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;
}