VM: Fix bug in aliasing computation.

tests/language/vm/load_to_load_forwarding_vm_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.
 
 // VMOptions=--optimization-counter-threshold=10
 
 import "package:expect/expect.dart";
 import "dart:typed_data";
 
@@ skipping 250 matching lines @@
 testIndexedAliasedStore2(a, b, i) {
   a[0] = 1;
   a[1] = 2;
   if (a == b) {
     b[i] = 3;
   }
   return a[0] + a[1];
 }
 var indices = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
 
+class Z {
+  var x = 42;
+}
+
+var global_array = new List<Z>(1);
+
+side_effect() {
+  global_array[0].x++;
+}
+
+testAliasingStoreIndexed(array) {
+  var z = new Z();
+  array[0] = z;
+  side_effect();
+  return z.x;
+}
+
 main() {
   final fixed = new List(10);
   final growable = [];
   testImmutableVMFields(fixed, true);
   testImmutableVMFields(growable, false);
   testImmutableVMFields(growable, false);
 
   final f64List = new Float64List(2);
   testPhiRepresentation(true, f64List);
   testPhiRepresentation(false, f64List);
@@ skipping 44 matching lines @@
   final array = new List(3);
   for (var i = 0; i < 20; i++) {
     Expect.equals(3, testIndexedNoAlias(array));
   }
   for (var i = 0; i < 20; i++) {
     Expect.equals(5, testIndexedAliasedStore1(array, array));
   }
   for (var i = 0; i < 20; i++) {
     Expect.equals(4, testIndexedAliasedStore2(array, array, indices[1]));
   }
+
+  var test_array = new List(1);
+  for (var i = 0; i < 20; i++) {
+    Expect.equals(43, testAliasingStoreIndexed(global_array));
+  }
 }