RE: Intel AVX10.1 Compiler Design and Support

["Jiang, Haochen" <haochen.jiang@intel.com>]

> -----Original Message-----
> From: Richard Biener <richard.guenther@gmail.com>
> Sent: Wednesday, August 23, 2023 3:32 PM
> To: Hongtao Liu <crazylht@gmail.com>
> Cc: Jakub Jelinek <jakub@redhat.com>; Jiang, Haochen
> <haochen.jiang@intel.com>; ZiNgA BuRgA <zingaburga@hotmail.com>; gcc-
> patches@gcc.gnu.org
> Subject: Re: Intel AVX10.1 Compiler Design and Support
> 
> On Tue, Aug 22, 2023 at 4:36 PM Hongtao Liu <crazylht@gmail.com> wrote:
> >
> > On Tue, Aug 22, 2023 at 9:54 PM Jakub Jelinek <jakub@redhat.com> wrote:
> > >
> > > On Tue, Aug 22, 2023 at 09:35:44PM +0800, Hongtao Liu wrote:
> > > > Ok, then we can't avoid TARGET_AVX10_1 in those existing 256/128-bit
> > > > evex instruction patterns.
> > >
> > > Why?
> > > Internally for md etc. purposes, we should have the current
> > > TARGET_AVX512* etc. ISA flags, plus one new one, whatever we call it
> > > (TARGET_EVEX512 even if it is not completely descriptive because of kandq
> > > etc., or some other name) which says if 512-bit vector modes can be used,
> > > if g modifier can be used, if the 64-bit mask operations can be used etc.
> > > Plus, if AVX10.1 contains any instructions not covered in the preexisting
> > > TARGET_AVX512* sets, TARGET_AVX10_1 which covers that delta, otherwise
> > > keep -mavx10.1 just as an command line option which enables/disables
> > Let's assume there's no detla now, AVX10.1-512 is equal to
> > AVX512{F,VL,BW,DQ,CD,BF16,FP16,VBMI,VBMI2,VNNI,IFMA,BITALG,
> VPOPCNTDQ}
> > > other stuff.
> > > The current common/config/i386/i386-common.cc OPTION_MASK_ISA*SET*
> would be
> > > like now, except that the current AVX512* sets imply also EVEX512/whatever
> > > it will be called, that option itself enables nothing (or TARGET_AVX512F),
> > > and unsetting it doesn't disable all the TARGET_AVX512*.
> > > -mavx10.1 would enable the AVX512* sets without EVEX512/whatever.
> > So for -mavx512bw -mavx10.1-256, -mavx512bw will set EVEX512, but
> > -mavx10.1-256 doesn't clear EVEX512 but just enable all AVX512* sets?.
> 
> As I said earlier -mavx10.1-256 (and -mavx10.1-512) should not exist.
> So instead
> we'd have -mavx512bw -mavx10.1 where -mavx512bw enables evex512 and
> -mavx10.1 will enable the 10.1 ISAs _not affecting_ whether evex512 is
> set or not.
> 
> We then have the -mevex512 flag (or whatever name we agree to) to enable
> (or disable) 512bit support.
> 
> If you insist on having -mavx10.1-256 that should alias to -mavx10.1 +
> -mno-evex512,
> but Jakub disagrees here, so I'd rather not have it at all.  We could have
> -mavx10.1-512 aliasing to -mavx10.1 + -mevex512 (Jakub would agree here).

We could first work on -mevex512 then further discuss -mavx10.1-256/512 since
these -mavx10.1-256/512 is quite controversial.

Just to clarify, -mno-evex512 -mavx512f should not enable 512 bit vector right?

Thx,
Haochen

> 
> Richard.