Re: [PATCH v3 RESEND 1/2] arm: lib: xor-neon: remove unnecessary GCC < 4.6 warning

[Arnd Bergmann]

On Mon, Jan 18, 2021 at 11:56 AM Adrian Ratiu
<adrian.ratiu@xxxxxxxxxxxxx> wrote:
>
> From: Nathan Chancellor <natechancellor@xxxxxxxxx>
>
> Drop warning because kernel now requires GCC >= v4.9 after
> commit 6ec4476ac825 ("Raise gcc version requirement to 4.9")
> and clarify that -ftree-vectorize now always needs enabling
> for GCC by directly testing the presence of CONFIG_CC_IS_GCC.
>
> Another reason to remove the warning is that Clang exposes
> itself as GCC < 4.6 so it triggers the warning about GCC
> which doesn't make much sense and risks misleading users.
>
> As a side-note remark, -fttree-vectorize is on by default in
> Clang, but it currently does not work (see linked issues).
>
> Link: https://github.com/ClangBuiltLinux/linux/issues/496
> Link: https://github.com/ClangBuiltLinux/linux/issues/503
> Reported-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
> Reviewed-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
> Signed-off-by: Nathan Chancellor <natechancellor@xxxxxxxxx>
> Signed-off-by: Adrian Ratiu <adrian.ratiu@xxxxxxxxxxxxx>

Shouldn't there be a check for whatever minimum version of clang
produces optimized code now? As I understand it, the warning
was originally meant to complain about both old gcc and any
version of clang, while waiting for a new version of clang to
produce vectorized code.

Has that happened now?

       Arnd