[heap] Iterate handles with special left-trim visitor

src/heap/heap-inl.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_INL_H_
 #define V8_HEAP_HEAP_INL_H_
 
 #include <cmath>
 
 #include "src/base/platform/platform.h"
@@ skipping 464 matching lines @@
   }
   UNREACHABLE();
   return false;
 }
 
 void Heap::CopyBlock(Address dst, Address src, int byte_size) {
   CopyWords(reinterpret_cast<Object**>(dst), reinterpret_cast<Object**>(src),
             static_cast<size_t>(byte_size / kPointerSize));
 }
 
-bool Heap::PurgeLeftTrimmedObject(Object** object) {
-  HeapObject* current = reinterpret_cast<HeapObject*>(*object);
-  const MapWord map_word = current->map_word();
-  if (current->IsFiller() && !map_word.IsForwardingAddress()) {
-#ifdef DEBUG
-    // We need to find a FixedArrayBase map after walking the fillers.
-    while (current->IsFiller()) {
-      Address next = reinterpret_cast<Address>(current);
-      if (current->map() == one_pointer_filler_map()) {
-        next += kPointerSize;
-      } else if (current->map() == two_pointer_filler_map()) {
-        next += 2 * kPointerSize;
-      } else {
-        next += current->Size();
-      }
-      current = reinterpret_cast<HeapObject*>(next);
-    }
-    DCHECK(current->IsFixedArrayBase());
-#endif  // DEBUG
-    *object = nullptr;
-    return true;
-  }
-  return false;
-}
-
 template <Heap::FindMementoMode mode>
 AllocationMemento* Heap::FindAllocationMemento(HeapObject* object) {
   // Check if there is potentially a memento behind the object. If
   // the last word of the memento is on another page we return
   // immediately.
   Address object_address = object->address();
   Address memento_address = object_address + object->Size();
   Address last_memento_word_address = memento_address + kPointerSize;
   if (!Page::OnSamePage(object_address, last_memento_word_address)) {
     return nullptr;
@@ skipping 272 matching lines @@
 
 void VerifySmisVisitor::VisitPointers(Object** start, Object** end) {
   for (Object** current = start; current < end; current++) {
     CHECK((*current)->IsSmi());
   }
 }
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_HEAP_INL_H_