x86 ISA v3 / v4 coverage

[Michael Matz]

Hello,

On Tue, 7 Jun 2022, H.J. Lu wrote:

> > > > 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.

Then we are in agreement.  I merely wouldn't call that "be part of", like 
I wouldn't call AVX to be a part of SSE2.


Ciao,
Michael.