On Wed, Aug 22, 2012 at 12:50:18PM +0100, Måns Rullgård wrote: > Mans Rullgard <m...@mansr.com> writes: > > > GCC 4.3 and later do the right thing with the plain C code. Earlier > > versions in 32-bit mode generate one extra instruction, needlessly > > zeroing what would be the high half of the shifted value. At least > > two gcc configurations miscompile the inline asm in some situations. > > > > In 64-bit mode, all gcc versions generate imul r64, r64 followed by > > shr. On Intel i7 and later, this imul is faster 32-bit mul. On > > older Intel and all AMD, it is slightly slower. On Atom it is much > > slower. > > > > Considering where the FASTDIV macro is used, any overall negative > > performance impact of this change should be negligible. If anyone > > cares, they should file a bug against gcc and get the instruction > > selection fixed. > > > > Signed-off-by: Mans Rullgard <m...@mansr.com> > > --- > > libavutil/intmath.h | 2 -- > > libavutil/x86/intmath.h | 37 ------------------------------------- > > 2 files changed, 39 deletions(-) > > delete mode 100644 libavutil/x86/intmath.h > > ping
no objections so it should be OK I'm in favour of this patch. _______________________________________________ libav-devel mailing list libav-devel@libav.org https://lists.libav.org/mailman/listinfo/libav-devel
