Re: [PATCH 7/8] Support APX NF

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

On Thu, Nov 2, 2023 at 3:47 AM Cui, Lili <lili.cui@intel.com> wrote:
>
> > Subject: Re: [PATCH 7/8] Support APX NF
> >
> > On 02.11.2023 11:15, Cui, Lili wrote:
> > >> On 19.09.2023 17:25, Cui, Lili wrote:
> > >>> @@ -7652,6 +7680,13 @@ match_template (char mnem_suffix)
> > >>>     continue;
> > >>>   }
> > >>>
> > >>> +      /* Check if nf prefix are valid.  */
> > >>> +      if (check_NfPrefix (t))
> > >>> + {
> > >>> +   specific_error = progress (i.error);
> > >>> +   continue;
> > >>> + }
> > >>
> > >> Is it helpful (e.g. diagnostic-wise) to have this check so late? If
> > >> so, is it useful to "continue" when this is the only thing that doesn't match?
> > >> No other template is going to match in such an event, afaict.
> > >>
> > >
> > > Yes, it is useful to continue.
> > > For example" {nf}  add  $123, %bl "
> > > In order, we first find legacy add, then the judgment finds they don’t match,
> > then continue to find the second template which has NF.
> > >
> > > add, 0x83/0, 0, Modrm|No_bSuf|No_sSuf|HLEPrefixLock, { Imm8S,
> > > Reg16|Reg32|Reg64|Word|Dword|Qword|Unspecified|BaseIndex } add,
> > > 0x83/0, APX_F, Modrm|No_bSuf|No_sSuf|EVex128|EVexMap4|NF, { Imm8S,
> > > Reg16|Reg32|Reg64|Word|Dword|Qword|Unspecified|BaseIndex }
> >
> > Hmm, I wonder whether NF-needed-but-no-permitted-by-template shouldn't
> > be a relatively early check: It's pretty cheap and avoids doing a number of
> > more involved checks then.
> >
> Agreed, it's better to put it in the front.
>
>       /* Check AT&T/Intel syntax.  */
>       specific_error = progress (unsupported_syntax);
>       if ((intel_syntax && t->opcode_modifier.attsyntax)
>           || (!intel_syntax && t->opcode_modifier.intelsyntax))
>         continue;
>
> +      /* Check NF support.  */
> +      specific_error = progress (unsupported_nf);
> +      if (i.has_nf && !t->opcode_modifier.nf)
> +       continue;
> +
>        /* Check Intel64/AMD64 ISA.   */
>
> Thanks,
> Lili

We have a long internal discussion.   "{nf} add $123, %eax" is the preferred
syntax.


-- 
H.J.