re PR middle-end/27116 (Incorrect integer division (wrong sign).)

2006-06-08  Richard Guenther  <rguenther@suse.de>

	PR middle-end/27116
	* fold-const.c (negate_expr_p): We can negate BIT_NOT_EXPR
	only, if overflow is defined and not trapping.
	(negate_expr): Likewise.

	* gcc.dg/torture/pr27116.c: New testcase.
	* gcc.dg/pr15785-1.c: Remove test for invalid transformation.

From-SVN: r114483

gcc/ChangeLog

+2006-06-08  Richard Guenther  <rguenther@suse.de>
+
+	PR middle-end/27116
+	* fold-const.c (negate_expr_p): We can negate BIT_NOT_EXPR
+	only, if overflow is defined and not trapping.
+	(negate_expr): Likewise.
+
 2006-06-07  Zdenek Dvorak <dvorakz@suse.cz>
 
 	PR tree-optimization/27872

gcc/fold-const.c

@@ -945,7 +945,9 @@ negate_expr_p (tree t)
       /* Check that -CST will not overflow type.  */
       return may_negate_without_overflow_p (t);
     case BIT_NOT_EXPR:
-       return INTEGRAL_TYPE_P (type);
+       return INTEGRAL_TYPE_P (type)
+       	      && (TYPE_UNSIGNED (type)
+	      	  || (flag_wrapv && !flag_trapv));
 
     case REAL_CST:
     case NEGATE_EXPR:
@@ -1047,7 +1049,9 @@ negate_expr (tree t)
     {
     /* Convert - (~A) to A + 1.  */
     case BIT_NOT_EXPR:
-      if (INTEGRAL_TYPE_P (type))
+      if (INTEGRAL_TYPE_P (type)
+      	  && (TYPE_UNSIGNED (type)
+	      || (flag_wrapv && !flag_trapv)))
         return fold_build2 (PLUS_EXPR, type, TREE_OPERAND (t, 0),
                             build_int_cst (type, 1));
       break;

gcc/testsuite/ChangeLog

+2006-06-08  Richard Guenther  <rguenther@suse.de>
+
+	PR middle-end/27116
+	* gcc.dg/torture/pr27116.c: New testcase.
+	* gcc.dg/pr15785-1.c: Remove test for invalid transformation.
+
 2006-06-07  Zdenek Dvorak <dvorakz@suse.cz>
 
 	PR rtl-optimization/26449

gcc/testsuite/gcc.dg/pr15785-1.c

@@ -11,11 +11,6 @@ void b (int x) {
 		link_error ();
 }
 
-void c (int x) {
-	if (!(- (~x) - x))
-		link_error ();
-}
-
 void d (int x) {
 	if (!(~ (-x) - x))
 		link_error ();
@@ -34,7 +29,6 @@ void f (int x) {
 int main (int argc, char *argv[]) {
 	a(argc);
 	b(argc);
-	c(argc);
 	d(argc);
 	e(argc);
 	f(argc);

gcc/testsuite/gcc.dg/torture/pr27116.c

+/* { dg-do run } */
+
+extern void abort(void);
+
+int f(int a, int b)
+{
+  return (-1 - a) / (-b);
+}
+
+int main()
+{
+  if (f(__INT_MAX__, 2) != __INT_MAX__/2 + 1)
+    abort ();
+  return 0;
+}