x86: Support Intel AVX VNNI

[H.J. Lu]

On Thu, Oct 15, 2020 at 11:10 PM Jan Beulich <jbeulich@suse.com> wrote:
>
> On 15.10.2020 18:15, H.J. Lu wrote:
> > On Thu, Oct 15, 2020 at 9:04 AM Jan Beulich <jbeulich@suse.com> wrote:
> >> On 15.10.2020 17:34, H.J. Lu wrote:
> >>> On Thu, Oct 15, 2020 at 8:28 AM Jan Beulich <jbeulich@suse.com> wrote:
> >>>> I continue to think that the behavior as implemented is not the best
> >>>> possible choice. Therefore I'd like to at least hear the arguments that
> >>>> led to this decision.
> >>>
> >>> Please send me your detailed comments.  I will forward it to our internal
> >>> group.
> >>
> >> I've given my two points already - there are two cases where the
> >> pseudo prefix shouldn't be required. Plus, as also said, the
> >> disassembler shouldn't display it by default.
> >
> > It needs to be much more than that to have any impact on a
> > decision made years ago.
>
> I'm sorry, but again: A decision made internally, years ago or not,
> cannot possibly be the final one in an open source world. It shouldn't
> even need me to provide extended arguments against, when the basic
> request is to first of all supply the reasoning behind that decision.
> Maybe once I know the the train of thought, I agree (and withdraw my
> counter arguments)?
>
> H.J., let me be very clear: Since there's a general pattern here in
> that it often looks like technical disagreement gets resolved simply
> by more or less harsh discarding of arguments (and, not just once,
> deliberate introduction of bugs), I'm very willing to let this
> escalate, as here you even prevent a technical discussion by hiding
> your arguments. The way you drive things in certain cases is, imo,
> not how things ought to be done for open source projects. And yes -
> I'm not forgetting that you're the maintainer, and hence you get the
> final say. (I wonder though whether, given my work over the last
> years, I shouldn't have my maintainership area extended beyond Intel
> syntax aspects, e.g. to all of x86's gas/ and opcodes/.)
>

When AVX VNNI was added, we could either use different mnemonics
from AVX512 VNNI or a {vex} prefix.  We went with {vex} and made it
mandatory to avoid any confusion.

-- 
H.J.