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Re: -freduce-all-*


Michael T. Babcock wrote:
I was doing some work with ATLAS and running the author's xmm_gc3 benchmark and noticed the comments associated with the -freduce-all-(movables|givs) options. For what its worth (best speeds are cited):

Without: (/usr/local/gcc-3.4.2/bin/gcc -O3 -fomit-frame-pointer -fforce-addr -march=pentium -mtune=athlon -ftracer -funit-at-a-time -fbranch-probabilities -fsched2-use-superblocks)
./xmm_gc3
ALGORITHM NB REPS TIME MFLOPS
========= ===== ===== ========== ==========
atlasmm 60 3000 0.700 1851.71


With: (/usr/local/gcc-3.4.2/bin/gcc -O3 -fomit-frame-pointer -fforce-addr -march=pentium -mtune=athlon -ftracer -funit-at-a-time -fbranch-probabilities -fmove-all-movables -freduce-all-giv)
./xmm_gc3
ALGORITHM NB REPS TIME MFLOPS
========= ===== ===== ========== ==========
atlasmm 60 3000 0.762 1701.05

Note that you didn't use -fsched2-use-superblocks in your second compile, so they're not completely comparable and do not _only_ test the addition of -fmove-all-movables -freduce-all-givs.


That said, I think I'm going to propose a patch to remove -fmove-all-movables and -freduce-all-givs because they were only useful in an old, and soon to be replaced, part of loop optimization.

--
Toon Moene - e-mail: toon@moene.indiv.nluug.nl - phone: +31 346 214290
Saturnushof 14, 3738 XG  Maartensdijk, The Netherlands
Maintainer, GNU Fortran 77: http://gcc.gnu.org/onlinedocs/g77_news.html
A maintainer of GNU Fortran 95: http://gcc.gnu.org/fortran/


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