On 07/11/2022 06:58, Michael Paquier wrote:
>>> #if defined(_WIN64)
>>> static __forceinline void
>>> spin_delay(void)
>>> {
>>> +#ifdef _M_ARM64
>>> + /*
>>> + * arm64 way of hinting processor for spin loops optimisations
>>> + * ref: https://community.arm.com/support-forums/f/infrastructure-solutions-forum/48654/ssetoneon-faq
>>> + */
>>> + __isb(_ARM64_BARRIER_SY);
>>> +#else
>>> _mm_pause();
>>> +#endif
>>> }
>>> #else
>>> static __forceinline void
>>
>> I think we should just apply this, there seems very little risk of making
>> anything worse, given the gating to _WIN64 && _M_ARM64.
>
> Seems so. Hmm, where does _ARM64_BARRIER_SY come from? Perhaps it
> would be better to have a comment referring to it from a different
> place than the forums of arm, like some actual docs?
_ARM64_BARRIER_SY is defined in Microsoft Arm64 intrinsic documentation
-
https://learn.microsoft.com/en-us/cpp/intrinsics/arm64-intrinsics?view=msvc-170#BarrierRestrictions
I couldn't find something more official for the sse2neon library part.
--
Niyas
