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
