> [AMD Public Use]
>
> Hi Honza,
>
> > -----Original Message-----
> > From: Jan Hubicka <[email protected]>
> > Sent: Wednesday, March 31, 2021 1:15 AM
> > To: Kumar, Venkataramanan <[email protected]>
> > Cc: Uros Bizjak <[email protected]>; [email protected]
> > Subject: Re: [PATCH] [X86_64]: Enable support for next generation AMD Zen3
> > CPU
> >
> > [CAUTION: External Email]
> >
> > Hi,
> > this patch backports the initial support to gcc10 branch. Since the
> > trunk and branch diverged there is non-trivial change to cpuinfo
> > discovery. I do;
> >
> > --- a/libgcc/config/i386/cpuinfo.c
> > +++ b/libgcc/config/i386/cpuinfo.c
> > @@ -111,6 +111,12 @@ get_amd_cpu (unsigned int family, unsigned int model)
> > if (model >= 0x30)
> > __cpu_model.__cpu_subtype = AMDFAM17H_ZNVER2;
> > break;
> > + case 0x19:
> > + __cpu_model.__cpu_type = AMDFAM19H;
> > + /* AMD family 19h version 1. */
> > + if (model <= 0x0f)
> > + __cpu_model.__cpu_subtype = AMDFAM19H_ZNVER3;
> > + break;
> > default:
> > break;
> > }
> >
> > While your patch also sets ZNVER3 for case where VAES is supporte that
> > would require backporting more of logic detecting VAES. Is that
> > necessary?
>
> I think you are referring to the below change.
>
> diff --git a/gcc/config/i386/driver-i386.c b/gcc/config/i386/driver-i386.c
> index ecdad5765d5..2bfa037dd8b 100644
> --- a/gcc/config/i386/driver-i386.c
> +++ b/gcc/config/i386/driver-i386.c
> @@ -455,6 +455,8 @@ const char *host_detect_local_cpu (int argc, const char
> **argv)
> processor = PROCESSOR_GEODE;
> else if (has_feature (FEATURE_MOVBE) && family == 22)
> processor = PROCESSOR_BTVER2;
> + else if (has_feature (FEATURE_VAES))
> + processor = PROCESSOR_ZNVER3;
> else if (has_feature (FEATURE_CLWB))
> processor = PROCESSOR_ZNVER2;
>
> My understanding is that when we use -march=native on znver3 machine it would
> check for "vaes" to detect the machine.
> Otherwise it would detect it as znver2 machine. So we need that detection
> logic.
I was wondering about
+ case 0x19:
+ cpu_model->__cpu_type = AMDFAM19H;
+ /* AMD family 19h version 1. */
+ if (model <= 0x0f)
+ {
+ cpu = "znver3";
+ CHECK___builtin_cpu_is ("znver3");
+ cpu_model->__cpu_subtype = AMDFAM19H_ZNVER3;
+ }
+ else if (has_cpu_feature (cpu_model, cpu_features2,
+ FEATURE_VAES))
+ {
+ cpu = "znver3";
+ CHECK___builtin_cpu_is ("znver3");
+ cpu_model->__cpu_subtype = AMDFAM19H_ZNVER3;
+ }
+ break;
For znver3 we detect the model number and I wonder why we also test the
VAES feature when we don't do that for other families.
Honza
