re PR middle-end/30656 (ICE with -ftrapv)

2007-02-01  Richard Guenther  <rguenther@suse.de>

	PR middle-end/30656
	* fold-const.c (fold_negate_expr): Allow negating a
	constant if overflow does not change.

From-SVN: r121460

gcc/ChangeLog

+2007-02-01  Richard Guenther  <rguenther@suse.de>
+
+	PR middle-end/30656
+	* fold-const.c (fold_negate_expr): Allow negating a
+	constant if overflow does not change.
+
 2007-02-01  Ralf Wildenhues  <Ralf.Wildenhues@gmx.de>
 
 	* doc/c-tree.texi (Expression trees): Improve markup.

gcc/fold-const.c

@@ -1109,7 +1109,7 @@ fold_negate_expr (tree t)
       
     case INTEGER_CST:
       tem = fold_negate_const (t, type);
-      if (!TREE_OVERFLOW (tem)
+      if (TREE_OVERFLOW (tem) == TREE_OVERFLOW (t)
 	  || !TYPE_OVERFLOW_TRAPS (type))
 	return tem;
       break;