[Bug target/32457] [4.3 Regression] Complete program optimized away (i686, -ftree-vectorize)

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

------- Comment #13 from spop at gcc dot gnu dot org  2007-06-26 16:03 -------
Subject: Re:  [4.3 Regression] Complete program optimized away (i686,
-ftree-vectorize)

I just reduced the problem to this snippet: the problem seems to be
that the data dependence analysis is wrong by answering that there is
no dependence on the first loop on RBOUND(N) and RBOUND(N-1) accesses
so I'll have to correct that.

      SUBROUTINE KEEL(RBOUND)
      REAL, DIMENSION(0:100) :: RBOUND
      DO N = 1, NP1
          RBOUND(N) = RBOUND(N-1) + 1
      END DO
      DO N = 1, NS
         WRITE (16,'(I5)') SRAD(N)
      END DO
      END SUBROUTINE KEEL

An auxiliary question, as I'm not programming in FORTRAN, is it okay
to have RBOUND(N-1) for N=1?  I thought that the array indices start
from 1, and not from 0.  As this is in the polyhedron benchmark, I
would say that it is valid code, but I'm a bit shocked ;-)

Sebastian


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32457