re PR middle-end/80533 (Alias analysis of zero length array does not recognize…

re PR middle-end/80533 (Alias analysis of zero length array does not recognize accesses beyond end of array)

2017-04-27  Richard Biener  <rguenther@suse.de>

	PR middle-end/80533
	* emit-rtl.c (set_mem_attributes_minus_bitpos): When
	stripping ARRAY_REFs from MEM_EXPR make sure we're not
	keeping a reference to a trailing array.

From-SVN: r247327

gcc/ChangeLog

 2017-04-27  Richard Biener  <rguenther@suse.de>
 
+	PR middle-end/80533
+	* emit-rtl.c (set_mem_attributes_minus_bitpos): When
+	stripping ARRAY_REFs from MEM_EXPR make sure we're not
+	keeping a reference to a trailing array.
+
+2017-04-27  Richard Biener  <rguenther@suse.de>
+
 	PR middle-end/80539
 	* tree-chrec.c (chrec_fold_plus_poly_poly): Deal with not
 	being in loop-closed SSA form conservatively.

gcc/emit-rtl.c

@@ -1954,7 +1954,10 @@ set_mem_attributes_minus_bitpos (rtx ref, tree t, int objectp,
 	  while (TREE_CODE (t2) == ARRAY_REF);
 
 	  if (DECL_P (t2)
-	      || TREE_CODE (t2) == COMPONENT_REF)
+	      || (TREE_CODE (t2) == COMPONENT_REF
+		  /* For trailing arrays t2 doesn't have a size that
+		     covers all valid accesses.  */
+		  && ! array_at_struct_end_p (t, false)))
 	    {
 	      attrs.expr = t2;
 	      attrs.offset_known_p = false;