re PR middle-end/32628 (bogus integer overflow warning)

2008-01-16  Richard Guenther  <rguenther@suse.de>

	PR middle-end/32628
	* fold-const.c (fold_convert_const_int_from_int): Do not
	set overflow if that occured only because of a sign extension
	change when converting from/to a sizetype with the same
	precision and signedness.

	* gcc.dg/overflow-warn-7.c: New testcase.

From-SVN: r131579

gcc/ChangeLog

+2008-01-16  Richard Guenther  <rguenther@suse.de>
+
+	PR middle-end/32628
+	* fold-const.c (fold_convert_const_int_from_int): Do not
+	set overflow if that occured only because of a sign extension
+	change when converting from/to a sizetype with the same
+	precision and signedness.
+
 2008-01-16  Uros Bizjak  <ubizjak@gmail.com>
 
 	PR debug/34249

gcc/fold-const.c

@@ -2122,8 +2122,22 @@ fold_convert_const_int_from_int (tree type, const_tree arg1)
   t = force_fit_type_double (type, TREE_INT_CST_LOW (arg1),
 			     TREE_INT_CST_HIGH (arg1),
 		             /* Don't set the overflow when
-		      		converting a pointer  */
-			     !POINTER_TYPE_P (TREE_TYPE (arg1)),
+		      		converting from a pointer,  */
+			     !POINTER_TYPE_P (TREE_TYPE (arg1))
+			     /* or to a sizetype with same signedness
+				and the precision is unchanged.
+				???  sizetype is always sign-extended,
+				but its signedness depends on the
+				frontend.  Thus we see spurious overflows
+				here if we do not check this.  */
+			     && !((TYPE_PRECISION (TREE_TYPE (arg1))
+				   == TYPE_PRECISION (type))
+				  && (TYPE_UNSIGNED (TREE_TYPE (arg1))
+				      == TYPE_UNSIGNED (type))
+				  && ((TREE_CODE (TREE_TYPE (arg1)) == INTEGER_TYPE
+				       && TYPE_IS_SIZETYPE (TREE_TYPE (arg1)))
+				      || (TREE_CODE (type) == INTEGER_TYPE
+					  && TYPE_IS_SIZETYPE (type)))),
 			     (TREE_INT_CST_HIGH (arg1) < 0
 		 	      && (TYPE_UNSIGNED (type)
 				  < TYPE_UNSIGNED (TREE_TYPE (arg1))))

gcc/testsuite/ChangeLog

+2008-01-16  Richard Guenther  <rguenther@suse.de>
+
+	PR middle-end/32628
+	* gcc.dg/overflow-warn-7.c: New testcase.
+
 2008-01-16  Kaveh R. Ghazi  <ghazi@caip.rutgers.edu>
 
 	* gcc.dg/tree-ssa/loop-19.c: Require nonpic.

gcc/testsuite/gcc.dg/overflow-warn-7.c

+/* { dg-do compile } */
+/* { dg-options "-Wall" } */
+
+int f(char *device)
+{
+  return device == ((char *)0 + ~0UL);  /* { dg-bogus "overflow" } */
+}
+