1 files changed, 46 insertions, 5 deletions
diff --git a/libavutil/intmath.h b/libavutil/intmath.h
index 0ad30123e8..b4b87e6059 100644
--- a/libavutil/intmath.h
+++ b/libavutil/intmath.h
@@ -21,6 +21,8 @@
 #ifndef AVUTIL_INTMATH_H
 #define AVUTIL_INTMATH_H
 
+#include <stdint.h>
+
 #include "config.h"
 #include "attributes.h"
 
@@ -31,15 +33,54 @@
 
 #if HAVE_FAST_CLZ && AV_GCC_VERSION_AT_LEAST(3,4)
 
-#ifndef av_log2
-#   define av_log2(x) (31 - __builtin_clz((x)|1))
-#   ifndef av_log2_16bit
-#      define av_log2_16bit av_log2
+#ifndef ff_log2
+#   define ff_log2(x) (31 - __builtin_clz((x)|1))
+#   ifndef ff_log2_16bit
+#      define ff_log2_16bit av_log2
 #   endif
-#endif /* av_log2 */
+#endif /* ff_log2 */
 
 #endif /* AV_GCC_VERSION_AT_LEAST(3,4) */
 
+extern const uint8_t ff_log2_tab[256];
+
+#ifndef ff_log2
+#define ff_log2 ff_log2_c
+static av_always_inline av_const int ff_log2_c(unsigned int v)
+{
+    int n = 0;
+    if (v & 0xffff0000) {
+        v >>= 16;
+        n += 16;
+    }
+    if (v & 0xff00) {
+        v >>= 8;
+        n += 8;
+    }
+    n += ff_log2_tab[v];
+
+    return n;
+}
+#endif
+
+#ifndef ff_log2_16bit
+#define ff_log2_16bit ff_log2_16bit_c
+static av_always_inline av_const int ff_log2_16bit_c(unsigned int v)
+{
+    int n = 0;
+    if (v & 0xff00) {
+        v >>= 8;
+        n += 8;
+    }
+    n += ff_log2_tab[v];
+
+    return n;
+}
+#endif
+
+#define av_log2       ff_log2
+#define av_log2_16bit ff_log2_16bit
+
 /**
  * @}
  */