fold-const.c (fold_unary_loc): Do not strip sign-changes for NEGATE_EXPR.

2011-07-07  Richard Guenther  <rguenther@suse.de>

	* fold-const.c (fold_unary_loc): Do not strip sign-changes
	for NEGATE_EXPR.

	* gcc.dg/ftrapv-3.c: New testcase.

From-SVN: r175976

gcc/ChangeLog

 2011-07-07  Richard Guenther  <rguenther@suse.de>
 
+	* fold-const.c (fold_unary_loc): Do not strip sign-changes
+	for NEGATE_EXPR.
+
+2011-07-07  Richard Guenther  <rguenther@suse.de>
+
 	* tree-vrp.c (simplify_conversion_using_ranges): New function.
 	(simplify_stmt_using_ranges): Call it.
 

gcc/fold-const.c

@@ -7561,7 +7561,7 @@ fold_unary_loc (location_t loc, enum tree_code code, tree type, tree op0)
   if (arg0)
     {
       if (CONVERT_EXPR_CODE_P (code)
-	  || code == FLOAT_EXPR || code == ABS_EXPR)
+	  || code == FLOAT_EXPR || code == ABS_EXPR || code == NEGATE_EXPR)
 	{
 	  /* Don't use STRIP_NOPS, because signedness of argument type
 	     matters.  */

gcc/testsuite/ChangeLog

 2011-07-07  Richard Guenther  <rguenther@suse.de>
 
+	* gcc.dg/ftrapv-3.c: New testcase.
+
+2011-07-07  Richard Guenther  <rguenther@suse.de>
+
 	* gcc.dg/tree-ssa/vrp58.c: New testcase.
 	* gcc.dg/tree-ssa/scev-cast.c: Adjust.
 

gcc/testsuite/gcc.dg/ftrapv-3.c

+/* { dg-do run } */
+/* { dg-options "-ftrapv" } */
+
+extern void abort (void);
+unsigned long
+foo (long i, long j)
+{
+  /* We may not fold this to (unsigned long)(i * j).  */
+  return -(unsigned long)(i * -j);
+}
+int main()
+{
+  if (foo (-__LONG_MAX__ - 1, -1) != -(unsigned long)(-__LONG_MAX__ - 1))
+    abort ();
+  return 0;
+}