Use clz instruction to calculate integer logarithms, speeds up decoding of one flac 8 sample by 12%.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@23783 a1c6a512-1295-4272-9138-f99709370657

1 files changed, 8 insertions, 0 deletions

diff --git a/apps/codecs/libffmpegFLAC/golomb.h b/apps/codecs/libffmpegFLAC/golomb.h
index 659ecc1579..11753fc4bb 100644
--- a/apps/codecs/libffmpegFLAC/golomb.h
+++ b/apps/codecs/libffmpegFLAC/golomb.h
@@ -21,6 +21,13 @@
 
 #include <limits.h>
 
+#if (defined(CPU_ARM) && (ARM_ARCH > 4))
+static inline int av_log2(uint32_t v)
+{
+    return 31 - __builtin_clz(v);
+}
+#else
+
 /* From libavutil/common.h */
 extern const uint8_t ff_log2_tab[256];
 
@@ -41,6 +48,7 @@ static inline int av_log2(unsigned int v)
 
     return n;
 }
+#endif
 
 /**
  * @file golomb.h