The following code produces an ICE when compiled with gfortran using the -O and
-fno-automatic flags together. This bug exists in gfortran 4.1.0-0.12, but not
in 4.0.2-8.

$ cat hwhew2.f
      SUBROUTINE HWHEW2(NPART)
      IMPLICIT NONE
      COMPLEX PT5,ZT,ZI
      DOUBLE PRECISION WRN(7)
      INTEGER J,I,NPART,IP1

      DO 11 I=1,NPART-1
      IP1=I+1
      DO 11 J=IP1,NPART

      IF(WRN(I).LT.0) ZT=ZT*ZI
      IF(WRN(J).LT.0) ZT=ZT*ZI

      PT5=CMPLX(.5,0.)

   11 CONTINUE

      RETURN
      END
$ gfortran -c -O -fno-automatic hwhew2.f
hwhew2.f: In function 'hwhew2':
hwhew2.f:1: internal compiler error: in referenced_var_lookup, at tree-dfa.c:591
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See <URL:http://bugzilla.redhat.com/bugzilla> for instructions.