Small cleanup and more test coverage for guarded fields.

tests/language/vm/optimized_guarded_field_test.dart

 // 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.
 // Test correct handling of phis with only environment uses that were inserted
 // by store to load forwarding.
 // VMOptions=--optimization_counter_threshold=10
 
 import "package:expect/expect.dart";
+import "dart:typed_data";
 
 class A {
   var foo;
 }
 
 class B {
   get foo => null;
 }
 
 test(obj) => obj.foo == null ? "null" : "other";
@@ skipping 26 matching lines @@
   try {
     create_error("bar");
   } catch (e) {
     Expect.equals("OK", check_stacktrace(e));
     for (var i=0; i<20; i++) { check_stacktrace(e); }
     Expect.equals("OK", check_stacktrace(e));
   }
 }
 
 
+class D {
+  final List f;
+  final Uint8List g;
+  D(this.f, this.g);
+  D.named(this.f, this.g);
+}
+
+
+test_guarded_length() {
+  var a = new D(new List(5), new Uint8List(5));
+  var b = new D.named(new List(5), new Uint8List(5));
+  Expect.equals(5, a.f.length);
+  Expect.equals(5, b.f.length);
+  Expect.equals(5, a.g.length);
+  Expect.equals(5, b.g.length);
+}
+
+
 main() {
   var a = new A();
   var b = new B();
   // Trigger optimization of test with a polymorphic load.
   // The guarded type of foo is null.
   test(a);
   test(b);
   for (var i = 0; i < 20; ++i) test(a);
   Expect.equals("null", test(a));
   Expect.equals("null", test(b));
 
   // Store a non-null object into foo to trigger deoptimization of test.
   a.foo = 123;
   Expect.equals("other", test(a));
   Expect.equals("null", test(b));
 
   // Test guarded fields with allocation sinking and deoptimization.
   Expect.equals(43, test_deopt(42, 1));
   for (var i = 0; i < 20; i++) { test_deopt(42, 1); }
   Expect.equals(43, test_deopt(42, 1));
   Expect.equals("aaabbb", test_deopt("aaa", "bbb"));
 
   // Regression test for fields initialized in native code (Error._stackTrace).
   test_stacktrace();
+
+  // Test guarded list length.
+  for (var i = 0; i < 20; i++) test_guarded_length();
 }