diff options
Diffstat (limited to 'libavutil')
| -rw-r--r-- | libavutil/x86/cpu.c | 17 |
1 files changed, 16 insertions, 1 deletions
diff --git a/libavutil/x86/cpu.c b/libavutil/x86/cpu.c index 4b6cb0df00..6fa4a46567 100644 --- a/libavutil/x86/cpu.c +++ b/libavutil/x86/cpu.c @@ -109,13 +109,28 @@ int ff_get_cpu_flags_x86(void) rval |= AV_CPU_FLAG_MMX; if (ext_caps & (1<<22)) rval |= AV_CPU_FLAG_MMX2; + + /* Allow for selectively disabling SSE2 functions on AMD processors + with SSE2 support but not SSE4a. This includes Athlon64, some + Opteron, and some Sempron processors. MMX, SSE, or 3DNow! are faster + than SSE2 often enough to utilize this special-case flag. + AV_CPU_FLAG_SSE2 and AV_CPU_FLAG_SSE2SLOW are both set in this case + so that SSE2 is used unless explicitly disabled by checking + AV_CPU_FLAG_SSE2SLOW. */ + if (!strncmp(vendor.c, "AuthenticAMD", 12) && + rval & AV_CPU_FLAG_SSE2 && !(ecx & 0x00000040)) { + rval |= AV_CPU_FLAG_SSE2SLOW; + } } if (!strncmp(vendor.c, "GenuineIntel", 12) && family == 6 && (model == 9 || model == 13 || model == 14)) { /* 6/9 (pentium-m "banias"), 6/13 (pentium-m "dothan"), and 6/14 (core1 "yonah") * theoretically support sse2, but it's usually slower than mmx, - * so let's just pretend they don't. */ + * so let's just pretend they don't. AV_CPU_FLAG_SSE2 is disabled and + * AV_CPU_FLAG_SSE2SLOW is enabled so that SSE2 is not used unless + * explicitly enabled by checking AV_CPU_FLAG_SSE2SLOW. The same + * situation applies for AV_CPU_FLAG_SSE3 and AV_CPU_FLAG_SSE3SLOW. */ if (rval & AV_CPU_FLAG_SSE2) rval ^= AV_CPU_FLAG_SSE2SLOW|AV_CPU_FLAG_SSE2; if (rval & AV_CPU_FLAG_SSE3) rval ^= AV_CPU_FLAG_SSE3SLOW|AV_CPU_FLAG_SSE3; } |