Implement map collection for incremental marking.

src/mark-compact.h

 // Copyright 2012 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 566 matching lines @@
   bool reduce_memory_footprint_;
 
   bool abort_incremental_marking_;
 
   // True if we are collecting slots to perform evacuation from evacuation
   // candidates.
   bool compacting_;
 
   bool was_marked_incrementally_;
 
-  bool collect_maps_;
+  bool clear_map_transitions_;
 
   bool flush_monomorphic_ics_;
 
   // A pointer to the current stack-allocated GC tracer object during a full
   // collection (NULL before and after).
   GCTracer* tracer_;
 
   SlotsBufferAllocator slots_buffer_allocator_;
 
   SlotsBuffer* migration_slots_buffer_;
 
   // Finishes GC, performs heap verification if enabled.
   void Finish();
 
   // -----------------------------------------------------------------------
   // Phase 1: Marking live objects.
   //
   //  Before: The heap has been prepared for garbage collection by
   //          MarkCompactCollector::Prepare() and is otherwise in its
   //          normal state.
   //
   //   After: Live objects are marked and non-live objects are unmarked.
 
-
   friend class RootMarkingVisitor;
   friend class MarkingVisitor;
   friend class StaticMarkingVisitor;
   friend class CodeMarkingVisitor;
   friend class SharedFunctionInfoMarkingVisitor;
+  friend class IncrementalMarking;
 
   // Mark non-optimize code for functions inlined into the given optimized
   // code. This will prevent it from being flushed.
   void MarkInlinedFunctionsCode(Code* code);
 
   // Mark code objects that are active on the stack to prevent them
   // from being flushed.
   void PrepareThreadForCodeFlushing(Isolate* isolate, ThreadLocalTop* top);
 
   void PrepareForCodeFlushing();
 
   // Marking operations for objects reachable from roots.
   void MarkLiveObjects();
 
   void AfterMarking();
 
   // Marks the object black and pushes it on the marking stack.
   // This is for non-incremental marking.
   INLINE(void MarkObject(HeapObject* obj, MarkBit mark_bit));
 
   INLINE(bool MarkObjectWithoutPush(HeapObject* object));
   INLINE(void MarkObjectAndPush(HeapObject* value));
 
   // Marks the object black.  This is for non-incremental marking.
   INLINE(void SetMark(HeapObject* obj, MarkBit mark_bit));
 
   void ProcessNewlyMarkedObject(HeapObject* obj);
 
-  // Mark a Map and its DescriptorArray together, skipping transitions.
-  void MarkMapContents(Map* map);
+  // Mark weak pointers in a Map and its DescriptorArray together, possibly
+  // skipping transitions or back pointers.
+  void MarkWeakMapContents(Map* map);
   void MarkAccessorPairSlot(HeapObject* accessors, int offset);
   void MarkDescriptorArray(DescriptorArray* descriptors);
 
   // Mark the heap roots and all objects reachable from them.
   void MarkRoots(RootMarkingVisitor* visitor);
 
   // Mark the symbol table specially.  References to symbols from the
   // symbol table are weak.
   void MarkSymbolTable();
 
@@ skipping 98 matching lines @@
 
   friend class Heap;
 };
 
 
 const char* AllocationSpaceName(AllocationSpace space);
 
 } }  // namespace v8::internal
 
 #endif  // V8_MARK_COMPACT_H_