This is the mail archive of the
gcc-bugs@gcc.gnu.org
mailing list for the GCC project.
[Bug target/27855] reassociation pass produces ~30% slower matrix multiplication code
- From: "ubizjak at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 9 Jul 2007 18:16:49 -0000
- Subject: [Bug target/27855] reassociation pass produces ~30% slower matrix multiplication code
- References: <bug-27855-1649@http.gcc.gnu.org/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Comment #15 from ubizjak at gmail dot com 2007-07-09 18:16 -------
New timings on x86_64 core2 (from [1])
The tests were performed on core2 in 64bit mode, using '-DREPS=10000 -O3 -msse3
-march=core2 -ffast-math' flags, with and without newly introduced
-fno-tree-reassoc flag.
The results were _interesting_, showing extreme differences in the run times:
w/o -fno-tree-reassoc:
ALGORITHM NB REPS TIME MFLOPS
========= ===== ===== ========== ==========
-DTYPE=float: atlasmm 60 10000 2.000 2159.87
-DTYPE=double: atlasmm 60 10000 2.500 1727.89
w/ -fno-tree-reassoc:
ALGORITHM NB REPS TIME MFLOPS
========= ===== ===== ========== ==========
-DTYPE=float: atlasmm 60 10000 0.932 4634.90
-DTYPE=double: atlasmm 60 10000 1.520 2841.93
[1] http://gcc.gnu.org/ml/gcc-patches/2007-07/msg00849.html
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27855