Sharing of descriptor arrays.

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 1991 matching lines @@
 
 
 void V8HeapExplorer::ExtractMapReferences(int entry, Map* map) {
   SetInternalReference(map, entry,
                        "prototype", map->prototype(), Map::kPrototypeOffset);
   SetInternalReference(map, entry,
                        "constructor", map->constructor(),
                        Map::kConstructorOffset);
   if (map->HasTransitionArray()) {
     TransitionArray* transitions = map->transitions();
-    if (!transitions->descriptors()->IsEmpty()) {
-      DescriptorArray* descriptors = transitions->descriptors();
-      TagObject(descriptors, "(map descriptors)");
-      SetInternalReference(transitions, entry,
-                           "descriptors", descriptors,
-                           TransitionArray::kDescriptorsOffset);
-      IndexedReferencesExtractor refs_extractor(
-          this, transitions, entry);
-      transitions->Iterate(&refs_extractor);
-    }
+    JSGlobalPropertyCell* pointer = transitions->descriptors_pointer();
+    DescriptorArray* descriptors = transitions->descriptors();
+    TagObject(descriptors, "(map descriptors)");
+    SetInternalReference(pointer, entry,
+                         "descriptors", descriptors,
+                         JSGlobalPropertyCell::kValueOffset);
+    IndexedReferencesExtractor pointer_refs(this, pointer, entry);
+    pointer->Iterate(&pointer_refs);
+
+    Object* back_pointer = transitions->back_pointer_storage();
+    TagObject(transitions->back_pointer_storage(), "(back pointer)");
+    SetInternalReference(transitions, entry,
+                         "backpointer", back_pointer,
+                         TransitionArray::kBackPointerStorageOffset);
+    IndexedReferencesExtractor transitions_refs(this, transitions, entry);
+    transitions->Iterate(&transitions_refs);
+
     TagObject(transitions, "(transition array)");
     SetInternalReference(map, entry,
                          "transitions", transitions,
                          Map::kTransitionsOrBackPointerOffset);
+  } else {
+    Object* back_pointer = map->GetBackPointer();
+    TagObject(back_pointer, "(back pointer)");
+    SetInternalReference(map, entry,
+                         "backpointer", back_pointer,
+                         Map::kTransitionsOrBackPointerOffset);
   }
   SetInternalReference(map, entry,
                        "code_cache", map->code_cache(),
                        Map::kCodeCacheOffset);
 }
 
 
 void V8HeapExplorer::ExtractSharedFunctionInfoReferences(
     int entry, SharedFunctionInfo* shared) {
   HeapObject* obj = shared;
@@ skipping 136 matching lines @@
         SetClosureReference(js_obj, entry, name, context->get(idx));
       }
     }
   }
 }
 
 
 void V8HeapExplorer::ExtractPropertyReferences(JSObject* js_obj, int entry) {
   if (js_obj->HasFastProperties()) {
     DescriptorArray* descs = js_obj->map()->instance_descriptors();
+    int real_size = js_obj->map()->NumberOfOwnDescriptors();
     for (int i = 0; i < descs->number_of_descriptors(); i++) {
+      if (descs->GetDetails(i).descriptor_index() > real_size) continue;
       switch (descs->GetType(i)) {
         case FIELD: {
           int index = descs->GetFieldIndex(i);
 
           String* k = descs->GetKey(i);
           if (index < js_obj->map()->inobject_properties()) {
             Object* value = js_obj->InObjectPropertyAt(index);
             if (k != heap_->hidden_symbol()) {
               SetPropertyReference(
                   js_obj, entry,
@@ skipping 1373 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