cppgc: Move AccessMode to globals.h

Bug: chromium:1056170
Change-Id: I697a33f51618c0b7b3b60a9a2abcb7bf4ab1d033
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2491032
Commit-Queue: Omer Katz <omerkatz@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70709}

src/heap/cppgc/concurrent-marker.cc

@@ -104,8 +104,7 @@ void ConcurrentMarkingTask::ProcessWorklists(
              &concurrent_marking_visitor](HeapObjectHeader* header) {
               BasePage::FromPayload(header)->SynchronizedLoad();
               concurrent_marking_state.AccountMarkedBytes(*header);
-              DynamicallyTraceMarkedObject<
-                  HeapObjectHeader::AccessMode::kAtomic>(
+              DynamicallyTraceMarkedObject<AccessMode::kAtomic>(
                   concurrent_marking_visitor, *header);
             })) {
       return;
@@ -121,9 +120,8 @@ void ConcurrentMarkingTask::ProcessWorklists(
                   ->SynchronizedLoad();
               const HeapObjectHeader& header =
                   HeapObjectHeader::FromPayload(item.base_object_payload);
-              DCHECK(!header.IsInConstruction<
-                      HeapObjectHeader::AccessMode::kAtomic>());
-              DCHECK(header.IsMarked<HeapObjectHeader::AccessMode::kAtomic>());
+              DCHECK(!header.IsInConstruction<AccessMode::kAtomic>());
+              DCHECK(header.IsMarked<AccessMode::kAtomic>());
               concurrent_marking_state.AccountMarkedBytes(header);
               item.callback(&concurrent_marking_visitor,
                             item.base_object_payload);
@@ -139,8 +137,7 @@ void ConcurrentMarkingTask::ProcessWorklists(
              &concurrent_marking_visitor](HeapObjectHeader* header) {
               BasePage::FromPayload(header)->SynchronizedLoad();
               concurrent_marking_state.AccountMarkedBytes(*header);
-              DynamicallyTraceMarkedObject<
-                  HeapObjectHeader::AccessMode::kAtomic>(
+              DynamicallyTraceMarkedObject<AccessMode::kAtomic>(
                   concurrent_marking_visitor, *header);
             })) {
       return;

src/heap/cppgc/globals.h

@@ -20,6 +20,9 @@ constexpr size_t kKB = 1024;
 constexpr size_t kMB = kKB * 1024;
 constexpr size_t kGB = kMB * 1024;
 
+// AccessMode used for choosing between atomic and non-atomic accesses.
+enum class AccessMode : uint8_t { kNonAtomic, kAtomic };
+
 // See 6.7.6 (http://eel.is/c++draft/basic.align) for alignment restrictions. We
 // do not fully support all alignment restrictions (following
 // alignof(std​::​max_­align_­t)) but limit to alignof(double).

src/heap/cppgc/heap-object-header.h

@@ -53,8 +53,6 @@ namespace internal {
 //    to allow potentially accessing them non-atomically.
 class HeapObjectHeader {
  public:
-  enum class AccessMode : uint8_t { kNonAtomic, kAtomic };
-
   static constexpr size_t kSizeLog2 = 17;
   static constexpr size_t kMaxSize = (size_t{1} << kSizeLog2) - 1;
   static constexpr uint16_t kLargeObjectSizeInHeader = 0;
@@ -181,14 +179,14 @@ Address HeapObjectHeader::Payload() const {
          sizeof(HeapObjectHeader);
 }
 
-template <HeapObjectHeader::AccessMode mode>
+template <AccessMode mode>
 GCInfoIndex HeapObjectHeader::GetGCInfoIndex() const {
   const uint16_t encoded =
       LoadEncoded<mode, EncodedHalf::kHigh, std::memory_order_acquire>();
   return GCInfoIndexField::decode(encoded);
 }
 
-template <HeapObjectHeader::AccessMode mode>
+template <AccessMode mode>
 size_t HeapObjectHeader::GetSize() const {
   // Size is immutable after construction while either marking or sweeping
   // is running so relaxed load (if mode == kAtomic) is enough.
@@ -203,12 +201,12 @@ void HeapObjectHeader::SetSize(size_t size) {
   encoded_low_ |= EncodeSize(size);
 }
 
-template <HeapObjectHeader::AccessMode mode>
+template <AccessMode mode>
 bool HeapObjectHeader::IsLargeObject() const {
   return GetSize<mode>() == kLargeObjectSizeInHeader;
 }
 
-template <HeapObjectHeader::AccessMode mode>
+template <AccessMode mode>
 bool HeapObjectHeader::IsInConstruction() const {
   const uint16_t encoded =
       LoadEncoded<mode, EncodedHalf::kHigh, std::memory_order_acquire>();
@@ -219,14 +217,14 @@ void HeapObjectHeader::MarkAsFullyConstructed() {
   MakeGarbageCollectedTraitInternal::MarkObjectAsFullyConstructed(Payload());
 }
 
-template <HeapObjectHeader::AccessMode mode>
+template <AccessMode mode>
 bool HeapObjectHeader::IsMarked() const {
   const uint16_t encoded =
       LoadEncoded<mode, EncodedHalf::kLow, std::memory_order_relaxed>();
   return MarkBitField::decode(encoded);
 }
 
-template <HeapObjectHeader::AccessMode mode>
+template <AccessMode mode>
 void HeapObjectHeader::Unmark() {
   DCHECK(IsMarked<mode>());
   StoreEncoded<mode, EncodedHalf::kLow, std::memory_order_relaxed>(
@@ -244,12 +242,12 @@ bool HeapObjectHeader::TryMarkAtomic() {
                                                  std::memory_order_relaxed);
 }
 
-template <HeapObjectHeader::AccessMode mode>
+template <AccessMode mode>
 bool HeapObjectHeader::IsYoung() const {
   return !IsMarked<mode>();
 }
 
-template <HeapObjectHeader::AccessMode mode>
+template <AccessMode mode>
 bool HeapObjectHeader::IsFree() const {
   return GetGCInfoIndex<mode>() == kFreeListGCInfoIndex;
 }
@@ -259,7 +257,7 @@ bool HeapObjectHeader::IsFinalizable() const {
   return gc_info.finalize;
 }
 
-template <HeapObjectHeader::AccessMode mode, HeapObjectHeader::EncodedHalf part,
+template <AccessMode mode, HeapObjectHeader::EncodedHalf part,
           std::memory_order memory_order>
 uint16_t HeapObjectHeader::LoadEncoded() const {
   const uint16_t& half =
@@ -268,7 +266,7 @@ uint16_t HeapObjectHeader::LoadEncoded() const {
   return v8::base::AsAtomicPtr(&half)->load(memory_order);
 }
 
-template <HeapObjectHeader::AccessMode mode, HeapObjectHeader::EncodedHalf part,
+template <AccessMode mode, HeapObjectHeader::EncodedHalf part,
           std::memory_order memory_order>
 void HeapObjectHeader::StoreEncoded(uint16_t bits, uint16_t mask) {
   // Caveat: Not all changes to HeapObjectHeader's bitfields go through

src/heap/cppgc/heap-page.h

@@ -48,11 +48,9 @@ class V8_EXPORT_PRIVATE BasePage {
   ConstAddress PayloadEnd() const;
 
   // |address| must refer to real object.
-  template <
-      HeapObjectHeader::AccessMode = HeapObjectHeader::AccessMode::kNonAtomic>
+  template <AccessMode = AccessMode::kNonAtomic>
   HeapObjectHeader& ObjectHeaderFromInnerAddress(void* address) const;
-  template <
-      HeapObjectHeader::AccessMode = HeapObjectHeader::AccessMode::kNonAtomic>
+  template <AccessMode = AccessMode::kNonAtomic>
   const HeapObjectHeader& ObjectHeaderFromInnerAddress(
       const void* address) const;
 
@@ -237,8 +235,7 @@ const BasePage* BasePage::FromPayload(const void* payload) {
       kGuardPageSize);
 }
 
-template <HeapObjectHeader::AccessMode mode =
-              HeapObjectHeader::AccessMode::kNonAtomic>
+template <AccessMode mode = AccessMode::kNonAtomic>
 const HeapObjectHeader* ObjectHeaderFromInnerAddressImpl(const BasePage* page,
                                                          const void* address) {
   if (page->is_large()) {
@@ -248,19 +245,18 @@ const HeapObjectHeader* ObjectHeaderFromInnerAddressImpl(const BasePage* page,
       NormalPage::From(page)->object_start_bitmap();
   const HeapObjectHeader* header =
       bitmap.FindHeader<mode>(static_cast<ConstAddress>(address));
-  DCHECK_LT(address,
-            reinterpret_cast<ConstAddress>(header) +
-                header->GetSize<HeapObjectHeader::AccessMode::kAtomic>());
+  DCHECK_LT(address, reinterpret_cast<ConstAddress>(header) +
+                         header->GetSize<AccessMode::kAtomic>());
   return header;
 }
 
-template <HeapObjectHeader::AccessMode mode>
+template <AccessMode mode>
 HeapObjectHeader& BasePage::ObjectHeaderFromInnerAddress(void* address) const {
   return const_cast<HeapObjectHeader&>(
       ObjectHeaderFromInnerAddress<mode>(const_cast<const void*>(address)));
 }
 
-template <HeapObjectHeader::AccessMode mode>
+template <AccessMode mode>
 const HeapObjectHeader& BasePage::ObjectHeaderFromInnerAddress(
     const void* address) const {
   // This method might be called for |address| found via a Trace method of

src/heap/cppgc/marker.cc

@@ -67,8 +67,7 @@ void VisitRememberedSlots(HeapBase& heap,
     // top level (with the guarantee that no objects are currently being in
     // construction). This can be ensured by running young GCs from safe points
     // or by reintroducing nested allocation scopes that avoid finalization.
-    DCHECK(
-        !header.IsInConstruction<HeapObjectHeader::AccessMode::kNonAtomic>());
+    DCHECK(!header.IsInConstruction<AccessMode::kNonAtomic>());
 
     void* value = *reinterpret_cast<void**>(slot);
     mutator_marking_state.DynamicallyMarkAddress(static_cast<Address>(value));
@@ -378,8 +377,8 @@ bool MarkerBase::ProcessWorklistsWithDeadline(
             mutator_marking_state_.previously_not_fully_constructed_worklist(),
             [this](HeapObjectHeader* header) {
               mutator_marking_state_.AccountMarkedBytes(*header);
-              DynamicallyTraceMarkedObject<
-                  HeapObjectHeader::AccessMode::kNonAtomic>(visitor(), *header);
+              DynamicallyTraceMarkedObject<AccessMode::kNonAtomic>(visitor(),
+                                                                   *header);
             })) {
       return false;
     }
@@ -390,10 +389,8 @@ bool MarkerBase::ProcessWorklistsWithDeadline(
             [this](const MarkingWorklists::MarkingItem& item) {
               const HeapObjectHeader& header =
                   HeapObjectHeader::FromPayload(item.base_object_payload);
-              DCHECK(!header.IsInConstruction<
-                      HeapObjectHeader::AccessMode::kNonAtomic>());
-              DCHECK(
-                  header.IsMarked<HeapObjectHeader::AccessMode::kNonAtomic>());
+              DCHECK(!header.IsInConstruction<AccessMode::kNonAtomic>());
+              DCHECK(header.IsMarked<AccessMode::kNonAtomic>());
               mutator_marking_state_.AccountMarkedBytes(header);
               item.callback(&visitor(), item.base_object_payload);
             })) {
@@ -405,8 +402,8 @@ bool MarkerBase::ProcessWorklistsWithDeadline(
             mutator_marking_state_.write_barrier_worklist(),
             [this](HeapObjectHeader* header) {
               mutator_marking_state_.AccountMarkedBytes(*header);
-              DynamicallyTraceMarkedObject<
-                  HeapObjectHeader::AccessMode::kNonAtomic>(visitor(), *header);
+              DynamicallyTraceMarkedObject<AccessMode::kNonAtomic>(visitor(),
+                                                                   *header);
             })) {
       return false;
     }

src/heap/cppgc/marker.h

@@ -214,8 +214,7 @@ class V8_EXPORT_PRIVATE Marker final : public MarkerBase {
 
 void MarkerBase::WriteBarrierForInConstructionObject(HeapObjectHeader& header) {
   mutator_marking_state_.not_fully_constructed_worklist()
-      .Push<MarkingWorklists::NotFullyConstructedWorklist::AccessMode::kAtomic>(
-          &header);
+      .Push<AccessMode::kAtomic>(&header);
 }
 
 void MarkerBase::WriteBarrierForObject(HeapObjectHeader& header) {

src/heap/cppgc/marking-state.cc

@@ -11,8 +11,7 @@ namespace internal {
 
 void MutatorMarkingState::FlushNotFullyConstructedObjects() {
   std::unordered_set<HeapObjectHeader*> objects =
-      not_fully_constructed_worklist_.Extract<
-          MarkingWorklists::NotFullyConstructedWorklist::AccessMode::kAtomic>();
+      not_fully_constructed_worklist_.Extract<AccessMode::kAtomic>();
   for (HeapObjectHeader* object : objects) {
     if (MarkNoPush(*object))
       previously_not_fully_constructed_worklist_.Push(object);

src/heap/cppgc/marking-state.h

@@ -150,10 +150,8 @@ void MarkingStateBase::MarkAndPush(HeapObjectHeader& header,
                                    TraceDescriptor desc) {
   DCHECK_NOT_NULL(desc.callback);
 
-  if (header.IsInConstruction<HeapObjectHeader::AccessMode::kAtomic>()) {
-    not_fully_constructed_worklist_.Push<
-        MarkingWorklists::NotFullyConstructedWorklist::AccessMode::kAtomic>(
-        &header);
+  if (header.IsInConstruction<AccessMode::kAtomic>()) {
+    not_fully_constructed_worklist_.Push<AccessMode::kAtomic>(&header);
   } else if (MarkNoPush(header)) {
     PushMarked(header, desc);
   }
@@ -164,7 +162,7 @@ bool MarkingStateBase::MarkNoPush(HeapObjectHeader& header) {
   DCHECK_EQ(&heap_, BasePage::FromPayload(&header)->heap());
   // Never mark free space objects. This would e.g. hint to marking a promptly
   // freed backing store.
-  DCHECK(!header.IsFree<HeapObjectHeader::AccessMode::kAtomic>());
+  DCHECK(!header.IsFree<AccessMode::kAtomic>());
   return header.TryMarkAtomic();
 }
 
@@ -177,8 +175,8 @@ void MarkingStateBase::MarkAndPush(HeapObjectHeader& header) {
 
 void MarkingStateBase::PushMarked(HeapObjectHeader& header,
                                   TraceDescriptor desc) {
-  DCHECK(header.IsMarked<HeapObjectHeader::AccessMode::kAtomic>());
-  DCHECK(!header.IsInConstruction<HeapObjectHeader::AccessMode::kAtomic>());
+  DCHECK(header.IsMarked<AccessMode::kAtomic>());
+  DCHECK(!header.IsInConstruction<AccessMode::kAtomic>());
   DCHECK_NOT_NULL(desc.callback);
 
   marking_worklist_.Push(desc);
@@ -192,7 +190,7 @@ void MarkingStateBase::RegisterWeakReferenceIfNeeded(const void* object,
   // ensures that any newly set value after this point is kept alive and does
   // not require the callback.
   if (HeapObjectHeader::FromPayload(desc.base_object_payload)
-          .IsMarked<HeapObjectHeader::AccessMode::kAtomic>())
+          .IsMarked<AccessMode::kAtomic>())
     return;
   RegisterWeakCallback(weak_callback, parameter);
 }
@@ -204,9 +202,7 @@ void MarkingStateBase::RegisterWeakCallback(WeakCallback callback,
 }
 
 void MarkingStateBase::RegisterWeakContainer(HeapObjectHeader& header) {
-  weak_containers_worklist_
-      .Push<MarkingWorklists::WeakContainersWorklist::AccessMode::kAtomic>(
-          &header);
+  weak_containers_worklist_.Push<AccessMode::kAtomic>(&header);
 }
 
 void MarkingStateBase::ProcessWeakContainer(const void* object,
@@ -218,10 +214,8 @@ void MarkingStateBase::ProcessWeakContainer(const void* object,
   HeapObjectHeader& header =
       HeapObjectHeader::FromPayload(const_cast<void*>(object));
 
-  if (header.IsInConstruction<HeapObjectHeader::AccessMode::kAtomic>()) {
-    not_fully_constructed_worklist_.Push<
-        MarkingWorklists::NotFullyConstructedWorklist::AccessMode::kAtomic>(
-        &header);
+  if (header.IsInConstruction<AccessMode::kAtomic>()) {
+    not_fully_constructed_worklist_.Push<AccessMode::kAtomic>(&header);
     return;
   }
 
@@ -245,8 +239,7 @@ void MarkingStateBase::ProcessEphemeron(const void* key,
   // Filter out already marked keys. The write barrier for WeakMember
   // ensures that any newly set value after this point is kept alive and does
   // not require the callback.
-  if (HeapObjectHeader::FromPayload(key)
-          .IsMarked<HeapObjectHeader::AccessMode::kAtomic>()) {
+  if (HeapObjectHeader::FromPayload(key).IsMarked<AccessMode::kAtomic>()) {
     MarkAndPush(value_desc.base_object_payload, value_desc);
     return;
   }
@@ -255,10 +248,10 @@ void MarkingStateBase::ProcessEphemeron(const void* key,
 
 void MarkingStateBase::AccountMarkedBytes(const HeapObjectHeader& header) {
   AccountMarkedBytes(
-      header.IsLargeObject<HeapObjectHeader::AccessMode::kAtomic>()
+      header.IsLargeObject<AccessMode::kAtomic>()
           ? reinterpret_cast<const LargePage*>(BasePage::FromPayload(&header))
                 ->PayloadSize()
-          : header.GetSize<HeapObjectHeader::AccessMode::kAtomic>());
+          : header.GetSize<AccessMode::kAtomic>());
 }
 
 void MarkingStateBase::AccountMarkedBytes(size_t marked_bytes) {
@@ -376,7 +369,7 @@ bool DrainWorklistWithPredicate(Predicate should_yield,
   return true;
 }
 
-template <HeapObjectHeader::AccessMode mode>
+template <AccessMode mode>
 void DynamicallyTraceMarkedObject(Visitor& visitor,
                                   const HeapObjectHeader& header) {
   DCHECK(!header.IsInConstruction<mode>());

src/heap/cppgc/marking-worklists.h

@@ -19,8 +19,6 @@ class MarkingWorklists {
  private:
   class V8_EXPORT_PRIVATE ExternalMarkingWorklist {
    public:
-    using AccessMode = HeapObjectHeader::AccessMode;
-
     template <AccessMode = AccessMode::kNonAtomic>
     void Push(HeapObjectHeader*);
     template <AccessMode = AccessMode::kNonAtomic>
@@ -132,27 +130,27 @@ class MarkingWorklists {
 
 template <>
 struct MarkingWorklists::ExternalMarkingWorklist::ConditionalMutexGuard<
-    MarkingWorklists::ExternalMarkingWorklist::AccessMode::kNonAtomic> {
+    AccessMode::kNonAtomic> {
   explicit ConditionalMutexGuard(v8::base::Mutex*) {}
 };
 
 template <>
 struct MarkingWorklists::ExternalMarkingWorklist::ConditionalMutexGuard<
-    MarkingWorklists::ExternalMarkingWorklist::AccessMode::kAtomic> {
+    AccessMode::kAtomic> {
   explicit ConditionalMutexGuard(v8::base::Mutex* lock) : guard_(lock) {}
 
  private:
   v8::base::MutexGuard guard_;
 };
 
-template <MarkingWorklists::ExternalMarkingWorklist::AccessMode mode>
+template <AccessMode mode>
 void MarkingWorklists::ExternalMarkingWorklist::Push(HeapObjectHeader* object) {
   DCHECK_NOT_NULL(object);
   ConditionalMutexGuard<mode> guard(&lock_);
   objects_.insert(object);
 }
 
-template <MarkingWorklists::ExternalMarkingWorklist::AccessMode mode>
+template <AccessMode mode>
 void MarkingWorklists::ExternalMarkingWorklist::Erase(
     HeapObjectHeader* object) {
   DCHECK_NOT_NULL(object);
@@ -160,14 +158,14 @@ void MarkingWorklists::ExternalMarkingWorklist::Erase(
   objects_.erase(object);
 }
 
-template <MarkingWorklists::ExternalMarkingWorklist::AccessMode mode>
+template <AccessMode mode>
 bool MarkingWorklists::ExternalMarkingWorklist::Contains(
     HeapObjectHeader* object) {
   ConditionalMutexGuard<mode> guard(&lock_);
   return objects_.find(object) != objects_.end();
 }
 
-template <MarkingWorklists::ExternalMarkingWorklist::AccessMode mode>
+template <AccessMode mode>
 std::unordered_set<HeapObjectHeader*>
 MarkingWorklists::ExternalMarkingWorklist::Extract() {
   ConditionalMutexGuard<mode> guard(&lock_);
@@ -177,13 +175,13 @@ MarkingWorklists::ExternalMarkingWorklist::Extract() {
   return extracted;
 }
 
-template <MarkingWorklists::ExternalMarkingWorklist::AccessMode mode>
+template <AccessMode mode>
 void MarkingWorklists::ExternalMarkingWorklist::Clear() {
   ConditionalMutexGuard<mode> guard(&lock_);
   objects_.clear();
 }
 
-template <MarkingWorklists::ExternalMarkingWorklist::AccessMode mode>
+template <AccessMode mode>
 bool MarkingWorklists::ExternalMarkingWorklist::IsEmpty() {
   ConditionalMutexGuard<mode> guard(&lock_);
   return objects_.empty();

src/heap/cppgc/object-allocator.h

@@ -131,8 +131,7 @@ void* ObjectAllocator::AllocateObjectOnSpace(NormalPageSpace* space,
   // The marker needs to find the object start concurrently.
   NormalPage::From(BasePage::FromPayload(header))
       ->object_start_bitmap()
-      .SetBit<HeapObjectHeader::AccessMode::kAtomic>(
-          reinterpret_cast<ConstAddress>(header));
+      .SetBit<AccessMode::kAtomic>(reinterpret_cast<ConstAddress>(header));
 
   return header->Payload();
 }

src/heap/cppgc/object-start-bitmap.h

@@ -44,19 +44,15 @@ class V8_EXPORT_PRIVATE ObjectStartBitmap {
   // Finds an object header based on a
   // address_maybe_pointing_to_the_middle_of_object. Will search for an object
   // start in decreasing address order.
-  template <
-      HeapObjectHeader::AccessMode = HeapObjectHeader::AccessMode::kNonAtomic>
+  template <AccessMode = AccessMode::kNonAtomic>
   inline HeapObjectHeader* FindHeader(
       ConstAddress address_maybe_pointing_to_the_middle_of_object) const;
 
-  template <
-      HeapObjectHeader::AccessMode = HeapObjectHeader::AccessMode::kNonAtomic>
+  template <AccessMode = AccessMode::kNonAtomic>
   inline void SetBit(ConstAddress);
-  template <
-      HeapObjectHeader::AccessMode = HeapObjectHeader::AccessMode::kNonAtomic>
+  template <AccessMode = AccessMode::kNonAtomic>
   inline void ClearBit(ConstAddress);
-  template <
-      HeapObjectHeader::AccessMode = HeapObjectHeader::AccessMode::kNonAtomic>
+  template <AccessMode = AccessMode::kNonAtomic>
   inline bool CheckBit(ConstAddress) const;
 
   // Iterates all object starts recorded in the bitmap.
@@ -71,11 +67,9 @@ class V8_EXPORT_PRIVATE ObjectStartBitmap {
   inline void Clear();
 
  private:
-  template <
-      HeapObjectHeader::AccessMode = HeapObjectHeader::AccessMode::kNonAtomic>
+  template <AccessMode = AccessMode::kNonAtomic>
   inline void store(size_t cell_index, uint8_t value);
-  template <
-      HeapObjectHeader::AccessMode = HeapObjectHeader::AccessMode::kNonAtomic>
+  template <AccessMode = AccessMode::kNonAtomic>
   inline uint8_t load(size_t cell_index) const;
 
   static constexpr size_t kBitsPerCell = sizeof(uint8_t) * CHAR_BIT;
@@ -98,7 +92,7 @@ ObjectStartBitmap::ObjectStartBitmap(Address offset) : offset_(offset) {
   Clear();
 }
 
-template <HeapObjectHeader::AccessMode mode>
+template <AccessMode mode>
 HeapObjectHeader* ObjectStartBitmap::FindHeader(
     ConstAddress address_maybe_pointing_to_the_middle_of_object) const {
   DCHECK_LE(offset_, address_maybe_pointing_to_the_middle_of_object);
@@ -120,7 +114,7 @@ HeapObjectHeader* ObjectStartBitmap::FindHeader(
   return reinterpret_cast<HeapObjectHeader*>(object_offset + offset_);
 }
 
-template <HeapObjectHeader::AccessMode mode>
+template <AccessMode mode>
 void ObjectStartBitmap::SetBit(ConstAddress header_address) {
   size_t cell_index, object_bit;
   ObjectStartIndexAndBit(header_address, &cell_index, &object_bit);
@@ -129,7 +123,7 @@ void ObjectStartBitmap::SetBit(ConstAddress header_address) {
               static_cast<uint8_t>(load(cell_index) | (1 << object_bit)));
 }
 
-template <HeapObjectHeader::AccessMode mode>
+template <AccessMode mode>
 void ObjectStartBitmap::ClearBit(ConstAddress header_address) {
   size_t cell_index, object_bit;
   ObjectStartIndexAndBit(header_address, &cell_index, &object_bit);
@@ -137,16 +131,16 @@ void ObjectStartBitmap::ClearBit(ConstAddress header_address) {
               static_cast<uint8_t>(load(cell_index) & ~(1 << object_bit)));
 }
 
-template <HeapObjectHeader::AccessMode mode>
+template <AccessMode mode>
 bool ObjectStartBitmap::CheckBit(ConstAddress header_address) const {
   size_t cell_index, object_bit;
   ObjectStartIndexAndBit(header_address, &cell_index, &object_bit);
   return load<mode>(cell_index) & (1 << object_bit);
 }
 
-template <HeapObjectHeader::AccessMode mode>
+template <AccessMode mode>
 void ObjectStartBitmap::store(size_t cell_index, uint8_t value) {
-  if (mode == HeapObjectHeader::AccessMode::kNonAtomic) {
+  if (mode == AccessMode::kNonAtomic) {
     object_start_bit_map_[cell_index] = value;
     return;
   }
@@ -154,9 +148,9 @@ void ObjectStartBitmap::store(size_t cell_index, uint8_t value) {
       ->store(value, std::memory_order_release);
 }
 
-template <HeapObjectHeader::AccessMode mode>
+template <AccessMode mode>
 uint8_t ObjectStartBitmap::load(size_t cell_index) const {
-  if (mode == HeapObjectHeader::AccessMode::kNonAtomic) {
+  if (mode == AccessMode::kNonAtomic) {
     return object_start_bit_map_[cell_index];
   }
   return v8::base::AsAtomicPtr(&object_start_bit_map_[cell_index])
@@ -204,15 +198,13 @@ class V8_EXPORT_PRIVATE PlatformAwareObjectStartBitmap
  public:
   explicit inline PlatformAwareObjectStartBitmap(Address offset);
 
-  template <
-      HeapObjectHeader::AccessMode = HeapObjectHeader::AccessMode::kNonAtomic>
+  template <AccessMode = AccessMode::kNonAtomic>
   inline void SetBit(ConstAddress);
-  template <
-      HeapObjectHeader::AccessMode = HeapObjectHeader::AccessMode::kNonAtomic>
+  template <AccessMode = AccessMode::kNonAtomic>
   inline void ClearBit(ConstAddress);
 
  private:
-  template <HeapObjectHeader::AccessMode>
+  template <AccessMode>
   static bool ShouldForceNonAtomic();
 };
 
@@ -220,11 +212,11 @@ PlatformAwareObjectStartBitmap::PlatformAwareObjectStartBitmap(Address offset)
     : ObjectStartBitmap(offset) {}
 
 // static
-template <HeapObjectHeader::AccessMode mode>
+template <AccessMode mode>
 bool PlatformAwareObjectStartBitmap::ShouldForceNonAtomic() {
 #if defined(V8_TARGET_ARCH_ARM)
   // Use non-atomic accesses on ARMv7 when marking is not active.
-  if (mode == HeapObjectHeader::AccessMode::kAtomic) {
+  if (mode == AccessMode::kAtomic) {
     if (V8_LIKELY(!ProcessHeap::IsAnyIncrementalOrConcurrentMarking()))
       return true;
   }
@@ -232,21 +224,19 @@ bool PlatformAwareObjectStartBitmap::ShouldForceNonAtomic() {
   return false;
 }
 
-template <HeapObjectHeader::AccessMode mode>
+template <AccessMode mode>
 void PlatformAwareObjectStartBitmap::SetBit(ConstAddress header_address) {
   if (ShouldForceNonAtomic<mode>()) {
-    ObjectStartBitmap::SetBit<HeapObjectHeader::AccessMode::kNonAtomic>(
-        header_address);
+    ObjectStartBitmap::SetBit<AccessMode::kNonAtomic>(header_address);
     return;
   }
   ObjectStartBitmap::SetBit<mode>(header_address);
 }
 
-template <HeapObjectHeader::AccessMode mode>
+template <AccessMode mode>
 void PlatformAwareObjectStartBitmap::ClearBit(ConstAddress header_address) {
   if (ShouldForceNonAtomic<mode>()) {
-    ObjectStartBitmap::ClearBit<HeapObjectHeader::AccessMode::kNonAtomic>(
-        header_address);
+    ObjectStartBitmap::ClearBit<AccessMode::kNonAtomic>(header_address);
     return;
   }
   ObjectStartBitmap::ClearBit<mode>(header_address);

src/heap/cppgc/sweeper.cc

@@ -114,7 +114,7 @@ using SpaceStates = std::vector<SpaceState>;
 void StickyUnmark(HeapObjectHeader* header) {
   // Young generation in Oilpan uses sticky mark bits.
 #if !defined(CPPGC_YOUNG_GENERATION)
-  header->Unmark<HeapObjectHeader::AccessMode::kAtomic>();
+  header->Unmark<AccessMode::kAtomic>();
 #endif
 }
 
@@ -178,7 +178,7 @@ class DeferredFinalizationBuilder final {
 
 template <typename FinalizationBuilder>
 typename FinalizationBuilder::ResultType SweepNormalPage(NormalPage* page) {
-  constexpr auto kAtomicAccess = HeapObjectHeader::AccessMode::kAtomic;
+  constexpr auto kAtomicAccess = AccessMode::kAtomic;
   FinalizationBuilder builder(page);
 
   PlatformAwareObjectStartBitmap& bitmap = page->object_start_bitmap();

src/heap/cppgc/trace-trait.cc

@@ -16,12 +16,10 @@ TraceDescriptor TraceTraitFromInnerAddressImpl::GetTraceDescriptor(
   // mixins.
   const HeapObjectHeader& header =
       BasePage::FromPayload(address)
-          ->ObjectHeaderFromInnerAddress<HeapObjectHeader::AccessMode::kAtomic>(
-              address);
-  return {header.Payload(),
-          GlobalGCInfoTable::GCInfoFromIndex(
-              header.GetGCInfoIndex<HeapObjectHeader::AccessMode::kAtomic>())
-              .trace};
+          ->ObjectHeaderFromInnerAddress<AccessMode::kAtomic>(address);
+  return {header.Payload(), GlobalGCInfoTable::GCInfoFromIndex(
+                                header.GetGCInfoIndex<AccessMode::kAtomic>())
+                                .trace};
 }
 
 }  // namespace internal

src/heap/cppgc/visitor.cc

@@ -68,7 +68,7 @@ void ConservativeTracingVisitor::TraceConservativelyIfNeeded(
 
 void ConservativeTracingVisitor::TraceConservativelyIfNeeded(
     HeapObjectHeader& header) {
-  if (!header.IsInConstruction<HeapObjectHeader::AccessMode::kNonAtomic>()) {
+  if (!header.IsInConstruction<AccessMode::kNonAtomic>()) {
     VisitFullyConstructedConservatively(header);
   } else {
     VisitInConstructionConservatively(header, TraceConservatively);

src/heap/cppgc/write-barrier.cc

@@ -34,14 +34,12 @@ void MarkValue(const BasePage* page, MarkerBase* marker, const void* value) {
 
   DCHECK(marker);
 
-  if (V8_UNLIKELY(
-          header
-              .IsInConstruction<HeapObjectHeader::AccessMode::kNonAtomic>())) {
+  if (V8_UNLIKELY(header.IsInConstruction<AccessMode::kNonAtomic>())) {
     // In construction objects are traced only if they are unmarked. If marking
     // reaches this object again when it is fully constructed, it will re-mark
     // it and tracing it as a previously not fully constructed object would know
     // to bail out.
-    header.Unmark<HeapObjectHeader::AccessMode::kAtomic>();
+    header.Unmark<AccessMode::kAtomic>();
     marker->WriteBarrierForInConstructionObject(header);
     return;
   }

test/unittests/heap/cppgc/heap-object-header-unittest.cc

@@ -40,8 +40,7 @@ TEST(HeapObjectHeaderTest, GetGCInfoIndex) {
   constexpr size_t kSize = kAllocationGranularity;
   HeapObjectHeader header(kSize, kGCInfoIndex);
   EXPECT_EQ(kGCInfoIndex, header.GetGCInfoIndex());
-  EXPECT_EQ(kGCInfoIndex,
-            header.GetGCInfoIndex<HeapObjectHeader::AccessMode::kAtomic>());
+  EXPECT_EQ(kGCInfoIndex, header.GetGCInfoIndex<AccessMode::kAtomic>());
 }
 
 TEST(HeapObjectHeaderTest, GetSize) {
@@ -49,7 +48,7 @@ TEST(HeapObjectHeaderTest, GetSize) {
   constexpr size_t kSize = kAllocationGranularity * 23;
   HeapObjectHeader header(kSize, kGCInfoIndex);
   EXPECT_EQ(kSize, header.GetSize());
-  EXPECT_EQ(kSize, header.GetSize<HeapObjectHeader::AccessMode::kAtomic>());
+  EXPECT_EQ(kSize, header.GetSize<AccessMode::kAtomic>());
 }
 
 TEST(HeapObjectHeaderTest, IsLargeObject) {
@@ -57,13 +56,10 @@ TEST(HeapObjectHeaderTest, IsLargeObject) {
   constexpr size_t kSize = kAllocationGranularity * 23;
   HeapObjectHeader header(kSize, kGCInfoIndex);
   EXPECT_EQ(false, header.IsLargeObject());
-  EXPECT_EQ(false,
-            header.IsLargeObject<HeapObjectHeader::AccessMode::kAtomic>());
+  EXPECT_EQ(false, header.IsLargeObject<AccessMode::kAtomic>());
   HeapObjectHeader large_header(0, kGCInfoIndex + 1);
   EXPECT_EQ(true, large_header.IsLargeObject());
-  EXPECT_EQ(
-      true,
-      large_header.IsLargeObject<HeapObjectHeader::AccessMode::kAtomic>());
+  EXPECT_EQ(true, large_header.IsLargeObject<AccessMode::kAtomic>());
 }
 
 TEST(HeapObjectHeaderTest, MarkObjectAsFullyConstructed) {
@@ -110,7 +106,7 @@ TEST(HeapObjectHeaderTest, Unmark) {
   EXPECT_FALSE(header2.IsMarked());
   EXPECT_TRUE(header2.TryMarkAtomic());
   EXPECT_TRUE(header2.IsMarked());
-  header2.Unmark<HeapObjectHeader::AccessMode::kAtomic>();
+  header2.Unmark<AccessMode::kAtomic>();
   // GCInfoIndex shares the same bitfield and should be unaffected by Unmark.
   EXPECT_EQ(kGCInfoIndex, header2.GetGCInfoIndex());
   EXPECT_FALSE(header2.IsMarked());
@@ -130,7 +126,7 @@ class ConcurrentGCThread final : public v8::base::Thread {
         payload_(payload) {}
 
   void Run() final {
-    while (header_->IsInConstruction<HeapObjectHeader::AccessMode::kAtomic>()) {
+    while (header_->IsInConstruction<AccessMode::kAtomic>()) {
     }
     USE(v8::base::AsAtomicPtr(const_cast<size_t*>(&payload_->value))
             ->load(std::memory_order_relaxed));