fold-const.c (fold_binary_loc): Fold (X * CST1) & CST2 to zero or to (X * CST1) & CST2' when...

2012-05-08  Richard Guenther  <rguenther@suse.de>

	* fold-const.c (fold_binary_loc): Fold (X * CST1) & CST2
	to zero or to (X * CST1) & CST2' when CST1 has trailing zeros.

	* gcc.dg/fold-bitand-4.c: New testcase.

From-SVN: r187280

gcc/ChangeLog

+2012-05-08  Richard Guenther  <rguenther@suse.de>
+
+	* fold-const.c (fold_binary_loc): Fold (X * CST1) & CST2
+	to zero or to (X * CST1) & CST2' when CST1 has trailing zeros.
+
 2012-05-08  Georg-Johann Lay  <avr@gjlay.de>
 
 	* Makefile.in (TEXI_GCC_FILES): Add avr-mmcu.texi.

gcc/fold-const.c

@@ -11449,6 +11449,30 @@ fold_binary_loc (location_t loc,
 	    return fold_convert_loc (loc, type, arg0);
 	}
 
+      /* Fold (X * CST1) & CST2 to zero if we can, or drop known zero
+         bits from CST2.  */
+      if (TREE_CODE (arg1) == INTEGER_CST
+	  && TREE_CODE (arg0) == MULT_EXPR
+	  && TREE_CODE (TREE_OPERAND (arg0, 1)) == INTEGER_CST)
+	{
+	  int arg1tz
+	    = double_int_ctz (tree_to_double_int (TREE_OPERAND (arg0, 1)));
+	  if (arg1tz > 0)
+	    {
+	      double_int arg1mask, masked;
+	      arg1mask = double_int_not (double_int_mask (arg1tz));
+	      arg1mask = double_int_ext (arg1mask, TYPE_PRECISION (type),
+					 TYPE_UNSIGNED (type));
+	      masked = double_int_and (arg1mask, tree_to_double_int (arg1));
+	      if (double_int_zero_p (masked))
+		return omit_two_operands_loc (loc, type, build_zero_cst (type),
+					      arg0, arg1);
+	      else if (!double_int_equal_p (masked, tree_to_double_int (arg1)))
+		return fold_build2_loc (loc, code, type, op0,
+					double_int_to_tree (type, masked));
+	    }
+	}
+
       /* 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

+2012-05-08  Richard Guenther  <rguenther@suse.de>
+
+	* gcc.dg/fold-bitand-4.c: New testcase.
+
 2012-05-08  Dehao Chen  <dehao@google.com>
 
 	* gcc.dg/predict-1.c: Check if LOOP_IV_COMPARE static predict

gcc/testsuite/gcc.dg/fold-bitand-4.c

+/* { dg-do compile } */
+/* { dg-options "-O -fdump-tree-original" } */
+
+int foo (int i)
+{
+  return (i * 8) & 5;
+}
+
+unsigned bar (unsigned i)
+{
+  return (i * 6) & 5;
+}
+
+/* { dg-final { scan-tree-dump-times "\\\&" 1 "original" } } */
+/* { dg-final { scan-tree-dump-times "\\\& 4;" 1 "original" } } */
+/* { dg-final { cleanup-tree-dump "original" } } */