On Wed, 2008-04-16 at 14:01 +0200, Christian Schoenebeck wrote: > Am Mittwoch, 16. April 2008 12:17:23 schrieb Jens M Andreasen: > > Then you will probably like this run of ./mixdown: > > > > Benchmarking mixdown (WITH coeff): > > pure C++ : 150 ms <-- pretty good, eh? ;-) > > ASM SSE : 140 ms > > GCC vector extensions : 150 ms > > > > This is with -ftree-vectorize added to your compile options. > > Hey, nice! :-) > > But that works only well for the inlined version. If the mixer C(++) function > is located in another object file and the compiler is forced to use real > function calls, then the C(++) result is still worse than the gcc vector > version, even with "-ftree-vectorize":
It is not the function call. Seems more like the vectorizer gets lost? You can get all kinds of information with -ftree-vectorizer-verbose=5 --8<------------------------------------------------------- cppmix.cpp:27: note: dependence distance = 0. cppmix.cpp:27: note: accesses have the same alignment. cppmix.cpp:27: note: dependence distance modulo vf == 0 between *D.2232_8 and *D.2232_8 cppmix.cpp:27: note: not vectorized: can't determine dependence between *D.2235_18 and *D.2232_8 cppmix.cpp:26: note: vectorized 0 loops in function. .. unfortunately, I have no idea excactly what to do with the information? Moving the cpp code back to the main file and adding -funsafe-math-optimizations proves a lot more interresting: Benchmarking mixdown (no coeff): pure C++ : 100 ms ASM SSE : 140 ms GCC vector extensions : 120 ms Benchmarking mixdown (WITH coeff): pure C++ : 120 ms ASM SSE : 150 ms GCC vector extensions : 170 ms One more time for those who missed it the first time, this time commenting out everything but 'pure cpp w coff': Benchmarking mixdown (WITH coeff): pure C++ : 120 ms <-- bloody murder! _______________________________________________ Linux-audio-dev mailing list [email protected] http://lists.linuxaudio.org/mailman/listinfo/linux-audio-dev
