Re: [PATCH] drm/amd: Guard IS_OLD_GCC assignment with CONFIG_CC_IS_GCC

Nick Desaulniers
2021-09-30T17:30:02Z

On Thu, Sep 30, 2021 at 9:02 AM Nathan Chancellor <nathan@kernel.org> wrote:
>
> cc-ifversion only works for GCC, as clang pretends to be GCC 4.2.1 for
> glibc compatibility, which means IS_OLD_GCC will get set and unsupported
> flags will be passed to clang when building certain code within the DCN
> files:
>
> clang-14: error: unknown argument: '-mpreferred-stack-boundary=4'
> make[5]: *** [scripts/Makefile.build:277: drivers/gpu/drm/amd/amdgpu/../display/dc/dcn201/dcn201_resource.o] Error 1
>
> Guard the call to cc-ifversion with CONFIG_CC_IS_GCC so that everything
> continues to work properly. See commit 00db297106e8 ("drm/amdgpu: fix stack
> alignment ABI mismatch for GCC 7.1+") for more context.
>
> Fixes: ff7e396f822f ("drm/amd/display: add cyan_skillfish display support")
> Link: https://github.com/ClangBuiltLinux/linux/issues/1468
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>

Thanks for the patch!
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

$ grep -rn "ifdef IS_OLD_GCC" drivers/gpu/drm/amd/display/dc/ | wc -l
11

It's probably time to put this pattern in a Makefile under scripts/
and include it in all of these Makefiles. Anything to minimize the
amount of code that has to be carried forward to new subdirs.

> ---
> drivers/gpu/drm/amd/display/dc/dcn201/Makefile | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/drivers/gpu/drm/amd/display/dc/dcn201/Makefile b/drivers/gpu/drm/amd/display/dc/dcn201/Makefile
> index d98d69705117..96cbd4ccd344 100644
> --- a/drivers/gpu/drm/amd/display/dc/dcn201/Makefile
> +++ b/drivers/gpu/drm/amd/display/dc/dcn201/Makefile
> @@ -14,9 +14,11 @@ ifdef CONFIG_PPC64
> CFLAGS_$(AMDDALPATH)/dc/dcn201/dcn201_resource.o := -mhard-float -maltivec
> endif
>
> +ifdef CONFIG_CC_IS_GCC
> ifeq ($(call cc-ifversion, -lt, 0701, y), y)
> IS_OLD_GCC = 1
> endif
> +endif
>
> ifdef CONFIG_X86
> ifdef IS_OLD_GCC
>
> base-commit: b47b99e30cca8906753c83205e8c6179045dd725
> --
> 2.33.0.591.gddb1055343
>

--
Thanks,
~Nick Desaulniers