tree-ssa-alias.c (indirect_refs_may_alias_p): Do not treat arrays with same type...

2016-12-01  Richard Biener  <rguenther@suse.de>

	* tree-ssa-alias.c (indirect_refs_may_alias_p): Do not
	treat arrays with same type as objects that cannot overlap.

	* gcc.dg/torture/alias-2.c: New testcase.

From-SVN: r243107

diff --git a/gcc/tree-ssa-alias.c b/gcc/tree-ssa-alias.c
index ebae6cf..10f1677 100644 (file)
--- a/gcc/tree-ssa-alias.c
+++ b/gcc/tree-ssa-alias.c
@@ -1355,7 +1355,10 @@ indirect_refs_may_alias_p (tree ref1 ATTRIBUTE_UNUSED, tree base1,
       && same_type_for_tbaa (TREE_TYPE (base1), TREE_TYPE (ptrtype1)) == 1
       && same_type_for_tbaa (TREE_TYPE (base2), TREE_TYPE (ptrtype2)) == 1
       && same_type_for_tbaa (TREE_TYPE (ptrtype1),
-                            TREE_TYPE (ptrtype2)) == 1)
+                            TREE_TYPE (ptrtype2)) == 1
+      /* But avoid treating arrays as "objects", instead assume they
+         can overlap by an exact multiple of their element size.  */
+      && TREE_CODE (TREE_TYPE (ptrtype1)) != ARRAY_TYPE)
     return ranges_overlap_p (offset1, max_size1, offset2, max_size2);
 
   /* Do type-based disambiguation.  */