@@ -911,6 +911,7 @@ HAVE_LIST="

     libdc1394_1

     libdc1394_2

     llrint

+    log2

     loongson

     lrint

     lrintf

@@ -2078,7 +2079,7 @@ check_lib math.h sin -lm

 check_lib va/va.h vaInitialize -lva

 # test for C99 functions in math.h

-for func in llrint lrint lrintf round roundf truncf; do

+for func in llrint log2 lrint lrintf round roundf truncf; do

     check_exec <<EOF && enable $func || disable $func

 #include <math.h>

 int main(void) { return ($func(3.999f) > 0)?0:1; }

@@ -265,6 +265,13 @@ static av_always_inline av_const long long llrint(double x)

 }

 #endif /* HAVE_LLRINT */

+#if !HAVE_LOG2

+static av_always_inline av_const double log2(double x)

+{

+    return log(x) * 1.44269504088896340736;

+}

+#endif /* HAVE_LOG2 */

+

 #if !HAVE_LRINT

 static av_always_inline av_const long int lrint(double x)

 {