x86: Support Intel AVX VNNI

[H.J. Lu]

On Thu, Oct 15, 2020 at 4:46 AM Cui, Lili <lili.cui@intel.com> wrote:
>
> > > >>> 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.

OK.

Thanks.


-- 
H.J.