re PR tree-optimization/15458 (Combine ~ and ^.)

	PR tree-optimization/15458
	* fold-const.c (fold_binary): Optimize ~X ^ C as X ^ ~C, where C
	is a constant.

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

From-SVN: r118152

gcc/ChangeLog

+2006-10-29  Roger Sayle  <roger@eyesopen.com>
+
+	PR tree-optimization/15458
+	* fold-const.c (fold_binary): Optimize ~X ^ C as X ^ ~C, where C
+	is a constant.
+
 2006-10-29  Richard Guenther  <rguenther@suse.de>
 
 	* config/i386/i386-protos.h (ix86_expand_trunc): Declare.

gcc/fold-const.c

@@ -9506,6 +9506,13 @@ 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)));
 
+      /* Convert ~X ^ C to X ^ ~C.  */
+      if (TREE_CODE (arg0) == BIT_NOT_EXPR
+	  && TREE_CODE (arg1) == INTEGER_CST)
+	return fold_build2 (code, type,
+			    fold_convert (type, TREE_OPERAND (arg0, 0)),
+			    fold_build1 (BIT_NOT_EXPR, type, arg1));
+
       /* Fold (X & 1) ^ 1 as (X & 1) == 0.  */
       if (TREE_CODE (arg0) == BIT_AND_EXPR
 	  && integer_onep (TREE_OPERAND (arg0, 1))

gcc/testsuite/ChangeLog

+2006-10-29  Roger Sayle  <roger@eyesopen.com>
+
+	PR tree-optimization/15458
+	* gcc.dg/fold-xornot-1.c: New test case.
+
 2006-10-29  Richard Guenther  <rguenther@suse.de>
 
 	* gcc.target/i386/math-torture/trunc.c: New testcase.

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

+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-original" } */
+
+int foo(int x)
+{
+  return ~(x ^ 4);
+}
+
+int bar(int y)
+{
+  return ~y ^ 4;
+}
+
+/* { dg-final { scan-tree-dump-times "x \\^ -5" 1 "original" } } */
+/* { dg-final { scan-tree-dump-times "y \\^ -5" 1 "original" } } */
+/* { dg-final { cleanup-tree-dump "original" } } */