Captured arguments object materialization

src/deoptimizer.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 755 matching lines @@
   // descriptions.
   int count = iterator.Next();
   iterator.Next();  // Drop JS frames count.
   ASSERT(output_ == NULL);
   output_ = new FrameDescription*[count];
   for (int i = 0; i < count; ++i) {
     output_[i] = NULL;
   }
   output_count_ = count;
 
+  Register fp_reg = JavaScriptFrame::fp_register();
+  stack_fp_ = reinterpret_cast<Address>(
+      input_->GetRegister(fp_reg.code()) +
+          has_alignment_padding_ * kPointerSize);
+
   // Translate each output frame.
   for (int i = 0; i < count; ++i) {
     // Read the ast node id, function, and frame height for this output frame.
     Translation::Opcode opcode =
         static_cast<Translation::Opcode>(iterator.Next());
     switch (opcode) {
       case Translation::JS_FRAME:
         DoComputeJSFrame(&iterator, i);
         jsframe_count_++;
         break;
@@ skipping 984 matching lines @@
     // Dispatch on the instance type of the object to be materialized.
     // We also need to make sure that the representation of all fields
     // in the given object are general enough to hold a tagged value.
     Handle<Map> map = Map::GeneralizeAllFieldRepresentations(
         Handle<Map>::cast(MaterializeNextValue()), Representation::Tagged());
     switch (map->instance_type()) {
       case HEAP_NUMBER_TYPE: {
         // Reuse the HeapNumber value directly as it is already properly
         // tagged and skip materializing the HeapNumber explicitly.
         Handle<Object> object = MaterializeNextValue();
-        materialized_objects_->Add(object);
+        if (object_index < prev_materialized_count_) {
+          materialized_objects_->Add(Handle<Object>(
+              previously_materialized_objects_->get(object_index), isolate_));
+        } else {
+          materialized_objects_->Add(object);
+        }
         materialization_value_index_ += kDoubleSize / kPointerSize - 1;
         break;
       }
       case JS_OBJECT_TYPE: {
         Handle<JSObject> object =
             isolate_->factory()->NewJSObjectFromMap(map, NOT_TENURED, false);
-        materialized_objects_->Add(object);
+        if (object_index < prev_materialized_count_) {
+          materialized_objects_->Add(Handle<Object>(
+              previously_materialized_objects_->get(object_index), isolate_));
+        } else {
+          materialized_objects_->Add(object);
+        }
         Handle<Object> properties = MaterializeNextValue();
         Handle<Object> elements = MaterializeNextValue();
         object->set_properties(FixedArray::cast(*properties));
         object->set_elements(FixedArrayBase::cast(*elements));
         for (int i = 0; i < length - 3; ++i) {
           Handle<Object> value = MaterializeNextValue();
           object->FastPropertyAtPut(i, *value);
         }
         break;
       }
       case JS_ARRAY_TYPE: {
         Handle<JSArray> object =
             isolate_->factory()->NewJSArray(0, map->elements_kind());
-        materialized_objects_->Add(object);
+        if (object_index < prev_materialized_count_) {
+          materialized_objects_->Add(Handle<Object>(
+              previously_materialized_objects_->get(object_index), isolate_));
+        } else {
+          materialized_objects_->Add(object);
+        }
         Handle<Object> properties = MaterializeNextValue();
         Handle<Object> elements = MaterializeNextValue();
         Handle<Object> length = MaterializeNextValue();
         object->set_properties(FixedArray::cast(*properties));
         object->set_elements(FixedArrayBase::cast(*elements));
         object->set_length(*length);
         break;
       }
       default:
         PrintF(stderr,
@@ skipping 12 matching lines @@
   if (*value == isolate_->heap()->arguments_marker()) {
     value = MaterializeNextHeapObject();
   }
   return value;
 }
 
 
 void Deoptimizer::MaterializeHeapObjects(JavaScriptFrameIterator* it) {
   ASSERT_NE(DEBUGGER, bailout_type_);
 
+  MaterializedObjectStore* materialized_store =
+      isolate_->materialized_object_store();
+  previously_materialized_objects_ = materialized_store->Get(stack_fp_);
+  prev_materialized_count_ = previously_materialized_objects_.is_null() ?
+      0 : previously_materialized_objects_->length();
+
   // Walk all JavaScript output frames with the given frame iterator.
   for (int frame_index = 0; frame_index < jsframe_count(); ++frame_index) {
     if (frame_index != 0) it->Advance();
     JavaScriptFrame* frame = it->frame();
     jsframe_functions_.Add(handle(frame->function(), isolate_));
     jsframe_has_adapted_arguments_.Add(frame->has_adapted_arguments());
   }
 
   // Handlify all tagged object values before triggering any allocation.
   List<Handle<Object> > values(deferred_objects_tagged_values_.length());
@@ skipping 69 matching lines @@
                  reinterpret_cast<void*>(descriptor.slot_address()));
         }
         object->ShortPrint(trace_scope_->file());
         PrintF(trace_scope_->file(), "\n");
       }
     }
 
     ASSERT(materialization_object_index_ == materialized_objects_->length());
     ASSERT(materialization_value_index_ == materialized_values_->length());
   }
+
+  if (prev_materialized_count_ > 0) {
+    materialized_store->Remove(stack_fp_);
+  }
 }
 
 
 #ifdef ENABLE_DEBUGGER_SUPPORT
 void Deoptimizer::MaterializeHeapNumbersForDebuggerInspectableFrame(
     Address parameters_top,
     uint32_t parameters_size,
     Address expressions_top,
     uint32_t expressions_size,
     DeoptimizedFrameInfo* info) {
@@ skipping 1008 matching lines @@
   UNREACHABLE();
   return "";
 }
 
 #endif
 
 
 // We can't intermix stack decoding and allocations because
 // deoptimization infrastracture is not GC safe.
 // Thus we build a temporary structure in malloced space.
-SlotRef SlotRef::ComputeSlotForNextArgument(TranslationIterator* iterator,
-                                            DeoptimizationInputData* data,
-                                            JavaScriptFrame* frame) {
-  Translation::Opcode opcode =
-      static_cast<Translation::Opcode>(iterator->Next());
-
+SlotRef SlotRefValueBuilder::ComputeSlotForNextArgument(
+    Translation::Opcode opcode,
+    TranslationIterator* iterator,
+    DeoptimizationInputData* data,
+    JavaScriptFrame* frame) {
   switch (opcode) {
     case Translation::BEGIN:
     case Translation::JS_FRAME:
     case Translation::ARGUMENTS_ADAPTOR_FRAME:
     case Translation::CONSTRUCT_STUB_FRAME:
     case Translation::GETTER_STUB_FRAME:
     case Translation::SETTER_STUB_FRAME:
       // Peeled off before getting here.
       break;
 
-    case Translation::DUPLICATED_OBJECT:
+    case Translation::DUPLICATED_OBJECT: {
+      return SlotRef::NewDuplicateObject(iterator->Next());
+    }
+
     case Translation::ARGUMENTS_OBJECT:
-    case Translation::CAPTURED_OBJECT:
       // This can be only emitted for local slots not for argument slots.
       break;
 
+    case Translation::CAPTURED_OBJECT: {
+      return SlotRef::NewDeferredObject(iterator->Next());
+    }
+
     case Translation::REGISTER:
     case Translation::INT32_REGISTER:
     case Translation::UINT32_REGISTER:
     case Translation::DOUBLE_REGISTER:
       // We are at safepoint which corresponds to call.  All registers are
       // saved by caller so there would be no live registers at this
       // point. Thus these translation commands should not be used.
       break;
 
     case Translation::STACK_SLOT: {
@@ skipping 29 matching lines @@
     case Translation::COMPILED_STUB_FRAME:
       UNREACHABLE();
       break;
   }
 
   UNREACHABLE();
   return SlotRef();
 }
 
 
-void SlotRef::ComputeSlotsForArguments(Vector<SlotRef>* args_slots,
-                                       TranslationIterator* it,
-                                       DeoptimizationInputData* data,
-                                       JavaScriptFrame* frame) {
-  // Process the translation commands for the arguments.
+SlotRefValueBuilder::SlotRefValueBuilder(JavaScriptFrame* frame,
+                                         int inlined_jsframe_index,
+                                         int formal_parameter_count)
+    : current_slot_(0), args_length_(-1), first_slot_index_(-1) {
+  DisallowHeapAllocation no_gc;
 
-  // Skip the translation command for the receiver.
-  it->Skip(Translation::NumberOfOperandsFor(
-      static_cast<Translation::Opcode>(it->Next())));
-
-  // Compute slots for arguments.
-  for (int i = 0; i < args_slots->length(); ++i) {
-    (*args_slots)[i] = ComputeSlotForNextArgument(it, data, frame);
-  }
-}
-
-
-Vector<SlotRef> SlotRef::ComputeSlotMappingForArguments(
-    JavaScriptFrame* frame,
-    int inlined_jsframe_index,
-    int formal_parameter_count) {
-  DisallowHeapAllocation no_gc;
   int deopt_index = Safepoint::kNoDeoptimizationIndex;
   DeoptimizationInputData* data =
       static_cast<OptimizedFrame*>(frame)->GetDeoptimizationData(&deopt_index);
   TranslationIterator it(data->TranslationByteArray(),
                          data->TranslationIndex(deopt_index)->value());
   Translation::Opcode opcode = static_cast<Translation::Opcode>(it.Next());
   ASSERT(opcode == Translation::BEGIN);
   it.Next();  // Drop frame count.
+
+  stack_frame_id_ = frame->fp();
+
   int jsframe_count = it.Next();
   USE(jsframe_count);
   ASSERT(jsframe_count > inlined_jsframe_index);
   int jsframes_to_skip = inlined_jsframe_index;
-  while (true) {
+  int number_of_slots = -1;  // Number of slots inside our frame (yet unknown)
+  bool should_deopt = false;
+  while (number_of_slots != 0) {
     opcode = static_cast<Translation::Opcode>(it.Next());
+    bool processed = false;
     if (opcode == Translation::ARGUMENTS_ADAPTOR_FRAME) {
       if (jsframes_to_skip == 0) {
         ASSERT(Translation::NumberOfOperandsFor(opcode) == 2);
 
         it.Skip(1);  // literal id
         int height = it.Next();
 
+        // Skip the translation command for the receiver.
+        it.Skip(Translation::NumberOfOperandsFor(
+            static_cast<Translation::Opcode>(it.Next())));
+
         // We reached the arguments adaptor frame corresponding to the
         // inlined function in question.  Number of arguments is height - 1.
-        Vector<SlotRef> args_slots =
-            Vector<SlotRef>::New(height - 1);  // Minus receiver.
-        ComputeSlotsForArguments(&args_slots, &it, data, frame);
-        return args_slots;
+        first_slot_index_ = slot_refs_.length();
+        args_length_ = height - 1;
+        number_of_slots = height - 1;
+        processed = true;
       }
     } else if (opcode == Translation::JS_FRAME) {
       if (jsframes_to_skip == 0) {
         // Skip over operands to advance to the next opcode.
         it.Skip(Translation::NumberOfOperandsFor(opcode));
 
+        // Skip the translation command for the receiver.
+        it.Skip(Translation::NumberOfOperandsFor(
+            static_cast<Translation::Opcode>(it.Next())));
+
         // We reached the frame corresponding to the inlined function
         // in question.  Process the translation commands for the
         // arguments.  Number of arguments is equal to the number of
         // format parameter count.
-        Vector<SlotRef> args_slots =
-            Vector<SlotRef>::New(formal_parameter_count);
-        ComputeSlotsForArguments(&args_slots, &it, data, frame);
-        return args_slots;
+        first_slot_index_ = slot_refs_.length();
+        args_length_ = formal_parameter_count;
+        number_of_slots = formal_parameter_count;
+        processed = true;
       }
       jsframes_to_skip--;
-    }
-
-    // Skip over operands to advance to the next opcode.
-    it.Skip(Translation::NumberOfOperandsFor(opcode));
+    } else if (opcode != Translation::BEGIN &&
+               opcode != Translation::CONSTRUCT_STUB_FRAME) {
+      slot_refs_.Add(ComputeSlotForNextArgument(opcode, &it, data, frame));
+
+      if (first_slot_index_ >= 0) {
+        // We have found the beginning of our frame -> make sure we count
+        // the nested slots of captured objects
+        number_of_slots--;
+        SlotRef& slot = slot_refs_.last();
+        if (slot.Representation() == SlotRef::DEFERRED_OBJECT) {
+          number_of_slots += slot.DeferredObjectLength();
+        }
+        if (slot.Representation() == SlotRef::DEFERRED_OBJECT ||
+            slot.Representation() == SlotRef::DUPLICATE_OBJECT) {
+          should_deopt = true;
+        }
+      }
+
+      processed = true;
+    }
+    if (!processed) {
+      // Skip over operands to advance to the next opcode.
+      it.Skip(Translation::NumberOfOperandsFor(opcode));
+    }
+  }
+  if (should_deopt) {
+    List<JSFunction*> functions(2);
+    frame->GetFunctions(&functions);
+    Deoptimizer::DeoptimizeFunction(functions[0]);
+  }
+}
+
+
+Handle<Object> SlotRef::GetValue(Isolate* isolate) {
+  switch (representation_) {
+    case TAGGED:
+      return Handle<Object>(Memory::Object_at(addr_), isolate);
+
+    case INT32: {
+      int value = Memory::int32_at(addr_);
+      if (Smi::IsValid(value)) {
+        return Handle<Object>(Smi::FromInt(value), isolate);
+      } else {
+        return isolate->factory()->NewNumberFromInt(value);
+      }
+    }
+
+    case UINT32: {
+      uint32_t value = Memory::uint32_at(addr_);
+      if (value <= static_cast<uint32_t>(Smi::kMaxValue)) {
+        return Handle<Object>(Smi::FromInt(static_cast<int>(value)), isolate);
+      } else {
+        return isolate->factory()->NewNumber(static_cast<double>(value));
+      }
+    }
+
+    case DOUBLE: {
+      double value = read_double_value(addr_);
+      return isolate->factory()->NewNumber(value);
+    }
+
+    case LITERAL:
+      return literal_;
+
+    default:
+      UNREACHABLE();
+      return Handle<Object>::null();
+  }
+}
+
+
+void SlotRefValueBuilder::Prepare(Isolate* isolate) {
+  MaterializedObjectStore* materialized_store =
+      isolate->materialized_object_store();
+  previously_materialized_objects_ = materialized_store->Get(stack_frame_id_);
+  prev_materialized_count_ = previously_materialized_objects_.is_null() ?

[danno, 2014/01/28 15:44:34]

nit: funky formatting. Put the ? on the next line with the 0

[Jarin, 2014/01/28 19:52:30]

Done.

+      0 : previously_materialized_objects_->length();
+
+  // Now skip the initial segment (we need to get over the segment

[danno, 2014/01/28 15:44:34]

What do you mean by "first segment"?

[Jarin, 2014/01/28 19:52:30]

I mean materialized objects of the callers inlined in the same frame.

+  // to recover the captured objects in case we have duplicate
+  // objects)
+  while (current_slot_ < first_slot_index_) {
+    GetNext(isolate, 0);
+  }
+  ASSERT(current_slot_ == first_slot_index_);
+}
+
+
+Handle<Object> SlotRefValueBuilder::GetPreviouslyMaterialized(
+    Isolate* isolate, int length) {
+    int object_index = materialized_objects_.length();

[danno, 2014/01/28 15:44:34]

nit: indent should be 2, not 4

[Jarin, 2014/01/28 19:52:30]

Done.

+    Handle<Object> return_value = Handle<Object>(
+        previously_materialized_objects_->get(object_index), isolate);
+    materialized_objects_.Add(return_value);
+
+    // Now need to skip all nested objects (and possibly read them from
+    // the materialization store, too)
+    for (int i = 0; i < length; i++) {
+      SlotRef& slot = slot_refs_[current_slot_];
+      current_slot_++;
+
+      // For nested deferred objects, we need to read its properties
+      if (slot.Representation() == SlotRef::DEFERRED_OBJECT) {
+        length += slot.DeferredObjectLength();
+      }
+
+      // For nested deferred and duplicate objects, we need to put them into
+      // our materialization array
+      if (slot.Representation() == SlotRef::DEFERRED_OBJECT ||
+          slot.Representation() == SlotRef::DUPLICATE_OBJECT) {
+        int nested_object_index = materialized_objects_.length();
+        Handle<Object> nested_object = Handle<Object>(
+            previously_materialized_objects_->get(nested_object_index),
+            isolate);
+        materialized_objects_.Add(nested_object);
+      }
+    }
+
+    return return_value;
+}
+
+
+Handle<Object> SlotRefValueBuilder::GetNext(Isolate* isolate, int lvl) {
+  SlotRef& slot = slot_refs_[current_slot_];
+  current_slot_++;
+  switch (slot.Representation()) {
+    case SlotRef::TAGGED:
+    case SlotRef::INT32:
+    case SlotRef::UINT32:
+    case SlotRef::DOUBLE:
+    case SlotRef::LITERAL: {
+      return slot.GetValue(isolate);
+    }
+    case SlotRef::DEFERRED_OBJECT: {
+      int length = slot.DeferredObjectLength();
+      ASSERT(slot_refs_[current_slot_].Representation() == SlotRef::LITERAL ||
+             slot_refs_[current_slot_].Representation() == SlotRef::TAGGED);
+
+      int object_index = materialized_objects_.length();
+      if (object_index <  prev_materialized_count_) {

[danno, 2014/01/28 15:44:34]

This confuses me a bit. Isn't it the case that when you materialize, you
materialize all objects in the frame? So it seems like either all objects will
be previously materialized or not, but this test makes it seem like it's an
object-by-object decision based on careful ordering of the materialized objects
and previous materialized count. 

E.g. why isn't:
if (prev_materialized_count_ != 0) {
  ASSERT(object_index < prev_materialized_count_);
  ...

also correct?

[Jarin, 2014/01/28 19:52:30]

At the moment, it would not be correct as the code does not materialize all the
objects in the frame; it only materializes the ones that are needed to build the
arguments object. (However, the deoptimizer will materialize the rest when it
kicks in.)

+        return GetPreviouslyMaterialized(isolate, length);
+      }
+
+      Handle<Object> map_object = slot_refs_[current_slot_].GetValue(isolate);
+      Handle<Map> map = Map::GeneralizeAllFieldRepresentations(
+          Handle<Map>::cast(map_object), Representation::Tagged());
+      current_slot_++;
+      // TODO(jarin) this should be unified with the code in
+      // Deoptimizer::MaterializeNextHeapObject()
+      switch (map->instance_type()) {
+        case HEAP_NUMBER_TYPE: {
+          // Reuse the HeapNumber value directly as it is already properly
+          // tagged and skip materializing the HeapNumber explicitly.
+          Handle<Object> object = GetNext(isolate, lvl + 1);
+          materialized_objects_.Add(object);
+          return object;
+        }
+        case JS_OBJECT_TYPE: {
+          Handle<JSObject> object =
+              isolate->factory()->NewJSObjectFromMap(map, NOT_TENURED, false);
+          materialized_objects_.Add(object);
+          Handle<Object> properties = GetNext(isolate, lvl + 1);
+          Handle<Object> elements = GetNext(isolate, lvl + 1);
+          object->set_properties(FixedArray::cast(*properties));
+          object->set_elements(FixedArrayBase::cast(*elements));
+          for (int i = 0; i < length - 3; ++i) {
+            Handle<Object> value = GetNext(isolate, lvl + 1);
+            object->FastPropertyAtPut(i, *value);
+          }
+          return object;
+        }
+        case JS_ARRAY_TYPE: {
+          Handle<JSArray> object =
+              isolate->factory()->NewJSArray(0, map->elements_kind());
+          materialized_objects_.Add(object);
+          Handle<Object> properties = GetNext(isolate, lvl + 1);
+          Handle<Object> elements = GetNext(isolate, lvl + 1);
+          Handle<Object> length = GetNext(isolate, lvl + 1);
+          object->set_properties(FixedArray::cast(*properties));
+          object->set_elements(FixedArrayBase::cast(*elements));
+          object->set_length(*length);
+          return object;
+        }
+        default:
+          PrintF(stderr,
+                 "[couldn't handle instance type %d]\n", map->instance_type());
+          UNREACHABLE();
+          break;
+      }
+      UNREACHABLE();
+    }
+
+    case SlotRef::DUPLICATE_OBJECT: {
+      int object_index = slot.DuplicateObjectId();
+      Handle<Object> object = materialized_objects_[object_index];
+      materialized_objects_.Add(object);
+      return object;
+    }
+    default:
+      UNREACHABLE();
+      break;
   }
 
   UNREACHABLE();
-  return Vector<SlotRef>();
+  return Handle<Object>::null();
+}
+
+
+void SlotRefValueBuilder::Finish(Isolate* isolate) {
+  // We should have processed all slot
+  ASSERT(slot_refs_.length() == current_slot_);
+
+  if (materialized_objects_.length() > prev_materialized_count_) {
+    // We have materialized some new objects, so we have to store them
+    // to prevent duplicate materialization
+    Handle<FixedArray> array = isolate->factory()->NewFixedArray(
+        materialized_objects_.length());
+    for (int i = 0; i < materialized_objects_.length(); i++) {
+      array->set(i, *(materialized_objects_.at(i)));
+    }
+    isolate->materialized_object_store()->Set(stack_frame_id_, array);
+  }
+}
+
+
+Handle<FixedArray> MaterializedObjectStore::Get(Address fp) {
+  int index = StackIdToIndex(fp);
+  if (index == -1) {
+    return Handle<FixedArray>::null();
+  }
+  Handle<FixedArray> array = GetStackEntries();
+  ASSERT(array->length() > index);
+  return Handle<FixedArray>::cast(Handle<Object>(array->get(index),
+                                                 isolate()));
+}
+
+
+void MaterializedObjectStore::Set(Address fp,
+    Handle<FixedArray> materialized_objects) {
+  int index = StackIdToIndex(fp);
+  if (index == -1) {
+    index = frame_fps_.length();
+    frame_fps_.Add(fp);
+  }
+  EnsureStackEntries(index + 1);
+  Handle<FixedArray> array = GetStackEntries();
+  array->set(index, *materialized_objects);
+}
+
+
+void MaterializedObjectStore::Remove(Address fp) {
+  int index = StackIdToIndex(fp);
+  ASSERT(index >= 0);
+
+  frame_fps_.Remove(index);
+  Handle<FixedArray> array = GetStackEntries();
+  ASSERT(array->length() > index);
+  for (int i = index; i < frame_fps_.length(); i++) {
+    array->set(i, array->get(i + 1));
+  }
+  array->set(frame_fps_.length(), isolate()->heap()->undefined_value());
+}
+
+
+int MaterializedObjectStore::StackIdToIndex(Address fp) {
+  for (int i = 0; i < frame_fps_.length(); i++) {
+    if (frame_fps_[i] == fp) {
+      return i;
+    }
+  }
+  return -1;
+}
+
+
+Handle<FixedArray> MaterializedObjectStore::GetStackEntries() {
+  return Handle<FixedArray>::cast(
+      Handle<Object>(isolate()->heap()->materialized_objects()->get(0),
+          isolate()));
+}
+
+
+Handle<FixedArray> MaterializedObjectStore::EnsureStackEntries(int length) {
+  Handle<FixedArray> array = GetStackEntries();
+  if (array->length() >= length) {
+    return array;
+  }
+
+  int new_length = length > 10 ? length : 10;
+  if (new_length < 2 * array->length()) {
+    new_length = 2 * array->length();
+  }
+
+  Handle<FixedArray> new_array =
+      isolate()->factory()->NewFixedArray(new_length, TENURED);
+  for (int i = 0; i < array->length(); i++) {
+    new_array->set(i, array->get(i));
+  }
+  for (int i = array->length(); i < length; i++) {
+    new_array->set(i, isolate()->heap()->undefined_value());
+  }
+  isolate()->heap()->materialized_objects()->set(0, *new_array);
+  return new_array;
 }
 
 #ifdef ENABLE_DEBUGGER_SUPPORT
 
 DeoptimizedFrameInfo::DeoptimizedFrameInfo(Deoptimizer* deoptimizer,
                                            int frame_index,
                                            bool has_arguments_adaptor,
                                            bool has_construct_stub) {
   FrameDescription* output_frame = deoptimizer->output_[frame_index];
   function_ = output_frame->GetFunction();
@@ skipping 30 matching lines @@
 
 void DeoptimizedFrameInfo::Iterate(ObjectVisitor* v) {
   v->VisitPointer(BitCast<Object**>(&function_));
   v->VisitPointers(parameters_, parameters_ + parameters_count_);
   v->VisitPointers(expression_stack_, expression_stack_ + expression_count_);
 }
 
 #endif  // ENABLE_DEBUGGER_SUPPORT
 
 } }  // namespace v8::internal