[Bug target/31897] New: [Regression 4.3] 30% speed regression with -m32 on Opteron with rnflow

[burnus at gcc dot gnu dot org]

The Polyhedron test case rnflow is runs since 20 April 30% slower than before.

gfortran -m32 -march=opteron -ffast-math -funroll-loops -ftree-vectorize
-ftree-loop-linear -O3 rnflow.f90

Today's gfortran: real    0m58.205s / user    0m56.600s
gfortran 2007-04-20 (r123986): real    0m58.237s / user    0m56.396s
gfortran 2007-04-16 (r123859): real    0m43.912s / user    0m42.403s
gfortran 4.2.0: real    0m45.449s / user    0m43.859s

This only affects that compiliation with that options.

Using the following option:

gfortran -m32 -march=opteron -ffast-math -funroll-loops -ftree-loop-linear
-ftree-vectorize -mfpmath=sse -msse3 -O3

or compiling for a 64bit system does not show this slowdown.

See also:
http://physik.fu-berlin.de/~tburnus/gcc-trunk/benchmark/run-rnflow.png
http://physik.fu-berlin.de/~tburnus/gcc-trunk/benchmark/
and for x86-64 which is not affected, see also:
http://www.suse.de/~gcctest/c++bench/polyhedron/polyhedron-summary.txt-2-0.html

The benchmark can be obtained from:
http://www.polyhedron.co.uk/pb05/polyhedron_benchmark_suite.html
directory: pb05/lin/source


-- 
           Summary: [Regression 4.3] 30% speed regression with -m32 on
                    Opteron with rnflow
           Product: gcc
           Version: 4.3.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: normal
          Priority: P3
         Component: target
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: burnus at gcc dot gnu dot org
GCC target triplet: x86_64-unknown-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31897