[PATCH] powerpc/64s: POWER10 CPU Kconfig build option

[Segher Boessenkool]

Hi!

On Fri, Sep 23, 2022 at 01:30:04PM +1000, Nicholas Piggin wrote:
> This adds basic POWER10_CPU option, which builds with -mcpu=power10.

> +# No prefix or pcrel
> +KBUILD_CFLAGS += $(call cc-option,-mno-prefixed)
> +KBUILD_CFLAGS += $(call cc-option,-mno-pcrel)

Why do you disable all prefixed insns?  What goes wrong if you don't?

Same question for pcrel.  I'm sure you want to optimise it better, but
it's not clear to me how it fails now?

Please say in the comment what is wrong, don't spread fear :-)

> +# No AltiVec or VSX or MMA instructions when building kernel
>  KBUILD_CFLAGS += $(call cc-option,-mno-altivec)
>  KBUILD_CFLAGS += $(call cc-option,-mno-vsx)
> +KBUILD_CFLAGS += $(call cc-option,-mno-mma)

MMA code is never generated unless the code asks for it explicitly.
This is fundamental, not just an implementations side effect.


Segher