New heap profiler: include all heap objects and refs into snapshot.

src/profile-generator.cc

Index: src/profile-generator.cc
diff --git a/src/profile-generator.cc b/src/profile-generator.cc
index 29f9ab4d3536c4714639ce92caa65dcdb635bd0a..55ae56662796b92b28d16e0276fd22e8a6ab626d 100644
--- a/src/profile-generator.cc
+++ b/src/profile-generator.cc
@@ -829,7 +829,10 @@ void ProfileGenerator::RecordTickSample(const TickSample& sample) {
 
 void HeapGraphEdge::Init(
     int child_index, Type type, const char* name, HeapEntry* to) {
-  ASSERT(type == kContextVariable || type == kProperty || type == kInternal);
+  ASSERT(type == kContextVariable
+         || type == kProperty
+         || type == kInternal
+         || type == kShortcut);
   child_index_ = child_index;
   type_ = type;
   name_ = name;
@@ -837,14 +840,20 @@ void HeapGraphEdge::Init(
 }
 
 
-void HeapGraphEdge::Init(int child_index, int index, HeapEntry* to) {
+void HeapGraphEdge::Init(int child_index, Type type, int index, HeapEntry* to) {
+  ASSERT(type == kElement || type == kHidden);
   child_index_ = child_index;
-  type_ = kElement;
+  type_ = type;
   index_ = index;
   to_ = to;
 }
 
 
+void HeapGraphEdge::Init(int child_index, int index, HeapEntry* to) {
+  Init(child_index, kElement, index, to);
+}
+
+
 HeapEntry* HeapGraphEdge::From() {
   return reinterpret_cast<HeapEntry*>(this - child_index_) - 1;
 }
@@ -879,9 +888,12 @@ void HeapEntry::SetNamedReference(HeapGraphEdge::Type type,
 }
 
 
-void HeapEntry::SetElementReference(
-    int child_index, int index, HeapEntry* entry, int retainer_index) {
-  children_arr()[child_index].Init(child_index, index, entry);
+void HeapEntry::SetIndexedReference(HeapGraphEdge::Type type,
+                                    int child_index,
+                                    int index,
+                                    HeapEntry* entry,
+                                    int retainer_index) {
+  children_arr()[child_index].Init(child_index, type, index, entry);
   entry->retainers_arr()[retainer_index] = children_arr() + child_index;
 }
 
@@ -929,6 +941,7 @@ void HeapEntry::ApplyAndPaintAllReachable(Visitor* visitor) {
     HeapEntry* entry = list.RemoveLast();
     Vector<HeapGraphEdge> children = entry->children();
     for (int i = 0; i < children.length(); ++i) {
+      if (children[i].type() == HeapGraphEdge::kShortcut) continue;
       HeapEntry* child = children[i].to();
       if (!child->painted_reachable()) {
         list.Add(child);
@@ -985,6 +998,12 @@ void HeapEntry::Print(int max_depth, int indent) {
       case HeapGraphEdge::kProperty:
         OS::Print("  %*c %s: ", indent, ' ', edge.name());
         break;
+      case HeapGraphEdge::kHidden:
+        OS::Print("  %*c $%d: ", indent, ' ', edge.index());
+        break;
+      case HeapGraphEdge::kShortcut:
+        OS::Print("  %*c ^%s: ", indent, ' ', edge.name());
+        break;
       default:
         OS::Print("!!! unknown edge type: %d ", edge.type());
     }
@@ -995,7 +1014,7 @@ void HeapEntry::Print(int max_depth, int indent) {
 
 const char* HeapEntry::TypeAsString() {
   switch (type()) {
-    case kInternal: return "/internal/";
+    case kHidden: return "/hidden/";
     case kObject: return "/object/";
     case kClosure: return "/closure/";
     case kString: return "/string/";
@@ -1094,6 +1113,7 @@ void HeapEntryCalculatedData::CalculateSizes(HeapEntry* entry) {
     HeapEntry* curr = list.RemoveLast();
     Vector<HeapGraphEdge> children = curr->children();
     for (int i = 0; i < children.length(); ++i) {
+      if (children[i].type() == HeapGraphEdge::kShortcut) continue;
       HeapEntry* child = children[i].to();
       if (child != entry && child->not_painted_reachable_from_others()) {
         list.Add(child);
@@ -1192,6 +1212,7 @@ void HeapGraphPath::Print() {
         OS::Print("[#%s] ", edge->name());
         break;
       case HeapGraphEdge::kElement:
+      case HeapGraphEdge::kHidden:
         OS::Print("[%d] ", edge->index());
         break;
       case HeapGraphEdge::kInternal:
@@ -1200,6 +1221,9 @@ void HeapGraphPath::Print() {
       case HeapGraphEdge::kProperty:
         OS::Print("[%s] ", edge->name());
         break;
+      case HeapGraphEdge::kShortcut:
+        OS::Print("[^%s] ", edge->name());
+        break;
       default:
         OS::Print("!!! unknown edge type: %d ", edge->type());
     }
@@ -1211,6 +1235,8 @@ void HeapGraphPath::Print() {
 
 HeapObject *const HeapSnapshot::kInternalRootObject =
     reinterpret_cast<HeapObject*>(1);
+HeapObject *const HeapSnapshot::kGcRootsObject =
+    reinterpret_cast<HeapObject*>(2);
 
 
 // It is very important to keep objects that form a heap snapshot
@@ -1240,6 +1266,7 @@ HeapSnapshot::HeapSnapshot(HeapSnapshotsCollection* collection,
       title_(title),
       uid_(uid),
       root_entry_(NULL),
+      gc_roots_entry_(NULL),
       raw_entries_(NULL),
       entries_sorted_(false) {
   STATIC_ASSERT(
@@ -1280,9 +1307,20 @@ HeapEntry* HeapSnapshot::AddEntry(HeapObject* object,
   if (object == kInternalRootObject) {
     ASSERT(root_entry_ == NULL);
     ASSERT(retainers_count == 0);
-    root_entry_ = AddEntry(
-        HeapEntry::kInternal, "", 0, 0, children_count, retainers_count);
-    return root_entry_;
+    return (root_entry_ = AddEntry(HeapEntry::kObject,
+                                   "",
+                                   HeapObjectsMap::kInternalRootObjectId,
+                                   0,
+                                   children_count,
+                                   retainers_count));
+  } else if (object == kGcRootsObject) {
+    ASSERT(gc_roots_entry_ == NULL);
+    return (gc_roots_entry_ = AddEntry(HeapEntry::kObject,
+                                       "(GC roots)",
+                                       HeapObjectsMap::kGcRootsObjectId,
+                                       0,
+                                       children_count,
+                                       retainers_count));
   } else if (object->IsJSFunction()) {
     JSFunction* func = JSFunction::cast(object);
     SharedFunctionInfo* shared = func->shared();
@@ -1345,22 +1383,11 @@ HeapEntry* HeapSnapshot::AddEntry(HeapObject* object,
                     children_count,
                     retainers_count);
   }
-  // No interest in this object.
-  return NULL;
-}
-
-
-bool HeapSnapshot::WillAddEntry(HeapObject* object) {
-  return object == kInternalRootObject
-      || object->IsJSFunction()
-      || object->IsJSRegExp()
-      || object->IsJSObject()
-      || object->IsString()
-      || object->IsCode()
-      || object->IsSharedFunctionInfo()
-      || object->IsScript()
-      || object->IsFixedArray()
-      || object->IsHeapNumber();
+  return AddEntry(object,
+                  HeapEntry::kHidden,
+                  "system",
+                  children_count,
+                  retainers_count);
 }
 
 
@@ -1387,7 +1414,7 @@ HeapEntry* HeapSnapshot::AddEntry(HeapObject* object,
   return AddEntry(type,
                   name,
                   collection_->GetObjectId(object->address()),
-                  GetObjectSize(object),
+                  object->Size(),
                   children_count,
                   retainers_count);
 }
@@ -1419,36 +1446,6 @@ HeapEntry* HeapSnapshot::GetNextEntryToInit() {
 }
 
 
-int HeapSnapshot::GetObjectSize(HeapObject* obj) {
-  return obj->IsJSObject() ?
-      CalculateNetworkSize(JSObject::cast(obj)) : obj->Size();
-}
-
-
-int HeapSnapshot::CalculateNetworkSize(JSObject* obj) {
-  int size = obj->Size();
-  // If 'properties' and 'elements' are non-empty (thus, non-shared),
-  // take their size into account.
-  if (obj->properties() != Heap::empty_fixed_array()) {
-    size += obj->properties()->Size();
-  }
-  if (obj->elements() != Heap::empty_fixed_array()) {
-    size += obj->elements()->Size();
-  }
-  // For functions, also account non-empty context and literals sizes.
-  if (obj->IsJSFunction()) {
-    JSFunction* f = JSFunction::cast(obj);
-    if (f->unchecked_context()->IsContext()) {
-      size += f->context()->Size();
-    }
-    if (f->literals()->length() != 0) {
-      size += f->literals()->Size();
-    }
-  }
-  return size;
-}
-
-
 HeapSnapshotsDiff* HeapSnapshot::CompareWith(HeapSnapshot* snapshot) {
   return collection_->CompareSnapshots(this, snapshot);
 }
@@ -1475,9 +1472,12 @@ void HeapSnapshot::Print(int max_depth) {
 }
 
 
+const uint64_t HeapObjectsMap::kInternalRootObjectId = 0;
+const uint64_t HeapObjectsMap::kGcRootsObjectId = 1;

[Søren Thygesen Gjesse, 2010/11/18 08:14:54]

Please add kNumReservedObjectsIds = 2 (maybe you can find a better name) and use
instead of 2 below.

[mnaganov (inactive), 2010/11/18 10:32:51]

OK, I've introduced kFirstAvailableObjectId.

+
 HeapObjectsMap::HeapObjectsMap()
     : initial_fill_mode_(true),
-      next_id_(1),
+      next_id_(2),  // Reserve 0..1 for internal root objects.
       entries_map_(AddressesMatch),
       entries_(new List<EntryInfo>()) { }
 
@@ -1628,17 +1628,7 @@ HeapEntriesMap::HeapEntriesMap()
 
 HeapEntriesMap::~HeapEntriesMap() {
   for (HashMap::Entry* p = entries_.Start(); p != NULL; p = entries_.Next(p)) {
-    if (!IsAlias(p->value)) delete reinterpret_cast<EntryInfo*>(p->value);
-  }
-}
-
-
-void HeapEntriesMap::Alias(HeapObject* from, HeapObject* to) {
-  HashMap::Entry* from_cache_entry = entries_.Lookup(from, Hash(from), true);
-  HashMap::Entry* to_cache_entry = entries_.Lookup(to, Hash(to), false);
-  if (from_cache_entry->value == NULL) {
-    ASSERT(to_cache_entry != NULL);
-    from_cache_entry->value = MakeAlias(to_cache_entry->value);
+    delete reinterpret_cast<EntryInfo*>(p->value);
   }
 }
 
@@ -1646,8 +1636,7 @@ void HeapEntriesMap::Alias(HeapObject* from, HeapObject* to) {
 HeapEntry* HeapEntriesMap::Map(HeapObject* object) {
   HashMap::Entry* cache_entry = entries_.Lookup(object, Hash(object), false);
   if (cache_entry != NULL) {
-    EntryInfo* entry_info =
-        reinterpret_cast<EntryInfo*>(Unalias(cache_entry->value));
+    EntryInfo* entry_info = reinterpret_cast<EntryInfo*>(cache_entry->value);
     return entry_info->entry;
   } else {
     return NULL;
@@ -1671,9 +1660,9 @@ void HeapEntriesMap::CountReference(HeapObject* from, HeapObject* to,
   ASSERT(from_cache_entry != NULL);
   ASSERT(to_cache_entry != NULL);
   EntryInfo* from_entry_info =
-      reinterpret_cast<EntryInfo*>(Unalias(from_cache_entry->value));
+      reinterpret_cast<EntryInfo*>(from_cache_entry->value);
   EntryInfo* to_entry_info =
-      reinterpret_cast<EntryInfo*>(Unalias(to_cache_entry->value));
+      reinterpret_cast<EntryInfo*>(to_cache_entry->value);
   if (prev_children_count)
     *prev_children_count = from_entry_info->children_count;
   if (prev_retainers_count)
@@ -1685,6 +1674,36 @@ void HeapEntriesMap::CountReference(HeapObject* from, HeapObject* to,
 }
 
 
+HeapObjectsSet::HeapObjectsSet()
+    : entries_(HeapEntriesMap::HeapObjectsMatch) {
+}
+
+
+void HeapObjectsSet::Clear() {
+  entries_.Clear();
+}
+
+
+bool HeapObjectsSet::Contains(Object* obj) {
+  if (!obj->IsHeapObject()) return false;
+  HeapObject* object = HeapObject::cast(obj);
+  HashMap::Entry* cache_entry =
+      entries_.Lookup(object, HeapEntriesMap::Hash(object), false);
+  return cache_entry != NULL;
+}
+
+
+void HeapObjectsSet::Insert(Object* obj) {
+  if (!obj->IsHeapObject()) return;
+  HeapObject* object = HeapObject::cast(obj);
+  HashMap::Entry* cache_entry =
+      entries_.Lookup(object, HeapEntriesMap::Hash(object), true);
+  if (cache_entry->value == NULL) {
+    cache_entry->value = HeapEntriesMap::kHeapEntryPlaceholder;
+  }
+}
+
+
 HeapSnapshotGenerator::HeapSnapshotGenerator(HeapSnapshot* snapshot)
     : snapshot_(snapshot),
       collection_(snapshot->collection()),
@@ -1699,7 +1718,8 @@ class SnapshotCounter : public HeapSnapshotGenerator::SnapshotFillerInterface {
     entries_->Pair(obj, HeapEntriesMap::kHeapEntryPlaceholder);
     return HeapEntriesMap::kHeapEntryPlaceholder;
   }
-  void SetElementReference(HeapObject* parent_obj,
+  void SetIndexedReference(HeapGraphEdge::Type,
+                           HeapObject* parent_obj,
                            HeapEntry*,
                            int,
                            Object* child_obj,
@@ -1714,10 +1734,18 @@ class SnapshotCounter : public HeapSnapshotGenerator::SnapshotFillerInterface {
                          HeapEntry*) {
     entries_->CountReference(parent_obj, HeapObject::cast(child_obj));
   }
-  void SetRootReference(Object* child_obj, HeapEntry*) {
+  void SetRootShortcutReference(Object* child_obj, HeapEntry*) {
     entries_->CountReference(
         HeapSnapshot::kInternalRootObject, HeapObject::cast(child_obj));
   }
+  void SetRootGcRootsReference() {
+    entries_->CountReference(
+        HeapSnapshot::kInternalRootObject, HeapSnapshot::kGcRootsObject);
+  }
+  void SetStrongRootReference(Object* child_obj, HeapEntry*) {
+    entries_->CountReference(
+        HeapSnapshot::kGcRootsObject, HeapObject::cast(child_obj));
+  }
  private:
   HeapEntriesMap* entries_;
 };
@@ -1733,16 +1761,19 @@ class SnapshotFiller : public HeapSnapshotGenerator::SnapshotFillerInterface {
     UNREACHABLE();
     return NULL;
   }
-  void SetElementReference(HeapObject* parent_obj,
+  void SetIndexedReference(HeapGraphEdge::Type type,
+                           HeapObject* parent_obj,
                            HeapEntry* parent_entry,
                            int index,
                            Object* child_obj,
                            HeapEntry* child_entry) {
     int child_index, retainer_index;
-    entries_->CountReference(parent_obj, HeapObject::cast(child_obj),
-                             &child_index, &retainer_index);
-    parent_entry->SetElementReference(
-        child_index, index, child_entry, retainer_index);
+    entries_->CountReference(parent_obj,
+                             HeapObject::cast(child_obj),
+                             &child_index,
+                             &retainer_index);
+    parent_entry->SetIndexedReference(
+        type, child_index, index, child_entry, retainer_index);
   }
   void SetNamedReference(HeapGraphEdge::Type type,
                          HeapObject* parent_obj,
@@ -1759,13 +1790,43 @@ class SnapshotFiller : public HeapSnapshotGenerator::SnapshotFillerInterface {
                               child_entry,
                               retainer_index);
   }
-  void SetRootReference(Object* child_obj, HeapEntry* child_entry) {
+  void SetRootGcRootsReference() {
     int child_index, retainer_index;
-    entries_->CountReference(
-        HeapSnapshot::kInternalRootObject, HeapObject::cast(child_obj),
-        &child_index, &retainer_index);
-    snapshot_->root()->SetElementReference(
-        child_index, child_index + 1, child_entry, retainer_index);
+    entries_->CountReference(HeapSnapshot::kInternalRootObject,
+                             HeapSnapshot::kGcRootsObject,
+                             &child_index,
+                             &retainer_index);
+    snapshot_->root()->SetIndexedReference(HeapGraphEdge::kElement,
+                                           child_index,
+                                           child_index + 1,
+                                           snapshot_->gc_roots(),
+                                           retainer_index);
+  }
+  void SetRootShortcutReference(Object* child_obj,
+                                HeapEntry* child_entry) {
+    int child_index, retainer_index;
+    entries_->CountReference(HeapSnapshot::kInternalRootObject,
+                             HeapObject::cast(child_obj),
+                             &child_index,
+                             &retainer_index);
+    snapshot_->root()->SetNamedReference(HeapGraphEdge::kShortcut,
+                                         child_index,
+                                         collection_->GetName(child_index + 1),
+                                         child_entry,
+                                         retainer_index);
+  }
+  void SetStrongRootReference(Object* child_obj,
+                              HeapEntry* child_entry) {
+    int child_index, retainer_index;
+    entries_->CountReference(HeapSnapshot::kGcRootsObject,
+                             HeapObject::cast(child_obj),
+                             &child_index,
+                             &retainer_index);
+    snapshot_->gc_roots()->SetIndexedReference(HeapGraphEdge::kElement,
+                                               child_index,
+                                               child_index + 1,
+                                               child_entry,
+                                               retainer_index);
   }
  private:
   HeapSnapshot* snapshot_;
@@ -1788,6 +1849,18 @@ class SnapshotAllocator {
   HeapSnapshot* snapshot_;
 };
 
+class RootsReferencesExtractor : public ObjectVisitor {
+ public:
+  explicit RootsReferencesExtractor(HeapSnapshotGenerator* generator)
+      : generator_(generator) {
+  }
+  void VisitPointers(Object** start, Object** end) {
+    for (Object** p = start; p < end; p++) generator_->SetGcRootsReference(*p);
+  }
+ private:
+  HeapSnapshotGenerator* generator_;
+};
+

[Søren Thygesen Gjesse, 2010/11/18 08:14:54]

Add empty line.

[mnaganov (inactive), 2010/11/18 10:32:51]

Done.

 void HeapSnapshotGenerator::GenerateSnapshot() {
   AssertNoAllocation no_alloc;
 
@@ -1795,12 +1868,14 @@ void HeapSnapshotGenerator::GenerateSnapshot() {
   SnapshotCounter counter(&entries_);
   filler_ = &counter;
   filler_->AddEntry(HeapSnapshot::kInternalRootObject);
-  HeapIterator iterator1;
-  for (HeapObject* obj = iterator1.next();
-       obj != NULL;
-       obj = iterator1.next()) {
+  filler_->AddEntry(HeapSnapshot::kGcRootsObject);
+  HeapIterator iterator(HeapIterator::kPreciseFiltering);
+  for (HeapObject* obj = iterator.next(); obj != NULL; obj = iterator.next()) {
     ExtractReferences(obj);
   }
+  SetRootGcRootsReference();
+  RootsReferencesExtractor extractor(this);
+  Heap::IterateRoots(&extractor, VISIT_ONLY_STRONG);
 
   // Allocate and fill entries in the snapshot, allocate references.
   snapshot_->AllocateEntries(entries_.entries_count(),
@@ -1812,12 +1887,12 @@ void HeapSnapshotGenerator::GenerateSnapshot() {
   // Pass 2. Fill references.
   SnapshotFiller filler(snapshot_, &entries_);
   filler_ = &filler;
-  HeapIterator iterator2;
-  for (HeapObject* obj = iterator2.next();
-       obj != NULL;
-       obj = iterator2.next()) {
+  iterator.reset();
+  for (HeapObject* obj = iterator.next(); obj != NULL; obj = iterator.next()) {
     ExtractReferences(obj);
   }
+  SetRootGcRootsReference();
+  Heap::IterateRoots(&extractor, VISIT_ONLY_STRONG);
 }
 
 
@@ -1825,25 +1900,8 @@ HeapEntry* HeapSnapshotGenerator::GetEntry(Object* obj) {
   if (!obj->IsHeapObject()) return NULL;
   HeapObject* object = HeapObject::cast(obj);
   HeapEntry* entry = entries_.Map(object);
-
   // A new entry.
-  if (entry == NULL) {
-    if (obj->IsJSGlobalPropertyCell()) {
-      Object* cell_target = JSGlobalPropertyCell::cast(obj)->value();
-      entry = GetEntry(cell_target);
-      // If GPC references an object that we have interest in (see
-      // HeapSnapshot::AddEntry, WillAddEntry), add the object.  We
-      // don't store HeapEntries for GPCs. Instead, we make our hash
-      // map to point to object's HeapEntry by GPCs address.
-      if (entry != NULL) {
-        entries_.Alias(object, HeapObject::cast(cell_target));
-      }
-      return entry;
-    }
-
-    if (snapshot_->WillAddEntry(object)) entry = filler_->AddEntry(object);
-  }
-
+  if (entry == NULL) entry = filler_->AddEntry(object);
   return entry;
 }
 
@@ -1852,43 +1910,44 @@ class IndexedReferencesExtractor : public ObjectVisitor {
  public:
   IndexedReferencesExtractor(HeapSnapshotGenerator* generator,
                              HeapObject* parent_obj,
-                             HeapEntry* parent_entry)
+                             HeapEntry* parent_entry,
+                             HeapObjectsSet* knownReferences = NULL)

[Søren Thygesen Gjesse, 2010/11/18 08:14:54]

knownReferences -> known_references

[mnaganov (inactive), 2010/11/18 10:32:51]

Done.

       : generator_(generator),
         parent_obj_(parent_obj),
         parent_(parent_entry),
+        known_references_(knownReferences),
         next_index_(1) {
   }
-
-  void VisitPointer(Object** o) {
-    generator_->SetElementReference(parent_obj_, parent_, next_index_++, *o);
-  }
-
   void VisitPointers(Object** start, Object** end) {
-    for (Object** p = start; p < end; p++) VisitPointer(p);
+    for (Object** p = start; p < end; p++) {
+      if (!known_references_ || !known_references_->Contains(*p)) {
+        generator_->SetHiddenReference(parent_obj_, parent_, next_index_++, *p);
+      }
+    }
   }
-
  private:
   HeapSnapshotGenerator* generator_;
   HeapObject* parent_obj_;
   HeapEntry* parent_;
+  HeapObjectsSet* known_references_;
   int next_index_;
 };
 
 
 void HeapSnapshotGenerator::ExtractReferences(HeapObject* obj) {
-  // We need to reference JS global objects from snapshot's root.
-  // We use JSGlobalProxy because this is what embedder (e.g. browser)
-  // uses for the global object.
-  if (obj->IsJSGlobalProxy()) {
-    JSGlobalProxy* proxy = JSGlobalProxy::cast(obj);
-    SetRootReference(proxy->map()->prototype());
-    return;
-  }
-
   HeapEntry* entry = GetEntry(obj);
   if (entry == NULL) return;  // No interest in this object.
 
-  if (obj->IsJSObject()) {
+  known_references_.Clear();
+  if (obj->IsJSGlobalProxy()) {
+    // We need to reference JS global objects from snapshot's root.
+    // We use JSGlobalProxy because this is what embedder (e.g. browser)
+    // uses for the global object.
+    JSGlobalProxy* proxy = JSGlobalProxy::cast(obj);
+    SetRootShortcutReference(proxy->map()->prototype());
+    IndexedReferencesExtractor refs_extractor(this, obj, entry);
+    obj->Iterate(&refs_extractor);
+  } else if (obj->IsJSObject()) {
     JSObject* js_obj = JSObject::cast(obj);
     ExtractClosureReferences(js_obj, entry);
     ExtractPropertyReferences(js_obj, entry);
@@ -1903,16 +1962,16 @@ void HeapSnapshotGenerator::ExtractReferences(HeapObject* obj) {
             obj, entry, Heap::prototype_symbol(), js_fun->prototype());
       }
     }
+    IndexedReferencesExtractor refs_extractor(
+        this, obj, entry, &known_references_);
+    obj->Iterate(&refs_extractor);
   } else if (obj->IsString()) {
     if (obj->IsConsString()) {
       ConsString* cs = ConsString::cast(obj);
-      SetInternalReference(obj, entry, "1", cs->first());
-      SetInternalReference(obj, entry, "2", cs->second());
+      SetInternalReference(obj, entry, 1, cs->first());
+      SetInternalReference(obj, entry, 2, cs->second());
     }
-  } else if (obj->IsCode() || obj->IsSharedFunctionInfo() || obj->IsScript()) {
-    IndexedReferencesExtractor refs_extractor(this, obj, entry);
-    obj->Iterate(&refs_extractor);
-  } else if (obj->IsFixedArray()) {
+  } else {
     IndexedReferencesExtractor refs_extractor(this, obj, entry);
     obj->Iterate(&refs_extractor);
   }
@@ -1967,8 +2026,17 @@ void HeapSnapshotGenerator::ExtractPropertyReferences(JSObject* js_obj,
     for (int i = 0; i < length; ++i) {
       Object* k = dictionary->KeyAt(i);
       if (dictionary->IsKey(k)) {
+        Object* target = dictionary->ValueAt(i);
         SetPropertyReference(
-            js_obj, entry, String::cast(k), dictionary->ValueAt(i));
+            js_obj, entry, String::cast(k), target);
+        // We assume that global objects can only have slow properties.
+        if (target->IsJSGlobalPropertyCell()) {
+          SetPropertyShortcutReference(js_obj,
+                                       entry,
+                                       String::cast(k),
+                                       JSGlobalPropertyCell::cast(
+                                           target)->value());
+        }
       }
     }
   }
@@ -2024,6 +2092,7 @@ void HeapSnapshotGenerator::SetClosureReference(HeapObject* parent_obj,
                                collection_->GetName(reference_name),
                                child_obj,
                                child_entry);
+    known_references_.Insert(child_obj);
   }
 }
 
@@ -2034,8 +2103,13 @@ void HeapSnapshotGenerator::SetElementReference(HeapObject* parent_obj,
                                                 Object* child_obj) {
   HeapEntry* child_entry = GetEntry(child_obj);
   if (child_entry != NULL) {
-    filler_->SetElementReference(
-        parent_obj, parent_entry, index, child_obj, child_entry);
+    filler_->SetIndexedReference(HeapGraphEdge::kElement,
+                                 parent_obj,
+                                 parent_entry,
+                                 index,
+                                 child_obj,
+                                 child_entry);
+    known_references_.Insert(child_obj);
   }
 }
 
@@ -2052,6 +2126,7 @@ void HeapSnapshotGenerator::SetInternalReference(HeapObject* parent_obj,
                                reference_name,
                                child_obj,
                                child_entry);
+    known_references_.Insert(child_obj);
   }
 }
 
@@ -2068,6 +2143,23 @@ void HeapSnapshotGenerator::SetInternalReference(HeapObject* parent_obj,
                                collection_->GetName(index),
                                child_obj,
                                child_entry);
+    known_references_.Insert(child_obj);
+  }
+}
+
+
+void HeapSnapshotGenerator::SetHiddenReference(HeapObject* parent_obj,
+                                               HeapEntry* parent_entry,
+                                               int index,
+                                               Object* child_obj) {
+  HeapEntry* child_entry = GetEntry(child_obj);
+  if (child_entry != NULL) {
+    filler_->SetIndexedReference(HeapGraphEdge::kHidden,
+                                 parent_obj,
+                                 parent_entry,
+                                 index,
+                                 child_obj,
+                                 child_entry);
   }
 }
 
@@ -2086,14 +2178,45 @@ void HeapSnapshotGenerator::SetPropertyReference(HeapObject* parent_obj,
                                collection_->GetName(reference_name),
                                child_obj,
                                child_entry);
+    known_references_.Insert(child_obj);
   }
 }
 
 
-void HeapSnapshotGenerator::SetRootReference(Object* child_obj) {
+void HeapSnapshotGenerator::SetPropertyShortcutReference(
+    HeapObject* parent_obj,
+    HeapEntry* parent_entry,
+    String* reference_name,
+    Object* child_obj) {
+  HeapEntry* child_entry = GetEntry(child_obj);
+  if (child_entry != NULL) {
+    filler_->SetNamedReference(HeapGraphEdge::kShortcut,
+                               parent_obj,
+                               parent_entry,
+                               collection_->GetName(reference_name),
+                               child_obj,
+                               child_entry);
+  }
+}
+
+
+void HeapSnapshotGenerator::SetRootGcRootsReference() {
+  filler_->SetRootGcRootsReference();
+}
+
+
+void HeapSnapshotGenerator::SetRootShortcutReference(Object* child_obj) {
   HeapEntry* child_entry = GetEntry(child_obj);
   ASSERT(child_entry != NULL);
-  filler_->SetRootReference(child_obj, child_entry);
+  filler_->SetRootShortcutReference(child_obj, child_entry);
+}
+
+
+void HeapSnapshotGenerator::SetGcRootsReference(Object* child_obj) {
+  HeapEntry* child_entry = GetEntry(child_obj);
+  if (child_entry != NULL) {
+    filler_->SetStrongRootReference(child_obj, child_entry);
+  }
 }
 
 
@@ -2101,11 +2224,11 @@ void HeapSnapshotsDiff::CreateRoots(int additions_count, int deletions_count) {
   raw_additions_root_ =
       NewArray<char>(HeapEntry::EntriesSize(1, additions_count, 0));
   additions_root()->Init(
-      snapshot2_, HeapEntry::kInternal, "", 0, 0, additions_count, 0);
+      snapshot2_, HeapEntry::kHidden, "", 0, 0, additions_count, 0);
   raw_deletions_root_ =
       NewArray<char>(HeapEntry::EntriesSize(1, deletions_count, 0));
   deletions_root()->Init(
-      snapshot1_, HeapEntry::kInternal, "", 0, 0, deletions_count, 0);
+      snapshot1_, HeapEntry::kHidden, "", 0, 0, deletions_count, 0);
 }
 
 
@@ -2324,7 +2447,8 @@ void HeapSnapshotJSONSerializer::SerializeEdge(HeapGraphEdge* edge) {
   writer_->AddCharacter(',');
   writer_->AddNumber(edge->type());
   writer_->AddCharacter(',');
-  if (edge->type() == HeapGraphEdge::kElement) {
+  if (edge->type() == HeapGraphEdge::kElement
+      || edge->type() == HeapGraphEdge::kHidden) {
     writer_->AddNumber(edge->index());
   } else {
     writer_->AddNumber(GetStringId(edge->name()));
@@ -2355,13 +2479,13 @@ void HeapSnapshotJSONSerializer::SerializeNode(HeapEntry* entry) {
 
 
 void HeapSnapshotJSONSerializer::SerializeNodes() {
-  // The first (zero) item of nodes array is a JSON-ified object
-  // describing node serialization layout.
-  // We use a set of macros to improve readability.
+  // The first (zero) item of nodes array is an object describing node
+  // serialization layout.  We use a set of macros to improve
+  // readability.
 #define JSON_A(s) "["s"]"
 #define JSON_O(s) "{"s"}"
-#define JSON_S(s) "\\\""s"\\\""
-  writer_->AddString("\"" JSON_O(
+#define JSON_S(s) "\""s"\""
+  writer_->AddString(JSON_O(
     JSON_S("fields") ":" JSON_A(
         JSON_S("type")
         "," JSON_S("name")
@@ -2371,7 +2495,7 @@ void HeapSnapshotJSONSerializer::SerializeNodes() {
         "," JSON_S("children"))
     "," JSON_S("types") ":" JSON_A(
         JSON_A(
-            JSON_S("internal")
+            JSON_S("hidden")
             "," JSON_S("array")
             "," JSON_S("string")
             "," JSON_S("object")
@@ -2393,9 +2517,11 @@ void HeapSnapshotJSONSerializer::SerializeNodes() {
                     JSON_S("context")
                     "," JSON_S("element")
                     "," JSON_S("property")
-                    "," JSON_S("internal"))
+                    "," JSON_S("internal")
+                    "," JSON_S("hidden")
+                    "," JSON_S("shortcut"))
                 "," JSON_S("string_or_number")
-                "," JSON_S("node"))))) "\"");
+                "," JSON_S("node"))))));
 #undef JSON_S
 #undef JSON_O
 #undef JSON_A