Implemented lazy sweeping of new space.

src/store-buffer.h

Index: src/store-buffer.h
diff --git a/src/store-buffer.h b/src/store-buffer.h
index 520cbc01626b698607928dbd83638ba220096fb2..01e7cbeb8d2a439784617f20a16a61793df14459 100644
--- a/src/store-buffer.h
+++ b/src/store-buffer.h
@@ -43,8 +43,10 @@ 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.
@@ -83,6 +85,10 @@ class StoreBuffer {
   // 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);
@@ -164,9 +170,15 @@ class StoreBuffer {
   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.
@@ -182,20 +194,24 @@ class StoreBuffer {
   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);