Re: [Qemu-devel] [PATCH v6 15/16] tcg/ppc: Update vector support to v2.07

[Aleksandar Markovic]

On Mon, Jul 1, 2019 at 12:29 PM Richard Henderson
<address@hidden> wrote:
>
> On 7/1/19 5:57 AM, Aleksandar Markovic wrote:
> >
> > On Jun 30, 2019 5:12 PM, "Richard Henderson" <address@hidden
> > <mailto:address@hidden>> wrote:
> >>
> >> On 6/30/19 3:37 PM, Aleksandar Markovic wrote:
> >> >>  bool have_isa_2_06;
> >> >>  bool have_isa_2_06_vsx;
> >> >> +bool have_isa_2_07_vsx;
> >> >
> >> > Does this flag indicate support for PowerISA 2.07 or VSX?
> >>
> >> VSX & 2.07,
> >>
> >> >> +    if (hwcap2 & PPC_FEATURE2_ARCH_2_07) {
> >> >> +        if (hwcap & PPC_FEATURE_HAS_VSX) {
> >> >> +            have_isa_2_07_vsx = true;
> >> >> +        }
> >> >> +    }
> >>
> >> Like so.
> >>
> >> While it would have been possible to have one single have_isa_vsx, we would
> >> then also have to check a second flag to see which revision.  Therefore I
> >> created these composite flags so that we only have to check one.
> >>
> >
> > Yes, but, in this patch, for example, among other things, the support for
> > doubleword integer max/min vector operation is implemented. Why is the
> > existence of that support dependant on VSX (PPC_FEATURE_HAS_VSX)?
>
> Because otherwise the instruction doesn't exist?
>

If we go back to my example, it appears to me that doubleword
integer max/min Altivec instruction do not depend on VSX in any
way, or, at least, I did not find anything in Altivec docs that
mentions it (I could be wrong). The same concern for majority
of Altivec instructions used in this patch. What is your reason
for considering all of them needing VSX?

Regards,
Aleksandar

>
> r~