I found this with gfortran (gcc version 4.3.0 20070328), it seems to work with the gfortran/gcc included in my Mandriva 2007 (gcc version 4.1.1 20060724), so I've marked it as a regression.
$ cat test.f90 SUBROUTINE Test IMPLICIT NONE INTEGER :: i, j REAL*8 :: C(3,100), rM(100), rMI COMMON /RInfo/ rMI DO i = 1, 3 DO j = 1, 100 rMI = C(1,j) + C(i,j) END DO END DO END $ gfortran -c -O2 -ftree-vectorize test.f90 test.f90: In function test: test.f90:1: internal compiler error: in affine_function_equal_p, at tree-data-ref.c:2072 Please submit a full bug report, with preprocessed source if appropriate. See <URL:http://gcc.gnu.org/bugs.html> for instructions. -- Summary: ICE with -O2 -ftree-vectorize (regression) Product: gcc Version: 4.3.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: regression AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: jellby at yahoo dot com http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31383