fold-const.c (fold_binary): Fold (X & 1) ^ 1 as (X & 1) == 0.

	* fold-const.c (fold_binary) <BIT_XOR_EXPR>: Fold (X & 1) ^ 1 as
	(X & 1) == 0.
	<BIT_AND_EXPR>: Fold (X ^ 1) & 1 and ~X & 1 as (X & 1) == 0.

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

From-SVN: r111454

gcc/ChangeLog

 2006-02-26  Roger Sayle  <roger@eyesopen.com>
+
+	* fold-const.c (fold_binary) <BIT_XOR_EXPR>: Fold (X & 1) ^ 1 as
+	(X & 1) == 0.
+	<BIT_AND_EXPR>: Fold (X ^ 1) & 1 and ~X & 1 as (X & 1) == 0.
+
+2006-02-26  Roger Sayle  <roger@eyesopen.com>
 	    James A. Morrison  <phython@gcc.gnu.org>
 
 	PR middle-end/21137

gcc/fold-const.c

@@ -8740,6 +8740,13 @@ fold_binary (enum tree_code code, tree type, tree op0, tree op1)
 			    fold_convert (type, TREE_OPERAND (arg0, 0)),
 			    fold_convert (type, TREE_OPERAND (arg1, 0)));
 
+      /* Fold (X & 1) ^ 1 as (X & 1) == 0.  */
+      if (TREE_CODE (arg0) == BIT_AND_EXPR
+	  && integer_onep (TREE_OPERAND (arg0, 1))
+	  && integer_onep (arg1))
+	return fold_build2 (EQ_EXPR, type, arg0,
+			    build_int_cst (TREE_TYPE (arg0), 0));
+
       /* See if this can be simplified into a rotate first.  If that
 	 is unsuccessful continue in the association code.  */
       goto bit_rotate;
@@ -8792,6 +8799,28 @@ fold_binary (enum tree_code code, tree type, tree op0, tree op1)
 	  && reorder_operands_p (arg0, TREE_OPERAND (arg1, 0)))
 	return omit_one_operand (type, arg0, TREE_OPERAND (arg1, 0));
 
+      /* Fold (X ^ 1) & 1 as (X & 1) == 0.  */
+      if (TREE_CODE (arg0) == BIT_XOR_EXPR
+	  && integer_onep (TREE_OPERAND (arg0, 1))
+	  && integer_onep (arg1))
+	{
+	  tem = TREE_OPERAND (arg0, 0);
+	  return fold_build2 (EQ_EXPR, type,
+			      fold_build2 (BIT_AND_EXPR, TREE_TYPE (tem), tem,
+					   build_int_cst (TREE_TYPE (tem), 1)),
+			      build_int_cst (TREE_TYPE (tem), 0));
+	}
+      /* Fold ~X & 1 as (X & 1) == 0.  */
+      if (TREE_CODE (arg0) == BIT_NOT_EXPR
+	  && integer_onep (arg1))
+	{
+	  tem = TREE_OPERAND (arg0, 0);
+	  return fold_build2 (EQ_EXPR, type,
+			      fold_build2 (BIT_AND_EXPR, TREE_TYPE (tem), tem,
+					   build_int_cst (TREE_TYPE (tem), 1)),
+			      build_int_cst (TREE_TYPE (tem), 0));
+	}
+
       t1 = distribute_bit_expr (code, type, arg0, arg1);
       if (t1 != NULL_TREE)
 	return t1;

gcc/testsuite/ChangeLog

 2006-02-26  Roger Sayle  <roger@eyesopen.com>
 
+	* gcc.dg/fold-even-1.c: New test case.
+
+2006-02-26  Roger Sayle  <roger@eyesopen.com>
+
 	PR middle-end/21137
 	* gcc.dg/fold-eqandshift-1.c: New test case.
 

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

+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-original" } */
+int test1(int a)
+{
+  return !(a & 1);
+}
+
+int test2(int b)
+{
+  return (b & 1) == 0;
+}
+
+int test3(int c)
+{
+  return (c & 1) ^ 1;
+}
+
+int test4(int d)
+{
+  return (d ^ 1) & 1;
+}
+
+int test5(int e)
+{
+  return ~e & 1;
+}
+
+/* { dg-final { scan-tree-dump-times "\\(a \& 1\\) == 0" 1 "original" } } */
+/* { dg-final { scan-tree-dump-times "\\(b \& 1\\) == 0" 1 "original" } } */
+/* { dg-final { scan-tree-dump-times "\\(c \& 1\\) == 0" 1 "original" } } */
+/* { dg-final { scan-tree-dump-times "\\(d \& 1\\) == 0" 1 "original" } } */
+/* { dg-final { scan-tree-dump-times "\\(e \& 1\\) == 0" 1 "original" } } */
+/* { dg-final { cleanup-tree-dump "original" } } */