ff_log2            39 libavutil/intmath.h #   define ff_log2(x) (31 - __builtin_clz((x)|1))
ff_log2            50 libavutil/intmath.h #define ff_log2 ff_log2_c
ff_log2            38 libavutil/x86/intmath.h #       define ff_log2(x) (_bit_scan_reverse((x)|1))
ff_log2            40 libavutil/x86/intmath.h #       define ff_log2 ff_log2_x86