Untangle slots buffer part 1: Make invalid slots filtering part of MarkCompactCollector.

src/heap/mark-compact.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_HEAP_MARK_COMPACT_H_
 #define V8_HEAP_MARK_COMPACT_H_
 
 #include "src/base/bits.h"
 #include "src/heap/spaces.h"
 
@@ skipping 288 matching lines @@
   void Add(ObjectSlot slot) {
     DCHECK(0 <= idx_ && idx_ < kNumberOfElements);
 #ifdef DEBUG
     if (slot >= reinterpret_cast<ObjectSlot>(NUMBER_OF_SLOT_TYPES)) {
       DCHECK_NOT_NULL(*slot);
     }
 #endif
     slots_[idx_++] = slot;
   }
 
-  // Should be used for testing only.
+  void Set(intptr_t i, ObjectSlot slot) { slots_[i] = slot; }
+
   ObjectSlot Get(intptr_t i) {
-    DCHECK(i >= 0 && i < kNumberOfElements);
+    DCHECK(i >= 0 && i < idx_);
     return slots_[i];
   }
 
+  size_t Size() const { return idx_; }
+
   enum SlotType {
     EMBEDDED_OBJECT_SLOT,
     OBJECT_SLOT,
     RELOCATED_CODE_OBJECT,
     CELL_TARGET_SLOT,
     CODE_TARGET_SLOT,
     CODE_ENTRY_SLOT,
     DEBUG_TARGET_SLOT,
     NUMBER_OF_SLOT_TYPES
   };
@@ skipping 64 matching lines @@
     buffer->Add(slot);
     return true;
   }
 
   static bool IsTypedSlot(ObjectSlot slot);
 
   static bool AddTo(SlotsBufferAllocator* allocator,
                     SlotsBuffer** buffer_address, SlotType type, Address addr,
                     AdditionMode mode);
 
-  // Eliminates all stale entries from the slots buffer, i.e., slots that
-  // are not part of live objects anymore. This method must be called after
-  // marking, when the whole transitive closure is known and must be called
-  // before sweeping when mark bits are still intact.
-  static void RemoveInvalidSlots(Heap* heap, SlotsBuffer* buffer);
-
   // Eliminate all slots that are within the given address range.
   static void RemoveObjectSlots(Heap* heap, SlotsBuffer* buffer,
                                 Address start_slot, Address end_slot);
 
-  // Ensures that there are no invalid slots in the chain of slots buffers.
-  static void VerifySlots(Heap* heap, SlotsBuffer* buffer);
-
   static const int kNumberOfElements = 1021;
 
  private:
   static const int kChainLengthThreshold = 15;
 
   intptr_t idx_;
   intptr_t chain_length_;
   SlotsBuffer* next_;
   ObjectSlot slots_[kNumberOfElements];
 };
@@ skipping 255 matching lines @@
   void RemoveObjectSlots(Address start_slot, Address end_slot);
 
  private:
   class SweeperTask;
 
   explicit MarkCompactCollector(Heap* heap);
   ~MarkCompactCollector();
 
   bool WillBeDeoptimized(Code* code);
   void EvictPopularEvacuationCandidate(Page* page);
+
+  // Clears invald store buffer and slots buffer entries. This method must
+  // be called after marking, when the whole transitive closure is known and
+  // must be called before sweeping when mark bits are still intact.
   void ClearInvalidStoreAndSlotsBufferEntries();
 
+  // Eliminates all stale entries from the slots buffer, i.e., slots that
+  // are not part of live objects anymore.
+  void ClearInvalidSlotsBufferEntries(SlotsBuffer* buffer);
+
   void StartSweeperThreads();
 
 #ifdef DEBUG
   enum CollectorState {
     IDLE,
     PREPARE_GC,
     MARK_LIVE_OBJECTS,
     SWEEP_SPACES,
     ENCODE_FORWARDING_ADDRESSES,
     UPDATE_POINTERS,
@@ skipping 278 matching lines @@
  private:
   MarkCompactCollector* collector_;
 };
 
 
 const char* AllocationSpaceName(AllocationSpace space);
 }
 }  // namespace v8::internal
 
 #endif  // V8_HEAP_MARK_COMPACT_H_