Enable redundancy elimination for array loads.

tests/language/optimize_redundant_array_load.dart

Index: tests/language/optimize_redundant_array_load.dart
===================================================================
--- tests/language/optimize_redundant_array_load.dart	(revision 0)
+++ tests/language/optimize_redundant_array_load.dart	(revision 0)
@@ -0,0 +1,29 @@
+// 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 optimization of redundant array loads.
+
+var A = [0,2,3];
+
+test1(a) {
+  int x = a[0];
+  int y = a[1];
+  ++a[0];
+  return a[0] + y + a[2];
+}
+
+
+int test2(a) {
+  return a[2] + a[2];
+}
+
+
+main() {
+  for (int i = 0; i < 10000; i++) {
+    test1(A);
+    test2(A);
+  }
+  Expect.equals(10006, test1(A));
+  Expect.equals(6, test2(A));
+}