Recognize pattern (a << b) & c with c being a positive Smi and allow left shift to truncate the res…

tests/standalone/left_shift_bit_and_op_test.dart

Index: tests/standalone/left_shift_bit_and_op_test.dart
===================================================================
--- tests/standalone/left_shift_bit_and_op_test.dart	(revision 0)
+++ tests/standalone/left_shift_bit_and_op_test.dart	(revision 0)
@@ -0,0 +1,75 @@
+// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+//
+// Tests optimizing (a << b) & c if c is a Smi constant.
+
+main() {
+  checkshiftAnd32();
+  checkShiftAnd64();
+  // Optimize shiftAnd32.
+  for (int i = 0; i < 10000; i++) {
+    A.shiftAnd32(12, 17);
+    A.shiftAnd64(12, 17);
+    Expect.equals(72, A.multipleConstantUses(3, 4));
+    Expect.equals(34493956096, A.multipleShiftUse(134742016, 8));
+  }
+  checkshiftAnd32();
+  checkShiftAnd64();
+
+  Expect.throws(() => A.shiftAnd32(12, -5));
+
+  // Check environment dependency.
+  final a = new A(), b = new B();
+  for (var i = 0; i < 10000; i++) {
+    Expect.equals(0, bar(a));
+  }
+  Expect.equals(4294967296, bar(b));
+}
+
+
+checkshiftAnd32() {
+  Expect.equals(1572864, A.shiftAnd32(12, 17));
+  Expect.equals(12, A.shiftAnd32(12, 0));
+  Expect.equals(285212672, A.shiftAnd32(16779392, 17));
+}
+
+
+checkShiftAnd64() {
+  Expect.equals(1125936481173504, A.shiftAnd64(4611694814806147072, 7));
+}
+
+
+class A {
+  static const int MASK_32 = (1 << 30) - 1;
+  static const int MASK_64 = (1 << 62) - 1;
+
+  static shiftAnd32(a, c) {
+    return (a << c) & MASK_32;
+  }
+
+  static shiftAnd64(a, c) {
+    return (a << c) & MASK_64;
+  }
+
+  static multipleConstantUses(a, c) {
+    var j = (a << c) & 0xFF;
+    var k = (a << 3) & 0xFF;
+    return j + k;
+  }
+
+  // Make sure that left shift is nor marked as truncating.
+  static multipleShiftUse(a, c) {
+    var y = (a << c);
+    var x = y & 0x7F;
+    return y + x;
+  }
+
+  foo(x) { return x & 0xf; }
+}
+
+class B { foo(x) { return x; } }
+
+bar (o) {
+  return o.foo(1 << 32);
+}