On Tue, Mar 8, 2016 at 9:10 PM, Rostislav Pehlivanov <atomnu...@gmail.com> wrote: > On 9 March 2016 at 01:02, Ronald S. Bultje <rsbul...@gmail.com> wrote: > >> Hi, >> >> On Mon, Mar 7, 2016 at 10:48 PM, Ganesh Ajjanagadde <gajja...@gmail.com> >> wrote: >> >> > This is ~2x faster for y not an integer on Haswell+GCC, and should >> > generally be faster due to the fact that anyway powf essentially does >> > this under the hood. >> > There's two changes here. Which gives the speedup? I don't like the second >> (pow -> exp(log())) if it doesn't give a speedup (I don't see why it would, >> also). >> >> Ronald > > > Since the function is supposed to be inlined maybe GCC is clever enough not > to have a separate branch for the case where nzslope == 2 for that > particular usage of the function? Not sure though. I did see a slight speed > increase just above the noise.
As discussed with Reimar, there are integer power optimizations for powf. The speedup actually comes from the pow -> exp(log()) as suggested by the commit heading. The reason the branch now needs to be manually inserted is that exp(log()*) can't use the integer optimizations. > _______________________________________________ > ffmpeg-devel mailing list > ffmpeg-devel@ffmpeg.org > http://ffmpeg.org/mailman/listinfo/ffmpeg-devel _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
