re PR middle-end/36227 (POINTER_PLUS folding introduces undefined overflow)

2008-05-13  Richard Guenther  <rguenther@suse.de>

	PR middle-end/36227
	* fold-const.c (fold_sign_changed_comparison): Do not allow
	changes in pointer-ness.

	* gcc.dg/pr36227.c: New testcase.

From-SVN: r135260

gcc/ChangeLog

+2008-05-13  Richard Guenther  <rguenther@suse.de>
+
+	PR middle-end/36227
+	* fold-const.c (fold_sign_changed_comparison): Do not allow
+	changes in pointer-ness.
+
 2008-05-12  Kaz Kojima  <kkojima@gcc.gnu.org>
 
 	PR target/24713

gcc/fold-const.c

@@ -6831,7 +6831,8 @@ fold_sign_changed_comparison (enum tree_code code, tree type,
 	   && TREE_TYPE (TREE_OPERAND (arg1, 0)) == inner_type))
     return NULL_TREE;
 
-  if (TYPE_UNSIGNED (inner_type) != TYPE_UNSIGNED (outer_type)
+  if ((TYPE_UNSIGNED (inner_type) != TYPE_UNSIGNED (outer_type)
+       || POINTER_TYPE_P (inner_type) != POINTER_TYPE_P (outer_type))
       && code != NE_EXPR
       && code != EQ_EXPR)
     return NULL_TREE;

gcc/testsuite/ChangeLog

+2008-05-13  Richard Guenther  <rguenther@suse.de>
+
+	PR middle-end/36227
+	* gcc.dg/pr36227.c: New testcase.
+
 2008-05-13  Eric Botcazou  <ebotcazou@adacore.com>
 
 	* gnat.dg/discr7.adb: New test

gcc/testsuite/gcc.dg/pr36227.c

+/* { dg-do compile } */
+/* { dg-options "-O2 -Wstrict-overflow=3" } */
+
+volatile unsigned long *
+sat_add(volatile unsigned long *ptr, unsigned long i, volatile unsigned long *end)
+{
+  if ((unsigned long)ptr + i * sizeof(*ptr) > (unsigned long)ptr) /* { dg-bogus "pointer wraparound" } */
+    return ptr + i;
+  else
+    return end;
+}
+