VM: Fix double comparisons using != and NaN in optimized code.

tests/language/double_nan_comparison_test.dart

Index: tests/language/double_nan_comparison_test.dart
===================================================================
--- tests/language/double_nan_comparison_test.dart	(revision 0)
+++ tests/language/double_nan_comparison_test.dart	(revision 0)
@@ -0,0 +1,33 @@
+// 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.
+// Tests double comparisons with NaN in different contexts.
+// VMOptions=--optimization-counter-threshold=10
+
+import "package:expect/expect.dart";
+
+test_expr(a, b) => a != b;
+
+test_conditional(a, b) => a != b ? true : false;
+
+test_branch(a, b) {
+  if (a != b) {
+    return true;
+  }
+  return false;
+}
+
+
+main() {
+  Expect.equals(true, test_expr(0.5, double.NAN));
+  for (var i = 0; i < 20; i++) test_expr(0.5, double.NAN);
+  Expect.equals(true, test_expr(0.5, double.NAN));
+
+  Expect.equals(true, test_conditional(0.5, double.NAN));
+  for (var i = 0; i < 20; i++) test_conditional(0.5, double.NAN);
+  Expect.equals(true, test_conditional(0.5, double.NAN));
+
+  Expect.equals(true, test_branch(0.5, double.NAN));
+  for (var i = 0; i < 20; i++) test_branch(0.5, double.NAN);
+  Expect.equals(true, test_branch(0.5, double.NAN));
+}