Emit stackmaps even in unoptimized code if slow path pushes untagged values.

tests/language/vm/regress_22621_vm_test.dart

 // Copyright (c) 2015, 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.
-
-// Regression test for http://dartbug.com/22487
-
-import 'package:expect/expect.dart';
-
-divIsInt(a, b) => (a / b) is int;
+// Test that BoxAllocationSlowPath for Mint emits stackmap in unoptimized code.
+// VMOptions=--gc_at_instance_allocation=_Mint --inline_alloc=false
 
 main() {
-  Expect.isFalse((divIsInt)(10, 3));
+  var re = new RegExp(r"IsolateStubs (.*)");
+  return re.firstMatch("oooo");

[koda, 2015/03/03 17:57:48]

Perhaps I should have added a comment here: "oooo" was chosen since the low bits
of 'o' make it neither a smi nor a well-formed pointer.

We could also consider making it "oooooooo" in case we add a 64-bit version of
LoadCodeUnits.

[Vyacheslav Egorov (Google), 2015/03/03 18:01:07]

Acknowledged.

 }