Fix bug with guarded fields and deserialization.

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";
 
 class A {
   var foo;
 }
 
 class B {
   get foo => null;
 }
 
 test(obj) => obj.foo == null ? "null" : "other";
 
+
+class C {
+  C(this.x, this.y);
+  final x;
+  final y;
+}
+
+test_deopt(a, b) {
+  var c = new C(a, b);
+  return c.x + c.y;
+}
+
+
+create_error (x) {
+  return x as int;
+}
+
+check_stacktrace(e) {
+  var s = e.stackTrace;
+  if (identical(s, null)) throw "FAIL";

[Ivan Posva, 2013/11/01 04:50:05]

Why not just s == null?

[Florian Schneider, 2013/11/01 10:39:27]

I can't have an IC call here: it will introduce a CheckClass and defeat cid
propagation. Instead cid-propagation will illegally optimize the
identical-comparison away.

+  // s should never be null.
+  return "OK";
+}
+
+test_stacktrace() {
+  try {
+    create_error("bar");
+  } catch (e) {
+    Expect.equals("OK", check_stacktrace(e));
+    for (var i=0; i<20; i++) check_stacktrace(e);

[Ivan Posva, 2013/11/01 04:50:05]

ditto

[Florian Schneider, 2013/11/01 10:39:27]

Done.

+    Expect.equals("OK", check_stacktrace(e));
+  }
+}
+
+
 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);

[Ivan Posva, 2013/11/01 04:50:05]

ditto

[Florian Schneider, 2013/11/01 10:39:27]

Done.

+  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();
 }