On Wed, May 29, 2013 at 04:08:57PM +0200, Martijn van Beurden wrote:
> I was surprised to see that the Windows compile on wine actually
> outperformed the native Linux one. Probably GCC 4.6 optimized a little
> better or something very weird is going on in wine, I don't know. The
> assembly optimizations work very well on encoding, but actually slow
> things down when decoding. The difference is not very large however.
In a quick test with a pre 4.8 gcc on a Core 2 CPU I see a small
improvement in decoding speed with assembly optimizations turned on,
but I think the difference used to be larger. Perhaps the compilers
got better or MMX is slower relative to normal code on current CPUs.
Disabling the FLAC__bitreader_read_rice_signed_block_asm_ia32_bswap
function seems to help a bit. (there is an #if disabling the function
with comment "OPT: not clearly faster, needs more testing" in the
src/libFLAC/stream_decoder.c file)
Here is the relative decoding speed with -5 and -8:
-5 -8
no asm 99.0% 97.0%
asm 100.0% 100.0%
asm (no ia32_bswap) 102.7% 102.7%
I think we should drop that assembly function as the C
version seems to be faster now.
Can anyone confirm this?
Thanks,
--
Miroslav Lichvar
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