Re: [PATCH 00/18] Support -mevex512 for AVX512

[ZiNgA BuRgA <zingaburga@hotmail.com>]

That sounds about right.  The code I had in mind would perhaps look like:


#if defined(__AVX512BW__) && defined(__AVX512VL__)
     #if defined(__EVEX256__) && !defined(__EVEX512__)
         // compiled code is AVX10.1/256 and AVX512 compatible
     #else
         // compiled code is only AVX512 compatible
     #endif

     // some code which only uses 256b instructions
     __m256i...
#endif


The '__EVEX256__' define would avoid needing to check compiler versions.
Hopefully you can align it with whatever Clang does: 
https://discourse.llvm.org/t/rfc-design-for-avx10-feature-support/72661/18

Thanks!

On 28/09/2023 12:26 pm, Hu, Lin1 wrote:
> Hi,
>
> Thanks for you reply.
>
> I'd like to verify that our understanding of your requirements is correct, and that __EVEX256__ can be considered a default macro to determine whether the compiler supports the __EVEX***__ series of switches.
>
> For example:
>
> I have a segment of code like:
> #if defined(__EVEX512__):
> __mm512.*__;
> #else
> __mm256.*__;
> #endif
>
> But __EVEX512__ is undefined that doesn't mean I only need 256bit, maybe I use gcc-13, so I can still use 512bit.
>
> So the code should be:
> #if defined(__EVEX512__):
> __mm512.*__;
> #elif defined(__EVEX256__):
> __mm256.*__;
> #else
> __mm512.*__;
> #endif
>
> If we understand correctly, we'll consider the request. But since we're about to have a vacation, follow-up replies may be a bit slower.
>
> BRs,
> Lin
>
> -----Original Message-----
> From: ZiNgA BuRgA <zingaburga@hotmail.com>
> Sent: Thursday, September 28, 2023 8:32 AM
> To: Hu, Lin1 <lin1.hu@intel.com>; gcc-patches@gcc.gnu.org
> Subject: Re: [PATCH 00/18] Support -mevex512 for AVX512
>
> Thanks for the new patch!
>
> I see that there's a new __EVEX512__ define.  Will there be some __EVEX256__ (or maybe some max EVEX width) define, so that code can detect whether the compiler supports AVX10.1/256 without resorting to version checks?
>
>