[Mesa-dev] [PATCH] gallium/util: fix nondeterministic avx512 detection

[Roland Scheidegger]

Makes sense to me.
Probably should go into stable?

Reviewed-by: Roland Scheidegger <sroland at vmware.com>

Am 19.07.2017 um 21:29 schrieb Tim Rowley:
> cpuid.7 requires cx=0 to select the extended feature leaf.
> 
> avx512 detection was using the non-indexed cpuid resulting
> in random non-detection of avx512.
> ---
>  src/gallium/auxiliary/util/u_cpu_detect.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/src/gallium/auxiliary/util/u_cpu_detect.c b/src/gallium/auxiliary/util/u_cpu_detect.c
> index 3d6ccb5822..4e71041bc9 100644
> --- a/src/gallium/auxiliary/util/u_cpu_detect.c
> +++ b/src/gallium/auxiliary/util/u_cpu_detect.c
> @@ -438,7 +438,7 @@ util_cpu_detect(void)
>            (xgetbv() & (0x7 << 5)) && // OPMASK: upper-256 enabled by OS
>            ((xgetbv() & 6) == 6)) { // XMM/YMM enabled by OS
>           uint32_t regs3[4];
> -         cpuid(0x00000007, regs3);
> +         cpuid_count(0x00000007, 0x00000000, regs3);
>           util_cpu_caps.has_avx512f    = (regs3[1] >> 16) & 1;
>           util_cpu_caps.has_avx512dq   = (regs3[1] >> 17) & 1;
>           util_cpu_caps.has_avx512ifma = (regs3[1] >> 21) & 1;
>