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