[Bug tree-optimization/18673] New: [4.0 Regression] PRE is O(N^4)

["belyshev at lubercy dot com" <gcc-bugzilla at gcc dot gnu dot org>]

using same awk script as in comment #2 to bug 18595 and -O1 -fno-ivopts one can
show that pre is O(N^4):

Nloops      Time, s
 50         1.12
 60         3.02
 70         6.41
 80        11.4
 90        19.4
100        30.1
110        44.7
120        64.8
150       163.5

-- 
           Summary: [4.0 Regression] PRE is O(N^4)
           Product: gcc
           Version: 4.0.0
            Status: UNCONFIRMED
          Keywords: compile-time-hog
          Severity: normal
          Priority: P2
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: belyshev at lubercy dot com
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18673