[PATCH] D158688: [Driver,ARM,AArch64] Ignore -mbranch-protection= diagnostics for assembler input

Wed Aug 30 00:40:28 PDT 2023

MaskRay added a comment.

In D158688#4625839 <https://reviews.llvm.org/D158688#4625839>, @MaskRay wrote:

> In D158688#4624267 <https://reviews.llvm.org/D158688#4624267>, @simon_tatham wrote:
>
>> The change LGTM, and "agree with gcc" seems like a reasonable justification in this case.
>
> Thank you both!
>
>> But I'm curious more generally about what options should / shouldn't be covered by `-Wunused-command-line-argument`. Doesn't the same reasoning apply to //most// options that C compilation uses and assembly doesn't? If you have a command of the form `clang -someoption -c foo.c`, it's surely //always// convenient for a user to be able to change the `.c` into a `.s`, or to put a variable list of files on the end of the command line which might or might not include any `.c` files.
>
> `-Wunused-command-line-argument` does fire for most options when the only input kind is assembly without preprocessing.
> It seems that the diagnostics are for `assembler` input, not `assembler-with-cpp`...
>
>> Why is this option in particular different from others? Is there a documented policy anywhere?
>
> I am not aware of a documented policy anywhere, but I have some notes on https://maskray.me/blog/2023-08-25-clang-wunused-command-line-argument#assembler-input .
>
> Let me ask on Discourse: https://discourse.llvm.org/t/wunused-command-line-argument-for-assembly-files/73111

I think we should do D159173 <https://reviews.llvm.org/D159173> .. The warnings are still useful, but we can do it in Driver.cpp to avoid the `ForAS` hacks.

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https://reviews.llvm.org/D158688