Re: x86 ISA v3 / v4 coverage

[Michael Matz <matz@suse.de>]

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".


Ciao,
Michael.