-freduce-all-givs and fortran

[Dan Nicolaescu]

How about the following code?

It shows another issue that occurs in swim from SPEC
(for the people that have access to SPEC, look at subroutine calc1)

      SUBROUTINE TEST
      PARAMETER(N=100,M=113)
      COMMON /COM/ A(N,M), B(N,M), C(N,M), D(N,M)
      DO I = 1, N
         DO J = 1, M
            A(I,J) = B(I+1,J) + C(I,J)
            D(I,J) = B(I+1,J) + C(I,J)
         ENDDO
      ENDDO
      END


      SUBROUTINE TEST2
      PARAMETER(N=100,M=113)
      COMMON /COM/ A(N,M), B(N,M), C(N,M), D(N,M)
      DO I = 1, N
         DO J = 1, M
            A(I,J) = B(I,J) + C(I,J)
            D(I,J) = B(I,J) + C(I,J)
         ENDDO
      ENDDO
      END


The innner loop for both functions as compiled by 3.0 -O2 on SPARC:

In the first subroutine:

.LL9:
        ld      [%i5], %f2
        addcc   %g1, -1, %g1
        ld      [%i2], %f3
        add     %i5, 400, %i5
        fadds   %f3, %f2, %f3
        st      %f3, [%i4]         <- after this store
        ld      [%i2], %f4         <- this is reloaded
        add     %i4, 400, %i4
        fadds   %f4, %f2, %f4
        add     %i2, 400, %i2
        st      %f4, [%i3]
        bpos    .LL9
        add     %i3, 400, %i3




In the second one everything is fine:


.LL22:
        ld      [%i5], %f2
        addcc   %g1, -1, %g1
        ld      [%i4], %f3
        add     %i5, 400, %i5
        fadds   %f2, %f3, %f2
        add     %i4, 400, %i4
        st      %f2, [%i3]
        st      %f2, [%i2]
        add     %i2, 400, %i2
        bpos    .LL22
        add     %i3, 400, %i3