[PATCH v3] Support Intel AVX10.2 media instructions

[Jiang, Haochen]

> From: Jan Beulich <jbeulich@suse.com>
> Sent: Tuesday, October 8, 2024 2:09 PM
> 
> On 08.10.2024 04:38, Jiang, Haochen wrote:
> >> From: Jan Beulich <jbeulich@suse.com>
> >> Sent: Monday, September 30, 2024 2:15 PM
> >>
> >> On 28.09.2024 17:12, Jiang, Haochen wrote:
> >>>> From: Jan Beulich <jbeulich@suse.com>
> >>>> Sent: Wednesday, September 25, 2024 10:42 PM
> >>>>
> >>>> On 25.09.2024 16:39, Haochen Jiang wrote:
> >>>>> --- a/opcodes/i386-opc.tbl
> >>>>> +++ b/opcodes/i386-opc.tbl
> >>>>> @@ -3057,11 +3057,15 @@ vpdpwssd<vnni><sat>,
> 0x6652|<sat:opc>,
> >>>> <vnni:avx>_VNNI, Modrm|Space0F38|Src1VVVV
> >>>>>
> >>>>>  // {AVX512,AVX}_VNNI instructions end
> >>>>>
> >>>>> +<vnni_vex:int8:int16:attr:reg:mem,
> $y:_VNNI_INT8:_VNNI_INT16:Vex::,
> >>>> $z:10_2:10_2:Masking|Broadcast|Disp8ShiftVL:RegZMM:Dword>
> >>>>
> >>>> If this really is needed (contrary to previously outlined plans), it
> >>>> wants wrapping across 3 lines (just like is done for other long-ish
> >>>> templates). However, despite you saying something about this in the
> >>>> description, I don't follow why this is needed.
> >>>>
> >>>
> >>> The problem here is for <vnni> template, which is used for
> >>> AVX512_VNNI/AVX_VNNI, $z comes first due to AVX512_VNNI is the
> >>> ISA introduced earlier and we need to place it before the VEX version
> >>> for table order.
> >>>
> >>> But for AVX_VNNI_INT8/16 and AVX10.2, VEX version comes first.
> >>> We need $y placed before $z for table order.
> >>
> >> Well, yes, with that <vnni> can't be re-used. That's why the purging of
> >> <vnni> is placed the way it is, ahead of the AVX-VNNI-INT{8,16} insns,
> >> which are the ones you mean to extend. You'll want a fresh new <vnni>,
> >> with - as you say - VEX ahead of EVEX. But yes, I clearly partially
> >> misguided you by saying to leave alone lines that are already there; I'm
> >> sorry for that. The two vpdpb<dpb>d<sat> and vpdpw<dpw>d<sat> lines
> will
> >> need touching, to add use of said 2nd instance of <vnni>. E.g.
> >>
> >> vpdpb<dpb>d<vnni><sat>, 0x<dpb:pfx>50|<sat:opc>, AVX<vnni:cpu>,
> >>
> Modrm|Space0F38|Src1VVVV|VexW0|<vnni:attr>|CheckOperandSize|NoSu
> >> f, { RegXMM|RegYMM|<vnni:reg>|<vnni:mem>|Unspecified|BaseIndex,
> >> RegXMM|RegYMM|<vnni:reg>, RegXMM|RegYMM|<vnni:reg> }
> >
> > Sorry for the late reply since I am confusing during my holiday when reading
> the
> > example w/o quick codebase access. However, I am even more confusing
> today
> > when I take a look into that.
> >
> > In <vnni> template, all the EVEX stuffs comes first, I suppose it could not be
> solved
> > only adding a <vnni:cpu> or I misunderstood it. The example will still put all
> the evex
> > attributes first.
> 
> Of course. May I emphasize what I said about <vnni> in my earlier reply:
> "That's why the purging of <vnni> is placed the way it is, ..." and "You'll
> want a fresh new <vnni>, with - as you say - VEX ahead of EVEX". Without
> explicit questions raised I'm in trouble seeing how this can be
> misunderstood.

Let's get it clear.

Currently, from my understanding in the discussion, the current code change
(adding a new <vnni_vex>) in assembler is correct and should be okayish to
commit. Is that right? I am confused by the example actually, it is using the old
<vnni>. If that is the case, I have no problem with that.

Thx,
Haochen

> 
> Jan