Cardmarking writebarrier.

src/mark-compact.h

Index: src/mark-compact.h
diff --git a/src/mark-compact.h b/src/mark-compact.h
index 3950e7538bfdaf48531223942cee901b59d9a5fa..1d289a75928aefa8fba0c6b2914e03a4769bd376 100644
--- a/src/mark-compact.h
+++ b/src/mark-compact.h
@@ -41,7 +41,8 @@ typedef bool (*IsAliveFunction)(HeapObject* obj, int* size, int* offset);
 // no attempt to add area to free list is made.
 typedef void (*DeallocateFunction)(Address start,
                                    int size_in_bytes,
-                                   bool add_to_freelist);
+                                   bool add_to_freelist,
+                                   bool last_on_page);
 
 
 // Forward declarations.
@@ -131,8 +132,7 @@ class MarkCompactCollector: public AllStatic {
     SWEEP_SPACES,
     ENCODE_FORWARDING_ADDRESSES,
     UPDATE_POINTERS,
-    RELOCATE_OBJECTS,
-    REBUILD_RSETS
+    RELOCATE_OBJECTS
   };
 
   // The current stage of the collector.
@@ -269,22 +269,22 @@ class MarkCompactCollector: public AllStatic {
   //          written to their map word's offset in the inactive
   //          semispace.
   //
-  //          Bookkeeping data is written to the remembered-set are of
+  //          Bookkeeping data is written to the page header of
   //          eached paged-space page that contains live objects after
   //          compaction:
   //
-  //          The 3rd word of the page (first word of the remembered
-  //          set) contains the relocation top address, the address of
-  //          the first word after the end of the last live object in
-  //          the page after compaction.
+  //          The allocation watermark field is used to track the
+  //          relocation top address, the address of the first word
+  //          after the end of the last live object in the page after
+  //          compaction.
   //
-  //          The 4th word contains the zero-based index of the page in
-  //          its space.  This word is only used for map space pages, in
+  //          The Page::mc_page_index field contains the zero-based index of the
+  //          page in its space.  This word is only used for map space pages, in
   //          order to encode the map addresses in 21 bits to free 11
   //          bits per map word for the forwarding address.
   //
-  //          The 5th word contains the (nonencoded) forwarding address
-  //          of the first live object in the page.
+  //          The Page::mc_first_forwarded field contains the (nonencoded)
+  //          forwarding address of the first live object in the page.
   //
   //          In both the new space and the paged spaces, a linked list
   //          of live regions is constructructed (linked through
@@ -319,23 +319,28 @@ class MarkCompactCollector: public AllStatic {
   // generation.
   static void DeallocateOldPointerBlock(Address start,
                                         int size_in_bytes,
-                                        bool add_to_freelist);
+                                        bool add_to_freelist,
+                                        bool last_on_page);
 
   static void DeallocateOldDataBlock(Address start,
                                      int size_in_bytes,
-                                     bool add_to_freelist);
+                                     bool add_to_freelist,
+                                     bool last_on_page);
 
   static void DeallocateCodeBlock(Address start,
                                   int size_in_bytes,
-                                  bool add_to_freelist);
+                                  bool add_to_freelist,
+                                  bool last_on_page);
 
   static void DeallocateMapBlock(Address start,
                                  int size_in_bytes,
-                                 bool add_to_freelist);
+                                 bool add_to_freelist,
+                                 bool last_on_page);
 
   static void DeallocateCellBlock(Address start,
                                   int size_in_bytes,
-                                  bool add_to_freelist);
+                                  bool add_to_freelist,
+                                  bool last_on_page);
 
   // If we are not compacting the heap, we simply sweep the spaces except
   // for the large object space, clearing mark bits and adding unmarked
@@ -349,9 +354,7 @@ class MarkCompactCollector: public AllStatic {
   //
   //   After: All pointers in live objects, including encoded map
   //          pointers, are updated to point to their target's new
-  //          location.  The remembered set area of each paged-space
-  //          page containing live objects still contains bookkeeping
-  //          information.
+  //          location.
 
   friend class UpdatingVisitor;  // helper for updating visited objects
 
@@ -373,13 +376,9 @@ class MarkCompactCollector: public AllStatic {
   // Phase 4: Relocating objects.
   //
   //  Before: Pointers to live objects are updated to point to their
-  //          target's new location.  The remembered set area of each
-  //          paged-space page containing live objects still contains
-  //          bookkeeping information.
+  //          target's new location.
   //
-  //   After: Objects have been moved to their new addresses. The
-  //          remembered set area of each paged-space page containing
-  //          live objects still contains bookkeeping information.
+  //   After: Objects have been moved to their new addresses.
 
   // Relocates objects in all spaces.
   static void RelocateObjects();
@@ -408,17 +407,6 @@ class MarkCompactCollector: public AllStatic {
   // Copy a new object.
   static int RelocateNewObject(HeapObject* obj);
 
-  // -----------------------------------------------------------------------
-  // Phase 5: Rebuilding remembered sets.
-  //
-  //  Before: The heap is in a normal state except that remembered sets
-  //          in the paged spaces are not correct.
-  //
-  //   After: The heap is in a normal state.
-
-  // Rebuild remembered set in old and map spaces.
-  static void RebuildRSets();
-
 #ifdef DEBUG
   // -----------------------------------------------------------------------
   // Debugging variables, functions and classes