[PATCH 05/14] powerpc: Remove linker flag from KBUILD_AFLAGS

[Nick Desaulniers]

On Wed, Jan 4, 2023 at 11:54 AM Nathan Chancellor <nathan at kernel.org> wrote:
>
> When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, it
> points out that KBUILD_AFLAGS contains a linker flag, which will be
> used:
>
>   clang: error: -Wl,-a32: 'linker' input unused [-Werror,-Wunused-command-line-argument]
>
> This was likely supposed to be '-Wa,-a$(BITS)'. However, this change is
> unnecessary, as all supported versions of clang and gcc will pass '-a64'
> or '-a32' to GNU as based on the value of '-m'; the behavior of the
> latest stable release of the oldest supported major version of each
> compiler is shown below and each compiler's latest release exhibits the
> same behavior (GCC 12.2.0 and Clang 15.0.6).
>
>   $ powerpc64-linux-gcc --version | head -1
>   powerpc64-linux-gcc (GCC) 5.5.0
>
>   $ powerpc64-linux-gcc -m64 -### -x assembler-with-cpp -c -o /dev/null /dev/null &| grep 'as '
>   .../as -a64 -mppc64 -many -mbig -o /dev/null /tmp/cctwuBzZ.s
>
>   $ powerpc64-linux-gcc -m32 -### -x assembler-with-cpp -c -o /dev/null /dev/null &| grep 'as '
>   .../as -a32 -mppc -many -mbig -o /dev/null /tmp/ccaZP4mF.sg
>
>   $ clang --version | head -1
>   Ubuntu clang version 11.1.0-++20211011094159+1fdec59bffc1-1~exp1~20211011214622.5
>
>   $ clang --target=powerpc64-linux-gnu -fno-integrated-as -m64 -### \
>     -x assembler-with-cpp -c -o /dev/null /dev/null &| grep gnu-as
>    "/usr/bin/powerpc64-linux-gnu-as" "-a64" "-mppc64" "-many" "-o" "/dev/null" "/tmp/null-80267c.s"
>
>   $ clang --target=powerpc64-linux-gnu -fno-integrated-as -m64 -### \
>     -x assembler-with-cpp -c -o /dev/null /dev/null &| grep gnu-as
>    "/usr/bin/powerpc64-linux-gnu-as" "-a32" "-mppc" "-many" "-o" "/dev/null" "/tmp/null-ab8f8d.s"
>
> Remove this flag altogether to avoid future issues.
>
> Fixes: 1421dc6d4829 ("powerpc/kbuild: Use flags variables rather than overriding LD/CC/AS")
> Signed-off-by: Nathan Chancellor <nathan at kernel.org>

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

> ---
> Cc: mpe at ellerman.id.au
> Cc: npiggin at gmail.com
> Cc: christophe.leroy at csgroup.eu
> Cc: linuxppc-dev at lists.ozlabs.org
> ---
>  arch/powerpc/Makefile | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
> index dc4cbf0a5ca9..4fd630efe39d 100644
> --- a/arch/powerpc/Makefile
> +++ b/arch/powerpc/Makefile
> @@ -90,7 +90,7 @@ aflags-$(CONFIG_CPU_LITTLE_ENDIAN)    += -mlittle-endian
>
>  ifeq ($(HAS_BIARCH),y)
>  KBUILD_CFLAGS  += -m$(BITS)
> -KBUILD_AFLAGS  += -m$(BITS) -Wl,-a$(BITS)
> +KBUILD_AFLAGS  += -m$(BITS)
>  KBUILD_LDFLAGS += -m elf$(BITS)$(LDEMULATION)
>  endif
>
>
> --
> 2.39.0



-- 
Thanks,
~Nick Desaulniers