[FFmpeg-devel] [PATCH 2/3] lavu/rational: use av_unlikely in av_d2q

[Ganesh Ajjanagadde]

From: Ganesh Ajjanagadde <gajjanagadde at gmail.com>

Merely a simple illustration of av_unlikely's utility; there are
certainly more interesting use cases.

Actual performance benefit is impossible to accurately quantify due to the
context-dependence of the branch predictor. Nonetheless, as a ballpark
estimate, it yields ~ 5% improvements in testing via FATE on x86-64, Haswell+GCC.

Signed-off-by: Ganesh Ajjanagadde <gajjanagadde at gmail.com>
---
 libavutil/rational.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/libavutil/rational.c b/libavutil/rational.c
index 6b3f50a..3e841ad 100644
--- a/libavutil/rational.c
+++ b/libavutil/rational.c
@@ -108,9 +108,9 @@ AVRational av_d2q(double d, int max)
     AVRational a;
     int exponent;
     int64_t den;
-    if (isnan(d))
+    if (av_unlikely(isnan(d)))
         return (AVRational) { 0,0 };
-    if (fabs(d) > INT_MAX + 3LL)
+    if (av_unlikely(fabs(d) > INT_MAX + 3LL))
         return (AVRational) { d < 0 ? -1 : 1, 0 };
     frexp(d, &exponent);
     exponent = FFMAX(exponent-1, 0);
-- 
2.7.1