Ensure that all phis inserted by load optimizer have consistent representation.

tests/language/load_to_load_forwarding_test.dart

-// Copyright (c) 2012, 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.
-// Test correctness of side effects tracking used by load to load forwarding.
-
-import "package:expect/expect.dart";
-
-class A {
-  var x, y;
-  A(this.x, this.y);
-}
-
-foo(a) {
-  var value1 = a.x;
-  var value2 = a.y;
-  for (var j = 1; j < 4; j++) {
-    value1 |= a.x << (j * 8);
-    a.y += 1;
-    a.x += 1;
-    value2 |= a.y << (j * 8);
-  }
-  return [value1, value2];
-}
-
-bar(a, mode) {
-  var value1 = a.x;
-  var value2 = a.y;
-  for (var j = 1; j < 4; j++) {
-    value1 |= a.x << (j * 8);
-    a.y += 1;
-    if (mode) a.x += 1;
-    a.x += 1;
-    value2 |= a.y << (j * 8);
-  }
-  return [value1, value2];
-}
-
-// Verify that immutable and mutable VM fields (array length in this case)
-// are not confused by load forwarding even if the access the same offset
-// in the object.
-testImmutableVMFields(arr, immutable) {
-  if (immutable) {
-    return arr.length;  // Immutable length load.
-  }
-
-  if (arr.length < 2) {  // Mutable length load, should not be forwarded.
-    arr.add(null);
-  }
-
-  return arr.length;
-}
-
-main() {
-  final fixed = new List(10);
-  final growable = [];
-  testImmutableVMFields(fixed, true);
-  testImmutableVMFields(growable, false);
-  testImmutableVMFields(growable, false);
-
-  for (var i = 0; i < 2000; i++) {
-    Expect.listEquals([0x02010000, 0x03020100], foo(new A(0, 0)));
-    Expect.listEquals([0x02010000, 0x03020100], bar(new A(0, 0), false));
-    Expect.listEquals([0x04020000, 0x03020100], bar(new A(0, 0), true));
-    testImmutableVMFields(fixed, true);
-  }
-
-  Expect.equals(1, testImmutableVMFields([], false));
-  Expect.equals(2, testImmutableVMFields([1], false));
-  Expect.equals(2, testImmutableVMFields([1, 2], false));
-  Expect.equals(3, testImmutableVMFields([1, 2, 3], false));
-}