Re: x86 ISA v3 / v4 coverage

["H.J. Lu" <hjl.tools@gmail.com>]

On Tue, Jun 7, 2022 at 6:13 AM Michael Matz <matz@suse.de> wrote:
>
> Hello,
>
> On Thu, 2 Jun 2022, H.J. Lu via Binutils wrote:
>
> > On Thu, Jun 2, 2022 at 7:31 AM Jan Beulich <jbeulich@suse.com> wrote:
> > >
> > > H.J.,
> > >
> > > the other day I came to notice two apparent anomalies:
> > >
> > > Shouldn't XOP and FMA4 be excluded from v3, just like LWP and TBM are?
> >
> > Yes, they should be excluded since they don't require v3.
> >
> > > Shouldn't AVX512_4FMAPS be excluded from v4, just like AVX512_4VNNIW is?
> >
> > Yes, it should be since it doesn't require v4.
> >
> > > And is it correct for new ISA additions (like not so long ago AVX512-FP16)
> > > to become part of what is covered by v3 or v4? AMX, for example, was
> >
> > AVX512_FP16 requires v4.
>
> But it can't be part of v3 or v4.  New ISA additions never can become
> part of an existing ISA level, once it's released it's fixated.  I just
> wanted to state this explicitely because it seems Jan used "part of vX"
> to mean "binaries stating to require vX can use ISA feature so-and-so",
> whereas you seem to mean "ISA feature so-and-so requires at least vX".
>

This is because the ISA level marker is a minimum requirement.


-- 
H.J.