Eliminate internal and hidden links to oddballs and other non-essential objects in heap snapshot.

src/profile-generator.cc

 // Copyright 2012 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 2443 matching lines @@
   if (object->IsJSGlobalObject()) {
     const char* tag = objects_tags_.GetTag(object);
     if (tag != NULL) {
       name = collection_->names()->GetFormatted("%s / %s", name, tag);
     }
   }
   GetEntry(object)->set_name(name);
 }
 
 
+bool V8HeapExplorer::IsEssentialObject(Object* object) {
+  // We have to use raw_unchecked_* versions because checked versions
+  // would fail during iteration over object properties.
+  return object->IsHeapObject()
+      && !object->IsOddball()
+      && object != heap_->raw_unchecked_empty_byte_array()
+      && object != heap_->raw_unchecked_empty_fixed_array()
+      && object != heap_->raw_unchecked_empty_descriptor_array()
+      && object != heap_->raw_unchecked_fixed_array_map()
+      && object != heap_->raw_unchecked_global_property_cell_map()
+      && object != heap_->raw_unchecked_shared_function_info_map();
+}
+
+
 void V8HeapExplorer::SetClosureReference(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::kContextVariable,
                                parent_obj,
                                parent_entry,
                                collection_->names()->GetName(reference_name),
@@ skipping 35 matching lines @@
 }
 
 
 void V8HeapExplorer::SetInternalReference(HeapObject* parent_obj,
                                           HeapEntry* parent_entry,
                                           const char* reference_name,
                                           Object* child_obj,
                                           int field_offset) {
   HeapEntry* child_entry = GetEntry(child_obj);
   if (child_entry == NULL) return;
-  // We have to use raw_unchecked_* version because when the
-  // empty_fixed_array itself is being processed all its inline properties
-  // are invalid and the check in empty_fixed_array() function fails.
-  if (child_obj != heap_->raw_unchecked_empty_fixed_array()) {
+  if (IsEssentialObject(child_obj)) {
     filler_->SetNamedReference(HeapGraphEdge::kInternal,
                                parent_obj, parent_entry,
                                reference_name,
                                child_obj, child_entry);
   }
   IndexedReferencesExtractor::MarkVisitedField(parent_obj, field_offset);
 }
 
 
 void V8HeapExplorer::SetInternalReference(HeapObject* parent_obj,
                                           HeapEntry* parent_entry,
                                           int index,
                                           Object* child_obj,
                                           int field_offset) {
   HeapEntry* child_entry = GetEntry(child_obj);
   if (child_entry == NULL) return;
-  // See the comment regarding raw_unchecked_* above.
-  if (child_obj != heap_->raw_unchecked_empty_fixed_array()) {
+  if (IsEssentialObject(child_obj)) {
     filler_->SetNamedReference(HeapGraphEdge::kInternal,
                                parent_obj, parent_entry,
                                collection_->names()->GetName(index),
                                child_obj, child_entry);
   }
   IndexedReferencesExtractor::MarkVisitedField(parent_obj, field_offset);
 }
 
 
 void V8HeapExplorer::SetHiddenReference(HeapObject* parent_obj,
                                         HeapEntry* parent_entry,
                                         int index,
                                         Object* child_obj) {
   HeapEntry* child_entry = GetEntry(child_obj);
-  if (child_entry != NULL) {
+  if (child_entry != NULL && IsEssentialObject(child_obj)) {
     filler_->SetIndexedReference(HeapGraphEdge::kHidden,
                                  parent_obj,
                                  parent_entry,
                                  index,
                                  child_obj,
                                  child_entry);
   }
 }
 
 
@@ skipping 119 matching lines @@
     SYMBOL_LIST(SYMBOL_NAME)
 #undef SYMBOL_NAME
 #undef NAME_ENTRY
     CHECK(!strong_gc_subroot_names_.is_empty());
   }
   return strong_gc_subroot_names_.GetTag(object);
 }
 
 
 void V8HeapExplorer::TagObject(Object* obj, const char* tag) {
-  if (obj->IsHeapObject() &&
-      !obj->IsOddball() &&
-      obj != heap_->raw_unchecked_empty_byte_array() &&
-      obj != heap_->raw_unchecked_empty_fixed_array() &&
-      obj != heap_->raw_unchecked_empty_descriptor_array()) {
+  if (IsEssentialObject(obj)) {
     objects_tags_.SetTag(obj, tag);
   }
 }
 
 
 class GlobalObjectsEnumerator : public ObjectVisitor {
  public:
   virtual void VisitPointers(Object** start, Object** end) {
     for (Object** p = start; p < end; p++) {
       if ((*p)->IsGlobalContext()) {
@@ skipping 1219 matching lines @@
 
 
 void HeapSnapshotJSONSerializer::SortHashMap(
     HashMap* map, List<HashMap::Entry*>* sorted_entries) {
   for (HashMap::Entry* p = map->Start(); p != NULL; p = map->Next(p))
     sorted_entries->Add(p);
   sorted_entries->Sort(SortUsingEntryValue);
 }
 
 } }  // namespace v8::internal