This patch fixes the problem in two steps:
(i) It reverts r162289; and
(ii) It adds the correct initialization for loop.reverse[] in
gfc_trans_assignment_1. This was implemented incorrectly in the fix
for PR24524 (in spite of the correct comment in dependency.c!) and
removed at sometime, I do not know why.
Bootstraps and regtests on x86_64/FC9. OK for trunk and 4.6?
Paul
2011-05-12 Paul Thomas <pa...@gcc.gnu.org>
PR fortran/48955
* dependency.c (gfc_dep_resolver): Revert r162829 which changed
the condition for setting this_dep to GFC_DEP_OVERLAP.
* trans-expr.c (gfc_trans_assignment_1): Enable loop reversal.
2011-05-12 Paul Thomas <pa...@gcc.gnu.org>
PR fortran/48955
* gfortran.dg/dependency_40.f90 : New test.
Index: gcc/fortran/trans-expr.c
===================================================================
*** gcc/fortran/trans-expr.c (revision 173649)
--- gcc/fortran/trans-expr.c (working copy)
*************** gfc_trans_assignment_1 (gfc_expr * expr1
*** 6052,6057 ****
--- 6052,6061 ----
/* Initialize the scalarizer. */
gfc_init_loopinfo (&loop);
+ /* Enable loop reversal. */
+ for (n = 0; n < GFC_MAX_DIMENSIONS; n++)
+ loop.reverse[n] = GFC_CAN_REVERSE;
+
/* Walk the rhs. */
rss = gfc_walk_expr (expr2);
if (rss == gfc_ss_terminator)
Index: gcc/fortran/dependency.c
===================================================================
*** gcc/fortran/dependency.c (revision 173649)
--- gcc/fortran/dependency.c (working copy)
*************** gfc_dep_resolver (gfc_ref *lref, gfc_ref
*** 1832,1839 ****
/* If no intention of reversing or reversing is explicitly
inhibited, convert backward dependence to overlap. */
! if (this_dep == GFC_DEP_BACKWARD
! && (reverse == NULL || reverse[n] == GFC_CANNOT_REVERSE))
this_dep = GFC_DEP_OVERLAP;
}
--- 1832,1839 ----
/* If no intention of reversing or reversing is explicitly
inhibited, convert backward dependence to overlap. */
! if ((reverse == NULL && this_dep == GFC_DEP_BACKWARD)
! || (reverse != NULL && reverse[n] == GFC_CANNOT_REVERSE))
this_dep = GFC_DEP_OVERLAP;
}
Index: gcc/testsuite/gfortran.dg/dependency_40.f90
===================================================================
*** gcc/testsuite/gfortran.dg/dependency_40.f90 (revision 0)
--- gcc/testsuite/gfortran.dg/dependency_40.f90 (revision 0)
***************
*** 0 ****
--- 1,17 ----
+ ! { dg-do run }
+ !Test the fix for PR48955, in which a temporary was not being generated for
+ ! the dependent assignment to 'V1'.
+ !
+ ! Reported by Tobias Burnus <bur...@gcc.gnu.org>
+ !
+ program ala
+ implicit none
+ integer, parameter :: n = 8
+ real, dimension(n) :: v0, v1, v2
+ v0 = [-10.0, -10., -10., -10., 10., 10., 10., 10.]
+ v1 = v0
+ v2 = v0
+ v1(2:n-1) = 0.5*(v1(1:n-2) + v1(3:n) + 2.0*v1(2:n-1)) ! Needs temporary
+ v2(2:n-1) = 0.5*(v0(1:n-2) + v0(3:n) + 2.0*v0(2:n-1))
+ if (any (v1 .ne. v2)) call abort
+ end program ala
