[heap] Filter out stale left-trimmed handles for scavenges

src/heap/heap.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_HEAP_H_
 #define V8_HEAP_HEAP_H_
 
 #include <cmath>
 #include <map>
 
@@ skipping 614 matching lines @@
   static double HeapGrowingFactor(double gc_speed, double mutator_speed);
 
   // Copy block of memory from src to dst. Size of block should be aligned
   // by pointer size.
   static inline void CopyBlock(Address dst, Address src, int byte_size);
 
   // Determines a static visitor id based on the given {map} that can then be
   // stored on the map to facilitate fast dispatch for {StaticVisitorBase}.
   static int GetStaticVisitorIdForMap(Map* map);
 
-  // We cannot avoid stale handles to left-trimmed objects, but can only make
-  // sure all handles still needed are updated. Filter out a stale pointer
-  // and clear the slot to allow post processing of handles (needed because
-  // the sweeper might actually free the underlying page).
-  inline bool PurgeLeftTrimmedObject(Object** object);
-
   // Notifies the heap that is ok to start marking or other activities that
   // should not happen during deserialization.
   void NotifyDeserializationComplete();
 
   intptr_t old_generation_allocation_limit() const {
     return old_generation_allocation_limit_;
   }
 
   bool always_allocate() { return always_allocate_scope_count_.Value() != 0; }
 
@@ skipping 786 matching lines @@
   void TracePathToObject(Object* target);
   void TracePathToGlobal();
 
   void Print();
   void PrintHandles();
 
   // Report heap statistics.
   void ReportHeapStatistics(const char* title);
   void ReportCodeStatistics(const char* title);
 #endif
+#ifdef ENABLE_SLOW_DCHECKS
+  int CountHandlesForObject(Object* object);
+#endif
 
  private:
   class PretenuringScope;
 
   // External strings table is a place where all external strings are
   // registered.  We need to keep track of such strings to properly
   // finalize them.
   class ExternalStringTable {
    public:
     // Registers an external string.
@@ skipping 1241 matching lines @@
   friend class LargeObjectSpace;
   friend class NewSpace;
   friend class PagedSpace;
   DISALLOW_COPY_AND_ASSIGN(AllocationObserver);
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_HEAP_H_