re PR tree-optimization/13827 ((a & b) != (c & b) should be transformed to ((a^c) & b) !=0)

	PR tree-optimization/13827
	* fold-const.c (fold_binary) <EQ_EXPR, NE_EXPR>: Fold (X&C) op (Y&C)
	as ((X^Y)&C) op 0.

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

From-SVN: r118727

gcc/ChangeLog

+2006-11-12  Roger Sayle  <roger@eyesopen.com>
+
+	PR tree-optimization/13827
+	* fold-const.c (fold_binary) <EQ_EXPR, NE_EXPR>: Fold (X&C) op (Y&C)
+	as ((X^Y)&C) op 0.
+
 2006-11-12  Zdenek Dvorak <dvorakz@suse.cz>
 
 	* cfgloopmanip.c (update_single_exit_for_duplicated_loop,

gcc/fold-const.c

@@ -10818,6 +10818,49 @@ fold_binary (enum tree_code code, tree type, tree op0, tree op1)
 			    TREE_OPERAND (arg0, 0),
 			    TREE_OPERAND (arg1, 0));
 
+      /* Fold (X & C) op (Y & C) as (X ^ Y) & C op 0", and symmetries.  */
+      if (TREE_CODE (arg0) == BIT_AND_EXPR
+	  && TREE_CODE (arg1) == BIT_AND_EXPR)
+	{
+	  tree arg00 = TREE_OPERAND (arg0, 0);
+	  tree arg01 = TREE_OPERAND (arg0, 1);
+	  tree arg10 = TREE_OPERAND (arg1, 0);
+	  tree arg11 = TREE_OPERAND (arg1, 1);
+	  tree itype = TREE_TYPE (arg0);
+
+	  if (operand_equal_p (arg01, arg11, 0))
+	    return fold_build2 (code, type,
+				fold_build2 (BIT_AND_EXPR, itype,
+					     fold_build2 (BIT_XOR_EXPR, itype,
+							  arg00, arg10),
+					     arg01),
+				build_int_cst (itype, 0));
+
+	  if (operand_equal_p (arg01, arg10, 0))
+	    return fold_build2 (code, type,
+				fold_build2 (BIT_AND_EXPR, itype,
+					     fold_build2 (BIT_XOR_EXPR, itype,
+							  arg00, arg11),
+					     arg01),
+				build_int_cst (itype, 0));
+
+	  if (operand_equal_p (arg00, arg11, 0))
+	    return fold_build2 (code, type,
+				fold_build2 (BIT_AND_EXPR, itype,
+					     fold_build2 (BIT_XOR_EXPR, itype,
+							  arg01, arg10),
+					     arg00),
+				build_int_cst (itype, 0));
+
+	  if (operand_equal_p (arg00, arg10, 0))
+	    return fold_build2 (code, type,
+				fold_build2 (BIT_AND_EXPR, itype,
+					     fold_build2 (BIT_XOR_EXPR, itype,
+							  arg01, arg11),
+					     arg00),
+				build_int_cst (itype, 0));
+	}
+
       return NULL_TREE;
 
     case LT_EXPR:

gcc/testsuite/ChangeLog

+2006-11-12  Roger Sayle  <roger@eyesopen.com>
+
+	PR tree-optimization/13827
+	* gcc.dg/fold-eqand-1.c: New test case.
+
 2006-11-11  Andrew Pinski  <andrew_pinski@playstation.sony.com>
 
 	PR rtl-opt/28812

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

+/* PR tree-optimization/13827 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-original" } */
+
+unsigned foo (unsigned a, unsigned b)
+{
+  return (a & 0xff00) != (b & 0xff00);
+}
+
+unsigned bar (unsigned c, unsigned d)
+{
+  return (c & 0xff00) == (d & 0xff00);
+}
+
+/* { dg-final { scan-tree-dump-times "a \\^ b" 1 "original" } } */
+/* { dg-final { scan-tree-dump-times "c \\^ d" 1 "original" } } */
+/* { dg-final { cleanup-tree-dump "original" } } */