Re: [PATCH 1/2] alpha: enable building with clang

On Mon, Aug 3, 2026 at 7:08 PM Matt Turner <[email protected]> wrote:
>
> Register the clang target triple for alpha, and pass -Wa,-mev6 only when
> building with gcc.  That flag exists to stop gas emulating instructions
> the assembler thinks the target lacks; it is a gas-only option, and
> clang's integrated assembler does not emulate instructions in the first
> place, so nothing is needed there.
>
> With this, LLVM=1 (and LLVM_IAS=1) builds work.  Note that the alpha
> backend is not in upstream LLVM yet; it lives in
>
>   https://github.com/alphalinux-org/llvm-project
>
> and is a work in progress.
>
> Signed-off-by: Matt Turner <[email protected]>
> ---
>  arch/alpha/Makefile    | 8 +++++++-
>  scripts/Makefile.clang | 1 +
>  2 files changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/arch/alpha/Makefile b/arch/alpha/Makefile
> index 35445ff2e489..54283705911f 100644
> --- a/arch/alpha/Makefile
> +++ b/arch/alpha/Makefile
> @@ -27,10 +27,16 @@ cpuflags-$(CONFIG_ALPHA_GENERIC)    := -mcpu=ev56 -mtune=ev6
>  cflags-y                               += $(cpuflags-y)
>
>
> +KBUILD_CFLAGS += $(cflags-y)
> +
>  # For TSUNAMI, we must have the assembler not emulate our instructions.
>  # The same is true for IRONGATE, POLARIS, PYXIS.
>  # BWX is most important, but we don't really want any emulation ever.
> -KBUILD_CFLAGS += $(cflags-y) -Wa,-mev6
> +# Only gas emulates instructions the target does not implement, and only gas
> +# understands -mev6; clang's integrated assembler never emulates.
> +ifdef CONFIG_CC_IS_GCC
> +KBUILD_CFLAGS += -Wa,-mev6
> +endif
>
>  libs-y                         += arch/alpha/lib/
>

Hi Matt,

I agree with Nathan's suggestion to leave the
CLANG_TARGET_FLAGS_alpha entry out for now and add it separately when
the Alpha backend is being upstreamed to LLVM.

Could you send a v2 containing just the arch/alpha/Makefile change?

Since -Wa,-mev6 is an assembler-specific option, I think maybe the condition
should also test the assembler rather than the compiler?

ifdef CONFIG_AS_IS_GNU
KBUILD_CFLAGS += -Wa,-mev6
endif

That preserves the option for both GCC and clang builds using GNU as,
including clang with LLVM_IAS=0, while omitting it for LLVM's integrated
assembler.

The revised Alpha Makefile patch can then go through the Alpha tree,
while the scripts/Makefile.clang change can wait until the backend is
available upstream.

Thanks,
Magnus