Avoid critical edge for loop-exits.

tests/language/critical_edge2_test.dart

+// Copyright (c) 2014, 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.
+
+// This test broke dart2js.
+// A compiler must not construct a critical edge on this program.

[ngeoffray, 2014/06/24 12:39:14]

Maybe add a comment of the reason a critical edge was originally created. Is it
the break + return, or can it be break + break?

[floitsch, 2014/06/24 14:44:38]

Added comment.

+
+import "package:expect/expect.dart";
+
+void parse(String uri) {
+  int index = 0;
+  int char = -1;
+
+  void parseAuth() {
+    index;
+    char;
+  }
+
+  while (index < 1000) {
+    char = uri.codeUnitAt(index);
+    if (char == 1234) {
+      break;
+    }
+    if (char == 0x3A) {
+      return "good";
+    }
+    index++;
+  }
+
+  print(char);
+  return "bad";
+}
+
+main() {
+  Expect.equals("good", parse("dart:_foreign_helper"));

[ngeoffray, 2014/06/24 12:39:14]

Not very unit for a unit test :-) Seems like the loop is simple enough to
trigger an error.

[floitsch, 2014/06/24 14:44:38]

I was not able to reduce the number of instructions in the "parse" functions.
This is pretty much a minimal example.

+}