Implemented lazy sweeping of new space.

src/store-buffer.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 25 matching lines @@
 
 namespace v8 {
 namespace internal {
 
 class Page;
 class PagedSpace;
 class StoreBuffer;
 
 typedef void (*ObjectSlotCallback)(HeapObject** from, HeapObject* to);
 
-typedef void (StoreBuffer::*RegionCallback)(
-    Address start, Address end, ObjectSlotCallback slot_callback);
+typedef void (StoreBuffer::*RegionCallback)(Address start,
+                                            Address end,
+                                            ObjectSlotCallback slot_callback,
+                                            bool clear_maps);
 
 // Used to implement the write barrier by collecting addresses of pointers
 // between spaces.
 class StoreBuffer {
  public:
   explicit StoreBuffer(Heap* heap);
 
   static void StoreBufferOverflow(Isolate* isolate);
 
   inline Address TopAddress();
@@ skipping 18 matching lines @@
   // exempt from the store buffer and process the promotion queue.  These steps
   // can overflow this buffer.  We check for this and on overflow we call the
   // callback set up with the StoreBufferRebuildScope object.
   inline void EnterDirectlyIntoStoreBuffer(Address addr);
 
   // Iterates over all pointers that go from old space to new space.  It will
   // delete the store buffer as it starts so the callback should reenter
   // surviving old-to-new pointers into the store buffer to rebuild it.
   void IteratePointersToNewSpace(ObjectSlotCallback callback);
 
+  // Same as IteratePointersToNewSpace but additonally clears maps in objects
+  // referenced from the store buffer that do not contain a forwarding pointer.
+  void IteratePointersToNewSpaceAndClearMaps(ObjectSlotCallback callback);
+
   static const int kStoreBufferOverflowBit = 1 << (14 + kPointerSizeLog2);
   static const int kStoreBufferSize = kStoreBufferOverflowBit;
   static const int kStoreBufferLength = kStoreBufferSize / sizeof(Address);
   static const int kOldStoreBufferLength = kStoreBufferLength * 16;
   static const int kHashSetLengthLog2 = 12;
   static const int kHashSetLength = 1 << kHashSetLengthLog2;
 
   void Compact();
 
   void GCPrologue();
@@ skipping 61 matching lines @@
   uintptr_t* hash_set_1_;
   uintptr_t* hash_set_2_;
   bool hash_sets_are_empty_;
 
   void ClearFilteringHashSets();
 
   bool SpaceAvailable(intptr_t space_needed);
   void Uniq();
   void ExemptPopularPages(int prime_sample_step, int threshold);
 
+  // Set the map field of the object to NULL if contains a map.
+  inline void ClearDeadObject(HeapObject *object);
+
+  void IteratePointersToNewSpace(ObjectSlotCallback callback, bool clear_maps);
+
   void FindPointersToNewSpaceInRegion(Address start,
                                       Address end,
-                                      ObjectSlotCallback slot_callback);
+                                      ObjectSlotCallback slot_callback,
+                                      bool clear_maps);
 
   // For each region of pointers on a page in use from an old space call
   // visit_pointer_region callback.
   // If either visit_pointer_region or callback can cause an allocation
   // in old space and changes in allocation watermark then
   // can_preallocate_during_iteration should be set to true.
   void IteratePointersOnPage(
       PagedSpace* space,
       Page* page,
       RegionCallback region_callback,
       ObjectSlotCallback slot_callback);
 
   void FindPointersToNewSpaceInMaps(
     Address start,
     Address end,
-    ObjectSlotCallback slot_callback);
+    ObjectSlotCallback slot_callback,
+    bool clear_maps);
 
   void FindPointersToNewSpaceInMapsRegion(
     Address start,
     Address end,
-    ObjectSlotCallback slot_callback);
+    ObjectSlotCallback slot_callback,
+    bool clear_maps);
 
   void FindPointersToNewSpaceOnPage(
     PagedSpace* space,
     Page* page,
     RegionCallback region_callback,
-    ObjectSlotCallback slot_callback);
+    ObjectSlotCallback slot_callback,
+    bool clear_maps);
 
-  void IteratePointersInStoreBuffer(ObjectSlotCallback slot_callback);
+  void IteratePointersInStoreBuffer(ObjectSlotCallback slot_callback,
+                                    bool clear_maps);
 
 #ifdef VERIFY_HEAP
   void VerifyPointers(PagedSpace* space, RegionCallback region_callback);
   void VerifyPointers(LargeObjectSpace* space);
 #endif
 
   friend class StoreBufferRebuildScope;
   friend class DontMoveStoreBufferEntriesScope;
 };
 
@@ skipping 36 matching lines @@
   }
 
  private:
   StoreBuffer* store_buffer_;
   bool stored_state_;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_STORE_BUFFER_H_