Hello!
The "[patch, vectorizer] misaligned store support" patch [1] resulted in more
than 10% longer execution time for Polyhedron test_fpu test on Core2.
The test is compiled with "-march=x86-64 -ffast-math -funroll-loops -O3",
results are:
time ./a.out
Benchmark running, hopefully as only ACTIVE task
Test1 - Gauss 2000 (101x101) inverts 2.5 sec Err= 0.000000000000006
Test2 - Crout 2000 (101x101) inverts 2.5 sec Err= 0.000000000000015
Test3 - Crout 2 (1001x1001) inverts 2.3 sec Err= 0.000000000000065
Test4 - Lapack 2 (1001x1001) inverts 2.4 sec Err= 0.000000000000250
total = 9.6 sec
real 0m9.864s
user 0m9.778s
sys 0m0.074s
with patch [1] included, vs.:
time ./a.out
Benchmark running, hopefully as only ACTIVE task
Test1 - Gauss 2000 (101x101) inverts 1.9 sec Err= 0.000000000000006
Test2 - Crout 2000 (101x101) inverts 2.5 sec Err= 0.000000000000015
Test3 - Crout 2 (1001x1001) inverts 2.3 sec Err= 0.000000000000065
Test4 - Lapack 2 (1001x1001) inverts 2.0 sec Err= 0.000000000000250
total = 8.6 sec
real 0m8.869s
user 0m8.788s
sys 0m0.068s
when patch [1] is reverted.
The compiler is from today's SVN, "xgcc (GCC) 4.5.0 20090704 (experimental)
[trunk revision 149223]".
The effect of this patch can also be seen on [2], see test_fpu chart between
2009-06-05 and 2009-06-06.
[1] http://gcc.gnu.org/ml/gcc-patches/2009-06/msg00492.html
[2] http://gcc.opensuse.org/c++bench/polyhedron/polyhedron-summary.txt-2-0.html
--
Summary: misaligned store vectorizer patch introduced 10% runtime
regression on Polyhedron test_fpu
Product: gcc
Version: 4.5.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: ubizjak at gmail dot com
GCC build triplet: x86_64-pc-linux-gnu
GCC host triplet: x86_64-pc-linux-gnu
GCC target triplet: x86_64-pc-linux-gnu
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40648
