re PR middle-end/52134 (Does not fold (x * 4) & -4)

2012-03-13  Richard Guenther  <rguenther@suse.de>

	PR middle-end/52134
	* fold-const.c (fold_binary_loc): Fold (X * Y) & -(1 << CST) to X * Y
	if Y is a constant multiple of 1 << CST.

	* gcc.dg/pr52134.c: New testcase.

From-SVN: r185334

gcc/ChangeLog

+2012-03-13  Richard Guenther  <rguenther@suse.de>
+
+	PR middle-end/52134
+	* fold-const.c (fold_binary_loc): Fold (X * Y) & -(1 << CST) to X * Y
+	if Y is a constant multiple of 1 << CST.
+
 2012-03-13  Georg-Johann Lay  <avr@gjlay.de>
 
 	PR target/52488

gcc/fold-const.c

@@ -11398,6 +11398,20 @@ fold_binary_loc (location_t loc,
 			      fold_convert_loc (loc, type, arg0));
 	}
 
+      /* Fold (X * Y) & -(1 << CST) to X * Y if Y is a constant
+         multiple of 1 << CST.  */
+      if (TREE_CODE (arg1) == INTEGER_CST)
+	{
+	  double_int cst1 = tree_to_double_int (arg1);
+	  double_int ncst1 = double_int_ext (double_int_neg (cst1),
+					     TYPE_PRECISION (TREE_TYPE (arg1)),
+					     TYPE_UNSIGNED (TREE_TYPE (arg1)));
+	  if (double_int_equal_p (double_int_and (cst1, ncst1), ncst1)
+	      && multiple_of_p (type, arg0,
+				double_int_to_tree (TREE_TYPE (arg1), ncst1)))
+	    return fold_convert_loc (loc, type, arg0);
+	}
+
       /* For constants M and N, if M == (1LL << cst) - 1 && (N & M) == M,
 	 ((A & N) + B) & M -> (A + B) & M
 	 Similarly if (N & M) == 0,

gcc/testsuite/ChangeLog

+2012-03-13  Richard Guenther  <rguenther@suse.de>
+
+	PR middle-end/52134
+	* gcc.dg/pr52134.c: New testcase.
+
 2012-03-13  Rainer Orth  <ro@CeBiTec.Uni-Bielefeld.DE>
 
 	* ada/acats/tests/cd/cdd1001.a (CDD1001): Fix typo.

gcc/testsuite/gcc.dg/pr52134.c

+/* { dg-do compile } */
+/* { dg-options "-fdump-tree-original" } */
+
+unsigned f(unsigned t)
+{
+    return (t*4)&-4;
+}
+int f1(int t)
+{
+    return (t*4)&-4;
+}
+
+/* { dg-final { scan-tree-dump-not "\\\&" "original" } } */
+/* { dg-final { cleanup-tree-dump "original" } } */