deps: update V8 to 5.7.492.69

PR-URL: https://github.com/nodejs/node/pull/11752
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Franziska Hinkelmann <franziska.hinkelmann@gmail.com>

29 files changed, 1190 insertions, 569 deletions

diff --git a/deps/v8/src/heap/array-buffer-tracker.cc b/deps/v8/src/heap/array-buffer-tracker.cc
index 62b848ef70..def84572b6 100644
--- a/deps/v8/src/heap/array-buffer-tracker.cc
+++ b/deps/v8/src/heap/array-buffer-tracker.cc
@@ -78,8 +78,8 @@ void LocalArrayBufferTracker::Process(Callback callback) {
 
 void ArrayBufferTracker::FreeDeadInNewSpace(Heap* heap) {
   DCHECK_EQ(heap->gc_state(), Heap::HeapState::SCAVENGE);
-  for (Page* page : NewSpacePageRange(heap->new_space()->FromSpaceStart(),
-                                      heap->new_space()->FromSpaceEnd())) {
+  for (Page* page : PageRange(heap->new_space()->FromSpaceStart(),
+                              heap->new_space()->FromSpaceEnd())) {
     bool empty = ProcessBuffers(page, kUpdateForwardedRemoveOthers);
     CHECK(empty);
   }
diff --git a/deps/v8/src/heap/embedder-tracing.cc b/deps/v8/src/heap/embedder-tracing.cc
new file mode 100644
index 0000000000..2d11724181
--- /dev/null
+++ b/deps/v8/src/heap/embedder-tracing.cc
@@ -0,0 +1,72 @@
+// Copyright 2016 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "src/heap/embedder-tracing.h"
+
+#include "src/base/logging.h"
+
+namespace v8 {
+namespace internal {
+
+void LocalEmbedderHeapTracer::TracePrologue() {
+  if (!InUse()) return;
+
+  CHECK(cached_wrappers_to_trace_.empty());
+  num_v8_marking_deque_was_empty_ = 0;
+  remote_tracer_->TracePrologue();
+}
+
+void LocalEmbedderHeapTracer::TraceEpilogue() {
+  if (!InUse()) return;
+
+  CHECK(cached_wrappers_to_trace_.empty());
+  remote_tracer_->TraceEpilogue();
+}
+
+void LocalEmbedderHeapTracer::AbortTracing() {
+  if (!InUse()) return;
+
+  cached_wrappers_to_trace_.clear();
+  remote_tracer_->AbortTracing();
+}
+
+void LocalEmbedderHeapTracer::EnterFinalPause() {
+  if (!InUse()) return;
+
+  remote_tracer_->EnterFinalPause();
+}
+
+bool LocalEmbedderHeapTracer::Trace(
+    double deadline, EmbedderHeapTracer::AdvanceTracingActions actions) {
+  if (!InUse()) return false;
+
+  DCHECK_EQ(0, NumberOfCachedWrappersToTrace());
+  return remote_tracer_->AdvanceTracing(deadline, actions);
+}
+
+size_t LocalEmbedderHeapTracer::NumberOfWrappersToTrace() {
+  return (InUse())
+             ? cached_wrappers_to_trace_.size() +
+                   remote_tracer_->NumberOfWrappersToTrace()
+             : 0;
+}
+
+void LocalEmbedderHeapTracer::RegisterWrappersWithRemoteTracer() {
+  if (!InUse()) return;
+
+  if (cached_wrappers_to_trace_.empty()) {
+    return;
+  }
+
+  remote_tracer_->RegisterV8References(cached_wrappers_to_trace_);
+  cached_wrappers_to_trace_.clear();
+}
+
+bool LocalEmbedderHeapTracer::RequiresImmediateWrapperProcessing() {
+  const size_t kTooManyWrappers = 16000;
+  return cached_wrappers_to_trace_.size() > kTooManyWrappers;
+}
+
+}  // namespace internal
+}  // namespace v8
diff --git a/deps/v8/src/heap/embedder-tracing.h b/deps/v8/src/heap/embedder-tracing.h
new file mode 100644
index 0000000000..5e10d6e2e8
--- /dev/null
+++ b/deps/v8/src/heap/embedder-tracing.h
@@ -0,0 +1,67 @@
+// Copyright 2016 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef V8_HEAP_EMBEDDER_TRACING_H_
+#define V8_HEAP_EMBEDDER_TRACING_H_
+
+#include "include/v8.h"
+#include "src/flags.h"
+#include "src/globals.h"
+
+namespace v8 {
+namespace internal {
+
+class Heap;
+
+class V8_EXPORT_PRIVATE LocalEmbedderHeapTracer final {
+ public:
+  typedef std::pair<void*, void*> WrapperInfo;
+
+  LocalEmbedderHeapTracer()
+      : remote_tracer_(nullptr), num_v8_marking_deque_was_empty_(0) {}
+
+  void SetRemoteTracer(EmbedderHeapTracer* tracer) { remote_tracer_ = tracer; }
+  bool InUse() { return remote_tracer_ != nullptr; }
+
+  void TracePrologue();
+  void TraceEpilogue();
+  void AbortTracing();
+  void EnterFinalPause();
+  bool Trace(double deadline,
+             EmbedderHeapTracer::AdvanceTracingActions actions);
+
+  size_t NumberOfWrappersToTrace();
+  size_t NumberOfCachedWrappersToTrace() {
+    return cached_wrappers_to_trace_.size();
+  }
+  void AddWrapperToTrace(WrapperInfo entry) {
+    cached_wrappers_to_trace_.push_back(entry);
+  }
+  void ClearCachedWrappersToTrace() { cached_wrappers_to_trace_.clear(); }
+  void RegisterWrappersWithRemoteTracer();
+
+  // In order to avoid running out of memory we force tracing wrappers if there
+  // are too many of them.
+  bool RequiresImmediateWrapperProcessing();
+
+  void NotifyV8MarkingDequeWasEmpty() { num_v8_marking_deque_was_empty_++; }
+  bool ShouldFinalizeIncrementalMarking() {
+    static const size_t kMaxIncrementalFixpointRounds = 3;
+    return !FLAG_incremental_marking_wrappers || !InUse() ||
+           NumberOfWrappersToTrace() == 0 ||
+           num_v8_marking_deque_was_empty_ > kMaxIncrementalFixpointRounds;
+  }
+
+ private:
+  typedef std::vector<WrapperInfo> WrapperCache;
+
+  EmbedderHeapTracer* remote_tracer_;
+  WrapperCache cached_wrappers_to_trace_;
+  size_t num_v8_marking_deque_was_empty_;
+};
+
+}  // namespace internal
+}  // namespace v8
+
+#endif  // V8_HEAP_EMBEDDER_TRACING_H_
diff --git a/deps/v8/src/heap/gc-idle-time-handler.cc b/deps/v8/src/heap/gc-idle-time-handler.cc
index 0c411f7b4c..905514c4bf 100644
--- a/deps/v8/src/heap/gc-idle-time-handler.cc
+++ b/deps/v8/src/heap/gc-idle-time-handler.cc
@@ -146,6 +146,7 @@ GCIdleTimeAction GCIdleTimeHandler::Compute(double idle_time_in_ms,
   return GCIdleTimeAction::IncrementalStep();
 }
 
+bool GCIdleTimeHandler::Enabled() { return FLAG_incremental_marking; }
 
 }  // namespace internal
 }  // namespace v8
diff --git a/deps/v8/src/heap/gc-idle-time-handler.h b/deps/v8/src/heap/gc-idle-time-handler.h
index 7ce0c1a2f6..b730a7bbba 100644
--- a/deps/v8/src/heap/gc-idle-time-handler.h
+++ b/deps/v8/src/heap/gc-idle-time-handler.h
@@ -125,6 +125,8 @@ class V8_EXPORT_PRIVATE GCIdleTimeHandler {
   GCIdleTimeAction Compute(double idle_time_in_ms,
                            GCIdleTimeHeapState heap_state);
 
+  bool Enabled();
+
   void ResetNoProgressCounter() { idle_times_which_made_no_progress_ = 0; }
 
   static size_t EstimateMarkingStepSize(double idle_time_in_ms,
diff --git a/deps/v8/src/heap/gc-tracer.cc b/deps/v8/src/heap/gc-tracer.cc
index dcd319fdae..cf881c473b 100644
--- a/deps/v8/src/heap/gc-tracer.cc
+++ b/deps/v8/src/heap/gc-tracer.cc
@@ -174,8 +174,7 @@ void GCTracer::Start(GarbageCollector collector,
   current_.start_object_size = heap_->SizeOfObjects();
   current_.start_memory_size = heap_->memory_allocator()->Size();
   current_.start_holes_size = CountTotalHolesSize(heap_);
-  current_.new_space_object_size =
-      heap_->new_space()->top() - heap_->new_space()->bottom();
+  current_.new_space_object_size = heap_->new_space()->Size();
 
   current_.incremental_marking_bytes = 0;
   current_.incremental_marking_duration = 0;
@@ -510,9 +509,14 @@ void GCTracer::PrintNVP() const {
           "pause=%.1f "
           "mutator=%.1f "
           "gc=%s "
-          "reduce_memory=%d\n",
-          duration, spent_in_mutator, current_.TypeName(true),
-          current_.reduce_memory);
+          "reduce_memory=%d "
+          "mark=%.2f "
+          "mark.roots=%.2f "
+          "mark.old_to_new=%.2f\n",
+          duration, spent_in_mutator, "mmc", current_.reduce_memory,
+          current_.scopes[Scope::MINOR_MC_MARK],
+          current_.scopes[Scope::MINOR_MC_MARK_ROOTS],
+          current_.scopes[Scope::MINOR_MC_MARK_OLD_TO_NEW_POINTERS]);
       break;
     case Event::MARK_COMPACTOR:
     case Event::INCREMENTAL_MARK_COMPACTOR:
diff --git a/deps/v8/src/heap/gc-tracer.h b/deps/v8/src/heap/gc-tracer.h
index ed62dee5f1..7aff1cf59d 100644
--- a/deps/v8/src/heap/gc-tracer.h
+++ b/deps/v8/src/heap/gc-tracer.h
@@ -79,6 +79,12 @@ enum ScavengeSpeedMode { kForAllObjects, kForSurvivedObjects };
   F(MC_SWEEP_CODE)                            \
   F(MC_SWEEP_MAP)                             \
   F(MC_SWEEP_OLD)                             \
+  F(MINOR_MC_MARK)                            \
+  F(MINOR_MC_MARK_CODE_FLUSH_CANDIDATES)      \
+  F(MINOR_MC_MARK_GLOBAL_HANDLES)             \
+  F(MINOR_MC_MARK_OLD_TO_NEW_POINTERS)        \
+  F(MINOR_MC_MARK_ROOTS)                      \
+  F(MINOR_MC_MARK_WEAK)                       \
   F(SCAVENGER_CODE_FLUSH_CANDIDATES)          \
   F(SCAVENGER_OLD_TO_NEW_POINTERS)            \
   F(SCAVENGER_ROOTS)                          \
diff --git a/deps/v8/src/heap/heap-inl.h b/deps/v8/src/heap/heap-inl.h
index 7d0d241289..4d060f8e43 100644
--- a/deps/v8/src/heap/heap-inl.h
+++ b/deps/v8/src/heap/heap-inl.h
@@ -21,6 +21,7 @@
 #include "src/log.h"
 #include "src/msan.h"
 #include "src/objects-inl.h"
+#include "src/objects/scope-info.h"
 #include "src/type-feedback-vector-inl.h"
 
 namespace v8 {
@@ -698,12 +699,15 @@ void Heap::ExternalStringTable::AddString(String* string) {
   }
 }
 
-
-void Heap::ExternalStringTable::Iterate(ObjectVisitor* v) {
+void Heap::ExternalStringTable::IterateNewSpaceStrings(ObjectVisitor* v) {
   if (!new_space_strings_.is_empty()) {
     Object** start = &new_space_strings_[0];
     v->VisitPointers(start, start + new_space_strings_.length());
   }
+}
+
+void Heap::ExternalStringTable::IterateAll(ObjectVisitor* v) {
+  IterateNewSpaceStrings(v);
   if (!old_space_strings_.is_empty()) {
     Object** start = &old_space_strings_[0];
     v->VisitPointers(start, start + old_space_strings_.length());
@@ -809,9 +813,16 @@ int Heap::GetNextTemplateSerialNumber() {
 
 void Heap::SetSerializedTemplates(FixedArray* templates) {
   DCHECK_EQ(empty_fixed_array(), serialized_templates());
+  DCHECK(isolate()->serializer_enabled());
   set_serialized_templates(templates);
 }
 
+void Heap::SetSerializedGlobalProxySizes(FixedArray* sizes) {
+  DCHECK_EQ(empty_fixed_array(), serialized_global_proxy_sizes());
+  DCHECK(isolate()->serializer_enabled());
+  set_serialized_global_proxy_sizes(sizes);
+}
+
 void Heap::CreateObjectStats() {
   if (V8_LIKELY(FLAG_gc_stats == 0)) return;
   if (!live_object_stats_) {
diff --git a/deps/v8/src/heap/heap.cc b/deps/v8/src/heap/heap.cc
index 2059dae6b7..478be1f03a 100644
--- a/deps/v8/src/heap/heap.cc
+++ b/deps/v8/src/heap/heap.cc
@@ -20,6 +20,7 @@
 #include "src/global-handles.h"
 #include "src/heap/array-buffer-tracker-inl.h"
 #include "src/heap/code-stats.h"
+#include "src/heap/embedder-tracing.h"
 #include "src/heap/gc-idle-time-handler.h"
 #include "src/heap/gc-tracer.h"
 #include "src/heap/incremental-marking.h"
@@ -80,6 +81,7 @@ Heap::Heap()
       max_semi_space_size_(8 * (kPointerSize / 4) * MB),
       initial_semispace_size_(MB),
       max_old_generation_size_(700ul * (kPointerSize / 4) * MB),
+      initial_max_old_generation_size_(max_old_generation_size_),
       initial_old_generation_size_(max_old_generation_size_ /
                                    kInitalOldGenerationLimitFactor),
       old_generation_size_configured_(false),
@@ -93,6 +95,8 @@ Heap::Heap()
       survived_last_scavenge_(0),
       always_allocate_scope_count_(0),
       memory_pressure_level_(MemoryPressureLevel::kNone),
+      out_of_memory_callback_(nullptr),
+      out_of_memory_callback_data_(nullptr),
       contexts_disposed_(0),
       number_of_disposed_maps_(0),
       global_ic_age_(0),
@@ -155,7 +159,7 @@ Heap::Heap()
       deserialization_complete_(false),
       strong_roots_list_(NULL),
       heap_iterator_depth_(0),
-      embedder_heap_tracer_(nullptr),
+      local_embedder_heap_tracer_(nullptr),
       force_oom_(false),
       delay_sweeper_tasks_for_testing_(false) {
 // Allow build-time customization of the max semispace size. Building
@@ -292,6 +296,9 @@ GarbageCollector Heap::SelectGarbageCollector(AllocationSpace space,
   return YoungGenerationCollector();
 }
 
+void Heap::SetGCState(HeapState state) {
+  gc_state_ = state;
+}
 
 // TODO(1238405): Combine the infrastructure for --heap-stats and
 // --log-gc to avoid the complicated preprocessor and flag testing.
@@ -442,7 +449,6 @@ void Heap::GarbageCollectionPrologue() {
   }
   CheckNewSpaceExpansionCriteria();
   UpdateNewSpaceAllocationCounter();
-  store_buffer()->MoveAllEntriesToRememberedSet();
 }
 
 size_t Heap::SizeOfObjects() {
@@ -510,6 +516,22 @@ void Heap::MergeAllocationSitePretenuringFeedback(
   }
 }
 
+class Heap::SkipStoreBufferScope {
+ public:
+  explicit SkipStoreBufferScope(StoreBuffer* store_buffer)
+      : store_buffer_(store_buffer) {
+    store_buffer_->MoveAllEntriesToRememberedSet();
+    store_buffer_->SetMode(StoreBuffer::IN_GC);
+  }
+
+  ~SkipStoreBufferScope() {
+    DCHECK(store_buffer_->Empty());
+    store_buffer_->SetMode(StoreBuffer::NOT_IN_GC);
+  }
+
+ private:
+  StoreBuffer* store_buffer_;
+};
 
 class Heap::PretenuringScope {
  public:
@@ -861,6 +883,10 @@ void Heap::CollectAllAvailableGarbage(GarbageCollectionReason gc_reason) {
   // Note: as weak callbacks can execute arbitrary code, we cannot
   // hope that eventually there will be no weak callbacks invocations.
   // Therefore stop recollecting after several attempts.
+  if (gc_reason == GarbageCollectionReason::kLastResort) {
+    InvokeOutOfMemoryCallback();
+  }
+  RuntimeCallTimerScope(isolate(), &RuntimeCallStats::GC_AllAvailableGarbage);
   if (isolate()->concurrent_recompilation_enabled()) {
     // The optimizing compiler may be unnecessarily holding on to memory.
     DisallowHeapAllocation no_recursive_gc;
@@ -943,6 +969,7 @@ bool Heap::CollectGarbage(GarbageCollector collector,
                           const v8::GCCallbackFlags gc_callback_flags) {
   // The VM is in the GC state until exiting this function.
   VMState<GC> state(isolate_);
+  RuntimeCallTimerScope(isolate(), &RuntimeCallStats::GC);
 
 #ifdef DEBUG
   // Reset the allocation timeout to the GC interval, but make sure to
@@ -1022,6 +1049,7 @@ bool Heap::CollectGarbage(GarbageCollector collector,
           (committed_memory_before > committed_memory_after + MB) ||
           HasHighFragmentation(used_memory_after, committed_memory_after) ||
           (detached_contexts()->length() > 0);
+      event.committed_memory = committed_memory_after;
       if (deserialization_complete_) {
         memory_reducer_->NotifyMarkCompact(event);
       }
@@ -1164,7 +1192,7 @@ bool Heap::ReserveSpace(Reservation* reservations, List<Address>* maps) {
             // deserializing.
             Address free_space_address = free_space->address();
             CreateFillerObjectAt(free_space_address, Map::kSize,
-                                 ClearRecordedSlots::kNo, ClearBlackArea::kNo);
+                                 ClearRecordedSlots::kNo);
             maps->Add(free_space_address);
           } else {
             perform_gc = true;
@@ -1195,7 +1223,7 @@ bool Heap::ReserveSpace(Reservation* reservations, List<Address>* maps) {
             // deserializing.
             Address free_space_address = free_space->address();
             CreateFillerObjectAt(free_space_address, size,
-                                 ClearRecordedSlots::kNo, ClearBlackArea::kNo);
+                                 ClearRecordedSlots::kNo);
             DCHECK(space < SerializerDeserializer::kNumberOfPreallocatedSpaces);
             chunk.start = free_space_address;
             chunk.end = free_space_address + size;
@@ -1313,6 +1341,7 @@ bool Heap::PerformGarbageCollection(
 
   {
     Heap::PretenuringScope pretenuring_scope(this);
+    Heap::SkipStoreBufferScope skip_store_buffer_scope(store_buffer_);
 
     switch (collector) {
       case MARK_COMPACTOR:
@@ -1394,6 +1423,7 @@ bool Heap::PerformGarbageCollection(
 
 
 void Heap::CallGCPrologueCallbacks(GCType gc_type, GCCallbackFlags flags) {
+  RuntimeCallTimerScope(isolate(), &RuntimeCallStats::GCPrologueCallback);
   for (int i = 0; i < gc_prologue_callbacks_.length(); ++i) {
     if (gc_type & gc_prologue_callbacks_[i].gc_type) {
       if (!gc_prologue_callbacks_[i].pass_isolate) {
@@ -1415,6 +1445,7 @@ void Heap::CallGCPrologueCallbacks(GCType gc_type, GCCallbackFlags flags) {
 
 void Heap::CallGCEpilogueCallbacks(GCType gc_type,
                                    GCCallbackFlags gc_callback_flags) {
+  RuntimeCallTimerScope(isolate(), &RuntimeCallStats::GCEpilogueCallback);
   for (int i = 0; i < gc_epilogue_callbacks_.length(); ++i) {
     if (gc_type & gc_epilogue_callbacks_[i].gc_type) {
       if (!gc_epilogue_callbacks_[i].pass_isolate) {
@@ -1433,7 +1464,8 @@ void Heap::CallGCEpilogueCallbacks(GCType gc_type,
 void Heap::MarkCompact() {
   PauseAllocationObserversScope pause_observers(this);
 
-  gc_state_ = MARK_COMPACT;
+  SetGCState(MARK_COMPACT);
+
   LOG(isolate_, ResourceEvent("markcompact", "begin"));
 
   uint64_t size_of_objects_before_gc = SizeOfObjects();
@@ -1459,7 +1491,7 @@ void Heap::MinorMarkCompact() { UNREACHABLE(); }
 
 void Heap::MarkCompactEpilogue() {
   TRACE_GC(tracer(), GCTracer::Scope::MC_EPILOGUE);
-  gc_state_ = NOT_IN_GC;
+  SetGCState(NOT_IN_GC);
 
   isolate_->counters()->objs_since_last_full()->Set(0);
 
@@ -1512,21 +1544,6 @@ static bool IsUnscavengedHeapObject(Heap* heap, Object** p) {
          !HeapObject::cast(*p)->map_word().IsForwardingAddress();
 }
 
-
-static bool IsUnmodifiedHeapObject(Object** p) {
-  Object* object = *p;
-  if (object->IsSmi()) return false;
-  HeapObject* heap_object = HeapObject::cast(object);
-  if (!object->IsJSObject()) return false;
-  JSObject* js_object = JSObject::cast(object);
-  if (!js_object->WasConstructedFromApiFunction()) return false;
-  JSFunction* constructor =
-      JSFunction::cast(js_object->map()->GetConstructor());
-
-  return constructor->initial_map() == heap_object->map();
-}
-
-
 void PromotionQueue::Initialize() {
   // The last to-space page may be used for promotion queue. On promotion
   // conflict, we use the emergency stack.
@@ -1605,7 +1622,7 @@ void Heap::Scavenge() {
 
   mark_compact_collector()->sweeper().EnsureNewSpaceCompleted();
 
-  gc_state_ = SCAVENGE;
+  SetGCState(SCAVENGE);
 
   // Implements Cheney's copying algorithm
   LOG(isolate_, ResourceEvent("scavenge", "begin"));
@@ -1615,13 +1632,6 @@ void Heap::Scavenge() {
 
   scavenge_collector_->SelectScavengingVisitorsTable();
 
-  if (UsingEmbedderHeapTracer()) {
-    // Register found wrappers with embedder so it can add them to its marking
-    // deque and correctly manage the case when v8 scavenger collects the
-    // wrappers by either keeping wrappables alive, or cleaning marking deque.
-    RegisterWrappersWithEmbedderHeapTracer();
-  }
-
   // Flip the semispaces.  After flipping, to space is empty, from space has
   // live objects.
   new_space_->Flip();
@@ -1701,8 +1711,10 @@ void Heap::Scavenge() {
   isolate()->global_handles()->MarkNewSpaceWeakUnmodifiedObjectsPending(
       &IsUnscavengedHeapObject);
 
-  isolate()->global_handles()->IterateNewSpaceWeakUnmodifiedRoots(
-      &scavenge_visitor);
+  isolate()
+      ->global_handles()
+      ->IterateNewSpaceWeakUnmodifiedRoots<
+          GlobalHandles::HANDLE_PHANTOM_NODES_VISIT_OTHERS>(&scavenge_visitor);
   new_space_front = DoScavenge(&scavenge_visitor, new_space_front);
 
   UpdateNewSpaceReferencesInExternalStringTable(
@@ -1727,9 +1739,13 @@ void Heap::Scavenge() {
   IncrementYoungSurvivorsCounter(PromotedSpaceSizeOfObjects() +
                                  new_space_->Size() - survived_watermark);
 
+  // Scavenger may find new wrappers by iterating objects promoted onto a black
+  // page.
+  local_embedder_heap_tracer()->RegisterWrappersWithRemoteTracer();
+
   LOG(isolate_, ResourceEvent("scavenge", "end"));
 
-  gc_state_ = NOT_IN_GC;
+  SetGCState(NOT_IN_GC);
 }
 
 
@@ -1882,7 +1898,7 @@ void Heap::VisitExternalResources(v8::ExternalResourceVisitor* visitor) {
     v8::ExternalResourceVisitor* visitor_;
   } external_string_table_visitor(visitor);
 
-  external_string_table_.Iterate(&external_string_table_visitor);
+  external_string_table_.IterateAll(&external_string_table_visitor);
 }
 
 Address Heap::DoScavenge(ObjectVisitor* scavenge_visitor,
@@ -2008,7 +2024,6 @@ void Heap::UnregisterArrayBuffer(JSArrayBuffer* buffer) {
   ArrayBufferTracker::Unregister(this, buffer);
 }
 
-
 void Heap::ConfigureInitialOldGenerationSize() {
   if (!old_generation_size_configured_ && tracer()->SurvivalEventsRecorded()) {
     old_generation_allocation_limit_ =
@@ -2019,7 +2034,6 @@ void Heap::ConfigureInitialOldGenerationSize() {
   }
 }
 
-
 AllocationResult Heap::AllocatePartialMap(InstanceType instance_type,
                                           int instance_size) {
   Object* result = nullptr;
@@ -2107,8 +2121,7 @@ AllocationResult Heap::AllocateFillerObject(int size, bool double_align,
   MemoryChunk* chunk = MemoryChunk::FromAddress(obj->address());
   DCHECK(chunk->owner()->identity() == space);
 #endif
-  CreateFillerObjectAt(obj->address(), size, ClearRecordedSlots::kNo,
-                       ClearBlackArea::kNo);
+  CreateFillerObjectAt(obj->address(), size, ClearRecordedSlots::kNo);
   return obj;
 }
 
@@ -2256,6 +2269,7 @@ bool Heap::CreateInitialMaps() {
 
     ALLOCATE_VARSIZE_MAP(FIXED_ARRAY_TYPE, scope_info)
     ALLOCATE_VARSIZE_MAP(FIXED_ARRAY_TYPE, module_info)
+    ALLOCATE_VARSIZE_MAP(FIXED_ARRAY_TYPE, type_feedback_vector)
     ALLOCATE_PRIMITIVE_MAP(HEAP_NUMBER_TYPE, HeapNumber::kSize, heap_number,
                            Context::NUMBER_FUNCTION_INDEX)
     ALLOCATE_MAP(MUTABLE_HEAP_NUMBER_TYPE, HeapNumber::kSize,
@@ -2279,6 +2293,9 @@ bool Heap::CreateInitialMaps() {
     ALLOCATE_MAP(ODDBALL_TYPE, Oddball::kSize, optimized_out);
     ALLOCATE_MAP(ODDBALL_TYPE, Oddball::kSize, stale_register);
 
+    ALLOCATE_MAP(JS_PROMISE_CAPABILITY_TYPE, JSPromiseCapability::kSize,
+                 js_promise_capability);
+
     for (unsigned i = 0; i < arraysize(string_type_table); i++) {
       const StringTypeTable& entry = string_type_table[i];
       {
@@ -2344,6 +2361,7 @@ bool Heap::CreateInitialMaps() {
     ALLOCATE_VARSIZE_MAP(FIXED_ARRAY_TYPE, debug_evaluate_context)
     ALLOCATE_VARSIZE_MAP(FIXED_ARRAY_TYPE, block_context)
     ALLOCATE_VARSIZE_MAP(FIXED_ARRAY_TYPE, module_context)
+    ALLOCATE_VARSIZE_MAP(FIXED_ARRAY_TYPE, eval_context)
     ALLOCATE_VARSIZE_MAP(FIXED_ARRAY_TYPE, script_context)
     ALLOCATE_VARSIZE_MAP(FIXED_ARRAY_TYPE, script_context_table)
 
@@ -2523,10 +2541,18 @@ AllocationResult Heap::AllocateTransitionArray(int capacity) {
   return array;
 }
 
-
-void Heap::CreateApiObjects() {
+bool Heap::CreateApiObjects() {
   HandleScope scope(isolate());
   set_message_listeners(*TemplateList::New(isolate(), 2));
+  HeapObject* obj = nullptr;
+  {
+    AllocationResult allocation = AllocateStruct(INTERCEPTOR_INFO_TYPE);
+    if (!allocation.To(&obj)) return false;
+  }
+  InterceptorInfo* info = InterceptorInfo::cast(obj);
+  info->set_flags(0);
+  set_noop_interceptor_info(info);
+  return true;
 }
 
 
@@ -2697,10 +2723,14 @@ void Heap::CreateInitialObjects() {
   }
 
   Handle<NameDictionary> empty_properties_dictionary =
-      NameDictionary::New(isolate(), 0, TENURED);
+      NameDictionary::NewEmpty(isolate(), TENURED);
   empty_properties_dictionary->SetRequiresCopyOnCapacityChange();
   set_empty_properties_dictionary(*empty_properties_dictionary);
 
+  set_public_symbol_table(*empty_properties_dictionary);
+  set_api_symbol_table(*empty_properties_dictionary);
+  set_api_private_symbol_table(*empty_properties_dictionary);
+
   set_number_string_cache(
       *factory->NewFixedArray(kInitialNumberStringCacheSize * 2, TENURED));
 
@@ -2729,9 +2759,6 @@ void Heap::CreateInitialObjects() {
 
   set_undefined_cell(*factory->NewCell(factory->undefined_value()));
 
-  // The symbol registry is initialized lazily.
-  set_symbol_registry(Smi::kZero);
-
   // Microtask queue uses the empty fixed array as a sentinel for "empty".
   // Number of queued microtasks stored in Isolate::pending_microtask_count().
   set_microtask_queue(empty_fixed_array());
@@ -2779,6 +2806,7 @@ void Heap::CreateInitialObjects() {
                                     empty_fixed_array());
     empty_type_feedback_vector->set(TypeFeedbackVector::kInvocationCountIndex,
                                     Smi::kZero);
+    empty_type_feedback_vector->set_map(type_feedback_vector_map());
     set_empty_type_feedback_vector(*empty_type_feedback_vector);
 
     // We use a canonical empty LiteralsArray for all functions that neither
@@ -2817,7 +2845,7 @@ void Heap::CreateInitialObjects() {
   set_script_list(Smi::kZero);
 
   Handle<SeededNumberDictionary> slow_element_dictionary =
-      SeededNumberDictionary::New(isolate(), 0, TENURED);
+      SeededNumberDictionary::NewEmpty(isolate(), TENURED);
   slow_element_dictionary->set_requires_slow_elements();
   set_empty_slow_element_dictionary(*slow_element_dictionary);
 
@@ -2864,7 +2892,12 @@ void Heap::CreateInitialObjects() {
       handle(Smi::FromInt(Isolate::kProtectorValid), isolate()));
   set_array_iterator_protector(*array_iterator_cell);
 
+  cell = factory->NewPropertyCell();
+  cell->set_value(Smi::FromInt(Isolate::kProtectorValid));
+  set_array_buffer_neutering_protector(*cell);
+
   set_serialized_templates(empty_fixed_array());
+  set_serialized_global_proxy_sizes(empty_fixed_array());
 
   set_weak_stack_trace_list(Smi::kZero);
 
@@ -2878,6 +2911,42 @@ void Heap::CreateInitialObjects() {
 
   // Initialize compilation cache.
   isolate_->compilation_cache()->Clear();
+
+  // Finish creating JSPromiseCapabilityMap
+  {
+    // TODO(caitp): This initialization can be removed once PromiseCapability
+    // object is no longer used by builtins implemented in javascript.
+    Handle<Map> map = factory->js_promise_capability_map();
+    map->set_inobject_properties_or_constructor_function_index(3);
+
+    Map::EnsureDescriptorSlack(map, 3);
+
+    PropertyAttributes attrs =
+        static_cast<PropertyAttributes>(READ_ONLY | DONT_DELETE);
+    {  // promise
+      Descriptor d = Descriptor::DataField(factory->promise_string(),
+                                           JSPromiseCapability::kPromiseIndex,
+                                           attrs, Representation::Tagged());
+      map->AppendDescriptor(&d);
+    }
+
+    {  // resolve
+      Descriptor d = Descriptor::DataField(factory->resolve_string(),
+                                           JSPromiseCapability::kResolveIndex,
+                                           attrs, Representation::Tagged());
+      map->AppendDescriptor(&d);
+    }
+
+    {  // reject
+      Descriptor d = Descriptor::DataField(factory->reject_string(),
+                                           JSPromiseCapability::kRejectIndex,
+                                           attrs, Representation::Tagged());
+      map->AppendDescriptor(&d);
+    }
+
+    map->set_is_extensible(false);
+    set_js_promise_capability_map(*map);
+  }
 }
 
 bool Heap::RootCanBeWrittenAfterInitialization(Heap::RootListIndex root_index) {
@@ -2888,7 +2957,6 @@ bool Heap::RootCanBeWrittenAfterInitialization(Heap::RootListIndex root_index) {
     case kInstanceofCacheAnswerRootIndex:
     case kCodeStubsRootIndex:
     case kEmptyScriptRootIndex:
-    case kSymbolRegistryRootIndex:
     case kScriptListRootIndex:
     case kMaterializedObjectsRootIndex:
     case kMicrotaskQueueRootIndex:
@@ -2899,6 +2967,10 @@ bool Heap::RootCanBeWrittenAfterInitialization(Heap::RootListIndex root_index) {
     case kNoScriptSharedFunctionInfosRootIndex:
     case kWeakStackTraceListRootIndex:
     case kSerializedTemplatesRootIndex:
+    case kSerializedGlobalProxySizesRootIndex:
+    case kPublicSymbolTableRootIndex:
+    case kApiSymbolTableRootIndex:
+    case kApiPrivateSymbolTableRootIndex:
 // Smi values
 #define SMI_ENTRY(type, name, Name) case k##Name##RootIndex:
       SMI_ROOT_LIST(SMI_ENTRY)
@@ -2918,6 +2990,18 @@ bool Heap::RootCanBeTreatedAsConstant(RootListIndex root_index) {
          !InNewSpace(root(root_index));
 }
 
+bool Heap::IsUnmodifiedHeapObject(Object** p) {
+  Object* object = *p;
+  if (object->IsSmi()) return false;
+  HeapObject* heap_object = HeapObject::cast(object);
+  if (!object->IsJSObject()) return false;
+  JSObject* js_object = JSObject::cast(object);
+  if (!js_object->WasConstructedFromApiFunction()) return false;
+  JSFunction* constructor =
+      JSFunction::cast(js_object->map()->GetConstructor());
+
+  return constructor->initial_map() == heap_object->map();
+}
 
 int Heap::FullSizeNumberStringCacheLength() {
   // Compute the size of the number string cache based on the max newspace size.
@@ -3042,6 +3126,7 @@ AllocationResult Heap::AllocateBytecodeArray(int length,
   instance->set_parameter_count(parameter_count);
   instance->set_interrupt_budget(interpreter::Interpreter::InterruptBudget());
   instance->set_osr_loop_nesting_level(0);
+  instance->set_bytecode_age(BytecodeArray::kNoAgeBytecodeAge);
   instance->set_constant_pool(constant_pool);
   instance->set_handler_table(empty_fixed_array());
   instance->set_source_position_table(empty_byte_array());
@@ -3050,9 +3135,9 @@ AllocationResult Heap::AllocateBytecodeArray(int length,
   return result;
 }
 
-void Heap::CreateFillerObjectAt(Address addr, int size, ClearRecordedSlots mode,
-                                ClearBlackArea black_area_mode) {
-  if (size == 0) return;
+HeapObject* Heap::CreateFillerObjectAt(Address addr, int size,
+                                       ClearRecordedSlots mode) {
+  if (size == 0) return nullptr;
   HeapObject* filler = HeapObject::FromAddress(addr);
   if (size == kPointerSize) {
     filler->set_map_no_write_barrier(
@@ -3070,20 +3155,11 @@ void Heap::CreateFillerObjectAt(Address addr, int size, ClearRecordedSlots mode,
     ClearRecordedSlotRange(addr, addr + size);
   }
 
-  // If the location where the filler is created is within a black area we have
-  // to clear the mark bits of the filler space.
-  if (black_area_mode == ClearBlackArea::kYes &&
-      incremental_marking()->black_allocation() &&
-      Marking::IsBlackOrGrey(ObjectMarking::MarkBitFrom(addr))) {
-    Page* page = Page::FromAddress(addr);
-    page->markbits()->ClearRange(page->AddressToMarkbitIndex(addr),
-                                 page->AddressToMarkbitIndex(addr + size));
-  }
-
   // At this point, we may be deserializing the heap from a snapshot, and
   // none of the maps have been created yet and are NULL.
   DCHECK((filler->map() == NULL && !deserialization_complete_) ||
          filler->map()->IsMap());
+  return filler;
 }
 
 
@@ -3101,8 +3177,12 @@ bool Heap::CanMoveObjectStart(HeapObject* object) {
   return Page::FromAddress(address)->SweepingDone();
 }
 
+bool Heap::IsImmovable(HeapObject* object) {
+  MemoryChunk* chunk = MemoryChunk::FromAddress(object->address());
+  return chunk->NeverEvacuate() || chunk->owner()->identity() == LO_SPACE;
+}
 
-void Heap::AdjustLiveBytes(HeapObject* object, int by, InvocationMode mode) {
+void Heap::AdjustLiveBytes(HeapObject* object, int by) {
   // As long as the inspected object is black and we are currently not iterating
   // the heap using HeapIterator, we can update the live byte count. We cannot
   // update while using HeapIterator because the iterator is temporarily
@@ -3111,12 +3191,9 @@ void Heap::AdjustLiveBytes(HeapObject* object, int by, InvocationMode mode) {
     lo_space()->AdjustLiveBytes(by);
   } else if (!in_heap_iterator() &&
              !mark_compact_collector()->sweeping_in_progress() &&
-             Marking::IsBlack(ObjectMarking::MarkBitFrom(object->address()))) {
-    if (mode == SEQUENTIAL_TO_SWEEPER) {
-      MemoryChunk::IncrementLiveBytesFromGC(object, by);
-    } else {
-      MemoryChunk::IncrementLiveBytesFromMutator(object, by);
-    }
+             Marking::IsBlack(ObjectMarking::MarkBitFrom(object))) {
+    DCHECK(MemoryChunk::FromAddress(object->address())->SweepingDone());
+    MemoryChunk::IncrementLiveBytes(object, by);
   }
 }
 
@@ -3150,14 +3227,27 @@ FixedArrayBase* Heap::LeftTrimFixedArray(FixedArrayBase* object,
   // Transfer the mark bits to their new location if the object is not within
   // a black area.
   if (!incremental_marking()->black_allocation() ||
-      !Marking::IsBlack(ObjectMarking::MarkBitFrom(new_start))) {
-    IncrementalMarking::TransferMark(this, old_start, new_start);
+      !Marking::IsBlack(
+          ObjectMarking::MarkBitFrom(HeapObject::FromAddress(new_start)))) {
+    IncrementalMarking::TransferMark(this, object,
+                                     HeapObject::FromAddress(new_start));
   }
 
   // Technically in new space this write might be omitted (except for
   // debug mode which iterates through the heap), but to play safer
   // we still do it.
   CreateFillerObjectAt(old_start, bytes_to_trim, ClearRecordedSlots::kYes);
+
+  // Clear the mark bits of the black area that belongs now to the filler.
+  // This is an optimization. The sweeper will release black fillers anyway.
+  if (incremental_marking()->black_allocation() &&
+      Marking::IsBlackOrGrey(ObjectMarking::MarkBitFrom(object))) {
+    Page* page = Page::FromAddress(old_start);
+    page->markbits()->ClearRange(
+        page->AddressToMarkbitIndex(old_start),
+        page->AddressToMarkbitIndex(old_start + bytes_to_trim));
+  }
+
   // Initialize header of the trimmed array. Since left trimming is only
   // performed on pages which are not concurrently swept creating a filler
   // object does not require synchronization.
@@ -3171,7 +3261,7 @@ FixedArrayBase* Heap::LeftTrimFixedArray(FixedArrayBase* object,
       FixedArrayBase::cast(HeapObject::FromAddress(new_start));
 
   // Maintain consistency of live bytes during incremental marking
-  AdjustLiveBytes(new_object, -bytes_to_trim, Heap::CONCURRENT_TO_SWEEPER);
+  AdjustLiveBytes(new_object, -bytes_to_trim);
 
   // Remove recorded slots for the new map and length offset.
   ClearRecordedSlot(new_object, HeapObject::RawField(new_object, 0));
@@ -3183,15 +3273,6 @@ FixedArrayBase* Heap::LeftTrimFixedArray(FixedArrayBase* object,
   return new_object;
 }
 
-
-// Force instantiation of templatized method.
-template void Heap::RightTrimFixedArray<Heap::SEQUENTIAL_TO_SWEEPER>(
-    FixedArrayBase*, int);
-template void Heap::RightTrimFixedArray<Heap::CONCURRENT_TO_SWEEPER>(
-    FixedArrayBase*, int);
-
-
-template<Heap::InvocationMode mode>
 void Heap::RightTrimFixedArray(FixedArrayBase* object, int elements_to_trim) {
   const int len = object->length();
   DCHECK_LE(elements_to_trim, len);
@@ -3235,7 +3316,18 @@ void Heap::RightTrimFixedArray(FixedArrayBase* object, int elements_to_trim) {
   // TODO(hpayer): We should shrink the large object page if the size
   // of the object changed significantly.
   if (!lo_space()->Contains(object)) {
-    CreateFillerObjectAt(new_end, bytes_to_trim, ClearRecordedSlots::kYes);
+    HeapObject* filler =
+        CreateFillerObjectAt(new_end, bytes_to_trim, ClearRecordedSlots::kYes);
+    DCHECK_NOT_NULL(filler);
+    // Clear the mark bits of the black area that belongs now to the filler.
+    // This is an optimization. The sweeper will release black fillers anyway.
+    if (incremental_marking()->black_allocation() &&
+        Marking::IsBlackOrGrey(ObjectMarking::MarkBitFrom(filler))) {
+      Page* page = Page::FromAddress(new_end);
+      page->markbits()->ClearRange(
+          page->AddressToMarkbitIndex(new_end),
+          page->AddressToMarkbitIndex(new_end + bytes_to_trim));
+    }
   }
 
   // Initialize header of the trimmed array. We are storing the new length
@@ -3244,7 +3336,7 @@ void Heap::RightTrimFixedArray(FixedArrayBase* object, int elements_to_trim) {
   object->synchronized_set_length(len - elements_to_trim);
 
   // Maintain consistency of live bytes during incremental marking
-  AdjustLiveBytes(object, -bytes_to_trim, mode);
+  AdjustLiveBytes(object, -bytes_to_trim);
 
   // Notify the heap profiler of change in object layout. The array may not be
   // moved during GC, and size has to be adjusted nevertheless.
@@ -3331,18 +3423,24 @@ AllocationResult Heap::AllocateCode(int object_size, bool immovable) {
   if (!allocation.To(&result)) return allocation;
   if (immovable) {
     Address address = result->address();
+    MemoryChunk* chunk = MemoryChunk::FromAddress(address);
     // Code objects which should stay at a fixed address are allocated either
     // in the first page of code space (objects on the first page of each space
-    // are never moved) or in large object space.
-    if (!code_space_->FirstPage()->Contains(address) &&
-        MemoryChunk::FromAddress(address)->owner()->identity() != LO_SPACE) {
-      // Discard the first code allocation, which was on a page where it could
-      // be moved.
-      CreateFillerObjectAt(result->address(), object_size,
-                           ClearRecordedSlots::kNo);
-      allocation = lo_space_->AllocateRaw(object_size, EXECUTABLE);
-      if (!allocation.To(&result)) return allocation;
-      OnAllocationEvent(result, object_size);
+    // are never moved), in large object space, or (during snapshot creation)
+    // the containing page is marked as immovable.
+    if (!Heap::IsImmovable(result) &&
+        !code_space_->FirstPage()->Contains(address)) {
+      if (isolate()->serializer_enabled()) {
+        chunk->MarkNeverEvacuate();
+      } else {
+        // Discard the first code allocation, which was on a page where it could
+        // be moved.
+        CreateFillerObjectAt(result->address(), object_size,
+                             ClearRecordedSlots::kNo);
+        allocation = lo_space_->AllocateRaw(object_size, EXECUTABLE);
+        if (!allocation.To(&result)) return allocation;
+        OnAllocationEvent(result, object_size);
+      }
     }
   }
 
@@ -3405,6 +3503,7 @@ AllocationResult Heap::CopyBytecodeArray(BytecodeArray* bytecode_array) {
   copy->set_source_position_table(bytecode_array->source_position_table());
   copy->set_interrupt_budget(bytecode_array->interrupt_budget());
   copy->set_osr_loop_nesting_level(bytecode_array->osr_loop_nesting_level());
+  copy->set_bytecode_age(bytecode_array->bytecode_age());
   bytecode_array->CopyBytecodesTo(copy);
   return copy;
 }
@@ -4045,9 +4144,7 @@ void Heap::MakeHeapIterable() {
     CollectAllGarbage(kMakeHeapIterableMask,
                       GarbageCollectionReason::kMakeHeapIterable);
   }
-  if (mark_compact_collector()->sweeping_in_progress()) {
-    mark_compact_collector()->EnsureSweepingCompleted();
-  }
+  mark_compact_collector()->EnsureSweepingCompleted();
   DCHECK(IsHeapIterable());
 }
 
@@ -4169,21 +4266,18 @@ void Heap::ReduceNewSpaceSize() {
   }
 }
 
-bool Heap::MarkingDequesAreEmpty() {
-  return mark_compact_collector()->marking_deque()->IsEmpty() &&
-         (!UsingEmbedderHeapTracer() ||
-          (wrappers_to_trace() == 0 &&
-           embedder_heap_tracer()->NumberOfWrappersToTrace() == 0));
-}
-
 void Heap::FinalizeIncrementalMarkingIfComplete(
     GarbageCollectionReason gc_reason) {
   if (incremental_marking()->IsMarking() &&
       (incremental_marking()->IsReadyToOverApproximateWeakClosure() ||
        (!incremental_marking()->finalize_marking_completed() &&
-        MarkingDequesAreEmpty()))) {
+        mark_compact_collector()->marking_deque()->IsEmpty() &&
+        local_embedder_heap_tracer()->ShouldFinalizeIncrementalMarking()))) {
     FinalizeIncrementalMarking(gc_reason);
-  } else if (incremental_marking()->IsComplete() || MarkingDequesAreEmpty()) {
+  } else if (incremental_marking()->IsComplete() ||
+             (mark_compact_collector()->marking_deque()->IsEmpty() &&
+              local_embedder_heap_tracer()
+                  ->ShouldFinalizeIncrementalMarking())) {
     CollectAllGarbage(current_gc_flags_, gc_reason);
   }
 }
@@ -4195,13 +4289,16 @@ bool Heap::TryFinalizeIdleIncrementalMarking(
       tracer()->FinalIncrementalMarkCompactSpeedInBytesPerMillisecond();
   if (incremental_marking()->IsReadyToOverApproximateWeakClosure() ||
       (!incremental_marking()->finalize_marking_completed() &&
-       MarkingDequesAreEmpty() &&
+       mark_compact_collector()->marking_deque()->IsEmpty() &&
+       local_embedder_heap_tracer()->ShouldFinalizeIncrementalMarking() &&
        gc_idle_time_handler_->ShouldDoOverApproximateWeakClosure(
            idle_time_in_ms))) {
     FinalizeIncrementalMarking(gc_reason);
     return true;
   } else if (incremental_marking()->IsComplete() ||
-             (MarkingDequesAreEmpty() &&
+             (mark_compact_collector()->marking_deque()->IsEmpty() &&
+              local_embedder_heap_tracer()
+                  ->ShouldFinalizeIncrementalMarking() &&
               gc_idle_time_handler_->ShouldDoFinalIncrementalMarkCompact(
                   idle_time_in_ms, size_of_objects,
                   final_incremental_mark_compact_speed_in_bytes_per_ms))) {
@@ -4484,6 +4581,18 @@ void Heap::MemoryPressureNotification(MemoryPressureLevel level,
   }
 }
 
+void Heap::SetOutOfMemoryCallback(v8::debug::OutOfMemoryCallback callback,
+                                  void* data) {
+  out_of_memory_callback_ = callback;
+  out_of_memory_callback_data_ = data;
+}
+
+void Heap::InvokeOutOfMemoryCallback() {
+  if (out_of_memory_callback_) {
+    out_of_memory_callback_(out_of_memory_callback_data_);
+  }
+}
+
 void Heap::CollectCodeStatistics() {
   CodeStatistics::ResetCodeAndMetadataStatistics(isolate());
   // We do not look for code in new space, or map space.  If code
@@ -4698,10 +4807,8 @@ void Heap::Verify() {
   CHECK(HasBeenSetUp());
   HandleScope scope(isolate());
 
-  if (mark_compact_collector()->sweeping_in_progress()) {
-    // We have to wait here for the sweeper threads to have an iterable heap.
-    mark_compact_collector()->EnsureSweepingCompleted();
-  }
+  // We have to wait here for the sweeper threads to have an iterable heap.
+  mark_compact_collector()->EnsureSweepingCompleted();
 
   VerifyPointersVisitor visitor;
   IterateRoots(&visitor, VISIT_ONLY_STRONG);
@@ -4729,8 +4836,8 @@ void Heap::Verify() {
 
 void Heap::ZapFromSpace() {
   if (!new_space_->IsFromSpaceCommitted()) return;
-  for (Page* page : NewSpacePageRange(new_space_->FromSpaceStart(),
-                                      new_space_->FromSpaceEnd())) {
+  for (Page* page :
+       PageRange(new_space_->FromSpaceStart(), new_space_->FromSpaceEnd())) {
     for (Address cursor = page->area_start(), limit = page->area_end();
          cursor < limit; cursor += kPointerSize) {
       Memory::Address_at(cursor) = kFromSpaceZapValue;
@@ -4838,7 +4945,7 @@ void Heap::IterateWeakRoots(ObjectVisitor* v, VisitMode mode) {
   v->Synchronize(VisitorSynchronization::kStringTable);
   if (mode != VISIT_ALL_IN_SCAVENGE && mode != VISIT_ALL_IN_SWEEP_NEWSPACE) {
     // Scavenge collections have special processing for this.
-    external_string_table_.Iterate(v);
+    external_string_table_.IterateAll(v);
   }
   v->Synchronize(VisitorSynchronization::kExternalStringsTable);
 }
@@ -4937,8 +5044,9 @@ void Heap::IterateStrongRoots(ObjectVisitor* v, VisitMode mode) {
     case VISIT_ONLY_STRONG_ROOT_LIST:
       UNREACHABLE();
       break;
-    case VISIT_ONLY_STRONG:
     case VISIT_ONLY_STRONG_FOR_SERIALIZATION:
+      break;
+    case VISIT_ONLY_STRONG:
       isolate_->global_handles()->IterateStrongRoots(v);
       break;
     case VISIT_ALL_IN_SCAVENGE:
@@ -5052,7 +5160,7 @@ bool Heap::ConfigureHeap(size_t max_semi_space_size, size_t max_old_space_size,
 
   // The old generation is paged and needs at least one page for each space.
   int paged_space_count = LAST_PAGED_SPACE - FIRST_PAGED_SPACE + 1;
-  max_old_generation_size_ =
+  initial_max_old_generation_size_ = max_old_generation_size_ =
       Max(static_cast<size_t>(paged_space_count * Page::kPageSize),
           max_old_generation_size_);
 
@@ -5307,6 +5415,13 @@ void Heap::DampenOldGenerationAllocationLimit(size_t old_gen_size,
   }
 }
 
+bool Heap::ShouldOptimizeForLoadTime() {
+  return isolate()->rail_mode() == PERFORMANCE_LOAD &&
+         !AllocationLimitOvershotByLargeMargin() &&
+         MonotonicallyIncreasingTimeInMs() <
+             isolate()->LoadStartTimeMs() + kMaxLoadTimeMs;
+}
+
 // This predicate is called when an old generation space cannot allocated from
 // the free list and is about to add a new page. Returning false will cause a
 // major GC. It happens when the old generation allocation limit is reached and
@@ -5318,6 +5433,8 @@ bool Heap::ShouldExpandOldGenerationOnSlowAllocation() {
 
   if (ShouldOptimizeForMemoryUsage()) return false;
 
+  if (ShouldOptimizeForLoadTime()) return true;
+
   if (incremental_marking()->NeedsFinalization()) {
     return !AllocationLimitOvershotByLargeMargin();
   }
@@ -5352,9 +5469,13 @@ Heap::IncrementalMarkingLimit Heap::IncrementalMarkingLimitReached() {
   if (old_generation_space_available > new_space_->Capacity()) {
     return IncrementalMarkingLimit::kNoLimit;
   }
-  // We are close to the allocation limit.
-  // Choose between the hard and the soft limits.
-  if (old_generation_space_available == 0 || ShouldOptimizeForMemoryUsage()) {
+  if (ShouldOptimizeForMemoryUsage()) {
+    return IncrementalMarkingLimit::kHardLimit;
+  }
+  if (ShouldOptimizeForLoadTime()) {
+    return IncrementalMarkingLimit::kNoLimit;
+  }
+  if (old_generation_space_available == 0) {
     return IncrementalMarkingLimit::kHardLimit;
   }
   return IncrementalMarkingLimit::kSoftLimit;
@@ -5477,6 +5598,7 @@ bool Heap::SetUp() {
     dead_object_stats_ = new ObjectStats(this);
   }
   scavenge_job_ = new ScavengeJob();
+  local_embedder_heap_tracer_ = new LocalEmbedderHeapTracer();
 
   LOG(isolate_, IntPtrTEvent("heap-capacity", Capacity()));
   LOG(isolate_, IntPtrTEvent("heap-available", Available()));
@@ -5496,7 +5618,7 @@ bool Heap::SetUp() {
 bool Heap::CreateHeapObjects() {
   // Create initial maps.
   if (!CreateInitialMaps()) return false;
-  CreateApiObjects();
+  if (!CreateApiObjects()) return false;
 
   // Create initial objects
   CreateInitialObjects();
@@ -5552,16 +5674,7 @@ void Heap::NotifyDeserializationComplete() {
 
 void Heap::SetEmbedderHeapTracer(EmbedderHeapTracer* tracer) {
   DCHECK_EQ(gc_state_, HeapState::NOT_IN_GC);
-  embedder_heap_tracer_ = tracer;
-}
-
-void Heap::RegisterWrappersWithEmbedderHeapTracer() {
-  DCHECK(UsingEmbedderHeapTracer());
-  if (wrappers_to_trace_.empty()) {
-    return;
-  }
-  embedder_heap_tracer()->RegisterV8References(wrappers_to_trace_);
-  wrappers_to_trace_.clear();
+  local_embedder_heap_tracer()->SetRemoteTracer(tracer);
 }
 
 void Heap::TracePossibleWrapper(JSObject* js_object) {
@@ -5571,17 +5684,12 @@ void Heap::TracePossibleWrapper(JSObject* js_object) {
       js_object->GetInternalField(0) != undefined_value() &&
       js_object->GetInternalField(1) != undefined_value()) {
     DCHECK(reinterpret_cast<intptr_t>(js_object->GetInternalField(0)) % 2 == 0);
-    wrappers_to_trace_.push_back(std::pair<void*, void*>(
+    local_embedder_heap_tracer()->AddWrapperToTrace(std::pair<void*, void*>(
         reinterpret_cast<void*>(js_object->GetInternalField(0)),
         reinterpret_cast<void*>(js_object->GetInternalField(1))));
   }
 }
 
-bool Heap::RequiresImmediateWrapperProcessing() {
-  const size_t kTooManyWrappers = 16000;
-  return wrappers_to_trace_.size() > kTooManyWrappers;
-}
-
 void Heap::RegisterExternallyReferencedObject(Object** object) {
   HeapObject* heap_object = HeapObject::cast(*object);
   DCHECK(Contains(heap_object));
@@ -5658,6 +5766,9 @@ void Heap::TearDown() {
     dead_object_stats_ = nullptr;
   }
 
+  delete local_embedder_heap_tracer_;
+  local_embedder_heap_tracer_ = nullptr;
+
   delete scavenge_job_;
   scavenge_job_ = nullptr;
 
@@ -5803,8 +5914,6 @@ void Heap::CompactWeakFixedArrays() {
         WeakFixedArray* array = WeakFixedArray::cast(prototype_users);
         array->Compact<JSObject::PrototypeRegistryCompactionCallback>();
       }
-    } else if (o->IsScript()) {
-      CompactWeakFixedArray(Script::cast(o)->shared_function_infos());
     }
   }
   CompactWeakFixedArray(noscript_shared_function_infos());
@@ -5909,6 +6018,18 @@ void Heap::ClearRecordedSlot(HeapObject* object, Object** slot) {
   }
 }
 
+bool Heap::HasRecordedSlot(HeapObject* object, Object** slot) {
+  if (InNewSpace(object)) {
+    return false;
+  }
+  Address slot_addr = reinterpret_cast<Address>(slot);
+  Page* page = Page::FromAddress(slot_addr);
+  DCHECK_EQ(page->owner()->identity(), OLD_SPACE);
+  store_buffer()->MoveAllEntriesToRememberedSet();
+  return RememberedSet<OLD_TO_NEW>::Contains(page, slot_addr) ||
+         RememberedSet<OLD_TO_OLD>::Contains(page, slot_addr);
+}
+
 void Heap::ClearRecordedSlotRange(Address start, Address end) {
   Page* page = Page::FromAddress(start);
   if (!page->InNewSpace()) {
@@ -6330,7 +6451,7 @@ void Heap::UpdateTotalGCTime(double duration) {
   }
 }
 
-void Heap::ExternalStringTable::CleanUp() {
+void Heap::ExternalStringTable::CleanUpNewSpaceStrings() {
   int last = 0;
   Isolate* isolate = heap_->isolate();
   for (int i = 0; i < new_space_strings_.length(); ++i) {
@@ -6346,8 +6467,12 @@ void Heap::ExternalStringTable::CleanUp() {
   }
   new_space_strings_.Rewind(last);
   new_space_strings_.Trim();
+}
 
-  last = 0;
+void Heap::ExternalStringTable::CleanUpAll() {
+  CleanUpNewSpaceStrings();
+  int last = 0;
+  Isolate* isolate = heap_->isolate();
   for (int i = 0; i < old_space_strings_.length(); ++i) {
     if (old_space_strings_[i]->IsTheHole(isolate)) {
       continue;
diff --git a/deps/v8/src/heap/heap.h b/deps/v8/src/heap/heap.h
index 013cd9a8fe..d8034891fc 100644
--- a/deps/v8/src/heap/heap.h
+++ b/deps/v8/src/heap/heap.h
@@ -14,6 +14,7 @@
 #include "src/allocation.h"
 #include "src/assert-scope.h"
 #include "src/base/atomic-utils.h"
+#include "src/debug/debug-interface.h"
 #include "src/globals.h"
 #include "src/heap-symbols.h"
 #include "src/list.h"
@@ -77,6 +78,7 @@ using v8::MemoryPressureLevel;
   /* Context maps */                                                           \
   V(Map, native_context_map, NativeContextMap)                                 \
   V(Map, module_context_map, ModuleContextMap)                                 \
+  V(Map, eval_context_map, EvalContextMap)                                     \
   V(Map, script_context_map, ScriptContextMap)                                 \
   V(Map, block_context_map, BlockContextMap)                                   \
   V(Map, catch_context_map, CatchContextMap)                                   \
@@ -93,6 +95,7 @@ using v8::MemoryPressureLevel;
   V(Map, external_map, ExternalMap)                                            \
   V(Map, bytecode_array_map, BytecodeArrayMap)                                 \
   V(Map, module_info_map, ModuleInfoMap)                                       \
+  V(Map, type_feedback_vector_map, TypeFeedbackVectorMap)                      \
   /* String maps */                                                            \
   V(Map, native_source_string_map, NativeSourceStringMap)                      \
   V(Map, string_map, StringMap)                                                \
@@ -168,6 +171,8 @@ using v8::MemoryPressureLevel;
   V(PropertyCell, string_length_protector, StringLengthProtector)              \
   V(Cell, fast_array_iteration_protector, FastArrayIterationProtector)         \
   V(Cell, array_iterator_protector, ArrayIteratorProtector)                    \
+  V(PropertyCell, array_buffer_neutering_protector,                            \
+    ArrayBufferNeuteringProtector)                                             \
   /* Special numbers */                                                        \
   V(HeapNumber, nan_value, NanValue)                                           \
   V(HeapNumber, hole_nan_value, HoleNanValue)                                  \
@@ -190,7 +195,9 @@ using v8::MemoryPressureLevel;
     ExperimentalExtraNativesSourceCache)                                       \
   /* Lists and dictionaries */                                                 \
   V(NameDictionary, empty_properties_dictionary, EmptyPropertiesDictionary)    \
-  V(Object, symbol_registry, SymbolRegistry)                                   \
+  V(NameDictionary, public_symbol_table, PublicSymbolTable)                    \
+  V(NameDictionary, api_symbol_table, ApiSymbolTable)                          \
+  V(NameDictionary, api_private_symbol_table, ApiPrivateSymbolTable)           \
   V(Object, script_list, ScriptList)                                           \
   V(UnseededNumberDictionary, code_stubs, CodeStubs)                           \
   V(FixedArray, materialized_objects, MaterializedObjects)                     \
@@ -206,8 +213,10 @@ using v8::MemoryPressureLevel;
   V(Object, weak_stack_trace_list, WeakStackTraceList)                         \
   V(Object, noscript_shared_function_infos, NoScriptSharedFunctionInfos)       \
   V(FixedArray, serialized_templates, SerializedTemplates)                     \
+  V(FixedArray, serialized_global_proxy_sizes, SerializedGlobalProxySizes)     \
   /* Configured values */                                                      \
   V(TemplateList, message_listeners, MessageListeners)                         \
+  V(InterceptorInfo, noop_interceptor_info, NoOpInterceptorInfo)               \
   V(Code, js_entry_code, JsEntryCode)                                          \
   V(Code, js_construct_entry_code, JsConstructEntryCode)                       \
   /* Oddball maps */                                                           \
@@ -221,7 +230,10 @@ using v8::MemoryPressureLevel;
   V(Map, exception_map, ExceptionMap)                                          \
   V(Map, termination_exception_map, TerminationExceptionMap)                   \
   V(Map, optimized_out_map, OptimizedOutMap)                                   \
-  V(Map, stale_register_map, StaleRegisterMap)
+  V(Map, stale_register_map, StaleRegisterMap)                                 \
+  /* per-Isolate map for JSPromiseCapability. */                               \
+  /* TODO(caitp): Make this a Struct */                                        \
+  V(Map, js_promise_capability_map, JSPromiseCapabilityMap)
 
 // Entries in this list are limited to Smis and are not visited during GC.
 #define SMI_ROOT_LIST(V)                                                       \
@@ -297,6 +309,7 @@ using v8::MemoryPressureLevel;
   V(WithContextMap)                     \
   V(BlockContextMap)                    \
   V(ModuleContextMap)                   \
+  V(EvalContextMap)                     \
   V(ScriptContextMap)                   \
   V(UndefinedMap)                       \
   V(TheHoleMap)                         \
@@ -325,6 +338,7 @@ class HeapObjectsFilter;
 class HeapStats;
 class HistogramTimer;
 class Isolate;
+class LocalEmbedderHeapTracer;
 class MemoryAllocator;
 class MemoryReducer;
 class ObjectIterator;
@@ -347,8 +361,6 @@ enum ArrayStorageAllocationMode {
 
 enum class ClearRecordedSlots { kYes, kNo };
 
-enum class ClearBlackArea { kYes, kNo };
-
 enum class GarbageCollectionReason {
   kUnknown = 0,
   kAllocationFailure = 1,
@@ -554,12 +566,6 @@ class Heap {
 
   enum HeapState { NOT_IN_GC, SCAVENGE, MARK_COMPACT };
 
-  // Indicates whether live bytes adjustment is triggered
-  // - from within the GC code before sweeping started (SEQUENTIAL_TO_SWEEPER),
-  // - or from within GC (CONCURRENT_TO_SWEEPER),
-  // - or mutator code (CONCURRENT_TO_SWEEPER).
-  enum InvocationMode { SEQUENTIAL_TO_SWEEPER, CONCURRENT_TO_SWEEPER };
-
   enum UpdateAllocationSiteMode { kGlobal, kCached };
 
   // Taking this lock prevents the GC from entering a phase that relocates
@@ -607,7 +613,7 @@ class Heap {
   static const int kMaxOldSpaceSizeMediumMemoryDevice =
       256 * kPointerMultiplier;
   static const int kMaxOldSpaceSizeHighMemoryDevice = 512 * kPointerMultiplier;
-  static const int kMaxOldSpaceSizeHugeMemoryDevice = 700 * kPointerMultiplier;
+  static const int kMaxOldSpaceSizeHugeMemoryDevice = 1024 * kPointerMultiplier;
 
   // The executable size has to be a multiple of Page::kPageSize.
   // Sizes are in MB.
@@ -673,6 +679,8 @@ class Heap {
   // they are in new space.
   static bool RootCanBeWrittenAfterInitialization(RootListIndex root_index);
 
+  static bool IsUnmodifiedHeapObject(Object** p);
+
   // Zapping is needed for verify heap, and always done in debug builds.
   static inline bool ShouldZapGarbage() {
 #ifdef DEBUG
@@ -739,24 +747,22 @@ class Heap {
   // Initialize a filler object to keep the ability to iterate over the heap
   // when introducing gaps within pages. If slots could have been recorded in
   // the freed area, then pass ClearRecordedSlots::kYes as the mode. Otherwise,
-  // pass ClearRecordedSlots::kNo. If the filler was created in a black area
-  // we may want to clear the corresponding mark bits with ClearBlackArea::kYes,
-  // which is the default. ClearBlackArea::kNo does not clear the mark bits.
-  void CreateFillerObjectAt(
-      Address addr, int size, ClearRecordedSlots mode,
-      ClearBlackArea black_area_mode = ClearBlackArea::kYes);
+  // pass ClearRecordedSlots::kNo.
+  HeapObject* CreateFillerObjectAt(Address addr, int size,
+                                   ClearRecordedSlots mode);
 
   bool CanMoveObjectStart(HeapObject* object);
 
+  static bool IsImmovable(HeapObject* object);
+
   // Maintain consistency of live bytes during incremental marking.
-  void AdjustLiveBytes(HeapObject* object, int by, InvocationMode mode);
+  void AdjustLiveBytes(HeapObject* object, int by);
 
   // Trim the given array from the left. Note that this relocates the object
   // start and hence is only valid if there is only a single reference to it.
   FixedArrayBase* LeftTrimFixedArray(FixedArrayBase* obj, int elements_to_trim);
 
   // Trim the given array from the right.
-  template<Heap::InvocationMode mode>
   void RightTrimFixedArray(FixedArrayBase* obj, int elements_to_trim);
 
   // Converts the given boolean condition to JavaScript boolean value.
@@ -787,6 +793,9 @@ class Heap {
   Object* encountered_weak_collections() const {
     return encountered_weak_collections_;
   }
+  void VisitEncounteredWeakCollections(ObjectVisitor* visitor) {
+    visitor->VisitPointer(&encountered_weak_collections_);
+  }
 
   void set_encountered_weak_cells(Object* weak_cell) {
     encountered_weak_cells_ = weak_cell;
@@ -816,6 +825,7 @@ class Heap {
   void PrintShortHeapStatistics();
 
   inline HeapState gc_state() { return gc_state_; }
+  void SetGCState(HeapState state);
 
   inline bool IsInGCPostProcessing() { return gc_post_processing_depth_ > 0; }
 
@@ -831,7 +841,7 @@ class Heap {
   // Support for the API.
   //
 
-  void CreateApiObjects();
+  bool CreateApiObjects();
 
   // Implements the corresponding V8 API function.
   bool IdleNotification(double deadline_in_seconds);
@@ -841,6 +851,9 @@ class Heap {
                                   bool is_isolate_locked);
   void CheckMemoryPressure();
 
+  void SetOutOfMemoryCallback(v8::debug::OutOfMemoryCallback callback,
+                              void* data);
+
   double MonotonicallyIncreasingTimeInMs();
 
   void RecordStats(HeapStats* stats, bool take_snapshot = false);
@@ -874,6 +887,7 @@ class Heap {
   inline int GetNextTemplateSerialNumber();
 
   inline void SetSerializedTemplates(FixedArray* templates);
+  inline void SetSerializedGlobalProxySizes(FixedArray* sizes);
 
   // For post mortem debugging.
   void RememberUnmappedPage(Address page, bool compacted);
@@ -948,6 +962,30 @@ class Heap {
     return memory_pressure_level_.Value() != MemoryPressureLevel::kNone;
   }
 
+  size_t HeapLimitForDebugging() {
+    const size_t kDebugHeapSizeFactor = 4;
+    size_t max_limit = std::numeric_limits<size_t>::max() / 4;
+    return Min(max_limit,
+               initial_max_old_generation_size_ * kDebugHeapSizeFactor);
+  }
+
+  void IncreaseHeapLimitForDebugging() {
+    max_old_generation_size_ =
+        Max(max_old_generation_size_, HeapLimitForDebugging());
+  }
+
+  void RestoreOriginalHeapLimit() {
+    // Do not set the limit lower than the live size + some slack.
+    size_t min_limit = SizeOfObjects() + SizeOfObjects() / 4;
+    max_old_generation_size_ =
+        Min(max_old_generation_size_,
+            Max(initial_max_old_generation_size_, min_limit));
+  }
+
+  bool IsHeapLimitIncreasedForDebugging() {
+    return max_old_generation_size_ == HeapLimitForDebugging();
+  }
+
   // ===========================================================================
   // Initialization. ===========================================================
   // ===========================================================================
@@ -1172,6 +1210,8 @@ class Heap {
   void ClearRecordedSlot(HeapObject* object, Object** slot);
   void ClearRecordedSlotRange(Address start, Address end);
 
+  bool HasRecordedSlot(HeapObject* object, Object** slot);
+
   // ===========================================================================
   // Incremental marking API. ==================================================
   // ===========================================================================
@@ -1203,24 +1243,13 @@ class Heap {
   // Embedder heap tracer support. =============================================
   // ===========================================================================
 
+  LocalEmbedderHeapTracer* local_embedder_heap_tracer() {
+    return local_embedder_heap_tracer_;
+  }
   void SetEmbedderHeapTracer(EmbedderHeapTracer* tracer);
-
-  bool UsingEmbedderHeapTracer() { return embedder_heap_tracer() != nullptr; }
-
   void TracePossibleWrapper(JSObject* js_object);
-
   void RegisterExternallyReferencedObject(Object** object);
 
-  void RegisterWrappersWithEmbedderHeapTracer();
-
-  // In order to avoid running out of memory we force tracing wrappers if there
-  // are too many of them.
-  bool RequiresImmediateWrapperProcessing();
-
-  EmbedderHeapTracer* embedder_heap_tracer() { return embedder_heap_tracer_; }
-
-  size_t wrappers_to_trace() { return wrappers_to_trace_.size(); }
-
   // ===========================================================================
   // External string table API. ================================================
   // ===========================================================================
@@ -1501,6 +1530,7 @@ class Heap {
       GarbageCollectionReason gc_reason);
 
  private:
+  class SkipStoreBufferScope;
   class PretenuringScope;
 
   // External strings table is a place where all external strings are
@@ -1511,11 +1541,13 @@ class Heap {
     // Registers an external string.
     inline void AddString(String* string);
 
-    inline void Iterate(ObjectVisitor* v);
+    inline void IterateAll(ObjectVisitor* v);
+    inline void IterateNewSpaceStrings(ObjectVisitor* v);
 
-    // Restores internal invariant and gets rid of collected strings.
-    // Must be called after each Iterate() that modified the strings.
-    void CleanUp();
+    // Restores internal invariant and gets rid of collected strings. Must be
+    // called after each Iterate*() that modified the strings.
+    void CleanUpAll();
+    void CleanUpNewSpaceStrings();
 
     // Destroys all allocated memory.
     void TearDown();
@@ -1632,10 +1664,6 @@ class Heap {
     return current_gc_flags_ & kFinalizeIncrementalMarkingMask;
   }
 
-  // Checks whether both, the internal marking deque, and the embedder provided
-  // one are empty. Avoid in fast path as it potentially calls through the API.
-  bool MarkingDequesAreEmpty();
-
   void PreprocessStackTraces();
 
   // Checks whether a global GC is necessary
@@ -1747,6 +1775,8 @@ class Heap {
 
   void CollectGarbageOnMemoryPressure();
 
+  void InvokeOutOfMemoryCallback();
+
   // Attempt to over-approximate the weak closure by marking object groups and
   // implicit references from global handles, but don't atomically complete
   // marking. If we continue to mark incrementally, we might have marked
@@ -1840,6 +1870,14 @@ class Heap {
   // Growing strategy. =========================================================
   // ===========================================================================
 
+  // For some webpages RAIL mode does not switch from PERFORMANCE_LOAD.
+  // This constant limits the effect of load RAIL mode on GC.
+  // The value is arbitrary and chosen as the largest load time observed in
+  // v8 browsing benchmarks.
+  static const int kMaxLoadTimeMs = 7000;
+
+  bool ShouldOptimizeForLoadTime();
+
   // Decrease the allocation limit if the new limit based on the given
   // parameters is lower than the current limit.
   void DampenOldGenerationAllocationLimit(size_t old_gen_size, double gc_speed,
@@ -2128,6 +2166,7 @@ class Heap {
   size_t max_semi_space_size_;
   size_t initial_semispace_size_;
   size_t max_old_generation_size_;
+  size_t initial_max_old_generation_size_;
   size_t initial_old_generation_size_;
   bool old_generation_size_configured_;
   size_t max_executable_size_;
@@ -2148,6 +2187,9 @@ class Heap {
   // and reset by a mark-compact garbage collection.
   base::AtomicValue<MemoryPressureLevel> memory_pressure_level_;
 
+  v8::debug::OutOfMemoryCallback out_of_memory_callback_;
+  void* out_of_memory_callback_data_;
+
   // For keeping track of context disposals.
   int contexts_disposed_;
 
@@ -2338,8 +2380,7 @@ class Heap {
   // The depth of HeapIterator nestings.
   int heap_iterator_depth_;
 
-  EmbedderHeapTracer* embedder_heap_tracer_;
-  std::vector<std::pair<void*, void*>> wrappers_to_trace_;
+  LocalEmbedderHeapTracer* local_embedder_heap_tracer_;
 
   // Used for testing purposes.
   bool force_oom_;
diff --git a/deps/v8/src/heap/incremental-marking.cc b/deps/v8/src/heap/incremental-marking.cc
index 4b1d7712a7..b0418686bf 100644
--- a/deps/v8/src/heap/incremental-marking.cc
+++ b/deps/v8/src/heap/incremental-marking.cc
@@ -32,6 +32,7 @@ IncrementalMarking::IncrementalMarking(Heap* heap)
       was_activated_(false),
       black_allocation_(false),
       finalize_marking_completed_(false),
+      trace_wrappers_toggle_(false),
       request_type_(NONE),
       new_generation_observer_(*this, kAllocatedThreshold),
       old_generation_observer_(*this, kAllocatedThreshold) {}
@@ -129,27 +130,27 @@ static void MarkObjectGreyDoNotEnqueue(Object* obj) {
     HeapObject* heap_obj = HeapObject::cast(obj);
     MarkBit mark_bit = ObjectMarking::MarkBitFrom(HeapObject::cast(obj));
     if (Marking::IsBlack(mark_bit)) {
-      MemoryChunk::IncrementLiveBytesFromGC(heap_obj, -heap_obj->Size());
+      MemoryChunk::IncrementLiveBytes(heap_obj, -heap_obj->Size());
     }
     Marking::AnyToGrey(mark_bit);
   }
 }
 
-void IncrementalMarking::TransferMark(Heap* heap, Address old_start,
-                                      Address new_start) {
+void IncrementalMarking::TransferMark(Heap* heap, HeapObject* from,
+                                      HeapObject* to) {
   // This is only used when resizing an object.
-  DCHECK(MemoryChunk::FromAddress(old_start) ==
-         MemoryChunk::FromAddress(new_start));
+  DCHECK(MemoryChunk::FromAddress(from->address()) ==
+         MemoryChunk::FromAddress(to->address()));
 
   if (!heap->incremental_marking()->IsMarking()) return;
 
   // If the mark doesn't move, we don't check the color of the object.
   // It doesn't matter whether the object is black, since it hasn't changed
   // size, so the adjustment to the live data count will be zero anyway.
-  if (old_start == new_start) return;
+  if (from == to) return;
 
-  MarkBit new_mark_bit = ObjectMarking::MarkBitFrom(new_start);
-  MarkBit old_mark_bit = ObjectMarking::MarkBitFrom(old_start);
+  MarkBit new_mark_bit = ObjectMarking::MarkBitFrom(to);
+  MarkBit old_mark_bit = ObjectMarking::MarkBitFrom(from);
 
 #ifdef DEBUG
   Marking::ObjectColor old_color = Marking::Color(old_mark_bit);
@@ -161,8 +162,7 @@ void IncrementalMarking::TransferMark(Heap* heap, Address old_start,
     return;
   } else if (Marking::IsGrey(old_mark_bit)) {
     Marking::GreyToWhite(old_mark_bit);
-    heap->incremental_marking()->WhiteToGreyAndPush(
-        HeapObject::FromAddress(new_start), new_mark_bit);
+    heap->incremental_marking()->WhiteToGreyAndPush(to, new_mark_bit);
     heap->incremental_marking()->RestartIfNotMarking();
   }
 
@@ -268,7 +268,7 @@ class IncrementalMarkingMarkingVisitor
     MarkBit mark_bit = ObjectMarking::MarkBitFrom(heap_object);
     if (Marking::IsWhite(mark_bit)) {
       Marking::MarkBlack(mark_bit);
-      MemoryChunk::IncrementLiveBytesFromGC(heap_object, heap_object->Size());
+      MemoryChunk::IncrementLiveBytes(heap_object, heap_object->Size());
       return true;
     }
     return false;
@@ -524,10 +524,10 @@ void IncrementalMarking::StartMarking() {
 
   state_ = MARKING;
 
-  if (heap_->UsingEmbedderHeapTracer()) {
+  {
     TRACE_GC(heap()->tracer(),
              GCTracer::Scope::MC_INCREMENTAL_WRAPPER_PROLOGUE);
-    heap_->embedder_heap_tracer()->TracePrologue();
+    heap_->local_embedder_heap_tracer()->TracePrologue();
   }
 
   RecordWriteStub::Mode mode = is_compacting_
@@ -603,7 +603,7 @@ void IncrementalMarking::MarkObjectGroups() {
   TRACE_GC(heap_->tracer(),
            GCTracer::Scope::MC_INCREMENTAL_FINALIZE_OBJECT_GROUPING);
 
-  DCHECK(!heap_->UsingEmbedderHeapTracer());
+  DCHECK(!heap_->local_embedder_heap_tracer()->InUse());
   DCHECK(!finalize_marking_completed_);
   DCHECK(IsMarking());
 
@@ -736,7 +736,8 @@ void IncrementalMarking::FinalizeIncrementally() {
   // 4) Remove weak cell with live values from the list of weak cells, they
   // do not need processing during GC.
   MarkRoots();
-  if (!heap_->UsingEmbedderHeapTracer()) {
+  if (!heap_->local_embedder_heap_tracer()->InUse() &&
+      FLAG_object_grouping_in_incremental_finalization) {
     MarkObjectGroups();
   }
   if (incremental_marking_finalization_rounds_ == 0) {
@@ -750,7 +751,8 @@ void IncrementalMarking::FinalizeIncrementally() {
       abs(old_marking_deque_top -
           heap_->mark_compact_collector()->marking_deque()->top());
 
-  marking_progress += static_cast<int>(heap_->wrappers_to_trace());
+  marking_progress += static_cast<int>(
+      heap_->local_embedder_heap_tracer()->NumberOfCachedWrappersToTrace());
 
   double end = heap_->MonotonicallyIncreasingTimeInMs();
   double delta = end - start;
@@ -806,8 +808,7 @@ void IncrementalMarking::UpdateMarkingDequeAfterScavenge() {
       // them.
       if (map_word.IsForwardingAddress()) {
         HeapObject* dest = map_word.ToForwardingAddress();
-        if (Marking::IsBlack(ObjectMarking::MarkBitFrom(dest->address())))
-          continue;
+        if (Marking::IsBlack(ObjectMarking::MarkBitFrom(dest))) continue;
         array[new_top] = dest;
         new_top = ((new_top + 1) & mask);
         DCHECK(new_top != marking_deque->bottom());
@@ -864,7 +865,7 @@ void IncrementalMarking::MarkBlack(HeapObject* obj, int size) {
   MarkBit mark_bit = ObjectMarking::MarkBitFrom(obj);
   if (Marking::IsBlack(mark_bit)) return;
   Marking::GreyToBlack(mark_bit);
-  MemoryChunk::IncrementLiveBytesFromGC(obj, size);
+  MemoryChunk::IncrementLiveBytes(obj, size);
 }
 
 intptr_t IncrementalMarking::ProcessMarkingDeque(
@@ -890,6 +891,11 @@ intptr_t IncrementalMarking::ProcessMarkingDeque(
     VisitObject(map, obj, size);
     bytes_processed += size - unscanned_bytes_of_large_object_;
   }
+  // Report all found wrappers to the embedder. This is necessary as the
+  // embedder could potentially invalidate wrappers as soon as V8 is done
+  // with its incremental marking processing. Any cached wrappers could
+  // result in broken pointers at this point.
+  heap_->local_embedder_heap_tracer()->RegisterWrappersWithRemoteTracer();
   return bytes_processed;
 }
 
@@ -933,7 +939,7 @@ void IncrementalMarking::Hurry() {
       MarkBit mark_bit = ObjectMarking::MarkBitFrom(cache);
       if (Marking::IsGrey(mark_bit)) {
         Marking::GreyToBlack(mark_bit);
-        MemoryChunk::IncrementLiveBytesFromGC(cache, cache->Size());
+        MemoryChunk::IncrementLiveBytes(cache, cache->Size());
       }
     }
     context = Context::cast(context)->next_context_link();
@@ -1026,15 +1032,40 @@ void IncrementalMarking::Epilogue() {
 double IncrementalMarking::AdvanceIncrementalMarking(
     double deadline_in_ms, CompletionAction completion_action,
     ForceCompletionAction force_completion, StepOrigin step_origin) {
+  HistogramTimerScope incremental_marking_scope(
+      heap_->isolate()->counters()->gc_incremental_marking());
+  TRACE_EVENT0("v8", "V8.GCIncrementalMarking");
+  TRACE_GC(heap_->tracer(), GCTracer::Scope::MC_INCREMENTAL);
   DCHECK(!IsStopped());
+  DCHECK_EQ(
+      0, heap_->local_embedder_heap_tracer()->NumberOfCachedWrappersToTrace());
 
   double remaining_time_in_ms = 0.0;
   intptr_t step_size_in_bytes = GCIdleTimeHandler::EstimateMarkingStepSize(
       kStepSizeInMs,
       heap()->tracer()->IncrementalMarkingSpeedInBytesPerMillisecond());
 
+  const bool incremental_wrapper_tracing =
+      state_ == MARKING && FLAG_incremental_marking_wrappers &&
+      heap_->local_embedder_heap_tracer()->InUse();
   do {
-    Step(step_size_in_bytes, completion_action, force_completion, step_origin);
+    if (incremental_wrapper_tracing && trace_wrappers_toggle_) {
+      TRACE_GC(heap()->tracer(),
+               GCTracer::Scope::MC_INCREMENTAL_WRAPPER_TRACING);
+      const double wrapper_deadline =
+          heap_->MonotonicallyIncreasingTimeInMs() + kStepSizeInMs;
+      if (!heap_->local_embedder_heap_tracer()
+               ->ShouldFinalizeIncrementalMarking()) {
+        heap_->local_embedder_heap_tracer()->Trace(
+            wrapper_deadline, EmbedderHeapTracer::AdvanceTracingActions(
+                                  EmbedderHeapTracer::ForceCompletionAction::
+                                      DO_NOT_FORCE_COMPLETION));
+      }
+    } else {
+      Step(step_size_in_bytes, completion_action, force_completion,
+           step_origin);
+    }
+    trace_wrappers_toggle_ = !trace_wrappers_toggle_;
     remaining_time_in_ms =
         deadline_in_ms - heap()->MonotonicallyIncreasingTimeInMs();
   } while (remaining_time_in_ms >= kStepSizeInMs && !IsComplete() &&
@@ -1109,6 +1140,10 @@ void IncrementalMarking::AdvanceIncrementalMarkingOnAllocation() {
       bytes_marked_ahead_of_schedule_ -= bytes_to_process;
       bytes_processed = bytes_to_process;
     } else {
+      HistogramTimerScope incremental_marking_scope(
+          heap_->isolate()->counters()->gc_incremental_marking());
+      TRACE_EVENT0("v8", "V8.GCIncrementalMarking");
+      TRACE_GC(heap_->tracer(), GCTracer::Scope::MC_INCREMENTAL);
       bytes_processed = Step(bytes_to_process, GC_VIA_STACK_GUARD,
                              FORCE_COMPLETION, StepOrigin::kV8);
     }
@@ -1120,10 +1155,6 @@ size_t IncrementalMarking::Step(size_t bytes_to_process,
                                 CompletionAction action,
                                 ForceCompletionAction completion,
                                 StepOrigin step_origin) {
-  HistogramTimerScope incremental_marking_scope(
-      heap_->isolate()->counters()->gc_incremental_marking());
-  TRACE_EVENT0("v8", "V8.GCIncrementalMarking");
-  TRACE_GC(heap_->tracer(), GCTracer::Scope::MC_INCREMENTAL);
   double start = heap_->MonotonicallyIncreasingTimeInMs();
 
   if (state_ == SWEEPING) {
@@ -1133,41 +1164,26 @@ size_t IncrementalMarking::Step(size_t bytes_to_process,
 
   size_t bytes_processed = 0;
   if (state_ == MARKING) {
-    const bool incremental_wrapper_tracing =
-        FLAG_incremental_marking_wrappers && heap_->UsingEmbedderHeapTracer();
-    const bool process_wrappers =
-        incremental_wrapper_tracing &&
-        (heap_->RequiresImmediateWrapperProcessing() ||
-         heap_->mark_compact_collector()->marking_deque()->IsEmpty());
-    bool wrapper_work_left = incremental_wrapper_tracing;
-    if (!process_wrappers) {
-      bytes_processed = ProcessMarkingDeque(bytes_to_process);
-      if (step_origin == StepOrigin::kTask) {
-        bytes_marked_ahead_of_schedule_ += bytes_processed;
-      }
-    } else {
-      const double wrapper_deadline =
-          heap_->MonotonicallyIncreasingTimeInMs() + kStepSizeInMs;
-      TRACE_GC(heap()->tracer(),
-               GCTracer::Scope::MC_INCREMENTAL_WRAPPER_TRACING);
-      heap_->RegisterWrappersWithEmbedderHeapTracer();
-      wrapper_work_left = heap_->embedder_heap_tracer()->AdvanceTracing(
-          wrapper_deadline, EmbedderHeapTracer::AdvanceTracingActions(
-                                EmbedderHeapTracer::ForceCompletionAction::
-                                    DO_NOT_FORCE_COMPLETION));
+    bytes_processed = ProcessMarkingDeque(bytes_to_process);
+    if (step_origin == StepOrigin::kTask) {
+      bytes_marked_ahead_of_schedule_ += bytes_processed;
     }
 
-    if (heap_->mark_compact_collector()->marking_deque()->IsEmpty() &&
-        !wrapper_work_left) {
-      if (completion == FORCE_COMPLETION ||
-          IsIdleMarkingDelayCounterLimitReached()) {
-        if (!finalize_marking_completed_) {
-          FinalizeMarking(action);
+    if (heap_->mark_compact_collector()->marking_deque()->IsEmpty()) {
+      if (heap_->local_embedder_heap_tracer()
+              ->ShouldFinalizeIncrementalMarking()) {
+        if (completion == FORCE_COMPLETION ||
+            IsIdleMarkingDelayCounterLimitReached()) {
+          if (!finalize_marking_completed_) {
+            FinalizeMarking(action);
+          } else {
+            MarkingComplete(action);
+          }
         } else {
-          MarkingComplete(action);
+          IncrementIdleMarkingDelayCounter();
         }
       } else {
-        IncrementIdleMarkingDelayCounter();
+        heap_->local_embedder_heap_tracer()->NotifyV8MarkingDequeWasEmpty();
       }
     }
   }
diff --git a/deps/v8/src/heap/incremental-marking.h b/deps/v8/src/heap/incremental-marking.h
index 7ce0ae2379..5464f129a7 100644
--- a/deps/v8/src/heap/incremental-marking.h
+++ b/deps/v8/src/heap/incremental-marking.h
@@ -22,7 +22,7 @@ class PagedSpace;
 
 enum class StepOrigin { kV8, kTask };
 
-class IncrementalMarking {
+class V8_EXPORT_PRIVATE IncrementalMarking {
  public:
   enum State { STOPPED, SWEEPING, MARKING, COMPLETE };
 
@@ -151,8 +151,7 @@ class IncrementalMarking {
   INLINE(void RecordWriteOfCodeEntry(JSFunction* host, Object** slot,
                                      Code* value));
 
-  V8_EXPORT_PRIVATE void RecordWriteSlow(HeapObject* obj, Object** slot,
-                                         Object* value);
+  void RecordWriteSlow(HeapObject* obj, Object** slot, Object* value);
   void RecordWriteIntoCodeSlow(Code* host, RelocInfo* rinfo, Object* value);
   void RecordWriteOfCodeEntrySlow(JSFunction* host, Object** slot, Code* value);
   void RecordCodeTargetPatch(Code* host, Address pc, HeapObject* value);
@@ -184,7 +183,7 @@ class IncrementalMarking {
 
   static void MarkBlack(HeapObject* object, int size);
 
-  static void TransferMark(Heap* heap, Address old_start, Address new_start);
+  static void TransferMark(Heap* heap, HeapObject* from, HeapObject* to);
 
   // Returns true if the color transfer requires live bytes updating.
   INLINE(static bool TransferColor(HeapObject* from, HeapObject* to,
@@ -298,6 +297,7 @@ class IncrementalMarking {
   bool was_activated_;
   bool black_allocation_;
   bool finalize_marking_completed_;
+  bool trace_wrappers_toggle_;
 
   GCRequestType request_type_;
 
diff --git a/deps/v8/src/heap/mark-compact-inl.h b/deps/v8/src/heap/mark-compact-inl.h
index 784a76f8bd..1973753b0c 100644
--- a/deps/v8/src/heap/mark-compact-inl.h
+++ b/deps/v8/src/heap/mark-compact-inl.h
@@ -15,7 +15,7 @@ namespace internal {
 void MarkCompactCollector::PushBlack(HeapObject* obj) {
   DCHECK(Marking::IsBlack(ObjectMarking::MarkBitFrom(obj)));
   if (marking_deque()->Push(obj)) {
-    MemoryChunk::IncrementLiveBytesFromGC(obj, obj->Size());
+    MemoryChunk::IncrementLiveBytes(obj, obj->Size());
   } else {
     MarkBit mark_bit = ObjectMarking::MarkBitFrom(obj);
     Marking::BlackToGrey(mark_bit);
@@ -26,7 +26,7 @@ void MarkCompactCollector::PushBlack(HeapObject* obj) {
 void MarkCompactCollector::UnshiftBlack(HeapObject* obj) {
   DCHECK(Marking::IsBlack(ObjectMarking::MarkBitFrom(obj)));
   if (!marking_deque()->Unshift(obj)) {
-    MemoryChunk::IncrementLiveBytesFromGC(obj, -obj->Size());
+    MemoryChunk::IncrementLiveBytes(obj, -obj->Size());
     MarkBit mark_bit = ObjectMarking::MarkBitFrom(obj);
     Marking::BlackToGrey(mark_bit);
   }
@@ -47,7 +47,7 @@ void MarkCompactCollector::SetMark(HeapObject* obj, MarkBit mark_bit) {
   DCHECK(Marking::IsWhite(mark_bit));
   DCHECK(ObjectMarking::MarkBitFrom(obj) == mark_bit);
   Marking::WhiteToBlack(mark_bit);
-  MemoryChunk::IncrementLiveBytesFromGC(obj, obj->Size());
+  MemoryChunk::IncrementLiveBytes(obj, obj->Size());
 }
 
 
@@ -195,12 +195,13 @@ HeapObject* LiveObjectIterator<T>::Next() {
           object = black_object;
         }
       } else if ((T == kGreyObjects || T == kAllLiveObjects)) {
+        map = base::NoBarrierAtomicValue<Map*>::FromAddress(addr)->Value();
         object = HeapObject::FromAddress(addr);
       }
 
       // We found a live object.
       if (object != nullptr) {
-        if (map != nullptr && map == heap()->one_pointer_filler_map()) {
+        if (map == heap()->one_pointer_filler_map()) {
           // Black areas together with slack tracking may result in black one
           // word filler objects. We filter these objects out in the iterator.
           object = nullptr;
diff --git a/deps/v8/src/heap/mark-compact.cc b/deps/v8/src/heap/mark-compact.cc
index 88e6983035..c931f520b7 100644
--- a/deps/v8/src/heap/mark-compact.cc
+++ b/deps/v8/src/heap/mark-compact.cc
@@ -53,7 +53,6 @@ MarkCompactCollector::MarkCompactCollector(Heap* heap)
 #ifdef DEBUG
       state_(IDLE),
 #endif
-      marking_parity_(ODD_MARKING_PARITY),
       was_marked_incrementally_(false),
       evacuation_(false),
       compacting_(false),
@@ -105,7 +104,9 @@ static void VerifyMarking(Heap* heap, Address bottom, Address top) {
   Address next_object_must_be_here_or_later = bottom;
   for (Address current = bottom; current < top;) {
     object = HeapObject::FromAddress(current);
-    if (MarkCompactCollector::IsMarked(object)) {
+    // One word fillers at the end of a black area can be grey.
+    if (MarkCompactCollector::IsMarked(object) &&
+        object->map() != heap->one_pointer_filler_map()) {
       CHECK(Marking::IsBlack(ObjectMarking::MarkBitFrom(object)));
       CHECK(current >= next_object_must_be_here_or_later);
       object->Iterate(&visitor);
@@ -133,7 +134,7 @@ static void VerifyMarking(NewSpace* space) {
   // page->area_start() as start of range on all pages.
   CHECK_EQ(space->bottom(), Page::FromAddress(space->bottom())->area_start());
 
-  NewSpacePageRange range(space->bottom(), end);
+  PageRange range(space->bottom(), end);
   for (auto it = range.begin(); it != range.end();) {
     Page* page = *(it++);
     Address limit = it != range.end() ? page->area_end() : end;
@@ -197,7 +198,7 @@ static void VerifyEvacuation(Page* page) {
 
 static void VerifyEvacuation(NewSpace* space) {
   VerifyEvacuationVisitor visitor;
-  NewSpacePageRange range(space->bottom(), space->top());
+  PageRange range(space->bottom(), space->top());
   for (auto it = range.begin(); it != range.end();) {
     Page* page = *(it++);
     Address current = page->area_start();
@@ -322,7 +323,6 @@ void MarkCompactCollector::CollectGarbage() {
   Finish();
 }
 
-
 #ifdef VERIFY_HEAP
 void MarkCompactCollector::VerifyMarkbitsAreClean(PagedSpace* space) {
   for (Page* p : *space) {
@@ -333,7 +333,7 @@ void MarkCompactCollector::VerifyMarkbitsAreClean(PagedSpace* space) {
 
 
 void MarkCompactCollector::VerifyMarkbitsAreClean(NewSpace* space) {
-  for (Page* p : NewSpacePageRange(space->bottom(), space->top())) {
+  for (Page* p : PageRange(space->bottom(), space->top())) {
     CHECK(p->markbits()->IsClean());
     CHECK_EQ(0, p->LiveBytes());
   }
@@ -354,7 +354,6 @@ void MarkCompactCollector::VerifyMarkbitsAreClean() {
   }
 }
 
-
 void MarkCompactCollector::VerifyWeakEmbeddedObjectsInCode() {
   HeapObjectIterator code_iterator(heap()->code_space());
   for (HeapObject* obj = code_iterator.Next(); obj != NULL;
@@ -779,10 +778,8 @@ void MarkCompactCollector::Prepare() {
 
   DCHECK(!FLAG_never_compact || !FLAG_always_compact);
 
-  if (sweeping_in_progress()) {
-    // Instead of waiting we could also abort the sweeper threads here.
-    EnsureSweepingCompleted();
-  }
+  // Instead of waiting we could also abort the sweeper threads here.
+  EnsureSweepingCompleted();
 
   if (heap()->incremental_marking()->IsSweeping()) {
     heap()->incremental_marking()->Stop();
@@ -801,22 +798,14 @@ void MarkCompactCollector::Prepare() {
     AbortWeakCells();
     AbortTransitionArrays();
     AbortCompaction();
-    if (heap_->UsingEmbedderHeapTracer()) {
-      heap_->embedder_heap_tracer()->AbortTracing();
-    }
+    heap_->local_embedder_heap_tracer()->AbortTracing();
     marking_deque()->Clear();
     was_marked_incrementally_ = false;
   }
 
   if (!was_marked_incrementally_) {
-    if (heap_->UsingEmbedderHeapTracer()) {
-      TRACE_GC(heap()->tracer(), GCTracer::Scope::MC_MARK_WRAPPER_PROLOGUE);
-      heap_->embedder_heap_tracer()->TracePrologue();
-    }
-  }
-
-  if (heap_->UsingEmbedderHeapTracer()) {
-    heap_->embedder_heap_tracer()->EnterFinalPause();
+    TRACE_GC(heap()->tracer(), GCTracer::Scope::MC_MARK_WRAPPER_PROLOGUE);
+    heap_->local_embedder_heap_tracer()->TracePrologue();
   }
 
   // Don't start compaction if we are in the middle of incremental
@@ -874,13 +863,6 @@ void MarkCompactCollector::Finish() {
   }
 
   heap_->incremental_marking()->ClearIdleMarkingDelayCounter();
-
-  if (marking_parity_ == EVEN_MARKING_PARITY) {
-    marking_parity_ = ODD_MARKING_PARITY;
-  } else {
-    DCHECK(marking_parity_ == ODD_MARKING_PARITY);
-    marking_parity_ = EVEN_MARKING_PARITY;
-  }
 }
 
 
@@ -914,6 +896,8 @@ void MarkCompactCollector::Finish() {
 
 void CodeFlusher::ProcessJSFunctionCandidates() {
   Code* lazy_compile = isolate_->builtins()->builtin(Builtins::kCompileLazy);
+  Code* interpreter_entry_trampoline =
+      isolate_->builtins()->builtin(Builtins::kInterpreterEntryTrampoline);
   Object* undefined = isolate_->heap()->undefined_value();
 
   JSFunction* candidate = jsfunction_candidates_head_;
@@ -936,8 +920,13 @@ void CodeFlusher::ProcessJSFunctionCandidates() {
       if (!shared->OptimizedCodeMapIsCleared()) {
         shared->ClearOptimizedCodeMap();
       }
-      shared->set_code(lazy_compile);
-      candidate->set_code(lazy_compile);
+      if (shared->HasBytecodeArray()) {
+        shared->set_code(interpreter_entry_trampoline);
+        candidate->set_code(interpreter_entry_trampoline);
+      } else {
+        shared->set_code(lazy_compile);
+        candidate->set_code(lazy_compile);
+      }
     } else {
       DCHECK(Marking::IsBlack(code_mark));
       candidate->set_code(code);
@@ -964,7 +953,8 @@ void CodeFlusher::ProcessJSFunctionCandidates() {
 
 void CodeFlusher::ProcessSharedFunctionInfoCandidates() {
   Code* lazy_compile = isolate_->builtins()->builtin(Builtins::kCompileLazy);
-
+  Code* interpreter_entry_trampoline =
+      isolate_->builtins()->builtin(Builtins::kInterpreterEntryTrampoline);
   SharedFunctionInfo* candidate = shared_function_info_candidates_head_;
   SharedFunctionInfo* next_candidate;
   while (candidate != NULL) {
@@ -983,7 +973,11 @@ void CodeFlusher::ProcessSharedFunctionInfoCandidates() {
       if (!candidate->OptimizedCodeMapIsCleared()) {
         candidate->ClearOptimizedCodeMap();
       }
-      candidate->set_code(lazy_compile);
+      if (candidate->HasBytecodeArray()) {
+        candidate->set_code(interpreter_entry_trampoline);
+      } else {
+        candidate->set_code(lazy_compile);
+      }
     }
 
     Object** code_slot =
@@ -1083,6 +1077,39 @@ void CodeFlusher::IteratePointersToFromSpace(ObjectVisitor* v) {
   }
 }
 
+class StaticYoungGenerationMarkingVisitor
+    : public StaticNewSpaceVisitor<StaticYoungGenerationMarkingVisitor> {
+ public:
+  static void Initialize(Heap* heap) {
+    StaticNewSpaceVisitor<StaticYoungGenerationMarkingVisitor>::Initialize();
+  }
+
+  inline static void VisitPointer(Heap* heap, HeapObject* object, Object** p) {
+    Object* target = *p;
+    if (heap->InNewSpace(target)) {
+      if (MarkRecursively(heap, HeapObject::cast(target))) return;
+      PushOnMarkingDeque(heap, target);
+    }
+  }
+
+ protected:
+  inline static void PushOnMarkingDeque(Heap* heap, Object* obj) {
+    HeapObject* object = HeapObject::cast(obj);
+    MarkBit mark_bit = ObjectMarking::MarkBitFrom(object);
+    heap->mark_compact_collector()->MarkObject(object, mark_bit);
+  }
+
+  inline static bool MarkRecursively(Heap* heap, HeapObject* object) {
+    StackLimitCheck check(heap->isolate());
+    if (check.HasOverflowed()) return false;
+
+    MarkBit mark = ObjectMarking::MarkBitFrom(object);
+    if (Marking::IsBlackOrGrey(mark)) return true;
+    heap->mark_compact_collector()->SetMark(object, mark);
+    IterateBody(object->map(), object);
+    return true;
+  }
+};
 
 class MarkCompactMarkingVisitor
     : public StaticMarkingVisitor<MarkCompactMarkingVisitor> {
@@ -1336,11 +1363,12 @@ void MarkCompactCollector::PrepareForCodeFlushing() {
   heap()->isolate()->compilation_cache()->IterateFunctions(&visitor);
   heap()->isolate()->handle_scope_implementer()->Iterate(&visitor);
 
-  ProcessMarkingDeque();
+  ProcessMarkingDeque<MarkCompactMode::FULL>();
 }
 
 
 // Visitor class for marking heap roots.
+template <MarkCompactMode mode>
 class RootMarkingVisitor : public ObjectVisitor {
  public:
   explicit RootMarkingVisitor(Heap* heap)
@@ -1362,6 +1390,10 @@ class RootMarkingVisitor : public ObjectVisitor {
 
     HeapObject* object = HeapObject::cast(*p);
 
+    if (mode == MarkCompactMode::YOUNG_GENERATION &&
+        !collector_->heap()->InNewSpace(object))
+      return;
+
     MarkBit mark_bit = ObjectMarking::MarkBitFrom(object);
     if (Marking::IsBlackOrGrey(mark_bit)) return;
 
@@ -1369,14 +1401,21 @@ class RootMarkingVisitor : public ObjectVisitor {
     // Mark the object.
     collector_->SetMark(object, mark_bit);
 
-    // Mark the map pointer and body, and push them on the marking stack.
-    MarkBit map_mark = ObjectMarking::MarkBitFrom(map);
-    collector_->MarkObject(map, map_mark);
-    MarkCompactMarkingVisitor::IterateBody(map, object);
+    switch (mode) {
+      case MarkCompactMode::FULL: {
+        // Mark the map pointer and body, and push them on the marking stack.
+        MarkBit map_mark = ObjectMarking::MarkBitFrom(map);
+        collector_->MarkObject(map, map_mark);
+        MarkCompactMarkingVisitor::IterateBody(map, object);
+      } break;
+      case MarkCompactMode::YOUNG_GENERATION:
+        StaticYoungGenerationMarkingVisitor::IterateBody(map, object);
+        break;
+    }
 
     // Mark all the objects reachable from the map and body.  May leave
     // overflowed objects in the heap.
-    collector_->EmptyMarkingDeque();
+    collector_->EmptyMarkingDeque<mode>();
   }
 
   MarkCompactCollector* collector_;
@@ -1921,7 +1960,7 @@ void MarkCompactCollector::DiscoverGreyObjectsInSpace(PagedSpace* space) {
 
 void MarkCompactCollector::DiscoverGreyObjectsInNewSpace() {
   NewSpace* space = heap()->new_space();
-  for (Page* page : NewSpacePageRange(space->bottom(), space->top())) {
+  for (Page* page : PageRange(space->bottom(), space->top())) {
     DiscoverGreyObjectsOnPage(page);
     if (marking_deque()->IsFull()) return;
   }
@@ -1946,8 +1985,8 @@ bool MarkCompactCollector::IsUnmarkedHeapObjectWithHeap(Heap* heap,
   return Marking::IsWhite(mark);
 }
 
-
-void MarkCompactCollector::MarkStringTable(RootMarkingVisitor* visitor) {
+void MarkCompactCollector::MarkStringTable(
+    RootMarkingVisitor<MarkCompactMode::FULL>* visitor) {
   StringTable* string_table = heap()->string_table();
   // Mark the string table itself.
   MarkBit string_table_mark = ObjectMarking::MarkBitFrom(string_table);
@@ -1957,7 +1996,7 @@ void MarkCompactCollector::MarkStringTable(RootMarkingVisitor* visitor) {
   }
   // Explicitly mark the prefix.
   string_table->IteratePrefix(visitor);
-  ProcessMarkingDeque();
+  ProcessMarkingDeque<MarkCompactMode::FULL>();
 }
 
 
@@ -1966,8 +2005,8 @@ void MarkCompactCollector::MarkAllocationSite(AllocationSite* site) {
   SetMark(site, mark_bit);
 }
 
-
-void MarkCompactCollector::MarkRoots(RootMarkingVisitor* visitor) {
+void MarkCompactCollector::MarkRoots(
+    RootMarkingVisitor<MarkCompactMode::FULL>* visitor) {
   // Mark the heap roots including global variables, stack variables,
   // etc., and all objects reachable from them.
   heap()->IterateStrongRoots(visitor, VISIT_ONLY_STRONG);
@@ -1977,8 +2016,8 @@ void MarkCompactCollector::MarkRoots(RootMarkingVisitor* visitor) {
 
   // There may be overflowed objects in the heap.  Visit them now.
   while (marking_deque()->overflowed()) {
-    RefillMarkingDeque();
-    EmptyMarkingDeque();
+    RefillMarkingDeque<MarkCompactMode::FULL>();
+    EmptyMarkingDeque<MarkCompactMode::FULL>();
   }
 }
 
@@ -2018,6 +2057,7 @@ void MarkCompactCollector::MarkImplicitRefGroups(
 // Before: the marking stack contains zero or more heap object pointers.
 // After: the marking stack is empty, and all objects reachable from the
 // marking stack have been marked, or are overflowed in the heap.
+template <MarkCompactMode mode>
 void MarkCompactCollector::EmptyMarkingDeque() {
   while (!marking_deque()->IsEmpty()) {
     HeapObject* object = marking_deque()->Pop();
@@ -2028,10 +2068,17 @@ void MarkCompactCollector::EmptyMarkingDeque() {
     DCHECK(!Marking::IsWhite(ObjectMarking::MarkBitFrom(object)));
 
     Map* map = object->map();
-    MarkBit map_mark = ObjectMarking::MarkBitFrom(map);
-    MarkObject(map, map_mark);
-
-    MarkCompactMarkingVisitor::IterateBody(map, object);
+    switch (mode) {
+      case MarkCompactMode::FULL: {
+        MarkBit map_mark = ObjectMarking::MarkBitFrom(map);
+        MarkObject(map, map_mark);
+        MarkCompactMarkingVisitor::IterateBody(map, object);
+      } break;
+      case MarkCompactMode::YOUNG_GENERATION: {
+        DCHECK(Marking::IsBlack(ObjectMarking::MarkBitFrom(object)));
+        StaticYoungGenerationMarkingVisitor::IterateBody(map, object);
+      } break;
+    }
   }
 }
 
@@ -2041,6 +2088,7 @@ void MarkCompactCollector::EmptyMarkingDeque() {
 // before sweeping completes.  If sweeping completes, there are no remaining
 // overflowed objects in the heap so the overflow flag on the markings stack
 // is cleared.
+template <MarkCompactMode mode>
 void MarkCompactCollector::RefillMarkingDeque() {
   isolate()->CountUsage(v8::Isolate::UseCounterFeature::kMarkDequeOverflow);
   DCHECK(marking_deque()->overflowed());
@@ -2048,18 +2096,17 @@ void MarkCompactCollector::RefillMarkingDeque() {
   DiscoverGreyObjectsInNewSpace();
   if (marking_deque()->IsFull()) return;
 
-  DiscoverGreyObjectsInSpace(heap()->old_space());
-  if (marking_deque()->IsFull()) return;
-
-  DiscoverGreyObjectsInSpace(heap()->code_space());
-  if (marking_deque()->IsFull()) return;
-
-  DiscoverGreyObjectsInSpace(heap()->map_space());
-  if (marking_deque()->IsFull()) return;
-
-  LargeObjectIterator lo_it(heap()->lo_space());
-  DiscoverGreyObjectsWithIterator(&lo_it);
-  if (marking_deque()->IsFull()) return;
+  if (mode == MarkCompactMode::FULL) {
+    DiscoverGreyObjectsInSpace(heap()->old_space());
+    if (marking_deque()->IsFull()) return;
+    DiscoverGreyObjectsInSpace(heap()->code_space());
+    if (marking_deque()->IsFull()) return;
+    DiscoverGreyObjectsInSpace(heap()->map_space());
+    if (marking_deque()->IsFull()) return;
+    LargeObjectIterator lo_it(heap()->lo_space());
+    DiscoverGreyObjectsWithIterator(&lo_it);
+    if (marking_deque()->IsFull()) return;
+  }
 
   marking_deque()->ClearOverflowed();
 }
@@ -2069,12 +2116,14 @@ void MarkCompactCollector::RefillMarkingDeque() {
 // stack.  Before: the marking stack contains zero or more heap object
 // pointers.  After: the marking stack is empty and there are no overflowed
 // objects in the heap.
+template <MarkCompactMode mode>
 void MarkCompactCollector::ProcessMarkingDeque() {
-  EmptyMarkingDeque();
+  EmptyMarkingDeque<mode>();
   while (marking_deque()->overflowed()) {
-    RefillMarkingDeque();
-    EmptyMarkingDeque();
+    RefillMarkingDeque<mode>();
+    EmptyMarkingDeque<mode>();
   }
+  DCHECK(marking_deque()->IsEmpty());
 }
 
 // Mark all objects reachable (transitively) from objects on the marking
@@ -2084,23 +2133,33 @@ void MarkCompactCollector::ProcessEphemeralMarking(
   DCHECK(marking_deque()->IsEmpty() && !marking_deque()->overflowed());
   bool work_to_do = true;
   while (work_to_do) {
-    if (heap_->UsingEmbedderHeapTracer()) {
-      TRACE_GC(heap()->tracer(), GCTracer::Scope::MC_MARK_WRAPPER_TRACING);
-      heap_->RegisterWrappersWithEmbedderHeapTracer();
-      heap_->embedder_heap_tracer()->AdvanceTracing(
-          0, EmbedderHeapTracer::AdvanceTracingActions(
-                 EmbedderHeapTracer::ForceCompletionAction::FORCE_COMPLETION));
-    }
     if (!only_process_harmony_weak_collections) {
-      TRACE_GC(heap()->tracer(), GCTracer::Scope::MC_MARK_OBJECT_GROUPING);
-      isolate()->global_handles()->IterateObjectGroups(
-          visitor, &IsUnmarkedHeapObjectWithHeap);
-      MarkImplicitRefGroups(&MarkCompactMarkingVisitor::MarkObject);
+      if (heap_->local_embedder_heap_tracer()->InUse()) {
+        TRACE_GC(heap()->tracer(), GCTracer::Scope::MC_MARK_WRAPPER_TRACING);
+        heap_->local_embedder_heap_tracer()->RegisterWrappersWithRemoteTracer();
+        heap_->local_embedder_heap_tracer()->Trace(
+            0,
+            EmbedderHeapTracer::AdvanceTracingActions(
+                EmbedderHeapTracer::ForceCompletionAction::FORCE_COMPLETION));
+      } else {
+        TRACE_GC(heap()->tracer(), GCTracer::Scope::MC_MARK_OBJECT_GROUPING);
+        isolate()->global_handles()->IterateObjectGroups(
+            visitor, &IsUnmarkedHeapObjectWithHeap);
+        MarkImplicitRefGroups(&MarkCompactMarkingVisitor::MarkObject);
+      }
+    } else {
+      // TODO(mlippautz): We currently do not trace through blink when
+      // discovering new objects reachable from weak roots (that have been made
+      // strong). This is a limitation of not having a separate handle type
+      // that doesn't require zapping before this phase. See crbug.com/668060.
+      heap_->local_embedder_heap_tracer()->ClearCachedWrappersToTrace();
     }
     ProcessWeakCollections();
     work_to_do = !marking_deque()->IsEmpty();
-    ProcessMarkingDeque();
+    ProcessMarkingDeque<MarkCompactMode::FULL>();
   }
+  CHECK(marking_deque()->IsEmpty());
+  CHECK_EQ(0, heap()->local_embedder_heap_tracer()->NumberOfWrappersToTrace());
 }
 
 void MarkCompactCollector::ProcessTopOptimizedFrame(ObjectVisitor* visitor) {
@@ -2114,7 +2173,7 @@ void MarkCompactCollector::ProcessTopOptimizedFrame(ObjectVisitor* visitor) {
       if (!code->CanDeoptAt(it.frame()->pc())) {
         Code::BodyDescriptor::IterateBody(code, visitor);
       }
-      ProcessMarkingDeque();
+      ProcessMarkingDeque<MarkCompactMode::FULL>();
       return;
     }
   }
@@ -2154,6 +2213,7 @@ void MarkingDeque::StartUsing() {
 
 void MarkingDeque::StopUsing() {
   base::LockGuard<base::Mutex> guard(&mutex_);
+  if (!in_use_) return;
   DCHECK(IsEmpty());
   DCHECK(!overflowed_);
   top_ = bottom_ = mask_ = 0;
@@ -2267,6 +2327,95 @@ void MarkCompactCollector::RecordObjectStats() {
   }
 }
 
+SlotCallbackResult MarkCompactCollector::CheckAndMarkObject(
+    Heap* heap, Address slot_address) {
+  Object* object = *reinterpret_cast<Object**>(slot_address);
+  if (heap->InNewSpace(object)) {
+    // Marking happens before flipping the young generation, so the object
+    // has to be in ToSpace.
+    DCHECK(heap->InToSpace(object));
+    HeapObject* heap_object = reinterpret_cast<HeapObject*>(object);
+    MarkBit mark_bit = ObjectMarking::MarkBitFrom(heap_object);
+    if (Marking::IsBlackOrGrey(mark_bit)) {
+      return KEEP_SLOT;
+    }
+    heap->mark_compact_collector()->SetMark(heap_object, mark_bit);
+    StaticYoungGenerationMarkingVisitor::IterateBody(heap_object->map(),
+                                                     heap_object);
+    return KEEP_SLOT;
+  }
+  return REMOVE_SLOT;
+}
+
+static bool IsUnmarkedObject(Heap* heap, Object** p) {
+  DCHECK_IMPLIES(heap->InNewSpace(*p), heap->InToSpace(*p));
+  return heap->InNewSpace(*p) &&
+         !Marking::IsBlack(ObjectMarking::MarkBitFrom(HeapObject::cast(*p)));
+}
+
+void MarkCompactCollector::MarkLiveObjectsInYoungGeneration() {
+  TRACE_GC(heap()->tracer(), GCTracer::Scope::MINOR_MC_MARK);
+
+  PostponeInterruptsScope postpone(isolate());
+
+  StaticYoungGenerationMarkingVisitor::Initialize(heap());
+  RootMarkingVisitor<MarkCompactMode::YOUNG_GENERATION> root_visitor(heap());
+
+  marking_deque()->StartUsing();
+
+  isolate()->global_handles()->IdentifyWeakUnmodifiedObjects(
+      &Heap::IsUnmodifiedHeapObject);
+
+  {
+    TRACE_GC(heap()->tracer(), GCTracer::Scope::MINOR_MC_MARK_ROOTS);
+    heap()->IterateRoots(&root_visitor, VISIT_ALL_IN_SCAVENGE);
+    ProcessMarkingDeque<MarkCompactMode::YOUNG_GENERATION>();
+  }
+
+  {
+    TRACE_GC(heap()->tracer(),
+             GCTracer::Scope::MINOR_MC_MARK_OLD_TO_NEW_POINTERS);
+    RememberedSet<OLD_TO_NEW>::Iterate(heap(), [this](Address addr) {
+      return CheckAndMarkObject(heap(), addr);
+    });
+    RememberedSet<OLD_TO_NEW>::IterateTyped(
+        heap(), [this](SlotType type, Address host_addr, Address addr) {
+          return UpdateTypedSlotHelper::UpdateTypedSlot(
+              isolate(), type, addr, [this](Object** addr) {
+                return CheckAndMarkObject(heap(),
+                                          reinterpret_cast<Address>(addr));
+              });
+        });
+    ProcessMarkingDeque<MarkCompactMode::YOUNG_GENERATION>();
+  }
+
+  {
+    TRACE_GC(heap()->tracer(), GCTracer::Scope::MINOR_MC_MARK_WEAK);
+    heap()->VisitEncounteredWeakCollections(&root_visitor);
+    ProcessMarkingDeque<MarkCompactMode::YOUNG_GENERATION>();
+  }
+
+  if (is_code_flushing_enabled()) {
+    TRACE_GC(heap()->tracer(),
+             GCTracer::Scope::MINOR_MC_MARK_CODE_FLUSH_CANDIDATES);
+    code_flusher()->IteratePointersToFromSpace(&root_visitor);
+    ProcessMarkingDeque<MarkCompactMode::YOUNG_GENERATION>();
+  }
+
+  {
+    TRACE_GC(heap()->tracer(), GCTracer::Scope::MINOR_MC_MARK_GLOBAL_HANDLES);
+    isolate()->global_handles()->MarkNewSpaceWeakUnmodifiedObjectsPending(
+        &IsUnmarkedObject);
+    isolate()
+        ->global_handles()
+        ->IterateNewSpaceWeakUnmodifiedRoots<GlobalHandles::VISIT_OTHERS>(
+            &root_visitor);
+    ProcessMarkingDeque<MarkCompactMode::YOUNG_GENERATION>();
+  }
+
+  marking_deque()->StopUsing();
+}
+
 void MarkCompactCollector::MarkLiveObjects() {
   TRACE_GC(heap()->tracer(), GCTracer::Scope::MC_MARK);
   // The recursive GC marker detects when it is nearing stack overflow,
@@ -2291,12 +2440,14 @@ void MarkCompactCollector::MarkLiveObjects() {
 
   marking_deque()->StartUsing();
 
+  heap_->local_embedder_heap_tracer()->EnterFinalPause();
+
   {
     TRACE_GC(heap()->tracer(), GCTracer::Scope::MC_MARK_PREPARE_CODE_FLUSH);
     PrepareForCodeFlushing();
   }
 
-  RootMarkingVisitor root_visitor(heap());
+  RootMarkingVisitor<MarkCompactMode::FULL> root_visitor(heap());
 
   {
     TRACE_GC(heap()->tracer(), GCTracer::Scope::MC_MARK_ROOTS);
@@ -2328,7 +2479,7 @@ void MarkCompactCollector::MarkLiveObjects() {
                GCTracer::Scope::MC_MARK_WEAK_CLOSURE_WEAK_HANDLES);
       heap()->isolate()->global_handles()->IdentifyWeakHandles(
           &IsUnmarkedHeapObject);
-      ProcessMarkingDeque();
+      ProcessMarkingDeque<MarkCompactMode::FULL>();
     }
     // Then we mark the objects.
 
@@ -2336,7 +2487,7 @@ void MarkCompactCollector::MarkLiveObjects() {
       TRACE_GC(heap()->tracer(),
                GCTracer::Scope::MC_MARK_WEAK_CLOSURE_WEAK_ROOTS);
       heap()->isolate()->global_handles()->IterateWeakRoots(&root_visitor);
-      ProcessMarkingDeque();
+      ProcessMarkingDeque<MarkCompactMode::FULL>();
     }
 
     // Repeat Harmony weak maps marking to mark unmarked objects reachable from
@@ -2347,9 +2498,9 @@ void MarkCompactCollector::MarkLiveObjects() {
     {
       TRACE_GC(heap()->tracer(), GCTracer::Scope::MC_MARK_WEAK_CLOSURE_HARMONY);
       ProcessEphemeralMarking(&root_visitor, true);
-      if (heap_->UsingEmbedderHeapTracer()) {
+      {
         TRACE_GC(heap()->tracer(), GCTracer::Scope::MC_MARK_WRAPPER_EPILOGUE);
-        heap()->embedder_heap_tracer()->TraceEpilogue();
+        heap()->local_embedder_heap_tracer()->TraceEpilogue();
       }
     }
   }
@@ -2371,8 +2522,8 @@ void MarkCompactCollector::ClearNonLiveReferences() {
     string_table->ElementsRemoved(internalized_visitor.PointersRemoved());
 
     ExternalStringTableCleaner external_visitor(heap(), nullptr);
-    heap()->external_string_table_.Iterate(&external_visitor);
-    heap()->external_string_table_.CleanUp();
+    heap()->external_string_table_.IterateAll(&external_visitor);
+    heap()->external_string_table_.CleanUpAll();
   }
 
   {
@@ -2578,8 +2729,8 @@ bool MarkCompactCollector::CompactTransitionArray(
   // array disappeared during GC.
   int trim = TransitionArray::Capacity(transitions) - transition_index;
   if (trim > 0) {
-    heap_->RightTrimFixedArray<Heap::SEQUENTIAL_TO_SWEEPER>(
-        transitions, trim * TransitionArray::kTransitionSize);
+    heap_->RightTrimFixedArray(transitions,
+                               trim * TransitionArray::kTransitionSize);
     transitions->SetNumberOfTransitions(transition_index);
   }
   return descriptors_owner_died;
@@ -2597,8 +2748,8 @@ void MarkCompactCollector::TrimDescriptorArray(Map* map,
   int number_of_descriptors = descriptors->number_of_descriptors_storage();
   int to_trim = number_of_descriptors - number_of_own_descriptors;
   if (to_trim > 0) {
-    heap_->RightTrimFixedArray<Heap::SEQUENTIAL_TO_SWEEPER>(
-        descriptors, to_trim * DescriptorArray::kDescriptorSize);
+    heap_->RightTrimFixedArray(descriptors,
+                               to_trim * DescriptorArray::kDescriptorSize);
     descriptors->SetNumberOfDescriptors(number_of_own_descriptors);
 
     if (descriptors->HasEnumCache()) TrimEnumCache(map, descriptors);
@@ -2629,13 +2780,11 @@ void MarkCompactCollector::TrimEnumCache(Map* map,
 
   int to_trim = enum_cache->length() - live_enum;
   if (to_trim <= 0) return;
-  heap_->RightTrimFixedArray<Heap::SEQUENTIAL_TO_SWEEPER>(
-      descriptors->GetEnumCache(), to_trim);
+  heap_->RightTrimFixedArray(descriptors->GetEnumCache(), to_trim);
 
   if (!descriptors->HasEnumIndicesCache()) return;
   FixedArray* enum_indices_cache = descriptors->GetEnumIndicesCache();
-  heap_->RightTrimFixedArray<Heap::SEQUENTIAL_TO_SWEEPER>(enum_indices_cache,
-                                                          to_trim);
+  heap_->RightTrimFixedArray(enum_indices_cache, to_trim);
 }
 
 
@@ -2890,7 +3039,7 @@ static String* UpdateReferenceInExternalStringTableEntry(Heap* heap,
 void MarkCompactCollector::EvacuateNewSpacePrologue() {
   NewSpace* new_space = heap()->new_space();
   // Append the list of new space pages to be processed.
-  for (Page* p : NewSpacePageRange(new_space->bottom(), new_space->top())) {
+  for (Page* p : PageRange(new_space->bottom(), new_space->top())) {
     newspace_evacuation_candidates_.Add(p);
   }
   new_space->Flip();
@@ -3676,7 +3825,7 @@ void UpdateToSpacePointersInParallel(Heap* heap, base::Semaphore* semaphore) {
       heap, heap->isolate()->cancelable_task_manager(), semaphore);
   Address space_start = heap->new_space()->bottom();
   Address space_end = heap->new_space()->top();
-  for (Page* page : NewSpacePageRange(space_start, space_end)) {
+  for (Page* page : PageRange(space_start, space_end)) {
     Address start =
         page->Contains(space_start) ? space_start : page->area_start();
     Address end = page->Contains(space_end) ? space_end : page->area_end();
diff --git a/deps/v8/src/heap/mark-compact.h b/deps/v8/src/heap/mark-compact.h
index de182073ea..9952b7953d 100644
--- a/deps/v8/src/heap/mark-compact.h
+++ b/deps/v8/src/heap/mark-compact.h
@@ -17,6 +17,8 @@
 namespace v8 {
 namespace internal {
 
+enum class MarkCompactMode { FULL, YOUNG_GENERATION };
+
 // Callback function, returns whether an object is alive. The heap size
 // of the object is returned in size. It optionally updates the offset
 // to the first live object in the page (only used for old and map objects).
@@ -29,17 +31,15 @@ typedef void (*MarkObjectFunction)(Heap* heap, HeapObject* object);
 class CodeFlusher;
 class MarkCompactCollector;
 class MarkingVisitor;
+template <MarkCompactMode mode>
 class RootMarkingVisitor;
 
 class ObjectMarking : public AllStatic {
  public:
-  INLINE(static MarkBit MarkBitFrom(Address addr)) {
-    MemoryChunk* p = MemoryChunk::FromAddress(addr);
-    return p->markbits()->MarkBitFromIndex(p->AddressToMarkbitIndex(addr));
-  }
-
-  INLINE(static MarkBit MarkBitFrom(HeapObject* obj)) {
-    return MarkBitFrom(reinterpret_cast<Address>(obj));
+  V8_INLINE static MarkBit MarkBitFrom(HeapObject* obj) {
+    const Address address = obj->address();
+    MemoryChunk* p = MemoryChunk::FromAddress(address);
+    return p->markbits()->MarkBitFromIndex(p->AddressToMarkbitIndex(address));
   }
 
   static Marking::ObjectColor Color(HeapObject* obj) {
@@ -416,6 +416,9 @@ class MarkCompactCollector {
 
   static void Initialize();
 
+  static SlotCallbackResult CheckAndMarkObject(Heap* heap,
+                                               Address slot_address);
+
   void SetUp();
 
   void TearDown();
@@ -435,12 +438,6 @@ class MarkCompactCollector {
 
   void AbortCompaction();
 
-#ifdef DEBUG
-  // Checks whether performing mark-compact collection.
-  bool in_use() { return state_ > PREPARE_GC; }
-  bool are_map_pointers_encoded() { return state_ == UPDATE_POINTERS; }
-#endif
-
   // Determine type of object and emit deletion log event.
   static void ReportDeleteIfNeeded(HeapObject* obj, Isolate* isolate);
 
@@ -458,15 +455,6 @@ class MarkCompactCollector {
   CodeFlusher* code_flusher() { return code_flusher_; }
   inline bool is_code_flushing_enabled() const { return code_flusher_ != NULL; }
 
-#ifdef VERIFY_HEAP
-  void VerifyValidStoreAndSlotsBufferEntries();
-  void VerifyMarkbitsAreClean();
-  static void VerifyMarkbitsAreClean(PagedSpace* space);
-  static void VerifyMarkbitsAreClean(NewSpace* space);
-  void VerifyWeakEmbeddedObjectsInCode();
-  void VerifyOmittedMapChecks();
-#endif
-
   INLINE(static bool ShouldSkipEvacuationSlotRecording(Object* host)) {
     return Page::FromAddress(reinterpret_cast<Address>(host))
         ->ShouldSkipEvacuationSlotRecording();
@@ -493,8 +481,6 @@ class MarkCompactCollector {
 
   bool is_compacting() const { return compacting_; }
 
-  MarkingParity marking_parity() { return marking_parity_; }
-
   // Ensures that sweeping is finished.
   //
   // Note: Can only be called safely from main thread.
@@ -525,6 +511,21 @@ class MarkCompactCollector {
 
   Sweeper& sweeper() { return sweeper_; }
 
+#ifdef DEBUG
+  // Checks whether performing mark-compact collection.
+  bool in_use() { return state_ > PREPARE_GC; }
+  bool are_map_pointers_encoded() { return state_ == UPDATE_POINTERS; }
+#endif
+
+#ifdef VERIFY_HEAP
+  void VerifyValidStoreAndSlotsBufferEntries();
+  void VerifyMarkbitsAreClean();
+  static void VerifyMarkbitsAreClean(PagedSpace* space);
+  static void VerifyMarkbitsAreClean(NewSpace* space);
+  void VerifyWeakEmbeddedObjectsInCode();
+  void VerifyOmittedMapChecks();
+#endif
+
  private:
   template <PageEvacuationMode mode>
   class EvacuateNewSpacePageVisitor;
@@ -564,8 +565,10 @@ class MarkCompactCollector {
   friend class MarkCompactMarkingVisitor;
   friend class MarkingVisitor;
   friend class RecordMigratedSlotVisitor;
+  template <MarkCompactMode mode>
   friend class RootMarkingVisitor;
   friend class SharedFunctionInfoMarkingVisitor;
+  friend class StaticYoungGenerationMarkingVisitor;
 
   // Mark code objects that are active on the stack to prevent them
   // from being flushed.
@@ -575,6 +578,8 @@ class MarkCompactCollector {
 
   // Marking operations for objects reachable from roots.
   void MarkLiveObjects();
+  // Mark the young generation.
+  void MarkLiveObjectsInYoungGeneration();
 
   // Pushes a black object onto the marking stack and accounts for live bytes.
   // Note that this assumes live bytes have not yet been counted.
@@ -593,14 +598,15 @@ class MarkCompactCollector {
   INLINE(void SetMark(HeapObject* obj, MarkBit mark_bit));
 
   // Mark the heap roots and all objects reachable from them.
-  void MarkRoots(RootMarkingVisitor* visitor);
+  void MarkRoots(RootMarkingVisitor<MarkCompactMode::FULL>* visitor);
 
   // Mark the string table specially.  References to internalized strings from
   // the string table are weak.
-  void MarkStringTable(RootMarkingVisitor* visitor);
+  void MarkStringTable(RootMarkingVisitor<MarkCompactMode::FULL>* visitor);
 
   // Mark objects reachable (transitively) from objects in the marking stack
   // or overflowed in the heap.
+  template <MarkCompactMode mode>
   void ProcessMarkingDeque();
 
   // Mark objects reachable (transitively) from objects in the marking stack
@@ -624,11 +630,13 @@ class MarkCompactCollector {
   // stack.  This function empties the marking stack, but may leave
   // overflowed objects in the heap, in which case the marking stack's
   // overflow flag will be set.
+  template <MarkCompactMode mode>
   void EmptyMarkingDeque();
 
   // Refill the marking stack with overflowed objects from the heap.  This
   // function either leaves the marking stack full or clears the overflow
   // flag on the marking stack.
+  template <MarkCompactMode mode>
   void RefillMarkingDeque();
 
   // Helper methods for refilling the marking stack by discovering grey objects
@@ -733,8 +741,6 @@ class MarkCompactCollector {
   CollectorState state_;
 #endif
 
-  MarkingParity marking_parity_;
-
   bool was_marked_incrementally_;
 
   bool evacuation_;
diff --git a/deps/v8/src/heap/memory-reducer.cc b/deps/v8/src/heap/memory-reducer.cc
index 2aed4c714a..3645547ef5 100644
--- a/deps/v8/src/heap/memory-reducer.cc
+++ b/deps/v8/src/heap/memory-reducer.cc
@@ -17,6 +17,8 @@ const int MemoryReducer::kLongDelayMs = 8000;
 const int MemoryReducer::kShortDelayMs = 500;
 const int MemoryReducer::kWatchdogDelayMs = 100000;
 const int MemoryReducer::kMaxNumberOfGCs = 3;
+const double MemoryReducer::kCommittedMemoryFactor = 1.1;
+const size_t MemoryReducer::kCommittedMemoryDelta = 10 * MB;
 
 MemoryReducer::TimerTask::TimerTask(MemoryReducer* memory_reducer)
     : CancelableTask(memory_reducer->heap()->isolate()),
@@ -47,6 +49,7 @@ void MemoryReducer::TimerTask::RunInternal() {
   event.can_start_incremental_gc =
       heap->incremental_marking()->IsStopped() &&
       (heap->incremental_marking()->CanBeActivated() || optimize_for_memory);
+  event.committed_memory = heap->CommittedOldGenerationMemory();
   memory_reducer_->NotifyTimer(event);
 }
 
@@ -128,17 +131,30 @@ bool MemoryReducer::WatchdogGC(const State& state, const Event& event) {
 MemoryReducer::State MemoryReducer::Step(const State& state,
                                          const Event& event) {
   if (!FLAG_incremental_marking || !FLAG_memory_reducer) {
-    return State(kDone, 0, 0, state.last_gc_time_ms);
+    return State(kDone, 0, 0, state.last_gc_time_ms, 0);
   }
   switch (state.action) {
     case kDone:
       if (event.type == kTimer) {
         return state;
+      } else if (event.type == kMarkCompact) {
+        if (event.committed_memory <
+            Max(static_cast<size_t>(state.committed_memory_at_last_run *
+                                    kCommittedMemoryFactor),
+                state.committed_memory_at_last_run + kCommittedMemoryDelta)) {
+          return state;
+        } else {
+          return State(kWait, 0, event.time_ms + kLongDelayMs,
+                       event.type == kMarkCompact ? event.time_ms
+                                                  : state.last_gc_time_ms,
+                       0);
+        }
       } else {
-        DCHECK(event.type == kPossibleGarbage || event.type == kMarkCompact);
+        DCHECK_EQ(kPossibleGarbage, event.type);
         return State(
             kWait, 0, event.time_ms + kLongDelayMs,
-            event.type == kMarkCompact ? event.time_ms : state.last_gc_time_ms);
+            event.type == kMarkCompact ? event.time_ms : state.last_gc_time_ms,
+            0);
       }
     case kWait:
       switch (event.type) {
@@ -146,23 +162,24 @@ MemoryReducer::State MemoryReducer::Step(const State& state,
           return state;
         case kTimer:
           if (state.started_gcs >= kMaxNumberOfGCs) {
-            return State(kDone, kMaxNumberOfGCs, 0.0, state.last_gc_time_ms);
+            return State(kDone, kMaxNumberOfGCs, 0.0, state.last_gc_time_ms,
+                         event.committed_memory);
           } else if (event.can_start_incremental_gc &&
                      (event.should_start_incremental_gc ||
                       WatchdogGC(state, event))) {
             if (state.next_gc_start_ms <= event.time_ms) {
               return State(kRun, state.started_gcs + 1, 0.0,
-                           state.last_gc_time_ms);
+                           state.last_gc_time_ms, 0);
             } else {
               return state;
             }
           } else {
             return State(kWait, state.started_gcs, event.time_ms + kLongDelayMs,
-                         state.last_gc_time_ms);
+                         state.last_gc_time_ms, 0);
           }
         case kMarkCompact:
           return State(kWait, state.started_gcs, event.time_ms + kLongDelayMs,
-                       event.time_ms);
+                       event.time_ms, 0);
       }
     case kRun:
       if (event.type != kMarkCompact) {
@@ -171,14 +188,15 @@ MemoryReducer::State MemoryReducer::Step(const State& state,
         if (state.started_gcs < kMaxNumberOfGCs &&
             (event.next_gc_likely_to_collect_more || state.started_gcs == 1)) {
           return State(kWait, state.started_gcs, event.time_ms + kShortDelayMs,
-                       event.time_ms);
+                       event.time_ms, 0);
         } else {
-          return State(kDone, kMaxNumberOfGCs, 0.0, event.time_ms);
+          return State(kDone, kMaxNumberOfGCs, 0.0, event.time_ms,
+                       event.committed_memory);
         }
       }
   }
   UNREACHABLE();
-  return State(kDone, 0, 0, 0.0);  // Make the compiler happy.
+  return State(kDone, 0, 0, 0.0, 0);  // Make the compiler happy.
 }
 
 
@@ -192,7 +210,7 @@ void MemoryReducer::ScheduleTimer(double time_ms, double delay_ms) {
       isolate, timer_task, (delay_ms + kSlackMs) / 1000.0);
 }
 
-void MemoryReducer::TearDown() { state_ = State(kDone, 0, 0, 0.0); }
+void MemoryReducer::TearDown() { state_ = State(kDone, 0, 0, 0.0, 0); }
 
 }  // namespace internal
 }  // namespace v8
diff --git a/deps/v8/src/heap/memory-reducer.h b/deps/v8/src/heap/memory-reducer.h
index 0421987a3c..0f0ad6eaa0 100644
--- a/deps/v8/src/heap/memory-reducer.h
+++ b/deps/v8/src/heap/memory-reducer.h
@@ -86,15 +86,17 @@ class V8_EXPORT_PRIVATE MemoryReducer {
 
   struct State {
     State(Action action, int started_gcs, double next_gc_start_ms,
-          double last_gc_time_ms)
+          double last_gc_time_ms, size_t committed_memory_at_last_run)
         : action(action),
           started_gcs(started_gcs),
           next_gc_start_ms(next_gc_start_ms),
-          last_gc_time_ms(last_gc_time_ms) {}
+          last_gc_time_ms(last_gc_time_ms),
+          committed_memory_at_last_run(committed_memory_at_last_run) {}
     Action action;
     int started_gcs;
     double next_gc_start_ms;
     double last_gc_time_ms;
+    size_t committed_memory_at_last_run;
   };
 
   enum EventType { kTimer, kMarkCompact, kPossibleGarbage };
@@ -102,6 +104,7 @@ class V8_EXPORT_PRIVATE MemoryReducer {
   struct Event {
     EventType type;
     double time_ms;
+    size_t committed_memory;
     bool next_gc_likely_to_collect_more;
     bool should_start_incremental_gc;
     bool can_start_incremental_gc;
@@ -109,7 +112,7 @@ class V8_EXPORT_PRIVATE MemoryReducer {
 
   explicit MemoryReducer(Heap* heap)
       : heap_(heap),
-        state_(kDone, 0, 0.0, 0.0),
+        state_(kDone, 0, 0.0, 0.0, 0),
         js_calls_counter_(0),
         js_calls_sample_time_ms_(0.0) {}
   // Callbacks.
@@ -126,6 +129,12 @@ class V8_EXPORT_PRIVATE MemoryReducer {
   static const int kShortDelayMs;
   static const int kWatchdogDelayMs;
   static const int kMaxNumberOfGCs;
+  // The committed memory has to increase by at least this factor since the
+  // last run in order to trigger a new run after mark-compact.
+  static const double kCommittedMemoryFactor;
+  // The committed memory has to increase by at least this amount since the
+  // last run in order to trigger a new run after mark-compact.
+  static const size_t kCommittedMemoryDelta;
 
   Heap* heap() { return heap_; }
 
diff --git a/deps/v8/src/heap/object-stats.cc b/deps/v8/src/heap/object-stats.cc
index ef5f65734e..9f534a20e4 100644
--- a/deps/v8/src/heap/object-stats.cc
+++ b/deps/v8/src/heap/object-stats.cc
@@ -441,10 +441,8 @@ void ObjectStatsCollector::RecordJSCollectionDetails(JSObject* obj) {
 }
 
 void ObjectStatsCollector::RecordScriptDetails(Script* obj) {
-  Object* infos = WeakFixedArray::cast(obj->shared_function_infos());
-  if (infos->IsWeakFixedArray())
-    RecordFixedArrayHelper(obj, WeakFixedArray::cast(infos),
-                           SHARED_FUNCTION_INFOS_SUB_TYPE, 0);
+  FixedArray* infos = FixedArray::cast(obj->shared_function_infos());
+  RecordFixedArrayHelper(obj, infos, SHARED_FUNCTION_INFOS_SUB_TYPE, 0);
 }
 
 void ObjectStatsCollector::RecordMapDetails(Map* map_obj) {
@@ -546,13 +544,6 @@ void ObjectStatsCollector::RecordSharedFunctionInfoDetails(
   if (!feedback_metadata->is_empty()) {
     RecordFixedArrayHelper(sfi, feedback_metadata,
                            TYPE_FEEDBACK_METADATA_SUB_TYPE, 0);
-    Object* names =
-        feedback_metadata->get(TypeFeedbackMetadata::kNamesTableIndex);
-    if (!names->IsSmi()) {
-      UnseededNumberDictionary* names = UnseededNumberDictionary::cast(
-          feedback_metadata->get(TypeFeedbackMetadata::kNamesTableIndex));
-      RecordHashTableHelper(sfi, names, TYPE_FEEDBACK_METADATA_SUB_TYPE);
-    }
   }
 
   if (!sfi->OptimizedCodeMapIsCleared()) {
diff --git a/deps/v8/src/heap/objects-visiting-inl.h b/deps/v8/src/heap/objects-visiting-inl.h
index f3502568d6..d86406bf5f 100644
--- a/deps/v8/src/heap/objects-visiting-inl.h
+++ b/deps/v8/src/heap/objects-visiting-inl.h
@@ -60,7 +60,6 @@ void StaticNewSpaceVisitor<StaticVisitor>::Initialize() {
                         int>::Visit);
 
   table_.Register(kVisitByteArray, &VisitByteArray);
-  table_.Register(kVisitBytecodeArray, &VisitBytecodeArray);
 
   table_.Register(
       kVisitSharedFunctionInfo,
@@ -103,19 +102,11 @@ void StaticNewSpaceVisitor<StaticVisitor>::Initialize() {
 
   table_.template RegisterSpecializations<StructVisitor, kVisitStruct,
                                           kVisitStructGeneric>();
-}
 
-template <typename StaticVisitor>
-int StaticNewSpaceVisitor<StaticVisitor>::VisitBytecodeArray(
-    Map* map, HeapObject* object) {
-  VisitPointers(
-      map->GetHeap(), object,
-      HeapObject::RawField(object, BytecodeArray::kConstantPoolOffset),
-      HeapObject::RawField(object, BytecodeArray::kFrameSizeOffset));
-  return reinterpret_cast<BytecodeArray*>(object)->BytecodeArraySize();
+  table_.Register(kVisitBytecodeArray, &UnreachableVisitor);
+  table_.Register(kVisitSharedFunctionInfo, &UnreachableVisitor);
 }
 
-
 template <typename StaticVisitor>
 void StaticMarkingVisitor<StaticVisitor>::Initialize() {
   table_.Register(kVisitShortcutCandidate,
@@ -157,10 +148,7 @@ void StaticMarkingVisitor<StaticVisitor>::Initialize() {
 
   table_.Register(kVisitByteArray, &DataObjectVisitor::Visit);
 
-  table_.Register(
-      kVisitBytecodeArray,
-      &FixedBodyVisitor<StaticVisitor, BytecodeArray::MarkingBodyDescriptor,
-                        void>::Visit);
+  table_.Register(kVisitBytecodeArray, &VisitBytecodeArray);
 
   table_.Register(kVisitFreeSpace, &DataObjectVisitor::Visit);
 
@@ -286,7 +274,6 @@ void StaticMarkingVisitor<StaticVisitor>::VisitCodeTarget(Heap* heap,
   StaticVisitor::MarkObject(heap, target);
 }
 
-
 template <typename StaticVisitor>
 void StaticMarkingVisitor<StaticVisitor>::VisitCodeAgeSequence(
     Heap* heap, RelocInfo* rinfo) {
@@ -298,6 +285,13 @@ void StaticMarkingVisitor<StaticVisitor>::VisitCodeAgeSequence(
   StaticVisitor::MarkObject(heap, target);
 }
 
+template <typename StaticVisitor>
+void StaticMarkingVisitor<StaticVisitor>::VisitBytecodeArray(
+    Map* map, HeapObject* object) {
+  FixedBodyVisitor<StaticVisitor, BytecodeArray::MarkingBodyDescriptor,
+                   void>::Visit(map, object);
+  BytecodeArray::cast(object)->MakeOlder();
+}
 
 template <typename StaticVisitor>
 void StaticMarkingVisitor<StaticVisitor>::VisitNativeContext(
@@ -421,7 +415,7 @@ void StaticMarkingVisitor<StaticVisitor>::VisitCode(Map* map,
   Heap* heap = map->GetHeap();
   Code* code = Code::cast(object);
   if (FLAG_age_code && !heap->isolate()->serializer_enabled()) {
-    code->MakeOlder(heap->mark_compact_collector()->marking_parity());
+    code->MakeOlder();
   }
   CodeBodyVisitor::Visit(map, object);
 }
@@ -435,12 +429,6 @@ void StaticMarkingVisitor<StaticVisitor>::VisitSharedFunctionInfo(
   if (shared->ic_age() != heap->global_ic_age()) {
     shared->ResetForNewContext(heap->global_ic_age());
   }
-  if (FLAG_flush_optimized_code_cache) {
-    if (!shared->OptimizedCodeMapIsCleared()) {
-      // Always flush the optimized code map if requested by flag.
-      shared->ClearOptimizedCodeMap();
-    }
-  }
   MarkCompactCollector* collector = heap->mark_compact_collector();
   if (collector->is_code_flushing_enabled()) {
     if (IsFlushable(heap, shared)) {
@@ -600,8 +588,8 @@ bool StaticMarkingVisitor<StaticVisitor>::IsFlushable(
     return false;
   }
 
-  // The function must not be a builtin.
-  if (shared_info->IsBuiltin()) {
+  // The function must be user code.
+  if (!shared_info->IsUserJavaScript()) {
     return false;
   }
 
diff --git a/deps/v8/src/heap/objects-visiting.cc b/deps/v8/src/heap/objects-visiting.cc
index d4aa8b2f00..146aa58675 100644
--- a/deps/v8/src/heap/objects-visiting.cc
+++ b/deps/v8/src/heap/objects-visiting.cc
@@ -107,7 +107,6 @@ StaticVisitorBase::VisitorId StaticVisitorBase::GetVisitorId(
     case JS_ARGUMENTS_TYPE:
     case JS_CONTEXT_EXTENSION_OBJECT_TYPE:
     case JS_GENERATOR_OBJECT_TYPE:
-    case JS_FIXED_ARRAY_ITERATOR_TYPE:
     case JS_MODULE_NAMESPACE_TYPE:
     case JS_VALUE_TYPE:
     case JS_DATE_TYPE:
@@ -159,6 +158,7 @@ StaticVisitorBase::VisitorId StaticVisitorBase::GetVisitorId(
     case JS_FAST_HOLEY_DOUBLE_ARRAY_VALUE_ITERATOR_TYPE:
     case JS_GENERIC_ARRAY_VALUE_ITERATOR_TYPE:
 
+    case JS_PROMISE_CAPABILITY_TYPE:
     case JS_PROMISE_TYPE:
     case JS_BOUND_FUNCTION_TYPE:
       return GetVisitorIdForSize(kVisitJSObject, kVisitJSObjectGeneric,
diff --git a/deps/v8/src/heap/objects-visiting.h b/deps/v8/src/heap/objects-visiting.h
index 633c277eb0..e35e47c3aa 100644
--- a/deps/v8/src/heap/objects-visiting.h
+++ b/deps/v8/src/heap/objects-visiting.h
@@ -6,6 +6,7 @@
 #define V8_OBJECTS_VISITING_H_
 
 #include "src/allocation.h"
+#include "src/heap/embedder-tracing.h"
 #include "src/heap/heap.h"
 #include "src/heap/spaces.h"
 #include "src/layout-descriptor.h"
@@ -267,12 +268,17 @@ class StaticNewSpaceVisitor : public StaticVisitorBase {
   // Although we are using the JSFunction body descriptor which does not
   // visit the code entry, compiler wants it to be accessible.
   // See JSFunction::BodyDescriptorImpl.
-  INLINE(static void VisitCodeEntry(Heap* heap, HeapObject* object,
-                                    Address entry_address)) {
+  inline static void VisitCodeEntry(Heap* heap, HeapObject* object,
+                                    Address entry_address) {
     UNREACHABLE();
   }
 
  private:
+  inline static int UnreachableVisitor(Map* map, HeapObject* object) {
+    UNREACHABLE();
+    return 0;
+  }
+
   INLINE(static int VisitByteArray(Map* map, HeapObject* object)) {
     return reinterpret_cast<ByteArray*>(object)->ByteArraySize();
   }
@@ -300,8 +306,6 @@ class StaticNewSpaceVisitor : public StaticVisitorBase {
     return FreeSpace::cast(object)->size();
   }
 
-  INLINE(static int VisitBytecodeArray(Map* map, HeapObject* object));
-
   class DataObjectVisitor {
    public:
     template <int object_size>
@@ -372,6 +376,7 @@ class StaticMarkingVisitor : public StaticVisitorBase {
  protected:
   INLINE(static void VisitMap(Map* map, HeapObject* object));
   INLINE(static void VisitCode(Map* map, HeapObject* object));
+  INLINE(static void VisitBytecodeArray(Map* map, HeapObject* object));
   INLINE(static void VisitSharedFunctionInfo(Map* map, HeapObject* object));
   INLINE(static void VisitWeakCollection(Map* map, HeapObject* object));
   INLINE(static void VisitJSFunction(Map* map, HeapObject* object));
@@ -420,7 +425,7 @@ class StaticMarkingVisitor : public StaticVisitorBase {
 
    private:
     INLINE(static void TracePossibleWrapper(HeapObject* object)) {
-      if (object->GetHeap()->UsingEmbedderHeapTracer()) {
+      if (object->GetHeap()->local_embedder_heap_tracer()->InUse()) {
         DCHECK(object->IsJSObject());
         object->GetHeap()->TracePossibleWrapper(JSObject::cast(object));
       }
diff --git a/deps/v8/src/heap/remembered-set.h b/deps/v8/src/heap/remembered-set.h
index a625b13dbf..cf17a46821 100644
--- a/deps/v8/src/heap/remembered-set.h
+++ b/deps/v8/src/heap/remembered-set.h
@@ -17,7 +17,7 @@ enum PointerDirection { OLD_TO_OLD, OLD_TO_NEW };
 
 // TODO(ulan): Investigate performance of de-templatizing this class.
 template <PointerDirection direction>
-class RememberedSet {
+class RememberedSet : public AllStatic {
  public:
   // Given a page and a slot in that page, this function adds the slot to the
   // remembered set.
@@ -31,6 +31,19 @@ class RememberedSet {
     slot_set[offset / Page::kPageSize].Insert(offset % Page::kPageSize);
   }
 
+  // Given a page and a slot in that page, this function returns true if
+  // the remembered set contains the slot.
+  static bool Contains(MemoryChunk* chunk, Address slot_addr) {
+    DCHECK(chunk->Contains(slot_addr));
+    SlotSet* slot_set = GetSlotSet(chunk);
+    if (slot_set == nullptr) {
+      return false;
+    }
+    uintptr_t offset = slot_addr - chunk->address();
+    return slot_set[offset / Page::kPageSize].Contains(offset %
+                                                       Page::kPageSize);
+  }
+
   // Given a page and a slot in that page, this function removes the slot from
   // the remembered set.
   // If the slot was never added, then the function does nothing.
diff --git a/deps/v8/src/heap/scavenger.cc b/deps/v8/src/heap/scavenger.cc
index cad0e8af25..f2722e81de 100644
--- a/deps/v8/src/heap/scavenger.cc
+++ b/deps/v8/src/heap/scavenger.cc
@@ -139,7 +139,7 @@ class ScavengingVisitor : public StaticVisitorBase {
 
     if (marks_handling == TRANSFER_MARKS) {
       if (IncrementalMarking::TransferColor(source, target, size)) {
-        MemoryChunk::IncrementLiveBytesFromGC(target, size);
+        MemoryChunk::IncrementLiveBytes(target, size);
       }
     }
   }
diff --git a/deps/v8/src/heap/slot-set.h b/deps/v8/src/heap/slot-set.h
index da61052b8a..7612199c3c 100644
--- a/deps/v8/src/heap/slot-set.h
+++ b/deps/v8/src/heap/slot-set.h
@@ -66,6 +66,18 @@ class SlotSet : public Malloced {
   }
 
   // The slot offset specifies a slot at address page_start_ + slot_offset.
+  // Returns true if the set contains the slot.
+  bool Contains(int slot_offset) {
+    int bucket_index, cell_index, bit_index;
+    SlotToIndices(slot_offset, &bucket_index, &cell_index, &bit_index);
+    base::AtomicValue<uint32_t>* current_bucket = bucket[bucket_index].Value();
+    if (current_bucket == nullptr) {
+      return false;
+    }
+    return (current_bucket[cell_index].Value() & (1u << bit_index)) != 0;
+  }
+
+  // The slot offset specifies a slot at address page_start_ + slot_offset.
   void Remove(int slot_offset) {
     int bucket_index, cell_index, bit_index;
     SlotToIndices(slot_offset, &bucket_index, &cell_index, &bit_index);
diff --git a/deps/v8/src/heap/spaces-inl.h b/deps/v8/src/heap/spaces-inl.h
index f3f9215f3d..2079a80a0b 100644
--- a/deps/v8/src/heap/spaces-inl.h
+++ b/deps/v8/src/heap/spaces-inl.h
@@ -28,10 +28,14 @@ PageIteratorImpl<PAGE_TYPE> PageIteratorImpl<PAGE_TYPE>::operator++(int) {
   return tmp;
 }
 
-NewSpacePageRange::NewSpacePageRange(Address start, Address limit)
-    : range_(Page::FromAddress(start),
-             Page::FromAllocationAreaAddress(limit)->next_page()) {
-  SemiSpace::AssertValidRange(start, limit);
+PageRange::PageRange(Address start, Address limit)
+    : begin_(Page::FromAddress(start)),
+      end_(Page::FromAllocationAreaAddress(limit)->next_page()) {
+#ifdef DEBUG
+  if (begin_->InNewSpace()) {
+    SemiSpace::AssertValidRange(start, limit);
+  }
+#endif  // DEBUG
 }
 
 // -----------------------------------------------------------------------------
@@ -221,7 +225,7 @@ void Page::InitializeFreeListCategories() {
   }
 }
 
-void MemoryChunk::IncrementLiveBytesFromGC(HeapObject* object, int by) {
+void MemoryChunk::IncrementLiveBytes(HeapObject* object, int by) {
   MemoryChunk::FromAddress(object->address())->IncrementLiveBytes(by);
 }
 
@@ -244,18 +248,8 @@ void MemoryChunk::IncrementLiveBytes(int by) {
   DCHECK_LE(static_cast<size_t>(live_byte_count_), size_);
 }
 
-void MemoryChunk::IncrementLiveBytesFromMutator(HeapObject* object, int by) {
-  MemoryChunk* chunk = MemoryChunk::FromAddress(object->address());
-  if (!chunk->InNewSpace() && !static_cast<Page*>(chunk)->SweepingDone()) {
-    static_cast<PagedSpace*>(chunk->owner())->Allocate(by);
-  }
-  chunk->IncrementLiveBytes(by);
-}
-
 bool PagedSpace::Contains(Address addr) {
-  Page* p = Page::FromAddress(addr);
-  if (!Page::IsValid(p)) return false;
-  return p->owner() == this;
+  return MemoryChunk::FromAnyPointerAddress(heap(), addr)->owner() == this;
 }
 
 bool PagedSpace::Contains(Object* o) {
@@ -288,7 +282,7 @@ MemoryChunk* MemoryChunk::FromAnyPointerAddress(Heap* heap, Address addr) {
   MemoryChunk* chunk = MemoryChunk::FromAddress(addr);
   uintptr_t offset = addr - chunk->address();
   if (offset < MemoryChunk::kHeaderSize || !chunk->HasPageHeader()) {
-    chunk = heap->lo_space()->FindPage(addr);
+    chunk = heap->lo_space()->FindPageThreadSafe(addr);
   }
   return chunk;
 }
@@ -436,11 +430,10 @@ AllocationResult PagedSpace::AllocateRawUnaligned(
     if (object == NULL) {
       object = SlowAllocateRaw(size_in_bytes);
     }
-    if (object != NULL) {
-      if (heap()->incremental_marking()->black_allocation()) {
-        Marking::MarkBlack(ObjectMarking::MarkBitFrom(object));
-        MemoryChunk::IncrementLiveBytesFromGC(object, size_in_bytes);
-      }
+    if (object != NULL && heap()->incremental_marking()->black_allocation()) {
+      Address start = object->address();
+      Address end = object->address() + size_in_bytes;
+      Page::FromAllocationAreaAddress(start)->CreateBlackArea(start, end);
     }
   }
 
@@ -479,12 +472,19 @@ AllocationResult PagedSpace::AllocateRawAligned(int size_in_bytes,
     if (object == NULL) {
       object = SlowAllocateRaw(allocation_size);
     }
-    if (object != NULL && filler_size != 0) {
-      object = heap()->AlignWithFiller(object, size_in_bytes, allocation_size,
-                                       alignment);
-      // Filler objects are initialized, so mark only the aligned object memory
-      // as uninitialized.
-      allocation_size = size_in_bytes;
+    if (object != NULL) {
+      if (heap()->incremental_marking()->black_allocation()) {
+        Address start = object->address();
+        Address end = object->address() + allocation_size;
+        Page::FromAllocationAreaAddress(start)->CreateBlackArea(start, end);
+      }
+      if (filler_size != 0) {
+        object = heap()->AlignWithFiller(object, size_in_bytes, allocation_size,
+                                         alignment);
+        // Filler objects are initialized, so mark only the aligned object
+        // memory as uninitialized.
+        allocation_size = size_in_bytes;
+      }
     }
   }
 
@@ -596,6 +596,17 @@ LargePage* LargePage::Initialize(Heap* heap, MemoryChunk* chunk,
     FATAL("Code page is too large.");
   }
   heap->incremental_marking()->SetOldSpacePageFlags(chunk);
+
+  MSAN_ALLOCATED_UNINITIALIZED_MEMORY(chunk->area_start(), chunk->area_size());
+
+  // Initialize the owner field for each contained page (except the first, which
+  // is initialized by MemoryChunk::Initialize).
+  for (Address addr = chunk->address() + Page::kPageSize + Page::kOwnerOffset;
+       addr < chunk->area_end(); addr += Page::kPageSize) {
+    // Clear out kPageHeaderTag.
+    Memory::Address_at(addr) = 0;
+  }
+
   return static_cast<LargePage*>(chunk);
 }
 
diff --git a/deps/v8/src/heap/spaces.cc b/deps/v8/src/heap/spaces.cc
index e0e6d12fda..8d98520d43 100644
--- a/deps/v8/src/heap/spaces.cc
+++ b/deps/v8/src/heap/spaces.cc
@@ -335,7 +335,7 @@ class MemoryAllocator::Unmapper::UnmapFreeMemoryTask : public v8::Task {
  private:
   // v8::Task overrides.
   void Run() override {
-    unmapper_->PerformFreeMemoryOnQueuedChunks();
+    unmapper_->PerformFreeMemoryOnQueuedChunks<FreeMode::kUncommitPooled>();
     unmapper_->pending_unmapping_tasks_semaphore_.Signal();
   }
 
@@ -350,7 +350,7 @@ void MemoryAllocator::Unmapper::FreeQueuedChunks() {
         new UnmapFreeMemoryTask(this), v8::Platform::kShortRunningTask);
     concurrent_unmapping_tasks_active_++;
   } else {
-    PerformFreeMemoryOnQueuedChunks();
+    PerformFreeMemoryOnQueuedChunks<FreeMode::kUncommitPooled>();
   }
 }
 
@@ -364,6 +364,7 @@ bool MemoryAllocator::Unmapper::WaitUntilCompleted() {
   return waited;
 }
 
+template <MemoryAllocator::Unmapper::FreeMode mode>
 void MemoryAllocator::Unmapper::PerformFreeMemoryOnQueuedChunks() {
   MemoryChunk* chunk = nullptr;
   // Regular chunks.
@@ -372,6 +373,14 @@ void MemoryAllocator::Unmapper::PerformFreeMemoryOnQueuedChunks() {
     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);
+    }
+  }
   // Non-regular chunks.
   while ((chunk = GetMemoryChunkSafe<kNonRegular>()) != nullptr) {
     allocator_->PerformFreeMemory(chunk);
@@ -382,7 +391,10 @@ void MemoryAllocator::Unmapper::TearDown() {
   WaitUntilCompleted();
   ReconsiderDelayedChunks();
   CHECK(delayed_regular_chunks_.empty());
-  PerformFreeMemoryOnQueuedChunks();
+  PerformFreeMemoryOnQueuedChunks<FreeMode::kReleasePooled>();
+  for (int i = 0; i < kNumberOfChunkQueues; i++) {
+    DCHECK(chunks_[i].empty());
+  }
 }
 
 void MemoryAllocator::Unmapper::ReconsiderDelayedChunks() {
@@ -833,6 +845,16 @@ size_t Page::ShrinkToHighWaterMark() {
   return unused;
 }
 
+void Page::CreateBlackArea(Address start, Address end) {
+  DCHECK(heap()->incremental_marking()->black_allocation());
+  DCHECK_EQ(Page::FromAddress(start), this);
+  DCHECK_NE(start, end);
+  DCHECK_EQ(Page::FromAddress(end - 1), this);
+  markbits()->SetRange(AddressToMarkbitIndex(start),
+                       AddressToMarkbitIndex(end));
+  IncrementLiveBytes(static_cast<int>(end - start));
+}
+
 void MemoryAllocator::PartialFreeMemory(MemoryChunk* chunk,
                                         Address start_free) {
   // We do not allow partial shrink for code.
@@ -899,6 +921,11 @@ void MemoryAllocator::Free(MemoryChunk* chunk) {
       PreFreeMemory(chunk);
       PerformFreeMemory(chunk);
       break;
+    case kAlreadyPooled:
+      // Pooled pages cannot be touched anymore as their memory is uncommitted.
+      FreeMemory(chunk->address(), static_cast<size_t>(MemoryChunk::kPageSize),
+                 Executability::NOT_EXECUTABLE);
+      break;
     case kPooledAndQueue:
       DCHECK_EQ(chunk->size(), static_cast<size_t>(MemoryChunk::kPageSize));
       DCHECK_EQ(chunk->executable(), NOT_EXECUTABLE);
@@ -909,13 +936,14 @@ void MemoryAllocator::Free(MemoryChunk* chunk) {
       // The chunks added to this queue will be freed by a concurrent thread.
       unmapper()->AddMemoryChunkSafe(chunk);
       break;
-    default:
-      UNREACHABLE();
   }
 }
 
 template void MemoryAllocator::Free<MemoryAllocator::kFull>(MemoryChunk* chunk);
 
+template void MemoryAllocator::Free<MemoryAllocator::kAlreadyPooled>(
+    MemoryChunk* chunk);
+
 template void MemoryAllocator::Free<MemoryAllocator::kPreFreeAndQueue>(
     MemoryChunk* chunk);
 
@@ -1287,25 +1315,6 @@ bool PagedSpace::ContainsSlow(Address addr) {
   return false;
 }
 
-
-Object* PagedSpace::FindObject(Address addr) {
-  // Note: this function can only be called on iterable spaces.
-  DCHECK(!heap()->mark_compact_collector()->in_use());
-
-  if (!Contains(addr)) return Smi::kZero;  // Signaling not found.
-
-  Page* p = Page::FromAddress(addr);
-  HeapObjectIterator it(p);
-  for (HeapObject* obj = it.Next(); obj != NULL; obj = it.Next()) {
-    Address cur = obj->address();
-    Address next = cur + obj->Size();
-    if ((cur <= addr) && (addr < next)) return obj;
-  }
-
-  UNREACHABLE();
-  return Smi::kZero;
-}
-
 void PagedSpace::ShrinkImmortalImmovablePages() {
   DCHECK(!heap()->deserialization_complete());
   MemoryChunk::UpdateHighWaterMark(allocation_info_.top());
@@ -1361,10 +1370,7 @@ void PagedSpace::SetAllocationInfo(Address top, Address limit) {
   SetTopAndLimit(top, limit);
   if (top != nullptr && top != limit &&
       heap()->incremental_marking()->black_allocation()) {
-    Page* page = Page::FromAllocationAreaAddress(top);
-    page->markbits()->SetRange(page->AddressToMarkbitIndex(top),
-                               page->AddressToMarkbitIndex(limit));
-    page->IncrementLiveBytes(static_cast<int>(limit - top));
+    Page::FromAllocationAreaAddress(top)->CreateBlackArea(top, limit);
   }
 }
 
@@ -1373,10 +1379,8 @@ void PagedSpace::MarkAllocationInfoBlack() {
   Address current_top = top();
   Address current_limit = limit();
   if (current_top != nullptr && current_top != current_limit) {
-    Page* page = Page::FromAllocationAreaAddress(current_top);
-    page->markbits()->SetRange(page->AddressToMarkbitIndex(current_top),
-                               page->AddressToMarkbitIndex(current_limit));
-    page->IncrementLiveBytes(static_cast<int>(current_limit - current_top));
+    Page::FromAllocationAreaAddress(current_top)
+        ->CreateBlackArea(current_top, current_limit);
   }
 }
 
@@ -2095,7 +2099,7 @@ 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 : NewSpacePageRange(space_start(), mark)) {
+  for (Page* p : PageRange(space_start(), mark)) {
     p->SetFlag(MemoryChunk::NEW_SPACE_BELOW_AGE_MARK);
   }
 }
@@ -2616,7 +2620,7 @@ HeapObject* FreeList::Allocate(size_t size_in_bytes) {
 
   // Memory in the linear allocation area is counted as allocated.  We may free
   // a little of this again immediately - see below.
-  owner_->Allocate(static_cast<int>(new_node_size));
+  owner_->AccountAllocatedBytes(new_node_size);
 
   if (owner_->heap()->inline_allocation_disabled()) {
     // Keep the linear allocation area empty if requested to do so, just
@@ -2806,7 +2810,6 @@ void PagedSpace::RepairFreeListsAfterDeserialization() {
   }
 }
 
-
 HeapObject* PagedSpace::SweepAndRetryAllocation(int size_in_bytes) {
   MarkCompactCollector* collector = heap()->mark_compact_collector();
   if (collector->sweeping_in_progress()) {
@@ -2820,7 +2823,6 @@ HeapObject* PagedSpace::SweepAndRetryAllocation(int size_in_bytes) {
   return nullptr;
 }
 
-
 HeapObject* CompactionSpace::SweepAndRetryAllocation(int size_in_bytes) {
   MarkCompactCollector* collector = heap()->mark_compact_collector();
   if (collector->sweeping_in_progress()) {
@@ -2877,9 +2879,7 @@ void PagedSpace::ReportStatistics() {
          ", available: %" V8PRIdPTR ", %%%d\n",
          Capacity(), Waste(), Available(), pct);
 
-  if (heap()->mark_compact_collector()->sweeping_in_progress()) {
-    heap()->mark_compact_collector()->EnsureSweepingCompleted();
-  }
+  heap()->mark_compact_collector()->EnsureSweepingCompleted();
   ClearHistograms(heap()->isolate());
   HeapObjectIterator obj_it(this);
   for (HeapObject* obj = obj_it.Next(); obj != NULL; obj = obj_it.Next())
@@ -2994,7 +2994,6 @@ AllocationResult LargeObjectSpace::AllocateRaw(int object_size,
   InsertChunkMapEntries(page);
 
   HeapObject* object = page->GetObject();
-  MSAN_ALLOCATED_UNINITIALIZED_MEMORY(object->address(), object_size);
 
   if (Heap::ShouldZapGarbage()) {
     // Make the object consistent so the heap can be verified in OldSpaceStep.
@@ -3010,7 +3009,7 @@ AllocationResult LargeObjectSpace::AllocateRaw(int object_size,
 
   if (heap()->incremental_marking()->black_allocation()) {
     Marking::MarkBlack(ObjectMarking::MarkBitFrom(object));
-    MemoryChunk::IncrementLiveBytesFromGC(object, object_size);
+    MemoryChunk::IncrementLiveBytes(object, object_size);
   }
   return object;
 }
@@ -3033,6 +3032,10 @@ Object* LargeObjectSpace::FindObject(Address a) {
   return Smi::kZero;  // Signaling not found.
 }
 
+LargePage* LargeObjectSpace::FindPageThreadSafe(Address a) {
+  base::LockGuard<base::Mutex> guard(&chunk_map_mutex_);
+  return FindPage(a);
+}
 
 LargePage* LargeObjectSpace::FindPage(Address a) {
   uintptr_t key = reinterpret_cast<uintptr_t>(a) / MemoryChunk::kAlignment;
@@ -3069,6 +3072,9 @@ void LargeObjectSpace::InsertChunkMapEntries(LargePage* page) {
   uintptr_t start = reinterpret_cast<uintptr_t>(page) / MemoryChunk::kAlignment;
   uintptr_t limit = (reinterpret_cast<uintptr_t>(page) + (page->size() - 1)) /
                     MemoryChunk::kAlignment;
+  // There may be concurrent access on the chunk map. We have to take the lock
+  // here.
+  base::LockGuard<base::Mutex> guard(&chunk_map_mutex_);
   for (uintptr_t key = start; key <= limit; key++) {
     base::HashMap::Entry* entry = chunk_map_.InsertNew(
         reinterpret_cast<void*>(key), static_cast<uint32_t>(key));
diff --git a/deps/v8/src/heap/spaces.h b/deps/v8/src/heap/spaces.h
index f5701adc69..48551fa264 100644
--- a/deps/v8/src/heap/spaces.h
+++ b/deps/v8/src/heap/spaces.h
@@ -317,8 +317,11 @@ class MemoryChunk {
   static const intptr_t kAlignmentMask = kAlignment - 1;
 
   static const intptr_t kSizeOffset = 0;
-
-  static const intptr_t kFlagsOffset = kSizeOffset + kPointerSize;
+  static const intptr_t kFlagsOffset = kSizeOffset + kSizetSize;
+  static const intptr_t kAreaStartOffset = kFlagsOffset + kIntptrSize;
+  static const intptr_t kAreaEndOffset = kAreaStartOffset + kPointerSize;
+  static const intptr_t kReservationOffset = kAreaEndOffset + kPointerSize;
+  static const intptr_t kOwnerOffset = kReservationOffset + 2 * kPointerSize;
 
   static const size_t kMinHeaderSize =
       kSizeOffset + kSizetSize  // size_t size
@@ -367,8 +370,7 @@ class MemoryChunk {
 
   static const int kAllocatableMemory = kPageSize - kObjectStartOffset;
 
-  static inline void IncrementLiveBytesFromMutator(HeapObject* object, int by);
-  static inline void IncrementLiveBytesFromGC(HeapObject* object, int by);
+  static inline void IncrementLiveBytes(HeapObject* object, int by);
 
   // Only works if the pointer is in the first kPageSize of the MemoryChunk.
   static MemoryChunk* FromAddress(Address a) {
@@ -553,10 +555,11 @@ class MemoryChunk {
   void set_prev_chunk(MemoryChunk* prev) { prev_chunk_.SetValue(prev); }
 
   Space* owner() const {
-    if ((reinterpret_cast<intptr_t>(owner_) & kPageHeaderTagMask) ==
-        kPageHeaderTag) {
-      return reinterpret_cast<Space*>(reinterpret_cast<intptr_t>(owner_) -
-                                      kPageHeaderTag);
+    intptr_t owner_value = base::NoBarrierAtomicValue<intptr_t>::FromAddress(
+                               const_cast<Address*>(&owner_))
+                               ->Value();
+    if ((owner_value & kPageHeaderTagMask) == kPageHeaderTag) {
+      return reinterpret_cast<Space*>(owner_value - kPageHeaderTag);
     } else {
       return nullptr;
     }
@@ -769,6 +772,8 @@ class Page : public MemoryChunk {
 
   size_t ShrinkToHighWaterMark();
 
+  void CreateBlackArea(Address start, Address end);
+
 #ifdef DEBUG
   void Print();
 #endif  // DEBUG
@@ -1092,7 +1097,7 @@ class SkipList {
 // A space acquires chunks of memory from the operating system. The memory
 // allocator allocates and deallocates pages for the paged heap spaces and large
 // pages for large object space.
-class MemoryAllocator {
+class V8_EXPORT_PRIVATE MemoryAllocator {
  public:
   // Unmapper takes care of concurrently unmapping and uncommitting memory
   // chunks.
@@ -1144,6 +1149,11 @@ class MemoryAllocator {
       kNumberOfChunkQueues,
     };
 
+    enum class FreeMode {
+      kUncommitPooled,
+      kReleasePooled,
+    };
+
     template <ChunkQueueType type>
     void AddMemoryChunkSafe(MemoryChunk* chunk) {
       base::LockGuard<base::Mutex> guard(&mutex_);
@@ -1165,6 +1175,7 @@ class MemoryAllocator {
     }
 
     void ReconsiderDelayedChunks();
+    template <FreeMode mode>
     void PerformFreeMemoryOnQueuedChunks();
 
     base::Mutex mutex_;
@@ -1187,6 +1198,7 @@ class MemoryAllocator {
 
   enum FreeMode {
     kFull,
+    kAlreadyPooled,
     kPreFreeAndQueue,
     kPooledAndQueue,
   };
@@ -1376,6 +1388,15 @@ class MemoryAllocator {
   DISALLOW_IMPLICIT_CONSTRUCTORS(MemoryAllocator);
 };
 
+extern template Page*
+MemoryAllocator::AllocatePage<MemoryAllocator::kRegular, PagedSpace>(
+    size_t size, PagedSpace* owner, Executability executable);
+extern template Page*
+MemoryAllocator::AllocatePage<MemoryAllocator::kRegular, SemiSpace>(
+    size_t size, SemiSpace* owner, Executability executable);
+extern template Page*
+MemoryAllocator::AllocatePage<MemoryAllocator::kPooled, SemiSpace>(
+    size_t size, SemiSpace* owner, Executability executable);
 
 // -----------------------------------------------------------------------------
 // Interface for heap object iterator to be implemented by all object space
@@ -1419,6 +1440,8 @@ class PageRange {
   typedef PageIterator iterator;
   PageRange(Page* begin, Page* end) : begin_(begin), end_(end) {}
   explicit PageRange(Page* page) : PageRange(page, page->next_page()) {}
+  inline PageRange(Address start, Address limit);
+
   iterator begin() { return iterator(begin_); }
   iterator end() { return iterator(end_); }
 
@@ -1641,7 +1664,7 @@ class AllocationStats BASE_EMBEDDED {
 //   words in size.
 // At least 16384 words (huge): This list is for objects of 2048 words or
 //   larger. Empty pages are also added to this list.
-class FreeList {
+class V8_EXPORT_PRIVATE FreeList {
  public:
   // This method returns how much memory can be allocated after freeing
   // maximum_freed memory.
@@ -1878,18 +1901,7 @@ class LocalAllocationBuffer {
   AllocationInfo allocation_info_;
 };
 
-class NewSpacePageRange {
- public:
-  typedef PageRange::iterator iterator;
-  inline NewSpacePageRange(Address start, Address limit);
-  iterator begin() { return range_.begin(); }
-  iterator end() { return range_.end(); }
-
- private:
-  PageRange range_;
-};
-
-class PagedSpace : public Space {
+class V8_EXPORT_PRIVATE PagedSpace : NON_EXPORTED_BASE(public Space) {
  public:
   typedef PageIterator iterator;
 
@@ -1915,12 +1927,6 @@ class PagedSpace : public Space {
   inline bool Contains(Object* o);
   bool ContainsSlow(Address addr);
 
-  // Given an address occupied by a live object, return that object if it is
-  // in this space, or a Smi if it is not.  The implementation iterates over
-  // objects in the page containing the address, the cost is linear in the
-  // number of objects in the page.  It may be slow.
-  Object* FindObject(Address addr);
-
   // During boot the free_space_map is created, and afterwards we may need
   // to write it into the free list nodes that were already created.
   void RepairFreeListsAfterDeserialization();
@@ -2034,7 +2040,9 @@ class PagedSpace : public Space {
 
   void MarkAllocationInfoBlack();
 
-  void Allocate(int bytes) { accounting_stats_.AllocateBytes(bytes); }
+  void AccountAllocatedBytes(size_t bytes) {
+    accounting_stats_.AllocateBytes(bytes);
+  }
 
   void IncreaseCapacity(size_t bytes);
 
@@ -2820,6 +2828,9 @@ class LargeObjectSpace : public Space {
   // The function iterates through all objects in this space, may be slow.
   Object* FindObject(Address a);
 
+  // Takes the chunk_map_mutex_ and calls FindPage after that.
+  LargePage* FindPageThreadSafe(Address a);
+
   // Finds a large object page containing the given address, returns NULL
   // if such a page doesn't exist.
   LargePage* FindPage(Address a);
@@ -2870,6 +2881,9 @@ class LargeObjectSpace : public Space {
   size_t size_;            // allocated bytes
   int page_count_;         // number of chunks
   size_t objects_size_;    // size of objects
+  // The chunk_map_mutex_ has to be used when the chunk map is accessed
+  // concurrently.
+  base::Mutex chunk_map_mutex_;
   // Map MemoryChunk::kAlignment-aligned chunks to large pages covering them
   base::HashMap chunk_map_;
 
diff --git a/deps/v8/src/heap/store-buffer.cc b/deps/v8/src/heap/store-buffer.cc
index 974b85e1c8..94a8ca81b7 100644
--- a/deps/v8/src/heap/store-buffer.cc
+++ b/deps/v8/src/heap/store-buffer.cc
@@ -16,13 +16,19 @@ namespace v8 {
 namespace internal {
 
 StoreBuffer::StoreBuffer(Heap* heap)
-    : heap_(heap), top_(nullptr), current_(0), virtual_memory_(nullptr) {
+    : heap_(heap),
+      top_(nullptr),
+      current_(0),
+      mode_(NOT_IN_GC),
+      virtual_memory_(nullptr) {
   for (int i = 0; i < kStoreBuffers; i++) {
     start_[i] = nullptr;
     limit_[i] = nullptr;
     lazy_top_[i] = nullptr;
   }
   task_running_ = false;
+  insertion_callback = &InsertDuringRuntime;
+  deletion_callback = &DeleteDuringRuntime;
 }
 
 void StoreBuffer::SetUp() {
@@ -85,7 +91,7 @@ void StoreBuffer::FlipStoreBuffers() {
   current_ = other;
   top_ = start_[current_];
 
-  if (!task_running_) {
+  if (!task_running_ && FLAG_concurrent_sweeping) {
     task_running_ = true;
     Task* task = new Task(heap_->isolate(), this);
     V8::GetCurrentPlatform()->CallOnBackgroundThread(
@@ -137,29 +143,5 @@ void StoreBuffer::ConcurrentlyProcessStoreBuffer() {
   task_running_ = false;
 }
 
-void StoreBuffer::DeleteEntry(Address start, Address end) {
-  // Deletions coming from the GC are directly deleted from the remembered
-  // set. Deletions coming from the runtime are added to the store buffer
-  // to allow concurrent processing.
-  if (heap_->gc_state() == Heap::NOT_IN_GC) {
-    if (top_ + sizeof(Address) * 2 > limit_[current_]) {
-      StoreBufferOverflow(heap_->isolate());
-    }
-    *top_ = MarkDeletionAddress(start);
-    top_++;
-    *top_ = end;
-    top_++;
-  } else {
-    // In GC the store buffer has to be empty at any time.
-    DCHECK(Empty());
-    Page* page = Page::FromAddress(start);
-    if (end) {
-      RememberedSet<OLD_TO_NEW>::RemoveRange(page, start, end,
-                                             SlotSet::PREFREE_EMPTY_BUCKETS);
-    } else {
-      RememberedSet<OLD_TO_NEW>::Remove(page, start);
-    }
-  }
-}
 }  // namespace internal
 }  // namespace v8
diff --git a/deps/v8/src/heap/store-buffer.h b/deps/v8/src/heap/store-buffer.h
index 09faf4dcbd..be46cb3242 100644
--- a/deps/v8/src/heap/store-buffer.h
+++ b/deps/v8/src/heap/store-buffer.h
@@ -24,7 +24,9 @@ namespace internal {
 // slots are moved to the remembered set.
 class StoreBuffer {
  public:
-  static const int kStoreBufferSize = 1 << (14 + kPointerSizeLog2);
+  enum StoreBufferMode { IN_GC, NOT_IN_GC };
+
+  static const int kStoreBufferSize = 1 << (11 + kPointerSizeLog2);
   static const int kStoreBufferMask = kStoreBufferSize - 1;
   static const int kStoreBuffers = 2;
   static const intptr_t kDeletionTag = 1;
@@ -63,22 +65,77 @@ class StoreBuffer {
   // If we only want to delete a single slot, end should be set to null which
   // will be written into the second field. When processing the store buffer
   // the more efficient Remove method will be called in this case.
-  void DeleteEntry(Address start, Address end = nullptr);
+  void DeleteEntry(Address start, Address end = nullptr) {
+    // Deletions coming from the GC are directly deleted from the remembered
+    // set. Deletions coming from the runtime are added to the store buffer
+    // to allow concurrent processing.
+    deletion_callback(this, start, end);
+  }
+
+  static void DeleteDuringGarbageCollection(StoreBuffer* store_buffer,
+                                            Address start, Address end) {
+    // In GC the store buffer has to be empty at any time.
+    DCHECK(store_buffer->Empty());
+    DCHECK(store_buffer->mode() != StoreBuffer::NOT_IN_GC);
+    Page* page = Page::FromAddress(start);
+    if (end) {
+      RememberedSet<OLD_TO_NEW>::RemoveRange(page, start, end,
+                                             SlotSet::PREFREE_EMPTY_BUCKETS);
+    } else {
+      RememberedSet<OLD_TO_NEW>::Remove(page, start);
+    }
+  }
+
+  static void DeleteDuringRuntime(StoreBuffer* store_buffer, Address start,
+                                  Address end) {
+    DCHECK(store_buffer->mode() == StoreBuffer::NOT_IN_GC);
+    store_buffer->InsertDeletionIntoStoreBuffer(start, end);
+  }
+
+  void InsertDeletionIntoStoreBuffer(Address start, Address end) {
+    if (top_ + sizeof(Address) * 2 > limit_[current_]) {
+      StoreBufferOverflow(heap_->isolate());
+    }
+    *top_ = MarkDeletionAddress(start);
+    top_++;
+    *top_ = end;
+    top_++;
+  }
+
+  static void InsertDuringGarbageCollection(StoreBuffer* store_buffer,
+                                            Address slot) {
+    DCHECK(store_buffer->mode() != StoreBuffer::NOT_IN_GC);
+    RememberedSet<OLD_TO_NEW>::Insert(Page::FromAddress(slot), slot);
+  }
+
+  static void InsertDuringRuntime(StoreBuffer* store_buffer, Address slot) {
+    DCHECK(store_buffer->mode() == StoreBuffer::NOT_IN_GC);
+    store_buffer->InsertIntoStoreBuffer(slot);
+  }
+
+  void InsertIntoStoreBuffer(Address slot) {
+    if (top_ + sizeof(Address) > limit_[current_]) {
+      StoreBufferOverflow(heap_->isolate());
+    }
+    *top_ = slot;
+    top_++;
+  }
 
   void InsertEntry(Address slot) {
     // Insertions coming from the GC are directly inserted into the remembered
     // set. Insertions coming from the runtime are added to the store buffer to
     // allow concurrent processing.
-    if (heap_->gc_state() == Heap::NOT_IN_GC) {
-      if (top_ + sizeof(Address) > limit_[current_]) {
-        StoreBufferOverflow(heap_->isolate());
-      }
-      *top_ = slot;
-      top_++;
+    insertion_callback(this, slot);
+  }
+
+  void SetMode(StoreBufferMode mode) {
+    mode_ = mode;
+    if (mode == NOT_IN_GC) {
+      insertion_callback = &InsertDuringRuntime;
+      deletion_callback = &DeleteDuringRuntime;
     } else {
-      // In GC the store buffer has to be empty at any time.
-      DCHECK(Empty());
-      RememberedSet<OLD_TO_NEW>::Insert(Page::FromAddress(slot), slot);
+      insertion_callback = &InsertDuringGarbageCollection;
+      deletion_callback = &DeleteDuringGarbageCollection;
     }
   }
 
@@ -95,6 +152,8 @@ class StoreBuffer {
     return top_ == start_[current_];
   }
 
+  Heap* heap() { return heap_; }
+
  private:
   // There are two store buffers. If one store buffer fills up, the main thread
   // publishes the top pointer of the store buffer that needs processing in its
@@ -119,6 +178,8 @@ class StoreBuffer {
     DISALLOW_COPY_AND_ASSIGN(Task);
   };
 
+  StoreBufferMode mode() const { return mode_; }
+
   void FlipStoreBuffers();
 
   Heap* heap_;
@@ -142,7 +203,17 @@ class StoreBuffer {
   // Points to the current buffer in use.
   int current_;
 
+  // During GC, entries are directly added to the remembered set without
+  // going through the store buffer. This is signaled by a special
+  // IN_GC mode.
+  StoreBufferMode mode_;
+
   base::VirtualMemory* virtual_memory_;
+
+  // Callbacks are more efficient than reading out the gc state for every
+  // store buffer operation.
+  std::function<void(StoreBuffer*, Address)> insertion_callback;
+  std::function<void(StoreBuffer*, Address, Address)> deletion_callback;
 };
 
 }  // namespace internal