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

src/heap/mark-compact.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_H_
 #define V8_HEAP_MARK_COMPACT_H_
 
 #include <deque>
 
 #include "src/base/bits.h"
@@ skipping 64 matching lines @@
 
   template <MarkBit::AccessMode access_mode = MarkBit::NON_ATOMIC>
   V8_INLINE static bool IsBlackOrGrey(HeapObject* obj,
                                       const MarkingState& state) {
     return Marking::IsBlackOrGrey<access_mode>(MarkBitFrom(obj, state));
   }
 
   template <MarkBit::AccessMode access_mode = MarkBit::NON_ATOMIC>
   V8_INLINE static bool BlackToGrey(HeapObject* obj,
                                     const MarkingState& state) {
-    DCHECK(
-        (access_mode == MarkBit::ATOMIC || IsBlack<access_mode>(obj, state)));
     MarkBit markbit = MarkBitFrom(obj, state);
     if (!Marking::BlackToGrey<access_mode>(markbit)) return false;
     state.IncrementLiveBytes<access_mode>(-obj->Size());
     return true;
   }
 
   template <MarkBit::AccessMode access_mode = MarkBit::NON_ATOMIC>
   V8_INLINE static bool WhiteToGrey(HeapObject* obj,
                                     const MarkingState& state) {
-    DCHECK(
-        (access_mode == MarkBit::ATOMIC || IsWhite<access_mode>(obj, state)));
     return Marking::WhiteToGrey<access_mode>(MarkBitFrom(obj, state));
   }
 
   template <MarkBit::AccessMode access_mode = MarkBit::NON_ATOMIC>
   V8_INLINE static bool WhiteToBlack(HeapObject* obj,
                                      const MarkingState& state) {
-    DCHECK(
-        (access_mode == MarkBit::ATOMIC || IsWhite<access_mode>(obj, state)));
-    if (!ObjectMarking::WhiteToGrey<access_mode>(obj, state)) return false;
-    return ObjectMarking::GreyToBlack<access_mode>(obj, state);
+    return ObjectMarking::WhiteToGrey<access_mode>(obj, state) &&
+           ObjectMarking::GreyToBlack<access_mode>(obj, state);
   }
 
   template <MarkBit::AccessMode access_mode = MarkBit::NON_ATOMIC>
   V8_INLINE static bool GreyToBlack(HeapObject* obj,
                                     const MarkingState& state) {
-    DCHECK((access_mode == MarkBit::ATOMIC || IsGrey<access_mode>(obj, state)));
     MarkBit markbit = MarkBitFrom(obj, state);
     if (!Marking::GreyToBlack<access_mode>(markbit)) return false;
     state.IncrementLiveBytes<access_mode>(obj->Size());
     return true;
   }
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(ObjectMarking);
 };
 
@@ skipping 628 matching lines @@
   ~EvacuationScope() { collector_->set_evacuation(false); }
 
  private:
   MarkCompactCollector* collector_;
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_MARK_COMPACT_H_