[Bug tree-optimization/43349] New: very long compile time for gamess with -floop-interchange

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

Benchmark test 416.gamess from SPEC CPU2006 takes a very long time to compile
with current trunk on powerpc64-linux (both -m32 and -m64) with "-O2
-floop-interchange".  The slowdown started between r157243 on 20100305 and
r157293 on 20100308.  Here's a minimized testcase that takes several minutes
now, but much less than a second before the slowdown:

      SUBROUTINE BUG(A,B,X,Y,Z,N)
      IMPLICIT NONE
      DOUBLE PRECISION A(*),B(*),X(*),Y(*),Z(*)
      INTEGER N,J,K
      K = 0
      DO J = 1,N
         K = K+1
         X(K) = B(J+N*7)
         Y(K) = B(J+N*8)
         Z(K) = B(J+N*2)  + A(J+N*2)
         K = K+1
         X(K) = B(J+N*3)  + A(J+N*3)
         Y(K) = B(J+N*9)  + A(J)
         Z(K) = B(J+N*15)
         K = K+1
         X(K) = B(J+N*4)  + A(J+N*4)
         Y(K) = B(J+N*15)
         Z(K) = B(J+N*10) + A(J)
         K = K+1
         X(K) = B(J+N*11) + A(J+N)
         Y(K) = B(J+N*5)  + A(J+N*5)
         Z(K) = B(J+N*16)
         K = K+1
         X(K) = B(J+N*16)
         Y(K) = B(J+N*6)  + A(J+N*6)
         Z(K) = B(J+N*12) + A(J+N)
         K = K+1
         X(K) = B(J+N*13) + A(J+N*2)
         Y(K) = B(J+N*17)
         Z(K) = B(J+N*7)  + A(J+N*7)
      ENDDO
      RETURN
      END


-- 
           Summary: very long compile time for gamess with -floop-
                    interchange
           Product: gcc
           Version: 4.5.0
            Status: UNCONFIRMED
          Keywords: compile-time-hog
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: janis at gcc dot gnu dot org
GCC target triplet: powerpc64-linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43349