[heap] Reland "Make non-atomic markbit operations consistent with atomic ones."

src/heap/mark-compact-inl.h

 // 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.
 
 #ifndef V8_HEAP_MARK_COMPACT_INL_H_
 #define V8_HEAP_MARK_COMPACT_INL_H_
 
 #include "src/heap/mark-compact.h"
 #include "src/heap/remembered-set.h"
 #include "src/isolate.h"
@@ skipping 20 matching lines @@
 }
 
 void MarkCompactCollector::UnshiftBlack(HeapObject* obj) {
   DCHECK(ObjectMarking::IsBlack(obj, MarkingState::Internal(obj)));
   if (!marking_deque()->Unshift(obj)) {
     ObjectMarking::BlackToGrey(obj, MarkingState::Internal(obj));
   }
 }
 
 void MarkCompactCollector::MarkObject(HeapObject* obj) {
-  if (ObjectMarking::IsWhite<MarkBit::NON_ATOMIC>(
+  if (ObjectMarking::WhiteToBlack<MarkBit::NON_ATOMIC>(
           obj, MarkingState::Internal(obj))) {
-    ObjectMarking::WhiteToBlack<MarkBit::NON_ATOMIC>(
-        obj, MarkingState::Internal(obj));
     PushBlack(obj);
   }
 }
 
 void MinorMarkCompactCollector::MarkObject(HeapObject* obj) {
-  if (ObjectMarking::IsWhite<MarkBit::NON_ATOMIC>(
+  if (ObjectMarking::WhiteToBlack<MarkBit::NON_ATOMIC>(
           obj, MarkingState::External(obj))) {
-    ObjectMarking::WhiteToBlack<MarkBit::NON_ATOMIC>(
-        obj, MarkingState::External(obj));
     PushBlack(obj);
   }
 }
 
 void MarkCompactCollector::RecordSlot(HeapObject* object, Object** slot,
                                       Object* target) {
   Page* target_page = Page::FromAddress(reinterpret_cast<Address>(target));
   Page* source_page = Page::FromAddress(reinterpret_cast<Address>(object));
   if (target_page->IsEvacuationCandidate() &&
       !ShouldSkipEvacuationSlotRecording(object)) {
@@ skipping 185 matching lines @@
     }
     if (object != nullptr) return object;
   }
   return nullptr;
 }
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_MARK_COMPACT_INL_H_