x86: Support Intel AVX VNNI

[Cui, Lili]

> > >>> Is this (including the new cpuvex_prefix attribute, which imo
> > >>> shouldn't be a Cpu* bit) really needed? Couldn't you achieve the
> > >>> same by placing the templates _after_ the AVX512 counterparts?
> > >>> Iirc templates get tried in order, and the first match wins. The
> > >>> {vex3} prefix would then prevent a match on the EVEX-encoded
> > >>> AVX512_VNNI
> > >> templates.
> > >>
> > >> Lili, please look into it.
> > >>
> > >
> > > I add an invalid test for it, we need cpuvex_prefix attribute for under
> scenario.
> > >
> > > .arch .noavx512_vnni
> > > vpdpbusd %xmm2,%xmm4,%xmm2
> > >
> > > As without the pseudo {vex} prefix, this instruction should be encoded
> with EVEX prefix.
> > > we should report error for it, I rename CpuVEX_PREFIX to
> > > PseudoVexPrefix and move it into opcode_modifier bit, thanks.
> >
> > I disagree, unless AVX-VNNI was specified to have a dependency on
> > AVX512-VNNI (which would seem pretty odd, as meanwhile I've noticed
> > that another reason for introducing these encodings may be to allow
> > their use on AVX512-incapable hardware). The above very much should
> > result in the VEX encoding despite the absence of a {vex} prefix.
> > It's really only the default case of everything being enabled where
> > the pseudo-prefix should be mandated. This particularly implies that
> > an explicit ".arch .avx_vnni" ought to _also_ eliminate the need for
> > the pseudo prefix.
> 
> AVX VNNI always requires the {vex} prefix.  It isn't optional.
> It is similar to
> 
> vmovdqu32 %xmm5, %xmm6
> 
> vs
> 
> vmovdqu %xmm5, %xmm6
> 
> It is the 32 suffix vs the {vex} prefix.
> 
> > > --- /dev/null
> > > +++ b/gas/testsuite/gas/i386/avx-vnni-inval.s
> > > @@ -0,0 +1,9 @@
> > > +# Check illegal in AVXVNNI instructions
> > > +
> > > +     .text
> > > +     .arch .noavx512_vnni
> > > +_start:
> > > +     vpdpbusd %xmm2,%xmm4,%xmm2
> > > +
> > > +     .intel_syntax noprefix
> > > +     vpdpbusd %xmm2,%xmm4,%xmm2
> >
> > I question the need for Intel syntax tests in test cases like this
> > one.
> 
> Please only keep the AT&T syntax test.

Done.
Thanks,
Lili.

> --
> H.J.
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