On Mon, Feb 25, 2013 at 4:04 PM, "René J.V. Bertin" <[email protected]> wrote: > >> René J.V. Bertin <rjvbertin@...> writes: >> >>> The SIMD version ran twice as fast as the scalar version >>> until I used gcc 4.7, which has auto-vectorisation >> >> Unfortunately, turning auto-vectorisation on triggers >> bugs in gcc and is therefore no option;-( > > I've had some time to check up on this. On my system (a Macbook Pro 13" with > a 2.6Ghz i7 running OS X 10.6.8), I only had 4 failing tests after building > for i386 with MacPort's gcc-4.7 with -ftree-vectorize . However, if the > duration of make check is any indication, auto-vectorisation does not give > any performance benefit (or hit); for both, the tests (2nd make check call) > take about 249 seconds.
That's because __builtin_assume_aligned isn't being called (most likely, didn't check). That results in **far** sub-optimal vectorization. I don't know about the failing tests though. _______________________________________________ Libav-user mailing list [email protected] http://ffmpeg.org/mailman/listinfo/libav-user
