[Bug tree-optimization/56415] New: Performance regression after fix for 56273

["ysrumyan at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56415

             Bug #: 56415
           Summary: Performance regression after fix for 56273
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: ysrumyan@gmail.com


In process of testing x86 platforms we found out that the fix for 56273 caused
-30% regression for one important benchmark. This regression can be
illustraated by attache test (it must be compiled with "-O3 -funroll-loops"
options:

before fix 
time ./t_before.exe 
19

real    0m4.324s
user    0m4.262s
sys     0m0.000s

after fix
time ./t_after.exe 
19

real    0m10.530s
user    0m10.400s
sys     0m0.000s

Note that for 32-bit mode timing is worse.

Test is attached.