re PR middle-end/80222 (may_alias folded away)

2017-03-28  Richard Biener  <rguenther@suse.de>

	PR middle-end/80222
	* gimple-fold.c (gimple_fold_indirect_ref): Do not touch
	TYPE_REF_CAN_ALIAS_ALL references.
	* fold-const.c (fold_indirect_ref_1): Likewise.

	* g++.dg/pr80222.C: New testcase.

From-SVN: r246527

gcc/ChangeLog

+2017-03-28  Richard Biener  <rguenther@suse.de>
+
+	PR middle-end/80222
+	* gimple-fold.c (gimple_fold_indirect_ref): Do not touch
+	TYPE_REF_CAN_ALIAS_ALL references.
+	* fold-const.c (fold_indirect_ref_1): Likewise.
+
 2017-03-28  Martin Liska  <mliska@suse.cz>
 
 	PR ipa/80104

gcc/fold-const.c

@@ -14006,7 +14006,8 @@ fold_indirect_ref_1 (location_t loc, tree type, tree op0)
 
   STRIP_NOPS (sub);
   subtype = TREE_TYPE (sub);
-  if (!POINTER_TYPE_P (subtype))
+  if (!POINTER_TYPE_P (subtype)
+      || TYPE_REF_CAN_ALIAS_ALL (TREE_TYPE (op0)))
     return NULL_TREE;
 
   if (TREE_CODE (sub) == ADDR_EXPR)

gcc/gimple-fold.c

@@ -6539,8 +6539,8 @@ gimple_get_virt_method_for_binfo (HOST_WIDE_INT token, tree known_binfo,
   return gimple_get_virt_method_for_vtable (token, v, offset, can_refer);
 }
 
-/* Given a pointer value OP0, return a simplified version of an
-   indirection through OP0, or NULL_TREE if no simplification is
+/* Given a pointer value T, return a simplified version of an
+   indirection through T, or NULL_TREE if no simplification is
    possible.  Note that the resulting type may be different from
    the type pointed to in the sense that it is still compatible
    from the langhooks point of view. */
@@ -6554,7 +6554,8 @@ gimple_fold_indirect_ref (tree t)
 
   STRIP_NOPS (sub);
   subtype = TREE_TYPE (sub);
-  if (!POINTER_TYPE_P (subtype))
+  if (!POINTER_TYPE_P (subtype)
+      || TYPE_REF_CAN_ALIAS_ALL (ptype))
     return NULL_TREE;
 
   if (TREE_CODE (sub) == ADDR_EXPR)

gcc/testsuite/ChangeLog

+2017-03-28  Richard Biener  <rguenther@suse.de>
+
+	PR middle-end/80222
+	* g++.dg/pr80222.C: New testcase.
+
 2017-03-28  Martin Liska  <mliska@suse.cz>
 
 	PR ipa/80104

gcc/testsuite/g++.dg/pr80222.C

+// { dg-do compile }
+// { dg-options "-O2 -fdump-tree-optimized" } */
+
+struct C { int i; }__attribute__((may_alias)) ;
+
+C a, b;
+
+int main()
+{
+  a = static_cast <C&> (b);
+}
+
+// { dg-final { scan-tree-dump "{ref-all}\\\)&b\];" "optimized" } } */