[PATCH] D153707: [Clang][LoongArch] Consume and check -mabi and -mfpu even if -m*-float is present

[WÁNG Xuěruì via Phabricator via cfe-commits]

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This kind of CLI flags duplication can sometimes be convenient for build
systems that may have to tinker with these.

For example, in the Linux kernel we almost always want to ensure no FP
instruction is emitted, so `-msoft-float` is present by default; but
sometimes we do want to allow FPU usage (e.g. certain parts of amdgpu DC
code), in which case we want the `-msoft-float` stripped and `-mfpu=64`
added. Here we face a dilemma without this change:

- Either `-mabi` is not supplied by `arch/loongarch` Makefile, in which case the correct ABI has to be supplied by the driver Makefile, potentially duplicating logic;
- Or `-mabi` is still supplied by `arch/loongarch` Makefile, and the build immediately errors out because `-Werror,-Wunused-command-line-argument` is unconditionally set for Clang builds.

To solve this, simply make sure to check `-mabi` and `-mfpu` (and gain
some useful diagnostics in case of conflicting settings) when
`-m*-float` is successfully parsed.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D153707

Files:
  clang/include/clang/Basic/DiagnosticDriverKinds.td
  clang/lib/Driver/ToolChains/Arch/LoongArch.cpp
  clang/test/Driver/loongarch-mdouble-float.c
  clang/test/Driver/loongarch-msingle-float.c
  clang/test/Driver/loongarch-msoft-float.c

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