Revert r4715.

src/mark-compact.h

Index: src/mark-compact.h
===================================================================
--- src/mark-compact.h	(revision 4722)
+++ src/mark-compact.h	(working copy)
@@ -41,8 +41,7 @@
 // no attempt to add area to free list is made.
 typedef void (*DeallocateFunction)(Address start,
                                    int size_in_bytes,
-                                   bool add_to_freelist,
-                                   bool last_on_page);
+                                   bool add_to_freelist);
 
 
 // Forward declarations.
@@ -132,7 +131,8 @@
     SWEEP_SPACES,
     ENCODE_FORWARDING_ADDRESSES,
     UPDATE_POINTERS,
-    RELOCATE_OBJECTS
+    RELOCATE_OBJECTS,
+    REBUILD_RSETS
   };
 
   // The current stage of the collector.
@@ -269,22 +269,22 @@
   //          written to their map word's offset in the inactive
   //          semispace.
   //
-  //          Bookkeeping data is written to the page header of
+  //          Bookkeeping data is written to the remembered-set are of
   //          eached paged-space page that contains live objects 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 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 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
+  //          The 4th word 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 Page::mc_first_forwarded field contains the (nonencoded)
-  //          forwarding address of the first live object in the page.
+  //          The 5th word 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
@@ -319,28 +319,23 @@
   // generation.
   static void DeallocateOldPointerBlock(Address start,
                                         int size_in_bytes,
-                                        bool add_to_freelist,
-                                        bool last_on_page);
+                                        bool add_to_freelist);
 
   static void DeallocateOldDataBlock(Address start,
                                      int size_in_bytes,
-                                     bool add_to_freelist,
-                                     bool last_on_page);
+                                     bool add_to_freelist);
 
   static void DeallocateCodeBlock(Address start,
                                   int size_in_bytes,
-                                  bool add_to_freelist,
-                                  bool last_on_page);
+                                  bool add_to_freelist);
 
   static void DeallocateMapBlock(Address start,
                                  int size_in_bytes,
-                                 bool add_to_freelist,
-                                 bool last_on_page);
+                                 bool add_to_freelist);
 
   static void DeallocateCellBlock(Address start,
                                   int size_in_bytes,
-                                  bool add_to_freelist,
-                                  bool last_on_page);
+                                  bool add_to_freelist);
 
   // If we are not compacting the heap, we simply sweep the spaces except
   // for the large object space, clearing mark bits and adding unmarked
@@ -354,7 +349,9 @@
   //
   //   After: All pointers in live objects, including encoded map
   //          pointers, are updated to point to their target's new
-  //          location.
+  //          location.  The remembered set area of each paged-space
+  //          page containing live objects still contains bookkeeping
+  //          information.
 
   friend class UpdatingVisitor;  // helper for updating visited objects
 
@@ -376,9 +373,13 @@
   // Phase 4: Relocating objects.
   //
   //  Before: Pointers to live objects are updated to point to their
-  //          target's new location.
+  //          target's new location.  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.
+  //   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.
 
   // Relocates objects in all spaces.
   static void RelocateObjects();
@@ -407,6 +408,17 @@
   // 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