~~~~~~~~~~~~~~~~
                       |      |   |
                       |      |   (7) calling 'free_boxed_int'
                       |
                   (etc)

       -fdiagnostics-show-path-depths
           This option provides additional information when printing control-flow paths associated
           with a diagnostic.

           If this is option is provided then the stack depth will be printed for each run of events
           within -fdiagnostics-path-format=separate-events.

           This is intended for use by GCC developers and plugin developers when debugging
           diagnostics that report interprocedural control flow.

       -fno-show-column
           Do not print column numbers in diagnostics.  This may be necessary if diagnostics are
           being scanned by a program that does not understand the column numbers, such as dejagnu.

       -fdiagnostics-column-unit=UNIT
           Select the units for the column number.  This affects traditional diagnostics (in the
           absence of -fno-show-column), as well as JSON format diagnostics if requested.

           The default UNIT, display, considers the number of display columns occupied by each
           character.  This may be larger than the number of bytes required to encode the character,
           in the case of tab characters, or it may be smaller, in the case of multibyte characters.
           For example, the character "GREEK SMALL LETTER PI (U+03C0)" occupies one display column,
           and its UTF-8 encoding requires two bytes; the character "SLIGHTLY SMILING FACE
           (U+1F642)" occupies two display columns, and its UTF-8 encoding requires four bytes.

           Setting UNIT to byte changes the column number to the raw byte count in all cases, as was
           traditionally output by GCC prior to version 11.1.0.

       -fdiagnostics-column-origin=ORIGIN
           Select the origin for column numbers, i.e. the column number assigned to the first
           column.  The default value of 1 corresponds to traditional GCC behavior and to the GNU
           style guide.  Some utilities may perform better with an origin of 0; any non-negative
           value may be specified.

       -fdiagnostics-format=FORMAT
           Select a different format for printing diagnostics.  FORMAT is text or json.  The default
           is text.

           The json format consists of a top-level JSON array containing JSON objects representing
           the diagnostics.

           The JSON is emitted as one line, without formatting; the examples below have been
           formatted for clarity.

           Diagnostics can have child diagnostics.  For example, this error and note:

                   misleading-indentation.c:15:3: warning: this 'if' clause does not
                     guard... [-Wmisleading-indentation]
                      15 |   if (flag)
                         |   ^~
                   misleading-indentation.c:17:5: note: ...this statement, but the latter
                     is misleadingly indented as if it were guarded by the 'if'
                      17 |     y = 2;
                         |     ^

           might be printed in JSON form (after formatting) like this:

                   [
                       {
                           "kind": "warning",
                           "locations": [
                               {
                                   "caret": {
                                       "display-column": 3,
                                       "byte-column": 3,
                                       "column": 3,
                                       "file": "misleading-indentation.c",
                                       "line": 15
                                   },
                                   "finish": {
                                       "display-column": 4,
                                       "byte-column": 4,
                                       "column": 4,
                                       "file": "misleading-indentation.c",
                                       "line": 15
                                   }
                               }
                           ],
                           "message": "this \u2018if\u2019 clause does not guard...",
                           "option": "-Wmisleading-indentation",
                           "option_url": "https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html#index-Wmisleading-indentation",
                           "children": [
                               {
                                   "kind": "note",
                                   "locations": [
                                       {
                                           "caret": {
                                               "display-column": 5,
                                               "byte-column": 5,
                                               "column": 5,
                                               "file": "misleading-indentation.c",
                                               "line": 17
                                           }
                                       }
                                   ],
                                   "message": "...this statement, but the latter is ..."
                               }
                           ]
                           "column-origin": 1,
                       },
                       ...
                   ]

           where the "note" is a child of the "warning".

           A diagnostic has a "kind".  If this is "warning", then there is an "option" key
           describing the command-line option controlling the warning.

           A diagnostic can contain zero or more locations.  Each location has an optional "label"
           string and up to three positions within it: a "caret" position and optional "start" and
           "finish" positions.  A position is described by a "file" name, a "line" number, and three
           numbers indicating a column position:

           *   "display-column" counts display columns, accounting for tabs and multibyte
               characters.

           *   "byte-column" counts raw bytes.

           *   "column" is equal to one of the previous two, as dictated by the
               -fdiagnostics-column-unit option.

           All three columns are relative to the origin specified by -fdiagnostics-column-origin,
           which is typically equal to 1 but may be set, for instance, to 0 for compatibility with
           other utilities that number columns from 0.  The column origin is recorded in the JSON
           output in the "column-origin" tag.  In the remaining examples below, the extra column
           number outputs have been omitted for brevity.

           For example, this error:

                   bad-binary-ops.c:64:23: error: invalid operands to binary + (have 'S' {aka
                      'struct s'} and 'T' {aka 'struct t'})
                      64 |   return callee_4a () + callee_4b ();
                         |          ~~~~~~~~~~~~ ^ ~~~~~~~~~~~~
                         |          |              |
                         |          |              T {aka struct t}
                         |          S {aka struct s}

           has three locations.  Its primary location is at the "+" token at column 23.  It has two
           secondary locations, describing the left and right-hand sides of the expression, which
           have labels.  It might be printed in JSON form as:

                       {
                           "children": [],
                           "kind": "error",
                           "locations": [
                               {
                                   "caret": {
                                       "column": 23, "file": "bad-binary-ops.c", "line": 64
                                   }
                               },
                               {
                                   "caret": {
                                       "column": 10, "file": "bad-binary-ops.c", "line": 64
                                   },
                                   "finish": {
                                       "column": 21, "file": "bad-binary-ops.c", "line": 64
                                   },
                                   "label": "S {aka struct s}"
                               },
                               {
                                   "caret": {
                                       "column": 25, "file": "bad-binary-ops.c", "line": 64
                                   },
                                   "finish": {
                                       "column": 36, "file": "bad-binary-ops.c", "line": 64
                                   },
                                   "label": "T {aka struct t}"
                               }
                           ],
                           "message": "invalid operands to binary + ..."
                       }

           If a diagnostic contains fix-it hints, it has a "fixits" array, consisting of half-open
           intervals, similar to the output of -fdiagnostics-parseable-fixits.  For example, this
           diagnostic with a replacement fix-it hint:

                   demo.c:8:15: error: 'struct s' has no member named 'colour'; did you
                     mean 'color'?
                       8 |   return ptr->colour;
                         |               ^~~~~~
                         |               color

           might be printed in JSON form as:

                       {
                           "children": [],
                           "fixits": [
                               {
                                   "next": {
                                       "column": 21,
                                       "file": "demo.c",
                                       "line": 8
                                   },
                                   "start": {
                                       "column": 15,
                                       "file": "demo.c",
                                       "line": 8
                                   },
                                   "string": "color"
                               }
                           ],
                           "kind": "error",
                           "locations": [
                               {
                                   "caret": {
                                       "column": 15,
                                       "file": "demo.c",
                                       "line": 8
                                   },
                                   "finish": {
                                       "column": 20,
                                       "file": "demo.c",
                                       "line": 8
                                   }
                               }
                           ],
                           "message": "\u2018struct s\u2019 has no member named ..."
                       }

           where the fix-it hint suggests replacing the text from "start" up to but not including
           "next" with "string"'s value.  Deletions are expressed via an empty value for "string",
           insertions by having "start" equal "next".

           If the diagnostic has a path of control-flow events associated with it, it has a "path"
           array of objects representing the events.  Each event object has a "description" string,
           a "location" object, along with a "function" string and a "depth" number for representing
           interprocedural paths.  The "function" represents the current function at that event, and
           the "depth" represents the stack depth relative to some baseline: the higher, the more
           frames are within the stack.

           For example, the intraprocedural example shown for -fdiagnostics-path-format= might have
           this JSON for its path:

                       "path": [
                           {
                               "depth": 0,
                               "description": "when 'PyList_New' fails, returning NULL",
                               "function": "test",
                               "location": {
                                   "column": 10,
                                   "file": "test.c",
                                   "line": 25
                               }
                           },
                           {
                               "depth": 0,
                               "description": "when 'i < count'",
                               "function": "test",
                               "location": {
                                   "column": 3,
                                   "file": "test.c",
                                   "line": 27
                               }
                           },
                           {
                               "depth": 0,
                               "description": "when calling 'PyList_Append', passing NULL from (1) as argument 1",
                               "function": "test",
                               "location": {
                                   "column": 5,
                                   "file": "test.c",
                                   "line": 29
                               }
                           }
                       ]

   Options to Request or Suppress Warnings
       Warnings are diagnostic messages that report constructions that are not inherently erroneous
       but that are risky or suggest there may have been an error.

       The following language-independent options do not enable specific warnings but control the
       kinds of diagnostics produced by GCC.

       -fsyntax-only
           Check the code for syntax errors, but don't do anything beyond that.

       -fmax-errors=n
           Limits the maximum number of error messages to n, at which point GCC bails out rather
           than attempting to continue processing the source code.  If n is 0 (the default), there
           is no limit on the number of error messages produced.  If -Wfatal-errors is also
           specified, then -Wfatal-errors takes precedence over this option.

       -w  Inhibit all warning messages.

       -Werror
           Make all warnings into errors.

       -Werror=
           Make the specified warning into an error.  The specifier for a warning is appended; for
           example -Werror=switch turns the warnings controlled by -Wswitch into errors.  This
           switch takes a negative form, to be used to negate -Werror for specific warnings; for
           example -Wno-error=switch makes -Wswitch warnings not be errors, even when -Werror is in
           effect.

           The warning message for each controllable warning includes the option that controls the
           warning.  That option can then be used with -Werror= and -Wno-error= as described above.
           (Printing of the option in the warning message can be disabled using the
           -fno-diagnostics-show-option flag.)

           Note that specifying -Werror=foo automatically implies -Wfoo.  However, -Wno-error=foo
           does not imply anything.

       -Wfatal-errors
           This option causes the compiler to abort compilation on the first error occurred rather
           than trying to keep going and printing further error messages.

       You can request many specific warnings with options beginning with -W, for example -Wimplicit
       to request warnings on implicit declarations.  Each of these specific warning options also
       has a negative form beginning -Wno- to turn off warnings; for example, -Wno-implicit.  This
       manual lists only one of the two forms, whichever is not the default.  For further language-
       specific options also refer to C++ Dialect Options and Objective-C and Objective-C++ Dialect
       Options.  Additional warnings can be produced by enabling the static analyzer;

       Some options, such as -Wall and -Wextra, turn on other options, such as -Wunused, which may
       turn on further options, such as -Wunused-value. The combined effect of positive and negative
       forms is that more specific options have priority over less specific ones, independently of
       their position in the command-line. For options of the same specificity, the last one takes
       effect. Options enabled or disabled via pragmas take effect as if they appeared at the end of
       the command-line.

       When an unrecognized warning option is requested (e.g., -Wunknown-warning), GCC emits a
       diagnostic stating that the option is not recognized.  However, if the -Wno- form is used,
       the behavior is slightly different: no diagnostic is produced for -Wno-unknown-warning unless
       other diagnostics are being produced.  This allows the use of new -Wno- options with old
       compilers, but if something goes wrong, the compiler warns that an unrecognized option is
       present.

       The effectiveness of some warnings depends on optimizations also being enabled. For example
       -Wsuggest-final-types is more effective with link-time optimization and -Wmaybe-uninitialized
       does not warn at all unless optimization is enabled.

       -Wpedantic
       -pedantic
           Issue all the warnings demanded by strict ISO C and ISO C++; reject all programs that use
           forbidden extensions, and some other programs that do not follow ISO C and ISO C++.  For
           ISO C, follows the version of the ISO C standard specified by any -std option used.

           Valid ISO C and ISO C++ programs should compile properly with or without this option
           (though a rare few require -ansi or a -std option specifying the required version of ISO
           C).  However, without this option, certain GNU extensions and traditional C and C++
           features are supported as well.  With this option, they are rejected.

           -Wpedantic does not cause warning messages for use of the alternate keywords whose names
           begin and end with __.  This alternate format can also be used to disable warnings for
           non-ISO __intN types, i.e. __intN__.  Pedantic warnings are also disabled in the
           expression that follows "__extension__".  However, only system header files should use
           these escape routes; application programs should avoid them.

           Some users try to use -Wpedantic to check programs for strict ISO C conformance.  They
           soon find that it does not do quite what they want: it finds some non-ISO practices, but
           not all---only those for which ISO C requires a diagnostic, and some others for which
           diagnostics have been added.

           A feature to report any failure to conform to ISO C might be useful in some instances,
           but would require considerable additional work and would be quite different from
           -Wpedantic.  We don't have plans to support such a feature in the near future.

           Where the standard specified with -std represents a GNU extended dialect of C, such as
           gnu90 or gnu99, there is a corresponding base standard, the version of ISO C on which the
           GNU extended dialect is based.  Warnings from -Wpedantic are given where they are
           required by the base standard.  (It does not make sense for such warnings to be given
           only for features not in the specified GNU C dialect, since by definition the GNU
           dialects of C include all features the compiler supports with the given option, and there
           would be nothing to warn about.)

       -pedantic-errors
           Give an error whenever the base standard (see -Wpedantic) requires a diagnostic, in some
           cases where there is undefined behavior at compile-time and in some other cases that do
           not prevent compilation of programs that are valid according to the standard. This is not
           equivalent to -Werror=pedantic, since there are errors enabled by this option and not
           enabled by the latter and vice versa.

       -Wall
           This enables all the warnings about constructions that some users consider questionable,
           and that are easy to avoid (or modify to prevent the warning), even in conjunction with
           macros.  This also enables some language-specific warnings described in C++ Dialect
           Options and Objective-C and Objective-C++ Dialect Options.

           -Wall turns on the following warning flags:

           -Waddress -Warray-bounds=1 (only with -O2) -Warray-parameter=2 (C and Objective-C only)
           -Wbool-compare -Wbool-operation -Wc++11-compat  -Wc++14-compat -Wcatch-value (C++ and
           Objective-C++ only) -Wchar-subscripts -Wcomment -Wduplicate-decl-specifier (C and
           Objective-C only) -Wenum-compare (in C/ObjC; this is on by default in C++) -Wformat
           -Wformat-overflow -Wformat-truncation -Wint-in-bool-context -Wimplicit (C and Objective-C
           only) -Wimplicit-int (C and Objective-C only) -Wimplicit-function-declaration (C and
           Objective-C only) -Winit-self (only for C++) -Wlogical-not-parentheses -Wmain (only for
           C/ObjC and unless -ffreestanding) -Wmaybe-uninitialized -Wmemset-elt-size
           -Wmemset-transposed-args -Wmisleading-indentation (only for C/C++) -Wmissing-attributes
           -Wmissing-braces (only for C/ObjC) -Wmultistatement-macros -Wnarrowing (only for C++)
           -Wnonnull -Wnonnull-compare -Wopenmp-simd -Wparentheses -Wpessimizing-move (only for C++)
           -Wpointer-sign -Wrange-loop-construct (only for C++) -Wreorder -Wrestrict -Wreturn-type
           -Wsequence-point -Wsign-compare (only in C++) -Wsizeof-array-div -Wsizeof-pointer-div
           -Wsizeof-pointer-memaccess -Wstrict-aliasing -Wstrict-overflow=1 -Wswitch
           -Wtautological-compare -Wtrigraphs -Wuninitialized -Wunknown-pragmas -Wunused-function
           -Wunused-label -Wunused-value -Wunused-variable -Wvla-parameter (C and Objective-C only)
           -Wvolatile-register-var -Wzero-length-bounds

           Note that some warning flags are not implied by -Wall.  Some of them warn about
           constructions that users generally do not consider questionable, but which occasionally
           you might wish to check for; others warn about constructions that are necessary or hard
           to avoid in some cases, and there is no simple way to modify the code to suppress the
           warning. Some of them are enabled by -Wextra but many of them must be enabled
           individually.

       -Wextra
           This enables some extra warning flags that are not enabled by -Wall. (This option used to
           be called -W.  The older name is still supported, but the newer name is more
           descriptive.)

           -Wclobbered -Wcast-function-type -Wdeprecated-copy (C++ only) -Wempty-body
           -Wenum-conversion (C only) -Wignored-qualifiers -Wimplicit-fallthrough=3
           -Wmissing-field-initializers -Wmissing-parameter-type (C only) -Wold-style-declaration (C
           only) -Woverride-init -Wsign-compare (C only) -Wstring-compare -Wredundant-move (only for
           C++) -Wtype-limits -Wuninitialized -Wshift-negative-value (in C++11 to C++17 and in C99
           and newer) -Wunused-parameter (only with -Wunused or -Wall) -Wunused-but-set-parameter
           (only with -Wunused or -Wall)

           The option -Wextra also prints warning messages for the following cases:

           *   A pointer is compared against integer zero with "<", "<=", ">", or ">=".

           *   (C++ only) An enumerator and a non-enumerator both appear in a conditional
               expression.

           *   (C++ only) Ambiguous virtual bases.

           *   (C++ only) Subscripting an array that has been declared "register".

           *   (C++ only) Taking the address of a variable that has been declared "register".

           *   (C++ only) A base class is not initialized in the copy constructor of a derived
               class.

       -Wabi (C, Objective-C, C++ and Objective-C++ only)
           Warn about code affected by ABI changes.  This includes code that may not be compatible
           with the vendor-neutral C++ ABI as well as the psABI for the particular target.

           Since G++ now defaults to updating the ABI with each major release, normally -Wabi warns
           only about C++ ABI compatibility problems if there is a check added later in a release
           series for an ABI issue discovered since the initial release.  -Wabi warns about more
           things if an older ABI version is selected (with -fabi-version=n).

           -Wabi can also be used with an explicit version number to warn about C++ ABI
           compatibility with a particular -fabi-version level, e.g. -Wabi=2 to warn about changes
           relative to -fabi-version=2.

           If an explicit version number is provided and -fabi-compat-version is not specified, the
           version number from this option is used for compatibility aliases.  If no explicit
           version number is provided with this option, but -fabi-compat-version is specified, that
           version number is used for C++ ABI warnings.

           Although an effort has been made to warn about all such cases, there are probably some
           cases that are not warned about, even though G++ is generating incompatible code.  There
           may also be cases where warnings are emitted even though the code that is generated is
           compatible.

           You should rewrite your code to avoid these warnings if you are concerned about the fact
           that code generated by G++ may not be binary compatible with code generated by other
           compilers.

           Known incompatibilities in -fabi-version=2 (which was the default from GCC 3.4 to 4.9)
           include:

           *   A template with a non-type template parameter of reference type was mangled
               incorrectly:

                       extern int N;
                       template <int &> struct S {};
                       void n (S<N>) {2}

               This was fixed in -fabi-version=3.

           *   SIMD vector types declared using "__attribute ((vector_size))" were mangled in a non-
               standard way that does not allow for overloading of functions taking vectors of
               different sizes.

               The mangling was changed in -fabi-version=4.

           *   "__attribute ((const))" and "noreturn" were mangled as type qualifiers, and
               "decltype" of a plain declaration was folded away.

               These mangling issues were fixed in -fabi-version=5.

           *   Scoped enumerators passed as arguments to a variadic function are promoted like
               unscoped enumerators, causing "va_arg" to complain.  On most targets this does not
               actually affect the parameter passing ABI, as there is no way to pass an argument
               smaller than "int".

               Also, the ABI changed the mangling of template argument packs, "const_cast",
               "static_cast", prefix increment/decrement, and a class scope function used as a
               template argument.

               These issues were corrected in -fabi-version=6.

           *   Lambdas in default argument scope were mangled incorrectly, and the ABI changed the
               mangling of "nullptr_t".

               These issues were corrected in -fabi-version=7.

           *   When mangling a function type with function-cv-qualifiers, the un-qualified function
               type was incorrectly treated as a substitution candidate.

               This was fixed in -fabi-version=8, the default for GCC 5.1.

           *   "decltype(nullptr)" incorrectly had an alignment of 1, leading to unaligned accesses.
               Note that this did not affect the ABI of a function with a "nullptr_t" parameter, as
               parameters have a minimum alignment.

               This was fixed in -fabi-version=9, the default for GCC 5.2.

           *   Target-specific attributes that affect the identity of a type, such as ia32 calling
               conventions on a function type (stdcall, regparm, etc.), did not affect the mangled
               name, leading to name collisions when function pointers were used as template
               arguments.

               This was fixed in -fabi-version=10, the default for GCC 6.1.

           This option also enables warnings about psABI-related changes.  The known psABI changes
           at this point include:

           *   For SysV/x86-64, unions with "long double" members are passed in memory as specified
               in psABI.  Prior to GCC 4.4, this was not the case.  For example:

                       union U {
                         long double ld;
                         int i;
                       };

               "union U" is now always passed in memory.

       -Wchar-subscripts
           Warn if an array subscript has type "char".  This is a common cause of error, as
           programmers often forget that this type is signed on some machines.  This warning is
           enabled by -Wall.

       -Wno-coverage-mismatch
           Warn if feedback profiles do not match when using the -fprofile-use option.  If a source
           file is changed between compiling with -fprofile-generate and with -fprofile-use, the
           files with the profile feedback can fail to match the source file and GCC cannot use the
           profile feedback information.  By default, this warning is enabled and is treated as an
           error.  -Wno-coverage-mismatch can be used to disable the warning or
           -Wno-error=coverage-mismatch can be used to disable the error.  Disabling the error for
           this warning can result in poorly optimized code and is useful only in the case of very
           minor changes such as bug fixes to an existing code-base.  Completely disabling the
           warning is not recommended.

       -Wno-cpp
           (C, Objective-C, C++, Objective-C++ and Fortran only) Suppress warning messages emitted
           by "#warning" directives.

       -Wdouble-promotion (C, C++, Objective-C and Objective-C++ only)
           Give a warning when a value of type "float" is implicitly promoted to "double".  CPUs
           with a 32-bit "single-precision" floating-point unit implement "float" in hardware, but
           emulate "double" in software.  On such a machine, doing computations using "double"
           values is much more expensive because of the overhead required for software emulation.

           It is easy to accidentally do computations with "double" because floating-point literals
           are implicitly of type "double".  For example, in:

                   float area(float radius)
                   {
                      return 3.14159 * radius * radius;
                   }

           the compiler performs the entire computation with "double" because the floating-point
           literal is a "double".

       -Wduplicate-decl-specifier (C and Objective-C only)
           Warn if a declaration has duplicate "const", "volatile", "restrict" or "_Atomic"
           specifier.  This warning is enabled by -Wall.

       -Wformat
       -Wformat=n
           Check calls to "printf" and "scanf", etc., to make sure that the arguments supplied have
           types appropriate to the format string specified, and that the conversions specified in
           the format string make sense.  This includes standard functions, and others specified by
           format attributes, in the "printf", "scanf", "strftime" and "strfmon" (an X/Open
           extension, not in the C standard) families (or other target-specific families).  Which
           functions are checked without format attributes having been specified depends on the
           standard version selected, and such checks of functions without the attribute specified
           are disabled by -ffreestanding or -fno-builtin.

           The formats are checked against the format features supported by GNU libc version 2.2.
           These include all ISO C90 and C99 features, as well as features from the Single Unix
           Specification and some BSD and GNU extensions.  Other library implementations may not
           support all these features; GCC does not support warning about features that go beyond a
           particular library's limitations.  However, if -Wpedantic is used with -Wformat, warnings
           are given about format features not in the selected standard version (but not for
           "strfmon" formats, since those are not in any version of the C standard).

           -Wformat=1
           -Wformat
               Option -Wformat is equivalent to -Wformat=1, and -Wno-format is equivalent to
               -Wformat=0.  Since -Wformat also checks for null format arguments for several
               functions, -Wformat also implies -Wnonnull.  Some aspects of this level of format
               checking can be disabled by the options: -Wno-format-contains-nul,
               -Wno-format-extra-args, and -Wno-format-zero-length.  -Wformat is enabled by -Wall.

           -Wformat=2
               Enable -Wformat plus additional format checks.  Currently equivalent to -Wformat
               -Wformat-nonliteral -Wformat-security -Wformat-y2k.

       -Wno-format-contains-nul
           If -Wformat is specified, do not warn about format strings that contain NUL bytes.

       -Wno-format-extra-args
           If -Wformat is specified, do not warn about excess arguments to a "printf" or "scanf"
           format function.  The C standard specifies that such arguments are ignored.

           Where the unused arguments lie between used arguments that are specified with $ operand
           number specifications, normally warnings are still given, since the implementation could
           not know what type to pass to "va_arg" to skip the unused arguments.  However, in the
           case of "scanf" formats, this option suppresses the warning if the unused arguments are
           all pointers, since the Single Unix Specification says that such unused arguments are
           allowed.

       -Wformat-overflow
       -Wformat-overflow=level
           Warn about calls to formatted input/output functions such as "sprintf" and "vsprintf"
           that might overflow the destination buffer.  When the exact number of bytes written by a
           format directive cannot be determined at compile-time it is estimated based on heuristics
           that depend on the level argument and on optimization.  While enabling optimization will
           in most cases improve the accuracy of the warning, it may also result in false positives.

           -Wformat-overflow
           -Wformat-overflow=1
               Level 1 of -Wformat-overflow enabled by -Wformat employs a conservative approach that
               warns only about calls that most likely overflow the buffer.  At this level, numeric
               arguments to format directives with unknown values are assumed to have the value of
               one, and strings of unknown length to be empty.  Numeric arguments that are known to
               be bounded to a subrange of their type, or string arguments whose output is bounded
               either by their directive's precision or by a finite set of string literals, are
               assumed to take on the value within the range that results in the most bytes on
               output.  For example, the call to "sprintf" below is diagnosed because even with both
               a and b equal to zero, the terminating NUL character ('\0') appended by the function
               to the destination buffer will be written past its end.  Increasing the size of the
               buffer by a single byte is sufficient to avoid the warning, though it may not be
               sufficient to avoid the overflow.

                       void f (int a, int b)
                       {
                         char buf [13];
                         sprintf (buf, "a = %i, b = %i\n", a, b);
                       }

           -Wformat-overflow=2
               Level 2 warns also about calls that might overflow the destination buffer given an
               argument of sufficient length or magnitude.  At level 2, unknown numeric arguments
               are assumed to have the minimum representable value for signed types with a precision
               greater than 1, and the maximum representable value otherwise.  Unknown string
               arguments whose length cannot be assumed to be bounded either by the directive's
               precision, or by a finite set of string literals they may evaluate to, or the
               character array they may point to, are assumed to be 1 character long.

               At level 2, the call in the example above is again diagnosed, but this time because
               with a equal to a 32-bit "INT_MIN" the first %i directive will write some of its
               digits beyond the end of the destination buffer.  To make the call safe regardless of
               the values of the two variables, the size of the destination buffer must be increased
               to at least 34 bytes.  GCC includes the minimum size of the buffer in an
               informational note following the warning.

               An alternative to increasing the size of the destination buffer is to constrain the
               range of formatted values.  The maximum length of string arguments can be bounded by
               specifying the precision in the format directive.  When numeric arguments of format
               directives can be assumed to be bounded by less than the precision of their type,
               choosing an appropriate length modifier to the format specifier will reduce the
               required buffer size.  For example, if a and b in the example above can be assumed to
               be within the precision of the "short int" type then using either the %hi format
               directive or casting the argument to "short" reduces the maximum required size of the
               buffer to 24 bytes.

                       void f (int a, int b)
                       {
                         char buf [23];
                         sprintf (buf, "a = %hi, b = %i\n", a, (short)b);
                       }

       -Wno-format-zero-length
           If -Wformat is specified, do not warn about zero-length formats.  The C standard
           specifies that zero-length formats are allowed.

       -Wformat-nonliteral
           If -Wformat is specified, also warn if the format string is not a string literal and so
           cannot be checked, unless the format function takes its format arguments as a "va_list".

       -Wformat-security
           If -Wformat is specified, also warn about uses of format functions that represent
           possible security problems.  At present, this warns about calls to "printf" and "scanf"
           functions where the format string is not a string literal and there are no format
           arguments, as in "printf (foo);".  This may be a security hole if the format string came
           from untrusted input and contains %n.  (This is currently a subset of what
           -Wformat-nonliteral warns about, but in future warnings may be added to -Wformat-security
           that are not included in -Wformat-nonliteral.)

       -Wformat-signedness
           If -Wformat is specified, also warn if the format string requires an unsigned argument
           and the argument is signed and vice versa.

       -Wformat-truncation
       -Wformat-truncation=level
           Warn about calls to formatted input/output functions such as "snprintf" and "vsnprintf"
           that might result in output truncation.  When the exact number of bytes written by a
           format directive cannot be determined at compile-time it is estimated based on heuristics
           that depend on the level argument and on optimization.  While enabling optimization will
           in most cases improve the accuracy of the warning, it may also result in false positives.
           Except as noted otherwise, the option uses the same logic -Wformat-overflow.

           -Wformat-truncation
           -Wformat-truncation=1
               Level 1 of -Wformat-truncation enabled by -Wformat employs a conservative approach
               that warns only about calls to bounded functions whose return value is unused and
               that will most likely result in output truncation.

           -Wformat-truncation=2
               Level 2 warns also about calls to bounded functions whose return value is used and
               that might result in truncation given an argument of sufficient length or magnitude.

       -Wformat-y2k
           If -Wformat is specified, also warn about "strftime" formats that may yield only a two-
           digit year.

       -Wnonnull
           Warn about passing a null pointer for arguments marked as requiring a non-null value by
           the "nonnull" function attribute.

           -Wnonnull is included in -Wall and -Wformat.  It can be disabled with the -Wno-nonnull
           option.

       -Wnonnull-compare
           Warn when comparing an argument marked with the "nonnull" function attribute against null
           inside the function.

           -Wnonnull-compare is included in -Wall.  It can be disabled with the -Wno-nonnull-compare
           option.

       -Wnull-dereference
           Warn if the compiler detects paths that trigger erroneous or undefined behavior due to
           dereferencing a null pointer.  This option is only active when
           -fdelete-null-pointer-checks is active, which is enabled by optimizations in most
           targets.  The precision of the warnings depends on the optimization options used.

       -Winit-self (C, C++, Objective-C and Objective-C++ only)
           Warn about uninitialized variables that are initialized with themselves.  Note this
           option can only be used with the -Wuninitialized option.

           For example, GCC warns about "i" being uninitialized in the following snippet only when
           -Winit-self has been specified:

                   int f()
                   {
                     int i = i;
                     return i;
                   }

           This warning is enabled by -Wall in C++.

       -Wno-implicit-int (C and Objective-C only)
           This option controls warnings when a declaration does not specify a type.  This warning
           is enabled by default in C99 and later dialects of C, and also by -Wall.

       -Wno-implicit-function-declaration (C and Objective-C only)
           This option controls warnings when a function is used before being declared.  This
           warning is enabled by default in C99 and later dialects of C, and also by -Wall.  The
           warning is made into an error by -pedantic-errors.

       -Wimplicit (C and Objective-C only)
           Same as -Wimplicit-int and -Wimplicit-function-declaration.  This warning is enabled by
           -Wall.

       -Wimplicit-fallthrough
           -Wimplicit-fallthrough is the same as -Wimplicit-fallthrough=3 and
           -Wno-implicit-fallthrough is the same as -Wimplicit-fallthrough=0.

       -Wimplicit-fallthrough=n
           Warn when a switch case falls through.  For example:

                   switch (cond)
                     {
                     case 1:
                       a = 1;
                       break;
                     case 2:
                       a = 2;
                     case 3:
                       a = 3;
                       break;
                     }

           This warning does not warn when the last statement of a case cannot fall through, e.g.
           when there is a return statement or a call to function declared with the noreturn
           attribute.  -Wimplicit-fallthrough= also takes into account control flow statements, such
           as ifs, and only warns when appropriate.  E.g.

                   switch (cond)
                     {
                     case 1:
                       if (i > 3) {
                         bar (5);
                         break;
                       } else if (i < 1) {
                         bar (0);
                       } else
                         return;
                     default:
                       ...
                     }

           Since there are occasions where a switch case fall through is desirable, GCC provides an
           attribute, "__attribute__ ((fallthrough))", that is to be used along with a null
           statement to suppress this warning that would normally occur:

                   switch (cond)
                     {
                     case 1:
                       bar (0);
                       __attribute__ ((fallthrough));
                     default:
                       ...
                     }

           C++17 provides a standard way to suppress the -Wimplicit-fallthrough warning using
           "[[fallthrough]];" instead of the GNU attribute.  In C++11 or C++14 users can use
           "[[gnu::fallthrough]];", which is a GNU extension.  Instead of these attributes, it is
           also possible to add a fallthrough comment to silence the warning.  The whole body of the
           C or C++ style comment should match the given regular expressions listed below.  The
           option argument n specifies what kind of comments are accepted:

           *<-Wimplicit-fallthrough=0 disables the warning altogether.>
           *<-Wimplicit-fallthrough=1 matches ".*" regular>
               expression, any comment is used as fallthrough comment.

           *<-Wimplicit-fallthrough=2 case insensitively matches>
               ".*falls?[ \t-]*thr(ough|u).*" regular expression.

           *<-Wimplicit-fallthrough=3 case sensitively matches one of the>
               following regular expressions:

               *<"-fallthrough">
               *<"@fallthrough@">
               *<"lint -fallthrough[ \t]*">
               *<"[ \t.!]*(ELSE,? |INTENTIONAL(LY)? )?FALL(S | |-)?THR(OUGH|U)[ \t.!]*(-[^\n\r]*)?">
               *<"[ \t.!]*(Else,? |Intentional(ly)? )?Fall((s | |-)[Tt]|t)hr(ough|u)[
               \t.!]*(-[^\n\r]*)?">
               *<"[ \t.!]*([Ee]lse,? |[Ii]ntentional(ly)? )?fall(s | |-)?thr(ough|u)[
               \t.!]*(-[^\n\r]*)?">
           *<-Wimplicit-fallthrough=4 case sensitively matches one of the>
               following regular expressions:

               *<"-fallthrough">
               *<"@fallthrough@">
               *<"lint -fallthrough[ \t]*">
               *<"[ \t]*FALLTHR(OUGH|U)[ \t]*">
           *<-Wimplicit-fallthrough=5 doesn't recognize any comments as>
               fallthrough comments, only attributes disable the warning.

           The comment needs to be followed after optional whitespace and other comments by "case"
           or "default" keywords or by a user label that precedes some "case" or "default" label.

                   switch (cond)
                     {
                     case 1:
                       bar (0);
                       /* FALLTHRU */
                     default:
                       ...
                     }

           The -Wimplicit-fallthrough=3 warning is enabled by -Wextra.

       -Wno-if-not-aligned (C, C++, Objective-C and Objective-C++ only)
           Control if warnings triggered by the "warn_if_not_aligned" attribute should be issued.
           These warnings are enabled by default.

       -Wignored-qualifiers (C and C++ only)
           Warn if the return type of a function has a type qualifier such as "const".  For ISO C
           such a type qualifier has no effect, since the value returned by a function is not an
           lvalue.  For C++, the warning is only emitted for scalar types or "void".  ISO C
           prohibits qualified "void" return types on function definitions, so such return types
           always receive a warning even without this option.

           This warning is also enabled by -Wextra.

       -Wno-ignored-attributes (C and C++ only)
           This option controls warnings when an attribute is ignored.  This is different from the
           -Wattributes option in that it warns whenever the compiler decides to drop an attribute,
           not that the attribute is either unknown, used in a wrong place, etc.  This warning is
           enabled by default.

       -Wmain
           Warn if the type of "main" is suspicious.  "main" should be a function with external
           linkage, returning int, taking either zero arguments, two, or three arguments of
           appropriate types.  This warning is enabled by default in C++ and is enabled by either
           -Wall or -Wpedantic.

       -Wmisleading-indentation (C and C++ only)
           Warn when the indentation of the code does not reflect the block structure.
           Specifically, a warning is issued for "if", "else", "while", and "for" clauses with a
           guarded statement that does not use braces, followed by an unguarded statement with the
           same indentation.

           In the following example, the call to "bar" is misleadingly indented as if it were
           guarded by the "if" conditional.

                     if (some_condition ())
                       foo ();
                       bar ();  /* Gotcha: this is not guarded by the "if".  */

           In the case of mixed tabs and spaces, the warning uses the -ftabstop= option to determine
           if the statements line up (defaulting to 8).

           The warning is not issued for code involving multiline preprocessor logic such as the
           following example.

                     if (flagA)
                       foo (0);
                   #if SOME_CONDITION_THAT_DOES_NOT_HOLD
                     if (flagB)
                   #endif
                       foo (1);

           The warning is not issued after a "#line" directive, since this typically indicates
           autogenerated code, and no assumptions can be made about the layout of the file that the
           directive references.

           This warning is enabled by -Wall in C and C++.

       -Wmissing-attributes
           Warn when a declaration of a function is missing one or more attributes that a related
           function is declared with and whose absence may adversely affect the correctness or
           efficiency of generated code.  For example, the warning is issued for declarations of
           aliases that use attributes to specify less restrictive requirements than those of their
           targets.  This typically represents a potential optimization opportunity.  By contrast,
           the -Wattribute-alias=2 option controls warnings issued when the alias is more
           restrictive than the target, which could lead to incorrect code generation.  Attributes
           considered include "alloc_align", "alloc_size", "cold", "const", "hot", "leaf", "malloc",
           "nonnull", "noreturn", "nothrow", "pure", "returns_nonnull", and "returns_twice".

           In C++, the warning is issued when an explicit specialization of a primary template
           declared with attribute "alloc_align", "alloc_size", "assume_aligned", "format",
           "format_arg", "malloc", or "nonnull" is declared without it.  Attributes "deprecated",
           "error", and "warning" suppress the warning..

           You can use the "copy" attribute to apply the same set of attributes to a declaration as
           that on another declaration without explicitly enumerating the attributes. This attribute
           can be applied to declarations of functions, variables, or types.

           -Wmissing-attributes is enabled by -Wall.

           For example, since the declaration of the primary function template below makes use of
           both attribute "malloc" and "alloc_size" the declaration of the explicit specialization
           of the template is diagnosed because it is missing one of the attributes.

                   template <class T>
                   T* __attribute__ ((malloc, alloc_size (1)))
                   allocate (size_t);

                   template <>
                   void* __attribute__ ((malloc))   // missing alloc_size
                   allocate<void> (size_t);

       -Wmissing-braces
           Warn if an aggregate or union initializer is not fully bracketed.  In the following
           example, the initializer for "a" is not fully bracketed, but that for "b" is fully
           bracketed.

                   int a[2][2] = { 0, 1, 2, 3 };
                   int b[2][2] = { { 0, 1 }, { 2, 3 } };

           This warning is enabled by -Wall.

       -Wmissing-include-dirs (C, C++, Objective-C and Objective-C++ only)
           Warn if a user-supplied include directory does not exist.

       -Wno-missing-profile
           This option controls warnings if feedback profiles are missing when using the
           -fprofile-use option.  This option diagnoses those cases where a new function or a new
           file is added between compiling with -fprofile-generate and with -fprofile-use, without
           regenerating the profiles.  In these cases, the profile feedback data files do not
           contain any profile feedback information for the newly added function or file
           respectively.  Also, in the case when profile count data (.gcda) files are removed, GCC
           cannot use any profile feedback information.  In all these cases, warnings are issued to
           inform you that a profile generation step is due.  Ignoring the warning can result in
           poorly optimized code.  -Wno-missing-profile can be used to disable the warning, but this
           is not recommended and should be done only when non-existent profile data is justified.

       -Wno-mismatched-dealloc
           Warn for calls to deallocation functions with pointer arguments returned from from
           allocations functions for which the former isn't a suitable deallocator.  A pair of
           functions can be associated as matching allocators and deallocators by use of attribute
           "malloc".  Unless disabled by the -fno-builtin option the standard functions "calloc",
           "malloc", "realloc", and "free", as well as the corresponding forms of C++ "operator new"
           and "operator delete" are implicitly associated as matching allocators and deallocators.
           In the following example "mydealloc" is the deallocator for pointers returned from
           "myalloc".

                   void mydealloc (void*);

                   __attribute__ ((malloc (mydealloc, 1))) void*
                   myalloc (size_t);

                   void f (void)
                   {
                     void *p = myalloc (32);
                     // ...use p...
                     free (p);   // warning: not a matching deallocator for myalloc
                     mydealloc (p);   // ok
                   }

           In C++, the related option -Wmismatched-new-delete diagnoses mismatches involving either
           "operator new" or "operator delete".

           Option -Wmismatched-dealloc is enabled by default.

       -Wmultistatement-macros
           Warn about unsafe multiple statement macros that appear to be guarded by a clause such as
           "if", "else", "for", "switch", or "while", in which only the first statement is actually
           guarded after the macro is expanded.

           For example:

                   #define DOIT x++; y++
                   if (c)
                     DOIT;

           will increment "y" unconditionally, not just when "c" holds.  The can usually be fixed by
           wrapping the macro in a do-while loop:

                   #define DOIT do { x++; y++; } while (0)
                   if (c)
                     DOIT;

           This warning is enabled by -Wall in C and C++.

       -Wparentheses
           Warn if parentheses are omitted in certain contexts, such as when there is an assignment
           in a context where a truth value is expected, or when operators are nested whose
           precedence people often get confused about.

           Also warn if a comparison like "x<=y<=z" appears; this is equivalent to "(x<=y ? 1 : 0)
           <= z", which is a different interpretation from that of ordinary mathematical notation.

           Also warn for dangerous uses of the GNU extension to "?:" with omitted middle operand.
           When the condition in the "?": operator is a boolean expression, the omitted value is
           always 1.  Often programmers expect it to be a value computed inside the conditional
           expression instead.

           For C++ this also warns for some cases of unnecessary parentheses in declarations, which
           can indicate an attempt at a function call instead of a declaration:

                   {
                     // Declares a local variable called mymutex.
                     std::unique_lock<std::mutex> (mymutex);
                     // User meant std::unique_lock<std::mutex> lock (mymutex);
                   }

           This warning is enabled by -Wall.

       -Wsequence-point
           Warn about code that may have undefined semantics because of violations of sequence point
           rules in the C and C++ standards.

           The C and C++ standards define the order in which expressions in a C/C++ program are
           evaluated in terms of sequence points, which represent a partial ordering between the
           execution of parts of the program: those executed before the sequence point, and those
           executed after it.  These occur after the evaluation of a full expression (one which is
           not part of a larger expression), after the evaluation of the first operand of a "&&",
           "||", "? :" or "," (comma) operator, before a function is called (but after the
           evaluation of its arguments and the expression denoting the called function), and in
           certain other places.  Other than as expressed by the sequence point rules, the order of
           evaluation of subexpressions of an expression is not specified.  All these rules describe
           only a partial order rather than a total order, since, for example, if two functions are
           called within one expression with no sequence point between them, the order in which the
           functions are called is not specified.  However, the standards committee have ruled that
           function calls do not overlap.

           It is not specified when between sequence points modifications to the values of objects
           take effect.  Programs whose behavior depends on this have undefined behavior; the C and
           C++ standards specify that "Between the previous and next sequence point an object shall
           have its stored value modified at most once by the evaluation of an expression.
           Furthermore, the prior value shall be read only to determine the value to be stored.".
           If a program breaks these rules, the results on any particular implementation are
           entirely unpredictable.

           Examples of code with undefined behavior are "a = a++;", "a[n] = b[n++]" and "a[i++] =
           i;".  Some more complicated cases are not diagnosed by this option, and it may give an
           occasional false positive result, but in general it has been found fairly effective at
           detecting this sort of problem in programs.

           The C++17 standard will define the order of evaluation of operands in more cases: in
           particular it requires that the right-hand side of an assignment be evaluated before the
           left-hand side, so the above examples are no longer undefined.  But this option will
           still warn about them, to help people avoid writing code that is undefined in C and
           earlier revisions of C++.

           The standard is worded confusingly, therefore there is some debate over the precise
           meaning of the sequence point rules in subtle cases.  Links to discussions of the
           problem, including proposed formal definitions, may be found on the GCC readings page, at
           <http://gcc.gnu.org/readings.html>.

           This warning is enabled by -Wall for C and C++.

       -Wno-return-local-addr
           Do not warn about returning a pointer (or in C++, a reference) to a variable that goes
           out of scope after the function returns.

       -Wreturn-type
           Warn whenever a function is defined with a return type that defaults to "int".  Also warn
           about any "return" statement with no return value in a function whose return type is not
           "void" (falling off the end of the function body is considered returning without a
           value).

           For C only, warn about a "return" statement with an expression in a function whose return
           type is "void", unless the expression type is also "void".  As a GNU extension, the
           latter case is accepted without a warning unless -Wpedantic is used.  Attempting to use
           the return value of a non-"void" function other than "main" that flows off the end by
           reaching the closing curly brace that terminates the function is undefined.

           Unlike in C, in C++, flowing off the end of a non-"void" function other than "main"
           results in undefined behavior even when the value of the function is not used.

           This warning is enabled by default in C++ and by -Wall otherwise.

       -Wno-shift-count-negative
           Controls warnings if a shift count is negative.  This warning is enabled by default.

       -Wno-shift-count-overflow
           Controls warnings if a shift count is greater than or equal to the bit width of the type.
           This warning is enabled by default.

       -Wshift-negative-value
           Warn if left shifting a negative value.  This warning is enabled by -Wextra in C99 (and
           newer) and C++11 to C++17 modes.

       -Wno-shift-overflow
       -Wshift-overflow=n
           These options control warnings about left shift overflows.

           -Wshift-overflow=1
               This is the warning level of -Wshift-overflow and is enabled by default in C99 and
               C++11 modes (and newer).  This warning level does not warn about left-shifting 1 into
               the sign bit.  (However, in C, such an overflow is still rejected in contexts where
               an integer constant expression is required.)  No warning is emitted in C++20 mode
               (and newer), as signed left shifts always wrap.

           -Wshift-overflow=2
               This warning level also warns about left-shifting 1 into the sign bit, unless C++14
               mode (or newer) is active.

       -Wswitch
           Warn whenever a "switch" statement has an index of enumerated type and lacks a "case" for
           one or more of the named codes of that enumeration.  (The presence of a "default" label
           prevents this warning.)  "case" labels outside the enumeration range also provoke
           warnings when this option is used (even if there is a "default" label).  This warning is
           enabled by -Wall.

       -Wswitch-default
           Warn whenever a "switch" statement does not have a "default" case.

       -Wswitch-enum
           Warn whenever a "switch" statement has an index of enumerated type and lacks a "case" for
           one or more of the named codes of that enumeration.  "case" labels outside the
           enumeration range also provoke warnings when this option is used.  The only difference
           between -Wswitch and this option is that this option gives a warning about an omitted
           enumeration code even if there is a "default" label.

       -Wno-switch-bool
           Do not warn when a "switch" statement has an index of boolean type and the case values
           are outside the range of a boolean type.  It is possible to suppress this warning by
           casting the controlling expression to a type other than "bool".  For example:

                   switch ((int) (a == 4))
                     {
                     ...
                     }

           This warning is enabled by default for C and C++ programs.

       -Wno-switch-outside-range
           This option controls warnings when a "switch" case has a value that is outside of its
           respective type range.  This warning is enabled by default for C and C++ programs.

       -Wno-switch-unreachable
           Do not warn when a "switch" statement contains statements between the controlling
           expression and the first case label, which will never be executed.  For example:

                   switch (cond)
                     {
                      i = 15;
                     ...
                      case 5:
                     ...
                     }

           -Wswitch-unreachable does not warn if the statement between the controlling expression
           and the first case label is just a declaration:

                   switch (cond)
                     {
                      int i;
                     ...
                      case 5:
                      i = 5;
                     ...
                     }

           This warning is enabled by default for C and C++ programs.

       -Wsync-nand (C and C++ only)
           Warn when "__sync_fetch_and_nand" and "__sync_nand_and_fetch" built-in functions are
           used.  These functions changed semantics in GCC 4.4.

       -Wunused-but-set-parameter
           Warn whenever a function parameter is assigned to, but otherwise unused (aside from its
           declaration).

           To suppress this warning use the "unused" attribute.

           This warning is also enabled by -Wunused together with -Wextra.

       -Wunused-but-set-variable
           Warn whenever a local variable is assigned to, but otherwise unused (aside from its
           declaration).  This warning is enabled by -Wall.

           To suppress this warning use the "unused" attribute.

           This warning is also enabled by -Wunused, which is enabled by -Wall.

       -Wunused-function
           Warn whenever a static function is declared but not defined or a non-inline static
           function is unused.  This warning is enabled by -Wall.

       -Wunused-label
           Warn whenever a label is declared but not used.  This warning is enabled by -Wall.

           To suppress this warning use the "unused" attribute.

       -Wunused-local-typedefs (C, Objective-C, C++ and Objective-C++ only)
           Warn when a typedef locally defined in a function is not used.  This warning is enabled
           by -Wall.

       -Wunused-parameter
           Warn whenever a function parameter is unused aside from its declaration.

           To suppress this warning use the "unused" attribute.

       -Wno-unused-result
           Do not warn if a caller of a function marked with attribute "warn_unused_result" does not
           use its return value. The default is -Wunused-result.

       -Wunused-variable
           Warn whenever a local or static variable is unused aside from its declaration. This
           option implies -Wunused-const-variable=1 for C, but not for C++. This warning is enabled
           by -Wall.

           To suppress this warning use the "unused" attribute.

       -Wunused-const-variable
       -Wunused-const-variable=n
           Warn whenever a constant static variable is unused aside from its declaration.
           -Wunused-const-variable=1 is enabled by -Wunused-variable for C, but not for C++. In C
           this declares variable storage, but in C++ this is not an error since const variables
           take the place of "#define"s.

           To suppress this warning use the "unused" attribute.

           -Wunused-const-variable=1
               This is the warning level that is enabled by -Wunused-variable for C.  It warns only
               about unused static const variables defined in the main compilation unit, but not
               about static const variables declared in any header included.

           -Wunused-const-variable=2
               This warning level also warns for unused constant static variables in headers
               (excluding system headers).  This is the warning level of -Wunused-const-variable and
               must be explicitly requested since in C++ this isn't an error and in C it might be
               harder to clean up all headers included.

       -Wunused-value
           Warn whenever a statement computes a result that is explicitly not used. To suppress this
           warning cast the unused expression to "void". This includes an expression-statement or
           the left-hand side of a comma expression that contains no side effects. For example, an
           expression such as "x[i,j]" causes a warning, while "x[(void)i,j]" does not.

           This warning is enabled by -Wall.

       -Wunused
           All the above -Wunused options combined.

           In order to get a warning about an unused function parameter, you must either specify
           -Wextra -Wunused (note that -Wall implies -Wunused), or separately specify
           -Wunused-parameter.

       -Wuninitialized
           Warn if an object with automatic or allocated storage duration is used without having
           been initialized.  In C++, also warn if a non-static reference or non-static "const"
           member appears in a class without constructors.

           In addition, passing a pointer (or in C++, a reference) to an uninitialized object to a
           "const"-qualified argument of a built-in function known to read the object is also
           diagnosed by this warning.  (-Wmaybe-uninitialized is issued for ordinary functions.)

           If you want to warn about code that uses the uninitialized value of the variable in its
           own initializer, use the -Winit-self option.

           These warnings occur for individual uninitialized elements of structure, union or array
           variables as well as for variables that are uninitialized as a whole.  They do not occur
           for variables or elements declared "volatile".  Because these warnings depend on
           optimization, the exact variables or elements for which there are warnings depend on the
           precise optimization options and version of GCC used.

           Note that there may be no warning about a variable that is used only to compute a value
           that itself is never used, because such computations may be deleted by data flow analysis
           before the warnings are printed.

       -Wno-invalid-memory-model
           This option controls warnings for invocations of __atomic Builtins, __sync Builtins, and
           the C11 atomic generic functions with a memory consistency argument that is either
           invalid for the operation or outside the range of values of the "memory_order"
           enumeration.  For example, since the "__atomic_store" and "__atomic_store_n" built-ins
           are only defined for the relaxed, release, and sequentially consistent memory orders the
           following code is diagnosed:

                   void store (int *i)
                   {
                     __atomic_store_n (i, 0, memory_order_consume);
                   }

           -Winvalid-memory-model is enabled by default.

       -Wmaybe-uninitialized
           For an object with automatic or allocated storage duration, if there exists a path from
           the function entry to a use of the object that is initialized, but there exist some other
           paths for which the object is not initialized, the compiler emits a warning if it cannot
           prove the uninitialized paths are not executed at run time.

           In addition, passing a pointer (or in C++, a reference) to an uninitialized object to a
           "const"-qualified function argument is also diagnosed by this warning.  (-Wuninitialized
           is issued for built-in functions known to read the object.)  Annotating the function with
           attribute "access (none)" indicates that the argument isn't used to access the object and
           avoids the warning.

           These warnings are only possible in optimizing compilation, because otherwise GCC does
           not keep track of the state of variables.

           These warnings are made optional because GCC may not be able to determine when the code
           is correct in spite of appearing to have an error.  Here is one example of how this can
           happen:

                   {
                     int x;
                     switch (y)
                       {
                       case 1: x = 1;
                         break;
                       case 2: x = 4;
                         break;
                       case 3: x = 5;
                       }
                     foo (x);
                   }

           If the value of "y" is always 1, 2 or 3, then "x" is always initialized, but GCC doesn't
           know this. To suppress the warning, you need to provide a default case with assert(0) or
           similar code.

           This option also warns when a non-volatile automatic variable might be changed by a call
           to "longjmp".  The compiler sees only the calls to "setjmp".  It cannot know where
           "longjmp" will be called; in fact, a signal handler could call it at any point in the
           code.  As a result, you may get a warning even when there is in fact no problem because
           "longjmp" cannot in fact be called at the place that would cause a problem.

           Some spurious warnings can be avoided if you declare all the functions you use that never
           return as "noreturn".

           This warning is enabled by -Wall or -Wextra.

       -Wunknown-pragmas
           Warn when a "#pragma" directive is encountered that is not understood by GCC.  If this
           command-line option is used, warnings are even issued for unknown pragmas in system
           header files.  This is not the case if the warnings are only enabled by the -Wall
           command-line option.

       -Wno-pragmas
           Do not warn about misuses of pragmas, such as incorrect parameters, invalid syntax, or
           conflicts between pragmas.  See also -Wunknown-pragmas.

       -Wno-prio-ctor-dtor
           Do not warn if a priority from 0 to 100 is used for constructor or destructor.  The use
           of constructor and destructor attributes allow you to assign a priority to the
           constructor/destructor to control its order of execution before "main" is called or after
           it returns.  The priority values must be greater than 100 as the compiler reserves
           priority values between 0--100 for the implementation.

       -Wstrict-aliasing
           This option is only active when -fstrict-aliasing is active.  It warns about code that
           might break the strict aliasing rules that the compiler is using for optimization.  The
           warning does not catch all cases, but does attempt to catch the more common pitfalls.  It
           is included in -Wall.  It is equivalent to -Wstrict-aliasing=3

       -Wstrict-aliasing=n
           This option is only active when -fstrict-aliasing is active.  It warns about code that
           might break the strict aliasing rules that the compiler is using for optimization.
           Higher levels correspond to higher accuracy (fewer false positives).  Higher levels also
           correspond to more effort, similar to the way -O works.  -Wstrict-aliasing is equivalent
           to -Wstrict-aliasing=3.

           Level 1: Most aggressive, quick, least accurate.  Possibly useful when higher levels do
           not warn but -fstrict-aliasing still breaks the code, as it has very few false negatives.
           However, it has many false positives.  Warns for all pointer conversions between possibly
           incompatible types, even if never dereferenced.  Runs in the front end only.

           Level 2: Aggressive, quick, not too precise.  May still have many false positives (not as
           many as level 1 though), and few false negatives (but possibly more than level 1).
           Unlike level 1, it only warns when an address is taken.  Warns about incomplete types.
           Runs in the front end only.

           Level 3 (default for -Wstrict-aliasing): Should have very few false positives and few
           false negatives.  Slightly slower than levels 1 or 2 when optimization is enabled.  Takes
           care of the common pun+dereference pattern in the front end: "*(int*)&some_float".  If
           optimization is enabled, it also runs in the back end, where it deals with multiple
           statement cases using flow-sensitive points-to information.  Only warns when the
           converted pointer is dereferenced.  Does not warn about incomplete types.

       -Wstrict-overflow
       -Wstrict-overflow=n
           This option is only active when signed overflow is undefined.  It warns about cases where
           the compiler optimizes based on the assumption that signed overflow does not occur.  Note
           that it does not warn about all cases where the code might overflow: it only warns about
           cases where the compiler implements some optimization.  Thus this warning depends on the
           optimization level.

           An optimization that assumes that signed overflow does not occur is perfectly safe if the
           values of the variables involved are such that overflow never does, in fact, occur.
           Therefore this warning can easily give a false positive: a warning about code that is not
           actually a problem.  To help focus on important issues, several warning levels are
           defined.  No warnings are issued for the use of undefined signed overflow when estimating
           how many iterations a loop requires, in particular when determining whether a loop will
           be executed at all.

           -Wstrict-overflow=1
               Warn about cases that are both questionable and easy to avoid.  For example the
               compiler simplifies "x + 1 > x" to 1.  This level of -Wstrict-overflow is enabled by
               -Wall; higher levels are not, and must be explicitly requested.

           -Wstrict-overflow=2
               Also warn about other cases where a comparison is simplified to a constant.  For
               example: "abs (x) >= 0".  This can only be simplified when signed integer overflow is
               undefined, because "abs (INT_MIN)" overflows to "INT_MIN", which is less than zero.
               -Wstrict-overflow (with no level) is the same as -Wstrict-overflow=2.

           -Wstrict-overflow=3
               Also warn about other cases where a comparison is simplified.  For example: "x + 1 >
               1" is simplified to "x > 0".

           -Wstrict-overflow=4
               Also warn about other simplifications not covered by the above cases.  For example:
               "(x * 10) / 5" is simplified to "x * 2".

           -Wstrict-overflow=5
               Also warn about cases where the compiler reduces the magnitude of a constant involved
               in a comparison.  For example: "x + 2 > y" is simplified to "x + 1 >= y".  This is
               reported only at the highest warning level because this simplification applies to
               many comparisons, so this warning level gives a very large number of false positives.

       -Wstring-compare
           Warn for calls to "strcmp" and "strncmp" whose result is determined to be either zero or
           non-zero in tests for such equality owing to the length of one argument being greater
           than the size of the array the other argument is stored in (or the bound in the case of
           "strncmp").  Such calls could be mistakes.  For example, the call to "strcmp" below is
           diagnosed because its result is necessarily non-zero irrespective of the contents of the
           array "a".

                   extern char a[4];
                   void f (char *d)
                   {
                     strcpy (d, "string");
                     ...
                     if (0 == strcmp (a, d))   // cannot be true
                       puts ("a and d are the same");
                   }

           -Wstring-compare is enabled by -Wextra.

       -Wno-stringop-overflow
       -Wstringop-overflow
       -Wstringop-overflow=type
           Warn for calls to string manipulation functions such as "memcpy" and "strcpy" that are
           determined to overflow the destination buffer.  The optional argument is one greater than
           the type of Object Size Checking to perform to determine the size of the destination.
           The argument is meaningful only for functions that operate on character arrays but not
           for raw memory functions like "memcpy" which always make use of Object Size type-0.  The
           option also warns for calls that specify a size in excess of the largest possible object
           or at most "SIZE_MAX / 2" bytes.  The option produces the best results with optimization
           enabled but can detect a small subset of simple buffer overflows even without
           optimization in calls to the GCC built-in functions like "__builtin_memcpy" that
           correspond to the standard functions.  In any case, the option warns about just a subset
           of buffer overflows detected by the corresponding overflow checking built-ins.  For
           example, the option issues a warning for the "strcpy" call below because it copies at
           least 5 characters (the string "blue" including the terminating NUL) into the buffer of
           size 4.

                   enum Color { blue, purple, yellow };
                   const char* f (enum Color clr)
                   {
                     static char buf [4];
                     const char *str;
                     switch (clr)
                       {
                         case blue: str = "blue"; break;
                         case purple: str = "purple"; break;
                         case yellow: str = "yellow"; break;
                       }

                     return strcpy (buf, str);   // warning here
                   }

           Option -Wstringop-overflow=2 is enabled by default.

           -Wstringop-overflow
           -Wstringop-overflow=1
               The -Wstringop-overflow=1 option uses type-zero Object Size Checking to determine the
               sizes of destination objects.  At this setting the option does not warn for writes
               past the end of subobjects of larger objects accessed by pointers unless the size of
               the largest surrounding object is known.  When the destination may be one of several
               objects it is assumed to be the largest one of them.  On Linux systems, when
               optimization is enabled at this setting the option warns for the same code as when
               the "_FORTIFY_SOURCE" macro is defined to a non-zero value.

           -Wstringop-overflow=2
               The -Wstringop-overflow=2 option uses type-one Object Size Checking to determine the
               sizes of destination objects.  At this setting the option warns about overflows when
               writing to members of the largest complete objects whose exact size is known.
               However, it does not warn for excessive writes to the same members of unknown objects
               referenced by pointers since they may point to arrays containing unknown numbers of
               elements.  This is the default setting of the option.

           -Wstringop-overflow=3
               The -Wstringop-overflow=3 option uses type-two Object Size Checking to determine the
               sizes of destination objects.  At this setting the option warns about overflowing the
               smallest object or data member.  This is the most restrictive setting of the option
               that may result in warnings for safe code.

           -Wstringop-overflow=4
               The -Wstringop-overflow=4 option uses type-three Object Size Checking to determine
               the sizes of destination objects.  At this setting the option warns about overflowing
               any data members, and when the destination is one of several objects it uses the size
               of the largest of them to decide whether to issue a warning.  Similarly to
               -Wstringop-overflow=3 this setting of the option may result in warnings for benign
               code.

       -Wno-stringop-overread
           Warn for calls to string manipulation functions such as "memchr", or "strcpy" that are
           determined to read past the end of the source sequence.

           Option -Wstringop-overread is enabled by default.

       -Wno-stringop-truncation
           Do not warn for calls to bounded string manipulation functions such as "strncat",
           "strncpy", and "stpncpy" that may either truncate the copied string or leave the
           destination unchanged.

           In the following example, the call to "strncat" specifies a bound that is less than the
           length of the source string.  As a result, the copy of the source will be truncated and
           so the call is diagnosed.  To avoid the warning use "bufsize - strlen (buf) - 1)" as the
           bound.

                   void append (char *buf, size_t bufsize)
                   {
                     strncat (buf, ".txt", 3);
                   }

           As another example, the following call to "strncpy" results in copying to "d" just the
           characters preceding the terminating NUL, without appending the NUL to the end.  Assuming
           the result of "strncpy" is necessarily a NUL-terminated string is a common mistake, and
           so the call is diagnosed.  To avoid the warning when the result is not expected to be
           NUL-terminated, call "memcpy" instead.

                   void copy (char *d, const char *s)
                   {
                     strncpy (d, s, strlen (s));
                   }

           In the following example, the call to "strncpy" specifies the size of the destination
           buffer as the bound.  If the length of the source string is equal to or greater than this
           size the result of the copy will not be NUL-terminated.  Therefore, the call is also
           diagnosed.  To avoid the warning, specify "sizeof buf - 1" as the bound and set the last
           element of the buffer to "NUL".

                   void copy (const char *s)
                   {
                     char buf[80];
                     strncpy (buf, s, sizeof buf);
                     ...
                   }

           In situations where a character array is intended to store a sequence of bytes with no
           terminating "NUL" such an array may be annotated with attribute "nonstring" to avoid this
           warning.  Such arrays, however, are not suitable arguments to functions that expect
           "NUL"-terminated strings.  To help detect accidental misuses of such arrays GCC issues
           warnings unless it can prove that the use is safe.

       -Wsuggest-attribute=[pure|const|noreturn|format|cold|malloc]
           Warn for cases where adding an attribute may be beneficial. The attributes currently
           supported are listed below.

           -Wsuggest-attribute=pure
           -Wsuggest-attribute=const
           -Wsuggest-attribute=noreturn
           -Wmissing-noreturn
           -Wsuggest-attribute=malloc
               Warn about functions that might be candidates for attributes "pure", "const" or
               "noreturn" or "malloc". The compiler only warns for functions visible in other
               compilation units or (in the case of "pure" and "const") if it cannot prove that the
               function returns normally. A function returns normally if it doesn't contain an
               infinite loop or return abnormally by throwing, calling "abort" or trapping.  This
               analysis requires option -fipa-pure-const, which is enabled by default at -O and
               higher.  Higher optimization levels improve the accuracy of the analysis.

           -Wsuggest-attribute=format
           -Wmissing-format-attribute
               Warn about function pointers that might be candidates for "format" attributes.  Note
               these are only possible candidates, not absolute ones.  GCC guesses that function
               pointers with "format" attributes that are used in assignment, initialization,
               parameter passing or return statements should have a corresponding "format" attribute
               in the resulting type.  I.e. the left-hand side of the assignment or initialization,
               the type of the parameter variable, or the return type of the containing function
               respectively should also have a "format" attribute to avoid the warning.

               GCC also warns about function definitions that might be candidates for "format"
               attributes.  Again, these are only possible candidates.  GCC guesses that "format"
               attributes might be appropriate for any function that calls a function like "vprintf"
               or "vscanf", but this might not always be the case, and some functions for which
               "format" attributes are appropriate may not be detected.

           -Wsuggest-attribute=cold
               Warn about functions that might be candidates for "cold" attribute.  This is based on
               static detection and generally only warns about functions which always leads to a
               call to another "cold" function such as wrappers of C++ "throw" or fatal error
               reporting functions leading to "abort".

       -Walloc-zero
           Warn about calls to allocation functions decorated with attribute "alloc_size" that
           specify zero bytes, including those to the built-in forms of the functions
           "aligned_alloc", "alloca", "calloc", "malloc", and "realloc".  Because the behavior of
           these functions when called with a zero size differs among implementations (and in the
           case of "realloc" has been deprecated) relying on it may result in subtle portability
           bugs and should be avoided.

       -Walloc-size-larger-than=byte-size
           Warn about calls to functions decorated with attribute "alloc_size" that attempt to
           allocate objects larger than the specified number of bytes, or where the result of the
           size computation in an integer type with infinite precision would exceed the value of
           PTRDIFF_MAX on the target.  -Walloc-size-larger-than=PTRDIFF_MAX is enabled by default.
           Warnings controlled by the option can be disabled either by specifying byte-size of
           SIZE_MAX or more or by -Wno-alloc-size-larger-than.

       -Wno-alloc-size-larger-than
           Disable -Walloc-size-larger-than= warnings.  The option is equivalent to
           -Walloc-size-larger-than=SIZE_MAX or larger.

       -Walloca
           This option warns on all uses of "alloca" in the source.

       -Walloca-larger-than=byte-size
           This option warns on calls to "alloca" with an integer argument whose value is either
           zero, or that is not bounded by a controlling predicate that limits its value to at most
           byte-size.  It also warns for calls to "alloca" where the bound value is unknown.
           Arguments of non-integer types are considered unbounded even if they appear to be
           constrained to the expected range.

           For example, a bounded case of "alloca" could be:

                   void func (size_t n)
                   {
                     void *p;
                     if (n <= 1000)
                       p = alloca (n);
                     else
                       p = malloc (n);
                     f (p);
                   }

           In the above example, passing "-Walloca-larger-than=1000" would not issue a warning
           because the call to "alloca" is known to be at most 1000 bytes.  However, if
           "-Walloca-larger-than=500" were passed, the compiler would emit a warning.

           Unbounded uses, on the other hand, are uses of "alloca" with no controlling predicate
           constraining its integer argument.  For example:

                   void func ()
                   {
                     void *p = alloca (n);
                     f (p);
                   }

           If "-Walloca-larger-than=500" were passed, the above would trigger a warning, but this
           time because of the lack of bounds checking.

           Note, that even seemingly correct code involving signed integers could cause a warning:

                   void func (signed int n)
                   {
                     if (n < 500)
                       {
                         p = alloca (n);
                         f (p);
                       }
                   }

           In the above example, n could be negative, causing a larger than expected argument to be
           implicitly cast into the "alloca" call.

           This option also warns when "alloca" is used in a loop.

           -Walloca-larger-than=PTRDIFF_MAX is enabled by default but is usually only effective
           when -ftree-vrp is active (default for -O2 and above).

           See also -Wvla-larger-than=byte-size.

       -Wno-alloca-larger-than
           Disable -Walloca-larger-than= warnings.  The option is equivalent to
           -Walloca-larger-than=SIZE_MAX or larger.

       -Warith-conversion
           Do warn about implicit conversions from arithmetic operations even when conversion of the
           operands to the same type cannot change their values.  This affects warnings from
           -Wconversion, -Wfloat-conversion, and -Wsign-conversion.

                   void f (char c, int i)
                   {
                     c = c + i; // warns with B<-Wconversion>
                     c = c + 1; // only warns with B<-Warith-conversion>
                   }

       -Warray-bounds
       -Warray-bounds=n
           This option is only active when -ftree-vrp is active (default for -O2 and above). It
           warns about subscripts to arrays that are always out of bounds. This warning is enabled
           by -Wall.

           -Warray-bounds=1
               This is the warning level of -Warray-bounds and is enabled by -Wall; higher levels
               are not, and must be explicitly requested.

           -Warray-bounds=2
               This warning level also warns about out of bounds access for arrays at the end of a
               struct and for arrays accessed through pointers. This warning level may give a larger
               number of false positives and is deactivated by default.

       -Warray-parameter
       -Warray-parameter=n
           Warn about redeclarations of functions involving arguments of array or pointer types of
           inconsistent kinds or forms, and enable the detection of out-of-bounds accesses to such
           parameters by warnings such as -Warray-bounds.

           If the first function declaration uses the array form the bound specified in the array is
           assumed to be the minimum number of elements expected to be provided in calls to the
           function and the maximum number of elements accessed by it.  Failing to provide arguments
           of sufficient size or accessing more than the maximum number of elements may be diagnosed
           by warnings such as -Warray-bounds.  At level 1 the warning diagnoses inconsistencies
           involving array parameters declared using the "T[static N]" form.

           For example, the warning triggers for the following redeclarations because the first one
           allows an array of any size to be passed to "f" while the second one with the keyword
           "static" specifies that the array argument must have at least four elements.

                   void f (int[static 4]);
                   void f (int[]);           // warning (inconsistent array form)

                   void g (void)
                   {
                     int *p = (int *)malloc (4);
                     f (p);                  // warning (array too small)
                     ...
                   }

           At level 2 the warning also triggers for redeclarations involving any other inconsistency
           in array or pointer argument forms denoting array sizes.  Pointers and arrays of
           unspecified bound are considered equivalent and do not trigger a warning.

                   void g (int*);
                   void g (int[]);     // no warning
                   void g (int[8]);    // warning (inconsistent array bound)

           -Warray-parameter=2 is included in -Wall.  The -Wvla-parameter option triggers warnings
           for similar inconsistencies involving Variable Length Array arguments.

       -Wattribute-alias=n
       -Wno-attribute-alias
           Warn about declarations using the "alias" and similar attributes whose target is
           incompatible with the type of the alias.

           -Wattribute-alias=1
               The default warning level of the -Wattribute-alias option diagnoses incompatibilities
               between the type of the alias declaration and that of its target.  Such
               incompatibilities are typically indicative of bugs.

           -Wattribute-alias=2
               At this level -Wattribute-alias also diagnoses cases where the attributes of the
               alias declaration are more restrictive than the attributes applied to its target.
               These mismatches can potentially result in incorrect code generation.  In other cases
               they may be benign and could be resolved simply by adding the missing attribute to
               the target.  For comparison, see the -Wmissing-attributes option, which controls
               diagnostics when the alias declaration is less restrictive than the target, rather
               than more restrictive.

               Attributes considered include "alloc_align", "alloc_size", "cold", "const", "hot",
               "leaf", "malloc", "nonnull", "noreturn", "nothrow", "pure", "returns_nonnull", and
               "returns_twice".

           -Wattribute-alias is equivalent to -Wattribute-alias=1.  This is the default.  You can
           disable these warnings with either -Wno-attribute-alias or -Wattribute-alias=0.

       -Wbool-compare
           Warn about boolean expression compared with an integer value different from
           "true"/"false".  For instance, the following comparison is always false:

                   int n = 5;
                   ...
                   if ((n > 1) == 2) { ... }

           This warning is enabled by -Wall.

       -Wbool-operation
           Warn about suspicious operations on expressions of a boolean type.  For instance, bitwise
           negation of a boolean is very likely a bug in the program.  For C, this warning also
           warns about incrementing or decrementing a boolean, which rarely makes sense.  (In C++,
           decrementing a boolean is always invalid.  Incrementing a boolean is invalid in C++17,
           and deprecated otherwise.)

           This warning is enabled by -Wall.

       -Wduplicated-branches
           Warn when an if-else has identical branches.  This warning detects cases like

                   if (p != NULL)
                     return 0;
                   else
                     return 0;

           It doesn't warn when both branches contain just a null statement.  This warning also warn
           for conditional operators:

                     int i = x ? *p : *p;

       -Wduplicated-cond
           Warn about duplicated conditions in an if-else-if chain.  For instance, warn for the
           following code:

                   if (p->q != NULL) { ... }
                   else if (p->q != NULL) { ... }

       -Wframe-address
           Warn when the __builtin_frame_address or __builtin_return_address is called with an
           argument greater than 0.  Such calls may return indeterminate values or crash the
           program.  The warning is included in -Wall.

       -Wno-discarded-qualifiers (C and Objective-C only)
           Do not warn if type qualifiers on pointers are being discarded.  Typically, the compiler
           warns if a "const char *" variable is passed to a function that takes a "char *"
           parameter.  This option can be used to suppress such a warning.

       -Wno-discarded-array-qualifiers (C and Objective-C only)
           Do not warn if type qualifiers on arrays which are pointer targets are being discarded.
           Typically, the compiler warns if a "const int (*)[]" variable is passed to a function
           that takes a "int (*)[]" parameter.  This option can be used to suppress such a warning.

       -Wno-incompatible-pointer-types (C and Objective-C only)
           Do not warn when there is a conversion between pointers that have incompatible types.
           This warning is for cases not covered by -Wno-pointer-sign, which warns for pointer
           argument passing or assignment with different signedness.

       -Wno-int-conversion (C and Objective-C only)
           Do not warn about incompatible integer to pointer and pointer to integer conversions.
           This warning is about implicit conversions; for explicit conversions the warnings
           -Wno-int-to-pointer-cast and -Wno-pointer-to-int-cast may be used.

       -Wzero-length-bounds
           Warn about accesses to elements of zero-length array members that might overlap other
           members of the same object.  Declaring interior zero-length arrays is discouraged because
           accesses to them are undefined.  See

           For example, the first two stores in function "bad" are diagnosed because the array
           elements overlap the subsequent members "b" and "c".  The third store is diagnosed by
           -Warray-bounds because it is beyond the bounds of the enclosing object.

                   struct X { int a[0]; int b, c; };
                   struct X x;

                   void bad (void)
                   {
                     x.a[0] = 0;   // -Wzero-length-bounds
                     x.a[1] = 1;   // -Wzero-length-bounds
                     x.a[2] = 2;   // -Warray-bounds
                   }

           Option -Wzero-length-bounds is enabled by -Warray-bounds.

       -Wno-div-by-zero
           Do not warn about compile-time integer division by zero.  Floating-point division by zero
           is not warned about, as it can be a legitimate way of obtaining infinities and NaNs.

       -Wsystem-headers
           Print warning messages for constructs found in system header files.  Warnings from system
           headers are normally suppressed, on the assumption that they usually do not indicate real
           problems and would only make the compiler output harder to read.  Using this command-line
           option tells GCC to emit warnings from system headers as if they occurred in user code.
           However, note that using -Wall in conjunction with this option does not warn about
           unknown pragmas in system headers---for that, -Wunknown-pragmas must also be used.

       -Wtautological-compare
           Warn if a self-comparison always evaluates to true or false.  This warning detects
           various mistakes such as:

                   int i = 1;
                   ...
                   if (i > i) { ... }

           This warning also warns about bitwise comparisons that always evaluate to true or false,
           for instance:

                   if ((a & 16) == 10) { ... }

           will always be false.

           This warning is enabled by -Wall.

       -Wtrampolines
           Warn about trampolines generated for pointers to nested functions.  A trampoline is a
           small piece of data or code that is created at run time on the stack when the address of
           a nested function is taken, and is used to call the nested function indirectly.  For some
           targets, it is made up of data only and thus requires no special treatment.  But, for
           most targets, it is made up of code and thus requires the stack to be made executable in
           order for the program to work properly.

       -Wfloat-equal
           Warn if floating-point values are used in equality comparisons.

           The idea behind this is that sometimes it is convenient (for the programmer) to consider
           floating-point values as approximations to infinitely precise real numbers.  If you are
           doing this, then you need to compute (by analyzing the code, or in some other way) the
           maximum or likely maximum error that the computation introduces, and allow for it when
           performing comparisons (and when producing output, but that's a different problem).  In
           particular, instead of testing for equality, you should check to see whether the two
           values have ranges that overlap; and this is done with the relational operators, so
           equality comparisons are probably mistaken.

       -Wtraditional (C and Objective-C only)
           Warn about certain constructs that behave differently in traditional and ISO C.  Also
           warn about ISO C constructs that have no traditional C equivalent, and/or problematic
           constructs that should be avoided.

           *   Macro parameters that appear within string literals in the macro body.  In
               traditional C macro replacement takes place within string literals, but in ISO C it
               does not.

           *   In traditional C, some preprocessor directives did not exist.  Traditional
               preprocessors only considered a line to be a directive if the # appeared in column 1
               on the line.  Therefore -Wtraditional warns about directives that traditional C
               understands but ignores because the # does not appear as the first character on the
               line.  It also suggests you hide directives like "#pragma" not understood by
               traditional C by indenting them.  Some traditional implementations do not recognize
               "#elif", so this option suggests avoiding it altogether.

           *   A function-like macro that appears without arguments.

           *   The unary plus operator.

           *   The U integer constant suffix, or the F or L floating-point constant suffixes.
               (Traditional C does support the L suffix on integer constants.)  Note, these suffixes
               appear in macros defined in the system headers of most modern systems, e.g. the
               _MIN/_MAX macros in "<limits.h>".  Use of these macros in user code might normally
               lead to spurious warnings, however GCC's integrated preprocessor has enough context
               to avoid warning in these cases.

           *   A function declared external in one block and then used after the end of the block.

           *   A "switch" statement has an operand of type "long".

           *   A non-"static" function declaration follows a "static" one.  This construct is not
               accepted by some traditional C compilers.

           *   The ISO type of an integer constant has a different width or signedness from its
               traditional type.  This warning is only issued if the base of the constant is ten.
               I.e. hexadecimal or octal values, which typically represent bit patterns, are not
               warned about.

           *   Usage of ISO string concatenation is detected.

           *   Initialization of automatic aggregates.

           *   Identifier conflicts with labels.  Traditional C lacks a separate namespace for
               labels.

           *   Initialization of unions.  If the initializer is zero, the warning is omitted.  This
               is done under the assumption that the zero initializer in user code appears
               conditioned on e.g. "__STDC__" to avoid missing initializer warnings and relies on
               default initialization to zero in the traditional C case.

           *   Conversions by prototypes between fixed/floating-point values and vice versa.  The
               absence of these prototypes when compiling with traditional C causes serious
               problems.  This is a subset of the possible conversion warnings; for the full set use
               -Wtraditional-conversion.

           *   Use of ISO C style function definitions.  This warning intentionally is not issued
               for prototype declarations or variadic functions because these ISO C features appear
               in your code when using libiberty's traditional C compatibility macros, "PARAMS" and
               "VPARAMS".  This warning is also bypassed for nested functions because that feature
               is already a GCC extension and thus not relevant to traditional C compatibility.

       -Wtraditional-conversion (C and Objective-C only)
           Warn if a prototype causes a type conversion that is different from what would happen to
           the same argument in the absence of a prototype.  This includes conversions of fixed
           point to floating and vice versa, and conversions changing the width or signedness of a
           fixed-point argument except when the same as the default promotion.

       -Wdeclaration-after-statement (C and Objective-C only)
           Warn when a declaration is found after a statement in a block.  This construct, known
           from C++, was introduced with ISO C99 and is by default allowed in GCC.  It is not
           supported by ISO C90.

       -Wshadow
           Warn whenever a local variable or type declaration shadows another variable, parameter,
           type, class member (in C++), or instance variable (in Objective-C) or whenever a built-in
           function is shadowed.  Note that in C++, the compiler warns if a local variable shadows
           an explicit typedef, but not if it shadows a struct/class/enum.  If this warning is
           enabled, it includes also all instances of local shadowing.  This means that
           -Wno-shadow=local and -Wno-shadow=compatible-local are ignored when -Wshadow is used.
           Same as -Wshadow=global.

       -Wno-shadow-ivar (Objective-C only)
           Do not warn whenever a local variable shadows an instance variable in an Objective-C
           method.

       -Wshadow=global
           Warn for any shadowing.  Same as -Wshadow.

       -Wshadow=local
           Warn when a local variable shadows another local variable or parameter.

       -Wshadow=compatible-local
           Warn when a local variable shadows another local variable or parameter whose type is
           compatible with that of the shadowing variable.  In C++, type compatibility here means
           the type of the shadowing variable can be converted to that of the shadowed variable.
           The creation of this flag (in addition to -Wshadow=local) is based on the idea that when
           a local variable shadows another one of incompatible type, it is most likely intentional,
           not a bug or typo, as shown in the following example:

                   for (SomeIterator i = SomeObj.begin(); i != SomeObj.end(); ++i)
                   {
                     for (int i = 0; i < N; ++i)
                     {
                       ...
                     }
                     ...
                   }

           Since the two variable "i" in the example above have incompatible types, enabling only
           -Wshadow=compatible-local does not emit a warning.  Because their types are incompatible,
           if a programmer accidentally uses one in place of the other, type checking is expected to
           catch that and emit an error or warning.  Use of this flag instead of -Wshadow=local can
           possibly reduce the number of warnings triggered by intentional shadowing.  Note that
           this also means that shadowing "const char *i" by "char *i" does not emit a warning.

           This warning is also enabled by -Wshadow=local.

       -Wlarger-than=byte-size
           Warn whenever an object is defined whose size exceeds byte-size.
           -Wlarger-than=PTRDIFF_MAX is enabled by default.  Warnings controlled by the option can
           be disabled either by specifying byte-size of SIZE_MAX or more or by -Wno-larger-than.

           Also warn for calls to bounded functions such as "memchr" or "strnlen" that specify a
           bound greater than the largest possible object, which is PTRDIFF_MAX bytes by default.
           These warnings can only be disabled by -Wno-larger-than.

       -Wno-larger-than
           Disable -Wlarger-than= warnings.  The option is equivalent to -Wlarger-than=SIZE_MAX or
           larger.

       -Wframe-larger-than=byte-size
           Warn if the size of a function frame exceeds byte-size.  The computation done to
           determine the stack frame size is approximate and not conservative.  The actual
           requirements may be somewhat greater than byte-size even if you do not get a warning.  In
           addition, any space allocated via "alloca", variable-length arrays, or related constructs
           is not included by the compiler when determining whether or not to issue a warning.
           -Wframe-larger-than=PTRDIFF_MAX is enabled by default.  Warnings controlled by the option
           can be disabled either by specifying byte-size of SIZE_MAX or more or by
           -Wno-frame-larger-than.

       -Wno-frame-larger-than
           Disable -Wframe-larger-than= warnings.  The option is equivalent to
           -Wframe-larger-than=SIZE_MAX or larger.

       -Wno-free-nonheap-object
           Warn when attempting to deallocate an object that was either not allocated on the heap,
           or by using a pointer that was not returned from a prior call to the corresponding
           allocation function.  For example, because the call to "stpcpy" returns a pointer to the
           terminating nul character and not to the begginning of the object, the call to "free"
           below is diagnosed.

                   void f (char *p)
                   {
                     p = stpcpy (p, "abc");
                     // ...
                     free (p);   // warning
                   }

           -Wfree-nonheap-object is enabled by default.

       -Wstack-usage=byte-size
           Warn if the stack usage of a function might exceed byte-size.  The computation done to
           determine the stack usage is conservative.  Any space allocated via "alloca", variable-
           length arrays, or related constructs is included by the compiler when determining whether
           or not to issue a warning.

           The message is in keeping with the output of -fstack-usage.

           *   If the stack usage is fully static but exceeds the specified amount, it's:

                         warning: stack usage is 1120 bytes

           *   If the stack usage is (partly) dynamic but bounded, it's:

                         warning: stack usage might be 1648 bytes

           *   If the stack usage is (partly) dynamic and not bounded, it's:

                         warning: stack usage might be unbounded

           -Wstack-usage=PTRDIFF_MAX is enabled by default.  Warnings controlled by the option can
           be disabled either by specifying byte-size of SIZE_MAX or more or by -Wno-stack-usage.

       -Wno-stack-usage
           Disable -Wstack-usage= warnings.  The option is equivalent to -Wstack-usage=SIZE_MAX or
           larger.

       -Wunsafe-loop-optimizations
           Warn if the loop cannot be optimized because the compiler cannot assume anything on the
           bounds of the loop indices.  With -funsafe-loop-optimizations warn if the compiler makes
           such assumptions.

       -Wno-pedantic-ms-format (MinGW targets only)
           When used in combination with -Wformat and -pedantic without GNU extensions, this option
           disables the warnings about non-ISO "printf" / "scanf" format width specifiers "I32",
           "I64", and "I" used on Windows targets, which depend on the MS runtime.

       -Wpointer-arith
           Warn about anything that depends on the "size of" a function type or of "void".  GNU C
           assigns these types a size of 1, for convenience in calculations with "void *" pointers
           and pointers to functions.  In C++, warn also when an arithmetic operation involves
           "NULL".  This warning is also enabled by -Wpedantic.

       -Wno-pointer-compare
           Do not warn if a pointer is compared with a zero character constant.  This usually means
           that the pointer was meant to be dereferenced.  For example:

                   const char *p = foo ();
                   if (p == '\0')
                     return 42;

           Note that the code above is invalid in C++11.

           This warning is enabled by default.

       -Wtsan
           Warn about unsupported features in ThreadSanitizer.

           ThreadSanitizer does not support "std::atomic_thread_fence" and can report false
           positives.

           This warning is enabled by default.

       -Wtype-limits
           Warn if a comparison is always true or always false due to the limited range of the data
           type, but do not warn for constant expressions.  For example, warn if an unsigned
           variable is compared against zero with "<" or ">=".  This warning is also enabled by
           -Wextra.

       -Wabsolute-value (C and Objective-C only)
           Warn for calls to standard functions that compute the absolute value of an argument when
           a more appropriate standard function is available.  For example, calling "abs(3.14)"
           triggers the warning because the appropriate function to call to compute the absolute
           value of a double argument is "fabs".  The option also triggers warnings when the
           argument in a call to such a function has an unsigned type.  This warning can be
           suppressed with an explicit type cast and it is also enabled by -Wextra.

       -Wcomment
       -Wcomments
           Warn whenever a comment-start sequence /* appears in a /* comment, or whenever a
           backslash-newline appears in a // comment.  This warning is enabled by -Wall.

       -Wtrigraphs
           Warn if any trigraphs are encountered that might change the meaning of the program.
           Trigraphs within comments are not warned about, except those that would form escaped
           newlines.

           This option is implied by -Wall.  If -Wall is not given, this option is still enabled
           unless trigraphs are enabled.  To get trigraph conversion without warnings, but get the
           other -Wall warnings, use -trigraphs -Wall -Wno-trigraphs.

       -Wundef
           Warn if an undefined identifier is evaluated in an "#if" directive.  Such identifiers are
           replaced with zero.

       -Wexpansion-to-defined
           Warn whenever defined is encountered in the expansion of a macro (including the case
           where the macro is expanded by an #if directive).  Such usage is not portable.  This
           warning is also enabled by -Wpedantic and -Wextra.

       -Wunused-macros
           Warn about macros defined in the main file that are unused.  A macro is used if it is
           expanded or tested for existence at least once.  The preprocessor also warns if the macro
           has not been used at the time it is redefined or undefined.

           Built-in macros, macros defined on the command line, and macros defined in include files
           are not warned about.

           Note: If a macro is actually used, but only used in skipped conditional blocks, then the
           preprocessor reports it as unused.  To avoid the warning in such a case, you might
           improve the scope of the macro's definition by, for example, moving it into the first
           skipped block.  Alternatively, you could provide a dummy use with something like:

                   #if defined the_macro_causing_the_warning
                   #endif

       -Wno-endif-labels
           Do not warn whenever an "#else" or an "#endif" are followed by text.  This sometimes
           happens in older programs with code of the form

                   #if FOO
                   ...
                   #else FOO
                   ...
                   #endif FOO

           The second and third "FOO" should be in comments.  This warning is on by default.

       -Wbad-function-cast (C and Objective-C only)
           Warn when a function call is cast to a non-matching type.  For example, warn if a call to
           a function returning an integer type is cast to a pointer type.

       -Wc90-c99-compat (C and Objective-C only)
           Warn about features not present in ISO C90, but present in ISO C99.  For instance, warn
           about use of variable length arrays, "long long" type, "bool" type, compound literals,
           designated initializers, and so on.  This option is independent of the standards mode.
           Warnings are disabled in the expression that follows "__extension__".

       -Wc99-c11-compat (C and Objective-C only)
           Warn about features not present in ISO C99, but present in ISO C11.  For instance, warn
           about use of anonymous structures and unions, "_Atomic" type qualifier, "_Thread_local"
           storage-class specifier, "_Alignas" specifier, "Alignof" operator, "_Generic" keyword,
           and so on.  This option is independent of the standards mode.  Warnings are disabled in
           the expression that follows "__extension__".

       -Wc11-c2x-compat (C and Objective-C only)
           Warn about features not present in ISO C11, but present in ISO C2X.  For instance, warn
           about omitting the string in "_Static_assert", use of [[]] syntax for attributes, use of
           decimal floating-point types, and so on.  This option is independent of the standards
           mode.  Warnings are disabled in the expression that follows "__extension__".

       -Wc++-compat (C and Objective-C only)
           Warn about ISO C constructs that are outside of the common subset of ISO C and ISO C++,
           e.g. request for implicit conversion from "void *" to a pointer to non-"void" type.

       -Wc++11-compat (C++ and Objective-C++ only)
           Warn about C++ constructs whose meaning differs between ISO C++ 1998 and ISO C++ 2011,
           e.g., identifiers in ISO C++ 1998 that are keywords in ISO C++ 2011.  This warning turns
           on -Wnarrowing and is enabled by -Wall.

       -Wc++14-compat (C++ and Objective-C++ only)
           Warn about C++ constructs whose meaning differs between ISO C++ 2011 and ISO C++ 2014.
           This warning is enabled by -Wall.

       -Wc++17-compat (C++ and Objective-C++ only)
           Warn about C++ constructs whose meaning differs between ISO C++ 2014 and ISO C++ 2017.
           This warning is enabled by -Wall.

       -Wc++20-compat (C++ and Objective-C++ only)
           Warn about C++ constructs whose meaning differs between ISO C++ 2017 and ISO C++ 2020.
           This warning is enabled by -Wall.

       -Wcast-qual
           Warn whenever a pointer is cast so as to remove a type qualifier from the target type.
           For example, warn if a "const char *" is cast to an ordinary "char *".

           Also warn when making a cast that introduces a type qualifier in an unsafe way.  For
           example, casting "char **" to "const char **" is unsafe, as in this example:

                     /* p is char ** value.  */
                     const char **q = (const char **) p;
                     /* Assignment of readonly string to const char * is OK.  */
                     *q = "string";
                     /* Now char** pointer points to read-only memory.  */
                     **p = 'b';

       -Wcast-align
           Warn whenever a pointer is cast such that the required alignment of the target is
           increased.  For example, warn if a "char *" is cast to an "int *" on machines where
           integers can only be accessed at two- or four-byte boundaries.

       -Wcast-align=strict
           Warn whenever a pointer is cast such that the required alignment of the target is
           increased.  For example, warn if a "char *" is cast to an "int *" regardless of the
           target machine.

       -Wcast-function-type
           Warn when a function pointer is cast to an incompatible function pointer.  In a cast
           involving function types with a variable argument list only the types of initial
           arguments that are provided are considered.  Any parameter of pointer-type matches any
           other pointer-type.  Any benign differences in integral types are ignored, like "int" vs.
           "long" on ILP32 targets.  Likewise type qualifiers are ignored.  The function type "void
           (*) (void)" is special and matches everything, which can be used to suppress this
           warning.  In a cast involving pointer to member types this warning warns whenever the
           type cast is changing the pointer to member type.  This warning is enabled by -Wextra.

       -Wwrite-strings
           When compiling C, give string constants the type "const char[length]" so that copying the
           address of one into a non-"const" "char *" pointer produces a warning.  These warnings
           help you find at compile time code that can try to write into a string constant, but only
           if you have been very careful about using "const" in declarations and prototypes.
           Otherwise, it is just a nuisance. This is why we did not make -Wall request these
           warnings.

           When compiling C++, warn about the deprecated conversion from string literals to "char
           *".  This warning is enabled by default for C++ programs.

       -Wclobbered
           Warn for variables that might be changed by "longjmp" or "vfork".  This warning is also
           enabled by -Wextra.

       -Wconversion
           Warn for implicit conversions that may alter a value. This includes conversions between
           real and integer, like "abs (x)" when "x" is "double"; conversions between signed and
           unsigned, like "unsigned ui = -1"; and conversions to smaller types, like "sqrtf (M_PI)".
           Do not warn for explicit casts like "abs ((int) x)" and "ui = (unsigned) -1", or if the
           value is not changed by the conversion like in "abs (2.0)".  Warnings about conversions
           between signed and unsigned integers can be disabled by using -Wno-sign-conversion.

           For C++, also warn for confusing overload resolution for user-defined conversions; and
           conversions that never use a type conversion operator: conversions to "void", the same
           type, a base class or a reference to them. Warnings about conversions between signed and
           unsigned integers are disabled by default in C++ unless -Wsign-conversion is explicitly
           enabled.

           Warnings about conversion from arithmetic on a small type back to that type are only
           given with -Warith-conversion.

       -Wdangling-else
           Warn about constructions where there may be confusion to which "if" statement an "else"
           branch belongs.  Here is an example of such a case:

                   {
                     if (a)
                       if (b)
                         foo ();
                     else
                       bar ();
                   }

           In C/C++, every "else" branch belongs to the innermost possible "if" statement, which in
           this example is "if (b)".  This is often not what the programmer expected, as illustrated
           in the above example by indentation the programmer chose.  When there is the potential
           for this confusion, GCC issues a warning when this flag is specified.  To eliminate the
           warning, add explicit braces around the innermost "if" statement so there is no way the
           "else" can belong to the enclosing "if".  The resulting code looks like this:

                   {
                     if (a)
                       {
                         if (b)
                           foo ();
                         else
                           bar ();
                       }
                   }

           This warning is enabled by -Wparentheses.

       -Wdate-time
           Warn when macros "__TIME__", "__DATE__" or "__TIMESTAMP__" are encountered as they might
           prevent bit-wise-identical reproducible compilations.

       -Wempty-body
           Warn if an empty body occurs in an "if", "else" or "do while" statement.  This warning is
           also enabled by -Wextra.

       -Wno-endif-labels
           Do not warn about stray tokens after "#else" and "#endif".

       -Wenum-compare
           Warn about a comparison between values of different enumerated types.  In C++ enumerated
           type mismatches in conditional expressions are also diagnosed and the warning is enabled
           by default.  In C this warning is enabled by -Wall.

       -Wenum-conversion
           Warn when a value of enumerated type is implicitly converted to a different enumerated
           type.  This warning is enabled by -Wextra in C.

       -Wjump-misses-init (C, Objective-C only)
           Warn if a "goto" statement or a "switch" statement jumps forward across the
           initialization of a variable, or jumps backward to a label after the variable has been
           initialized.  This only warns about variables that are initialized when they are
           declared.  This warning is only supported for C and Objective-C; in C++ this sort of
           branch is an error in any case.

           -Wjump-misses-init is included in -Wc++-compat.  It can be disabled with the
           -Wno-jump-misses-init option.

       -Wsign-compare
           Warn when a comparison between signed and unsigned values could produce an incorrect
           result when the signed value is converted to unsigned.  In C++, this warning is also
           enabled by -Wall.  In C, it is also enabled by -Wextra.

       -Wsign-conversion
           Warn for implicit conversions that may change the sign of an integer value, like
           assigning a signed integer expression to an unsigned integer variable. An explicit cast
           silences the warning. In C, this option is enabled also by -Wconversion.

       -Wfloat-conversion
           Warn for implicit conversions that reduce the precision of a real value.  This includes
           conversions from real to integer, and from higher precision real to lower precision real
           values.  This option is also enabled by -Wconversion.

       -Wno-scalar-storage-order
           Do not warn on suspicious constructs involving reverse scalar storage order.

       -Wsizeof-array-div
           Warn about divisions of two sizeof operators when the first one is applied to an array
           and the divisor does not equal the size of the array element.  In such a case, the
           computation will not yield the number of elements in the array, which is likely what the
           user intended.  This warning warns e.g. about

                   int fn ()
                   {
                     int arr[10];
                     return sizeof (arr) / sizeof (short);
                   }

           This warning is enabled by -Wall.

       -Wsizeof-pointer-div
           Warn for suspicious divisions of two sizeof expressions that divide the pointer size by
           the element size, which is the usual way to compute the array size but won't work out
           correctly with pointers.  This warning warns e.g. about "sizeof (ptr) / sizeof (ptr[0])"
           if "ptr" is not an array, but a pointer.  This warning is enabled by -Wall.

       -Wsizeof-pointer-memaccess
           Warn for suspicious length parameters to certain string and memory built-in functions if
           the argument uses "sizeof".  This warning triggers for example for "memset (ptr, 0,
           sizeof (ptr));" if "ptr" is not an array, but a pointer, and suggests a possible fix, or
           about "memcpy (&foo, ptr, sizeof (&foo));".  -Wsizeof-pointer-memaccess also warns about
           calls to bounded string copy functions like "strncat" or "strncpy" that specify as the
           bound a "sizeof" expression of the source array.  For example, in the following function
           the call to "strncat" specifies the size of the source string as the bound.  That is
           almost certainly a mistake and so the call is diagnosed.

                   void make_file (const char *name)
                   {
                     char path[PATH_MAX];
                     strncpy (path, name, sizeof path - 1);
                     strncat (path, ".text", sizeof ".text");
                     ...
                   }

           The -Wsizeof-pointer-memaccess option is enabled by -Wall.

       -Wno-sizeof-array-argument
           Do not warn when the "sizeof" operator is applied to a parameter that is declared as an
           array in a function definition.  This warning is enabled by default for C and C++
           programs.

       -Wmemset-elt-size
           Warn for suspicious calls to the "memset" built-in function, if the first argument
           references an array, and the third argument is a number equal to the number of elements,
           but not equal to the size of the array in memory.  This indicates that the user has
           omitted a multiplication by the element size.  This warning is enabled by -Wall.

       -Wmemset-transposed-args
           Warn for suspicious calls to the "memset" built-in function where the second argument is
           not zero and the third argument is zero.  For example, the call "memset (buf, sizeof buf,
           0)" is diagnosed because "memset (buf, 0, sizeof buf)" was meant instead.  The diagnostic
           is only emitted if the third argument is a literal zero.  Otherwise, if it is an
           expression that is folded to zero, or a cast of zero to some type, it is far less likely
           that the arguments have been mistakenly transposed and no warning is emitted.  This
           warning is enabled by -Wall.

       -Waddress
           Warn about suspicious uses of memory addresses. These include using the address of a
           function in a conditional expression, such as "void func(void); if (func)", and
           comparisons against the memory address of a string literal, such as "if (x == "abc")".
           Such uses typically indicate a programmer error: the address of a function always
           evaluates to true, so their use in a conditional usually indicate that the programmer
           forgot the parentheses in a function call; and comparisons against string literals result
           in unspecified behavior and are not portable in C, so they usually indicate that the
           programmer intended to use "strcmp".  This warning is enabled by -Wall.

       -Wno-address-of-packed-member
           Do not warn when the address of packed member of struct or union is taken, which usually
           results in an unaligned pointer value.  This is enabled by default.

       -Wlogical-op
           Warn about suspicious uses of logical operators in expressions.  This includes using
           logical operators in contexts where a bit-wise operator is likely to be expected.  Also
           warns when the operands of a logical operator are the same:

                   extern int a;
                   if (a < 0 && a < 0) { ... }

       -Wlogical-not-parentheses
           Warn about logical not used on the left hand side operand of a comparison.  This option
           does not warn if the right operand is considered to be a boolean expression.  Its purpose
           is to detect suspicious code like the following:

                   int a;
                   ...
                   if (!a > 1) { ... }

           It is possible to suppress the warning by wrapping the LHS into parentheses:

                   if ((!a) > 1) { ... }

           This warning is enabled by -Wall.

       -Waggregate-return
           Warn if any functions that return structures or unions are defined or called.  (In
           languages where you can return an array, this also elicits a warning.)

       -Wno-aggressive-loop-optimizations
           Warn if in a loop with constant number of iterations the compiler detects undefined
           behavior in some statement during one or more of the iterations.

       -Wno-attributes
           Do not warn if an unexpected "__attribute__" is used, such as unrecognized attributes,
           function attributes applied to variables, etc.  This does not stop errors for incorrect
           use of supported attributes.

       -Wno-builtin-declaration-mismatch
           Warn if a built-in function is declared with an incompatible signature or as a non-
           function, or when a built-in function declared with a type that does not include a
           prototype is called with arguments whose promoted types do not match those expected by
           the function.  When -Wextra is specified, also warn when a built-in function that takes
           arguments is declared without a prototype.  The -Wbuiltin-declaration-mismatch warning is
           enabled by default.  To avoid the warning include the appropriate header to bring the
           prototypes of built-in functions into scope.

           For example, the call to "memset" below is diagnosed by the warning because the function
           expects a value of type "size_t" as its argument but the type of 32 is "int".  With
           -Wextra, the declaration of the function is diagnosed as well.

                   extern void* memset ();
                   void f (void *d)
                   {
                     memset (d, '\0', 32);
                   }

       -Wno-builtin-macro-redefined
           Do not warn if certain built-in macros are redefined.  This suppresses warnings for
           redefinition of "__TIMESTAMP__", "__TIME__", "__DATE__", "__FILE__", and "__BASE_FILE__".

       -Wstrict-prototypes (C and Objective-C only)
           Warn if a function is declared or defined without specifying the argument types.  (An
           old-style function definition is permitted without a warning if preceded by a declaration
           that specifies the argument types.)

       -Wold-style-declaration (C and Objective-C only)
           Warn for obsolescent usages, according to the C Standard, in a declaration. For example,
           warn if storage-class specifiers like "static" are not the first things in a declaration.
           This warning is also enabled by -Wextra.

       -Wold-style-definition (C and Objective-C only)
           Warn if an old-style function definition is used.  A warning is given even if there is a
           previous prototype.  A definition using () is not considered an old-style definition in
           C2X mode, because it is equivalent to (void) in that case, but is considered an old-style
           definition for older standards.

       -Wmissing-parameter-type (C and Objective-C only)
           A function parameter is declared without a type specifier in K&R-style functions:

                   void foo(bar) { }

           This warning is also enabled by -Wextra.

       -Wmissing-prototypes (C and Objective-C only)
           Warn if a global function is defined without a previous prototype declaration.  This
           warning is issued even if the definition itself provides a prototype.  Use this option to
           detect global functions that do not have a matching prototype declaration in a header
           file.  This option is not valid for C++ because all function declarations provide
           prototypes and a non-matching declaration declares an overload rather than conflict with
           an earlier declaration.  Use -Wmissing-declarations to detect missing declarations in
           C++.

       -Wmissing-declarations
           Warn if a global function is defined without a previous declaration.  Do so even if the
           definition itself provides a prototype.  Use this option to detect global functions that
           are not declared in header files.  In C, no warnings are issued for functions with
           previous non-prototype declarations; use -Wmissing-prototypes to detect missing
           prototypes.  In C++, no warnings are issued for function templates, or for inline
           functions, or for functions in anonymous namespaces.

       -Wmissing-field-initializers
           Warn if a structure's initializer has some fields missing.  For example, the following
           code causes such a warning, because "x.h" is implicitly zero:

                   struct s { int f, g, h; };
                   struct s x = { 3, 4 };

           This option does not warn about designated initializers, so the following modification
           does not trigger a warning:

                   struct s { int f, g, h; };
                   struct s x = { .f = 3, .g = 4 };

           In C this option does not warn about the universal zero initializer { 0 }:

                   struct s { int f, g, h; };
                   struct s x = { 0 };

           Likewise, in C++ this option does not warn about the empty { } initializer, for example:

                   struct s { int f, g, h; };
                   s x = { };

           This warning is included in -Wextra.  To get other -Wextra warnings without this one, use
           -Wextra -Wno-missing-field-initializers.

       -Wno-multichar
           Do not warn if a multicharacter constant ('FOOF') is used.  Usually they indicate a typo
           in the user's code, as they have implementation-defined values, and should not be used in
           portable code.

       -Wnormalized=[none|id|nfc|nfkc]
           In ISO C and ISO C++, two identifiers are different if they are different sequences of
           characters.  However, sometimes when characters outside the basic ASCII character set are
           used, you can have two different character sequences that look the same.  To avoid
           confusion, the ISO 10646 standard sets out some normalization rules which when applied
           ensure that two sequences that look the same are turned into the same sequence.  GCC can
           warn you if you are using identifiers that have not been normalized; this option controls
           that warning.

           There are four levels of warning supported by GCC.  The default is -Wnormalized=nfc,
           which warns about any identifier that is not in the ISO 10646 "C" normalized form, NFC.
           NFC is the recommended form for most uses.  It is equivalent to -Wnormalized.

           Unfortunately, there are some characters allowed in identifiers by ISO C and ISO C++
           that, when turned into NFC, are not allowed in identifiers.  That is, there's no way to
           use these symbols in portable ISO C or C++ and have all your identifiers in NFC.
           -Wnormalized=id suppresses the warning for these characters.  It is hoped that future
           versions of the standards involved will correct this, which is why this option is not the
           default.

           You can switch the warning off for all characters by writing -Wnormalized=none or
           -Wno-normalized.  You should only do this if you are using some other normalization
           scheme (like "D"), because otherwise you can easily create bugs that are literally
           impossible to see.

           Some characters in ISO 10646 have distinct meanings but look identical in some fonts or
           display methodologies, especially once formatting has been applied.  For instance
           "\u207F", "SUPERSCRIPT LATIN SMALL LETTER N", displays just like a regular "n" that has
           been placed in a superscript.  ISO 10646 defines the NFKC normalization scheme to convert
           all these into a standard form as well, and GCC warns if your code is not in NFKC if you
           use -Wnormalized=nfkc.  This warning is comparable to warning about every identifier that
           contains the letter O because it might be confused with the digit 0, and so is not the
           default, but may be useful as a local coding convention if the programming environment
           cannot be fixed to display these characters distinctly.

       -Wno-attribute-warning
           Do not warn about usage of functions declared with "warning" attribute.  By default, this
           warning is enabled.  -Wno-attribute-warning can be used to disable the warning or
           -Wno-error=attribute-warning can be used to disable the error when compiled with -Werror
           flag.

       -Wno-deprecated
           Do not warn about usage of deprecated features.

       -Wno-deprecated-declarations
           Do not warn about uses of functions, variables, and types marked as deprecated by using
           the "deprecated" attribute.

       -Wno-overflow
           Do not warn about compile-time overflow in constant expressions.

       -Wno-odr
           Warn about One Definition Rule violations during link-time optimization.  Enabled by
           default.

       -Wopenmp-simd
           Warn if the vectorizer cost model overrides the OpenMP simd directive set by user.  The
           -fsimd-cost-model=unlimited option can be used to relax the cost model.

       -Woverride-init (C and Objective-C only)
           Warn if an initialized field without side effects is overridden when using designated
           initializers.

           This warning is included in -Wextra.  To get other -Wextra warnings without this one, use
           -Wextra -Wno-override-init.

       -Wno-override-init-side-effects (C and Objective-C only)
           Do not warn if an initialized field with side effects is overridden when using designated
           initializers.  This warning is enabled by default.

       -Wpacked
           Warn if a structure is given the packed attribute, but the packed attribute has no effect
           on the layout or size of the structure.  Such structures may be mis-aligned for little
           benefit.  For instance, in this code, the variable "f.x" in "struct bar" is misaligned
           even though "struct bar" does not itself have the packed attribute:

                   struct foo {
                     int x;
                     char a, b, c, d;
                   } __attribute__((packed));
                   struct bar {
                     char z;
                     struct foo f;
                   };

       -Wnopacked-bitfield-compat
           The 4.1, 4.2 and 4.3 series of GCC ignore the "packed" attribute on bit-fields of type
           "char".  This was fixed in GCC 4.4 but the change can lead to differences in the
           structure layout.  GCC informs you when the offset of such a field has changed in GCC
           4.4.  For example there is no longer a 4-bit padding between field "a" and "b" in this
           structure:

                   struct foo
                   {
                     char a:4;
                     char b:8;
                   } __attribute__ ((packed));

           This warning is enabled by default.  Use -Wno-packed-bitfield-compat to disable this
           warning.

       -Wpacked-not-aligned (C, C++, Objective-C and Objective-C++ only)
           Warn if a structure field with explicitly specified alignment in a packed struct or union
           is misaligned.  For example, a warning will be issued on "struct S", like, "warning:
           alignment 1 of 'struct S' is less than 8", in this code:

                   struct __attribute__ ((aligned (8))) S8 { char a[8]; };
                   struct __attribute__ ((packed)) S {
                     struct S8 s8;
                   };

           This warning is enabled by -Wall.

       -Wpadded
           Warn if padding is included in a structure, either to align an element of the structure
           or to align the whole structure.  Sometimes when this happens it is possible to rearrange
           the fields of the structure to reduce the padding and so make the structure smaller.

       -Wredundant-decls
           Warn if anything is declared more than once in the same scope, even in cases where
           multiple declaration is valid and changes nothing.

       -Wrestrict
           Warn when an object referenced by a "restrict"-qualified parameter (or, in C++, a
           "__restrict"-qualified parameter) is aliased by another argument, or when copies between
           such objects overlap.  For example, the call to the "strcpy" function below attempts to
           truncate the string by replacing its initial characters with the last four.  However,
           because the call writes the terminating NUL into "a[4]", the copies overlap and the call
           is diagnosed.

                   void foo (void)
                   {
                     char a[] = "abcd1234";
                     strcpy (a, a + 4);
                     ...
                   }

           The -Wrestrict option detects some instances of simple overlap even without optimization
           but works best at -O2 and above.  It is included in -Wall.

       -Wnested-externs (C and Objective-C only)
           Warn if an "extern" declaration is encountered within a function.

       -Winline
           Warn if a function that is declared as inline cannot be inlined.  Even with this option,
           the compiler does not warn about failures to inline functions declared in system headers.

           The compiler uses a variety of heuristics to determine whether or not to inline a
           function.  For example, the compiler takes into account the size of the function being
           inlined and the amount of inlining that has already been done in the current function.
           Therefore, seemingly insignificant changes in the source program can cause the warnings
           produced by -Winline to appear or disappear.

       -Wint-in-bool-context
           Warn for suspicious use of integer values where boolean values are expected, such as
           conditional expressions (?:) using non-boolean integer constants in boolean context, like
           "if (a <= b ? 2 : 3)".  Or left shifting of signed integers in boolean context, like "for
           (a = 0; 1 << a; a++);".  Likewise for all kinds of multiplications regardless of the data
           type.  This warning is enabled by -Wall.

       -Wno-int-to-pointer-cast
           Suppress warnings from casts to pointer type of an integer of a different size. In C++,
           casting to a pointer type of smaller size is an error. Wint-to-pointer-cast is enabled by
           default.

       -Wno-pointer-to-int-cast (C and Objective-C only)
           Suppress warnings from casts from a pointer to an integer type of a different size.

       -Winvalid-pch
           Warn if a precompiled header is found in the search path but cannot be used.

       -Wlong-long
           Warn if "long long" type is used.  This is enabled by either -Wpedantic or -Wtraditional
           in ISO C90 and C++98 modes.  To inhibit the warning messages, use -Wno-long-long.

       -Wvariadic-macros
           Warn if variadic macros are used in ISO C90 mode, or if the GNU alternate syntax is used
           in ISO C99 mode.  This is enabled by either -Wpedantic or -Wtraditional.  To inhibit the
           warning messages, use -Wno-variadic-macros.

       -Wno-varargs
           Do not warn upon questionable usage of the macros used to handle variable arguments like
           "va_start".  These warnings are enabled by default.

       -Wvector-operation-performance
           Warn if vector operation is not implemented via SIMD capabilities of the architecture.
           Mainly useful for the performance tuning.  Vector operation can be implemented
           "piecewise", which means that the scalar operation is performed on every vector element;
           "in parallel", which means that the vector operation is implemented using scalars of
           wider type, which normally is more performance efficient; and "as a single scalar", which
           means that vector fits into a scalar type.

       -Wvla
           Warn if a variable-length array is used in the code.  -Wno-vla prevents the -Wpedantic
           warning of the variable-length array.

       -Wvla-larger-than=byte-size
           If this option is used, the compiler warns for declarations of variable-length arrays
           whose size is either unbounded, or bounded by an argument that allows the array size to
           exceed byte-size bytes.  This is similar to how -Walloca-larger-than=byte-size works, but
           with variable-length arrays.

           Note that GCC may optimize small variable-length arrays of a known value into plain
           arrays, so this warning may not get triggered for such arrays.

           -Wvla-larger-than=PTRDIFF_MAX is enabled by default but is typically only effective when
           -ftree-vrp is active (default for -O2 and above).

           See also -Walloca-larger-than=byte-size.

       -Wno-vla-larger-than
           Disable -Wvla-larger-than= warnings.  The option is equivalent to
           -Wvla-larger-than=SIZE_MAX or larger.

       -Wvla-parameter
           Warn about redeclarations of functions involving arguments of Variable Length Array types
           of inconsistent kinds or forms, and enable the detection of out-of-bounds accesses to
           such parameters by warnings such as -Warray-bounds.

           If the first function declaration uses the VLA form the bound specified in the array is
           assumed to be the minimum number of elements expected to be provided in calls to the
           function and the maximum number of elements accessed by it.  Failing to provide arguments
           of sufficient size or accessing more than the maximum number of elements may be
           diagnosed.

           For example, the warning triggers for the following redeclarations because the first one
           allows an array of any size to be passed to "f" while the second one specifies that the
           array argument must have at least "n" elements.  In addition, calling "f" with the
           assotiated VLA bound parameter in excess of the actual VLA bound triggers a warning as
           well.

                   void f (int n, int[n]);
                   void f (int, int[]);     // warning: argument 2 previously declared as a VLA

                   void g (int n)
                   {
                       if (n > 4)
                         return;
                       int a[n];
                       f (sizeof a, a);     // warning: access to a by f may be out of bounds
                     ...
                   }

           -Wvla-parameter is included in -Wall.  The -Warray-parameter option triggers warnings for
           similar problems involving ordinary array arguments.

       -Wvolatile-register-var
           Warn if a register variable is declared volatile.  The volatile modifier does not inhibit
           all optimizations that may eliminate reads and/or writes to register variables.  This
           warning is enabled by -Wall.

       -Wdisabled-optimization
           Warn if a requested optimization pass is disabled.  This warning does not generally
           indicate that there is anything wrong with your code; it merely indicates that GCC's
           optimizers are unable to handle the code effectively.  Often, the problem is that your
           code is too big or too complex; GCC refuses to optimize programs when the optimization
           itself is likely to take inordinate amounts of time.

       -Wpointer-sign (C and Objective-C only)
           Warn for pointer argument passing or assignment with different signedness.  This option
           is only supported for C and Objective-C.  It is implied by -Wall and by -Wpedantic, which
           can be disabled with -Wno-pointer-sign.

       -Wstack-protector
           This option is only active when -fstack-protector is active.  It warns about functions
           that are not protected against stack smashing.

       -Woverlength-strings
           Warn about string constants that are longer than the "minimum maximum" length specified
           in the C standard.  Modern compilers generally allow string constants that are much
           longer than the standard's minimum limit, but very portable programs should avoid using
           longer strings.

           The limit applies after string constant concatenation, and does not count the trailing
           NUL.  In C90, the limit was 509 characters; in C99, it was raised to 4095.  C++98 does
           not specify a normative minimum maximum, so we do not diagnose overlength strings in C++.

           This option is implied by -Wpedantic, and can be disabled with -Wno-overlength-strings.

       -Wunsuffixed-float-constants (C and Objective-C only)
           Issue a warning for any floating constant that does not have a suffix.  When used
           together with -Wsystem-headers it warns about such constants in system header files.
           This can be useful when preparing code to use with the "FLOAT_CONST_DECIMAL64" pragma
           from the decimal floating-point extension to C99.

       -Wno-lto-type-mismatch
           During the link-time optimization, do not warn about type mismatches in global
           declarations from different compilation units.  Requires -flto to be enabled.  Enabled by
           default.

       -Wno-designated-init (C and Objective-C only)
           Suppress warnings when a positional initializer is used to initialize a structure that
           has been marked with the "designated_init" attribute.

   Options That Control Static Analysis
       -fanalyzer
           This option enables an static analysis of program flow which looks for "interesting"
           interprocedural paths through the code, and issues warnings for problems found on them.

           This analysis is much more expensive than other GCC warnings.

           Enabling this option effectively enables the following warnings:

           -Wanalyzer-double-fclose -Wanalyzer-double-free -Wanalyzer-exposure-through-output-file
           -Wanalyzer-file-leak -Wanalyzer-free-of-non-heap -Wanalyzer-malloc-leak
           -Wanalyzer-mismatching-deallocation -Wanalyzer-possible-null-argument
           -Wanalyzer-possible-null-dereference -Wanalyzer-null-argument -Wanalyzer-null-dereference
           -Wanalyzer-shift-count-negative -Wanalyzer-shift-count-overflow
           -Wanalyzer-stale-setjmp-buffer -Wanalyzer-tainted-array-index
           -Wanalyzer-unsafe-call-within-signal-handler -Wanalyzer-use-after-free
           -Wanalyzer-use-of-pointer-in-stale-stack-frame -Wanalyzer-write-to-const
           -Wanalyzer-write-to-string-literal

           This option is only available if GCC was configured with analyzer support enabled.

       -Wanalyzer-too-complex
           If -fanalyzer is enabled, the analyzer uses various heuristics to attempt to explore the
           control flow and data flow in the program, but these can be defeated by sufficiently
           complicated code.

           By default, the analysis silently stops if the code is too complicated for the analyzer
           to fully explore and it reaches an internal limit.  The -Wanalyzer-too-complex option
           warns if this occurs.

       -Wno-analyzer-double-fclose
           This warning requires -fanalyzer, which enables it; use -Wno-analyzer-double-fclose to
           disable it.

           This diagnostic warns for paths through the code in which a "FILE *" can have "fclose"
           called on it more than once.

       -Wno-analyzer-double-free
           This warning requires -fanalyzer, which enables it; use -Wno-analyzer-double-free to
           disable it.

           This diagnostic warns for paths through the code in which a pointer can have a
           deallocator called on it more than once, either "free", or a deallocator referenced by
           attribute "malloc".

       -Wno-analyzer-exposure-through-output-file
           This warning requires -fanalyzer, which enables it; use
           -Wno-analyzer-exposure-through-output-file to disable it.

           This diagnostic warns for paths through the code in which a security-sensitive value is
           written to an output file (such as writing a password to a log file).

       -Wno-analyzer-file-leak
           This warning requires -fanalyzer, which enables it; use -Wno-analyzer-file-leak to
           disable it.

           This diagnostic warns for paths through the code in which a "<stdio.h>" "FILE *" stream
           object is leaked.

       -Wno-analyzer-free-of-non-heap
           This warning requires -fanalyzer, which enables it; use -Wno-analyzer-free-of-non-heap to
           disable it.

           This diagnostic warns for paths through the code in which "free" is called on a non-heap
           pointer (e.g. an on-stack buffer, or a global).

       -Wno-analyzer-malloc-leak
           This warning requires -fanalyzer, which enables it; use -Wno-analyzer-malloc-leak to
           disable it.

           This diagnostic warns for paths through the code in which a pointer allocated via an
           allocator is leaked: either "malloc", or a function marked with attribute "malloc".

       -Wno-analyzer-mismatching-deallocation
           This warning requires -fanalyzer, which enables it; use
           -Wno-analyzer-mismatching-deallocation to disable it.

           This diagnostic warns for paths through the code in which the wrong deallocation function
           is called on a pointer value, based on which function was used to allocate the pointer
           value.  The diagnostic will warn about mismatches between "free", scalar "delete" and
           vector "delete[]", and those marked as allocator/deallocator pairs using attribute
           "malloc".

       -Wno-analyzer-possible-null-argument
           This warning requires -fanalyzer, which enables it; use
           -Wno-analyzer-possible-null-argument to disable it.

           This diagnostic warns for paths through the code in which a possibly-NULL value is passed
           to a function argument marked with "__attribute__((nonnull))" as requiring a non-NULL
           value.

       -Wno-analyzer-possible-null-dereference
           This warning requires -fanalyzer, which enables it; use
           -Wno-analyzer-possible-null-dereference to disable it.

           This diagnostic warns for paths through the code in which a possibly-NULL value is
           dereferenced.

       -Wno-analyzer-null-argument
           This warning requires -fanalyzer, which enables it; use -Wno-analyzer-null-argument to
           disable it.

           This diagnostic warns for paths through the code in which a value known to be NULL is
           passed to a function argument marked with "__attribute__((nonnull))" as requiring a non-
           NULL value.

       -Wno-analyzer-null-dereference
           This warning requires -fanalyzer, which enables it; use -Wno-analyzer-null-dereference to
           disable it.

           This diagnostic warns for paths through the code in which a value known to be NULL is
           dereferenced.

       -Wno-analyzer-shift-count-negative
           This warning requires -fanalyzer, which enables it; use
           -Wno-analyzer-shift-count-negative to disable it.

           This diagnostic warns for paths through the code in which a shift is attempted with a
           negative count.  It is analogous to the -Wshift-count-negative diagnostic implemented in
           the C/C++ front ends, but is implemented based on analyzing interprocedural paths, rather
           than merely parsing the syntax tree.  However, the analyzer does not prioritize detection
           of such paths, so false negatives are more likely relative to other warnings.

       -Wno-analyzer-shift-count-overflow
           This warning requires -fanalyzer, which enables it; use
           -Wno-analyzer-shift-count-overflow to disable it.

           This diagnostic warns for paths through the code in which a shift is attempted with a
           count greater than or equal to the precision of the operand's type.  It is analogous to
           the -Wshift-count-overflow diagnostic implemented in the C/C++ front ends, but is
           implemented based on analyzing interprocedural paths, rather than merely parsing the
           syntax tree.  However, the analyzer does not prioritize detection of such paths, so false
           negatives are more likely relative to other warnings.

       -Wno-analyzer-stale-setjmp-buffer
           This warning requires -fanalyzer, which enables it; use -Wno-analyzer-stale-setjmp-buffer
           to disable it.

           This diagnostic warns for paths through the code in which "longjmp" is called to rewind
           to a "jmp_buf" relating to a "setjmp" call in a function that has returned.

           When "setjmp" is called on a "jmp_buf" to record a rewind location, it records the stack
           frame.  The stack frame becomes invalid when the function containing the "setjmp" call
           returns.  Attempting to rewind to it via "longjmp" would reference a stack frame that no
           longer exists, and likely lead to a crash (or worse).

       -Wno-analyzer-tainted-array-index
           This warning requires both -fanalyzer and -fanalyzer-checker=taint to enable it; use
           -Wno-analyzer-tainted-array-index to disable it.

           This diagnostic warns for paths through the code in which a value that could be under an
           attacker's control is used as the index of an array access without being sanitized.

       -Wno-analyzer-unsafe-call-within-signal-handler
           This warning requires -fanalyzer, which enables it; use
           -Wno-analyzer-unsafe-call-within-signal-handler to disable it.

           This diagnostic warns for paths through the code in which a function known to be async-
           signal-unsafe (such as "fprintf") is called from a signal handler.

       -Wno-analyzer-use-after-free
           This warning requires -fanalyzer, which enables it; use -Wno-analyzer-use-after-free to
           disable it.

           This diagnostic warns for paths through the code in which a pointer is used after a
           deallocator is called on it: either "free", or a deallocator referenced by attribute
           "malloc".

       -Wno-analyzer-use-of-pointer-in-stale-stack-frame
           This warning requires -fanalyzer, which enables it; use
           -Wno-analyzer-use-of-pointer-in-stale-stack-frame to disable it.

           This diagnostic warns for paths through the code in which a pointer is dereferenced that
           points to a variable in a stale stack frame.

       -Wno-analyzer-write-to-const
           This warning requires -fanalyzer, which enables it; use -Wno-analyzer-write-to-const to
           disable it.

           This diagnostic warns for paths through the code in which the analyzer detects an attempt
           to write through a pointer to a "const" object.  However, the analyzer does not
           prioritize detection of such paths, so false negatives are more likely relative to other
           warnings.

       -Wno-analyzer-write-to-string-literal
           This warning requires -fanalyzer, which enables it; use
           -Wno-analyzer-write-to-string-literal to disable it.

           This diagnostic warns for paths through the code in which the analyzer detects an attempt
           to write through a pointer to a string literal.  However, the analyzer does not
           prioritize detection of such paths, so false negatives are more likely relative to other
           warnings.

       Pertinent parameters for controlling the exploration are: --param
       analyzer-bb-explosion-factor=value, --param analyzer-max-enodes-per-program-point=value,
       --param analyzer-max-recursion-depth=value, and --param
       analyzer-min-snodes-for-call-summary=value.

       The following options control the analyzer.

       -fanalyzer-call-summaries
           Simplify interprocedural analysis by computing the effect of certain calls, rather than
           exploring all paths through the function from callsite to each possible return.

           If enabled, call summaries are only used for functions with more than one call site, and
           that are sufficiently complicated (as per --param
           analyzer-min-snodes-for-call-summary=value).

       -fanalyzer-checker=name
           Restrict the analyzer to run just the named checker, and enable it.

           Some checkers are disabled by default (even with -fanalyzer), such as the "taint" checker
           that implements -Wanalyzer-tainted-array-index, and this option is required to enable
           them.

       -fno-analyzer-feasibility
           This option is intended for analyzer developers.

           By default the analyzer verifies that there is a feasible control flow path for each
           diagnostic it emits: that the conditions that hold are not mutually exclusive.
           Diagnostics for which no feasible path can be found are rejected.  This filtering can be
           suppressed with -fno-analyzer-feasibility, for debugging issues in this code.

       -fanalyzer-fine-grained
           This option is intended for analyzer developers.

           Internally the analyzer builds an "exploded graph" that combines control flow graphs with
           data flow information.

           By default, an edge in this graph can contain the effects of a run of multiple statements
           within a basic block.  With -fanalyzer-fine-grained, each statement gets its own edge.

       -fanalyzer-show-duplicate-count
           This option is intended for analyzer developers: if multiple diagnostics have been
           detected as being duplicates of each other, it emits a note when reporting the best
           diagnostic, giving the number of additional diagnostics that were suppressed by the
           deduplication logic.

       -fno-analyzer-state-merge
           This option is intended for analyzer developers.

           By default the analyzer attempts to simplify analysis by merging sufficiently similar
           states at each program point as it builds its "exploded graph".  With
           -fno-analyzer-state-merge this merging can be suppressed, for debugging state-handling
           issues.

       -fno-analyzer-state-purge
           This option is intended for analyzer developers.

           By default the analyzer attempts to simplify analysis by purging aspects of state at a
           program point that appear to no longer be relevant e.g. the values of locals that aren't
           accessed later in the function and which aren't relevant to leak analysis.

           With -fno-analyzer-state-purge this purging of state can be suppressed, for debugging
           state-handling issues.

       -fanalyzer-transitivity
           This option enables transitivity of constraints within the analyzer.

       -fanalyzer-verbose-edges
           This option is intended for analyzer developers.  It enables more verbose, lower-level
           detail in the descriptions of control flow within diagnostic paths.

       -fanalyzer-verbose-state-changes
           This option is intended for analyzer developers.  It enables more verbose, lower-level
           detail in the descriptions of events relating to state machines within diagnostic paths.

       -fanalyzer-verbosity=level
           This option controls the complexity of the control flow paths that are emitted for
           analyzer diagnostics.

           The level can be one of:

           0   At this level, interprocedural call and return events are displayed, along with the
               most pertinent state-change events relating to a diagnostic.  For example, for a
               double-"free" diagnostic, both calls to "free" will be shown.

           1   As per the previous level, but also show events for the entry to each function.

           2   As per the previous level, but also show events relating to control flow that are
               significant to triggering the issue (e.g. "true path taken" at a conditional).

               This level is the default.

           3   As per the previous level, but show all control flow events, not just significant
               ones.

           4   This level is intended for analyzer developers; it adds various other events intended
               for debugging the analyzer.

       -fdump-analyzer
           Dump internal details about what the analyzer is doing to file.analyzer.txt.  This option
           is overridden by -fdump-analyzer-stderr.

       -fdump-analyzer-stderr
           Dump internal details about what the analyzer is doing to stderr.  This option overrides
           -fdump-analyzer.

       -fdump-analyzer-callgraph
           Dump a representation of the call graph suitable for viewing with GraphViz to
           file.callgraph.dot.

       -fdump-analyzer-exploded-graph
           Dump a representation of the "exploded graph" suitable for viewing with GraphViz to
           file.eg.dot.  Nodes are color-coded based on state-machine states to emphasize state
           changes.

       -fdump-analyzer-exploded-nodes
           Emit diagnostics showing where nodes in the "exploded graph" are in relation to the
           program source.

       -fdump-analyzer-exploded-nodes-2
           Dump a textual representation of the "exploded graph" to file.eg.txt.

       -fdump-analyzer-exploded-nodes-3
           Dump a textual representation of the "exploded graph" to one dump file per node, to
           file.eg-id.txt.  This is typically a large number of dump files.

       -fdump-analyzer-feasibility
           Dump internal details about the analyzer's search for feasible paths.  The details are
           written in a form suitable for viewing with GraphViz to filenames of the form
           file.*.fg.dot and file.*.tg.dot.

       -fdump-analyzer-json
           Dump a compressed JSON representation of analyzer internals to file.analyzer.json.gz.
           The precise format is subject to change.

       -fdump-analyzer-state-purge
           As per -fdump-analyzer-supergraph, dump a representation of the "supergraph" suitable for
           viewing with GraphViz, but annotate the graph with information on what state will be
           purged at each node.  The graph is written to file.state-purge.dot.

       -fdump-analyzer-supergraph
           Dump representations of the "supergraph" suitable for viewing with GraphViz to
           file.supergraph.dot and to file.supergraph-eg.dot.  These show all of the control flow
           graphs in the program, with interprocedural edges for calls and returns.  The second dump
           contains annotations showing nodes in the "exploded graph" and diagnostics associated
           with them.

   Options for Debugging Your Program
       To tell GCC to emit extra information for use by a debugger, in almost all cases you need
       only to add -g to your other options.

       GCC allows you to use -g with -O.  The shortcuts taken by optimized code may occasionally be
       surprising: some variables you declared may not exist at all; flow of control may briefly
       move where you did not expect it; some statements may not be executed because they compute
       constant results or their values are already at hand; some statements may execute in
       different places because they have been moved out of loops.  Nevertheless it is possible to
       debug optimized output.  This makes it reasonable to use the optimizer for programs that
       might have bugs.

       If you are not using some other optimization option, consider using -Og with -g.  With no -O
       option at all, some compiler passes that collect information useful for debugging do not run
       at all, so that -Og may result in a better debugging experience.

       -g  Produce debugging information in the operating system's native format (stabs, COFF,
           XCOFF, or DWARF).  GDB can work with this debugging information.

           On most systems that use stabs format, -g enables use of extra debugging information that
           only GDB can use; this extra information makes debugging work better in GDB but probably
           makes other debuggers crash or refuse to read the program.  If you want to control for
           certain whether to generate the extra information, use -gstabs+, -gstabs, -gxcoff+,
           -gxcoff, or -gvms (see below).

       -ggdb
           Produce debugging information for use by GDB.  This means to use the most expressive
           format available (DWARF, stabs, or the native format if neither of those are supported),
           including GDB extensions if at all possible.

       -gdwarf
       -gdwarf-version
           Produce debugging information in DWARF format (if that is supported).  The value of
           version may be either 2, 3, 4 or 5; the default version for most targets is 5 (with the
           exception of VxWorks, TPF and Darwin/Mac OS X, which default to version 2, and AIX, which
           defaults to version 4).

           Note that with DWARF Version 2, some ports require and always use some non-conflicting
           DWARF 3 extensions in the unwind tables.

           Version 4 may require GDB 7.0 and -fvar-tracking-assignments for maximum benefit. Version
           5 requires GDB 8.0 or higher.

           GCC no longer supports DWARF Version 1, which is substantially different than Version 2
           and later.  For historical reasons, some other DWARF-related options such as
           -fno-dwarf2-cfi-asm) retain a reference to DWARF Version 2 in their names, but apply to
           all currently-supported versions of DWARF.

       -gstabs
           Produce debugging information in stabs format (if that is supported), without GDB
           extensions.  This is the format used by DBX on most BSD systems.  On MIPS, Alpha and
           System V Release 4 systems this option produces stabs debugging output that is not
           understood by DBX.  On System V Release 4 systems this option requires the GNU assembler.

       -gstabs+
           Produce debugging information in stabs format (if that is supported), using GNU
           extensions understood only by the GNU debugger (GDB).  The use of these extensions is
           likely to make other debuggers crash or refuse to read the program.

       -gxcoff
           Produce debugging information in XCOFF format (if that is supported).  This is the format
           used by the DBX debugger on IBM RS/6000 systems.

       -gxcoff+
           Produce debugging information in XCOFF format (if that is supported), using GNU
           extensions understood only by the GNU debugger (GDB).  The use of these extensions is
           likely to make other debuggers crash or refuse to read the program, and may cause
           assemblers other than the GNU assembler (GAS) to fail with an error.

       -gvms
           Produce debugging information in Alpha/VMS debug format (if that is supported).  This is
           the format used by DEBUG on Alpha/VMS systems.

       -glevel
       -ggdblevel
       -gstabslevel
       -gxcofflevel
       -gvmslevel
           Request debugging information and also use level to specify how much information.  The
           default level is 2.

           Level 0 produces no debug information at all.  Thus, -g0 negates -g.

           Level 1 produces minimal information, enough for making backtraces in parts of the
           program that you don't plan to debug.  This includes descriptions of functions and
           external variables, and line number tables, but no information about local variables.

           Level 3 includes extra information, such as all the macro definitions present in the
           program.  Some debuggers support macro expansion when you use -g3.

           If you use multiple -g options, with or without level numbers, the last such option is
           the one that is effective.

           -gdwarf does not accept a concatenated debug level, to avoid confusion with
           -gdwarf-level.  Instead use an additional -glevel option to change the debug level for
           DWARF.

       -fno-eliminate-unused-debug-symbols
           By default, no debug information is produced for symbols that are not actually used. Use
           this option if you want debug information for all symbols.

       -femit-class-debug-always
           Instead of emitting debugging information for a C++ class in only one object file, emit
           it in all object files using the class.  This option should be used only with debuggers
           that are unable to handle the way GCC normally emits debugging information for classes
           because using this option increases the size of debugging information by as much as a
           factor of two.

       -fno-merge-debug-strings
           Direct the linker to not merge together strings in the debugging information that are
           identical in different object files.  Merging is not supported by all assemblers or
           linkers.  Merging decreases the size of the debug information in the output file at the
           cost of increasing link processing time.  Merging is enabled by default.

       -fdebug-prefix-map=old=new
           When compiling files residing in directory old, record debugging information describing
           them as if the files resided in directory new instead.  This can be used to replace a
           build-time path with an install-time path in the debug info.  It can also be used to
           change an absolute path to a relative path by using . for new.  This can give more
           reproducible builds, which are location independent, but may require an extra command to
           tell GDB where to find the source files. See also -ffile-prefix-map.

       -fvar-tracking
           Run variable tracking pass.  It computes where variables are stored at each position in
           code.  Better debugging information is then generated (if the debugging information
           format supports this information).

           It is enabled by default when compiling with optimization (-Os, -O, -O2, ...), debugging
           information (-g) and the debug info format supports it.

       -fvar-tracking-assignments
           Annotate assignments to user variables early in the compilation and attempt to carry the
           annotations over throughout the compilation all the way to the end, in an attempt to
           improve debug information while optimizing.  Use of -gdwarf-4 is recommended along with
           it.

           It can be enabled even if var-tracking is disabled, in which case annotations are created
           and maintained, but discarded at the end.  By default, this flag is enabled together with
           -fvar-tracking, except when selective scheduling is enabled.

       -gsplit-dwarf
           If DWARF debugging information is enabled, separate as much debugging information as
           possible into a separate output file with the extension .dwo.  This option allows the
           build system to avoid linking files with debug information.  To be useful, this option
           requires a debugger capable of reading .dwo files.

       -gdwarf32
       -gdwarf64
           If DWARF debugging information is enabled, the -gdwarf32 selects the 32-bit DWARF format
           and the -gdwarf64 selects the 64-bit DWARF format.  The default is target specific, on
           most targets it is -gdwarf32 though.  The 32-bit DWARF format is smaller, but can't
           support more than 2GiB of debug information in any of the DWARF debug information
           sections.  The 64-bit DWARF format allows larger debug information and might not be well
           supported by all consumers yet.

       -gdescribe-dies
           Add description attributes to some DWARF DIEs that have no name attribute, such as
           artificial variables, external references and call site parameter DIEs.

       -gpubnames
           Generate DWARF ".debug_pubnames" and ".debug_pubtypes" sections.

       -ggnu-pubnames
           Generate ".debug_pubnames" and ".debug_pubtypes" sections in a format suitable for
           conversion into a GDB index.  This option is only useful with a linker that can produce
           GDB index version 7.

       -fdebug-types-section
           When using DWARF Version 4 or higher, type DIEs can be put into their own ".debug_types"
           section instead of making them part of the ".debug_info" section.  It is more efficient
           to put them in a separate comdat section since the linker can then remove duplicates.
           But not all DWARF consumers support ".debug_types" sections yet and on some objects
           ".debug_types" produces larger instead of smaller debugging information.

       -grecord-gcc-switches
       -gno-record-gcc-switches
           This switch causes the command-line options used to invoke the compiler that may affect
           code generation to be appended to the DW_AT_producer attribute in DWARF debugging
           information.  The options are concatenated with spaces separating them from each other
           and from the compiler version.  It is enabled by default.  See also -frecord-gcc-switches
           for another way of storing compiler options into the object file.

       -gstrict-dwarf
           Disallow using extensions of later DWARF standard version than selected with
           -gdwarf-version.  On most targets using non-conflicting DWARF extensions from later
           standard versions is allowed.

       -gno-strict-dwarf
           Allow using extensions of later DWARF standard version than selected with
           -gdwarf-version.

       -gas-loc-support
           Inform the compiler that the assembler supports ".loc" directives.  It may then use them
           for the assembler to generate DWARF2+ line number tables.

           This is generally desirable, because assembler-generated line-number tables are a lot
           more compact than those the compiler can generate itself.

           This option will be enabled by default if, at GCC configure time, the assembler was found
           to support such directives.

       -gno-as-loc-support
           Force GCC to generate DWARF2+ line number tables internally, if DWARF2+ line number
           tables are to be generated.

       -gas-locview-support
           Inform the compiler that the assembler supports "view" assignment and reset assertion
           checking in ".loc" directives.

           This option will be enabled by default if, at GCC configure time, the assembler was found
           to support them.

       -gno-as-locview-support
           Force GCC to assign view numbers internally, if -gvariable-location-views are explicitly
           requested.

       -gcolumn-info
       -gno-column-info
           Emit location column information into DWARF debugging information, rather than just file
           and line.  This option is enabled by default.

       -gstatement-frontiers
       -gno-statement-frontiers
           This option causes GCC to create markers in the internal representation at the beginning
           of statements, and to keep them roughly in place throughout compilation, using them to
           guide the output of "is_stmt" markers in the line number table.  This is enabled by
           default when compiling with optimization (-Os, -O, -O2, ...), and outputting DWARF 2
           debug information at the normal level.

       -gvariable-location-views
       -gvariable-location-views=incompat5
       -gno-variable-location-views
           Augment variable location lists with progressive view numbers implied from the line
           number table.  This enables debug information consumers to inspect state at certain
           points of the program, even if no instructions associated with the corresponding source
           locations are present at that point.  If the assembler lacks support for view numbers in
           line number tables, this will cause the compiler to emit the line number table, which
           generally makes them somewhat less compact.  The augmented line number tables and
           location lists are fully backward-compatible, so they can be consumed by debug
           information consumers that are not aware of these augmentations, but they won't derive
           any benefit from them either.

           This is enabled by default when outputting DWARF 2 debug information at the normal level,
           as long as there is assembler support, -fvar-tracking-assignments is enabled and
           -gstrict-dwarf is not.  When assembler support is not available, this may still be
           enabled, but it will force GCC to output internal line number tables, and if
           -ginternal-reset-location-views is not enabled, that will most certainly lead to silently
           mismatching location views.

           There is a proposed representation for view numbers that is not backward compatible with
           the location list format introduced in DWARF 5, that can be enabled with
           -gvariable-location-views=incompat5.  This option may be removed in the future, is only
           provided as a reference implementation of the proposed representation.  Debug information
           consumers are not expected to support this extended format, and they would be rendered
           unable to decode location lists using it.

       -ginternal-reset-location-views
       -gno-internal-reset-location-views
           Attempt to determine location views that can be omitted from location view lists.  This
           requires the compiler to have very accurate insn length estimates, which isn't always the
           case, and it may cause incorrect view lists to be generated silently when using an
           assembler that does not support location view lists.  The GNU assembler will flag any
           such error as a "view number mismatch".  This is only enabled on ports that define a
           reliable estimation function.

       -ginline-points
       -gno-inline-points
           Generate extended debug information for inlined functions.  Location view tracking
           markers are inserted at inlined entry points, so that address and view numbers can be
           computed and output in debug information.  This can be enabled independently of location
           views, in which case the view numbers won't be output, but it can only be enabled along
           with statement frontiers, and it is only enabled by default if location views are
           enabled.

       -gz[=type]
           Produce compressed debug sections in DWARF format, if that is supported.  If type is not
           given, the default type depends on the capabilities of the assembler and linker used.
           type may be one of none (don't compress debug sections), zlib (use zlib compression in
           ELF gABI format), or zlib-gnu (use zlib compression in traditional GNU format).  If the
           linker doesn't support writing compressed debug sections, the option is rejected.
           Otherwise, if the assembler does not support them, -gz is silently ignored when producing
           object files.

       -femit-struct-debug-baseonly
           Emit debug information for struct-like types only when the base name of the compilation
           source file matches the base name of file in which the struct is defined.

           This option substantially reduces the size of debugging information, but at significant
           potential loss in type information to the debugger.  See -femit-struct-debug-reduced for
           a less aggressive option.  See -femit-struct-debug-detailed for more detailed control.

           This option works only with DWARF debug output.

       -femit-struct-debug-reduced
           Emit debug information for struct-like types only when the base name of the compilation
           source file matches the base name of file in which the type is defined, unless the struct
           is a template or defined in a system header.

           This option significantly reduces the size of debugging information, with some potential
           loss in type information to the debugger.  See -femit-struct-debug-baseonly for a more
           aggressive option.  See -femit-struct-debug-detailed for more detailed control.

           This option works only with DWARF debug output.

       -femit-struct-debug-detailed[=spec-list]
           Specify the struct-like types for which the compiler generates debug information.  The
           intent is to reduce duplicate struct debug information between different object files
           within the same program.

           This option is a detailed version of -femit-struct-debug-reduced and
           -femit-struct-debug-baseonly, which serves for most needs.

           A specification has the syntax[dir:|ind:][ord:|gen:](any|sys|base|none)

           The optional first word limits the specification to structs that are used directly (dir:)
           or used indirectly (ind:).  A struct type is used directly when it is the type of a
           variable, member.  Indirect uses arise through pointers to structs.  That is, when use of
           an incomplete struct is valid, the use is indirect.  An example is struct one direct;
           struct two * indirect;.

           The optional second word limits the specification to ordinary structs (ord:) or generic
           structs (gen:).  Generic structs are a bit complicated to explain.  For C++, these are
           non-explicit specializations of template classes, or non-template classes within the
           above.  Other programming languages have generics, but -femit-struct-debug-detailed does
           not yet implement them.

           The third word specifies the source files for those structs for which the compiler should
           emit debug information.  The values none and any have the normal meaning.  The value base
           means that the base of name of the file in which the type declaration appears must match
           the base of the name of the main compilation file.  In practice, this means that when
           compiling foo.c, debug information is generated for types declared in that file and
           foo.h, but not other header files.  The value sys means those types satisfying base or
           declared in system or compiler headers.

           You may need to experiment to determine the best settings for your application.

           The default is -femit-struct-debug-detailed=all.

           This option works only with DWARF debug output.

       -fno-dwarf2-cfi-asm
           Emit DWARF unwind info as compiler generated ".eh_frame" section instead of using GAS
           ".cfi_*" directives.

       -fno-eliminate-unused-debug-types
           Normally, when producing DWARF output, GCC avoids producing debug symbol output for types
           that are nowhere used in the source file being compiled.  Sometimes it is useful to have
           GCC emit debugging information for all types declared in a compilation unit, regardless
           of whether or not they are actually used in that compilation unit, for example if, in the
           debugger, you want to cast a value to a type that is not actually used in your program
           (but is declared).  More often, however, this results in a significant amount of wasted
           space.

   Options That Control Optimization
       These options control various sorts of optimizations.

       Without any optimization option, the compiler's goal is to reduce the cost of compilation and
       to make debugging produce the expected results.  Statements are independent: if you stop the
       program with a breakpoint between statements, you can then assign a new value to any variable
       or change the program counter to any other statement in the function and get exactly the
       results you expect from the source code.

       Turning on optimization flags makes the compiler attempt to improve the performance and/or
       code size at the expense of compilation time and possibly the ability to debug the program.

       The compiler performs optimization based on the knowledge it has of the program.  Compiling
       multiple files at once to a single output file mode allows the compiler to use information
       gained from all of the files when compiling each of them.

       Not all optimizations are controlled directly by a flag.  Only optimizations that have a flag
       are listed in this section.

       Most optimizations are completely disabled at -O0 or if an -O level is not set on the command
       line, even if individual optimization flags are specified.  Similarly, -Og suppresses many
       optimization passes.

       Depending on the target and how GCC was configured, a slightly different set of optimizations
       may be enabled at each -O level than those listed here.  You can invoke GCC with -Q
       --help=optimizers to find out the exact set of optimizations that are enabled at each level.

       -O
       -O1 Optimize.  Optimizing compilation takes somewhat more time, and a lot more memory for a
           large function.

           With -O, the compiler tries to reduce code size and execution time, without performing
           any optimizations that take a great deal of compilation time.

           -O turns on the following optimization flags:

           -fauto-inc-dec -fbranch-count-reg -fcombine-stack-adjustments -fcompare-elim
           -fcprop-registers -fdce -fdefer-pop -fdelayed-branch -fdse -fforward-propagate
           -fguess-branch-probability -fif-conversion -fif-conversion2
           -finline-functions-called-once -fipa-modref -fipa-profile -fipa-pure-const
           -fipa-reference -fipa-reference-addressable -fmerge-constants -fmove-loop-invariants
           -fomit-frame-pointer -freorder-blocks -fshrink-wrap -fshrink-wrap-separate
           -fsplit-wide-types -fssa-backprop -fssa-phiopt -ftree-bit-ccp -ftree-ccp -ftree-ch
           -ftree-coalesce-vars -ftree-copy-prop -ftree-dce -ftree-dominator-opts -ftree-dse
           -ftree-forwprop -ftree-fre -ftree-phiprop -ftree-pta -ftree-scev-cprop -ftree-sink
           -ftree-slsr -ftree-sra -ftree-ter -funit-at-a-time

       -O2 Optimize even more.  GCC performs nearly all supported optimizations that do not involve
           a space-speed tradeoff.  As compared to -O, this option increases both compilation time
           and the performance of the generated code.

           -O2 turns on all optimization flags specified by -O.  It also turns on the following
           optimization flags:

           -falign-functions  -falign-jumps -falign-labels  -falign-loops -fcaller-saves
           -fcode-hoisting -fcrossjumping -fcse-follow-jumps  -fcse-skip-blocks
           -fdelete-null-pointer-checks -fdevirtualize  -fdevirtualize-speculatively
           -fexpensive-optimizations -ffinite-loops -fgcse  -fgcse-lm -fhoist-adjacent-loads
           -finline-functions -finline-small-functions -findirect-inlining -fipa-bit-cp  -fipa-cp
           -fipa-icf -fipa-ra  -fipa-sra  -fipa-vrp -fisolate-erroneous-paths-dereference
           -flra-remat -foptimize-sibling-calls -foptimize-strlen -fpartial-inlining -fpeephole2
           -freorder-blocks-algorithm=stc -freorder-blocks-and-partition  -freorder-functions
           -frerun-cse-after-loop -fschedule-insns  -fschedule-insns2 -fsched-interblock
           -fsched-spec -fstore-merging -fstrict-aliasing -fthread-jumps -ftree-builtin-call-dce
           -ftree-pre -ftree-switch-conversion  -ftree-tail-merge -ftree-vrp

           Please note the warning under -fgcse about invoking -O2 on programs that use computed
           gotos.

           NOTE: In Ubuntu 8.10 and later versions, -D_FORTIFY_SOURCE=2 is set by default, and is
           activated when -O is set to 2 or higher.  This enables additional compile-time and run-
           time checks for several libc functions.  To disable, specify either -U_FORTIFY_SOURCE or
           -D_FORTIFY_SOURCE=0.

       -O3 Optimize yet more.  -O3 turns on all optimizations specified by -O2 and also turns on the
           following optimization flags:

           -fgcse-after-reload -fipa-cp-clone -floop-interchange -floop-unroll-and-jam -fpeel-loops
           -fpredictive-commoning -fsplit-loops -fsplit-paths -ftree-loop-distribution
           -ftree-loop-vectorize -ftree-partial-pre -ftree-slp-vectorize -funswitch-loops
           -fvect-cost-model -fvect-cost-model=dynamic -fversion-loops-for-strides

       -O0 Reduce compilation time and make debugging produce the expected results.  This is the
           default.

       -Os Optimize for size.  -Os enables all -O2 optimizations except those that often increase
           code size:

           -falign-functions  -falign-jumps -falign-labels  -falign-loops -fprefetch-loop-arrays
           -freorder-blocks-algorithm=stc

           It also enables -finline-functions, causes the compiler to tune for code size rather than
           execution speed, and performs further optimizations designed to reduce code size.

       -Ofast
           Disregard strict standards compliance.  -Ofast enables all -O3 optimizations.  It also
           enables optimizations that are not valid for all standard-compliant programs.  It turns
           on -ffast-math, -fallow-store-data-races and the Fortran-specific -fstack-arrays, unless
           -fmax-stack-var-size is specified, and -fno-protect-parens.

       -Og Optimize debugging experience.  -Og should be the optimization level of choice for the
           standard edit-compile-debug cycle, offering a reasonable level of optimization while
           maintaining fast compilation and a good debugging experience.  It is a better choice than
           -O0 for producing debuggable code because some compiler passes that collect debug
           information are disabled at -O0.

           Like -O0, -Og completely disables a number of optimization passes so that individual
           options controlling them have no effect.  Otherwise -Og enables all -O1 optimization
           flags except for those that may interfere with debugging:

           -fbranch-count-reg  -fdelayed-branch -fdse  -fif-conversion  -fif-conversion2
           -finline-functions-called-once -fmove-loop-invariants  -fssa-phiopt -ftree-bit-ccp
           -ftree-dse  -ftree-pta  -ftree-sra

       If you use multiple -O options, with or without level numbers, the last such option is the
       one that is effective.

       Options of the form -fflag specify machine-independent flags.  Most flags have both positive
       and negative forms; the negative form of -ffoo is -fno-foo.  In the table below, only one of
       the forms is listed---the one you typically use.  You can figure out the other form by either
       removing no- or adding it.

       The following options control specific optimizations.  They are either activated by -O
       options or are related to ones that are.  You can use the following flags in the rare cases
       when "fine-tuning" of optimizations to be performed is desired.

       -fno-defer-pop
           For machines that must pop arguments after a function call, always pop the arguments as
           soon as each function returns.  At levels -O1 and higher, -fdefer-pop is the default;
           this allows the compiler to let arguments accumulate on the stack for several function
           calls and pop them all at once.

       -fforward-propagate
           Perform a forward propagation pass on RTL.  The pass tries to combine two instructions
           and checks if the result can be simplified.  If loop unrolling is active, two passes are
           performed and the second is scheduled after loop unrolling.

           This option is enabled by default at optimization levels -O, -O2, -O3, -Os.

       -ffp-contract=style
           -ffp-contract=off disables floating-point expression contraction.  -ffp-contract=fast
           enables floating-point expression contraction such as forming of fused multiply-add
           operations if the target has native support for them.  -ffp-contract=on enables floating-
           point expression contraction if allowed by the language standard.  This is currently not
           implemented and treated equal to -ffp-contract=off.

           The default is -ffp-contract=fast.

       -fomit-frame-pointer
           Omit the frame pointer in functions that don't need one.  This avoids the instructions to
           save, set up and restore the frame pointer; on many targets it also makes an extra
           register available.

           On some targets this flag has no effect because the standard calling sequence always uses
           a frame pointer, so it cannot be omitted.

           Note that -fno-omit-frame-pointer doesn't guarantee the frame pointer is used in all
           functions.  Several targets always omit the frame pointer in leaf functions.

           Enabled by default at -O and higher.

       -foptimize-sibling-calls
           Optimize sibling and tail recursive calls.

           Enabled at levels -O2, -O3, -Os.

       -foptimize-strlen
           Optimize various standard C string functions (e.g. "strlen", "strchr" or "strcpy") and
           their "_FORTIFY_SOURCE" counterparts into faster alternatives.

           Enabled at levels -O2, -O3.

       -fno-inline
           Do not expand any functions inline apart from those marked with the "always_inline"
           attribute.  This is the default when not optimizing.

           Single functions can be exempted from inlining by marking them with the "noinline"
           attribute.

       -finline-small-functions
           Integrate functions into their callers when their body is smaller than expected function
           call code (so overall size of program gets smaller).  The compiler heuristically decides
           which functions are simple enough to be worth integrating in this way.  This inlining
           applies to all functions, even those not declared inline.

           Enabled at levels -O2, -O3, -Os.

       -findirect-inlining
           Inline also indirect calls that are discovered to be known at compile time thanks to
           previous inlining.  This option has any effect only when inlining itself is turned on by
           the -finline-functions or -finline-small-functions options.

           Enabled at levels -O2, -O3, -Os.

       -finline-functions
           Consider all functions for inlining, even if they are not declared inline.  The compiler
           heuristically decides which functions are worth integrating in this way.

           If all calls to a given function are integrated, and the function is declared "static",
           then the function is normally not output as assembler code in its own right.

           Enabled at levels -O2, -O3, -Os.  Also enabled by -fprofile-use and -fauto-profile.

       -finline-functions-called-once
           Consider all "static" functions called once for inlining into their caller even if they
           are not marked "inline".  If a call to a given function is integrated, then the function
           is not output as assembler code in its own right.

           Enabled at levels -O1, -O2, -O3 and -Os, but not -Og.

       -fearly-inlining
           Inline functions marked by "always_inline" and functions whose body seems smaller than
           the function call overhead early before doing -fprofile-generate instrumentation and real
           inlining pass.  Doing so makes profiling significantly cheaper and usually inlining
           faster on programs having large chains of nested wrapper functions.

           Enabled by default.

       -fipa-sra
           Perform interprocedural scalar replacement of aggregates, removal of unused parameters
           and replacement of parameters passed by reference by parameters passed by value.

           Enabled at levels -O2, -O3 and -Os.

       -finline-limit=n
           By default, GCC limits the size of functions that can be inlined.  This flag allows
           coarse control of this limit.  n is the size of functions that can be inlined in number
           of pseudo instructions.

           Inlining is actually controlled by a number of parameters, which may be specified
           individually by using --param name=value.  The -finline-limit=n option sets some of these
           parameters as follows:

           max-inline-insns-single
               is set to n/2.

           max-inline-insns-auto
               is set to n/2.

           See below for a documentation of the individual parameters controlling inlining and for
           the defaults of these parameters.

           Note: there may be no value to -finline-limit that results in default behavior.

           Note: pseudo instruction represents, in this particular context, an abstract measurement
           of function's size.  In no way does it represent a count of assembly instructions and as
           such its exact meaning might change from one release to an another.

       -fno-keep-inline-dllexport
           This is a more fine-grained version of -fkeep-inline-functions, which applies only to
           functions that are declared using the "dllexport" attribute or declspec.

       -fkeep-inline-functions
           In C, emit "static" functions that are declared "inline" into the object file, even if
           the function has been inlined into all of its callers.  This switch does not affect
           functions using the "extern inline" extension in GNU C90.  In C++, emit any and all
           inline functions into the object file.

       -fkeep-static-functions
           Emit "static" functions into the object file, even if the function is never used.

       -fkeep-static-consts
           Emit variables declared "static const" when optimization isn't turned on, even if the
           variables aren't referenced.

           GCC enables this option by default.  If you want to force the compiler to check if a
           variable is referenced, regardless of whether or not optimization is turned on, use the
           -fno-keep-static-consts option.

       -fmerge-constants
           Attempt to merge identical constants (string constants and floating-point constants)
           across compilation units.

           This option is the default for optimized compilation if the assembler and linker support
           it.  Use -fno-merge-constants to inhibit this behavior.

           Enabled at levels -O, -O2, -O3, -Os.

       -fmerge-all-constants
           Attempt to merge identical constants and identical variables.

           This option implies -fmerge-constants.  In addition to -fmerge-constants this considers
           e.g. even constant initialized arrays or initialized constant variables with integral or
           floating-point types.  Languages like C or C++ require each variable, including multiple
           instances of the same variable in recursive calls, to have distinct locations, so using
           this option results in non-conforming behavior.

       -fmodulo-sched
           Perform swing modulo scheduling immediately before the first scheduling pass.  This pass
           looks at innermost loops and reorders their instructions by overlapping different
           iterations.

       -fmodulo-sched-allow-regmoves
           Perform more aggressive SMS-based modulo scheduling with register moves allowed.  By
           setting this flag certain anti-dependences edges are deleted, which triggers the
           generation of reg-moves based on the life-range analysis.  This option is effective only
           with -fmodulo-sched enabled.

       -fno-branch-count-reg
           Disable the optimization pass that scans for opportunities to use "decrement and branch"
           instructions on a count register instead of instruction sequences that decrement a
           register, compare it against zero, and then branch based upon the result.  This option is
           only meaningful on architectures that support such instructions, which include x86,
           PowerPC, IA-64 and S/390.  Note that the -fno-branch-count-reg option doesn't remove the
           decrement and branch instructions from the generated instruction stream introduced by
           other optimization passes.

           The default is -fbranch-count-reg at -O1 and higher, except for -Og.

       -fno-function-cse
           Do not put function addresses in registers; make each instruction that calls a constant
           function contain the function's address explicitly.

           This option results in less efficient code, but some strange hacks that alter the
           assembler output may be confused by the optimizations performed when this option is not
           used.

           The default is -ffunction-cse

       -fno-zero-initialized-in-bss
           If the target supports a BSS section, GCC by default puts variables that are initialized
           to zero into BSS.  This can save space in the resulting code.

           This option turns off this behavior because some programs explicitly rely on variables
           going to the data section---e.g., so that the resulting executable can find the beginning
           of that section and/or make assumptions based on that.

           The default is -fzero-initialized-in-bss.

       -fthread-jumps
           Perform optimizations that check to see if a jump branches to a location where another
           comparison subsumed by the first is found.  If so, the first branch is redirected to
           either the destination of the second branch or a point immediately following it,
           depending on whether the condition is known to be true or false.

           Enabled at levels -O2, -O3, -Os.

       -fsplit-wide-types
           When using a type that occupies multiple registers, such as "long long" on a 32-bit
           system, split the registers apart and allocate them independently.  This normally
           generates better code for those types, but may make debugging more difficult.

           Enabled at levels -O, -O2, -O3, -Os.

       -fsplit-wide-types-early
           Fully split wide types early, instead of very late.  This option has no effect unless
           -fsplit-wide-types is turned on.

           This is the default on some targets.

       -fcse-follow-jumps
           In common subexpression elimination (CSE), scan through jump instructions when the target
           of the jump is not reached by any other path.  For example, when CSE encounters an "if"
           statement with an "else" clause, CSE follows the jump when the condition tested is false.

           Enabled at levels -O2, -O3, -Os.

       -fcse-skip-blocks
           This is similar to -fcse-follow-jumps, but causes CSE to follow jumps that conditionally
           skip over blocks.  When CSE encounters a simple "if" statement with no else clause,
           -fcse-skip-blocks causes CSE to follow the jump around the body of the "if".

           Enabled at levels -O2, -O3, -Os.

       -frerun-cse-after-loop
           Re-run common subexpression elimination after loop optimizations are performed.

           Enabled at levels -O2, -O3, -Os.

       -fgcse
           Perform a global common subexpression elimination pass.  This pass also performs global
           constant and copy propagation.

           Note: When compiling a program using computed gotos, a GCC extension, you may get better
           run-time performance if you disable the global common subexpression elimination pass by
           adding -fno-gcse to the command line.

           Enabled at levels -O2, -O3, -Os.

       -fgcse-lm
           When -fgcse-lm is enabled, global common subexpression elimination attempts to move loads
           that are only killed by stores into themselves.  This allows a loop containing a
           load/store sequence to be changed to a load outside the loop, and a copy/store within the
           loop.

           Enabled by default when -fgcse is enabled.

       -fgcse-sm
           When -fgcse-sm is enabled, a store motion pass is run after global common subexpression
           elimination.  This pass attempts to move stores out of loops.  When used in conjunction
           with -fgcse-lm, loops containing a load/store sequence can be changed to a load before
           the loop and a store after the loop.

           Not enabled at any optimization level.

       -fgcse-las
           When -fgcse-las is enabled, the global common subexpression elimination pass eliminates
           redundant loads that come after stores to the same memory location (both partial and full
           redundancies).

           Not enabled at any optimization level.

       -fgcse-after-reload
           When -fgcse-after-reload is enabled, a redundant load elimination pass is performed after
           reload.  The purpose of this pass is to clean up redundant spilling.

           Enabled by -fprofile-use and -fauto-profile.

       -faggressive-loop-optimizations
           This option tells the loop optimizer to use language constraints to derive bounds for the
           number of iterations of a loop.  This assumes that loop code does not invoke undefined
           behavior by for example causing signed integer overflows or out-of-bound array accesses.
           The bounds for the number of iterations of a loop are used to guide loop unrolling and
           peeling and loop exit test optimizations.  This option is enabled by default.

       -funconstrained-commons
           This option tells the compiler that variables declared in common blocks (e.g. Fortran)
           may later be overridden with longer trailing arrays. This prevents certain optimizations
           that depend on knowing the array bounds.

       -fcrossjumping
           Perform cross-jumping transformation.  This transformation unifies equivalent code and
           saves code size.  The resulting code may or may not perform better than without cross-
           jumping.

           Enabled at levels -O2, -O3, -Os.

       -fauto-inc-dec
           Combine increments or decrements of addresses with memory accesses.  This pass is always
           skipped on architectures that do not have instructions to support this.  Enabled by
           default at -O and higher on architectures that support this.

       -fdce
           Perform dead code elimination (DCE) on RTL.  Enabled by default at -O and higher.

       -fdse
           Perform dead store elimination (DSE) on RTL.  Enabled by default at -O and higher.

       -fif-conversion
           Attempt to transform conditional jumps into branch-less equivalents.  This includes use
           of conditional moves, min, max, set flags and abs instructions, and some tricks doable by
           standard arithmetics.  The use of conditional execution on chips where it is available is
           controlled by -fif-conversion2.

           Enabled at levels -O, -O2, -O3, -Os, but not with -Og.

       -fif-conversion2
           Use conditional execution (where available) to transform conditional jumps into branch-
           less equivalents.

           Enabled at levels -O, -O2, -O3, -Os, but not with -Og.

       -fdeclone-ctor-dtor
           The C++ ABI requires multiple entry points for constructors and destructors: one for a
           base subobject, one for a complete object, and one for a virtual destructor that calls
           operator delete afterwards.  For a hierarchy with virtual bases, the base and complete
           variants are clones, which means two copies of the function.  With this option, the base
           and complete variants are changed to be thunks that call a common implementation.

           Enabled by -Os.

       -fdelete-null-pointer-checks
           Assume that programs cannot safely dereference null pointers, and that no code or data
           element resides at address zero.  This option enables simple constant folding
           optimizations at all optimization levels.  In addition, other optimization passes in GCC
           use this flag to control global dataflow analyses that eliminate useless checks for null
           pointers; these assume that a memory access to address zero always results in a trap, so
           that if a pointer is checked after it has already been dereferenced, it cannot be null.

           Note however that in some environments this assumption is not true.  Use
           -fno-delete-null-pointer-checks to disable this optimization for programs that depend on
           that behavior.

           This option is enabled by default on most targets.  On Nios II ELF, it defaults to off.
           On AVR, CR16, and MSP430, this option is completely disabled.

           Passes that use the dataflow information are enabled independently at different
           optimization levels.

       -fdevirtualize
           Attempt to convert calls to virtual functions to direct calls.  This is done both within
           a procedure and interprocedurally as part of indirect inlining (-findirect-inlining) and
           interprocedural constant propagation (-fipa-cp).  Enabled at levels -O2, -O3, -Os.

       -fdevirtualize-speculatively
           Attempt to convert calls to virtual functions to speculative direct calls.  Based on the
           analysis of the type inheritance graph, determine for a given call the set of likely
           targets. If the set is small, preferably of size 1, change the call into a conditional
           deciding between direct and indirect calls.  The speculative calls enable more
           optimizations, such as inlining.  When they seem useless after further optimization, they
           are converted back into original form.

       -fdevirtualize-at-ltrans
           Stream extra information needed for aggressive devirtualization when running the link-
           time optimizer in local transformation mode.  This option enables more devirtualization
           but significantly increases the size of streamed data. For this reason it is disabled by
           default.

       -fexpensive-optimizations
           Perform a number of minor optimizations that are relatively expensive.

           Enabled at levels -O2, -O3, -Os.

       -free
           Attempt to remove redundant extension instructions.  This is especially helpful for the
           x86-64 architecture, which implicitly zero-extends in 64-bit registers after writing to
           their lower 32-bit half.

           Enabled for Alpha, AArch64 and x86 at levels -O2, -O3, -Os.

       -fno-lifetime-dse
           In C++ the value of an object is only affected by changes within its lifetime: when the
           constructor begins, the object has an indeterminate value, and any changes during the
           lifetime of the object are dead when the object is destroyed.  Normally dead store
           elimination will take advantage of this; if your code relies on the value of the object
           storage persisting beyond the lifetime of the object, you can use this flag to disable
           this optimization.  To preserve stores before the constructor starts (e.g. because your
           operator new clears the object storage) but still treat the object as dead after the
           destructor, you can use -flifetime-dse=1.  The default behavior can be explicitly
           selected with -flifetime-dse=2.  -flifetime-dse=0 is equivalent to -fno-lifetime-dse.

       -flive-range-shrinkage
           Attempt to decrease register pressure through register live range shrinkage.  This is
           helpful for fast processors with small or moderate size register sets.

       -fira-algorithm=algorithm
           Use the specified coloring algorithm for the integrated register allocator.  The
           algorithm argument can be priority, which specifies Chow's priority coloring, or CB,
           which specifies Chaitin-Briggs coloring.  Chaitin-Briggs coloring is not implemented for
           all architectures, but for those targets that do support it, it is the default because it
           generates better code.

       -fira-region=region
           Use specified regions for the integrated register allocator.  The region argument should
           be one of the following:

           all Use all loops as register allocation regions.  This can give the best results for
               machines with a small and/or irregular register set.

           mixed
               Use all loops except for loops with small register pressure as the regions.  This
               value usually gives the best results in most cases and for most architectures, and is
               enabled by default when compiling with optimization for speed (-O, -O2, ...).

           one Use all functions as a single region.  This typically results in the smallest code
               size, and is enabled by default for -Os or -O0.

       -fira-hoist-pressure
           Use IRA to evaluate register pressure in the code hoisting pass for decisions to hoist
           expressions.  This option usually results in smaller code, but it can slow the compiler
           down.

           This option is enabled at level -Os for all targets.

       -fira-loop-pressure
           Use IRA to evaluate register pressure in loops for decisions to move loop invariants.
           This option usually results in generation of faster and smaller code on machines with
           large register files (>= 32 registers), but it can slow the compiler down.

           This option is enabled at level -O3 for some targets.

       -fno-ira-share-save-slots
           Disable sharing of stack slots used for saving call-used hard registers living through a
           call.  Each hard register gets a separate stack slot, and as a result function stack
           frames are larger.

       -fno-ira-share-spill-slots
           Disable sharing of stack slots allocated for pseudo-registers.  Each pseudo-register that
           does not get a hard register gets a separate stack slot, and as a result function stack
           frames are larger.

       -flra-remat
           Enable CFG-sensitive rematerialization in LRA.  Instead of loading values of spilled
           pseudos, LRA tries to rematerialize (recalculate) values if it is profitable.

           Enabled at levels -O2, -O3, -Os.

       -fdelayed-branch
           If supported for the target machine, attempt to reorder instructions to exploit
           instruction slots available after delayed branch instructions.

           Enabled at levels -O, -O2, -O3, -Os, but not at -Og.

       -fschedule-insns
           If supported for the target machine, attempt to reorder instructions to eliminate
           execution stalls due to required data being unavailable.  This helps machines that have
           slow floating point or memory load instructions by allowing other instructions to be
           issued until the result of the load or floating-point instruction is required.

           Enabled at levels -O2, -O3.

       -fschedule-insns2
           Similar to -fschedule-insns, but requests an additional pass of instruction scheduling
           after register allocation has been done.  This is especially useful on machines with a
           relatively small number of registers and where memory load instructions take more than
           one cycle.

           Enabled at levels -O2, -O3, -Os.

       -fno-sched-interblock
           Disable instruction scheduling across basic blocks, which is normally enabled when
           scheduling before register allocation, i.e.  with -fschedule-insns or at -O2 or higher.

       -fno-sched-spec
           Disable speculative motion of non-load instructions, which is normally enabled when
           scheduling before register allocation, i.e.  with -fschedule-insns or at -O2 or higher.

       -fsched-pressure
           Enable register pressure sensitive insn scheduling before register allocation.  This only
           makes sense when scheduling before register allocation is enabled, i.e. with
           -fschedule-insns or at -O2 or higher.  Usage of this option can improve the generated
           code and decrease its size by preventing register pressure increase above the number of
           available hard registers and subsequent spills in register allocation.

       -fsched-spec-load
           Allow speculative motion of some load instructions.  This only makes sense when
           scheduling before register allocation, i.e. with -fschedule-insns or at -O2 or higher.

       -fsched-spec-load-dangerous
           Allow speculative motion of more load instructions.  This only makes sense when
           scheduling before register allocation, i.e. with -fschedule-insns or at -O2 or higher.

       -fsched-stalled-insns
       -fsched-stalled-insns=n
           Define how many insns (if any) can be moved prematurely from the queue of stalled insns
           into the ready list during the second scheduling pass.  -fno-sched-stalled-insns means
           that no insns are moved prematurely, -fsched-stalled-insns=0 means there is no limit on
           how many queued insns can be moved prematurely.  -fsched-stalled-insns without a value is
           equivalent to -fsched-stalled-insns=1.

       -fsched-stalled-insns-dep
       -fsched-stalled-insns-dep=n
           Define how many insn groups (cycles) are examined for a dependency on a stalled insn that
           is a candidate for premature removal from the queue of stalled insns.  This has an effect
           only during the second scheduling pass, and only if -fsched-stalled-insns is used.
           -fno-sched-stalled-insns-dep is equivalent to -fsched-stalled-insns-dep=0.
           -fsched-stalled-insns-dep without a value is equivalent to -fsched-stalled-insns-dep=1.

       -fsched2-use-superblocks
           When scheduling after register allocation, use superblock scheduling.  This allows motion
           across basic block boundaries, resulting in faster schedules.  This option is
           experimental, as not all machine descriptions used by GCC model the CPU closely enough to
           avoid unreliable results from the algorithm.

           This only makes sense when scheduling after register allocation, i.e. with
           -fschedule-insns2 or at -O2 or higher.

       -fsched-group-heuristic
           Enable the group heuristic in the scheduler.  This heuristic favors the instruction that
           belongs to a schedule group.  This is enabled by default when scheduling is enabled, i.e.
           with -fschedule-insns or -fschedule-insns2 or at -O2 or higher.

       -fsched-critical-path-heuristic
           Enable the critical-path heuristic in the scheduler.  This heuristic favors instructions
           on the critical path.  This is enabled by default when scheduling is enabled, i.e. with
           -fschedule-insns or -fschedule-insns2 or at -O2 or higher.

       -fsched-spec-insn-heuristic
           Enable the speculative instruction heuristic in the scheduler.  This heuristic favors
           speculative instructions with greater dependency weakness.  This is enabled by default
           when scheduling is enabled, i.e.  with -fschedule-insns or -fschedule-insns2 or at -O2 or
           higher.

       -fsched-rank-heuristic
           Enable the rank heuristic in the scheduler.  This heuristic favors the instruction
           belonging to a basic block with greater size or frequency.  This is enabled by default
           when scheduling is enabled, i.e.  with -fschedule-insns or -fschedule-insns2 or at -O2 or
           higher.

       -fsched-last-insn-heuristic
           Enable the last-instruction heuristic in the scheduler.  This heuristic favors the
           instruction that is less dependent on the last instruction scheduled.  This is enabled by
           default when scheduling is enabled, i.e. with -fschedule-insns or -fschedule-insns2 or at
           -O2 or higher.

       -fsched-dep-count-heuristic
           Enable the dependent-count heuristic in the scheduler.  This heuristic favors the
           instruction that has more instructions depending on it.  This is enabled by default when
           scheduling is enabled, i.e.  with -fschedule-insns or -fschedule-insns2 or at -O2 or
           higher.

       -freschedule-modulo-scheduled-loops
           Modulo scheduling is performed before traditional scheduling.  If a loop is modulo
           scheduled, later scheduling passes may change its schedule.  Use this option to control
           that behavior.

       -fselective-scheduling
           Schedule instructions using selective scheduling algorithm.  Selective scheduling runs
           instead of the first scheduler pass.

       -fselective-scheduling2
           Schedule instructions using selective scheduling algorithm.  Selective scheduling runs
           instead of the second scheduler pass.

       -fsel-sched-pipelining
           Enable software pipelining of innermost loops during selective scheduling.  This option
           has no effect unless one of -fselective-scheduling or -fselective-scheduling2 is turned
           on.

       -fsel-sched-pipelining-outer-loops
           When pipelining loops during selective scheduling, also pipeline outer loops.  This
           option has no effect unless -fsel-sched-pipelining is turned on.

       -fsemantic-interposition
           Some object formats, like ELF, allow interposing of symbols by the dynamic linker.  This
           means that for symbols exported from the DSO, the compiler cannot perform interprocedural
           propagation, inlining and other optimizations in anticipation that the function or
           variable in question may change. While this feature is useful, for example, to rewrite
           memory allocation functions by a debugging implementation, it is expensive in the terms
           of code quality.  With -fno-semantic-interposition the compiler assumes that if
           interposition happens for functions the overwriting function will have precisely the same
           semantics (and side effects).  Similarly if interposition happens for variables, the
           constructor of the variable will be the same. The flag has no effect for functions
           explicitly declared inline (where it is never allowed for interposition to change
           semantics) and for symbols explicitly declared weak.

       -fshrink-wrap
           Emit function prologues only before parts of the function that need it, rather than at
           the top of the function.  This flag is enabled by default at -O and higher.

       -fshrink-wrap-separate
           Shrink-wrap separate parts of the prologue and epilogue separately, so that those parts
           are only executed when needed.  This option is on by default, but has no effect unless
           -fshrink-wrap is also turned on and the target supports this.

       -fcaller-saves
           Enable allocation of values to registers that are clobbered by function calls, by
           emitting extra instructions to save and restore the registers around such calls.  Such
           allocation is done only when it seems to result in better code.

           This option is always enabled by default on certain machines, usually those which have no
           call-preserved registers to use instead.

           Enabled at levels -O2, -O3, -Os.

       -fcombine-stack-adjustments
           Tracks stack adjustments (pushes and pops) and stack memory references and then tries to
           find ways to combine them.

           Enabled by default at -O1 and higher.

       -fipa-ra
           Use caller save registers for allocation if those registers are not used by any called
           function.  In that case it is not necessary to save and restore them around calls.  This
           is only possible if called functions are part of same compilation unit as current
           function and they are compiled before it.

           Enabled at levels -O2, -O3, -Os, however the option is disabled if generated code will be
           instrumented for profiling (-p, or -pg) or if callee's register usage cannot be known
           exactly (this happens on targets that do not expose prologues and epilogues in RTL).

       -fconserve-stack
           Attempt to minimize stack usage.  The compiler attempts to use less stack space, even if
           that makes the program slower.  This option implies setting the large-stack-frame
           parameter to 100 and the large-stack-frame-growth parameter to 400.

       -ftree-reassoc
           Perform reassociation on trees.  This flag is enabled by default at -O and higher.

       -fcode-hoisting
           Perform code hoisting.  Code hoisting tries to move the evaluation of expressions
           executed on all paths to the function exit as early as possible.  This is especially
           useful as a code size optimization, but it often helps for code speed as well.  This flag
           is enabled by default at -O2 and higher.

       -ftree-pre
           Perform partial redundancy elimination (PRE) on trees.  This flag is enabled by default
           at -O2 and -O3.

       -ftree-partial-pre
           Make partial redundancy elimination (PRE) more aggressive.  This flag is enabled by
           default at -O3.

       -ftree-forwprop
           Perform forward propagation on trees.  This flag is enabled by default at -O and higher.

       -ftree-fre
           Perform full redundancy elimination (FRE) on trees.  The difference between FRE and PRE
           is that FRE only considers expressions that are computed on all paths leading to the
           redundant computation.  This analysis is faster than PRE, though it exposes fewer
           redundancies.  This flag is enabled by default at -O and higher.

       -ftree-phiprop
           Perform hoisting of loads from conditional pointers on trees.  This pass is enabled by
           default at -O and higher.

       -fhoist-adjacent-loads
           Speculatively hoist loads from both branches of an if-then-else if the loads are from
           adjacent locations in the same structure and the target architecture has a conditional
           move instruction.  This flag is enabled by default at -O2 and higher.

       -ftree-copy-prop
           Perform copy propagation on trees.  This pass eliminates unnecessary copy operations.
           This flag is enabled by default at -O and higher.

       -fipa-pure-const
           Discover which functions are pure or constant.  Enabled by default at -O and higher.

       -fipa-reference
           Discover which static variables do not escape the compilation unit.  Enabled by default
           at -O and higher.

       -fipa-reference-addressable
           Discover read-only, write-only and non-addressable static variables.  Enabled by default
           at -O and higher.

       -fipa-stack-alignment
           Reduce stack alignment on call sites if possible.  Enabled by default.

       -fipa-pta
           Perform interprocedural pointer analysis and interprocedural modification and reference
           analysis.  This option can cause excessive memory and compile-time usage on large
           compilation units.  It is not enabled by default at any optimization level.

       -fipa-profile
           Perform interprocedural profile propagation.  The functions called only from cold
           functions are marked as cold. Also functions executed once (such as "cold", "noreturn",
           static constructors or destructors) are identified. Cold functions and loop less parts of
           functions executed once are then optimized for size.  Enabled by default at -O and
           higher.

       -fipa-modref
           Perform interprocedural mod/ref analysis.  This optimization analyzes the side effects of
           functions (memory locations that are modified or referenced) and enables better
           optimization across the function call boundary.  This flag is enabled by default at -O
           and higher.

       -fipa-cp
           Perform interprocedural constant propagation.  This optimization analyzes the program to
           determine when values passed to functions are constants and then optimizes accordingly.
           This optimization can substantially increase performance if the application has constants
           passed to functions.  This flag is enabled by default at -O2, -Os and -O3.  It is also
           enabled by -fprofile-use and -fauto-profile.

       -fipa-cp-clone
           Perform function cloning to make interprocedural constant propagation stronger.  When
           enabled, interprocedural constant propagation performs function cloning when externally
           visible function can be called with constant arguments.  Because this optimization can
           create multiple copies of functions, it may significantly increase code size (see --param
           ipa-cp-unit-growth=value).  This flag is enabled by default at -O3.  It is also enabled
           by -fprofile-use and -fauto-profile.

       -fipa-bit-cp
           When enabled, perform interprocedural bitwise constant propagation. This flag is enabled
           by default at -O2 and by -fprofile-use and -fauto-profile.  It requires that -fipa-cp is
           enabled.

       -fipa-vrp
           When enabled, perform interprocedural propagation of value ranges. This flag is enabled
           by default at -O2. It requires that -fipa-cp is enabled.

       -fipa-icf
           Perform Identical Code Folding for functions and read-only variables.  The optimization
           reduces code size and may disturb unwind stacks by replacing a function by equivalent one
           with a different name. The optimization works more effectively with link-time
           optimization enabled.

           Although the behavior is similar to the Gold Linker's ICF optimization, GCC ICF works on
           different levels and thus the optimizations are not same - there are equivalences that
           are found only by GCC and equivalences found only by Gold.

           This flag is enabled by default at -O2 and -Os.

       -flive-patching=level
           Control GCC's optimizations to produce output suitable for live-patching.

           If the compiler's optimization uses a function's body or information extracted from its
           body to optimize/change another function, the latter is called an impacted function of
           the former.  If a function is patched, its impacted functions should be patched too.

           The impacted functions are determined by the compiler's interprocedural optimizations.
           For example, a caller is impacted when inlining a function into its caller, cloning a
           function and changing its caller to call this new clone, or extracting a function's
           pureness/constness information to optimize its direct or indirect callers, etc.

           Usually, the more IPA optimizations enabled, the larger the number of impacted functions
           for each function.  In order to control the number of impacted functions and more easily
           compute the list of impacted function, IPA optimizations can be partially enabled at two
           different levels.

           The level argument should be one of the following:

           inline-clone
               Only enable inlining and cloning optimizations, which includes inlining, cloning,
               interprocedural scalar replacement of aggregates and partial inlining.  As a result,
               when patching a function, all its callers and its clones' callers are impacted,
               therefore need to be patched as well.

               -flive-patching=inline-clone disables the following optimization flags:
               -fwhole-program  -fipa-pta  -fipa-reference  -fipa-ra -fipa-icf  -fipa-icf-functions
               -fipa-icf-variables -fipa-bit-cp  -fipa-vrp  -fipa-pure-const
               -fipa-reference-addressable -fipa-stack-alignment -fipa-modref

           inline-only-static
               Only enable inlining of static functions.  As a result, when patching a static
               function, all its callers are impacted and so need to be patched as well.

               In addition to all the flags that -flive-patching=inline-clone disables,
               -flive-patching=inline-only-static disables the following additional optimization
               flags: -fipa-cp-clone  -fipa-sra  -fpartial-inlining  -fipa-cp

           When -flive-patching is specified without any value, the default value is inline-clone.

           This flag is disabled by default.

           Note that -flive-patching is not supported with link-time optimization (-flto).

       -fisolate-erroneous-paths-dereference
           Detect paths that trigger erroneous or undefined behavior due to dereferencing a null
           pointer.  Isolate those paths from the main control flow and turn the statement with
           erroneous or undefined behavior into a trap.  This flag is enabled by default at -O2 and
           higher and depends on -fdelete-null-pointer-checks also being enabled.

       -fisolate-erroneous-paths-attribute
           Detect paths that trigger erroneous or undefined behavior due to a null value being used
           in a way forbidden by a "returns_nonnull" or "nonnull" attribute.  Isolate those paths
           from the main control flow and turn the statement with erroneous or undefined behavior
           into a trap.  This is not currently enabled, but may be enabled by -O2 in the future.

       -ftree-sink
           Perform forward store motion on trees.  This flag is enabled by default at -O and higher.

       -ftree-bit-ccp
           Perform sparse conditional bit constant propagation on trees and propagate pointer
           alignment information.  This pass only operates on local scalar variables and is enabled
           by default at -O1 and higher, except for -Og.  It requires that -ftree-ccp is enabled.

       -ftree-ccp
           Perform sparse conditional constant propagation (CCP) on trees.  This pass only operates
           on local scalar variables and is enabled by default at -O and higher.

       -fssa-backprop
           Propagate information about uses of a value up the definition chain in order to simplify
           the definitions.  For example, this pass strips sign operations if the sign of a value
           never matters.  The flag is enabled by default at -O and higher.

       -fssa-phiopt
           Perform pattern matching on SSA PHI nodes to optimize conditional code.  This pass is
           enabled by default at -O1 and higher, except for -Og.

       -ftree-switch-conversion
           Perform conversion of simple initializations in a switch to initializations from a scalar
           array.  This flag is enabled by default at -O2 and higher.

       -ftree-tail-merge
           Look for identical code sequences.  When found, replace one with a jump to the other.
           This optimization is known as tail merging or cross jumping.  This flag is enabled by
           default at -O2 and higher.  The compilation time in this pass can be limited using max-
           tail-merge-comparisons parameter and max-tail-merge-iterations parameter.

       -ftree-dce
           Perform dead code elimination (DCE) on trees.  This flag is enabled by default at -O and
           higher.

       -ftree-builtin-call-dce
           Perform conditional dead code elimination (DCE) for calls to built-in functions that may
           set "errno" but are otherwise free of side effects.  This flag is enabled by default at
           -O2 and higher if -Os is not also specified.

       -ffinite-loops
           Assume that a loop with an exit will eventually take the exit and not loop indefinitely.
           This allows the compiler to remove loops that otherwise have no side-effects, not
           considering eventual endless looping as such.

           This option is enabled by default at -O2 for C++ with -std=c++11 or higher.

       -ftree-dominator-opts
           Perform a variety of simple scalar cleanups (constant/copy propagation, redundancy
           elimination, range propagation and expression simplification) based on a dominator tree
           traversal.  This also performs jump threading (to reduce jumps to jumps). This flag is
           enabled by default at -O and higher.

       -ftree-dse
           Perform dead store elimination (DSE) on trees.  A dead store is a store into a memory
           location that is later overwritten by another store without any intervening loads.  In
           this case the earlier store can be deleted.  This flag is enabled by default at -O and
           higher.

       -ftree-ch
           Perform loop header copying on trees.  This is beneficial since it increases
           effectiveness of code motion optimizations.  It also saves one jump.  This flag is
           enabled by default at -O and higher.  It is not enabled for -Os, since it usually
           increases code size.

       -ftree-loop-optimize
           Perform loop optimizations on trees.  This flag is enabled by default at -O and higher.

       -ftree-loop-linear
       -floop-strip-mine
       -floop-block
           Perform loop nest optimizations.  Same as -floop-nest-optimize.  To use this code
           transformation, GCC has to be configured with --with-isl to enable the Graphite loop
           transformation infrastructure.

       -fgraphite-identity
           Enable the identity transformation for graphite.  For every SCoP we generate the
           polyhedral representation and transform it back to gimple.  Using -fgraphite-identity we
           can check the costs or benefits of the GIMPLE -> GRAPHITE -> GIMPLE transformation.  Some
           minimal optimizations are also performed by the code generator isl, like index splitting
           and dead code elimination in loops.

       -floop-nest-optimize
           Enable the isl based loop nest optimizer.  This is a generic loop nest optimizer based on
           the Pluto optimization algorithms.  It calculates a loop structure optimized for data-
           locality and parallelism.  This option is experimental.

       -floop-parallelize-all
           Use the Graphite data dependence analysis to identify loops that can be parallelized.
           Parallelize all the loops that can be analyzed to not contain loop carried dependences
           without checking that it is profitable to parallelize the loops.

       -ftree-coalesce-vars
           While transforming the program out of the SSA representation, attempt to reduce copying
           by coalescing versions of different user-defined variables, instead of just compiler
           temporaries.  This may severely limit the ability to debug an optimized program compiled
           with -fno-var-tracking-assignments.  In the negated form, this flag prevents SSA
           coalescing of user variables.  This option is enabled by default if optimization is
           enabled, and it does very little otherwise.

       -ftree-loop-if-convert
           Attempt to transform conditional jumps in the innermost loops to branch-less equivalents.
           The intent is to remove control-flow from the innermost loops in order to improve the
           ability of the vectorization pass to handle these loops.  This is enabled by default if
           vectorization is enabled.

       -ftree-loop-distribution
           Perform loop distribution.  This flag can improve cache performance on big loop bodies
           and allow further loop optimizations, like parallelization or vectorization, to take
           place.  For example, the loop

                   DO I = 1, N
                     A(I) = B(I) + C
                     D(I) = E(I) * F
                   ENDDO

           is transformed to

                   DO I = 1, N
                      A(I) = B(I) + C
                   ENDDO
                   DO I = 1, N
                      D(I) = E(I) * F
                   ENDDO

           This flag is enabled by default at -O3.  It is also enabled by -fprofile-use and
           -fauto-profile.

       -ftree-loop-distribute-patterns
           Perform loop distribution of patterns that can be code generated with calls to a library.
           This flag is enabled by default at -O2 and higher, and by -fprofile-use and
           -fauto-profile.

           This pass distributes the initialization loops and generates a call to memset zero.  For
           example, the loop

                   DO I = 1, N
                     A(I) = 0
                     B(I) = A(I) + I
                   ENDDO

           is transformed to

                   DO I = 1, N
                      A(I) = 0
                   ENDDO
                   DO I = 1, N
                      B(I) = A(I) + I
                   ENDDO

           and the initialization loop is transformed into a call to memset zero.  This flag is
           enabled by default at -O3.  It is also enabled by -fprofile-use and -fauto-profile.

       -floop-interchange
           Perform loop interchange outside of graphite.  This flag can improve cache performance on
           loop nest and allow further loop optimizations, like vectorization, to take place.  For
           example, the loop

                   for (int i = 0; i < N; i++)
                     for (int j = 0; j < N; j++)
                       for (int k = 0; k < N; k++)
                         c[i][j] = c[i][j] + a[i][k]*b[k][j];

           is transformed to

                   for (int i = 0; i < N; i++)
                     for (int k = 0; k < N; k++)
                       for (int j = 0; j < N; j++)
                         c[i][j] = c[i][j] + a[i][k]*b[k][j];

           This flag is enabled by default at -O3.  It is also enabled by -fprofile-use and
           -fauto-profile.

       -floop-unroll-and-jam
           Apply unroll and jam transformations on feasible loops.  In a loop nest this unrolls the
           outer loop by some factor and fuses the resulting multiple inner loops.  This flag is
           enabled by default at -O3.  It is also enabled by -fprofile-use and -fauto-profile.

       -ftree-loop-im
           Perform loop invariant motion on trees.  This pass moves only invariants that are hard to
           handle at RTL level (function calls, operations that expand to nontrivial sequences of
           insns).  With -funswitch-loops it also moves operands of conditions that are invariant
           out of the loop, so that we can use just trivial invariantness analysis in loop
           unswitching.  The pass also includes store motion.

       -ftree-loop-ivcanon
           Create a canonical counter for number of iterations in loops for which determining number
           of iterations requires complicated analysis.  Later optimizations then may determine the
           number easily.  Useful especially in connection with unrolling.

       -ftree-scev-cprop
           Perform final value replacement.  If a variable is modified in a loop in such a way that
           its value when exiting the loop can be determined using only its initial value and the
           number of loop iterations, replace uses of the final value by such a computation,
           provided it is sufficiently cheap.  This reduces data dependencies and may allow further
           simplifications.  Enabled by default at -O and higher.

       -fivopts
           Perform induction variable optimizations (strength reduction, induction variable merging
           and induction variable elimination) on trees.

       -ftree-parallelize-loops=n
           Parallelize loops, i.e., split their iteration space to run in n threads.  This is only
           possible for loops whose iterations are independent and can be arbitrarily reordered.
           The optimization is only profitable on multiprocessor machines, for loops that are CPU-
           intensive, rather than constrained e.g. by memory bandwidth.  This option implies
           -pthread, and thus is only supported on targets that have support for -pthread.

       -ftree-pta
           Perform function-local points-to analysis on trees.  This flag is enabled by default at
           -O1 and higher, except for -Og.

       -ftree-sra
           Perform scalar replacement of aggregates.  This pass replaces structure references with
           scalars to prevent committing structures to memory too early.  This flag is enabled by
           default at -O1 and higher, except for -Og.

       -fstore-merging
           Perform merging of narrow stores to consecutive memory addresses.  This pass merges
           contiguous stores of immediate values narrower than a word into fewer wider stores to
           reduce the number of instructions.  This is enabled by default at -O2 and higher as well
           as -Os.

       -ftree-ter
           Perform temporary expression replacement during the SSA->normal phase.  Single use/single
           def temporaries are replaced at their use location with their defining expression.  This
           results in non-GIMPLE code, but gives the expanders much more complex trees to work on
           resulting in better RTL generation.  This is enabled by default at -O and higher.

       -ftree-slsr
           Perform straight-line strength reduction on trees.  This recognizes related expressions
           involving multiplications and replaces them by less expensive calculations when possible.
           This is enabled by default at -O and higher.

       -ftree-vectorize
           Perform vectorization on trees. This flag enables -ftree-loop-vectorize and
           -ftree-slp-vectorize if not explicitly specified.

       -ftree-loop-vectorize
           Perform loop vectorization on trees. This flag is enabled by default at -O3 and by
           -ftree-vectorize, -fprofile-use, and -fauto-profile.

       -ftree-slp-vectorize
           Perform basic block vectorization on trees. This flag is enabled by default at -O3 and by
           -ftree-vectorize, -fprofile-use, and -fauto-profile.

       -fvect-cost-model=model
           Alter the cost model used for vectorization.  The model argument should be one of
           unlimited, dynamic, cheap or very-cheap.  With the unlimited model the vectorized code-
           path is assumed to be profitable while with the dynamic model a runtime check guards the
           vectorized code-path to enable it only for iteration counts that will likely execute
           faster than when executing the original scalar loop.  The cheap model disables
           vectorization of loops where doing so would be cost prohibitive for example due to
           required runtime checks for data dependence or alignment but otherwise is equal to the
           dynamic model.  The very-cheap model only allows vectorization if the vector code would
           entirely replace the scalar code that is being vectorized.  For example, if each
           iteration of a vectorized loop would only be able to handle exactly four iterations of
           the scalar loop, the very-cheap model would only allow vectorization if the scalar
           iteration count is known to be a multiple of four.

           The default cost model depends on other optimization flags and is either dynamic or
           cheap.

       -fsimd-cost-model=model
           Alter the cost model used for vectorization of loops marked with the OpenMP simd
           directive.  The model argument should be one of unlimited, dynamic, cheap.  All values of
           model have the same meaning as described in -fvect-cost-model and by default a cost model
           defined with -fvect-cost-model is used.

       -ftree-vrp
           Perform Value Range Propagation on trees.  This is similar to the constant propagation
           pass, but instead of values, ranges of values are propagated.  This allows the optimizers
           to remove unnecessary range checks like array bound checks and null pointer checks.  This
           is enabled by default at -O2 and higher.  Null pointer check elimination is only done if
           -fdelete-null-pointer-checks is enabled.

       -fsplit-paths
           Split paths leading to loop backedges.  This can improve dead code elimination and common
           subexpression elimination.  This is enabled by default at -O3 and above.

       -fsplit-ivs-in-unroller
           Enables expression of values of induction variables in later iterations of the unrolled
           loop using the value in the first iteration.  This breaks long dependency chains, thus
           improving efficiency of the scheduling passes.

           A combination of -fweb and CSE is often sufficient to obtain the same effect.  However,
           that is not reliable in cases where the loop body is more complicated than a single basic
           block.  It also does not work at all on some architectures due to restrictions in the CSE
           pass.

           This optimization is enabled by default.

       -fvariable-expansion-in-unroller
           With this option, the compiler creates multiple copies of some local variables when
           unrolling a loop, which can result in superior code.

           This optimization is enabled by default for PowerPC targets, but disabled by default
           otherwise.

       -fpartial-inlining
           Inline parts of functions.  This option has any effect only when inlining itself is
           turned on by the -finline-functions or -finline-small-functions options.

           Enabled at levels -O2, -O3, -Os.

       -fpredictive-commoning
           Perform predictive commoning optimization, i.e., reusing computations (especially memory
           loads and stores) performed in previous iterations of loops.

           This option is enabled at level -O3.  It is also enabled by -fprofile-use and
           -fauto-profile.

       -fprefetch-loop-arrays
           If supported by the target machine, generate instructions to prefetch memory to improve
           the performance of loops that access large arrays.

           This option may generate better or worse code; results are highly dependent on the
           structure of loops within the source code.

           Disabled at level -Os.

       -fno-printf-return-value
           Do not substitute constants for known return value of formatted output functions such as
           "sprintf", "snprintf", "vsprintf", and "vsnprintf" (but not "printf" of "fprintf").  This
           transformation allows GCC to optimize or even eliminate branches based on the known
           return value of these functions called with arguments that are either constant, or whose
           values are known to be in a range that makes determining the exact return value possible.
           For example, when -fprintf-return-value is in effect, both the branch and the body of the
           "if" statement (but not the call to "snprint") can be optimized away when "i" is a 32-bit
           or smaller integer because the return value is guaranteed to be at most 8.

                   char buf[9];
                   if (snprintf (buf, "%08x", i) >= sizeof buf)
                     ...

           The -fprintf-return-value option relies on other optimizations and yields best results
           with -O2 and above.  It works in tandem with the -Wformat-overflow and
           -Wformat-truncation options.  The -fprintf-return-value option is enabled by default.

       -fno-peephole
       -fno-peephole2
           Disable any machine-specific peephole optimizations.  The difference between
           -fno-peephole and -fno-peephole2 is in how they are implemented in the compiler; some
           targets use one, some use the other, a few use both.

           -fpeephole is enabled by default.  -fpeephole2 enabled at levels -O2, -O3, -Os.

       -fno-guess-branch-probability
           Do not guess branch probabilities using heuristics.

           GCC uses heuristics to guess branch probabilities if they are not provided by profiling
           feedback (-fprofile-arcs).  These heuristics are based on the control flow graph.  If
           some branch probabilities are specified by "__builtin_expect", then the heuristics are
           used to guess branch probabilities for the rest of the control flow graph, taking the
           "__builtin_expect" info into account.  The interactions between the heuristics and
           "__builtin_expect" can be complex, and in some cases, it may be useful to disable the
           heuristics so that the effects of "__builtin_expect" are easier to understand.

           It is also possible to specify expected probability of the expression with
           "__builtin_expect_with_probability" built-in function.

           The default is -fguess-branch-probability at levels -O, -O2, -O3, -Os.

       -freorder-blocks
           Reorder basic blocks in the compiled function in order to reduce number of taken branches
           and improve code locality.

           Enabled at levels -O, -O2, -O3, -Os.

       -freorder-blocks-algorithm=algorithm
           Use the specified algorithm for basic block reordering.  The algorithm argument can be
           simple, which does not increase code size (except sometimes due to secondary effects like
           alignment), or stc, the "software trace cache" algorithm, which tries to put all often
           executed code together, minimizing the number of branches executed by making extra copies
           of code.

           The default is simple at levels -O, -Os, and stc at levels -O2, -O3.

       -freorder-blocks-and-partition
           In addition to reordering basic blocks in the compiled function, in order to reduce
           number of taken branches, partitions hot and cold basic blocks into separate sections of
           the assembly and .o files, to improve paging and cache locality performance.

           This optimization is automatically turned off in the presence of exception handling or
           unwind tables (on targets using setjump/longjump or target specific scheme), for linkonce
           sections, for functions with a user-defined section attribute and on any architecture
           that does not support named sections.  When -fsplit-stack is used this option is not
           enabled by default (to avoid linker errors), but may be enabled explicitly (if using a
           working linker).

           Enabled for x86 at levels -O2, -O3, -Os.

       -freorder-functions
           Reorder functions in the object file in order to improve code locality.  This is
           implemented by using special subsections ".text.hot" for most frequently executed
           functions and ".text.unlikely" for unlikely executed functions.  Reordering is done by
           the linker so object file format must support named sections and linker must place them
           in a reasonable way.

           This option isn't effective unless you either provide profile feedback (see
           -fprofile-arcs for details) or manually annotate functions with "hot" or "cold"
           attributes.

           Enabled at levels -O2, -O3, -Os.

       -fstrict-aliasing
           Allow the compiler to assume the strictest aliasing rules applicable to the language
           being compiled.  For C (and C++), this activates optimizations based on the type of
           expressions.  In particular, an object of one type is assumed never to reside at the same
           address as an object of a different type, unless the types are almost the same.  For
           example, an "unsigned int" can alias an "int", but not a "void*" or a "double".  A
           character type may alias any other type.

           Pay special attention to code like this:

                   union a_union {
                     int i;
                     double d;
                   };

                   int f() {
                     union a_union t;
                     t.d = 3.0;
                     return t.i;
                   }

           The practice of reading from a different union member than the one most recently written
           to (called "type-punning") is common.  Even with -fstrict-aliasing, type-punning is
           allowed, provided the memory is accessed through the union type.  So, the code above
           works as expected.    However, this code might not:

                   int f() {
                     union a_union t;
                     int* ip;
                     t.d = 3.0;
                     ip = &t.i;
                     return *ip;
                   }

           Similarly, access by taking the address, casting the resulting pointer and dereferencing
           the result has undefined behavior, even if the cast uses a union type, e.g.:

                   int f() {
                     double d = 3.0;
                     return ((union a_union *) &d)->i;
                   }

           The -fstrict-aliasing option is enabled at levels -O2, -O3, -Os.

       -falign-functions
       -falign-functions=n
       -falign-functions=n:m
       -falign-functions=n:m:n2
       -falign-functions=n:m:n2:m2
           Align the start of functions to the next power-of-two greater than or equal to n,
           skipping up to m-1 bytes.  This ensures that at least the first m bytes of the function
           can be fetched by the CPU without crossing an n-byte alignment boundary.

           If m is not specified, it defaults to n.

           Examples: -falign-functions=32 aligns functions to the next 32-byte boundary,
           -falign-functions=24 aligns to the next 32-byte boundary only if this can be done by
           skipping 23 bytes or less, -falign-functions=32:7 aligns to the next 32-byte boundary
           only if this can be done by skipping 6 bytes or less.

           The second pair of n2:m2 values allows you to specify a secondary alignment:
           -falign-functions=64:7:32:3 aligns to the next 64-byte boundary if this can be done by
           skipping 6 bytes or less, otherwise aligns to the next 32-byte boundary if this can be
           done by skipping 2 bytes or less.  If m2 is not specified, it defaults to n2.

           Some assemblers only support this flag when n is a power of two; in that case, it is
           rounded up.

           -fno-align-functions and -falign-functions=1 are equivalent and mean that functions are
           not aligned.

           If n is not specified or is zero, use a machine-dependent default.  The maximum allowed n
           option value is 65536.

           Enabled at levels -O2, -O3.

       -flimit-function-alignment
           If this option is enabled, the compiler tries to avoid unnecessarily overaligning
           functions. It attempts to instruct the assembler to align by the amount specified by
           -falign-functions, but not to skip more bytes than the size of the function.

       -falign-labels
       -falign-labels=n
       -falign-labels=n:m
       -falign-labels=n:m:n2
       -falign-labels=n:m:n2:m2
           Align all branch targets to a power-of-two boundary.

           Parameters of this option are analogous to the -falign-functions option.
           -fno-align-labels and -falign-labels=1 are equivalent and mean that labels are not
           aligned.

           If -falign-loops or -falign-jumps are applicable and are greater than this value, then
           their values are used instead.

           If n is not specified or is zero, use a machine-dependent default which is very likely to
           be 1, meaning no alignment.  The maximum allowed n option value is 65536.

           Enabled at levels -O2, -O3.

       -falign-loops
       -falign-loops=n
       -falign-loops=n:m
       -falign-loops=n:m:n2
       -falign-loops=n:m:n2:m2
           Align loops to a power-of-two boundary.  If the loops are executed many times, this makes
           up for any execution of the dummy padding instructions.

           If -falign-labels is greater than this value, then its value is used instead.

           Parameters of this option are analogous to the -falign-functions option.
           -fno-align-loops and -falign-loops=1 are equivalent and mean that loops are not aligned.
           The maximum allowed n option value is 65536.

           If n is not specified or is zero, use a machine-dependent default.

           Enabled at levels -O2, -O3.

       -falign-jumps
       -falign-jumps=n
       -falign-jumps=n:m
       -falign-jumps=n:m:n2
       -falign-jumps=n:m:n2:m2
           Align branch targets to a power-of-two boundary, for branch targets where the targets can
           only be reached by jumping.  In this case, no dummy operations need be executed.

           If -falign-labels is greater than this value, then its value is used instead.

           Parameters of this option are analogous to the -falign-functions option.
           -fno-align-jumps and -falign-jumps=1 are equivalent and mean that loops are not aligned.

           If n is not specified or is zero, use a machine-dependent default.  The maximum allowed n
           option value is 65536.

           Enabled at levels -O2, -O3.

       -fno-allocation-dce
           Do not remove unused C++ allocations in dead code elimination.

       -fallow-store-data-races
           Allow the compiler to perform optimizations that may introduce new data races on stores,
           without proving that the variable cannot be concurrently accessed by other threads.  Does
           not affect optimization of local data.  It is safe to use this option if it is known that
           global data will not be accessed by multiple threads.

           Examples of optimizations enabled by -fallow-store-data-races include hoisting or if-
           conversions that may cause a value that was already in memory to be re-written with that
           same value.  Such re-writing is safe in a single threaded context but may be unsafe in a
           multi-threaded context.  Note that on some processors, if-conversions may be required in
           order to enable vectorization.

           Enabled at level -Ofast.

       -funit-at-a-time
           This option is left for compatibility reasons. -funit-at-a-time has no effect, while
           -fno-unit-at-a-time implies -fno-toplevel-reorder and -fno-section-anchors.

           Enabled by default.

       -fno-toplevel-reorder
           Do not reorder top-level functions, variables, and "asm" statements.  Output them in the
           same order that they appear in the input file.  When this option is used, unreferenced
           static variables are not removed.  This option is intended to support existing code that
           relies on a particular ordering.  For new code, it is better to use attributes when
           possible.

           -ftoplevel-reorder is the default at -O1 and higher, and also at -O0 if -fsection-anchors
           is explicitly requested.  Additionally -fno-toplevel-reorder implies
           -fno-section-anchors.

       -fweb
           Constructs webs as commonly used for register allocation purposes and assign each web
           individual pseudo register.  This allows the register allocation pass to operate on
           pseudos directly, but also strengthens several other optimization passes, such as CSE,
           loop optimizer and trivial dead code remover.  It can, however, make debugging
           impossible, since variables no longer stay in a "home register".

           Enabled by default with -funroll-loops.

       -fwhole-program
           Assume that the current compilation unit represents the whole program being compiled.
           All public functions and variables with the exception of "main" and those merged by
           attribute "externally_visible" become static functions and in effect are optimized more
           aggressively by interprocedural optimizers.

           This option should not be used in combination with -flto.  Instead relying on a linker
           plugin should provide safer and more precise information.

       -flto[=n]
           This option runs the standard link-time optimizer.  When invoked with source code, it
           generates GIMPLE (one of GCC's internal representations) and writes it to special ELF
           sections in the object file.  When the object files are linked together, all the function
           bodies are read from these ELF sections and instantiated as if they had been part of the
           same translation unit.

           To use the link-time optimizer, -flto and optimization options should be specified at
           compile time and during the final link.  It is recommended that you compile all the files
           participating in the same link with the same options and also specify those options at
           link time.  For example:

                   gcc -c -O2 -flto foo.c
                   gcc -c -O2 -flto bar.c
                   gcc -o myprog -flto -O2 foo.o bar.o

           The first two invocations to GCC save a bytecode representation of GIMPLE into special
           ELF sections inside foo.o and bar.o.  The final invocation reads the GIMPLE bytecode from
           foo.o and bar.o, merges the two files into a single internal image, and compiles the
           result as usual.  Since both foo.o and bar.o are merged into a single image, this causes
           all the interprocedural analyses and optimizations in GCC to work across the two files as
           if they were a single one.  This means, for example, that the inliner is able to inline
           functions in bar.o into functions in foo.o and vice-versa.

           Another (simpler) way to enable link-time optimization is:

                   gcc -o myprog -flto -O2 foo.c bar.c

           The above generates bytecode for foo.c and bar.c, merges them together into a single
           GIMPLE representation and optimizes them as usual to produce myprog.

           The important thing to keep in mind is that to enable link-time optimizations you need to
           use the GCC driver to perform the link step.  GCC automatically performs link-time
           optimization if any of the objects involved were compiled with the -flto command-line
           option.  You can always override the automatic decision to do link-time optimization by
           passing -fno-lto to the link command.

           To make whole program optimization effective, it is necessary to make certain whole
           program assumptions.  The compiler needs to know what functions and variables can be
           accessed by libraries and runtime outside of the link-time optimized unit.  When
           supported by the linker, the linker plugin (see -fuse-linker-plugin) passes information
           to the compiler about used and externally visible symbols.  When the linker plugin is not
           available, -fwhole-program should be used to allow the compiler to make these
           assumptions, which leads to more aggressive optimization decisions.

           When a file is compiled with -flto without -fuse-linker-plugin, the generated object file
           is larger than a regular object file because it contains GIMPLE bytecodes and the usual
           final code (see -ffat-lto-objects).  This means that object files with LTO information
           can be linked as normal object files; if -fno-lto is passed to the linker, no
           interprocedural optimizations are applied.  Note that when -fno-fat-lto-objects is
           enabled the compile stage is faster but you cannot perform a regular, non-LTO link on
           them.

           When producing the final binary, GCC only applies link-time optimizations to those files
           that contain bytecode.  Therefore, you can mix and match object files and libraries with
           GIMPLE bytecodes and final object code.  GCC automatically selects which files to
           optimize in LTO mode and which files to link without further processing.

           Generally, options specified at link time override those specified at compile time,
           although in some cases GCC attempts to infer link-time options from the settings used to
           compile the input files.

           If you do not specify an optimization level option -O at link time, then GCC uses the
           highest optimization level used when compiling the object files.  Note that it is
           generally ineffective to specify an optimization level option only at link time and not
           at compile time, for two reasons.  First, compiling without optimization suppresses
           compiler passes that gather information needed for effective optimization at link time.
           Second, some early optimization passes can be performed only at compile time and not at
           link time.

           There are some code generation flags preserved by GCC when generating bytecodes, as they
           need to be used during the final link.  Currently, the following options and their
           settings are taken from the first object file that explicitly specifies them: -fcommon,
           -fexceptions, -fnon-call-exceptions, -fgnu-tm and all the -m target flags.

           The following options -fPIC, -fpic, -fpie and -fPIE are combined based on the following
           scheme:

                   B<-fPIC> + B<-fpic> = B<-fpic>
                   B<-fPIC> + B<-fno-pic> = B<-fno-pic>
                   B<-fpic/-fPIC> + (no option) = (no option)
                   B<-fPIC> + B<-fPIE> = B<-fPIE>
                   B<-fpic> + B<-fPIE> = B<-fpie>
                   B<-fPIC/-fpic> + B<-fpie> = B<-fpie>

           Certain ABI-changing flags are required to match in all compilation units, and trying to
           override this at link time with a conflicting value is ignored.  This includes options
           such as -freg-struct-return and -fpcc-struct-return.

           Other options such as -ffp-contract, -fno-strict-overflow, -fwrapv, -fno-trapv or
           -fno-strict-aliasing are passed through to the link stage and merged conservatively for
           conflicting translation units.  Specifically -fno-strict-overflow, -fwrapv and -fno-trapv
           take precedence; and for example -ffp-contract=off takes precedence over
           -ffp-contract=fast.  You can override them at link time.

           Diagnostic options such as -Wstringop-overflow are passed through to the link stage and
           their setting matches that of the compile-step at function granularity.  Note that this
           matters only for diagnostics emitted during optimization.  Note that code transforms such
           as inlining can lead to warnings being enabled or disabled for regions if code not
           consistent with the setting at compile time.

           When you need to pass options to the assembler via -Wa or -Xassembler make sure to either
           compile such translation units with -fno-lto or consistently use the same assembler
           options on all translation units.  You can alternatively also specify assembler options
           at LTO link time.

           To enable debug info generation you need to supply -g at compile time.  If any of the
           input files at link time were built with debug info generation enabled the link will
           enable debug info generation as well.  Any elaborate debug info settings like the dwarf
           level -gdwarf-5 need to be explicitly repeated at the linker command line and mixing
           different settings in different translation units is discouraged.

           If LTO encounters objects with C linkage declared with incompatible types in separate
           translation units to be linked together (undefined behavior according to ISO C99 6.2.7),
           a non-fatal diagnostic may be issued.  The behavior is still undefined at run time.
           Similar diagnostics may be raised for other languages.

           Another feature of LTO is that it is possible to apply interprocedural optimizations on
           files written in different languages:

                   gcc -c -flto foo.c
                   g++ -c -flto bar.cc
                   gfortran -c -flto baz.f90
                   g++ -o myprog -flto -O3 foo.o bar.o baz.o -lgfortran

           Notice that the final link is done with g++ to get the C++ runtime libraries and
           -lgfortran is added to get the Fortran runtime libraries.  In general, when mixing
           languages in LTO mode, you should use the same link command options as when mixing
           languages in a regular (non-LTO) compilation.

           If object files containing GIMPLE bytecode are stored in a library archive, say libfoo.a,
           it is possible to extract and use them in an LTO link if you are using a linker with
           plugin support.  To create static libraries suitable for LTO, use gcc-ar and gcc-ranlib
           instead of ar and ranlib; to show the symbols of object files with GIMPLE bytecode, use
           gcc-nm.  Those commands require that ar, ranlib and nm have been compiled with plugin
           support.  At link time, use the flag -fuse-linker-plugin to ensure that the library
           participates in the LTO optimization process:

                   gcc -o myprog -O2 -flto -fuse-linker-plugin a.o b.o -lfoo

           With the linker plugin enabled, the linker extracts the needed GIMPLE files from libfoo.a
           and passes them on to the running GCC to make them part of the aggregated GIMPLE image to
           be optimized.

           If you are not using a linker with plugin support and/or do not enable the linker plugin,
           then the objects inside libfoo.a are extracted and linked as usual, but they do not
           participate in the LTO optimization process.  In order to make a static library suitable
           for both LTO optimization and usual linkage, compile its object files with -flto
           -ffat-lto-objects.

           Link-time optimizations do not require the presence of the whole program to operate.  If
           the program does not require any symbols to be exported, it is possible to combine -flto
           and -fwhole-program to allow the interprocedural optimizers to use more aggressive
           assumptions which may lead to improved optimization opportunities.  Use of
           -fwhole-program is not needed when linker plugin is active (see -fuse-linker-plugin).

           The current implementation of LTO makes no attempt to generate bytecode that is portable
           between different types of hosts.  The bytecode files are versioned and there is a strict
           version check, so bytecode files generated in one version of GCC do not work with an
           older or newer version of GCC.

           Link-time optimization does not work well with generation of debugging information on
           systems other than those using a combination of ELF and DWARF.

           If you specify the optional n, the optimization and code generation done at link time is
           executed in parallel using n parallel jobs by utilizing an installed make program.  The
           environment variable MAKE may be used to override the program used.

           You can also specify -flto=jobserver to use GNU make's job server mode to determine the
           number of parallel jobs. This is useful when the Makefile calling GCC is already
           executing in parallel.  You must prepend a + to the command recipe in the parent Makefile
           for this to work.  This option likely only works if MAKE is GNU make.  Even without the
           option value, GCC tries to automatically detect a running GNU make's job server.

           Use -flto=auto to use GNU make's job server, if available, or otherwise fall back to
           autodetection of the number of CPU threads present in your system.

       -flto-partition=alg
           Specify the partitioning algorithm used by the link-time optimizer.  The value is either
           1to1 to specify a partitioning mirroring the original source files or balanced to specify
           partitioning into equally sized chunks (whenever possible) or max to create new partition
           for every symbol where possible.  Specifying none as an algorithm disables partitioning
           and streaming completely.  The default value is balanced. While 1to1 can be used as an
           workaround for various code ordering issues, the max partitioning is intended for
           internal testing only.  The value one specifies that exactly one partition should be used
           while the value none bypasses partitioning and executes the link-time optimization step
           directly from the WPA phase.

       -flto-compression-level=n
           This option specifies the level of compression used for intermediate language written to
           LTO object files, and is only meaningful in conjunction with LTO mode (-flto).  GCC
           currently supports two LTO compression algorithms. For zstd, valid values are 0 (no
           compression) to 19 (maximum compression), while zlib supports values from 0 to 9.  Values
           outside this range are clamped to either minimum or maximum of the supported values.  If
           the option is not given, a default balanced compression setting is used.

       -fuse-linker-plugin
           Enables the use of a linker plugin during link-time optimization.  This option relies on
           plugin support in the linker, which is available in gold or in GNU ld 2.21 or newer.

           This option enables the extraction of object files with GIMPLE bytecode out of library
           archives. This improves the quality of optimization by exposing more code to the link-
           time optimizer.  This information specifies what symbols can be accessed externally (by
           non-LTO object or during dynamic linking).  Resulting code quality improvements on
           binaries (and shared libraries that use hidden visibility) are similar to
           -fwhole-program.  See -flto for a description of the effect of this flag and how to use
           it.

           This option is enabled by default when LTO support in GCC is enabled and GCC was
           configured for use with a linker supporting plugins (GNU ld 2.21 or newer or gold).

       -ffat-lto-objects
           Fat LTO objects are object files that contain both the intermediate language and the
           object code. This makes them usable for both LTO linking and normal linking. This option
           is effective only when compiling with -flto and is ignored at link time.

           -fno-fat-lto-objects improves compilation time over plain LTO, but requires the complete
           toolchain to be aware of LTO. It requires a linker with linker plugin support for basic
           functionality.  Additionally, nm, ar and ranlib need to support linker plugins to allow a
           full-featured build environment (capable of building static libraries etc).  GCC provides
           the gcc-ar, gcc-nm, gcc-ranlib wrappers to pass the right options to these tools. With
           non fat LTO makefiles need to be modified to use them.

           Note that modern binutils provide plugin auto-load mechanism.  Installing the linker
           plugin into $libdir/bfd-plugins has the same effect as usage of the command wrappers
           (gcc-ar, gcc-nm and gcc-ranlib).

           The default is -fno-fat-lto-objects on targets with linker plugin support.

       -fcompare-elim
           After register allocation and post-register allocation instruction splitting, identify
           arithmetic instructions that compute processor flags similar to a comparison operation
           based on that arithmetic.  If possible, eliminate the explicit comparison operation.

           This pass only applies to certain targets that cannot explicitly represent the comparison
           operation before register allocation is complete.

           Enabled at levels -O, -O2, -O3, -Os.

       -fcprop-registers
           After register allocation and post-register allocation instruction splitting, perform a
           copy-propagation pass to try to reduce scheduling dependencies and occasionally eliminate
           the copy.

           Enabled at levels -O, -O2, -O3, -Os.

       -fprofile-correction
           Profiles collected using an instrumented binary for multi-threaded programs may be
           inconsistent due to missed counter updates. When this option is specified, GCC uses
           heuristics to correct or smooth out such inconsistencies. By default, GCC emits an error
           message when an inconsistent profile is detected.

           This option is enabled by -fauto-profile.

       -fprofile-partial-training
           With "-fprofile-use" all portions of programs not executed during train run are optimized
           agressively for size rather than speed.  In some cases it is not practical to train all
           possible hot paths in the program. (For example, program may contain functions specific
           for a given hardware and trianing may not cover all hardware configurations program is
           run on.)  With "-fprofile-partial-training" profile feedback will be ignored for all
           functions not executed during the train run leading them to be optimized as if they were
           compiled without profile feedback. This leads to better performance when train run is not
           representative but also leads to significantly bigger code.

       -fprofile-use
       -fprofile-use=path
           Enable profile feedback-directed optimizations, and the following optimizations, many of
           which are generally profitable only with profile feedback available:

           -fbranch-probabilities  -fprofile-values -funroll-loops  -fpeel-loops  -ftracer  -fvpt
           -finline-functions  -fipa-cp  -fipa-cp-clone  -fipa-bit-cp -fpredictive-commoning
           -fsplit-loops  -funswitch-loops -fgcse-after-reload  -ftree-loop-vectorize
           -ftree-slp-vectorize -fvect-cost-model=dynamic  -ftree-loop-distribute-patterns
           -fprofile-reorder-functions

           Before you can use this option, you must first generate profiling information.

           By default, GCC emits an error message if the feedback profiles do not match the source
           code.  This error can be turned into a warning by using -Wno-error=coverage-mismatch.
           Note this may result in poorly optimized code.  Additionally, by default, GCC also emits
           a warning message if the feedback profiles do not exist (see -Wmissing-profile).

           If path is specified, GCC looks at the path to find the profile feedback data files. See
           -fprofile-dir.

       -fauto-profile
       -fauto-profile=path
           Enable sampling-based feedback-directed optimizations, and the following optimizations,
           many of which are generally profitable only with profile feedback available:

           -fbranch-probabilities  -fprofile-values -funroll-loops  -fpeel-loops  -ftracer  -fvpt
           -finline-functions  -fipa-cp  -fipa-cp-clone  -fipa-bit-cp -fpredictive-commoning
           -fsplit-loops  -funswitch-loops -fgcse-after-reload  -ftree-loop-vectorize
           -ftree-slp-vectorize -fvect-cost-model=dynamic  -ftree-loop-distribute-patterns
           -fprofile-correction

           path is the name of a file containing AutoFDO profile information.  If omitted, it
           defaults to fbdata.afdo in the current directory.

           Producing an AutoFDO profile data file requires running your program with the perf
           utility on a supported GNU/Linux target system.  For more information, see
           <https://perf.wiki.kernel.org/>.

           E.g.

                   perf record -e br_inst_retired:near_taken -b -o perf.data \
                       -- your_program

           Then use the create_gcov tool to convert the raw profile data to a format that can be
           used by GCC.  You must also supply the unstripped binary for your program to this tool.
           See <https://github.com/google/autofdo>.

           E.g.

                   create_gcov --binary=your_program.unstripped --profile=perf.data \
                       --gcov=profile.afdo

       The following options control compiler behavior regarding floating-point arithmetic.  These
       options trade off between speed and correctness.  All must be specifically enabled.

       -ffloat-store
           Do not store floating-point variables in registers, and inhibit other options that might
           change whether a floating-point value is taken from a register or memory.

           This option prevents undesirable excess precision on machines such as the 68000 where the
           floating registers (of the 68881) keep more precision than a "double" is supposed to
           have.  Similarly for the x86 architecture.  For most programs, the excess precision does
           only good, but a few programs rely on the precise definition of IEEE floating point.  Use
           -ffloat-store for such programs, after modifying them to store all pertinent intermediate
           computations into variables.

       -fexcess-precision=style
           This option allows further control over excess precision on machines where floating-point
           operations occur in a format with more precision or range than the IEEE standard and
           interchange floating-point types.  By default, -fexcess-precision=fast is in effect; this
           means that operations may be carried out in a wider precision than the types specified in
           the source if that would result in faster code, and it is unpredictable when rounding to
           the types specified in the source code takes place.  When compiling C, if
           -fexcess-precision=standard is specified then excess precision follows the rules
           specified in ISO C99; in particular, both casts and assignments cause values to be
           rounded to their semantic types (whereas -ffloat-store only affects assignments).  This
           option is enabled by default for C if a strict conformance option such as -std=c99 is
           used.  -ffast-math enables -fexcess-precision=fast by default regardless of whether a
           strict conformance option is used.

           -fexcess-precision=standard is not implemented for languages other than C.  On the x86,
           it has no effect if -mfpmath=sse or -mfpmath=sse+387 is specified; in the former case,
           IEEE semantics apply without excess precision, and in the latter, rounding is
           unpredictable.

       -ffast-math
           Sets the options -fno-math-errno, -funsafe-math-optimizations, -ffinite-math-only,
           -fno-rounding-math, -fno-signaling-nans, -fcx-limited-range and -fexcess-precision=fast.

           This option causes the preprocessor macro "__FAST_MATH__" to be defined.

           This option is not turned on by any -O option besides -Ofast since it can result in
           incorrect output for programs that depend on an exact implementation of IEEE or ISO
           rules/specifications for math functions. It may, however, yield faster code for programs
           that do not require the guarantees of these specifications.

       -fno-math-errno
           Do not set "errno" after calling math functions that are executed with a single
           instruction, e.g., "sqrt".  A program that relies on IEEE exceptions for math error
           handling may want to use this flag for speed while maintaining IEEE arithmetic
           compatibility.

           This option is not turned on by any -O option since it can result in incorrect output for
           programs that depend on an exact implementation of IEEE or ISO rules/specifications for
           math functions. It may, however, yield faster code for programs that do not require the
           guarantees of these specifications.

           The default is -fmath-errno.

           On Darwin systems, the math library never sets "errno".  There is therefore no reason for
           the compiler to consider the possibility that it might, and -fno-math-errno is the
           default.

       -funsafe-math-optimizations
           Allow optimizations for floating-point arithmetic that (a) assume that arguments and
           results are valid and (b) may violate IEEE or ANSI standards.  When used at link time, it
           may include libraries or startup files that change the default FPU control word or other
           similar optimizations.

           This option is not turned on by any -O option since it can result in incorrect output for
           programs that depend on an exact implementation of IEEE or ISO rules/specifications for
           math functions. It may, however, yield faster code for programs that do not require the
           guarantees of these specifications.  Enables -fno-signed-zeros, -fno-trapping-math,
           -fassociative-math and -freciprocal-math.

           The default is -fno-unsafe-math-optimizations.

       -fassociative-math
           Allow re-association of operands in series of floating-point operations.  This violates
           the ISO C and C++ language standard by possibly changing computation result.  NOTE: re-
           ordering may change the sign of zero as well as ignore NaNs and inhibit or create
           underflow or overflow (and thus cannot be used on code that relies on rounding behavior
           like "(x + 2**52) - 2**52".  May also reorder floating-point comparisons and thus may not
           be used when ordered comparisons are required.  This option requires that both
           -fno-signed-zeros and -fno-trapping-math be in effect.  Moreover, it doesn't make much
           sense with -frounding-math. For Fortran the option is automatically enabled when both
           -fno-signed-zeros and -fno-trapping-math are in effect.

           The default is -fno-associative-math.

       -freciprocal-math
           Allow the reciprocal of a value to be used instead of dividing by the value if this
           enables optimizations.  For example "x / y" can be replaced with "x * (1/y)", which is
           useful if "(1/y)" is subject to common subexpression elimination.  Note that this loses
           precision and increases the number of flops operating on the value.

           The default is -fno-reciprocal-math.

       -ffinite-math-only
           Allow optimizations for floating-point arithmetic that assume that arguments and results
           are not NaNs or +-Infs.

           This option is not turned on by any -O option since it can result in incorrect output for
           programs that depend on an exact implementation of IEEE or ISO rules/specifications for
           math functions. It may, however, yield faster code for programs that do not require the
           guarantees of these specifications.

           The default is -fno-finite-math-only.

       -fno-signed-zeros
           Allow optimizations for floating-point arithmetic that ignore the signedness of zero.
           IEEE arithmetic specifies the behavior of distinct +0.0 and -0.0 values, which then
           prohibits simplification of expressions such as x+0.0 or 0.0*x (even with
           -ffinite-math-only).  This option implies that the sign of a zero result isn't
           significant.

           The default is -fsigned-zeros.

       -fno-trapping-math
           Compile code assuming that floating-point operations cannot generate user-visible traps.
           These traps include division by zero, overflow, underflow, inexact result and invalid
           operation.  This option requires that -fno-signaling-nans be in effect.  Setting this
           option may allow faster code if one relies on "non-stop" IEEE arithmetic, for example.

           This option should never be turned on by any -O option since it can result in incorrect
           output for programs that depend on an exact implementation of IEEE or ISO
           rules/specifications for math functions.

           The default is -ftrapping-math.

       -frounding-math
           Disable transformations and optimizations that assume default floating-point rounding
           behavior.  This is round-to-zero for all floating point to integer conversions, and
           round-to-nearest for all other arithmetic truncations.  This option should be specified
           for programs that change the FP rounding mode dynamically, or that may be executed with a
           non-default rounding mode.  This option disables constant folding of floating-point
           expressions at compile time (which may be affected by rounding mode) and arithmetic
           transformations that are unsafe in the presence of sign-dependent rounding modes.

           The default is -fno-rounding-math.

           This option is experimental and does not currently guarantee to disable all GCC
           optimizations that are affected by rounding mode.  Future versions of GCC may provide
           finer control of this setting using C99's "FENV_ACCESS" pragma.  This command-line option
           will be used to specify the default state for "FENV_ACCESS".

       -fsignaling-nans
           Compile code assuming that IEEE signaling NaNs may generate user-visible traps during
           floating-point operations.  Setting this option disables optimizations that may change
           the number of exceptions visible with signaling NaNs.  This option implies
           -ftrapping-math.

           This option causes the preprocessor macro "__SUPPORT_SNAN__" to be defined.

           The default is -fno-signaling-nans.

           This option is experimental and does not currently guarantee to disable all GCC
           optimizations that affect signaling NaN behavior.

       -fno-fp-int-builtin-inexact
           Do not allow the built-in functions "ceil", "floor", "round" and "trunc", and their
           "float" and "long double" variants, to generate code that raises the "inexact" floating-
           point exception for noninteger arguments.  ISO C99 and C11 allow these functions to raise
           the "inexact" exception, but ISO/IEC TS 18661-1:2014, the C bindings to IEEE 754-2008, as
           integrated into ISO C2X, does not allow these functions to do so.

           The default is -ffp-int-builtin-inexact, allowing the exception to be raised, unless C2X
           or a later C standard is selected.  This option does nothing unless -ftrapping-math is in
           effect.

           Even if -fno-fp-int-builtin-inexact is used, if the functions generate a call to a
           library function then the "inexact" exception may be raised if the library implementation
           does not follow TS 18661.

       -fsingle-precision-constant
           Treat floating-point constants as single precision instead of implicitly converting them
           to double-precision constants.

       -fcx-limited-range
           When enabled, this option states that a range reduction step is not needed when
           performing complex division.  Also, there is no checking whether the result of a complex
           multiplication or division is "NaN + I*NaN", with an attempt to rescue the situation in
           that case.  The default is -fno-cx-limited-range, but is enabled by -ffast-math.

           This option controls the default setting of the ISO C99 "CX_LIMITED_RANGE" pragma.
           Nevertheless, the option applies to all languages.

       -fcx-fortran-rules
           Complex multiplication and division follow Fortran rules.  Range reduction is done as
           part of complex division, but there is no checking whether the result of a complex
           multiplication or division is "NaN + I*NaN", with an attempt to rescue the situation in
           that case.

           The default is -fno-cx-fortran-rules.

       The following options control optimizations that may improve performance, but are not enabled
       by any -O options.  This section includes experimental options that may produce broken code.

       -fbranch-probabilities
           After running a program compiled with -fprofile-arcs, you can compile it a second time
           using -fbranch-probabilities, to improve optimizations based on the number of times each
           branch was taken.  When a program compiled with -fprofile-arcs exits, it saves arc
           execution counts to a file called sourcename.gcda for each source file.  The information
           in this data file is very dependent on the structure of the generated code, so you must
           use the same source code and the same optimization options for both compilations.

           With -fbranch-probabilities, GCC puts a REG_BR_PROB note on each JUMP_INSN and CALL_INSN.
           These can be used to improve optimization.  Currently, they are only used in one place:
           in reorg.c, instead of guessing which path a branch is most likely to take, the
           REG_BR_PROB values are used to exactly determine which path is taken more often.

           Enabled by -fprofile-use and -fauto-profile.

       -fprofile-values
           If combined with -fprofile-arcs, it adds code so that some data about values of
           expressions in the program is gathered.

           With -fbranch-probabilities, it reads back the data gathered from profiling values of
           expressions for usage in optimizations.

           Enabled by -fprofile-generate, -fprofile-use, and -fauto-profile.

       -fprofile-reorder-functions
           Function reordering based on profile instrumentation collects first time of execution of
           a function and orders these functions in ascending order.

           Enabled with -fprofile-use.

       -fvpt
           If combined with -fprofile-arcs, this option instructs the compiler to add code to gather
           information about values of expressions.

           With -fbranch-probabilities, it reads back the data gathered and actually performs the
           optimizations based on them.  Currently the optimizations include specialization of
           division operations using the knowledge about the value of the denominator.

           Enabled with -fprofile-use and -fauto-profile.

       -frename-registers
           Attempt to avoid false dependencies in scheduled code by making use of registers left
           over after register allocation.  This optimization most benefits processors with lots of
           registers.  Depending on the debug information format adopted by the target, however, it
           can make debugging impossible, since variables no longer stay in a "home register".

           Enabled by default with -funroll-loops.

       -fschedule-fusion
           Performs a target dependent pass over the instruction stream to schedule instructions of
           same type together because target machine can execute them more efficiently if they are
           adjacent to each other in the instruction flow.

           Enabled at levels -O2, -O3, -Os.

       -ftracer
           Perform tail duplication to enlarge superblock size.  This transformation simplifies the
           control flow of the function allowing other optimizations to do a better job.

           Enabled by -fprofile-use and -fauto-profile.

       -funroll-loops
           Unroll loops whose number of iterations can be determined at compile time or upon entry
           to the loop.  -funroll-loops implies -frerun-cse-after-loop, -fweb and
           -frename-registers.  It also turns on complete loop peeling (i.e. complete removal of
           loops with a small constant number of iterations).  This option makes code larger, and
           may or may not make it run faster.

           Enabled by -fprofile-use and -fauto-profile.

       -funroll-all-loops
           Unroll all loops, even if their number of iterations is uncertain when the loop is
           entered.  This usually makes programs run more slowly.  -funroll-all-loops implies the
           same options as -funroll-loops.

       -fpeel-loops
           Peels loops for which there is enough information that they do not roll much (from
           profile feedback or static analysis).  It also turns on complete loop peeling (i.e.
           complete removal of loops with small constant number of iterations).

           Enabled by -O3, -fprofile-use, and -fauto-profile.

       -fmove-loop-invariants
           Enables the loop invariant motion pass in the RTL loop optimizer.  Enabled at level -O1
           and higher, except for -Og.

       -fsplit-loops
           Split a loop into two if it contains a condition that's always true for one side of the
           iteration space and false for the other.

           Enabled by -fprofile-use and -fauto-profile.

       -funswitch-loops
           Move branches with loop invariant conditions out of the loop, with duplicates of the loop
           on both branches (modified according to result of the condition).

           Enabled by -fprofile-use and -fauto-profile.

       -fversion-loops-for-strides
           If a loop iterates over an array with a variable stride, create another version of the
           loop that assumes the stride is always one.  For example:

                   for (int i = 0; i < n; ++i)
                     x[i * stride] = ...;

           becomes:

                   if (stride == 1)
                     for (int i = 0; i < n; ++i)
                       x[i] = ...;
                   else
                     for (int i = 0; i < n; ++i)
                       x[i * stride] = ...;

           This is particularly useful for assumed-shape arrays in Fortran where (for example) it
           allows better vectorization assuming contiguous accesses.  This flag is enabled by
           default at -O3.  It is also enabled by -fprofile-use and -fauto-profile.

       -ffunction-sections
       -fdata-sections
           Place each function or data item into its own section in the output file if the target
           supports arbitrary sections.  The name of the function or the name of the data item
           determines the section's name in the output file.

           Use these options on systems where the linker can perform optimizations to improve
           locality of reference in the instruction space.  Most systems using the ELF object format
           have linkers with such optimizations.  On AIX, the linker rearranges sections (CSECTs)
           based on the call graph.  The performance impact varies.

           Together with a linker garbage collection (linker --gc-sections option) these options may
           lead to smaller statically-linked executables (after stripping).

           On ELF/DWARF systems these options do not degenerate the quality of the debug
           information.  There could be issues with other object files/debug info formats.

           Only use these options when there are significant benefits from doing so.  When you
           specify these options, the assembler and linker create larger object and executable files
           and are also slower.  These options affect code generation.  They prevent optimizations
           by the compiler and assembler using relative locations inside a translation unit since
           the locations are unknown until link time.  An example of such an optimization is
           relaxing calls to short call instructions.

       -fstdarg-opt
           Optimize the prologue of variadic argument functions with respect to usage of those
           arguments.

           NOTE: In Ubuntu 14.10 and later versions, -fstack-protector-strong is enabled by default
           for C, C++, ObjC, ObjC++, if none of -fno-stack-protector, -nostdlib, nor -ffreestanding
           are found.

       -fsection-anchors
           Try to reduce the number of symbolic address calculations by using shared "anchor"
           symbols to address nearby objects.  This transformation can help to reduce the number of
           GOT entries and GOT accesses on some targets.

           For example, the implementation of the following function "foo":

                   static int a, b, c;
                   int foo (void) { return a + b + c; }

           usually calculates the addresses of all three variables, but if you compile it with
           -fsection-anchors, it accesses the variables from a common anchor point instead.  The
           effect is similar to the following pseudocode (which isn't valid C):

                   int foo (void)
                   {
                     register int *xr = &x;
                     return xr[&a - &x] + xr[&b - &x] + xr[&c - &x];
                   }

           Not all targets support this option.

       -fzero-call-used-regs=choice
           Zero call-used registers at function return to increase program security by either
           mitigating Return-Oriented Programming (ROP) attacks or preventing information leakage
           through registers.

           The possible values of choice are the same as for the "zero_call_used_regs" attribute.
           The default is skip.

           You can control this behavior for a specific function by using the function attribute
           "zero_call_used_regs".

       --param name=value
           In some places, GCC uses various constants to control the amount of optimization that is
           done.  For example, GCC does not inline functions that contain more than a certain number
           of instructions.  You can control some of these constants on the command line using the
           --param option.

           The names of specific parameters, and the meaning of the values, are tied to the
           internals of the compiler, and are subject to change without notice in future releases.

           In order to get minimal, maximal and default value of a parameter, one can use
           --help=param -Q options.

           In each case, the value is an integer.  The following choices of name are recognized for
           all targets:

           predictable-branch-outcome
               When branch is predicted to be taken with probability lower than this threshold (in
               percent), then it is considered well predictable.

           max-rtl-if-conversion-insns
               RTL if-conversion tries to remove conditional branches around a block and replace
               them with conditionally executed instructions.  This parameter gives the maximum
               number of instructions in a block which should be considered for if-conversion.  The
               compiler will also use other heuristics to decide whether if-conversion is likely to
               be profitable.

           max-rtl-if-conversion-predictable-cost
               RTL if-conversion will try to remove conditional branches around a block and replace
               them with conditionally executed instructions.  These parameters give the maximum
               permissible cost for the sequence that would be generated by if-conversion depending
               on whether the branch is statically determined to be predictable or not.  The units
               for this parameter are the same as those for the GCC internal seq_cost metric.  The
               compiler will try to provide a reasonable default for this parameter using the
               BRANCH_COST target macro.

           max-crossjump-edges
               The maximum number of incoming edges to consider for cross-jumping.  The algorithm
               used by -fcrossjumping is O(N^2) in the number of edges incoming to each block.
               Increasing values mean more aggressive optimization, making the compilation time
               increase with probably small improvement in executable size.

           min-crossjump-insns
               The minimum number of instructions that must be matched at the end of two blocks
               before cross-jumping is performed on them.  This value is ignored in the case where
               all instructions in the block being cross-jumped from are matched.

           max-grow-copy-bb-insns
               The maximum code size expansion factor when copying basic blocks instead of jumping.
               The expansion is relative to a jump instruction.

           max-goto-duplication-insns
               The maximum number of instructions to duplicate to a block that jumps to a computed
               goto.  To avoid O(N^2) behavior in a number of passes, GCC factors computed gotos
               early in the compilation process, and unfactors them as late as possible.  Only
               computed jumps at the end of a basic blocks with no more than max-goto-duplication-
               insns are unfactored.

           max-delay-slot-insn-search
               The maximum number of instructions to consider when looking for an instruction to
               fill a delay slot.  If more than this arbitrary number of instructions are searched,
               the time savings from filling the delay slot are minimal, so stop searching.
               Increasing values mean more aggressive optimization, making the compilation time
               increase with probably small improvement in execution time.

           max-delay-slot-live-search
               When trying to fill delay slots, the maximum number of instructions to consider when
               searching for a block with valid live register information.  Increasing this
               arbitrarily chosen value means more aggressive optimization, increasing the
               compilation time.  This parameter should be removed when the delay slot code is
               rewritten to maintain the control-flow graph.

           max-gcse-memory
               The approximate maximum amount of memory in "kB" that can be allocated in order to
               perform the global common subexpression elimination optimization.  If more memory
               than specified is required, the optimization is not done.

           max-gcse-insertion-ratio
               If the ratio of expression insertions to deletions is larger than this value for any
               expression, then RTL PRE inserts or removes the expression and thus leaves partially
               redundant computations in the instruction stream.

           max-pending-list-length
               The maximum number of pending dependencies scheduling allows before flushing the
               current state and starting over.  Large functions with few branches or calls can
               create excessively large lists which needlessly consume memory and resources.

           max-modulo-backtrack-attempts
               The maximum number of backtrack attempts the scheduler should make when modulo
               scheduling a loop.  Larger values can exponentially increase compilation time.

           max-inline-insns-single
               Several parameters control the tree inliner used in GCC.  This number sets the
               maximum number of instructions (counted in GCC's internal representation) in a single
               function that the tree inliner considers for inlining.  This only affects functions
               declared inline and methods implemented in a class declaration (C++).

           max-inline-insns-auto
               When you use -finline-functions (included in -O3), a lot of functions that would
               otherwise not be considered for inlining by the compiler are investigated.  To those
               functions, a different (more restrictive) limit compared to functions declared inline
               can be applied (--param max-inline-insns-auto).

           max-inline-insns-small
               This is bound applied to calls which are considered relevant with
               -finline-small-functions.

           max-inline-insns-size
               This is bound applied to calls which are optimized for size. Small growth may be
               desirable to anticipate optimization oppurtunities exposed by inlining.

           uninlined-function-insns
               Number of instructions accounted by inliner for function overhead such as function
               prologue and epilogue.

           uninlined-function-time
               Extra time accounted by inliner for function overhead such as time needed to execute
               function prologue and epilogue

           inline-heuristics-hint-percent
               The scale (in percents) applied to inline-insns-single, inline-insns-single-O2,
               inline-insns-auto when inline heuristics hints that inlining is very profitable (will
               enable later optimizations).

           uninlined-thunk-insns
           uninlined-thunk-time
               Same as --param uninlined-function-insns and --param uninlined-function-time but
               applied to function thunks

           inline-min-speedup
               When estimated performance improvement of caller + callee runtime exceeds this
               threshold (in percent), the function can be inlined regardless of the limit on
               --param max-inline-insns-single and --param max-inline-insns-auto.

           large-function-insns
               The limit specifying really large functions.  For functions larger than this limit
               after inlining, inlining is constrained by --param large-function-growth.  This
               parameter is useful primarily to avoid extreme compilation time caused by non-linear
               algorithms used by the back end.

           large-function-growth
               Specifies maximal growth of large function caused by inlining in percents.  For
               example, parameter value 100 limits large function growth to 2.0 times the original
               size.

           large-unit-insns
               The limit specifying large translation unit.  Growth caused by inlining of units
               larger than this limit is limited by --param inline-unit-growth.  For small units
               this might be too tight.  For example, consider a unit consisting of function A that
               is inline and B that just calls A three times.  If B is small relative to A, the
               growth of unit is 300\% and yet such inlining is very sane.  For very large units
               consisting of small inlineable functions, however, the overall unit growth limit is
               needed to avoid exponential explosion of code size.  Thus for smaller units, the size
               is increased to --param large-unit-insns before applying --param inline-unit-growth.

           lazy-modules
               Maximum number of concurrently open C++ module files when lazy loading.

           inline-unit-growth
               Specifies maximal overall growth of the compilation unit caused by inlining.  For
               example, parameter value 20 limits unit growth to 1.2 times the original size. Cold
               functions (either marked cold via an attribute or by profile feedback) are not
               accounted into the unit size.

           ipa-cp-unit-growth
               Specifies maximal overall growth of the compilation unit caused by interprocedural
               constant propagation.  For example, parameter value 10 limits unit growth to 1.1
               times the original size.

           ipa-cp-large-unit-insns
               The size of translation unit that IPA-CP pass considers large.

           large-stack-frame
               The limit specifying large stack frames.  While inlining the algorithm is trying to
               not grow past this limit too much.

           large-stack-frame-growth
               Specifies maximal growth of large stack frames caused by inlining in percents.  For
               example, parameter value 1000 limits large stack frame growth to 11 times the
               original size.

           max-inline-insns-recursive
           max-inline-insns-recursive-auto
               Specifies the maximum number of instructions an out-of-line copy of a self-recursive
               inline function can grow into by performing recursive inlining.

               --param max-inline-insns-recursive applies to functions declared inline.  For
               functions not declared inline, recursive inlining happens only when
               -finline-functions (included in -O3) is enabled; --param max-inline-insns-recursive-
               auto applies instead.

           max-inline-recursive-depth
           max-inline-recursive-depth-auto
               Specifies the maximum recursion depth used for recursive inlining.

               --param max-inline-recursive-depth applies to functions declared inline.  For
               functions not declared inline, recursive inlining happens only when
               -finline-functions (included in -O3) is enabled; --param max-inline-recursive-depth-
               auto applies instead.

           min-inline-recursive-probability
               Recursive inlining is profitable only for function having deep recursion in average
               and can hurt for function having little recursion depth by increasing the prologue
               size or complexity of function body to other optimizers.

               When profile feedback is available (see -fprofile-generate) the actual recursion
               depth can be guessed from the probability that function recurses via a given call
               expression.  This parameter limits inlining only to call expressions whose
               probability exceeds the given threshold (in percents).

           early-inlining-insns
               Specify growth that the early inliner can make.  In effect it increases the amount of
               inlining for code having a large abstraction penalty.

           max-early-inliner-iterations
               Limit of iterations of the early inliner.  This basically bounds the number of nested
               indirect calls the early inliner can resolve.  Deeper chains are still handled by
               late inlining.

           comdat-sharing-probability
               Probability (in percent) that C++ inline function with comdat visibility are shared
               across multiple compilation units.

           modref-max-bases
           modref-max-refs
           modref-max-accesses
               Specifies the maximal number of base pointers, references and accesses stored for a
               single function by mod/ref analysis.

           modref-max-tests
               Specifies the maxmal number of tests alias oracle can perform to disambiguate memory
               locations using the mod/ref information.  This parameter ought to be bigger than
               --param modref-max-bases and --param modref-max-refs.

           modref-max-depth
               Specifies the maximum depth of DFS walk used by modref escape analysis.  Setting to 0
               disables the analysis completely.

           modref-max-escape-points
               Specifies the maximum number of escape points tracked by modref per SSA-name.

           profile-func-internal-id
               A parameter to control whether to use function internal id in profile database
               lookup. If the value is 0, the compiler uses an id that is based on function
               assembler name and filename, which makes old profile data more tolerant to source
               changes such as function reordering etc.

           min-vect-loop-bound
               The minimum number of iterations under which loops are not vectorized when
               -ftree-vectorize is used.  The number of iterations after vectorization needs to be
               greater than the value specified by this option to allow vectorization.

           gcse-cost-distance-ratio
               Scaling factor in calculation of maximum distance an expression can be moved by GCSE
               optimizations.  This is currently supported only in the code hoisting pass.  The
               bigger the ratio, the more aggressive code hoisting is with simple expressions, i.e.,
               the expressions that have cost less than gcse-unrestricted-cost.  Specifying 0
               disables hoisting of simple expressions.

           gcse-unrestricted-cost
               Cost, roughly measured as the cost of a single typical machine instruction, at which
               GCSE optimizations do not constrain the distance an expression can travel.  This is
               currently supported only in the code hoisting pass.  The lesser the cost, the more
               aggressive code hoisting is.  Specifying 0 allows all expressions to travel
               unrestricted distances.

           max-hoist-depth
               The depth of search in the dominator tree for expressions to hoist.  This is used to
               avoid quadratic behavior in hoisting algorithm.  The value of 0 does not limit on the
               search, but may slow down compilation of huge functions.

           max-tail-merge-comparisons
               The maximum amount of similar bbs to compare a bb with.  This is used to avoid
               quadratic behavior in tree tail merging.

           max-tail-merge-iterations
               The maximum amount of iterations of the pass over the function.  This is used to
               limit compilation time in tree tail merging.

           store-merging-allow-unaligned
               Allow the store merging pass to introduce unaligned stores if it is legal to do so.

           max-stores-to-merge
               The maximum number of stores to attempt to merge into wider stores in the store
               merging pass.

           max-store-chains-to-track
               The maximum number of store chains to track at the same time in the attempt to merge
               them into wider stores in the store merging pass.

           max-stores-to-track
               The maximum number of stores to track at the same time in the attemt to to merge them
               into wider stores in the store merging pass.

           max-unrolled-insns
               The maximum number of instructions that a loop may have to be unrolled.  If a loop is
               unrolled, this parameter also determines how many times the loop code is unrolled.

           max-average-unrolled-insns
               The maximum number of instructions biased by probabilities of their execution that a
               loop may have to be unrolled.  If a loop is unrolled, this parameter also determines
               how many times the loop code is unrolled.

           max-unroll-times
               The maximum number of unrollings of a single loop.

           max-peeled-insns
               The maximum number of instructions that a loop may have to be peeled.  If a loop is
               peeled, this parameter also determines how many times the loop code is peeled.

           max-peel-times
               The maximum number of peelings of a single loop.

           max-peel-branches
               The maximum number of branches on the hot path through the peeled sequence.

           max-completely-peeled-insns
               The maximum number of insns of a completely peeled loop.

           max-completely-peel-times
               The maximum number of iterations of a loop to be suitable for complete peeling.

           max-completely-peel-loop-nest-depth
               The maximum depth of a loop nest suitable for complete peeling.

           max-unswitch-insns
               The maximum number of insns of an unswitched loop.

           max-unswitch-level
               The maximum number of branches unswitched in a single loop.

           lim-expensive
               The minimum cost of an expensive expression in the loop invariant motion.

           min-loop-cond-split-prob
               When FDO profile information is available, min-loop-cond-split-prob specifies minimum
               threshold for probability of semi-invariant condition statement to trigger loop
               split.

           iv-consider-all-candidates-bound
               Bound on number of candidates for induction variables, below which all candidates are
               considered for each use in induction variable optimizations.  If there are more
               candidates than this, only the most relevant ones are considered to avoid quadratic
               time complexity.

           iv-max-considered-uses
               The induction variable optimizations give up on loops that contain more induction
               variable uses.

           iv-always-prune-cand-set-bound
               If the number of candidates in the set is smaller than this value, always try to
               remove unnecessary ivs from the set when adding a new one.

           avg-loop-niter
               Average number of iterations of a loop.

           dse-max-object-size
               Maximum size (in bytes) of objects tracked bytewise by dead store elimination.
               Larger values may result in larger compilation times.

           dse-max-alias-queries-per-store
               Maximum number of queries into the alias oracle per store.  Larger values result in
               larger compilation times and may result in more removed dead stores.

           scev-max-expr-size
               Bound on size of expressions used in the scalar evolutions analyzer.  Large
               expressions slow the analyzer.

           scev-max-expr-complexity
               Bound on the complexity of the expressions in the scalar evolutions analyzer.
               Complex expressions slow the analyzer.

           max-tree-if-conversion-phi-args
               Maximum number of arguments in a PHI supported by TREE if conversion unless the loop
               is marked with simd pragma.

           vect-max-version-for-alignment-checks
               The maximum number of run-time checks that can be performed when doing loop
               versioning for alignment in the vectorizer.

           vect-max-version-for-alias-checks
               The maximum number of run-time checks that can be performed when doing loop
               versioning for alias in the vectorizer.

           vect-max-peeling-for-alignment
               The maximum number of loop peels to enhance access alignment for vectorizer. Value -1
               means no limit.

           max-iterations-to-track
               The maximum number of iterations of a loop the brute-force algorithm for analysis of
               the number of iterations of the loop tries to evaluate.

           hot-bb-count-fraction
               The denominator n of fraction 1/n of the maximal execution count of a basic block in
               the entire program that a basic block needs to at least have in order to be
               considered hot.  The default is 10000, which means that a basic block is considered
               hot if its execution count is greater than 1/10000 of the maximal execution count.  0
               means that it is never considered hot.  Used in non-LTO mode.

           hot-bb-count-ws-permille
               The number of most executed permilles, ranging from 0 to 1000, of the profiled
               execution of the entire program to which the execution count of a basic block must be
               part of in order to be considered hot.  The default is 990, which means that a basic
               block is considered hot if its execution count contributes to the upper 990
               permilles, or 99.0%, of the profiled execution of the entire program.  0 means that
               it is never considered hot.  Used in LTO mode.

           hot-bb-frequency-fraction
               The denominator n of fraction 1/n of the execution frequency of the entry block of a
               function that a basic block of this function needs to at least have in order to be
               considered hot.  The default is 1000, which means that a basic block is considered
               hot in a function if it is executed more frequently than 1/1000 of the frequency of
               the entry block of the function.  0 means that it is never considered hot.

           unlikely-bb-count-fraction
               The denominator n of fraction 1/n of the number of profiled runs of the entire
               program below which the execution count of a basic block must be in order for the
               basic block to be considered unlikely executed.  The default is 20, which means that
               a basic block is considered unlikely executed if it is executed in fewer than 1/20,
               or 5%, of the runs of the program.  0 means that it is always considered unlikely
               executed.

           max-predicted-iterations
               The maximum number of loop iterations we predict statically.  This is useful in cases
               where a function contains a single loop with known bound and another loop with
               unknown bound.  The known number of iterations is predicted correctly, while the
               unknown number of iterations average to roughly 10.  This means that the loop without
               bounds appears artificially cold relative to the other one.

           builtin-expect-probability
               Control the probability of the expression having the specified value. This parameter
               takes a percentage (i.e. 0 ... 100) as input.

           builtin-string-cmp-inline-length
               The maximum length of a constant string for a builtin string cmp call eligible for
               inlining.

           align-threshold
               Select fraction of the maximal frequency of executions of a basic block in a function
               to align the basic block.

           align-loop-iterations
               A loop expected to iterate at least the selected number of iterations is aligned.

           tracer-dynamic-coverage
           tracer-dynamic-coverage-feedback
               This value is used to limit superblock formation once the given percentage of
               executed instructions is covered.  This limits unnecessary code size expansion.

               The tracer-dynamic-coverage-feedback parameter is used only when profile feedback is
               available.  The real profiles (as opposed to statically estimated ones) are much less
               balanced allowing the threshold to be larger value.

           tracer-max-code-growth
               Stop tail duplication once code growth has reached given percentage.  This is a
               rather artificial limit, as most of the duplicates are eliminated later in cross
               jumping, so it may be set to much higher values than is the desired code growth.

           tracer-min-branch-ratio
               Stop reverse growth when the reverse probability of best edge is less than this
               threshold (in percent).

           tracer-min-branch-probability
           tracer-min-branch-probability-feedback
               Stop forward growth if the best edge has probability lower than this threshold.

               Similarly to tracer-dynamic-coverage two parameters are provided.  tracer-min-branch-
               probability-feedback is used for compilation with profile feedback and tracer-min-
               branch-probability compilation without.  The value for compilation with profile
               feedback needs to be more conservative (higher) in order to make tracer effective.

           stack-clash-protection-guard-size
               Specify the size of the operating system provided stack guard as 2 raised to num
               bytes.  Higher values may reduce the number of explicit probes, but a value larger
               than the operating system provided guard will leave code vulnerable to stack clash
               style attacks.

           stack-clash-protection-probe-interval
               Stack clash protection involves probing stack space as it is allocated.  This param
               controls the maximum distance between probes into the stack as 2 raised to num bytes.
               Higher values may reduce the number of explicit probes, but a value larger than the
               operating system provided guard will leave code vulnerable to stack clash style
               attacks.

           max-cse-path-length
               The maximum number of basic blocks on path that CSE considers.

           max-cse-insns
               The maximum number of instructions CSE processes before flushing.

           ggc-min-expand
               GCC uses a garbage collector to manage its own memory allocation.  This parameter
               specifies the minimum percentage by which the garbage collector's heap should be
               allowed to expand between collections.  Tuning this may improve compilation speed; it
               has no effect on code generation.

               The default is 30% + 70% * (RAM/1GB) with an upper bound of 100% when RAM >= 1GB.  If
               "getrlimit" is available, the notion of "RAM" is the smallest of actual RAM and
               "RLIMIT_DATA" or "RLIMIT_AS".  If GCC is not able to calculate RAM on a particular
               platform, the lower bound of 30% is used.  Setting this parameter and ggc-min-
               heapsize to zero causes a full collection to occur at every opportunity.  This is
               extremely slow, but can be useful for debugging.

           ggc-min-heapsize
               Minimum size of the garbage collector's heap before it begins bothering to collect
               garbage.  The first collection occurs after the heap expands by ggc-min-expand%
               beyond ggc-min-heapsize.  Again, tuning this may improve compilation speed, and has
               no effect on code generation.

               The default is the smaller of RAM/8, RLIMIT_RSS, or a limit that tries to ensure that
               RLIMIT_DATA or RLIMIT_AS are not exceeded, but with a lower bound of 4096 (four
               megabytes) and an upper bound of 131072 (128 megabytes).  If GCC is not able to
               calculate RAM on a particular platform, the lower bound is used.  Setting this
               parameter very large effectively disables garbage collection.  Setting this parameter
               and ggc-min-expand to zero causes a full collection to occur at every opportunity.

           max-reload-search-insns
               The maximum number of instruction reload should look backward for equivalent
               register.  Increasing values mean more aggressive optimization, making the
               compilation time increase with probably slightly better performance.

           max-cselib-memory-locations
               The maximum number of memory locations cselib should take into account.  Increasing
               values mean more aggressive optimization, making the compilation time increase with
               probably slightly better performance.

           max-sched-ready-insns
               The maximum number of instructions ready to be issued the scheduler should consider
               at any given time during the first scheduling pass.  Increasing values mean more
               thorough searches, making the compilation time increase with probably little benefit.

           max-sched-region-blocks
               The maximum number of blocks in a region to be considered for interblock scheduling.

           max-pipeline-region-blocks
               The maximum number of blocks in a region to be considered for pipelining in the
               selective scheduler.

           max-sched-region-insns
               The maximum number of insns in a region to be considered for interblock scheduling.

           max-pipeline-region-insns
               The maximum number of insns in a region to be considered for pipelining in the
               selective scheduler.

           min-spec-prob
               The minimum probability (in percents) of reaching a source block for interblock
               speculative scheduling.

           max-sched-extend-regions-iters
               The maximum number of iterations through CFG to extend regions.  A value of 0
               disables region extensions.

           max-sched-insn-conflict-delay
               The maximum conflict delay for an insn to be considered for speculative motion.

           sched-spec-prob-cutoff
               The minimal probability of speculation success (in percents), so that speculative
               insns are scheduled.

           sched-state-edge-prob-cutoff
               The minimum probability an edge must have for the scheduler to save its state across
               it.

           sched-mem-true-dep-cost
               Minimal distance (in CPU cycles) between store and load targeting same memory
               locations.

           selsched-max-lookahead
               The maximum size of the lookahead window of selective scheduling.  It is a depth of
               search for available instructions.

           selsched-max-sched-times
               The maximum number of times that an instruction is scheduled during selective
               scheduling.  This is the limit on the number of iterations through which the
               instruction may be pipelined.

           selsched-insns-to-rename
               The maximum number of best instructions in the ready list that are considered for
               renaming in the selective scheduler.

           sms-min-sc
               The minimum value of stage count that swing modulo scheduler generates.

           max-last-value-rtl
               The maximum size measured as number of RTLs that can be recorded in an expression in
               combiner for a pseudo register as last known value of that register.

           max-combine-insns
               The maximum number of instructions the RTL combiner tries to combine.

           integer-share-limit
               Small integer constants can use a shared data structure, reducing the compiler's
               memory usage and increasing its speed.  This sets the maximum value of a shared
               integer constant.

           ssp-buffer-size
               The minimum size of buffers (i.e. arrays) that receive stack smashing protection when
               -fstack-protection is used.

               This default before Ubuntu 10.10 was "8". Currently it is "4", to increase the number
               of functions protected by the stack protector.

           min-size-for-stack-sharing
               The minimum size of variables taking part in stack slot sharing when not optimizing.

           max-jump-thread-duplication-stmts
               Maximum number of statements allowed in a block that needs to be duplicated when
               threading jumps.

           max-fields-for-field-sensitive
               Maximum number of fields in a structure treated in a field sensitive manner during
               pointer analysis.

           prefetch-latency
               Estimate on average number of instructions that are executed before prefetch
               finishes.  The distance prefetched ahead is proportional to this constant.
               Increasing this number may also lead to less streams being prefetched (see
               simultaneous-prefetches).

           simultaneous-prefetches
               Maximum number of prefetches that can run at the same time.

           l1-cache-line-size
               The size of cache line in L1 data cache, in bytes.

           l1-cache-size
               The size of L1 data cache, in kilobytes.

           l2-cache-size
               The size of L2 data cache, in kilobytes.

           prefetch-dynamic-strides
               Whether the loop array prefetch pass should issue software prefetch hints for strides
               that are non-constant.  In some cases this may be beneficial, though the fact the
               stride is non-constant may make it hard to predict when there is clear benefit to
               issuing these hints.

               Set to 1 if the prefetch hints should be issued for non-constant strides.  Set to 0
               if prefetch hints should be issued only for strides that are known to be constant and
               below prefetch-minimum-stride.

           prefetch-minimum-stride
               Minimum constant stride, in bytes, to start using prefetch hints for.  If the stride
               is less than this threshold, prefetch hints will not be issued.

               This setting is useful for processors that have hardware prefetchers, in which case
               there may be conflicts between the hardware prefetchers and the software prefetchers.
               If the hardware prefetchers have a maximum stride they can handle, it should be used
               here to improve the use of software prefetchers.

               A value of -1 means we don't have a threshold and therefore prefetch hints can be
               issued for any constant stride.

               This setting is only useful for strides that are known and constant.

           loop-interchange-max-num-stmts
               The maximum number of stmts in a loop to be interchanged.

           loop-interchange-stride-ratio
               The minimum ratio between stride of two loops for interchange to be profitable.

           min-insn-to-prefetch-ratio
               The minimum ratio between the number of instructions and the number of prefetches to
               enable prefetching in a loop.

           prefetch-min-insn-to-mem-ratio
               The minimum ratio between the number of instructions and the number of memory
               references to enable prefetching in a loop.

           use-canonical-types
               Whether the compiler should use the "canonical" type system.  Should always be 1,
               which uses a more efficient internal mechanism for comparing types in C++ and
               Objective-C++.  However, if bugs in the canonical type system are causing compilation
               failures, set this value to 0 to disable canonical types.

           switch-conversion-max-branch-ratio
               Switch initialization conversion refuses to create arrays that are bigger than
               switch-conversion-max-branch-ratio times the number of branches in the switch.

           max-partial-antic-length
               Maximum length of the partial antic set computed during the tree partial redundancy
               elimination optimization (-ftree-pre) when optimizing at -O3 and above.  For some
               sorts of source code the enhanced partial redundancy elimination optimization can run
               away, consuming all of the memory available on the host machine.  This parameter sets
               a limit on the length of the sets that are computed, which prevents the runaway
               behavior.  Setting a value of 0 for this parameter allows an unlimited set length.

           rpo-vn-max-loop-depth
               Maximum loop depth that is value-numbered optimistically.  When the limit hits the
               innermost rpo-vn-max-loop-depth loops and the outermost loop in the loop nest are
               value-numbered optimistically and the remaining ones not.

           sccvn-max-alias-queries-per-access
               Maximum number of alias-oracle queries we perform when looking for redundancies for
               loads and stores.  If this limit is hit the search is aborted and the load or store
               is not considered redundant.  The number of queries is algorithmically limited to the
               number of stores on all paths from the load to the function entry.

           ira-max-loops-num
               IRA uses regional register allocation by default.  If a function contains more loops
               than the number given by this parameter, only at most the given number of the most
               frequently-executed loops form regions for regional register allocation.

           ira-max-conflict-table-size
               Although IRA uses a sophisticated algorithm to compress the conflict table, the table
               can still require excessive amounts of memory for huge functions.  If the conflict
               table for a function could be more than the size in MB given by this parameter, the
               register allocator instead uses a faster, simpler, and lower-quality algorithm that
               does not require building a pseudo-register conflict table.

           ira-loop-reserved-regs
               IRA can be used to evaluate more accurate register pressure in loops for decisions to
               move loop invariants (see -O3).  The number of available registers reserved for some
               other purposes is given by this parameter.  Default of the parameter is the best
               found from numerous experiments.

           lra-inheritance-ebb-probability-cutoff
               LRA tries to reuse values reloaded in registers in subsequent insns.  This
               optimization is called inheritance.  EBB is used as a region to do this optimization.
               The parameter defines a minimal fall-through edge probability in percentage used to
               add BB to inheritance EBB in LRA.  The default value was chosen from numerous runs of
               SPEC2000 on x86-64.

           loop-invariant-max-bbs-in-loop
               Loop invariant motion can be very expensive, both in compilation time and in amount
               of needed compile-time memory, with very large loops.  Loops with more basic blocks
               than this parameter won't have loop invariant motion optimization performed on them.

           loop-max-datarefs-for-datadeps
               Building data dependencies is expensive for very large loops.  This parameter limits
               the number of data references in loops that are considered for data dependence
               analysis.  These large loops are no handled by the optimizations using loop data
               dependencies.

           max-vartrack-size
               Sets a maximum number of hash table slots to use during variable tracking dataflow
               analysis of any function.  If this limit is exceeded with variable tracking at
               assignments enabled, analysis for that function is retried without it, after removing
               all debug insns from the function.  If the limit is exceeded even without debug
               insns, var tracking analysis is completely disabled for the function.  Setting the
               parameter to zero makes it unlimited.

           max-vartrack-expr-depth
               Sets a maximum number of recursion levels when attempting to map variable names or
               debug temporaries to value expressions.  This trades compilation time for more
               complete debug information.  If this is set too low, value expressions that are
               available and could be represented in debug information may end up not being used;
               setting this higher may enable the compiler to find more complex debug expressions,
               but compile time and memory use may grow.

           max-debug-marker-count
               Sets a threshold on the number of debug markers (e.g. begin stmt markers) to avoid
               complexity explosion at inlining or expanding to RTL.  If a function has more such
               gimple stmts than the set limit, such stmts will be dropped from the inlined copy of
               a function, and from its RTL expansion.

           min-nondebug-insn-uid
               Use uids starting at this parameter for nondebug insns.  The range below the
               parameter is reserved exclusively for debug insns created by
               -fvar-tracking-assignments, but debug insns may get (non-overlapping) uids above it
               if the reserved range is exhausted.

           ipa-sra-ptr-growth-factor
               IPA-SRA replaces a pointer to an aggregate with one or more new parameters only when
               their cumulative size is less or equal to ipa-sra-ptr-growth-factor times the size of
               the original pointer parameter.

           ipa-sra-max-replacements
               Maximum pieces of an aggregate that IPA-SRA tracks.  As a consequence, it is also the
               maximum number of replacements of a formal parameter.

           sra-max-scalarization-size-Ospeed
           sra-max-scalarization-size-Osize
               The two Scalar Reduction of Aggregates passes (SRA and IPA-SRA) aim to replace scalar
               parts of aggregates with uses of independent scalar variables.  These parameters
               control the maximum size, in storage units, of aggregate which is considered for
               replacement when compiling for speed (sra-max-scalarization-size-Ospeed) or size
               (sra-max-scalarization-size-Osize) respectively.

           sra-max-propagations
               The maximum number of artificial accesses that Scalar Replacement of Aggregates (SRA)
               will track, per one local variable, in order to facilitate copy propagation.

           tm-max-aggregate-size
               When making copies of thread-local variables in a transaction, this parameter
               specifies the size in bytes after which variables are saved with the logging
               functions as opposed to save/restore code sequence pairs.  This option only applies
               when using -fgnu-tm.

           graphite-max-nb-scop-params
               To avoid exponential effects in the Graphite loop transforms, the number of
               parameters in a Static Control Part (SCoP) is bounded.  A value of zero can be used
               to lift the bound.  A variable whose value is unknown at compilation time and defined
               outside a SCoP is a parameter of the SCoP.

           loop-block-tile-size
               Loop blocking or strip mining transforms, enabled with -floop-block or
               -floop-strip-mine, strip mine each loop in the loop nest by a given number of
               iterations.  The strip length can be changed using the loop-block-tile-size
               parameter.

           ipa-jump-function-lookups
               Specifies number of statements visited during jump function offset discovery.

           ipa-cp-value-list-size
               IPA-CP attempts to track all possible values and types passed to a function's
               parameter in order to propagate them and perform devirtualization.  ipa-cp-value-
               list-size is the maximum number of values and types it stores per one formal
               parameter of a function.

           ipa-cp-eval-threshold
               IPA-CP calculates its own score of cloning profitability heuristics and performs
               those cloning opportunities with scores that exceed ipa-cp-eval-threshold.

           ipa-cp-max-recursive-depth
               Maximum depth of recursive cloning for self-recursive function.

           ipa-cp-min-recursive-probability
               Recursive cloning only when the probability of call being executed exceeds the
               parameter.

           ipa-cp-recursion-penalty
               Percentage penalty the recursive functions will receive when they are evaluated for
               cloning.

           ipa-cp-single-call-penalty
               Percentage penalty functions containing a single call to another function will
               receive when they are evaluated for cloning.

           ipa-max-agg-items
               IPA-CP is also capable to propagate a number of scalar values passed in an aggregate.
               ipa-max-agg-items controls the maximum number of such values per one parameter.

           ipa-cp-loop-hint-bonus
               When IPA-CP determines that a cloning candidate would make the number of iterations
               of a loop known, it adds a bonus of ipa-cp-loop-hint-bonus to the profitability score
               of the candidate.

           ipa-max-loop-predicates
               The maximum number of different predicates IPA will use to describe when loops in a
               function have known properties.

           ipa-max-aa-steps
               During its analysis of function bodies, IPA-CP employs alias analysis in order to
               track values pointed to by function parameters.  In order not spend too much time
               analyzing huge functions, it gives up and consider all memory clobbered after
               examining ipa-max-aa-steps statements modifying memory.

           ipa-max-switch-predicate-bounds
               Maximal number of boundary endpoints of case ranges of switch statement.  For switch
               exceeding this limit, IPA-CP will not construct cloning cost predicate, which is used
               to estimate cloning benefit, for default case of the switch statement.

           ipa-max-param-expr-ops
               IPA-CP will analyze conditional statement that references some function parameter to
               estimate benefit for cloning upon certain constant value.  But if number of
               operations in a parameter expression exceeds ipa-max-param-expr-ops, the expression
               is treated as complicated one, and is not handled by IPA analysis.

           lto-partitions
               Specify desired number of partitions produced during WHOPR compilation.  The number
               of partitions should exceed the number of CPUs used for compilation.

           lto-min-partition
               Size of minimal partition for WHOPR (in estimated instructions).  This prevents
               expenses of splitting very small programs into too many partitions.

           lto-max-partition
               Size of max partition for WHOPR (in estimated instructions).  to provide an upper
               bound for individual size of partition.  Meant to be used only with balanced
               partitioning.

           lto-max-streaming-parallelism
               Maximal number of parallel processes used for LTO streaming.

           cxx-max-namespaces-for-diagnostic-help
               The maximum number of namespaces to consult for suggestions when C++ name lookup
               fails for an identifier.

           sink-frequency-threshold
               The maximum relative execution frequency (in percents) of the target block relative
               to a statement's original block to allow statement sinking of a statement.  Larger
               numbers result in more aggressive statement sinking.  A small positive adjustment is
               applied for statements with memory operands as those are even more profitable so
               sink.

           max-stores-to-sink
               The maximum number of conditional store pairs that can be sunk.  Set to 0 if either
               vectorization (-ftree-vectorize) or if-conversion (-ftree-loop-if-convert) is
               disabled.

           case-values-threshold
               The smallest number of different values for which it is best to use a jump-table
               instead of a tree of conditional branches.  If the value is 0, use the default for
               the machine.

           jump-table-max-growth-ratio-for-size
               The maximum code size growth ratio when expanding into a jump table (in percent).
               The parameter is used when optimizing for size.

           jump-table-max-growth-ratio-for-speed
               The maximum code size growth ratio when expanding into a jump table (in percent).
               The parameter is used when optimizing for speed.

           tree-reassoc-width
               Set the maximum number of instructions executed in parallel in reassociated tree.
               This parameter overrides target dependent heuristics used by default if has non zero
               value.

           sched-pressure-algorithm
               Choose between the two available implementations of -fsched-pressure.  Algorithm 1 is
               the original implementation and is the more likely to prevent instructions from being
               reordered.  Algorithm 2 was designed to be a compromise between the relatively
               conservative approach taken by algorithm 1 and the rather aggressive approach taken
               by the default scheduler.  It relies more heavily on having a regular register file
               and accurate register pressure classes.  See haifa-sched.c in the GCC sources for
               more details.

               The default choice depends on the target.

           max-slsr-cand-scan
               Set the maximum number of existing candidates that are considered when seeking a
               basis for a new straight-line strength reduction candidate.

           asan-globals
               Enable buffer overflow detection for global objects.  This kind of protection is
               enabled by default if you are using -fsanitize=address option.  To disable global
               objects protection use --param asan-globals=0.

           asan-stack
               Enable buffer overflow detection for stack objects.  This kind of protection is
               enabled by default when using -fsanitize=address.  To disable stack protection use
               --param asan-stack=0 option.

           asan-instrument-reads
               Enable buffer overflow detection for memory reads.  This kind of protection is
               enabled by default when using -fsanitize=address.  To disable memory reads protection
               use --param asan-instrument-reads=0.

           asan-instrument-writes
               Enable buffer overflow detection for memory writes.  This kind of protection is
               enabled by default when using -fsanitize=address.  To disable memory writes
               protection use --param asan-instrument-writes=0 option.

           asan-memintrin
               Enable detection for built-in functions.  This kind of protection is enabled by
               default when using -fsanitize=address.  To disable built-in functions protection use
               --param asan-memintrin=0.

           asan-use-after-return
               Enable detection of use-after-return.  This kind of protection is enabled by default
               when using the -fsanitize=address option.  To disable it use --param
               asan-use-after-return=0.

               Note: By default the check is disabled at run time.  To enable it, add
               "detect_stack_use_after_return=1" to the environment variable ASAN_OPTIONS.

           asan-instrumentation-with-call-threshold
               If number of memory accesses in function being instrumented is greater or equal to
               this number, use callbacks instead of inline checks.  E.g. to disable inline code use
               --param asan-instrumentation-with-call-threshold=0.

           hwasan-instrument-stack
               Enable hwasan instrumentation of statically sized stack-allocated variables.  This
               kind of instrumentation is enabled by default when using -fsanitize=hwaddress and
               disabled by default when using -fsanitize=kernel-hwaddress.  To disable stack
               instrumentation use --param hwasan-instrument-stack=0, and to enable it use --param
               hwasan-instrument-stack=1.

           hwasan-random-frame-tag
               When using stack instrumentation, decide tags for stack variables using a
               deterministic sequence beginning at a random tag for each frame.  With this parameter
               unset tags are chosen using the same sequence but beginning from 1.  This is enabled
               by default for -fsanitize=hwaddress and unavailable for -fsanitize=kernel-hwaddress.
               To disable it use --param hwasan-random-frame-tag=0.

           hwasan-instrument-allocas
               Enable hwasan instrumentation of dynamically sized stack-allocated variables.  This
               kind of instrumentation is enabled by default when using -fsanitize=hwaddress and
               disabled by default when using -fsanitize=kernel-hwaddress.  To disable
               instrumentation of such variables use --param hwasan-instrument-allocas=0, and to
               enable it use --param hwasan-instrument-allocas=1.

           hwasan-instrument-reads
               Enable hwasan checks on memory reads.  Instrumentation of reads is enabled by default
               for both -fsanitize=hwaddress and -fsanitize=kernel-hwaddress.  To disable checking
               memory reads use --param hwasan-instrument-reads=0.

           hwasan-instrument-writes
               Enable hwasan checks on memory writes.  Instrumentation of writes is enabled by
               default for both -fsanitize=hwaddress and -fsanitize=kernel-hwaddress.  To disable
               checking memory writes use --param hwasan-instrument-writes=0.

           hwasan-instrument-mem-intrinsics
               Enable hwasan instrumentation of builtin functions.  Instrumentation of these builtin
               functions is enabled by default for both -fsanitize=hwaddress and
               -fsanitize=kernel-hwaddress.  To disable instrumentation of builtin functions use
               --param hwasan-instrument-mem-intrinsics=0.

           use-after-scope-direct-emission-threshold
               If the size of a local variable in bytes is smaller or equal to this number, directly
               poison (or unpoison) shadow memory instead of using run-time callbacks.

           tsan-distinguish-volatile
               Emit special instrumentation for accesses to volatiles.

           tsan-instrument-func-entry-exit
               Emit instrumentation calls to __tsan_func_entry() and __tsan_func_exit().

           max-fsm-thread-path-insns
               Maximum number of instructions to copy when duplicating blocks on a finite state
               automaton jump thread path.

           max-fsm-thread-length
               Maximum number of basic blocks on a finite state automaton jump thread path.

           max-fsm-thread-paths
               Maximum number of new jump thread paths to create for a finite state automaton.

           parloops-chunk-size
               Chunk size of omp schedule for loops parallelized by parloops.

           parloops-schedule
               Schedule type of omp schedule for loops parallelized by parloops (static, dynamic,
               guided, auto, runtime).

           parloops-min-per-thread
               The minimum number of iterations per thread of an innermost parallelized loop for
               which the parallelized variant is preferred over the single threaded one.  Note that
               for a parallelized loop nest the minimum number of iterations of the outermost loop
               per thread is two.

           max-ssa-name-query-depth
               Maximum depth of recursion when querying properties of SSA names in things like fold
               routines.  One level of recursion corresponds to following a use-def chain.

           max-speculative-devirt-maydefs
               The maximum number of may-defs we analyze when looking for a must-def specifying the
               dynamic type of an object that invokes a virtual call we may be able to devirtualize
               speculatively.

           max-vrp-switch-assertions
               The maximum number of assertions to add along the default edge of a switch statement
               during VRP.

           evrp-mode
               Specifies the mode Early VRP should operate in.

           unroll-jam-min-percent
               The minimum percentage of memory references that must be optimized away for the
               unroll-and-jam transformation to be considered profitable.

           unroll-jam-max-unroll
               The maximum number of times the outer loop should be unrolled by the unroll-and-jam
               transformation.

           max-rtl-if-conversion-unpredictable-cost
               Maximum permissible cost for the sequence that would be generated by the RTL if-
               conversion pass for a branch that is considered unpredictable.

           max-variable-expansions-in-unroller
               If -fvariable-expansion-in-unroller is used, the maximum number of times that an
               individual variable will be expanded during loop unrolling.

           tracer-min-branch-probability-feedback
               Stop forward growth if the probability of best edge is less than this threshold (in
               percent). Used when profile feedback is available.

           partial-inlining-entry-probability
               Maximum probability of the entry BB of split region (in percent relative to entry BB
               of the function) to make partial inlining happen.

           max-tracked-strlens
               Maximum number of strings for which strlen optimization pass will track string
               lengths.

           gcse-after-reload-partial-fraction
               The threshold ratio for performing partial redundancy elimination after reload.

           gcse-after-reload-critical-fraction
               The threshold ratio of critical edges execution count that permit performing
               redundancy elimination after reload.

           max-loop-header-insns
               The maximum number of insns in loop header duplicated by the copy loop headers pass.

           vect-epilogues-nomask
               Enable loop epilogue vectorization using smaller vector size.

           vect-partial-vector-usage
               Controls when the loop vectorizer considers using partial vector loads and stores as
               an alternative to falling back to scalar code.  0 stops the vectorizer from ever
               using partial vector loads and stores.  1 allows partial vector loads and stores if
               vectorization removes the need for the code to iterate.  2 allows partial vector
               loads and stores in all loops.  The parameter only has an effect on targets that
               support partial vector loads and stores.

           avoid-fma-max-bits
               Maximum number of bits for which we avoid creating FMAs.

           sms-loop-average-count-threshold
               A threshold on the average loop count considered by the swing modulo scheduler.

           sms-dfa-history
               The number of cycles the swing modulo scheduler considers when checking conflicts
               using DFA.

           max-inline-insns-recursive-auto
               The maximum number of instructions non-inline function can grow to via recursive
               inlining.

           graphite-allow-codegen-errors
               Whether codegen errors should be ICEs when -fchecking.

           sms-max-ii-factor
               A factor for tuning the upper bound that swing modulo scheduler uses for scheduling a
               loop.

           lra-max-considered-reload-pseudos
               The max number of reload pseudos which are considered during spilling a non-reload
               pseudo.

           max-pow-sqrt-depth
               Maximum depth of sqrt chains to use when synthesizing exponentiation by a real
               constant.

           max-dse-active-local-stores
               Maximum number of active local stores in RTL dead store elimination.

           asan-instrument-allocas
               Enable asan allocas/VLAs protection.

           max-iterations-computation-cost
               Bound on the cost of an expression to compute the number of iterations.

           max-isl-operations
               Maximum number of isl operations, 0 means unlimited.

           graphite-max-arrays-per-scop
               Maximum number of arrays per scop.

           max-vartrack-reverse-op-size
               Max. size of loc list for which reverse ops should be added.

           tracer-dynamic-coverage-feedback
               The percentage of function, weighted by execution frequency, that must be covered by
               trace formation.  Used when profile feedback is available.

           max-inline-recursive-depth-auto
               The maximum depth of recursive inlining for non-inline functions.

           fsm-scale-path-stmts
               Scale factor to apply to the number of statements in a threading path when comparing
               to the number of (scaled) blocks.

           fsm-maximum-phi-arguments
               Maximum number of arguments a PHI may have before the FSM threader will not try to
               thread through its block.

           uninit-control-dep-attempts
               Maximum number of nested calls to search for control dependencies during
               uninitialized variable analysis.

           sra-max-scalarization-size-Osize
               Maximum size, in storage units, of an aggregate which should be considered for
               scalarization when compiling for size.

           fsm-scale-path-blocks
               Scale factor to apply to the number of blocks in a threading path when comparing to
               the number of (scaled) statements.

           sched-autopref-queue-depth
               Hardware autoprefetcher scheduler model control flag.  Number of lookahead cycles the
               model looks into; at ' ' only enable instruction sorting heuristic.

           loop-versioning-max-inner-insns
               The maximum number of instructions that an inner loop can have before the loop
               versioning pass considers it too big to copy.

           loop-versioning-max-outer-insns
               The maximum number of instructions that an outer loop can have before the loop
               versioning pass considers it too big to copy, discounting any instructions in inner
               loops that directly benefit from versioning.

           ssa-name-def-chain-limit
               The maximum number of SSA_NAME assignments to follow in determining a property of a
               variable such as its value.  This limits the number of iterations or recursive calls
               GCC performs when optimizing certain statements or when determining their validity
               prior to issuing diagnostics.

           store-merging-max-size
               Maximum size of a single store merging region in bytes.

           hash-table-verification-limit
               The number of elements for which hash table verification is done for each searched
               element.

           max-find-base-term-values
               Maximum number of VALUEs handled during a single find_base_term call.

           analyzer-max-enodes-per-program-point
               The maximum number of exploded nodes per program point within the analyzer, before
               terminating analysis of that point.

           analyzer-max-constraints
               The maximum number of constraints per state.

           analyzer-min-snodes-for-call-summary
               The minimum number of supernodes within a function for the analyzer to consider
               summarizing its effects at call sites.

           analyzer-max-enodes-for-full-dump
               The maximum depth of exploded nodes that should appear in a dot dump before switching
               to a less verbose format.

           analyzer-max-recursion-depth
               The maximum number of times a callsite can appear in a call stack within the
               analyzer, before terminating analysis of a call that would recurse deeper.

           analyzer-max-svalue-depth
               The maximum depth of a symbolic value, before approximating the value as unknown.

           analyzer-max-infeasible-edges
               The maximum number of infeasible edges to reject before declaring a diagnostic as
               infeasible.

           gimple-fe-computed-hot-bb-threshold
               The number of executions of a basic block which is considered hot.  The parameter is
               used only in GIMPLE FE.

           analyzer-bb-explosion-factor
               The maximum number of 'after supernode' exploded nodes within the analyzer per
               supernode, before terminating analysis.

           ranger-logical-depth
               Maximum depth of logical expression evaluation ranger will look through when
               evaluating outgoing edge ranges.

           openacc-kernels
               Specify mode of OpenACC `kernels' constructs handling.  With
               --param=openacc-kernels=decompose, OpenACC `kernels' constructs are decomposed into
               parts, a sequence of compute constructs, each then handled individually.  This is
               work in progress.  With --param=openacc-kernels=parloops, OpenACC `kernels'
               constructs are handled by the parloops pass, en bloc.  This is the current default.

           The following choices of name are available on AArch64 targets:

           aarch64-sve-compare-costs
               When vectorizing for SVE, consider using "unpacked" vectors for smaller elements and
               use the cost model to pick the cheapest approach.  Also use the cost model to choose
               between SVE and Advanced SIMD vectorization.

               Using unpacked vectors includes storing smaller elements in larger containers and
               accessing elements with extending loads and truncating stores.

           aarch64-float-recp-precision
               The number of Newton iterations for calculating the reciprocal for float type.  The
               precision of division is proportional to this param when division approximation is
               enabled.  The default value is 1.

           aarch64-double-recp-precision
               The number of Newton iterations for calculating the reciprocal for double type.  The
               precision of division is propotional to this param when division approximation is
               enabled.  The default value is 2.

           aarch64-autovec-preference
               Force an ISA selection strategy for auto-vectorization.  Accepts values from 0 to 4,
               inclusive.

               0   Use the default heuristics.

               1   Use only Advanced SIMD for auto-vectorization.

               2   Use only SVE for auto-vectorization.

               3   Use both Advanced SIMD and SVE.  Prefer Advanced SIMD when the costs are deemed
                   equal.

               4   Use both Advanced SIMD and SVE.  Prefer SVE when the costs are deemed equal.

               The default value is 0.

           aarch64-loop-vect-issue-rate-niters
               The tuning for some AArch64 CPUs tries to take both latencies and issue rates into
               account when deciding whether a loop should be vectorized using SVE, vectorized using
               Advanced SIMD, or not vectorized at all.  If this parameter is set to n, GCC will not
               use this heuristic for loops that are known to execute in fewer than n Advanced SIMD
               iterations.

   Program Instrumentation Options
       GCC supports a number of command-line options that control adding run-time instrumentation to
       the code it normally generates.  For example, one purpose of instrumentation is collect
       profiling statistics for use in finding program hot spots, code coverage analysis, or
       profile-guided optimizations.  Another class of program instrumentation is adding run-time
       checking to detect programming errors like invalid pointer dereferences or out-of-bounds
       array accesses, as well as deliberately hostile attacks such as stack smashing or C++ vtable
       hijacking.  There is also a general hook which can be used to implement other forms of
       tracing or function-level instrumentation for debug or program analysis purposes.

       -p
       -pg Generate extra code to write profile information suitable for the analysis program prof
           (for -p) or gprof (for -pg).  You must use this option when compiling the source files
           you want data about, and you must also use it when linking.

           You can use the function attribute "no_instrument_function" to suppress profiling of
           individual functions when compiling with these options.

       -fprofile-arcs
           Add code so that program flow arcs are instrumented.  During execution the program
           records how many times each branch and call is executed and how many times it is taken or
           returns.  On targets that support constructors with priority support, profiling properly
           handles constructors, destructors and C++ constructors (and destructors) of classes which
           are used as a type of a global variable.

           When the compiled program exits it saves this data to a file called auxname.gcda for each
           source file.  The data may be used for profile-directed optimizations
           (-fbranch-probabilities), or for test coverage analysis (-ftest-coverage).  Each object
           file's auxname is generated from the name of the output file, if explicitly specified and
           it is not the final executable, otherwise it is the basename of the source file.  In both
           cases any suffix is removed (e.g. foo.gcda for input file dir/foo.c, or dir/foo.gcda for
           output file specified as -o dir/foo.o).

       --coverage
           This option is used to compile and link code instrumented for coverage analysis.  The
           option is a synonym for -fprofile-arcs -ftest-coverage (when compiling) and -lgcov (when
           linking).  See the documentation for those options for more details.

           *   Compile the source files with -fprofile-arcs plus optimization and code generation
               options.  For test coverage analysis, use the additional -ftest-coverage option.  You
               do not need to profile every source file in a program.

           *   Compile the source files additionally with -fprofile-abs-path to create absolute path
               names in the .gcno files.  This allows gcov to find the correct sources in projects
               where compilations occur with different working directories.

           *   Link your object files with -lgcov or -fprofile-arcs (the latter implies the former).

           *   Run the program on a representative workload to generate the arc profile information.
               This may be repeated any number of times.  You can run concurrent instances of your
               program, and provided that the file system supports locking, the data files will be
               correctly updated.  Unless a strict ISO C dialect option is in effect, "fork" calls
               are detected and correctly handled without double counting.

           *   For profile-directed optimizations, compile the source files again with the same
               optimization and code generation options plus -fbranch-probabilities.

           *   For test coverage analysis, use gcov to produce human readable information from the
               .gcno and .gcda files.  Refer to the gcov documentation for further information.

           With -fprofile-arcs, for each function of your program GCC creates a program flow graph,
           then finds a spanning tree for the graph.  Only arcs that are not on the spanning tree
           have to be instrumented: the compiler adds code to count the number of times that these
           arcs are executed.  When an arc is the only exit or only entrance to a block, the
           instrumentation code can be added to the block; otherwise, a new basic block must be
           created to hold the instrumentation code.

       -ftest-coverage
           Produce a notes file that the gcov code-coverage utility can use to show program
           coverage.  Each source file's note file is called auxname.gcno.  Refer to the
           -fprofile-arcs option above for a description of auxname and instructions on how to
           generate test coverage data.  Coverage data matches the source files more closely if you
           do not optimize.

       -fprofile-abs-path
           Automatically convert relative source file names to absolute path names in the .gcno
           files.  This allows gcov to find the correct sources in projects where compilations occur
           with different working directories.

       -fprofile-dir=path
           Set the directory to search for the profile data files in to path.  This option affects
           only the profile data generated by -fprofile-generate, -ftest-coverage, -fprofile-arcs
           and used by -fprofile-use and -fbranch-probabilities and its related options.  Both
           absolute and relative paths can be used.  By default, GCC uses the current directory as
           path, thus the profile data file appears in the same directory as the object file.  In
           order to prevent the file name clashing, if the object file name is not an absolute path,
           we mangle the absolute path of the sourcename.gcda file and use it as the file name of a
           .gcda file.  See similar option -fprofile-note.

           When an executable is run in a massive parallel environment, it is recommended to save
           profile to different folders.  That can be done with variables in path that are exported
           during run-time:

           %p  process ID.

           %q{VAR}
               value of environment variable VAR

       -fprofile-generate
       -fprofile-generate=path
           Enable options usually used for instrumenting application to produce profile useful for
           later recompilation with profile feedback based optimization.  You must use
           -fprofile-generate both when compiling and when linking your program.

           The following options are enabled: -fprofile-arcs, -fprofile-values, -finline-functions,
           and -fipa-bit-cp.

           If path is specified, GCC looks at the path to find the profile feedback data files. See
           -fprofile-dir.

           To optimize the program based on the collected profile information, use -fprofile-use.

       -fprofile-info-section
       -fprofile-info-section=name
           Register the profile information in the specified section instead of using a
           constructor/destructor.  The section name is name if it is specified, otherwise the
           section name defaults to ".gcov_info".  A pointer to the profile information generated by
           -fprofile-arcs or -ftest-coverage is placed in the specified section for each translation
           unit.  This option disables the profile information registration through a constructor
           and it disables the profile information processing through a destructor.  This option is
           not intended to be used in hosted environments such as GNU/Linux.  It targets systems
           with limited resources which do not support constructors and destructors.  The linker
           could collect the input sections in a continuous memory block and define start and end
           symbols.  The runtime support could dump the profiling information registered in this
           linker set during program termination to a serial line for example.  A GNU linker script
           example which defines a linker output section follows:

                     .gcov_info      :
                     {
                       PROVIDE (__gcov_info_start = .);
                       KEEP (*(.gcov_info))
                       PROVIDE (__gcov_info_end = .);
                     }

       -fprofile-note=path
           If path is specified, GCC saves .gcno file into path location.  If you combine the option
           with multiple source files, the .gcno file will be overwritten.

       -fprofile-prefix-path=path
           This option can be used in combination with profile-generate=profile_dir and
           profile-use=profile_dir to inform GCC where is the base directory of built source tree.
           By default profile_dir will contain files with mangled absolute paths of all object files
           in the built project.  This is not desirable when directory used to build the
           instrumented binary differs from the directory used to build the binary optimized with
           profile feedback because the profile data will not be found during the optimized build.
           In such setups -fprofile-prefix-path=path with path pointing to the base directory of the
           build can be used to strip the irrelevant part of the path and keep all file names
           relative to the main build directory.

       -fprofile-update=method
           Alter the update method for an application instrumented for profile feedback based
           optimization.  The method argument should be one of single, atomic or prefer-atomic.  The
           first one is useful for single-threaded applications, while the second one prevents
           profile corruption by emitting thread-safe code.

           Warning: When an application does not properly join all threads (or creates an detached
           thread), a profile file can be still corrupted.

           Using prefer-atomic would be transformed either to atomic, when supported by a target, or
           to single otherwise.  The GCC driver automatically selects prefer-atomic when -pthread is
           present in the command line.

       -fprofile-filter-files=regex
           Instrument only functions from files whose name matches any of the regular expressions
           (separated by semi-colons).

           For example, -fprofile-filter-files=main\.c;module.*\.c will instrument only main.c and
           all C files starting with 'module'.

       -fprofile-exclude-files=regex
           Instrument only functions from files whose name does not match any of the regular
           expressions (separated by semi-colons).

           For example, -fprofile-exclude-files=/usr/.* will prevent instrumentation of all files
           that are located in the /usr/ folder.

       -fprofile-reproducible=[multithreaded|parallel-runs|serial]
           Control level of reproducibility of profile gathered by "-fprofile-generate".  This makes
           it possible to rebuild program with same outcome which is useful, for example, for
           distribution packages.

           With -fprofile-reproducible=serial the profile gathered by -fprofile-generate is
           reproducible provided the trained program behaves the same at each invocation of the
           train run, it is not multi-threaded and profile data streaming is always done in the same
           order.  Note that profile streaming happens at the end of program run but also before
           "fork" function is invoked.

           Note that it is quite common that execution counts of some part of programs depends, for
           example, on length of temporary file names or memory space randomization (that may affect
           hash-table collision rate).  Such non-reproducible part of programs may be annotated by
           "no_instrument_function" function attribute. gcov-dump with -l can be used to dump
           gathered data and verify that they are indeed reproducible.

           With -fprofile-reproducible=parallel-runs collected profile stays reproducible regardless
           the order of streaming of the data into gcda files.  This setting makes it possible to
           run multiple instances of instrumented program in parallel (such as with "make -j"). This
           reduces quality of gathered data, in particular of indirect call profiling.

       -fsanitize=address
           Enable AddressSanitizer, a fast memory error detector.  Memory access instructions are
           instrumented to detect out-of-bounds and use-after-free bugs.  The option enables
           -fsanitize-address-use-after-scope.  See
           <https://github.com/google/sanitizers/wiki/AddressSanitizer> for more details.  The run-
           time behavior can be influenced using the ASAN_OPTIONS environment variable.  When set to
           "help=1", the available options are shown at startup of the instrumented program.  See
           <https://github.com/google/sanitizers/wiki/AddressSanitizerFlags#run-time-flags> for a
           list of supported options.  The option cannot be combined with -fsanitize=thread or
           -fsanitize=hwaddress.  Note that the only target -fsanitize=hwaddress is currently
           supported on is AArch64.

       -fsanitize=kernel-address
           Enable AddressSanitizer for Linux kernel.  See <https://github.com/google/kasan> for more
           details.

       -fsanitize=hwaddress
           Enable Hardware-assisted AddressSanitizer, which uses a hardware ability to ignore the
           top byte of a pointer to allow the detection of memory errors with a low memory overhead.
           Memory access instructions are instrumented to detect out-of-bounds and use-after-free
           bugs.  The option enables -fsanitize-address-use-after-scope.  See
           <https://clang.llvm.org/docs/HardwareAssistedAddressSanitizerDesign.html> for more
           details.  The run-time behavior can be influenced using the HWASAN_OPTIONS environment
           variable.  When set to "help=1", the available options are shown at startup of the
           instrumented program.  The option cannot be combined with -fsanitize=thread or
           -fsanitize=address, and is currently only available on AArch64.

       -fsanitize=kernel-hwaddress
           Enable Hardware-assisted AddressSanitizer for compilation of the Linux kernel.  Similar
           to -fsanitize=kernel-address but using an alternate instrumentation method, and similar
           to -fsanitize=hwaddress but with instrumentation differences necessary for compiling the
           Linux kernel.  These differences are to avoid hwasan library initialization calls and to
           account for the stack pointer having a different value in its top byte.

           Note: This option has different defaults to the -fsanitize=hwaddress.  Instrumenting the
           stack and alloca calls are not on by default but are still possible by specifying the
           command-line options --param hwasan-instrument-stack=1 and --param
           hwasan-instrument-allocas=1 respectively. Using a random frame tag is not implemented for
           kernel instrumentation.

       -fsanitize=pointer-compare
           Instrument comparison operation (<, <=, >, >=) with pointer operands.  The option must be
           combined with either -fsanitize=kernel-address or -fsanitize=address The option cannot be
           combined with -fsanitize=thread.  Note: By default the check is disabled at run time.  To
           enable it, add "detect_invalid_pointer_pairs=2" to the environment variable ASAN_OPTIONS.
           Using "detect_invalid_pointer_pairs=1" detects invalid operation only when both pointers
           are non-null.

       -fsanitize=pointer-subtract
           Instrument subtraction with pointer operands.  The option must be combined with either
           -fsanitize=kernel-address or -fsanitize=address The option cannot be combined with
           -fsanitize=thread.  Note: By default the check is disabled at run time.  To enable it,
           add "detect_invalid_pointer_pairs=2" to the environment variable ASAN_OPTIONS. Using
           "detect_invalid_pointer_pairs=1" detects invalid operation only when both pointers are
           non-null.

       -fsanitize=thread
           Enable ThreadSanitizer, a fast data race detector.  Memory access instructions are
           instrumented to detect data race bugs.  See
           <https://github.com/google/sanitizers/wiki#threadsanitizer> for more details. The run-
           time behavior can be influenced using the TSAN_OPTIONS environment variable; see
           <https://github.com/google/sanitizers/wiki/ThreadSanitizerFlags> for a list of supported
           options.  The option cannot be combined with -fsanitize=address, -fsanitize=leak.

           Note that sanitized atomic builtins cannot throw exceptions when operating on invalid
           memory addresses with non-call exceptions (-fnon-call-exceptions).

       -fsanitize=leak
           Enable LeakSanitizer, a memory leak detector.  This option only matters for linking of
           executables and the executable is linked against a library that overrides "malloc" and
           other allocator functions.  See
           <https://github.com/google/sanitizers/wiki/AddressSanitizerLeakSanitizer> for more
           details.  The run-time behavior can be influenced using the LSAN_OPTIONS environment
           variable.  The option cannot be combined with -fsanitize=thread.

       -fsanitize=undefined
           Enable UndefinedBehaviorSanitizer, a fast undefined behavior detector.  Various
           computations are instrumented to detect undefined behavior at runtime.  See
           <https://clang.llvm.org/docs/UndefinedBehaviorSanitizer.html> for more details.   The
           run-time behavior can be influenced using the UBSAN_OPTIONS environment variable.
           Current suboptions are:

           -fsanitize=shift
               This option enables checking that the result of a shift operation is not undefined.
               Note that what exactly is considered undefined differs slightly between C and C++, as
               well as between ISO C90 and C99, etc.  This option has two suboptions,
               -fsanitize=shift-base and -fsanitize=shift-exponent.

           -fsanitize=shift-exponent
               This option enables checking that the second argument of a shift operation is not
               negative and is smaller than the precision of the promoted first argument.

           -fsanitize=shift-base
               If the second argument of a shift operation is within range, check that the result of
               a shift operation is not undefined.  Note that what exactly is considered undefined
               differs slightly between C and C++, as well as between ISO C90 and C99, etc.

           -fsanitize=integer-divide-by-zero
               Detect integer division by zero as well as "INT_MIN / -1" division.

           -fsanitize=unreachable
               With this option, the compiler turns the "__builtin_unreachable" call into a
               diagnostics message call instead.  When reaching the "__builtin_unreachable" call,
               the behavior is undefined.

           -fsanitize=vla-bound
               This option instructs the compiler to check that the size of a variable length array
               is positive.

           -fsanitize=null
               This option enables pointer checking.  Particularly, the application built with this
               option turned on will issue an error message when it tries to dereference a NULL
               pointer, or if a reference (possibly an rvalue reference) is bound to a NULL pointer,
               or if a method is invoked on an object pointed by a NULL pointer.

           -fsanitize=return
               This option enables return statement checking.  Programs built with this option
               turned on will issue an error message when the end of a non-void function is reached
               without actually returning a value.  This option works in C++ only.

           -fsanitize=signed-integer-overflow
               This option enables signed integer overflow checking.  We check that the result of
               "+", "*", and both unary and binary "-" does not overflow in the signed arithmetics.
               Note, integer promotion rules must be taken into account.  That is, the following is
               not an overflow:

                       signed char a = SCHAR_MAX;
                       a++;

           -fsanitize=bounds
               This option enables instrumentation of array bounds.  Various out of bounds accesses
               are detected.  Flexible array members, flexible array member-like arrays, and
               initializers of variables with static storage are not instrumented.

           -fsanitize=bounds-strict
               This option enables strict instrumentation of array bounds.  Most out of bounds
               accesses are detected, including flexible array members and flexible array member-
               like arrays.  Initializers of variables with static storage are not instrumented.

           -fsanitize=alignment
               This option enables checking of alignment of pointers when they are dereferenced, or
               when a reference is bound to insufficiently aligned target, or when a method or
               constructor is invoked on insufficiently aligned object.

           -fsanitize=object-size
               This option enables instrumentation of memory references using the
               "__builtin_object_size" function.  Various out of bounds pointer accesses are
               detected.

           -fsanitize=float-divide-by-zero
               Detect floating-point division by zero.  Unlike other similar options,
               -fsanitize=float-divide-by-zero is not enabled by -fsanitize=undefined, since
               floating-point division by zero can be a legitimate way of obtaining infinities and
               NaNs.

           -fsanitize=float-cast-overflow
               This option enables floating-point type to integer conversion checking.  We check
               that the result of the conversion does not overflow.  Unlike other similar options,
               -fsanitize=float-cast-overflow is not enabled by -fsanitize=undefined.  This option
               does not work well with "FE_INVALID" exceptions enabled.

           -fsanitize=nonnull-attribute
               This option enables instrumentation of calls, checking whether null values are not
               passed to arguments marked as requiring a non-null value by the "nonnull" function
               attribute.

           -fsanitize=returns-nonnull-attribute
               This option enables instrumentation of return statements in functions marked with
               "returns_nonnull" function attribute, to detect returning of null values from such
               functions.

           -fsanitize=bool
               This option enables instrumentation of loads from bool.  If a value other than 0/1 is
               loaded, a run-time error is issued.

           -fsanitize=enum
               This option enables instrumentation of loads from an enum type.  If a value outside
               the range of values for the enum type is loaded, a run-time error is issued.

           -fsanitize=vptr
               This option enables instrumentation of C++ member function calls, member accesses and
               some conversions between pointers to base and derived classes, to verify the
               referenced object has the correct dynamic type.

           -fsanitize=pointer-overflow
               This option enables instrumentation of pointer arithmetics.  If the pointer
               arithmetics overflows, a run-time error is issued.

           -fsanitize=builtin
               This option enables instrumentation of arguments to selected builtin functions.  If
               an invalid value is passed to such arguments, a run-time error is issued.  E.g.
               passing 0 as the argument to "__builtin_ctz" or "__builtin_clz" invokes undefined
               behavior and is diagnosed by this option.

           While -ftrapv causes traps for signed overflows to be emitted, -fsanitize=undefined gives
           a diagnostic message.  This currently works only for the C family of languages.

       -fno-sanitize=all
           This option disables all previously enabled sanitizers.  -fsanitize=all is not allowed,
           as some sanitizers cannot be used together.

       -fasan-shadow-offset=number
           This option forces GCC to use custom shadow offset in AddressSanitizer checks.  It is
           useful for experimenting with different shadow memory layouts in Kernel AddressSanitizer.

       -fsanitize-sections=s1,s2,...
           Sanitize global variables in selected user-defined sections.  si may contain wildcards.

       -fsanitize-recover[=opts]
           -fsanitize-recover= controls error recovery mode for sanitizers mentioned in comma-
           separated list of opts.  Enabling this option for a sanitizer component causes it to
           attempt to continue running the program as if no error happened.  This means multiple
           runtime errors can be reported in a single program run, and the exit code of the program
           may indicate success even when errors have been reported.  The -fno-sanitize-recover=
           option can be used to alter this behavior: only the first detected error is reported and
           program then exits with a non-zero exit code.

           Currently this feature only works for -fsanitize=undefined (and its suboptions except for
           -fsanitize=unreachable and -fsanitize=return), -fsanitize=float-cast-overflow,
           -fsanitize=float-divide-by-zero, -fsanitize=bounds-strict, -fsanitize=kernel-address and
           -fsanitize=address.  For these sanitizers error recovery is turned on by default, except
           -fsanitize=address, for which this feature is experimental.  -fsanitize-recover=all and
           -fno-sanitize-recover=all is also accepted, the former enables recovery for all
           sanitizers that support it, the latter disables recovery for all sanitizers that support
           it.

           Even if a recovery mode is turned on the compiler side, it needs to be also enabled on
           the runtime library side, otherwise the failures are still fatal.  The runtime library
           defaults to "halt_on_error=0" for ThreadSanitizer and UndefinedBehaviorSanitizer, while
           default value for AddressSanitizer is "halt_on_error=1". This can be overridden through
           setting the "halt_on_error" flag in the corresponding environment variable.

           Syntax without an explicit opts parameter is deprecated.  It is equivalent to specifying
           an opts list of:

                   undefined,float-cast-overflow,float-divide-by-zero,bounds-strict

       -fsanitize-address-use-after-scope
           Enable sanitization of local variables to detect use-after-scope bugs.  The option sets
           -fstack-reuse to none.

       -fsanitize-undefined-trap-on-error
           The -fsanitize-undefined-trap-on-error option instructs the compiler to report undefined
           behavior using "__builtin_trap" rather than a "libubsan" library routine.  The advantage
           of this is that the "libubsan" library is not needed and is not linked in, so this is
           usable even in freestanding environments.

       -fsanitize-coverage=trace-pc
           Enable coverage-guided fuzzing code instrumentation.  Inserts a call to
           "__sanitizer_cov_trace_pc" into every basic block.

       -fsanitize-coverage=trace-cmp
           Enable dataflow guided fuzzing code instrumentation.  Inserts a call to
           "__sanitizer_cov_trace_cmp1", "__sanitizer_cov_trace_cmp2", "__sanitizer_cov_trace_cmp4"
           or "__sanitizer_cov_trace_cmp8" for integral comparison with both operands variable or
           "__sanitizer_cov_trace_const_cmp1", "__sanitizer_cov_trace_const_cmp2",
           "__sanitizer_cov_trace_const_cmp4" or "__sanitizer_cov_trace_const_cmp8" for integral
           comparison with one operand constant, "__sanitizer_cov_trace_cmpf" or
           "__sanitizer_cov_trace_cmpd" for float or double comparisons and
           "__sanitizer_cov_trace_switch" for switch statements.

       -fcf-protection=[full|branch|return|none|check]
           Enable code instrumentation of control-flow transfers to increase program security by
           checking that target addresses of control-flow transfer instructions (such as indirect
           function call, function return, indirect jump) are valid.  This prevents diverting the
           flow of control to an unexpected target.  This is intended to protect against such
           threats as Return-oriented Programming (ROP), and similarly call/jmp-oriented programming
           (COP/JOP).

           The value "branch" tells the compiler to implement checking of validity of control-flow
           transfer at the point of indirect branch instructions, i.e. call/jmp instructions.  The
           value "return" implements checking of validity at the point of returning from a function.
           The value "full" is an alias for specifying both "branch" and "return". The value "none"
           turns off instrumentation.

           The value "check" is used for the final link with link-time optimization (LTO).  An error
           is issued if LTO object files are compiled with different -fcf-protection values.  The
           value "check" is ignored at the compile time.

           The macro "__CET__" is defined when -fcf-protection is used.  The first bit of "__CET__"
           is set to 1 for the value "branch" and the second bit of "__CET__" is set to 1 for the
           "return".

           You can also use the "nocf_check" attribute to identify which functions and calls should
           be skipped from instrumentation.

           Currently the x86 GNU/Linux target provides an implementation based on Intel Control-flow
           Enforcement Technology (CET) which works for i686 processor or newer.

           NOTE: In Ubuntu 19.10 and later versions, -fcf-protection is enabled by default for C,
           C++, ObjC, ObjC++, if none of -fno-cf-protection nor -fcf-protection=* are found.

       -fstack-protector
           Emit extra code to check for buffer overflows, such as stack smashing attacks.  This is
           done by adding a guard variable to functions with vulnerable objects.  This includes
           functions that call "alloca", and functions with buffers larger than or equal to 8 bytes.
           The guards are initialized when a function is entered and then checked when the function
           exits.  If a guard check fails, an error message is printed and the program exits.  Only
           variables that are actually allocated on the stack are considered, optimized away
           variables or variables allocated in registers don't count.

       -fstack-protector-all
           Like -fstack-protector except that all functions are protected.

       -fstack-protector-strong
           Like -fstack-protector but includes additional functions to be protected --- those that
           have local array definitions, or have references to local frame addresses.  Only
           variables that are actually allocated on the stack are considered, optimized away
           variables or variables allocated in registers don't count.

       -fstack-protector-explicit
           Like -fstack-protector but only protects those functions which have the "stack_protect"
           attribute.

       -fstack-check
           Generate code to verify that you do not go beyond the boundary of the stack.  You should
           specify this flag if you are running in an environment with multiple threads, but you
           only rarely need to specify it in a single-threaded environment since stack overflow is
           automatically detected on nearly all systems if there is only one stack.

           Note that this switch does not actually cause checking to be done; the operating system
           or the language runtime must do that.  The switch causes generation of code to ensure
           that they see the stack being extended.

           You can additionally specify a string parameter: no means no checking, generic means
           force the use of old-style checking, specific means use the best checking method and is
           equivalent to bare -fstack-check.

           Old-style checking is a generic mechanism that requires no specific target support in the
           compiler but comes with the following drawbacks:

           1.  Modified allocation strategy for large objects: they are always allocated dynamically
               if their size exceeds a fixed threshold.  Note this may change the semantics of some
               code.

           2.  Fixed limit on the size of the static frame of functions: when it is topped by a
               particular function, stack checking is not reliable and a warning is issued by the
               compiler.

           3.  Inefficiency: because of both the modified allocation strategy and the generic
               implementation, code performance is hampered.

           Note that old-style stack checking is also the fallback method for specific if no target
           support has been added in the compiler.

           -fstack-check= is designed for Ada's needs to detect infinite recursion and stack
           overflows.  specific is an excellent choice when compiling Ada code.  It is not generally
           sufficient to protect against stack-clash attacks.  To protect against those you want
           -fstack-clash-protection.

       -fstack-clash-protection
           Generate code to prevent stack clash style attacks.  When this option is enabled, the
           compiler will only allocate one page of stack space at a time and each page is accessed
           immediately after allocation.  Thus, it prevents allocations from jumping over any stack
           guard page provided by the operating system.

           Most targets do not fully support stack clash protection.  However, on those targets
           -fstack-clash-protection will protect dynamic stack allocations.
           -fstack-clash-protection may also provide limited protection for static stack allocations
           if the target supports -fstack-check=specific.

           NOTE: In Ubuntu 19.10 and later versions, -fstack-clash-protection is enabled by default
           for C, C++, ObjC, ObjC++, unless -fno-stack-clash-protection is found.

       -fstack-limit-register=reg
       -fstack-limit-symbol=sym
       -fno-stack-limit
           Generate code to ensure that the stack does not grow beyond a certain value, either the
           value of a register or the address of a symbol.  If a larger stack is required, a signal
           is raised at run time.  For most targets, the signal is raised before the stack overruns
           the boundary, so it is possible to catch the signal without taking special precautions.

           For instance, if the stack starts at absolute address 0x80000000 and grows downwards, you
           can use the flags -fstack-limit-symbol=__stack_limit and
           -Wl,--defsym,__stack_limit=0x7ffe0000 to enforce a stack limit of 128KB.  Note that this
           may only work with the GNU linker.

           You can locally override stack limit checking by using the "no_stack_limit" function
           attribute.

       -fsplit-stack
           Generate code to automatically split the stack before it overflows.  The resulting
           program has a discontiguous stack which can only overflow if the program is unable to
           allocate any more memory.  This is most useful when running threaded programs, as it is
           no longer necessary to calculate a good stack size to use for each thread.  This is
           currently only implemented for the x86 targets running GNU/Linux.

           When code compiled with -fsplit-stack calls code compiled without -fsplit-stack, there
           may not be much stack space available for the latter code to run.  If compiling all code,
           including library code, with -fsplit-stack is not an option, then the linker can fix up
           these calls so that the code compiled without -fsplit-stack always has a large stack.
           Support for this is implemented in the gold linker in GNU binutils release 2.21 and
           later.

       -fvtable-verify=[std|preinit|none]
           This option is only available when compiling C++ code.  It turns on (or off, if using
           -fvtable-verify=none) the security feature that verifies at run time, for every virtual
           call, that the vtable pointer through which the call is made is valid for the type of the
           object, and has not been corrupted or overwritten.  If an invalid vtable pointer is
           detected at run time, an error is reported and execution of the program is immediately
           halted.

           This option causes run-time data structures to be built at program startup, which are
           used for verifying the vtable pointers.  The options std and preinit control the timing
           of when these data structures are built.  In both cases the data structures are built
           before execution reaches "main".  Using -fvtable-verify=std causes the data structures to
           be built after shared libraries have been loaded and initialized.
           -fvtable-verify=preinit causes them to be built before shared libraries have been loaded
           and initialized.

           If this option appears multiple times in the command line with different values
           specified, none takes highest priority over both std and preinit; preinit takes priority
           over std.

       -fvtv-debug
           When used in conjunction with -fvtable-verify=std or -fvtable-verify=preinit, causes
           debug versions of the runtime functions for the vtable verification feature to be called.
           This flag also causes the compiler to log information about which vtable pointers it
           finds for each class.  This information is written to a file named vtv_set_ptr_data.log
           in the directory named by the environment variable VTV_LOGS_DIR if that is defined or the
           current working directory otherwise.

           Note:  This feature appends data to the log file. If you want a fresh log file, be sure
           to delete any existing one.

       -fvtv-counts
           This is a debugging flag.  When used in conjunction with -fvtable-verify=std or
           -fvtable-verify=preinit, this causes the compiler to keep track of the total number of
           virtual calls it encounters and the number of verifications it inserts.  It also counts
           the number of calls to certain run-time library functions that it inserts and logs this
           information for each compilation unit.  The compiler writes this information to a file
           named vtv_count_data.log in the directory named by the environment variable VTV_LOGS_DIR
           if that is defined or the current working directory otherwise.  It also counts the size
           of the vtable pointer sets for each class, and writes this information to
           vtv_class_set_sizes.log in the same directory.

           Note:  This feature appends data to the log files.  To get fresh log files, be sure to
           delete any existing ones.

       -finstrument-functions
           Generate instrumentation calls for entry and exit to functions.  Just after function
           entry and just before function exit, the following profiling functions are called with
           the address of the current function and its call site.  (On some platforms,
           "__builtin_return_address" does not work beyond the current function, so the call site
           information may not be available to the profiling functions otherwise.)

                   void __cyg_profile_func_enter (void *this_fn,
                                                  void *call_site);
                   void __cyg_profile_func_exit  (void *this_fn,
                                                  void *call_site);

           The first argument is the address of the start of the current function, which may be
           looked up exactly in the symbol table.

           This instrumentation is also done for functions expanded inline in other functions.  The
           profiling calls indicate where, conceptually, the inline function is entered and exited.
           This means that addressable versions of such functions must be available.  If all your
           uses of a function are expanded inline, this may mean an additional expansion of code
           size.  If you use "extern inline" in your C code, an addressable version of such
           functions must be provided.  (This is normally the case anyway, but if you get lucky and
           the optimizer always expands the functions inline, you might have gotten away without
           providing static copies.)

           A function may be given the attribute "no_instrument_function", in which case this
           instrumentation is not done.  This can be used, for example, for the profiling functions
           listed above, high-priority interrupt routines, and any functions from which the
           profiling functions cannot safely be called (perhaps signal handlers, if the profiling
           routines generate output or allocate memory).

       -finstrument-functions-exclude-file-list=file,file,...
           Set the list of functions that are excluded from instrumentation (see the description of
           -finstrument-functions).  If the file that contains a function definition matches with
           one of file, then that function is not instrumented.  The match is done on substrings: if
           the file parameter is a substring of the file name, it is considered to be a match.

           For example:

                   -finstrument-functions-exclude-file-list=/bits/stl,include/sys

           excludes any inline function defined in files whose pathnames contain /bits/stl or
           include/sys.

           If, for some reason, you want to include letter , in one of sym, write ,. For example,
           -finstrument-functions-exclude-file-list=',,tmp' (note the single quote surrounding the
           option).

       -finstrument-functions-exclude-function-list=sym,sym,...
           This is similar to -finstrument-functions-exclude-file-list, but this option sets the
           list of function names to be excluded from instrumentation.  The function name to be
           matched is its user-visible name, such as "vector<int> blah(const vector<int> &)", not
           the internal mangled name (e.g., "_Z4blahRSt6vectorIiSaIiEE").  The match is done on
           substrings: if the sym parameter is a substring of the function name, it is considered to
           be a match.  For C99 and C++ extended identifiers, the function name must be given in
           UTF-8, not using universal character names.

       -fpatchable-function-entry=N[,M]
           Generate N NOPs right at the beginning of each function, with the function entry point
           before the Mth NOP.  If M is omitted, it defaults to 0 so the function entry points to
           the address just at the first NOP.  The NOP instructions reserve extra space which can be
           used to patch in any desired instrumentation at run time, provided that the code segment
           is writable.  The amount of space is controllable indirectly via the number of NOPs; the
           NOP instruction used corresponds to the instruction emitted by the internal GCC back-end
           interface "gen_nop".  This behavior is target-specific and may also depend on the
           architecture variant and/or other compilation options.

           For run-time identification, the starting addresses of these areas, which correspond to
           their respective function entries minus M, are additionally collected in the
           "__patchable_function_entries" section of the resulting binary.

           Note that the value of "__attribute__ ((patchable_function_entry (N,M)))" takes
           precedence over command-line option -fpatchable-function-entry=N,M.  This can be used to
           increase the area size or to remove it completely on a single function.  If "N=0", no pad
           location is recorded.

           The NOP instructions are inserted at---and maybe before, depending on M---the function
           entry address, even before the prologue.

           The maximum value of N and M is 65535.

   Options Controlling the Preprocessor
       These options control the C preprocessor, which is run on each C source file before actual
       compilation.

       If you use the -E option, nothing is done except preprocessing.  Some of these options make
       sense only together with -E because they cause the preprocessor output to be unsuitable for
       actual compilation.

       In addition to the options listed here, there are a number of options to control search paths
       for include files documented in Directory Options.  Options to control preprocessor
       diagnostics are listed in Warning Options.

       -D name
           Predefine name as a macro, with definition 1.

       -D name=definition
           The contents of definition are tokenized and processed as if they appeared during
           translation phase three in a #define directive.  In particular, the definition is
           truncated by embedded newline characters.

           If you are invoking the preprocessor from a shell or shell-like program you may need to
           use the shell's quoting syntax to protect characters such as spaces that have a meaning
           in the shell syntax.

           If you wish to define a function-like macro on the command line, write its argument list
           with surrounding parentheses before the equals sign (if any).  Parentheses are meaningful
           to most shells, so you should quote the option.  With sh and csh,
           -D'name(args...)=definition' works.

           -D and -U options are processed in the order they are given on the command line.  All
           -imacros file and -include file options are processed after all -D and -U options.

       -U name
           Cancel any previous definition of name, either built in or provided with a -D option.

       -include file
           Process file as if "#include "file"" appeared as the first line of the primary source
           file.  However, the first directory searched for file is the preprocessor's working
           directory instead of the directory containing the main source file.  If not found there,
           it is searched for in the remainder of the "#include "..."" search chain as normal.

           If multiple -include options are given, the files are included in the order they appear
           on the command line.

       -imacros file
           Exactly like -include, except that any output produced by scanning file is thrown away.
           Macros it defines remain defined.  This allows you to acquire all the macros from a
           header without also processing its declarations.

           All files specified by -imacros are processed before all files specified by -include.

       -undef
           Do not predefine any system-specific or GCC-specific macros.  The standard predefined
           macros remain defined.

       -pthread
           Define additional macros required for using the POSIX threads library.  You should use
           this option consistently for both compilation and linking.  This option is supported on
           GNU/Linux targets, most other Unix derivatives, and also on x86 Cygwin and MinGW targets.

       -M  Instead of outputting the result of preprocessing, output a rule suitable for make
           describing the dependencies of the main source file.  The preprocessor outputs one make
           rule containing the object file name for that source file, a colon, and the names of all
           the included files, including those coming from -include or -imacros command-line
           options.

           Unless specified explicitly (with -MT or -MQ), the object file name consists of the name
           of the source file with any suffix replaced with object file suffix and with any leading
           directory parts removed.  If there are many included files then the rule is split into
           several lines using \-newline.  The rule has no commands.

           This option does not suppress the preprocessor's debug output, such as -dM.  To avoid
           mixing such debug output with the dependency rules you should explicitly specify the
           dependency output file with -MF, or use an environment variable like DEPENDENCIES_OUTPUT.
           Debug output is still sent to the regular output stream as normal.

           Passing -M to the driver implies -E, and suppresses warnings with an implicit -w.

       -MM Like -M but do not mention header files that are found in system header directories, nor
           header files that are included, directly or indirectly, from such a header.

           This implies that the choice of angle brackets or double quotes in an #include directive
           does not in itself determine whether that header appears in -MM dependency output.

       -MF file
           When used with -M or -MM, specifies a file to write the dependencies to.  If no -MF
           switch is given the preprocessor sends the rules to the same place it would send
           preprocessed output.

           When used with the driver options -MD or -MMD, -MF overrides the default dependency
           output file.

           If file is -, then the dependencies are written to stdout.

       -MG In conjunction with an option such as -M requesting dependency generation, -MG assumes
           missing header files are generated files and adds them to the dependency list without
           raising an error.  The dependency filename is taken directly from the "#include"
           directive without prepending any path.  -MG also suppresses preprocessed output, as a
           missing header file renders this useless.

           This feature is used in automatic updating of makefiles.

       -Mno-modules
           Disable dependency generation for compiled module interfaces.

       -MP This option instructs CPP to add a phony target for each dependency other than the main
           file, causing each to depend on nothing.  These dummy rules work around errors make gives
           if you remove header files without updating the Makefile to match.

           This is typical output:

                   test.o: test.c test.h

                   test.h:

       -MT target
           Change the target of the rule emitted by dependency generation.  By default CPP takes the
           name of the main input file, deletes any directory components and any file suffix such as
           .c, and appends the platform's usual object suffix.  The result is the target.

           An -MT option sets the target to be exactly the string you specify.  If you want multiple
           targets, you can specify them as a single argument to -MT, or use multiple -MT options.

           For example, -MT '$(objpfx)foo.o' might give

                   $(objpfx)foo.o: foo.c

       -MQ target
           Same as -MT, but it quotes any characters which are special to Make.
           -MQ '$(objpfx)foo.o' gives

                   $$(objpfx)foo.o: foo.c

           The default target is automatically quoted, as if it were given with -MQ.

       -MD -MD is equivalent to -M -MF file, except that -E is not implied.  The driver determines
           file based on whether an -o option is given.  If it is, the driver uses its argument but
           with a suffix of .d, otherwise it takes the name of the input file, removes any directory
           components and suffix, and applies a .d suffix.

           If -MD is used in conjunction with -E, any -o switch is understood to specify the
           dependency output file, but if used without -E, each -o is understood to specify a target
           object file.

           Since -E is not implied, -MD can be used to generate a dependency output file as a side
           effect of the compilation process.

       -MMD
           Like -MD except mention only user header files, not system header files.

       -fpreprocessed
           Indicate to the preprocessor that the input file has already been preprocessed.  This
           suppresses things like macro expansion, trigraph conversion, escaped newline splicing,
           and processing of most directives.  The preprocessor still recognizes and removes
           comments, so that you can pass a file preprocessed with -C to the compiler without
           problems.  In this mode the integrated preprocessor is little more than a tokenizer for
           the front ends.

           -fpreprocessed is implicit if the input file has one of the extensions .i, .ii or .mi.
           These are the extensions that GCC uses for preprocessed files created by -save-temps.

       -fdirectives-only
           When preprocessing, handle directives, but do not expand macros.

           The option's behavior depends on the -E and -fpreprocessed options.

           With -E, preprocessing is limited to the handling of directives such as "#define",
           "#ifdef", and "#error".  Other preprocessor operations, such as macro expansion and
           trigraph conversion are not performed.  In addition, the -dD option is implicitly
           enabled.

           With -fpreprocessed, predefinition of command line and most builtin macros is disabled.
           Macros such as "__LINE__", which are contextually dependent, are handled normally.  This
           enables compilation of files previously preprocessed with "-E -fdirectives-only".

           With both -E and -fpreprocessed, the rules for -fpreprocessed take precedence.  This
           enables full preprocessing of files previously preprocessed with "-E -fdirectives-only".

       -fdollars-in-identifiers
           Accept $ in identifiers.

       -fextended-identifiers
           Accept universal character names and extended characters in identifiers.  This option is
           enabled by default for C99 (and later C standard versions) and C++.

       -fno-canonical-system-headers
           When preprocessing, do not shorten system header paths with canonicalization.

       -fmax-include-depth=depth
           Set the maximum depth of the nested #include. The default is 200.

       -ftabstop=width
           Set the distance between tab stops.  This helps the preprocessor report correct column
           numbers in warnings or errors, even if tabs appear on the line.  If the value is less
           than 1 or greater than 100, the option is ignored.  The default is 8.

       -ftrack-macro-expansion[=level]
           Track locations of tokens across macro expansions. This allows the compiler to emit
           diagnostic about the current macro expansion stack when a compilation error occurs in a
           macro expansion. Using this option makes the preprocessor and the compiler consume more
           memory. The level parameter can be used to choose the level of precision of token
           location tracking thus decreasing the memory consumption if necessary. Value 0 of level
           de-activates this option. Value 1 tracks tokens locations in a degraded mode for the sake
           of minimal memory overhead. In this mode all tokens resulting from the expansion of an
           argument of a function-like macro have the same location. Value 2 tracks tokens locations
           completely. This value is the most memory hungry.  When this option is given no argument,
           the default parameter value is 2.

           Note that "-ftrack-macro-expansion=2" is activated by default.

       -fmacro-prefix-map=old=new
           When preprocessing files residing in directory old, expand the "__FILE__" and
           "__BASE_FILE__" macros as if the files resided in directory new instead.  This can be
           used to change an absolute path to a relative path by using . for new which can result in
           more reproducible builds that are location independent.  This option also affects
           "__builtin_FILE()" during compilation.  See also -ffile-prefix-map.

       -fexec-charset=charset
           Set the execution character set, used for string and character constants.  The default is
           UTF-8.  charset can be any encoding supported by the system's "iconv" library routine.

       -fwide-exec-charset=charset
           Set the wide execution character set, used for wide string and character constants.  The
           default is one of UTF-32BE, UTF-32LE, UTF-16BE, or UTF-16LE, whichever corresponds to the
           width of "wchar_t" and the big-endian or little-endian byte order being used for code
           generation.  As with -fexec-charset, charset can be any encoding supported by the
           system's "iconv" library routine; however, you will have problems with encodings that do
           not fit exactly in "wchar_t".

       -finput-charset=charset
           Set the input character set, used for translation from the character set of the input
           file to the source character set used by GCC.  If the locale does not specify, or GCC
           cannot get this information from the locale, the default is UTF-8.  This can be
           overridden by either the locale or this command-line option.  Currently the command-line
           option takes precedence if there's a conflict.  charset can be any encoding supported by
           the system's "iconv" library routine.

       -fpch-deps
           When using precompiled headers, this flag causes the dependency-output flags to also list
           the files from the precompiled header's dependencies.  If not specified, only the
           precompiled header are listed and not the files that were used to create it, because
           those files are not consulted when a precompiled header is used.

       -fpch-preprocess
           This option allows use of a precompiled header together with -E.  It inserts a special
           "#pragma", "#pragma GCC pch_preprocess "filename"" in the output to mark the place where
           the precompiled header was found, and its filename.  When -fpreprocessed is in use, GCC
           recognizes this "#pragma" and loads the PCH.

           This option is off by default, because the resulting preprocessed output is only really
           suitable as input to GCC.  It is switched on by -save-temps.

           You should not write this "#pragma" in your own code, but it is safe to edit the filename
           if the PCH file is available in a different location.  The filename may be absolute or it
           may be relative to GCC's current directory.

       -fworking-directory
           Enable generation of linemarkers in the preprocessor output that let the compiler know
           the current working directory at the time of preprocessing.  When this option is enabled,
           the preprocessor emits, after the initial linemarker, a second linemarker with the
           current working directory followed by two slashes.  GCC uses this directory, when it's
           present in the preprocessed input, as the directory emitted as the current working
           directory in some debugging information formats.  This option is implicitly enabled if
           debugging information is enabled, but this can be inhibited with the negated form
           -fno-working-directory.  If the -P flag is present in the command line, this option has
           no effect, since no "#line" directives are emitted whatsoever.

       -A predicate=answer
           Make an assertion with the predicate predicate and answer answer.  This form is preferred
           to the older form -A predicate(answer), which is still supported, because it does not use
           shell special characters.

       -A -predicate=answer
           Cancel an assertion with the predicate predicate and answer answer.

       -C  Do not discard comments.  All comments are passed through to the output file, except for
           comments in processed directives, which are deleted along with the directive.

           You should be prepared for side effects when using -C; it causes the preprocessor to
           treat comments as tokens in their own right.  For example, comments appearing at the
           start of what would be a directive line have the effect of turning that line into an
           ordinary source line, since the first token on the line is no longer a #.

       -CC Do not discard comments, including during macro expansion.  This is like -C, except that
           comments contained within macros are also passed through to the output file where the
           macro is expanded.

           In addition to the side effects of the -C option, the -CC option causes all C++-style
           comments inside a macro to be converted to C-style comments.  This is to prevent later
           use of that macro from inadvertently commenting out the remainder of the source line.

           The -CC option is generally used to support lint comments.

       -P  Inhibit generation of linemarkers in the output from the preprocessor.  This might be
           useful when running the preprocessor on something that is not C code, and will be sent to
           a program which might be confused by the linemarkers.

       -traditional
       -traditional-cpp
           Try to imitate the behavior of pre-standard C preprocessors, as opposed to ISO C
           preprocessors.  See the GNU CPP manual for details.

           Note that GCC does not otherwise attempt to emulate a pre-standard C compiler, and these
           options are only supported with the -E switch, or when invoking CPP explicitly.

       -trigraphs
           Support ISO C trigraphs.  These are three-character sequences, all starting with ??, that
           are defined by ISO C to stand for single characters.  For example, ??/ stands for \, so
           '??/n' is a character constant for a newline.

           The nine trigraphs and their replacements are

                   Trigraph:       ??(  ??)  ??<  ??>  ??=  ??/  ??'  ??!  ??-
                   Replacement:      [    ]    {    }    #    \    ^    |    ~

           By default, GCC ignores trigraphs, but in standard-conforming modes it converts them.
           See the -std and -ansi options.

       -remap
           Enable special code to work around file systems which only permit very short file names,
           such as MS-DOS.

       -H  Print the name of each header file used, in addition to other normal activities.  Each
           name is indented to show how deep in the #include stack it is.  Precompiled header files
           are also printed, even if they are found to be invalid; an invalid precompiled header
           file is printed with ...x and a valid one with ...! .

       -dletters
           Says to make debugging dumps during compilation as specified by letters.  The flags
           documented here are those relevant to the preprocessor.  Other letters are interpreted by
           the compiler proper, or reserved for future versions of GCC, and so are silently ignored.
           If you specify letters whose behavior conflicts, the result is undefined.

           -dM Instead of the normal output, generate a list of #define directives for all the
               macros defined during the execution of the preprocessor, including predefined macros.
               This gives you a way of finding out what is predefined in your version of the
               preprocessor.  Assuming you have no file foo.h, the command

                       touch foo.h; cpp -dM foo.h

               shows all the predefined macros.

               If you use -dM without the -E option, -dM is interpreted as a synonym for
               -fdump-rtl-mach.

           -dD Like -dM except in two respects: it does not include the predefined macros, and it
               outputs both the #define directives and the result of preprocessing.  Both kinds of
               output go to the standard output file.

           -dN Like -dD, but emit only the macro names, not their expansions.

           -dI Output #include directives in addition to the result of preprocessing.

           -dU Like -dD except that only macros that are expanded, or whose definedness is tested in
               preprocessor directives, are output; the output is delayed until the use or test of
               the macro; and #undef directives are also output for macros tested but undefined at
               the time.

       -fdebug-cpp
           This option is only useful for debugging GCC.  When used from CPP or with -E, it dumps
           debugging information about location maps.  Every token in the output is preceded by the
           dump of the map its location belongs to.

           When used from GCC without -E, this option has no effect.

       -Wp,option
           You can use -Wp,option to bypass the compiler driver and pass option directly through to
           the preprocessor.  If option contains commas, it is split into multiple options at the
           commas.  However, many options are modified, translated or interpreted by the compiler
           driver before being passed to the preprocessor, and -Wp forcibly bypasses this phase.
           The preprocessor's direct interface is undocumented and subject to change, so whenever
           possible you should avoid using -Wp and let the driver handle the options instead.

       -Xpreprocessor option
           Pass option as an option to the preprocessor.  You can use this to supply system-specific
           preprocessor options that GCC does not recognize.

           If you want to pass an option that takes an argument, you must use -Xpreprocessor twice,
           once for the option and once for the argument.

       -no-integrated-cpp
           Perform preprocessing as a separate pass before compilation.  By default, GCC performs
           preprocessing as an integrated part of input tokenization and parsing.  If this option is
           provided, the appropriate language front end (cc1, cc1plus, or cc1obj for C, C++, and
           Objective-C, respectively) is instead invoked twice, once for preprocessing only and once
           for actual compilation of the preprocessed input.  This option may be useful in
           conjunction with the -B or -wrapper options to specify an alternate preprocessor or
           perform additional processing of the program source between normal preprocessing and
           compilation.

       -flarge-source-files
           Adjust GCC to expect large source files, at the expense of slower compilation and higher
           memory usage.

           Specifically, GCC normally tracks both column numbers and line numbers within source
           files and it normally prints both of these numbers in diagnostics.  However, once it has
           processed a certain number of source lines, it stops tracking column numbers and only
           tracks line numbers.  This means that diagnostics for later lines do not include column
           numbers.  It also means that options like -Wmisleading-indentation cease to work at that
           point, although the compiler prints a note if this happens.  Passing -flarge-source-files
           significantly increases the number of source lines that GCC can process before it stops
           tracking columns.

   Passing Options to the Assembler
       You can pass options to the assembler.

       -Wa,option
           Pass option as an option to the assembler.  If option contains commas, it is split into
           multiple options at the commas.

       -Xassembler option
           Pass option as an option to the assembler.  You can use this to supply system-specific
           assembler options that GCC does not recognize.

           If you want to pass an option that takes an argument, you must use -Xassembler twice,
           once for the option and once for the argument.

   Options for Linking
       These options come into play when the compiler links object files into an executable output
       file.  They are meaningless if the compiler is not doing a link step.

       object-file-name
           A file name that does not end in a special recognized suffix is considered to name an
           object file or library.  (Object files are distinguished from libraries by the linker
           according to the file contents.)  If linking is done, these object files are used as
           input to the linker.

       -c
       -S
       -E  If any of these options is used, then the linker is not run, and object file names should
           not be used as arguments.

       -flinker-output=type
           This option controls code generation of the link-time optimizer.  By default the linker
           output is automatically determined by the linker plugin.  For debugging the compiler and
           if incremental linking with a non-LTO object file is desired, it may be useful to control
           the type manually.

           If type is exec, code generation produces a static binary. In this case -fpic and -fpie
           are both disabled.

           If type is dyn, code generation produces a shared library.  In this case -fpic or -fPIC
           is preserved, but not enabled automatically.  This allows to build shared libraries
           without position-independent code on architectures where this is possible, i.e. on x86.

           If type is pie, code generation produces an -fpie executable. This results in similar
           optimizations as exec except that -fpie is not disabled if specified at compilation time.

           If type is rel, the compiler assumes that incremental linking is done.  The sections
           containing intermediate code for link-time optimization are merged, pre-optimized, and
           output to the resulting object file. In addition, if -ffat-lto-objects is specified,
           binary code is produced for future non-LTO linking. The object file produced by
           incremental linking is smaller than a static library produced from the same object files.
           At link time the result of incremental linking also loads faster than a static library
           assuming that the majority of objects in the library are used.

           Finally nolto-rel configures the compiler for incremental linking where code generation
           is forced, a final binary is produced, and the intermediate code for later link-time
           optimization is stripped. When multiple object files are linked together the resulting
           code is better optimized than with link-time optimizations disabled (for example, cross-
           module inlining happens), but most of benefits of whole program optimizations are lost.

           During the incremental link (by -r) the linker plugin defaults to rel. With current
           interfaces to GNU Binutils it is however not possible to incrementally link LTO objects
           and non-LTO objects into a single mixed object file.  If any of object files in
           incremental link cannot be used for link-time optimization, the linker plugin issues a
           warning and uses nolto-rel. To maintain whole program optimization, it is recommended to
           link such objects into static library instead. Alternatively it is possible to use H.J.
           Lu's binutils with support for mixed objects.

       -fuse-ld=bfd
           Use the bfd linker instead of the default linker.

       -fuse-ld=gold
           Use the gold linker instead of the default linker.

       -fuse-ld=lld
           Use the LLVM lld linker instead of the default linker.

       -fuse-ld=mold
           Use the Modern Linker (mold) instead of the default linker.

       -llibrary
       -l library
           Search the library named library when linking.  (The second alternative with the library
           as a separate argument is only for POSIX compliance and is not recommended.)

           The -l option is passed directly to the linker by GCC.  Refer to your linker
           documentation for exact details.  The general description below applies to the GNU
           linker.

           The linker searches a standard list of directories for the library.  The directories
           searched include several standard system directories plus any that you specify with -L.

           Static libraries are archives of object files, and have file names like liblibrary.a.
           Some targets also support shared libraries, which typically have names like
           liblibrary.so.  If both static and shared libraries are found, the linker gives
           preference to linking with the shared library unless the -static option is used.

           It makes a difference where in the command you write this option; the linker searches and
           processes libraries and object files in the order they are specified.  Thus, foo.o -lz
           bar.o searches library z after file foo.o but before bar.o.  If bar.o refers to functions
           in z, those functions may not be loaded.

       -lobjc
           You need this special case of the -l option in order to link an Objective-C or
           Objective-C++ program.

       -nostartfiles
           Do not use the standard system startup files when linking.  The standard system libraries
           are used normally, unless -nostdlib, -nolibc, or -nodefaultlibs is used.

       -nodefaultlibs
           Do not use the standard system libraries when linking.  Only the libraries you specify
           are passed to the linker, and options specifying linkage of the system libraries, such as
           -static-libgcc or -shared-libgcc, are ignored.  The standard startup files are used
           normally, unless -nostartfiles is used.

           The compiler may generate calls to "memcmp", "memset", "memcpy" and "memmove".  These
           entries are usually resolved by entries in libc.  These entry points should be supplied
           through some other mechanism when this option is specified.

       -nolibc
           Do not use the C library or system libraries tightly coupled with it when linking.  Still
           link with the startup files, libgcc or toolchain provided language support libraries such
           as libgnat, libgfortran or libstdc++ unless options preventing their inclusion are used
           as well.  This typically removes -lc from the link command line, as well as system
           libraries that normally go with it and become meaningless when absence of a C library is
           assumed, for example -lpthread or -lm in some configurations.  This is intended for bare-
           board targets when there is indeed no C library available.

       -nostdlib
           Do not use the standard system startup files or libraries when linking.  No startup files
           and only the libraries you specify are passed to the linker, and options specifying
           linkage of the system libraries, such as -static-libgcc or -shared-libgcc, are ignored.

           The compiler may generate calls to "memcmp", "memset", "memcpy" and "memmove".  These
           entries are usually resolved by entries in libc.  These entry points should be supplied
           through some other mechanism when this option is specified.

           One of the standard libraries bypassed by -nostdlib and -nodefaultlibs is libgcc.a, a
           library of internal subroutines which GCC uses to overcome shortcomings of particular
           machines, or special needs for some languages.

           In most cases, you need libgcc.a even when you want to avoid other standard libraries.
           In other words, when you specify -nostdlib or -nodefaultlibs you should usually specify
           -lgcc as well.  This ensures that you have no unresolved references to internal GCC
           library subroutines.  (An example of such an internal subroutine is "__main", used to
           ensure C++ constructors are called.)

       -e entry
       --entry=entry
           Specify that the program entry point is entry.  The argument is interpreted by the
           linker; the GNU linker accepts either a symbol name or an address.

       -pie
           Produce a dynamically linked position independent executable on targets that support it.
           For predictable results, you must also specify the same set of options used for
           compilation (-fpie, -fPIE, or model suboptions) when you specify this linker option.

       -no-pie
           Don't produce a dynamically linked position independent executable.

       -static-pie
           Produce a static position independent executable on targets that support it.  A static
           position independent executable is similar to a static executable, but can be loaded at
           any address without a dynamic linker.  For predictable results, you must also specify the
           same set of options used for compilation (-fpie, -fPIE, or model suboptions) when you
           specify this linker option.

       -pthread
           Link with the POSIX threads library.  This option is supported on GNU/Linux targets, most
           other Unix derivatives, and also on x86 Cygwin and MinGW targets.  On some targets this
           option also sets flags for the preprocessor, so it should be used consistently for both
           compilation and linking.

       -r  Produce a relocatable object as output.  This is also known as partial linking.

       -rdynamic
           Pass the flag -export-dynamic to the ELF linker, on targets that support it. This
           instructs the linker to add all symbols, not only used ones, to the dynamic symbol table.
           This option is needed for some uses of "dlopen" or to allow obtaining backtraces from
           within a program.

       -s  Remove all symbol table and relocation information from the executable.

       -static
           On systems that support dynamic linking, this overrides -pie and prevents linking with
           the shared libraries.  On other systems, this option has no effect.

       -shared
           Produce a shared object which can then be linked with other objects to form an
           executable.  Not all systems support this option.  For predictable results, you must also
           specify the same set of options used for compilation (-fpic, -fPIC, or model suboptions)
           when you specify this linker option.[1]

       -shared-libgcc
       -static-libgcc
           On systems that provide libgcc as a shared library, these options force the use of either
           the shared or static version, respectively.  If no shared version of libgcc was built
           when the compiler was configured, these options have no effect.

           There are several situations in which an application should use the shared libgcc instead
           of the static version.  The most common of these is when the application wishes to throw
           and catch exceptions across different shared libraries.  In that case, each of the
           libraries as well as the application itself should use the shared libgcc.

           Therefore, the G++ driver automatically adds -shared-libgcc whenever you build a shared
           library or a main executable, because C++ programs typically use exceptions, so this is
           the right thing to do.

           If, instead, you use the GCC driver to create shared libraries, you may find that they
           are not always linked with the shared libgcc.  If GCC finds, at its configuration time,
           that you have a non-GNU linker or a GNU linker that does not support option
           --eh-frame-hdr, it links the shared version of libgcc into shared libraries by default.
           Otherwise, it takes advantage of the linker and optimizes away the linking with the
           shared version of libgcc, linking with the static version of libgcc by default.  This
           allows exceptions to propagate through such shared libraries, without incurring
           relocation costs at library load time.

           However, if a library or main executable is supposed to throw or catch exceptions, you
           must link it using the G++ driver, or using the option -shared-libgcc, such that it is
           linked with the shared libgcc.

       -static-libasan
           When the -fsanitize=address option is used to link a program, the GCC driver
           automatically links against libasan.  If libasan is available as a shared library, and
           the -static option is not used, then this links against the shared version of libasan.
           The -static-libasan option directs the GCC driver to link libasan statically, without
           necessarily linking other libraries statically.

       -static-libtsan
           When the -fsanitize=thread option is used to link a program, the GCC driver automatically
           links against libtsan.  If libtsan is available as a shared library, and the -static
           option is not used, then this links against the shared version of libtsan.  The
           -static-libtsan option directs the GCC driver to link libtsan statically, without
           necessarily linking other libraries statically.

       -static-liblsan
           When the -fsanitize=leak option is used to link a program, the GCC driver automatically
           links against liblsan.  If liblsan is available as a shared library, and the -static
           option is not used, then this links against the shared version of liblsan.  The
           -static-liblsan option directs the GCC driver to link liblsan statically, without
           necessarily linking other libraries statically.

       -static-libubsan
           When the -fsanitize=undefined option is used to link a program, the GCC driver
           automatically links against libubsan.  If libubsan is available as a shared library, and
           the -static option is not used, then this links against the shared version of libubsan.
           The -static-libubsan option directs the GCC driver to link libubsan statically, without
           necessarily linking other libraries statically.

       -static-libstdc++
           When the g++ program is used to link a C++ program, it normally automatically links
           against libstdc++.  If libstdc++ is available as a shared library, and the -static option
           is not used, then this links against the shared version of libstdc++.  That is normally
           fine.  However, it is sometimes useful to freeze the version of libstdc++ used by the
           program without going all the way to a fully static link.  The -static-libstdc++ option
           directs the g++ driver to link libstdc++ statically, without necessarily linking other
           libraries statically.

       -symbolic
           Bind references to global symbols when building a shared object.  Warn about any
           unresolved references (unless overridden by the link editor option -Xlinker -z -Xlinker
           defs).  Only a few systems support this option.

       -T script
           Use script as the linker script.  This option is supported by most systems using the GNU
           linker.  On some targets, such as bare-board targets without an operating system, the -T
           option may be required when linking to avoid references to undefined symbols.

       -Xlinker option
           Pass option as an option to the linker.  You can use this to supply system-specific
           linker options that GCC does not recognize.

           If you want to pass an option that takes a separate argument, you must use -Xlinker
           twice, once for the option and once for the argument.  For example, to pass -assert
           definitions, you must write -Xlinker -assert -Xlinker definitions.  It does not work to
           write -Xlinker "-assert definitions", because this passes the entire string as a single
           argument, which is not what the linker expects.

           When using the GNU linker, it is usually more convenient to pass arguments to linker
           options using the option=value syntax than as separate arguments.  For example, you can
           specify -Xlinker -Map=output.map rather than -Xlinker -Map -Xlinker output.map.  Other
           linkers may not support this syntax for command-line options.

       -Wl,option
           Pass option as an option to the linker.  If option contains commas, it is split into
           multiple options at the commas.  You can use this syntax to pass an argument to the
           option.  For example, -Wl,-Map,output.map passes -Map output.map to the linker.  When
           using the GNU linker, you can also get the same effect with -Wl,-Map=output.map.

           NOTE: In Ubuntu 8.10 and later versions, for LDFLAGS, the option -Wl,-z,relro is used.
           To disable, use -Wl,-z,norelro.

       -u symbol
           Pretend the symbol symbol is undefined, to force linking of library modules to define it.
           You can use -u multiple times with different symbols to force loading of additional
           library modules.

       -z keyword
           -z is passed directly on to the linker along with the keyword keyword. See the section in
           the documentation of your linker for permitted values and their meanings.

   Options for Directory Search
       These options specify directories to search for header files, for libraries and for parts of
       the compiler:

       -I dir
       -iquote dir
       -isystem dir
       -idirafter dir
           Add the directory dir to the list of directories to be searched for header files during
           preprocessing.  If dir begins with = or $SYSROOT, then the = or $SYSROOT is replaced by
           the sysroot prefix; see --sysroot and -isysroot.

           Directories specified with -iquote apply only to the quote form of the directive,
           "#include "file"".  Directories specified with -I, -isystem, or -idirafter apply to
           lookup for both the "#include "file"" and "#include <file>" directives.

           You can specify any number or combination of these options on the command line to search
           for header files in several directories.  The lookup order is as follows:

           1.  For the quote form of the include directive, the directory of the current file is
               searched first.

           2.  For the quote form of the include directive, the directories specified by -iquote
               options are searched in left-to-right order, as they appear on the command line.

           3.  Directories specified with -I options are scanned in left-to-right order.

           4.  Directories specified with -isystem options are scanned in left-to-right order.

           5.  Standard system directories are scanned.

           6.  Directories specified with -idirafter options are scanned in left-to-right order.

           You can use -I to override a system header file, substituting your own version, since
           these directories are searched before the standard system header file directories.
           However, you should not use this option to add directories that contain vendor-supplied
           system header files; use -isystem for that.

           The -isystem and -idirafter options also mark the directory as a system directory, so
           that it gets the same special treatment that is applied to the standard system
           directories.

           If a standard system include directory, or a directory specified with -isystem, is also
           specified with -I, the -I option is ignored.  The directory is still searched but as a
           system directory at its normal position in the system include chain.  This is to ensure
           that GCC's procedure to fix buggy system headers and the ordering for the "#include_next"
           directive are not inadvertently changed.  If you really need to change the search order
           for system directories, use the -nostdinc and/or -isystem options.

       -I- Split the include path.  This option has been deprecated.  Please use -iquote instead for
           -I directories before the -I- and remove the -I- option.

           Any directories specified with -I options before -I- are searched only for headers
           requested with "#include "file""; they are not searched for "#include <file>".  If
           additional directories are specified with -I options after the -I-, those directories are
           searched for all #include directives.

           In addition, -I- inhibits the use of the directory of the current file directory as the
           first search directory for "#include "file"".  There is no way to override this effect of
           -I-.

       -iprefix prefix
           Specify prefix as the prefix for subsequent -iwithprefix options.  If the prefix
           represents a directory, you should include the final /.

       -iwithprefix dir
       -iwithprefixbefore dir
           Append dir to the prefix specified previously with -iprefix, and add the resulting
           directory to the include search path.  -iwithprefixbefore puts it in the same place -I
           would; -iwithprefix puts it where -idirafter would.

       -isysroot dir
           This option is like the --sysroot option, but applies only to header files (except for
           Darwin targets, where it applies to both header files and libraries).  See the --sysroot
           option for more information.

       -imultilib dir
           Use dir as a subdirectory of the directory containing target-specific C++ headers.

       -nostdinc
           Do not search the standard system directories for header files.  Only the directories
           explicitly specified with -I, -iquote, -isystem, and/or -idirafter options (and the
           directory of the current file, if appropriate) are searched.

       -nostdinc++
           Do not search for header files in the C++-specific standard directories, but do still
           search the other standard directories.  (This option is used when building the C++
           library.)

       -iplugindir=dir
           Set the directory to search for plugins that are passed by -fplugin=name instead of
           -fplugin=path/name.so.  This option is not meant to be used by the user, but only passed
           by the driver.

       -Ldir
           Add directory dir to the list of directories to be searched for -l.

       -Bprefix
           This option specifies where to find the executables, libraries, include files, and data
           files of the compiler itself.

           The compiler driver program runs one or more of the subprograms cpp, cc1, as and ld.  It
           tries prefix as a prefix for each program it tries to run, both with and without
           machine/version/ for the corresponding target machine and compiler version.

           For each subprogram to be run, the compiler driver first tries the -B prefix, if any.  If
           that name is not found, or if -B is not specified, the driver tries two standard
           prefixes, /usr/lib/gcc/ and /usr/local/lib/gcc/.  If neither of those results in a file
           name that is found, the unmodified program name is searched for using the directories
           specified in your PATH environment variable.

           The compiler checks to see if the path provided by -B refers to a directory, and if
           necessary it adds a directory separator character at the end of the path.

           -B prefixes that effectively specify directory names also apply to libraries in the
           linker, because the compiler translates these options into -L options for the linker.
           They also apply to include files in the preprocessor, because the compiler translates
           these options into -isystem options for the preprocessor.  In this case, the compiler
           appends include to the prefix.

           The runtime support file libgcc.a can also be searched for using the -B prefix, if
           needed.  If it is not found there, the two standard prefixes above are tried, and that is
           all.  The file is left out of the link if it is not found by those means.

           Another way to specify a prefix much like the -B prefix is to use the environment
           variable GCC_EXEC_PREFIX.

           As a special kludge, if the path provided by -B is [dir/]stageN/, where N is a number in
           the range 0 to 9, then it is replaced by [dir/]include.  This is to help with boot-
           strapping the compiler.

       -no-canonical-prefixes
           Do not expand any symbolic links, resolve references to /../ or /./, or make the path
           absolute when generating a relative prefix.

       --sysroot=dir
           Use dir as the logical root directory for headers and libraries.  For example, if the
           compiler normally searches for headers in /usr/include and libraries in /usr/lib, it
           instead searches dir/usr/include and dir/usr/lib.

           If you use both this option and the -isysroot option, then the --sysroot option applies
           to libraries, but the -isysroot option applies to header files.

           The GNU linker (beginning with version 2.16) has the necessary support for this option.
           If your linker does not support this option, the header file aspect of --sysroot still
           works, but the library aspect does not.

       --no-sysroot-suffix
           For some targets, a suffix is added to the root directory specified with --sysroot,
           depending on the other options used, so that headers may for example be found in
           dir/suffix/usr/include instead of dir/usr/include.  This option disables the addition of
           such a suffix.

   Options for Code Generation Conventions
       These machine-independent options control the interface conventions used in code generation.

       Most of them have both positive and negative forms; the negative form of -ffoo is -fno-foo.
       In the table below, only one of the forms is listed---the one that is not the default.  You
       can figure out the other form by either removing no- or adding it.

       -fstack-reuse=reuse-level
           This option controls stack space reuse for user declared local/auto variables and
           compiler generated temporaries.  reuse_level can be all, named_vars, or none. all enables
           stack reuse for all local variables and temporaries, named_vars enables the reuse only
           for user defined local variables with names, and none disables stack reuse completely.
           The default value is all. The option is needed when the program extends the lifetime of a
           scoped local variable or a compiler generated temporary beyond the end point defined by
           the language.  When a lifetime of a variable ends, and if the variable lives in memory,
           the optimizing compiler has the freedom to reuse its stack space with other temporaries
           or scoped local variables whose live range does not overlap with it. Legacy code
           extending local lifetime is likely to break with the stack reuse optimization.

           For example,

                      int *p;
                      {
                        int local1;

                        p = &local1;
                        local1 = 10;
                        ....
                      }
                      {
                         int local2;
                         local2 = 20;
                         ...
                      }

                      if (*p == 10)  // out of scope use of local1
                        {

                        }

           Another example:

                      struct A
                      {
                          A(int k) : i(k), j(k) { }
                          int i;
                          int j;
                      };

                      A *ap;

                      void foo(const A& ar)
                      {
                         ap = &ar;
                      }

                      void bar()
                      {
                         foo(A(10)); // temp object's lifetime ends when foo returns

                         {
                           A a(20);
                           ....
                         }
                         ap->i+= 10;  // ap references out of scope temp whose space
                                      // is reused with a. What is the value of ap->i?
                      }

           The lifetime of a compiler generated temporary is well defined by the C++ standard. When
           a lifetime of a temporary ends, and if the temporary lives in memory, the optimizing
           compiler has the freedom to reuse its stack space with other temporaries or scoped local
           variables whose live range does not overlap with it. However some of the legacy code
           relies on the behavior of older compilers in which temporaries' stack space is not
           reused, the aggressive stack reuse can lead to runtime errors. This option is used to
           control the temporary stack reuse optimization.

       -ftrapv
           This option generates traps for signed overflow on addition, subtraction, multiplication
           operations.  The options -ftrapv and -fwrapv override each other, so using -ftrapv
           -fwrapv on the command-line results in -fwrapv being effective.  Note that only active
           options override, so using -ftrapv -fwrapv -fno-wrapv on the command-line results in
           -ftrapv being effective.

       -fwrapv
           This option instructs the compiler to assume that signed arithmetic overflow of addition,
           subtraction and multiplication wraps around using twos-complement representation.  This
           flag enables some optimizations and disables others.  The options -ftrapv and -fwrapv
           override each other, so using -ftrapv -fwrapv on the command-line results in -fwrapv
           being effective.  Note that only active options override, so using -ftrapv -fwrapv
           -fno-wrapv on the command-line results in -ftrapv being effective.

       -fwrapv-pointer
           This option instructs the compiler to assume that pointer arithmetic overflow on addition
           and subtraction wraps around using twos-complement representation.  This flag disables
           some optimizations which assume pointer overflow is invalid.

       -fstrict-overflow
           This option implies -fno-wrapv -fno-wrapv-pointer and when negated implies -fwrapv
           -fwrapv-pointer.

       -fexceptions
           Enable exception handling.  Generates extra code needed to propagate exceptions.  For
           some targets, this implies GCC generates frame unwind information for all functions,
           which can produce significant data size overhead, although it does not affect execution.
           If you do not specify this option, GCC enables it by default for languages like C++ that
           normally require exception handling, and disables it for languages like C that do not
           normally require it.  However, you may need to enable this option when compiling C code
           that needs to interoperate properly with exception handlers written in C++.  You may also
           wish to disable this option if you are compiling older C++ programs that don't use
           exception handling.

       -fnon-call-exceptions
           Generate code that allows trapping instructions to throw exceptions.  Note that this
           requires platform-specific runtime support that does not exist everywhere.  Moreover, it
           only allows trapping instructions to throw exceptions, i.e. memory references or
           floating-point instructions.  It does not allow exceptions to be thrown from arbitrary
           signal handlers such as "SIGALRM".

       -fdelete-dead-exceptions
           Consider that instructions that may throw exceptions but don't otherwise contribute to
           the execution of the program can be optimized away.  This option is enabled by default
           for the Ada compiler, as permitted by the Ada language specification.  Optimization
           passes that cause dead exceptions to be removed are enabled independently at different
           optimization levels.

       -funwind-tables
           Similar to -fexceptions, except that it just generates any needed static data, but does
           not affect the generated code in any other way.  You normally do not need to enable this
           option; instead, a language processor that needs this handling enables it on your behalf.

       -fasynchronous-unwind-tables
           Generate unwind table in DWARF format, if supported by target machine.  The table is
           exact at each instruction boundary, so it can be used for stack unwinding from
           asynchronous events (such as debugger or garbage collector).

       -fno-gnu-unique
           On systems with recent GNU assembler and C library, the C++ compiler uses the
           "STB_GNU_UNIQUE" binding to make sure that definitions of template static data members
           and static local variables in inline functions are unique even in the presence of
           "RTLD_LOCAL"; this is necessary to avoid problems with a library used by two different
           "RTLD_LOCAL" plugins depending on a definition in one of them and therefore disagreeing
           with the other one about the binding of the symbol.  But this causes "dlclose" to be
           ignored for affected DSOs; if your program relies on reinitialization of a DSO via
           "dlclose" and "dlopen", you can use -fno-gnu-unique.

       -fpcc-struct-return
           Return "short" "struct" and "union" values in memory like longer ones, rather than in
           registers.  This convention is less efficient, but it has the advantage of allowing
           intercallability between GCC-compiled files and files compiled with other compilers,
           particularly the Portable C Compiler (pcc).

           The precise convention for returning structures in memory depends on the target
           configuration macros.

           Short structures and unions are those whose size and alignment match that of some integer
           type.

           Warning: code compiled with the -fpcc-struct-return switch is not binary compatible with
           code compiled with the -freg-struct-return switch.  Use it to conform to a non-default
           application binary interface.

       -freg-struct-return
           Return "struct" and "union" values in registers when possible.  This is more efficient
           for small structures than -fpcc-struct-return.

           If you specify neither -fpcc-struct-return nor -freg-struct-return, GCC defaults to
           whichever convention is standard for the target.  If there is no standard convention, GCC
           defaults to -fpcc-struct-return, except on targets where GCC is the principal compiler.
           In those cases, we can choose the standard, and we chose the more efficient register
           return alternative.

           Warning: code compiled with the -freg-struct-return switch is not binary compatible with
           code compiled with the -fpcc-struct-return switch.  Use it to conform to a non-default
           application binary interface.

       -fshort-enums
           Allocate to an "enum" type only as many bytes as it needs for the declared range of
           possible values.  Specifically, the "enum" type is equivalent to the smallest integer
           type that has enough room.

           Warning: the -fshort-enums switch causes GCC to generate code that is not binary
           compatible with code generated without that switch.  Use it to conform to a non-default
           application binary interface.

       -fshort-wchar
           Override the underlying type for "wchar_t" to be "short unsigned int" instead of the
           default for the target.  This option is useful for building programs to run under WINE.

           Warning: the -fshort-wchar switch causes GCC to generate code that is not binary
           compatible with code generated without that switch.  Use it to conform to a non-default
           application binary interface.

       -fcommon
           In C code, this option controls the placement of global variables defined without an
           initializer, known as tentative definitions in the C standard.  Tentative definitions are
           distinct from declarations of a variable with the "extern" keyword, which do not allocate
           storage.

           The default is -fno-common, which specifies that the compiler places uninitialized global
           variables in the BSS section of the object file.  This inhibits the merging of tentative
           definitions by the linker so you get a multiple-definition error if the same variable is
           accidentally defined in more than one compilation unit.

           The -fcommon places uninitialized global variables in a common block.  This allows the
           linker to resolve all tentative definitions of the same variable in different compilation
           units to the same object, or to a non-tentative definition.  This behavior is
           inconsistent with C++, and on many targets implies a speed and code size penalty on
           global variable references.  It is mainly useful to enable legacy code to link without
           errors.

       -fno-ident
           Ignore the "#ident" directive.

       -finhibit-size-directive
           Don't output a ".size" assembler directive, or anything else that would cause trouble if
           the function is split in the middle, and the two halves are placed at locations far apart
           in memory.  This option is used when compiling crtstuff.c; you should not need to use it
           for anything else.

       -fverbose-asm
           Put extra commentary information in the generated assembly code to make it more readable.
           This option is generally only of use to those who actually need to read the generated
           assembly code (perhaps while debugging the compiler itself).

           -fno-verbose-asm, the default, causes the extra information to be omitted and is useful
           when comparing two assembler files.

           The added comments include:

           *   information on the compiler version and command-line options,

           *   the source code lines associated with the assembly instructions, in the form
               FILENAME:LINENUMBER:CONTENT OF LINE,

           *   hints on which high-level expressions correspond to the various assembly instruction
               operands.

           For example, given this C source file:

                   int test (int n)
                   {
                     int i;
                     int total = 0;

                     for (i = 0; i < n; i++)
                       total += i * i;

                     return total;
                   }

           compiling to (x86_64) assembly via -S and emitting the result direct to stdout via -o -

                   gcc -S test.c -fverbose-asm -Os -o -

           gives output similar to this:

                           .file   "test.c"
                   # GNU C11 (GCC) version 7.0.0 20160809 (experimental) (x86_64-pc-linux-gnu)
                     [...snip...]
                   # options passed:
                     [...snip...]

                           .text
                           .globl  test
                           .type   test, @function
                   test:
                   .LFB0:
                           .cfi_startproc
                   # test.c:4:   int total = 0;
                           xorl    %eax, %eax      # <retval>
                   # test.c:6:   for (i = 0; i < n; i++)
                           xorl    %edx, %edx      # i
                   .L2:
                   # test.c:6:   for (i = 0; i < n; i++)
                           cmpl    %edi, %edx      # n, i
                           jge     .L5     #,
                   # test.c:7:     total += i * i;
                           movl    %edx, %ecx      # i, tmp92
                           imull   %edx, %ecx      # i, tmp92
                   # test.c:6:   for (i = 0; i < n; i++)
                           incl    %edx    # i
                   # test.c:7:     total += i * i;
                           addl    %ecx, %eax      # tmp92, <retval>
                           jmp     .L2     #
                   .L5:
                   # test.c:10: }
                           ret
                           .cfi_endproc
                   .LFE0:
                           .size   test, .-test
                           .ident  "GCC: (GNU) 7.0.0 20160809 (experimental)"
                           .section        .note.GNU-stack,"",@progbits

           The comments are intended for humans rather than machines and hence the precise format of
           the comments is subject to change.

       -frecord-gcc-switches
           This switch causes the command line used to invoke the compiler to be recorded into the
           object file that is being created.  This switch is only implemented on some targets and
           the exact format of the recording is target and binary file format dependent, but it
           usually takes the form of a section containing ASCII text.  This switch is related to the
           -fverbose-asm switch, but that switch only records information in the assembler output
           file as comments, so it never reaches the object file.  See also -grecord-gcc-switches
           for another way of storing compiler options into the object file.

       -fpic
           Generate position-independent code (PIC) suitable for use in a shared library, if
           supported for the target machine.  Such code accesses all constant addresses through a
           global offset table (GOT).  The dynamic loader resolves the GOT entries when the program
           starts (the dynamic loader is not part of GCC; it is part of the operating system).  If
           the GOT size for the linked executable exceeds a machine-specific maximum size, you get
           an error message from the linker indicating that -fpic does not work; in that case,
           recompile with -fPIC instead.  (These maximums are 8k on the SPARC, 28k on AArch64 and
           32k on the m68k and RS/6000.  The x86 has no such limit.)

           Position-independent code requires special support, and therefore works only on certain
           machines.  For the x86, GCC supports PIC for System V but not for the Sun 386i.  Code
           generated for the IBM RS/6000 is always position-independent.

           When this flag is set, the macros "__pic__" and "__PIC__" are defined to 1.

       -fPIC
           If supported for the target machine, emit position-independent code, suitable for dynamic
           linking and avoiding any limit on the size of the global offset table.  This option makes
           a difference on AArch64, m68k, PowerPC and SPARC.

           Position-independent code requires special support, and therefore works only on certain
           machines.

           When this flag is set, the macros "__pic__" and "__PIC__" are defined to 2.

       -fpie
       -fPIE
           These options are similar to -fpic and -fPIC, but the generated position-independent code
           can be only linked into executables.  Usually these options are used to compile code that
           will be linked using the -pie GCC option.

           -fpie and -fPIE both define the macros "__pie__" and "__PIE__".  The macros have the
           value 1 for -fpie and 2 for -fPIE.

       -fno-plt
           Do not use the PLT for external function calls in position-independent code.  Instead,
           load the callee address at call sites from the GOT and branch to it.  This leads to more
           efficient code by eliminating PLT stubs and exposing GOT loads to optimizations.  On
           architectures such as 32-bit x86 where PLT stubs expect the GOT pointer in a specific
           register, this gives more register allocation freedom to the compiler.  Lazy binding
           requires use of the PLT; with -fno-plt all external symbols are resolved at load time.

           Alternatively, the function attribute "noplt" can be used to avoid calls through the PLT
           for specific external functions.

           In position-dependent code, a few targets also convert calls to functions that are marked
           to not use the PLT to use the GOT instead.

       -fno-jump-tables
           Do not use jump tables for switch statements even where it would be more efficient than
           other code generation strategies.  This option is of use in conjunction with -fpic or
           -fPIC for building code that forms part of a dynamic linker and cannot reference the
           address of a jump table.  On some targets, jump tables do not require a GOT and this
           option is not needed.

       -fno-bit-tests
           Do not use bit tests for switch statements even where it would be more efficient than
           other code generation strategies.

       -ffixed-reg
           Treat the register named reg as a fixed register; generated code should never refer to it
           (except perhaps as a stack pointer, frame pointer or in some other fixed role).

           reg must be the name of a register.  The register names accepted are machine-specific and
           are defined in the "REGISTER_NAMES" macro in the machine description macro file.

           This flag does not have a negative form, because it specifies a three-way choice.

       -fcall-used-reg
           Treat the register named reg as an allocable register that is clobbered by function
           calls.  It may be allocated for temporaries or variables that do not live across a call.
           Functions compiled this way do not save and restore the register reg.

           It is an error to use this flag with the frame pointer or stack pointer.  Use of this
           flag for other registers that have fixed pervasive roles in the machine's execution model
           produces disastrous results.

           This flag does not have a negative form, because it specifies a three-way choice.

       -fcall-saved-reg
           Treat the register named reg as an allocable register saved by functions.  It may be
           allocated even for temporaries or variables that live across a call.  Functions compiled
           this way save and restore the register reg if they use it.

           It is an error to use this flag with the frame pointer or stack pointer.  Use of this
           flag for other registers that have fixed pervasive roles in the machine's execution model
           produces disastrous results.

           A different sort of disaster results from the use of this flag for a register in which
           function values may be returned.

           This flag does not have a negative form, because it specifies a three-way choice.

       -fpack-struct[=n]
           Without a value specified, pack all structure members together without holes.  When a
           value is specified (which must be a small power of two), pack structure members according
           to this value, representing the maximum alignment (that is, objects with default
           alignment requirements larger than this are output potentially unaligned at the next
           fitting location.

           Warning: the -fpack-struct switch causes GCC to generate code that is not binary
           compatible with code generated without that switch.  Additionally, it makes the code
           suboptimal.  Use it to conform to a non-default application binary interface.

       -fleading-underscore
           This option and its counterpart, -fno-leading-underscore, forcibly change the way C
           symbols are represented in the object file.  One use is to help link with legacy assembly
           code.

           Warning: the -fleading-underscore switch causes GCC to generate code that is not binary
           compatible with code generated without that switch.  Use it to conform to a non-default
           application binary interface.  Not all targets provide complete support for this switch.

       -ftls-model=model
           Alter the thread-local storage model to be used.  The model argument should be one of
           global-dynamic, local-dynamic, initial-exec or local-exec.  Note that the choice is
           subject to optimization: the compiler may use a more efficient model for symbols not
           visible outside of the translation unit, or if -fpic is not given on the command line.

           The default without -fpic is initial-exec; with -fpic the default is global-dynamic.

       -ftrampolines
           For targets that normally need trampolines for nested functions, always generate them
           instead of using descriptors.  Otherwise, for targets that do not need them, like for
           example HP-PA or IA-64, do nothing.

           A trampoline is a small piece of code that is created at run time on the stack when the
           address of a nested function is taken, and is used to call the nested function
           indirectly.  Therefore, it requires the stack to be made executable in order for the
           program to work properly.

           -fno-trampolines is enabled by default on a language by language basis to let the
           compiler avoid generating them, if it computes that this is safe, and replace them with
           descriptors.  Descriptors are made up of data only, but the generated code must be
           prepared to deal with them.  As of this writing, -fno-trampolines is enabled by default
           only for Ada.

           Moreover, code compiled with -ftrampolines and code compiled with -fno-trampolines are
           not binary compatible if nested functions are present.  This option must therefore be
           used on a program-wide basis and be manipulated with extreme care.

       -fvisibility=[default|internal|hidden|protected]
           Set the default ELF image symbol visibility to the specified option---all symbols are
           marked with this unless overridden within the code.  Using this feature can very
           substantially improve linking and load times of shared object libraries, produce more
           optimized code, provide near-perfect API export and prevent symbol clashes.  It is
           strongly recommended that you use this in any shared objects you distribute.

           Despite the nomenclature, default always means public; i.e., available to be linked
           against from outside the shared object.  protected and internal are pretty useless in
           real-world usage so the only other commonly used option is hidden.  The default if
           -fvisibility isn't specified is default, i.e., make every symbol public.

           A good explanation of the benefits offered by ensuring ELF symbols have the correct
           visibility is given by "How To Write Shared Libraries" by Ulrich Drepper (which can be
           found at <https://www.akkadia.org/drepper/>)---however a superior solution made possible
           by this option to marking things hidden when the default is public is to make the default
           hidden and mark things public.  This is the norm with DLLs on Windows and with
           -fvisibility=hidden and "__attribute__ ((visibility("default")))" instead of
           "__declspec(dllexport)" you get almost identical semantics with identical syntax.  This
           is a great boon to those working with cross-platform projects.

           For those adding visibility support to existing code, you may find "#pragma GCC
           visibility" of use.  This works by you enclosing the declarations you wish to set
           visibility for with (for example) "#pragma GCC visibility push(hidden)" and "#pragma GCC
           visibility pop".  Bear in mind that symbol visibility should be viewed as part of the API
           interface contract and thus all new code should always specify visibility when it is not
           the default; i.e., declarations only for use within the local DSO should always be marked
           explicitly as hidden as so to avoid PLT indirection overheads---making this abundantly
           clear also aids readability and self-documentation of the code.  Note that due to ISO C++
           specification requirements, "operator new" and "operator delete" must always be of
           default visibility.

           Be aware that headers from outside your project, in particular system headers and headers
           from any other library you use, may not be expecting to be compiled with visibility other
           than the default.  You may need to explicitly say "#pragma GCC visibility push(default)"
           before including any such headers.

           "extern" declarations are not affected by -fvisibility, so a lot of code can be
           recompiled with -fvisibility=hidden with no modifications.  However, this means that
           calls to "extern" functions with no explicit visibility use the PLT, so it is more
           effective to use "__attribute ((visibility))" and/or "#pragma GCC visibility" to tell the
           compiler which "extern" declarations should be treated as hidden.

           Note that -fvisibility does affect C++ vague linkage entities. This means that, for
           instance, an exception class that is be thrown between DSOs must be explicitly marked
           with default visibility so that the type_info nodes are unified between the DSOs.

           An overview of these techniques, their benefits and how to use them is at
           <http://gcc.gnu.org/wiki/Visibility>.

       -fstrict-volatile-bitfields
           This option should be used if accesses to volatile bit-fields (or other structure fields,
           although the compiler usually honors those types anyway) should use a single access of
           the width of the field's type, aligned to a natural alignment if possible.  For example,
           targets with memory-mapped peripheral registers might require all such accesses to be 16
           bits wide; with this flag you can declare all peripheral bit-fields as "unsigned short"
           (assuming short is 16 bits on these targets) to force GCC to use 16-bit accesses instead
           of, perhaps, a more efficient 32-bit access.

           If this option is disabled, the compiler uses the most efficient instruction.  In the
           previous example, that might be a 32-bit load instruction, even though that accesses
           bytes that do not contain any portion of the bit-field, or memory-mapped registers
           unrelated to the one being updated.

           In some cases, such as when the "packed" attribute is applied to a structure field, it
           may not be possible to access the field with a single read or write that is correctly
           aligned for the target machine.  In this case GCC falls back to generating multiple
           accesses rather than code that will fault or truncate the result at run time.

           Note:  Due to restrictions of the C/C++11 memory model, write accesses are not allowed to
           touch non bit-field members.  It is therefore recommended to define all bits of the
           field's type as bit-field members.

           The default value of this option is determined by the application binary interface for
           the target processor.

       -fsync-libcalls
           This option controls whether any out-of-line instance of the "__sync" family of functions
           may be used to implement the C++11 "__atomic" family of functions.

           The default value of this option is enabled, thus the only useful form of the option is
           -fno-sync-libcalls.  This option is used in the implementation of the libatomic runtime
           library.

   GCC Developer Options
       This section describes command-line options that are primarily of interest to GCC developers,
       including options to support compiler testing and investigation of compiler bugs and compile-
       time performance problems.  This includes options that produce debug dumps at various points
       in the compilation; that print statistics such as memory use and execution time; and that
       print information about GCC's configuration, such as where it searches for libraries.  You
       should rarely need to use any of these options for ordinary compilation and linking tasks.

       Many developer options that cause GCC to dump output to a file take an optional =filename
       suffix. You can specify stdout or - to dump to standard output, and stderr for standard
       error.

       If =filename is omitted, a default dump file name is constructed by concatenating the base
       dump file name, a pass number, phase letter, and pass name.  The base dump file name is the
       name of output file produced by the compiler if explicitly specified and not an executable;
       otherwise it is the source file name.  The pass number is determined by the order passes are
       registered with the compiler's pass manager.  This is generally the same as the order of
       execution, but passes registered by plugins, target-specific passes, or passes that are
       otherwise registered late are numbered higher than the pass named final, even if they are
       executed earlier.  The phase letter is one of i (inter-procedural analysis), l (language-
       specific), r (RTL), or t (tree).  The files are created in the directory of the output file.

       -fcallgraph-info
       -fcallgraph-info=MARKERS
           Makes the compiler output callgraph information for the program, on a per-object-file
           basis.  The information is generated in the common VCG format.  It can be decorated with
           additional, per-node and/or per-edge information, if a list of comma-separated markers is
           additionally specified.  When the "su" marker is specified, the callgraph is decorated
           with stack usage information; it is equivalent to -fstack-usage.  When the "da" marker is
           specified, the callgraph is decorated with information about dynamically allocated
           objects.

           When compiling with -flto, no callgraph information is output along with the object file.
           At LTO link time, -fcallgraph-info may generate multiple callgraph information files next
           to intermediate LTO output files.

       -dletters
       -fdump-rtl-pass
       -fdump-rtl-pass=filename
           Says to make debugging dumps during compilation at times specified by letters.  This is
           used for debugging the RTL-based passes of the compiler.

           Some -dletters switches have different meaning when -E is used for preprocessing.

           Debug dumps can be enabled with a -fdump-rtl switch or some -d option letters.  Here are
           the possible letters for use in pass and letters, and their meanings:

           -fdump-rtl-alignments
               Dump after branch alignments have been computed.

           -fdump-rtl-asmcons
               Dump after fixing rtl statements that have unsatisfied in/out constraints.

           -fdump-rtl-auto_inc_dec
               Dump after auto-inc-dec discovery.  This pass is only run on architectures that have
               auto inc or auto dec instructions.

           -fdump-rtl-barriers
               Dump after cleaning up the barrier instructions.

           -fdump-rtl-bbpart
               Dump after partitioning hot and cold basic blocks.

           -fdump-rtl-bbro
               Dump after block reordering.

           -fdump-rtl-btl1
           -fdump-rtl-btl2
               -fdump-rtl-btl1 and -fdump-rtl-btl2 enable dumping after the two branch target load
               optimization passes.

           -fdump-rtl-bypass
               Dump after jump bypassing and control flow optimizations.

           -fdump-rtl-combine
               Dump after the RTL instruction combination pass.

           -fdump-rtl-compgotos
               Dump after duplicating the computed gotos.

           -fdump-rtl-ce1
           -fdump-rtl-ce2
           -fdump-rtl-ce3
               -fdump-rtl-ce1, -fdump-rtl-ce2, and -fdump-rtl-ce3 enable dumping after the three if
               conversion passes.

           -fdump-rtl-cprop_hardreg
               Dump after hard register copy propagation.

           -fdump-rtl-csa
               Dump after combining stack adjustments.

           -fdump-rtl-cse1
           -fdump-rtl-cse2
               -fdump-rtl-cse1 and -fdump-rtl-cse2 enable dumping after the two common subexpression
               elimination passes.

           -fdump-rtl-dce
               Dump after the standalone dead code elimination passes.

           -fdump-rtl-dbr
               Dump after delayed branch scheduling.

           -fdump-rtl-dce1
           -fdump-rtl-dce2
               -fdump-rtl-dce1 and -fdump-rtl-dce2 enable dumping after the two dead store
               elimination passes.

           -fdump-rtl-eh
               Dump after finalization of EH handling code.

           -fdump-rtl-eh_ranges
               Dump after conversion of EH handling range regions.

           -fdump-rtl-expand
               Dump after RTL generation.

           -fdump-rtl-fwprop1
           -fdump-rtl-fwprop2
               -fdump-rtl-fwprop1 and -fdump-rtl-fwprop2 enable dumping after the two forward
               propagation passes.

           -fdump-rtl-gcse1
           -fdump-rtl-gcse2
               -fdump-rtl-gcse1 and -fdump-rtl-gcse2 enable dumping after global common
               subexpression elimination.

           -fdump-rtl-init-regs
               Dump after the initialization of the registers.

           -fdump-rtl-initvals
               Dump after the computation of the initial value sets.

           -fdump-rtl-into_cfglayout
               Dump after converting to cfglayout mode.

           -fdump-rtl-ira
               Dump after iterated register allocation.

           -fdump-rtl-jump
               Dump after the second jump optimization.

           -fdump-rtl-loop2
               -fdump-rtl-loop2 enables dumping after the rtl loop optimization passes.

           -fdump-rtl-mach
               Dump after performing the machine dependent reorganization pass, if that pass exists.

           -fdump-rtl-mode_sw
               Dump after removing redundant mode switches.

           -fdump-rtl-rnreg
               Dump after register renumbering.

           -fdump-rtl-outof_cfglayout
               Dump after converting from cfglayout mode.

           -fdump-rtl-peephole2
               Dump after the peephole pass.

           -fdump-rtl-postreload
               Dump after post-reload optimizations.

           -fdump-rtl-pro_and_epilogue
               Dump after generating the function prologues and epilogues.

           -fdump-rtl-sched1
           -fdump-rtl-sched2
               -fdump-rtl-sched1 and -fdump-rtl-sched2 enable dumping after the basic block
               scheduling passes.

           -fdump-rtl-ree
               Dump after sign/zero extension elimination.

           -fdump-rtl-seqabstr
               Dump after common sequence discovery.

           -fdump-rtl-shorten
               Dump after shortening branches.

           -fdump-rtl-sibling
               Dump after sibling call optimizations.

           -fdump-rtl-split1
           -fdump-rtl-split2
           -fdump-rtl-split3
           -fdump-rtl-split4
           -fdump-rtl-split5
               These options enable dumping after five rounds of instruction splitting.

           -fdump-rtl-sms
               Dump after modulo scheduling.  This pass is only run on some architectures.

           -fdump-rtl-stack
               Dump after conversion from GCC's "flat register file" registers to the x87's stack-
               like registers.  This pass is only run on x86 variants.

           -fdump-rtl-subreg1
           -fdump-rtl-subreg2
               -fdump-rtl-subreg1 and -fdump-rtl-subreg2 enable dumping after the two subreg
               expansion passes.

           -fdump-rtl-unshare
               Dump after all rtl has been unshared.

           -fdump-rtl-vartrack
               Dump after variable tracking.

           -fdump-rtl-vregs
               Dump after converting virtual registers to hard registers.

           -fdump-rtl-web
               Dump after live range splitting.

           -fdump-rtl-regclass
           -fdump-rtl-subregs_of_mode_init
           -fdump-rtl-subregs_of_mode_finish
           -fdump-rtl-dfinit
           -fdump-rtl-dfinish
               These dumps are defined but always produce empty files.

           -da
           -fdump-rtl-all
               Produce all the dumps listed above.

           -dA Annotate the assembler output with miscellaneous debugging information.

           -dD Dump all macro definitions, at the end of preprocessing, in addition to normal
               output.

           -dH Produce a core dump whenever an error occurs.

           -dp Annotate the assembler output with a comment indicating which pattern and alternative
               is used.  The length and cost of each instruction are also printed.

           -dP Dump the RTL in the assembler output as a comment before each instruction.  Also
               turns on -dp annotation.

           -dx Just generate RTL for a function instead of compiling it.  Usually used with
               -fdump-rtl-expand.

       -fdump-debug
           Dump debugging information generated during the debug generation phase.

       -fdump-earlydebug
           Dump debugging information generated during the early debug generation phase.

       -fdump-noaddr
           When doing debugging dumps, suppress address output.  This makes it more feasible to use
           diff on debugging dumps for compiler invocations with different compiler binaries and/or
           different text / bss / data / heap / stack / dso start locations.

       -freport-bug
           Collect and dump debug information into a temporary file if an internal compiler error
           (ICE) occurs.

       -fdump-unnumbered
           When doing debugging dumps, suppress instruction numbers and address output.  This makes
           it more feasible to use diff on debugging dumps for compiler invocations with different
           options, in particular with and without -g.

       -fdump-unnumbered-links
           When doing debugging dumps (see -d option above), suppress instruction numbers for the
           links to the previous and next instructions in a sequence.

       -fdump-ipa-switch
       -fdump-ipa-switch-options
           Control the dumping at various stages of inter-procedural analysis language tree to a
           file.  The file name is generated by appending a switch specific suffix to the source
           file name, and the file is created in the same directory as the output file.  The
           following dumps are possible:

           all Enables all inter-procedural analysis dumps.

           cgraph
               Dumps information about call-graph optimization, unused function removal, and
               inlining decisions.

           inline
               Dump after function inlining.

           Additionally, the options -optimized, -missed, -note, and -all can be provided, with the
           same meaning as for -fopt-info, defaulting to -optimized.

           For example, -fdump-ipa-inline-optimized-missed will emit information on callsites that
           were inlined, along with callsites that were not inlined.

           By default, the dump will contain messages about successful optimizations (equivalent to
           -optimized) together with low-level details about the analysis.

       -fdump-lang
           Dump language-specific information.  The file name is made by appending .lang to the
           source file name.

       -fdump-lang-all
       -fdump-lang-switch
       -fdump-lang-switch-options
       -fdump-lang-switch-options=filename
           Control the dumping of language-specific information.  The options and filename portions
           behave as described in the -fdump-tree option.  The following switch values are accepted:

           all Enable all language-specific dumps.

           class
               Dump class hierarchy information.  Virtual table information is emitted unless 'slim'
               is specified.  This option is applicable to C++ only.

           module
               Dump module information.  Options lineno (locations), graph (reachability), blocks
               (clusters), uid (serialization), alias (mergeable), asmname (Elrond), eh (mapper) &
               vops (macros) may provide additional information.  This option is applicable to C++
               only.

           raw Dump the raw internal tree data.  This option is applicable to C++ only.

       -fdump-passes
           Print on stderr the list of optimization passes that are turned on and off by the current
           command-line options.

       -fdump-statistics-option
           Enable and control dumping of pass statistics in a separate file.  The file name is
           generated by appending a suffix ending in .statistics to the source file name, and the
           file is created in the same directory as the output file.  If the -option form is used,
           -stats causes counters to be summed over the whole compilation unit while -details dumps
           every event as the passes generate them.  The default with no option is to sum counters
           for each function compiled.

       -fdump-tree-all
       -fdump-tree-switch
       -fdump-tree-switch-options
       -fdump-tree-switch-options=filename
           Control the dumping at various stages of processing the intermediate language tree to a
           file.  If the -options form is used, options is a list of - separated options which
           control the details of the dump.  Not all options are applicable to all dumps; those that
           are not meaningful are ignored.  The following options are available

           address
               Print the address of each node.  Usually this is not meaningful as it changes
               according to the environment and source file.  Its primary use is for tying up a dump
               file with a debug environment.

           asmname
               If "DECL_ASSEMBLER_NAME" has been set for a given decl, use that in the dump instead
               of "DECL_NAME".  Its primary use is ease of use working backward from mangled names
               in the assembly file.

           slim
               When dumping front-end intermediate representations, inhibit dumping of members of a
               scope or body of a function merely because that scope has been reached.  Only dump
               such items when they are directly reachable by some other path.

               When dumping pretty-printed trees, this option inhibits dumping the bodies of control
               structures.

               When dumping RTL, print the RTL in slim (condensed) form instead of the default LISP-
               like representation.

           raw Print a raw representation of the tree.  By default, trees are pretty-printed into a
               C-like representation.

           details
               Enable more detailed dumps (not honored by every dump option). Also include
               information from the optimization passes.

           stats
               Enable dumping various statistics about the pass (not honored by every dump option).

           blocks
               Enable showing basic block boundaries (disabled in raw dumps).

           graph
               For each of the other indicated dump files (-fdump-rtl-pass), dump a representation
               of the control flow graph suitable for viewing with GraphViz to file.passid.pass.dot.
               Each function in the file is pretty-printed as a subgraph, so that GraphViz can
               render them all in a single plot.

               This option currently only works for RTL dumps, and the RTL is always dumped in slim
               form.

           vops
               Enable showing virtual operands for every statement.

           lineno
               Enable showing line numbers for statements.

           uid Enable showing the unique ID ("DECL_UID") for each variable.

           verbose
               Enable showing the tree dump for each statement.

           eh  Enable showing the EH region number holding each statement.

           scev
               Enable showing scalar evolution analysis details.

           optimized
               Enable showing optimization information (only available in certain passes).

           missed
               Enable showing missed optimization information (only available in certain passes).

           note
               Enable other detailed optimization information (only available in certain passes).

           all Turn on all options, except raw, slim, verbose and lineno.

           optall
               Turn on all optimization options, i.e., optimized, missed, and note.

           To determine what tree dumps are available or find the dump for a pass of interest follow
           the steps below.

           1.  Invoke GCC with -fdump-passes and in the stderr output look for a code that
               corresponds to the pass you are interested in.  For example, the codes "tree-evrp",
               "tree-vrp1", and "tree-vrp2" correspond to the three Value Range Propagation passes.
               The number at the end distinguishes distinct invocations of the same pass.

           2.  To enable the creation of the dump file, append the pass code to the -fdump- option
               prefix and invoke GCC with it.  For example, to enable the dump from the Early Value
               Range Propagation pass, invoke GCC with the -fdump-tree-evrp option.  Optionally, you
               may specify the name of the dump file.  If you don't specify one, GCC creates as
               described below.

           3.  Find the pass dump in a file whose name is composed of three components separated by
               a period: the name of the source file GCC was invoked to compile, a numeric suffix
               indicating the pass number followed by the letter t for tree passes (and the letter r
               for RTL passes), and finally the pass code.  For example, the Early VRP pass dump
               might be in a file named myfile.c.038t.evrp in the current working directory.  Note
               that the numeric codes are not stable and may change from one version of GCC to
               another.

       -fopt-info
       -fopt-info-options
       -fopt-info-options=filename
           Controls optimization dumps from various optimization passes. If the -options form is
           used, options is a list of - separated option keywords to select the dump details and
           optimizations.

           The options can be divided into three groups:

           1.  options describing what kinds of messages should be emitted,

           2.  options describing the verbosity of the dump, and

           3.  options describing which optimizations should be included.

           The options from each group can be freely mixed as they are non-overlapping. However, in
           case of any conflicts, the later options override the earlier options on the command
           line.

           The following options control which kinds of messages should be emitted:

           optimized
               Print information when an optimization is successfully applied. It is up to a pass to
               decide which information is relevant. For example, the vectorizer passes print the
               source location of loops which are successfully vectorized.

           missed
               Print information about missed optimizations. Individual passes control which
               information to include in the output.

           note
               Print verbose information about optimizations, such as certain transformations, more
               detailed messages about decisions etc.

           all Print detailed optimization information. This includes optimized, missed, and note.

           The following option controls the dump verbosity:

           internals
               By default, only "high-level" messages are emitted. This option enables additional,
               more detailed, messages, which are likely to only be of interest to GCC developers.

           One or more of the following option keywords can be used to describe a group of
           optimizations:

           ipa Enable dumps from all interprocedural optimizations.

           loop
               Enable dumps from all loop optimizations.

           inline
               Enable dumps from all inlining optimizations.

           omp Enable dumps from all OMP (Offloading and Multi Processing) optimizations.

           vec Enable dumps from all vectorization optimizations.

           optall
               Enable dumps from all optimizations. This is a superset of the optimization groups
               listed above.

           If options is omitted, it defaults to optimized-optall, which means to dump messages
           about successful optimizations from all the passes, omitting messages that are treated as
           "internals".

           If the filename is provided, then the dumps from all the applicable optimizations are
           concatenated into the filename.  Otherwise the dump is output onto stderr. Though
           multiple -fopt-info options are accepted, only one of them can include a filename. If
           other filenames are provided then all but the first such option are ignored.

           Note that the output filename is overwritten in case of multiple translation units. If a
           combined output from multiple translation units is desired, stderr should be used
           instead.

           In the following example, the optimization info is output to stderr:

                   gcc -O3 -fopt-info

           This example:

                   gcc -O3 -fopt-info-missed=missed.all

           outputs missed optimization report from all the passes into missed.all, and this one:

                   gcc -O2 -ftree-vectorize -fopt-info-vec-missed

           prints information about missed optimization opportunities from vectorization passes on
           stderr.  Note that -fopt-info-vec-missed is equivalent to -fopt-info-missed-vec.  The
           order of the optimization group names and message types listed after -fopt-info does not
           matter.

           As another example,

                   gcc -O3 -fopt-info-inline-optimized-missed=inline.txt

           outputs information about missed optimizations as well as optimized locations from all
           the inlining passes into inline.txt.

           Finally, consider:

                   gcc -fopt-info-vec-missed=vec.miss -fopt-info-loop-optimized=loop.opt

           Here the two output filenames vec.miss and loop.opt are in conflict since only one output
           file is allowed. In this case, only the first option takes effect and the subsequent
           options are ignored. Thus only vec.miss is produced which contains dumps from the
           vectorizer about missed opportunities.

       -fsave-optimization-record
           Write a SRCFILE.opt-record.json.gz file detailing what optimizations were performed, for
           those optimizations that support -fopt-info.

           This option is experimental and the format of the data within the compressed JSON file is
           subject to change.

           It is roughly equivalent to a machine-readable version of -fopt-info-all, as a collection
           of messages with source file, line number and column number, with the following
           additional data for each message:

           *   the execution count of the code being optimized, along with metadata about whether
               this was from actual profile data, or just an estimate, allowing consumers to
               prioritize messages by code hotness,

           *   the function name of the code being optimized, where applicable,

           *   the "inlining chain" for the code being optimized, so that when a function is inlined
               into several different places (which might themselves be inlined), the reader can
               distinguish between the copies,

           *   objects identifying those parts of the message that refer to expressions, statements
               or symbol-table nodes, which of these categories they are, and, when available, their
               source code location,

           *   the GCC pass that emitted the message, and

           *   the location in GCC's own code from which the message was emitted

           Additionally, some messages are logically nested within other messages, reflecting
           implementation details of the optimization passes.

       -fsched-verbose=n
           On targets that use instruction scheduling, this option controls the amount of debugging
           output the scheduler prints to the dump files.

           For n greater than zero, -fsched-verbose outputs the same information as
           -fdump-rtl-sched1 and -fdump-rtl-sched2.  For n greater than one, it also output basic
           block probabilities, detailed ready list information and unit/insn info.  For n greater
           than two, it includes RTL at abort point, control-flow and regions info.  And for n over
           four, -fsched-verbose also includes dependence info.

       -fenable-kind-pass
       -fdisable-kind-pass=range-list
           This is a set of options that are used to explicitly disable/enable optimization passes.
           These options are intended for use for debugging GCC.  Compiler users should use regular
           options for enabling/disabling passes instead.

           -fdisable-ipa-pass
               Disable IPA pass pass. pass is the pass name.  If the same pass is statically invoked
               in the compiler multiple times, the pass name should be appended with a sequential
               number starting from 1.

           -fdisable-rtl-pass
           -fdisable-rtl-pass=range-list
               Disable RTL pass pass.  pass is the pass name.  If the same pass is statically
               invoked in the compiler multiple times, the pass name should be appended with a
               sequential number starting from 1.  range-list is a comma-separated list of function
               ranges or assembler names.  Each range is a number pair separated by a colon.  The
               range is inclusive in both ends.  If the range is trivial, the number pair can be
               simplified as a single number.  If the function's call graph node's uid falls within
               one of the specified ranges, the pass is disabled for that function.  The uid is
               shown in the function header of a dump file, and the pass names can be dumped by
               using option -fdump-passes.

           -fdisable-tree-pass
           -fdisable-tree-pass=range-list
               Disable tree pass pass.  See -fdisable-rtl for the description of option arguments.

           -fenable-ipa-pass
               Enable IPA pass pass.  pass is the pass name.  If the same pass is statically invoked
               in the compiler multiple times, the pass name should be appended with a sequential
               number starting from 1.

           -fenable-rtl-pass
           -fenable-rtl-pass=range-list
               Enable RTL pass pass.  See -fdisable-rtl for option argument description and
               examples.

           -fenable-tree-pass
           -fenable-tree-pass=range-list
               Enable tree pass pass.  See -fdisable-rtl for the description of option arguments.

           Here are some examples showing uses of these options.

                   # disable ccp1 for all functions
                      -fdisable-tree-ccp1
                   # disable complete unroll for function whose cgraph node uid is 1
                      -fenable-tree-cunroll=1
                   # disable gcse2 for functions at the following ranges [1,1],
                   # [300,400], and [400,1000]
                   # disable gcse2 for functions foo and foo2
                      -fdisable-rtl-gcse2=foo,foo2
                   # disable early inlining
                      -fdisable-tree-einline
                   # disable ipa inlining
                      -fdisable-ipa-inline
                   # enable tree full unroll
                      -fenable-tree-unroll

       -fchecking
       -fchecking=n
           Enable internal consistency checking.  The default depends on the compiler configuration.
           -fchecking=2 enables further internal consistency checking that might affect code
           generation.

       -frandom-seed=string
           This option provides a seed that GCC uses in place of random numbers in generating
           certain symbol names that have to be different in every compiled file.  It is also used
           to place unique stamps in coverage data files and the object files that produce them.
           You can use the -frandom-seed option to produce reproducibly identical object files.

           The string can either be a number (decimal, octal or hex) or an arbitrary string (in
           which case it's converted to a number by computing CRC32).

           The string should be different for every file you compile.

       -save-temps
           Store the usual "temporary" intermediate files permanently; name them as auxiliary output
           files, as specified described under -dumpbase and -dumpdir.

           When used in combination with the -x command-line option, -save-temps is sensible enough
           to avoid overwriting an input source file with the same extension as an intermediate
           file.  The corresponding intermediate file may be obtained by renaming the source file
           before using -save-temps.

       -save-temps=cwd
           Equivalent to -save-temps -dumpdir ./.

       -save-temps=obj
           Equivalent to -save-temps -dumpdir outdir/, where outdir/ is the directory of the output
           file specified after the -o option, including any directory separators.  If the -o option
           is not used, the -save-temps=obj switch behaves like -save-temps=cwd.

       -time[=file]
           Report the CPU time taken by each subprocess in the compilation sequence.  For C source
           files, this is the compiler proper and assembler (plus the linker if linking is done).

           Without the specification of an output file, the output looks like this:

                   # cc1 0.12 0.01
                   # as 0.00 0.01

           The first number on each line is the "user time", that is time spent executing the
           program itself.  The second number is "system time", time spent executing operating
           system routines on behalf of the program.  Both numbers are in seconds.

           With the specification of an output file, the output is appended to the named file, and
           it looks like this:

                   0.12 0.01 cc1 <options>
                   0.00 0.01 as <options>

           The "user time" and the "system time" are moved before the program name, and the options
           passed to the program are displayed, so that one can later tell what file was being
           compiled, and with which options.

       -fdump-final-insns[=file]
           Dump the final internal representation (RTL) to file.  If the optional argument is
           omitted (or if file is "."), the name of the dump file is determined by appending ".gkd"
           to the dump base name, see -dumpbase.

       -fcompare-debug[=opts]
           If no error occurs during compilation, run the compiler a second time, adding opts and
           -fcompare-debug-second to the arguments passed to the second compilation.  Dump the final
           internal representation in both compilations, and print an error if they differ.

           If the equal sign is omitted, the default -gtoggle is used.

           The environment variable GCC_COMPARE_DEBUG, if defined, non-empty and nonzero, implicitly
           enables -fcompare-debug.  If GCC_COMPARE_DEBUG is defined to a string starting with a
           dash, then it is used for opts, otherwise the default -gtoggle is used.

           -fcompare-debug=, with the equal sign but without opts, is equivalent to
           -fno-compare-debug, which disables the dumping of the final representation and the second
           compilation, preventing even GCC_COMPARE_DEBUG from taking effect.

           To verify full coverage during -fcompare-debug testing, set GCC_COMPARE_DEBUG to say
           -fcompare-debug-not-overridden, which GCC rejects as an invalid option in any actual
           compilation (rather than preprocessing, assembly or linking).  To get just a warning,
           setting GCC_COMPARE_DEBUG to -w%n-fcompare-debug not overridden will do.

       -fcompare-debug-second
           This option is implicitly passed to the compiler for the second compilation requested by
           -fcompare-debug, along with options to silence warnings, and omitting other options that
           would cause the compiler to produce output to files or to standard output as a side
           effect.  Dump files and preserved temporary files are renamed so as to contain the ".gk"
           additional extension during the second compilation, to avoid overwriting those generated
           by the first.

           When this option is passed to the compiler driver, it causes the first compilation to be
           skipped, which makes it useful for little other than debugging the compiler proper.

       -gtoggle
           Turn off generation of debug info, if leaving out this option generates it, or turn it on
           at level 2 otherwise.  The position of this argument in the command line does not matter;
           it takes effect after all other options are processed, and it does so only once, no
           matter how many times it is given.  This is mainly intended to be used with
           -fcompare-debug.

       -fvar-tracking-assignments-toggle
           Toggle -fvar-tracking-assignments, in the same way that -gtoggle toggles -g.

       -Q  Makes the compiler print out each function name as it is compiled, and print some
           statistics about each pass when it finishes.

       -ftime-report
           Makes the compiler print some statistics about the time consumed by each pass when it
           finishes.

       -ftime-report-details
           Record the time consumed by infrastructure parts separately for each pass.

       -fira-verbose=n
           Control the verbosity of the dump file for the integrated register allocator.  The
           default value is 5.  If the value n is greater or equal to 10, the dump output is sent to
           stderr using the same format as n minus 10.

       -flto-report
           Prints a report with internal details on the workings of the link-time optimizer.  The
           contents of this report vary from version to version.  It is meant to be useful to GCC
           developers when processing object files in LTO mode (via -flto).

           Disabled by default.

       -flto-report-wpa
           Like -flto-report, but only print for the WPA phase of link-time optimization.

       -fmem-report
           Makes the compiler print some statistics about permanent memory allocation when it
           finishes.

       -fmem-report-wpa
           Makes the compiler print some statistics about permanent memory allocation for the WPA
           phase only.

       -fpre-ipa-mem-report
       -fpost-ipa-mem-report
           Makes the compiler print some statistics about permanent memory allocation before or
           after interprocedural optimization.

       -fprofile-report
           Makes the compiler print some statistics about consistency of the (estimated) profile and
           effect of individual passes.

       -fstack-usage
           Makes the compiler output stack usage information for the program, on a per-function
           basis.  The filename for the dump is made by appending .su to the auxname.  auxname is
           generated from the name of the output file, if explicitly specified and it is not an
           executable, otherwise it is the basename of the source file.  An entry is made up of
           three fields:

           *   The name of the function.

           *   A number of bytes.

           *   One or more qualifiers: "static", "dynamic", "bounded".

           The qualifier "static" means that the function manipulates the stack statically: a fixed
           number of bytes are allocated for the frame on function entry and released on function
           exit; no stack adjustments are otherwise made in the function.  The second field is this
           fixed number of bytes.

           The qualifier "dynamic" means that the function manipulates the stack dynamically: in
           addition to the static allocation described above, stack adjustments are made in the body
           of the function, for example to push/pop arguments around function calls.  If the
           qualifier "bounded" is also present, the amount of these adjustments is bounded at
           compile time and the second field is an upper bound of the total amount of stack used by
           the function.  If it is not present, the amount of these adjustments is not bounded at
           compile time and the second field only represents the bounded part.

       -fstats
           Emit statistics about front-end processing at the end of the compilation.  This option is
           supported only by the C++ front end, and the information is generally only useful to the
           G++ development team.

       -fdbg-cnt-list
           Print the name and the counter upper bound for all debug counters.

       -fdbg-cnt=counter-value-list
           Set the internal debug counter lower and upper bound.  counter-value-list is a comma-
           separated list of name:lower_bound1-upper_bound1 [:lower_bound2-upper_bound2...] tuples
           which sets the name of the counter and list of closed intervals.  The lower_bound is
           optional and is zero initialized if not set.  For example, with
           -fdbg-cnt=dce:2-4:10-11,tail_call:10, "dbg_cnt(dce)" returns true only for second, third,
           fourth, tenth and eleventh invocation.  For "dbg_cnt(tail_call)" true is returned for
           first 10 invocations.

       -print-file-name=library
           Print the full absolute name of the library file library that would be used when
           linking---and don't do anything else.  With this option, GCC does not compile or link
           anything; it just prints the file name.

       -print-multi-directory
           Print the directory name corresponding to the multilib selected by any other switches
           present in the command line.  This directory is supposed to exist in GCC_EXEC_PREFIX.

       -print-multi-lib
           Print the mapping from multilib directory names to compiler switches that enable them.
           The directory name is separated from the switches by ;, and each switch starts with an @
           instead of the -, without spaces between multiple switches.  This is supposed to ease
           shell processing.

       -print-multi-os-directory
           Print the path to OS libraries for the selected multilib, relative to some lib
           subdirectory.  If OS libraries are present in the lib subdirectory and no multilibs are
           used, this is usually just ., if OS libraries are present in libsuffix sibling
           directories this prints e.g. ../lib64, ../lib or ../lib32, or if OS libraries are present
           in lib/subdir subdirectories it prints e.g. amd64, sparcv9 or ev6.

       -print-multiarch
           Print the path to OS libraries for the selected multiarch, relative to some lib
           subdirectory.

       -print-prog-name=program
           Like -print-file-name, but searches for a program such as cpp.

       -print-libgcc-file-name
           Same as -print-file-name=libgcc.a.

           This is useful when you use -nostdlib or -nodefaultlibs but you do want to link with
           libgcc.a.  You can do:

                   gcc -nostdlib <files>... `gcc -print-libgcc-file-name`

       -print-search-dirs
           Print the name of the configured installation directory and a list of program and library
           directories gcc searches---and don't do anything else.

           This is useful when gcc prints the error message installation problem, cannot exec cpp0:
           No such file or directory.  To resolve this you either need to put cpp0 and the other
           compiler components where gcc expects to find them, or you can set the environment
           variable GCC_EXEC_PREFIX to the directory where you installed them.  Don't forget the
           trailing /.

       -print-sysroot
           Print the target sysroot directory that is used during compilation.  This is the target
           sysroot specified either at configure time or using the --sysroot option, possibly with
           an extra suffix that depends on compilation options.  If no target sysroot is specified,
           the option prints nothing.

       -print-sysroot-headers-suffix
           Print the suffix added to the target sysroot when searching for headers, or give an error
           if the compiler is not configured with such a suffix---and don't do anything else.

       -dumpmachine
           Print the compiler's target machine (for example, i686-pc-linux-gnu)---and don't do
           anything else.

       -dumpversion
           Print the compiler version (for example, 3.0, 6.3.0 or 7)---and don't do anything else.
           This is the compiler version used in filesystem paths and specs. Depending on how the
           compiler has been configured it can be just a single number (major version), two numbers
           separated by a dot (major and minor version) or three numbers separated by dots (major,
           minor and patchlevel version).

       -dumpfullversion
           Print the full compiler version---and don't do anything else. The output is always three
           numbers separated by dots, major, minor and patchlevel version.

       -dumpspecs
           Print the compiler's built-in specs---and don't do anything else.  (This is used when GCC
           itself is being built.)

   Machine-Dependent Options
       Each target machine supported by GCC can have its own options---for example, to allow you to
       compile for a particular processor variant or ABI, or to control optimizations specific to
       that machine.  By convention, the names of machine-specific options start with -m.

       Some configurations of the compiler also support additional target-specific options, usually
       for compatibility with other compilers on the same platform.

       AArch64 Options

       These options are defined for AArch64 implementations:

       -mabi=name
           Generate code for the specified data model.  Permissible values are ilp32 for SysV-like
           data model where int, long int and pointers are 32 bits, and lp64 for SysV-like data
           model where int is 32 bits, but long int and pointers are 64 bits.

           The default depends on the specific target configuration.  Note that the LP64 and ILP32
           ABIs are not link-compatible; you must compile your entire program with the same ABI, and
           link with a compatible set of libraries.

       -mbig-endian
           Generate big-endian code.  This is the default when GCC is configured for an
           aarch64_be-*-* target.

       -mgeneral-regs-only
           Generate code which uses only the general-purpose registers.  This will prevent the
           compiler from using floating-point and Advanced SIMD registers but will not impose any
           restrictions on the assembler.

       -mlittle-endian
           Generate little-endian code.  This is the default when GCC is configured for an
           aarch64-*-* but not an aarch64_be-*-* target.

       -mcmodel=tiny
           Generate code for the tiny code model.  The program and its statically defined symbols
           must be within 1MB of each other.  Programs can be statically or dynamically linked.

       -mcmodel=small
           Generate code for the small code model.  The program and its statically defined symbols
           must be within 4GB of each other.  Programs can be statically or dynamically linked.
           This is the default code model.

       -mcmodel=large
           Generate code for the large code model.  This makes no assumptions about addresses and
           sizes of sections.  Programs can be statically linked only.  The -mcmodel=large option is
           incompatible with -mabi=ilp32, -fpic and -fPIC.

       -mstrict-align
       -mno-strict-align
           Avoid or allow generating memory accesses that may not be aligned on a natural object
           boundary as described in the architecture specification.

       -momit-leaf-frame-pointer
       -mno-omit-leaf-frame-pointer
           Omit or keep the frame pointer in leaf functions.  The former behavior is the default.

       -mstack-protector-guard=guard
       -mstack-protector-guard-reg=reg
       -mstack-protector-guard-offset=offset
           Generate stack protection code using canary at guard.  Supported locations are global for
           a global canary or sysreg for a canary in an appropriate system register.

           With the latter choice the options -mstack-protector-guard-reg=reg and
           -mstack-protector-guard-offset=offset furthermore specify which system register to use as
           base register for reading the canary, and from what offset from that base register. There
           is no default register or offset as this is entirely for use within the Linux kernel.

       -mtls-dialect=desc
           Use TLS descriptors as the thread-local storage mechanism for dynamic accesses of TLS
           variables.  This is the default.

       -mtls-dialect=traditional
           Use traditional TLS as the thread-local storage mechanism for dynamic accesses of TLS
           variables.

       -mtls-size=size
           Specify bit size of immediate TLS offsets.  Valid values are 12, 24, 32, 48.  This option
           requires binutils 2.26 or newer.

       -mfix-cortex-a53-835769
       -mno-fix-cortex-a53-835769
           Enable or disable the workaround for the ARM Cortex-A53 erratum number 835769.  This
           involves inserting a NOP instruction between memory instructions and 64-bit integer
           multiply-accumulate instructions.

       -mfix-cortex-a53-843419
       -mno-fix-cortex-a53-843419
           Enable or disable the workaround for the ARM Cortex-A53 erratum number 843419.  This
           erratum workaround is made at link time and this will only pass the corresponding flag to
           the linker.

       -mlow-precision-recip-sqrt
       -mno-low-precision-recip-sqrt
           Enable or disable the reciprocal square root approximation.  This option only has an
           effect if -ffast-math or -funsafe-math-optimizations is used as well.  Enabling this
           reduces precision of reciprocal square root results to about 16 bits for single precision
           and to 32 bits for double precision.

       -mlow-precision-sqrt
       -mno-low-precision-sqrt
           Enable or disable the square root approximation.  This option only has an effect if
           -ffast-math or -funsafe-math-optimizations is used as well.  Enabling this reduces
           precision of square root results to about 16 bits for single precision and to 32 bits for
           double precision.  If enabled, it implies -mlow-precision-recip-sqrt.

       -mlow-precision-div
       -mno-low-precision-div
           Enable or disable the division approximation.  This option only has an effect if
           -ffast-math or -funsafe-math-optimizations is used as well.  Enabling this reduces
           precision of division results to about 16 bits for single precision and to 32 bits for
           double precision.

       -mtrack-speculation
       -mno-track-speculation
           Enable or disable generation of additional code to track speculative execution through
           conditional branches.  The tracking state can then be used by the compiler when expanding
           calls to "__builtin_speculation_safe_copy" to permit a more efficient code sequence to be
           generated.

       -moutline-atomics
       -mno-outline-atomics
           Enable or disable calls to out-of-line helpers to implement atomic operations.  These
           helpers will, at runtime, determine if the LSE instructions from ARMv8.1-A can be used;
           if not, they will use the load/store-exclusive instructions that are present in the base
           ARMv8.0 ISA.

           This option is only applicable when compiling for the base ARMv8.0 instruction set.  If
           using a later revision, e.g. -march=armv8.1-a or -march=armv8-a+lse, the ARMv8.1-Atomics
           instructions will be used directly.  The same applies when using -mcpu= when the selected
           cpu supports the lse feature.  This option is on by default.

       -march=name
           Specify the name of the target architecture and, optionally, one or more feature
           modifiers.  This option has the form -march=arch{+[no]feature}*.

           The table below summarizes the permissible values for arch and the features that they
           enable by default:

           arch value : Architecture : Includes by default
           armv8-a : Armv8-A : +fp, +simd
           armv8.1-a : Armv8.1-A : armv8-a, +crc, +lse, +rdma
           armv8.2-a : Armv8.2-A : armv8.1-a
           armv8.3-a : Armv8.3-A : armv8.2-a, +pauth
           armv8.4-a : Armv8.4-A : armv8.3-a, +flagm, +fp16fml, +dotprod
           armv8.5-a : Armv8.5-A : armv8.4-a, +sb, +ssbs, +predres
           armv8.6-a : Armv8.6-A : armv8.5-a, +bf16, +i8mm
           armv8-r : Armv8-R : armv8-r

           The value native is available on native AArch64 GNU/Linux and causes the compiler to pick
           the architecture of the host system.  This option has no effect if the compiler is unable
           to recognize the architecture of the host system,

           The permissible values for feature are listed in the sub-section on
           aarch64-feature-modifiers,,-march and -mcpu Feature Modifiers.  Where conflicting feature
           modifiers are specified, the right-most feature is used.

           GCC uses name to determine what kind of instructions it can emit when generating assembly
           code.  If -march is specified without either of -mtune or -mcpu also being specified, the
           code is tuned to perform well across a range of target processors implementing the target
           architecture.

       -mtune=name
           Specify the name of the target processor for which GCC should tune the performance of the
           code.  Permissible values for this option are: generic, cortex-a35, cortex-a53,
           cortex-a55, cortex-a57, cortex-a72, cortex-a73, cortex-a75, cortex-a76, cortex-a76ae,
           cortex-a77, cortex-a65, cortex-a65ae, cortex-a34, cortex-a78, cortex-a78ae, cortex-a78c,
           ares, exynos-m1, emag, falkor, neoverse-512tvb, neoverse-e1, neoverse-n1, neoverse-n2,
           neoverse-v1,neoverse-v2, qdf24xx, saphira, phecda, xgene1, vulcan, octeontx, octeontx81,
           octeontx83, octeontx2, octeontx2t98, octeontx2t96 octeontx2t93, octeontx2f95,
           octeontx2f95n, octeontx2f95mm, a64fx, thunderx, thunderxt88, thunderxt88p1, thunderxt81,
           tsv110, thunderxt83, thunderx2t99, thunderx3t110, zeus, cortex-a57.cortex-a53,
           cortex-a72.cortex-a53, cortex-a73.cortex-a35, cortex-a73.cortex-a53,
           cortex-a75.cortex-a55, cortex-a76.cortex-a55, cortex-r82, cortex-x1, ampere1, ampere1a,
           native.

           The values cortex-a57.cortex-a53, cortex-a72.cortex-a53, cortex-a73.cortex-a35,
           cortex-a73.cortex-a53, cortex-a75.cortex-a55, cortex-a76.cortex-a55 specify that GCC
           should tune for a big.LITTLE system.

           The value neoverse-512tvb specifies that GCC should tune for Neoverse cores that (a)
           implement SVE and (b) have a total vector bandwidth of 512 bits per cycle.  In other
           words, the option tells GCC to tune for Neoverse cores that can execute 4 128-bit
           Advanced SIMD arithmetic instructions a cycle and that can execute an equivalent number
           of SVE arithmetic instructions per cycle (2 for 256-bit SVE, 4 for 128-bit SVE).  This is
           more general than tuning for a specific core like Neoverse V1 but is more specific than
           the default tuning described below.

           Additionally on native AArch64 GNU/Linux systems the value native tunes performance to
           the host system.  This option has no effect if the compiler is unable to recognize the
           processor of the host system.

           Where none of -mtune=, -mcpu= or -march= are specified, the code is tuned to perform well
           across a range of target processors.

           This option cannot be suffixed by feature modifiers.

       -mcpu=name
           Specify the name of the target processor, optionally suffixed by one or more feature
           modifiers.  This option has the form -mcpu=cpu{+[no]feature}*, where the permissible
           values for cpu are the same as those available for -mtune.  The permissible values for
           feature are documented in the sub-section on aarch64-feature-modifiers,,-march and -mcpu
           Feature Modifiers.  Where conflicting feature modifiers are specified, the right-most
           feature is used.

           GCC uses name to determine what kind of instructions it can emit when generating assembly
           code (as if by -march) and to determine the target processor for which to tune for
           performance (as if by -mtune).  Where this option is used in conjunction with -march or
           -mtune, those options take precedence over the appropriate part of this option.

           -mcpu=neoverse-512tvb is special in that it does not refer to a specific core, but
           instead refers to all Neoverse cores that (a) implement SVE and (b) have a total vector
           bandwidth of 512 bits a cycle.  Unless overridden by -march, -mcpu=neoverse-512tvb
           generates code that can run on a Neoverse V1 core, since Neoverse V1 is the first
           Neoverse core with these properties.  Unless overridden by -mtune, -mcpu=neoverse-512tvb
           tunes code in the same way as for -mtune=neoverse-512tvb.

       -moverride=string
           Override tuning decisions made by the back-end in response to a -mtune= switch.  The
           syntax, semantics, and accepted values for string in this option are not guaranteed to be
           consistent across releases.

           This option is only intended to be useful when developing GCC.

       -mverbose-cost-dump
           Enable verbose cost model dumping in the debug dump files.  This option is provided for
           use in debugging the compiler.

       -mpc-relative-literal-loads
       -mno-pc-relative-literal-loads
           Enable or disable PC-relative literal loads.  With this option literal pools are accessed
           using a single instruction and emitted after each function.  This limits the maximum size
           of functions to 1MB.  This is enabled by default for -mcmodel=tiny.

       -msign-return-address=scope
           Select the function scope on which return address signing will be applied.  Permissible
           values are none, which disables return address signing, non-leaf, which enables pointer
           signing for functions which are not leaf functions, and all, which enables pointer
           signing for all functions.  The default value is none. This option has been deprecated by
           -mbranch-protection.

       -mbranch-protection=none|standard|pac-ret[+leaf+b-key]|bti
           Select the branch protection features to use.  none is the default and turns off all
           types of branch protection.  standard turns on all types of branch protection features.
           If a feature has additional tuning options, then standard sets it to its standard level.
           pac-ret[+leaf] turns on return address signing to its standard level: signing functions
           that save the return address to memory (non-leaf functions will practically always do
           this) using the a-key.  The optional argument leaf can be used to extend the signing to
           include leaf functions.  The optional argument b-key can be used to sign the functions
           with the B-key instead of the A-key.  bti turns on branch target identification
           mechanism.

       -mharden-sls=opts
           Enable compiler hardening against straight line speculation (SLS).  opts is a comma-
           separated list of the following options:

           retbr
           blr

           In addition, -mharden-sls=all enables all SLS hardening while -mharden-sls=none disables
           all SLS hardening.

       -msve-vector-bits=bits
           Specify the number of bits in an SVE vector register.  This option only has an effect
           when SVE is enabled.

           GCC supports two forms of SVE code generation: "vector-length agnostic" output that works
           with any size of vector register and "vector-length specific" output that allows GCC to
           make assumptions about the vector length when it is useful for optimization reasons.  The
           possible values of bits are: scalable, 128, 256, 512, 1024 and 2048.  Specifying scalable
           selects vector-length agnostic output.  At present -msve-vector-bits=128 also generates
           vector-length agnostic output for big-endian targets.  All other values generate vector-
           length specific code.  The behavior of these values may change in future releases and no
           value except scalable should be relied on for producing code that is portable across
           different hardware SVE vector lengths.

           The default is -msve-vector-bits=scalable, which produces vector-length agnostic code.

       -march and -mcpu Feature Modifiers

       Feature modifiers used with -march and -mcpu can be any of the following and their inverses
       nofeature:

       crc Enable CRC extension.  This is on by default for -march=armv8.1-a.

       crypto
           Enable Crypto extension.  This also enables Advanced SIMD and floating-point
           instructions.

       fp  Enable floating-point instructions.  This is on by default for all possible values for
           options -march and -mcpu.

       simd
           Enable Advanced SIMD instructions.  This also enables floating-point instructions.  This
           is on by default for all possible values for options -march and -mcpu.

       sve Enable Scalable Vector Extension instructions.  This also enables Advanced SIMD and
           floating-point instructions.

       lse Enable Large System Extension instructions.  This is on by default for -march=armv8.1-a.

       rdma
           Enable Round Double Multiply Accumulate instructions.  This is on by default for
           -march=armv8.1-a.

       fp16
           Enable FP16 extension.  This also enables floating-point instructions.

       fp16fml
           Enable FP16 fmla extension.  This also enables FP16 extensions and floating-point
           instructions. This option is enabled by default for -march=armv8.4-a. Use of this option
           with architectures prior to Armv8.2-A is not supported.

       rcpc
           Enable the RcPc extension.  This does not change code generation from GCC, but is passed
           on to the assembler, enabling inline asm statements to use instructions from the RcPc
           extension.

       dotprod
           Enable the Dot Product extension.  This also enables Advanced SIMD instructions.

       aes Enable the Armv8-a aes and pmull crypto extension.  This also enables Advanced SIMD
           instructions.

       sha2
           Enable the Armv8-a sha2 crypto extension.  This also enables Advanced SIMD instructions.

       sha3
           Enable the sha512 and sha3 crypto extension.  This also enables Advanced SIMD
           instructions. Use of this option with architectures prior to Armv8.2-A is not supported.

       sm4 Enable the sm3 and sm4 crypto extension.  This also enables Advanced SIMD instructions.
           Use of this option with architectures prior to Armv8.2-A is not supported.

       profile
           Enable the Statistical Profiling extension.  This option is only to enable the extension
           at the assembler level and does not affect code generation.

       rng Enable the Armv8.5-a Random Number instructions.  This option is only to enable the
           extension at the assembler level and does not affect code generation.

       memtag
           Enable the Armv8.5-a Memory Tagging Extensions.  Use of this option with architectures
           prior to Armv8.5-A is not supported.

       sb  Enable the Armv8-a Speculation Barrier instruction.  This option is only to enable the
           extension at the assembler level and does not affect code generation.  This option is
           enabled by default for -march=armv8.5-a.

       ssbs
           Enable the Armv8-a Speculative Store Bypass Safe instruction.  This option is only to
           enable the extension at the assembler level and does not affect code generation.  This
           option is enabled by default for -march=armv8.5-a.

       predres
           Enable the Armv8-a Execution and Data Prediction Restriction instructions.  This option
           is only to enable the extension at the assembler level and does not affect code
           generation.  This option is enabled by default for -march=armv8.5-a.

       sve2
           Enable the Armv8-a Scalable Vector Extension 2.  This also enables SVE instructions.

       sve2-bitperm
           Enable SVE2 bitperm instructions.  This also enables SVE2 instructions.

       sve2-sm4
           Enable SVE2 sm4 instructions.  This also enables SVE2 instructions.

       sve2-aes
           Enable SVE2 aes instructions.  This also enables SVE2 instructions.

       sve2-sha3
           Enable SVE2 sha3 instructions.  This also enables SVE2 instructions.

       tme Enable the Transactional Memory Extension.

       i8mm
           Enable 8-bit Integer Matrix Multiply instructions.  This also enables Advanced SIMD and
           floating-point instructions.  This option is enabled by default for -march=armv8.6-a.
           Use of this option with architectures prior to Armv8.2-A is not supported.

       f32mm
           Enable 32-bit Floating point Matrix Multiply instructions.  This also enables SVE
           instructions.  Use of this option with architectures prior to Armv8.2-A is not supported.

       f64mm
           Enable 64-bit Floating point Matrix Multiply instructions.  This also enables SVE
           instructions.  Use of this option with architectures prior to Armv8.2-A is not supported.

       bf16
           Enable brain half-precision floating-point instructions.  This also enables Advanced SIMD
           and floating-point instructions.  This option is enabled by default for -march=armv8.6-a.
           Use of this option with architectures prior to Armv8.2-A is not supported.

       flagm
           Enable the Flag Manipulation instructions Extension.

       pauth
           Enable the Pointer Authentication Extension.

       Feature crypto implies aes, sha2, and simd, which implies fp.  Conversely, nofp implies
       nosimd, which implies nocrypto, noaes and nosha2.

       Adapteva Epiphany Options

       These -m options are defined for Adapteva Epiphany:

       -mhalf-reg-file
           Don't allocate any register in the range "r32"..."r63".  That allows code to run on
           hardware variants that lack these registers.

       -mprefer-short-insn-regs
           Preferentially allocate registers that allow short instruction generation.  This can
           result in increased instruction count, so this may either reduce or increase overall code
           size.

       -mbranch-cost=num
           Set the cost of branches to roughly num "simple" instructions.  This cost is only a
           heuristic and is not guaranteed to produce consistent results across releases.

       -mcmove
           Enable the generation of conditional moves.

       -mnops=num
           Emit num NOPs before every other generated instruction.

       -mno-soft-cmpsf
           For single-precision floating-point comparisons, emit an "fsub" instruction and test the
           flags.  This is faster than a software comparison, but can get incorrect results in the
           presence of NaNs, or when two different small numbers are compared such that their
           difference is calculated as zero.  The default is -msoft-cmpsf, which uses slower, but
           IEEE-compliant, software comparisons.

       -mstack-offset=num
           Set the offset between the top of the stack and the stack pointer.  E.g., a value of 8
           means that the eight bytes in the range "sp+0...sp+7" can be used by leaf functions
           without stack allocation.  Values other than 8 or 16 are untested and unlikely to work.
           Note also that this option changes the ABI; compiling a program with a different stack
           offset than the libraries have been compiled with generally does not work.  This option
           can be useful if you want to evaluate if a different stack offset would give you better
           code, but to actually use a different stack offset to build working programs, it is
           recommended to configure the toolchain with the appropriate --with-stack-offset=num
           option.

       -mno-round-nearest
           Make the scheduler assume that the rounding mode has been set to truncating.  The default
           is -mround-nearest.

       -mlong-calls
           If not otherwise specified by an attribute, assume all calls might be beyond the offset
           range of the "b" / "bl" instructions, and therefore load the function address into a
           register before performing a (otherwise direct) call.  This is the default.

       -mshort-calls
           If not otherwise specified by an attribute, assume all direct calls are in the range of
           the "b" / "bl" instructions, so use these instructions for direct calls.  The default is
           -mlong-calls.

       -msmall16
           Assume addresses can be loaded as 16-bit unsigned values.  This does not apply to
           function addresses for which -mlong-calls semantics are in effect.

       -mfp-mode=mode
           Set the prevailing mode of the floating-point unit.  This determines the floating-point
           mode that is provided and expected at function call and return time.  Making this mode
           match the mode you predominantly need at function start can make your programs smaller
           and faster by avoiding unnecessary mode switches.

           mode can be set to one the following values:

           caller
               Any mode at function entry is valid, and retained or restored when the function
               returns, and when it calls other functions.  This mode is useful for compiling
               libraries or other compilation units you might want to incorporate into different
               programs with different prevailing FPU modes, and the convenience of being able to
               use a single object file outweighs the size and speed overhead for any extra mode
               switching that might be needed, compared with what would be needed with a more
               specific choice of prevailing FPU mode.

           truncate
               This is the mode used for floating-point calculations with truncating (i.e. round
               towards zero) rounding mode.  That includes conversion from floating point to
               integer.

           round-nearest
               This is the mode used for floating-point calculations with round-to-nearest-or-even
               rounding mode.

           int This is the mode used to perform integer calculations in the FPU, e.g.  integer
               multiply, or integer multiply-and-accumulate.

           The default is -mfp-mode=caller

       -mno-split-lohi
       -mno-postinc
       -mno-postmodify
           Code generation tweaks that disable, respectively, splitting of 32-bit loads, generation
           of post-increment addresses, and generation of post-modify addresses.  The defaults are
           msplit-lohi, -mpost-inc, and -mpost-modify.

       -mnovect-double
           Change the preferred SIMD mode to SImode.  The default is -mvect-double, which uses
           DImode as preferred SIMD mode.

       -max-vect-align=num
           The maximum alignment for SIMD vector mode types.  num may be 4 or 8.  The default is 8.
           Note that this is an ABI change, even though many library function interfaces are
           unaffected if they don't use SIMD vector modes in places that affect size and/or
           alignment of relevant types.

       -msplit-vecmove-early
           Split vector moves into single word moves before reload.  In theory this can give better
           register allocation, but so far the reverse seems to be generally the case.

       -m1reg-reg
           Specify a register to hold the constant -1, which makes loading small negative constants
           and certain bitmasks faster.  Allowable values for reg are r43 and r63, which specify use
           of that register as a fixed register, and none, which means that no register is used for
           this purpose.  The default is -m1reg-none.

       AMD GCN Options

       These options are defined specifically for the AMD GCN port.

       -march=gpu
       -mtune=gpu
           Set architecture type or tuning for gpu. Supported values for gpu are

           fiji
               Compile for GCN3 Fiji devices (gfx803).

           gfx900
               Compile for GCN5 Vega 10 devices (gfx900).

           gfx906
               Compile for GCN5 Vega 20 devices (gfx906).

       -msram-ecc=on
       -msram-ecc=off
       -msram-ecc=any
           Compile binaries suitable for devices with the SRAM-ECC feature enabled, disabled, or
           either mode.  This feature can be enabled per-process on some devices.  The compiled code
           must match the device mode. The default is any, for devices that support it.

       -mstack-size=bytes
           Specify how many bytes of stack space will be requested for each GPU thread (wave-front).
           Beware that there may be many threads and limited memory available.  The size of the
           stack allocation may also have an impact on run-time performance.  The default is 32KB
           when using OpenACC or OpenMP, and 1MB otherwise.

       -mxnack
           Compile binaries suitable for devices with the XNACK feature enabled.  Some devices
           always require XNACK and some allow the user to configure XNACK.  The compiled code must
           match the device mode.  The default is -mno-xnack.  At present this option is a
           placeholder for support that is not yet implemented.

       ARC Options

       The following options control the architecture variant for which code is being compiled:

       -mbarrel-shifter
           Generate instructions supported by barrel shifter.  This is the default unless
           -mcpu=ARC601 or -mcpu=ARCEM is in effect.

       -mjli-always
           Force to call a function using jli_s instruction.  This option is valid only for ARCv2
           architecture.

       -mcpu=cpu
           Set architecture type, register usage, and instruction scheduling parameters for cpu.
           There are also shortcut alias options available for backward compatibility and
           convenience.  Supported values for cpu are

           arc600
               Compile for ARC600.  Aliases: -mA6, -mARC600.

           arc601
               Compile for ARC601.  Alias: -mARC601.

           arc700
               Compile for ARC700.  Aliases: -mA7, -mARC700.  This is the default when configured
               with --with-cpu=arc700.

           arcem
               Compile for ARC EM.

           archs
               Compile for ARC HS.

           em  Compile for ARC EM CPU with no hardware extensions.

           em4 Compile for ARC EM4 CPU.

           em4_dmips
               Compile for ARC EM4 DMIPS CPU.

           em4_fpus
               Compile for ARC EM4 DMIPS CPU with the single-precision floating-point extension.

           em4_fpuda
               Compile for ARC EM4 DMIPS CPU with single-precision floating-point and double assist
               instructions.

           hs  Compile for ARC HS CPU with no hardware extensions except the atomic instructions.

           hs34
               Compile for ARC HS34 CPU.

           hs38
               Compile for ARC HS38 CPU.

           hs38_linux
               Compile for ARC HS38 CPU with all hardware extensions on.

           arc600_norm
               Compile for ARC 600 CPU with "norm" instructions enabled.

           arc600_mul32x16
               Compile for ARC 600 CPU with "norm" and 32x16-bit multiply instructions enabled.

           arc600_mul64
               Compile for ARC 600 CPU with "norm" and "mul64"-family instructions enabled.

           arc601_norm
               Compile for ARC 601 CPU with "norm" instructions enabled.

           arc601_mul32x16
               Compile for ARC 601 CPU with "norm" and 32x16-bit multiply instructions enabled.

           arc601_mul64
               Compile for ARC 601 CPU with "norm" and "mul64"-family instructions enabled.

           nps400
               Compile for ARC 700 on NPS400 chip.

           em_mini
               Compile for ARC EM minimalist configuration featuring reduced register set.

       -mdpfp
       -mdpfp-compact
           Generate double-precision FPX instructions, tuned for the compact implementation.

       -mdpfp-fast
           Generate double-precision FPX instructions, tuned for the fast implementation.

       -mno-dpfp-lrsr
           Disable "lr" and "sr" instructions from using FPX extension aux registers.

       -mea
           Generate extended arithmetic instructions.  Currently only "divaw", "adds", "subs", and
           "sat16" are supported.  Only valid for -mcpu=ARC700.

       -mno-mpy
           Do not generate "mpy"-family instructions for ARC700.  This option is deprecated.

       -mmul32x16
           Generate 32x16-bit multiply and multiply-accumulate instructions.

       -mmul64
           Generate "mul64" and "mulu64" instructions.  Only valid for -mcpu=ARC600.

       -mnorm
           Generate "norm" instructions.  This is the default if -mcpu=ARC700 is in effect.

       -mspfp
       -mspfp-compact
           Generate single-precision FPX instructions, tuned for the compact implementation.

       -mspfp-fast
           Generate single-precision FPX instructions, tuned for the fast implementation.

       -msimd
           Enable generation of ARC SIMD instructions via target-specific builtins.  Only valid for
           -mcpu=ARC700.

       -msoft-float
           This option ignored; it is provided for compatibility purposes only.  Software floating-
           point code is emitted by default, and this default can overridden by FPX options; -mspfp,
           -mspfp-compact, or -mspfp-fast for single precision, and -mdpfp, -mdpfp-compact, or
           -mdpfp-fast for double precision.

       -mswap
           Generate "swap" instructions.

       -matomic
           This enables use of the locked load/store conditional extension to implement atomic
           memory built-in functions.  Not available for ARC 6xx or ARC EM cores.

       -mdiv-rem
           Enable "div" and "rem" instructions for ARCv2 cores.

       -mcode-density
           Enable code density instructions for ARC EM.  This option is on by default for ARC HS.

       -mll64
           Enable double load/store operations for ARC HS cores.

       -mtp-regno=regno
           Specify thread pointer register number.

       -mmpy-option=multo
           Compile ARCv2 code with a multiplier design option.  You can specify the option using
           either a string or numeric value for multo.  wlh1 is the default value.  The recognized
           values are:

           0
           none
               No multiplier available.

           1
           w   16x16 multiplier, fully pipelined.  The following instructions are enabled: "mpyw"
               and "mpyuw".

           2
           wlh1
               32x32 multiplier, fully pipelined (1 stage).  The following instructions are
               additionally enabled: "mpy", "mpyu", "mpym", "mpymu", and "mpy_s".

           3
           wlh2
               32x32 multiplier, fully pipelined (2 stages).  The following instructions are
               additionally enabled: "mpy", "mpyu", "mpym", "mpymu", and "mpy_s".

           4
           wlh3
               Two 16x16 multipliers, blocking, sequential.  The following instructions are
               additionally enabled: "mpy", "mpyu", "mpym", "mpymu", and "mpy_s".

           5
           wlh4
               One 16x16 multiplier, blocking, sequential.  The following instructions are
               additionally enabled: "mpy", "mpyu", "mpym", "mpymu", and "mpy_s".

           6
           wlh5
               One 32x4 multiplier, blocking, sequential.  The following instructions are
               additionally enabled: "mpy", "mpyu", "mpym", "mpymu", and "mpy_s".

           7
           plus_dmpy
               ARC HS SIMD support.

           8
           plus_macd
               ARC HS SIMD support.

           9
           plus_qmacw
               ARC HS SIMD support.

           This option is only available for ARCv2 cores.

       -mfpu=fpu
           Enables support for specific floating-point hardware extensions for ARCv2 cores.
           Supported values for fpu are:

           fpus
               Enables support for single-precision floating-point hardware extensions.

           fpud
               Enables support for double-precision floating-point hardware extensions.  The single-
               precision floating-point extension is also enabled.  Not available for ARC EM.

           fpuda
               Enables support for double-precision floating-point hardware extensions using double-
               precision assist instructions.  The single-precision floating-point extension is also
               enabled.  This option is only available for ARC EM.

           fpuda_div
               Enables support for double-precision floating-point hardware extensions using double-
               precision assist instructions.  The single-precision floating-point, square-root, and
               divide extensions are also enabled.  This option is only available for ARC EM.

           fpuda_fma
               Enables support for double-precision floating-point hardware extensions using double-
               precision assist instructions.  The single-precision floating-point and fused
               multiply and add hardware extensions are also enabled.  This option is only available
               for ARC EM.

           fpuda_all
               Enables support for double-precision floating-point hardware extensions using double-
               precision assist instructions.  All single-precision floating-point hardware
               extensions are also enabled.  This option is only available for ARC EM.

           fpus_div
               Enables support for single-precision floating-point, square-root and divide hardware
               extensions.

           fpud_div
               Enables support for double-precision floating-point, square-root and divide hardware
               extensions.  This option includes option fpus_div. Not available for ARC EM.

           fpus_fma
               Enables support for single-precision floating-point and fused multiply and add
               hardware extensions.

           fpud_fma
               Enables support for double-precision floating-point and fused multiply and add
               hardware extensions.  This option includes option fpus_fma.  Not available for ARC
               EM.

           fpus_all
               Enables support for all single-precision floating-point hardware extensions.

           fpud_all
               Enables support for all single- and double-precision floating-point hardware
               extensions.  Not available for ARC EM.

       -mirq-ctrl-saved=register-range, blink, lp_count
           Specifies general-purposes registers that the processor automatically saves/restores on
           interrupt entry and exit.  register-range is specified as two registers separated by a
           dash.  The register range always starts with "r0", the upper limit is "fp" register.
           blink and lp_count are optional.  This option is only valid for ARC EM and ARC HS cores.

       -mrgf-banked-regs=number
           Specifies the number of registers replicated in second register bank on entry to fast
           interrupt.  Fast interrupts are interrupts with the highest priority level P0.  These
           interrupts save only PC and STATUS32 registers to avoid memory transactions during
           interrupt entry and exit sequences.  Use this option when you are using fast interrupts
           in an ARC V2 family processor.  Permitted values are 4, 8, 16, and 32.

       -mlpc-width=width
           Specify the width of the "lp_count" register.  Valid values for width are 8, 16, 20, 24,
           28 and 32 bits.  The default width is fixed to 32 bits.  If the width is less than 32,
           the compiler does not attempt to transform loops in your program to use the zero-delay
           loop mechanism unless it is known that the "lp_count" register can hold the required
           loop-counter value.  Depending on the width specified, the compiler and run-time library
           might continue to use the loop mechanism for various needs.  This option defines macro
           "__ARC_LPC_WIDTH__" with the value of width.

       -mrf16
           This option instructs the compiler to generate code for a 16-entry register file.  This
           option defines the "__ARC_RF16__" preprocessor macro.

       -mbranch-index
           Enable use of "bi" or "bih" instructions to implement jump tables.

       The following options are passed through to the assembler, and also define preprocessor macro
       symbols.

       -mdsp-packa
           Passed down to the assembler to enable the DSP Pack A extensions.  Also sets the
           preprocessor symbol "__Xdsp_packa".  This option is deprecated.

       -mdvbf
           Passed down to the assembler to enable the dual Viterbi butterfly extension.  Also sets
           the preprocessor symbol "__Xdvbf".  This option is deprecated.

       -mlock
           Passed down to the assembler to enable the locked load/store conditional extension.  Also
           sets the preprocessor symbol "__Xlock".

       -mmac-d16
           Passed down to the assembler.  Also sets the preprocessor symbol "__Xxmac_d16".  This
           option is deprecated.

       -mmac-24
           Passed down to the assembler.  Also sets the preprocessor symbol "__Xxmac_24".  This
           option is deprecated.

       -mrtsc
           Passed down to the assembler to enable the 64-bit time-stamp counter extension
           instruction.  Also sets the preprocessor symbol "__Xrtsc".  This option is deprecated.

       -mswape
           Passed down to the assembler to enable the swap byte ordering extension instruction.
           Also sets the preprocessor symbol "__Xswape".

       -mtelephony
           Passed down to the assembler to enable dual- and single-operand instructions for
           telephony.  Also sets the preprocessor symbol "__Xtelephony".  This option is deprecated.

       -mxy
           Passed down to the assembler to enable the XY memory extension.  Also sets the
           preprocessor symbol "__Xxy".

       The following options control how the assembly code is annotated:

       -misize
           Annotate assembler instructions with estimated addresses.

       -mannotate-align
           Explain what alignment considerations lead to the decision to make an instruction short
           or long.

       The following options are passed through to the linker:

       -marclinux
           Passed through to the linker, to specify use of the "arclinux" emulation.  This option is
           enabled by default in tool chains built for "arc-linux-uclibc" and "arceb-linux-uclibc"
           targets when profiling is not requested.

       -marclinux_prof
           Passed through to the linker, to specify use of the "arclinux_prof" emulation.  This
           option is enabled by default in tool chains built for "arc-linux-uclibc" and
           "arceb-linux-uclibc" targets when profiling is requested.

       The following options control the semantics of generated code:

       -mlong-calls
           Generate calls as register indirect calls, thus providing access to the full 32-bit
           address range.

       -mmedium-calls
           Don't use less than 25-bit addressing range for calls, which is the offset available for
           an unconditional branch-and-link instruction.  Conditional execution of function calls is
           suppressed, to allow use of the 25-bit range, rather than the 21-bit range with
           conditional branch-and-link.  This is the default for tool chains built for
           "arc-linux-uclibc" and "arceb-linux-uclibc" targets.

       -G num
           Put definitions of externally-visible data in a small data section if that data is no
           bigger than num bytes.  The default value of num is 4 for any ARC configuration, or 8
           when we have double load/store operations.

       -mno-sdata
           Do not generate sdata references.  This is the default for tool chains built for
           "arc-linux-uclibc" and "arceb-linux-uclibc" targets.

       -mvolatile-cache
           Use ordinarily cached memory accesses for volatile references.  This is the default.

       -mno-volatile-cache
           Enable cache bypass for volatile references.

       The following options fine tune code generation:

       -malign-call
           Do alignment optimizations for call instructions.

       -mauto-modify-reg
           Enable the use of pre/post modify with register displacement.

       -mbbit-peephole
           Enable bbit peephole2.

       -mno-brcc
           This option disables a target-specific pass in arc_reorg to generate compare-and-branch
           ("brcc") instructions.  It has no effect on generation of these instructions driven by
           the combiner pass.

       -mcase-vector-pcrel
           Use PC-relative switch case tables to enable case table shortening.  This is the default
           for -Os.

       -mcompact-casesi
           Enable compact "casesi" pattern.  This is the default for -Os, and only available for
           ARCv1 cores.  This option is deprecated.

       -mno-cond-exec
           Disable the ARCompact-specific pass to generate conditional execution instructions.

           Due to delay slot scheduling and interactions between operand numbers, literal sizes,
           instruction lengths, and the support for conditional execution, the target-independent
           pass to generate conditional execution is often lacking, so the ARC port has kept a
           special pass around that tries to find more conditional execution generation
           opportunities after register allocation, branch shortening, and delay slot scheduling
           have been done.  This pass generally, but not always, improves performance and code size,
           at the cost of extra compilation time, which is why there is an option to switch it off.
           If you have a problem with call instructions exceeding their allowable offset range
           because they are conditionalized, you should consider using -mmedium-calls instead.

       -mearly-cbranchsi
           Enable pre-reload use of the "cbranchsi" pattern.

       -mexpand-adddi
           Expand "adddi3" and "subdi3" at RTL generation time into "add.f", "adc" etc.  This option
           is deprecated.

       -mindexed-loads
           Enable the use of indexed loads.  This can be problematic because some optimizers then
           assume that indexed stores exist, which is not the case.

       -mlra
           Enable Local Register Allocation.  This is still experimental for ARC, so by default the
           compiler uses standard reload (i.e. -mno-lra).

       -mlra-priority-none
           Don't indicate any priority for target registers.

       -mlra-priority-compact
           Indicate target register priority for r0..r3 / r12..r15.

       -mlra-priority-noncompact
           Reduce target register priority for r0..r3 / r12..r15.

       -mmillicode
           When optimizing for size (using -Os), prologues and epilogues that have to save or
           restore a large number of registers are often shortened by using call to a special
           function in libgcc; this is referred to as a millicode call.  As these calls can pose
           performance issues, and/or cause linking issues when linking in a nonstandard way, this
           option is provided to turn on or off millicode call generation.

       -mcode-density-frame
           This option enable the compiler to emit "enter" and "leave" instructions.  These
           instructions are only valid for CPUs with code-density feature.

       -mmixed-code
           Tweak register allocation to help 16-bit instruction generation.  This generally has the
           effect of decreasing the average instruction size while increasing the instruction count.

       -mq-class
           Ths option is deprecated.  Enable q instruction alternatives.  This is the default for
           -Os.

       -mRcq
           Enable Rcq constraint handling.  Most short code generation depends on this.  This is the
           default.

       -mRcw
           Enable Rcw constraint handling.  Most ccfsm condexec mostly depends on this.  This is the
           default.

       -msize-level=level
           Fine-tune size optimization with regards to instruction lengths and alignment.  The
           recognized values for level are:

           0   No size optimization.  This level is deprecated and treated like 1.

           1   Short instructions are used opportunistically.

           2   In addition, alignment of loops and of code after barriers are dropped.

           3   In addition, optional data alignment is dropped, and the option Os is enabled.

           This defaults to 3 when -Os is in effect.  Otherwise, the behavior when this is not set
           is equivalent to level 1.

       -mtune=cpu
           Set instruction scheduling parameters for cpu, overriding any implied by -mcpu=.

           Supported values for cpu are

           ARC600
               Tune for ARC600 CPU.

           ARC601
               Tune for ARC601 CPU.

           ARC700
               Tune for ARC700 CPU with standard multiplier block.

           ARC700-xmac
               Tune for ARC700 CPU with XMAC block.

           ARC725D
               Tune for ARC725D CPU.

           ARC750D
               Tune for ARC750D CPU.

       -mmultcost=num
           Cost to assume for a multiply instruction, with 4 being equal to a normal instruction.

       -munalign-prob-threshold=probability
           Set probability threshold for unaligning branches.  When tuning for ARC700 and optimizing
           for speed, branches without filled delay slot are preferably emitted unaligned and long,
           unless profiling indicates that the probability for the branch to be taken is below
           probability.  The default is (REG_BR_PROB_BASE/2), i.e. 5000.

       The following options are maintained for backward compatibility, but are now deprecated and
       will be removed in a future release:

       -margonaut
           Obsolete FPX.

       -mbig-endian
       -EB Compile code for big-endian targets.  Use of these options is now deprecated.  Big-endian
           code is supported by configuring GCC to build "arceb-elf32" and "arceb-linux-uclibc"
           targets, for which big endian is the default.

       -mlittle-endian
       -EL Compile code for little-endian targets.  Use of these options is now deprecated.  Little-
           endian code is supported by configuring GCC to build "arc-elf32" and "arc-linux-uclibc"
           targets, for which little endian is the default.

       -mbarrel_shifter
           Replaced by -mbarrel-shifter.

       -mdpfp_compact
           Replaced by -mdpfp-compact.

       -mdpfp_fast
           Replaced by -mdpfp-fast.

       -mdsp_packa
           Replaced by -mdsp-packa.

       -mEA
           Replaced by -mea.

       -mmac_24
           Replaced by -mmac-24.

       -mmac_d16
           Replaced by -mmac-d16.

       -mspfp_compact
           Replaced by -mspfp-compact.

       -mspfp_fast
           Replaced by -mspfp-fast.

       -mtune=cpu
           Values arc600, arc601, arc700 and arc700-xmac for cpu are replaced by ARC600, ARC601,
           ARC700 and ARC700-xmac respectively.

       -multcost=num
           Replaced by -mmultcost.

       ARM Options

       These -m options are defined for the ARM port:

       -mabi=name
           Generate code for the specified ABI.  Permissible values are: apcs-gnu, atpcs, aapcs,
           aapcs-linux and iwmmxt.

       -mapcs-frame
           Generate a stack frame that is compliant with the ARM Procedure Call Standard for all
           functions, even if this is not strictly necessary for correct execution of the code.
           Specifying -fomit-frame-pointer with this option causes the stack frames not to be
           generated for leaf functions.  The default is -mno-apcs-frame.  This option is
           deprecated.

       -mapcs
           This is a synonym for -mapcs-frame and is deprecated.

       -mthumb-interwork
           Generate code that supports calling between the ARM and Thumb instruction sets.  Without
           this option, on pre-v5 architectures, the two instruction sets cannot be reliably used
           inside one program.  The default is -mno-thumb-interwork, since slightly larger code is
           generated when -mthumb-interwork is specified.  In AAPCS configurations this option is
           meaningless.

       -mno-sched-prolog
           Prevent the reordering of instructions in the function prologue, or the merging of those
           instruction with the instructions in the function's body.  This means that all functions
           start with a recognizable set of instructions (or in fact one of a choice from a small
           set of different function prologues), and this information can be used to locate the
           start of functions inside an executable piece of code.  The default is -msched-prolog.

       -mfloat-abi=name
           Specifies which floating-point ABI to use.  Permissible values are: soft, softfp and
           hard.

           Specifying soft causes GCC to generate output containing library calls for floating-point
           operations.  softfp allows the generation of code using hardware floating-point
           instructions, but still uses the soft-float calling conventions.  hard allows generation
           of floating-point instructions and uses FPU-specific calling conventions.

           The default depends on the specific target configuration.  Note that the hard-float and
           soft-float ABIs are not link-compatible; you must compile your entire program with the
           same ABI, and link with a compatible set of libraries.

       -mgeneral-regs-only
           Generate code which uses only the general-purpose registers.  This will prevent the
           compiler from using floating-point and Advanced SIMD registers but will not impose any
           restrictions on the assembler.

       -mlittle-endian
           Generate code for a processor running in little-endian mode.  This is the default for all
           standard configurations.

       -mbig-endian
           Generate code for a processor running in big-endian mode; the default is to compile code
           for a little-endian processor.

       -mbe8
       -mbe32
           When linking a big-endian image select between BE8 and BE32 formats.  The option has no
           effect for little-endian images and is ignored.  The default is dependent on the selected
           target architecture.  For ARMv6 and later architectures the default is BE8, for older
           architectures the default is BE32.  BE32 format has been deprecated by ARM.

       -march=name[+extension...]
           This specifies the name of the target ARM architecture.  GCC uses this name to determine
           what kind of instructions it can emit when generating assembly code.  This option can be
           used in conjunction with or instead of the -mcpu= option.

           Permissible names are: armv4t, armv5t, armv5te, armv6, armv6j, armv6k, armv6kz, armv6t2,
           armv6z, armv6zk, armv7, armv7-a, armv7ve, armv8-a, armv8.1-a, armv8.2-a, armv8.3-a,
           armv8.4-a, armv8.5-a, armv8.6-a, armv7-r, armv8-r, armv6-m, armv6s-m, armv7-m, armv7e-m,
           armv8-m.base, armv8-m.main, armv8.1-m.main, iwmmxt and iwmmxt2.

           Additionally, the following architectures, which lack support for the Thumb execution
           state, are recognized but support is deprecated: armv4.

           Many of the architectures support extensions.  These can be added by appending +extension
           to the architecture name.  Extension options are processed in order and capabilities
           accumulate.  An extension will also enable any necessary base extensions upon which it
           depends.  For example, the +crypto extension will always enable the +simd extension.  The
           exception to the additive construction is for extensions that are prefixed with +no...:
           these extensions disable the specified option and any other extensions that may depend on
           the presence of that extension.

           For example, -march=armv7-a+simd+nofp+vfpv4 is equivalent to writing -march=armv7-a+vfpv4
           since the +simd option is entirely disabled by the +nofp option that follows it.

           Most extension names are generically named, but have an effect that is dependent upon the
           architecture to which it is applied.  For example, the +simd option can be applied to
           both armv7-a and armv8-a architectures, but will enable the original ARMv7-A Advanced
           SIMD (Neon) extensions for armv7-a and the ARMv8-A variant for armv8-a.

           The table below lists the supported extensions for each architecture.  Architectures not
           mentioned do not support any extensions.

           armv5te
           armv6
           armv6j
           armv6k
           armv6kz
           armv6t2
           armv6z
           armv6zk
               +fp The VFPv2 floating-point instructions.  The extension +vfpv2 can be used as an
                   alias for this extension.

               +nofp
                   Disable the floating-point instructions.

           armv7
               The common subset of the ARMv7-A, ARMv7-R and ARMv7-M architectures.

               +fp The VFPv3 floating-point instructions, with 16 double-precision registers.  The
                   extension +vfpv3-d16 can be used as an alias for this extension.  Note that
                   floating-point is not supported by the base ARMv7-M architecture, but is
                   compatible with both the ARMv7-A and ARMv7-R architectures.

               +nofp
                   Disable the floating-point instructions.

           armv7-a
               +mp The multiprocessing extension.

               +sec
                   The security extension.

               +fp The VFPv3 floating-point instructions, with 16 double-precision registers.  The
                   extension +vfpv3-d16 can be used as an alias for this extension.

               +simd
                   The Advanced SIMD (Neon) v1 and the VFPv3 floating-point instructions.  The
                   extensions +neon and +neon-vfpv3 can be used as aliases for this extension.

               +vfpv3
                   The VFPv3 floating-point instructions, with 32 double-precision registers.

               +vfpv3-d16-fp16
                   The VFPv3 floating-point instructions, with 16 double-precision registers and the
                   half-precision floating-point conversion operations.

               +vfpv3-fp16
                   The VFPv3 floating-point instructions, with 32 double-precision registers and the
                   half-precision floating-point conversion operations.

               +vfpv4-d16
                   The VFPv4 floating-point instructions, with 16 double-precision registers.

               +vfpv4
                   The VFPv4 floating-point instructions, with 32 double-precision registers.

               +neon-fp16
                   The Advanced SIMD (Neon) v1 and the VFPv3 floating-point instructions, with the
                   half-precision floating-point conversion operations.

               +neon-vfpv4
                   The Advanced SIMD (Neon) v2 and the VFPv4 floating-point instructions.

               +nosimd
                   Disable the Advanced SIMD instructions (does not disable floating point).

               +nofp
                   Disable the floating-point and Advanced SIMD instructions.

           armv7ve
               The extended version of the ARMv7-A architecture with support for virtualization.

               +fp The VFPv4 floating-point instructions, with 16 double-precision registers.  The
                   extension +vfpv4-d16 can be used as an alias for this extension.

               +simd
                   The Advanced SIMD (Neon) v2 and the VFPv4 floating-point instructions.  The
                   extension +neon-vfpv4 can be used as an alias for this extension.

               +vfpv3-d16
                   The VFPv3 floating-point instructions, with 16 double-precision registers.

               +vfpv3
                   The VFPv3 floating-point instructions, with 32 double-precision registers.

               +vfpv3-d16-fp16
                   The VFPv3 floating-point instructions, with 16 double-precision registers and the
                   half-precision floating-point conversion operations.

               +vfpv3-fp16
                   The VFPv3 floating-point instructions, with 32 double-precision registers and the
                   half-precision floating-point conversion operations.

               +vfpv4-d16
                   The VFPv4 floating-point instructions, with 16 double-precision registers.

               +vfpv4
                   The VFPv4 floating-point instructions, with 32 double-precision registers.

               +neon
                   The Advanced SIMD (Neon) v1 and the VFPv3 floating-point instructions.  The
                   extension +neon-vfpv3 can be used as an alias for this extension.

               +neon-fp16
                   The Advanced SIMD (Neon) v1 and the VFPv3 floating-point instructions, with the
                   half-precision floating-point conversion operations.

               +nosimd
                   Disable the Advanced SIMD instructions (does not disable floating point).

               +nofp
                   Disable the floating-point and Advanced SIMD instructions.

           armv8-a
               +crc
                   The Cyclic Redundancy Check (CRC) instructions.

               +simd
                   The ARMv8-A Advanced SIMD and floating-point instructions.

               +crypto
                   The cryptographic instructions.

               +nocrypto
                   Disable the cryptographic instructions.

               +nofp
                   Disable the floating-point, Advanced SIMD and cryptographic instructions.

               +sb Speculation Barrier Instruction.

               +predres
                   Execution and Data Prediction Restriction Instructions.

           armv8.1-a
               +simd
                   The ARMv8.1-A Advanced SIMD and floating-point instructions.

               +crypto
                   The cryptographic instructions.  This also enables the Advanced SIMD and
                   floating-point instructions.

               +nocrypto
                   Disable the cryptographic instructions.

               +nofp
                   Disable the floating-point, Advanced SIMD and cryptographic instructions.

               +sb Speculation Barrier Instruction.

               +predres
                   Execution and Data Prediction Restriction Instructions.

           armv8.2-a
           armv8.3-a
               +fp16
                   The half-precision floating-point data processing instructions.  This also
                   enables the Advanced SIMD and floating-point instructions.

               +fp16fml
                   The half-precision floating-point fmla extension.  This also enables the half-
                   precision floating-point extension and Advanced SIMD and floating-point
                   instructions.

               +simd
                   The ARMv8.1-A Advanced SIMD and floating-point instructions.

               +crypto
                   The cryptographic instructions.  This also enables the Advanced SIMD and
                   floating-point instructions.

               +dotprod
                   Enable the Dot Product extension.  This also enables Advanced SIMD instructions.

               +nocrypto
                   Disable the cryptographic extension.

               +nofp
                   Disable the floating-point, Advanced SIMD and cryptographic instructions.

               +sb Speculation Barrier Instruction.

               +predres
                   Execution and Data Prediction Restriction Instructions.

               +i8mm
                   8-bit Integer Matrix Multiply instructions.  This also enables Advanced SIMD and
                   floating-point instructions.

               +bf16
                   Brain half-precision floating-point instructions.  This also enables Advanced
                   SIMD and floating-point instructions.

           armv8.4-a
               +fp16
                   The half-precision floating-point data processing instructions.  This also
                   enables the Advanced SIMD and floating-point instructions as well as the Dot
                   Product extension and the half-precision floating-point fmla extension.

               +simd
                   The ARMv8.3-A Advanced SIMD and floating-point instructions as well as the Dot
                   Product extension.

               +crypto
                   The cryptographic instructions.  This also enables the Advanced SIMD and
                   floating-point instructions as well as the Dot Product extension.

               +nocrypto
                   Disable the cryptographic extension.

               +nofp
                   Disable the floating-point, Advanced SIMD and cryptographic instructions.

               +sb Speculation Barrier Instruction.

               +predres
                   Execution and Data Prediction Restriction Instructions.

               +i8mm
                   8-bit Integer Matrix Multiply instructions.  This also enables Advanced SIMD and
                   floating-point instructions.

               +bf16
                   Brain half-precision floating-point instructions.  This also enables Advanced
                   SIMD and floating-point instructions.

           armv8.5-a
               +fp16
                   The half-precision floating-point data processing instructions.  This also
                   enables the Advanced SIMD and floating-point instructions as well as the Dot
                   Product extension and the half-precision floating-point fmla extension.

               +simd
                   The ARMv8.3-A Advanced SIMD and floating-point instructions as well as the Dot
                   Product extension.

               +crypto
                   The cryptographic instructions.  This also enables the Advanced SIMD and
                   floating-point instructions as well as the Dot Product extension.

               +nocrypto
                   Disable the cryptographic extension.

               +nofp
                   Disable the floating-point, Advanced SIMD and cryptographic instructions.

               +i8mm
                   8-bit Integer Matrix Multiply instructions.  This also enables Advanced SIMD and
                   floating-point instructions.

               +bf16
                   Brain half-precision floating-point instructions.  This also enables Advanced
                   SIMD and floating-point instructions.

           armv8.6-a
               +fp16
                   The half-precision floating-point data processing instructions.  This also
                   enables the Advanced SIMD and floating-point instructions as well as the Dot
                   Product extension and the half-precision floating-point fmla extension.

               +simd
                   The ARMv8.3-A Advanced SIMD and floating-point instructions as well as the Dot
                   Product extension.

               +crypto
                   The cryptographic instructions.  This also enables the Advanced SIMD and
                   floating-point instructions as well as the Dot Product extension.

               +nocrypto
                   Disable the cryptographic extension.

               +nofp
                   Disable the floating-point, Advanced SIMD and cryptographic instructions.

               +i8mm
                   8-bit Integer Matrix Multiply instructions.  This also enables Advanced SIMD and
                   floating-point instructions.

               +bf16
                   Brain half-precision floating-point instructions.  This also enables Advanced
                   SIMD and floating-point instructions.

           armv7-r
               +fp.sp
                   The single-precision VFPv3 floating-point instructions.  The extension +vfpv3xd
                   can be used as an alias for this extension.

               +fp The VFPv3 floating-point instructions with 16 double-precision registers.  The
                   extension +vfpv3-d16 can be used as an alias for this extension.

               +vfpv3xd-d16-fp16
                   The single-precision VFPv3 floating-point instructions with 16 double-precision
                   registers and the half-precision floating-point conversion operations.

               +vfpv3-d16-fp16
                   The VFPv3 floating-point instructions with 16 double-precision registers and the
                   half-precision floating-point conversion operations.

               +nofp
                   Disable the floating-point extension.

               +idiv
                   The ARM-state integer division instructions.

               +noidiv
                   Disable the ARM-state integer division extension.

           armv7e-m
               +fp The single-precision VFPv4 floating-point instructions.

               +fpv5
                   The single-precision FPv5 floating-point instructions.

               +fp.dp
                   The single- and double-precision FPv5 floating-point instructions.

               +nofp
                   Disable the floating-point extensions.

           armv8.1-m.main
               +dsp
                   The DSP instructions.

               +mve
                   The M-Profile Vector Extension (MVE) integer instructions.

               +mve.fp
                   The M-Profile Vector Extension (MVE) integer and single precision floating-point
                   instructions.

               +fp The single-precision floating-point instructions.

               +fp.dp
                   The single- and double-precision floating-point instructions.

               +nofp
                   Disable the floating-point extension.

               +cdecp0, +cdecp1, ... , +cdecp7
                   Enable the Custom Datapath Extension (CDE) on selected coprocessors according to
                   the numbers given in the options in the range 0 to 7.

           armv8-m.main
               +dsp
                   The DSP instructions.

               +nodsp
                   Disable the DSP extension.

               +fp The single-precision floating-point instructions.

               +fp.dp
                   The single- and double-precision floating-point instructions.

               +nofp
                   Disable the floating-point extension.

               +cdecp0, +cdecp1, ... , +cdecp7
                   Enable the Custom Datapath Extension (CDE) on selected coprocessors according to
                   the numbers given in the options in the range 0 to 7.

           armv8-r
               +crc
                   The Cyclic Redundancy Check (CRC) instructions.

               +fp.sp
                   The single-precision FPv5 floating-point instructions.

               +simd
                   The ARMv8-A Advanced SIMD and floating-point instructions.

               +crypto
                   The cryptographic instructions.

               +nocrypto
                   Disable the cryptographic instructions.

               +nofp
                   Disable the floating-point, Advanced SIMD and cryptographic instructions.

           -march=native causes the compiler to auto-detect the architecture of the build computer.
           At present, this feature is only supported on GNU/Linux, and not all architectures are
           recognized.  If the auto-detect is unsuccessful the option has no effect.

       -mtune=name
           This option specifies the name of the target ARM processor for which GCC should tune the
           performance of the code.  For some ARM implementations better performance can be obtained
           by using this option.  Permissible names are: arm7tdmi, arm7tdmi-s, arm710t, arm720t,
           arm740t, strongarm, strongarm110, strongarm1100, 0strongarm1110, arm8, arm810, arm9,
           arm9e, arm920, arm920t, arm922t, arm946e-s, arm966e-s, arm968e-s, arm926ej-s, arm940t,
           arm9tdmi, arm10tdmi, arm1020t, arm1026ej-s, arm10e, arm1020e, arm1022e, arm1136j-s,
           arm1136jf-s, mpcore, mpcorenovfp, arm1156t2-s, arm1156t2f-s, arm1176jz-s, arm1176jzf-s,
           generic-armv7-a, cortex-a5, cortex-a7, cortex-a8, cortex-a9, cortex-a12, cortex-a15,
           cortex-a17, cortex-a32, cortex-a35, cortex-a53, cortex-a55, cortex-a57, cortex-a72,
           cortex-a73, cortex-a75, cortex-a76, cortex-a76ae, cortex-a77, cortex-a78, cortex-a78ae,
           cortex-a78c, ares, cortex-r4, cortex-r4f, cortex-r5, cortex-r7, cortex-r8, cortex-r52,
           cortex-m0, cortex-m0plus, cortex-m1, cortex-m3, cortex-m4, cortex-m7, cortex-m23,
           cortex-m33, cortex-m35p, cortex-m55, cortex-x1, cortex-m1.small-multiply,
           cortex-m0.small-multiply, cortex-m0plus.small-multiply, exynos-m1, marvell-pj4,
           neoverse-n1, neoverse-n2, neoverse-v1, xscale, iwmmxt, iwmmxt2, ep9312, fa526, fa626,
           fa606te, fa626te, fmp626, fa726te, xgene1.

           Additionally, this option can specify that GCC should tune the performance of the code
           for a big.LITTLE system.  Permissible names are: cortex-a15.cortex-a7,
           cortex-a17.cortex-a7, cortex-a57.cortex-a53, cortex-a72.cortex-a53,
           cortex-a72.cortex-a35, cortex-a73.cortex-a53, cortex-a75.cortex-a55,
           cortex-a76.cortex-a55.

           -mtune=generic-arch specifies that GCC should tune the performance for a blend of
           processors within architecture arch.  The aim is to generate code that run well on the
           current most popular processors, balancing between optimizations that benefit some CPUs
           in the range, and avoiding performance pitfalls of other CPUs.  The effects of this
           option may change in future GCC versions as CPU models come and go.

           -mtune permits the same extension options as -mcpu, but the extension options do not
           affect the tuning of the generated code.

           -mtune=native causes the compiler to auto-detect the CPU of the build computer.  At
           present, this feature is only supported on GNU/Linux, and not all architectures are
           recognized.  If the auto-detect is unsuccessful the option has no effect.

       -mcpu=name[+extension...]
           This specifies the name of the target ARM processor.  GCC uses this name to derive the
           name of the target ARM architecture (as if specified by -march) and the ARM processor
           type for which to tune for performance (as if specified by -mtune).  Where this option is
           used in conjunction with -march or -mtune, those options take precedence over the
           appropriate part of this option.

           Many of the supported CPUs implement optional architectural extensions.  Where this is so
           the architectural extensions are normally enabled by default.  If implementations that
           lack the extension exist, then the extension syntax can be used to disable those
           extensions that have been omitted.  For floating-point and Advanced SIMD (Neon)
           instructions, the settings of the options -mfloat-abi and -mfpu must also be considered:
           floating-point and Advanced SIMD instructions will only be used if -mfloat-abi is not set
           to soft; and any setting of -mfpu other than auto will override the available floating-
           point and SIMD extension instructions.

           For example, cortex-a9 can be found in three major configurations: integer only, with
           just a floating-point unit or with floating-point and Advanced SIMD.  The default is to
           enable all the instructions, but the extensions +nosimd and +nofp can be used to disable
           just the SIMD or both the SIMD and floating-point instructions respectively.

           Permissible names for this option are the same as those for -mtune.

           The following extension options are common to the listed CPUs:

           +nodsp
               Disable the DSP instructions on cortex-m33, cortex-m35p.

           +nofp
               Disables the floating-point instructions on arm9e, arm946e-s, arm966e-s, arm968e-s,
               arm10e, arm1020e, arm1022e, arm926ej-s, arm1026ej-s, cortex-r5, cortex-r7, cortex-r8,
               cortex-m4, cortex-m7, cortex-m33 and cortex-m35p.  Disables the floating-point and
               SIMD instructions on generic-armv7-a, cortex-a5, cortex-a7, cortex-a8, cortex-a9,
               cortex-a12, cortex-a15, cortex-a17, cortex-a15.cortex-a7, cortex-a17.cortex-a7,
               cortex-a32, cortex-a35, cortex-a53 and cortex-a55.

           +nofp.dp
               Disables the double-precision component of the floating-point instructions on
               cortex-r5, cortex-r7, cortex-r8, cortex-r52 and cortex-m7.

           +nosimd
               Disables the SIMD (but not floating-point) instructions on generic-armv7-a,
               cortex-a5, cortex-a7 and cortex-a9.

           +crypto
               Enables the cryptographic instructions on cortex-a32, cortex-a35, cortex-a53,
               cortex-a55, cortex-a57, cortex-a72, cortex-a73, cortex-a75, exynos-m1, xgene1,
               cortex-a57.cortex-a53, cortex-a72.cortex-a53, cortex-a73.cortex-a35,
               cortex-a73.cortex-a53 and cortex-a75.cortex-a55.

           Additionally the generic-armv7-a pseudo target defaults to VFPv3 with 16 double-precision
           registers.  It supports the following extension options: mp, sec, vfpv3-d16, vfpv3,
           vfpv3-d16-fp16, vfpv3-fp16, vfpv4-d16, vfpv4, neon, neon-vfpv3, neon-fp16, neon-vfpv4.
           The meanings are the same as for the extensions to -march=armv7-a.

           -mcpu=generic-arch is also permissible, and is equivalent to -march=arch
           -mtune=generic-arch.  See -mtune for more information.

           -mcpu=native causes the compiler to auto-detect the CPU of the build computer.  At
           present, this feature is only supported on GNU/Linux, and not all architectures are
           recognized.  If the auto-detect is unsuccessful the option has no effect.

       -mfpu=name
           This specifies what floating-point hardware (or hardware emulation) is available on the
           target.  Permissible names are: auto, vfpv2, vfpv3, vfpv3-fp16, vfpv3-d16,
           vfpv3-d16-fp16, vfpv3xd, vfpv3xd-fp16, neon-vfpv3, neon-fp16, vfpv4, vfpv4-d16,
           fpv4-sp-d16, neon-vfpv4, fpv5-d16, fpv5-sp-d16, fp-armv8, neon-fp-armv8 and
           crypto-neon-fp-armv8.  Note that neon is an alias for neon-vfpv3 and vfp is an alias for
           vfpv2.

           The setting auto is the default and is special.  It causes the compiler to select the
           floating-point and Advanced SIMD instructions based on the settings of -mcpu and -march.

           If the selected floating-point hardware includes the NEON extension (e.g. -mfpu=neon),
           note that floating-point operations are not generated by GCC's auto-vectorization pass
           unless -funsafe-math-optimizations is also specified.  This is because NEON hardware does
           not fully implement the IEEE 754 standard for floating-point arithmetic (in particular
           denormal values are treated as zero), so the use of NEON instructions may lead to a loss
           of precision.

           You can also set the fpu name at function level by using the "target("fpu=")" function
           attributes or pragmas.

       -mfp16-format=name
           Specify the format of the "__fp16" half-precision floating-point type.  Permissible names
           are none, ieee, and alternative; the default is none, in which case the "__fp16" type is
           not defined.

       -mstructure-size-boundary=n
           The sizes of all structures and unions are rounded up to a multiple of the number of bits
           set by this option.  Permissible values are 8, 32 and 64.  The default value varies for
           different toolchains.  For the COFF targeted toolchain the default value is 8.  A value
           of 64 is only allowed if the underlying ABI supports it.

           Specifying a larger number can produce faster, more efficient code, but can also increase
           the size of the program.  Different values are potentially incompatible.  Code compiled
           with one value cannot necessarily expect to work with code or libraries compiled with
           another value, if they exchange information using structures or unions.

           This option is deprecated.

       -mabort-on-noreturn
           Generate a call to the function "abort" at the end of a "noreturn" function.  It is
           executed if the function tries to return.

       -mlong-calls
       -mno-long-calls
           Tells the compiler to perform function calls by first loading the address of the function
           into a register and then performing a subroutine call on this register.  This switch is
           needed if the target function lies outside of the 64-megabyte addressing range of the
           offset-based version of subroutine call instruction.

           Even if this switch is enabled, not all function calls are turned into long calls.  The
           heuristic is that static functions, functions that have the "short_call" attribute,
           functions that are inside the scope of a "#pragma no_long_calls" directive, and functions
           whose definitions have already been compiled within the current compilation unit are not
           turned into long calls.  The exceptions to this rule are that weak function definitions,
           functions with the "long_call" attribute or the "section" attribute, and functions that
           are within the scope of a "#pragma long_calls" directive are always turned into long
           calls.

           This feature is not enabled by default.  Specifying -mno-long-calls restores the default
           behavior, as does placing the function calls within the scope of a "#pragma
           long_calls_off" directive.  Note these switches have no effect on how the compiler
           generates code to handle function calls via function pointers.

       -msingle-pic-base
           Treat the register used for PIC addressing as read-only, rather than loading it in the
           prologue for each function.  The runtime system is responsible for initializing this
           register with an appropriate value before execution begins.

       -mpic-register=reg
           Specify the register to be used for PIC addressing.  For standard PIC base case, the
           default is any suitable register determined by compiler.  For single PIC base case, the
           default is R9 if target is EABI based or stack-checking is enabled, otherwise the default
           is R10.

       -mpic-data-is-text-relative
           Assume that the displacement between the text and data segments is fixed at static link
           time.  This permits using PC-relative addressing operations to access data known to be in
           the data segment.  For non-VxWorks RTP targets, this option is enabled by default.  When
           disabled on such targets, it will enable -msingle-pic-base by default.

       -mpoke-function-name
           Write the name of each function into the text section, directly preceding the function
           prologue.  The generated code is similar to this:

                        t0
                            .ascii "arm_poke_function_name", 0
                            .align
                        t1
                            .word 0xff000000 + (t1 - t0)
                        arm_poke_function_name
                            mov     ip, sp
                            stmfd   sp!, {fp, ip, lr, pc}
                            sub     fp, ip, #4

           When performing a stack backtrace, code can inspect the value of "pc" stored at "fp + 0".
           If the trace function then looks at location "pc - 12" and the top 8 bits are set, then
           we know that there is a function name embedded immediately preceding this location and
           has length "((pc[-3]) & 0xff000000)".

       -mthumb
       -marm
           Select between generating code that executes in ARM and Thumb states.  The default for
           most configurations is to generate code that executes in ARM state, but the default can
           be changed by configuring GCC with the --with-mode=state configure option.

           You can also override the ARM and Thumb mode for each function by using the
           "target("thumb")" and "target("arm")" function attributes or pragmas.

       -mflip-thumb
           Switch ARM/Thumb modes on alternating functions.  This option is provided for regression
           testing of mixed Thumb/ARM code generation, and is not intended for ordinary use in
           compiling code.

       -mtpcs-frame
           Generate a stack frame that is compliant with the Thumb Procedure Call Standard for all
           non-leaf functions.  (A leaf function is one that does not call any other functions.)
           The default is -mno-tpcs-frame.

       -mtpcs-leaf-frame
           Generate a stack frame that is compliant with the Thumb Procedure Call Standard for all
           leaf functions.  (A leaf function is one that does not call any other functions.)  The
           default is -mno-apcs-leaf-frame.

       -mcallee-super-interworking
           Gives all externally visible functions in the file being compiled an ARM instruction set
           header which switches to Thumb mode before executing the rest of the function.  This
           allows these functions to be called from non-interworking code.  This option is not valid
           in AAPCS configurations because interworking is enabled by default.

       -mcaller-super-interworking
           Allows calls via function pointers (including virtual functions) to execute correctly
           regardless of whether the target code has been compiled for interworking or not.  There
           is a small overhead in the cost of executing a function pointer if this option is
           enabled.  This option is not valid in AAPCS configurations because interworking is
           enabled by default.

       -mtp=name
           Specify the access model for the thread local storage pointer.  The valid models are
           soft, which generates calls to "__aeabi_read_tp", cp15, which fetches the thread pointer
           from "cp15" directly (supported in the arm6k architecture), and auto, which uses the best
           available method for the selected processor.  The default setting is auto.

       -mtls-dialect=dialect
           Specify the dialect to use for accessing thread local storage.  Two dialects are
           supported---gnu and gnu2.  The gnu dialect selects the original GNU scheme for supporting
           local and global dynamic TLS models.  The gnu2 dialect selects the GNU descriptor scheme,
           which provides better performance for shared libraries.  The GNU descriptor scheme is
           compatible with the original scheme, but does require new assembler, linker and library
           support.  Initial and local exec TLS models are unaffected by this option and always use
           the original scheme.

       -mword-relocations
           Only generate absolute relocations on word-sized values (i.e. R_ARM_ABS32).  This is
           enabled by default on targets (uClinux, SymbianOS) where the runtime loader imposes this
           restriction, and when -fpic or -fPIC is specified. This option conflicts with
           -mslow-flash-data.

       -mfix-cortex-m3-ldrd
           Some Cortex-M3 cores can cause data corruption when "ldrd" instructions with overlapping
           destination and base registers are used.  This option avoids generating these
           instructions.  This option is enabled by default when -mcpu=cortex-m3 is specified.

       -munaligned-access
       -mno-unaligned-access
           Enables (or disables) reading and writing of 16- and 32- bit values from addresses that
           are not 16- or 32- bit aligned.  By default unaligned access is disabled for all
           pre-ARMv6, all ARMv6-M and for ARMv8-M Baseline architectures, and enabled for all other
           architectures.  If unaligned access is not enabled then words in packed data structures
           are accessed a byte at a time.

           The ARM attribute "Tag_CPU_unaligned_access" is set in the generated object file to
           either true or false, depending upon the setting of this option.  If unaligned access is
           enabled then the preprocessor symbol "__ARM_FEATURE_UNALIGNED" is also defined.

       -mneon-for-64bits
           This option is deprecated and has no effect.

       -mslow-flash-data
           Assume loading data from flash is slower than fetching instruction.  Therefore literal
           load is minimized for better performance.  This option is only supported when compiling
           for ARMv7 M-profile and off by default. It conflicts with -mword-relocations.

       -masm-syntax-unified
           Assume inline assembler is using unified asm syntax.  The default is currently off which
           implies divided syntax.  This option has no impact on Thumb2. However, this may change in
           future releases of GCC.  Divided syntax should be considered deprecated.

       -mrestrict-it
           Restricts generation of IT blocks to conform to the rules of ARMv8-A.  IT blocks can only
           contain a single 16-bit instruction from a select set of instructions. This option is on
           by default for ARMv8-A Thumb mode.

       -mprint-tune-info
           Print CPU tuning information as comment in assembler file.  This is an option used only
           for regression testing of the compiler and not intended for ordinary use in compiling
           code.  This option is disabled by default.

       -mverbose-cost-dump
           Enable verbose cost model dumping in the debug dump files.  This option is provided for
           use in debugging the compiler.

       -mpure-code
           Do not allow constant data to be placed in code sections.  Additionally, when compiling
           for ELF object format give all text sections the ELF processor-specific section attribute
           "SHF_ARM_PURECODE".  This option is only available when generating non-pic code for
           M-profile targets.

       -mcmse
           Generate secure code as per the "ARMv8-M Security Extensions: Requirements on Development
           Tools Engineering Specification", which can be found on
           <https://developer.arm.com/documentation/ecm0359818/latest/>.

       -mfix-cmse-cve-2021-35465
           Mitigate against a potential security issue with the "VLLDM" instruction in some
           M-profile devices when using CMSE (CVE-2021-365465).  This option is enabled by default
           when the option -mcpu= is used with "cortex-m33", "cortex-m35p" or "cortex-m55".  The
           option -mno-fix-cmse-cve-2021-35465 can be used to disable the mitigation.

       -mfdpic
       -mno-fdpic
           Select the FDPIC ABI, which uses 64-bit function descriptors to represent pointers to
           functions.  When the compiler is configured for "arm-*-uclinuxfdpiceabi" targets, this
           option is on by default and implies -fPIE if none of the PIC/PIE-related options is
           provided.  On other targets, it only enables the FDPIC-specific code generation features,
           and the user should explicitly provide the PIC/PIE-related options as needed.

           Note that static linking is not supported because it would still involve the dynamic
           linker when the program self-relocates.  If such behavior is acceptable, use -static and
           -Wl,-dynamic-linker options.

           The opposite -mno-fdpic option is useful (and required) to build the Linux kernel using
           the same ("arm-*-uclinuxfdpiceabi") toolchain as the one used to build the userland
           programs.

       AVR Options

       These options are defined for AVR implementations:

       -mmcu=mcu
           Specify Atmel AVR instruction set architectures (ISA) or MCU type.

           The default for this option is avr2.

           GCC supports the following AVR devices and ISAs:

           "avr2"
               "Classic" devices with up to 8 KiB of program memory.  mcu = "attiny22", "attiny26",
               "at90s2313", "at90s2323", "at90s2333", "at90s2343", "at90s4414", "at90s4433",
               "at90s4434", "at90c8534", "at90s8515", "at90s8535".

           "avr25"
               "Classic" devices with up to 8 KiB of program memory and with the "MOVW" instruction.
               mcu = "attiny13", "attiny13a", "attiny24", "attiny24a", "attiny25", "attiny261",
               "attiny261a", "attiny2313", "attiny2313a", "attiny43u", "attiny44", "attiny44a",
               "attiny45", "attiny48", "attiny441", "attiny461", "attiny461a", "attiny4313",
               "attiny84", "attiny84a", "attiny85", "attiny87", "attiny88", "attiny828",
               "attiny841", "attiny861", "attiny861a", "ata5272", "ata6616c", "at86rf401".

           "avr3"
               "Classic" devices with 16 KiB up to 64 KiB of program memory.  mcu = "at76c711",
               "at43usb355".

           "avr31"
               "Classic" devices with 128 KiB of program memory.  mcu = "atmega103", "at43usb320".

           "avr35"
               "Classic" devices with 16 KiB up to 64 KiB of program memory and with the "MOVW"
               instruction.  mcu = "attiny167", "attiny1634", "atmega8u2", "atmega16u2",
               "atmega32u2", "ata5505", "ata6617c", "ata664251", "at90usb82", "at90usb162".

           "avr4"
               "Enhanced" devices with up to 8 KiB of program memory.  mcu = "atmega48",
               "atmega48a", "atmega48p", "atmega48pa", "atmega48pb", "atmega8", "atmega8a",
               "atmega8hva", "atmega88", "atmega88a", "atmega88p", "atmega88pa", "atmega88pb",
               "atmega8515", "atmega8535", "ata6285", "ata6286", "ata6289", "ata6612c", "at90pwm1",
               "at90pwm2", "at90pwm2b", "at90pwm3", "at90pwm3b", "at90pwm81".

           "avr5"
               "Enhanced" devices with 16 KiB up to 64 KiB of program memory.  mcu = "atmega16",
               "atmega16a", "atmega16hva", "atmega16hva2", "atmega16hvb", "atmega16hvbrevb",
               "atmega16m1", "atmega16u4", "atmega161", "atmega162", "atmega163", "atmega164a",
               "atmega164p", "atmega164pa", "atmega165", "atmega165a", "atmega165p", "atmega165pa",
               "atmega168", "atmega168a", "atmega168p", "atmega168pa", "atmega168pb", "atmega169",
               "atmega169a", "atmega169p", "atmega169pa", "atmega32", "atmega32a", "atmega32c1",
               "atmega32hvb", "atmega32hvbrevb", "atmega32m1", "atmega32u4", "atmega32u6",
               "atmega323", "atmega324a", "atmega324p", "atmega324pa", "atmega325", "atmega325a",
               "atmega325p", "atmega325pa", "atmega328", "atmega328p", "atmega328pb", "atmega329",
               "atmega329a", "atmega329p", "atmega329pa", "atmega3250", "atmega3250a",
               "atmega3250p", "atmega3250pa", "atmega3290", "atmega3290a", "atmega3290p",
               "atmega3290pa", "atmega406", "atmega64", "atmega64a", "atmega64c1", "atmega64hve",
               "atmega64hve2", "atmega64m1", "atmega64rfr2", "atmega640", "atmega644", "atmega644a",
               "atmega644p", "atmega644pa", "atmega644rfr2", "atmega645", "atmega645a",
               "atmega645p", "atmega649", "atmega649a", "atmega649p", "atmega6450", "atmega6450a",
               "atmega6450p", "atmega6490", "atmega6490a", "atmega6490p", "ata5795", "ata5790",
               "ata5790n", "ata5791", "ata6613c", "ata6614q", "ata5782", "ata5831", "ata8210",
               "ata8510", "ata5702m322", "at90pwm161", "at90pwm216", "at90pwm316", "at90can32",
               "at90can64", "at90scr100", "at90usb646", "at90usb647", "at94k", "m3000".

           "avr51"
               "Enhanced" devices with 128 KiB of program memory.  mcu = "atmega128", "atmega128a",
               "atmega128rfa1", "atmega128rfr2", "atmega1280", "atmega1281", "atmega1284",
               "atmega1284p", "atmega1284rfr2", "at90can128", "at90usb1286", "at90usb1287".

           "avr6"
               "Enhanced" devices with 3-byte PC, i.e. with more than 128 KiB of program memory.
               mcu = "atmega256rfr2", "atmega2560", "atmega2561", "atmega2564rfr2".

           "avrxmega2"
               "XMEGA" devices with more than 8 KiB and up to 64 KiB of program memory.  mcu =
               "atxmega8e5", "atxmega16a4", "atxmega16a4u", "atxmega16c4", "atxmega16d4",
               "atxmega16e5", "atxmega32a4", "atxmega32a4u", "atxmega32c3", "atxmega32c4",
               "atxmega32d3", "atxmega32d4", "atxmega32e5".

           "avrxmega3"
               "XMEGA" devices with up to 64 KiB of combined program memory and RAM, and with
               program memory visible in the RAM address space.  mcu = "attiny202", "attiny204",
               "attiny212", "attiny214", "attiny402", "attiny404", "attiny406", "attiny412",
               "attiny414", "attiny416", "attiny417", "attiny804", "attiny806", "attiny807",
               "attiny814", "attiny816", "attiny817", "attiny1604", "attiny1606", "attiny1607",
               "attiny1614", "attiny1616", "attiny1617", "attiny3214", "attiny3216", "attiny3217",
               "atmega808", "atmega809", "atmega1608", "atmega1609", "atmega3208", "atmega3209",
               "atmega4808", "atmega4809".

           "avrxmega4"
               "XMEGA" devices with more than 64 KiB and up to 128 KiB of program memory.  mcu =
               "atxmega64a3", "atxmega64a3u", "atxmega64a4u", "atxmega64b1", "atxmega64b3",
               "atxmega64c3", "atxmega64d3", "atxmega64d4".

           "avrxmega5"
               "XMEGA" devices with more than 64 KiB and up to 128 KiB of program memory and more
               than 64 KiB of RAM.  mcu = "atxmega64a1", "atxmega64a1u".

           "avrxmega6"
               "XMEGA" devices with more than 128 KiB of program memory.  mcu = "atxmega128a3",
               "atxmega128a3u", "atxmega128b1", "atxmega128b3", "atxmega128c3", "atxmega128d3",
               "atxmega128d4", "atxmega192a3", "atxmega192a3u", "atxmega192c3", "atxmega192d3",
               "atxmega256a3", "atxmega256a3b", "atxmega256a3bu", "atxmega256a3u", "atxmega256c3",
               "atxmega256d3", "atxmega384c3", "atxmega384d3".

           "avrxmega7"
               "XMEGA" devices with more than 128 KiB of program memory and more than 64 KiB of RAM.
               mcu = "atxmega128a1", "atxmega128a1u", "atxmega128a4u".

           "avrtiny"
               "TINY" Tiny core devices with 512 B up to 4 KiB of program memory.  mcu = "attiny4",
               "attiny5", "attiny9", "attiny10", "attiny20", "attiny40".

           "avr1"
               This ISA is implemented by the minimal AVR core and supported for assembler only.
               mcu = "attiny11", "attiny12", "attiny15", "attiny28", "at90s1200".

       -mabsdata
           Assume that all data in static storage can be accessed by LDS / STS instructions.  This
           option has only an effect on reduced Tiny devices like ATtiny40.  See also the "absdata"
           AVR Variable Attributes,variable attribute.

       -maccumulate-args
           Accumulate outgoing function arguments and acquire/release the needed stack space for
           outgoing function arguments once in function prologue/epilogue.  Without this option,
           outgoing arguments are pushed before calling a function and popped afterwards.

           Popping the arguments after the function call can be expensive on AVR so that
           accumulating the stack space might lead to smaller executables because arguments need not
           be removed from the stack after such a function call.

           This option can lead to reduced code size for functions that perform several calls to
           functions that get their arguments on the stack like calls to printf-like functions.

       -mbranch-cost=cost
           Set the branch costs for conditional branch instructions to cost.  Reasonable values for
           cost are small, non-negative integers. The default branch cost is 0.

       -mcall-prologues
           Functions prologues/epilogues are expanded as calls to appropriate subroutines.  Code
           size is smaller.

       -mdouble=bits
       -mlong-double=bits
           Set the size (in bits) of the "double" or "long double" type, respectively.  Possible
           values for bits are 32 and 64.  Whether or not a specific value for bits is allowed
           depends on the "--with-double=" and "--with-long-double=" configure options
           ("https://gcc.gnu.org/install/configure.html#avr"), and the same applies for the default
           values of the options.

       -mgas-isr-prologues
           Interrupt service routines (ISRs) may use the "__gcc_isr" pseudo instruction supported by
           GNU Binutils.  If this option is on, the feature can still be disabled for individual
           ISRs by means of the AVR Function Attributes,,"no_gccisr" function attribute.  This
           feature is activated per default if optimization is on (but not with -Og, @pxref{Optimize
           Options}), and if GNU Binutils support PR21683 ("https://sourceware.org/PR21683").

       -mint8
           Assume "int" to be 8-bit integer.  This affects the sizes of all types: a "char" is 1
           byte, an "int" is 1 byte, a "long" is 2 bytes, and "long long" is 4 bytes.  Please note
           that this option does not conform to the C standards, but it results in smaller code
           size.

       -mmain-is-OS_task
           Do not save registers in "main".  The effect is the same like attaching attribute AVR
           Function Attributes,,"OS_task" to "main". It is activated per default if optimization is
           on.

       -mn-flash=num
           Assume that the flash memory has a size of num times 64 KiB.

       -mno-interrupts
           Generated code is not compatible with hardware interrupts.  Code size is smaller.

       -mrelax
           Try to replace "CALL" resp. "JMP" instruction by the shorter "RCALL" resp. "RJMP"
           instruction if applicable.  Setting -mrelax just adds the --mlink-relax option to the
           assembler's command line and the --relax option to the linker's command line.

           Jump relaxing is performed by the linker because jump offsets are not known before code
           is located. Therefore, the assembler code generated by the compiler is the same, but the
           instructions in the executable may differ from instructions in the assembler code.

           Relaxing must be turned on if linker stubs are needed, see the section on "EIND" and
           linker stubs below.

       -mrmw
           Assume that the device supports the Read-Modify-Write instructions "XCH", "LAC", "LAS"
           and "LAT".

       -mshort-calls
           Assume that "RJMP" and "RCALL" can target the whole program memory.

           This option is used internally for multilib selection.  It is not an optimization option,
           and you don't need to set it by hand.

       -msp8
           Treat the stack pointer register as an 8-bit register, i.e. assume the high byte of the
           stack pointer is zero.  In general, you don't need to set this option by hand.

           This option is used internally by the compiler to select and build multilibs for
           architectures "avr2" and "avr25".  These architectures mix devices with and without
           "SPH".  For any setting other than -mmcu=avr2 or -mmcu=avr25 the compiler driver adds or
           removes this option from the compiler proper's command line, because the compiler then
           knows if the device or architecture has an 8-bit stack pointer and thus no "SPH" register
           or not.

       -mstrict-X
           Use address register "X" in a way proposed by the hardware.  This means that "X" is only
           used in indirect, post-increment or pre-decrement addressing.

           Without this option, the "X" register may be used in the same way as "Y" or "Z" which
           then is emulated by additional instructions.  For example, loading a value with "X+const"
           addressing with a small non-negative "const < 64" to a register Rn is performed as

                   adiw r26, const   ; X += const
                   ld   <Rn>, X        ; <Rn> = *X
                   sbiw r26, const   ; X -= const

       -mtiny-stack
           Only change the lower 8 bits of the stack pointer.

       -mfract-convert-truncate
           Allow to use truncation instead of rounding towards zero for fractional fixed-point
           types.

       -nodevicelib
           Don't link against AVR-LibC's device specific library "lib<mcu>.a".

       -nodevicespecs
           Don't add -specs=device-specs/specs-mcu to the compiler driver's command line.  The user
           takes responsibility for supplying the sub-processes like compiler proper, assembler and
           linker with appropriate command line options.  This means that the user has to supply her
           private device specs file by means of -specs=path-to-specs-file.  There is no more need
           for option -mmcu=mcu.

           This option can also serve as a replacement for the older way of specifying custom
           device-specs files that needed -B some-path to point to a directory which contains a
           folder named "device-specs" which contains a specs file named "specs-mcu", where mcu was
           specified by -mmcu=mcu.

       -Waddr-space-convert
           Warn about conversions between address spaces in the case where the resulting address
           space is not contained in the incoming address space.

       -Wmisspelled-isr
           Warn if the ISR is misspelled, i.e. without __vector prefix.  Enabled by default.

       "EIND" and Devices with More Than 128 Ki Bytes of Flash

       Pointers in the implementation are 16 bits wide.  The address of a function or label is
       represented as word address so that indirect jumps and calls can target any code address in
       the range of 64 Ki words.

       In order to facilitate indirect jump on devices with more than 128 Ki bytes of program memory
       space, there is a special function register called "EIND" that serves as most significant
       part of the target address when "EICALL" or "EIJMP" instructions are used.

       Indirect jumps and calls on these devices are handled as follows by the compiler and are
       subject to some limitations:

       *   The compiler never sets "EIND".

       *   The compiler uses "EIND" implicitly in "EICALL"/"EIJMP" instructions or might read "EIND"
           directly in order to emulate an indirect call/jump by means of a "RET" instruction.

       *   The compiler assumes that "EIND" never changes during the startup code or during the
           application. In particular, "EIND" is not saved/restored in function or interrupt service
           routine prologue/epilogue.

       *   For indirect calls to functions and computed goto, the linker generates stubs. Stubs are
           jump pads sometimes also called trampolines. Thus, the indirect call/jump jumps to such a
           stub.  The stub contains a direct jump to the desired address.

       *   Linker relaxation must be turned on so that the linker generates the stubs correctly in
           all situations. See the compiler option -mrelax and the linker option --relax.  There are
           corner cases where the linker is supposed to generate stubs but aborts without relaxation
           and without a helpful error message.

       *   The default linker script is arranged for code with "EIND = 0".  If code is supposed to
           work for a setup with "EIND != 0", a custom linker script has to be used in order to
           place the sections whose name start with ".trampolines" into the segment where "EIND"
           points to.

       *   The startup code from libgcc never sets "EIND".  Notice that startup code is a blend of
           code from libgcc and AVR-LibC.  For the impact of AVR-LibC on "EIND", see the AVR-
           LibC user manual ("http://nongnu.org/avr-libc/user-manual/").

       *   It is legitimate for user-specific startup code to set up "EIND" early, for example by
           means of initialization code located in section ".init3". Such code runs prior to general
           startup code that initializes RAM and calls constructors, but after the bit of startup
           code from AVR-LibC that sets "EIND" to the segment where the vector table is located.

                   #include <avr/io.h>

                   static void
                   __attribute__((section(".init3"),naked,used,no_instrument_function))
                   init3_set_eind (void)
                   {
                     __asm volatile ("ldi r24,pm_hh8(__trampolines_start)\n\t"
                                     "out %i0,r24" :: "n" (&EIND) : "r24","memory");
                   }

           The "__trampolines_start" symbol is defined in the linker script.

       *   Stubs are generated automatically by the linker if the following two conditions are met:

           -<The address of a label is taken by means of the "gs" modifier>
               (short for generate stubs) like so:

                       LDI r24, lo8(gs(<func>))
                       LDI r25, hi8(gs(<func>))

           -<The final location of that label is in a code segment>
               outside the segment where the stubs are located.

       *   The compiler emits such "gs" modifiers for code labels in the following situations:

           -<Taking address of a function or code label.>
           -<Computed goto.>
           -<If prologue-save function is used, see -mcall-prologues>
               command-line option.

           -<Switch/case dispatch tables. If you do not want such dispatch>
               tables you can specify the -fno-jump-tables command-line option.

           -<C and C++ constructors/destructors called during startup/shutdown.>
           -<If the tools hit a "gs()" modifier explained above.>
       *   Jumping to non-symbolic addresses like so is not supported:

                   int main (void)
                   {
                       /* Call function at word address 0x2 */
                       return ((int(*)(void)) 0x2)();
                   }

           Instead, a stub has to be set up, i.e. the function has to be called through a symbol
           ("func_4" in the example):

                   int main (void)
                   {
                       extern int func_4 (void);

                       /* Call function at byte address 0x4 */
                       return func_4();
                   }

           and the application be linked with -Wl,--defsym,func_4=0x4.  Alternatively, "func_4" can
           be defined in the linker script.

       Handling of the "RAMPD", "RAMPX", "RAMPY" and "RAMPZ" Special Function Registers

       Some AVR devices support memories larger than the 64 KiB range that can be accessed with
       16-bit pointers.  To access memory locations outside this 64 KiB range, the content of a
       "RAMP" register is used as high part of the address: The "X", "Y", "Z" address register is
       concatenated with the "RAMPX", "RAMPY", "RAMPZ" special function register, respectively, to
       get a wide address. Similarly, "RAMPD" is used together with direct addressing.

       *   The startup code initializes the "RAMP" special function registers with zero.

       *   If a AVR Named Address Spaces,named address space other than generic or "__flash" is
           used, then "RAMPZ" is set as needed before the operation.

       *   If the device supports RAM larger than 64 KiB and the compiler needs to change "RAMPZ" to
           accomplish an operation, "RAMPZ" is reset to zero after the operation.

       *   If the device comes with a specific "RAMP" register, the ISR prologue/epilogue
           saves/restores that SFR and initializes it with zero in case the ISR code might
           (implicitly) use it.

       *   RAM larger than 64 KiB is not supported by GCC for AVR targets.  If you use inline
           assembler to read from locations outside the 16-bit address range and change one of the
           "RAMP" registers, you must reset it to zero after the access.

       AVR Built-in Macros

       GCC defines several built-in macros so that the user code can test for the presence or
       absence of features.  Almost any of the following built-in macros are deduced from device
       capabilities and thus triggered by the -mmcu= command-line option.

       For even more AVR-specific built-in macros see AVR Named Address Spaces and AVR Built-in
       Functions.

       "__AVR_ARCH__"
           Build-in macro that resolves to a decimal number that identifies the architecture and
           depends on the -mmcu=mcu option.  Possible values are:

           2, 25, 3, 31, 35, 4, 5, 51, 6

           for mcu="avr2", "avr25", "avr3", "avr31", "avr35", "avr4", "avr5", "avr51", "avr6",

           respectively and

           100, 102, 103, 104, 105, 106, 107

           for mcu="avrtiny", "avrxmega2", "avrxmega3", "avrxmega4", "avrxmega5", "avrxmega6",
           "avrxmega7", respectively.  If mcu specifies a device, this built-in macro is set
           accordingly. For example, with -mmcu=atmega8 the macro is defined to 4.

       "__AVR_Device__"
           Setting -mmcu=device defines this built-in macro which reflects the device's name. For
           example, -mmcu=atmega8 defines the built-in macro "__AVR_ATmega8__", -mmcu=attiny261a
           defines "__AVR_ATtiny261A__", etc.

           The built-in macros' names follow the scheme "__AVR_Device__" where Device is the device
           name as from the AVR user manual. The difference between Device in the built-in macro and
           device in -mmcu=device is that the latter is always lowercase.

           If device is not a device but only a core architecture like avr51, this macro is not
           defined.

       "__AVR_DEVICE_NAME__"
           Setting -mmcu=device defines this built-in macro to the device's name. For example, with
           -mmcu=atmega8 the macro is defined to "atmega8".

           If device is not a device but only a core architecture like avr51, this macro is not
           defined.

       "__AVR_XMEGA__"
           The device / architecture belongs to the XMEGA family of devices.

       "__AVR_HAVE_ELPM__"
           The device has the "ELPM" instruction.

       "__AVR_HAVE_ELPMX__"
           The device has the "ELPM Rn,Z" and "ELPM Rn,Z+" instructions.

       "__AVR_HAVE_MOVW__"
           The device has the "MOVW" instruction to perform 16-bit register-register moves.

       "__AVR_HAVE_LPMX__"
           The device has the "LPM Rn,Z" and "LPM Rn,Z+" instructions.

       "__AVR_HAVE_MUL__"
           The device has a hardware multiplier.

       "__AVR_HAVE_JMP_CALL__"
           The device has the "JMP" and "CALL" instructions.  This is the case for devices with more
           than 8 KiB of program memory.

       "__AVR_HAVE_EIJMP_EICALL__"
       "__AVR_3_BYTE_PC__"
           The device has the "EIJMP" and "EICALL" instructions.  This is the case for devices with
           more than 128 KiB of program memory.  This also means that the program counter (PC) is 3
           bytes wide.

       "__AVR_2_BYTE_PC__"
           The program counter (PC) is 2 bytes wide. This is the case for devices with up to 128 KiB
           of program memory.

       "__AVR_HAVE_8BIT_SP__"
       "__AVR_HAVE_16BIT_SP__"
           The stack pointer (SP) register is treated as 8-bit respectively 16-bit register by the
           compiler.  The definition of these macros is affected by -mtiny-stack.

       "__AVR_HAVE_SPH__"
       "__AVR_SP8__"
           The device has the SPH (high part of stack pointer) special function register or has an
           8-bit stack pointer, respectively.  The definition of these macros is affected by -mmcu=
           and in the cases of -mmcu=avr2 and -mmcu=avr25 also by -msp8.

       "__AVR_HAVE_RAMPD__"
       "__AVR_HAVE_RAMPX__"
       "__AVR_HAVE_RAMPY__"
       "__AVR_HAVE_RAMPZ__"
           The device has the "RAMPD", "RAMPX", "RAMPY", "RAMPZ" special function register,
           respectively.

       "__NO_INTERRUPTS__"
           This macro reflects the -mno-interrupts command-line option.

       "__AVR_ERRATA_SKIP__"
       "__AVR_ERRATA_SKIP_JMP_CALL__"
           Some AVR devices (AT90S8515, ATmega103) must not skip 32-bit instructions because of a
           hardware erratum.  Skip instructions are "SBRS", "SBRC", "SBIS", "SBIC" and "CPSE".  The
           second macro is only defined if "__AVR_HAVE_JMP_CALL__" is also set.

       "__AVR_ISA_RMW__"
           The device has Read-Modify-Write instructions (XCH, LAC, LAS and LAT).

       "__AVR_SFR_OFFSET__=offset"
           Instructions that can address I/O special function registers directly like "IN", "OUT",
           "SBI", etc. may use a different address as if addressed by an instruction to access RAM
           like "LD" or "STS". This offset depends on the device architecture and has to be
           subtracted from the RAM address in order to get the respective I/O address.

       "__AVR_SHORT_CALLS__"
           The -mshort-calls command line option is set.

       "__AVR_PM_BASE_ADDRESS__=addr"
           Some devices support reading from flash memory by means of "LD*" instructions.  The flash
           memory is seen in the data address space at an offset of "__AVR_PM_BASE_ADDRESS__".  If
           this macro is not defined, this feature is not available.  If defined, the address space
           is linear and there is no need to put ".rodata" into RAM.  This is handled by the default
           linker description file, and is currently available for "avrtiny" and "avrxmega3".  Even
           more convenient, there is no need to use address spaces like "__flash" or features like
           attribute "progmem" and "pgm_read_*".

       "__WITH_AVRLIBC__"
           The compiler is configured to be used together with AVR-Libc.  See the --with-avrlibc
           configure option.

       "__HAVE_DOUBLE_MULTILIB__"
           Defined if -mdouble= acts as a multilib option.

       "__HAVE_DOUBLE32__"
       "__HAVE_DOUBLE64__"
           Defined if the compiler supports 32-bit double resp. 64-bit double.  The actual layout is
           specified by option -mdouble=.

       "__DEFAULT_DOUBLE__"
           The size in bits of "double" if -mdouble= is not set.  To test the layout of "double" in
           a program, use the built-in macro "__SIZEOF_DOUBLE__".

       "__HAVE_LONG_DOUBLE32__"
       "__HAVE_LONG_DOUBLE64__"
       "__HAVE_LONG_DOUBLE_MULTILIB__"
       "__DEFAULT_LONG_DOUBLE__"
           Same as above, but for "long double" instead of "double".

       "__WITH_DOUBLE_COMPARISON__"
           Reflects the "--with-double-comparison={tristate|bool|libf7}" configure option
           ("https://gcc.gnu.org/install/configure.html#avr") and is defined to 2 or 3.

       "__WITH_LIBF7_LIBGCC__"
       "__WITH_LIBF7_MATH__"
       "__WITH_LIBF7_MATH_SYMBOLS__"
           Reflects the "--with-libf7={libgcc|math|math-symbols}" configure option
           ("https://gcc.gnu.org/install/configure.html#avr").

       Blackfin Options

       -mcpu=cpu[-sirevision]
           Specifies the name of the target Blackfin processor.  Currently, cpu can be one of bf512,
           bf514, bf516, bf518, bf522, bf523, bf524, bf525, bf526, bf527, bf531, bf532, bf533,
           bf534, bf536, bf537, bf538, bf539, bf542, bf544, bf547, bf548, bf549, bf542m, bf544m,
           bf547m, bf548m, bf549m, bf561, bf592.

           The optional sirevision specifies the silicon revision of the target Blackfin processor.
           Any workarounds available for the targeted silicon revision are enabled.  If sirevision
           is none, no workarounds are enabled.  If sirevision is any, all workarounds for the
           targeted processor are enabled.  The "__SILICON_REVISION__" macro is defined to two
           hexadecimal digits representing the major and minor numbers in the silicon revision.  If
           sirevision is none, the "__SILICON_REVISION__" is not defined.  If sirevision is any, the
           "__SILICON_REVISION__" is defined to be 0xffff.  If this optional sirevision is not used,
           GCC assumes the latest known silicon revision of the targeted Blackfin processor.

           GCC defines a preprocessor macro for the specified cpu.  For the bfin-elf toolchain, this
           option causes the hardware BSP provided by libgloss to be linked in if -msim is not
           given.

           Without this option, bf532 is used as the processor by default.

           Note that support for bf561 is incomplete.  For bf561, only the preprocessor macro is
           defined.

       -msim
           Specifies that the program will be run on the simulator.  This causes the simulator BSP
           provided by libgloss to be linked in.  This option has effect only for bfin-elf
           toolchain.  Certain other options, such as -mid-shared-library and -mfdpic, imply -msim.

       -momit-leaf-frame-pointer
           Don't keep the frame pointer in a register for leaf functions.  This avoids the
           instructions to save, set up and restore frame pointers and makes an extra register
           available in leaf functions.

       -mspecld-anomaly
           When enabled, the compiler ensures that the generated code does not contain speculative
           loads after jump instructions. If this option is used, "__WORKAROUND_SPECULATIVE_LOADS"
           is defined.

       -mno-specld-anomaly
           Don't generate extra code to prevent speculative loads from occurring.

       -mcsync-anomaly
           When enabled, the compiler ensures that the generated code does not contain CSYNC or
           SSYNC instructions too soon after conditional branches.  If this option is used,
           "__WORKAROUND_SPECULATIVE_SYNCS" is defined.

       -mno-csync-anomaly
           Don't generate extra code to prevent CSYNC or SSYNC instructions from occurring too soon
           after a conditional branch.

       -mlow64k
           When enabled, the compiler is free to take advantage of the knowledge that the entire
           program fits into the low 64k of memory.

       -mno-low64k
           Assume that the program is arbitrarily large.  This is the default.

       -mstack-check-l1
           Do stack checking using information placed into L1 scratchpad memory by the uClinux
           kernel.

       -mid-shared-library
           Generate code that supports shared libraries via the library ID method.  This allows for
           execute in place and shared libraries in an environment without virtual memory
           management.  This option implies -fPIC.  With a bfin-elf target, this option implies
           -msim.

       -mno-id-shared-library
           Generate code that doesn't assume ID-based shared libraries are being used.  This is the
           default.

       -mleaf-id-shared-library
           Generate code that supports shared libraries via the library ID method, but assumes that
           this library or executable won't link against any other ID shared libraries.  That allows
           the compiler to use faster code for jumps and calls.

       -mno-leaf-id-shared-library
           Do not assume that the code being compiled won't link against any ID shared libraries.
           Slower code is generated for jump and call insns.

       -mshared-library-id=n
           Specifies the identification number of the ID-based shared library being compiled.
           Specifying a value of 0 generates more compact code; specifying other values forces the
           allocation of that number to the current library but is no more space- or time-efficient
           than omitting this option.

       -msep-data
           Generate code that allows the data segment to be located in a different area of memory
           from the text segment.  This allows for execute in place in an environment without
           virtual memory management by eliminating relocations against the text section.

       -mno-sep-data
           Generate code that assumes that the data segment follows the text segment.  This is the
           default.

       -mlong-calls
       -mno-long-calls
           Tells the compiler to perform function calls by first loading the address of the function
           into a register and then performing a subroutine call on this register.  This switch is
           needed if the target function lies outside of the 24-bit addressing range of the offset-
           based version of subroutine call instruction.

           This feature is not enabled by default.  Specifying -mno-long-calls restores the default
           behavior.  Note these switches have no effect on how the compiler generates code to
           handle function calls via function pointers.

       -mfast-fp
           Link with the fast floating-point library. This library relaxes some of the IEEE
           floating-point standard's rules for checking inputs against Not-a-Number (NAN), in the
           interest of performance.

       -minline-plt
           Enable inlining of PLT entries in function calls to functions that are not known to bind
           locally.  It has no effect without -mfdpic.

       -mmulticore
           Build a standalone application for multicore Blackfin processors.  This option causes
           proper start files and link scripts supporting multicore to be used, and defines the
           macro "__BFIN_MULTICORE".  It can only be used with -mcpu=bf561[-sirevision].

           This option can be used with -mcorea or -mcoreb, which selects the one-application-per-
           core programming model.  Without -mcorea or -mcoreb, the single-application/dual-core
           programming model is used. In this model, the main function of Core B should be named as
           "coreb_main".

           If this option is not used, the single-core application programming model is used.

       -mcorea
           Build a standalone application for Core A of BF561 when using the one-application-per-
           core programming model. Proper start files and link scripts are used to support Core A,
           and the macro "__BFIN_COREA" is defined.  This option can only be used in conjunction
           with -mmulticore.

       -mcoreb
           Build a standalone application for Core B of BF561 when using the one-application-per-
           core programming model. Proper start files and link scripts are used to support Core B,
           and the macro "__BFIN_COREB" is defined. When this option is used, "coreb_main" should be
           used instead of "main".  This option can only be used in conjunction with -mmulticore.

       -msdram
           Build a standalone application for SDRAM. Proper start files and link scripts are used to
           put the application into SDRAM, and the macro "__BFIN_SDRAM" is defined.  The loader
           should initialize SDRAM before loading the application.

       -micplb
           Assume that ICPLBs are enabled at run time.  This has an effect on certain anomaly
           workarounds.  For Linux targets, the default is to assume ICPLBs are enabled; for
           standalone applications the default is off.

       C6X Options

       -march=name
           This specifies the name of the target architecture.  GCC uses this name to determine what
           kind of instructions it can emit when generating assembly code.  Permissible names are:
           c62x, c64x, c64x+, c67x, c67x+, c674x.

       -mbig-endian
           Generate code for a big-endian target.

       -mlittle-endian
           Generate code for a little-endian target.  This is the default.

       -msim
           Choose startup files and linker script suitable for the simulator.

       -msdata=default
           Put small global and static data in the ".neardata" section, which is pointed to by
           register "B14".  Put small uninitialized global and static data in the ".bss" section,
           which is adjacent to the ".neardata" section.  Put small read-only data into the
           ".rodata" section.  The corresponding sections used for large pieces of data are
           ".fardata", ".far" and ".const".

       -msdata=all
           Put all data, not just small objects, into the sections reserved for small data, and use
           addressing relative to the "B14" register to access them.

       -msdata=none
           Make no use of the sections reserved for small data, and use absolute addresses to access
           all data.  Put all initialized global and static data in the ".fardata" section, and all
           uninitialized data in the ".far" section.  Put all constant data into the ".const"
           section.

       CRIS Options

       These options are defined specifically for the CRIS ports.

       -march=architecture-type
       -mcpu=architecture-type
           Generate code for the specified architecture.  The choices for architecture-type are v3,
           v8 and v10 for respectively ETRAX 4, ETRAX 100, and ETRAX 100 LX.  Default is v0.

       -mtune=architecture-type
           Tune to architecture-type everything applicable about the generated code, except for the
           ABI and the set of available instructions.  The choices for architecture-type are the
           same as for -march=architecture-type.

       -mmax-stack-frame=n
           Warn when the stack frame of a function exceeds n bytes.

       -metrax4
       -metrax100
           The options -metrax4 and -metrax100 are synonyms for -march=v3 and -march=v8
           respectively.

       -mmul-bug-workaround
       -mno-mul-bug-workaround
           Work around a bug in the "muls" and "mulu" instructions for CPU models where it applies.
           This option is active by default.

       -mpdebug
           Enable CRIS-specific verbose debug-related information in the assembly code.  This option
           also has the effect of turning off the #NO_APP formatted-code indicator to the assembler
           at the beginning of the assembly file.

       -mcc-init
           Do not use condition-code results from previous instruction; always emit compare and test
           instructions before use of condition codes.

       -mno-side-effects
           Do not emit instructions with side effects in addressing modes other than post-increment.

       -mstack-align
       -mno-stack-align
       -mdata-align
       -mno-data-align
       -mconst-align
       -mno-const-align
           These options (no- options) arrange (eliminate arrangements) for the stack frame,
           individual data and constants to be aligned for the maximum single data access size for
           the chosen CPU model.  The default is to arrange for 32-bit alignment.  ABI details such
           as structure layout are not affected by these options.

       -m32-bit
       -m16-bit
       -m8-bit
           Similar to the stack- data- and const-align options above, these options arrange for
           stack frame, writable data and constants to all be 32-bit, 16-bit or 8-bit aligned.  The
           default is 32-bit alignment.

       -mno-prologue-epilogue
       -mprologue-epilogue
           With -mno-prologue-epilogue, the normal function prologue and epilogue which set up the
           stack frame are omitted and no return instructions or return sequences are generated in
           the code.  Use this option only together with visual inspection of the compiled code: no
           warnings or errors are generated when call-saved registers must be saved, or storage for
           local variables needs to be allocated.

       -melf
           Legacy no-op option.

       -sim
           This option arranges to link with input-output functions from a simulator library.  Code,
           initialized data and zero-initialized data are allocated consecutively.

       -sim2
           Like -sim, but pass linker options to locate initialized data at 0x40000000 and zero-
           initialized data at 0x80000000.

       CR16 Options

       These options are defined specifically for the CR16 ports.

       -mmac
           Enable the use of multiply-accumulate instructions. Disabled by default.

       -mcr16cplus
       -mcr16c
           Generate code for CR16C or CR16C+ architecture. CR16C+ architecture is default.

       -msim
           Links the library libsim.a which is in compatible with simulator. Applicable to ELF
           compiler only.

       -mint32
           Choose integer type as 32-bit wide.

       -mbit-ops
           Generates "sbit"/"cbit" instructions for bit manipulations.

       -mdata-model=model
           Choose a data model. The choices for model are near, far or medium. medium is default.
           However, far is not valid with -mcr16c, as the CR16C architecture does not support the
           far data model.

       C-SKY Options

       GCC supports these options when compiling for C-SKY V2 processors.

       -march=arch
           Specify the C-SKY target architecture.  Valid values for arch are: ck801, ck802, ck803,
           ck807, and ck810.  The default is ck810.

       -mcpu=cpu
           Specify the C-SKY target processor.  Valid values for cpu are: ck801, ck801t, ck802,
           ck802t, ck802j, ck803, ck803h, ck803t, ck803ht, ck803f, ck803fh, ck803e, ck803eh,
           ck803et, ck803eht, ck803ef, ck803efh, ck803ft, ck803eft, ck803efht, ck803r1, ck803hr1,
           ck803tr1, ck803htr1, ck803fr1, ck803fhr1, ck803er1, ck803ehr1, ck803etr1, ck803ehtr1,
           ck803efr1, ck803efhr1, ck803ftr1, ck803eftr1, ck803efhtr1, ck803s, ck803st, ck803se,
           ck803sf, ck803sef, ck803seft, ck807e, ck807ef, ck807, ck807f, ck810e, ck810et, ck810ef,
           ck810eft, ck810, ck810v, ck810f, ck810t, ck810fv, ck810tv, ck810ft, and ck810ftv.

       -mbig-endian
       -EB
       -mlittle-endian
       -EL Select big- or little-endian code.  The default is little-endian.

       -mfloat-abi=name
           Specifies which floating-point ABI to use.  Permissible values are: soft, softfp and
           hard.

           Specifying soft causes GCC to generate output containing library calls for floating-point
           operations.  softfp allows the generation of code using hardware floating-point
           instructions, but still uses the soft-float calling conventions.  hard allows generation
           of floating-point instructions and uses FPU-specific calling conventions.

           The default depends on the specific target configuration.  Note that the hard-float and
           soft-float ABIs are not link-compatible; you must compile your entire program with the
           same ABI, and link with a compatible set of libraries.

       -mhard-float
       -msoft-float
           Select hardware or software floating-point implementations.  The default is soft float.

       -mdouble-float
       -mno-double-float
           When -mhard-float is in effect, enable generation of double-precision float instructions.
           This is the default except when compiling for CK803.

       -mfdivdu
       -mno-fdivdu
           When -mhard-float is in effect, enable generation of "frecipd", "fsqrtd", and "fdivd"
           instructions.  This is the default except when compiling for CK803.

       -mfpu=fpu
           Select the floating-point processor.  This option can only be used with -mhard-float.
           Values for fpu are fpv2_sf (equivalent to -mno-double-float -mno-fdivdu), fpv2
           (-mdouble-float -mno-divdu), and fpv2_divd (-mdouble-float -mdivdu).

       -melrw
       -mno-elrw
           Enable the extended "lrw" instruction.  This option defaults to on for CK801 and off
           otherwise.

       -mistack
       -mno-istack
           Enable interrupt stack instructions; the default is off.

           The -mistack option is required to handle the "interrupt" and "isr" function attributes.

       -mmp
           Enable multiprocessor instructions; the default is off.

       -mcp
           Enable coprocessor instructions; the default is off.

       -mcache
           Enable coprocessor instructions; the default is off.

       -msecurity
           Enable C-SKY security instructions; the default is off.

       -mtrust
           Enable C-SKY trust instructions; the default is off.

       -mdsp
       -medsp
       -mvdsp
           Enable C-SKY DSP, Enhanced DSP, or Vector DSP instructions, respectively.  All of these
           options default to off.

       -mdiv
       -mno-div
           Generate divide instructions.  Default is off.

       -msmart
       -mno-smart
           Generate code for Smart Mode, using only registers numbered 0-7 to allow use of 16-bit
           instructions.  This option is ignored for CK801 where this is the required behavior, and
           it defaults to on for CK802.  For other targets, the default is off.

       -mhigh-registers
       -mno-high-registers
           Generate code using the high registers numbered 16-31.  This option is not supported on
           CK801, CK802, or CK803, and is enabled by default for other processors.

       -manchor
       -mno-anchor
           Generate code using global anchor symbol addresses.

       -mpushpop
       -mno-pushpop
           Generate code using "push" and "pop" instructions.  This option defaults to on.

       -mmultiple-stld
       -mstm
       -mno-multiple-stld
       -mno-stm
           Generate code using "stm" and "ldm" instructions.  This option isn't supported on CK801
           but is enabled by default on other processors.

       -mconstpool
       -mno-constpool
           Create constant pools in the compiler instead of deferring it to the assembler.  This
           option is the default and required for correct code generation on CK801 and CK802, and is
           optional on other processors.

       -mstack-size
       -mno-stack-size
           Emit ".stack_size" directives for each function in the assembly output.  This option
           defaults to off.

       -mccrt
       -mno-ccrt
           Generate code for the C-SKY compiler runtime instead of libgcc.  This option defaults to
           off.

       -mbranch-cost=n
           Set the branch costs to roughly "n" instructions.  The default is 1.

       -msched-prolog
       -mno-sched-prolog
           Permit scheduling of function prologue and epilogue sequences.  Using this option can
           result in code that is not compliant with the C-SKY V2 ABI prologue requirements and that
           cannot be debugged or backtraced.  It is disabled by default.

       -msim
           Links the library libsemi.a which is in compatible with simulator. Applicable to ELF
           compiler only.

       Darwin Options

       These options are defined for all architectures running the Darwin operating system.

       FSF GCC on Darwin does not create "fat" object files; it creates an object file for the
       single architecture that GCC was built to target.  Apple's GCC on Darwin does create "fat"
       files if multiple -arch options are used; it does so by running the compiler or linker
       multiple times and joining the results together with lipo.

       The subtype of the file created (like ppc7400 or ppc970 or i686) is determined by the flags
       that specify the ISA that GCC is targeting, like -mcpu or -march.  The -force_cpusubtype_ALL
       option can be used to override this.

       The Darwin tools vary in their behavior when presented with an ISA mismatch.  The assembler,
       as, only permits instructions to be used that are valid for the subtype of the file it is
       generating, so you cannot put 64-bit instructions in a ppc750 object file.  The linker for
       shared libraries, /usr/bin/libtool, fails and prints an error if asked to create a shared
       library with a less restrictive subtype than its input files (for instance, trying to put a
       ppc970 object file in a ppc7400 library).  The linker for executables, ld, quietly gives the
       executable the most restrictive subtype of any of its input files.

       -Fdir
           Add the framework directory dir to the head of the list of directories to be searched for
           header files.  These directories are interleaved with those specified by -I options and
           are scanned in a left-to-right order.

           A framework directory is a directory with frameworks in it.  A framework is a directory
           with a Headers and/or PrivateHeaders directory contained directly in it that ends in
           .framework.  The name of a framework is the name of this directory excluding the
           .framework.  Headers associated with the framework are found in one of those two
           directories, with Headers being searched first.  A subframework is a framework directory
           that is in a framework's Frameworks directory.  Includes of subframework headers can only
           appear in a header of a framework that contains the subframework, or in a sibling
           subframework header.  Two subframeworks are siblings if they occur in the same framework.
           A subframework should not have the same name as a framework; a warning is issued if this
           is violated.  Currently a subframework cannot have subframeworks; in the future, the
           mechanism may be extended to support this.  The standard frameworks can be found in
           /System/Library/Frameworks and /Library/Frameworks.  An example include looks like
           "#include <Framework/header.h>", where Framework denotes the name of the framework and
           header.h is found in the PrivateHeaders or Headers directory.

       -iframeworkdir
           Like -F except the directory is a treated as a system directory.  The main difference
           between this -iframework and -F is that with -iframework the compiler does not warn about
           constructs contained within header files found via dir.  This option is valid only for
           the C family of languages.

       -gused
           Emit debugging information for symbols that are used.  For stabs debugging format, this
           enables -feliminate-unused-debug-symbols.  This is by default ON.

       -gfull
           Emit debugging information for all symbols and types.

       -mmacosx-version-min=version
           The earliest version of MacOS X that this executable will run on is version.  Typical
           values of version include 10.1, 10.2, and 10.3.9.

           If the compiler was built to use the system's headers by default, then the default for
           this option is the system version on which the compiler is running, otherwise the default
           is to make choices that are compatible with as many systems and code bases as possible.

       -mkernel
           Enable kernel development mode.  The -mkernel option sets -static, -fno-common,
           -fno-use-cxa-atexit, -fno-exceptions, -fno-non-call-exceptions, -fapple-kext, -fno-weak
           and -fno-rtti where applicable.  This mode also sets -mno-altivec, -msoft-float,
           -fno-builtin and -mlong-branch for PowerPC targets.

       -mone-byte-bool
           Override the defaults for "bool" so that "sizeof(bool)==1".  By default "sizeof(bool)" is
           4 when compiling for Darwin/PowerPC and 1 when compiling for Darwin/x86, so this option
           has no effect on x86.

           Warning: The -mone-byte-bool switch causes GCC to generate code that is not binary
           compatible with code generated without that switch.  Using this switch may require
           recompiling all other modules in a program, including system libraries.  Use this switch
           to conform to a non-default data model.

       -mfix-and-continue
       -ffix-and-continue
       -findirect-data
           Generate code suitable for fast turnaround development, such as to allow GDB to
           dynamically load .o files into already-running programs.  -findirect-data and
           -ffix-and-continue are provided for backwards compatibility.

       -all_load
           Loads all members of static archive libraries.  See man ld(1) for more information.

       -arch_errors_fatal
           Cause the errors having to do with files that have the wrong architecture to be fatal.

       -bind_at_load
           Causes the output file to be marked such that the dynamic linker will bind all undefined
           references when the file is loaded or launched.

       -bundle
           Produce a Mach-o bundle format file.  See man ld(1) for more information.

       -bundle_loader executable
           This option specifies the executable that will load the build output file being linked.
           See man ld(1) for more information.

       -dynamiclib
           When passed this option, GCC produces a dynamic library instead of an executable when
           linking, using the Darwin libtool command.

       -force_cpusubtype_ALL
           This causes GCC's output file to have the ALL subtype, instead of one controlled by the
           -mcpu or -march option.

       -allowable_client  client_name
       -client_name
       -compatibility_version
       -current_version
       -dead_strip
       -dependency-file
       -dylib_file
       -dylinker_install_name
       -dynamic
       -exported_symbols_list
       -filelist
       -flat_namespace
       -force_flat_namespace
       -headerpad_max_install_names
       -image_base
       -init
       -install_name
       -keep_private_externs
       -multi_module
       -multiply_defined
       -multiply_defined_unused
       -noall_load
       -no_dead_strip_inits_and_terms
       -nofixprebinding
       -nomultidefs
       -noprebind
       -noseglinkedit
       -pagezero_size
       -prebind
       -prebind_all_twolevel_modules
       -private_bundle
       -read_only_relocs
       -sectalign
       -sectobjectsymbols
       -whyload
       -seg1addr
       -sectcreate
       -sectobjectsymbols
       -sectorder
       -segaddr
       -segs_read_only_addr
       -segs_read_write_addr
       -seg_addr_table
       -seg_addr_table_filename
       -seglinkedit
       -segprot
       -segs_read_only_addr
       -segs_read_write_addr
       -single_module
       -static
       -sub_library
       -sub_umbrella
       -twolevel_namespace
       -umbrella
       -undefined
       -unexported_symbols_list
       -weak_reference_mismatches
       -whatsloaded
           These options are passed to the Darwin linker.  The Darwin linker man page describes them
           in detail.

       DEC Alpha Options

       These -m options are defined for the DEC Alpha implementations:

       -mno-soft-float
       -msoft-float
           Use (do not use) the hardware floating-point instructions for floating-point operations.
           When -msoft-float is specified, functions in libgcc.a are used to perform floating-point
           operations.  Unless they are replaced by routines that emulate the floating-point
           operations, or compiled in such a way as to call such emulations routines, these routines
           issue floating-point operations.   If you are compiling for an Alpha without floating-
           point operations, you must ensure that the library is built so as not to call them.

           Note that Alpha implementations without floating-point operations are required to have
           floating-point registers.

       -mfp-reg
       -mno-fp-regs
           Generate code that uses (does not use) the floating-point register set.  -mno-fp-regs
           implies -msoft-float.  If the floating-point register set is not used, floating-point
           operands are passed in integer registers as if they were integers and floating-point
           results are passed in $0 instead of $f0.  This is a non-standard calling sequence, so any
           function with a floating-point argument or return value called by code compiled with
           -mno-fp-regs must also be compiled with that option.

           A typical use of this option is building a kernel that does not use, and hence need not
           save and restore, any floating-point registers.

       -mieee
           The Alpha architecture implements floating-point hardware optimized for maximum
           performance.  It is mostly compliant with the IEEE floating-point standard.  However, for
           full compliance, software assistance is required.  This option generates code fully IEEE-
           compliant code except that the inexact-flag is not maintained (see below).  If this
           option is turned on, the preprocessor macro "_IEEE_FP" is defined during compilation.
           The resulting code is less efficient but is able to correctly support denormalized
           numbers and exceptional IEEE values such as not-a-number and plus/minus infinity.  Other
           Alpha compilers call this option -ieee_with_no_inexact.

       -mieee-with-inexact
           This is like -mieee except the generated code also maintains the IEEE inexact-flag.
           Turning on this option causes the generated code to implement fully-compliant IEEE math.
           In addition to "_IEEE_FP", "_IEEE_FP_EXACT" is defined as a preprocessor macro.  On some
           Alpha implementations the resulting code may execute significantly slower than the code
           generated by default.  Since there is very little code that depends on the inexact-flag,
           you should normally not specify this option.  Other Alpha compilers call this option
           -ieee_with_inexact.

       -mfp-trap-mode=trap-mode
           This option controls what floating-point related traps are enabled.  Other Alpha
           compilers call this option -fptm trap-mode.  The trap mode can be set to one of four
           values:

           n   This is the default (normal) setting.  The only traps that are enabled are the ones
               that cannot be disabled in software (e.g., division by zero trap).

           u   In addition to the traps enabled by n, underflow traps are enabled as well.

           su  Like u, but the instructions are marked to be safe for software completion (see Alpha
               architecture manual for details).

           sui Like su, but inexact traps are enabled as well.

       -mfp-rounding-mode=rounding-mode
           Selects the IEEE rounding mode.  Other Alpha compilers call this option -fprm rounding-
           mode.  The rounding-mode can be one of:

           n   Normal IEEE rounding mode.  Floating-point numbers are rounded towards the nearest
               machine number or towards the even machine number in case of a tie.

           m   Round towards minus infinity.

           c   Chopped rounding mode.  Floating-point numbers are rounded towards zero.

           d   Dynamic rounding mode.  A field in the floating-point control register (fpcr, see
               Alpha architecture reference manual) controls the rounding mode in effect.  The C
               library initializes this register for rounding towards plus infinity.  Thus, unless
               your program modifies the fpcr, d corresponds to round towards plus infinity.

       -mtrap-precision=trap-precision
           In the Alpha architecture, floating-point traps are imprecise.  This means without
           software assistance it is impossible to recover from a floating trap and program
           execution normally needs to be terminated.  GCC can generate code that can assist
           operating system trap handlers in determining the exact location that caused a floating-
           point trap.  Depending on the requirements of an application, different levels of
           precisions can be selected:

           p   Program precision.  This option is the default and means a trap handler can only
               identify which program caused a floating-point exception.

           f   Function precision.  The trap handler can determine the function that caused a
               floating-point exception.

           i   Instruction precision.  The trap handler can determine the exact instruction that
               caused a floating-point exception.

           Other Alpha compilers provide the equivalent options called -scope_safe and
           -resumption_safe.

       -mieee-conformant
           This option marks the generated code as IEEE conformant.  You must not use this option
           unless you also specify -mtrap-precision=i and either -mfp-trap-mode=su or
           -mfp-trap-mode=sui.  Its only effect is to emit the line .eflag 48 in the function
           prologue of the generated assembly file.

       -mbuild-constants
           Normally GCC examines a 32- or 64-bit integer constant to see if it can construct it from
           smaller constants in two or three instructions.  If it cannot, it outputs the constant as
           a literal and generates code to load it from the data segment at run time.

           Use this option to require GCC to construct all integer constants using code, even if it
           takes more instructions (the maximum is six).

           You typically use this option to build a shared library dynamic loader.  Itself a shared
           library, it must relocate itself in memory before it can find the variables and constants
           in its own data segment.

       -mbwx
       -mno-bwx
       -mcix
       -mno-cix
       -mfix
       -mno-fix
       -mmax
       -mno-max
           Indicate whether GCC should generate code to use the optional BWX, CIX, FIX and MAX
           instruction sets.  The default is to use the instruction sets supported by the CPU type
           specified via -mcpu= option or that of the CPU on which GCC was built if none is
           specified.

       -mfloat-vax
       -mfloat-ieee
           Generate code that uses (does not use) VAX F and G floating-point arithmetic instead of
           IEEE single and double precision.

       -mexplicit-relocs
       -mno-explicit-relocs
           Older Alpha assemblers provided no way to generate symbol relocations except via
           assembler macros.  Use of these macros does not allow optimal instruction scheduling.
           GNU binutils as of version 2.12 supports a new syntax that allows the compiler to
           explicitly mark which relocations should apply to which instructions.  This option is
           mostly useful for debugging, as GCC detects the capabilities of the assembler when it is
           built and sets the default accordingly.

       -msmall-data
       -mlarge-data
           When -mexplicit-relocs is in effect, static data is accessed via gp-relative relocations.
           When -msmall-data is used, objects 8 bytes long or smaller are placed in a small data
           area (the ".sdata" and ".sbss" sections) and are accessed via 16-bit relocations off of
           the $gp register.  This limits the size of the small data area to 64KB, but allows the
           variables to be directly accessed via a single instruction.

           The default is -mlarge-data.  With this option the data area is limited to just below
           2GB.  Programs that require more than 2GB of data must use "malloc" or "mmap" to allocate
           the data in the heap instead of in the program's data segment.

           When generating code for shared libraries, -fpic implies -msmall-data and -fPIC implies
           -mlarge-data.

       -msmall-text
       -mlarge-text
           When -msmall-text is used, the compiler assumes that the code of the entire program (or
           shared library) fits in 4MB, and is thus reachable with a branch instruction.  When
           -msmall-data is used, the compiler can assume that all local symbols share the same $gp
           value, and thus reduce the number of instructions required for a function call from 4 to
           1.

           The default is -mlarge-text.

       -mcpu=cpu_type
           Set the instruction set and instruction scheduling parameters for machine type cpu_type.
           You can specify either the EV style name or the corresponding chip number.  GCC supports
           scheduling parameters for the EV4, EV5 and EV6 family of processors and chooses the
           default values for the instruction set from the processor you specify.  If you do not
           specify a processor type, GCC defaults to the processor on which the compiler was built.

           Supported values for cpu_type are

           ev4
           ev45
           21064
               Schedules as an EV4 and has no instruction set extensions.

           ev5
           21164
               Schedules as an EV5 and has no instruction set extensions.

           ev56
           21164a
               Schedules as an EV5 and supports the BWX extension.

           pca56
           21164pc
           21164PC
               Schedules as an EV5 and supports the BWX and MAX extensions.

           ev6
           21264
               Schedules as an EV6 and supports the BWX, FIX, and MAX extensions.

           ev67
           21264a
               Schedules as an EV6 and supports the BWX, CIX, FIX, and MAX extensions.

           Native toolchains also support the value native, which selects the best architecture
           option for the host processor.  -mcpu=native has no effect if GCC does not recognize the
           processor.

       -mtune=cpu_type
           Set only the instruction scheduling parameters for machine type cpu_type.  The
           instruction set is not changed.

           Native toolchains also support the value native, which selects the best architecture
           option for the host processor.  -mtune=native has no effect if GCC does not recognize the
           processor.

       -mmemory-latency=time
           Sets the latency the scheduler should assume for typical memory references as seen by the
           application.  This number is highly dependent on the memory access patterns used by the
           application and the size of the external cache on the machine.

           Valid options for time are

           number
               A decimal number representing clock cycles.

           L1
           L2
           L3
           main
               The compiler contains estimates of the number of clock cycles for "typical" EV4 & EV5
               hardware for the Level 1, 2 & 3 caches (also called Dcache, Scache, and Bcache), as
               well as to main memory.  Note that L3 is only valid for EV5.

       eBPF Options

       -mframe-limit=bytes
           This specifies the hard limit for frame sizes, in bytes.  Currently, the value that can
           be specified should be less than or equal to 32767.  Defaults to whatever limit is
           imposed by the version of the Linux kernel targeted.

       -mkernel=version
           This specifies the minimum version of the kernel that will run the compiled program.  GCC
           uses this version to determine which instructions to use, what kernel helpers to allow,
           etc.  Currently, version can be one of 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9,
           4.10, 4.11, 4.12, 4.13, 4.14, 4.15, 4.16, 4.17, 4.18, 4.19, 4.20, 5.0, 5.1, 5.2, latest
           and native.

       -mbig-endian
           Generate code for a big-endian target.

       -mlittle-endian
           Generate code for a little-endian target.  This is the default.

       -mxbpf
           Generate code for an expanded version of BPF, which relaxes some of the restrictions
           imposed by the BPF architecture:

           -<Save and restore callee-saved registers at function entry and>
               exit, respectively.

       FR30 Options

       These options are defined specifically for the FR30 port.

       -msmall-model
           Use the small address space model.  This can produce smaller code, but it does assume
           that all symbolic values and addresses fit into a 20-bit range.

       -mno-lsim
           Assume that runtime support has been provided and so there is no need to include the
           simulator library (libsim.a) on the linker command line.

       FT32 Options

       These options are defined specifically for the FT32 port.

       -msim
           Specifies that the program will be run on the simulator.  This causes an alternate
           runtime startup and library to be linked.  You must not use this option when generating
           programs that will run on real hardware; you must provide your own runtime library for
           whatever I/O functions are needed.

       -mlra
           Enable Local Register Allocation.  This is still experimental for FT32, so by default the
           compiler uses standard reload.

       -mnodiv
           Do not use div and mod instructions.

       -mft32b
           Enable use of the extended instructions of the FT32B processor.

       -mcompress
           Compress all code using the Ft32B code compression scheme.

       -mnopm
           Do not generate code that reads program memory.

       FRV Options

       -mgpr-32
           Only use the first 32 general-purpose registers.

       -mgpr-64
           Use all 64 general-purpose registers.

       -mfpr-32
           Use only the first 32 floating-point registers.

       -mfpr-64
           Use all 64 floating-point registers.

       -mhard-float
           Use hardware instructions for floating-point operations.

       -msoft-float
           Use library routines for floating-point operations.

       -malloc-cc
           Dynamically allocate condition code registers.

       -mfixed-cc
           Do not try to dynamically allocate condition code registers, only use "icc0" and "fcc0".

       -mdword
           Change ABI to use double word insns.

       -mno-dword
           Do not use double word instructions.

       -mdouble
           Use floating-point double instructions.

       -mno-double
           Do not use floating-point double instructions.

       -mmedia
           Use media instructions.

       -mno-media
           Do not use media instructions.

       -mmuladd
           Use multiply and add/subtract instructions.

       -mno-muladd
           Do not use multiply and add/subtract instructions.

       -mfdpic
           Select the FDPIC ABI, which uses function descriptors to represent pointers to functions.
           Without any PIC/PIE-related options, it implies -fPIE.  With -fpic or -fpie, it assumes
           GOT entries and small data are within a 12-bit range from the GOT base address; with
           -fPIC or -fPIE, GOT offsets are computed with 32 bits.  With a bfin-elf target, this
           option implies -msim.

       -minline-plt
           Enable inlining of PLT entries in function calls to functions that are not known to bind
           locally.  It has no effect without -mfdpic.  It's enabled by default if optimizing for
           speed and compiling for shared libraries (i.e., -fPIC or -fpic), or when an optimization
           option such as -O3 or above is present in the command line.

       -mTLS
           Assume a large TLS segment when generating thread-local code.

       -mtls
           Do not assume a large TLS segment when generating thread-local code.

       -mgprel-ro
           Enable the use of "GPREL" relocations in the FDPIC ABI for data that is known to be in
           read-only sections.  It's enabled by default, except for -fpic or -fpie: even though it
           may help make the global offset table smaller, it trades 1 instruction for 4.  With -fPIC
           or -fPIE, it trades 3 instructions for 4, one of which may be shared by multiple symbols,
           and it avoids the need for a GOT entry for the referenced symbol, so it's more likely to
           be a win.  If it is not, -mno-gprel-ro can be used to disable it.

       -multilib-library-pic
           Link with the (library, not FD) pic libraries.  It's implied by -mlibrary-pic, as well as
           by -fPIC and -fpic without -mfdpic.  You should never have to use it explicitly.

       -mlinked-fp
           Follow the EABI requirement of always creating a frame pointer whenever a stack frame is
           allocated.  This option is enabled by default and can be disabled with -mno-linked-fp.

       -mlong-calls
           Use indirect addressing to call functions outside the current compilation unit.  This
           allows the functions to be placed anywhere within the 32-bit address space.

       -malign-labels
           Try to align labels to an 8-byte boundary by inserting NOPs into the previous packet.
           This option only has an effect when VLIW packing is enabled.  It doesn't create new
           packets; it merely adds NOPs to existing ones.

       -mlibrary-pic
           Generate position-independent EABI code.

       -macc-4
           Use only the first four media accumulator registers.

       -macc-8
           Use all eight media accumulator registers.

       -mpack
           Pack VLIW instructions.

       -mno-pack
           Do not pack VLIW instructions.

       -mno-eflags
           Do not mark ABI switches in e_flags.

       -mcond-move
           Enable the use of conditional-move instructions (default).

           This switch is mainly for debugging the compiler and will likely be removed in a future
           version.

       -mno-cond-move
           Disable the use of conditional-move instructions.

           This switch is mainly for debugging the compiler and will likely be removed in a future
           version.

       -mscc
           Enable the use of conditional set instructions (default).

           This switch is mainly for debugging the compiler and will likely be removed in a future
           version.

       -mno-scc
           Disable the use of conditional set instructions.

           This switch is mainly for debugging the compiler and will likely be removed in a future
           version.

       -mcond-exec
           Enable the use of conditional execution (default).

           This switch is mainly for debugging the compiler and will likely be removed in a future
           version.

       -mno-cond-exec
           Disable the use of conditional execution.

           This switch is mainly for debugging the compiler and will likely be removed in a future
           version.

       -mvliw-branch
           Run a pass to pack branches into VLIW instructions (default).

           This switch is mainly for debugging the compiler and will likely be removed in a future
           version.

       -mno-vliw-branch
           Do not run a pass to pack branches into VLIW instructions.

           This switch is mainly for debugging the compiler and will likely be removed in a future
           version.

       -mmulti-cond-exec
           Enable optimization of "&&" and "||" in conditional execution (default).

           This switch is mainly for debugging the compiler and will likely be removed in a future
           version.

       -mno-multi-cond-exec
           Disable optimization of "&&" and "||" in conditional execution.

           This switch is mainly for debugging the compiler and will likely be removed in a future
           version.

       -mnested-cond-exec
           Enable nested conditional execution optimizations (default).

           This switch is mainly for debugging the compiler and will likely be removed in a future
           version.

       -mno-nested-cond-exec
           Disable nested conditional execution optimizations.

           This switch is mainly for debugging the compiler and will likely be removed in a future
           version.

       -moptimize-membar
           This switch removes redundant "membar" instructions from the compiler-generated code.  It
           is enabled by default.

       -mno-optimize-membar
           This switch disables the automatic removal of redundant "membar" instructions from the
           generated code.

       -mtomcat-stats
           Cause gas to print out tomcat statistics.

       -mcpu=cpu
           Select the processor type for which to generate code.  Possible values are frv, fr550,
           tomcat, fr500, fr450, fr405, fr400, fr300 and simple.

       GNU/Linux Options

       These -m options are defined for GNU/Linux targets:

       -mglibc
           Use the GNU C library.  This is the default except on *-*-linux-*uclibc*,
           *-*-linux-*musl* and *-*-linux-*android* targets.

       -muclibc
           Use uClibc C library.  This is the default on *-*-linux-*uclibc* targets.

       -mmusl
           Use the musl C library.  This is the default on *-*-linux-*musl* targets.

       -mbionic
           Use Bionic C library.  This is the default on *-*-linux-*android* targets.

       -mandroid
           Compile code compatible with Android platform.  This is the default on
           *-*-linux-*android* targets.

           When compiling, this option enables -mbionic, -fPIC, -fno-exceptions and -fno-rtti by
           default.  When linking, this option makes the GCC driver pass Android-specific options to
           the linker.  Finally, this option causes the preprocessor macro "__ANDROID__" to be
           defined.

       -tno-android-cc
           Disable compilation effects of -mandroid, i.e., do not enable -mbionic, -fPIC,
           -fno-exceptions and -fno-rtti by default.

       -tno-android-ld
           Disable linking effects of -mandroid, i.e., pass standard Linux linking options to the
           linker.

       H8/300 Options

       These -m options are defined for the H8/300 implementations:

       -mrelax
           Shorten some address references at link time, when possible; uses the linker option
           -relax.

       -mh Generate code for the H8/300H.

       -ms Generate code for the H8S.

       -mn Generate code for the H8S and H8/300H in the normal mode.  This switch must be used
           either with -mh or -ms.

       -ms2600
           Generate code for the H8S/2600.  This switch must be used with -ms.

       -mexr
           Extended registers are stored on stack before execution of function with monitor
           attribute. Default option is -mexr.  This option is valid only for H8S targets.

       -mno-exr
           Extended registers are not stored on stack before execution of function with monitor
           attribute. Default option is -mno-exr.  This option is valid only for H8S targets.

       -mint32
           Make "int" data 32 bits by default.

       -malign-300
           On the H8/300H and H8S, use the same alignment rules as for the H8/300.  The default for
           the H8/300H and H8S is to align longs and floats on 4-byte boundaries.  -malign-300
           causes them to be aligned on 2-byte boundaries.  This option has no effect on the H8/300.

       HPPA Options

       These -m options are defined for the HPPA family of computers:

       -march=architecture-type
           Generate code for the specified architecture.  The choices for architecture-type are 1.0
           for PA 1.0, 1.1 for PA 1.1, and 2.0 for PA 2.0 processors.  Refer to
           /usr/lib/sched.models on an HP-UX system to determine the proper architecture option for
           your machine.  Code compiled for lower numbered architectures runs on higher numbered
           architectures, but not the other way around.

       -mpa-risc-1-0
       -mpa-risc-1-1
       -mpa-risc-2-0
           Synonyms for -march=1.0, -march=1.1, and -march=2.0 respectively.

       -mcaller-copies
           The caller copies function arguments passed by hidden reference.  This option should be
           used with care as it is not compatible with the default 32-bit runtime.  However, only
           aggregates larger than eight bytes are passed by hidden reference and the option provides
           better compatibility with OpenMP.

       -mjump-in-delay
           This option is ignored and provided for compatibility purposes only.

       -mdisable-fpregs
           Prevent floating-point registers from being used in any manner.  This is necessary for
           compiling kernels that perform lazy context switching of floating-point registers.  If
           you use this option and attempt to perform floating-point operations, the compiler
           aborts.

       -mdisable-indexing
           Prevent the compiler from using indexing address modes.  This avoids some rather obscure
           problems when compiling MIG generated code under MACH.

       -mno-space-regs
           Generate code that assumes the target has no space registers.  This allows GCC to
           generate faster indirect calls and use unscaled index address modes.

           Such code is suitable for level 0 PA systems and kernels.

       -mfast-indirect-calls
           Generate code that assumes calls never cross space boundaries.  This allows GCC to emit
           code that performs faster indirect calls.

           This option does not work in the presence of shared libraries or nested functions.

       -mfixed-range=register-range
           Generate code treating the given register range as fixed registers.  A fixed register is
           one that the register allocator cannot use.  This is useful when compiling kernel code.
           A register range is specified as two registers separated by a dash.  Multiple register
           ranges can be specified separated by a comma.

       -mlong-load-store
           Generate 3-instruction load and store sequences as sometimes required by the HP-UX 10
           linker.  This is equivalent to the +k option to the HP compilers.

       -mportable-runtime
           Use the portable calling conventions proposed by HP for ELF systems.

       -mgas
           Enable the use of assembler directives only GAS understands.

       -mschedule=cpu-type
           Schedule code according to the constraints for the machine type cpu-type.  The choices
           for cpu-type are 700 7100, 7100LC, 7200, 7300 and 8000.  Refer to /usr/lib/sched.models
           on an HP-UX system to determine the proper scheduling option for your machine.  The
           default scheduling is 8000.

       -mlinker-opt
           Enable the optimization pass in the HP-UX linker.  Note this makes symbolic debugging
           impossible.  It also triggers a bug in the HP-UX 8 and HP-UX 9 linkers in which they give
           bogus error messages when linking some programs.

       -msoft-float
           Generate output containing library calls for floating point.  Warning: the requisite
           libraries are not available for all HPPA targets.  Normally the facilities of the
           machine's usual C compiler are used, but this cannot be done directly in cross-
           compilation.  You must make your own arrangements to provide suitable library functions
           for cross-compilation.

           -msoft-float changes the calling convention in the output file; therefore, it is only
           useful if you compile all of a program with this option.  In particular, you need to
           compile libgcc.a, the library that comes with GCC, with -msoft-float in order for this to
           work.

       -msio
           Generate the predefine, "_SIO", for server IO.  The default is -mwsio.  This generates
           the predefines, "__hp9000s700", "__hp9000s700__" and "_WSIO", for workstation IO.  These
           options are available under HP-UX and HI-UX.

       -mgnu-ld
           Use options specific to GNU ld.  This passes -shared to ld when building a shared
           library.  It is the default when GCC is configured, explicitly or implicitly, with the
           GNU linker.  This option does not affect which ld is called; it only changes what
           parameters are passed to that ld.  The ld that is called is determined by the --with-ld
           configure option, GCC's program search path, and finally by the user's PATH.  The linker
           used by GCC can be printed using which `gcc -print-prog-name=ld`.  This option is only
           available on the 64-bit HP-UX GCC, i.e. configured with hppa*64*-*-hpux*.

       -mhp-ld
           Use options specific to HP ld.  This passes -b to ld when building a shared library and
           passes +Accept TypeMismatch to ld on all links.  It is the default when GCC is
           configured, explicitly or implicitly, with the HP linker.  This option does not affect
           which ld is called; it only changes what parameters are passed to that ld.  The ld that
           is called is determined by the --with-ld configure option, GCC's program search path, and
           finally by the user's PATH.  The linker used by GCC can be printed using which `gcc
           -print-prog-name=ld`.  This option is only available on the 64-bit HP-UX GCC, i.e.
           configured with hppa*64*-*-hpux*.

       -mlong-calls
           Generate code that uses long call sequences.  This ensures that a call is always able to
           reach linker generated stubs.  The default is to generate long calls only when the
           distance from the call site to the beginning of the function or translation unit, as the
           case may be, exceeds a predefined limit set by the branch type being used.  The limits
           for normal calls are 7,600,000 and 240,000 bytes, respectively for the PA 2.0 and PA 1.X
           architectures.  Sibcalls are always limited at 240,000 bytes.

           Distances are measured from the beginning of functions when using the -ffunction-sections
           option, or when using the -mgas and -mno-portable-runtime options together under HP-UX
           with the SOM linker.

           It is normally not desirable to use this option as it degrades performance.  However, it
           may be useful in large applications, particularly when partial linking is used to build
           the application.

           The types of long calls used depends on the capabilities of the assembler and linker, and
           the type of code being generated.  The impact on systems that support long absolute
           calls, and long pic symbol-difference or pc-relative calls should be relatively small.
           However, an indirect call is used on 32-bit ELF systems in pic code and it is quite long.

       -munix=unix-std
           Generate compiler predefines and select a startfile for the specified UNIX standard.  The
           choices for unix-std are 93, 95 and 98.  93 is supported on all HP-UX versions.  95 is
           available on HP-UX 10.10 and later.  98 is available on HP-UX 11.11 and later.  The
           default values are 93 for HP-UX 10.00, 95 for HP-UX 10.10 though to 11.00, and 98 for HP-
           UX 11.11 and later.

           -munix=93 provides the same predefines as GCC 3.3 and 3.4.  -munix=95 provides additional
           predefines for "XOPEN_UNIX" and "_XOPEN_SOURCE_EXTENDED", and the startfile unix95.o.
           -munix=98 provides additional predefines for "_XOPEN_UNIX", "_XOPEN_SOURCE_EXTENDED",
           "_INCLUDE__STDC_A1_SOURCE" and "_INCLUDE_XOPEN_SOURCE_500", and the startfile unix98.o.

           It is important to note that this option changes the interfaces for various library
           routines.  It also affects the operational behavior of the C library.  Thus, extreme care
           is needed in using this option.

           Library code that is intended to operate with more than one UNIX standard must test, set
           and restore the variable "__xpg4_extended_mask" as appropriate.  Most GNU software
           doesn't provide this capability.

       -nolibdld
           Suppress the generation of link options to search libdld.sl when the -static option is
           specified on HP-UX 10 and later.

       -static
           The HP-UX implementation of setlocale in libc has a dependency on libdld.sl.  There isn't
           an archive version of libdld.sl.  Thus, when the -static option is specified, special
           link options are needed to resolve this dependency.

           On HP-UX 10 and later, the GCC driver adds the necessary options to link with libdld.sl
           when the -static option is specified.  This causes the resulting binary to be dynamic.
           On the 64-bit port, the linkers generate dynamic binaries by default in any case.  The
           -nolibdld option can be used to prevent the GCC driver from adding these link options.

       -threads
           Add support for multithreading with the dce thread library under HP-UX.  This option sets
           flags for both the preprocessor and linker.

       IA-64 Options

       These are the -m options defined for the Intel IA-64 architecture.

       -mbig-endian
           Generate code for a big-endian target.  This is the default for HP-UX.

       -mlittle-endian
           Generate code for a little-endian target.  This is the default for AIX5 and GNU/Linux.

       -mgnu-as
       -mno-gnu-as
           Generate (or don't) code for the GNU assembler.  This is the default.

       -mgnu-ld
       -mno-gnu-ld
           Generate (or don't) code for the GNU linker.  This is the default.

       -mno-pic
           Generate code that does not use a global pointer register.  The result is not position
           independent code, and violates the IA-64 ABI.

       -mvolatile-asm-stop
       -mno-volatile-asm-stop
           Generate (or don't) a stop bit immediately before and after volatile asm statements.

       -mregister-names
       -mno-register-names
           Generate (or don't) in, loc, and out register names for the stacked registers.  This may
           make assembler output more readable.

       -mno-sdata
       -msdata
           Disable (or enable) optimizations that use the small data section.  This may be useful
           for working around optimizer bugs.

       -mconstant-gp
           Generate code that uses a single constant global pointer value.  This is useful when
           compiling kernel code.

       -mauto-pic
           Generate code that is self-relocatable.  This implies -mconstant-gp.  This is useful when
           compiling firmware code.

       -minline-float-divide-min-latency
           Generate code for inline divides of floating-point values using the minimum latency
           algorithm.

       -minline-float-divide-max-throughput
           Generate code for inline divides of floating-point values using the maximum throughput
           algorithm.

       -mno-inline-float-divide
           Do not generate inline code for divides of floating-point values.

       -minline-int-divide-min-latency
           Generate code for inline divides of integer values using the minimum latency algorithm.

       -minline-int-divide-max-throughput
           Generate code for inline divides of integer values using the maximum throughput
           algorithm.

       -mno-inline-int-divide
           Do not generate inline code for divides of integer values.

       -minline-sqrt-min-latency
           Generate code for inline square roots using the minimum latency algorithm.

       -minline-sqrt-max-throughput
           Generate code for inline square roots using the maximum throughput algorithm.

       -mno-inline-sqrt
           Do not generate inline code for "sqrt".

       -mfused-madd
       -mno-fused-madd
           Do (don't) generate code that uses the fused multiply/add or multiply/subtract
           instructions.  The default is to use these instructions.

       -mno-dwarf2-asm
       -mdwarf2-asm
           Don't (or do) generate assembler code for the DWARF line number debugging info.  This may
           be useful when not using the GNU assembler.

       -mearly-stop-bits
       -mno-early-stop-bits
           Allow stop bits to be placed earlier than immediately preceding the instruction that
           triggered the stop bit.  This can improve instruction scheduling, but does not always do
           so.

       -mfixed-range=register-range
           Generate code treating the given register range as fixed registers.  A fixed register is
           one that the register allocator cannot use.  This is useful when compiling kernel code.
           A register range is specified as two registers separated by a dash.  Multiple register
           ranges can be specified separated by a comma.

       -mtls-size=tls-size
           Specify bit size of immediate TLS offsets.  Valid values are 14, 22, and 64.

       -mtune=cpu-type
           Tune the instruction scheduling for a particular CPU, Valid values are itanium, itanium1,
           merced, itanium2, and mckinley.

       -milp32
       -mlp64
           Generate code for a 32-bit or 64-bit environment.  The 32-bit environment sets int, long
           and pointer to 32 bits.  The 64-bit environment sets int to 32 bits and long and pointer
           to 64 bits.  These are HP-UX specific flags.

       -mno-sched-br-data-spec
       -msched-br-data-spec
           (Dis/En)able data speculative scheduling before reload.  This results in generation of
           "ld.a" instructions and the corresponding check instructions ("ld.c" / "chk.a").  The
           default setting is disabled.

       -msched-ar-data-spec
       -mno-sched-ar-data-spec
           (En/Dis)able data speculative scheduling after reload.  This results in generation of
           "ld.a" instructions and the corresponding check instructions ("ld.c" / "chk.a").  The
           default setting is enabled.

       -mno-sched-control-spec
       -msched-control-spec
           (Dis/En)able control speculative scheduling.  This feature is available only during
           region scheduling (i.e. before reload).  This results in generation of the "ld.s"
           instructions and the corresponding check instructions "chk.s".  The default setting is
           disabled.

       -msched-br-in-data-spec
       -mno-sched-br-in-data-spec
           (En/Dis)able speculative scheduling of the instructions that are dependent on the data
           speculative loads before reload.  This is effective only with -msched-br-data-spec
           enabled.  The default setting is enabled.

       -msched-ar-in-data-spec
       -mno-sched-ar-in-data-spec
           (En/Dis)able speculative scheduling of the instructions that are dependent on the data
           speculative loads after reload.  This is effective only with -msched-ar-data-spec
           enabled.  The default setting is enabled.

       -msched-in-control-spec
       -mno-sched-in-control-spec
           (En/Dis)able speculative scheduling of the instructions that are dependent on the control
           speculative loads.  This is effective only with -msched-control-spec enabled.  The
           default setting is enabled.

       -mno-sched-prefer-non-data-spec-insns
       -msched-prefer-non-data-spec-insns
           If enabled, data-speculative instructions are chosen for schedule only if there are no
           other choices at the moment.  This makes the use of the data speculation much more
           conservative.  The default setting is disabled.

       -mno-sched-prefer-non-control-spec-insns
       -msched-prefer-non-control-spec-insns
           If enabled, control-speculative instructions are chosen for schedule only if there are no
           other choices at the moment.  This makes the use of the control speculation much more
           conservative.  The default setting is disabled.

       -mno-sched-count-spec-in-critical-path
       -msched-count-spec-in-critical-path
           If enabled, speculative dependencies are considered during computation of the
           instructions priorities.  This makes the use of the speculation a bit more conservative.
           The default setting is disabled.

       -msched-spec-ldc
           Use a simple data speculation check.  This option is on by default.

       -msched-control-spec-ldc
           Use a simple check for control speculation.  This option is on by default.

       -msched-stop-bits-after-every-cycle
           Place a stop bit after every cycle when scheduling.  This option is on by default.

       -msched-fp-mem-deps-zero-cost
           Assume that floating-point stores and loads are not likely to cause a conflict when
           placed into the same instruction group.  This option is disabled by default.

       -msel-sched-dont-check-control-spec
           Generate checks for control speculation in selective scheduling.  This flag is disabled
           by default.

       -msched-max-memory-insns=max-insns
           Limit on the number of memory insns per instruction group, giving lower priority to
           subsequent memory insns attempting to schedule in the same instruction group. Frequently
           useful to prevent cache bank conflicts.  The default value is 1.

       -msched-max-memory-insns-hard-limit
           Makes the limit specified by msched-max-memory-insns a hard limit, disallowing more than
           that number in an instruction group.  Otherwise, the limit is "soft", meaning that non-
           memory operations are preferred when the limit is reached, but memory operations may
           still be scheduled.

       LM32 Options

       These -m options are defined for the LatticeMico32 architecture:

       -mbarrel-shift-enabled
           Enable barrel-shift instructions.

       -mdivide-enabled
           Enable divide and modulus instructions.

       -mmultiply-enabled
           Enable multiply instructions.

       -msign-extend-enabled
           Enable sign extend instructions.

       -muser-enabled
           Enable user-defined instructions.

       M32C Options

       -mcpu=name
           Select the CPU for which code is generated.  name may be one of r8c for the R8C/Tiny
           series, m16c for the M16C (up to /60) series, m32cm for the M16C/80 series, or m32c for
           the M32C/80 series.

       -msim
           Specifies that the program will be run on the simulator.  This causes an alternate
           runtime library to be linked in which supports, for example, file I/O.  You must not use
           this option when generating programs that will run on real hardware; you must provide
           your own runtime library for whatever I/O functions are needed.

       -memregs=number
           Specifies the number of memory-based pseudo-registers GCC uses during code generation.
           These pseudo-registers are used like real registers, so there is a tradeoff between GCC's
           ability to fit the code into available registers, and the performance penalty of using
           memory instead of registers.  Note that all modules in a program must be compiled with
           the same value for this option.  Because of that, you must not use this option with GCC's
           default runtime libraries.

       M32R/D Options

       These -m options are defined for Renesas M32R/D architectures:

       -m32r2
           Generate code for the M32R/2.

       -m32rx
           Generate code for the M32R/X.

       -m32r
           Generate code for the M32R.  This is the default.

       -mmodel=small
           Assume all objects live in the lower 16MB of memory (so that their addresses can be
           loaded with the "ld24" instruction), and assume all subroutines are reachable with the
           "bl" instruction.  This is the default.

           The addressability of a particular object can be set with the "model" attribute.

       -mmodel=medium
           Assume objects may be anywhere in the 32-bit address space (the compiler generates
           "seth/add3" instructions to load their addresses), and assume all subroutines are
           reachable with the "bl" instruction.

       -mmodel=large
           Assume objects may be anywhere in the 32-bit address space (the compiler generates
           "seth/add3" instructions to load their addresses), and assume subroutines may not be
           reachable with the "bl" instruction (the compiler generates the much slower
           "seth/add3/jl" instruction sequence).

       -msdata=none
           Disable use of the small data area.  Variables are put into one of ".data", ".bss", or
           ".rodata" (unless the "section" attribute has been specified).  This is the default.

           The small data area consists of sections ".sdata" and ".sbss".  Objects may be explicitly
           put in the small data area with the "section" attribute using one of these sections.

       -msdata=sdata
           Put small global and static data in the small data area, but do not generate special code
           to reference them.

       -msdata=use
           Put small global and static data in the small data area, and generate special
           instructions to reference them.

       -G num
           Put global and static objects less than or equal to num bytes into the small data or BSS
           sections instead of the normal data or BSS sections.  The default value of num is 8.  The
           -msdata option must be set to one of sdata or use for this option to have any effect.

           All modules should be compiled with the same -G num value.  Compiling with different
           values of num may or may not work; if it doesn't the linker gives an error
           message---incorrect code is not generated.

       -mdebug
           Makes the M32R-specific code in the compiler display some statistics that might help in
           debugging programs.

       -malign-loops
           Align all loops to a 32-byte boundary.

       -mno-align-loops
           Do not enforce a 32-byte alignment for loops.  This is the default.

       -missue-rate=number
           Issue number instructions per cycle.  number can only be 1 or 2.

       -mbranch-cost=number
           number can only be 1 or 2.  If it is 1 then branches are preferred over conditional code,
           if it is 2, then the opposite applies.

       -mflush-trap=number
           Specifies the trap number to use to flush the cache.  The default is 12.  Valid numbers
           are between 0 and 15 inclusive.

       -mno-flush-trap
           Specifies that the cache cannot be flushed by using a trap.

       -mflush-func=name
           Specifies the name of the operating system function to call to flush the cache.  The
           default is _flush_cache, but a function call is only used if a trap is not available.

       -mno-flush-func
           Indicates that there is no OS function for flushing the cache.

       M680x0 Options

       These are the -m options defined for M680x0 and ColdFire processors.  The default settings
       depend on which architecture was selected when the compiler was configured; the defaults for
       the most common choices are given below.

       -march=arch
           Generate code for a specific M680x0 or ColdFire instruction set architecture.
           Permissible values of arch for M680x0 architectures are: 68000, 68010, 68020, 68030,
           68040, 68060 and cpu32.  ColdFire architectures are selected according to Freescale's ISA
           classification and the permissible values are: isaa, isaaplus, isab and isac.

           GCC defines a macro "__mcfarch__" whenever it is generating code for a ColdFire target.
           The arch in this macro is one of the -march arguments given above.

           When used together, -march and -mtune select code that runs on a family of similar
           processors but that is optimized for a particular microarchitecture.

       -mcpu=cpu
           Generate code for a specific M680x0 or ColdFire processor.  The M680x0 cpus are: 68000,
           68010, 68020, 68030, 68040, 68060, 68302, 68332 and cpu32.  The ColdFire cpus are given
           by the table below, which also classifies the CPUs into families:

           Family : -mcpu arguments
           51 : 51 51ac 51ag 51cn 51em 51je 51jf 51jg 51jm 51mm 51qe 51qm
           5206 : 5202 5204 5206
           5206e : 5206e
           5208 : 5207 5208
           5211a : 5210a 5211a
           5213 : 5211 5212 5213
           5216 : 5214 5216
           52235 : 52230 52231 52232 52233 52234 52235
           5225 : 5224 5225
           52259 : 52252 52254 52255 52256 52258 52259
           5235 : 5232 5233 5234 5235 523x
           5249 : 5249
           5250 : 5250
           5271 : 5270 5271
           5272 : 5272
           5275 : 5274 5275
           5282 : 5280 5281 5282 528x
           53017 : 53011 53012 53013 53014 53015 53016 53017
           5307 : 5307
           5329 : 5327 5328 5329 532x
           5373 : 5372 5373 537x
           5407 : 5407
           5475 : 5470 5471 5472 5473 5474 5475 547x 5480 5481 5482 5483 5484 5485

           -mcpu=cpu overrides -march=arch if arch is compatible with cpu.  Other combinations of
           -mcpu and -march are rejected.

           GCC defines the macro "__mcf_cpu_cpu" when ColdFire target cpu is selected.  It also
           defines "__mcf_family_family", where the value of family is given by the table above.

       -mtune=tune
           Tune the code for a particular microarchitecture within the constraints set by -march and
           -mcpu.  The M680x0 microarchitectures are: 68000, 68010, 68020, 68030, 68040, 68060 and
           cpu32.  The ColdFire microarchitectures are: cfv1, cfv2, cfv3, cfv4 and cfv4e.

           You can also use -mtune=68020-40 for code that needs to run relatively well on 68020,
           68030 and 68040 targets.  -mtune=68020-60 is similar but includes 68060 targets as well.
           These two options select the same tuning decisions as -m68020-40 and -m68020-60
           respectively.

           GCC defines the macros "__mcarch" and "__mcarch__" when tuning for 680x0 architecture
           arch.  It also defines "mcarch" unless either -ansi or a non-GNU -std option is used.  If
           GCC is tuning for a range of architectures, as selected by -mtune=68020-40 or
           -mtune=68020-60, it defines the macros for every architecture in the range.

           GCC also defines the macro "__muarch__" when tuning for ColdFire microarchitecture uarch,
           where uarch is one of the arguments given above.

       -m68000
       -mc68000
           Generate output for a 68000.  This is the default when the compiler is configured for
           68000-based systems.  It is equivalent to -march=68000.

           Use this option for microcontrollers with a 68000 or EC000 core, including the 68008,
           68302, 68306, 68307, 68322, 68328 and 68356.

       -m68010
           Generate output for a 68010.  This is the default when the compiler is configured for
           68010-based systems.  It is equivalent to -march=68010.

       -m68020
       -mc68020
           Generate output for a 68020.  This is the default when the compiler is configured for
           68020-based systems.  It is equivalent to -march=68020.

       -m68030
           Generate output for a 68030.  This is the default when the compiler is configured for
           68030-based systems.  It is equivalent to -march=68030.

       -m68040
           Generate output for a 68040.  This is the default when the compiler is configured for
           68040-based systems.  It is equivalent to -march=68040.

           This option inhibits the use of 68881/68882 instructions that have to be emulated by
           software on the 68040.  Use this option if your 68040 does not have code to emulate those
           instructions.

       -m68060
           Generate output for a 68060.  This is the default when the compiler is configured for
           68060-based systems.  It is equivalent to -march=68060.

           This option inhibits the use of 68020 and 68881/68882 instructions that have to be
           emulated by software on the 68060.  Use this option if your 68060 does not have code to
           emulate those instructions.

       -mcpu32
           Generate output for a CPU32.  This is the default when the compiler is configured for
           CPU32-based systems.  It is equivalent to -march=cpu32.

           Use this option for microcontrollers with a CPU32 or CPU32+ core, including the 68330,
           68331, 68332, 68333, 68334, 68336, 68340, 68341, 68349 and 68360.

       -m5200
           Generate output for a 520X ColdFire CPU.  This is the default when the compiler is
           configured for 520X-based systems.  It is equivalent to -mcpu=5206, and is now deprecated
           in favor of that option.

           Use this option for microcontroller with a 5200 core, including the MCF5202, MCF5203,
           MCF5204 and MCF5206.

       -m5206e
           Generate output for a 5206e ColdFire CPU.  The option is now deprecated in favor of the
           equivalent -mcpu=5206e.

       -m528x
           Generate output for a member of the ColdFire 528X family.  The option is now deprecated
           in favor of the equivalent -mcpu=528x.

       -m5307
           Generate output for a ColdFire 5307 CPU.  The option is now deprecated in favor of the
           equivalent -mcpu=5307.

       -m5407
           Generate output for a ColdFire 5407 CPU.  The option is now deprecated in favor of the
           equivalent -mcpu=5407.

       -mcfv4e
           Generate output for a ColdFire V4e family CPU (e.g. 547x/548x).  This includes use of
           hardware floating-point instructions.  The option is equivalent to -mcpu=547x, and is now
           deprecated in favor of that option.

       -m68020-40
           Generate output for a 68040, without using any of the new instructions.  This results in
           code that can run relatively efficiently on either a 68020/68881 or a 68030 or a 68040.
           The generated code does use the 68881 instructions that are emulated on the 68040.

           The option is equivalent to -march=68020 -mtune=68020-40.

       -m68020-60
           Generate output for a 68060, without using any of the new instructions.  This results in
           code that can run relatively efficiently on either a 68020/68881 or a 68030 or a 68040.
           The generated code does use the 68881 instructions that are emulated on the 68060.

           The option is equivalent to -march=68020 -mtune=68020-60.

       -mhard-float
       -m68881
           Generate floating-point instructions.  This is the default for 68020 and above, and for
           ColdFire devices that have an FPU.  It defines the macro "__HAVE_68881__" on M680x0
           targets and "__mcffpu__" on ColdFire targets.

       -msoft-float
           Do not generate floating-point instructions; use library calls instead.  This is the
           default for 68000, 68010, and 68832 targets.  It is also the default for ColdFire devices
           that have no FPU.

       -mdiv
       -mno-div
           Generate (do not generate) ColdFire hardware divide and remainder instructions.  If
           -march is used without -mcpu, the default is "on" for ColdFire architectures and "off"
           for M680x0 architectures.  Otherwise, the default is taken from the target CPU (either
           the default CPU, or the one specified by -mcpu).  For example, the default is "off" for
           -mcpu=5206 and "on" for -mcpu=5206e.

           GCC defines the macro "__mcfhwdiv__" when this option is enabled.

       -mshort
           Consider type "int" to be 16 bits wide, like "short int".  Additionally, parameters
           passed on the stack are also aligned to a 16-bit boundary even on targets whose API
           mandates promotion to 32-bit.

       -mno-short
           Do not consider type "int" to be 16 bits wide.  This is the default.

       -mnobitfield
       -mno-bitfield
           Do not use the bit-field instructions.  The -m68000, -mcpu32 and -m5200 options imply
           -mnobitfield.

       -mbitfield
           Do use the bit-field instructions.  The -m68020 option implies -mbitfield.  This is the
           default if you use a configuration designed for a 68020.

       -mrtd
           Use a different function-calling convention, in which functions that take a fixed number
           of arguments return with the "rtd" instruction, which pops their arguments while
           returning.  This saves one instruction in the caller since there is no need to pop the
           arguments there.

           This calling convention is incompatible with the one normally used on Unix, so you cannot
           use it if you need to call libraries compiled with the Unix compiler.

           Also, you must provide function prototypes for all functions that take variable numbers
           of arguments (including "printf"); otherwise incorrect code is generated for calls to
           those functions.

           In addition, seriously incorrect code results if you call a function with too many
           arguments.  (Normally, extra arguments are harmlessly ignored.)

           The "rtd" instruction is supported by the 68010, 68020, 68030, 68040, 68060 and CPU32
           processors, but not by the 68000 or 5200.

           The default is -mno-rtd.

       -malign-int
       -mno-align-int
           Control whether GCC aligns "int", "long", "long long", "float", "double", and "long
           double" variables on a 32-bit boundary (-malign-int) or a 16-bit boundary
           (-mno-align-int).  Aligning variables on 32-bit boundaries produces code that runs
           somewhat faster on processors with 32-bit busses at the expense of more memory.

           Warning: if you use the -malign-int switch, GCC aligns structures containing the above
           types differently than most published application binary interface specifications for the
           m68k.

           Use the pc-relative addressing mode of the 68000 directly, instead of using a global
           offset table.  At present, this option implies -fpic, allowing at most a 16-bit offset
           for pc-relative addressing.  -fPIC is not presently supported with -mpcrel, though this
           could be supported for 68020 and higher processors.

       -mno-strict-align
       -mstrict-align
           Do not (do) assume that unaligned memory references are handled by the system.

       -msep-data
           Generate code that allows the data segment to be located in a different area of memory
           from the text segment.  This allows for execute-in-place in an environment without
           virtual memory management.  This option implies -fPIC.

       -mno-sep-data
           Generate code that assumes that the data segment follows the text segment.  This is the
           default.

       -mid-shared-library
           Generate code that supports shared libraries via the library ID method.  This allows for
           execute-in-place and shared libraries in an environment without virtual memory
           management.  This option implies -fPIC.

       -mno-id-shared-library
           Generate code that doesn't assume ID-based shared libraries are being used.  This is the
           default.

       -mshared-library-id=n
           Specifies the identification number of the ID-based shared library being compiled.
           Specifying a value of 0 generates more compact code; specifying other values forces the
           allocation of that number to the current library, but is no more space- or time-efficient
           than omitting this option.

       -mxgot
       -mno-xgot
           When generating position-independent code for ColdFire, generate code that works if the
           GOT has more than 8192 entries.  This code is larger and slower than code generated
           without this option.  On M680x0 processors, this option is not needed; -fPIC suffices.

           GCC normally uses a single instruction to load values from the GOT.  While this is
           relatively efficient, it only works if the GOT is smaller than about 64k.  Anything
           larger causes the linker to report an error such as:

                   relocation truncated to fit: R_68K_GOT16O foobar

           If this happens, you should recompile your code with -mxgot.  It should then work with
           very large GOTs.  However, code generated with -mxgot is less efficient, since it takes 4
           instructions to fetch the value of a global symbol.

           Note that some linkers, including newer versions of the GNU linker, can create multiple
           GOTs and sort GOT entries.  If you have such a linker, you should only need to use -mxgot
           when compiling a single object file that accesses more than 8192 GOT entries.  Very few
           do.

           These options have no effect unless GCC is generating position-independent code.

       -mlong-jump-table-offsets
           Use 32-bit offsets in "switch" tables.  The default is to use 16-bit offsets.

       MCore Options

       These are the -m options defined for the Motorola M*Core processors.

       -mhardlit
       -mno-hardlit
           Inline constants into the code stream if it can be done in two instructions or less.

       -mdiv
       -mno-div
           Use the divide instruction.  (Enabled by default).

       -mrelax-immediate
       -mno-relax-immediate
           Allow arbitrary-sized immediates in bit operations.

       -mwide-bitfields
       -mno-wide-bitfields
           Always treat bit-fields as "int"-sized.

       -m4byte-functions
       -mno-4byte-functions
           Force all functions to be aligned to a 4-byte boundary.

       -mcallgraph-data
       -mno-callgraph-data
           Emit callgraph information.

       -mslow-bytes
       -mno-slow-bytes
           Prefer word access when reading byte quantities.

       -mlittle-endian
       -mbig-endian
           Generate code for a little-endian target.

       -m210
       -m340
           Generate code for the 210 processor.

       -mno-lsim
           Assume that runtime support has been provided and so omit the simulator library
           (libsim.a) from the linker command line.

       -mstack-increment=size
           Set the maximum amount for a single stack increment operation.  Large values can increase
           the speed of programs that contain functions that need a large amount of stack space, but
           they can also trigger a segmentation fault if the stack is extended too much.  The
           default value is 0x1000.

       MeP Options

       -mabsdiff
           Enables the "abs" instruction, which is the absolute difference between two registers.

       -mall-opts
           Enables all the optional instructions---average, multiply, divide, bit operations,
           leading zero, absolute difference, min/max, clip, and saturation.

       -maverage
           Enables the "ave" instruction, which computes the average of two registers.

       -mbased=n
           Variables of size n bytes or smaller are placed in the ".based" section by default.
           Based variables use the $tp register as a base register, and there is a 128-byte limit to
           the ".based" section.

       -mbitops
           Enables the bit operation instructions---bit test ("btstm"), set ("bsetm"), clear
           ("bclrm"), invert ("bnotm"), and test-and-set ("tas").

       -mc=name
           Selects which section constant data is placed in.  name may be tiny, near, or far.

       -mclip
           Enables the "clip" instruction.  Note that -mclip is not useful unless you also provide
           -mminmax.

       -mconfig=name
           Selects one of the built-in core configurations.  Each MeP chip has one or more modules
           in it; each module has a core CPU and a variety of coprocessors, optional instructions,
           and peripherals.  The "MeP-Integrator" tool, not part of GCC, provides these
           configurations through this option; using this option is the same as using all the
           corresponding command-line options.  The default configuration is default.

       -mcop
           Enables the coprocessor instructions.  By default, this is a 32-bit coprocessor.  Note
           that the coprocessor is normally enabled via the -mconfig= option.

       -mcop32
           Enables the 32-bit coprocessor's instructions.

       -mcop64
           Enables the 64-bit coprocessor's instructions.

       -mivc2
           Enables IVC2 scheduling.  IVC2 is a 64-bit VLIW coprocessor.

       -mdc
           Causes constant variables to be placed in the ".near" section.

       -mdiv
           Enables the "div" and "divu" instructions.

       -meb
           Generate big-endian code.

       -mel
           Generate little-endian code.

       -mio-volatile
           Tells the compiler that any variable marked with the "io" attribute is to be considered
           volatile.

       -ml Causes variables to be assigned to the ".far" section by default.

       -mleadz
           Enables the "leadz" (leading zero) instruction.

       -mm Causes variables to be assigned to the ".near" section by default.

       -mminmax
           Enables the "min" and "max" instructions.

       -mmult
           Enables the multiplication and multiply-accumulate instructions.

       -mno-opts
           Disables all the optional instructions enabled by -mall-opts.

       -mrepeat
           Enables the "repeat" and "erepeat" instructions, used for low-overhead looping.

       -ms Causes all variables to default to the ".tiny" section.  Note that there is a 65536-byte
           limit to this section.  Accesses to these variables use the %gp base register.

       -msatur
           Enables the saturation instructions.  Note that the compiler does not currently generate
           these itself, but this option is included for compatibility with other tools, like "as".

       -msdram
           Link the SDRAM-based runtime instead of the default ROM-based runtime.

       -msim
           Link the simulator run-time libraries.

       -msimnovec
           Link the simulator runtime libraries, excluding built-in support for reset and exception
           vectors and tables.

       -mtf
           Causes all functions to default to the ".far" section.  Without this option, functions
           default to the ".near" section.

       -mtiny=n
           Variables that are n bytes or smaller are allocated to the ".tiny" section.  These
           variables use the $gp base register.  The default for this option is 4, but note that
           there's a 65536-byte limit to the ".tiny" section.

       MicroBlaze Options

       -msoft-float
           Use software emulation for floating point (default).

       -mhard-float
           Use hardware floating-point instructions.

       -mmemcpy
           Do not optimize block moves, use "memcpy".

       -mno-clearbss
           This option is deprecated.  Use -fno-zero-initialized-in-bss instead.

       -mcpu=cpu-type
           Use features of, and schedule code for, the given CPU.  Supported values are in the
           format vX.YY.Z, where X is a major version, YY is the minor version, and Z is
           compatibility code.  Example values are v3.00.a, v4.00.b, v5.00.a, v5.00.b, v6.00.a.

       -mxl-soft-mul
           Use software multiply emulation (default).

       -mxl-soft-div
           Use software emulation for divides (default).

       -mxl-barrel-shift
           Use the hardware barrel shifter.

       -mxl-pattern-compare
           Use pattern compare instructions.

       -msmall-divides
           Use table lookup optimization for small signed integer divisions.

       -mxl-stack-check
           This option is deprecated.  Use -fstack-check instead.

       -mxl-gp-opt
           Use GP-relative ".sdata"/".sbss" sections.

       -mxl-multiply-high
           Use multiply high instructions for high part of 32x32 multiply.

       -mxl-float-convert
           Use hardware floating-point conversion instructions.

       -mxl-float-sqrt
           Use hardware floating-point square root instruction.

       -mbig-endian
           Generate code for a big-endian target.

       -mlittle-endian
           Generate code for a little-endian target.

       -mxl-reorder
           Use reorder instructions (swap and byte reversed load/store).

       -mxl-mode-app-model
           Select application model app-model.  Valid models are

           executable
               normal executable (default), uses startup code crt0.o.

           -mpic-data-is-text-relative
               Assume that the displacement between the text and data segments is fixed at static
               link time.  This allows data to be referenced by offset from start of text address
               instead of GOT since PC-relative addressing is not supported.

           xmdstub
               for use with Xilinx Microprocessor Debugger (XMD) based software intrusive debug
               agent called xmdstub. This uses startup file crt1.o and sets the start address of the
               program to 0x800.

           bootstrap
               for applications that are loaded using a bootloader.  This model uses startup file
               crt2.o which does not contain a processor reset vector handler. This is suitable for
               transferring control on a processor reset to the bootloader rather than the
               application.

           novectors
               for applications that do not require any of the MicroBlaze vectors. This option may
               be useful for applications running within a monitoring application. This model uses
               crt3.o as a startup file.

           Option -xl-mode-app-model is a deprecated alias for -mxl-mode-app-model.

       MIPS Options

       -EB Generate big-endian code.

       -EL Generate little-endian code.  This is the default for mips*el-*-* configurations.

       -march=arch
           Generate code that runs on arch, which can be the name of a generic MIPS ISA, or the name
           of a particular processor.  The ISA names are: mips1, mips2, mips3, mips4, mips32,
           mips32r2, mips32r3, mips32r5, mips32r6, mips64, mips64r2, mips64r3, mips64r5 and
           mips64r6.  The processor names are: 4kc, 4km, 4kp, 4ksc, 4kec, 4kem, 4kep, 4ksd, 5kc,
           5kf, 20kc, 24kc, 24kf2_1, 24kf1_1, 24kec, 24kef2_1, 24kef1_1, 34kc, 34kf2_1, 34kf1_1,
           34kn, 74kc, 74kf2_1, 74kf1_1, 74kf3_2, 1004kc, 1004kf2_1, 1004kf1_1, i6400, i6500,
           interaptiv, loongson2e, loongson2f, loongson3a, gs464, gs464e, gs264e, m4k, m14k, m14kc,
           m14ke, m14kec, m5100, m5101, octeon, octeon+, octeon2, octeon3, orion, p5600, p6600,
           r2000, r3000, r3900, r4000, r4400, r4600, r4650, r4700, r5900, r6000, r8000, rm7000,
           rm9000, r10000, r12000, r14000, r16000, sb1, sr71000, vr4100, vr4111, vr4120, vr4130,
           vr4300, vr5000, vr5400, vr5500, xlr and xlp.  The special value from-abi selects the most
           compatible architecture for the selected ABI (that is, mips1 for 32-bit ABIs and mips3
           for 64-bit ABIs).

           The native Linux/GNU toolchain also supports the value native, which selects the best
           architecture option for the host processor.  -march=native has no effect if GCC does not
           recognize the processor.

           In processor names, a final 000 can be abbreviated as k (for example, -march=r2k).
           Prefixes are optional, and vr may be written r.

           Names of the form nf2_1 refer to processors with FPUs clocked at half the rate of the
           core, names of the form nf1_1 refer to processors with FPUs clocked at the same rate as
           the core, and names of the form nf3_2 refer to processors with FPUs clocked a ratio of
           3:2 with respect to the core.  For compatibility reasons, nf is accepted as a synonym for
           nf2_1 while nx and bfx are accepted as synonyms for nf1_1.

           GCC defines two macros based on the value of this option.  The first is "_MIPS_ARCH",
           which gives the name of target architecture, as a string.  The second has the form
           "_MIPS_ARCH_foo", where foo is the capitalized value of "_MIPS_ARCH".  For example,
           -march=r2000 sets "_MIPS_ARCH" to "r2000" and defines the macro "_MIPS_ARCH_R2000".

           Note that the "_MIPS_ARCH" macro uses the processor names given above.  In other words,
           it has the full prefix and does not abbreviate 000 as k.  In the case of from-abi, the
           macro names the resolved architecture (either "mips1" or "mips3").  It names the default
           architecture when no -march option is given.

       -mtune=arch
           Optimize for arch.  Among other things, this option controls the way instructions are
           scheduled, and the perceived cost of arithmetic operations.  The list of arch values is
           the same as for -march.

           When this option is not used, GCC optimizes for the processor specified by -march.  By
           using -march and -mtune together, it is possible to generate code that runs on a family
           of processors, but optimize the code for one particular member of that family.

           -mtune defines the macros "_MIPS_TUNE" and "_MIPS_TUNE_foo", which work in the same way
           as the -march ones described above.

       -mips1
           Equivalent to -march=mips1.

       -mips2
           Equivalent to -march=mips2.

       -mips3
           Equivalent to -march=mips3.

       -mips4
           Equivalent to -march=mips4.

       -mips32
           Equivalent to -march=mips32.

       -mips32r3
           Equivalent to -march=mips32r3.

       -mips32r5
           Equivalent to -march=mips32r5.

       -mips32r6
           Equivalent to -march=mips32r6.

       -mips64
           Equivalent to -march=mips64.

       -mips64r2
           Equivalent to -march=mips64r2.

       -mips64r3
           Equivalent to -march=mips64r3.

       -mips64r5
           Equivalent to -march=mips64r5.

       -mips64r6
           Equivalent to -march=mips64r6.

       -mips16
       -mno-mips16
           Generate (do not generate) MIPS16 code.  If GCC is targeting a MIPS32 or MIPS64
           architecture, it makes use of the MIPS16e ASE.

           MIPS16 code generation can also be controlled on a per-function basis by means of
           "mips16" and "nomips16" attributes.

       -mflip-mips16
           Generate MIPS16 code on alternating functions.  This option is provided for regression
           testing of mixed MIPS16/non-MIPS16 code generation, and is not intended for ordinary use
           in compiling user code.

       -minterlink-compressed
       -mno-interlink-compressed
           Require (do not require) that code using the standard (uncompressed) MIPS ISA be link-
           compatible with MIPS16 and microMIPS code, and vice versa.

           For example, code using the standard ISA encoding cannot jump directly to MIPS16 or
           microMIPS code; it must either use a call or an indirect jump.  -minterlink-compressed
           therefore disables direct jumps unless GCC knows that the target of the jump is not
           compressed.

       -minterlink-mips16
       -mno-interlink-mips16
           Aliases of -minterlink-compressed and -mno-interlink-compressed.  These options predate
           the microMIPS ASE and are retained for backwards compatibility.

       -mabi=32
       -mabi=o64
       -mabi=n32
       -mabi=64
       -mabi=eabi
           Generate code for the given ABI.

           Note that the EABI has a 32-bit and a 64-bit variant.  GCC normally generates 64-bit code
           when you select a 64-bit architecture, but you can use -mgp32 to get 32-bit code instead.

           For information about the O64 ABI, see <http://gcc.gnu.org/projects/mipso64-abi.html>.

           GCC supports a variant of the o32 ABI in which floating-point registers are 64 rather
           than 32 bits wide.  You can select this combination with -mabi=32 -mfp64.  This ABI
           relies on the "mthc1" and "mfhc1" instructions and is therefore only supported for
           MIPS32R2, MIPS32R3 and MIPS32R5 processors.

           The register assignments for arguments and return values remain the same, but each scalar
           value is passed in a single 64-bit register rather than a pair of 32-bit registers.  For
           example, scalar floating-point values are returned in $f0 only, not a $f0/$f1 pair.  The
           set of call-saved registers also remains the same in that the even-numbered double-
           precision registers are saved.

           Two additional variants of the o32 ABI are supported to enable a transition from 32-bit
           to 64-bit registers.  These are FPXX (-mfpxx) and FP64A (-mfp64 -mno-odd-spreg).  The
           FPXX extension mandates that all code must execute correctly when run using 32-bit or
           64-bit registers.  The code can be interlinked with either FP32 or FP64, but not both.
           The FP64A extension is similar to the FP64 extension but forbids the use of odd-numbered
           single-precision registers.  This can be used in conjunction with the "FRE" mode of FPUs
           in MIPS32R5 processors and allows both FP32 and FP64A code to interlink and run in the
           same process without changing FPU modes.

       -mabicalls
       -mno-abicalls
           Generate (do not generate) code that is suitable for SVR4-style dynamic objects.
           -mabicalls is the default for SVR4-based systems.

       -mshared
       -mno-shared
           Generate (do not generate) code that is fully position-independent, and that can
           therefore be linked into shared libraries.  This option only affects -mabicalls.

           All -mabicalls code has traditionally been position-independent, regardless of options
           like -fPIC and -fpic.  However, as an extension, the GNU toolchain allows executables to
           use absolute accesses for locally-binding symbols.  It can also use shorter GP
           initialization sequences and generate direct calls to locally-defined functions.  This
           mode is selected by -mno-shared.

           -mno-shared depends on binutils 2.16 or higher and generates objects that can only be
           linked by the GNU linker.  However, the option does not affect the ABI of the final
           executable; it only affects the ABI of relocatable objects.  Using -mno-shared generally
           makes executables both smaller and quicker.

           -mshared is the default.

       -mplt
       -mno-plt
           Assume (do not assume) that the static and dynamic linkers support PLTs and copy
           relocations.  This option only affects -mno-shared -mabicalls.  For the n64 ABI, this
           option has no effect without -msym32.

           You can make -mplt the default by configuring GCC with --with-mips-plt.  The default is
           -mno-plt otherwise.

       -mxgot
       -mno-xgot
           Lift (do not lift) the usual restrictions on the size of the global offset table.

           GCC normally uses a single instruction to load values from the GOT.  While this is
           relatively efficient, it only works if the GOT is smaller than about 64k.  Anything
           larger causes the linker to report an error such as:

                   relocation truncated to fit: R_MIPS_GOT16 foobar

           If this happens, you should recompile your code with -mxgot.  This works with very large
           GOTs, although the code is also less efficient, since it takes three instructions to
           fetch the value of a global symbol.

           Note that some linkers can create multiple GOTs.  If you have such a linker, you should
           only need to use -mxgot when a single object file accesses more than 64k's worth of GOT
           entries.  Very few do.

           These options have no effect unless GCC is generating position independent code.

       -mgp32
           Assume that general-purpose registers are 32 bits wide.

       -mgp64
           Assume that general-purpose registers are 64 bits wide.

       -mfp32
           Assume that floating-point registers are 32 bits wide.

       -mfp64
           Assume that floating-point registers are 64 bits wide.

       -mfpxx
           Do not assume the width of floating-point registers.

       -mhard-float
           Use floating-point coprocessor instructions.

       -msoft-float
           Do not use floating-point coprocessor instructions.  Implement floating-point
           calculations using library calls instead.

       -mno-float
           Equivalent to -msoft-float, but additionally asserts that the program being compiled does
           not perform any floating-point operations.  This option is presently supported only by
           some bare-metal MIPS configurations, where it may select a special set of libraries that
           lack all floating-point support (including, for example, the floating-point "printf"
           formats).  If code compiled with -mno-float accidentally contains floating-point
           operations, it is likely to suffer a link-time or run-time failure.

       -msingle-float
           Assume that the floating-point coprocessor only supports single-precision operations.

       -mdouble-float
           Assume that the floating-point coprocessor supports double-precision operations.  This is
           the default.

       -modd-spreg
       -mno-odd-spreg
           Enable the use of odd-numbered single-precision floating-point registers for the o32 ABI.
           This is the default for processors that are known to support these registers.  When using
           the o32 FPXX ABI, -mno-odd-spreg is set by default.

       -mabs=2008
       -mabs=legacy
           These options control the treatment of the special not-a-number (NaN) IEEE 754 floating-
           point data with the "abs.fmt" and "neg.fmt" machine instructions.

           By default or when -mabs=legacy is used the legacy treatment is selected.  In this case
           these instructions are considered arithmetic and avoided where correct operation is
           required and the input operand might be a NaN.  A longer sequence of instructions that
           manipulate the sign bit of floating-point datum manually is used instead unless the
           -ffinite-math-only option has also been specified.

           The -mabs=2008 option selects the IEEE 754-2008 treatment.  In this case these
           instructions are considered non-arithmetic and therefore operating correctly in all
           cases, including in particular where the input operand is a NaN.  These instructions are
           therefore always used for the respective operations.

       -mnan=2008
       -mnan=legacy
           These options control the encoding of the special not-a-number (NaN) IEEE 754 floating-
           point data.

           The -mnan=legacy option selects the legacy encoding.  In this case quiet NaNs (qNaNs) are
           denoted by the first bit of their trailing significand field being 0, whereas signaling
           NaNs (sNaNs) are denoted by the first bit of their trailing significand field being 1.

           The -mnan=2008 option selects the IEEE 754-2008 encoding.  In this case qNaNs are denoted
           by the first bit of their trailing significand field being 1, whereas sNaNs are denoted
           by the first bit of their trailing significand field being 0.

           The default is -mnan=legacy unless GCC has been configured with --with-nan=2008.

       -mllsc
       -mno-llsc
           Use (do not use) ll, sc, and sync instructions to implement atomic memory built-in
           functions.  When neither option is specified, GCC uses the instructions if the target
           architecture supports them.

           -mllsc is useful if the runtime environment can emulate the instructions and -mno-llsc
           can be useful when compiling for nonstandard ISAs.  You can make either option the
           default by configuring GCC with --with-llsc and --without-llsc respectively.  --with-llsc
           is the default for some configurations; see the installation documentation for details.

       -mdsp
       -mno-dsp
           Use (do not use) revision 1 of the MIPS DSP ASE.
             This option defines the preprocessor macro "__mips_dsp".  It also defines
           "__mips_dsp_rev" to 1.

       -mdspr2
       -mno-dspr2
           Use (do not use) revision 2 of the MIPS DSP ASE.
             This option defines the preprocessor macros "__mips_dsp" and "__mips_dspr2".  It also
           defines "__mips_dsp_rev" to 2.

       -msmartmips
       -mno-smartmips
           Use (do not use) the MIPS SmartMIPS ASE.

       -mpaired-single
       -mno-paired-single
           Use (do not use) paired-single floating-point instructions.
             This option requires hardware floating-point support to be enabled.

       -mdmx
       -mno-mdmx
           Use (do not use) MIPS Digital Media Extension instructions.  This option can only be used
           when generating 64-bit code and requires hardware floating-point support to be enabled.

       -mips3d
       -mno-mips3d
           Use (do not use) the MIPS-3D ASE.  The option -mips3d implies -mpaired-single.

       -mmicromips
       -mno-micromips
           Generate (do not generate) microMIPS code.

           MicroMIPS code generation can also be controlled on a per-function basis by means of
           "micromips" and "nomicromips" attributes.

       -mmt
       -mno-mt
           Use (do not use) MT Multithreading instructions.

       -mmcu
       -mno-mcu
           Use (do not use) the MIPS MCU ASE instructions.

       -meva
       -mno-eva
           Use (do not use) the MIPS Enhanced Virtual Addressing instructions.

       -mvirt
       -mno-virt
           Use (do not use) the MIPS Virtualization (VZ) instructions.

       -mxpa
       -mno-xpa
           Use (do not use) the MIPS eXtended Physical Address (XPA) instructions.

       -mcrc
       -mno-crc
           Use (do not use) the MIPS Cyclic Redundancy Check (CRC) instructions.

       -mginv
       -mno-ginv
           Use (do not use) the MIPS Global INValidate (GINV) instructions.

       -mloongson-mmi
       -mno-loongson-mmi
           Use (do not use) the MIPS Loongson MultiMedia extensions Instructions (MMI).

       -mloongson-ext
       -mno-loongson-ext
           Use (do not use) the MIPS Loongson EXTensions (EXT) instructions.

       -mloongson-ext2
       -mno-loongson-ext2
           Use (do not use) the MIPS Loongson EXTensions r2 (EXT2) instructions.

       -mlong64
           Force "long" types to be 64 bits wide.  See -mlong32 for an explanation of the default
           and the way that the pointer size is determined.

       -mlong32
           Force "long", "int", and pointer types to be 32 bits wide.

           The default size of "int"s, "long"s and pointers depends on the ABI.  All the supported
           ABIs use 32-bit "int"s.  The n64 ABI uses 64-bit "long"s, as does the 64-bit EABI; the
           others use 32-bit "long"s.  Pointers are the same size as "long"s, or the same size as
           integer registers, whichever is smaller.

       -msym32
       -mno-sym32
           Assume (do not assume) that all symbols have 32-bit values, regardless of the selected
           ABI.  This option is useful in combination with -mabi=64 and -mno-abicalls because it
           allows GCC to generate shorter and faster references to symbolic addresses.

       -G num
           Put definitions of externally-visible data in a small data section if that data is no
           bigger than num bytes.  GCC can then generate more efficient accesses to the data; see
           -mgpopt for details.

           The default -G option depends on the configuration.

       -mlocal-sdata
       -mno-local-sdata
           Extend (do not extend) the -G behavior to local data too, such as to static variables in
           C.  -mlocal-sdata is the default for all configurations.

           If the linker complains that an application is using too much small data, you might want
           to try rebuilding the less performance-critical parts with -mno-local-sdata.  You might
           also want to build large libraries with -mno-local-sdata, so that the libraries leave
           more room for the main program.

       -mextern-sdata
       -mno-extern-sdata
           Assume (do not assume) that externally-defined data is in a small data section if the
           size of that data is within the -G limit.  -mextern-sdata is the default for all
           configurations.

           If you compile a module Mod with -mextern-sdata -G num -mgpopt, and Mod references a
           variable Var that is no bigger than num bytes, you must make sure that Var is placed in a
           small data section.  If Var is defined by another module, you must either compile that
           module with a high-enough -G setting or attach a "section" attribute to Var's definition.
           If Var is common, you must link the application with a high-enough -G setting.

           The easiest way of satisfying these restrictions is to compile and link every module with
           the same -G option.  However, you may wish to build a library that supports several
           different small data limits.  You can do this by compiling the library with the highest
           supported -G setting and additionally using -mno-extern-sdata to stop the library from
           making assumptions about externally-defined data.

       -mgpopt
       -mno-gpopt
           Use (do not use) GP-relative accesses for symbols that are known to be in a small data
           section; see -G, -mlocal-sdata and -mextern-sdata.  -mgpopt is the default for all
           configurations.

           -mno-gpopt is useful for cases where the $gp register might not hold the value of "_gp".
           For example, if the code is part of a library that might be used in a boot monitor,
           programs that call boot monitor routines pass an unknown value in $gp.  (In such
           situations, the boot monitor itself is usually compiled with -G0.)

           -mno-gpopt implies -mno-local-sdata and -mno-extern-sdata.

       -membedded-data
       -mno-embedded-data
           Allocate variables to the read-only data section first if possible, then next in the
           small data section if possible, otherwise in data.  This gives slightly slower code than
           the default, but reduces the amount of RAM required when executing, and thus may be
           preferred for some embedded systems.

       -muninit-const-in-rodata
       -mno-uninit-const-in-rodata
           Put uninitialized "const" variables in the read-only data section.  This option is only
           meaningful in conjunction with -membedded-data.

       -mcode-readable=setting
           Specify whether GCC may generate code that reads from executable sections.  There are
           three possible settings:

           -mcode-readable=yes
               Instructions may freely access executable sections.  This is the default setting.

           -mcode-readable=pcrel
               MIPS16 PC-relative load instructions can access executable sections, but other
               instructions must not do so.  This option is useful on 4KSc and 4KSd processors when
               the code TLBs have the Read Inhibit bit set.  It is also useful on processors that
               can be configured to have a dual instruction/data SRAM interface and that, like the
               M4K, automatically redirect PC-relative loads to the instruction RAM.

           -mcode-readable=no
               Instructions must not access executable sections.  This option can be useful on
               targets that are configured to have a dual instruction/data SRAM interface but that
               (unlike the M4K) do not automatically redirect PC-relative loads to the instruction
               RAM.

       -msplit-addresses
       -mno-split-addresses
           Enable (disable) use of the "%hi()" and "%lo()" assembler relocation operators.  This
           option has been superseded by -mexplicit-relocs but is retained for backwards
           compatibility.

       -mexplicit-relocs
       -mno-explicit-relocs
           Use (do not use) assembler relocation operators when dealing with symbolic addresses.
           The alternative, selected by -mno-explicit-relocs, is to use assembler macros instead.

           -mexplicit-relocs is the default if GCC was configured to use an assembler that supports
           relocation operators.

       -mcheck-zero-division
       -mno-check-zero-division
           Trap (do not trap) on integer division by zero.

           The default is -mcheck-zero-division.

       -mdivide-traps
       -mdivide-breaks
           MIPS systems check for division by zero by generating either a conditional trap or a
           break instruction.  Using traps results in smaller code, but is only supported on MIPS II
           and later.  Also, some versions of the Linux kernel have a bug that prevents trap from
           generating the proper signal ("SIGFPE").  Use -mdivide-traps to allow conditional traps
           on architectures that support them and -mdivide-breaks to force the use of breaks.

           The default is usually -mdivide-traps, but this can be overridden at configure time using
           --with-divide=breaks.  Divide-by-zero checks can be completely disabled using
           -mno-check-zero-division.

       -mload-store-pairs
       -mno-load-store-pairs
           Enable (disable) an optimization that pairs consecutive load or store instructions to
           enable load/store bonding.  This option is enabled by default but only takes effect when
           the selected architecture is known to support bonding.

       -mmemcpy
       -mno-memcpy
           Force (do not force) the use of "memcpy" for non-trivial block moves.  The default is
           -mno-memcpy, which allows GCC to inline most constant-sized copies.

       -mlong-calls
       -mno-long-calls
           Disable (do not disable) use of the "jal" instruction.  Calling functions using "jal" is
           more efficient but requires the caller and callee to be in the same 256 megabyte segment.

           This option has no effect on abicalls code.  The default is -mno-long-calls.

       -mmad
       -mno-mad
           Enable (disable) use of the "mad", "madu" and "mul" instructions, as provided by the
           R4650 ISA.

       -mimadd
       -mno-imadd
           Enable (disable) use of the "madd" and "msub" integer instructions.  The default is
           -mimadd on architectures that support "madd" and "msub" except for the 74k architecture
           where it was found to generate slower code.

       -mfused-madd
       -mno-fused-madd
           Enable (disable) use of the floating-point multiply-accumulate instructions, when they
           are available.  The default is -mfused-madd.

           On the R8000 CPU when multiply-accumulate instructions are used, the intermediate product
           is calculated to infinite precision and is not subject to the FCSR Flush to Zero bit.
           This may be undesirable in some circumstances.  On other processors the result is
           numerically identical to the equivalent computation using separate multiply, add,
           subtract and negate instructions.

       -nocpp
           Tell the MIPS assembler to not run its preprocessor over user assembler files (with a .s
           suffix) when assembling them.

       -mfix-24k
       -mno-fix-24k
           Work around the 24K E48 (lost data on stores during refill) errata.  The workarounds are
           implemented by the assembler rather than by GCC.

       -mfix-r4000
       -mno-fix-r4000
           Work around certain R4000 CPU errata:

           -   A double-word or a variable shift may give an incorrect result if executed
               immediately after starting an integer division.

           -   A double-word or a variable shift may give an incorrect result if executed while an
               integer multiplication is in progress.

           -   An integer division may give an incorrect result if started in a delay slot of a
               taken branch or a jump.

       -mfix-r4400
       -mno-fix-r4400
           Work around certain R4400 CPU errata:

           -   A double-word or a variable shift may give an incorrect result if executed
               immediately after starting an integer division.

       -mfix-r10000
       -mno-fix-r10000
           Work around certain R10000 errata:

           -   "ll"/"sc" sequences may not behave atomically on revisions prior to 3.0.  They may
               deadlock on revisions 2.6 and earlier.

           This option can only be used if the target architecture supports branch-likely
           instructions.  -mfix-r10000 is the default when -march=r10000 is used; -mno-fix-r10000 is
           the default otherwise.

       -mfix-r5900
       -mno-fix-r5900
           Do not attempt to schedule the preceding instruction into the delay slot of a branch
           instruction placed at the end of a short loop of six instructions or fewer and always
           schedule a "nop" instruction there instead.  The short loop bug under certain conditions
           causes loops to execute only once or twice, due to a hardware bug in the R5900 chip.  The
           workaround is implemented by the assembler rather than by GCC.

       -mfix-rm7000
       -mno-fix-rm7000
           Work around the RM7000 "dmult"/"dmultu" errata.  The workarounds are implemented by the
           assembler rather than by GCC.

       -mfix-vr4120
       -mno-fix-vr4120
           Work around certain VR4120 errata:

           -   "dmultu" does not always produce the correct result.

           -   "div" and "ddiv" do not always produce the correct result if one of the operands is
               negative.

           The workarounds for the division errata rely on special functions in libgcc.a.  At
           present, these functions are only provided by the "mips64vr*-elf" configurations.

           Other VR4120 errata require a NOP to be inserted between certain pairs of instructions.
           These errata are handled by the assembler, not by GCC itself.

       -mfix-vr4130
           Work around the VR4130 "mflo"/"mfhi" errata.  The workarounds are implemented by the
           assembler rather than by GCC, although GCC avoids using "mflo" and "mfhi" if the VR4130
           "macc", "macchi", "dmacc" and "dmacchi" instructions are available instead.

       -mfix-sb1
       -mno-fix-sb1
           Work around certain SB-1 CPU core errata.  (This flag currently works around the SB-1
           revision 2 "F1" and "F2" floating-point errata.)

       -mr10k-cache-barrier=setting
           Specify whether GCC should insert cache barriers to avoid the side effects of speculation
           on R10K processors.

           In common with many processors, the R10K tries to predict the outcome of a conditional
           branch and speculatively executes instructions from the "taken" branch.  It later aborts
           these instructions if the predicted outcome is wrong.  However, on the R10K, even aborted
           instructions can have side effects.

           This problem only affects kernel stores and, depending on the system, kernel loads.  As
           an example, a speculatively-executed store may load the target memory into cache and mark
           the cache line as dirty, even if the store itself is later aborted.  If a DMA operation
           writes to the same area of memory before the "dirty" line is flushed, the cached data
           overwrites the DMA-ed data.  See the R10K processor manual for a full description,
           including other potential problems.

           One workaround is to insert cache barrier instructions before every memory access that
           might be speculatively executed and that might have side effects even if aborted.
           -mr10k-cache-barrier=setting controls GCC's implementation of this workaround.  It
           assumes that aborted accesses to any byte in the following regions does not have side
           effects:

           1.  the memory occupied by the current function's stack frame;

           2.  the memory occupied by an incoming stack argument;

           3.  the memory occupied by an object with a link-time-constant address.

           It is the kernel's responsibility to ensure that speculative accesses to these regions
           are indeed safe.

           If the input program contains a function declaration such as:

                   void foo (void);

           then the implementation of "foo" must allow "j foo" and "jal foo" to be executed
           speculatively.  GCC honors this restriction for functions it compiles itself.  It expects
           non-GCC functions (such as hand-written assembly code) to do the same.

           The option has three forms:

           -mr10k-cache-barrier=load-store
               Insert a cache barrier before a load or store that might be speculatively executed
               and that might have side effects even if aborted.

           -mr10k-cache-barrier=store
               Insert a cache barrier before a store that might be speculatively executed and that
               might have side effects even if aborted.

           -mr10k-cache-barrier=none
               Disable the insertion of cache barriers.  This is the default setting.

       -mflush-func=func
       -mno-flush-func
           Specifies the function to call to flush the I and D caches, or to not call any such
           function.  If called, the function must take the same arguments as the common
           "_flush_func", that is, the address of the memory range for which the cache is being
           flushed, the size of the memory range, and the number 3 (to flush both caches).  The
           default depends on the target GCC was configured for, but commonly is either
           "_flush_func" or "__cpu_flush".

       mbranch-cost=num
           Set the cost of branches to roughly num "simple" instructions.  This cost is only a
           heuristic and is not guaranteed to produce consistent results across releases.  A zero
           cost redundantly selects the default, which is based on the -mtune setting.

       -mbranch-likely
       -mno-branch-likely
           Enable or disable use of Branch Likely instructions, regardless of the default for the
           selected architecture.  By default, Branch Likely instructions may be generated if they
           are supported by the selected architecture.  An exception is for the MIPS32 and MIPS64
           architectures and processors that implement those architectures; for those, Branch Likely
           instructions are not be generated by default because the MIPS32 and MIPS64 architectures
           specifically deprecate their use.

       -mcompact-branches=never
       -mcompact-branches=optimal
       -mcompact-branches=always
           These options control which form of branches will be generated.  The default is
           -mcompact-branches=optimal.

           The -mcompact-branches=never option ensures that compact branch instructions will never
           be generated.

           The -mcompact-branches=always option ensures that a compact branch instruction will be
           generated if available.  If a compact branch instruction is not available, a delay slot
           form of the branch will be used instead.

           This option is supported from MIPS Release 6 onwards.

           The -mcompact-branches=optimal option will cause a delay slot branch to be used if one is
           available in the current ISA and the delay slot is successfully filled.  If the delay
           slot is not filled, a compact branch will be chosen if one is available.

       -mfp-exceptions
       -mno-fp-exceptions
           Specifies whether FP exceptions are enabled.  This affects how FP instructions are
           scheduled for some processors.  The default is that FP exceptions are enabled.

           For instance, on the SB-1, if FP exceptions are disabled, and we are emitting 64-bit
           code, then we can use both FP pipes.  Otherwise, we can only use one FP pipe.

       -mvr4130-align
       -mno-vr4130-align
           The VR4130 pipeline is two-way superscalar, but can only issue two instructions together
           if the first one is 8-byte aligned.  When this option is enabled, GCC aligns pairs of
           instructions that it thinks should execute in parallel.

           This option only has an effect when optimizing for the VR4130.  It normally makes code
           faster, but at the expense of making it bigger.  It is enabled by default at optimization
           level -O3.

       -msynci
       -mno-synci
           Enable (disable) generation of "synci" instructions on architectures that support it.
           The "synci" instructions (if enabled) are generated when "__builtin___clear_cache" is
           compiled.

           This option defaults to -mno-synci, but the default can be overridden by configuring GCC
           with --with-synci.

           When compiling code for single processor systems, it is generally safe to use "synci".
           However, on many multi-core (SMP) systems, it does not invalidate the instruction caches
           on all cores and may lead to undefined behavior.

       -mrelax-pic-calls
       -mno-relax-pic-calls
           Try to turn PIC calls that are normally dispatched via register $25 into direct calls.
           This is only possible if the linker can resolve the destination at link time and if the
           destination is within range for a direct call.

           -mrelax-pic-calls is the default if GCC was configured to use an assembler and a linker
           that support the ".reloc" assembly directive and -mexplicit-relocs is in effect.  With
           -mno-explicit-relocs, this optimization can be performed by the assembler and the linker
           alone without help from the compiler.

       -mmcount-ra-address
       -mno-mcount-ra-address
           Emit (do not emit) code that allows "_mcount" to modify the calling function's return
           address.  When enabled, this option extends the usual "_mcount" interface with a new ra-
           address parameter, which has type "intptr_t *" and is passed in register $12.  "_mcount"
           can then modify the return address by doing both of the following:

           *   Returning the new address in register $31.

           *   Storing the new address in "*ra-address", if ra-address is nonnull.

           The default is -mno-mcount-ra-address.

       -mframe-header-opt
       -mno-frame-header-opt
           Enable (disable) frame header optimization in the o32 ABI.  When using the o32 ABI,
           calling functions will allocate 16 bytes on the stack for the called function to write
           out register arguments.  When enabled, this optimization will suppress the allocation of
           the frame header if it can be determined that it is unused.

           This optimization is off by default at all optimization levels.

       -mlxc1-sxc1
       -mno-lxc1-sxc1
           When applicable, enable (disable) the generation of "lwxc1", "swxc1", "ldxc1", "sdxc1"
           instructions.  Enabled by default.

       -mmadd4
       -mno-madd4
           When applicable, enable (disable) the generation of 4-operand "madd.s", "madd.d" and
           related instructions.  Enabled by default.

       MMIX Options

       These options are defined for the MMIX:

       -mlibfuncs
       -mno-libfuncs
           Specify that intrinsic library functions are being compiled, passing all values in
           registers, no matter the size.

       -mepsilon
       -mno-epsilon
           Generate floating-point comparison instructions that compare with respect to the "rE"
           epsilon register.

       -mabi=mmixware
       -mabi=gnu
           Generate code that passes function parameters and return values that (in the called
           function) are seen as registers $0 and up, as opposed to the GNU ABI which uses global
           registers $231 and up.

       -mzero-extend
       -mno-zero-extend
           When reading data from memory in sizes shorter than 64 bits, use (do not use) zero-
           extending load instructions by default, rather than sign-extending ones.

       -mknuthdiv
       -mno-knuthdiv
           Make the result of a division yielding a remainder have the same sign as the divisor.
           With the default, -mno-knuthdiv, the sign of the remainder follows the sign of the
           dividend.  Both methods are arithmetically valid, the latter being almost exclusively
           used.

       -mtoplevel-symbols
       -mno-toplevel-symbols
           Prepend (do not prepend) a : to all global symbols, so the assembly code can be used with
           the "PREFIX" assembly directive.

       -melf
           Generate an executable in the ELF format, rather than the default mmo format used by the
           mmix simulator.

       -mbranch-predict
       -mno-branch-predict
           Use (do not use) the probable-branch instructions, when static branch prediction
           indicates a probable branch.

       -mbase-addresses
       -mno-base-addresses
           Generate (do not generate) code that uses base addresses.  Using a base address
           automatically generates a request (handled by the assembler and the linker) for a
           constant to be set up in a global register.  The register is used for one or more base
           address requests within the range 0 to 255 from the value held in the register.  The
           generally leads to short and fast code, but the number of different data items that can
           be addressed is limited.  This means that a program that uses lots of static data may
           require -mno-base-addresses.

       -msingle-exit
       -mno-single-exit
           Force (do not force) generated code to have a single exit point in each function.

       MN10300 Options

       These -m options are defined for Matsushita MN10300 architectures:

       -mmult-bug
           Generate code to avoid bugs in the multiply instructions for the MN10300 processors.
           This is the default.

       -mno-mult-bug
           Do not generate code to avoid bugs in the multiply instructions for the MN10300
           processors.

       -mam33
           Generate code using features specific to the AM33 processor.

       -mno-am33
           Do not generate code using features specific to the AM33 processor.  This is the default.

       -mam33-2
           Generate code using features specific to the AM33/2.0 processor.

       -mam34
           Generate code using features specific to the AM34 processor.

       -mtune=cpu-type
           Use the timing characteristics of the indicated CPU type when scheduling instructions.
           This does not change the targeted processor type.  The CPU type must be one of mn10300,
           am33, am33-2 or am34.

       -mreturn-pointer-on-d0
           When generating a function that returns a pointer, return the pointer in both "a0" and
           "d0".  Otherwise, the pointer is returned only in "a0", and attempts to call such
           functions without a prototype result in errors.  Note that this option is on by default;
           use -mno-return-pointer-on-d0 to disable it.

       -mno-crt0
           Do not link in the C run-time initialization object file.

       -mrelax
           Indicate to the linker that it should perform a relaxation optimization pass to shorten
           branches, calls and absolute memory addresses.  This option only has an effect when used
           on the command line for the final link step.

           This option makes symbolic debugging impossible.

       -mliw
           Allow the compiler to generate Long Instruction Word instructions if the target is the
           AM33 or later.  This is the default.  This option defines the preprocessor macro
           "__LIW__".

       -mno-liw
           Do not allow the compiler to generate Long Instruction Word instructions.  This option
           defines the preprocessor macro "__NO_LIW__".

       -msetlb
           Allow the compiler to generate the SETLB and Lcc instructions if the target is the AM33
           or later.  This is the default.  This option defines the preprocessor macro "__SETLB__".

       -mno-setlb
           Do not allow the compiler to generate SETLB or Lcc instructions.  This option defines the
           preprocessor macro "__NO_SETLB__".

       Moxie Options

       -meb
           Generate big-endian code.  This is the default for moxie-*-* configurations.

       -mel
           Generate little-endian code.

       -mmul.x
           Generate mul.x and umul.x instructions.  This is the default for moxiebox-*-*
           configurations.

       -mno-crt0
           Do not link in the C run-time initialization object file.

       MSP430 Options

       These options are defined for the MSP430:

       -masm-hex
           Force assembly output to always use hex constants.  Normally such constants are signed
           decimals, but this option is available for testsuite and/or aesthetic purposes.

       -mmcu=
           Select the MCU to target.  This is used to create a C preprocessor symbol based upon the
           MCU name, converted to upper case and pre- and post-fixed with __.  This in turn is used
           by the msp430.h header file to select an MCU-specific supplementary header file.

           The option also sets the ISA to use.  If the MCU name is one that is known to only
           support the 430 ISA then that is selected, otherwise the 430X ISA is selected.  A generic
           MCU name of msp430 can also be used to select the 430 ISA.  Similarly the generic msp430x
           MCU name selects the 430X ISA.

           In addition an MCU-specific linker script is added to the linker command line.  The
           script's name is the name of the MCU with .ld appended.  Thus specifying -mmcu=xxx on the
           gcc command line defines the C preprocessor symbol "__XXX__" and cause the linker to
           search for a script called xxx.ld.

           The ISA and hardware multiply supported for the different MCUs is hard-coded into GCC.
           However, an external devices.csv file can be used to extend device support beyond those
           that have been hard-coded.

           GCC searches for the devices.csv file using the following methods in the given precedence
           order, where the first method takes precendence over the second which takes precedence
           over the third.

           Include path specified with "-I" and "-L"
               devices.csv will be searched for in each of the directories specified by include
               paths and linker library search paths.

           Path specified by the environment variable MSP430_GCC_INCLUDE_DIR
               Define the value of the global environment variable MSP430_GCC_INCLUDE_DIR to the
               full path to the directory containing devices.csv, and GCC will search this directory
               for devices.csv.  If devices.csv is found, this directory will also be registered as
               an include path, and linker library path.  Header files and linker scripts in this
               directory can therefore be used without manually specifying "-I" and "-L" on the
               command line.

           The msp430-elf{,bare}/include/devices directory
               Finally, GCC will examine msp430-elf{,bare}/include/devices from the toolchain root
               directory.  This directory does not exist in a default installation, but if the user
               has created it and copied devices.csv there, then the MCU data will be read.  As
               above, this directory will also be registered as an include path, and linker library
               path.

           If none of the above search methods find devices.csv, then the hard-coded MCU data is
           used.

       -mwarn-mcu
       -mno-warn-mcu
           This option enables or disables warnings about conflicts between the MCU name specified
           by the -mmcu option and the ISA set by the -mcpu option and/or the hardware multiply
           support set by the -mhwmult option.  It also toggles warnings about unrecognized MCU
           names.  This option is on by default.

       -mcpu=
           Specifies the ISA to use.  Accepted values are msp430, msp430x and msp430xv2.  This
           option is deprecated.  The -mmcu= option should be used to select the ISA.

       -msim
           Link to the simulator runtime libraries and linker script.  Overrides any scripts that
           would be selected by the -mmcu= option.

       -mlarge
           Use large-model addressing (20-bit pointers, 20-bit "size_t").

       -msmall
           Use small-model addressing (16-bit pointers, 16-bit "size_t").

       -mrelax
           This option is passed to the assembler and linker, and allows the linker to perform
           certain optimizations that cannot be done until the final link.

       mhwmult=
           Describes the type of hardware multiply supported by the target.  Accepted values are
           none for no hardware multiply, 16bit for the original 16-bit-only multiply supported by
           early MCUs.  32bit for the 16/32-bit multiply supported by later MCUs and f5series for
           the 16/32-bit multiply supported by F5-series MCUs.  A value of auto can also be given.
           This tells GCC to deduce the hardware multiply support based upon the MCU name provided
           by the -mmcu option.  If no -mmcu option is specified or if the MCU name is not
           recognized then no hardware multiply support is assumed.  "auto" is the default setting.

           Hardware multiplies are normally performed by calling a library routine.  This saves
           space in the generated code.  When compiling at -O3 or higher however the hardware
           multiplier is invoked inline.  This makes for bigger, but faster code.

           The hardware multiply routines disable interrupts whilst running and restore the previous
           interrupt state when they finish.  This makes them safe to use inside interrupt handlers
           as well as in normal code.

       -minrt
           Enable the use of a minimum runtime environment - no static initializers or constructors.
           This is intended for memory-constrained devices.  The compiler includes special symbols
           in some objects that tell the linker and runtime which code fragments are required.

       -mtiny-printf
           Enable reduced code size "printf" and "puts" library functions.  The tiny implementations
           of these functions are not reentrant, so must be used with caution in multi-threaded
           applications.

           Support for streams has been removed and the string to be printed will always be sent to
           stdout via the "write" syscall.  The string is not buffered before it is sent to write.

           This option requires Newlib Nano IO, so GCC must be configured with
           --enable-newlib-nano-formatted-io.

       -mmax-inline-shift=
           This option takes an integer between 0 and 64 inclusive, and sets the maximum number of
           inline shift instructions which should be emitted to perform a shift operation by a
           constant amount.  When this value needs to be exceeded, an mspabi helper function is used
           instead.  The default value is 4.

           This only affects cases where a shift by multiple positions cannot be completed with a
           single instruction (e.g. all shifts >1 on the 430 ISA).

           Shifts of a 32-bit value are at least twice as costly, so the value passed for this
           option is divided by 2 and the resulting value used instead.

       -mcode-region=
       -mdata-region=
           These options tell the compiler where to place functions and data that do not have one of
           the "lower", "upper", "either" or "section" attributes.  Possible values are "lower",
           "upper", "either" or "any".  The first three behave like the corresponding attribute.
           The fourth possible value - "any" - is the default.  It leaves placement entirely up to
           the linker script and how it assigns the standard sections (".text", ".data", etc) to the
           memory regions.

       -msilicon-errata=
           This option passes on a request to assembler to enable the fixes for the named silicon
           errata.

       -msilicon-errata-warn=
           This option passes on a request to the assembler to enable warning messages when a
           silicon errata might need to be applied.

       -mwarn-devices-csv
       -mno-warn-devices-csv
           Warn if devices.csv is not found or there are problem parsing it (default: on).

       NDS32 Options

       These options are defined for NDS32 implementations:

       -mbig-endian
           Generate code in big-endian mode.

       -mlittle-endian
           Generate code in little-endian mode.

       -mreduced-regs
           Use reduced-set registers for register allocation.

       -mfull-regs
           Use full-set registers for register allocation.

       -mcmov
           Generate conditional move instructions.

       -mno-cmov
           Do not generate conditional move instructions.

       -mext-perf
           Generate performance extension instructions.

       -mno-ext-perf
           Do not generate performance extension instructions.

       -mext-perf2
           Generate performance extension 2 instructions.

       -mno-ext-perf2
           Do not generate performance extension 2 instructions.

       -mext-string
           Generate string extension instructions.

       -mno-ext-string
           Do not generate string extension instructions.

       -mv3push
           Generate v3 push25/pop25 instructions.

       -mno-v3push
           Do not generate v3 push25/pop25 instructions.

       -m16-bit
           Generate 16-bit instructions.

       -mno-16-bit
           Do not generate 16-bit instructions.

       -misr-vector-size=num
           Specify the size of each interrupt vector, which must be 4 or 16.

       -mcache-block-size=num
           Specify the size of each cache block, which must be a power of 2 between 4 and 512.

       -march=arch
           Specify the name of the target architecture.

       -mcmodel=code-model
           Set the code model to one of

           small
               All the data and read-only data segments must be within 512KB addressing space.  The
               text segment must be within 16MB addressing space.

           medium
               The data segment must be within 512KB while the read-only data segment can be within
               4GB addressing space.  The text segment should be still within 16MB addressing space.

           large
               All the text and data segments can be within 4GB addressing space.

       -mctor-dtor
           Enable constructor/destructor feature.

       -mrelax
           Guide linker to relax instructions.

       Nios II Options

       These are the options defined for the Altera Nios II processor.

       -G num
           Put global and static objects less than or equal to num bytes into the small data or BSS
           sections instead of the normal data or BSS sections.  The default value of num is 8.

       -mgpopt=option
       -mgpopt
       -mno-gpopt
           Generate (do not generate) GP-relative accesses.  The following option names are
           recognized:

           none
               Do not generate GP-relative accesses.

           local
               Generate GP-relative accesses for small data objects that are not external, weak, or
               uninitialized common symbols.  Also use GP-relative addressing for objects that have
               been explicitly placed in a small data section via a "section" attribute.

           global
               As for local, but also generate GP-relative accesses for small data objects that are
               external, weak, or common.  If you use this option, you must ensure that all parts of
               your program (including libraries) are compiled with the same -G setting.

           data
               Generate GP-relative accesses for all data objects in the program.  If you use this
               option, the entire data and BSS segments of your program must fit in 64K of memory
               and you must use an appropriate linker script to allocate them within the addressable
               range of the global pointer.

           all Generate GP-relative addresses for function pointers as well as data pointers.  If
               you use this option, the entire text, data, and BSS segments of your program must fit
               in 64K of memory and you must use an appropriate linker script to allocate them
               within the addressable range of the global pointer.

           -mgpopt is equivalent to -mgpopt=local, and -mno-gpopt is equivalent to -mgpopt=none.

           The default is -mgpopt except when -fpic or -fPIC is specified to generate position-
           independent code.  Note that the Nios II ABI does not permit GP-relative accesses from
           shared libraries.

           You may need to specify -mno-gpopt explicitly when building programs that include large
           amounts of small data, including large GOT data sections.  In this case, the 16-bit
           offset for GP-relative addressing may not be large enough to allow access to the entire
           small data section.

       -mgprel-sec=regexp
           This option specifies additional section names that can be accessed via GP-relative
           addressing.  It is most useful in conjunction with "section" attributes on variable
           declarations and a custom linker script.  The regexp is a POSIX Extended Regular
           Expression.

           This option does not affect the behavior of the -G option, and the specified sections are
           in addition to the standard ".sdata" and ".sbss" small-data sections that are recognized
           by -mgpopt.

       -mr0rel-sec=regexp
           This option specifies names of sections that can be accessed via a 16-bit offset from
           "r0"; that is, in the low 32K or high 32K of the 32-bit address space.  It is most useful
           in conjunction with "section" attributes on variable declarations and a custom linker
           script.  The regexp is a POSIX Extended Regular Expression.

           In contrast to the use of GP-relative addressing for small data, zero-based addressing is
           never generated by default and there are no conventional section names used in standard
           linker scripts for sections in the low or high areas of memory.

       -mel
       -meb
           Generate little-endian (default) or big-endian (experimental) code, respectively.

       -march=arch
           This specifies the name of the target Nios II architecture.  GCC uses this name to
           determine what kind of instructions it can emit when generating assembly code.
           Permissible names are: r1, r2.

           The preprocessor macro "__nios2_arch__" is available to programs, with value 1 or 2,
           indicating the targeted ISA level.

       -mbypass-cache
       -mno-bypass-cache
           Force all load and store instructions to always bypass cache by using I/O variants of the
           instructions. The default is not to bypass the cache.

       -mno-cache-volatile
       -mcache-volatile
           Volatile memory access bypass the cache using the I/O variants of the load and store
           instructions. The default is not to bypass the cache.

       -mno-fast-sw-div
       -mfast-sw-div
           Do not use table-based fast divide for small numbers. The default is to use the fast
           divide at -O3 and above.

       -mno-hw-mul
       -mhw-mul
       -mno-hw-mulx
       -mhw-mulx
       -mno-hw-div
       -mhw-div
           Enable or disable emitting "mul", "mulx" and "div" family of instructions by the
           compiler. The default is to emit "mul" and not emit "div" and "mulx".

       -mbmx
       -mno-bmx
       -mcdx
       -mno-cdx
           Enable or disable generation of Nios II R2 BMX (bit manipulation) and CDX (code density)
           instructions.  Enabling these instructions also requires -march=r2.  Since these
           instructions are optional extensions to the R2 architecture, the default is not to emit
           them.

       -mcustom-insn=N
       -mno-custom-insn
           Each -mcustom-insn=N option enables use of a custom instruction with encoding N when
           generating code that uses insn.  For example, -mcustom-fadds=253 generates custom
           instruction 253 for single-precision floating-point add operations instead of the default
           behavior of using a library call.

           The following values of insn are supported.  Except as otherwise noted, floating-point
           operations are expected to be implemented with normal IEEE 754 semantics and correspond
           directly to the C operators or the equivalent GCC built-in functions.

           Single-precision floating point:

           fadds, fsubs, fdivs, fmuls
               Binary arithmetic operations.

           fnegs
               Unary negation.

           fabss
               Unary absolute value.

           fcmpeqs, fcmpges, fcmpgts, fcmples, fcmplts, fcmpnes
               Comparison operations.

           fmins, fmaxs
               Floating-point minimum and maximum.  These instructions are only generated if
               -ffinite-math-only is specified.

           fsqrts
               Unary square root operation.

           fcoss, fsins, ftans, fatans, fexps, flogs
               Floating-point trigonometric and exponential functions.  These instructions are only
               generated if -funsafe-math-optimizations is also specified.

           Double-precision floating point:

           faddd, fsubd, fdivd, fmuld
               Binary arithmetic operations.

           fnegd
               Unary negation.

           fabsd
               Unary absolute value.

           fcmpeqd, fcmpged, fcmpgtd, fcmpled, fcmpltd, fcmpned
               Comparison operations.

           fmind, fmaxd
               Double-precision minimum and maximum.  These instructions are only generated if
               -ffinite-math-only is specified.

           fsqrtd
               Unary square root operation.

           fcosd, fsind, ftand, fatand, fexpd, flogd
               Double-precision trigonometric and exponential functions.  These instructions are
               only generated if -funsafe-math-optimizations is also specified.

           Conversions:

           fextsd
               Conversion from single precision to double precision.

           ftruncds
               Conversion from double precision to single precision.

           fixsi, fixsu, fixdi, fixdu
               Conversion from floating point to signed or unsigned integer types, with truncation
               towards zero.

           round
               Conversion from single-precision floating point to signed integer, rounding to the
               nearest integer and ties away from zero.  This corresponds to the "__builtin_lroundf"
               function when -fno-math-errno is used.

           floatis, floatus, floatid, floatud
               Conversion from signed or unsigned integer types to floating-point types.

           In addition, all of the following transfer instructions for internal registers X and Y
           must be provided to use any of the double-precision floating-point instructions.  Custom
           instructions taking two double-precision source operands expect the first operand in the
           64-bit register X.  The other operand (or only operand of a unary operation) is given to
           the custom arithmetic instruction with the least significant half in source register src1
           and the most significant half in src2.  A custom instruction that returns a double-
           precision result returns the most significant 32 bits in the destination register and the
           other half in 32-bit register Y.  GCC automatically generates the necessary code
           sequences to write register X and/or read register Y when double-precision floating-point
           instructions are used.

           fwrx
               Write src1 into the least significant half of X and src2 into the most significant
               half of X.

           fwry
               Write src1 into Y.

           frdxhi, frdxlo
               Read the most or least (respectively) significant half of X and store it in dest.

           frdy
               Read the value of Y and store it into dest.

           Note that you can gain more local control over generation of Nios II custom instructions
           by using the "target("custom-insn=N")" and "target("no-custom-insn")" function attributes
           or pragmas.

       -mcustom-fpu-cfg=name
           This option enables a predefined, named set of custom instruction encodings (see
           -mcustom-insn above).  Currently, the following sets are defined:

           -mcustom-fpu-cfg=60-1 is equivalent to: -mcustom-fmuls=252 -mcustom-fadds=253
           -mcustom-fsubs=254 -fsingle-precision-constant

           -mcustom-fpu-cfg=60-2 is equivalent to: -mcustom-fmuls=252 -mcustom-fadds=253
           -mcustom-fsubs=254 -mcustom-fdivs=255 -fsingle-precision-constant

           -mcustom-fpu-cfg=72-3 is equivalent to: -mcustom-floatus=243 -mcustom-fixsi=244
           -mcustom-floatis=245 -mcustom-fcmpgts=246 -mcustom-fcmples=249 -mcustom-fcmpeqs=250
           -mcustom-fcmpnes=251 -mcustom-fmuls=252 -mcustom-fadds=253 -mcustom-fsubs=254
           -mcustom-fdivs=255 -fsingle-precision-constant

           -mcustom-fpu-cfg=fph2 is equivalent to: -mcustom-fabss=224 -mcustom-fnegs=225
           -mcustom-fcmpnes=226 -mcustom-fcmpeqs=227 -mcustom-fcmpges=228 -mcustom-fcmpgts=229
           -mcustom-fcmples=230 -mcustom-fcmplts=231 -mcustom-fmaxs=232 -mcustom-fmins=233
           -mcustom-round=248 -mcustom-fixsi=249 -mcustom-floatis=250 -mcustom-fsqrts=251
           -mcustom-fmuls=252 -mcustom-fadds=253 -mcustom-fsubs=254 -mcustom-fdivs=255

           Custom instruction assignments given by individual -mcustom-insn= options override those
           given by -mcustom-fpu-cfg=, regardless of the order of the options on the command line.

           Note that you can gain more local control over selection of a FPU configuration by using
           the "target("custom-fpu-cfg=name")" function attribute or pragma.

           The name fph2 is an abbreviation for Nios II Floating Point Hardware 2 Component.  Please
           note that the custom instructions enabled by -mcustom-fmins=233 and -mcustom-fmaxs=234
           are only generated if -ffinite-math-only is specified.  The custom instruction enabled by
           -mcustom-round=248 is only generated if -fno-math-errno is specified.  In contrast to the
           other configurations, -fsingle-precision-constant is not set.

       These additional -m options are available for the Altera Nios II ELF (bare-metal) target:

       -mhal
           Link with HAL BSP.  This suppresses linking with the GCC-provided C runtime startup and
           termination code, and is typically used in conjunction with -msys-crt0= to specify the
           location of the alternate startup code provided by the HAL BSP.

       -msmallc
           Link with a limited version of the C library, -lsmallc, rather than Newlib.

       -msys-crt0=startfile
           startfile is the file name of the startfile (crt0) to use when linking.  This option is
           only useful in conjunction with -mhal.

       -msys-lib=systemlib
           systemlib is the library name of the library that provides low-level system calls
           required by the C library, e.g. "read" and "write".  This option is typically used to
           link with a library provided by a HAL BSP.

       Nvidia PTX Options

       These options are defined for Nvidia PTX:

       -m64
           Ignored, but preserved for backward compatibility.  Only 64-bit ABI is supported.

       -misa=ISA-string
           Generate code for given the specified PTX ISA (e.g. sm_35).  ISA strings must be lower-
           case.  Valid ISA strings include sm_30 and sm_35.  The default ISA is sm_35.

       -mmainkernel
           Link in code for a __main kernel.  This is for stand-alone instead of offloading
           execution.

       -moptimize
           Apply partitioned execution optimizations.  This is the default when any level of
           optimization is selected.

       -msoft-stack
           Generate code that does not use ".local" memory directly for stack storage. Instead, a
           per-warp stack pointer is maintained explicitly. This enables variable-length stack
           allocation (with variable-length arrays or "alloca"), and when global memory is used for
           underlying storage, makes it possible to access automatic variables from other threads,
           or with atomic instructions. This code generation variant is used for OpenMP offloading,
           but the option is exposed on its own for the purpose of testing the compiler; to generate
           code suitable for linking into programs using OpenMP offloading, use option -mgomp.

       -muniform-simt
           Switch to code generation variant that allows to execute all threads in each warp, while
           maintaining memory state and side effects as if only one thread in each warp was active
           outside of OpenMP SIMD regions.  All atomic operations and calls to runtime (malloc,
           free, vprintf) are conditionally executed (iff current lane index equals the master lane
           index), and the register being assigned is copied via a shuffle instruction from the
           master lane.  Outside of SIMD regions lane 0 is the master; inside, each thread sees
           itself as the master.  Shared memory array "int __nvptx_uni[]" stores all-zeros or all-
           ones bitmasks for each warp, indicating current mode (0 outside of SIMD regions).  Each
           thread can bitwise-and the bitmask at position "tid.y" with current lane index to compute
           the master lane index.

       -mgomp
           Generate code for use in OpenMP offloading: enables -msoft-stack and -muniform-simt
           options, and selects corresponding multilib variant.

       OpenRISC Options

       These options are defined for OpenRISC:

       -mboard=name
           Configure a board specific runtime.  This will be passed to the linker for newlib board
           library linking.  The default is "or1ksim".

       -mnewlib
           This option is ignored; it is for compatibility purposes only.  This used to select
           linker and preprocessor options for use with newlib.

       -msoft-div
       -mhard-div
           Select software or hardware divide ("l.div", "l.divu") instructions.  This default is
           hardware divide.

       -msoft-mul
       -mhard-mul
           Select software or hardware multiply ("l.mul", "l.muli") instructions.  This default is
           hardware multiply.

       -msoft-float
       -mhard-float
           Select software or hardware for floating point operations.  The default is software.

       -mdouble-float
           When -mhard-float is selected, enables generation of double-precision floating point
           instructions.  By default functions from libgcc are used to perform double-precision
           floating point operations.

       -munordered-float
           When -mhard-float is selected, enables generation of unordered floating point compare and
           set flag ("lf.sfun*") instructions.  By default functions from libgcc are used to perform
           unordered floating point compare and set flag operations.

       -mcmov
           Enable generation of conditional move ("l.cmov") instructions.  By default the equivalent
           will be generated using set and branch.

       -mror
           Enable generation of rotate right ("l.ror") instructions.  By default functions from
           libgcc are used to perform rotate right operations.

       -mrori
           Enable generation of rotate right with immediate ("l.rori") instructions.  By default
           functions from libgcc are used to perform rotate right with immediate operations.

       -msext
           Enable generation of sign extension ("l.ext*") instructions.  By default memory loads are
           used to perform sign extension.

       -msfimm
           Enable generation of compare and set flag with immediate ("l.sf*i") instructions.  By
           default extra instructions will be generated to store the immediate to a register first.

       -mshftimm
           Enable generation of shift with immediate ("l.srai", "l.srli", "l.slli") instructions.
           By default extra instructions will be generated to store the immediate to a register
           first.

       PDP-11 Options

       These options are defined for the PDP-11:

       -mfpu
           Use hardware FPP floating point.  This is the default.  (FIS floating point on the
           PDP-11/40 is not supported.)  Implies -m45.

       -msoft-float
           Do not use hardware floating point.

       -mac0
           Return floating-point results in ac0 (fr0 in Unix assembler syntax).

       -mno-ac0
           Return floating-point results in memory.  This is the default.

       -m40
           Generate code for a PDP-11/40.  Implies -msoft-float -mno-split.

       -m45
           Generate code for a PDP-11/45.  This is the default.

       -m10
           Generate code for a PDP-11/10.  Implies -msoft-float -mno-split.

       -mint16
       -mno-int32
           Use 16-bit "int".  This is the default.

       -mint32
       -mno-int16
           Use 32-bit "int".

       -msplit
           Target has split instruction and data space.  Implies -m45.

       -munix-asm
           Use Unix assembler syntax.

       -mdec-asm
           Use DEC assembler syntax.

       -mgnu-asm
           Use GNU assembler syntax.  This is the default.

       -mlra
           Use the new LRA register allocator.  By default, the old "reload" allocator is used.

       picoChip Options

       These -m options are defined for picoChip implementations:

       -mae=ae_type
           Set the instruction set, register set, and instruction scheduling parameters for array
           element type ae_type.  Supported values for ae_type are ANY, MUL, and MAC.

           -mae=ANY selects a completely generic AE type.  Code generated with this option runs on
           any of the other AE types.  The code is not as efficient as it would be if compiled for a
           specific AE type, and some types of operation (e.g., multiplication) do not work properly
           on all types of AE.

           -mae=MUL selects a MUL AE type.  This is the most useful AE type for compiled code, and
           is the default.

           -mae=MAC selects a DSP-style MAC AE.  Code compiled with this option may suffer from poor
           performance of byte (char) manipulation, since the DSP AE does not provide hardware
           support for byte load/stores.

       -msymbol-as-address
           Enable the compiler to directly use a symbol name as an address in a load/store
           instruction, without first loading it into a register.  Typically, the use of this option
           generates larger programs, which run faster than when the option isn't used.  However,
           the results vary from program to program, so it is left as a user option, rather than
           being permanently enabled.

       -mno-inefficient-warnings
           Disables warnings about the generation of inefficient code.  These warnings can be
           generated, for example, when compiling code that performs byte-level memory operations on
           the MAC AE type.  The MAC AE has no hardware support for byte-level memory operations, so
           all byte load/stores must be synthesized from word load/store operations.  This is
           inefficient and a warning is generated to indicate that you should rewrite the code to
           avoid byte operations, or to target an AE type that has the necessary hardware support.
           This option disables these warnings.

       PowerPC Options

       These are listed under

       PRU Options

       These command-line options are defined for PRU target:

       -minrt
           Link with a minimum runtime environment, with no support for static initializers and
           constructors.  Using this option can significantly reduce the size of the final ELF
           binary.  Beware that the compiler could still generate code with static initializers and
           constructors.  It is up to the programmer to ensure that the source program will not use
           those features.

       -mmcu=mcu
           Specify the PRU MCU variant to use.  Check Newlib for the exact list of supported MCUs.

       -mno-relax
           Make GCC pass the --no-relax command-line option to the linker instead of the --relax
           option.

       -mloop
           Allow (or do not allow) GCC to use the LOOP instruction.

       -mabi=variant
           Specify the ABI variant to output code for.  -mabi=ti selects the unmodified TI ABI while
           -mabi=gnu selects a GNU variant that copes more naturally with certain GCC assumptions.
           These are the differences:

           Function Pointer Size
               TI ABI specifies that function (code) pointers are 16-bit, whereas GNU supports only
               32-bit data and code pointers.

           Optional Return Value Pointer
               Function return values larger than 64 bits are passed by using a hidden pointer as
               the first argument of the function.  TI ABI, though, mandates that the pointer can be
               NULL in case the caller is not using the returned value.  GNU always passes and
               expects a valid return value pointer.

           The current -mabi=ti implementation simply raises a compile error when any of the above
           code constructs is detected.  As a consequence the standard C library cannot be built and
           it is omitted when linking with -mabi=ti.

           Relaxation is a GNU feature and for safety reasons is disabled when using -mabi=ti.  The
           TI toolchain does not emit relocations for QBBx instructions, so the GNU linker cannot
           adjust them when shortening adjacent LDI32 pseudo instructions.

       RISC-V Options

       These command-line options are defined for RISC-V targets:

       -mbranch-cost=n
           Set the cost of branches to roughly n instructions.

       -mplt
       -mno-plt
           When generating PIC code, do or don't allow the use of PLTs. Ignored for non-PIC.  The
           default is -mplt.

       -mabi=ABI-string
           Specify integer and floating-point calling convention.  ABI-string contains two parts:
           the size of integer types and the registers used for floating-point types.  For example
           -march=rv64ifd -mabi=lp64d means that long and pointers are 64-bit (implicitly defining
           int to be 32-bit), and that floating-point values up to 64 bits wide are passed in F
           registers.  Contrast this with -march=rv64ifd -mabi=lp64f, which still allows the
           compiler to generate code that uses the F and D extensions but only allows floating-point
           values up to 32 bits long to be passed in registers; or -march=rv64ifd -mabi=lp64, in
           which no floating-point arguments will be passed in registers.

           The default for this argument is system dependent, users who want a specific calling
           convention should specify one explicitly.  The valid calling conventions are: ilp32,
           ilp32f, ilp32d, lp64, lp64f, and lp64d.  Some calling conventions are impossible to
           implement on some ISAs: for example, -march=rv32if -mabi=ilp32d is invalid because the
           ABI requires 64-bit values be passed in F registers, but F registers are only 32 bits
           wide.  There is also the ilp32e ABI that can only be used with the rv32e architecture.
           This ABI is not well specified at present, and is subject to change.

       -mfdiv
       -mno-fdiv
           Do or don't use hardware floating-point divide and square root instructions.  This
           requires the F or D extensions for floating-point registers.  The default is to use them
           if the specified architecture has these instructions.

       -mdiv
       -mno-div
           Do or don't use hardware instructions for integer division.  This requires the M
           extension.  The default is to use them if the specified architecture has these
           instructions.

       -march=ISA-string
           Generate code for given RISC-V ISA (e.g. rv64im).  ISA strings must be lower-case.
           Examples include rv64i, rv32g, rv32e, and rv32imaf.

           When -march= is not specified, use the setting from -mcpu.

           If both -march and -mcpu= are not specified, the default for this argument is system
           dependent, users who want a specific architecture extensions should specify one
           explicitly.

       -mcpu=processor-string
           Use architecture of and optimize the output for the given processor, specified by
           particular CPU name.  Permissible values for this option are: sifive-e20, sifive-e21,
           sifive-e24, sifive-e31, sifive-e34, sifive-e76, sifive-s21, sifive-s51, sifive-s54,
           sifive-s76, sifive-u54, and sifive-u74.

       -mtune=processor-string
           Optimize the output for the given processor, specified by microarchitecture or particular
           CPU name.  Permissible values for this option are: rocket, sifive-3-series,
           sifive-5-series, sifive-7-series, size, and all valid options for -mcpu=.

           When -mtune= is not specified, use the setting from -mcpu, the default is rocket if both
           are not specified.

           The size choice is not intended for use by end-users.  This is used when -Os is
           specified.  It overrides the instruction cost info provided by -mtune=, but does not
           override the pipeline info.  This helps reduce code size while still giving good
           performance.

       -mpreferred-stack-boundary=num
           Attempt to keep the stack boundary aligned to a 2 raised to num byte boundary.  If
           -mpreferred-stack-boundary is not specified, the default is 4 (16 bytes or 128-bits).

           Warning: If you use this switch, then you must build all modules with the same value,
           including any libraries.  This includes the system libraries and startup modules.

       -msmall-data-limit=n
           Put global and static data smaller than n bytes into a special section (on some targets).

       -msave-restore
       -mno-save-restore
           Do or don't use smaller but slower prologue and epilogue code that uses library function
           calls.  The default is to use fast inline prologues and epilogues.

       -mshorten-memrefs
       -mno-shorten-memrefs
           Do or do not attempt to make more use of compressed load/store instructions by replacing
           a load/store of 'base register + large offset' with a new load/store of 'new base + small
           offset'.  If the new base gets stored in a compressed register, then the new load/store
           can be compressed.  Currently targets 32-bit integer load/stores only.

       -mstrict-align
       -mno-strict-align
           Do not or do generate unaligned memory accesses.  The default is set depending on whether
           the processor we are optimizing for supports fast unaligned access or not.

       -mcmodel=medlow
           Generate code for the medium-low code model. The program and its statically defined
           symbols must lie within a single 2 GiB address range and must lie between absolute
           addresses -2 GiB and +2 GiB. Programs can be statically or dynamically linked. This is
           the default code model.

       -mcmodel=medany
           Generate code for the medium-any code model. The program and its statically defined
           symbols must be within any single 2 GiB address range. Programs can be statically or
           dynamically linked.

       -mexplicit-relocs
       -mno-exlicit-relocs
           Use or do not use assembler relocation operators when dealing with symbolic addresses.
           The alternative is to use assembler macros instead, which may limit optimization.

       -mrelax
       -mno-relax
           Take advantage of linker relaxations to reduce the number of instructions required to
           materialize symbol addresses. The default is to take advantage of linker relaxations.

       -memit-attribute
       -mno-emit-attribute
           Emit (do not emit) RISC-V attribute to record extra information into ELF objects.  This
           feature requires at least binutils 2.32.

       -malign-data=type
           Control how GCC aligns variables and constants of array, structure, or union types.
           Supported values for type are xlen which uses x register width as the alignment value,
           and natural which uses natural alignment.  xlen is the default.

       -mbig-endian
           Generate big-endian code.  This is the default when GCC is configured for a riscv64be-*-*
           or riscv32be-*-* target.

       -mlittle-endian
           Generate little-endian code.  This is the default when GCC is configured for a
           riscv64-*-* or riscv32-*-* but not a riscv64be-*-* or riscv32be-*-* target.

       -mstack-protector-guard=guard
       -mstack-protector-guard-reg=reg
       -mstack-protector-guard-offset=offset
           Generate stack protection code using canary at guard.  Supported locations are global for
           a global canary or tls for per-thread canary in the TLS block.

           With the latter choice the options -mstack-protector-guard-reg=reg and
           -mstack-protector-guard-offset=offset furthermore specify which register to use as base
           register for reading the canary, and from what offset from that base register. There is
           no default register or offset as this is entirely for use within the Linux kernel.

       RL78 Options

       -msim
           Links in additional target libraries to support operation within a simulator.

       -mmul=none
       -mmul=g10
       -mmul=g13
       -mmul=g14
       -mmul=rl78
           Specifies the type of hardware multiplication and division support to be used.  The
           simplest is "none", which uses software for both multiplication and division.  This is
           the default.  The "g13" value is for the hardware multiply/divide peripheral found on the
           RL78/G13 (S2 core) targets.  The "g14" value selects the use of the multiplication and
           division instructions supported by the RL78/G14 (S3 core) parts.  The value "rl78" is an
           alias for "g14" and the value "mg10" is an alias for "none".

           In addition a C preprocessor macro is defined, based upon the setting of this option.
           Possible values are: "__RL78_MUL_NONE__", "__RL78_MUL_G13__" or "__RL78_MUL_G14__".

       -mcpu=g10
       -mcpu=g13
       -mcpu=g14
       -mcpu=rl78
           Specifies the RL78 core to target.  The default is the G14 core, also known as an S3 core
           or just RL78.  The G13 or S2 core does not have multiply or divide instructions, instead
           it uses a hardware peripheral for these operations.  The G10 or S1 core does not have
           register banks, so it uses a different calling convention.

           If this option is set it also selects the type of hardware multiply support to use,
           unless this is overridden by an explicit -mmul=none option on the command line.  Thus
           specifying -mcpu=g13 enables the use of the G13 hardware multiply peripheral and
           specifying -mcpu=g10 disables the use of hardware multiplications altogether.

           Note, although the RL78/G14 core is the default target, specifying -mcpu=g14 or
           -mcpu=rl78 on the command line does change the behavior of the toolchain since it also
           enables G14 hardware multiply support.  If these options are not specified on the command
           line then software multiplication routines will be used even though the code targets the
           RL78 core.  This is for backwards compatibility with older toolchains which did not have
           hardware multiply and divide support.

           In addition a C preprocessor macro is defined, based upon the setting of this option.
           Possible values are: "__RL78_G10__", "__RL78_G13__" or "__RL78_G14__".

       -mg10
       -mg13
       -mg14
       -mrl78
           These are aliases for the corresponding -mcpu= option.  They are provided for backwards
           compatibility.

       -mallregs
           Allow the compiler to use all of the available registers.  By default registers
           "r24..r31" are reserved for use in interrupt handlers.  With this option enabled these
           registers can be used in ordinary functions as well.

       -m64bit-doubles
       -m32bit-doubles
           Make the "double" data type be 64 bits (-m64bit-doubles) or 32 bits (-m32bit-doubles) in
           size.  The default is -m32bit-doubles.

       -msave-mduc-in-interrupts
       -mno-save-mduc-in-interrupts
           Specifies that interrupt handler functions should preserve the MDUC registers.  This is
           only necessary if normal code might use the MDUC registers, for example because it
           performs multiplication and division operations.  The default is to ignore the MDUC
           registers as this makes the interrupt handlers faster.  The target option -mg13 needs to
           be passed for this to work as this feature is only available on the G13 target (S2 core).
           The MDUC registers will only be saved if the interrupt handler performs a multiplication
           or division operation or it calls another function.

       IBM RS/6000 and PowerPC Options

       These -m options are defined for the IBM RS/6000 and PowerPC:

       -mpowerpc-gpopt
       -mno-powerpc-gpopt
       -mpowerpc-gfxopt
       -mno-powerpc-gfxopt
       -mpowerpc64
       -mno-powerpc64
       -mmfcrf
       -mno-mfcrf
       -mpopcntb
       -mno-popcntb
       -mpopcntd
       -mno-popcntd
       -mfprnd
       -mno-fprnd
       -mcmpb
       -mno-cmpb
       -mhard-dfp
       -mno-hard-dfp
           You use these options to specify which instructions are available on the processor you
           are using.  The default value of these options is determined when configuring GCC.
           Specifying the -mcpu=cpu_type overrides the specification of these options.  We recommend
           you use the -mcpu=cpu_type option rather than the options listed above.

           Specifying -mpowerpc-gpopt allows GCC to use the optional PowerPC architecture
           instructions in the General Purpose group, including floating-point square root.
           Specifying -mpowerpc-gfxopt allows GCC to use the optional PowerPC architecture
           instructions in the Graphics group, including floating-point select.

           The -mmfcrf option allows GCC to generate the move from condition register field
           instruction implemented on the POWER4 processor and other processors that support the
           PowerPC V2.01 architecture.  The -mpopcntb option allows GCC to generate the popcount and
           double-precision FP reciprocal estimate instruction implemented on the POWER5 processor
           and other processors that support the PowerPC V2.02 architecture.  The -mpopcntd option
           allows GCC to generate the popcount instruction implemented on the POWER7 processor and
           other processors that support the PowerPC V2.06 architecture.  The -mfprnd option allows
           GCC to generate the FP round to integer instructions implemented on the POWER5+ processor
           and other processors that support the PowerPC V2.03 architecture.  The -mcmpb option
           allows GCC to generate the compare bytes instruction implemented on the POWER6 processor
           and other processors that support the PowerPC V2.05 architecture.  The -mhard-dfp option
           allows GCC to generate the decimal floating-point instructions implemented on some POWER
           processors.

           The -mpowerpc64 option allows GCC to generate the additional 64-bit instructions that are
           found in the full PowerPC64 architecture and to treat GPRs as 64-bit, doubleword
           quantities.  GCC defaults to -mno-powerpc64.

       -mcpu=cpu_type
           Set architecture type, register usage, and instruction scheduling parameters for machine
           type cpu_type.  Supported values for cpu_type are 401, 403, 405, 405fp, 440, 440fp, 464,
           464fp, 476, 476fp, 505, 601, 602, 603, 603e, 604, 604e, 620, 630, 740, 7400, 7450, 750,
           801, 821, 823, 860, 970, 8540, a2, e300c2, e300c3, e500mc, e500mc64, e5500, e6500,
           ec603e, G3, G4, G5, titan, power3, power4, power5, power5+, power6, power6x, power7,
           power8, power9, power10, powerpc, powerpc64, powerpc64le, rs64, and native.

           -mcpu=powerpc, -mcpu=powerpc64, and -mcpu=powerpc64le specify pure 32-bit PowerPC (either
           endian), 64-bit big endian PowerPC and 64-bit little endian PowerPC architecture machine
           types, with an appropriate, generic processor model assumed for scheduling purposes.

           Specifying native as cpu type detects and selects the architecture option that
           corresponds to the host processor of the system performing the compilation.  -mcpu=native
           has no effect if GCC does not recognize the processor.

           The other options specify a specific processor.  Code generated under those options runs
           best on that processor, and may not run at all on others.

           The -mcpu options automatically enable or disable the following options:

           -maltivec  -mfprnd  -mhard-float  -mmfcrf  -mmultiple -mpopcntb  -mpopcntd  -mpowerpc64
           -mpowerpc-gpopt  -mpowerpc-gfxopt -mmulhw  -mdlmzb  -mmfpgpr  -mvsx -mcrypto  -mhtm
           -mpower8-fusion  -mpower8-vector -mquad-memory  -mquad-memory-atomic  -mfloat128
           -mfloat128-hardware -mprefixed -mpcrel -mmma -mrop-protect

           The particular options set for any particular CPU varies between compiler versions,
           depending on what setting seems to produce optimal code for that CPU; it doesn't
           necessarily reflect the actual hardware's capabilities.  If you wish to set an individual
           option to a particular value, you may specify it after the -mcpu option, like -mcpu=970
           -mno-altivec.

           On AIX, the -maltivec and -mpowerpc64 options are not enabled or disabled by the -mcpu
           option at present because AIX does not have full support for these options.  You may
           still enable or disable them individually if you're sure it'll work in your environment.

       -mtune=cpu_type
           Set the instruction scheduling parameters for machine type cpu_type, but do not set the
           architecture type or register usage, as -mcpu=cpu_type does.  The same values for
           cpu_type are used for -mtune as for -mcpu.  If both are specified, the code generated
           uses the architecture and registers set by -mcpu, but the scheduling parameters set by
           -mtune.

       -mcmodel=small
           Generate PowerPC64 code for the small model: The TOC is limited to 64k.

       -mcmodel=medium
           Generate PowerPC64 code for the medium model: The TOC and other static data may be up to
           a total of 4G in size.  This is the default for 64-bit Linux.

       -mcmodel=large
           Generate PowerPC64 code for the large model: The TOC may be up to 4G in size.  Other data
           and code is only limited by the 64-bit address space.

       -maltivec
       -mno-altivec
           Generate code that uses (does not use) AltiVec instructions, and also enable the use of
           built-in functions that allow more direct access to the AltiVec instruction set.  You may
           also need to set -mabi=altivec to adjust the current ABI with AltiVec ABI enhancements.

           When -maltivec is used, the element order for AltiVec intrinsics such as "vec_splat",
           "vec_extract", and "vec_insert" match array element order corresponding to the endianness
           of the target.  That is, element zero identifies the leftmost element in a vector
           register when targeting a big-endian platform, and identifies the rightmost element in a
           vector register when targeting a little-endian platform.

       -mvrsave
       -mno-vrsave
           Generate VRSAVE instructions when generating AltiVec code.

       -msecure-plt
           Generate code that allows ld and ld.so to build executables and shared libraries with
           non-executable ".plt" and ".got" sections.  This is a PowerPC 32-bit SYSV ABI option.

       -mbss-plt
           Generate code that uses a BSS ".plt" section that ld.so fills in, and requires ".plt" and
           ".got" sections that are both writable and executable.  This is a PowerPC 32-bit SYSV ABI
           option.

       -misel
       -mno-isel
           This switch enables or disables the generation of ISEL instructions.

       -mvsx
       -mno-vsx
           Generate code that uses (does not use) vector/scalar (VSX) instructions, and also enable
           the use of built-in functions that allow more direct access to the VSX instruction set.

       -mcrypto
       -mno-crypto
           Enable the use (disable) of the built-in functions that allow direct access to the
           cryptographic instructions that were added in version 2.07 of the PowerPC ISA.

       -mhtm
       -mno-htm
           Enable (disable) the use of the built-in functions that allow direct access to the
           Hardware Transactional Memory (HTM) instructions that were added in version 2.07 of the
           PowerPC ISA.

       -mpower8-fusion
       -mno-power8-fusion
           Generate code that keeps (does not keeps) some integer operations adjacent so that the
           instructions can be fused together on power8 and later processors.

       -mpower8-vector
       -mno-power8-vector
           Generate code that uses (does not use) the vector and scalar instructions that were added
           in version 2.07 of the PowerPC ISA.  Also enable the use of built-in functions that allow
           more direct access to the vector instructions.

       -mquad-memory
       -mno-quad-memory
           Generate code that uses (does not use) the non-atomic quad word memory instructions.  The
           -mquad-memory option requires use of 64-bit mode.

       -mquad-memory-atomic
       -mno-quad-memory-atomic
           Generate code that uses (does not use) the atomic quad word memory instructions.  The
           -mquad-memory-atomic option requires use of 64-bit mode.

       -mfloat128
       -mno-float128
           Enable/disable the __float128 keyword for IEEE 128-bit floating point and use either
           software emulation for IEEE 128-bit floating point or hardware instructions.

           The VSX instruction set (-mvsx) must be enabled to use the IEEE 128-bit floating point
           support.  The IEEE 128-bit floating point is only supported on Linux.

           The default for -mfloat128 is enabled on PowerPC Linux systems using the VSX instruction
           set, and disabled on other systems.

           If you use the ISA 3.0 instruction set (-mpower9-vector or -mcpu=power9) on a 64-bit
           system, the IEEE 128-bit floating point support will also enable the generation of ISA
           3.0 IEEE 128-bit floating point instructions.  Otherwise, if you do not specify to
           generate ISA 3.0 instructions or you are targeting a 32-bit big endian system, IEEE
           128-bit floating point will be done with software emulation.

       -mfloat128-hardware
       -mno-float128-hardware
           Enable/disable using ISA 3.0 hardware instructions to support the __float128 data type.

           The default for -mfloat128-hardware is enabled on PowerPC Linux systems using the ISA 3.0
           instruction set, and disabled on other systems.

       -m32
       -m64
           Generate code for 32-bit or 64-bit environments of Darwin and SVR4 targets (including
           GNU/Linux).  The 32-bit environment sets int, long and pointer to 32 bits and generates
           code that runs on any PowerPC variant.  The 64-bit environment sets int to 32 bits and
           long and pointer to 64 bits, and generates code for PowerPC64, as for -mpowerpc64.

       -mfull-toc
       -mno-fp-in-toc
       -mno-sum-in-toc
       -mminimal-toc
           Modify generation of the TOC (Table Of Contents), which is created for every executable
           file.  The -mfull-toc option is selected by default.  In that case, GCC allocates at
           least one TOC entry for each unique non-automatic variable reference in your program.
           GCC also places floating-point constants in the TOC.  However, only 16,384 entries are
           available in the TOC.

           If you receive a linker error message that saying you have overflowed the available TOC
           space, you can reduce the amount of TOC space used with the -mno-fp-in-toc and
           -mno-sum-in-toc options.  -mno-fp-in-toc prevents GCC from putting floating-point
           constants in the TOC and -mno-sum-in-toc forces GCC to generate code to calculate the sum
           of an address and a constant at run time instead of putting that sum into the TOC.  You
           may specify one or both of these options.  Each causes GCC to produce very slightly
           slower and larger code at the expense of conserving TOC space.

           If you still run out of space in the TOC even when you specify both of these options,
           specify -mminimal-toc instead.  This option causes GCC to make only one TOC entry for
           every file.  When you specify this option, GCC produces code that is slower and larger
           but which uses extremely little TOC space.  You may wish to use this option only on files
           that contain less frequently-executed code.

       -maix64
       -maix32
           Enable 64-bit AIX ABI and calling convention: 64-bit pointers, 64-bit "long" type, and
           the infrastructure needed to support them.  Specifying -maix64 implies -mpowerpc64, while
           -maix32 disables the 64-bit ABI and implies -mno-powerpc64.  GCC defaults to -maix32.

       -mxl-compat
       -mno-xl-compat
           Produce code that conforms more closely to IBM XL compiler semantics when using AIX-
           compatible ABI.  Pass floating-point arguments to prototyped functions beyond the
           register save area (RSA) on the stack in addition to argument FPRs.  Do not assume that
           most significant double in 128-bit long double value is properly rounded when comparing
           values and converting to double.  Use XL symbol names for long double support routines.

           The AIX calling convention was extended but not initially documented to handle an obscure
           K&R C case of calling a function that takes the address of its arguments with fewer
           arguments than declared.  IBM XL compilers access floating-point arguments that do not
           fit in the RSA from the stack when a subroutine is compiled without optimization.
           Because always storing floating-point arguments on the stack is inefficient and rarely
           needed, this option is not enabled by default and only is necessary when calling
           subroutines compiled by IBM XL compilers without optimization.

       -mpe
           Support IBM RS/6000 SP Parallel Environment (PE).  Link an application written to use
           message passing with special startup code to enable the application to run.  The system
           must have PE installed in the standard location (/usr/lpp/ppe.poe/), or the specs file
           must be overridden with the -specs= option to specify the appropriate directory location.
           The Parallel Environment does not support threads, so the -mpe option and the -pthread
           option are incompatible.

       -malign-natural
       -malign-power
           On AIX, 32-bit Darwin, and 64-bit PowerPC GNU/Linux, the option -malign-natural overrides
           the ABI-defined alignment of larger types, such as floating-point doubles, on their
           natural size-based boundary.  The option -malign-power instructs GCC to follow the ABI-
           specified alignment rules.  GCC defaults to the standard alignment defined in the ABI.

           On 64-bit Darwin, natural alignment is the default, and -malign-power is not supported.

       -msoft-float
       -mhard-float
           Generate code that does not use (uses) the floating-point register set.  Software
           floating-point emulation is provided if you use the -msoft-float option, and pass the
           option to GCC when linking.

       -mmultiple
       -mno-multiple
           Generate code that uses (does not use) the load multiple word instructions and the store
           multiple word instructions.  These instructions are generated by default on POWER
           systems, and not generated on PowerPC systems.  Do not use -mmultiple on little-endian
           PowerPC systems, since those instructions do not work when the processor is in little-
           endian mode.  The exceptions are PPC740 and PPC750 which permit these instructions in
           little-endian mode.

       -mupdate
       -mno-update
           Generate code that uses (does not use) the load or store instructions that update the
           base register to the address of the calculated memory location.  These instructions are
           generated by default.  If you use -mno-update, there is a small window between the time
           that the stack pointer is updated and the address of the previous frame is stored, which
           means code that walks the stack frame across interrupts or signals may get corrupted
           data.

       -mavoid-indexed-addresses
       -mno-avoid-indexed-addresses
           Generate code that tries to avoid (not avoid) the use of indexed load or store
           instructions. These instructions can incur a performance penalty on Power6 processors in
           certain situations, such as when stepping through large arrays that cross a 16M boundary.
           This option is enabled by default when targeting Power6 and disabled otherwise.

       -mfused-madd
       -mno-fused-madd
           Generate code that uses (does not use) the floating-point multiply and accumulate
           instructions.  These instructions are generated by default if hardware floating point is
           used.  The machine-dependent -mfused-madd option is now mapped to the machine-independent
           -ffp-contract=fast option, and -mno-fused-madd is mapped to -ffp-contract=off.

       -mmulhw
       -mno-mulhw
           Generate code that uses (does not use) the half-word multiply and multiply-accumulate
           instructions on the IBM 405, 440, 464 and 476 processors.  These instructions are
           generated by default when targeting those processors.

       -mdlmzb
       -mno-dlmzb
           Generate code that uses (does not use) the string-search dlmzb instruction on the IBM
           405, 440, 464 and 476 processors.  This instruction is generated by default when
           targeting those processors.

       -mno-bit-align
       -mbit-align
           On System V.4 and embedded PowerPC systems do not (do) force structures and unions that
           contain bit-fields to be aligned to the base type of the bit-field.

           For example, by default a structure containing nothing but 8 "unsigned" bit-fields of
           length 1 is aligned to a 4-byte boundary and has a size of 4 bytes.  By using
           -mno-bit-align, the structure is aligned to a 1-byte boundary and is 1 byte in size.

       -mno-strict-align
       -mstrict-align
           On System V.4 and embedded PowerPC systems do not (do) assume that unaligned memory
           references are handled by the system.

       -mrelocatable
       -mno-relocatable
           Generate code that allows (does not allow) a static executable to be relocated to a
           different address at run time.  A simple embedded PowerPC system loader should relocate
           the entire contents of ".got2" and 4-byte locations listed in the ".fixup" section, a
           table of 32-bit addresses generated by this option.  For this to work, all objects linked
           together must be compiled with -mrelocatable or -mrelocatable-lib.  -mrelocatable code
           aligns the stack to an 8-byte boundary.

       -mrelocatable-lib
       -mno-relocatable-lib
           Like -mrelocatable, -mrelocatable-lib generates a ".fixup" section to allow static
           executables to be relocated at run time, but -mrelocatable-lib does not use the smaller
           stack alignment of -mrelocatable.  Objects compiled with -mrelocatable-lib may be linked
           with objects compiled with any combination of the -mrelocatable options.

       -mno-toc
       -mtoc
           On System V.4 and embedded PowerPC systems do not (do) assume that register 2 contains a
           pointer to a global area pointing to the addresses used in the program.

       -mlittle
       -mlittle-endian
           On System V.4 and embedded PowerPC systems compile code for the processor in little-
           endian mode.  The -mlittle-endian option is the same as -mlittle.

       -mbig
       -mbig-endian
           On System V.4 and embedded PowerPC systems compile code for the processor in big-endian
           mode.  The -mbig-endian option is the same as -mbig.

       -mdynamic-no-pic
           On Darwin and Mac OS X systems, compile code so that it is not relocatable, but that its
           external references are relocatable.  The resulting code is suitable for applications,
           but not shared libraries.

       -msingle-pic-base
           Treat the register used for PIC addressing as read-only, rather than loading it in the
           prologue for each function.  The runtime system is responsible for initializing this
           register with an appropriate value before execution begins.

       -mprioritize-restricted-insns=priority
           This option controls the priority that is assigned to dispatch-slot restricted
           instructions during the second scheduling pass.  The argument priority takes the value 0,
           1, or 2 to assign no, highest, or second-highest (respectively) priority to dispatch-slot
           restricted instructions.

       -msched-costly-dep=dependence_type
           This option controls which dependences are considered costly by the target during
           instruction scheduling.  The argument dependence_type takes one of the following values:

           no  No dependence is costly.

           all All dependences are costly.

           true_store_to_load
               A true dependence from store to load is costly.

           store_to_load
               Any dependence from store to load is costly.

           number
               Any dependence for which the latency is greater than or equal to number is costly.

       -minsert-sched-nops=scheme
           This option controls which NOP insertion scheme is used during the second scheduling
           pass.  The argument scheme takes one of the following values:

           no  Don't insert NOPs.

           pad Pad with NOPs any dispatch group that has vacant issue slots, according to the
               scheduler's grouping.

           regroup_exact
               Insert NOPs to force costly dependent insns into separate groups.  Insert exactly as
               many NOPs as needed to force an insn to a new group, according to the estimated
               processor grouping.

           number
               Insert NOPs to force costly dependent insns into separate groups.  Insert number NOPs
               to force an insn to a new group.

       -mcall-sysv
           On System V.4 and embedded PowerPC systems compile code using calling conventions that
           adhere to the March 1995 draft of the System V Application Binary Interface, PowerPC
           processor supplement.  This is the default unless you configured GCC using
           powerpc-*-eabiaix.

       -mcall-sysv-eabi
       -mcall-eabi
           Specify both -mcall-sysv and -meabi options.

       -mcall-sysv-noeabi
           Specify both -mcall-sysv and -mno-eabi options.

       -mcall-aixdesc
           On System V.4 and embedded PowerPC systems compile code for the AIX operating system.

       -mcall-linux
           On System V.4 and embedded PowerPC systems compile code for the Linux-based GNU system.

       -mcall-freebsd
           On System V.4 and embedded PowerPC systems compile code for the FreeBSD operating system.

       -mcall-netbsd
           On System V.4 and embedded PowerPC systems compile code for the NetBSD operating system.

       -mcall-openbsd
           On System V.4 and embedded PowerPC systems compile code for the OpenBSD operating system.

       -mtraceback=traceback_type
           Select the type of traceback table. Valid values for traceback_type are full, part, and
           no.

       -maix-struct-return
           Return all structures in memory (as specified by the AIX ABI).

       -msvr4-struct-return
           Return structures smaller than 8 bytes in registers (as specified by the SVR4 ABI).

       -mabi=abi-type
           Extend the current ABI with a particular extension, or remove such extension.  Valid
           values are: altivec, no-altivec, ibmlongdouble, ieeelongdouble, elfv1, elfv2, and for
           AIX: vec-extabi, vec-default.

       -mabi=ibmlongdouble
           Change the current ABI to use IBM extended-precision long double.  This is not likely to
           work if your system defaults to using IEEE extended-precision long double.  If you change
           the long double type from IEEE extended-precision, the compiler will issue a warning
           unless you use the -Wno-psabi option.  Requires -mlong-double-128 to be enabled.

       -mabi=ieeelongdouble
           Change the current ABI to use IEEE extended-precision long double.  This is not likely to
           work if your system defaults to using IBM extended-precision long double.  If you change
           the long double type from IBM extended-precision, the compiler will issue a warning
           unless you use the -Wno-psabi option.  Requires -mlong-double-128 to be enabled.

       -mabi=elfv1
           Change the current ABI to use the ELFv1 ABI.  This is the default ABI for big-endian
           PowerPC 64-bit Linux.  Overriding the default ABI requires special system support and is
           likely to fail in spectacular ways.

       -mabi=elfv2
           Change the current ABI to use the ELFv2 ABI.  This is the default ABI for little-endian
           PowerPC 64-bit Linux.  Overriding the default ABI requires special system support and is
           likely to fail in spectacular ways.

       -mgnu-attribute
       -mno-gnu-attribute
           Emit .gnu_attribute assembly directives to set tag/value pairs in a .gnu.attributes
           section that specify ABI variations in function parameters or return values.

       -mprototype
       -mno-prototype
           On System V.4 and embedded PowerPC systems assume that all calls to variable argument
           functions are properly prototyped.  Otherwise, the compiler must insert an instruction
           before every non-prototyped call to set or clear bit 6 of the condition code register
           ("CR") to indicate whether floating-point values are passed in the floating-point
           registers in case the function takes variable arguments.  With -mprototype, only calls to
           prototyped variable argument functions set or clear the bit.

       -msim
           On embedded PowerPC systems, assume that the startup module is called sim-crt0.o and that
           the standard C libraries are libsim.a and libc.a.  This is the default for
           powerpc-*-eabisim configurations.

       -mmvme
           On embedded PowerPC systems, assume that the startup module is called crt0.o and the
           standard C libraries are libmvme.a and libc.a.

       -mads
           On embedded PowerPC systems, assume that the startup module is called crt0.o and the
           standard C libraries are libads.a and libc.a.

       -myellowknife
           On embedded PowerPC systems, assume that the startup module is called crt0.o and the
           standard C libraries are libyk.a and libc.a.

       -mvxworks
           On System V.4 and embedded PowerPC systems, specify that you are compiling for a VxWorks
           system.

       -memb
           On embedded PowerPC systems, set the "PPC_EMB" bit in the ELF flags header to indicate
           that eabi extended relocations are used.

       -meabi
       -mno-eabi
           On System V.4 and embedded PowerPC systems do (do not) adhere to the Embedded
           Applications Binary Interface (EABI), which is a set of modifications to the System V.4
           specifications.  Selecting -meabi means that the stack is aligned to an 8-byte boundary,
           a function "__eabi" is called from "main" to set up the EABI environment, and the -msdata
           option can use both "r2" and "r13" to point to two separate small data areas.  Selecting
           -mno-eabi means that the stack is aligned to a 16-byte boundary, no EABI initialization
           function is called from "main", and the -msdata option only uses "r13" to point to a
           single small data area.  The -meabi option is on by default if you configured GCC using
           one of the powerpc*-*-eabi* options.

       -msdata=eabi
           On System V.4 and embedded PowerPC systems, put small initialized "const" global and
           static data in the ".sdata2" section, which is pointed to by register "r2".  Put small
           initialized non-"const" global and static data in the ".sdata" section, which is pointed
           to by register "r13".  Put small uninitialized global and static data in the ".sbss"
           section, which is adjacent to the ".sdata" section.  The -msdata=eabi option is
           incompatible with the -mrelocatable option.  The -msdata=eabi option also sets the -memb
           option.

       -msdata=sysv
           On System V.4 and embedded PowerPC systems, put small global and static data in the
           ".sdata" section, which is pointed to by register "r13".  Put small uninitialized global
           and static data in the ".sbss" section, which is adjacent to the ".sdata" section.  The
           -msdata=sysv option is incompatible with the -mrelocatable option.

       -msdata=default
       -msdata
           On System V.4 and embedded PowerPC systems, if -meabi is used, compile code the same as
           -msdata=eabi, otherwise compile code the same as -msdata=sysv.

       -msdata=data
           On System V.4 and embedded PowerPC systems, put small global data in the ".sdata"
           section.  Put small uninitialized global data in the ".sbss" section.  Do not use
           register "r13" to address small data however.  This is the default behavior unless other
           -msdata options are used.

       -msdata=none
       -mno-sdata
           On embedded PowerPC systems, put all initialized global and static data in the ".data"
           section, and all uninitialized data in the ".bss" section.

       -mreadonly-in-sdata
           Put read-only objects in the ".sdata" section as well.  This is the default.

       -mblock-move-inline-limit=num
           Inline all block moves (such as calls to "memcpy" or structure copies) less than or equal
           to num bytes.  The minimum value for num is 32 bytes on 32-bit targets and 64 bytes on
           64-bit targets.  The default value is target-specific.

       -mblock-compare-inline-limit=num
           Generate non-looping inline code for all block compares (such as calls to "memcmp" or
           structure compares) less than or equal to num bytes. If num is 0, all inline expansion
           (non-loop and loop) of block compare is disabled. The default value is target-specific.

       -mblock-compare-inline-loop-limit=num
           Generate an inline expansion using loop code for all block compares that are less than or
           equal to num bytes, but greater than the limit for non-loop inline block compare
           expansion. If the block length is not constant, at most num bytes will be compared before
           "memcmp" is called to compare the remainder of the block. The default value is target-
           specific.

       -mstring-compare-inline-limit=num
           Compare at most num string bytes with inline code.  If the difference or end of string is
           not found at the end of the inline compare a call to "strcmp" or "strncmp" will take care
           of the rest of the comparison. The default is 64 bytes.

       -G num
           On embedded PowerPC systems, put global and static items less than or equal to num bytes
           into the small data or BSS sections instead of the normal data or BSS section.  By
           default, num is 8.  The -G num switch is also passed to the linker.  All modules should
           be compiled with the same -G num value.

       -mregnames
       -mno-regnames
           On System V.4 and embedded PowerPC systems do (do not) emit register names in the
           assembly language output using symbolic forms.

       -mlongcall
       -mno-longcall
           By default assume that all calls are far away so that a longer and more expensive calling
           sequence is required.  This is required for calls farther than 32 megabytes (33,554,432
           bytes) from the current location.  A short call is generated if the compiler knows the
           call cannot be that far away.  This setting can be overridden by the "shortcall" function
           attribute, or by "#pragma longcall(0)".

           Some linkers are capable of detecting out-of-range calls and generating glue code on the
           fly.  On these systems, long calls are unnecessary and generate slower code.  As of this
           writing, the AIX linker can do this, as can the GNU linker for PowerPC/64.  It is planned
           to add this feature to the GNU linker for 32-bit PowerPC systems as well.

           On PowerPC64 ELFv2 and 32-bit PowerPC systems with newer GNU linkers, GCC can generate
           long calls using an inline PLT call sequence (see -mpltseq).  PowerPC with -mbss-plt and
           PowerPC64 ELFv1 (big-endian) do not support inline PLT calls.

           On Darwin/PPC systems, "#pragma longcall" generates "jbsr callee, L42", plus a branch
           island (glue code).  The two target addresses represent the callee and the branch island.
           The Darwin/PPC linker prefers the first address and generates a "bl callee" if the PPC
           "bl" instruction reaches the callee directly; otherwise, the linker generates "bl L42" to
           call the branch island.  The branch island is appended to the body of the calling
           function; it computes the full 32-bit address of the callee and jumps to it.

           On Mach-O (Darwin) systems, this option directs the compiler emit to the glue for every
           direct call, and the Darwin linker decides whether to use or discard it.

           In the future, GCC may ignore all longcall specifications when the linker is known to
           generate glue.

       -mpltseq
       -mno-pltseq
           Implement (do not implement) -fno-plt and long calls using an inline PLT call sequence
           that supports lazy linking and long calls to functions in dlopen'd shared libraries.
           Inline PLT calls are only supported on PowerPC64 ELFv2 and 32-bit PowerPC systems with
           newer GNU linkers, and are enabled by default if the support is detected when configuring
           GCC, and, in the case of 32-bit PowerPC, if GCC is configured with --enable-secureplt.
           -mpltseq code and -mbss-plt 32-bit PowerPC relocatable objects may not be linked
           together.

       -mtls-markers
       -mno-tls-markers
           Mark (do not mark) calls to "__tls_get_addr" with a relocation specifying the function
           argument.  The relocation allows the linker to reliably associate function call with
           argument setup instructions for TLS optimization, which in turn allows GCC to better
           schedule the sequence.

       -mrecip
       -mno-recip
           This option enables use of the reciprocal estimate and reciprocal square root estimate
           instructions with additional Newton-Raphson steps to increase precision instead of doing
           a divide or square root and divide for floating-point arguments.  You should use the
           -ffast-math option when using -mrecip (or at least -funsafe-math-optimizations,
           -ffinite-math-only, -freciprocal-math and -fno-trapping-math).  Note that while the
           throughput of the sequence is generally higher than the throughput of the non-reciprocal
           instruction, the precision of the sequence can be decreased by up to 2 ulp (i.e. the
           inverse of 1.0 equals 0.99999994) for reciprocal square roots.

       -mrecip=opt
           This option controls which reciprocal estimate instructions may be used.  opt is a comma-
           separated list of options, which may be preceded by a "!" to invert the option:

           all Enable all estimate instructions.

           default
               Enable the default instructions, equivalent to -mrecip.

           none
               Disable all estimate instructions, equivalent to -mno-recip.

           div Enable the reciprocal approximation instructions for both single and double
               precision.

           divf
               Enable the single-precision reciprocal approximation instructions.

           divd
               Enable the double-precision reciprocal approximation instructions.

           rsqrt
               Enable the reciprocal square root approximation instructions for both single and
               double precision.

           rsqrtf
               Enable the single-precision reciprocal square root approximation instructions.

           rsqrtd
               Enable the double-precision reciprocal square root approximation instructions.

           So, for example, -mrecip=all,!rsqrtd enables all of the reciprocal estimate instructions,
           except for the "FRSQRTE", "XSRSQRTEDP", and "XVRSQRTEDP" instructions which handle the
           double-precision reciprocal square root calculations.

       -mrecip-precision
       -mno-recip-precision
           Assume (do not assume) that the reciprocal estimate instructions provide higher-precision
           estimates than is mandated by the PowerPC ABI.  Selecting -mcpu=power6, -mcpu=power7 or
           -mcpu=power8 automatically selects -mrecip-precision.  The double-precision square root
           estimate instructions are not generated by default on low-precision machines, since they
           do not provide an estimate that converges after three steps.

       -mveclibabi=type
           Specifies the ABI type to use for vectorizing intrinsics using an external library.  The
           only type supported at present is mass, which specifies to use IBM's Mathematical
           Acceleration Subsystem (MASS) libraries for vectorizing intrinsics using external
           libraries.  GCC currently emits calls to "acosd2", "acosf4", "acoshd2", "acoshf4",
           "asind2", "asinf4", "asinhd2", "asinhf4", "atan2d2", "atan2f4", "atand2", "atanf4",
           "atanhd2", "atanhf4", "cbrtd2", "cbrtf4", "cosd2", "cosf4", "coshd2", "coshf4", "erfcd2",
           "erfcf4", "erfd2", "erff4", "exp2d2", "exp2f4", "expd2", "expf4", "expm1d2", "expm1f4",
           "hypotd2", "hypotf4", "lgammad2", "lgammaf4", "log10d2", "log10f4", "log1pd2", "log1pf4",
           "log2d2", "log2f4", "logd2", "logf4", "powd2", "powf4", "sind2", "sinf4", "sinhd2",
           "sinhf4", "sqrtd2", "sqrtf4", "tand2", "tanf4", "tanhd2", and "tanhf4" when generating
           code for power7.  Both -ftree-vectorize and -funsafe-math-optimizations must also be
           enabled.  The MASS libraries must be specified at link time.

       -mfriz
       -mno-friz
           Generate (do not generate) the "friz" instruction when the -funsafe-math-optimizations
           option is used to optimize rounding of floating-point values to 64-bit integer and back
           to floating point.  The "friz" instruction does not return the same value if the
           floating-point number is too large to fit in an integer.

       -mpointers-to-nested-functions
       -mno-pointers-to-nested-functions
           Generate (do not generate) code to load up the static chain register ("r11") when calling
           through a pointer on AIX and 64-bit Linux systems where a function pointer points to a
           3-word descriptor giving the function address, TOC value to be loaded in register "r2",
           and static chain value to be loaded in register "r11".  The
           -mpointers-to-nested-functions is on by default.  You cannot call through pointers to
           nested functions or pointers to functions compiled in other languages that use the static
           chain if you use -mno-pointers-to-nested-functions.

       -msave-toc-indirect
       -mno-save-toc-indirect
           Generate (do not generate) code to save the TOC value in the reserved stack location in
           the function prologue if the function calls through a pointer on AIX and 64-bit Linux
           systems.  If the TOC value is not saved in the prologue, it is saved just before the call
           through the pointer.  The -mno-save-toc-indirect option is the default.

       -mcompat-align-parm
       -mno-compat-align-parm
           Generate (do not generate) code to pass structure parameters with a maximum alignment of
           64 bits, for compatibility with older versions of GCC.

           Older versions of GCC (prior to 4.9.0) incorrectly did not align a structure parameter on
           a 128-bit boundary when that structure contained a member requiring 128-bit alignment.
           This is corrected in more recent versions of GCC.  This option may be used to generate
           code that is compatible with functions compiled with older versions of GCC.

           The -mno-compat-align-parm option is the default.

       -mstack-protector-guard=guard
       -mstack-protector-guard-reg=reg
       -mstack-protector-guard-offset=offset
       -mstack-protector-guard-symbol=symbol
           Generate stack protection code using canary at guard.  Supported locations are global for
           global canary or tls for per-thread canary in the TLS block (the default with GNU libc
           version 2.4 or later).

           With the latter choice the options -mstack-protector-guard-reg=reg and
           -mstack-protector-guard-offset=offset furthermore specify which register to use as base
           register for reading the canary, and from what offset from that base register. The
           default for those is as specified in the relevant ABI.
           -mstack-protector-guard-symbol=symbol overrides the offset with a symbol reference to a
           canary in the TLS block.

       -mpcrel
       -mno-pcrel
           Generate (do not generate) pc-relative addressing.  The -mpcrel option requires that the
           medium code model (-mcmodel=medium) and prefixed addressing (-mprefixed) options are
           enabled.

       -mprefixed
       -mno-prefixed
           Generate (do not generate) addressing modes using prefixed load and store instructions.
           The -mprefixed option requires that the option -mcpu=power10 (or later) is enabled.

       -mmma
       -mno-mma
           Generate (do not generate) the MMA instructions.  The -mma option requires that the
           option -mcpu=power10 (or later) is enabled.

       -mrop-protect
       -mno-rop-protect
           Generate (do not generate) ROP protection instructions when the target processor supports
           them.  Currently this option disables the shrink-wrap optimization (-fshrink-wrap).

       -mprivileged
       -mno-privileged
           Generate (do not generate) code that will run in privileged state.

       -mblock-ops-unaligned-vsx
       -mno-block-ops-unaligned-vsx
           Generate (do not generate) unaligned vsx loads and stores for inline expansion of
           "memcpy" and "memmove".

       RX Options

       These command-line options are defined for RX targets:

       -m64bit-doubles
       -m32bit-doubles
           Make the "double" data type be 64 bits (-m64bit-doubles) or 32 bits (-m32bit-doubles) in
           size.  The default is -m32bit-doubles.  Note RX floating-point hardware only works on
           32-bit values, which is why the default is -m32bit-doubles.

       -fpu
       -nofpu
           Enables (-fpu) or disables (-nofpu) the use of RX floating-point hardware.  The default
           is enabled for the RX600 series and disabled for the RX200 series.

           Floating-point instructions are only generated for 32-bit floating-point values, however,
           so the FPU hardware is not used for doubles if the -m64bit-doubles option is used.

           Note If the -fpu option is enabled then -funsafe-math-optimizations is also enabled
           automatically.  This is because the RX FPU instructions are themselves unsafe.

       -mcpu=name
           Selects the type of RX CPU to be targeted.  Currently three types are supported, the
           generic RX600 and RX200 series hardware and the specific RX610 CPU.  The default is
           RX600.

           The only difference between RX600 and RX610 is that the RX610 does not support the
           "MVTIPL" instruction.

           The RX200 series does not have a hardware floating-point unit and so -nofpu is enabled by
           default when this type is selected.

       -mbig-endian-data
       -mlittle-endian-data
           Store data (but not code) in the big-endian format.  The default is -mlittle-endian-data,
           i.e. to store data in the little-endian format.

       -msmall-data-limit=N
           Specifies the maximum size in bytes of global and static variables which can be placed
           into the small data area.  Using the small data area can lead to smaller and faster code,
           but the size of area is limited and it is up to the programmer to ensure that the area
           does not overflow.  Also when the small data area is used one of the RX's registers
           (usually "r13") is reserved for use pointing to this area, so it is no longer available
           for use by the compiler.  This could result in slower and/or larger code if variables are
           pushed onto the stack instead of being held in this register.

           Note, common variables (variables that have not been initialized) and constants are not
           placed into the small data area as they are assigned to other sections in the output
           executable.

           The default value is zero, which disables this feature.  Note, this feature is not
           enabled by default with higher optimization levels (-O2 etc) because of the potentially
           detrimental effects of reserving a register.  It is up to the programmer to experiment
           and discover whether this feature is of benefit to their program.  See the description of
           the -mpid option for a description of how the actual register to hold the small data area
           pointer is chosen.

       -msim
       -mno-sim
           Use the simulator runtime.  The default is to use the libgloss board-specific runtime.

       -mas100-syntax
       -mno-as100-syntax
           When generating assembler output use a syntax that is compatible with Renesas's AS100
           assembler.  This syntax can also be handled by the GAS assembler, but it has some
           restrictions so it is not generated by default.

       -mmax-constant-size=N
           Specifies the maximum size, in bytes, of a constant that can be used as an operand in a
           RX instruction.  Although the RX instruction set does allow constants of up to 4 bytes in
           length to be used in instructions, a longer value equates to a longer instruction.  Thus
           in some circumstances it can be beneficial to restrict the size of constants that are
           used in instructions.  Constants that are too big are instead placed into a constant pool
           and referenced via register indirection.

           The value N can be between 0 and 4.  A value of 0 (the default) or 4 means that constants
           of any size are allowed.

       -mrelax
           Enable linker relaxation.  Linker relaxation is a process whereby the linker attempts to
           reduce the size of a program by finding shorter versions of various instructions.
           Disabled by default.

       -mint-register=N
           Specify the number of registers to reserve for fast interrupt handler functions.  The
           value N can be between 0 and 4.  A value of 1 means that register "r13" is reserved for
           the exclusive use of fast interrupt handlers.  A value of 2 reserves "r13" and "r12".  A
           value of 3 reserves "r13", "r12" and "r11", and a value of 4 reserves "r13" through
           "r10".  A value of 0, the default, does not reserve any registers.

       -msave-acc-in-interrupts
           Specifies that interrupt handler functions should preserve the accumulator register.
           This is only necessary if normal code might use the accumulator register, for example
           because it performs 64-bit multiplications.  The default is to ignore the accumulator as
           this makes the interrupt handlers faster.

       -mpid
       -mno-pid
           Enables the generation of position independent data.  When enabled any access to constant
           data is done via an offset from a base address held in a register.  This allows the
           location of constant data to be determined at run time without requiring the executable
           to be relocated, which is a benefit to embedded applications with tight memory
           constraints.  Data that can be modified is not affected by this option.

           Note, using this feature reserves a register, usually "r13", for the constant data base
           address.  This can result in slower and/or larger code, especially in complicated
           functions.

           The actual register chosen to hold the constant data base address depends upon whether
           the -msmall-data-limit and/or the -mint-register command-line options are enabled.
           Starting with register "r13" and proceeding downwards, registers are allocated first to
           satisfy the requirements of -mint-register, then -mpid and finally -msmall-data-limit.
           Thus it is possible for the small data area register to be "r8" if both -mint-register=4
           and -mpid are specified on the command line.

           By default this feature is not enabled.  The default can be restored via the -mno-pid
           command-line option.

       -mno-warn-multiple-fast-interrupts
       -mwarn-multiple-fast-interrupts
           Prevents GCC from issuing a warning message if it finds more than one fast interrupt
           handler when it is compiling a file.  The default is to issue a warning for each extra
           fast interrupt handler found, as the RX only supports one such interrupt.

       -mallow-string-insns
       -mno-allow-string-insns
           Enables or disables the use of the string manipulation instructions "SMOVF", "SCMPU",
           "SMOVB", "SMOVU", "SUNTIL" "SWHILE" and also the "RMPA" instruction.  These instructions
           may prefetch data, which is not safe to do if accessing an I/O register.  (See section
           12.2.7 of the RX62N Group User's Manual for more information).

           The default is to allow these instructions, but it is not possible for GCC to reliably
           detect all circumstances where a string instruction might be used to access an I/O
           register, so their use cannot be disabled automatically.  Instead it is reliant upon the
           programmer to use the -mno-allow-string-insns option if their program accesses I/O space.

           When the instructions are enabled GCC defines the C preprocessor symbol
           "__RX_ALLOW_STRING_INSNS__", otherwise it defines the symbol
           "__RX_DISALLOW_STRING_INSNS__".

       -mjsr
       -mno-jsr
           Use only (or not only) "JSR" instructions to access functions.  This option can be used
           when code size exceeds the range of "BSR" instructions.  Note that -mno-jsr does not mean
           to not use "JSR" but instead means that any type of branch may be used.

       Note: The generic GCC command-line option -ffixed-reg has special significance to the RX port
       when used with the "interrupt" function attribute.  This attribute indicates a function
       intended to process fast interrupts.  GCC ensures that it only uses the registers "r10",
       "r11", "r12" and/or "r13" and only provided that the normal use of the corresponding
       registers have been restricted via the -ffixed-reg or -mint-register command-line options.

       S/390 and zSeries Options

       These are the -m options defined for the S/390 and zSeries architecture.

       -mhard-float
       -msoft-float
           Use (do not use) the hardware floating-point instructions and registers for floating-
           point operations.  When -msoft-float is specified, functions in libgcc.a are used to
           perform floating-point operations.  When -mhard-float is specified, the compiler
           generates IEEE floating-point instructions.  This is the default.

       -mhard-dfp
       -mno-hard-dfp
           Use (do not use) the hardware decimal-floating-point instructions for decimal-floating-
           point operations.  When -mno-hard-dfp is specified, functions in libgcc.a are used to
           perform decimal-floating-point operations.  When -mhard-dfp is specified, the compiler
           generates decimal-floating-point hardware instructions.  This is the default for
           -march=z9-ec or higher.

       -mlong-double-64
       -mlong-double-128
           These switches control the size of "long double" type. A size of 64 bits makes the "long
           double" type equivalent to the "double" type. This is the default.

       -mbackchain
       -mno-backchain
           Store (do not store) the address of the caller's frame as backchain pointer into the
           callee's stack frame.  A backchain may be needed to allow debugging using tools that do
           not understand DWARF call frame information.  When -mno-packed-stack is in effect, the
           backchain pointer is stored at the bottom of the stack frame; when -mpacked-stack is in
           effect, the backchain is placed into the topmost word of the 96/160 byte register save
           area.

           In general, code compiled with -mbackchain is call-compatible with code compiled with
           -mno-backchain; however, use of the backchain for debugging purposes usually requires
           that the whole binary is built with -mbackchain.  Note that the combination of
           -mbackchain, -mpacked-stack and -mhard-float is not supported.  In order to build a linux
           kernel use -msoft-float.

           The default is to not maintain the backchain.

       -mpacked-stack
       -mno-packed-stack
           Use (do not use) the packed stack layout.  When -mno-packed-stack is specified, the
           compiler uses the all fields of the 96/160 byte register save area only for their default
           purpose; unused fields still take up stack space.  When -mpacked-stack is specified,
           register save slots are densely packed at the top of the register save area; unused space
           is reused for other purposes, allowing for more efficient use of the available stack
           space.  However, when -mbackchain is also in effect, the topmost word of the save area is
           always used to store the backchain, and the return address register is always saved two
           words below the backchain.

           As long as the stack frame backchain is not used, code generated with -mpacked-stack is
           call-compatible with code generated with -mno-packed-stack.  Note that some non-FSF
           releases of GCC 2.95 for S/390 or zSeries generated code that uses the stack frame
           backchain at run time, not just for debugging purposes.  Such code is not call-compatible
           with code compiled with -mpacked-stack.  Also, note that the combination of -mbackchain,
           -mpacked-stack and -mhard-float is not supported.  In order to build a linux kernel use
           -msoft-float.

           The default is to not use the packed stack layout.

       -msmall-exec
       -mno-small-exec
           Generate (or do not generate) code using the "bras" instruction to do subroutine calls.
           This only works reliably if the total executable size does not exceed 64k.  The default
           is to use the "basr" instruction instead, which does not have this limitation.

       -m64
       -m31
           When -m31 is specified, generate code compliant to the GNU/Linux for S/390 ABI.  When
           -m64 is specified, generate code compliant to the GNU/Linux for zSeries ABI.  This allows
           GCC in particular to generate 64-bit instructions.  For the s390 targets, the default is
           -m31, while the s390x targets default to -m64.

       -mzarch
       -mesa
           When -mzarch is specified, generate code using the instructions available on
           z/Architecture.  When -mesa is specified, generate code using the instructions available
           on ESA/390.  Note that -mesa is not possible with -m64.  When generating code compliant
           to the GNU/Linux for S/390 ABI, the default is -mesa.  When generating code compliant to
           the GNU/Linux for zSeries ABI, the default is -mzarch.

       -mhtm
       -mno-htm
           The -mhtm option enables a set of builtins making use of instructions available with the
           transactional execution facility introduced with the IBM zEnterprise EC12 machine
           generation S/390 System z Built-in Functions.  -mhtm is enabled by default when using
           -march=zEC12.

       -mvx
       -mno-vx
           When -mvx is specified, generate code using the instructions available with the vector
           extension facility introduced with the IBM z13 machine generation.  This option changes
           the ABI for some vector type values with regard to alignment and calling conventions.  In
           case vector type values are being used in an ABI-relevant context a GAS .gnu_attribute
           command will be added to mark the resulting binary with the ABI used.  -mvx is enabled by
           default when using -march=z13.

       -mzvector
       -mno-zvector
           The -mzvector option enables vector language extensions and builtins using instructions
           available with the vector extension facility introduced with the IBM z13 machine
           generation.  This option adds support for vector to be used as a keyword to define vector
           type variables and arguments.  vector is only available when GNU extensions are enabled.
           It will not be expanded when requesting strict standard compliance e.g. with -std=c99.
           In addition to the GCC low-level builtins -mzvector enables a set of builtins added for
           compatibility with AltiVec-style implementations like Power and Cell.  In order to make
           use of these builtins the header file vecintrin.h needs to be included.  -mzvector is
           disabled by default.

       -mmvcle
       -mno-mvcle
           Generate (or do not generate) code using the "mvcle" instruction to perform block moves.
           When -mno-mvcle is specified, use a "mvc" loop instead.  This is the default unless
           optimizing for size.

       -mdebug
       -mno-debug
           Print (or do not print) additional debug information when compiling.  The default is to
           not print debug information.

       -march=cpu-type
           Generate code that runs on cpu-type, which is the name of a system representing a certain
           processor type.  Possible values for cpu-type are z900/arch5, z990/arch6, z9-109,
           z9-ec/arch7, z10/arch8, z196/arch9, zEC12, z13/arch11, z14/arch12, z15/arch13,
           z16/arch14, and native.

           The default is -march=z900.

           Specifying native as cpu type can be used to select the best architecture option for the
           host processor.  -march=native has no effect if GCC does not recognize the processor.

       -mtune=cpu-type
           Tune to cpu-type everything applicable about the generated code, except for the ABI and
           the set of available instructions.  The list of cpu-type values is the same as for
           -march.  The default is the value used for -march.

       -mtpf-trace
       -mno-tpf-trace
           Generate code that adds (does not add) in TPF OS specific branches to trace routines in
           the operating system.  This option is off by default, even when compiling for the TPF OS.

       -mtpf-trace-skip
       -mno-tpf-trace-skip
           Generate code that changes (does not change) the default branch targets enabled by
           -mtpf-trace to point to specialized trace routines providing the ability of selectively
           skipping function trace entries for the TPF OS.  This option is off by default, even when
           compiling for the TPF OS and specifying -mtpf-trace.

       -mfused-madd
       -mno-fused-madd
           Generate code that uses (does not use) the floating-point multiply and accumulate
           instructions.  These instructions are generated by default if hardware floating point is
           used.

       -mwarn-framesize=framesize
           Emit a warning if the current function exceeds the given frame size.  Because this is a
           compile-time check it doesn't need to be a real problem when the program runs.  It is
           intended to identify functions that most probably cause a stack overflow.  It is useful
           to be used in an environment with limited stack size e.g. the linux kernel.

       -mwarn-dynamicstack
           Emit a warning if the function calls "alloca" or uses dynamically-sized arrays.  This is
           generally a bad idea with a limited stack size.

       -mstack-guard=stack-guard
       -mstack-size=stack-size
           If these options are provided the S/390 back end emits additional instructions in the
           function prologue that trigger a trap if the stack size is stack-guard bytes above the
           stack-size (remember that the stack on S/390 grows downward).  If the stack-guard option
           is omitted the smallest power of 2 larger than the frame size of the compiled function is
           chosen.  These options are intended to be used to help debugging stack overflow problems.
           The additionally emitted code causes only little overhead and hence can also be used in
           production-like systems without greater performance degradation.  The given values have
           to be exact powers of 2 and stack-size has to be greater than stack-guard without
           exceeding 64k.  In order to be efficient the extra code makes the assumption that the
           stack starts at an address aligned to the value given by stack-size.  The stack-guard
           option can only be used in conjunction with stack-size.

       -mhotpatch=pre-halfwords,post-halfwords
           If the hotpatch option is enabled, a "hot-patching" function prologue is generated for
           all functions in the compilation unit.  The funtion label is prepended with the given
           number of two-byte NOP instructions (pre-halfwords, maximum 1000000).  After the label, 2
           * post-halfwords bytes are appended, using the largest NOP like instructions the
           architecture allows (maximum 1000000).

           If both arguments are zero, hotpatching is disabled.

           This option can be overridden for individual functions with the "hotpatch" attribute.

       Score Options

       These options are defined for Score implementations:

       -meb
           Compile code for big-endian mode.  This is the default.

       -mel
           Compile code for little-endian mode.

       -mnhwloop
           Disable generation of "bcnz" instructions.

       -muls
           Enable generation of unaligned load and store instructions.

       -mmac
           Enable the use of multiply-accumulate instructions. Disabled by default.

       -mscore5
           Specify the SCORE5 as the target architecture.

       -mscore5u
           Specify the SCORE5U of the target architecture.

       -mscore7
           Specify the SCORE7 as the target architecture. This is the default.

       -mscore7d
           Specify the SCORE7D as the target architecture.

       SH Options

       These -m options are defined for the SH implementations:

       -m1 Generate code for the SH1.

       -m2 Generate code for the SH2.

       -m2e
           Generate code for the SH2e.

       -m2a-nofpu
           Generate code for the SH2a without FPU, or for a SH2a-FPU in such a way that the
           floating-point unit is not used.

       -m2a-single-only
           Generate code for the SH2a-FPU, in such a way that no double-precision floating-point
           operations are used.

       -m2a-single
           Generate code for the SH2a-FPU assuming the floating-point unit is in single-precision
           mode by default.

       -m2a
           Generate code for the SH2a-FPU assuming the floating-point unit is in double-precision
           mode by default.

       -m3 Generate code for the SH3.

       -m3e
           Generate code for the SH3e.

       -m4-nofpu
           Generate code for the SH4 without a floating-point unit.

       -m4-single-only
           Generate code for the SH4 with a floating-point unit that only supports single-precision
           arithmetic.

       -m4-single
           Generate code for the SH4 assuming the floating-point unit is in single-precision mode by
           default.

       -m4 Generate code for the SH4.

       -m4-100
           Generate code for SH4-100.

       -m4-100-nofpu
           Generate code for SH4-100 in such a way that the floating-point unit is not used.

       -m4-100-single
           Generate code for SH4-100 assuming the floating-point unit is in single-precision mode by
           default.

       -m4-100-single-only
           Generate code for SH4-100 in such a way that no double-precision floating-point
           operations are used.

       -m4-200
           Generate code for SH4-200.

       -m4-200-nofpu
           Generate code for SH4-200 without in such a way that the floating-point unit is not used.

       -m4-200-single
           Generate code for SH4-200 assuming the floating-point unit is in single-precision mode by
           default.

       -m4-200-single-only
           Generate code for SH4-200 in such a way that no double-precision floating-point
           operations are used.

       -m4-300
           Generate code for SH4-300.

       -m4-300-nofpu
           Generate code for SH4-300 without in such a way that the floating-point unit is not used.

       -m4-300-single
           Generate code for SH4-300 in such a way that no double-precision floating-point
           operations are used.

       -m4-300-single-only
           Generate code for SH4-300 in such a way that no double-precision floating-point
           operations are used.

       -m4-340
           Generate code for SH4-340 (no MMU, no FPU).

       -m4-500
           Generate code for SH4-500 (no FPU).  Passes -isa=sh4-nofpu to the assembler.

       -m4a-nofpu
           Generate code for the SH4al-dsp, or for a SH4a in such a way that the floating-point unit
           is not used.

       -m4a-single-only
           Generate code for the SH4a, in such a way that no double-precision floating-point
           operations are used.

       -m4a-single
           Generate code for the SH4a assuming the floating-point unit is in single-precision mode
           by default.

       -m4a
           Generate code for the SH4a.

       -m4al
           Same as -m4a-nofpu, except that it implicitly passes -dsp to the assembler.  GCC doesn't
           generate any DSP instructions at the moment.

       -mb Compile code for the processor in big-endian mode.

       -ml Compile code for the processor in little-endian mode.

       -mdalign
           Align doubles at 64-bit boundaries.  Note that this changes the calling conventions, and
           thus some functions from the standard C library do not work unless you recompile it first
           with -mdalign.

       -mrelax
           Shorten some address references at link time, when possible; uses the linker option
           -relax.

       -mbigtable
           Use 32-bit offsets in "switch" tables.  The default is to use 16-bit offsets.

       -mbitops
           Enable the use of bit manipulation instructions on SH2A.

       -mfmovd
           Enable the use of the instruction "fmovd".  Check -mdalign for alignment constraints.

       -mrenesas
           Comply with the calling conventions defined by Renesas.

       -mno-renesas
           Comply with the calling conventions defined for GCC before the Renesas conventions were
           available.  This option is the default for all targets of the SH toolchain.

       -mnomacsave
           Mark the "MAC" register as call-clobbered, even if -mrenesas is given.

       -mieee
       -mno-ieee
           Control the IEEE compliance of floating-point comparisons, which affects the handling of
           cases where the result of a comparison is unordered.  By default -mieee is implicitly
           enabled.  If -ffinite-math-only is enabled -mno-ieee is implicitly set, which results in
           faster floating-point greater-equal and less-equal comparisons.  The implicit settings
           can be overridden by specifying either -mieee or -mno-ieee.

       -minline-ic_invalidate
           Inline code to invalidate instruction cache entries after setting up nested function
           trampolines.  This option has no effect if -musermode is in effect and the selected code
           generation option (e.g. -m4) does not allow the use of the "icbi" instruction.  If the
           selected code generation option does not allow the use of the "icbi" instruction, and
           -musermode is not in effect, the inlined code manipulates the instruction cache address
           array directly with an associative write.  This not only requires privileged mode at run
           time, but it also fails if the cache line had been mapped via the TLB and has become
           unmapped.

       -misize
           Dump instruction size and location in the assembly code.

       -mpadstruct
           This option is deprecated.  It pads structures to multiple of 4 bytes, which is
           incompatible with the SH ABI.

       -matomic-model=model
           Sets the model of atomic operations and additional parameters as a comma separated list.
           For details on the atomic built-in functions see __atomic Builtins.  The following models
           and parameters are supported:

           none
               Disable compiler generated atomic sequences and emit library calls for atomic
               operations.  This is the default if the target is not "sh*-*-linux*".

           soft-gusa
               Generate GNU/Linux compatible gUSA software atomic sequences for the atomic built-in
               functions.  The generated atomic sequences require additional support from the
               interrupt/exception handling code of the system and are only suitable for SH3* and
               SH4* single-core systems.  This option is enabled by default when the target is
               "sh*-*-linux*" and SH3* or SH4*.  When the target is SH4A, this option also partially
               utilizes the hardware atomic instructions "movli.l" and "movco.l" to create more
               efficient code, unless strict is specified.

           soft-tcb
               Generate software atomic sequences that use a variable in the thread control block.
               This is a variation of the gUSA sequences which can also be used on SH1* and SH2*
               targets.  The generated atomic sequences require additional support from the
               interrupt/exception handling code of the system and are only suitable for single-core
               systems.  When using this model, the gbr-offset= parameter has to be specified as
               well.

           soft-imask
               Generate software atomic sequences that temporarily disable interrupts by setting
               "SR.IMASK = 1111".  This model works only when the program runs in privileged mode
               and is only suitable for single-core systems.  Additional support from the
               interrupt/exception handling code of the system is not required.  This model is
               enabled by default when the target is "sh*-*-linux*" and SH1* or SH2*.

           hard-llcs
               Generate hardware atomic sequences using the "movli.l" and "movco.l" instructions
               only.  This is only available on SH4A and is suitable for multi-core systems.  Since
               the hardware instructions support only 32 bit atomic variables access to 8 or 16 bit
               variables is emulated with 32 bit accesses.  Code compiled with this option is also
               compatible with other software atomic model interrupt/exception handling systems if
               executed on an SH4A system.  Additional support from the interrupt/exception handling
               code of the system is not required for this model.

           gbr-offset=
               This parameter specifies the offset in bytes of the variable in the thread control
               block structure that should be used by the generated atomic sequences when the soft-
               tcb model has been selected.  For other models this parameter is ignored.  The
               specified value must be an integer multiple of four and in the range 0-1020.

           strict
               This parameter prevents mixed usage of multiple atomic models, even if they are
               compatible, and makes the compiler generate atomic sequences of the specified model
               only.

       -mtas
           Generate the "tas.b" opcode for "__atomic_test_and_set".  Notice that depending on the
           particular hardware and software configuration this can degrade overall performance due
           to the operand cache line flushes that are implied by the "tas.b" instruction.  On multi-
           core SH4A processors the "tas.b" instruction must be used with caution since it can
           result in data corruption for certain cache configurations.

       -mprefergot
           When generating position-independent code, emit function calls using the Global Offset
           Table instead of the Procedure Linkage Table.

       -musermode
       -mno-usermode
           Don't allow (allow) the compiler generating privileged mode code.  Specifying -musermode
           also implies -mno-inline-ic_invalidate if the inlined code would not work in user mode.
           -musermode is the default when the target is "sh*-*-linux*".  If the target is SH1* or
           SH2* -musermode has no effect, since there is no user mode.

       -multcost=number
           Set the cost to assume for a multiply insn.

       -mdiv=strategy
           Set the division strategy to be used for integer division operations.  strategy can be
           one of:

           call-div1
               Calls a library function that uses the single-step division instruction "div1" to
               perform the operation.  Division by zero calculates an unspecified result and does
               not trap.  This is the default except for SH4, SH2A and SHcompact.

           call-fp
               Calls a library function that performs the operation in double precision floating
               point.  Division by zero causes a floating-point exception.  This is the default for
               SHcompact with FPU.  Specifying this for targets that do not have a double precision
               FPU defaults to "call-div1".

           call-table
               Calls a library function that uses a lookup table for small divisors and the "div1"
               instruction with case distinction for larger divisors.  Division by zero calculates
               an unspecified result and does not trap.  This is the default for SH4.  Specifying
               this for targets that do not have dynamic shift instructions defaults to "call-div1".

           When a division strategy has not been specified the default strategy is selected based on
           the current target.  For SH2A the default strategy is to use the "divs" and "divu"
           instructions instead of library function calls.

       -maccumulate-outgoing-args
           Reserve space once for outgoing arguments in the function prologue rather than around
           each call.  Generally beneficial for performance and size.  Also needed for unwinding to
           avoid changing the stack frame around conditional code.

       -mdivsi3_libfunc=name
           Set the name of the library function used for 32-bit signed division to name.  This only
           affects the name used in the call division strategies, and the compiler still expects the
           same sets of input/output/clobbered registers as if this option were not present.

       -mfixed-range=register-range
           Generate code treating the given register range as fixed registers.  A fixed register is
           one that the register allocator cannot use.  This is useful when compiling kernel code.
           A register range is specified as two registers separated by a dash.  Multiple register
           ranges can be specified separated by a comma.

       -mbranch-cost=num
           Assume num to be the cost for a branch instruction.  Higher numbers make the compiler try
           to generate more branch-free code if possible.  If not specified the value is selected
           depending on the processor type that is being compiled for.

       -mzdcbranch
       -mno-zdcbranch
           Assume (do not assume) that zero displacement conditional branch instructions "bt" and
           "bf" are fast.  If -mzdcbranch is specified, the compiler prefers zero displacement
           branch code sequences.  This is enabled by default when generating code for SH4 and SH4A.
           It can be explicitly disabled by specifying -mno-zdcbranch.

       -mcbranch-force-delay-slot
           Force the usage of delay slots for conditional branches, which stuffs the delay slot with
           a "nop" if a suitable instruction cannot be found.  By default this option is disabled.
           It can be enabled to work around hardware bugs as found in the original SH7055.

       -mfused-madd
       -mno-fused-madd
           Generate code that uses (does not use) the floating-point multiply and accumulate
           instructions.  These instructions are generated by default if hardware floating point is
           used.  The machine-dependent -mfused-madd option is now mapped to the machine-independent
           -ffp-contract=fast option, and -mno-fused-madd is mapped to -ffp-contract=off.

       -mfsca
       -mno-fsca
           Allow or disallow the compiler to emit the "fsca" instruction for sine and cosine
           approximations.  The option -mfsca must be used in combination with
           -funsafe-math-optimizations.  It is enabled by default when generating code for SH4A.
           Using -mno-fsca disables sine and cosine approximations even if
           -funsafe-math-optimizations is in effect.

       -mfsrra
       -mno-fsrra
           Allow or disallow the compiler to emit the "fsrra" instruction for reciprocal square root
           approximations.  The option -mfsrra must be used in combination with
           -funsafe-math-optimizations and -ffinite-math-only.  It is enabled by default when
           generating code for SH4A.  Using -mno-fsrra disables reciprocal square root
           approximations even if -funsafe-math-optimizations and -ffinite-math-only are in effect.

       -mpretend-cmove
           Prefer zero-displacement conditional branches for conditional move instruction patterns.
           This can result in faster code on the SH4 processor.

       -mfdpic
           Generate code using the FDPIC ABI.

       Solaris 2 Options

       These -m options are supported on Solaris 2:

       -mclear-hwcap
           -mclear-hwcap tells the compiler to remove the hardware capabilities generated by the
           Solaris assembler.  This is only necessary when object files use ISA extensions not
           supported by the current machine, but check at runtime whether or not to use them.

       -mimpure-text
           -mimpure-text, used in addition to -shared, tells the compiler to not pass -z text to the
           linker when linking a shared object.  Using this option, you can link position-dependent
           code into a shared object.

           -mimpure-text suppresses the "relocations remain against allocatable but non-writable
           sections" linker error message.  However, the necessary relocations trigger copy-on-
           write, and the shared object is not actually shared across processes.  Instead of using
           -mimpure-text, you should compile all source code with -fpic or -fPIC.

       These switches are supported in addition to the above on Solaris 2:

       -pthreads
           This is a synonym for -pthread.

       SPARC Options

       These -m options are supported on the SPARC:

       -mno-app-regs
       -mapp-regs
           Specify -mapp-regs to generate output using the global registers 2 through 4, which the
           SPARC SVR4 ABI reserves for applications.  Like the global register 1, each global
           register 2 through 4 is then treated as an allocable register that is clobbered by
           function calls.  This is the default.

           To be fully SVR4 ABI-compliant at the cost of some performance loss, specify
           -mno-app-regs.  You should compile libraries and system software with this option.

       -mflat
       -mno-flat
           With -mflat, the compiler does not generate save/restore instructions and uses a "flat"
           or single register window model.  This model is compatible with the regular register
           window model.  The local registers and the input registers (0--5) are still treated as
           "call-saved" registers and are saved on the stack as needed.

           With -mno-flat (the default), the compiler generates save/restore instructions (except
           for leaf functions).  This is the normal operating mode.

       -mfpu
       -mhard-float
           Generate output containing floating-point instructions.  This is the default.

       -mno-fpu
       -msoft-float
           Generate output containing library calls for floating point.  Warning: the requisite
           libraries are not available for all SPARC targets.  Normally the facilities of the
           machine's usual C compiler are used, but this cannot be done directly in cross-
           compilation.  You must make your own arrangements to provide suitable library functions
           for cross-compilation.  The embedded targets sparc-*-aout and sparclite-*-* do provide
           software floating-point support.

           -msoft-float changes the calling convention in the output file; therefore, it is only
           useful if you compile all of a program with this option.  In particular, you need to
           compile libgcc.a, the library that comes with GCC, with -msoft-float in order for this to
           work.

       -mhard-quad-float
           Generate output containing quad-word (long double) floating-point instructions.

       -msoft-quad-float
           Generate output containing library calls for quad-word (long double) floating-point
           instructions.  The functions called are those specified in the SPARC ABI.  This is the
           default.

           As of this writing, there are no SPARC implementations that have hardware support for the
           quad-word floating-point instructions.  They all invoke a trap handler for one of these
           instructions, and then the trap handler emulates the effect of the instruction.  Because
           of the trap handler overhead, this is much slower than calling the ABI library routines.
           Thus the -msoft-quad-float option is the default.

       -mno-unaligned-doubles
       -munaligned-doubles
           Assume that doubles have 8-byte alignment.  This is the default.

           With -munaligned-doubles, GCC assumes that doubles have 8-byte alignment only if they are
           contained in another type, or if they have an absolute address.  Otherwise, it assumes
           they have 4-byte alignment.  Specifying this option avoids some rare compatibility
           problems with code generated by other compilers.  It is not the default because it
           results in a performance loss, especially for floating-point code.

       -muser-mode
       -mno-user-mode
           Do not generate code that can only run in supervisor mode.  This is relevant only for the
           "casa" instruction emitted for the LEON3 processor.  This is the default.

       -mfaster-structs
       -mno-faster-structs
           With -mfaster-structs, the compiler assumes that structures should have 8-byte alignment.
           This enables the use of pairs of "ldd" and "std" instructions for copies in structure
           assignment, in place of twice as many "ld" and "st" pairs.  However, the use of this
           changed alignment directly violates the SPARC ABI.  Thus, it's intended only for use on
           targets where the developer acknowledges that their resulting code is not directly in
           line with the rules of the ABI.

       -mstd-struct-return
       -mno-std-struct-return
           With -mstd-struct-return, the compiler generates checking code in functions returning
           structures or unions to detect size mismatches between the two sides of function calls,
           as per the 32-bit ABI.

           The default is -mno-std-struct-return.  This option has no effect in 64-bit mode.

       -mlra
       -mno-lra
           Enable Local Register Allocation.  This is the default for SPARC since GCC 7 so -mno-lra
           needs to be passed to get old Reload.

       -mcpu=cpu_type
           Set the instruction set, register set, and instruction scheduling parameters for machine
           type cpu_type.  Supported values for cpu_type are v7, cypress, v8, supersparc,
           hypersparc, leon, leon3, leon3v7, leon5, sparclite, f930, f934, sparclite86x, sparclet,
           tsc701, v9, ultrasparc, ultrasparc3, niagara, niagara2, niagara3, niagara4, niagara7 and
           m8.

           Native Solaris and GNU/Linux toolchains also support the value native, which selects the
           best architecture option for the host processor.  -mcpu=native has no effect if GCC does
           not recognize the processor.

           Default instruction scheduling parameters are used for values that select an architecture
           and not an implementation.  These are v7, v8, sparclite, sparclet, v9.

           Here is a list of each supported architecture and their supported implementations.

           v7  cypress, leon3v7

           v8  supersparc, hypersparc, leon, leon3, leon5

           sparclite
               f930, f934, sparclite86x

           sparclet
               tsc701

           v9  ultrasparc, ultrasparc3, niagara, niagara2, niagara3, niagara4, niagara7, m8

           By default (unless configured otherwise), GCC generates code for the V7 variant of the
           SPARC architecture.  With -mcpu=cypress, the compiler additionally optimizes it for the
           Cypress CY7C602 chip, as used in the SPARCStation/SPARCServer 3xx series.  This is also
           appropriate for the older SPARCStation 1, 2, IPX etc.

           With -mcpu=v8, GCC generates code for the V8 variant of the SPARC architecture.  The only
           difference from V7 code is that the compiler emits the integer multiply and integer
           divide instructions which exist in SPARC-V8 but not in SPARC-V7.  With -mcpu=supersparc,
           the compiler additionally optimizes it for the SuperSPARC chip, as used in the
           SPARCStation 10, 1000 and 2000 series.

           With -mcpu=sparclite, GCC generates code for the SPARClite variant of the SPARC
           architecture.  This adds the integer multiply, integer divide step and scan ("ffs")
           instructions which exist in SPARClite but not in SPARC-V7.  With -mcpu=f930, the compiler
           additionally optimizes it for the Fujitsu MB86930 chip, which is the original SPARClite,
           with no FPU.  With -mcpu=f934, the compiler additionally optimizes it for the Fujitsu
           MB86934 chip, which is the more recent SPARClite with FPU.

           With -mcpu=sparclet, GCC generates code for the SPARClet variant of the SPARC
           architecture.  This adds the integer multiply, multiply/accumulate, integer divide step
           and scan ("ffs") instructions which exist in SPARClet but not in SPARC-V7.  With
           -mcpu=tsc701, the compiler additionally optimizes it for the TEMIC SPARClet chip.

           With -mcpu=v9, GCC generates code for the V9 variant of the SPARC architecture.  This
           adds 64-bit integer and floating-point move instructions, 3 additional floating-point
           condition code registers and conditional move instructions.  With -mcpu=ultrasparc, the
           compiler additionally optimizes it for the Sun UltraSPARC I/II/IIi chips.  With
           -mcpu=ultrasparc3, the compiler additionally optimizes it for the Sun UltraSPARC
           III/III+/IIIi/IIIi+/IV/IV+ chips.  With -mcpu=niagara, the compiler additionally
           optimizes it for Sun UltraSPARC T1 chips.  With -mcpu=niagara2, the compiler additionally
           optimizes it for Sun UltraSPARC T2 chips. With -mcpu=niagara3, the compiler additionally
           optimizes it for Sun UltraSPARC T3 chips.  With -mcpu=niagara4, the compiler additionally
           optimizes it for Sun UltraSPARC T4 chips.  With -mcpu=niagara7, the compiler additionally
           optimizes it for Oracle SPARC M7 chips.  With -mcpu=m8, the compiler additionally
           optimizes it for Oracle M8 chips.

       -mtune=cpu_type
           Set the instruction scheduling parameters for machine type cpu_type, but do not set the
           instruction set or register set that the option -mcpu=cpu_type does.

           The same values for -mcpu=cpu_type can be used for -mtune=cpu_type, but the only useful
           values are those that select a particular CPU implementation.  Those are cypress,
           supersparc, hypersparc, leon, leon3, leon3v7, leon5, f930, f934, sparclite86x, tsc701,
           ultrasparc, ultrasparc3, niagara, niagara2, niagara3, niagara4, niagara7 and m8.  With
           native Solaris and GNU/Linux toolchains, native can also be used.

       -mv8plus
       -mno-v8plus
           With -mv8plus, GCC generates code for the SPARC-V8+ ABI.  The difference from the V8 ABI
           is that the global and out registers are considered 64 bits wide.  This is enabled by
           default on Solaris in 32-bit mode for all SPARC-V9 processors.

       -mvis
       -mno-vis
           With -mvis, GCC generates code that takes advantage of the UltraSPARC Visual Instruction
           Set extensions.  The default is -mno-vis.

       -mvis2
       -mno-vis2
           With -mvis2, GCC generates code that takes advantage of version 2.0 of the UltraSPARC
           Visual Instruction Set extensions.  The default is -mvis2 when targeting a cpu that
           supports such instructions, such as UltraSPARC-III and later.  Setting -mvis2 also sets
           -mvis.

       -mvis3
       -mno-vis3
           With -mvis3, GCC generates code that takes advantage of version 3.0 of the UltraSPARC
           Visual Instruction Set extensions.  The default is -mvis3 when targeting a cpu that
           supports such instructions, such as niagara-3 and later.  Setting -mvis3 also sets -mvis2
           and -mvis.

       -mvis4
       -mno-vis4
           With -mvis4, GCC generates code that takes advantage of version 4.0 of the UltraSPARC
           Visual Instruction Set extensions.  The default is -mvis4 when targeting a cpu that
           supports such instructions, such as niagara-7 and later.  Setting -mvis4 also sets
           -mvis3, -mvis2 and -mvis.

       -mvis4b
       -mno-vis4b
           With -mvis4b, GCC generates code that takes advantage of version 4.0 of the UltraSPARC
           Visual Instruction Set extensions, plus the additional VIS instructions introduced in the
           Oracle SPARC Architecture 2017.  The default is -mvis4b when targeting a cpu that
           supports such instructions, such as m8 and later.  Setting -mvis4b also sets -mvis4,
           -mvis3, -mvis2 and -mvis.

       -mcbcond
       -mno-cbcond
           With -mcbcond, GCC generates code that takes advantage of the UltraSPARC Compare-and-
           Branch-on-Condition instructions.  The default is -mcbcond when targeting a CPU that
           supports such instructions, such as Niagara-4 and later.

       -mfmaf
       -mno-fmaf
           With -mfmaf, GCC generates code that takes advantage of the UltraSPARC Fused Multiply-Add
           Floating-point instructions.  The default is -mfmaf when targeting a CPU that supports
           such instructions, such as Niagara-3 and later.

       -mfsmuld
       -mno-fsmuld
           With -mfsmuld, GCC generates code that takes advantage of the Floating-point Multiply
           Single to Double (FsMULd) instruction.  The default is -mfsmuld when targeting a CPU
           supporting the architecture versions V8 or V9 with FPU except -mcpu=leon.

       -mpopc
       -mno-popc
           With -mpopc, GCC generates code that takes advantage of the UltraSPARC Population Count
           instruction.  The default is -mpopc when targeting a CPU that supports such an
           instruction, such as Niagara-2 and later.

       -msubxc
       -mno-subxc
           With -msubxc, GCC generates code that takes advantage of the UltraSPARC Subtract-
           Extended-with-Carry instruction.  The default is -msubxc when targeting a CPU that
           supports such an instruction, such as Niagara-7 and later.

       -mfix-at697f
           Enable the documented workaround for the single erratum of the Atmel AT697F processor
           (which corresponds to erratum #13 of the AT697E processor).

       -mfix-ut699
           Enable the documented workarounds for the floating-point errata and the data cache
           nullify errata of the UT699 processor.

       -mfix-ut700
           Enable the documented workaround for the back-to-back store errata of the UT699E/UT700
           processor.

       -mfix-gr712rc
           Enable the documented workaround for the back-to-back store errata of the GR712RC
           processor.

       These -m options are supported in addition to the above on SPARC-V9 processors in 64-bit
       environments:

       -m32
       -m64
           Generate code for a 32-bit or 64-bit environment.  The 32-bit environment sets int, long
           and pointer to 32 bits.  The 64-bit environment sets int to 32 bits and long and pointer
           to 64 bits.

       -mcmodel=which
           Set the code model to one of

           medlow
               The Medium/Low code model: 64-bit addresses, programs must be linked in the low 32
               bits of memory.  Programs can be statically or dynamically linked.

           medmid
               The Medium/Middle code model: 64-bit addresses, programs must be linked in the low 44
               bits of memory, the text and data segments must be less than 2GB in size and the data
               segment must be located within 2GB of the text segment.

           medany
               The Medium/Anywhere code model: 64-bit addresses, programs may be linked anywhere in
               memory, the text and data segments must be less than 2GB in size and the data segment
               must be located within 2GB of the text segment.

           embmedany
               The Medium/Anywhere code model for embedded systems: 64-bit addresses, the text and
               data segments must be less than 2GB in size, both starting anywhere in memory
               (determined at link time).  The global register %g4 points to the base of the data
               segment.  Programs are statically linked and PIC is not supported.

       -mmemory-model=mem-model
           Set the memory model in force on the processor to one of

           default
               The default memory model for the processor and operating system.

           rmo Relaxed Memory Order

           pso Partial Store Order

           tso Total Store Order

           sc  Sequential Consistency

           These memory models are formally defined in Appendix D of the SPARC-V9 architecture
           manual, as set in the processor's "PSTATE.MM" field.

       -mstack-bias
       -mno-stack-bias
           With -mstack-bias, GCC assumes that the stack pointer, and frame pointer if present, are
           offset by -2047 which must be added back when making stack frame references.  This is the
           default in 64-bit mode.  Otherwise, assume no such offset is present.

       Options for System V

       These additional options are available on System V Release 4 for compatibility with other
       compilers on those systems:

       -G  Create a shared object.  It is recommended that -symbolic or -shared be used instead.

       -Qy Identify the versions of each tool used by the compiler, in a ".ident" assembler
           directive in the output.

       -Qn Refrain from adding ".ident" directives to the output file (this is the default).

       -YP,dirs
           Search the directories dirs, and no others, for libraries specified with -l.

       -Ym,dir
           Look in the directory dir to find the M4 preprocessor.  The assembler uses this option.

       TILE-Gx Options

       These -m options are supported on the TILE-Gx:

       -mcmodel=small
           Generate code for the small model.  The distance for direct calls is limited to 500M in
           either direction.  PC-relative addresses are 32 bits.  Absolute addresses support the
           full address range.

       -mcmodel=large
           Generate code for the large model.  There is no limitation on call distance, pc-relative
           addresses, or absolute addresses.

       -mcpu=name
           Selects the type of CPU to be targeted.  Currently the only supported type is tilegx.

       -m32
       -m64
           Generate code for a 32-bit or 64-bit environment.  The 32-bit environment sets int, long,
           and pointer to 32 bits.  The 64-bit environment sets int to 32 bits and long and pointer
           to 64 bits.

       -mbig-endian
       -mlittle-endian
           Generate code in big/little endian mode, respectively.

       TILEPro Options

       These -m options are supported on the TILEPro:

       -mcpu=name
           Selects the type of CPU to be targeted.  Currently the only supported type is tilepro.

       -m32
           Generate code for a 32-bit environment, which sets int, long, and pointer to 32 bits.
           This is the only supported behavior so the flag is essentially ignored.

       V850 Options

       These -m options are defined for V850 implementations:

       -mlong-calls
       -mno-long-calls
           Treat all calls as being far away (near).  If calls are assumed to be far away, the
           compiler always loads the function's address into a register, and calls indirect through
           the pointer.

       -mno-ep
       -mep
           Do not optimize (do optimize) basic blocks that use the same index pointer 4 or more
           times to copy pointer into the "ep" register, and use the shorter "sld" and "sst"
           instructions.  The -mep option is on by default if you optimize.

       -mno-prolog-function
       -mprolog-function
           Do not use (do use) external functions to save and restore registers at the prologue and
           epilogue of a function.  The external functions are slower, but use less code space if
           more than one function saves the same number of registers.  The -mprolog-function option
           is on by default if you optimize.

       -mspace
           Try to make the code as small as possible.  At present, this just turns on the -mep and
           -mprolog-function options.

       -mtda=n
           Put static or global variables whose size is n bytes or less into the tiny data area that
           register "ep" points to.  The tiny data area can hold up to 256 bytes in total (128 bytes
           for byte references).

       -msda=n
           Put static or global variables whose size is n bytes or less into the small data area
           that register "gp" points to.  The small data area can hold up to 64 kilobytes.

       -mzda=n
           Put static or global variables whose size is n bytes or less into the first 32 kilobytes
           of memory.

       -mv850
           Specify that the target processor is the V850.

       -mv850e3v5
           Specify that the target processor is the V850E3V5.  The preprocessor constant
           "__v850e3v5__" is defined if this option is used.

       -mv850e2v4
           Specify that the target processor is the V850E3V5.  This is an alias for the -mv850e3v5
           option.

       -mv850e2v3
           Specify that the target processor is the V850E2V3.  The preprocessor constant
           "__v850e2v3__" is defined if this option is used.

       -mv850e2
           Specify that the target processor is the V850E2.  The preprocessor constant "__v850e2__"
           is defined if this option is used.

       -mv850e1
           Specify that the target processor is the V850E1.  The preprocessor constants "__v850e1__"
           and "__v850e__" are defined if this option is used.

       -mv850es
           Specify that the target processor is the V850ES.  This is an alias for the -mv850e1
           option.

       -mv850e
           Specify that the target processor is the V850E.  The preprocessor constant "__v850e__" is
           defined if this option is used.

           If neither -mv850 nor -mv850e nor -mv850e1 nor -mv850e2 nor -mv850e2v3 nor -mv850e3v5 are
           defined then a default target processor is chosen and the relevant __v850*__ preprocessor
           constant is defined.

           The preprocessor constants "__v850" and "__v851__" are always defined, regardless of
           which processor variant is the target.

       -mdisable-callt
       -mno-disable-callt
           This option suppresses generation of the "CALLT" instruction for the v850e, v850e1,
           v850e2, v850e2v3 and v850e3v5 flavors of the v850 architecture.

           This option is enabled by default when the RH850 ABI is in use (see -mrh850-abi), and
           disabled by default when the GCC ABI is in use.  If "CALLT" instructions are being
           generated then the C preprocessor symbol "__V850_CALLT__" is defined.

       -mrelax
       -mno-relax
           Pass on (or do not pass on) the -mrelax command-line option to the assembler.

       -mlong-jumps
       -mno-long-jumps
           Disable (or re-enable) the generation of PC-relative jump instructions.

       -msoft-float
       -mhard-float
           Disable (or re-enable) the generation of hardware floating point instructions.  This
           option is only significant when the target architecture is V850E2V3 or higher.  If
           hardware floating point instructions are being generated then the C preprocessor symbol
           "__FPU_OK__" is defined, otherwise the symbol "__NO_FPU__" is defined.

       -mloop
           Enables the use of the e3v5 LOOP instruction.  The use of this instruction is not enabled
           by default when the e3v5 architecture is selected because its use is still experimental.

       -mrh850-abi
       -mghs
           Enables support for the RH850 version of the V850 ABI.  This is the default.  With this
           version of the ABI the following rules apply:

           *   Integer sized structures and unions are returned via a memory pointer rather than a
               register.

           *   Large structures and unions (more than 8 bytes in size) are passed by value.

           *   Functions are aligned to 16-bit boundaries.

           *   The -m8byte-align command-line option is supported.

           *   The -mdisable-callt command-line option is enabled by default.  The
               -mno-disable-callt command-line option is not supported.

           When this version of the ABI is enabled the C preprocessor symbol "__V850_RH850_ABI__" is
           defined.

       -mgcc-abi
           Enables support for the old GCC version of the V850 ABI.  With this version of the ABI
           the following rules apply:

           *   Integer sized structures and unions are returned in register "r10".

           *   Large structures and unions (more than 8 bytes in size) are passed by reference.

           *   Functions are aligned to 32-bit boundaries, unless optimizing for size.

           *   The -m8byte-align command-line option is not supported.

           *   The -mdisable-callt command-line option is supported but not enabled by default.

           When this version of the ABI is enabled the C preprocessor symbol "__V850_GCC_ABI__" is
           defined.

       -m8byte-align
       -mno-8byte-align
           Enables support for "double" and "long long" types to be aligned on 8-byte boundaries.
           The default is to restrict the alignment of all objects to at most 4-bytes.  When
           -m8byte-align is in effect the C preprocessor symbol "__V850_8BYTE_ALIGN__" is defined.

       -mbig-switch
           Generate code suitable for big switch tables.  Use this option only if the
           assembler/linker complain about out of range branches within a switch table.

       -mapp-regs
           This option causes r2 and r5 to be used in the code generated by the compiler.  This
           setting is the default.

       -mno-app-regs
           This option causes r2 and r5 to be treated as fixed registers.

       VAX Options

       These -m options are defined for the VAX:

       -munix
           Do not output certain jump instructions ("aobleq" and so on) that the Unix assembler for
           the VAX cannot handle across long ranges.

       -mgnu
           Do output those jump instructions, on the assumption that the GNU assembler is being
           used.

       -mg Output code for G-format floating-point numbers instead of D-format.

       Visium Options

       -mdebug
           A program which performs file I/O and is destined to run on an MCM target should be
           linked with this option.  It causes the libraries libc.a and libdebug.a to be linked.
           The program should be run on the target under the control of the GDB remote debugging
           stub.

       -msim
           A program which performs file I/O and is destined to run on the simulator should be
           linked with option.  This causes libraries libc.a and libsim.a to be linked.

       -mfpu
       -mhard-float
           Generate code containing floating-point instructions.  This is the default.

       -mno-fpu
       -msoft-float
           Generate code containing library calls for floating-point.

           -msoft-float changes the calling convention in the output file; therefore, it is only
           useful if you compile all of a program with this option.  In particular, you need to
           compile libgcc.a, the library that comes with GCC, with -msoft-float in order for this to
           work.

       -mcpu=cpu_type
           Set the instruction set, register set, and instruction scheduling parameters for machine
           type cpu_type.  Supported values for cpu_type are mcm, gr5 and gr6.

           mcm is a synonym of gr5 present for backward compatibility.

           By default (unless configured otherwise), GCC generates code for the GR5 variant of the
           Visium architecture.

           With -mcpu=gr6, GCC generates code for the GR6 variant of the Visium architecture.  The
           only difference from GR5 code is that the compiler will generate block move instructions.

       -mtune=cpu_type
           Set the instruction scheduling parameters for machine type cpu_type, but do not set the
           instruction set or register set that the option -mcpu=cpu_type would.

       -msv-mode
           Generate code for the supervisor mode, where there are no restrictions on the access to
           general registers.  This is the default.

       -muser-mode
           Generate code for the user mode, where the access to some general registers is forbidden:
           on the GR5, registers r24 to r31 cannot be accessed in this mode; on the GR6, only
           registers r29 to r31 are affected.

       VMS Options

       These -m options are defined for the VMS implementations:

       -mvms-return-codes
           Return VMS condition codes from "main". The default is to return POSIX-style condition
           (e.g. error) codes.

       -mdebug-main=prefix
           Flag the first routine whose name starts with prefix as the main routine for the
           debugger.

       -mmalloc64
           Default to 64-bit memory allocation routines.

       -mpointer-size=size
           Set the default size of pointers. Possible options for size are 32 or short for 32 bit
           pointers, 64 or long for 64 bit pointers, and no for supporting only 32 bit pointers.
           The later option disables "pragma pointer_size".

       VxWorks Options

       The options in this section are defined for all VxWorks targets.  Options specific to the
       target hardware are listed with the other options for that target.

       -mrtp
           GCC can generate code for both VxWorks kernels and real time processes (RTPs).  This
           option switches from the former to the latter.  It also defines the preprocessor macro
           "__RTP__".

       -non-static
           Link an RTP executable against shared libraries rather than static libraries.  The
           options -static and -shared can also be used for RTPs; -static is the default.

       -Bstatic
       -Bdynamic
           These options are passed down to the linker.  They are defined for compatibility with
           Diab.

       -Xbind-lazy
           Enable lazy binding of function calls.  This option is equivalent to -Wl,-z,now and is
           defined for compatibility with Diab.

       -Xbind-now
           Disable lazy binding of function calls.  This option is the default and is defined for
           compatibility with Diab.

       x86 Options

       These -m options are defined for the x86 family of computers.

       -march=cpu-type
           Generate instructions for the machine type cpu-type.  In contrast to -mtune=cpu-type,
           which merely tunes the generated code for the specified cpu-type, -march=cpu-type allows
           GCC to generate code that may not run at all on processors other than the one indicated.
           Specifying -march=cpu-type implies -mtune=cpu-type, except where noted otherwise.

           The choices for cpu-type are:

           native
               This selects the CPU to generate code for at compilation time by determining the
               processor type of the compiling machine.  Using -march=native enables all instruction
               subsets supported by the local machine (hence the result might not run on different
               machines).  Using -mtune=native produces code optimized for the local machine under
               the constraints of the selected instruction set.

           x86-64
               A generic CPU with 64-bit extensions.

           x86-64-v2
           x86-64-v3
           x86-64-v4
               These choices for cpu-type select the corresponding micro-architecture level from the
               x86-64 psABI.  On ABIs other than the x86-64 psABI they select the same CPU features
               as the x86-64 psABI documents for the particular micro-architecture level.

               Since these cpu-type values do not have a corresponding -mtune setting, using -march
               with these values enables generic tuning.  Specific tuning can be enabled using the
               -mtune=other-cpu-type option with an appropriate other-cpu-type value.

           i386
               Original Intel i386 CPU.

           i486
               Intel i486 CPU.  (No scheduling is implemented for this chip.)

           i586
           pentium
               Intel Pentium CPU with no MMX support.

           lakemont
               Intel Lakemont MCU, based on Intel Pentium CPU.

           pentium-mmx
               Intel Pentium MMX CPU, based on Pentium core with MMX instruction set support.

           pentiumpro
               Intel Pentium Pro CPU.

           i686
               When used with -march, the Pentium Pro instruction set is used, so the code runs on
               all i686 family chips.  When used with -mtune, it has the same meaning as generic.

           pentium2
               Intel Pentium II CPU, based on Pentium Pro core with MMX instruction set support.

           pentium3
           pentium3m
               Intel Pentium III CPU, based on Pentium Pro core with MMX and SSE instruction set
               support.

           pentium-m
               Intel Pentium M; low-power version of Intel Pentium III CPU with MMX, SSE and SSE2
               instruction set support.  Used by Centrino notebooks.

           pentium4
           pentium4m
               Intel Pentium 4 CPU with MMX, SSE and SSE2 instruction set support.

           prescott
               Improved version of Intel Pentium 4 CPU with MMX, SSE, SSE2 and SSE3 instruction set
               support.

           nocona
               Improved version of Intel Pentium 4 CPU with 64-bit extensions, MMX, SSE, SSE2 and
               SSE3 instruction set support.

           core2
               Intel Core 2 CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3 and SSSE3 instruction
               set support.

           nehalem
               Intel Nehalem CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2
               and POPCNT instruction set support.

           westmere
               Intel Westmere CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1,
               SSE4.2, POPCNT, AES and PCLMUL instruction set support.

           sandybridge
               Intel Sandy Bridge CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1,
               SSE4.2, POPCNT, AVX, AES and PCLMUL instruction set support.

           ivybridge
               Intel Ivy Bridge CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1,
               SSE4.2, POPCNT, AVX, AES, PCLMUL, FSGSBASE, RDRND and F16C instruction set support.

           haswell
               Intel Haswell CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1,
               SSE4.2, POPCNT, AVX, AVX2, AES, PCLMUL, FSGSBASE, RDRND, FMA, BMI, BMI2 and F16C
               instruction set support.

           broadwell
               Intel Broadwell CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3,
               SSE4.1, SSE4.2, POPCNT, AVX, AVX2, AES, PCLMUL, FSGSBASE, RDRND, FMA, BMI, BMI2,
               F16C, RDSEED ADCX and PREFETCHW instruction set support.

           skylake
               Intel Skylake CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1,
               SSE4.2, POPCNT, AVX, AVX2, AES, PCLMUL, FSGSBASE, RDRND, FMA, BMI, BMI2, F16C,
               RDSEED, ADCX, PREFETCHW, CLFLUSHOPT, XSAVEC and XSAVES instruction set support.

           bonnell
               Intel Bonnell CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3 and SSSE3
               instruction set support.

           silvermont
               Intel Silvermont CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3,
               SSE4.1, SSE4.2, POPCNT, AES, PREFETCHW, PCLMUL and RDRND instruction set support.

           goldmont
               Intel Goldmont CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3,
               SSE4.1, SSE4.2, POPCNT, AES, PREFETCHW, PCLMUL, RDRND, XSAVE, XSAVEC, XSAVES,
               XSAVEOPT and FSGSBASE instruction set support.

           goldmont-plus
               Intel Goldmont Plus CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3,
               SSE4.1, SSE4.2, POPCNT, AES, PREFETCHW, PCLMUL, RDRND, XSAVE, XSAVEC, XSAVES,
               XSAVEOPT, FSGSBASE, PTWRITE, RDPID, SGX and UMIP instruction set support.

           tremont
               Intel Tremont CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1,
               SSE4.2, POPCNT, AES, PREFETCHW, PCLMUL, RDRND, XSAVE, XSAVEC, XSAVES, XSAVEOPT,
               FSGSBASE, PTWRITE, RDPID, SGX, UMIP, GFNI-SSE, CLWB, MOVDIRI, MOVDIR64B, CLDEMOTE and
               WAITPKG instruction set support.

           knl Intel Knight's Landing CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3,
               SSSE3, SSE4.1, SSE4.2, POPCNT, AVX, AVX2, AES, PCLMUL, FSGSBASE, RDRND, FMA, BMI,
               BMI2, F16C, RDSEED, ADCX, PREFETCHW, PREFETCHWT1, AVX512F, AVX512PF, AVX512ER and
               AVX512CD instruction set support.

           knm Intel Knights Mill CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3,
               SSE4.1, SSE4.2, POPCNT, AVX, AVX2, AES, PCLMUL, FSGSBASE, RDRND, FMA, BMI, BMI2,
               F16C, RDSEED, ADCX, PREFETCHW, PREFETCHWT1, AVX512F, AVX512PF, AVX512ER, AVX512CD,
               AVX5124VNNIW, AVX5124FMAPS and AVX512VPOPCNTDQ instruction set support.

           skylake-avx512
               Intel Skylake Server CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3,
               SSE4.1, SSE4.2, POPCNT, PKU, AVX, AVX2, AES, PCLMUL, FSGSBASE, RDRND, FMA, BMI, BMI2,
               F16C, RDSEED, ADCX, PREFETCHW, CLFLUSHOPT, XSAVEC, XSAVES, AVX512F, CLWB, AVX512VL,
               AVX512BW, AVX512DQ and AVX512CD instruction set support.

           cannonlake
               Intel Cannonlake Server CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3,
               SSSE3, SSE4.1, SSE4.2, POPCNT, PKU, AVX, AVX2, AES, PCLMUL, FSGSBASE, RDRND, FMA,
               BMI, BMI2, F16C, RDSEED, ADCX, PREFETCHW, CLFLUSHOPT, XSAVEC, XSAVES, AVX512F,
               AVX512VL, AVX512BW, AVX512DQ, AVX512CD, AVX512VBMI, AVX512IFMA, SHA and UMIP
               instruction set support.

           icelake-client
               Intel Icelake Client CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3,
               SSE4.1, SSE4.2, POPCNT, PKU, AVX, AVX2, AES, PCLMUL, FSGSBASE, RDRND, FMA, BMI, BMI2,
               F16C, RDSEED, ADCX, PREFETCHW, CLFLUSHOPT, XSAVEC, XSAVES, AVX512F, AVX512VL,
               AVX512BW, AVX512DQ, AVX512CD, AVX512VBMI, AVX512IFMA, SHA, CLWB, UMIP, RDPID, GFNI,
               AVX512VBMI2, AVX512VPOPCNTDQ, AVX512BITALG, AVX512VNNI, VPCLMULQDQ, VAES instruction
               set support.

           icelake-server
               Intel Icelake Server CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3,
               SSE4.1, SSE4.2, POPCNT, PKU, AVX, AVX2, AES, PCLMUL, FSGSBASE, RDRND, FMA, BMI, BMI2,
               F16C, RDSEED, ADCX, PREFETCHW, CLFLUSHOPT, XSAVEC, XSAVES, AVX512F, AVX512VL,
               AVX512BW, AVX512DQ, AVX512CD, AVX512VBMI, AVX512IFMA, SHA, CLWB, UMIP, RDPID, GFNI,
               AVX512VBMI2, AVX512VPOPCNTDQ, AVX512BITALG, AVX512VNNI, VPCLMULQDQ, VAES, PCONFIG and
               WBNOINVD instruction set support.

           cascadelake
               Intel Cascadelake CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3,
               SSE4.1, SSE4.2, POPCNT, PKU, AVX, AVX2, AES, PCLMUL, FSGSBASE, RDRND, FMA, BMI, BMI2,
               F16C, RDSEED, ADCX, PREFETCHW, CLFLUSHOPT, XSAVEC, XSAVES, AVX512F, CLWB, AVX512VL,
               AVX512BW, AVX512DQ, AVX512CD and AVX512VNNI instruction set support.

           cooperlake
               Intel cooperlake CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3,
               SSE4.1, SSE4.2, POPCNT, PKU, AVX, AVX2, AES, PCLMUL, FSGSBASE, RDRND, FMA, BMI, BMI2,
               F16C, RDSEED, ADCX, PREFETCHW, CLFLUSHOPT, XSAVEC, XSAVES, AVX512F, CLWB, AVX512VL,
               AVX512BW, AVX512DQ, AVX512CD, AVX512VNNI and AVX512BF16 instruction set support.

           tigerlake
               Intel Tigerlake CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3,
               SSE4.1, SSE4.2, POPCNT, PKU, AVX, AVX2, AES, PCLMUL, FSGSBASE, RDRND, FMA, BMI, BMI2,
               F16C, RDSEED, ADCX, PREFETCHW, CLFLUSHOPT, XSAVEC, XSAVES, AVX512F, AVX512VL,
               AVX512BW, AVX512DQ, AVX512CD, AVX512VBMI, AVX512IFMA, SHA, CLWB, UMIP, RDPID, GFNI,
               AVX512VBMI2, AVX512VPOPCNTDQ, AVX512BITALG, AVX512VNNI, VPCLMULQDQ, VAES, PCONFIG,
               WBNOINVD, MOVDIRI, MOVDIR64B, AVX512VP2INTERSECT and KEYLOCKER instruction set
               support.

           sapphirerapids
               Intel sapphirerapids CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3,
               SSE4.1, SSE4.2, POPCNT, CX16, SAHF, FXSR, AVX, XSAVE, PCLMUL, FSGSBASE, RDRND, F16C,
               AVX2, BMI, BMI2, LZCNT, FMA, MOVBE, HLE, RDSEED, ADCX, PREFETCHW, AES, CLFLUSHOPT,
               XSAVEC, XSAVES, SGX, AVX512F, AVX512VL, AVX512BW, AVX512DQ, AVX512CD, PKU,
               AVX512VBMI, AVX512IFMA, SHA, AVX512VNNI, GFNI, VAES, AVX512VBMI2 VPCLMULQDQ,
               AVX512BITALG, RDPID, AVX512VPOPCNTDQ, PCONFIG, WBNOINVD, CLWB, MOVDIRI, MOVDIR64B,
               AVX512VP2INTERSECT, ENQCMD, CLDEMOTE, PTWRITE, WAITPKG, SERIALIZE, TSXLDTRK, UINTR,
               AMX-BF16, AMX-TILE, AMX-INT8, AVX-VNNI and AVX512BF16 instruction set support.

           alderlake
               Intel Alderlake CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3,
               SSE4.1, SSE4.2, POPCNT, AES, PREFETCHW, PCLMUL, RDRND, XSAVE, XSAVEC, XSAVES,
               XSAVEOPT, FSGSBASE, PTWRITE, RDPID, SGX, UMIP, GFNI-SSE, CLWB, MOVDIRI, MOVDIR64B,
               CLDEMOTE, WAITPKG, ADCX, AVX, AVX2, BMI, BMI2, F16C, FMA, LZCNT, PCONFIG, PKU, VAES,
               VPCLMULQDQ, SERIALIZE, HRESET, KL, WIDEKL and AVX-VNNI instruction set support.

           rocketlake
               Intel Rocketlake CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3,
               SSE4.1, SSE4.2, POPCNT, PKU, AVX, AVX2, AES, PCLMUL, FSGSBASE, RDRND, FMA, BMI, BMI2,
               F16C, RDSEED, ADCX, PREFETCHW, CLFLUSHOPT, XSAVEC, XSAVES, AVX512F, AVX512VL,
               AVX512BW, AVX512DQ, AVX512CD, AVX512VBMI, AVX512IFMA, SHA, CLWB, UMIP, RDPID, GFNI,
               AVX512VBMI2, AVX512VPOPCNTDQ, AVX512BITALG, AVX512VNNI, VPCLMULQDQ, VAES instruction
               set support.

           k6  AMD K6 CPU with MMX instruction set support.

           k6-2
           k6-3
               Improved versions of AMD K6 CPU with MMX and 3DNow! instruction set support.

           athlon
           athlon-tbird
               AMD Athlon CPU with MMX, 3dNOW!, enhanced 3DNow! and SSE prefetch instructions
               support.

           athlon-4
           athlon-xp
           athlon-mp
               Improved AMD Athlon CPU with MMX, 3DNow!, enhanced 3DNow! and full SSE instruction
               set support.

           k8
           opteron
           athlon64
           athlon-fx
               Processors based on the AMD K8 core with x86-64 instruction set support, including
               the AMD Opteron, Athlon 64, and Athlon 64 FX processors.  (This supersets MMX, SSE,
               SSE2, 3DNow!, enhanced 3DNow! and 64-bit instruction set extensions.)

           k8-sse3
           opteron-sse3
           athlon64-sse3
               Improved versions of AMD K8 cores with SSE3 instruction set support.

           amdfam10
           barcelona
               CPUs based on AMD Family 10h cores with x86-64 instruction set support.  (This
               supersets MMX, SSE, SSE2, SSE3, SSE4A, 3DNow!, enhanced 3DNow!, ABM and 64-bit
               instruction set extensions.)

           bdver1
               CPUs based on AMD Family 15h cores with x86-64 instruction set support.  (This
               supersets FMA4, AVX, XOP, LWP, AES, PCLMUL, CX16, MMX, SSE, SSE2, SSE3, SSE4A, SSSE3,
               SSE4.1, SSE4.2, ABM and 64-bit instruction set extensions.)

           bdver2
               AMD Family 15h core based CPUs with x86-64 instruction set support.  (This supersets
               BMI, TBM, F16C, FMA, FMA4, AVX, XOP, LWP, AES, PCLMUL, CX16, MMX, SSE, SSE2, SSE3,
               SSE4A, SSSE3, SSE4.1, SSE4.2, ABM and 64-bit instruction set extensions.)

           bdver3
               AMD Family 15h core based CPUs with x86-64 instruction set support.  (This supersets
               BMI, TBM, F16C, FMA, FMA4, FSGSBASE, AVX, XOP, LWP, AES, PCLMUL, CX16, MMX, SSE,
               SSE2, SSE3, SSE4A, SSSE3, SSE4.1, SSE4.2, ABM and 64-bit instruction set extensions.)

           bdver4
               AMD Family 15h core based CPUs with x86-64 instruction set support.  (This supersets
               BMI, BMI2, TBM, F16C, FMA, FMA4, FSGSBASE, AVX, AVX2, XOP, LWP, AES, PCLMUL, CX16,
               MOVBE, MMX, SSE, SSE2, SSE3, SSE4A, SSSE3, SSE4.1, SSE4.2, ABM and 64-bit instruction
               set extensions.)

           znver1
               AMD Family 17h core based CPUs with x86-64 instruction set support.  (This supersets
               BMI, BMI2, F16C, FMA, FSGSBASE, AVX, AVX2, ADCX, RDSEED, MWAITX, SHA, CLZERO, AES,
               PCLMUL, CX16, MOVBE, MMX, SSE, SSE2, SSE3, SSE4A, SSSE3, SSE4.1, SSE4.2, ABM, XSAVEC,
               XSAVES, CLFLUSHOPT, POPCNT, and 64-bit instruction set extensions.)

           znver2
               AMD Family 17h core based CPUs with x86-64 instruction set support. (This supersets
               BMI, BMI2, CLWB, F16C, FMA, FSGSBASE, AVX, AVX2, ADCX, RDSEED, MWAITX, SHA, CLZERO,
               AES, PCLMUL, CX16, MOVBE, MMX, SSE, SSE2, SSE3, SSE4A, SSSE3, SSE4.1, SSE4.2, ABM,
               XSAVEC, XSAVES, CLFLUSHOPT, POPCNT, RDPID, WBNOINVD, and 64-bit instruction set
               extensions.)

           znver3
               AMD Family 19h core based CPUs with x86-64 instruction set support. (This supersets
               BMI, BMI2, CLWB, F16C, FMA, FSGSBASE, AVX, AVX2, ADCX, RDSEED, MWAITX, SHA, CLZERO,
               AES, PCLMUL, CX16, MOVBE, MMX, SSE, SSE2, SSE3, SSE4A, SSSE3, SSE4.1, SSE4.2, ABM,
               XSAVEC, XSAVES, CLFLUSHOPT, POPCNT, RDPID, WBNOINVD, PKU, VPCLMULQDQ, VAES, and
               64-bit instruction set extensions.)

           btver1
               CPUs based on AMD Family 14h cores with x86-64 instruction set support.  (This
               supersets MMX, SSE, SSE2, SSE3, SSSE3, SSE4A, CX16, ABM and 64-bit instruction set
               extensions.)

           btver2
               CPUs based on AMD Family 16h cores with x86-64 instruction set support. This includes
               MOVBE, F16C, BMI, AVX, PCLMUL, AES, SSE4.2, SSE4.1, CX16, ABM, SSE4A, SSSE3, SSE3,
               SSE2, SSE, MMX and 64-bit instruction set extensions.

           winchip-c6
               IDT WinChip C6 CPU, dealt in same way as i486 with additional MMX instruction set
               support.

           winchip2
               IDT WinChip 2 CPU, dealt in same way as i486 with additional MMX and 3DNow!
               instruction set support.

           c3  VIA C3 CPU with MMX and 3DNow! instruction set support.  (No scheduling is
               implemented for this chip.)

           c3-2
               VIA C3-2 (Nehemiah/C5XL) CPU with MMX and SSE instruction set support.  (No
               scheduling is implemented for this chip.)

           c7  VIA C7 (Esther) CPU with MMX, SSE, SSE2 and SSE3 instruction set support.  (No
               scheduling is implemented for this chip.)

           samuel-2
               VIA Eden Samuel 2 CPU with MMX and 3DNow! instruction set support.  (No scheduling is
               implemented for this chip.)

           nehemiah
               VIA Eden Nehemiah CPU with MMX and SSE instruction set support.  (No scheduling is
               implemented for this chip.)

           esther
               VIA Eden Esther CPU with MMX, SSE, SSE2 and SSE3 instruction set support.  (No
               scheduling is implemented for this chip.)

           eden-x2
               VIA Eden X2 CPU with x86-64, MMX, SSE, SSE2 and SSE3 instruction set support.  (No
               scheduling is implemented for this chip.)

           eden-x4
               VIA Eden X4 CPU with x86-64, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, AVX and
               AVX2 instruction set support.  (No scheduling is implemented for this chip.)

           nano
               Generic VIA Nano CPU with x86-64, MMX, SSE, SSE2, SSE3 and SSSE3 instruction set
               support.  (No scheduling is implemented for this chip.)

           nano-1000
               VIA Nano 1xxx CPU with x86-64, MMX, SSE, SSE2, SSE3 and SSSE3 instruction set
               support.  (No scheduling is implemented for this chip.)

           nano-2000
               VIA Nano 2xxx CPU with x86-64, MMX, SSE, SSE2, SSE3 and SSSE3 instruction set
               support.  (No scheduling is implemented for this chip.)

           nano-3000
               VIA Nano 3xxx CPU with x86-64, MMX, SSE, SSE2, SSE3, SSSE3 and SSE4.1 instruction set
               support.  (No scheduling is implemented for this chip.)

           nano-x2
               VIA Nano Dual Core CPU with x86-64, MMX, SSE, SSE2, SSE3, SSSE3 and SSE4.1
               instruction set support.  (No scheduling is implemented for this chip.)

           nano-x4
               VIA Nano Quad Core CPU with x86-64, MMX, SSE, SSE2, SSE3, SSSE3 and SSE4.1
               instruction set support.  (No scheduling is implemented for this chip.)

           geode
               AMD Geode embedded processor with MMX and 3DNow! instruction set support.

       -mtune=cpu-type
           Tune to cpu-type everything applicable about the generated code, except for the ABI and
           the set of available instructions.  While picking a specific cpu-type schedules things
           appropriately for that particular chip, the compiler does not generate any code that
           cannot run on the default machine type unless you use a -march=cpu-type option.  For
           example, if GCC is configured for i686-pc-linux-gnu then -mtune=pentium4 generates code
           that is tuned for Pentium 4 but still runs on i686 machines.

           The choices for cpu-type are the same as for -march.  In addition, -mtune supports 2
           extra choices for cpu-type:

           generic
               Produce code optimized for the most common IA32/AMD64/EM64T processors.  If you know
               the CPU on which your code will run, then you should use the corresponding -mtune or
               -march option instead of -mtune=generic.  But, if you do not know exactly what CPU
               users of your application will have, then you should use this option.

               As new processors are deployed in the marketplace, the behavior of this option will
               change.  Therefore, if you upgrade to a newer version of GCC, code generation
               controlled by this option will change to reflect the processors that are most common
               at the time that version of GCC is released.

               There is no -march=generic option because -march indicates the instruction set the
               compiler can use, and there is no generic instruction set applicable to all
               processors.  In contrast, -mtune indicates the processor (or, in this case,
               collection of processors) for which the code is optimized.

           intel
               Produce code optimized for the most current Intel processors, which are Haswell and
               Silvermont for this version of GCC.  If you know the CPU on which your code will run,
               then you should use the corresponding -mtune or -march option instead of
               -mtune=intel.  But, if you want your application performs better on both Haswell and
               Silvermont, then you should use this option.

               As new Intel processors are deployed in the marketplace, the behavior of this option
               will change.  Therefore, if you upgrade to a newer version of GCC, code generation
               controlled by this option will change to reflect the most current Intel processors at
               the time that version of GCC is released.

               There is no -march=intel option because -march indicates the instruction set the
               compiler can use, and there is no common instruction set applicable to all
               processors.  In contrast, -mtune indicates the processor (or, in this case,
               collection of processors) for which the code is optimized.

       -mcpu=cpu-type
           A deprecated synonym for -mtune.

       -mfpmath=unit
           Generate floating-point arithmetic for selected unit unit.  The choices for unit are:

           387 Use the standard 387 floating-point coprocessor present on the majority of chips and
               emulated otherwise.  Code compiled with this option runs almost everywhere.  The
               temporary results are computed in 80-bit precision instead of the precision specified
               by the type, resulting in slightly different results compared to most of other chips.
               See -ffloat-store for more detailed description.

               This is the default choice for non-Darwin x86-32 targets.

           sse Use scalar floating-point instructions present in the SSE instruction set.  This
               instruction set is supported by Pentium III and newer chips, and in the AMD line by
               Athlon-4, Athlon XP and Athlon MP chips.  The earlier version of the SSE instruction
               set supports only single-precision arithmetic, thus the double and extended-precision
               arithmetic are still done using 387.  A later version, present only in Pentium 4 and
               AMD x86-64 chips, supports double-precision arithmetic too.

               For the x86-32 compiler, you must use -march=cpu-type, -msse or -msse2 switches to
               enable SSE extensions and make this option effective.  For the x86-64 compiler, these
               extensions are enabled by default.

               The resulting code should be considerably faster in the majority of cases and avoid
               the numerical instability problems of 387 code, but may break some existing code that
               expects temporaries to be 80 bits.

               This is the default choice for the x86-64 compiler, Darwin x86-32 targets, and the
               default choice for x86-32 targets with the SSE2 instruction set when -ffast-math is
               enabled.

           sse,387
           sse+387
           both
               Attempt to utilize both instruction sets at once.  This effectively doubles the
               amount of available registers, and on chips with separate execution units for 387 and
               SSE the execution resources too.  Use this option with care, as it is still
               experimental, because the GCC register allocator does not model separate functional
               units well, resulting in unstable performance.

       -masm=dialect
           Output assembly instructions using selected dialect.  Also affects which dialect is used
           for basic "asm" and extended "asm". Supported choices (in dialect order) are att or
           intel. The default is att. Darwin does not support intel.

       -mieee-fp
       -mno-ieee-fp
           Control whether or not the compiler uses IEEE floating-point comparisons.  These
           correctly handle the case where the result of a comparison is unordered.

       -m80387
       -mhard-float
           Generate output containing 80387 instructions for floating point.

       -mno-80387
       -msoft-float
           Generate output containing library calls for floating point.

           Warning: the requisite libraries are not part of GCC.  Normally the facilities of the
           machine's usual C compiler are used, but this cannot be done directly in cross-
           compilation.  You must make your own arrangements to provide suitable library functions
           for cross-compilation.

           On machines where a function returns floating-point results in the 80387 register stack,
           some floating-point opcodes may be emitted even if -msoft-float is used.

       -mno-fp-ret-in-387
           Do not use the FPU registers for return values of functions.

           The usual calling convention has functions return values of types "float" and "double" in
           an FPU register, even if there is no FPU.  The idea is that the operating system should
           emulate an FPU.

           The option -mno-fp-ret-in-387 causes such values to be returned in ordinary CPU registers
           instead.

       -mno-fancy-math-387
           Some 387 emulators do not support the "sin", "cos" and "sqrt" instructions for the 387.
           Specify this option to avoid generating those instructions.  This option is overridden
           when -march indicates that the target CPU always has an FPU and so the instruction does
           not need emulation.  These instructions are not generated unless you also use the
           -funsafe-math-optimizations switch.

       -malign-double
       -mno-align-double
           Control whether GCC aligns "double", "long double", and "long long" variables on a two-
           word boundary or a one-word boundary.  Aligning "double" variables on a two-word boundary
           produces code that runs somewhat faster on a Pentium at the expense of more memory.

           On x86-64, -malign-double is enabled by default.

           Warning: if you use the -malign-double switch, structures containing the above types are
           aligned differently than the published application binary interface specifications for
           the x86-32 and are not binary compatible with structures in code compiled without that
           switch.

       -m96bit-long-double
       -m128bit-long-double
           These switches control the size of "long double" type.  The x86-32 application binary
           interface specifies the size to be 96 bits, so -m96bit-long-double is the default in
           32-bit mode.

           Modern architectures (Pentium and newer) prefer "long double" to be aligned to an 8- or
           16-byte boundary.  In arrays or structures conforming to the ABI, this is not possible.
           So specifying -m128bit-long-double aligns "long double" to a 16-byte boundary by padding
           the "long double" with an additional 32-bit zero.

           In the x86-64 compiler, -m128bit-long-double is the default choice as its ABI specifies
           that "long double" is aligned on 16-byte boundary.

           Notice that neither of these options enable any extra precision over the x87 standard of
           80 bits for a "long double".

           Warning: if you override the default value for your target ABI, this changes the size of
           structures and arrays containing "long double" variables, as well as modifying the
           function calling convention for functions taking "long double".  Hence they are not
           binary-compatible with code compiled without that switch.

       -mlong-double-64
       -mlong-double-80
       -mlong-double-128
           These switches control the size of "long double" type. A size of 64 bits makes the "long
           double" type equivalent to the "double" type. This is the default for 32-bit Bionic C
           library.  A size of 128 bits makes the "long double" type equivalent to the "__float128"
           type. This is the default for 64-bit Bionic C library.

           Warning: if you override the default value for your target ABI, this changes the size of
           structures and arrays containing "long double" variables, as well as modifying the
           function calling convention for functions taking "long double".  Hence they are not
           binary-compatible with code compiled without that switch.

       -malign-data=type
           Control how GCC aligns variables.  Supported values for type are compat uses increased
           alignment value compatible uses GCC 4.8 and earlier, abi uses alignment value as
           specified by the psABI, and cacheline uses increased alignment value to match the cache
           line size.  compat is the default.

       -mlarge-data-threshold=threshold
           When -mcmodel=medium is specified, data objects larger than threshold are placed in the
           large data section.  This value must be the same across all objects linked into the
           binary, and defaults to 65535.

       -mrtd
           Use a different function-calling convention, in which functions that take a fixed number
           of arguments return with the "ret num" instruction, which pops their arguments while
           returning.  This saves one instruction in the caller since there is no need to pop the
           arguments there.

           You can specify that an individual function is called with this calling sequence with the
           function attribute "stdcall".  You can also override the -mrtd option by using the
           function attribute "cdecl".

           Warning: this calling convention is incompatible with the one normally used on Unix, so
           you cannot use it if you need to call libraries compiled with the Unix compiler.

           Also, you must provide function prototypes for all functions that take variable numbers
           of arguments (including "printf"); otherwise incorrect code is generated for calls to
           those functions.

           In addition, seriously incorrect code results if you call a function with too many
           arguments.  (Normally, extra arguments are harmlessly ignored.)

       -mregparm=num
           Control how many registers are used to pass integer arguments.  By default, no registers
           are used to pass arguments, and at most 3 registers can be used.  You can control this
           behavior for a specific function by using the function attribute "regparm".

           Warning: if you use this switch, and num is nonzero, then you must build all modules with
           the same value, including any libraries.  This includes the system libraries and startup
           modules.

       -msseregparm
           Use SSE register passing conventions for float and double arguments and return values.
           You can control this behavior for a specific function by using the function attribute
           "sseregparm".

           Warning: if you use this switch then you must build all modules with the same value,
           including any libraries.  This includes the system libraries and startup modules.

       -mvect8-ret-in-mem
           Return 8-byte vectors in memory instead of MMX registers.  This is the default on VxWorks
           to match the ABI of the Sun Studio compilers until version 12.  Only use this option if
           you need to remain compatible with existing code produced by those previous compiler
           versions or older versions of GCC.

       -mpc32
       -mpc64
       -mpc80
           Set 80387 floating-point precision to 32, 64 or 80 bits.  When -mpc32 is specified, the
           significands of results of floating-point operations are rounded to 24 bits (single
           precision); -mpc64 rounds the significands of results of floating-point operations to 53
           bits (double precision) and -mpc80 rounds the significands of results of floating-point
           operations to 64 bits (extended double precision), which is the default.  When this
           option is used, floating-point operations in higher precisions are not available to the
           programmer without setting the FPU control word explicitly.

           Setting the rounding of floating-point operations to less than the default 80 bits can
           speed some programs by 2% or more.  Note that some mathematical libraries assume that
           extended-precision (80-bit) floating-point operations are enabled by default; routines in
           such libraries could suffer significant loss of accuracy, typically through so-called
           "catastrophic cancellation", when this option is used to set the precision to less than
           extended precision.

       -mdaz-ftz
           The flush-to-zero (FTZ) and denormals-are-zero (DAZ) flags in the MXCSR register are used
           to control floating-point calculations.SSE and AVX instructions including scalar and
           vector instructions could benefit from enabling the FTZ and DAZ flags when -mdaz-ftz is
           specified. Don't set FTZ/DAZ flags when -mno-daz-ftz is specified.

       -mstackrealign
           Realign the stack at entry.  On the x86, the -mstackrealign option generates an alternate
           prologue and epilogue that realigns the run-time stack if necessary.  This supports
           mixing legacy codes that keep 4-byte stack alignment with modern codes that keep 16-byte
           stack alignment for SSE compatibility.  See also the attribute "force_align_arg_pointer",
           applicable to individual functions.

       -mpreferred-stack-boundary=num
           Attempt to keep the stack boundary aligned to a 2 raised to num byte boundary.  If
           -mpreferred-stack-boundary is not specified, the default is 4 (16 bytes or 128 bits).

           Warning: When generating code for the x86-64 architecture with SSE extensions disabled,
           -mpreferred-stack-boundary=3 can be used to keep the stack boundary aligned to 8 byte
           boundary.  Since x86-64 ABI require 16 byte stack alignment, this is ABI incompatible and
           intended to be used in controlled environment where stack space is important limitation.
           This option leads to wrong code when functions compiled with 16 byte stack alignment
           (such as functions from a standard library) are called with misaligned stack.  In this
           case, SSE instructions may lead to misaligned memory access traps.  In addition, variable
           arguments are handled incorrectly for 16 byte aligned objects (including x87 long double
           and __int128), leading to wrong results.  You must build all modules with
           -mpreferred-stack-boundary=3, including any libraries.  This includes the system
           libraries and startup modules.

       -mincoming-stack-boundary=num
           Assume the incoming stack is aligned to a 2 raised to num byte boundary.  If
           -mincoming-stack-boundary is not specified, the one specified by
           -mpreferred-stack-boundary is used.

           On Pentium and Pentium Pro, "double" and "long double" values should be aligned to an
           8-byte boundary (see -malign-double) or suffer significant run time performance
           penalties.  On Pentium III, the Streaming SIMD Extension (SSE) data type "__m128" may not
           work properly if it is not 16-byte aligned.

           To ensure proper alignment of this values on the stack, the stack boundary must be as
           aligned as that required by any value stored on the stack.  Further, every function must
           be generated such that it keeps the stack aligned.  Thus calling a function compiled with
           a higher preferred stack boundary from a function compiled with a lower preferred stack
           boundary most likely misaligns the stack.  It is recommended that libraries that use
           callbacks always use the default setting.

           This extra alignment does consume extra stack space, and generally increases code size.
           Code that is sensitive to stack space usage, such as embedded systems and operating
           system kernels, may want to reduce the preferred alignment to
           -mpreferred-stack-boundary=2.

       -mmmx
       -msse
       -msse2
       -msse3
       -mssse3
       -msse4
       -msse4a
       -msse4.1
       -msse4.2
       -mavx
       -mavx2
       -mavx512f
       -mavx512pf
       -mavx512er
       -mavx512cd
       -mavx512vl
       -mavx512bw
       -mavx512dq
       -mavx512ifma
       -mavx512vbmi
       -msha
       -maes
       -mpclmul
       -mclflushopt
       -mclwb
       -mfsgsbase
       -mptwrite
       -mrdrnd
       -mf16c
       -mfma
       -mpconfig
       -mwbnoinvd
       -mfma4
       -mprfchw
       -mrdpid
       -mprefetchwt1
       -mrdseed
       -msgx
       -mxop
       -mlwp
       -m3dnow
       -m3dnowa
       -mpopcnt
       -mabm
       -madx
       -mbmi
       -mbmi2
       -mlzcnt
       -mfxsr
       -mxsave
       -mxsaveopt
       -mxsavec
       -mxsaves
       -mrtm
       -mhle
       -mtbm
       -mmwaitx
       -mclzero
       -mpku
       -mavx512vbmi2
       -mavx512bf16
       -mgfni
       -mvaes
       -mwaitpkg
       -mvpclmulqdq
       -mavx512bitalg
       -mmovdiri
       -mmovdir64b
       -menqcmd
       -muintr
       -mtsxldtrk
       -mavx512vpopcntdq
       -mavx512vp2intersect
       -mavx5124fmaps
       -mavx512vnni
       -mavxvnni
       -mavx5124vnniw
       -mcldemote
       -mserialize
       -mamx-tile
       -mamx-int8
       -mamx-bf16
       -mhreset
       -mkl
       -mwidekl
           These switches enable the use of instructions in the MMX, SSE, SSE2, SSE3, SSSE3, SSE4,
           SSE4A, SSE4.1, SSE4.2, AVX, AVX2, AVX512F, AVX512PF, AVX512ER, AVX512CD, AVX512VL,
           AVX512BW, AVX512DQ, AVX512IFMA, AVX512VBMI, SHA, AES, PCLMUL, CLFLUSHOPT, CLWB, FSGSBASE,
           PTWRITE, RDRND, F16C, FMA, PCONFIG, WBNOINVD, FMA4, PREFETCHW, RDPID, PREFETCHWT1,
           RDSEED, SGX, XOP, LWP, 3DNow!, enhanced 3DNow!, POPCNT, ABM, ADX, BMI, BMI2, LZCNT, FXSR,
           XSAVE, XSAVEOPT, XSAVEC, XSAVES, RTM, HLE, TBM, MWAITX, CLZERO, PKU, AVX512VBMI2, GFNI,
           VAES, WAITPKG, VPCLMULQDQ, AVX512BITALG, MOVDIRI, MOVDIR64B, AVX512BF16, ENQCMD,
           AVX512VPOPCNTDQ, AVX5124FMAPS, AVX512VNNI, AVX5124VNNIW, SERIALIZE, UINTR, HRESET,
           AMXTILE, AMXINT8, AMXBF16, KL, WIDEKL, AVXVNNI or CLDEMOTE extended instruction sets.
           Each has a corresponding -mno- option to disable use of these instructions.

           These extensions are also available as built-in functions: see x86 Built-in Functions,
           for details of the functions enabled and disabled by these switches.

           To generate SSE/SSE2 instructions automatically from floating-point code (as opposed to
           387 instructions), see -mfpmath=sse.

           GCC depresses SSEx instructions when -mavx is used. Instead, it generates new AVX
           instructions or AVX equivalence for all SSEx instructions when needed.

           These options enable GCC to use these extended instructions in generated code, even
           without -mfpmath=sse.  Applications that perform run-time CPU detection must compile
           separate files for each supported architecture, using the appropriate flags.  In
           particular, the file containing the CPU detection code should be compiled without these
           options.

       -mdump-tune-features
           This option instructs GCC to dump the names of the x86 performance tuning features and
           default settings. The names can be used in -mtune-ctrl=feature-list.

       -mtune-ctrl=feature-list
           This option is used to do fine grain control of x86 code generation features.  feature-
           list is a comma separated list of feature names. See also -mdump-tune-features. When
           specified, the feature is turned on if it is not preceded with ^, otherwise, it is turned
           off.  -mtune-ctrl=feature-list is intended to be used by GCC developers. Using it may
           lead to code paths not covered by testing and can potentially result in compiler ICEs or
           runtime errors.

       -mno-default
           This option instructs GCC to turn off all tunable features. See also -mtune-ctrl=feature-
           list and -mdump-tune-features.

       -mcld
           This option instructs GCC to emit a "cld" instruction in the prologue of functions that
           use string instructions.  String instructions depend on the DF flag to select between
           autoincrement or autodecrement mode.  While the ABI specifies the DF flag to be cleared
           on function entry, some operating systems violate this specification by not clearing the
           DF flag in their exception dispatchers.  The exception handler can be invoked with the DF
           flag set, which leads to wrong direction mode when string instructions are used.  This
           option can be enabled by default on 32-bit x86 targets by configuring GCC with the
           --enable-cld configure option.  Generation of "cld" instructions can be suppressed with
           the -mno-cld compiler option in this case.

       -mvzeroupper
           This option instructs GCC to emit a "vzeroupper" instruction before a transfer of control
           flow out of the function to minimize the AVX to SSE transition penalty as well as remove
           unnecessary "zeroupper" intrinsics.

       -mprefer-avx128
           This option instructs GCC to use 128-bit AVX instructions instead of 256-bit AVX
           instructions in the auto-vectorizer.

       -mprefer-vector-width=opt
           This option instructs GCC to use opt-bit vector width in instructions instead of default
           on the selected platform.

           none
               No extra limitations applied to GCC other than defined by the selected platform.

           128 Prefer 128-bit vector width for instructions.

           256 Prefer 256-bit vector width for instructions.

           512 Prefer 512-bit vector width for instructions.

       -mcx16
           This option enables GCC to generate "CMPXCHG16B" instructions in 64-bit code to implement
           compare-and-exchange operations on 16-byte aligned 128-bit objects.  This is useful for
           atomic updates of data structures exceeding one machine word in size.  The compiler uses
           this instruction to implement __sync Builtins.  However, for __atomic Builtins operating
           on 128-bit integers, a library call is always used.

       -msahf
           This option enables generation of "SAHF" instructions in 64-bit code.  Early Intel
           Pentium 4 CPUs with Intel 64 support, prior to the introduction of Pentium 4 G1 step in
           December 2005, lacked the "LAHF" and "SAHF" instructions which are supported by AMD64.
           These are load and store instructions, respectively, for certain status flags.  In 64-bit
           mode, the "SAHF" instruction is used to optimize "fmod", "drem", and "remainder" built-in
           functions; see Other Builtins for details.

       -mmovbe
           This option enables use of the "movbe" instruction to implement "__builtin_bswap32" and
           "__builtin_bswap64".

       -mshstk
           The -mshstk option enables shadow stack built-in functions from x86 Control-flow
           Enforcement Technology (CET).

       -mcrc32
           This option enables built-in functions "__builtin_ia32_crc32qi",
           "__builtin_ia32_crc32hi", "__builtin_ia32_crc32si" and "__builtin_ia32_crc32di" to
           generate the "crc32" machine instruction.

       -mmwait
           This option enables built-in functions "__builtin_ia32_monitor", and
           "__builtin_ia32_mwait" to generate the "monitor" and "mwait" machine instructions.

       -mrecip
           This option enables use of "RCPSS" and "RSQRTSS" instructions (and their vectorized
           variants "RCPPS" and "RSQRTPS") with an additional Newton-Raphson step to increase
           precision instead of "DIVSS" and "SQRTSS" (and their vectorized variants) for single-
           precision floating-point arguments.  These instructions are generated only when
           -funsafe-math-optimizations is enabled together with -ffinite-math-only and
           -fno-trapping-math.  Note that while the throughput of the sequence is higher than the
           throughput of the non-reciprocal instruction, the precision of the sequence can be
           decreased by up to 2 ulp (i.e. the inverse of 1.0 equals 0.99999994).

           Note that GCC implements "1.0f/sqrtf(x)" in terms of "RSQRTSS" (or "RSQRTPS") already
           with -ffast-math (or the above option combination), and doesn't need -mrecip.

           Also note that GCC emits the above sequence with additional Newton-Raphson step for
           vectorized single-float division and vectorized "sqrtf(x)" already with -ffast-math (or
           the above option combination), and doesn't need -mrecip.

       -mrecip=opt
           This option controls which reciprocal estimate instructions may be used.  opt is a comma-
           separated list of options, which may be preceded by a ! to invert the option:

           all Enable all estimate instructions.

           default
               Enable the default instructions, equivalent to -mrecip.

           none
               Disable all estimate instructions, equivalent to -mno-recip.

           div Enable the approximation for scalar division.

           vec-div
               Enable the approximation for vectorized division.

           sqrt
               Enable the approximation for scalar square root.

           vec-sqrt
               Enable the approximation for vectorized square root.

           So, for example, -mrecip=all,!sqrt enables all of the reciprocal approximations, except
           for square root.

       -mveclibabi=type
           Specifies the ABI type to use for vectorizing intrinsics using an external library.
           Supported values for type are svml for the Intel short vector math library and acml for
           the AMD math core library.  To use this option, both -ftree-vectorize and
           -funsafe-math-optimizations have to be enabled, and an SVML or ACML ABI-compatible
           library must be specified at link time.

           GCC currently emits calls to "vmldExp2", "vmldLn2", "vmldLog102", "vmldPow2",
           "vmldTanh2", "vmldTan2", "vmldAtan2", "vmldAtanh2", "vmldCbrt2", "vmldSinh2", "vmldSin2",
           "vmldAsinh2", "vmldAsin2", "vmldCosh2", "vmldCos2", "vmldAcosh2", "vmldAcos2",
           "vmlsExp4", "vmlsLn4", "vmlsLog104", "vmlsPow4", "vmlsTanh4", "vmlsTan4", "vmlsAtan4",
           "vmlsAtanh4", "vmlsCbrt4", "vmlsSinh4", "vmlsSin4", "vmlsAsinh4", "vmlsAsin4",
           "vmlsCosh4", "vmlsCos4", "vmlsAcosh4" and "vmlsAcos4" for corresponding function type
           when -mveclibabi=svml is used, and "__vrd2_sin", "__vrd2_cos", "__vrd2_exp",
           "__vrd2_log", "__vrd2_log2", "__vrd2_log10", "__vrs4_sinf", "__vrs4_cosf", "__vrs4_expf",
           "__vrs4_logf", "__vrs4_log2f", "__vrs4_log10f" and "__vrs4_powf" for the corresponding
           function type when -mveclibabi=acml is used.

       -mabi=name
           Generate code for the specified calling convention.  Permissible values are sysv for the
           ABI used on GNU/Linux and other systems, and ms for the Microsoft ABI.  The default is to
           use the Microsoft ABI when targeting Microsoft Windows and the SysV ABI on all other
           systems.  You can control this behavior for specific functions by using the function
           attributes "ms_abi" and "sysv_abi".

       -mforce-indirect-call
           Force all calls to functions to be indirect. This is useful when using Intel Processor
           Trace where it generates more precise timing information for function calls.

       -mmanual-endbr
           Insert ENDBR instruction at function entry only via the "cf_check" function attribute.
           This is useful when used with the option -fcf-protection=branch to control ENDBR
           insertion at the function entry.

       -mcall-ms2sysv-xlogues
           Due to differences in 64-bit ABIs, any Microsoft ABI function that calls a System V ABI
           function must consider RSI, RDI and XMM6-15 as clobbered.  By default, the code for
           saving and restoring these registers is emitted inline, resulting in fairly lengthy
           prologues and epilogues.  Using -mcall-ms2sysv-xlogues emits prologues and epilogues that
           use stubs in the static portion of libgcc to perform these saves and restores, thus
           reducing function size at the cost of a few extra instructions.

       -mtls-dialect=type
           Generate code to access thread-local storage using the gnu or gnu2 conventions.  gnu is
           the conservative default; gnu2 is more efficient, but it may add compile- and run-time
           requirements that cannot be satisfied on all systems.

       -mpush-args
       -mno-push-args
           Use PUSH operations to store outgoing parameters.  This method is shorter and usually
           equally fast as method using SUB/MOV operations and is enabled by default.  In some cases
           disabling it may improve performance because of improved scheduling and reduced
           dependencies.

       -maccumulate-outgoing-args
           If enabled, the maximum amount of space required for outgoing arguments is computed in
           the function prologue.  This is faster on most modern CPUs because of reduced
           dependencies, improved scheduling and reduced stack usage when the preferred stack
           boundary is not equal to 2.  The drawback is a notable increase in code size.  This
           switch implies -mno-push-args.

       -mthreads
           Support thread-safe exception handling on MinGW.  Programs that rely on thread-safe
           exception handling must compile and link all code with the -mthreads option.  When
           compiling, -mthreads defines -D_MT; when linking, it links in a special thread helper
           library -lmingwthrd which cleans up per-thread exception-handling data.

       -mms-bitfields
       -mno-ms-bitfields
           Enable/disable bit-field layout compatible with the native Microsoft Windows compiler.

           If "packed" is used on a structure, or if bit-fields are used, it may be that the
           Microsoft ABI lays out the structure differently than the way GCC normally does.
           Particularly when moving packed data between functions compiled with GCC and the native
           Microsoft compiler (either via function call or as data in a file), it may be necessary
           to access either format.

           This option is enabled by default for Microsoft Windows targets.  This behavior can also
           be controlled locally by use of variable or type attributes.  For more information, see
           x86 Variable Attributes and x86 Type Attributes.

           The Microsoft structure layout algorithm is fairly simple with the exception of the bit-
           field packing.  The padding and alignment of members of structures and whether a bit-
           field can straddle a storage-unit boundary are determine by these rules:

           1. Structure members are stored sequentially in the order in which they are
               declared: the first member has the lowest memory address and the last member the
               highest.

           2. Every data object has an alignment requirement.  The alignment requirement
               for all data except structures, unions, and arrays is either the size of the object
               or the current packing size (specified with either the "aligned" attribute or the
               "pack" pragma), whichever is less.  For structures, unions, and arrays, the alignment
               requirement is the largest alignment requirement of its members.  Every object is
               allocated an offset so that:

                       offset % alignment_requirement == 0

           3. Adjacent bit-fields are packed into the same 1-, 2-, or 4-byte allocation
               unit if the integral types are the same size and if the next bit-field fits into the
               current allocation unit without crossing the boundary imposed by the common alignment
               requirements of the bit-fields.

           MSVC interprets zero-length bit-fields in the following ways:

           1. If a zero-length bit-field is inserted between two bit-fields that
               are normally coalesced, the bit-fields are not coalesced.

               For example:

                       struct
                        {
                          unsigned long bf_1 : 12;
                          unsigned long : 0;
                          unsigned long bf_2 : 12;
                        } t1;

               The size of "t1" is 8 bytes with the zero-length bit-field.  If the zero-length bit-
               field were removed, "t1"'s size would be 4 bytes.

           2. If a zero-length bit-field is inserted after a bit-field, "foo", and the
               alignment of the zero-length bit-field is greater than the member that follows it,
               "bar", "bar" is aligned as the type of the zero-length bit-field.

               For example:

                       struct
                        {
                          char foo : 4;
                          short : 0;
                          char bar;
                        } t2;

                       struct
                        {
                          char foo : 4;
                          short : 0;
                          double bar;
                        } t3;

               For "t2", "bar" is placed at offset 2, rather than offset 1.  Accordingly, the size
               of "t2" is 4.  For "t3", the zero-length bit-field does not affect the alignment of
               "bar" or, as a result, the size of the structure.

               Taking this into account, it is important to note the following:

               1. If a zero-length bit-field follows a normal bit-field, the type of the
                   zero-length bit-field may affect the alignment of the structure as whole. For
                   example, "t2" has a size of 4 bytes, since the zero-length bit-field follows a
                   normal bit-field, and is of type short.

               2. Even if a zero-length bit-field is not followed by a normal bit-field, it may
                   still affect the alignment of the structure:

                           struct
                            {
                              char foo : 6;
                              long : 0;
                            } t4;

                   Here, "t4" takes up 4 bytes.

           3. Zero-length bit-fields following non-bit-field members are ignored:
                       struct
                        {
                          char foo;
                          long : 0;
                          char bar;
                        } t5;

               Here, "t5" takes up 2 bytes.

       -mno-align-stringops
           Do not align the destination of inlined string operations.  This switch reduces code size
           and improves performance in case the destination is already aligned, but GCC doesn't know
           about it.

       -minline-all-stringops
           By default GCC inlines string operations only when the destination is known to be aligned
           to least a 4-byte boundary.  This enables more inlining and increases code size, but may
           improve performance of code that depends on fast "memcpy" and "memset" for short lengths.
           The option enables inline expansion of "strlen" for all pointer alignments.

       -minline-stringops-dynamically
           For string operations of unknown size, use run-time checks with inline code for small
           blocks and a library call for large blocks.

       -mstringop-strategy=alg
           Override the internal decision heuristic for the particular algorithm to use for inlining
           string operations.  The allowed values for alg are:

           rep_byte
           rep_4byte
           rep_8byte
               Expand using i386 "rep" prefix of the specified size.

           byte_loop
           loop
           unrolled_loop
               Expand into an inline loop.

           libcall
               Always use a library call.

       -mmemcpy-strategy=strategy
           Override the internal decision heuristic to decide if "__builtin_memcpy" should be
           inlined and what inline algorithm to use when the expected size of the copy operation is
           known. strategy is a comma-separated list of alg:max_size:dest_align triplets.  alg is
           specified in -mstringop-strategy, max_size specifies the max byte size with which inline
           algorithm alg is allowed.  For the last triplet, the max_size must be "-1". The max_size
           of the triplets in the list must be specified in increasing order.  The minimal byte size
           for alg is 0 for the first triplet and "max_size + 1" of the preceding range.

       -mmemset-strategy=strategy
           The option is similar to -mmemcpy-strategy= except that it is to control
           "__builtin_memset" expansion.

       -momit-leaf-frame-pointer
           Don't keep the frame pointer in a register for leaf functions.  This avoids the
           instructions to save, set up, and restore frame pointers and makes an extra register
           available in leaf functions.  The option -fomit-leaf-frame-pointer removes the frame
           pointer for leaf functions, which might make debugging harder.

       -mtls-direct-seg-refs
       -mno-tls-direct-seg-refs
           Controls whether TLS variables may be accessed with offsets from the TLS segment register
           (%gs for 32-bit, %fs for 64-bit), or whether the thread base pointer must be added.
           Whether or not this is valid depends on the operating system, and whether it maps the
           segment to cover the entire TLS area.

           For systems that use the GNU C Library, the default is on.

       -msse2avx
       -mno-sse2avx
           Specify that the assembler should encode SSE instructions with VEX prefix.  The option
           -mavx turns this on by default.

       -mfentry
       -mno-fentry
           If profiling is active (-pg), put the profiling counter call before the prologue.  Note:
           On x86 architectures the attribute "ms_hook_prologue" isn't possible at the moment for
           -mfentry and -pg.

       -mrecord-mcount
       -mno-record-mcount
           If profiling is active (-pg), generate a __mcount_loc section that contains pointers to
           each profiling call. This is useful for automatically patching and out calls.

       -mnop-mcount
       -mno-nop-mcount
           If profiling is active (-pg), generate the calls to the profiling functions as NOPs. This
           is useful when they should be patched in later dynamically. This is likely only useful
           together with -mrecord-mcount.

       -minstrument-return=type
           Instrument function exit in -pg -mfentry instrumented functions with call to specified
           function. This only instruments true returns ending with ret, but not sibling calls
           ending with jump. Valid types are none to not instrument, call to generate a call to
           __return__, or nop5 to generate a 5 byte nop.

       -mrecord-return
       -mno-record-return
           Generate a __return_loc section pointing to all return instrumentation code.

       -mfentry-name=name
           Set name of __fentry__ symbol called at function entry for -pg -mfentry functions.

       -mfentry-section=name
           Set name of section to record -mrecord-mcount calls (default __mcount_loc).

       -mskip-rax-setup
       -mno-skip-rax-setup
           When generating code for the x86-64 architecture with SSE extensions disabled,
           -mskip-rax-setup can be used to skip setting up RAX register when there are no variable
           arguments passed in vector registers.

           Warning: Since RAX register is used to avoid unnecessarily saving vector registers on
           stack when passing variable arguments, the impacts of this option are callees may waste
           some stack space, misbehave or jump to a random location.  GCC 4.4 or newer don't have
           those issues, regardless the RAX register value.

       -m8bit-idiv
       -mno-8bit-idiv
           On some processors, like Intel Atom, 8-bit unsigned integer divide is much faster than
           32-bit/64-bit integer divide.  This option generates a run-time check.  If both dividend
           and divisor are within range of 0 to 255, 8-bit unsigned integer divide is used instead
           of 32-bit/64-bit integer divide.

       -mavx256-split-unaligned-load
       -mavx256-split-unaligned-store
           Split 32-byte AVX unaligned load and store.

       -mstack-protector-guard=guard
       -mstack-protector-guard-reg=reg
       -mstack-protector-guard-offset=offset
           Generate stack protection code using canary at guard.  Supported locations are global for
           global canary or tls for per-thread canary in the TLS block (the default).  This option
           has effect only when -fstack-protector or -fstack-protector-all is specified.

           With the latter choice the options -mstack-protector-guard-reg=reg and
           -mstack-protector-guard-offset=offset furthermore specify which segment register (%fs or
           %gs) to use as base register for reading the canary, and from what offset from that base
           register.  The default for those is as specified in the relevant ABI.

       -mgeneral-regs-only
           Generate code that uses only the general-purpose registers.  This prevents the compiler
           from using floating-point, vector, mask and bound registers.

       -mindirect-branch=choice
           Convert indirect call and jump with choice.  The default is keep, which keeps indirect
           call and jump unmodified.  thunk converts indirect call and jump to call and return
           thunk.  thunk-inline converts indirect call and jump to inlined call and return thunk.
           thunk-extern converts indirect call and jump to external call and return thunk provided
           in a separate object file.  You can control this behavior for a specific function by
           using the function attribute "indirect_branch".

           Note that -mcmodel=large is incompatible with -mindirect-branch=thunk and
           -mindirect-branch=thunk-extern since the thunk function may not be reachable in the large
           code model.

           Note that -mindirect-branch=thunk-extern is compatible with -fcf-protection=branch since
           the external thunk can be made to enable control-flow check.

       -mfunction-return=choice
           Convert function return with choice.  The default is keep, which keeps function return
           unmodified.  thunk converts function return to call and return thunk.  thunk-inline
           converts function return to inlined call and return thunk.  thunk-extern converts
           function return to external call and return thunk provided in a separate object file.
           You can control this behavior for a specific function by using the function attribute
           "function_return".

           Note that -mindirect-return=thunk-extern is compatible with -fcf-protection=branch since
           the external thunk can be made to enable control-flow check.

           Note that -mcmodel=large is incompatible with -mfunction-return=thunk and
           -mfunction-return=thunk-extern since the thunk function may not be reachable in the large
           code model.

       -mindirect-branch-register
           Force indirect call and jump via register.

       -mharden-sls=choice
           Generate code to mitigate against straight line speculation (SLS) with choice.  The
           default is none which disables all SLS hardening.  return enables SLS hardening for
           function returns.  indirect-jmp enables SLS hardening for indirect jumps.  all enables
           all SLS hardening.

       -mindirect-branch-cs-prefix
           Add CS prefix to call and jmp to indirect thunk with branch target in r8-r15 registers so
           that the call and jmp instruction length is 6 bytes to allow them to be replaced with
           lfence; call *%r8-r15 or lfence; jmp *%r8-r15 at run-time.

       These -m switches are supported in addition to the above on x86-64 processors in 64-bit
       environments.

       -m32
       -m64
       -mx32
       -m16
       -miamcu
           Generate code for a 16-bit, 32-bit or 64-bit environment.  The -m32 option sets "int",
           "long", and pointer types to 32 bits, and generates code that runs on any i386 system.

           The -m64 option sets "int" to 32 bits and "long" and pointer types to 64 bits, and
           generates code for the x86-64 architecture.  For Darwin only the -m64 option also turns
           off the -fno-pic and -mdynamic-no-pic options.

           The -mx32 option sets "int", "long", and pointer types to 32 bits, and generates code for
           the x86-64 architecture.

           The -m16 option is the same as -m32, except for that it outputs the ".code16gcc" assembly
           directive at the beginning of the assembly output so that the binary can run in 16-bit
           mode.

           The -miamcu option generates code which conforms to Intel MCU psABI.  It requires the
           -m32 option to be turned on.

       -mno-red-zone
           Do not use a so-called "red zone" for x86-64 code.  The red zone is mandated by the
           x86-64 ABI; it is a 128-byte area beyond the location of the stack pointer that is not
           modified by signal or interrupt handlers and therefore can be used for temporary data
           without adjusting the stack pointer.  The flag -mno-red-zone disables this red zone.

       -mcmodel=small
           Generate code for the small code model: the program and its symbols must be linked in the
           lower 2 GB of the address space.  Pointers are 64 bits.  Programs can be statically or
           dynamically linked.  This is the default code model.

       -mcmodel=kernel
           Generate code for the kernel code model.  The kernel runs in the negative 2 GB of the
           address space.  This model has to be used for Linux kernel code.

       -mcmodel=medium
           Generate code for the medium model: the program is linked in the lower 2 GB of the
           address space.  Small symbols are also placed there.  Symbols with sizes larger than
           -mlarge-data-threshold are put into large data or BSS sections and can be located above
           2GB.  Programs can be statically or dynamically linked.

       -mcmodel=large
           Generate code for the large model.  This model makes no assumptions about addresses and
           sizes of sections.

       -maddress-mode=long
           Generate code for long address mode.  This is only supported for 64-bit and x32
           environments.  It is the default address mode for 64-bit environments.

       -maddress-mode=short
           Generate code for short address mode.  This is only supported for 32-bit and x32
           environments.  It is the default address mode for 32-bit and x32 environments.

       -mneeded
       -mno-needed
           Emit GNU_PROPERTY_X86_ISA_1_NEEDED GNU property for Linux target to indicate the micro-
           architecture ISA level required to execute the binary.

       x86 Windows Options

       These additional options are available for Microsoft Windows targets:

       -mconsole
           This option specifies that a console application is to be generated, by instructing the
           linker to set the PE header subsystem type required for console applications.  This
           option is available for Cygwin and MinGW targets and is enabled by default on those
           targets.

       -mdll
           This option is available for Cygwin and MinGW targets.  It specifies that a DLL---a
           dynamic link library---is to be generated, enabling the selection of the required runtime
           startup object and entry point.

       -mnop-fun-dllimport
           This option is available for Cygwin and MinGW targets.  It specifies that the "dllimport"
           attribute should be ignored.

       -mthread
           This option is available for MinGW targets. It specifies that MinGW-specific thread
           support is to be used.

       -municode
           This option is available for MinGW-w64 targets.  It causes the "UNICODE" preprocessor
           macro to be predefined, and chooses Unicode-capable runtime startup code.

       -mwin32
           This option is available for Cygwin and MinGW targets.  It specifies that the typical
           Microsoft Windows predefined macros are to be set in the pre-processor, but does not
           influence the choice of runtime library/startup code.

       -mwindows
           This option is available for Cygwin and MinGW targets.  It specifies that a GUI
           application is to be generated by instructing the linker to set the PE header subsystem
           type appropriately.

       -fno-set-stack-executable
           This option is available for MinGW targets. It specifies that the executable flag for the
           stack used by nested functions isn't set. This is necessary for binaries running in
           kernel mode of Microsoft Windows, as there the User32 API, which is used to set
           executable privileges, isn't available.

       -fwritable-relocated-rdata
           This option is available for MinGW and Cygwin targets.  It specifies that relocated-data
           in read-only section is put into the ".data" section.  This is a necessary for older
           runtimes not supporting modification of ".rdata" sections for pseudo-relocation.

       -mpe-aligned-commons
           This option is available for Cygwin and MinGW targets.  It specifies that the GNU
           extension to the PE file format that permits the correct alignment of COMMON variables
           should be used when generating code.  It is enabled by default if GCC detects that the
           target assembler found during configuration supports the feature.

       See also under x86 Options for standard options.

       Xstormy16 Options

       These options are defined for Xstormy16:

       -msim
           Choose startup files and linker script suitable for the simulator.

       Xtensa Options

       These options are supported for Xtensa targets:

       -mconst16
       -mno-const16
           Enable or disable use of "CONST16" instructions for loading constant values.  The
           "CONST16" instruction is currently not a standard option from Tensilica.  When enabled,
           "CONST16" instructions are always used in place of the standard "L32R" instructions.  The
           use of "CONST16" is enabled by default only if the "L32R" instruction is not available.

       -mfused-madd
       -mno-fused-madd
           Enable or disable use of fused multiply/add and multiply/subtract instructions in the
           floating-point option.  This has no effect if the floating-point option is not also
           enabled.  Disabling fused multiply/add and multiply/subtract instructions forces the
           compiler to use separate instructions for the multiply and add/subtract operations.  This
           may be desirable in some cases where strict IEEE 754-compliant results are required: the
           fused multiply add/subtract instructions do not round the intermediate result, thereby
           producing results with more bits of precision than specified by the IEEE standard.
           Disabling fused multiply add/subtract instructions also ensures that the program output
           is not sensitive to the compiler's ability to combine multiply and add/subtract
           operations.

       -mserialize-volatile
       -mno-serialize-volatile
           When this option is enabled, GCC inserts "MEMW" instructions before "volatile" memory
           references to guarantee sequential consistency.  The default is -mserialize-volatile.
           Use -mno-serialize-volatile to omit the "MEMW" instructions.

       -mforce-no-pic
           For targets, like GNU/Linux, where all user-mode Xtensa code must be position-independent
           code (PIC), this option disables PIC for compiling kernel code.

       -mtext-section-literals
       -mno-text-section-literals
           These options control the treatment of literal pools.  The default is
           -mno-text-section-literals, which places literals in a separate section in the output
           file.  This allows the literal pool to be placed in a data RAM/ROM, and it also allows
           the linker to combine literal pools from separate object files to remove redundant
           literals and improve code size.  With -mtext-section-literals, the literals are
           interspersed in the text section in order to keep them as close as possible to their
           references.  This may be necessary for large assembly files.  Literals for each function
           are placed right before that function.

       -mauto-litpools
       -mno-auto-litpools
           These options control the treatment of literal pools.  The default is -mno-auto-litpools,
           which places literals in a separate section in the output file unless
           -mtext-section-literals is used.  With -mauto-litpools the literals are interspersed in
           the text section by the assembler.  Compiler does not produce explicit ".literal"
           directives and loads literals into registers with "MOVI" instructions instead of "L32R"
           to let the assembler do relaxation and place literals as necessary.  This option allows
           assembler to create several literal pools per function and assemble very big functions,
           which may not be possible with -mtext-section-literals.

       -mtarget-align
       -mno-target-align
           When this option is enabled, GCC instructs the assembler to automatically align
           instructions to reduce branch penalties at the expense of some code density.  The
           assembler attempts to widen density instructions to align branch targets and the
           instructions following call instructions.  If there are not enough preceding safe density
           instructions to align a target, no widening is performed.  The default is -mtarget-align.
           These options do not affect the treatment of auto-aligned instructions like "LOOP", which
           the assembler always aligns, either by widening density instructions or by inserting NOP
           instructions.

       -mlongcalls
       -mno-longcalls
           When this option is enabled, GCC instructs the assembler to translate direct calls to
           indirect calls unless it can determine that the target of a direct call is in the range
           allowed by the call instruction.  This translation typically occurs for calls to
           functions in other source files.  Specifically, the assembler translates a direct "CALL"
           instruction into an "L32R" followed by a "CALLX" instruction.  The default is
           -mno-longcalls.  This option should be used in programs where the call target can
           potentially be out of range.  This option is implemented in the assembler, not the
           compiler, so the assembly code generated by GCC still shows direct call
           instructions---look at the disassembled object code to see the actual instructions.  Note
           that the assembler uses an indirect call for every cross-file call, not just those that
           really are out of range.

       -mabi=name
           Generate code for the specified ABI.  Permissible values are: call0, windowed.  Default
           ABI is chosen by the Xtensa core configuration.

       -mabi=call0
           When this option is enabled function parameters are passed in registers "a2" through
           "a7", registers "a12" through "a15" are caller-saved, and register "a15" may be used as a
           frame pointer.  When this version of the ABI is enabled the C preprocessor symbol
           "__XTENSA_CALL0_ABI__" is defined.

       -mabi=windowed
           When this option is enabled function parameters are passed in registers "a10" through
           "a15", and called function rotates register window by 8 registers on entry so that its
           arguments are found in registers "a2" through "a7".  Register "a7" may be used as a frame
           pointer.  Register window is rotated 8 registers back upon return.  When this version of
           the ABI is enabled the C preprocessor symbol "__XTENSA_WINDOWED_ABI__" is defined.

       zSeries Options

       These are listed under

ENVIRONMENT
       This section describes several environment variables that affect how GCC operates.  Some of
       them work by specifying directories or prefixes to use when searching for various kinds of
       files.  Some are used to specify other aspects of the compilation environment.

       Note that you can also specify places to search using options such as -B, -I and -L.  These
       take precedence over places specified using environment variables, which in turn take
       precedence over those specified by the configuration of GCC.

       LANG
       LC_CTYPE
       LC_MESSAGES
       LC_ALL
           These environment variables control the way that GCC uses localization information which
           allows GCC to work with different national conventions.  GCC inspects the locale
           categories LC_CTYPE and LC_MESSAGES if it has been configured to do so.  These locale
           categories can be set to any value supported by your installation.  A typical value is
           en_GB.UTF-8 for English in the United Kingdom encoded in UTF-8.

           The LC_CTYPE environment variable specifies character classification.  GCC uses it to
           determine the character boundaries in a string; this is needed for some multibyte
           encodings that contain quote and escape characters that are otherwise interpreted as a
           string end or escape.

           The LC_MESSAGES environment variable specifies the language to use in diagnostic
           messages.

           If the LC_ALL environment variable is set, it overrides the value of LC_CTYPE and
           LC_MESSAGES; otherwise, LC_CTYPE and LC_MESSAGES default to the value of the LANG
           environment variable.  If none of these variables are set, GCC defaults to traditional C
           English behavior.

       TMPDIR
           If TMPDIR is set, it specifies the directory to use for temporary files.  GCC uses
           temporary files to hold the output of one stage of compilation which is to be used as
           input to the next stage: for example, the output of the preprocessor, which is the input
           to the compiler proper.

       GCC_COMPARE_DEBUG
           Setting GCC_COMPARE_DEBUG is nearly equivalent to passing -fcompare-debug to the compiler
           driver.  See the documentation of this option for more details.

       GCC_EXEC_PREFIX
           If GCC_EXEC_PREFIX is set, it specifies a prefix to use in the names of the subprograms
           executed by the compiler.  No slash is added when this prefix is combined with the name
           of a subprogram, but you can specify a prefix that ends with a slash if you wish.

           If GCC_EXEC_PREFIX is not set, GCC attempts to figure out an appropriate prefix to use
           based on the pathname it is invoked with.

           If GCC cannot find the subprogram using the specified prefix, it tries looking in the
           usual places for the subprogram.

           The default value of GCC_EXEC_PREFIX is prefix/lib/gcc/ where prefix is the prefix to the
           installed compiler. In many cases prefix is the value of "prefix" when you ran the
           configure script.

           Other prefixes specified with -B take precedence over this prefix.

           This prefix is also used for finding files such as crt0.o that are used for linking.

           In addition, the prefix is used in an unusual way in finding the directories to search
           for header files.  For each of the standard directories whose name normally begins with
           /usr/local/lib/gcc (more precisely, with the value of GCC_INCLUDE_DIR), GCC tries
           replacing that beginning with the specified prefix to produce an alternate directory
           name.  Thus, with -Bfoo/, GCC searches foo/bar just before it searches the standard
           directory /usr/local/lib/bar.  If a standard directory begins with the configured prefix
           then the value of prefix is replaced by GCC_EXEC_PREFIX when looking for header files.

       COMPILER_PATH
           The value of COMPILER_PATH is a colon-separated list of directories, much like PATH.  GCC
           tries the directories thus specified when searching for subprograms, if it cannot find
           the subprograms using GCC_EXEC_PREFIX.

       LIBRARY_PATH
           The value of LIBRARY_PATH is a colon-separated list of directories, much like PATH.  When
           configured as a native compiler, GCC tries the directories thus specified when searching
           for special linker files, if it cannot find them using GCC_EXEC_PREFIX.  Linking using
           GCC also uses these directories when searching for ordinary libraries for the -l option
           (but directories specified with -L come first).

       LANG
           This variable is used to pass locale information to the compiler.  One way in which this
           information is used is to determine the character set to be used when character literals,
           string literals and comments are parsed in C and C++.  When the compiler is configured to
           allow multibyte characters, the following values for LANG are recognized:

           C-JIS
               Recognize JIS characters.

           C-SJIS
               Recognize SJIS characters.

           C-EUCJP
               Recognize EUCJP characters.

           If LANG is not defined, or if it has some other value, then the compiler uses "mblen" and
           "mbtowc" as defined by the default locale to recognize and translate multibyte
           characters.

       GCC_EXTRA_DIAGNOSTIC_OUTPUT
           If GCC_EXTRA_DIAGNOSTIC_OUTPUT is set to one of the following values, then additional
           text will be emitted to stderr when fix-it hints are emitted.
           -fdiagnostics-parseable-fixits and -fno-diagnostics-parseable-fixits take precedence over
           this environment variable.

           fixits-v1
               Emit parseable fix-it hints, equivalent to -fdiagnostics-parseable-fixits.  In
               particular, columns are expressed as a count of bytes, starting at byte 1 for the
               initial column.

           fixits-v2
               As "fixits-v1", but columns are expressed as display columns, as per
               -fdiagnostics-column-unit=display.

       Some additional environment variables affect the behavior of the preprocessor.

       CPATH
       C_INCLUDE_PATH
       CPLUS_INCLUDE_PATH
       OBJC_INCLUDE_PATH
           Each variable's value is a list of directories separated by a special character, much
           like PATH, in which to look for header files.  The special character, "PATH_SEPARATOR",
           is target-dependent and determined at GCC build time.  For Microsoft Windows-based
           targets it is a semicolon, and for almost all other targets it is a colon.

           CPATH specifies a list of directories to be searched as if specified with -I, but after
           any paths given with -I options on the command line.  This environment variable is used
           regardless of which language is being preprocessed.

           The remaining environment variables apply only when preprocessing the particular language
           indicated.  Each specifies a list of directories to be searched as if specified with
           -isystem, but after any paths given with -isystem options on the command line.

           In all these variables, an empty element instructs the compiler to search its current
           working directory.  Empty elements can appear at the beginning or end of a path.  For
           instance, if the value of CPATH is ":/special/include", that has the same effect as
           -I. -I/special/include.

       DEPENDENCIES_OUTPUT
           If this variable is set, its value specifies how to output dependencies for Make based on
           the non-system header files processed by the compiler.  System header files are ignored
           in the dependency output.

           The value of DEPENDENCIES_OUTPUT can be just a file name, in which case the Make rules
           are written to that file, guessing the target name from the source file name.  Or the
           value can have the form file target, in which case the rules are written to file file
           using target as the target name.

           In other words, this environment variable is equivalent to combining the options -MM and
           -MF, with an optional -MT switch too.

       SUNPRO_DEPENDENCIES
           This variable is the same as DEPENDENCIES_OUTPUT (see above), except that system header
           files are not ignored, so it implies -M rather than -MM.  However, the dependence on the
           main input file is omitted.

       SOURCE_DATE_EPOCH
           If this variable is set, its value specifies a UNIX timestamp to be used in replacement
           of the current date and time in the "__DATE__" and "__TIME__" macros, so that the
           embedded timestamps become reproducible.

           The value of SOURCE_DATE_EPOCH must be a UNIX timestamp, defined as the number of seconds
           (excluding leap seconds) since 01 Jan 1970 00:00:00 represented in ASCII; identical to
           the output of "date +%s" on GNU/Linux and other systems that support the %s extension in
           the "date" command.

           The value should be a known timestamp such as the last modification time of the source or
           package and it should be set by the build process.

BUGS
       For instructions on reporting bugs, see <file:///usr/share/doc/gcc-11/README.Bugs>.

FOOTNOTES
       1.  On some systems, gcc -shared needs to build supplementary stub code for constructors to
           work.  On multi-libbed systems, gcc -shared must select the correct support libraries to
           link against.  Failing to supply the correct flags may lead to subtle defects.  Supplying
           them in cases where they are not necessary is innocuous.

SEE ALSO
       gpl(7), gfdl(7), fsf-funding(7), cpp(1), gcov(1), as(1), ld(1), gdb(1), dbx(1) and the Info
       entries for gcc, cpp, as, ld, binutils and gdb.

AUTHOR
       See the Info entry for gcc, or <http://gcc.gnu.org/onlinedocs/gcc/Contributors.html>, for
       contributors to GCC.

COPYRIGHT
       Copyright (c) 1988-2021 Free Software Foundation, Inc.

       Permission is granted to copy, distribute and/or modify this document under the terms of the
       GNU Free Documentation License, Version 1.3 or any later version published by the Free
       Software Foundation; with the Invariant Sections being "GNU General Public License" and
       "Funding Free Software", the Front-Cover texts being (a) (see below), and with the Back-Cover
       Texts being (b) (see below).  A copy of the license is included in the gfdl(7) man page.

       (a) The FSF's Front-Cover Text is:

            A GNU Manual

       (b) The FSF's Back-Cover Text is:

            You have freedom to copy and modify this GNU Manual, like GNU
            software.  Copies published by the Free Software Foundation raise
            funds for GNU development.



gcc-11                                       2023-05-28                                       GCC(1)

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