[heap] Provide ObjectMarking with marking transitions

src/heap/mark-compact.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/heap/mark-compact.h"
 
 #include "src/base/atomicops.h"
 #include "src/base/bits.h"
 #include "src/base/sys-info.h"
 #include "src/code-stubs.h"
@@ skipping 89 matching lines @@
 
 static void VerifyMarking(Heap* heap, Address bottom, Address top) {
   VerifyMarkingVisitor visitor(heap);
   HeapObject* object;
   Address next_object_must_be_here_or_later = bottom;
   for (Address current = bottom; current < top;) {
     object = HeapObject::FromAddress(current);
     // 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(ObjectMarking::IsBlack(object));
       CHECK(current >= next_object_must_be_here_or_later);
       object->Iterate(&visitor);
       next_object_must_be_here_or_later = current + object->Size();
       // The object is either part of a black area of black allocation or a
       // regular black object
       Page* page = Page::FromAddress(current);
       CHECK(
           page->markbits()->AllBitsSetInRange(
               page->AddressToMarkbitIndex(current),
               page->AddressToMarkbitIndex(next_object_must_be_here_or_later)) ||
@@ skipping 220 matching lines @@
 
 
 void MarkCompactCollector::VerifyMarkbitsAreClean() {
   VerifyMarkbitsAreClean(heap_->old_space());
   VerifyMarkbitsAreClean(heap_->code_space());
   VerifyMarkbitsAreClean(heap_->map_space());
   VerifyMarkbitsAreClean(heap_->new_space());
 
   LargeObjectIterator it(heap_->lo_space());
   for (HeapObject* obj = it.Next(); obj != NULL; obj = it.Next()) {
-    MarkBit mark_bit = ObjectMarking::MarkBitFrom(obj);
-    CHECK(Marking::IsWhite(mark_bit));
+    CHECK(ObjectMarking::IsWhite(obj));
     CHECK_EQ(0, Page::FromAddress(obj->address())->LiveBytes());
   }
 }
 
 void MarkCompactCollector::VerifyWeakEmbeddedObjectsInCode() {
   HeapObjectIterator code_iterator(heap()->code_space());
   for (HeapObject* obj = code_iterator.Next(); obj != NULL;
        obj = code_iterator.Next()) {
     Code* code = Code::cast(obj);
     if (!code->is_optimized_code()) continue;
@@ skipping 28 matching lines @@
 
 
 void MarkCompactCollector::ClearMarkbits() {
   ClearMarkbitsInPagedSpace(heap_->code_space());
   ClearMarkbitsInPagedSpace(heap_->map_space());
   ClearMarkbitsInPagedSpace(heap_->old_space());
   ClearMarkbitsInNewSpace(heap_->new_space());
 
   LargeObjectIterator it(heap_->lo_space());
   for (HeapObject* obj = it.Next(); obj != NULL; obj = it.Next()) {
-    Marking::MarkWhite(ObjectMarking::MarkBitFrom(obj));
+    ObjectMarking::ClearMarkBit(obj);
     MemoryChunk* chunk = MemoryChunk::FromAddress(obj->address());
     chunk->ResetProgressBar();
     chunk->ResetLiveBytes();
   }
 }
 
 class MarkCompactCollector::Sweeper::SweeperTask : public v8::Task {
  public:
   SweeperTask(Sweeper* sweeper, base::Semaphore* pending_sweeper_tasks,
               AllocationSpace space_to_start)
@@ skipping 490 matching lines @@
 
   JSFunction* candidate = jsfunction_candidates_head_;
   JSFunction* next_candidate;
   while (candidate != NULL) {
     next_candidate = GetNextCandidate(candidate);
     ClearNextCandidate(candidate, undefined);
 
     SharedFunctionInfo* shared = candidate->shared();
 
     Code* code = shared->code();
-    MarkBit code_mark = ObjectMarking::MarkBitFrom(code);
-    if (Marking::IsWhite(code_mark)) {
+    if (ObjectMarking::IsWhite(code)) {
       if (FLAG_trace_code_flushing && shared->is_compiled()) {
         PrintF("[code-flushing clears: ");
         shared->ShortPrint();
         PrintF(" - age: %d]\n", code->GetAge());
       }
       // Always flush the optimized code map if there is one.
       if (!shared->OptimizedCodeMapIsCleared()) {
         shared->ClearOptimizedCodeMap();
       }
       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));
+      DCHECK(ObjectMarking::IsBlack(code));
       candidate->set_code(code);
     }
 
     // We are in the middle of a GC cycle so the write barrier in the code
     // setter did not record the slot update and we have to do that manually.
     Address slot = candidate->address() + JSFunction::kCodeEntryOffset;
     Code* target = Code::cast(Code::GetObjectFromEntryAddress(slot));
     isolate_->heap()->mark_compact_collector()->RecordCodeEntrySlot(
         candidate, slot, target);
 
@@ skipping 13 matching lines @@
   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) {
     next_candidate = GetNextCandidate(candidate);
     ClearNextCandidate(candidate);
 
     Code* code = candidate->code();
-    MarkBit code_mark = ObjectMarking::MarkBitFrom(code);
-    if (Marking::IsWhite(code_mark)) {
+    if (ObjectMarking::IsWhite(code)) {
       if (FLAG_trace_code_flushing && candidate->is_compiled()) {
         PrintF("[code-flushing clears: ");
         candidate->ShortPrint();
         PrintF(" - age: %d]\n", code->GetAge());
       }
       // Always flush the optimized code map if there is one.
       if (!candidate->OptimizedCodeMapIsCleared()) {
         candidate->ClearOptimizedCodeMap();
       }
       if (candidate->HasBytecodeArray()) {
@@ skipping 119 matching lines @@
   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);
+    if (ObjectMarking::IsBlackOrGrey(object)) return true;
+    heap->mark_compact_collector()->SetMark(object);
     IterateBody(object->map(), object);
     return true;
   }
 };
 
 class MarkCompactMarkingVisitor
     : public StaticMarkingVisitor<MarkCompactMarkingVisitor> {
  public:
   static void Initialize();
 
@@ skipping 17 matching lines @@
 
   // Marks the object black and pushes it on the marking stack.
   INLINE(static void MarkObject(Heap* heap, HeapObject* object)) {
     MarkBit mark = ObjectMarking::MarkBitFrom(object);
     heap->mark_compact_collector()->MarkObject(object, mark);
   }
 
   // Marks the object black without pushing it on the marking stack.
   // Returns true if object needed marking and false otherwise.
   INLINE(static bool MarkObjectWithoutPush(Heap* heap, HeapObject* object)) {
-    MarkBit mark_bit = ObjectMarking::MarkBitFrom(object);
-    if (Marking::IsWhite(mark_bit)) {
-      heap->mark_compact_collector()->SetMark(object, mark_bit);
+    if (ObjectMarking::IsWhite(object)) {
+      heap->mark_compact_collector()->SetMark(object);
       return true;
     }
     return false;
   }
 
   // Mark object pointed to by p.
   INLINE(static void MarkObjectByPointer(MarkCompactCollector* collector,
                                          HeapObject* object, Object** p)) {
     if (!(*p)->IsHeapObject()) return;
     HeapObject* target_object = HeapObject::cast(*p);
     collector->RecordSlot(object, p, target_object);
     MarkBit mark = ObjectMarking::MarkBitFrom(target_object);
     collector->MarkObject(target_object, mark);
   }
 
 
   // Visit an unmarked object.
   INLINE(static void VisitUnmarkedObject(MarkCompactCollector* collector,
                                          HeapObject* obj)) {
 #ifdef DEBUG
     DCHECK(collector->heap()->Contains(obj));
     DCHECK(!collector->heap()->mark_compact_collector()->IsMarked(obj));
 #endif
     Map* map = obj->map();
     Heap* heap = obj->GetHeap();
-    MarkBit mark = ObjectMarking::MarkBitFrom(obj);
-    heap->mark_compact_collector()->SetMark(obj, mark);
+    heap->mark_compact_collector()->SetMark(obj);
     // Mark the map pointer and the body.
     MarkBit map_mark = ObjectMarking::MarkBitFrom(map);
     heap->mark_compact_collector()->MarkObject(map, map_mark);
     IterateBody(map, obj);
   }
 
   // Visit all unmarked objects pointed to by [start, end).
   // Returns false if the operation fails (lack of stack space).
   INLINE(static bool VisitUnmarkedObjects(Heap* heap, HeapObject* object,
                                           Object** start, Object** end)) {
     // Return false is we are close to the stack limit.
     StackLimitCheck check(heap->isolate());
     if (check.HasOverflowed()) return false;
 
     MarkCompactCollector* collector = heap->mark_compact_collector();
     // Visit the unmarked objects.
     for (Object** p = start; p < end; p++) {
       Object* o = *p;
       if (!o->IsHeapObject()) continue;
       collector->RecordSlot(object, p, o);
       HeapObject* obj = HeapObject::cast(o);
-      MarkBit mark = ObjectMarking::MarkBitFrom(obj);
-      if (Marking::IsBlackOrGrey(mark)) continue;
+      if (ObjectMarking::IsBlackOrGrey(obj)) continue;
       VisitUnmarkedObject(collector, obj);
     }
     return true;
   }
 
  private:
   // Code flushing support.
 
   static const int kRegExpCodeThreshold = 5;
 
@@ skipping 12 matching lines @@
     if (!code->IsSmi() &&
         HeapObject::cast(code)->map()->instance_type() == CODE_TYPE) {
       // Save a copy that can be reinstated if we need the code again.
       re->SetDataAt(JSRegExp::saved_code_index(is_one_byte), code);
 
       // Saving a copy might create a pointer into compaction candidate
       // that was not observed by marker.  This might happen if JSRegExp data
       // was marked through the compilation cache before marker reached JSRegExp
       // object.
       FixedArray* data = FixedArray::cast(re->data());
-      if (Marking::IsBlackOrGrey(ObjectMarking::MarkBitFrom(data))) {
+      if (ObjectMarking::IsBlackOrGrey(data)) {
         Object** slot =
             data->data_start() + JSRegExp::saved_code_index(is_one_byte);
         heap->mark_compact_collector()->RecordSlot(data, slot, code);
       }
 
       // Set a number in the 0-255 range to guarantee no smi overflow.
       re->SetDataAt(JSRegExp::code_index(is_one_byte),
                     Smi::FromInt(heap->ms_count() & 0xff));
     } else if (code->IsSmi()) {
       int value = Smi::cast(code)->value();
@@ skipping 145 matching lines @@
  private:
   void MarkObjectByPointer(Object** p) {
     if (!(*p)->IsHeapObject()) return;
 
     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;
+    if (ObjectMarking::IsBlackOrGrey(object)) return;
 
     Map* map = object->map();
     // Mark the object.
-    collector_->SetMark(object, mark_bit);
+    collector_->SetMark(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);
@@ skipping 17 matching lines @@
       : heap_(heap), pointers_removed_(0), table_(table) {
     DCHECK(!record_slots || table != nullptr);
   }
 
   void VisitPointers(Object** start, Object** end) override {
     // Visit all HeapObject pointers in [start, end).
     MarkCompactCollector* collector = heap_->mark_compact_collector();
     for (Object** p = start; p < end; p++) {
       Object* o = *p;
       if (o->IsHeapObject()) {
-        if (Marking::IsWhite(ObjectMarking::MarkBitFrom(HeapObject::cast(o)))) {
+        if (ObjectMarking::IsWhite(HeapObject::cast(o))) {
           if (finalize_external_strings) {
             DCHECK(o->IsExternalString());
             heap_->FinalizeExternalString(String::cast(*p));
           } else {
             pointers_removed_++;
           }
           // Set the entry to the_hole_value (as deleted).
           *p = heap_->the_hole_value();
         } else if (record_slots) {
           // StringTable contains only old space strings.
@@ skipping 16 matching lines @@
 };
 
 typedef StringTableCleaner<false, true> InternalizedStringTableCleaner;
 typedef StringTableCleaner<true, false> ExternalStringTableCleaner;
 
 // Implementation of WeakObjectRetainer for mark compact GCs. All marked objects
 // are retained.
 class MarkCompactWeakObjectRetainer : public WeakObjectRetainer {
  public:
   virtual Object* RetainAs(Object* object) {
-    MarkBit mark_bit = ObjectMarking::MarkBitFrom(HeapObject::cast(object));
-    DCHECK(!Marking::IsGrey(mark_bit));
-    if (Marking::IsBlack(mark_bit)) {
+    DCHECK(!ObjectMarking::IsGrey(HeapObject::cast(object)));
+    if (ObjectMarking::IsBlack(HeapObject::cast(object))) {
       return object;
     } else if (object->IsAllocationSite() &&
                !(AllocationSite::cast(object)->IsZombie())) {
       // "dead" AllocationSites need to live long enough for a traversal of new
       // space. These sites get a one-time reprieve.
       AllocationSite* site = AllocationSite::cast(object);
       site->MarkZombie();
       site->GetHeap()->mark_compact_collector()->MarkAllocationSite(site);
       return object;
     } else {
       return NULL;
     }
   }
 };
 
 
 // Fill the marking stack with overflowed objects returned by the given
 // iterator.  Stop when the marking stack is filled or the end of the space
 // is reached, whichever comes first.
 template <class T>
 void MarkCompactCollector::DiscoverGreyObjectsWithIterator(T* it) {
   // The caller should ensure that the marking stack is initially not full,
   // so that we don't waste effort pointlessly scanning for objects.
   DCHECK(!marking_deque()->IsFull());
 
   Map* filler_map = heap()->one_pointer_filler_map();
   for (HeapObject* object = it->Next(); object != NULL; object = it->Next()) {
-    MarkBit markbit = ObjectMarking::MarkBitFrom(object);
-    if ((object->map() != filler_map) && Marking::IsGrey(markbit)) {
-      Marking::GreyToBlack(markbit);
+    if ((object->map() != filler_map) && ObjectMarking::IsGrey(object)) {
+      ObjectMarking::GreyToBlack(object);
       PushBlack(object);
       if (marking_deque()->IsFull()) return;
     }
   }
 }
 
 void MarkCompactCollector::DiscoverGreyObjectsOnPage(MemoryChunk* p) {
   DCHECK(!marking_deque()->IsFull());
   LiveObjectIterator<kGreyObjects> it(p);
   HeapObject* object = NULL;
   while ((object = it.Next()) != NULL) {
-    MarkBit markbit = ObjectMarking::MarkBitFrom(object);
-    DCHECK(Marking::IsGrey(markbit));
-    Marking::GreyToBlack(markbit);
+    DCHECK(ObjectMarking::IsGrey(object));
+    ObjectMarking::GreyToBlack(object);
     PushBlack(object);
     if (marking_deque()->IsFull()) return;
   }
 }
 
 class RecordMigratedSlotVisitor final : public ObjectVisitor {
  public:
   explicit RecordMigratedSlotVisitor(MarkCompactCollector* collector)
       : collector_(collector) {}
 
@@ skipping 429 matching lines @@
   for (Page* page : PageRange(space->bottom(), space->top())) {
     DiscoverGreyObjectsOnPage(page);
     if (marking_deque()->IsFull()) return;
   }
 }
 
 
 bool MarkCompactCollector::IsUnmarkedHeapObject(Object** p) {
   Object* o = *p;
   if (!o->IsHeapObject()) return false;
-  HeapObject* heap_object = HeapObject::cast(o);
-  MarkBit mark = ObjectMarking::MarkBitFrom(heap_object);
-  return Marking::IsWhite(mark);
+  return ObjectMarking::IsWhite(HeapObject::cast(o));
 }
 
 
 bool MarkCompactCollector::IsUnmarkedHeapObjectWithHeap(Heap* heap,
                                                         Object** p) {
   Object* o = *p;
   DCHECK(o->IsHeapObject());
-  HeapObject* heap_object = HeapObject::cast(o);
-  MarkBit mark = ObjectMarking::MarkBitFrom(heap_object);
-  return Marking::IsWhite(mark);
+  return ObjectMarking::IsWhite(HeapObject::cast(o));
 }
 
 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);
-  if (Marking::IsWhite(string_table_mark)) {
+  if (ObjectMarking::IsWhite(string_table)) {
     // String table could have already been marked by visiting the handles list.
-    SetMark(string_table, string_table_mark);
+    SetMark(string_table);
   }
   // Explicitly mark the prefix.
   string_table->IteratePrefix(visitor);
   ProcessMarkingDeque<MarkCompactMode::FULL>();
 }
 
 
 void MarkCompactCollector::MarkAllocationSite(AllocationSite* site) {
-  MarkBit mark_bit = ObjectMarking::MarkBitFrom(site);
-  SetMark(site, mark_bit);
+  SetMark(site);

[Hannes Payer (out of office), 2017/01/19 14:41:51]

We may want to unify the marking functions a bit. Why is this on not MarkBlack?
Can you have a look in a follow-up cl?

[Michael Lippautz, 2017/01/19 18:50:12]

Acknowledged.

 }
 
 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);
 
   // Handle the string table specially.
   MarkStringTable(visitor);
@@ skipping 42 matching lines @@
 // 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();
 
     DCHECK(!object->IsFiller());
     DCHECK(object->IsHeapObject());
     DCHECK(heap()->Contains(object));
-    DCHECK(!Marking::IsWhite(ObjectMarking::MarkBitFrom(object)));
+    DCHECK(!ObjectMarking::IsWhite(object));
 
     Map* map = object->map();
     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)));
+        DCHECK(ObjectMarking::IsBlack(object));
         StaticYoungGenerationMarkingVisitor::IterateBody(map, object);
       } break;
     }
   }
 }
 
 
 // Sweep the heap for overflowed objects, clear their overflow bits, and
 // push them on the marking stack.  Stop early if the marking stack fills
 // before sweeping completes.  If sweeping completes, there are no remaining
@@ skipping 180 matching lines @@
   ObjectStatsVisitor(Heap* heap, ObjectStats* live_stats,
                      ObjectStats* dead_stats)
       : live_collector_(heap, live_stats), dead_collector_(heap, dead_stats) {
     DCHECK_NOT_NULL(live_stats);
     DCHECK_NOT_NULL(dead_stats);
     // Global objects are roots and thus recorded as live.
     live_collector_.CollectGlobalStatistics();
   }
 
   bool Visit(HeapObject* obj) override {
-    if (Marking::IsBlack(ObjectMarking::MarkBitFrom(obj))) {
+    if (ObjectMarking::IsBlack(obj)) {
       live_collector_.CollectStatistics(obj);
     } else {
-      DCHECK(!Marking::IsGrey(ObjectMarking::MarkBitFrom(obj)));
+      DCHECK(!ObjectMarking::IsGrey(obj));
       dead_collector_.CollectStatistics(obj);
     }
     return true;
   }
 
  private:
   ObjectStatsCollector live_collector_;
   ObjectStatsCollector dead_collector_;
 };
 
@@ skipping 35 matching lines @@
 }
 
 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)) {
+    if (ObjectMarking::IsBlackOrGrey(heap_object)) {
       return KEEP_SLOT;
     }
-    heap->mark_compact_collector()->SetMark(heap_object, mark_bit);
+    heap->mark_compact_collector()->SetMark(heap_object);
     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)));
+  return heap->InNewSpace(*p) && !ObjectMarking::IsBlack(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());
 
@@ skipping 261 matching lines @@
 }
 
 
 void MarkCompactCollector::ClearSimpleMapTransitions(
     Object* non_live_map_list) {
   Object* the_hole_value = heap()->the_hole_value();
   Object* weak_cell_obj = non_live_map_list;
   while (weak_cell_obj != Smi::kZero) {
     WeakCell* weak_cell = WeakCell::cast(weak_cell_obj);
     Map* map = Map::cast(weak_cell->value());
-    DCHECK(Marking::IsWhite(ObjectMarking::MarkBitFrom(map)));
+    DCHECK(ObjectMarking::IsWhite(map));
     Object* potential_parent = map->constructor_or_backpointer();
     if (potential_parent->IsMap()) {
       Map* parent = Map::cast(potential_parent);
-      if (Marking::IsBlackOrGrey(ObjectMarking::MarkBitFrom(parent)) &&
+      if (ObjectMarking::IsBlackOrGrey(parent) &&
           parent->raw_transitions() == weak_cell) {
         ClearSimpleMapTransition(parent, map);
       }
     }
     weak_cell->clear();
     weak_cell_obj = weak_cell->next();
     weak_cell->clear_next(the_hole_value);
   }
 }
 
@@ skipping 18 matching lines @@
 void MarkCompactCollector::ClearFullMapTransitions() {
   HeapObject* undefined = heap()->undefined_value();
   Object* obj = heap()->encountered_transition_arrays();
   while (obj != Smi::kZero) {
     TransitionArray* array = TransitionArray::cast(obj);
     int num_transitions = array->number_of_entries();
     DCHECK_EQ(TransitionArray::NumberOfTransitions(array), num_transitions);
     if (num_transitions > 0) {
       Map* map = array->GetTarget(0);
       Map* parent = Map::cast(map->constructor_or_backpointer());
-      bool parent_is_alive =
-          Marking::IsBlackOrGrey(ObjectMarking::MarkBitFrom(parent));
+      bool parent_is_alive = ObjectMarking::IsBlackOrGrey(parent);
       DescriptorArray* descriptors =
           parent_is_alive ? parent->instance_descriptors() : nullptr;
       bool descriptors_owner_died =
           CompactTransitionArray(parent, array, descriptors);
       if (descriptors_owner_died) {
         TrimDescriptorArray(parent, descriptors);
       }
     }
     obj = array->next_link();
     array->set_next_link(undefined, SKIP_WRITE_BARRIER);
   }
   heap()->set_encountered_transition_arrays(Smi::kZero);
 }
 
 
 bool MarkCompactCollector::CompactTransitionArray(
     Map* map, TransitionArray* transitions, DescriptorArray* descriptors) {
   int num_transitions = transitions->number_of_entries();
   bool descriptors_owner_died = false;
   int transition_index = 0;
   // Compact all live transitions to the left.
   for (int i = 0; i < num_transitions; ++i) {
     Map* target = transitions->GetTarget(i);
     DCHECK_EQ(target->constructor_or_backpointer(), map);
-    if (Marking::IsWhite(ObjectMarking::MarkBitFrom(target))) {
+    if (ObjectMarking::IsWhite(target)) {
       if (descriptors != nullptr &&
           target->instance_descriptors() == descriptors) {
         descriptors_owner_died = true;
       }
     } else {
       if (i != transition_index) {
         Name* key = transitions->GetKey(i);
         transitions->SetKey(transition_index, key);
         Object** key_slot = transitions->GetKeySlot(transition_index);
         RecordSlot(transitions, key_slot, key);
@@ skipping 154 matching lines @@
       // Cells for new-space objects embedded in optimized code are wrapped in
       // WeakCell and put into Heap::weak_object_to_code_table.
       // Such cells do not have any strong references but we want to keep them
       // alive as long as the cell value is alive.
       // TODO(ulan): remove this once we remove Heap::weak_object_to_code_table.
       if (value->IsCell()) {
         Object* cell_value = Cell::cast(value)->value();
         if (cell_value->IsHeapObject() &&
             MarkCompactCollector::IsMarked(HeapObject::cast(cell_value))) {
           // Resurrect the cell.
-          MarkBit mark = ObjectMarking::MarkBitFrom(value);
-          SetMark(value, mark);
+          SetMark(value);
           Object** slot = HeapObject::RawField(value, Cell::kValueOffset);
           RecordSlot(value, slot, *slot);
           slot = HeapObject::RawField(weak_cell, WeakCell::kValueOffset);
           RecordSlot(weak_cell, slot, *slot);
           clear_value = false;
         }
       }
       if (value->IsMap()) {
         // The map is non-live.
         Map* map = Map::cast(value);
@@ skipping 521 matching lines @@
   }
 
   intptr_t freed_bytes = 0;
   intptr_t max_freed_bytes = 0;
   int curr_region = -1;
 
   LiveObjectIterator<kBlackObjects> it(p);
   HeapObject* object = NULL;
 
   while ((object = it.Next()) != NULL) {
-    DCHECK(Marking::IsBlack(ObjectMarking::MarkBitFrom(object)));
+    DCHECK(ObjectMarking::IsBlack(object));
     Address free_end = object->address();
     if (free_end != free_start) {
       CHECK_GT(free_end, free_start);
       size_t size = static_cast<size_t>(free_end - free_start);
       if (free_space_mode == ZAP_FREE_SPACE) {
         memset(free_start, 0xcc, size);
       }
       if (free_list_mode == REBUILD_FREE_LIST) {
         freed_bytes = reinterpret_cast<PagedSpace*>(space)->UnaccountedFree(
             free_start, size);
@@ skipping 69 matching lines @@
   Address start = code->instruction_start();
   Address end = code->address() + code->Size();
 
   RememberedSet<OLD_TO_NEW>::RemoveRangeTyped(page, start, end);
 
   if (heap_->incremental_marking()->IsCompacting() &&
       !ShouldSkipEvacuationSlotRecording(code)) {
     DCHECK(compacting_);
 
     // If the object is white than no slots were recorded on it yet.
-    MarkBit mark_bit = ObjectMarking::MarkBitFrom(code);
-    if (Marking::IsWhite(mark_bit)) return;
+    if (ObjectMarking::IsWhite(code)) return;
 
     // Ignore all slots that might have been recorded in the body of the
     // deoptimized code object. Assumption: no slots will be recorded for
     // this object after invalidating it.
     RememberedSet<OLD_TO_OLD>::RemoveRangeTyped(page, start, end);
   }
 }
 
 
 // Return true if the given code is deoptimized or will be deoptimized.
 bool MarkCompactCollector::WillBeDeoptimized(Code* code) {
   return code->is_optimized_code() && code->marked_for_deoptimization();
 }
 
 
 #ifdef VERIFY_HEAP
 static void VerifyAllBlackObjects(MemoryChunk* page) {
   LiveObjectIterator<kAllLiveObjects> it(page);
   HeapObject* object = NULL;
   while ((object = it.Next()) != NULL) {
-    CHECK(Marking::IsBlack(ObjectMarking::MarkBitFrom(object)));
+    CHECK(ObjectMarking::IsBlack(object));
   }
 }
 #endif  // VERIFY_HEAP
 
 template <class Visitor>
 bool MarkCompactCollector::VisitLiveObjects(MemoryChunk* page, Visitor* visitor,
                                             IterationMode mode) {
 #ifdef VERIFY_HEAP
   VerifyAllBlackObjects(page);
 #endif  // VERIFY_HEAP
 
   LiveObjectIterator<kBlackObjects> it(page);
   HeapObject* object = nullptr;
   while ((object = it.Next()) != nullptr) {
-    DCHECK(Marking::IsBlack(ObjectMarking::MarkBitFrom(object)));
+    DCHECK(ObjectMarking::IsBlack(object));
     if (!visitor->Visit(object)) {
       if (mode == kClearMarkbits) {
         page->markbits()->ClearRange(
             page->AddressToMarkbitIndex(page->area_start()),
             page->AddressToMarkbitIndex(object->address()));
         if (page->old_to_new_slots() != nullptr) {
           page->old_to_new_slots()->RemoveRange(
               0, static_cast<int>(object->address() - page->address()),
               SlotSet::PREFREE_EMPTY_BUCKETS);
         }
@@ skipping 176 matching lines @@
       // Unfortunately, we do not know about the slot. It could be in a
       // just freed free space object.
       if (heap->InToSpace(slot->Value())) {
         return KEEP_SLOT;
       }
     } else if (heap->InToSpace(slot_reference)) {
       // Slots can point to "to" space if the page has been moved, or if the
       // slot has been recorded multiple times in the remembered set. Since
       // there is no forwarding information present we need to check the
       // markbits to determine liveness.
-      if (Marking::IsBlack(ObjectMarking::MarkBitFrom(
-              reinterpret_cast<HeapObject*>(slot_reference))))
+      if (ObjectMarking::IsBlack(reinterpret_cast<HeapObject*>(slot_reference)))
         return KEEP_SLOT;
     } else {
       DCHECK(!heap->InNewSpace(slot_reference));
     }
     return REMOVE_SLOT;
   }
 };
 
 int NumberOfPointerUpdateTasks(int pages) {
   if (!FLAG_parallel_pointer_update) return 1;
@@ skipping 313 matching lines @@
   }
 }
 
 
 void MarkCompactCollector::RecordCodeTargetPatch(Address pc, Code* target) {
   DCHECK(heap()->gc_state() == Heap::MARK_COMPACT);
   if (is_compacting()) {
     Code* host =
         isolate()->inner_pointer_to_code_cache()->GcSafeFindCodeForInnerPointer(
             pc);
-    MarkBit mark_bit = ObjectMarking::MarkBitFrom(host);
-    if (Marking::IsBlack(mark_bit)) {
+    if (ObjectMarking::IsBlack(host)) {
       RelocInfo rinfo(isolate(), pc, RelocInfo::CODE_TARGET, 0, host);
       // The target is always in old space, we don't have to record the slot in
       // the old-to-new remembered set.
       DCHECK(!heap()->InNewSpace(target));
       RecordRelocSlot(host, &rinfo, target);
     }
   }
 }
 
 }  // namespace internal
 }  // namespace v8