On 25 February 2016 at 13:20, Ganesh Ajjanagadde <gajja...@gmail.com> wrote:
> From: Ganesh Ajjanagadde <gajjanaga...@gmail.com> > > These use __builtin_expect, and may be useful for optimizing nearly > certain branches, to yield size and/or speed improvements. > > Note that this is used in the Linux kernel for the same purpose. For > some idea as to potential benefits, see e.g > http://blog.man7.org/2012/10/how-much-do-builtinexpect-likely-and.html. > > Signed-off-by: Ganesh Ajjanagadde <gajjanaga...@gmail.com> > --- > libavutil/attributes.h | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/libavutil/attributes.h b/libavutil/attributes.h > index 5c6b9de..1547033 100644 > --- a/libavutil/attributes.h > +++ b/libavutil/attributes.h > @@ -58,6 +58,14 @@ > # define av_warn_unused_result > #endif > > +#if AV_GCC_VERSION_AT_LEAST(3,0) > +# define av_likely(x) __builtin_expect(!!(x), 1) > +# define av_unlikely(x) __builtin_expect(!!(x), 0) > +#else > +# define av_likely(x) (x) > +# define av_unlikely(x) (x) > +#endif > + > #if AV_GCC_VERSION_AT_LEAST(3,1) > # define av_noinline __attribute__((noinline)) > #elif defined(_MSC_VER) > Ive used these builtins before and can confirm that they are useful (although requires devs to use them obviously). I will also point out that these are also supported by ICC/ICL as well. _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
