[Bug target/32086] New: 10% to 20% Performance Regression Between 4.1.3 and 4.3

["burnus at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

The program induct.f90 of the Polyhedron testsuite,
http://www.polyhedron.co.uk/pb05/polyhedron_benchmark_suite.html, runs about
10% slower under 4.3 than under 4.1.3 (20070430 prerelease SUSE Linux).

A cut-down testcase "test2.f90 (attachment 13611 of PR 32084) shows the same
result. At least for the testcase, the original tree is almost identical for
4.3 and 4.1.3 which means that the difference must be the middle or backend.

Timings (w/o "volatile"):

a) gfortran -march=opteron -ffast-math -funroll-loops -ftree-vectorize
-ftree-loop-linear -msse3 -O3

induct.f90: 51.65 [100%] vs 46.94 [ 90%] for gfortran 4.3 vs. 4.1.3
test2.f90:   4.60 [100%] vs  4.18 [ 91%]

b) gfortran -m32 -march=opteron -ffast-math -funroll-loops -ftree-vectorize
-ftree-loop-linear -O3

induct.f90: 61.41 [100%] vs 46.94 [ 76%]
test2.f90:   5.45 [100%] vs  4.54 [ 83%]

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

induct.f90: 46.12 [100%] vs 46.94 [102%]  (4.3 is better :-)
test2.f90:   4.14 [100%] vs  3.96 [ 96%]

(For the other polyhedron test cases, the performance loss is less: tfft 4%
slower, protein 3%, doduc 3%, channel 2%; in total 4.3 is faster, for fatigue
4.1.3 takes twice as long as 4.3. See:
http://physik.fu-berlin.de/~tburnus/gcc-trunk/benchmark/#rt)


-- 
           Summary: 10% to 20% Performance Regression Between 4.1.3 and 4.3
           Product: gcc
           Version: 4.3.0
            Status: UNCONFIRMED
          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
OtherBugsDependingO 32084
             nThis:


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32086