[Bug tree-optimization/20742] New: [4.0/4.1 Regression] Hang in tree_ssa_iv_optimize_loop

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

The following testcase (simplified from lmbench) causes major compile time
regression in tree_ssa_iv_optimize_loop.
Without -DHANG (and with -O2), HEAD gcc needs 0m34.176s, while with GCC 3.4.x
0m0.035s.  On 4.0 branch it even takes substantially longer.
lmbench has 100 such lines, which would take longer than anybody could wait.

-- 
           Summary: [4.0/4.1 Regression] Hang in tree_ssa_iv_optimize_loop
           Product: gcc
           Version: 4.0.0
            Status: UNCONFIRMED
          Severity: critical
          Priority: P2
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: jakub at gcc dot gnu dot org
                CC: gcc-bugs at gcc dot gnu dot org,rakdver at gcc dot gnu
                    dot org,sebastian dot pop at cri dot ensmp dot fr


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20742