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Re: New GCC releases comparison and comparison of GCC4.4 and LLVM2.5 on SPEC2000


>> 3. Your SPEC FP benchmarks tell me two things: GCC 4.4's fortran support is
>> dramatically better than 4.2's (which llvm 2.5 uses), and your art/mgrid
>> hacks apparently do great stuff :).
> 
> Something like the "art hack" is in ipa-struct-reorg, but it is not
> enabled at any level. If gcc outperforms llvm on art by much, it's
> more likely that some important opportunities for art are being
> overlooked by llvm.
> 
> There also isn't anything special done for mgrid, except predictive
> commoning (CSE around loops) which is not a hack, in the sense it is
> helpful for a lot of numerical code and triggers several times in
> things like generic Fortran blas/lapack routines.

Indeed, we have a couple of benchmark-inspired optimizations for
SPEC2006 (division/modulo power-of-two, see PR26026; and ifcombine), and
we optimize MATMUL (TRANSPOSE (A), B) which helps galgel a lot.  But
both of this may trigger quite a lot on other code, and LLVM also
benefits from the galgel one :-) because it's done in the front-end.

Paolo


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