Performance regression on the 4.3 branch?

H. J. Lu hjl@lucon.org
Wed Feb 14 14:22:00 GMT 2007


On Wed, Feb 14, 2007 at 02:34:24PM +0100, Paweł Sikora wrote:
> François-Xavier Coudert napisał(a):
> 
> >$ gcc -march=pentium4 -O3 a.c && time ./a.out
> >064069fbc13963b920219c3e939225e38e38e38e3956d81c71c71c71c0ba0f00
> >./a.out  1.81s user 0.00s system 99% cpu 1.818 total
> >$ gcc-4.3 -march=pentium4 -O3 a.c && time ./a.out
> >064069fbc13963b920219c3e939225e38e38e38e3956d81c71c71c71c0ba0f00
> >./a.out  2.40s user 0.01s system 87% cpu 2.746 total
> >
> >where gcc is gcc version 4.1.1 20070105 (Red Hat 4.1.1-51) and gcc-4.3
> >is gcc version 4.3.0 20070209 (experimental). I don't have a 4.1 or
> >4.2 compiler at hand, so I don't know if it's a 4.2 or 4.3 regression,
> >or even if there's a special patch in redhat 4.1 that makes it
> >lightning fast. But in any case, I wondered if it was known, and if it
> >was worth opening a PR.
> 
> I see this on 4.2 vs 4.3 on my k8 box.
> 
> $ gcc42 -O3 a.c --save-temps && time ./a.out
> 064069fbc13963b920219c3e939225e38e38e38e3956d81c71c71c71c0ba0f00
> ./a.out  0.43s user 0.00s system 92% cpu 0.462 total
> 
> $ gcc43 -O3 a.c --save-temps && time ./a.out
> 064069fbc13963b920219c3e939225e38e38e38e3956d81c71c71c71c0ba0f00
> ./a.out  0.60s user 0.00s system 98% cpu 0.610 total

Is this the saem as

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30735

Can you try gcc 4.3 revision 119759?


H.J.



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