https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64365
--- Comment #13 from Brooks Moses <brooks at gcc dot gnu.org> ---
FWIW, if you haven't done the 4.9 backport yet, this is what I ended up with.
I'm not sure it's optimal, but it seems to work.
Index: gcc/tree-data-ref.c
===================================================================
--- gcc/tree-data-ref.c (revision 220259)
+++ gcc/tree-data-ref.c (working copy)
@@ -973,6 +973,24 @@
fold_convert (ssizetype, memoff));
memoff = build_int_cst (TREE_TYPE (memoff), 0);
}
+ /* Adjust the offset so it is a multiple of the access type
+ size and thus we separate bases that can possibly be used
+ to produce partial overlaps (which the access_fn machinery
+ cannot handle). */
+ double_int rem;
+ if (TYPE_SIZE_UNIT (TREE_TYPE (ref))
+ && TREE_CODE (TYPE_SIZE_UNIT (TREE_TYPE (ref))) == INTEGER_CST
+ && !integer_zerop (TYPE_SIZE_UNIT (TREE_TYPE (ref))))
+ rem = tree_to_double_int (off).mod
+ (tree_to_double_int (TYPE_SIZE_UNIT (TREE_TYPE (ref))), false,
+ TRUNC_MOD_EXPR);
+ else
+ /* If we can't compute the remainder simply force the initial
+ condition to zero. */
+ rem = tree_to_double_int (off);
+ off = double_int_to_tree (ssizetype, tree_to_double_int (off) - rem);
+ memoff = double_int_to_tree (TREE_TYPE (memoff), rem);
+ /* And finally replace the initial condition. */
access_fn = chrec_replace_initial_condition
(access_fn, fold_convert (orig_type, off));
/* ??? This is still not a suitable base object for
