On Fri, Sep 09, 2011 at 10:26:22AM -0400, Vladimir Makarov wrote: > Yes, Jakub. It would be better to use corei7 with avx for GCC. > Unfortunately, the last tuning which llvm 2.9 supports is core2 > therefore I used -march=core2 for comparison on x86-64. So I think > it would be unfair to use corei7 and avx for GCC without using it > for LLVM.
LLVM 2.9 seems to accept -march=corei7 (though, maybe it just accepts it and tunes fore core2 anyway, haven't checked), doesn't accept -march=corei7-avx. I wonder for which CPUs LLVM actually tunes, because e.g. when I looked at Phoronix benchmarks (PovRay in particular), GCC on that particular "benchmark" lost to LLVM because the configury uses -march=k8 -mtune=k8 for x86_64-linux unconditionally, which wasn't the best tuning for the contemporary Intel CPUs, while LLVM apparently didn't show much difference between k8 and core2i7 tuning, see http://phoronix.com/forums/showthread.php?59341-AMD-Llano-Compiler-Performance&p=224367#post224367 Jakub
