Pass field to mutator thread so that it can be marked as boxed and all dependent code deoptimized

runtime/vm/isolate.cc

Index: runtime/vm/isolate.cc
diff --git a/runtime/vm/isolate.cc b/runtime/vm/isolate.cc
index 3214d5f048da92426e00d18bc2d9105b86759acf..67989928418c935825643bbfca1f086d9f3ab987 100644
--- a/runtime/vm/isolate.cc
+++ b/runtime/vm/isolate.cc
@@ -831,6 +831,8 @@ Isolate::Isolate(const Dart_IsolateFlags& api_flags)
       cha_invalidation_gen_(kInvalidGen),
       field_invalidation_gen_(kInvalidGen),
       prefix_invalidation_gen_(kInvalidGen),
+      boxed_field_list_monitor_(new Monitor()),
+      boxed_field_list_(GrowableObjectArray::null()),
       spawn_count_monitor_(new Monitor()),
       spawn_count_(0) {
   flags_.CopyFrom(api_flags);
@@ -868,6 +870,8 @@ Isolate::~Isolate() {
   object_id_ring_ = NULL;
   delete pause_loop_monitor_;
   pause_loop_monitor_ = NULL;
+  delete boxed_field_list_monitor_;
+  boxed_field_list_monitor_ = NULL;
   ASSERT(spawn_count_ == 0);
   delete spawn_count_monitor_;

[siva, 2016/02/10 17:57:35]

We seem to have added a number of monitors to the isolate, I am wondering if
some of these can be shared.

[srdjan, 2016/02/10 19:18:51]

Added a TODO at Isolate constructor:

TODO(srdjan): Some Isolate monitors can be shared. Replace their usage with that
shared monitor.

   if (compiler_stats_ != NULL) {
@@ -1846,6 +1850,9 @@ void Isolate::VisitObjectPointers(ObjectPointerVisitor* visitor,
   visitor->VisitPointer(
       reinterpret_cast<RawObject**>(&registered_service_extension_handlers_));
 
+  // Visit the boxed_field_list.
+  visitor->VisitPointer(reinterpret_cast<RawObject**>(&boxed_field_list_));

[siva, 2016/02/10 17:57:35]

This will work only if the visitor is at a safepoint or is holding the
boxed_field_list_monitor_ lock. Maybe you should document that.

[srdjan, 2016/02/10 19:18:51]

  // 'boxed_field_list_' access via mutator and background compilation threads
  // is guarded with a monitor. This means that we can visit it only
  // when at safepoint or the boxed_field_list_monitor_ lock has been taken.

+
   // Visit objects in the debugger.
   if (FLAG_support_debugger) {
     debugger()->VisitObjectPointers(visitor);
@@ -2050,6 +2057,31 @@ void Isolate::set_registered_service_extension_handlers(
 }
 
 
+void Isolate::AddDeoptimizingBoxedField(const Field& field) {
+  MonitorLocker ml(boxed_field_list_monitor_);
+  if (boxed_field_list_ == GrowableObjectArray::null()) {
+    boxed_field_list_ = GrowableObjectArray::New(Heap::kOld);
+  }
+  const GrowableObjectArray& array =
+      GrowableObjectArray::Handle(boxed_field_list_);
+  array.Add(field, Heap::kOld);
+}
+
+
+RawField* Isolate::GetDeoptimizingBoxedField() {
+  MonitorLocker ml(boxed_field_list_monitor_);
+  if (boxed_field_list_ == GrowableObjectArray::null()) {
+    return Field::null();
+  }
+  const GrowableObjectArray& array =
+      GrowableObjectArray::Handle(boxed_field_list_);
+  if (array.Length() == 0) {
+    return Field::null();
+  }
+  return Field::RawCast(array.RemoveLast());
+}
+
+
 RawObject* Isolate::InvokePendingServiceExtensionCalls() {
   if (!FLAG_support_service) {
     return Object::null();