Re: [PATCH 07/12] percpu: #ifndef __SIZEOF_INT128__

[Arnd Bergmann]

On Wed, May 31, 2023, at 15:08, Peter Zijlstra wrote:
> Some 64bit architectures do not advertise __SIZEOF_INT128__ on all
> supported compiler versions. Notably the HPPA64 only started doing
> with GCC-11.

I checked the other compilers to be sure that anything else
we support (gcc-5.1 and up) across all 64-bit architectures
does support int128.

It would be nice to have the hack more localized to parisc
and guarded with a CONFIG_GCC_VERSION check so we can kill
it off in the future, once we drop either gcc-10 or parisc
support.

> +#ifndef __SIZEOF_INT128__
> +#define raw_cpu_generic_try_cmpxchg_memcmp(pcp, ovalp, nval)		\
> +({									\
> +	typeof(pcp) *__p = raw_cpu_ptr(&(pcp));				\
> +	typeof(pcp) __val = *__p, __old = *(ovalp);			\
> +	bool __ret;							\
> +	if (!__builtin_memcmp(&__val, &__old, sizeof(pcp))) {		\
> +		*__p = nval;						\
> +		__ret = true;						\
> +	} else {							\
> +		*(ovalp) = __val;					\
> +		__ret = false;						\
> +	}								\
> +	__ret;								\
> +})
> +
> +#define raw_cpu_generic_cmpxchg_memcmp(pcp, oval, nval)			\
> +({									\
> +	typeof(pcp) __old = (oval);					\
> +	raw_cpu_generic_try_cmpxchg_memcpy(pcp, &__old, nval);		\
> +	__old;								\
> +})

Instead of having this in include/asm-generic under
!__SIZEOF_INT128__, could you just move this into the parisc
files with a compiler version check?

     Arnd