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x86/cpu: set avxslow cpuflag on btver2 CPUs 

They are also slow when using 256 bit wide registers

Reviewed-by: Hendrik Leppkes <h.leppkes@gmail.com>
Signed-off-by: James Almer <jamrial@gmail.com>
This commit is contained in:
James Almer 2016-02-07 00:04:59 -03:00
parent ba618bde7f
commit be22bd32fe
1 changed files with 4 additions and 6 deletions
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10
libavutil/x86/cpu.c
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@ -182,13 +182,11 @@ int ff_get_cpu_flags_x86(void)
/* Similar to the above but for AVX functions on AMD processors.
This is necessary only for functions using YMM registers on Bulldozer
based CPUs as they lack 256-bits execution units. SSE/AVX functions
using XMM registers are always faster on them.
and Jaguar based CPUs as they lack 256-bits execution units. SSE/AVX
functions using XMM registers are always faster on them.
AV_CPU_FLAG_AVX and AV_CPU_FLAG_AVXSLOW are both set so that AVX is
used unless explicitly disabled by checking AV_CPU_FLAG_AVXSLOW.
TODO: Confirm if Excavator is affected or not by this once it's
released, and update the check if necessary. Same for btver2. */
if (family == 0x15 && (rval & AV_CPU_FLAG_AVX))
used unless explicitly disabled by checking AV_CPU_FLAG_AVXSLOW. */
if ((family == 0x15 || family == 0x16) && (rval & AV_CPU_FLAG_AVX))
rval |= AV_CPU_FLAG_AVXSLOW;
}