[Bug target/53967] GCC produces slow code for convolution algorithm with -mfpmath=sse (the AMD_64 default)

[evstupac at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53967

Stupachenko Evgeny <evstupac at gmail dot com> changed:

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--- Comment #12 from Stupachenko Evgeny <evstupac at gmail dot com> 2012-07-18 09:45:15 UTC ---
I tried it at "-O2" and got low performance with -mfpmath=sse. It looks like it
is caused by register dependency (%xmm0) between:

addss    %xmm0, %xmm1
cvtsi2ss    %eax, %xmm0

Renaming %xmm0 in cvtsi2ss to another free register in all such cases resolves
the issue. 

Also you can try "-O2 -funroll-loops", which made "sse" code even faster and
and "-O2 -fschedule-insns" which significantly reduced performance loses in
"sse" case.