[heap] Untangle Marking and friends from heap dependencies.

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 19 matching lines @@
 
 namespace v8 {
 namespace internal {
 
 
 const char* Marking::kWhiteBitPattern = "00";
 const char* Marking::kBlackBitPattern = "11";
 const char* Marking::kGreyBitPattern = "10";
 const char* Marking::kImpossibleBitPattern = "01";
 
-
-// The following has to hold in order for {Marking::MarkBitFrom} to not produce
+// The following has to hold in order for {ObjectMarking::MarkBitFrom} to not
+// produce

[Michael Lippautz, 2016/07/12 14:22:31]

nit: formatting off

[Hannes Payer (out of office), 2016/07/12 14:44:26]

Done.

 // invalid {kImpossibleBitPattern} in the marking bitmap by overlapping.
 STATIC_ASSERT(Heap::kMinObjectSizeInWords >= 2);
 
 
 // -------------------------------------------------------------------------
 // MarkCompactCollector
 
 MarkCompactCollector::MarkCompactCollector(Heap* heap)
     :  // NOLINT
       heap_(heap),
@@ skipping 50 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; current += kPointerSize) {
     object = HeapObject::FromAddress(current);
     if (MarkCompactCollector::IsMarked(object)) {
-      CHECK(Marking::IsBlack(Marking::MarkBitFrom(object)));
+      CHECK(Marking::IsBlack(ObjectMarking::MarkBitFrom(object)));
       CHECK(current >= next_object_must_be_here_or_later);
       object->Iterate(&visitor);
       next_object_must_be_here_or_later = current + object->Size();
       // The next word for sure belongs to the current object, jump over it.
       current += kPointerSize;
     }
   }
 }
 
 static void VerifyMarkingBlackPage(Heap* heap, Page* page) {
   CHECK(page->IsFlagSet(Page::BLACK_PAGE));
   VerifyMarkingVisitor visitor(heap);
   HeapObjectIterator it(page);
   for (HeapObject* object = it.Next(); object != NULL; object = it.Next()) {
-    CHECK(Marking::IsBlack(Marking::MarkBitFrom(object)));
+    CHECK(Marking::IsBlack(ObjectMarking::MarkBitFrom(object)));
     object->Iterate(&visitor);
   }
 }
 
 static void VerifyMarking(NewSpace* space) {
   Address end = space->top();
   // The bottom position is at the start of its page. Allows us to use
   // page->area_start() as start of range on all pages.
   CHECK_EQ(space->bottom(), Page::FromAddress(space->bottom())->area_start());
 
@@ skipping 232 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 = Marking::MarkBitFrom(obj);
+    MarkBit mark_bit = ObjectMarking::MarkBitFrom(obj);
     CHECK(Marking::IsWhite(mark_bit));
     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()) {
@@ skipping 10 matching lines @@
   for (HeapObject* obj = iterator.Next(); obj != NULL; obj = iterator.Next()) {
     Map* map = Map::cast(obj);
     map->VerifyOmittedMapChecks();
   }
 }
 #endif  // VERIFY_HEAP
 
 
 static void ClearMarkbitsInPagedSpace(PagedSpace* space) {
   for (Page* p : *space) {
-    Bitmap::Clear(p);
+    p->ClearLiveness();
     if (p->IsFlagSet(Page::BLACK_PAGE)) {
       p->ClearFlag(Page::BLACK_PAGE);
     }
   }
 }
 
 
 static void ClearMarkbitsInNewSpace(NewSpace* space) {
   for (Page* page : *space) {
-    Bitmap::Clear(page);
+    page->ClearLiveness();
   }
 }
 
 
 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(Marking::MarkBitFrom(obj));
+    Marking::MarkWhite(ObjectMarking::MarkBitFrom(obj));
     MemoryChunk* chunk = MemoryChunk::FromAddress(obj->address());
     chunk->ResetProgressBar();
     chunk->ResetLiveBytes();
     if (chunk->IsFlagSet(Page::BLACK_PAGE)) {
       chunk->ClearFlag(Page::BLACK_PAGE);
     }
   }
 }
 
 class MarkCompactCollector::Sweeper::SweeperTask : public v8::Task {
@@ skipping 132 matching lines @@
 }
 
 bool MarkCompactCollector::Sweeper::IsSweepingCompleted() {
   while (pending_sweeper_tasks_semaphore_.WaitFor(
       base::TimeDelta::FromSeconds(0))) {
     num_sweeping_tasks_.Increment(-1);
   }
   return num_sweeping_tasks_.Value() == 0;
 }
 
-void Marking::TransferMark(Heap* heap, Address old_start, Address new_start) {
-  // This is only used when resizing an object.
-  DCHECK(MemoryChunk::FromAddress(old_start) ==
-         MemoryChunk::FromAddress(new_start));
-
-  if (!heap->incremental_marking()->IsMarking() ||
-      Page::FromAddress(old_start)->IsFlagSet(Page::BLACK_PAGE))
-    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;
-
-  MarkBit new_mark_bit = MarkBitFrom(new_start);
-  MarkBit old_mark_bit = MarkBitFrom(old_start);
-
-#ifdef DEBUG
-  ObjectColor old_color = Color(old_mark_bit);
-#endif
-
-  if (Marking::IsBlack(old_mark_bit)) {
-    Marking::BlackToWhite(old_mark_bit);
-    Marking::MarkBlack(new_mark_bit);
-    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()->RestartIfNotMarking();
-  }
-
-#ifdef DEBUG
-  ObjectColor new_color = Color(new_mark_bit);
-  DCHECK(new_color == old_color);
-#endif
-}
-
-
 const char* AllocationSpaceName(AllocationSpace space) {
   switch (space) {
     case NEW_SPACE:
       return "NEW_SPACE";
     case OLD_SPACE:
       return "OLD_SPACE";
     case CODE_SPACE:
       return "CODE_SPACE";
     case MAP_SPACE:
       return "MAP_SPACE";
@@ skipping 329 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 = Marking::MarkBitFrom(code);
+    MarkBit code_mark = ObjectMarking::MarkBitFrom(code);
     if (Marking::IsWhite(code_mark)) {
       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();
       }
@@ skipping 26 matching lines @@
 void CodeFlusher::ProcessSharedFunctionInfoCandidates() {
   Code* lazy_compile = isolate_->builtins()->builtin(Builtins::kCompileLazy);
 
   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 = Marking::MarkBitFrom(code);
+    MarkBit code_mark = ObjectMarking::MarkBitFrom(code);
     if (Marking::IsWhite(code_mark)) {
       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();
       }
@@ skipping 116 matching lines @@
       // We are close to a stack overflow, so just mark the objects.
     }
     MarkCompactCollector* collector = heap->mark_compact_collector();
     for (Object** p = start; p < end; p++) {
       MarkObjectByPointer(collector, object, p);
     }
   }
 
   // Marks the object black and pushes it on the marking stack.
   INLINE(static void MarkObject(Heap* heap, HeapObject* object)) {
-    MarkBit mark = Marking::MarkBitFrom(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 = Marking::MarkBitFrom(object);
+    MarkBit mark_bit = ObjectMarking::MarkBitFrom(object);
     if (Marking::IsWhite(mark_bit)) {
       heap->mark_compact_collector()->SetMark(object, mark_bit);
       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 = Marking::MarkBitFrom(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 = Marking::MarkBitFrom(obj);
+    MarkBit mark = ObjectMarking::MarkBitFrom(obj);
     heap->mark_compact_collector()->SetMark(obj, mark);
     // Mark the map pointer and the body.
-    MarkBit map_mark = Marking::MarkBitFrom(map);
+    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 = Marking::MarkBitFrom(obj);
+      MarkBit mark = ObjectMarking::MarkBitFrom(obj);
       if (Marking::IsBlackOrGrey(mark)) continue;
       VisitUnmarkedObject(collector, obj);
     }
     return true;
   }
 
  private:
   // Code flushing support.
 
   static const int kRegExpCodeThreshold = 5;
@@ skipping 13 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(Marking::MarkBitFrom(data))) {
+      if (Marking::IsBlackOrGrey(ObjectMarking::MarkBitFrom(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 67 matching lines @@
       : collector_(collector) {}
 
   void VisitPointers(Object** start, Object** end) override {
     for (Object** p = start; p < end; p++) VisitPointer(p);
   }
 
   void VisitPointer(Object** slot) override {
     Object* obj = *slot;
     if (obj->IsSharedFunctionInfo()) {
       SharedFunctionInfo* shared = reinterpret_cast<SharedFunctionInfo*>(obj);
-      MarkBit shared_mark = Marking::MarkBitFrom(shared);
-      MarkBit code_mark = Marking::MarkBitFrom(shared->code());
+      MarkBit shared_mark = ObjectMarking::MarkBitFrom(shared);
+      MarkBit code_mark = ObjectMarking::MarkBitFrom(shared->code());
       collector_->MarkObject(shared->code(), code_mark);
       collector_->MarkObject(shared, shared_mark);
     }
   }
 
  private:
   MarkCompactCollector* collector_;
 };
 
 
 void MarkCompactCollector::PrepareThreadForCodeFlushing(Isolate* isolate,
                                                         ThreadLocalTop* top) {
   for (StackFrameIterator it(isolate, top); !it.done(); it.Advance()) {
     // Note: for the frame that has a pending lazy deoptimization
     // StackFrame::unchecked_code will return a non-optimized code object for
     // the outermost function and StackFrame::LookupCode will return
     // actual optimized code object.
     StackFrame* frame = it.frame();
     Code* code = frame->unchecked_code();
-    MarkBit code_mark = Marking::MarkBitFrom(code);
+    MarkBit code_mark = ObjectMarking::MarkBitFrom(code);
     MarkObject(code, code_mark);
     if (frame->is_optimized()) {
       Code* optimized_code = frame->LookupCode();
-      MarkBit optimized_code_mark = Marking::MarkBitFrom(optimized_code);
+      MarkBit optimized_code_mark = ObjectMarking::MarkBitFrom(optimized_code);
       MarkObject(optimized_code, optimized_code_mark);
     }
   }
 }
 
 
 void MarkCompactCollector::PrepareForCodeFlushing() {
   // If code flushing is disabled, there is no need to prepare for it.
   if (!is_code_flushing_enabled()) return;
 
@@ skipping 31 matching lines @@
   // Skip the weak next code link in a code object, which is visited in
   // ProcessTopOptimizedFrame.
   void VisitNextCodeLink(Object** p) override {}
 
  private:
   void MarkObjectByPointer(Object** p) {
     if (!(*p)->IsHeapObject()) return;
 
     HeapObject* object = HeapObject::cast(*p);
 
-    MarkBit mark_bit = Marking::MarkBitFrom(object);
+    MarkBit mark_bit = ObjectMarking::MarkBitFrom(object);
     if (Marking::IsBlackOrGrey(mark_bit)) return;
 
     Map* map = object->map();
     // Mark the object.
     collector_->SetMark(object, mark_bit);
 
     // Mark the map pointer and body, and push them on the marking stack.
-    MarkBit map_mark = Marking::MarkBitFrom(map);
+    MarkBit map_mark = ObjectMarking::MarkBitFrom(map);
     collector_->MarkObject(map, map_mark);
     MarkCompactMarkingVisitor::IterateBody(map, object);
 
     // Mark all the objects reachable from the map and body.  May leave
     // overflowed objects in the heap.
     collector_->EmptyMarkingDeque();
   }
 
   MarkCompactCollector* collector_;
 };
 
 
 // Helper class for pruning the string table.
 template <bool finalize_external_strings, bool record_slots>
 class StringTableCleaner : public ObjectVisitor {
  public:
   StringTableCleaner(Heap* heap, HeapObject* table)
       : 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(Marking::MarkBitFrom(HeapObject::cast(o)))) {
+        if (Marking::IsWhite(ObjectMarking::MarkBitFrom(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 = Marking::MarkBitFrom(HeapObject::cast(object));
+    MarkBit mark_bit = ObjectMarking::MarkBitFrom(HeapObject::cast(object));
     DCHECK(!Marking::IsGrey(mark_bit));
     if (Marking::IsBlack(mark_bit)) {
       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 = Marking::MarkBitFrom(object);
+    MarkBit markbit = ObjectMarking::MarkBitFrom(object);
     if ((object->map() != filler_map) && Marking::IsGrey(markbit)) {
       Marking::GreyToBlack(markbit);
       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 = Marking::MarkBitFrom(object);
+    MarkBit markbit = ObjectMarking::MarkBitFrom(object);
     DCHECK(Marking::IsGrey(markbit));
     Marking::GreyToBlack(markbit);
     PushBlack(object);
     if (marking_deque()->IsFull()) return;
   }
 }
 
 class RecordMigratedSlotVisitor final : public ObjectVisitor {
  public:
   explicit RecordMigratedSlotVisitor(MarkCompactCollector* collector)
@@ skipping 425 matching lines @@
     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 = Marking::MarkBitFrom(heap_object);
+  MarkBit mark = ObjectMarking::MarkBitFrom(heap_object);
   return Marking::IsWhite(mark);
 }
 
 
 bool MarkCompactCollector::IsUnmarkedHeapObjectWithHeap(Heap* heap,
                                                         Object** p) {
   Object* o = *p;
   DCHECK(o->IsHeapObject());
   HeapObject* heap_object = HeapObject::cast(o);
-  MarkBit mark = Marking::MarkBitFrom(heap_object);
+  MarkBit mark = ObjectMarking::MarkBitFrom(heap_object);
   return Marking::IsWhite(mark);
 }
 
 
 void MarkCompactCollector::MarkStringTable(RootMarkingVisitor* visitor) {
   StringTable* string_table = heap()->string_table();
   // Mark the string table itself.
-  MarkBit string_table_mark = Marking::MarkBitFrom(string_table);
+  MarkBit string_table_mark = ObjectMarking::MarkBitFrom(string_table);
   if (Marking::IsWhite(string_table_mark)) {
     // String table could have already been marked by visiting the handles list.
     SetMark(string_table, string_table_mark);
   }
   // Explicitly mark the prefix.
   string_table->IteratePrefix(visitor);
   ProcessMarkingDeque();
 }
 
 
 void MarkCompactCollector::MarkAllocationSite(AllocationSite* site) {
-  MarkBit mark_bit = Marking::MarkBitFrom(site);
+  MarkBit mark_bit = ObjectMarking::MarkBitFrom(site);
   SetMark(site, mark_bit);
 }
 
 
 void MarkCompactCollector::MarkRoots(RootMarkingVisitor* 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.
@@ skipping 46 matching lines @@
   Map* filler_map = heap_->one_pointer_filler_map();
   while (!marking_deque_.IsEmpty()) {
     HeapObject* object = marking_deque_.Pop();
     // Explicitly skip one word fillers. Incremental markbit patterns are
     // correct only for objects that occupy at least two words.
     Map* map = object->map();
     if (map == filler_map) continue;
 
     DCHECK(object->IsHeapObject());
     DCHECK(heap()->Contains(object));
-    DCHECK(!Marking::IsWhite(Marking::MarkBitFrom(object)));
+    DCHECK(!Marking::IsWhite(ObjectMarking::MarkBitFrom(object)));
 
-    MarkBit map_mark = Marking::MarkBitFrom(map);
+    MarkBit map_mark = ObjectMarking::MarkBitFrom(map);
     MarkObject(map, map_mark);
 
     MarkCompactMarkingVisitor::IterateBody(map, object);
   }
 }
 
 
 // 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 182 matching lines @@
     wrappers_to_trace_.push_back(std::pair<void*, void*>(
         reinterpret_cast<void*>(js_object->GetInternalField(0)),
         reinterpret_cast<void*>(js_object->GetInternalField(1))));
   }
 }
 
 void MarkCompactCollector::RegisterExternallyReferencedObject(Object** object) {
   DCHECK(in_use());
   HeapObject* heap_object = HeapObject::cast(*object);
   DCHECK(heap_->Contains(heap_object));
-  MarkBit mark_bit = Marking::MarkBitFrom(heap_object);
+  MarkBit mark_bit = ObjectMarking::MarkBitFrom(heap_object);
   MarkObject(heap_object, mark_bit);
 }
 
 void MarkCompactCollector::MarkLiveObjects() {
   TRACE_GC(heap()->tracer(), GCTracer::Scope::MC_MARK);
   double start_time = 0.0;
   if (FLAG_print_cumulative_gc_stat) {
     start_time = heap_->MonotonicallyIncreasingTimeInMs();
   }
   // The recursive GC marker detects when it is nearing stack overflow,
@@ skipping 222 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::FromInt(0)) {
     WeakCell* weak_cell = WeakCell::cast(weak_cell_obj);
     Map* map = Map::cast(weak_cell->value());
-    DCHECK(Marking::IsWhite(Marking::MarkBitFrom(map)));
+    DCHECK(Marking::IsWhite(ObjectMarking::MarkBitFrom(map)));
     Object* potential_parent = map->constructor_or_backpointer();
     if (potential_parent->IsMap()) {
       Map* parent = Map::cast(potential_parent);
-      if (Marking::IsBlackOrGrey(Marking::MarkBitFrom(parent)) &&
+      if (Marking::IsBlackOrGrey(ObjectMarking::MarkBitFrom(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 19 matching lines @@
   HeapObject* undefined = heap()->undefined_value();
   Object* obj = heap()->encountered_transition_arrays();
   while (obj != Smi::FromInt(0)) {
     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(Marking::MarkBitFrom(parent));
+          Marking::IsBlackOrGrey(ObjectMarking::MarkBitFrom(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::FromInt(0));
 }
 
 
 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(Marking::MarkBitFrom(target))) {
+    if (Marking::IsWhite(ObjectMarking::MarkBitFrom(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 156 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 = Marking::MarkBitFrom(value);
+          MarkBit mark = ObjectMarking::MarkBitFrom(value);
           SetMark(value, mark);
           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.
@@ skipping 214 matching lines @@
   // Find the last live object in the cell.
   unsigned int leading_zeros =
       base::bits::CountLeadingZeros32(current_cell & slot_mask);
   CHECK(leading_zeros != Bitmap::kBitsPerCell);
   int offset = static_cast<int>(Bitmap::kBitIndexMask - leading_zeros) - 1;
 
   base_address += (cell_index - base_address_cell_index) *
                   Bitmap::kBitsPerCell * kPointerSize;
   Address address = base_address + offset * kPointerSize;
   HeapObject* object = HeapObject::FromAddress(address);
-  CHECK(Marking::IsBlack(Marking::MarkBitFrom(object)));
+  CHECK(Marking::IsBlack(ObjectMarking::MarkBitFrom(object)));
   CHECK(object->address() < reinterpret_cast<Address>(slot));
   if ((object->address() + kPointerSize) <= slot &&
       (object->address() + object->Size()) > slot) {
     // If the slot is within the last found object in the cell, the slot is
     // in a live object.
     // Slots pointing to the first word of an object are invalid and removed.
     // This can happen when we move the object header while left trimming.
     return true;
   }
   return false;
@@ skipping 391 matching lines @@
     skip_list->Clear();
   }
 
   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(Marking::MarkBitFrom(object)));
+    DCHECK(Marking::IsBlack(ObjectMarking::MarkBitFrom(object)));
     Address free_end = object->address();
     if (free_end != free_start) {
       int size = static_cast<int>(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);
         max_freed_bytes = Max(freed_bytes, max_freed_bytes);
@@ skipping 10 matching lines @@
           SkipList::RegionNumber(free_end + size - kPointerSize);
       if (new_region_start != curr_region || new_region_end != curr_region) {
         skip_list->AddObject(free_end, size);
         curr_region = new_region_end;
       }
     }
     free_start = free_end + size;
   }
 
   // Clear the mark bits of that page and reset live bytes count.
-  Bitmap::Clear(p);
+  p->ClearLiveness();
 
   if (free_start != p->area_end()) {
     int size = static_cast<int>(p->area_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);
       max_freed_bytes = Max(freed_bytes, max_freed_bytes);
@@ skipping 12 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 = Marking::MarkBitFrom(code);
+    MarkBit mark_bit = ObjectMarking::MarkBitFrom(code);
     if (Marking::IsWhite(mark_bit)) 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(Marking::MarkBitFrom(object)));
+    CHECK(Marking::IsBlack(ObjectMarking::MarkBitFrom(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(Marking::MarkBitFrom(object)));
+    DCHECK(Marking::IsBlack(ObjectMarking::MarkBitFrom(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()));
         }
         if (page->typed_old_to_new_slots() != nullptr) {
           RememberedSet<OLD_TO_NEW>::RemoveRangeTyped(page, page->address(),
                                                       object->address());
         }
         RecomputeLiveBytes(page);
       }
       return false;
     }
   }
   if (mode == kClearMarkbits) {
-    Bitmap::Clear(page);
+    page->ClearLiveness();
   }
   return true;
 }
 
 
 void MarkCompactCollector::RecomputeLiveBytes(MemoryChunk* page) {
   LiveObjectIterator<kBlackObjects> it(page);
   int new_live_size = 0;
   HeapObject* object = nullptr;
   while ((object = it.Next()) != nullptr) {
     new_live_size += object->Size();
   }
   page->SetLiveBytes(new_live_size);
 }
 
 
 void MarkCompactCollector::VisitLiveObjectsBody(Page* page,
                                                 ObjectVisitor* visitor) {
 #ifdef VERIFY_HEAP
   VerifyAllBlackObjects(page);
 #endif  // VERIFY_HEAP
 
   LiveObjectIterator<kBlackObjects> it(page);
   HeapObject* object = NULL;
   while ((object = it.Next()) != NULL) {
-    DCHECK(Marking::IsBlack(Marking::MarkBitFrom(object)));
+    DCHECK(Marking::IsBlack(ObjectMarking::MarkBitFrom(object)));
     Map* map = object->synchronized_map();
     int size = object->SizeFromMap(map);
     object->IterateBody(map->instance_type(), size, visitor);
   }
 }
 
 void MarkCompactCollector::Sweeper::AddSweptPageSafe(PagedSpace* space,
                                                      Page* page) {
   base::LockGuard<base::Mutex> guard(&mutex_);
   swept_list_[space->identity()].Add(page);
@@ skipping 133 matching lines @@
       // just freed free space object.
       if (heap->InToSpace(*slot)) {
         return KEEP_SLOT;
       }
     } else if (heap->InToSpace(*slot)) {
       // 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(
-              Marking::MarkBitFrom(reinterpret_cast<HeapObject*>(*slot))))
+              ObjectMarking::MarkBitFrom(reinterpret_cast<HeapObject*>(*slot))))
         return KEEP_SLOT;
     } else {
       DCHECK(!heap->InNewSpace(*slot));
     }
     return REMOVE_SLOT;
   }
 };
 
 int NumberOfPointerUpdateTasks(int pages) {
   if (!FLAG_parallel_pointer_update) return 1;
@@ skipping 225 matching lines @@
 
     if (p->IsEvacuationCandidate()) {
       // Will be processed in EvacuateNewSpaceAndCandidates.
       DCHECK(evacuation_candidates_.length() > 0);
       continue;
     }
 
     // We can not sweep black pages, since all mark bits are set for these
     // pages.
     if (p->IsFlagSet(Page::BLACK_PAGE)) {
-      Bitmap::Clear(p);
+      p->ClearLiveness();
       p->concurrent_sweeping_state().SetValue(Page::kSweepingDone);
       p->ClearFlag(Page::BLACK_PAGE);
       // Area above the high watermark is free.
       Address free_start = p->HighWaterMark();
       // Check if the space top was in this page, which means that the
       // high watermark is not up-to-date.
       if (free_start < space_top && space_top <= p->area_end()) {
         free_start = space_top;
       }
       int size = static_cast<int>(p->area_end() - free_start);
@@ skipping 98 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 = Marking::MarkBitFrom(host);
+    MarkBit mark_bit = ObjectMarking::MarkBitFrom(host);
     if (Marking::IsBlack(mark_bit)) {
       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