BASELINE: Update Chromium to 85.0.4183.14085-based

Change-Id: Iaa42f4680837c57725b1344f108c0196741f6057
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>

1 files changed, 26 insertions, 3415 deletions

diff --git a/chromium/v8/src/heap/spaces.cc b/chromium/v8/src/heap/spaces.cc
index 5e8874fafde..45c1de44c20 100644
--- a/chromium/v8/src/heap/spaces.cc
+++ b/chromium/v8/src/heap/spaces.cc
@@ -9,12 +9,9 @@
 #include <utility>
 
 #include "src/base/bits.h"
+#include "src/base/bounded-page-allocator.h"
 #include "src/base/macros.h"
-#include "src/base/optional.h"
-#include "src/base/platform/semaphore.h"
 #include "src/common/globals.h"
-#include "src/execution/vm-state-inl.h"
-#include "src/heap/array-buffer-sweeper.h"
 #include "src/heap/array-buffer-tracker-inl.h"
 #include "src/heap/combined-heap.h"
 #include "src/heap/concurrent-marking.h"
@@ -26,9 +23,8 @@
 #include "src/heap/large-spaces.h"
 #include "src/heap/mark-compact.h"
 #include "src/heap/read-only-heap.h"
-#include "src/heap/remembered-set-inl.h"
+#include "src/heap/remembered-set.h"
 #include "src/heap/slot-set.h"
-#include "src/heap/sweeper.h"
 #include "src/init/v8.h"
 #include "src/logging/counters.h"
 #include "src/objects/free-space-inl.h"
@@ -49,55 +45,6 @@ namespace internal {
 STATIC_ASSERT(kClearedWeakHeapObjectLower32 > 0);
 STATIC_ASSERT(kClearedWeakHeapObjectLower32 < Page::kHeaderSize);
 
-// ----------------------------------------------------------------------------
-// PagedSpaceObjectIterator
-
-PagedSpaceObjectIterator::PagedSpaceObjectIterator(Heap* heap,
-                                                   PagedSpace* space)
-    : cur_addr_(kNullAddress),
-      cur_end_(kNullAddress),
-      space_(space),
-      page_range_(space->first_page(), nullptr),
-      current_page_(page_range_.begin()) {
-  heap->mark_compact_collector()->EnsureSweepingCompleted();
-}
-
-PagedSpaceObjectIterator::PagedSpaceObjectIterator(Heap* heap,
-                                                   PagedSpace* space,
-                                                   Page* page)
-    : cur_addr_(kNullAddress),
-      cur_end_(kNullAddress),
-      space_(space),
-      page_range_(page),
-      current_page_(page_range_.begin()) {
-  heap->mark_compact_collector()->EnsureSweepingCompleted();
-#ifdef DEBUG
-  AllocationSpace owner = page->owner_identity();
-  DCHECK(owner == RO_SPACE || owner == OLD_SPACE || owner == MAP_SPACE ||
-         owner == CODE_SPACE);
-#endif  // DEBUG
-}
-
-PagedSpaceObjectIterator::PagedSpaceObjectIterator(OffThreadSpace* space)
-    : cur_addr_(kNullAddress),
-      cur_end_(kNullAddress),
-      space_(space),
-      page_range_(space->first_page(), nullptr),
-      current_page_(page_range_.begin()) {}
-
-// We have hit the end of the page and should advance to the next block of
-// objects.  This happens at the end of the page.
-bool PagedSpaceObjectIterator::AdvanceToNextPage() {
-  DCHECK_EQ(cur_addr_, cur_end_);
-  if (current_page_ == page_range_.end()) return false;
-  Page* cur_page = *(current_page_++);
-
-  cur_addr_ = cur_page->area_start();
-  cur_end_ = cur_page->area_end();
-  DCHECK(cur_page->SweepingDone());
-  return true;
-}
-
 PauseAllocationObserversScope::PauseAllocationObserversScope(Heap* heap)
     : heap_(heap) {
   DCHECK_EQ(heap->gc_state(), Heap::NOT_IN_GC);
@@ -113,541 +60,6 @@ PauseAllocationObserversScope::~PauseAllocationObserversScope() {
   }
 }
 
-static base::LazyInstance<CodeRangeAddressHint>::type code_range_address_hint =
-    LAZY_INSTANCE_INITIALIZER;
-
-Address CodeRangeAddressHint::GetAddressHint(size_t code_range_size) {
-  base::MutexGuard guard(&mutex_);
-  auto it = recently_freed_.find(code_range_size);
-  if (it == recently_freed_.end() || it->second.empty()) {
-    return reinterpret_cast<Address>(GetRandomMmapAddr());
-  }
-  Address result = it->second.back();
-  it->second.pop_back();
-  return result;
-}
-
-void CodeRangeAddressHint::NotifyFreedCodeRange(Address code_range_start,
-                                                size_t code_range_size) {
-  base::MutexGuard guard(&mutex_);
-  recently_freed_[code_range_size].push_back(code_range_start);
-}
-
-// -----------------------------------------------------------------------------
-// MemoryAllocator
-//
-
-MemoryAllocator::MemoryAllocator(Isolate* isolate, size_t capacity,
-                                 size_t code_range_size)
-    : isolate_(isolate),
-      data_page_allocator_(isolate->page_allocator()),
-      code_page_allocator_(nullptr),
-      capacity_(RoundUp(capacity, Page::kPageSize)),
-      size_(0),
-      size_executable_(0),
-      lowest_ever_allocated_(static_cast<Address>(-1ll)),
-      highest_ever_allocated_(kNullAddress),
-      unmapper_(isolate->heap(), this) {
-  InitializeCodePageAllocator(data_page_allocator_, code_range_size);
-}
-
-void MemoryAllocator::InitializeCodePageAllocator(
-    v8::PageAllocator* page_allocator, size_t requested) {
-  DCHECK_NULL(code_page_allocator_instance_.get());
-
-  code_page_allocator_ = page_allocator;
-
-  if (requested == 0) {
-    if (!isolate_->RequiresCodeRange()) return;
-    // When a target requires the code range feature, we put all code objects
-    // in a kMaximalCodeRangeSize range of virtual address space, so that
-    // they can call each other with near calls.
-    requested = kMaximalCodeRangeSize;
-  } else if (requested <= kMinimumCodeRangeSize) {
-    requested = kMinimumCodeRangeSize;
-  }
-
-  const size_t reserved_area =
-      kReservedCodeRangePages * MemoryAllocator::GetCommitPageSize();
-  if (requested < (kMaximalCodeRangeSize - reserved_area)) {
-    requested += RoundUp(reserved_area, MemoryChunk::kPageSize);
-    // Fullfilling both reserved pages requirement and huge code area
-    // alignments is not supported (requires re-implementation).
-    DCHECK_LE(kMinExpectedOSPageSize, page_allocator->AllocatePageSize());
-  }
-  DCHECK(!isolate_->RequiresCodeRange() || requested <= kMaximalCodeRangeSize);
-
-  Address hint =
-      RoundDown(code_range_address_hint.Pointer()->GetAddressHint(requested),
-                page_allocator->AllocatePageSize());
-  VirtualMemory reservation(
-      page_allocator, requested, reinterpret_cast<void*>(hint),
-      Max(kMinExpectedOSPageSize, page_allocator->AllocatePageSize()));
-  if (!reservation.IsReserved()) {
-    V8::FatalProcessOutOfMemory(isolate_,
-                                "CodeRange setup: allocate virtual memory");
-  }
-  code_range_ = reservation.region();
-  isolate_->AddCodeRange(code_range_.begin(), code_range_.size());
-
-  // We are sure that we have mapped a block of requested addresses.
-  DCHECK_GE(reservation.size(), requested);
-  Address base = reservation.address();
-
-  // On some platforms, specifically Win64, we need to reserve some pages at
-  // the beginning of an executable space. See
-  //   https://cs.chromium.org/chromium/src/components/crash/content/
-  //     app/crashpad_win.cc?rcl=fd680447881449fba2edcf0589320e7253719212&l=204
-  // for details.
-  if (reserved_area > 0) {
-    if (!reservation.SetPermissions(base, reserved_area,
-                                    PageAllocator::kReadWrite))
-      V8::FatalProcessOutOfMemory(isolate_, "CodeRange setup: set permissions");
-
-    base += reserved_area;
-  }
-  Address aligned_base = RoundUp(base, MemoryChunk::kAlignment);
-  size_t size =
-      RoundDown(reservation.size() - (aligned_base - base) - reserved_area,
-                MemoryChunk::kPageSize);
-  DCHECK(IsAligned(aligned_base, kMinExpectedOSPageSize));
-
-  LOG(isolate_,
-      NewEvent("CodeRange", reinterpret_cast<void*>(reservation.address()),
-               requested));
-
-  code_reservation_ = std::move(reservation);
-  code_page_allocator_instance_ = std::make_unique<base::BoundedPageAllocator>(
-      page_allocator, aligned_base, size,
-      static_cast<size_t>(MemoryChunk::kAlignment));
-  code_page_allocator_ = code_page_allocator_instance_.get();
-}
-
-void MemoryAllocator::TearDown() {
-  unmapper()->TearDown();
-
-  // Check that spaces were torn down before MemoryAllocator.
-  DCHECK_EQ(size_, 0u);
-  // TODO(gc) this will be true again when we fix FreeMemory.
-  // DCHECK_EQ(0, size_executable_);
-  capacity_ = 0;
-
-  if (last_chunk_.IsReserved()) {
-    last_chunk_.Free();
-  }
-
-  if (code_page_allocator_instance_.get()) {
-    DCHECK(!code_range_.is_empty());
-    code_range_address_hint.Pointer()->NotifyFreedCodeRange(code_range_.begin(),
-                                                            code_range_.size());
-    code_range_ = base::AddressRegion();
-    code_page_allocator_instance_.reset();
-  }
-  code_page_allocator_ = nullptr;
-  data_page_allocator_ = nullptr;
-}
-
-class MemoryAllocator::Unmapper::UnmapFreeMemoryTask : public CancelableTask {
- public:
-  explicit UnmapFreeMemoryTask(Isolate* isolate, Unmapper* unmapper)
-      : CancelableTask(isolate),
-        unmapper_(unmapper),
-        tracer_(isolate->heap()->tracer()) {}
-
- private:
-  void RunInternal() override {
-    TRACE_BACKGROUND_GC(tracer_,
-                        GCTracer::BackgroundScope::BACKGROUND_UNMAPPER);
-    unmapper_->PerformFreeMemoryOnQueuedChunks<FreeMode::kUncommitPooled>();
-    unmapper_->active_unmapping_tasks_--;
-    unmapper_->pending_unmapping_tasks_semaphore_.Signal();
-    if (FLAG_trace_unmapper) {
-      PrintIsolate(unmapper_->heap_->isolate(),
-                   "UnmapFreeMemoryTask Done: id=%" PRIu64 "\n", id());
-    }
-  }
-
-  Unmapper* const unmapper_;
-  GCTracer* const tracer_;
-  DISALLOW_COPY_AND_ASSIGN(UnmapFreeMemoryTask);
-};
-
-void MemoryAllocator::Unmapper::FreeQueuedChunks() {
-  if (!heap_->IsTearingDown() && FLAG_concurrent_sweeping) {
-    if (!MakeRoomForNewTasks()) {
-      // kMaxUnmapperTasks are already running. Avoid creating any more.
-      if (FLAG_trace_unmapper) {
-        PrintIsolate(heap_->isolate(),
-                     "Unmapper::FreeQueuedChunks: reached task limit (%d)\n",
-                     kMaxUnmapperTasks);
-      }
-      return;
-    }
-    auto task = std::make_unique<UnmapFreeMemoryTask>(heap_->isolate(), this);
-    if (FLAG_trace_unmapper) {
-      PrintIsolate(heap_->isolate(),
-                   "Unmapper::FreeQueuedChunks: new task id=%" PRIu64 "\n",
-                   task->id());
-    }
-    DCHECK_LT(pending_unmapping_tasks_, kMaxUnmapperTasks);
-    DCHECK_LE(active_unmapping_tasks_, pending_unmapping_tasks_);
-    DCHECK_GE(active_unmapping_tasks_, 0);
-    active_unmapping_tasks_++;
-    task_ids_[pending_unmapping_tasks_++] = task->id();
-    V8::GetCurrentPlatform()->CallOnWorkerThread(std::move(task));
-  } else {
-    PerformFreeMemoryOnQueuedChunks<FreeMode::kUncommitPooled>();
-  }
-}
-
-void MemoryAllocator::Unmapper::CancelAndWaitForPendingTasks() {
-  for (int i = 0; i < pending_unmapping_tasks_; i++) {
-    if (heap_->isolate()->cancelable_task_manager()->TryAbort(task_ids_[i]) !=
-        TryAbortResult::kTaskAborted) {
-      pending_unmapping_tasks_semaphore_.Wait();
-    }
-  }
-  pending_unmapping_tasks_ = 0;
-  active_unmapping_tasks_ = 0;
-
-  if (FLAG_trace_unmapper) {
-    PrintIsolate(
-        heap_->isolate(),
-        "Unmapper::CancelAndWaitForPendingTasks: no tasks remaining\n");
-  }
-}
-
-void MemoryAllocator::Unmapper::PrepareForGC() {
-  // Free non-regular chunks because they cannot be re-used.
-  PerformFreeMemoryOnQueuedNonRegularChunks();
-}
-
-void MemoryAllocator::Unmapper::EnsureUnmappingCompleted() {
-  CancelAndWaitForPendingTasks();
-  PerformFreeMemoryOnQueuedChunks<FreeMode::kReleasePooled>();
-}
-
-bool MemoryAllocator::Unmapper::MakeRoomForNewTasks() {
-  DCHECK_LE(pending_unmapping_tasks_, kMaxUnmapperTasks);
-
-  if (active_unmapping_tasks_ == 0 && pending_unmapping_tasks_ > 0) {
-    // All previous unmapping tasks have been run to completion.
-    // Finalize those tasks to make room for new ones.
-    CancelAndWaitForPendingTasks();
-  }
-  return pending_unmapping_tasks_ != kMaxUnmapperTasks;
-}
-
-void MemoryAllocator::Unmapper::PerformFreeMemoryOnQueuedNonRegularChunks() {
-  MemoryChunk* chunk = nullptr;
-  while ((chunk = GetMemoryChunkSafe<kNonRegular>()) != nullptr) {
-    allocator_->PerformFreeMemory(chunk);
-  }
-}
-
-template <MemoryAllocator::Unmapper::FreeMode mode>
-void MemoryAllocator::Unmapper::PerformFreeMemoryOnQueuedChunks() {
-  MemoryChunk* chunk = nullptr;
-  if (FLAG_trace_unmapper) {
-    PrintIsolate(
-        heap_->isolate(),
-        "Unmapper::PerformFreeMemoryOnQueuedChunks: %d queued chunks\n",
-        NumberOfChunks());
-  }
-  // Regular chunks.
-  while ((chunk = GetMemoryChunkSafe<kRegular>()) != nullptr) {
-    bool pooled = chunk->IsFlagSet(MemoryChunk::POOLED);
-    allocator_->PerformFreeMemory(chunk);
-    if (pooled) AddMemoryChunkSafe<kPooled>(chunk);
-  }
-  if (mode == MemoryAllocator::Unmapper::FreeMode::kReleasePooled) {
-    // The previous loop uncommitted any pages marked as pooled and added them
-    // to the pooled list. In case of kReleasePooled we need to free them
-    // though.
-    while ((chunk = GetMemoryChunkSafe<kPooled>()) != nullptr) {
-      allocator_->Free<MemoryAllocator::kAlreadyPooled>(chunk);
-    }
-  }
-  PerformFreeMemoryOnQueuedNonRegularChunks();
-}
-
-void MemoryAllocator::Unmapper::TearDown() {
-  CHECK_EQ(0, pending_unmapping_tasks_);
-  PerformFreeMemoryOnQueuedChunks<FreeMode::kReleasePooled>();
-  for (int i = 0; i < kNumberOfChunkQueues; i++) {
-    DCHECK(chunks_[i].empty());
-  }
-}
-
-size_t MemoryAllocator::Unmapper::NumberOfCommittedChunks() {
-  base::MutexGuard guard(&mutex_);
-  return chunks_[kRegular].size() + chunks_[kNonRegular].size();
-}
-
-int MemoryAllocator::Unmapper::NumberOfChunks() {
-  base::MutexGuard guard(&mutex_);
-  size_t result = 0;
-  for (int i = 0; i < kNumberOfChunkQueues; i++) {
-    result += chunks_[i].size();
-  }
-  return static_cast<int>(result);
-}
-
-size_t MemoryAllocator::Unmapper::CommittedBufferedMemory() {
-  base::MutexGuard guard(&mutex_);
-
-  size_t sum = 0;
-  // kPooled chunks are already uncommited. We only have to account for
-  // kRegular and kNonRegular chunks.
-  for (auto& chunk : chunks_[kRegular]) {
-    sum += chunk->size();
-  }
-  for (auto& chunk : chunks_[kNonRegular]) {
-    sum += chunk->size();
-  }
-  return sum;
-}
-
-bool MemoryAllocator::CommitMemory(VirtualMemory* reservation) {
-  Address base = reservation->address();
-  size_t size = reservation->size();
-  if (!reservation->SetPermissions(base, size, PageAllocator::kReadWrite)) {
-    return false;
-  }
-  UpdateAllocatedSpaceLimits(base, base + size);
-  return true;
-}
-
-bool MemoryAllocator::UncommitMemory(VirtualMemory* reservation) {
-  size_t size = reservation->size();
-  if (!reservation->SetPermissions(reservation->address(), size,
-                                   PageAllocator::kNoAccess)) {
-    return false;
-  }
-  return true;
-}
-
-void MemoryAllocator::FreeMemory(v8::PageAllocator* page_allocator,
-                                 Address base, size_t size) {
-  CHECK(FreePages(page_allocator, reinterpret_cast<void*>(base), size));
-}
-
-Address MemoryAllocator::AllocateAlignedMemory(
-    size_t reserve_size, size_t commit_size, size_t alignment,
-    Executability executable, void* hint, VirtualMemory* controller) {
-  v8::PageAllocator* page_allocator = this->page_allocator(executable);
-  DCHECK(commit_size <= reserve_size);
-  VirtualMemory reservation(page_allocator, reserve_size, hint, alignment);
-  if (!reservation.IsReserved()) return kNullAddress;
-  Address base = reservation.address();
-  size_ += reservation.size();
-
-  if (executable == EXECUTABLE) {
-    if (!CommitExecutableMemory(&reservation, base, commit_size,
-                                reserve_size)) {
-      base = kNullAddress;
-    }
-  } else {
-    if (reservation.SetPermissions(base, commit_size,
-                                   PageAllocator::kReadWrite)) {
-      UpdateAllocatedSpaceLimits(base, base + commit_size);
-    } else {
-      base = kNullAddress;
-    }
-  }
-
-  if (base == kNullAddress) {
-    // Failed to commit the body. Free the mapping and any partially committed
-    // regions inside it.
-    reservation.Free();
-    size_ -= reserve_size;
-    return kNullAddress;
-  }
-
-  *controller = std::move(reservation);
-  return base;
-}
-
-void CodeObjectRegistry::RegisterNewlyAllocatedCodeObject(Address code) {
-  auto result = code_object_registry_newly_allocated_.insert(code);
-  USE(result);
-  DCHECK(result.second);
-}
-
-void CodeObjectRegistry::RegisterAlreadyExistingCodeObject(Address code) {
-  code_object_registry_already_existing_.push_back(code);
-}
-
-void CodeObjectRegistry::Clear() {
-  code_object_registry_already_existing_.clear();
-  code_object_registry_newly_allocated_.clear();
-}
-
-void CodeObjectRegistry::Finalize() {
-  code_object_registry_already_existing_.shrink_to_fit();
-}
-
-bool CodeObjectRegistry::Contains(Address object) const {
-  return (code_object_registry_newly_allocated_.find(object) !=
-          code_object_registry_newly_allocated_.end()) ||
-         (std::binary_search(code_object_registry_already_existing_.begin(),
-                             code_object_registry_already_existing_.end(),
-                             object));
-}
-
-Address CodeObjectRegistry::GetCodeObjectStartFromInnerAddress(
-    Address address) const {
-  // Let's first find the object which comes right before address in the vector
-  // of already existing code objects.
-  Address already_existing_set_ = 0;
-  Address newly_allocated_set_ = 0;
-  if (!code_object_registry_already_existing_.empty()) {
-    auto it =
-        std::upper_bound(code_object_registry_already_existing_.begin(),
-                         code_object_registry_already_existing_.end(), address);
-    if (it != code_object_registry_already_existing_.begin()) {
-      already_existing_set_ = *(--it);
-    }
-  }
-
-  // Next, let's find the object which comes right before address in the set
-  // of newly allocated code objects.
-  if (!code_object_registry_newly_allocated_.empty()) {
-    auto it = code_object_registry_newly_allocated_.upper_bound(address);
-    if (it != code_object_registry_newly_allocated_.begin()) {
-      newly_allocated_set_ = *(--it);
-    }
-  }
-
-  // The code objects which contains address has to be in one of the two
-  // data structures.
-  DCHECK(already_existing_set_ != 0 || newly_allocated_set_ != 0);
-
-  // The address which is closest to the given address is the code object.
-  return already_existing_set_ > newly_allocated_set_ ? already_existing_set_
-                                                      : newly_allocated_set_;
-}
-
-namespace {
-
-PageAllocator::Permission DefaultWritableCodePermissions() {
-  return FLAG_jitless ? PageAllocator::kReadWrite
-                      : PageAllocator::kReadWriteExecute;
-}
-
-}  // namespace
-
-MemoryChunk* MemoryChunk::Initialize(Heap* heap, Address base, size_t size,
-                                     Address area_start, Address area_end,
-                                     Executability executable, Space* owner,
-                                     VirtualMemory reservation) {
-  MemoryChunk* chunk = FromAddress(base);
-  DCHECK_EQ(base, chunk->address());
-  new (chunk) BasicMemoryChunk(size, area_start, area_end);
-
-  chunk->heap_ = heap;
-  chunk->set_owner(owner);
-  chunk->InitializeReservedMemory();
-  base::AsAtomicPointer::Release_Store(&chunk->slot_set_[OLD_TO_NEW], nullptr);
-  base::AsAtomicPointer::Release_Store(&chunk->slot_set_[OLD_TO_OLD], nullptr);
-  base::AsAtomicPointer::Release_Store(&chunk->sweeping_slot_set_, nullptr);
-  base::AsAtomicPointer::Release_Store(&chunk->typed_slot_set_[OLD_TO_NEW],
-                                       nullptr);
-  base::AsAtomicPointer::Release_Store(&chunk->typed_slot_set_[OLD_TO_OLD],
-                                       nullptr);
-  chunk->invalidated_slots_[OLD_TO_NEW] = nullptr;
-  chunk->invalidated_slots_[OLD_TO_OLD] = nullptr;
-  chunk->progress_bar_ = 0;
-  chunk->high_water_mark_ = static_cast<intptr_t>(area_start - base);
-  chunk->set_concurrent_sweeping_state(ConcurrentSweepingState::kDone);
-  chunk->page_protection_change_mutex_ = new base::Mutex();
-  chunk->write_unprotect_counter_ = 0;
-  chunk->mutex_ = new base::Mutex();
-  chunk->allocated_bytes_ = chunk->area_size();
-  chunk->wasted_memory_ = 0;
-  chunk->young_generation_bitmap_ = nullptr;
-  chunk->local_tracker_ = nullptr;
-
-  chunk->external_backing_store_bytes_[ExternalBackingStoreType::kArrayBuffer] =
-      0;
-  chunk->external_backing_store_bytes_
-      [ExternalBackingStoreType::kExternalString] = 0;
-
-  chunk->categories_ = nullptr;
-
-  heap->incremental_marking()->non_atomic_marking_state()->SetLiveBytes(chunk,
-                                                                        0);
-  if (owner->identity() == RO_SPACE) {
-    heap->incremental_marking()
-        ->non_atomic_marking_state()
-        ->bitmap(chunk)
-        ->MarkAllBits();
-    chunk->SetFlag(READ_ONLY_HEAP);
-  }
-
-  if (executable == EXECUTABLE) {
-    chunk->SetFlag(IS_EXECUTABLE);
-    if (heap->write_protect_code_memory()) {
-      chunk->write_unprotect_counter_ =
-          heap->code_space_memory_modification_scope_depth();
-    } else {
-      size_t page_size = MemoryAllocator::GetCommitPageSize();
-      DCHECK(IsAligned(area_start, page_size));
-      size_t area_size = RoundUp(area_end - area_start, page_size);
-      CHECK(reservation.SetPermissions(area_start, area_size,
-                                       DefaultWritableCodePermissions()));
-    }
-  }
-
-  chunk->reservation_ = std::move(reservation);
-
-  if (owner->identity() == CODE_SPACE) {
-    chunk->code_object_registry_ = new CodeObjectRegistry();
-  } else {
-    chunk->code_object_registry_ = nullptr;
-  }
-
-  chunk->possibly_empty_buckets_.Initialize();
-
-  return chunk;
-}
-
-Page* PagedSpace::InitializePage(MemoryChunk* chunk) {
-  Page* page = static_cast<Page*>(chunk);
-  DCHECK_EQ(
-      MemoryChunkLayout::AllocatableMemoryInMemoryChunk(page->owner_identity()),
-      page->area_size());
-  // Make sure that categories are initialized before freeing the area.
-  page->ResetAllocationStatistics();
-  page->SetOldGenerationPageFlags(!is_off_thread_space() &&
-                                  heap()->incremental_marking()->IsMarking());
-  page->AllocateFreeListCategories();
-  page->InitializeFreeListCategories();
-  page->list_node().Initialize();
-  page->InitializationMemoryFence();
-  return page;
-}
-
-Page* SemiSpace::InitializePage(MemoryChunk* chunk) {
-  bool in_to_space = (id() != kFromSpace);
-  chunk->SetFlag(in_to_space ? MemoryChunk::TO_PAGE : MemoryChunk::FROM_PAGE);
-  Page* page = static_cast<Page*>(chunk);
-  page->SetYoungGenerationPageFlags(heap()->incremental_marking()->IsMarking());
-  page->AllocateLocalTracker();
-  page->list_node().Initialize();
-#ifdef ENABLE_MINOR_MC
-  if (FLAG_minor_mc) {
-    page->AllocateYoungGenerationBitmap();
-    heap()
-        ->minor_mark_compact_collector()
-        ->non_atomic_marking_state()
-        ->ClearLiveness(page);
-  }
-#endif  // ENABLE_MINOR_MC
-  page->InitializationMemoryFence();
-  return page;
-}
-
 void Page::AllocateFreeListCategories() {
   DCHECK_NULL(categories_);
   categories_ =
@@ -718,169 +130,6 @@ void Page::MergeOldToNewRememberedSets() {
   sweeping_slot_set_ = nullptr;
 }
 
-size_t MemoryChunk::CommittedPhysicalMemory() {
-  if (!base::OS::HasLazyCommits() || owner_identity() == LO_SPACE)
-    return size();
-  return high_water_mark_;
-}
-
-bool MemoryChunk::InOldSpace() const { return owner_identity() == OLD_SPACE; }
-
-bool MemoryChunk::InLargeObjectSpace() const {
-  return owner_identity() == LO_SPACE;
-}
-
-MemoryChunk* MemoryAllocator::AllocateChunk(size_t reserve_area_size,
-                                            size_t commit_area_size,
-                                            Executability executable,
-                                            Space* owner) {
-  DCHECK_LE(commit_area_size, reserve_area_size);
-
-  size_t chunk_size;
-  Heap* heap = isolate_->heap();
-  Address base = kNullAddress;
-  VirtualMemory reservation;
-  Address area_start = kNullAddress;
-  Address area_end = kNullAddress;
-  void* address_hint =
-      AlignedAddress(heap->GetRandomMmapAddr(), MemoryChunk::kAlignment);
-
-  //
-  // MemoryChunk layout:
-  //
-  //             Executable
-  // +----------------------------+<- base aligned with MemoryChunk::kAlignment
-  // |           Header           |
-  // +----------------------------+<- base + CodePageGuardStartOffset
-  // |           Guard            |
-  // +----------------------------+<- area_start_
-  // |           Area             |
-  // +----------------------------+<- area_end_ (area_start + commit_area_size)
-  // |   Committed but not used   |
-  // +----------------------------+<- aligned at OS page boundary
-  // | Reserved but not committed |
-  // +----------------------------+<- aligned at OS page boundary
-  // |           Guard            |
-  // +----------------------------+<- base + chunk_size
-  //
-  //           Non-executable
-  // +----------------------------+<- base aligned with MemoryChunk::kAlignment
-  // |          Header            |
-  // +----------------------------+<- area_start_ (base + area_start_)
-  // |           Area             |
-  // +----------------------------+<- area_end_ (area_start + commit_area_size)
-  // |  Committed but not used    |
-  // +----------------------------+<- aligned at OS page boundary
-  // | Reserved but not committed |
-  // +----------------------------+<- base + chunk_size
-  //
-
-  if (executable == EXECUTABLE) {
-    chunk_size = ::RoundUp(MemoryChunkLayout::ObjectStartOffsetInCodePage() +
-                               reserve_area_size +
-                               MemoryChunkLayout::CodePageGuardSize(),
-                           GetCommitPageSize());
-
-    // Size of header (not executable) plus area (executable).
-    size_t commit_size = ::RoundUp(
-        MemoryChunkLayout::CodePageGuardStartOffset() + commit_area_size,
-        GetCommitPageSize());
-    base =
-        AllocateAlignedMemory(chunk_size, commit_size, MemoryChunk::kAlignment,
-                              executable, address_hint, &reservation);
-    if (base == kNullAddress) return nullptr;
-    // Update executable memory size.
-    size_executable_ += reservation.size();
-
-    if (Heap::ShouldZapGarbage()) {
-      ZapBlock(base, MemoryChunkLayout::CodePageGuardStartOffset(), kZapValue);
-      ZapBlock(base + MemoryChunkLayout::ObjectStartOffsetInCodePage(),
-               commit_area_size, kZapValue);
-    }
-
-    area_start = base + MemoryChunkLayout::ObjectStartOffsetInCodePage();
-    area_end = area_start + commit_area_size;
-  } else {
-    chunk_size = ::RoundUp(
-        MemoryChunkLayout::ObjectStartOffsetInDataPage() + reserve_area_size,
-        GetCommitPageSize());
-    size_t commit_size = ::RoundUp(
-        MemoryChunkLayout::ObjectStartOffsetInDataPage() + commit_area_size,
-        GetCommitPageSize());
-    base =
-        AllocateAlignedMemory(chunk_size, commit_size, MemoryChunk::kAlignment,
-                              executable, address_hint, &reservation);
-
-    if (base == kNullAddress) return nullptr;
-
-    if (Heap::ShouldZapGarbage()) {
-      ZapBlock(
-          base,
-          MemoryChunkLayout::ObjectStartOffsetInDataPage() + commit_area_size,
-          kZapValue);
-    }
-
-    area_start = base + MemoryChunkLayout::ObjectStartOffsetInDataPage();
-    area_end = area_start + commit_area_size;
-  }
-
-  // Use chunk_size for statistics because we assume that  treat reserved but
-  // not-yet committed memory regions of chunks as allocated.
-  LOG(isolate_,
-      NewEvent("MemoryChunk", reinterpret_cast<void*>(base), chunk_size));
-
-  // We cannot use the last chunk in the address space because we would
-  // overflow when comparing top and limit if this chunk is used for a
-  // linear allocation area.
-  if ((base + chunk_size) == 0u) {
-    CHECK(!last_chunk_.IsReserved());
-    last_chunk_ = std::move(reservation);
-    UncommitMemory(&last_chunk_);
-    size_ -= chunk_size;
-    if (executable == EXECUTABLE) {
-      size_executable_ -= chunk_size;
-    }
-    CHECK(last_chunk_.IsReserved());
-    return AllocateChunk(reserve_area_size, commit_area_size, executable,
-                         owner);
-  }
-
-  MemoryChunk* chunk =
-      MemoryChunk::Initialize(heap, base, chunk_size, area_start, area_end,
-                              executable, owner, std::move(reservation));
-
-  if (chunk->executable()) RegisterExecutableMemoryChunk(chunk);
-  return chunk;
-}
-
-void MemoryChunk::SetOldGenerationPageFlags(bool is_marking) {
-  if (is_marking) {
-    SetFlag(MemoryChunk::POINTERS_TO_HERE_ARE_INTERESTING);
-    SetFlag(MemoryChunk::POINTERS_FROM_HERE_ARE_INTERESTING);
-    SetFlag(MemoryChunk::INCREMENTAL_MARKING);
-  } else {
-    ClearFlag(MemoryChunk::POINTERS_TO_HERE_ARE_INTERESTING);
-    SetFlag(MemoryChunk::POINTERS_FROM_HERE_ARE_INTERESTING);
-    ClearFlag(MemoryChunk::INCREMENTAL_MARKING);
-  }
-}
-
-void MemoryChunk::SetYoungGenerationPageFlags(bool is_marking) {
-  SetFlag(MemoryChunk::POINTERS_TO_HERE_ARE_INTERESTING);
-  if (is_marking) {
-    SetFlag(MemoryChunk::POINTERS_FROM_HERE_ARE_INTERESTING);
-    SetFlag(MemoryChunk::INCREMENTAL_MARKING);
-  } else {
-    ClearFlag(MemoryChunk::POINTERS_FROM_HERE_ARE_INTERESTING);
-    ClearFlag(MemoryChunk::INCREMENTAL_MARKING);
-  }
-}
-
-void Page::ResetAllocationStatistics() {
-  allocated_bytes_ = area_size();
-  wasted_memory_ = 0;
-}
-
 void Page::AllocateLocalTracker() {
   DCHECK_NULL(local_tracker_);
   local_tracker_ = new LocalArrayBufferTracker(this);
@@ -972,6 +221,19 @@ void Page::CreateBlackArea(Address start, Address end) {
   marking_state->IncrementLiveBytes(this, static_cast<intptr_t>(end - start));
 }
 
+void Page::CreateBlackAreaBackground(Address start, Address end) {
+  DCHECK(heap()->incremental_marking()->black_allocation());
+  DCHECK_EQ(Page::FromAddress(start), this);
+  DCHECK_LT(start, end);
+  DCHECK_EQ(Page::FromAddress(end - 1), this);
+  IncrementalMarking::AtomicMarkingState* marking_state =
+      heap()->incremental_marking()->atomic_marking_state();
+  marking_state->bitmap(this)->SetRange(AddressToMarkbitIndex(start),
+                                        AddressToMarkbitIndex(end));
+  heap()->incremental_marking()->IncrementLiveBytesBackground(
+      this, static_cast<intptr_t>(end - start));
+}
+
 void Page::DestroyBlackArea(Address start, Address end) {
   DCHECK(heap()->incremental_marking()->black_allocation());
   DCHECK_EQ(Page::FromAddress(start), this);
@@ -984,441 +246,17 @@ void Page::DestroyBlackArea(Address start, Address end) {
   marking_state->IncrementLiveBytes(this, -static_cast<intptr_t>(end - start));
 }
 
-void MemoryAllocator::PartialFreeMemory(MemoryChunk* chunk, Address start_free,
-                                        size_t bytes_to_free,
-                                        Address new_area_end) {
-  VirtualMemory* reservation = chunk->reserved_memory();
-  DCHECK(reservation->IsReserved());
-  chunk->set_size(chunk->size() - bytes_to_free);
-  chunk->set_area_end(new_area_end);
-  if (chunk->IsFlagSet(MemoryChunk::IS_EXECUTABLE)) {
-    // Add guard page at the end.
-    size_t page_size = GetCommitPageSize();
-    DCHECK_EQ(0, chunk->area_end() % static_cast<Address>(page_size));
-    DCHECK_EQ(chunk->address() + chunk->size(),
-              chunk->area_end() + MemoryChunkLayout::CodePageGuardSize());
-    reservation->SetPermissions(chunk->area_end(), page_size,
-                                PageAllocator::kNoAccess);
-  }
-  // On e.g. Windows, a reservation may be larger than a page and releasing
-  // partially starting at |start_free| will also release the potentially
-  // unused part behind the current page.
-  const size_t released_bytes = reservation->Release(start_free);
-  DCHECK_GE(size_, released_bytes);
-  size_ -= released_bytes;
-}
-
-void MemoryAllocator::UnregisterMemory(MemoryChunk* chunk) {
-  DCHECK(!chunk->IsFlagSet(MemoryChunk::UNREGISTERED));
-  VirtualMemory* reservation = chunk->reserved_memory();
-  const size_t size =
-      reservation->IsReserved() ? reservation->size() : chunk->size();
-  DCHECK_GE(size_, static_cast<size_t>(size));
-  size_ -= size;
-  if (chunk->executable() == EXECUTABLE) {
-    DCHECK_GE(size_executable_, size);
-    size_executable_ -= size;
-  }
-
-  if (chunk->executable()) UnregisterExecutableMemoryChunk(chunk);
-  chunk->SetFlag(MemoryChunk::UNREGISTERED);
-}
-
-void MemoryAllocator::PreFreeMemory(MemoryChunk* chunk) {
-  DCHECK(!chunk->IsFlagSet(MemoryChunk::PRE_FREED));
-  LOG(isolate_, DeleteEvent("MemoryChunk", chunk));
-  UnregisterMemory(chunk);
-  isolate_->heap()->RememberUnmappedPage(reinterpret_cast<Address>(chunk),
-                                         chunk->IsEvacuationCandidate());
-  chunk->SetFlag(MemoryChunk::PRE_FREED);
-}
-
-void MemoryAllocator::PerformFreeMemory(MemoryChunk* chunk) {
-  DCHECK(chunk->IsFlagSet(MemoryChunk::UNREGISTERED));
-  DCHECK(chunk->IsFlagSet(MemoryChunk::PRE_FREED));
-  chunk->ReleaseAllAllocatedMemory();
-
-  VirtualMemory* reservation = chunk->reserved_memory();
-  if (chunk->IsFlagSet(MemoryChunk::POOLED)) {
-    UncommitMemory(reservation);
-  } else {
-    if (reservation->IsReserved()) {
-      reservation->Free();
-    } else {
-      // Only read-only pages can have non-initialized reservation object.
-      DCHECK_EQ(RO_SPACE, chunk->owner_identity());
-      FreeMemory(page_allocator(chunk->executable()), chunk->address(),
-                 chunk->size());
-    }
-  }
-}
-
-template <MemoryAllocator::FreeMode mode>
-void MemoryAllocator::Free(MemoryChunk* chunk) {
-  switch (mode) {
-    case kFull:
-      PreFreeMemory(chunk);
-      PerformFreeMemory(chunk);
-      break;
-    case kAlreadyPooled:
-      // Pooled pages cannot be touched anymore as their memory is uncommitted.
-      // Pooled pages are not-executable.
-      FreeMemory(data_page_allocator(), chunk->address(),
-                 static_cast<size_t>(MemoryChunk::kPageSize));
-      break;
-    case kPooledAndQueue:
-      DCHECK_EQ(chunk->size(), static_cast<size_t>(MemoryChunk::kPageSize));
-      DCHECK_EQ(chunk->executable(), NOT_EXECUTABLE);
-      chunk->SetFlag(MemoryChunk::POOLED);
-      V8_FALLTHROUGH;
-    case kPreFreeAndQueue:
-      PreFreeMemory(chunk);
-      // The chunks added to this queue will be freed by a concurrent thread.
-      unmapper()->AddMemoryChunkSafe(chunk);
-      break;
-  }
-}
-
-template EXPORT_TEMPLATE_DEFINE(V8_EXPORT_PRIVATE) void MemoryAllocator::Free<
-    MemoryAllocator::kFull>(MemoryChunk* chunk);
-
-template EXPORT_TEMPLATE_DEFINE(V8_EXPORT_PRIVATE) void MemoryAllocator::Free<
-    MemoryAllocator::kAlreadyPooled>(MemoryChunk* chunk);
-
-template EXPORT_TEMPLATE_DEFINE(V8_EXPORT_PRIVATE) void MemoryAllocator::Free<
-    MemoryAllocator::kPreFreeAndQueue>(MemoryChunk* chunk);
-
-template EXPORT_TEMPLATE_DEFINE(V8_EXPORT_PRIVATE) void MemoryAllocator::Free<
-    MemoryAllocator::kPooledAndQueue>(MemoryChunk* chunk);
-
-template <MemoryAllocator::AllocationMode alloc_mode, typename SpaceType>
-Page* MemoryAllocator::AllocatePage(size_t size, SpaceType* owner,
-                                    Executability executable) {
-  MemoryChunk* chunk = nullptr;
-  if (alloc_mode == kPooled) {
-    DCHECK_EQ(size, static_cast<size_t>(
-                        MemoryChunkLayout::AllocatableMemoryInMemoryChunk(
-                            owner->identity())));
-    DCHECK_EQ(executable, NOT_EXECUTABLE);
-    chunk = AllocatePagePooled(owner);
-  }
-  if (chunk == nullptr) {
-    chunk = AllocateChunk(size, size, executable, owner);
-  }
-  if (chunk == nullptr) return nullptr;
-  return owner->InitializePage(chunk);
-}
-
-template EXPORT_TEMPLATE_DEFINE(V8_EXPORT_PRIVATE)
-    Page* MemoryAllocator::AllocatePage<MemoryAllocator::kRegular, PagedSpace>(
-        size_t size, PagedSpace* owner, Executability executable);
-template EXPORT_TEMPLATE_DEFINE(V8_EXPORT_PRIVATE)
-    Page* MemoryAllocator::AllocatePage<MemoryAllocator::kRegular, SemiSpace>(
-        size_t size, SemiSpace* owner, Executability executable);
-template EXPORT_TEMPLATE_DEFINE(V8_EXPORT_PRIVATE)
-    Page* MemoryAllocator::AllocatePage<MemoryAllocator::kPooled, SemiSpace>(
-        size_t size, SemiSpace* owner, Executability executable);
-
-LargePage* MemoryAllocator::AllocateLargePage(size_t size,
-                                              LargeObjectSpace* owner,
-                                              Executability executable) {
-  MemoryChunk* chunk = AllocateChunk(size, size, executable, owner);
-  if (chunk == nullptr) return nullptr;
-  return LargePage::Initialize(isolate_->heap(), chunk, executable);
-}
-
-template <typename SpaceType>
-MemoryChunk* MemoryAllocator::AllocatePagePooled(SpaceType* owner) {
-  MemoryChunk* chunk = unmapper()->TryGetPooledMemoryChunkSafe();
-  if (chunk == nullptr) return nullptr;
-  const int size = MemoryChunk::kPageSize;
-  const Address start = reinterpret_cast<Address>(chunk);
-  const Address area_start =
-      start +
-      MemoryChunkLayout::ObjectStartOffsetInMemoryChunk(owner->identity());
-  const Address area_end = start + size;
-  // Pooled pages are always regular data pages.
-  DCHECK_NE(CODE_SPACE, owner->identity());
-  VirtualMemory reservation(data_page_allocator(), start, size);
-  if (!CommitMemory(&reservation)) return nullptr;
-  if (Heap::ShouldZapGarbage()) {
-    ZapBlock(start, size, kZapValue);
-  }
-  MemoryChunk::Initialize(isolate_->heap(), start, size, area_start, area_end,
-                          NOT_EXECUTABLE, owner, std::move(reservation));
-  size_ += size;
-  return chunk;
-}
-
-void MemoryAllocator::ZapBlock(Address start, size_t size,
-                               uintptr_t zap_value) {
-  DCHECK(IsAligned(start, kTaggedSize));
-  DCHECK(IsAligned(size, kTaggedSize));
-  MemsetTagged(ObjectSlot(start), Object(static_cast<Address>(zap_value)),
-               size >> kTaggedSizeLog2);
-}
-
-intptr_t MemoryAllocator::GetCommitPageSize() {
-  if (FLAG_v8_os_page_size != 0) {
-    DCHECK(base::bits::IsPowerOfTwo(FLAG_v8_os_page_size));
-    return FLAG_v8_os_page_size * KB;
-  } else {
-    return CommitPageSize();
-  }
-}
-
-base::AddressRegion MemoryAllocator::ComputeDiscardMemoryArea(Address addr,
-                                                              size_t size) {
-  size_t page_size = MemoryAllocator::GetCommitPageSize();
-  if (size < page_size + FreeSpace::kSize) {
-    return base::AddressRegion(0, 0);
-  }
-  Address discardable_start = RoundUp(addr + FreeSpace::kSize, page_size);
-  Address discardable_end = RoundDown(addr + size, page_size);
-  if (discardable_start >= discardable_end) return base::AddressRegion(0, 0);
-  return base::AddressRegion(discardable_start,
-                             discardable_end - discardable_start);
-}
-
-bool MemoryAllocator::CommitExecutableMemory(VirtualMemory* vm, Address start,
-                                             size_t commit_size,
-                                             size_t reserved_size) {
-  const size_t page_size = GetCommitPageSize();
-  // All addresses and sizes must be aligned to the commit page size.
-  DCHECK(IsAligned(start, page_size));
-  DCHECK_EQ(0, commit_size % page_size);
-  DCHECK_EQ(0, reserved_size % page_size);
-  const size_t guard_size = MemoryChunkLayout::CodePageGuardSize();
-  const size_t pre_guard_offset = MemoryChunkLayout::CodePageGuardStartOffset();
-  const size_t code_area_offset =
-      MemoryChunkLayout::ObjectStartOffsetInCodePage();
-  // reserved_size includes two guard regions, commit_size does not.
-  DCHECK_LE(commit_size, reserved_size - 2 * guard_size);
-  const Address pre_guard_page = start + pre_guard_offset;
-  const Address code_area = start + code_area_offset;
-  const Address post_guard_page = start + reserved_size - guard_size;
-  // Commit the non-executable header, from start to pre-code guard page.
-  if (vm->SetPermissions(start, pre_guard_offset, PageAllocator::kReadWrite)) {
-    // Create the pre-code guard page, following the header.
-    if (vm->SetPermissions(pre_guard_page, page_size,
-                           PageAllocator::kNoAccess)) {
-      // Commit the executable code body.
-      if (vm->SetPermissions(code_area, commit_size - pre_guard_offset,
-                             PageAllocator::kReadWrite)) {
-        // Create the post-code guard page.
-        if (vm->SetPermissions(post_guard_page, page_size,
-                               PageAllocator::kNoAccess)) {
-          UpdateAllocatedSpaceLimits(start, code_area + commit_size);
-          return true;
-        }
-        vm->SetPermissions(code_area, commit_size, PageAllocator::kNoAccess);
-      }
-    }
-    vm->SetPermissions(start, pre_guard_offset, PageAllocator::kNoAccess);
-  }
-  return false;
-}
-
-
-// -----------------------------------------------------------------------------
-// MemoryChunk implementation
-
-void MemoryChunk::ReleaseAllocatedMemoryNeededForWritableChunk() {
-  if (mutex_ != nullptr) {
-    delete mutex_;
-    mutex_ = nullptr;
-  }
-  if (page_protection_change_mutex_ != nullptr) {
-    delete page_protection_change_mutex_;
-    page_protection_change_mutex_ = nullptr;
-  }
-  if (code_object_registry_ != nullptr) {
-    delete code_object_registry_;
-    code_object_registry_ = nullptr;
-  }
-
-  possibly_empty_buckets_.Release();
-  ReleaseSlotSet<OLD_TO_NEW>();
-  ReleaseSweepingSlotSet();
-  ReleaseSlotSet<OLD_TO_OLD>();
-  ReleaseTypedSlotSet<OLD_TO_NEW>();
-  ReleaseTypedSlotSet<OLD_TO_OLD>();
-  ReleaseInvalidatedSlots<OLD_TO_NEW>();
-  ReleaseInvalidatedSlots<OLD_TO_OLD>();
-
-  if (local_tracker_ != nullptr) ReleaseLocalTracker();
-  if (young_generation_bitmap_ != nullptr) ReleaseYoungGenerationBitmap();
-
-  if (!IsLargePage()) {
-    Page* page = static_cast<Page*>(this);
-    page->ReleaseFreeListCategories();
-  }
-}
-
-void MemoryChunk::ReleaseAllAllocatedMemory() {
-  ReleaseAllocatedMemoryNeededForWritableChunk();
-  if (marking_bitmap_ != nullptr) ReleaseMarkingBitmap();
-}
-
-template V8_EXPORT_PRIVATE SlotSet* MemoryChunk::AllocateSlotSet<OLD_TO_NEW>();
-template V8_EXPORT_PRIVATE SlotSet* MemoryChunk::AllocateSlotSet<OLD_TO_OLD>();
-
-template <RememberedSetType type>
-SlotSet* MemoryChunk::AllocateSlotSet() {
-  return AllocateSlotSet(&slot_set_[type]);
-}
-
-SlotSet* MemoryChunk::AllocateSweepingSlotSet() {
-  return AllocateSlotSet(&sweeping_slot_set_);
-}
-
-SlotSet* MemoryChunk::AllocateSlotSet(SlotSet** slot_set) {
-  SlotSet* new_slot_set = SlotSet::Allocate(buckets());
-  SlotSet* old_slot_set = base::AsAtomicPointer::AcquireRelease_CompareAndSwap(
-      slot_set, nullptr, new_slot_set);
-  if (old_slot_set != nullptr) {
-    SlotSet::Delete(new_slot_set, buckets());
-    new_slot_set = old_slot_set;
-  }
-  DCHECK(new_slot_set);
-  return new_slot_set;
-}
-
-template void MemoryChunk::ReleaseSlotSet<OLD_TO_NEW>();
-template void MemoryChunk::ReleaseSlotSet<OLD_TO_OLD>();
-
-template <RememberedSetType type>
-void MemoryChunk::ReleaseSlotSet() {
-  ReleaseSlotSet(&slot_set_[type]);
-}
-
-void MemoryChunk::ReleaseSweepingSlotSet() {
-  ReleaseSlotSet(&sweeping_slot_set_);
-}
-
-void MemoryChunk::ReleaseSlotSet(SlotSet** slot_set) {
-  if (*slot_set) {
-    SlotSet::Delete(*slot_set, buckets());
-    *slot_set = nullptr;
-  }
-}
-
-template TypedSlotSet* MemoryChunk::AllocateTypedSlotSet<OLD_TO_NEW>();
-template TypedSlotSet* MemoryChunk::AllocateTypedSlotSet<OLD_TO_OLD>();
-
-template <RememberedSetType type>
-TypedSlotSet* MemoryChunk::AllocateTypedSlotSet() {
-  TypedSlotSet* typed_slot_set = new TypedSlotSet(address());
-  TypedSlotSet* old_value = base::AsAtomicPointer::Release_CompareAndSwap(
-      &typed_slot_set_[type], nullptr, typed_slot_set);
-  if (old_value != nullptr) {
-    delete typed_slot_set;
-    typed_slot_set = old_value;
-  }
-  DCHECK(typed_slot_set);
-  return typed_slot_set;
-}
-
-template void MemoryChunk::ReleaseTypedSlotSet<OLD_TO_NEW>();
-template void MemoryChunk::ReleaseTypedSlotSet<OLD_TO_OLD>();
-
-template <RememberedSetType type>
-void MemoryChunk::ReleaseTypedSlotSet() {
-  TypedSlotSet* typed_slot_set = typed_slot_set_[type];
-  if (typed_slot_set) {
-    typed_slot_set_[type] = nullptr;
-    delete typed_slot_set;
-  }
-}
-
-template InvalidatedSlots* MemoryChunk::AllocateInvalidatedSlots<OLD_TO_NEW>();
-template InvalidatedSlots* MemoryChunk::AllocateInvalidatedSlots<OLD_TO_OLD>();
-
-template <RememberedSetType type>
-InvalidatedSlots* MemoryChunk::AllocateInvalidatedSlots() {
-  DCHECK_NULL(invalidated_slots_[type]);
-  invalidated_slots_[type] = new InvalidatedSlots();
-  return invalidated_slots_[type];
-}
-
-template void MemoryChunk::ReleaseInvalidatedSlots<OLD_TO_NEW>();
-template void MemoryChunk::ReleaseInvalidatedSlots<OLD_TO_OLD>();
-
-template <RememberedSetType type>
-void MemoryChunk::ReleaseInvalidatedSlots() {
-  if (invalidated_slots_[type]) {
-    delete invalidated_slots_[type];
-    invalidated_slots_[type] = nullptr;
-  }
-}
-
-template V8_EXPORT_PRIVATE void
-MemoryChunk::RegisterObjectWithInvalidatedSlots<OLD_TO_NEW>(HeapObject object);
-template V8_EXPORT_PRIVATE void
-MemoryChunk::RegisterObjectWithInvalidatedSlots<OLD_TO_OLD>(HeapObject object);
-
-template <RememberedSetType type>
-void MemoryChunk::RegisterObjectWithInvalidatedSlots(HeapObject object) {
-  bool skip_slot_recording;
-
-  if (type == OLD_TO_NEW) {
-    skip_slot_recording = InYoungGeneration();
-  } else {
-    skip_slot_recording = ShouldSkipEvacuationSlotRecording();
-  }
-
-  if (skip_slot_recording) {
-    return;
-  }
-
-  if (invalidated_slots<type>() == nullptr) {
-    AllocateInvalidatedSlots<type>();
-  }
-
-  invalidated_slots<type>()->insert(object);
-}
-
-void MemoryChunk::InvalidateRecordedSlots(HeapObject object) {
-  if (V8_DISABLE_WRITE_BARRIERS_BOOL) return;
-  if (heap()->incremental_marking()->IsCompacting()) {
-    // We cannot check slot_set_[OLD_TO_OLD] here, since the
-    // concurrent markers might insert slots concurrently.
-    RegisterObjectWithInvalidatedSlots<OLD_TO_OLD>(object);
-  }
-
-  if (!FLAG_always_promote_young_mc || slot_set_[OLD_TO_NEW] != nullptr)
-    RegisterObjectWithInvalidatedSlots<OLD_TO_NEW>(object);
-}
-
-template bool MemoryChunk::RegisteredObjectWithInvalidatedSlots<OLD_TO_NEW>(
-    HeapObject object);
-template bool MemoryChunk::RegisteredObjectWithInvalidatedSlots<OLD_TO_OLD>(
-    HeapObject object);
-
-template <RememberedSetType type>
-bool MemoryChunk::RegisteredObjectWithInvalidatedSlots(HeapObject object) {
-  if (invalidated_slots<type>() == nullptr) {
-    return false;
-  }
-  return invalidated_slots<type>()->find(object) !=
-         invalidated_slots<type>()->end();
-}
-
-void MemoryChunk::ReleaseLocalTracker() {
-  DCHECK_NOT_NULL(local_tracker_);
-  delete local_tracker_;
-  local_tracker_ = nullptr;
-}
-
-void MemoryChunk::AllocateYoungGenerationBitmap() {
-  DCHECK_NULL(young_generation_bitmap_);
-  young_generation_bitmap_ = static_cast<Bitmap*>(calloc(1, Bitmap::kSize));
-}
-
-void MemoryChunk::ReleaseYoungGenerationBitmap() {
-  DCHECK_NOT_NULL(young_generation_bitmap_);
-  free(young_generation_bitmap_);
-  young_generation_bitmap_ = nullptr;
+void Page::DestroyBlackAreaBackground(Address start, Address end) {
+  DCHECK(heap()->incremental_marking()->black_allocation());
+  DCHECK_EQ(Page::FromAddress(start), this);
+  DCHECK_LT(start, end);
+  DCHECK_EQ(Page::FromAddress(end - 1), this);
+  IncrementalMarking::AtomicMarkingState* marking_state =
+      heap()->incremental_marking()->atomic_marking_state();
+  marking_state->bitmap(this)->ClearRange(AddressToMarkbitIndex(start),
+                                          AddressToMarkbitIndex(end));
+  heap()->incremental_marking()->IncrementLiveBytesBackground(
+      this, -static_cast<intptr_t>(end - start));
 }
 
 // -----------------------------------------------------------------------------
@@ -1481,293 +319,6 @@ intptr_t Space::GetNextInlineAllocationStepSize() {
   return next_step;
 }
 
-PagedSpace::PagedSpace(Heap* heap, AllocationSpace space,
-                       Executability executable, FreeList* free_list,
-                       LocalSpaceKind local_space_kind)
-    : SpaceWithLinearArea(heap, space, free_list),
-      executable_(executable),
-      local_space_kind_(local_space_kind) {
-  area_size_ = MemoryChunkLayout::AllocatableMemoryInMemoryChunk(space);
-  accounting_stats_.Clear();
-}
-
-void PagedSpace::TearDown() {
-  while (!memory_chunk_list_.Empty()) {
-    MemoryChunk* chunk = memory_chunk_list_.front();
-    memory_chunk_list_.Remove(chunk);
-    heap()->memory_allocator()->Free<MemoryAllocator::kFull>(chunk);
-  }
-  accounting_stats_.Clear();
-}
-
-void PagedSpace::RefillFreeList() {
-  // Any PagedSpace might invoke RefillFreeList. We filter all but our old
-  // generation spaces out.
-  if (identity() != OLD_SPACE && identity() != CODE_SPACE &&
-      identity() != MAP_SPACE && identity() != RO_SPACE) {
-    return;
-  }
-  DCHECK_NE(local_space_kind(), LocalSpaceKind::kOffThreadSpace);
-  DCHECK_IMPLIES(is_local_space(), is_compaction_space());
-  DCHECK(!IsDetached());
-  MarkCompactCollector* collector = heap()->mark_compact_collector();
-  size_t added = 0;
-
-  {
-    Page* p = nullptr;
-    while ((p = collector->sweeper()->GetSweptPageSafe(this)) != nullptr) {
-      // We regularly sweep NEVER_ALLOCATE_ON_PAGE pages. We drop the freelist
-      // entries here to make them unavailable for allocations.
-      if (p->IsFlagSet(Page::NEVER_ALLOCATE_ON_PAGE)) {
-        p->ForAllFreeListCategories([this](FreeListCategory* category) {
-          category->Reset(free_list());
-        });
-      }
-
-      // Also merge old-to-new remembered sets if not scavenging because of
-      // data races: One thread might iterate remembered set, while another
-      // thread merges them.
-      if (local_space_kind() != LocalSpaceKind::kCompactionSpaceForScavenge) {
-        p->MergeOldToNewRememberedSets();
-      }
-
-      // Only during compaction pages can actually change ownership. This is
-      // safe because there exists no other competing action on the page links
-      // during compaction.
-      if (is_compaction_space()) {
-        DCHECK_NE(this, p->owner());
-        PagedSpace* owner = reinterpret_cast<PagedSpace*>(p->owner());
-        base::MutexGuard guard(owner->mutex());
-        owner->RefineAllocatedBytesAfterSweeping(p);
-        owner->RemovePage(p);
-        added += AddPage(p);
-      } else {
-        base::MutexGuard guard(mutex());
-        DCHECK_EQ(this, p->owner());
-        RefineAllocatedBytesAfterSweeping(p);
-        added += RelinkFreeListCategories(p);
-      }
-      added += p->wasted_memory();
-      if (is_compaction_space() && (added > kCompactionMemoryWanted)) break;
-    }
-  }
-}
-
-void OffThreadSpace::RefillFreeList() {
-  // We should never try to refill the free list in off-thread space, because
-  // we know it will always be fully linear.
-  UNREACHABLE();
-}
-
-void PagedSpace::MergeLocalSpace(LocalSpace* other) {
-  base::MutexGuard guard(mutex());
-
-  DCHECK(identity() == other->identity());
-
-  // Unmerged fields:
-  //   area_size_
-  other->FreeLinearAllocationArea();
-
-  for (int i = static_cast<int>(AllocationOrigin::kFirstAllocationOrigin);
-       i <= static_cast<int>(AllocationOrigin::kLastAllocationOrigin); i++) {
-    allocations_origins_[i] += other->allocations_origins_[i];
-  }
-
-  // The linear allocation area of {other} should be destroyed now.
-  DCHECK_EQ(kNullAddress, other->top());
-  DCHECK_EQ(kNullAddress, other->limit());
-
-  bool merging_from_off_thread = other->is_off_thread_space();
-
-  // Move over pages.
-  for (auto it = other->begin(); it != other->end();) {
-    Page* p = *(it++);
-
-    if (merging_from_off_thread) {
-      DCHECK_NULL(p->sweeping_slot_set());
-      p->SetOldGenerationPageFlags(heap()->incremental_marking()->IsMarking());
-      if (heap()->incremental_marking()->black_allocation()) {
-        p->CreateBlackArea(p->area_start(), p->HighWaterMark());
-      }
-    } else {
-      p->MergeOldToNewRememberedSets();
-    }
-
-    // Relinking requires the category to be unlinked.
-    other->RemovePage(p);
-    AddPage(p);
-    // These code pages were allocated by the CompactionSpace.
-    if (identity() == CODE_SPACE) heap()->isolate()->AddCodeMemoryChunk(p);
-    DCHECK_IMPLIES(
-        !p->IsFlagSet(Page::NEVER_ALLOCATE_ON_PAGE),
-        p->AvailableInFreeList() == p->AvailableInFreeListFromAllocatedBytes());
-
-    // TODO(leszeks): Here we should allocation step, but:
-    //   1. Allocation groups are currently not handled properly by the sampling
-    //      allocation profiler, and
-    //   2. Observers might try to take the space lock, which isn't reentrant.
-    // We'll have to come up with a better solution for allocation stepping
-    // before shipping, which will likely be using LocalHeap.
-  }
-
-  DCHECK_EQ(0u, other->Size());
-  DCHECK_EQ(0u, other->Capacity());
-}
-
-size_t PagedSpace::CommittedPhysicalMemory() {
-  if (!base::OS::HasLazyCommits()) return CommittedMemory();
-  MemoryChunk::UpdateHighWaterMark(allocation_info_.top());
-  size_t size = 0;
-  for (Page* page : *this) {
-    size += page->CommittedPhysicalMemory();
-  }
-  return size;
-}
-
-bool PagedSpace::ContainsSlow(Address addr) {
-  Page* p = Page::FromAddress(addr);
-  for (Page* page : *this) {
-    if (page == p) return true;
-  }
-  return false;
-}
-
-void PagedSpace::RefineAllocatedBytesAfterSweeping(Page* page) {
-  CHECK(page->SweepingDone());
-  auto marking_state =
-      heap()->incremental_marking()->non_atomic_marking_state();
-  // The live_byte on the page was accounted in the space allocated
-  // bytes counter. After sweeping allocated_bytes() contains the
-  // accurate live byte count on the page.
-  size_t old_counter = marking_state->live_bytes(page);
-  size_t new_counter = page->allocated_bytes();
-  DCHECK_GE(old_counter, new_counter);
-  if (old_counter > new_counter) {
-    DecreaseAllocatedBytes(old_counter - new_counter, page);
-    // Give the heap a chance to adjust counters in response to the
-    // more precise and smaller old generation size.
-    heap()->NotifyRefinedOldGenerationSize(old_counter - new_counter);
-  }
-  marking_state->SetLiveBytes(page, 0);
-}
-
-Page* PagedSpace::RemovePageSafe(int size_in_bytes) {
-  base::MutexGuard guard(mutex());
-  Page* page = free_list()->GetPageForSize(size_in_bytes);
-  if (!page) return nullptr;
-  RemovePage(page);
-  return page;
-}
-
-size_t PagedSpace::AddPage(Page* page) {
-  CHECK(page->SweepingDone());
-  page->set_owner(this);
-  memory_chunk_list_.PushBack(page);
-  AccountCommitted(page->size());
-  IncreaseCapacity(page->area_size());
-  IncreaseAllocatedBytes(page->allocated_bytes(), page);
-  for (size_t i = 0; i < ExternalBackingStoreType::kNumTypes; i++) {
-    ExternalBackingStoreType t = static_cast<ExternalBackingStoreType>(i);
-    IncrementExternalBackingStoreBytes(t, page->ExternalBackingStoreBytes(t));
-  }
-  return RelinkFreeListCategories(page);
-}
-
-void PagedSpace::RemovePage(Page* page) {
-  CHECK(page->SweepingDone());
-  memory_chunk_list_.Remove(page);
-  UnlinkFreeListCategories(page);
-  DecreaseAllocatedBytes(page->allocated_bytes(), page);
-  DecreaseCapacity(page->area_size());
-  AccountUncommitted(page->size());
-  for (size_t i = 0; i < ExternalBackingStoreType::kNumTypes; i++) {
-    ExternalBackingStoreType t = static_cast<ExternalBackingStoreType>(i);
-    DecrementExternalBackingStoreBytes(t, page->ExternalBackingStoreBytes(t));
-  }
-}
-
-size_t PagedSpace::ShrinkPageToHighWaterMark(Page* page) {
-  size_t unused = page->ShrinkToHighWaterMark();
-  accounting_stats_.DecreaseCapacity(static_cast<intptr_t>(unused));
-  AccountUncommitted(unused);
-  return unused;
-}
-
-void PagedSpace::ResetFreeList() {
-  for (Page* page : *this) {
-    free_list_->EvictFreeListItems(page);
-  }
-  DCHECK(free_list_->IsEmpty());
-}
-
-void PagedSpace::ShrinkImmortalImmovablePages() {
-  DCHECK(!heap()->deserialization_complete());
-  MemoryChunk::UpdateHighWaterMark(allocation_info_.top());
-  FreeLinearAllocationArea();
-  ResetFreeList();
-  for (Page* page : *this) {
-    DCHECK(page->IsFlagSet(Page::NEVER_EVACUATE));
-    ShrinkPageToHighWaterMark(page);
-  }
-}
-
-bool PagedSpace::Expand() {
-  // Always lock against the main space as we can only adjust capacity and
-  // pages concurrently for the main paged space.
-  base::MutexGuard guard(heap()->paged_space(identity())->mutex());
-
-  const int size = AreaSize();
-
-  if (!heap()->CanExpandOldGeneration(size)) return false;
-
-  Page* page =
-      heap()->memory_allocator()->AllocatePage(size, this, executable());
-  if (page == nullptr) return false;
-  // Pages created during bootstrapping may contain immortal immovable objects.
-  if (!heap()->deserialization_complete()) page->MarkNeverEvacuate();
-  AddPage(page);
-  // If this is a non-compaction code space, this is a previously unseen page.
-  if (identity() == CODE_SPACE && !is_compaction_space()) {
-    heap()->isolate()->AddCodeMemoryChunk(page);
-  }
-  Free(page->area_start(), page->area_size(),
-       SpaceAccountingMode::kSpaceAccounted);
-  heap()->NotifyOldGenerationExpansion();
-  return true;
-}
-
-int PagedSpace::CountTotalPages() {
-  int count = 0;
-  for (Page* page : *this) {
-    count++;
-    USE(page);
-  }
-  return count;
-}
-
-void PagedSpace::SetLinearAllocationArea(Address top, Address limit) {
-  SetTopAndLimit(top, limit);
-  if (top != kNullAddress && top != limit && !is_off_thread_space() &&
-      heap()->incremental_marking()->black_allocation()) {
-    Page::FromAllocationAreaAddress(top)->CreateBlackArea(top, limit);
-  }
-}
-
-void PagedSpace::DecreaseLimit(Address new_limit) {
-  Address old_limit = limit();
-  DCHECK_LE(top(), new_limit);
-  DCHECK_GE(old_limit, new_limit);
-  if (new_limit != old_limit) {
-    SetTopAndLimit(top(), new_limit);
-    Free(new_limit, old_limit - new_limit,
-         SpaceAccountingMode::kSpaceAccounted);
-    if (heap()->incremental_marking()->black_allocation()) {
-      Page::FromAllocationAreaAddress(new_limit)->DestroyBlackArea(new_limit,
-                                                                   old_limit);
-    }
-  }
-}
-
 Address SpaceWithLinearArea::ComputeLimit(Address start, Address end,
                                           size_t min_size) {
   DCHECK_GE(end - start, min_size);
@@ -1802,560 +353,6 @@ void SpaceWithLinearArea::PrintAllocationsOrigins() {
       allocations_origins_[2]);
 }
 
-void PagedSpace::MarkLinearAllocationAreaBlack() {
-  DCHECK(heap()->incremental_marking()->black_allocation());
-  Address current_top = top();
-  Address current_limit = limit();
-  if (current_top != kNullAddress && current_top != current_limit) {
-    Page::FromAllocationAreaAddress(current_top)
-        ->CreateBlackArea(current_top, current_limit);
-  }
-}
-
-void PagedSpace::UnmarkLinearAllocationArea() {
-  Address current_top = top();
-  Address current_limit = limit();
-  if (current_top != kNullAddress && current_top != current_limit) {
-    Page::FromAllocationAreaAddress(current_top)
-        ->DestroyBlackArea(current_top, current_limit);
-  }
-}
-
-void PagedSpace::FreeLinearAllocationArea() {
-  // Mark the old linear allocation area with a free space map so it can be
-  // skipped when scanning the heap.
-  Address current_top = top();
-  Address current_limit = limit();
-  if (current_top == kNullAddress) {
-    DCHECK_EQ(kNullAddress, current_limit);
-    return;
-  }
-
-  if (!is_off_thread_space() &&
-      heap()->incremental_marking()->black_allocation()) {
-    Page* page = Page::FromAllocationAreaAddress(current_top);
-
-    // Clear the bits in the unused black area.
-    if (current_top != current_limit) {
-      IncrementalMarking::MarkingState* marking_state =
-          heap()->incremental_marking()->marking_state();
-      marking_state->bitmap(page)->ClearRange(
-          page->AddressToMarkbitIndex(current_top),
-          page->AddressToMarkbitIndex(current_limit));
-      marking_state->IncrementLiveBytes(
-          page, -static_cast<int>(current_limit - current_top));
-    }
-  }
-
-  InlineAllocationStep(current_top, kNullAddress, kNullAddress, 0);
-  SetTopAndLimit(kNullAddress, kNullAddress);
-  DCHECK_GE(current_limit, current_top);
-
-  // The code page of the linear allocation area needs to be unprotected
-  // because we are going to write a filler into that memory area below.
-  if (identity() == CODE_SPACE) {
-    heap()->UnprotectAndRegisterMemoryChunk(
-        MemoryChunk::FromAddress(current_top));
-  }
-  Free(current_top, current_limit - current_top,
-       SpaceAccountingMode::kSpaceAccounted);
-}
-
-void PagedSpace::ReleasePage(Page* page) {
-  DCHECK_EQ(
-      0, heap()->incremental_marking()->non_atomic_marking_state()->live_bytes(
-             page));
-  DCHECK_EQ(page->owner(), this);
-
-  free_list_->EvictFreeListItems(page);
-
-  if (Page::FromAllocationAreaAddress(allocation_info_.top()) == page) {
-    DCHECK(!top_on_previous_step_);
-    allocation_info_.Reset(kNullAddress, kNullAddress);
-  }
-
-  heap()->isolate()->RemoveCodeMemoryChunk(page);
-
-  AccountUncommitted(page->size());
-  accounting_stats_.DecreaseCapacity(page->area_size());
-  heap()->memory_allocator()->Free<MemoryAllocator::kPreFreeAndQueue>(page);
-}
-
-void PagedSpace::SetReadable() {
-  DCHECK(identity() == CODE_SPACE);
-  for (Page* page : *this) {
-    CHECK(heap()->memory_allocator()->IsMemoryChunkExecutable(page));
-    page->SetReadable();
-  }
-}
-
-void PagedSpace::SetReadAndExecutable() {
-  DCHECK(identity() == CODE_SPACE);
-  for (Page* page : *this) {
-    CHECK(heap()->memory_allocator()->IsMemoryChunkExecutable(page));
-    page->SetReadAndExecutable();
-  }
-}
-
-void PagedSpace::SetReadAndWritable() {
-  DCHECK(identity() == CODE_SPACE);
-  for (Page* page : *this) {
-    CHECK(heap()->memory_allocator()->IsMemoryChunkExecutable(page));
-    page->SetReadAndWritable();
-  }
-}
-
-std::unique_ptr<ObjectIterator> PagedSpace::GetObjectIterator(Heap* heap) {
-  return std::unique_ptr<ObjectIterator>(
-      new PagedSpaceObjectIterator(heap, this));
-}
-
-bool PagedSpace::RefillLinearAllocationAreaFromFreeList(
-    size_t size_in_bytes, AllocationOrigin origin) {
-  DCHECK(IsAligned(size_in_bytes, kTaggedSize));
-  DCHECK_LE(top(), limit());
-#ifdef DEBUG
-  if (top() != limit()) {
-    DCHECK_EQ(Page::FromAddress(top()), Page::FromAddress(limit() - 1));
-  }
-#endif
-  // Don't free list allocate if there is linear space available.
-  DCHECK_LT(static_cast<size_t>(limit() - top()), size_in_bytes);
-
-  // Mark the old linear allocation area with a free space map so it can be
-  // skipped when scanning the heap.  This also puts it back in the free list
-  // if it is big enough.
-  FreeLinearAllocationArea();
-
-  if (!is_local_space()) {
-    heap()->StartIncrementalMarkingIfAllocationLimitIsReached(
-        heap()->GCFlagsForIncrementalMarking(),
-        kGCCallbackScheduleIdleGarbageCollection);
-  }
-
-  size_t new_node_size = 0;
-  FreeSpace new_node =
-      free_list_->Allocate(size_in_bytes, &new_node_size, origin);
-  if (new_node.is_null()) return false;
-  DCHECK_GE(new_node_size, size_in_bytes);
-
-  // The old-space-step might have finished sweeping and restarted marking.
-  // Verify that it did not turn the page of the new node into an evacuation
-  // candidate.
-  DCHECK(!MarkCompactCollector::IsOnEvacuationCandidate(new_node));
-
-  // Memory in the linear allocation area is counted as allocated.  We may free
-  // a little of this again immediately - see below.
-  Page* page = Page::FromHeapObject(new_node);
-  IncreaseAllocatedBytes(new_node_size, page);
-
-  Address start = new_node.address();
-  Address end = new_node.address() + new_node_size;
-  Address limit = ComputeLimit(start, end, size_in_bytes);
-  DCHECK_LE(limit, end);
-  DCHECK_LE(size_in_bytes, limit - start);
-  if (limit != end) {
-    if (identity() == CODE_SPACE) {
-      heap()->UnprotectAndRegisterMemoryChunk(page);
-    }
-    Free(limit, end - limit, SpaceAccountingMode::kSpaceAccounted);
-  }
-  SetLinearAllocationArea(start, limit);
-
-  return true;
-}
-
-base::Optional<std::pair<Address, size_t>>
-PagedSpace::SlowGetLinearAllocationAreaBackground(LocalHeap* local_heap,
-                                                  size_t min_size_in_bytes,
-                                                  size_t max_size_in_bytes,
-                                                  AllocationAlignment alignment,
-                                                  AllocationOrigin origin) {
-  DCHECK(!is_local_space() && identity() == OLD_SPACE);
-  DCHECK_EQ(origin, AllocationOrigin::kRuntime);
-  base::MutexGuard lock(&allocation_mutex_);
-
-  auto result = TryAllocationFromFreeListBackground(
-      min_size_in_bytes, max_size_in_bytes, alignment, origin);
-  if (result) return result;
-
-  MarkCompactCollector* collector = heap()->mark_compact_collector();
-  // Sweeping is still in progress.
-  if (collector->sweeping_in_progress()) {
-    // First try to refill the free-list, concurrent sweeper threads
-    // may have freed some objects in the meantime.
-    RefillFreeList();
-
-    // Retry the free list allocation.
-    auto result = TryAllocationFromFreeListBackground(
-        min_size_in_bytes, max_size_in_bytes, alignment, origin);
-    if (result) return result;
-
-    Sweeper::FreeSpaceMayContainInvalidatedSlots
-        invalidated_slots_in_free_space =
-            Sweeper::FreeSpaceMayContainInvalidatedSlots::kNo;
-
-    const int kMaxPagesToSweep = 1;
-    int max_freed = collector->sweeper()->ParallelSweepSpace(
-        identity(), static_cast<int>(min_size_in_bytes), kMaxPagesToSweep,
-        invalidated_slots_in_free_space);
-    RefillFreeList();
-    if (static_cast<size_t>(max_freed) >= min_size_in_bytes)
-      return TryAllocationFromFreeListBackground(
-          min_size_in_bytes, max_size_in_bytes, alignment, origin);
-  }
-
-  if (heap()->ShouldExpandOldGenerationOnSlowAllocation(local_heap) &&
-      Expand()) {
-    DCHECK((CountTotalPages() > 1) ||
-           (min_size_in_bytes <= free_list_->Available()));
-    return TryAllocationFromFreeListBackground(
-        min_size_in_bytes, max_size_in_bytes, alignment, origin);
-  }
-
-  // TODO(dinfuehr): Complete sweeping here and try allocation again.
-
-  return {};
-}
-
-base::Optional<std::pair<Address, size_t>>
-PagedSpace::TryAllocationFromFreeListBackground(size_t min_size_in_bytes,
-                                                size_t max_size_in_bytes,
-                                                AllocationAlignment alignment,
-                                                AllocationOrigin origin) {
-  DCHECK_LE(min_size_in_bytes, max_size_in_bytes);
-  DCHECK_EQ(identity(), OLD_SPACE);
-
-  size_t new_node_size = 0;
-  FreeSpace new_node =
-      free_list_->Allocate(min_size_in_bytes, &new_node_size, origin);
-  if (new_node.is_null()) return {};
-  DCHECK_GE(new_node_size, min_size_in_bytes);
-
-  // The old-space-step might have finished sweeping and restarted marking.
-  // Verify that it did not turn the page of the new node into an evacuation
-  // candidate.
-  DCHECK(!MarkCompactCollector::IsOnEvacuationCandidate(new_node));
-
-  // Memory in the linear allocation area is counted as allocated.  We may free
-  // a little of this again immediately - see below.
-  Page* page = Page::FromHeapObject(new_node);
-  IncreaseAllocatedBytes(new_node_size, page);
-
-  heap()->StartIncrementalMarkingIfAllocationLimitIsReachedBackground();
-
-  size_t used_size_in_bytes = Min(new_node_size, max_size_in_bytes);
-
-  Address start = new_node.address();
-  Address end = new_node.address() + new_node_size;
-  Address limit = new_node.address() + used_size_in_bytes;
-  DCHECK_LE(limit, end);
-  DCHECK_LE(min_size_in_bytes, limit - start);
-  if (limit != end) {
-    Free(limit, end - limit, SpaceAccountingMode::kSpaceAccounted);
-  }
-
-  return std::make_pair(start, used_size_in_bytes);
-}
-
-#ifdef DEBUG
-void PagedSpace::Print() {}
-#endif
-
-#ifdef VERIFY_HEAP
-void PagedSpace::Verify(Isolate* isolate, ObjectVisitor* visitor) {
-  bool allocation_pointer_found_in_space =
-      (allocation_info_.top() == allocation_info_.limit());
-  size_t external_space_bytes[kNumTypes];
-  size_t external_page_bytes[kNumTypes];
-
-  for (int i = 0; i < kNumTypes; i++) {
-    external_space_bytes[static_cast<ExternalBackingStoreType>(i)] = 0;
-  }
-
-  for (Page* page : *this) {
-#ifdef V8_SHARED_RO_HEAP
-    if (identity() == RO_SPACE) {
-      CHECK_NULL(page->owner());
-    } else {
-      CHECK_EQ(page->owner(), this);
-    }
-#else
-    CHECK_EQ(page->owner(), this);
-#endif
-
-    for (int i = 0; i < kNumTypes; i++) {
-      external_page_bytes[static_cast<ExternalBackingStoreType>(i)] = 0;
-    }
-
-    if (page == Page::FromAllocationAreaAddress(allocation_info_.top())) {
-      allocation_pointer_found_in_space = true;
-    }
-    CHECK(page->SweepingDone());
-    PagedSpaceObjectIterator it(isolate->heap(), this, page);
-    Address end_of_previous_object = page->area_start();
-    Address top = page->area_end();
-
-    for (HeapObject object = it.Next(); !object.is_null(); object = it.Next()) {
-      CHECK(end_of_previous_object <= object.address());
-
-      // The first word should be a map, and we expect all map pointers to
-      // be in map space.
-      Map map = object.map();
-      CHECK(map.IsMap());
-      CHECK(ReadOnlyHeap::Contains(map) ||
-            isolate->heap()->map_space()->Contains(map));
-
-      // Perform space-specific object verification.
-      VerifyObject(object);
-
-      // The object itself should look OK.
-      object.ObjectVerify(isolate);
-
-      if (!FLAG_verify_heap_skip_remembered_set) {
-        isolate->heap()->VerifyRememberedSetFor(object);
-      }
-
-      // All the interior pointers should be contained in the heap.
-      int size = object.Size();
-      object.IterateBody(map, size, visitor);
-      CHECK(object.address() + size <= top);
-      end_of_previous_object = object.address() + size;
-
-      if (object.IsExternalString()) {
-        ExternalString external_string = ExternalString::cast(object);
-        size_t size = external_string.ExternalPayloadSize();
-        external_page_bytes[ExternalBackingStoreType::kExternalString] += size;
-      } else if (object.IsJSArrayBuffer()) {
-        JSArrayBuffer array_buffer = JSArrayBuffer::cast(object);
-        if (ArrayBufferTracker::IsTracked(array_buffer)) {
-          size_t size =
-              ArrayBufferTracker::Lookup(isolate->heap(), array_buffer)
-                  ->PerIsolateAccountingLength();
-          external_page_bytes[ExternalBackingStoreType::kArrayBuffer] += size;
-        }
-      }
-    }
-    for (int i = 0; i < kNumTypes; i++) {
-      ExternalBackingStoreType t = static_cast<ExternalBackingStoreType>(i);
-      CHECK_EQ(external_page_bytes[t], page->ExternalBackingStoreBytes(t));
-      external_space_bytes[t] += external_page_bytes[t];
-    }
-  }
-  for (int i = 0; i < kNumTypes; i++) {
-    if (V8_ARRAY_BUFFER_EXTENSION_BOOL &&
-        i == ExternalBackingStoreType::kArrayBuffer)
-      continue;
-    ExternalBackingStoreType t = static_cast<ExternalBackingStoreType>(i);
-    CHECK_EQ(external_space_bytes[t], ExternalBackingStoreBytes(t));
-  }
-  CHECK(allocation_pointer_found_in_space);
-
-  if (identity() == OLD_SPACE && V8_ARRAY_BUFFER_EXTENSION_BOOL) {
-    size_t bytes = heap()->array_buffer_sweeper()->old().BytesSlow();
-    CHECK_EQ(bytes,
-             ExternalBackingStoreBytes(ExternalBackingStoreType::kArrayBuffer));
-  }
-
-#ifdef DEBUG
-  VerifyCountersAfterSweeping(isolate->heap());
-#endif
-}
-
-void PagedSpace::VerifyLiveBytes() {
-  DCHECK_NE(identity(), RO_SPACE);
-  IncrementalMarking::MarkingState* marking_state =
-      heap()->incremental_marking()->marking_state();
-  for (Page* page : *this) {
-    CHECK(page->SweepingDone());
-    PagedSpaceObjectIterator it(heap(), this, page);
-    int black_size = 0;
-    for (HeapObject object = it.Next(); !object.is_null(); object = it.Next()) {
-      // All the interior pointers should be contained in the heap.
-      if (marking_state->IsBlack(object)) {
-        black_size += object.Size();
-      }
-    }
-    CHECK_LE(black_size, marking_state->live_bytes(page));
-  }
-}
-#endif  // VERIFY_HEAP
-
-#ifdef DEBUG
-void PagedSpace::VerifyCountersAfterSweeping(Heap* heap) {
-  size_t total_capacity = 0;
-  size_t total_allocated = 0;
-  for (Page* page : *this) {
-    DCHECK(page->SweepingDone());
-    total_capacity += page->area_size();
-    PagedSpaceObjectIterator it(heap, this, page);
-    size_t real_allocated = 0;
-    for (HeapObject object = it.Next(); !object.is_null(); object = it.Next()) {
-      if (!object.IsFreeSpaceOrFiller()) {
-        real_allocated += object.Size();
-      }
-    }
-    total_allocated += page->allocated_bytes();
-    // The real size can be smaller than the accounted size if array trimming,
-    // object slack tracking happened after sweeping.
-    DCHECK_LE(real_allocated, accounting_stats_.AllocatedOnPage(page));
-    DCHECK_EQ(page->allocated_bytes(), accounting_stats_.AllocatedOnPage(page));
-  }
-  DCHECK_EQ(total_capacity, accounting_stats_.Capacity());
-  DCHECK_EQ(total_allocated, accounting_stats_.Size());
-}
-
-void PagedSpace::VerifyCountersBeforeConcurrentSweeping() {
-  // We need to refine the counters on pages that are already swept and have
-  // not been moved over to the actual space. Otherwise, the AccountingStats
-  // are just an over approximation.
-  RefillFreeList();
-
-  size_t total_capacity = 0;
-  size_t total_allocated = 0;
-  auto marking_state =
-      heap()->incremental_marking()->non_atomic_marking_state();
-  for (Page* page : *this) {
-    size_t page_allocated =
-        page->SweepingDone()
-            ? page->allocated_bytes()
-            : static_cast<size_t>(marking_state->live_bytes(page));
-    total_capacity += page->area_size();
-    total_allocated += page_allocated;
-    DCHECK_EQ(page_allocated, accounting_stats_.AllocatedOnPage(page));
-  }
-  DCHECK_EQ(total_capacity, accounting_stats_.Capacity());
-  DCHECK_EQ(total_allocated, accounting_stats_.Size());
-}
-#endif
-
-// -----------------------------------------------------------------------------
-// NewSpace implementation
-
-NewSpace::NewSpace(Heap* heap, v8::PageAllocator* page_allocator,
-                   size_t initial_semispace_capacity,
-                   size_t max_semispace_capacity)
-    : SpaceWithLinearArea(heap, NEW_SPACE, new NoFreeList()),
-      to_space_(heap, kToSpace),
-      from_space_(heap, kFromSpace) {
-  DCHECK(initial_semispace_capacity <= max_semispace_capacity);
-
-  to_space_.SetUp(initial_semispace_capacity, max_semispace_capacity);
-  from_space_.SetUp(initial_semispace_capacity, max_semispace_capacity);
-  if (!to_space_.Commit()) {
-    V8::FatalProcessOutOfMemory(heap->isolate(), "New space setup");
-  }
-  DCHECK(!from_space_.is_committed());  // No need to use memory yet.
-  ResetLinearAllocationArea();
-}
-
-void NewSpace::TearDown() {
-  allocation_info_.Reset(kNullAddress, kNullAddress);
-
-  to_space_.TearDown();
-  from_space_.TearDown();
-}
-
-void NewSpace::Flip() { SemiSpace::Swap(&from_space_, &to_space_); }
-
-
-void NewSpace::Grow() {
-  // Double the semispace size but only up to maximum capacity.
-  DCHECK(TotalCapacity() < MaximumCapacity());
-  size_t new_capacity =
-      Min(MaximumCapacity(),
-          static_cast<size_t>(FLAG_semi_space_growth_factor) * TotalCapacity());
-  if (to_space_.GrowTo(new_capacity)) {
-    // Only grow from space if we managed to grow to-space.
-    if (!from_space_.GrowTo(new_capacity)) {
-      // If we managed to grow to-space but couldn't grow from-space,
-      // attempt to shrink to-space.
-      if (!to_space_.ShrinkTo(from_space_.current_capacity())) {
-        // We are in an inconsistent state because we could not
-        // commit/uncommit memory from new space.
-        FATAL("inconsistent state");
-      }
-    }
-  }
-  DCHECK_SEMISPACE_ALLOCATION_INFO(allocation_info_, to_space_);
-}
-
-
-void NewSpace::Shrink() {
-  size_t new_capacity = Max(InitialTotalCapacity(), 2 * Size());
-  size_t rounded_new_capacity = ::RoundUp(new_capacity, Page::kPageSize);
-  if (rounded_new_capacity < TotalCapacity() &&
-      to_space_.ShrinkTo(rounded_new_capacity)) {
-    // Only shrink from-space if we managed to shrink to-space.
-    from_space_.Reset();
-    if (!from_space_.ShrinkTo(rounded_new_capacity)) {
-      // If we managed to shrink to-space but couldn't shrink from
-      // space, attempt to grow to-space again.
-      if (!to_space_.GrowTo(from_space_.current_capacity())) {
-        // We are in an inconsistent state because we could not
-        // commit/uncommit memory from new space.
-        FATAL("inconsistent state");
-      }
-    }
-  }
-  DCHECK_SEMISPACE_ALLOCATION_INFO(allocation_info_, to_space_);
-}
-
-bool NewSpace::Rebalance() {
-  // Order here is important to make use of the page pool.
-  return to_space_.EnsureCurrentCapacity() &&
-         from_space_.EnsureCurrentCapacity();
-}
-
-bool SemiSpace::EnsureCurrentCapacity() {
-  if (is_committed()) {
-    const int expected_pages =
-        static_cast<int>(current_capacity_ / Page::kPageSize);
-    MemoryChunk* current_page = first_page();
-    int actual_pages = 0;
-
-    // First iterate through the pages list until expected pages if so many
-    // pages exist.
-    while (current_page != nullptr && actual_pages < expected_pages) {
-      actual_pages++;
-      current_page = current_page->list_node().next();
-    }
-
-    // Free all overallocated pages which are behind current_page.
-    while (current_page) {
-      MemoryChunk* next_current = current_page->list_node().next();
-      memory_chunk_list_.Remove(current_page);
-      // Clear new space flags to avoid this page being treated as a new
-      // space page that is potentially being swept.
-      current_page->SetFlags(0, Page::kIsInYoungGenerationMask);
-      heap()->memory_allocator()->Free<MemoryAllocator::kPooledAndQueue>(
-          current_page);
-      current_page = next_current;
-    }
-
-    // Add more pages if we have less than expected_pages.
-    IncrementalMarking::NonAtomicMarkingState* marking_state =
-        heap()->incremental_marking()->non_atomic_marking_state();
-    while (actual_pages < expected_pages) {
-      actual_pages++;
-      current_page =
-          heap()->memory_allocator()->AllocatePage<MemoryAllocator::kPooled>(
-              MemoryChunkLayout::AllocatableMemoryInDataPage(), this,
-              NOT_EXECUTABLE);
-      if (current_page == nullptr) return false;
-      DCHECK_NOT_NULL(current_page);
-      memory_chunk_list_.PushBack(current_page);
-      marking_state->ClearLiveness(current_page);
-      current_page->SetFlags(first_page()->GetFlags(),
-                             static_cast<uintptr_t>(Page::kCopyAllFlags));
-      heap()->CreateFillerObjectAt(current_page->area_start(),
-                                   static_cast<int>(current_page->area_size()),
-                                   ClearRecordedSlots::kNo);
-    }
-  }
-  return true;
-}
-
 LinearAllocationArea LocalAllocationBuffer::CloseAndMakeIterable() {
   if (IsValid()) {
     MakeIterable();
@@ -2400,110 +397,6 @@ LocalAllocationBuffer& LocalAllocationBuffer::operator=(
   other.allocation_info_.Reset(kNullAddress, kNullAddress);
   return *this;
 }
-
-void NewSpace::UpdateLinearAllocationArea() {
-  // Make sure there is no unaccounted allocations.
-  DCHECK(!AllocationObserversActive() || top_on_previous_step_ == top());
-
-  Address new_top = to_space_.page_low();
-  MemoryChunk::UpdateHighWaterMark(allocation_info_.top());
-  allocation_info_.Reset(new_top, to_space_.page_high());
-  // The order of the following two stores is important.
-  // See the corresponding loads in ConcurrentMarking::Run.
-  original_limit_.store(limit(), std::memory_order_relaxed);
-  original_top_.store(top(), std::memory_order_release);
-  StartNextInlineAllocationStep();
-  DCHECK_SEMISPACE_ALLOCATION_INFO(allocation_info_, to_space_);
-}
-
-void NewSpace::ResetLinearAllocationArea() {
-  // Do a step to account for memory allocated so far before resetting.
-  InlineAllocationStep(top(), top(), kNullAddress, 0);
-  to_space_.Reset();
-  UpdateLinearAllocationArea();
-  // Clear all mark-bits in the to-space.
-  IncrementalMarking::NonAtomicMarkingState* marking_state =
-      heap()->incremental_marking()->non_atomic_marking_state();
-  for (Page* p : to_space_) {
-    marking_state->ClearLiveness(p);
-    // Concurrent marking may have local live bytes for this page.
-    heap()->concurrent_marking()->ClearMemoryChunkData(p);
-  }
-}
-
-void NewSpace::UpdateInlineAllocationLimit(size_t min_size) {
-  Address new_limit = ComputeLimit(top(), to_space_.page_high(), min_size);
-  allocation_info_.set_limit(new_limit);
-  DCHECK_SEMISPACE_ALLOCATION_INFO(allocation_info_, to_space_);
-}
-
-void PagedSpace::UpdateInlineAllocationLimit(size_t min_size) {
-  Address new_limit = ComputeLimit(top(), limit(), min_size);
-  DCHECK_LE(new_limit, limit());
-  DecreaseLimit(new_limit);
-}
-
-bool NewSpace::AddFreshPage() {
-  Address top = allocation_info_.top();
-  DCHECK(!OldSpace::IsAtPageStart(top));
-
-  // Do a step to account for memory allocated on previous page.
-  InlineAllocationStep(top, top, kNullAddress, 0);
-
-  if (!to_space_.AdvancePage()) {
-    // No more pages left to advance.
-    return false;
-  }
-
-  // Clear remainder of current page.
-  Address limit = Page::FromAllocationAreaAddress(top)->area_end();
-  int remaining_in_page = static_cast<int>(limit - top);
-  heap()->CreateFillerObjectAt(top, remaining_in_page, ClearRecordedSlots::kNo);
-  UpdateLinearAllocationArea();
-
-  return true;
-}
-
-
-bool NewSpace::AddFreshPageSynchronized() {
-  base::MutexGuard guard(&mutex_);
-  return AddFreshPage();
-}
-
-
-bool NewSpace::EnsureAllocation(int size_in_bytes,
-                                AllocationAlignment alignment) {
-  Address old_top = allocation_info_.top();
-  Address high = to_space_.page_high();
-  int filler_size = Heap::GetFillToAlign(old_top, alignment);
-  int aligned_size_in_bytes = size_in_bytes + filler_size;
-
-  if (old_top + aligned_size_in_bytes > high) {
-    // Not enough room in the page, try to allocate a new one.
-    if (!AddFreshPage()) {
-      return false;
-    }
-
-    old_top = allocation_info_.top();
-    high = to_space_.page_high();
-    filler_size = Heap::GetFillToAlign(old_top, alignment);
-  }
-
-  DCHECK(old_top + aligned_size_in_bytes <= high);
-
-  if (allocation_info_.limit() < high) {
-    // Either the limit has been lowered because linear allocation was disabled
-    // or because incremental marking wants to get a chance to do a step,
-    // or because idle scavenge job wants to get a chance to post a task.
-    // Set the new limit accordingly.
-    Address new_top = old_top + aligned_size_in_bytes;
-    Address soon_object = old_top + filler_size;
-    InlineAllocationStep(new_top, new_top, soon_object, size_in_bytes);
-    UpdateInlineAllocationLimit(aligned_size_in_bytes);
-  }
-  return true;
-}
-
 void SpaceWithLinearArea::StartNextInlineAllocationStep() {
   if (heap()->allocation_step_in_progress()) {
     // If we are mid-way through an existing step, don't start a new one.
@@ -2570,1043 +463,6 @@ void SpaceWithLinearArea::InlineAllocationStep(Address top,
   }
 }
 
-std::unique_ptr<ObjectIterator> NewSpace::GetObjectIterator(Heap* heap) {
-  return std::unique_ptr<ObjectIterator>(new SemiSpaceObjectIterator(this));
-}
-
-#ifdef VERIFY_HEAP
-// We do not use the SemiSpaceObjectIterator because verification doesn't assume
-// that it works (it depends on the invariants we are checking).
-void NewSpace::Verify(Isolate* isolate) {
-  // The allocation pointer should be in the space or at the very end.
-  DCHECK_SEMISPACE_ALLOCATION_INFO(allocation_info_, to_space_);
-
-  // There should be objects packed in from the low address up to the
-  // allocation pointer.
-  Address current = to_space_.first_page()->area_start();
-  CHECK_EQ(current, to_space_.space_start());
-
-  size_t external_space_bytes[kNumTypes];
-  for (int i = 0; i < kNumTypes; i++) {
-    external_space_bytes[static_cast<ExternalBackingStoreType>(i)] = 0;
-  }
-
-  while (current != top()) {
-    if (!Page::IsAlignedToPageSize(current)) {
-      // The allocation pointer should not be in the middle of an object.
-      CHECK(!Page::FromAllocationAreaAddress(current)->ContainsLimit(top()) ||
-            current < top());
-
-      HeapObject object = HeapObject::FromAddress(current);
-
-      // The first word should be a map, and we expect all map pointers to
-      // be in map space or read-only space.
-      Map map = object.map();
-      CHECK(map.IsMap());
-      CHECK(ReadOnlyHeap::Contains(map) || heap()->map_space()->Contains(map));
-
-      // The object should not be code or a map.
-      CHECK(!object.IsMap());
-      CHECK(!object.IsAbstractCode());
-
-      // The object itself should look OK.
-      object.ObjectVerify(isolate);
-
-      // All the interior pointers should be contained in the heap.
-      VerifyPointersVisitor visitor(heap());
-      int size = object.Size();
-      object.IterateBody(map, size, &visitor);
-
-      if (object.IsExternalString()) {
-        ExternalString external_string = ExternalString::cast(object);
-        size_t size = external_string.ExternalPayloadSize();
-        external_space_bytes[ExternalBackingStoreType::kExternalString] += size;
-      } else if (object.IsJSArrayBuffer()) {
-        JSArrayBuffer array_buffer = JSArrayBuffer::cast(object);
-        if (ArrayBufferTracker::IsTracked(array_buffer)) {
-          size_t size = ArrayBufferTracker::Lookup(heap(), array_buffer)
-                            ->PerIsolateAccountingLength();
-          external_space_bytes[ExternalBackingStoreType::kArrayBuffer] += size;
-        }
-      }
-
-      current += size;
-    } else {
-      // At end of page, switch to next page.
-      Page* page = Page::FromAllocationAreaAddress(current)->next_page();
-      current = page->area_start();
-    }
-  }
-
-  for (int i = 0; i < kNumTypes; i++) {
-    if (V8_ARRAY_BUFFER_EXTENSION_BOOL &&
-        i == ExternalBackingStoreType::kArrayBuffer)
-      continue;
-    ExternalBackingStoreType t = static_cast<ExternalBackingStoreType>(i);
-    CHECK_EQ(external_space_bytes[t], ExternalBackingStoreBytes(t));
-  }
-
-  if (V8_ARRAY_BUFFER_EXTENSION_BOOL) {
-    size_t bytes = heap()->array_buffer_sweeper()->young().BytesSlow();
-    CHECK_EQ(bytes,
-             ExternalBackingStoreBytes(ExternalBackingStoreType::kArrayBuffer));
-  }
-
-  // Check semi-spaces.
-  CHECK_EQ(from_space_.id(), kFromSpace);
-  CHECK_EQ(to_space_.id(), kToSpace);
-  from_space_.Verify();
-  to_space_.Verify();
-}
-#endif
-
-// -----------------------------------------------------------------------------
-// SemiSpace implementation
-
-void SemiSpace::SetUp(size_t initial_capacity, size_t maximum_capacity) {
-  DCHECK_GE(maximum_capacity, static_cast<size_t>(Page::kPageSize));
-  minimum_capacity_ = RoundDown(initial_capacity, Page::kPageSize);
-  current_capacity_ = minimum_capacity_;
-  maximum_capacity_ = RoundDown(maximum_capacity, Page::kPageSize);
-  committed_ = false;
-}
-
-
-void SemiSpace::TearDown() {
-  // Properly uncommit memory to keep the allocator counters in sync.
-  if (is_committed()) {
-    Uncommit();
-  }
-  current_capacity_ = maximum_capacity_ = 0;
-}
-
-
-bool SemiSpace::Commit() {
-  DCHECK(!is_committed());
-  const int num_pages = static_cast<int>(current_capacity_ / Page::kPageSize);
-  for (int pages_added = 0; pages_added < num_pages; pages_added++) {
-    // Pages in the new spaces can be moved to the old space by the full
-    // collector. Therefore, they must be initialized with the same FreeList as
-    // old pages.
-    Page* new_page =
-        heap()->memory_allocator()->AllocatePage<MemoryAllocator::kPooled>(
-            MemoryChunkLayout::AllocatableMemoryInDataPage(), this,
-            NOT_EXECUTABLE);
-    if (new_page == nullptr) {
-      if (pages_added) RewindPages(pages_added);
-      return false;
-    }
-    memory_chunk_list_.PushBack(new_page);
-  }
-  Reset();
-  AccountCommitted(current_capacity_);
-  if (age_mark_ == kNullAddress) {
-    age_mark_ = first_page()->area_start();
-  }
-  committed_ = true;
-  return true;
-}
-
-
-bool SemiSpace::Uncommit() {
-  DCHECK(is_committed());
-  while (!memory_chunk_list_.Empty()) {
-    MemoryChunk* chunk = memory_chunk_list_.front();
-    memory_chunk_list_.Remove(chunk);
-    heap()->memory_allocator()->Free<MemoryAllocator::kPooledAndQueue>(chunk);
-  }
-  current_page_ = nullptr;
-  AccountUncommitted(current_capacity_);
-  committed_ = false;
-  heap()->memory_allocator()->unmapper()->FreeQueuedChunks();
-  return true;
-}
-
-
-size_t SemiSpace::CommittedPhysicalMemory() {
-  if (!is_committed()) return 0;
-  size_t size = 0;
-  for (Page* p : *this) {
-    size += p->CommittedPhysicalMemory();
-  }
-  return size;
-}
-
-bool SemiSpace::GrowTo(size_t new_capacity) {
-  if (!is_committed()) {
-    if (!Commit()) return false;
-  }
-  DCHECK_EQ(new_capacity & kPageAlignmentMask, 0u);
-  DCHECK_LE(new_capacity, maximum_capacity_);
-  DCHECK_GT(new_capacity, current_capacity_);
-  const size_t delta = new_capacity - current_capacity_;
-  DCHECK(IsAligned(delta, AllocatePageSize()));
-  const int delta_pages = static_cast<int>(delta / Page::kPageSize);
-  DCHECK(last_page());
-  IncrementalMarking::NonAtomicMarkingState* marking_state =
-      heap()->incremental_marking()->non_atomic_marking_state();
-  for (int pages_added = 0; pages_added < delta_pages; pages_added++) {
-    Page* new_page =
-        heap()->memory_allocator()->AllocatePage<MemoryAllocator::kPooled>(
-            MemoryChunkLayout::AllocatableMemoryInDataPage(), this,
-            NOT_EXECUTABLE);
-    if (new_page == nullptr) {
-      if (pages_added) RewindPages(pages_added);
-      return false;
-    }
-    memory_chunk_list_.PushBack(new_page);
-    marking_state->ClearLiveness(new_page);
-    // Duplicate the flags that was set on the old page.
-    new_page->SetFlags(last_page()->GetFlags(), Page::kCopyOnFlipFlagsMask);
-  }
-  AccountCommitted(delta);
-  current_capacity_ = new_capacity;
-  return true;
-}
-
-void SemiSpace::RewindPages(int num_pages) {
-  DCHECK_GT(num_pages, 0);
-  DCHECK(last_page());
-  while (num_pages > 0) {
-    MemoryChunk* last = last_page();
-    memory_chunk_list_.Remove(last);
-    heap()->memory_allocator()->Free<MemoryAllocator::kPooledAndQueue>(last);
-    num_pages--;
-  }
-}
-
-bool SemiSpace::ShrinkTo(size_t new_capacity) {
-  DCHECK_EQ(new_capacity & kPageAlignmentMask, 0u);
-  DCHECK_GE(new_capacity, minimum_capacity_);
-  DCHECK_LT(new_capacity, current_capacity_);
-  if (is_committed()) {
-    const size_t delta = current_capacity_ - new_capacity;
-    DCHECK(IsAligned(delta, Page::kPageSize));
-    int delta_pages = static_cast<int>(delta / Page::kPageSize);
-    RewindPages(delta_pages);
-    AccountUncommitted(delta);
-    heap()->memory_allocator()->unmapper()->FreeQueuedChunks();
-  }
-  current_capacity_ = new_capacity;
-  return true;
-}
-
-void SemiSpace::FixPagesFlags(intptr_t flags, intptr_t mask) {
-  for (Page* page : *this) {
-    page->set_owner(this);
-    page->SetFlags(flags, mask);
-    if (id_ == kToSpace) {
-      page->ClearFlag(MemoryChunk::FROM_PAGE);
-      page->SetFlag(MemoryChunk::TO_PAGE);
-      page->ClearFlag(MemoryChunk::NEW_SPACE_BELOW_AGE_MARK);
-      heap()->incremental_marking()->non_atomic_marking_state()->SetLiveBytes(
-          page, 0);
-    } else {
-      page->SetFlag(MemoryChunk::FROM_PAGE);
-      page->ClearFlag(MemoryChunk::TO_PAGE);
-    }
-    DCHECK(page->InYoungGeneration());
-  }
-}
-
-
-void SemiSpace::Reset() {
-  DCHECK(first_page());
-  DCHECK(last_page());
-  current_page_ = first_page();
-  pages_used_ = 0;
-}
-
-void SemiSpace::RemovePage(Page* page) {
-  if (current_page_ == page) {
-    if (page->prev_page()) {
-      current_page_ = page->prev_page();
-    }
-  }
-  memory_chunk_list_.Remove(page);
-  for (size_t i = 0; i < ExternalBackingStoreType::kNumTypes; i++) {
-    ExternalBackingStoreType t = static_cast<ExternalBackingStoreType>(i);
-    DecrementExternalBackingStoreBytes(t, page->ExternalBackingStoreBytes(t));
-  }
-}
-
-void SemiSpace::PrependPage(Page* page) {
-  page->SetFlags(current_page()->GetFlags(),
-                 static_cast<uintptr_t>(Page::kCopyAllFlags));
-  page->set_owner(this);
-  memory_chunk_list_.PushFront(page);
-  pages_used_++;
-  for (size_t i = 0; i < ExternalBackingStoreType::kNumTypes; i++) {
-    ExternalBackingStoreType t = static_cast<ExternalBackingStoreType>(i);
-    IncrementExternalBackingStoreBytes(t, page->ExternalBackingStoreBytes(t));
-  }
-}
-
-void SemiSpace::Swap(SemiSpace* from, SemiSpace* to) {
-  // We won't be swapping semispaces without data in them.
-  DCHECK(from->first_page());
-  DCHECK(to->first_page());
-
-  intptr_t saved_to_space_flags = to->current_page()->GetFlags();
-
-  // We swap all properties but id_.
-  std::swap(from->current_capacity_, to->current_capacity_);
-  std::swap(from->maximum_capacity_, to->maximum_capacity_);
-  std::swap(from->minimum_capacity_, to->minimum_capacity_);
-  std::swap(from->age_mark_, to->age_mark_);
-  std::swap(from->committed_, to->committed_);
-  std::swap(from->memory_chunk_list_, to->memory_chunk_list_);
-  std::swap(from->current_page_, to->current_page_);
-  std::swap(from->external_backing_store_bytes_,
-            to->external_backing_store_bytes_);
-
-  to->FixPagesFlags(saved_to_space_flags, Page::kCopyOnFlipFlagsMask);
-  from->FixPagesFlags(0, 0);
-}
-
-void SemiSpace::set_age_mark(Address mark) {
-  DCHECK_EQ(Page::FromAllocationAreaAddress(mark)->owner(), this);
-  age_mark_ = mark;
-  // Mark all pages up to the one containing mark.
-  for (Page* p : PageRange(space_start(), mark)) {
-    p->SetFlag(MemoryChunk::NEW_SPACE_BELOW_AGE_MARK);
-  }
-}
-
-std::unique_ptr<ObjectIterator> SemiSpace::GetObjectIterator(Heap* heap) {
-  // Use the NewSpace::NewObjectIterator to iterate the ToSpace.
-  UNREACHABLE();
-}
-
-#ifdef DEBUG
-void SemiSpace::Print() {}
-#endif
-
-#ifdef VERIFY_HEAP
-void SemiSpace::Verify() {
-  bool is_from_space = (id_ == kFromSpace);
-  size_t external_backing_store_bytes[kNumTypes];
-
-  for (int i = 0; i < kNumTypes; i++) {
-    external_backing_store_bytes[static_cast<ExternalBackingStoreType>(i)] = 0;
-  }
-
-  for (Page* page : *this) {
-    CHECK_EQ(page->owner(), this);
-    CHECK(page->InNewSpace());
-    CHECK(page->IsFlagSet(is_from_space ? MemoryChunk::FROM_PAGE
-                                        : MemoryChunk::TO_PAGE));
-    CHECK(!page->IsFlagSet(is_from_space ? MemoryChunk::TO_PAGE
-                                         : MemoryChunk::FROM_PAGE));
-    CHECK(page->IsFlagSet(MemoryChunk::POINTERS_TO_HERE_ARE_INTERESTING));
-    if (!is_from_space) {
-      // The pointers-from-here-are-interesting flag isn't updated dynamically
-      // on from-space pages, so it might be out of sync with the marking state.
-      if (page->heap()->incremental_marking()->IsMarking()) {
-        CHECK(page->IsFlagSet(MemoryChunk::POINTERS_FROM_HERE_ARE_INTERESTING));
-      } else {
-        CHECK(
-            !page->IsFlagSet(MemoryChunk::POINTERS_FROM_HERE_ARE_INTERESTING));
-      }
-    }
-    for (int i = 0; i < kNumTypes; i++) {
-      ExternalBackingStoreType t = static_cast<ExternalBackingStoreType>(i);
-      external_backing_store_bytes[t] += page->ExternalBackingStoreBytes(t);
-    }
-
-    CHECK_IMPLIES(page->list_node().prev(),
-                  page->list_node().prev()->list_node().next() == page);
-  }
-  for (int i = 0; i < kNumTypes; i++) {
-    ExternalBackingStoreType t = static_cast<ExternalBackingStoreType>(i);
-    CHECK_EQ(external_backing_store_bytes[t], ExternalBackingStoreBytes(t));
-  }
-}
-#endif
-
-#ifdef DEBUG
-void SemiSpace::AssertValidRange(Address start, Address end) {
-  // Addresses belong to same semi-space
-  Page* page = Page::FromAllocationAreaAddress(start);
-  Page* end_page = Page::FromAllocationAreaAddress(end);
-  SemiSpace* space = reinterpret_cast<SemiSpace*>(page->owner());
-  DCHECK_EQ(space, end_page->owner());
-  // Start address is before end address, either on same page,
-  // or end address is on a later page in the linked list of
-  // semi-space pages.
-  if (page == end_page) {
-    DCHECK_LE(start, end);
-  } else {
-    while (page != end_page) {
-      page = page->next_page();
-    }
-    DCHECK(page);
-  }
-}
-#endif
-
-// -----------------------------------------------------------------------------
-// SemiSpaceObjectIterator implementation.
-
-SemiSpaceObjectIterator::SemiSpaceObjectIterator(NewSpace* space) {
-  Initialize(space->first_allocatable_address(), space->top());
-}
-
-void SemiSpaceObjectIterator::Initialize(Address start, Address end) {
-  SemiSpace::AssertValidRange(start, end);
-  current_ = start;
-  limit_ = end;
-}
-
-size_t NewSpace::CommittedPhysicalMemory() {
-  if (!base::OS::HasLazyCommits()) return CommittedMemory();
-  MemoryChunk::UpdateHighWaterMark(allocation_info_.top());
-  size_t size = to_space_.CommittedPhysicalMemory();
-  if (from_space_.is_committed()) {
-    size += from_space_.CommittedPhysicalMemory();
-  }
-  return size;
-}
-
-
-// -----------------------------------------------------------------------------
-// Free lists for old object spaces implementation
-
-void FreeListCategory::Reset(FreeList* owner) {
-  if (is_linked(owner) && !top().is_null()) {
-    owner->DecreaseAvailableBytes(available_);
-  }
-  set_top(FreeSpace());
-  set_prev(nullptr);
-  set_next(nullptr);
-  available_ = 0;
-}
-
-FreeSpace FreeListCategory::PickNodeFromList(size_t minimum_size,
-                                             size_t* node_size) {
-  FreeSpace node = top();
-  DCHECK(!node.is_null());
-  DCHECK(Page::FromHeapObject(node)->CanAllocate());
-  if (static_cast<size_t>(node.Size()) < minimum_size) {
-    *node_size = 0;
-    return FreeSpace();
-  }
-  set_top(node.next());
-  *node_size = node.Size();
-  UpdateCountersAfterAllocation(*node_size);
-  return node;
-}
-
-FreeSpace FreeListCategory::SearchForNodeInList(size_t minimum_size,
-                                                size_t* node_size) {
-  FreeSpace prev_non_evac_node;
-  for (FreeSpace cur_node = top(); !cur_node.is_null();
-       cur_node = cur_node.next()) {
-    DCHECK(Page::FromHeapObject(cur_node)->CanAllocate());
-    size_t size = cur_node.size();
-    if (size >= minimum_size) {
-      DCHECK_GE(available_, size);
-      UpdateCountersAfterAllocation(size);
-      if (cur_node == top()) {
-        set_top(cur_node.next());
-      }
-      if (!prev_non_evac_node.is_null()) {
-        MemoryChunk* chunk = MemoryChunk::FromHeapObject(prev_non_evac_node);
-        if (chunk->owner_identity() == CODE_SPACE) {
-          chunk->heap()->UnprotectAndRegisterMemoryChunk(chunk);
-        }
-        prev_non_evac_node.set_next(cur_node.next());
-      }
-      *node_size = size;
-      return cur_node;
-    }
-
-    prev_non_evac_node = cur_node;
-  }
-  return FreeSpace();
-}
-
-void FreeListCategory::Free(Address start, size_t size_in_bytes, FreeMode mode,
-                            FreeList* owner) {
-  FreeSpace free_space = FreeSpace::cast(HeapObject::FromAddress(start));
-  free_space.set_next(top());
-  set_top(free_space);
-  available_ += size_in_bytes;
-  if (mode == kLinkCategory) {
-    if (is_linked(owner)) {
-      owner->IncreaseAvailableBytes(size_in_bytes);
-    } else {
-      owner->AddCategory(this);
-    }
-  }
-}
-
-void FreeListCategory::RepairFreeList(Heap* heap) {
-  Map free_space_map = ReadOnlyRoots(heap).free_space_map();
-  FreeSpace n = top();
-  while (!n.is_null()) {
-    ObjectSlot map_slot = n.map_slot();
-    if (map_slot.contains_value(kNullAddress)) {
-      map_slot.store(free_space_map);
-    } else {
-      DCHECK(map_slot.contains_value(free_space_map.ptr()));
-    }
-    n = n.next();
-  }
-}
-
-void FreeListCategory::Relink(FreeList* owner) {
-  DCHECK(!is_linked(owner));
-  owner->AddCategory(this);
-}
-
-// ------------------------------------------------
-// Generic FreeList methods (alloc/free related)
-
-FreeList* FreeList::CreateFreeList() {
-  switch (FLAG_gc_freelist_strategy) {
-    case 0:
-      return new FreeListLegacy();
-    case 1:
-      return new FreeListFastAlloc();
-    case 2:
-      return new FreeListMany();
-    case 3:
-      return new FreeListManyCached();
-    case 4:
-      return new FreeListManyCachedFastPath();
-    case 5:
-      return new FreeListManyCachedOrigin();
-    default:
-      FATAL("Invalid FreeList strategy");
-  }
-}
-
-FreeSpace FreeList::TryFindNodeIn(FreeListCategoryType type,
-                                  size_t minimum_size, size_t* node_size) {
-  FreeListCategory* category = categories_[type];
-  if (category == nullptr) return FreeSpace();
-  FreeSpace node = category->PickNodeFromList(minimum_size, node_size);
-  if (!node.is_null()) {
-    DecreaseAvailableBytes(*node_size);
-    DCHECK(IsVeryLong() || Available() == SumFreeLists());
-  }
-  if (category->is_empty()) {
-    RemoveCategory(category);
-  }
-  return node;
-}
-
-FreeSpace FreeList::SearchForNodeInList(FreeListCategoryType type,
-                                        size_t minimum_size,
-                                        size_t* node_size) {
-  FreeListCategoryIterator it(this, type);
-  FreeSpace node;
-  while (it.HasNext()) {
-    FreeListCategory* current = it.Next();
-    node = current->SearchForNodeInList(minimum_size, node_size);
-    if (!node.is_null()) {
-      DecreaseAvailableBytes(*node_size);
-      DCHECK(IsVeryLong() || Available() == SumFreeLists());
-      if (current->is_empty()) {
-        RemoveCategory(current);
-      }
-      return node;
-    }
-  }
-  return node;
-}
-
-size_t FreeList::Free(Address start, size_t size_in_bytes, FreeMode mode) {
-  Page* page = Page::FromAddress(start);
-  page->DecreaseAllocatedBytes(size_in_bytes);
-
-  // Blocks have to be a minimum size to hold free list items.
-  if (size_in_bytes < min_block_size_) {
-    page->add_wasted_memory(size_in_bytes);
-    wasted_bytes_ += size_in_bytes;
-    return size_in_bytes;
-  }
-
-  // Insert other blocks at the head of a free list of the appropriate
-  // magnitude.
-  FreeListCategoryType type = SelectFreeListCategoryType(size_in_bytes);
-  page->free_list_category(type)->Free(start, size_in_bytes, mode, this);
-  DCHECK_EQ(page->AvailableInFreeList(),
-            page->AvailableInFreeListFromAllocatedBytes());
-  return 0;
-}
-
-// ------------------------------------------------
-// FreeListLegacy implementation
-
-FreeListLegacy::FreeListLegacy() {
-  // Initializing base (FreeList) fields
-  number_of_categories_ = kHuge + 1;
-  last_category_ = kHuge;
-  min_block_size_ = kMinBlockSize;
-  categories_ = new FreeListCategory*[number_of_categories_]();
-
-  Reset();
-}
-
-FreeListLegacy::~FreeListLegacy() { delete[] categories_; }
-
-FreeSpace FreeListLegacy::Allocate(size_t size_in_bytes, size_t* node_size,
-                                   AllocationOrigin origin) {
-  DCHECK_GE(kMaxBlockSize, size_in_bytes);
-  FreeSpace node;
-  // First try the allocation fast path: try to allocate the minimum element
-  // size of a free list category. This operation is constant time.
-  FreeListCategoryType type =
-      SelectFastAllocationFreeListCategoryType(size_in_bytes);
-  for (int i = type; i < kHuge && node.is_null(); i++) {
-    node = TryFindNodeIn(static_cast<FreeListCategoryType>(i), size_in_bytes,
-                         node_size);
-  }
-
-  if (node.is_null()) {
-    // Next search the huge list for free list nodes. This takes linear time in
-    // the number of huge elements.
-    node = SearchForNodeInList(kHuge, size_in_bytes, node_size);
-  }
-
-  if (node.is_null() && type != kHuge) {
-    // We didn't find anything in the huge list.
-    type = SelectFreeListCategoryType(size_in_bytes);
-
-    if (type == kTiniest) {
-      // For this tiniest object, the tiny list hasn't been searched yet.
-      // Now searching the tiny list.
-      node = TryFindNodeIn(kTiny, size_in_bytes, node_size);
-    }
-
-    if (node.is_null()) {
-      // Now search the best fitting free list for a node that has at least the
-      // requested size.
-      node = TryFindNodeIn(type, size_in_bytes, node_size);
-    }
-  }
-
-  if (!node.is_null()) {
-    Page::FromHeapObject(node)->IncreaseAllocatedBytes(*node_size);
-  }
-
-  DCHECK(IsVeryLong() || Available() == SumFreeLists());
-  return node;
-}
-
-// ------------------------------------------------
-// FreeListFastAlloc implementation
-
-FreeListFastAlloc::FreeListFastAlloc() {
-  // Initializing base (FreeList) fields
-  number_of_categories_ = kHuge + 1;
-  last_category_ = kHuge;
-  min_block_size_ = kMinBlockSize;
-  categories_ = new FreeListCategory*[number_of_categories_]();
-
-  Reset();
-}
-
-FreeListFastAlloc::~FreeListFastAlloc() { delete[] categories_; }
-
-FreeSpace FreeListFastAlloc::Allocate(size_t size_in_bytes, size_t* node_size,
-                                      AllocationOrigin origin) {
-  DCHECK_GE(kMaxBlockSize, size_in_bytes);
-  FreeSpace node;
-  // Try to allocate the biggest element possible (to make the most of later
-  // bump-pointer allocations).
-  FreeListCategoryType type = SelectFreeListCategoryType(size_in_bytes);
-  for (int i = kHuge; i >= type && node.is_null(); i--) {
-    node = TryFindNodeIn(static_cast<FreeListCategoryType>(i), size_in_bytes,
-                         node_size);
-  }
-
-  if (!node.is_null()) {
-    Page::FromHeapObject(node)->IncreaseAllocatedBytes(*node_size);
-  }
-
-  DCHECK(IsVeryLong() || Available() == SumFreeLists());
-  return node;
-}
-
-// ------------------------------------------------
-// FreeListMany implementation
-
-constexpr unsigned int FreeListMany::categories_min[kNumberOfCategories];
-
-FreeListMany::FreeListMany() {
-  // Initializing base (FreeList) fields
-  number_of_categories_ = kNumberOfCategories;
-  last_category_ = number_of_categories_ - 1;
-  min_block_size_ = kMinBlockSize;
-  categories_ = new FreeListCategory*[number_of_categories_]();
-
-  Reset();
-}
-
-FreeListMany::~FreeListMany() { delete[] categories_; }
-
-size_t FreeListMany::GuaranteedAllocatable(size_t maximum_freed) {
-  if (maximum_freed < categories_min[0]) {
-    return 0;
-  }
-  for (int cat = kFirstCategory + 1; cat <= last_category_; cat++) {
-    if (maximum_freed < categories_min[cat]) {
-      return categories_min[cat - 1];
-    }
-  }
-  return maximum_freed;
-}
-
-Page* FreeListMany::GetPageForSize(size_t size_in_bytes) {
-  FreeListCategoryType minimum_category =
-      SelectFreeListCategoryType(size_in_bytes);
-  Page* page = nullptr;
-  for (int cat = minimum_category + 1; !page && cat <= last_category_; cat++) {
-    page = GetPageForCategoryType(cat);
-  }
-  if (!page) {
-    // Might return a page in which |size_in_bytes| will not fit.
-    page = GetPageForCategoryType(minimum_category);
-  }
-  return page;
-}
-
-FreeSpace FreeListMany::Allocate(size_t size_in_bytes, size_t* node_size,
-                                 AllocationOrigin origin) {
-  DCHECK_GE(kMaxBlockSize, size_in_bytes);
-  FreeSpace node;
-  FreeListCategoryType type = SelectFreeListCategoryType(size_in_bytes);
-  for (int i = type; i < last_category_ && node.is_null(); i++) {
-    node = TryFindNodeIn(static_cast<FreeListCategoryType>(i), size_in_bytes,
-                         node_size);
-  }
-
-  if (node.is_null()) {
-    // Searching each element of the last category.
-    node = SearchForNodeInList(last_category_, size_in_bytes, node_size);
-  }
-
-  if (!node.is_null()) {
-    Page::FromHeapObject(node)->IncreaseAllocatedBytes(*node_size);
-  }
-
-  DCHECK(IsVeryLong() || Available() == SumFreeLists());
-  return node;
-}
-
-// ------------------------------------------------
-// FreeListManyCached implementation
-
-FreeListManyCached::FreeListManyCached() { ResetCache(); }
-
-void FreeListManyCached::Reset() {
-  ResetCache();
-  FreeListMany::Reset();
-}
-
-bool FreeListManyCached::AddCategory(FreeListCategory* category) {
-  bool was_added = FreeList::AddCategory(category);
-
-  // Updating cache
-  if (was_added) {
-    UpdateCacheAfterAddition(category->type_);
-  }
-
-#ifdef DEBUG
-  CheckCacheIntegrity();
-#endif
-
-  return was_added;
-}
-
-void FreeListManyCached::RemoveCategory(FreeListCategory* category) {
-  FreeList::RemoveCategory(category);
-
-  // Updating cache
-  int type = category->type_;
-  if (categories_[type] == nullptr) {
-    UpdateCacheAfterRemoval(type);
-  }
-
-#ifdef DEBUG
-  CheckCacheIntegrity();
-#endif
-}
-
-size_t FreeListManyCached::Free(Address start, size_t size_in_bytes,
-                                FreeMode mode) {
-  Page* page = Page::FromAddress(start);
-  page->DecreaseAllocatedBytes(size_in_bytes);
-
-  // Blocks have to be a minimum size to hold free list items.
-  if (size_in_bytes < min_block_size_) {
-    page->add_wasted_memory(size_in_bytes);
-    wasted_bytes_ += size_in_bytes;
-    return size_in_bytes;
-  }
-
-  // Insert other blocks at the head of a free list of the appropriate
-  // magnitude.
-  FreeListCategoryType type = SelectFreeListCategoryType(size_in_bytes);
-  page->free_list_category(type)->Free(start, size_in_bytes, mode, this);
-
-  // Updating cache
-  if (mode == kLinkCategory) {
-    UpdateCacheAfterAddition(type);
-
-#ifdef DEBUG
-    CheckCacheIntegrity();
-#endif
-  }
-
-  DCHECK_EQ(page->AvailableInFreeList(),
-            page->AvailableInFreeListFromAllocatedBytes());
-  return 0;
-}
-
-FreeSpace FreeListManyCached::Allocate(size_t size_in_bytes, size_t* node_size,
-                                       AllocationOrigin origin) {
-  USE(origin);
-  DCHECK_GE(kMaxBlockSize, size_in_bytes);
-
-  FreeSpace node;
-  FreeListCategoryType type = SelectFreeListCategoryType(size_in_bytes);
-  type = next_nonempty_category[type];
-  for (; type < last_category_; type = next_nonempty_category[type + 1]) {
-    node = TryFindNodeIn(type, size_in_bytes, node_size);
-    if (!node.is_null()) break;
-  }
-
-  if (node.is_null()) {
-    // Searching each element of the last category.
-    type = last_category_;
-    node = SearchForNodeInList(type, size_in_bytes, node_size);
-  }
-
-  // Updating cache
-  if (!node.is_null() && categories_[type] == nullptr) {
-    UpdateCacheAfterRemoval(type);
-  }
-
-#ifdef DEBUG
-  CheckCacheIntegrity();
-#endif
-
-  if (!node.is_null()) {
-    Page::FromHeapObject(node)->IncreaseAllocatedBytes(*node_size);
-  }
-
-  DCHECK(IsVeryLong() || Available() == SumFreeLists());
-  return node;
-}
-
-// ------------------------------------------------
-// FreeListManyCachedFastPath implementation
-
-FreeSpace FreeListManyCachedFastPath::Allocate(size_t size_in_bytes,
-                                               size_t* node_size,
-                                               AllocationOrigin origin) {
-  USE(origin);
-  DCHECK_GE(kMaxBlockSize, size_in_bytes);
-  FreeSpace node;
-
-  // Fast path part 1: searching the last categories
-  FreeListCategoryType first_category =
-      SelectFastAllocationFreeListCategoryType(size_in_bytes);
-  FreeListCategoryType type = first_category;
-  for (type = next_nonempty_category[type]; type <= last_category_;
-       type = next_nonempty_category[type + 1]) {
-    node = TryFindNodeIn(type, size_in_bytes, node_size);
-    if (!node.is_null()) break;
-  }
-
-  // Fast path part 2: searching the medium categories for tiny objects
-  if (node.is_null()) {
-    if (size_in_bytes <= kTinyObjectMaxSize) {
-      for (type = next_nonempty_category[kFastPathFallBackTiny];
-           type < kFastPathFirstCategory;
-           type = next_nonempty_category[type + 1]) {
-        node = TryFindNodeIn(type, size_in_bytes, node_size);
-        if (!node.is_null()) break;
-      }
-    }
-  }
-
-  // Searching the last category
-  if (node.is_null()) {
-    // Searching each element of the last category.
-    type = last_category_;
-    node = SearchForNodeInList(type, size_in_bytes, node_size);
-  }
-
-  // Finally, search the most precise category
-  if (node.is_null()) {
-    type = SelectFreeListCategoryType(size_in_bytes);
-    for (type = next_nonempty_category[type]; type < first_category;
-         type = next_nonempty_category[type + 1]) {
-      node = TryFindNodeIn(type, size_in_bytes, node_size);
-      if (!node.is_null()) break;
-    }
-  }
-
-  // Updating cache
-  if (!node.is_null() && categories_[type] == nullptr) {
-    UpdateCacheAfterRemoval(type);
-  }
-
-#ifdef DEBUG
-  CheckCacheIntegrity();
-#endif
-
-  if (!node.is_null()) {
-    Page::FromHeapObject(node)->IncreaseAllocatedBytes(*node_size);
-  }
-
-  DCHECK(IsVeryLong() || Available() == SumFreeLists());
-  return node;
-}
-
-// ------------------------------------------------
-// FreeListManyCachedOrigin implementation
-
-FreeSpace FreeListManyCachedOrigin::Allocate(size_t size_in_bytes,
-                                             size_t* node_size,
-                                             AllocationOrigin origin) {
-  if (origin == AllocationOrigin::kGC) {
-    return FreeListManyCached::Allocate(size_in_bytes, node_size, origin);
-  } else {
-    return FreeListManyCachedFastPath::Allocate(size_in_bytes, node_size,
-                                                origin);
-  }
-}
-
-// ------------------------------------------------
-// FreeListMap implementation
-
-FreeListMap::FreeListMap() {
-  // Initializing base (FreeList) fields
-  number_of_categories_ = 1;
-  last_category_ = kOnlyCategory;
-  min_block_size_ = kMinBlockSize;
-  categories_ = new FreeListCategory*[number_of_categories_]();
-
-  Reset();
-}
-
-size_t FreeListMap::GuaranteedAllocatable(size_t maximum_freed) {
-  return maximum_freed;
-}
-
-Page* FreeListMap::GetPageForSize(size_t size_in_bytes) {
-  return GetPageForCategoryType(kOnlyCategory);
-}
-
-FreeListMap::~FreeListMap() { delete[] categories_; }
-
-FreeSpace FreeListMap::Allocate(size_t size_in_bytes, size_t* node_size,
-                                AllocationOrigin origin) {
-  DCHECK_GE(kMaxBlockSize, size_in_bytes);
-
-  // The following DCHECK ensures that maps are allocated one by one (ie,
-  // without folding). This assumption currently holds. However, if it were to
-  // become untrue in the future, you'll get an error here. To fix it, I would
-  // suggest removing the DCHECK, and replacing TryFindNodeIn by
-  // SearchForNodeInList below.
-  DCHECK_EQ(size_in_bytes, Map::kSize);
-
-  FreeSpace node = TryFindNodeIn(kOnlyCategory, size_in_bytes, node_size);
-
-  if (!node.is_null()) {
-    Page::FromHeapObject(node)->IncreaseAllocatedBytes(*node_size);
-  }
-
-  DCHECK_IMPLIES(node.is_null(), IsEmpty());
-  return node;
-}
-
-// ------------------------------------------------
-// Generic FreeList methods (non alloc/free related)
-
-void FreeList::Reset() {
-  ForAllFreeListCategories(
-      [this](FreeListCategory* category) { category->Reset(this); });
-  for (int i = kFirstCategory; i < number_of_categories_; i++) {
-    categories_[i] = nullptr;
-  }
-  wasted_bytes_ = 0;
-  available_ = 0;
-}
-
-size_t FreeList::EvictFreeListItems(Page* page) {
-  size_t sum = 0;
-  page->ForAllFreeListCategories([this, &sum](FreeListCategory* category) {
-    sum += category->available();
-    RemoveCategory(category);
-    category->Reset(this);
-  });
-  return sum;
-}
-
-void FreeList::RepairLists(Heap* heap) {
-  ForAllFreeListCategories(
-      [heap](FreeListCategory* category) { category->RepairFreeList(heap); });
-}
-
-bool FreeList::AddCategory(FreeListCategory* category) {
-  FreeListCategoryType type = category->type_;
-  DCHECK_LT(type, number_of_categories_);
-  FreeListCategory* top = categories_[type];
-
-  if (category->is_empty()) return false;
-  DCHECK_NE(top, category);
-
-  // Common double-linked list insertion.
-  if (top != nullptr) {
-    top->set_prev(category);
-  }
-  category->set_next(top);
-  categories_[type] = category;
-
-  IncreaseAvailableBytes(category->available());
-  return true;
-}
-
-void FreeList::RemoveCategory(FreeListCategory* category) {
-  FreeListCategoryType type = category->type_;
-  DCHECK_LT(type, number_of_categories_);
-  FreeListCategory* top = categories_[type];
-
-  if (category->is_linked(this)) {
-    DecreaseAvailableBytes(category->available());
-  }
-
-  // Common double-linked list removal.
-  if (top == category) {
-    categories_[type] = category->next();
-  }
-  if (category->prev() != nullptr) {
-    category->prev()->set_next(category->next());
-  }
-  if (category->next() != nullptr) {
-    category->next()->set_prev(category->prev());
-  }
-  category->set_next(nullptr);
-  category->set_prev(nullptr);
-}
-
-void FreeList::PrintCategories(FreeListCategoryType type) {
-  FreeListCategoryIterator it(this, type);
-  PrintF("FreeList[%p, top=%p, %d] ", static_cast<void*>(this),
-         static_cast<void*>(categories_[type]), type);
-  while (it.HasNext()) {
-    FreeListCategory* current = it.Next();
-    PrintF("%p -> ", static_cast<void*>(current));
-  }
-  PrintF("null\n");
-}
 
 int MemoryChunk::FreeListsLength() {
   int length = 0;
@@ -3619,250 +475,5 @@ int MemoryChunk::FreeListsLength() {
   return length;
 }
 
-size_t FreeListCategory::SumFreeList() {
-  size_t sum = 0;
-  FreeSpace cur = top();
-  while (!cur.is_null()) {
-    // We can't use "cur->map()" here because both cur's map and the
-    // root can be null during bootstrapping.
-    DCHECK(cur.map_slot().contains_value(Page::FromHeapObject(cur)
-                                             ->heap()
-                                             ->isolate()
-                                             ->root(RootIndex::kFreeSpaceMap)
-                                             .ptr()));
-    sum += cur.relaxed_read_size();
-    cur = cur.next();
-  }
-  return sum;
-}
-int FreeListCategory::FreeListLength() {
-  int length = 0;
-  FreeSpace cur = top();
-  while (!cur.is_null()) {
-    length++;
-    cur = cur.next();
-  }
-  return length;
-}
-
-#ifdef DEBUG
-bool FreeList::IsVeryLong() {
-  int len = 0;
-  for (int i = kFirstCategory; i < number_of_categories_; i++) {
-    FreeListCategoryIterator it(this, static_cast<FreeListCategoryType>(i));
-    while (it.HasNext()) {
-      len += it.Next()->FreeListLength();
-      if (len >= FreeListCategory::kVeryLongFreeList) return true;
-    }
-  }
-  return false;
-}
-
-
-// This can take a very long time because it is linear in the number of entries
-// on the free list, so it should not be called if FreeListLength returns
-// kVeryLongFreeList.
-size_t FreeList::SumFreeLists() {
-  size_t sum = 0;
-  ForAllFreeListCategories(
-      [&sum](FreeListCategory* category) { sum += category->SumFreeList(); });
-  return sum;
-}
-#endif
-
-
-// -----------------------------------------------------------------------------
-// OldSpace implementation
-
-void PagedSpace::PrepareForMarkCompact() {
-  // We don't have a linear allocation area while sweeping.  It will be restored
-  // on the first allocation after the sweep.
-  FreeLinearAllocationArea();
-
-  // Clear the free list before a full GC---it will be rebuilt afterward.
-  free_list_->Reset();
-}
-
-size_t PagedSpace::SizeOfObjects() {
-  CHECK_GE(limit(), top());
-  DCHECK_GE(Size(), static_cast<size_t>(limit() - top()));
-  return Size() - (limit() - top());
-}
-
-bool PagedSpace::EnsureSweptAndRetryAllocation(int size_in_bytes,
-                                               AllocationOrigin origin) {
-  DCHECK(!is_local_space());
-  MarkCompactCollector* collector = heap()->mark_compact_collector();
-  if (collector->sweeping_in_progress()) {
-    // Wait for the sweeper threads here and complete the sweeping phase.
-    collector->EnsureSweepingCompleted();
-
-    // After waiting for the sweeper threads, there may be new free-list
-    // entries.
-    return RefillLinearAllocationAreaFromFreeList(size_in_bytes, origin);
-  }
-  return false;
-}
-
-bool PagedSpace::SlowRefillLinearAllocationArea(int size_in_bytes,
-                                                AllocationOrigin origin) {
-  VMState<GC> state(heap()->isolate());
-  RuntimeCallTimerScope runtime_timer(
-      heap()->isolate(), RuntimeCallCounterId::kGC_Custom_SlowAllocateRaw);
-  base::Optional<base::MutexGuard> optional_mutex;
-
-  if (FLAG_concurrent_allocation && origin != AllocationOrigin::kGC &&
-      identity() == OLD_SPACE) {
-    optional_mutex.emplace(&allocation_mutex_);
-  }
-
-  return RawSlowRefillLinearAllocationArea(size_in_bytes, origin);
-}
-
-bool CompactionSpace::SlowRefillLinearAllocationArea(int size_in_bytes,
-                                                     AllocationOrigin origin) {
-  return RawSlowRefillLinearAllocationArea(size_in_bytes, origin);
-}
-
-bool OffThreadSpace::SlowRefillLinearAllocationArea(int size_in_bytes,
-                                                    AllocationOrigin origin) {
-  if (RefillLinearAllocationAreaFromFreeList(size_in_bytes, origin))
-    return true;
-
-  if (Expand()) {
-    DCHECK((CountTotalPages() > 1) ||
-           (static_cast<size_t>(size_in_bytes) <= free_list_->Available()));
-    return RefillLinearAllocationAreaFromFreeList(
-        static_cast<size_t>(size_in_bytes), origin);
-  }
-
-  return false;
-}
-
-bool PagedSpace::RawSlowRefillLinearAllocationArea(int size_in_bytes,
-                                                   AllocationOrigin origin) {
-  // Non-compaction local spaces are not supported.
-  DCHECK_IMPLIES(is_local_space(), is_compaction_space());
-
-  // Allocation in this space has failed.
-  DCHECK_GE(size_in_bytes, 0);
-  const int kMaxPagesToSweep = 1;
-
-  if (RefillLinearAllocationAreaFromFreeList(size_in_bytes, origin))
-    return true;
-
-  MarkCompactCollector* collector = heap()->mark_compact_collector();
-  // Sweeping is still in progress.
-  if (collector->sweeping_in_progress()) {
-    if (FLAG_concurrent_sweeping && !is_compaction_space() &&
-        !collector->sweeper()->AreSweeperTasksRunning()) {
-      collector->EnsureSweepingCompleted();
-    }
-
-    // First try to refill the free-list, concurrent sweeper threads
-    // may have freed some objects in the meantime.
-    RefillFreeList();
-
-    // Retry the free list allocation.
-    if (RefillLinearAllocationAreaFromFreeList(
-            static_cast<size_t>(size_in_bytes), origin))
-      return true;
-
-    if (SweepAndRetryAllocation(size_in_bytes, kMaxPagesToSweep, size_in_bytes,
-                                origin))
-      return true;
-  }
-
-  if (is_compaction_space()) {
-    // The main thread may have acquired all swept pages. Try to steal from
-    // it. This can only happen during young generation evacuation.
-    PagedSpace* main_space = heap()->paged_space(identity());
-    Page* page = main_space->RemovePageSafe(size_in_bytes);
-    if (page != nullptr) {
-      AddPage(page);
-      if (RefillLinearAllocationAreaFromFreeList(
-              static_cast<size_t>(size_in_bytes), origin))
-        return true;
-    }
-  }
-
-  if (heap()->ShouldExpandOldGenerationOnSlowAllocation() && Expand()) {
-    DCHECK((CountTotalPages() > 1) ||
-           (static_cast<size_t>(size_in_bytes) <= free_list_->Available()));
-    return RefillLinearAllocationAreaFromFreeList(
-        static_cast<size_t>(size_in_bytes), origin);
-  }
-
-  if (is_compaction_space()) {
-    return SweepAndRetryAllocation(0, 0, size_in_bytes, origin);
-
-  } else {
-    // If sweeper threads are active, wait for them at that point and steal
-    // elements from their free-lists. Allocation may still fail here which
-    // would indicate that there is not enough memory for the given allocation.
-    return EnsureSweptAndRetryAllocation(size_in_bytes, origin);
-  }
-}
-
-bool PagedSpace::SweepAndRetryAllocation(int required_freed_bytes,
-                                         int max_pages, int size_in_bytes,
-                                         AllocationOrigin origin) {
-  // Cleanup invalidated old-to-new refs for compaction space in the
-  // final atomic pause.
-  Sweeper::FreeSpaceMayContainInvalidatedSlots invalidated_slots_in_free_space =
-      is_compaction_space() ? Sweeper::FreeSpaceMayContainInvalidatedSlots::kYes
-                            : Sweeper::FreeSpaceMayContainInvalidatedSlots::kNo;
-
-  MarkCompactCollector* collector = heap()->mark_compact_collector();
-  if (collector->sweeping_in_progress()) {
-    int max_freed = collector->sweeper()->ParallelSweepSpace(
-        identity(), required_freed_bytes, max_pages,
-        invalidated_slots_in_free_space);
-    RefillFreeList();
-    if (max_freed >= size_in_bytes)
-      return RefillLinearAllocationAreaFromFreeList(size_in_bytes, origin);
-  }
-  return false;
-}
-
-// -----------------------------------------------------------------------------
-// MapSpace implementation
-
-// TODO(dmercadier): use a heap instead of sorting like that.
-// Using a heap will have multiple benefits:
-//   - for now, SortFreeList is only called after sweeping, which is somewhat
-//   late. Using a heap, sorting could be done online: FreeListCategories would
-//   be inserted in a heap (ie, in a sorted manner).
-//   - SortFreeList is a bit fragile: any change to FreeListMap (or to
-//   MapSpace::free_list_) could break it.
-void MapSpace::SortFreeList() {
-  using LiveBytesPagePair = std::pair<size_t, Page*>;
-  std::vector<LiveBytesPagePair> pages;
-  pages.reserve(CountTotalPages());
-
-  for (Page* p : *this) {
-    free_list()->RemoveCategory(p->free_list_category(kFirstCategory));
-    pages.push_back(std::make_pair(p->allocated_bytes(), p));
-  }
-
-  // Sorting by least-allocated-bytes first.
-  std::sort(pages.begin(), pages.end(),
-            [](const LiveBytesPagePair& a, const LiveBytesPagePair& b) {
-              return a.first < b.first;
-            });
-
-  for (LiveBytesPagePair const& p : pages) {
-    // Since AddCategory inserts in head position, it reverts the order produced
-    // by the sort above: least-allocated-bytes will be Added first, and will
-    // therefore be the last element (and the first one will be
-    // most-allocated-bytes).
-    free_list()->AddCategory(p.second->free_list_category(kFirstCategory));
-  }
-}
-
-#ifdef VERIFY_HEAP
-void MapSpace::VerifyObject(HeapObject object) { CHECK(object.IsMap()); }
-#endif
-
 }  // namespace internal
 }  // namespace v8