re PR middle-end/30322 (((-i-1) + i) +1) is turned into ~i + (i+1) and never…

re PR middle-end/30322 (((-i-1) + i) +1) is turned into ~i + (i+1) and never into 0 on the tree level)


	PR middle-end/30322
	* fold-const.c (fold_binary): Fold X + ~X and ~X + X into -1 when
	we don't care about trapping overflow.  Only convert -A - 1 into ~A
	when we don't care about trapping overflow.

	* gcc.dg/fold-plusnot-1.c: New test case.

From-SVN: r120300

gcc/ChangeLog

+2006-12-31  Roger Sayle  <roger@eyesopen.com>
+
+	PR middle-end/30322
+	* fold-const.c (fold_binary): Fold X + ~X and ~X + X into -1 when
+	we don't care about trapping overflow.  Only convert -A - 1 into ~A
+	when we don't care about trapping overflow.
+
 2006-12-31  Richard Guenther  <rguenther@suse.de>
 
 	PR middle-end/30338

gcc/fold-const.c

@@ -8662,6 +8662,26 @@ fold_binary (enum tree_code code, tree type, tree op0, tree op1)
 	  if (integer_zerop (arg1))
 	    return non_lvalue (fold_convert (type, arg0));
 
+	  /* ~X + X is -1.  */
+	  if (TREE_CODE (arg0) == BIT_NOT_EXPR
+	      && operand_equal_p (TREE_OPERAND (arg0, 0), arg1, 0)
+	      && !TYPE_TRAP_SIGNED (type))
+	    {
+	      t1 = build_int_cst (type, -1);
+	      t1 = force_fit_type (t1, 0, false, false);
+	      return omit_one_operand (type, t1, arg1);
+	    }
+
+	  /* X + ~X is -1.  */
+	  if (TREE_CODE (arg1) == BIT_NOT_EXPR
+	      && operand_equal_p (arg0, TREE_OPERAND (arg1, 0), 0)
+	      && !TYPE_TRAP_SIGNED (type))
+	    {
+	      t1 = build_int_cst (type, -1);
+	      t1 = force_fit_type (t1, 0, false, false);
+	      return omit_one_operand (type, t1, arg0);
+	  }
+
 	  /* If we are adding two BIT_AND_EXPR's, both of which are and'ing
 	     with a constant, and the two constants have no bits in common,
 	     we should treat this as a BIT_IOR_EXPR since this may produce more
@@ -9002,7 +9022,8 @@ fold_binary (enum tree_code code, tree type, tree op0, tree op1)
       /* Convert -A - 1 to ~A.  */
       if (INTEGRAL_TYPE_P (type)
 	  && TREE_CODE (arg0) == NEGATE_EXPR
-	  && integer_onep (arg1))
+	  && integer_onep (arg1)
+	  && !TYPE_TRAP_SIGNED (type))
 	return fold_build1 (BIT_NOT_EXPR, type,
 			    fold_convert (type, TREE_OPERAND (arg0, 0)));
 

gcc/testsuite/ChangeLog

+2006-12-31  Roger Sayle  <roger@eyesopen.com>
+
+	PR middle-end/30322
+	* gcc.dg/fold-plusnot-1.c: New test case.
+
 2006-12-31  Simon Martin  <simartin@users.sourceforge.net>
 
 	PR c++/29731

gcc/testsuite/gcc.dg/fold-plusnot-1.c

+/* PR middle-end/30322 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-original" } */
+
+int test1(int a)
+{
+  return a + ~a;
+}
+
+int test2(int b)
+{
+  return ~b + b;
+}
+
+unsigned int test3(unsigned int c)
+{
+  return c + ~c;
+}
+
+unsigned int test4(unsigned int d)
+{
+  return ~d + d;
+}
+
+/* { dg-final { scan-tree-dump-times "\\+ a" 0 "original" } } */
+/* { dg-final { scan-tree-dump-times "\\+ b" 0 "original" } } */
+/* { dg-final { scan-tree-dump-times "\\+ c" 0 "original" } } */
+/* { dg-final { scan-tree-dump-times "\\+ d" 0 "original" } } */
+/* { dg-final { cleanup-tree-dump "original" } } */
+