[FFmpeg-devel] [PATCH 1/2] libavutil/cpu: Add AV_CPU_FLAG_SLOW_GATHER.
Alan Kelly
alankelly at google.com
Tue Dec 21 21:56:41 EET 2021
This flag is set on Haswell and earlier and all AMD cpus.
---
Checks for family for Haswell. All checks are done where AVX2 flag is
set as this is clearer.
libavutil/cpu.h | 1 +
libavutil/x86/cpu.c | 15 ++++++++++++++-
2 files changed, 15 insertions(+), 1 deletion(-)
diff --git a/libavutil/cpu.h b/libavutil/cpu.h
index ae443eccad..ce9bf14bf7 100644
--- a/libavutil/cpu.h
+++ b/libavutil/cpu.h
@@ -54,6 +54,7 @@
#define AV_CPU_FLAG_BMI1 0x20000 ///< Bit Manipulation Instruction Set 1
#define AV_CPU_FLAG_BMI2 0x40000 ///< Bit Manipulation Instruction Set 2
#define AV_CPU_FLAG_AVX512 0x100000 ///< AVX-512 functions: requires OS support even if YMM/ZMM registers aren't used
+#define AV_CPU_FLAG_SLOW_GATHER 0x2000000 ///< CPU has slow gathers.
#define AV_CPU_FLAG_ALTIVEC 0x0001 ///< standard
#define AV_CPU_FLAG_VSX 0x0002 ///< ISA 2.06
diff --git a/libavutil/x86/cpu.c b/libavutil/x86/cpu.c
index bcd41a50a2..441b4695d5 100644
--- a/libavutil/x86/cpu.c
+++ b/libavutil/x86/cpu.c
@@ -146,8 +146,21 @@ int ff_get_cpu_flags_x86(void)
if (max_std_level >= 7) {
cpuid(7, eax, ebx, ecx, edx);
#if HAVE_AVX2
- if ((rval & AV_CPU_FLAG_AVX) && (ebx & 0x00000020))
+ if ((rval & AV_CPU_FLAG_AVX) && (ebx & 0x00000020)) {
rval |= AV_CPU_FLAG_AVX2;
+ cpuid(1, eax, ebx, ecx, std_caps);
+ family = ((eax >> 8) & 0xf) + ((eax >> 20) & 0xff);
+ model = ((eax >> 4) & 0xf) + ((eax >> 12) & 0xf0);
+ /* Haswell has slow gather */
+ if (!strncmp(vendor.c, "GenuineIntel", 12))
+ if (family == 6 && model < 70)
+ rval |= AV_CPU_FLAG_SLOW_GATHER;
+ /* Zen 3 and earlier have slow gather */
+ if (!strncmp(vendor.c, "AuthenticAMD", 12))
+ if (family <= 0x19)
+ rval |= AV_CPU_FLAG_SLOW_GATHER;
+ }
+
#if HAVE_AVX512 /* F, CD, BW, DQ, VL */
if ((xcr0_lo & 0xe0) == 0xe0) { /* OPMASK/ZMM state */
if ((rval & AV_CPU_FLAG_AVX2) && (ebx & 0xd0030000) == 0xd0030000)
--
2.34.1.173.g76aa8bc2d0-goog
More information about the ffmpeg-devel
mailing list