New GC APIs, try 2.

src/global-handles.h

 // Copyright 2011 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 10 matching lines @@
 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 #ifndef V8_GLOBAL_HANDLES_H_
 #define V8_GLOBAL_HANDLES_H_
 
+#include "../include/v8.h"
 #include "../include/v8-profiler.h"
 
 #include "list.h"
 #include "v8utils.h"
 
 namespace v8 {
 namespace internal {
 
 class GCTracer;
 class HeapStats;
 class ObjectVisitor;
 
 // Structure for tracking global handles.
 // A single list keeps all the allocated global handles.
 // Destroyed handles stay in the list but is added to the free list.
 // At GC the destroyed global handles are removed from the free list
 // and deallocated.
 
+// Data structures for tracking object groups and implicit references.
+
 // An object group is treated like a single JS object: if one of object in
 // the group is alive, all objects in the same group are considered alive.
 // An object group is used to simulate object relationship in a DOM tree.
-class ObjectGroup {
- public:
-  static ObjectGroup* New(Object*** handles,
-                          size_t length,
-                          v8::RetainedObjectInfo* info) {
+
+// An implicit references group consists of two parts: a parent object and a
+// list of children objects.  If the parent is alive, all the children are alive
+// too.
+
+struct ObjectGroup {
+  explicit ObjectGroup(size_t length)
+      : info(NULL), length(length) {
     ASSERT(length > 0);
-    ObjectGroup* group = reinterpret_cast<ObjectGroup*>(
-        malloc(OFFSET_OF(ObjectGroup, objects_[length])));
-    group->length_ = length;
-    group->info_ = info;
-    CopyWords(group->objects_, handles, static_cast<int>(length));
-    return group;
+    objects = new Object**[length];
   }
+  ~ObjectGroup();
 
-  void Dispose() {
-    if (info_ != NULL) info_->Dispose();
-    free(this);
-  }
-
-  size_t length_;
-  v8::RetainedObjectInfo* info_;
-  Object** objects_[1];  // Variable sized array.
-
- private:
-  void* operator new(size_t size);
-  void operator delete(void* p);
-  ~ObjectGroup();
-  DISALLOW_IMPLICIT_CONSTRUCTORS(ObjectGroup);
+  v8::RetainedObjectInfo* info;
+  Object*** objects;
+  size_t length;
 };
 
 
-// An implicit references group consists of two parts: a parent object and
-// a list of children objects.  If the parent is alive, all the children
-// are alive too.
-class ImplicitRefGroup {
- public:
-  static ImplicitRefGroup* New(HeapObject** parent,
-                               Object*** children,
-                               size_t length) {
+struct ImplicitRefGroup {
+  ImplicitRefGroup(HeapObject** parent, size_t length)
+      : parent(parent), length(length) {
     ASSERT(length > 0);
-    ImplicitRefGroup* group = reinterpret_cast<ImplicitRefGroup*>(
-        malloc(OFFSET_OF(ImplicitRefGroup, children_[length])));
-    group->parent_ = parent;
-    group->length_ = length;
-    CopyWords(group->children_, children, length);
-    return group;
+    children = new Object**[length];
   }
+  ~ImplicitRefGroup();
 
-  void Dispose() {
-    free(this);
-  }
-
-  HeapObject** parent_;
-  size_t length_;
-  Object** children_[1];  // Variable sized array.
-
- private:
-  void* operator new(size_t size);
-  void operator delete(void* p);
-  ~ImplicitRefGroup();
-  DISALLOW_IMPLICIT_CONSTRUCTORS(ImplicitRefGroup);
+  HeapObject** parent;
+  Object*** children;
+  size_t length;
 };
 
 
+// For internal bookkeeping.
+struct ObjectGroupConnection {
+  ObjectGroupConnection(UniqueId id, Object** object)
+      : id(id), object(object) {}
+
+  bool operator==(const ObjectGroupConnection& other) const {
+    return id == other.id;
+  }
+
+  bool operator<(const ObjectGroupConnection& other) const {
+    return id < other.id;
+  }
+
+  UniqueId id;
+  Object** object;
+};
+
+
+struct ObjectGroupRetainerInfo {
+  ObjectGroupRetainerInfo(UniqueId id, RetainedObjectInfo* info)
+      : id(id), info(info) {}
+
+  bool operator==(const ObjectGroupRetainerInfo& other) const {
+    return id == other.id;
+  }
+
+  bool operator<(const ObjectGroupRetainerInfo& other) const {
+    return id < other.id;
+  }
+
+  UniqueId id;
+  RetainedObjectInfo* info;
+};
+
+
 class GlobalHandles {
  public:
   ~GlobalHandles();
 
   // Creates a new global handle that is alive until Destroy is called.
   Handle<Object> Create(Object* value);
 
   // Destroy a global handle.
   void Destroy(Object** location);
 
@@ skipping 85 matching lines @@
   // can be skipped and false otherwise.
   bool IterateObjectGroups(ObjectVisitor* v, WeakSlotCallbackWithHeap can_skip);
 
   // Add an object group.
   // Should be only used in GC callback function before a collection.
   // All groups are destroyed after a garbage collection.
   void AddObjectGroup(Object*** handles,
                       size_t length,
                       v8::RetainedObjectInfo* info);
 
+  // Associates handle with the object group represented by id.
+  // Should be only used in GC callback function before a collection.
+  // All groups are destroyed after a garbage collection.
+  void SetObjectGroupId(Object** handle, UniqueId id);
+
+  // Set RetainedObjectInfo for an object group. Should not be called more than
+  // once for a group. Should not be called for a group which contains no
+  // handles.
+  void SetRetainedObjectInfo(UniqueId id, RetainedObjectInfo* info);
+
   // Add an implicit references' group.
   // Should be only used in GC callback function before a collection.
   // All groups are destroyed after a mark-compact collection.
   void AddImplicitReferences(HeapObject** parent,
                              Object*** children,
                              size_t length);
 
-  // Returns the object groups.
-  List<ObjectGroup*>* object_groups() { return &object_groups_; }
+  // Adds an implicit reference from a group to an object. Should be only used
+  // in GC callback function before a collection. All implicit references are
+  // destroyed after a mark-compact collection.
+  void SetReferenceFromGroup(UniqueId id, Object** child);
 
-  // Returns the implicit references' groups.
+  // Adds an implicit reference from a parent object to a child object. Should
+  // be only used in GC callback function before a collection. All implicit
+  // references are destroyed after a mark-compact collection.
+  void SetReference(HeapObject** parent, Object** child);
+
+  List<ObjectGroup*>* object_groups() {
+    ComputeObjectGroupsAndImplicitReferences();
+    return &object_groups_;
+  }
+
   List<ImplicitRefGroup*>* implicit_ref_groups() {
+    ComputeObjectGroupsAndImplicitReferences();
     return &implicit_ref_groups_;
   }
 
   // Remove bags, this should only happen after GC.
   void RemoveObjectGroups();
   void RemoveImplicitRefGroups();
 
   // Tear down the global handle structure.
   void TearDown();
 
   Isolate* isolate() { return isolate_; }
 
 #ifdef DEBUG
   void PrintStats();
   void Print();
 #endif
 
  private:
   explicit GlobalHandles(Isolate* isolate);
 
+  // Migrates data from the internal representation (object_group_connections_,
+  // retainer_infos_ and implicit_ref_connections_) to the public and more
+  // efficient representation (object_groups_ and implicit_ref_groups_).
+  void ComputeObjectGroupsAndImplicitReferences();
+
+  // v8::internal::List is inefficient even for small number of elements, if we
+  // don't assign any initial capacity.
+  static const int kObjectGroupConnectionsCapacity = 20;
+
   // Internal node structures.
   class Node;
   class NodeBlock;
   class NodeIterator;
 
   Isolate* isolate_;
 
   // Field always containing the number of handles to global objects.
   int number_of_global_handles_;
 
   // List of all allocated node blocks.
   NodeBlock* first_block_;
 
   // List of node blocks with used nodes.
   NodeBlock* first_used_block_;
 
   // Free list of nodes.
   Node* first_free_;
 
   // Contains all nodes holding new space objects. Note: when the list
   // is accessed, some of the objects may have been promoted already.
   List<Node*> new_space_nodes_;
 
   int post_gc_processing_count_;
 
+  // Object groups and implicit references, public and more efficient
+  // representation.
   List<ObjectGroup*> object_groups_;
   List<ImplicitRefGroup*> implicit_ref_groups_;
 
+  // Object groups and implicit references, temporary representation while
+  // constructing the groups.
+  List<ObjectGroupConnection> object_group_connections_;
+  List<ObjectGroupRetainerInfo> retainer_infos_;
+  List<ObjectGroupConnection> implicit_ref_connections_;
+
   friend class Isolate;
 
   DISALLOW_COPY_AND_ASSIGN(GlobalHandles);
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_GLOBAL_HANDLES_H_