RE: [PATCH v2] Support Intel AVX10.1

["Jiang, Haochen" <haochen.jiang@intel.com>]

> -----Original Message-----
> From: Jan Beulich <jbeulich@suse.com>
> Sent: Friday, August 18, 2023 9:03 PM
> To: Jiang, Haochen <haochen.jiang@intel.com>
> Cc: hjl.tools@gmail.com; binutils@sourceware.org
> Subject: Re: [PATCH v2] Support Intel AVX10.1
> 
> On 14.08.2023 08:45, Haochen Jiang wrote:
> > @@ -1315,6 +1321,20 @@ output_i386_opcode (FILE *table, const char
> *name, char *str,
> >    ident = mkident (name);
> >    fprintf (table, "  { MN_%s, 0x%0*llx%s, %u,",
> >  	   ident, 2 * (int)length, opcode, end, i);
> > +
> > +  j = strlen(ident);
> > +  /* All AVX512F based instructions are usable for AVX10.1 except
> > +     AVX512PF/ER/4FMAPS/4VNNIW/VP2INTERSECT.  */  if (strstr
> > + (cpu_flags, "AVX512")
> > +      && !strstr (cpu_flags, "AVX512PF")
> > +      && !strstr (cpu_flags, "AVX512ER")
> > +      && !strstr (cpu_flags, "4FMAPS")
> > +      && !strstr (cpu_flags, "4VNNIW")
> > +      && !strstr (cpu_flags, "VP2INTERSECT"))
> > +    {
> > +      cpu_flags = concat (cpu_flags, "|AVX10_1", NULL);
> > +      k = 1;
> > +    }
> >    free (ident);
> 
> While making a patch myself along the lines of what I had outlined, I came to
> realize that the above isn't enough. (I'm pretty sure I wouldn't have spotted
> this by merely reviewing your patch.) This may be a result of the spec being
> somewhat ambiguous when it comes to GFNI, VAES, and VPCLMULQDQ.
> There's a note there saying something about the respective EVEX encodings.
> But that still requires the VEX encodings connected to these three features to
> also become suitably available. While this works fine for GFNI, it doesn't for
> the other two: The 128-bit VEX encodings, which surely are available when the
> 256-bit ones are, would become impossible to use. The assembler would pick
> the (larger) EVEX forms instead. There are two ways to solve this that I can see
> right away:
> 1) AES becomes a dependency of VAES (and PCLMULQDQ one of
> VPCLMULQDQ)
> 2) We put in place extra templates.
> I'm wary of the first option as long as not at least informally supported by you
> (Intel). Hence I went with option 2 for now.
> 
> I'm only done with the /512 patch, so I won't post right away. I'm still
> debating with myself whether to control maximum vector length via a new
> directive, or via a special form of .arch.

Hi Jan,

Do you think a command line option like -mavx10maxvl=256/512 with default 512
is ok for this scenario? I am working to revise the AVX10.1 patch like that.

Thx,
Haochen

> 
> Jan