[PATCH] D159173: [Driver] Report warnings for unlaimed TargetSpecific options for assembler input

[Fangrui Song via Phabricator via cfe-commits]

MaskRay created this revision.
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This patch amends D151590 <https://reviews.llvm.org/D151590> to not error for unlaimed TargetSpecific
options for `-x assembler` input files. This input type causes Driver to
construct tools::ClangAs (-fintegrated-as) or other assemblers (e.g.
tools::gnutools::Assembler) Their ConstructJobs methods, unlike
Clang::ConstructJobs, claim very few options. If an option is unclaimed,
it either leads to a -Wunused-command-line-argument warning or an error
(if `TargetSpecific` is set):

  % clang '-###' --target=aarch64 -mbranch-protection=bti -c a.s
  clang: error: unsupported option '-mbranch-protection=' for target 'aarch64'

It seems that downgrading the diagnostic to warning is most useful as
many users use CFLAGS even for `.s` files:

  clang --target=aarch64 -mbranch-protection=bti -S a.c
  clang --target=aarch64 -mbranch-protection=bti -c a.s

I decide not to suppress the warning so that
-Wunused-command-line-argument lovers still get a warning, and help
projects use proper ASFLAGS/CFLAGS/etc.

Note: `-mbranch-protection=bti a.S` currently has no warning as `-x assembler-with-cpp`
instructs clangDriver to select tools::Clang and claim most options.

Revert D159010 <https://reviews.llvm.org/D159010> to demonstrate that we emit a warning for -mfpmath= for
`-x assembler` input.

Modify my AIX cleanup cd18efb61d759405956dbd30e4b5f2720d8e1783 <https://reviews.llvm.org/rGcd18efb61d759405956dbd30e4b5f2720d8e1783> to
add an err_drv_unsupported_opt_for_target.

Planned for main and release/17.x


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D159173

Files:
  clang/lib/Driver/Driver.cpp
  clang/lib/Driver/ToolChains/AIX.cpp
  clang/lib/Driver/ToolChains/Arch/X86.cpp
  clang/lib/Driver/ToolChains/Arch/X86.h
  clang/lib/Driver/ToolChains/CommonArgs.cpp
  clang/test/Driver/aarch64-target-as-march.s
  clang/test/Driver/target-specific.s
  clang/test/Driver/x86-mfpmath.c

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