[FFmpeg-devel] [RFC] use av_get_cpu_flags for real runtime CPU detection in swscale

[Janne Grunau]

Hi,

attached patch implements runtime CPU detection in libswscale. One minor
problem is that it changes behaviour on existing code which sets
individual flags but obviously not the new SWS_CPU_CAPS_FORCE. I think
it's acceptable since the flags have no effect with
!CONFIG_RUNTIME_CPUDETECT.

Janne
-------------- next part --------------
diff --git a/swscale.h b/swscale.h
index 4e11c9a..ca63796 100644
--- a/swscale.h
+++ b/swscale.h
@@ -30,7 +30,7 @@
 #include "libavutil/avutil.h"
 
 #define LIBSWSCALE_VERSION_MAJOR 0
-#define LIBSWSCALE_VERSION_MINOR 11
+#define LIBSWSCALE_VERSION_MINOR 12
 #define LIBSWSCALE_VERSION_MICRO 0
 
 #define LIBSWSCALE_VERSION_INT  AV_VERSION_INT(LIBSWSCALE_VERSION_MAJOR, \
@@ -93,6 +93,7 @@ const char *swscale_license(void);
 #define SWS_CPU_CAPS_ALTIVEC  0x10000000
 #define SWS_CPU_CAPS_BFIN     0x01000000
 #define SWS_CPU_CAPS_SSE2     0x02000000
+#define SWS_CPU_CAPS_FORCE    0x00100000
 
 #define SWS_MAX_REDUCE_CUTOFF 0.002
 
diff --git a/utils.c b/utils.c
index e9400f8..9375489 100644
--- a/utils.c
+++ b/utils.c
@@ -44,6 +44,7 @@
 #include "libavutil/avutil.h"
 #include "libavutil/bswap.h"
 #include "libavutil/pixdesc.h"
+#include "libavutil/cpu.h"
 
 unsigned swscale_version(void)
 {
@@ -722,7 +723,26 @@ static int handle_jpeg(enum PixelFormat *format)
 
 static int update_flags_cpu(int flags)
 {
-#if !CONFIG_RUNTIME_CPUDETECT //ensure that the flags match the compiled variant if cpudetect is off
+#if CONFIG_RUNTIME_CPUDETECT
+    int cpuflags;
+
+    if (!(flags & SWS_CPU_CAPS_FORCE)) {
+        flags &= ~(SWS_CPU_CAPS_MMX|SWS_CPU_CAPS_MMX2|SWS_CPU_CAPS_3DNOW|SWS_CPU_CAPS_ALTIVEC|SWS_CPU_CAPS_BFIN);
+
+        cpuflags = av_get_cpu_flags();
+
+        if (ARCH_X86 && cpuflags & AV_CPU_FLAG_MMX)
+            flags |= SWS_CPU_CAPS_MMX;
+        if (ARCH_X86 && cpuflags & AV_CPU_FLAG_MMX2)
+            flags |= SWS_CPU_CAPS_MMX2;
+        if (ARCH_X86 && cpuflags & AV_CPU_FLAG_3DNOW)
+            flags |= SWS_CPU_CAPS_3DNOW;;
+        if (ARCH_X86 && cpuflags & AV_CPU_FLAG_SSE2)
+            flags |= SWS_CPU_CAPS_SSE2;
+        if (ARCH_PPC && cpuflags & AV_CPU_FLAG_ALTIVEC)
+            flags |= SWS_CPU_CAPS_ALTIVEC;
+    }
+#else //ensure that the flags match the compiled variant if cpudetect is off
     flags &= ~(SWS_CPU_CAPS_MMX|SWS_CPU_CAPS_MMX2|SWS_CPU_CAPS_3DNOW|SWS_CPU_CAPS_ALTIVEC|SWS_CPU_CAPS_BFIN);
     flags |= ff_hardcodedcpuflags();
 #endif /* CONFIG_RUNTIME_CPUDETECT */