Version 3.6.5

src/spaces-inl.h

Index: src/spaces-inl.h
===================================================================
--- src/spaces-inl.h	(revision 9531)
+++ src/spaces-inl.h	(working copy)
@@ -1,4 +1,4 @@
-// Copyright 2006-2010 the V8 project authors. All rights reserved.
+// Copyright 2011 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:
@@ -37,371 +37,228 @@
 
 
 // -----------------------------------------------------------------------------
-// PageIterator
+// Bitmap
 
-bool PageIterator::has_next() {
-  return prev_page_ != stop_page_;
+void Bitmap::Clear(MemoryChunk* chunk) {
+  Bitmap* bitmap = chunk->markbits();
+  for (int i = 0; i < bitmap->CellsCount(); i++) bitmap->cells()[i] = 0;
+  chunk->ResetLiveBytes();
 }
 
 
-Page* PageIterator::next() {
-  ASSERT(has_next());
-  prev_page_ = (prev_page_ == NULL)
-               ? space_->first_page_
-               : prev_page_->next_page();
-  return prev_page_;
-}
-
-
 // -----------------------------------------------------------------------------
-// Page
+// PageIterator
 
-Page* Page::next_page() {
-  return heap_->isolate()->memory_allocator()->GetNextPage(this);
-}
 
+PageIterator::PageIterator(PagedSpace* space)
+    : space_(space),
+      prev_page_(&space->anchor_),
+      next_page_(prev_page_->next_page()) { }
 
-Address Page::AllocationTop() {
-  PagedSpace* owner = heap_->isolate()->memory_allocator()->PageOwner(this);
-  return owner->PageAllocationTop(this);
-}
 
-
-Address Page::AllocationWatermark() {
-  PagedSpace* owner = heap_->isolate()->memory_allocator()->PageOwner(this);
-  if (this == owner->AllocationTopPage()) {
-    return owner->top();
-  }
-  return address() + AllocationWatermarkOffset();
+bool PageIterator::has_next() {
+  return next_page_ != &space_->anchor_;
 }
 
 
-uint32_t Page::AllocationWatermarkOffset() {
-  return static_cast<uint32_t>((flags_ & kAllocationWatermarkOffsetMask) >>
-                               kAllocationWatermarkOffsetShift);
+Page* PageIterator::next() {
+  ASSERT(has_next());
+  prev_page_ = next_page_;
+  next_page_ = next_page_->next_page();
+  return prev_page_;
 }
 
 
-void Page::SetAllocationWatermark(Address allocation_watermark) {
-  if ((heap_->gc_state() == Heap::SCAVENGE) && IsWatermarkValid()) {
-    // When iterating intergenerational references during scavenge
-    // we might decide to promote an encountered young object.
-    // We will allocate a space for such an object and put it
-    // into the promotion queue to process it later.
-    // If space for object was allocated somewhere beyond allocation
-    // watermark this might cause garbage pointers to appear under allocation
-    // watermark. To avoid visiting them during dirty regions iteration
-    // which might be still in progress we store a valid allocation watermark
-    // value and mark this page as having an invalid watermark.
-    SetCachedAllocationWatermark(AllocationWatermark());
-    InvalidateWatermark(true);
-  }
+// -----------------------------------------------------------------------------
+// NewSpacePageIterator
 
-  flags_ = (flags_ & kFlagsMask) |
-           Offset(allocation_watermark) << kAllocationWatermarkOffsetShift;
-  ASSERT(AllocationWatermarkOffset()
-         == static_cast<uint32_t>(Offset(allocation_watermark)));
-}
 
+NewSpacePageIterator::NewSpacePageIterator(NewSpace* space)
+    : prev_page_(NewSpacePage::FromAddress(space->ToSpaceStart())->prev_page()),
+      next_page_(NewSpacePage::FromAddress(space->ToSpaceStart())),
+      last_page_(NewSpacePage::FromLimit(space->ToSpaceEnd())) { }
 
-void Page::SetCachedAllocationWatermark(Address allocation_watermark) {
-  mc_first_forwarded = allocation_watermark;
-}
+NewSpacePageIterator::NewSpacePageIterator(SemiSpace* space)
+    : prev_page_(space->anchor()),
+      next_page_(prev_page_->next_page()),
+      last_page_(prev_page_->prev_page()) { }
 
-
-Address Page::CachedAllocationWatermark() {
-  return mc_first_forwarded;
+NewSpacePageIterator::NewSpacePageIterator(Address start, Address limit)
+    : prev_page_(NewSpacePage::FromAddress(start)->prev_page()),
+      next_page_(NewSpacePage::FromAddress(start)),
+      last_page_(NewSpacePage::FromLimit(limit)) {
+  SemiSpace::AssertValidRange(start, limit);
 }
 
 
-uint32_t Page::GetRegionMarks() {
-  return dirty_regions_;
+bool NewSpacePageIterator::has_next() {
+  return prev_page_ != last_page_;
 }
 
 
-void Page::SetRegionMarks(uint32_t marks) {
-  dirty_regions_ = marks;
+NewSpacePage* NewSpacePageIterator::next() {
+  ASSERT(has_next());
+  prev_page_ = next_page_;
+  next_page_ = next_page_->next_page();
+  return prev_page_;
 }
 
 
-int Page::GetRegionNumberForAddress(Address addr) {
-  // Each page is divided into 256 byte regions. Each region has a corresponding
-  // dirty mark bit in the page header. Region can contain intergenerational
-  // references iff its dirty mark is set.
-  // A normal 8K page contains exactly 32 regions so all region marks fit
-  // into 32-bit integer field. To calculate a region number we just divide
-  // offset inside page by region size.
-  // A large page can contain more then 32 regions. But we want to avoid
-  // additional write barrier code for distinguishing between large and normal
-  // pages so we just ignore the fact that addr points into a large page and
-  // calculate region number as if addr pointed into a normal 8K page. This way
-  // we get a region number modulo 32 so for large pages several regions might
-  // be mapped to a single dirty mark.
-  ASSERT_PAGE_ALIGNED(this->address());
-  STATIC_ASSERT((kPageAlignmentMask >> kRegionSizeLog2) < kBitsPerInt);
-
-  // We are using masking with kPageAlignmentMask instead of Page::Offset()
-  // to get an offset to the beginning of 8K page containing addr not to the
-  // beginning of actual page which can be bigger then 8K.
-  intptr_t offset_inside_normal_page = OffsetFrom(addr) & kPageAlignmentMask;
-  return static_cast<int>(offset_inside_normal_page >> kRegionSizeLog2);
-}
-
-
-uint32_t Page::GetRegionMaskForAddress(Address addr) {
-  return 1 << GetRegionNumberForAddress(addr);
-}
-
-
-uint32_t Page::GetRegionMaskForSpan(Address start, int length_in_bytes) {
-  uint32_t result = 0;
-  static const intptr_t kRegionMask = (1 << kRegionSizeLog2) - 1;
-  if (length_in_bytes + (OffsetFrom(start) & kRegionMask) >= kPageSize) {
-    result = kAllRegionsDirtyMarks;
-  } else if (length_in_bytes > 0) {
-    int start_region = GetRegionNumberForAddress(start);
-    int end_region =
-        GetRegionNumberForAddress(start + length_in_bytes - kPointerSize);
-    uint32_t start_mask = (~0) << start_region;
-    uint32_t end_mask = ~((~1) << end_region);
-    result = start_mask & end_mask;
-    // if end_region < start_region, the mask is ored.
-    if (result == 0) result = start_mask | end_mask;
-  }
-#ifdef DEBUG
-  if (FLAG_enable_slow_asserts) {
-    uint32_t expected = 0;
-    for (Address a = start; a < start + length_in_bytes; a += kPointerSize) {
-      expected |= GetRegionMaskForAddress(a);
+// -----------------------------------------------------------------------------
+// HeapObjectIterator
+HeapObject* HeapObjectIterator::FromCurrentPage() {
+  while (cur_addr_ != cur_end_) {
+    if (cur_addr_ == space_->top() && cur_addr_ != space_->limit()) {
+      cur_addr_ = space_->limit();
+      continue;
     }
-    ASSERT(expected == result);
+    HeapObject* obj = HeapObject::FromAddress(cur_addr_);
+    int obj_size = (size_func_ == NULL) ? obj->Size() : size_func_(obj);
+    cur_addr_ += obj_size;
+    ASSERT(cur_addr_ <= cur_end_);
+    if (!obj->IsFiller()) {
+      ASSERT_OBJECT_SIZE(obj_size);
+      return obj;
+    }
   }
-#endif
-  return result;
+  return NULL;
 }
 
 
-void Page::MarkRegionDirty(Address address) {
-  SetRegionMarks(GetRegionMarks() | GetRegionMaskForAddress(address));
-}
+// -----------------------------------------------------------------------------
+// MemoryAllocator
 
+#ifdef ENABLE_HEAP_PROTECTION
 
-bool Page::IsRegionDirty(Address address) {
-  return GetRegionMarks() & GetRegionMaskForAddress(address);
+void MemoryAllocator::Protect(Address start, size_t size) {
+  OS::Protect(start, size);
 }
 
 
-void Page::ClearRegionMarks(Address start, Address end, bool reaches_limit) {
-  int rstart = GetRegionNumberForAddress(start);
-  int rend = GetRegionNumberForAddress(end);
+void MemoryAllocator::Unprotect(Address start,
+                                size_t size,
+                                Executability executable) {
+  OS::Unprotect(start, size, executable);
+}
 
-  if (reaches_limit) {
-    end += 1;
-  }
 
-  if ((rend - rstart) == 0) {
-    return;
-  }
-
-  uint32_t bitmask = 0;
-
-  if ((OffsetFrom(start) & kRegionAlignmentMask) == 0
-      || (start == ObjectAreaStart())) {
-    // First region is fully covered
-    bitmask = 1 << rstart;
-  }
-
-  while (++rstart < rend) {
-    bitmask |= 1 << rstart;
-  }
-
-  if (bitmask) {
-    SetRegionMarks(GetRegionMarks() & ~bitmask);
-  }
+void MemoryAllocator::ProtectChunkFromPage(Page* page) {
+  int id = GetChunkId(page);
+  OS::Protect(chunks_[id].address(), chunks_[id].size());
 }
 
 
-void Page::FlipMeaningOfInvalidatedWatermarkFlag(Heap* heap) {
-  heap->page_watermark_invalidated_mark_ ^= 1 << WATERMARK_INVALIDATED;
+void MemoryAllocator::UnprotectChunkFromPage(Page* page) {
+  int id = GetChunkId(page);
+  OS::Unprotect(chunks_[id].address(), chunks_[id].size(),
+                chunks_[id].owner()->executable() == EXECUTABLE);
 }
 
+#endif
 
-bool Page::IsWatermarkValid() {
-  return (flags_ & (1 << WATERMARK_INVALIDATED)) !=
-      heap_->page_watermark_invalidated_mark_;
-}
 
+// --------------------------------------------------------------------------
+// PagedSpace
+Page* Page::Initialize(Heap* heap,
+                       MemoryChunk* chunk,
+                       Executability executable,
+                       PagedSpace* owner) {
+  Page* page = reinterpret_cast<Page*>(chunk);
+  ASSERT(chunk->size() == static_cast<size_t>(kPageSize));
+  ASSERT(chunk->owner() == owner);
+  owner->IncreaseCapacity(Page::kObjectAreaSize);
+  owner->Free(page->ObjectAreaStart(),
+              static_cast<int>(page->ObjectAreaEnd() -
+                               page->ObjectAreaStart()));
 
-void Page::InvalidateWatermark(bool value) {
-  if (value) {
-    flags_ = (flags_ & ~(1 << WATERMARK_INVALIDATED)) |
-             heap_->page_watermark_invalidated_mark_;
-  } else {
-    flags_ =
-        (flags_ & ~(1 << WATERMARK_INVALIDATED)) |
-        (heap_->page_watermark_invalidated_mark_ ^
-         (1 << WATERMARK_INVALIDATED));
-  }
+  heap->incremental_marking()->SetOldSpacePageFlags(chunk);
 
-  ASSERT(IsWatermarkValid() == !value);
+  return page;
 }
 
 
-bool Page::GetPageFlag(PageFlag flag) {
-  return (flags_ & static_cast<intptr_t>(1 << flag)) != 0;
+bool PagedSpace::Contains(Address addr) {
+  Page* p = Page::FromAddress(addr);
+  if (!p->is_valid()) return false;
+  return p->owner() == this;
 }
 
 
-void Page::SetPageFlag(PageFlag flag, bool value) {
-  if (value) {
-    flags_ |= static_cast<intptr_t>(1 << flag);
+void MemoryChunk::set_scan_on_scavenge(bool scan) {
+  if (scan) {
+    if (!scan_on_scavenge()) heap_->increment_scan_on_scavenge_pages();
+    SetFlag(SCAN_ON_SCAVENGE);
   } else {
-    flags_ &= ~static_cast<intptr_t>(1 << flag);
+    if (scan_on_scavenge()) heap_->decrement_scan_on_scavenge_pages();
+    ClearFlag(SCAN_ON_SCAVENGE);
   }
+  heap_->incremental_marking()->SetOldSpacePageFlags(this);
 }
 
 
-void Page::ClearPageFlags() {
-  flags_ = 0;
-}
-
-
-void Page::ClearGCFields() {
-  InvalidateWatermark(true);
-  SetAllocationWatermark(ObjectAreaStart());
-  if (heap_->gc_state() == Heap::SCAVENGE) {
-    SetCachedAllocationWatermark(ObjectAreaStart());
+MemoryChunk* MemoryChunk::FromAnyPointerAddress(Address addr) {
+  MemoryChunk* maybe = reinterpret_cast<MemoryChunk*>(
+      OffsetFrom(addr) & ~Page::kPageAlignmentMask);
+  if (maybe->owner() != NULL) return maybe;
+  LargeObjectIterator iterator(HEAP->lo_space());
+  for (HeapObject* o = iterator.Next(); o != NULL; o = iterator.Next()) {
+    // Fixed arrays are the only pointer-containing objects in large object
+    // space.
+    if (o->IsFixedArray()) {
+      MemoryChunk* chunk = MemoryChunk::FromAddress(o->address());
+      if (chunk->Contains(addr)) {
+        return chunk;
+      }
+    }
   }
-  SetRegionMarks(kAllRegionsCleanMarks);
+  UNREACHABLE();
+  return NULL;
 }
 
 
-bool Page::WasInUseBeforeMC() {
-  return GetPageFlag(WAS_IN_USE_BEFORE_MC);
-}
+PointerChunkIterator::PointerChunkIterator(Heap* heap)
+    : state_(kOldPointerState),
+      old_pointer_iterator_(heap->old_pointer_space()),
+      map_iterator_(heap->map_space()),
+      lo_iterator_(heap->lo_space()) { }
 
 
-void Page::SetWasInUseBeforeMC(bool was_in_use) {
-  SetPageFlag(WAS_IN_USE_BEFORE_MC, was_in_use);
+Page* Page::next_page() {
+  ASSERT(next_chunk()->owner() == owner());
+  return static_cast<Page*>(next_chunk());
 }
 
 
-bool Page::IsLargeObjectPage() {
-  return !GetPageFlag(IS_NORMAL_PAGE);
+Page* Page::prev_page() {
+  ASSERT(prev_chunk()->owner() == owner());
+  return static_cast<Page*>(prev_chunk());
 }
 
 
-void Page::SetIsLargeObjectPage(bool is_large_object_page) {
-  SetPageFlag(IS_NORMAL_PAGE, !is_large_object_page);
+void Page::set_next_page(Page* page) {
+  ASSERT(page->owner() == owner());
+  set_next_chunk(page);
 }
 
-Executability Page::PageExecutability() {
-  return GetPageFlag(IS_EXECUTABLE) ? EXECUTABLE : NOT_EXECUTABLE;
-}
 
-
-void Page::SetPageExecutability(Executability executable) {
-  SetPageFlag(IS_EXECUTABLE, executable == EXECUTABLE);
+void Page::set_prev_page(Page* page) {
+  ASSERT(page->owner() == owner());
+  set_prev_chunk(page);
 }
 
 
-// -----------------------------------------------------------------------------
-// MemoryAllocator
-
-void MemoryAllocator::ChunkInfo::init(Address a, size_t s, PagedSpace* o) {
-  address_ = a;
-  size_ = s;
-  owner_ = o;
-  executable_ = (o == NULL) ? NOT_EXECUTABLE : o->executable();
-  owner_identity_ = (o == NULL) ? FIRST_SPACE : o->identity();
-}
-
-
-bool MemoryAllocator::IsValidChunk(int chunk_id) {
-  if (!IsValidChunkId(chunk_id)) return false;
-
-  ChunkInfo& c = chunks_[chunk_id];
-  return (c.address() != NULL) && (c.size() != 0) && (c.owner() != NULL);
-}
-
-
-bool MemoryAllocator::IsValidChunkId(int chunk_id) {
-  return (0 <= chunk_id) && (chunk_id < max_nof_chunks_);
-}
-
-
-bool MemoryAllocator::IsPageInSpace(Page* p, PagedSpace* space) {
-  ASSERT(p->is_valid());
-
-  int chunk_id = GetChunkId(p);
-  if (!IsValidChunkId(chunk_id)) return false;
-
-  ChunkInfo& c = chunks_[chunk_id];
-  return (c.address() <= p->address()) &&
-         (p->address() < c.address() + c.size()) &&
-         (space == c.owner());
-}
-
-
-Page* MemoryAllocator::GetNextPage(Page* p) {
-  ASSERT(p->is_valid());
-  intptr_t raw_addr = p->opaque_header & ~Page::kPageAlignmentMask;
-  return Page::FromAddress(AddressFrom<Address>(raw_addr));
-}
-
-
-int MemoryAllocator::GetChunkId(Page* p) {
-  ASSERT(p->is_valid());
-  return static_cast<int>(p->opaque_header & Page::kPageAlignmentMask);
-}
-
-
-void MemoryAllocator::SetNextPage(Page* prev, Page* next) {
-  ASSERT(prev->is_valid());
-  int chunk_id = GetChunkId(prev);
-  ASSERT_PAGE_ALIGNED(next->address());
-  prev->opaque_header = OffsetFrom(next->address()) | chunk_id;
-}
-
-
-PagedSpace* MemoryAllocator::PageOwner(Page* page) {
-  int chunk_id = GetChunkId(page);
-  ASSERT(IsValidChunk(chunk_id));
-  return chunks_[chunk_id].owner();
-}
-
-
-bool MemoryAllocator::InInitialChunk(Address address) {
-  if (initial_chunk_ == NULL) return false;
-
-  Address start = static_cast<Address>(initial_chunk_->address());
-  return (start <= address) && (address < start + initial_chunk_->size());
-}
-
-
-// --------------------------------------------------------------------------
-// PagedSpace
-
-bool PagedSpace::Contains(Address addr) {
-  Page* p = Page::FromAddress(addr);
-  if (!p->is_valid()) return false;
-  return heap()->isolate()->memory_allocator()->IsPageInSpace(p, this);
-}
-
-
 // Try linear allocation in the page of alloc_info's allocation top.  Does
 // not contain slow case logic (eg, move to the next page or try free list
 // allocation) so it can be used by all the allocation functions and for all
 // the paged spaces.
-HeapObject* PagedSpace::AllocateLinearly(AllocationInfo* alloc_info,
-                                         int size_in_bytes) {
-  Address current_top = alloc_info->top;
+HeapObject* PagedSpace::AllocateLinearly(int size_in_bytes) {
+  Address current_top = allocation_info_.top;
   Address new_top = current_top + size_in_bytes;
-  if (new_top > alloc_info->limit) return NULL;
+  if (new_top > allocation_info_.limit) return NULL;
 
-  alloc_info->top = new_top;
-  ASSERT(alloc_info->VerifyPagedAllocation());
-  accounting_stats_.AllocateBytes(size_in_bytes);
+  allocation_info_.top = new_top;
+  ASSERT(allocation_info_.VerifyPagedAllocation());
+  ASSERT(current_top != NULL);
   return HeapObject::FromAddress(current_top);
 }
 
@@ -410,54 +267,78 @@
 MaybeObject* PagedSpace::AllocateRaw(int size_in_bytes) {
   ASSERT(HasBeenSetup());
   ASSERT_OBJECT_SIZE(size_in_bytes);
-  HeapObject* object = AllocateLinearly(&allocation_info_, size_in_bytes);
-  if (object != NULL) return object;
+  HeapObject* object = AllocateLinearly(size_in_bytes);
+  if (object != NULL) {
+    if (identity() == CODE_SPACE) {
+      SkipList::Update(object->address(), size_in_bytes);
+    }
+    return object;
+  }
 
+  object = free_list_.Allocate(size_in_bytes);
+  if (object != NULL) {
+    if (identity() == CODE_SPACE) {
+      SkipList::Update(object->address(), size_in_bytes);
+    }
+    return object;
+  }
+
   object = SlowAllocateRaw(size_in_bytes);
-  if (object != NULL) return object;
+  if (object != NULL) {
+    if (identity() == CODE_SPACE) {
+      SkipList::Update(object->address(), size_in_bytes);
+    }
+    return object;
+  }
 
   return Failure::RetryAfterGC(identity());
 }
 
 
-// Reallocating (and promoting) objects during a compacting collection.
-MaybeObject* PagedSpace::MCAllocateRaw(int size_in_bytes) {
-  ASSERT(HasBeenSetup());
-  ASSERT_OBJECT_SIZE(size_in_bytes);
-  HeapObject* object = AllocateLinearly(&mc_forwarding_info_, size_in_bytes);
-  if (object != NULL) return object;
-
-  object = SlowMCAllocateRaw(size_in_bytes);
-  if (object != NULL) return object;
-
-  return Failure::RetryAfterGC(identity());
-}
-
-
 // -----------------------------------------------------------------------------
 // NewSpace
+MaybeObject* NewSpace::AllocateRawInternal(int size_in_bytes) {
+  Address old_top = allocation_info_.top;
+  if (allocation_info_.limit - old_top < size_in_bytes) {
+    Address new_top = old_top + size_in_bytes;
+    Address high = to_space_.page_high();
+    if (allocation_info_.limit < high) {
+      // Incremental marking has lowered the limit to get a
+      // chance to do a step.
+      allocation_info_.limit = Min(
+          allocation_info_.limit + inline_allocation_limit_step_,
+          high);
+      int bytes_allocated = static_cast<int>(new_top - top_on_previous_step_);
+      heap()->incremental_marking()->Step(bytes_allocated);
+      top_on_previous_step_ = new_top;
+      return AllocateRawInternal(size_in_bytes);
+    } else if (AddFreshPage()) {
+      // Switched to new page. Try allocating again.
+      int bytes_allocated = static_cast<int>(old_top - top_on_previous_step_);
+      heap()->incremental_marking()->Step(bytes_allocated);
+      top_on_previous_step_ = to_space_.page_low();
+      return AllocateRawInternal(size_in_bytes);
+    } else {
+      return Failure::RetryAfterGC();
+    }
+  }
 
-MaybeObject* NewSpace::AllocateRawInternal(int size_in_bytes,
-                                           AllocationInfo* alloc_info) {
-  Address new_top = alloc_info->top + size_in_bytes;
-  if (new_top > alloc_info->limit) return Failure::RetryAfterGC();
+  Object* obj = HeapObject::FromAddress(allocation_info_.top);
+  allocation_info_.top += size_in_bytes;
+  ASSERT_SEMISPACE_ALLOCATION_INFO(allocation_info_, to_space_);
 
-  Object* obj = HeapObject::FromAddress(alloc_info->top);
-  alloc_info->top = new_top;
-#ifdef DEBUG
-  SemiSpace* space =
-      (alloc_info == &allocation_info_) ? &to_space_ : &from_space_;
-  ASSERT(space->low() <= alloc_info->top
-         && alloc_info->top <= space->high()
-         && alloc_info->limit == space->high());
-#endif
   return obj;
 }
 
 
+LargePage* LargePage::Initialize(Heap* heap, MemoryChunk* chunk) {
+  heap->incremental_marking()->SetOldSpacePageFlags(chunk);
+  return static_cast<LargePage*>(chunk);
+}
+
+
 intptr_t LargeObjectSpace::Available() {
-  return LargeObjectChunk::ObjectSizeFor(
-      heap()->isolate()->memory_allocator()->Available());
+  return ObjectSizeFor(heap()->isolate()->memory_allocator()->Available());
 }
 
 
@@ -467,16 +348,23 @@
   ASSERT(string->IsSeqString());
   ASSERT(string->address() + StringType::SizeFor(string->length()) ==
          allocation_info_.top);
+  Address old_top = allocation_info_.top;
   allocation_info_.top =
       string->address() + StringType::SizeFor(length);
   string->set_length(length);
+  if (Marking::IsBlack(Marking::MarkBitFrom(string))) {
+    int delta = static_cast<int>(old_top - allocation_info_.top);
+    MemoryChunk::IncrementLiveBytes(string->address(), -delta);
+  }
 }
 
 
 bool FreeListNode::IsFreeListNode(HeapObject* object) {
-  return object->map() == HEAP->raw_unchecked_byte_array_map()
-      || object->map() == HEAP->raw_unchecked_one_pointer_filler_map()
-      || object->map() == HEAP->raw_unchecked_two_pointer_filler_map();
+  Map* map = object->map();
+  Heap* heap = object->GetHeap();
+  return map == heap->raw_unchecked_free_space_map()
+      || map == heap->raw_unchecked_one_pointer_filler_map()
+      || map == heap->raw_unchecked_two_pointer_filler_map();
 }
 
 } }  // namespace v8::internal