text: // 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_HEAP_INL_H_
  #define V8_HEAP_HEAP_INL_H_
  
  #include <atomic>
  #include <cmath>
  
  // Clients of this interface shouldn't depend on lots of heap internals.
  // Avoid including anything but `heap.h` from `src/heap` where possible.
  #include "src/base/atomic-utils.h"
  #include "src/base/atomicops.h"
  #include "src/base/platform/mutex.h"
  #include "src/base/platform/platform.h"
  #include "src/base/sanitizer/msan.h"
  #include "src/common/assert-scope.h"
  #include "src/execution/isolate-data.h"
  #include "src/execution/isolate.h"
  #include "src/heap/code-object-registry.h"
  #include "src/heap/concurrent-allocator-inl.h"
  #include "src/heap/heap-write-barrier.h"
  #include "src/heap/heap.h"
  #include "src/heap/large-spaces.h"
  #include "src/heap/memory-allocator.h"
  #include "src/heap/memory-chunk-layout.h"
  #include "src/heap/memory-chunk.h"
  #include "src/heap/new-spaces-inl.h"
  #include "src/heap/paged-spaces-inl.h"
  #include "src/heap/read-only-heap.h"
  #include "src/heap/read-only-spaces.h"
  #include "src/heap/spaces-inl.h"
  #include "src/heap/third-party/heap-api.h"
  #include "src/objects/allocation-site-inl.h"
  #include "src/objects/cell-inl.h"
  #include "src/objects/descriptor-array.h"
  #include "src/objects/feedback-cell-inl.h"
  #include "src/objects/feedback-vector.h"
  #include "src/objects/objects-inl.h"
  #include "src/objects/oddball.h"
  #include "src/objects/property-cell.h"
  #include "src/objects/scope-info.h"
  #include "src/objects/slots-inl.h"
  #include "src/objects/struct-inl.h"
  #include "src/objects/visitors-inl.h"
  #include "src/profiler/heap-profiler.h"
  #include "src/strings/string-hasher.h"
  #include "src/utils/ostreams.h"
  #include "src/zone/zone-list-inl.h"
  
  namespace v8 {
  namespace internal {
  
  template <typename T>
  T ForwardingAddress(T heap_obj) {
    MapWord map_word = heap_obj.map_word(kRelaxedLoad);
  
    if (map_word.IsForwardingAddress()) {
      return T::cast(map_word.ToForwardingAddress());
    } else if (Heap::InFromPage(heap_obj)) {
      return T();
    } else {
      return heap_obj;
    }
  }
  
  AllocationSpace AllocationResult::RetrySpace() {
    DCHECK(IsRetry());
    return static_cast<AllocationSpace>(Smi::ToInt(object_));
  }
  
  HeapObject AllocationResult::ToObjectChecked() {
    CHECK(!IsRetry());
    return HeapObject::cast(object_);
  }
  
  HeapObject AllocationResult::ToObject() {
    DCHECK(!IsRetry());
    return HeapObject::cast(object_);
  }
  
  Address AllocationResult::ToAddress() {
    DCHECK(!IsRetry());
    return HeapObject::cast(object_).address();
  }
  
  // static
  base::EnumSet<CodeFlushMode> Heap::GetCodeFlushMode(Isolate* isolate) {
    if (isolate->disable_bytecode_flushing()) {
      return base::EnumSet<CodeFlushMode>();
    }
  
    base::EnumSet<CodeFlushMode> code_flush_mode;
    if (FLAG_flush_bytecode) {
      code_flush_mode.Add(CodeFlushMode::kFlushBytecode);
    }
  
    if (FLAG_flush_baseline_code) {
      code_flush_mode.Add(CodeFlushMode::kFlushBaselineCode);
    }
  
    if (FLAG_stress_flush_code) {
      // This is to check tests accidentally don't miss out on adding either flush
      // bytecode or flush code along with stress flush code. stress_flush_code
      // doesn't do anything if either one of them isn't enabled.
      DCHECK(FLAG_fuzzing || FLAG_flush_baseline_code || FLAG_flush_bytecode);
      code_flush_mode.Add(CodeFlushMode::kStressFlushCode);
    }
  
    return code_flush_mode;
  }
  
  Isolate* Heap::isolate() {
    return reinterpret_cast<Isolate*>(
        reinterpret_cast<intptr_t>(this) -
        reinterpret_cast<size_t>(reinterpret_cast<Isolate*>(16)->heap()) + 16);
  }
  
  int64_t Heap::external_memory() { return external_memory_.total(); }
  
  int64_t Heap::update_external_memory(int64_t delta) {
    return external_memory_.Update(delta);
  }
  
  RootsTable& Heap::roots_table() { return isolate()->roots_table(); }
  
  #define ROOT_ACCESSOR(Type, name, CamelName)                           \
    Type Heap::name() {                                                  \
      return Type::cast(Object(roots_table()[RootIndex::k##CamelName])); \
    }
  MUTABLE_ROOT_LIST(ROOT_ACCESSOR)
  #undef ROOT_ACCESSOR
  
  #define ROOT_ACCESSOR(type, name, CamelName)                                   \
    void Heap::set_##name(type value) {                                          \
      /* The deserializer makes use of the fact that these common roots are */   \
      /* never in new space and never on a page that is being compacted.    */   \
      DCHECK_IMPLIES(deserialization_complete(),                                 \
                     !RootsTable::IsImmortalImmovable(RootIndex::k##CamelName)); \
      DCHECK_IMPLIES(RootsTable::IsImmortalImmovable(RootIndex::k##CamelName),   \
                     IsImmovable(HeapObject::cast(value)));                      \
      roots_table()[RootIndex::k##CamelName] = value.ptr();                      \
    }
  ROOT_LIST(ROOT_ACCESSOR)
  #undef ROOT_ACCESSOR
  
  void Heap::SetRootMaterializedObjects(FixedArray objects) {
    roots_table()[RootIndex::kMaterializedObjects] = objects.ptr();
  }
  
  void Heap::SetRootScriptList(Object value) {
    roots_table()[RootIndex::kScriptList] = value.ptr();
  }
  
  void Heap::SetMessageListeners(TemplateList value) {
    roots_table()[RootIndex::kMessageListeners] = value.ptr();
  }
  
  void Heap::SetPendingOptimizeForTestBytecode(Object hash_table) {
    DCHECK(hash_table.IsObjectHashTable() || hash_table.IsUndefined(isolate()));
    roots_table()[RootIndex::kPendingOptimizeForTestBytecode] = hash_table.ptr();
  }
  
  PagedSpace* Heap::paged_space(int idx) {
    DCHECK(idx == OLD_SPACE || idx == CODE_SPACE || idx == MAP_SPACE);
    return static_cast<PagedSpace*>(space_[idx]);
  }
  
  Space* Heap::space(int idx) { return space_[idx]; }
  
  Address* Heap::NewSpaceAllocationTopAddress() {
    return new_space_ ? new_space_->allocation_top_address() : nullptr;
  }
  
  Address* Heap::NewSpaceAllocationLimitAddress() {
    return new_space_ ? new_space_->allocation_limit_address() : nullptr;
  }
  
  Address* Heap::OldSpaceAllocationTopAddress() {
    return old_space_->allocation_top_address();
  }
  
  Address* Heap::OldSpaceAllocationLimitAddress() {
    return old_space_->allocation_limit_address();
  }
  
  inline const base::AddressRegion& Heap::code_region() {
  #ifdef V8_ENABLE_THIRD_PARTY_HEAP
    return tp_heap_->GetCodeRange();
  #else
    static constexpr base::AddressRegion kEmptyRegion;
    return code_range_ ? code_range_->reservation()->region() : kEmptyRegion;
  #endif
  }
  
  int Heap::MaxRegularHeapObjectSize(AllocationType allocation) {
    if (!V8_ENABLE_THIRD_PARTY_HEAP_BOOL &&
        (allocation == AllocationType::kCode)) {
      DCHECK_EQ(MemoryChunkLayout::MaxRegularCodeObjectSize(),
                max_regular_code_object_size_);
      return max_regular_code_object_size_;
    }
    return kMaxRegularHeapObjectSize;
  }
  
  AllocationResult Heap::AllocateRaw(int size_in_bytes, AllocationType type,
                                     AllocationOrigin origin,
                                     AllocationAlignment alignment) {
    DCHECK(AllowHandleAllocation::IsAllowed());
    DCHECK(AllowHeapAllocation::IsAllowed());
    DCHECK_IMPLIES(type == AllocationType::kCode || type == AllocationType::kMap,
                   alignment == AllocationAlignment::kWordAligned);
    DCHECK_EQ(gc_state(), NOT_IN_GC);
  #ifdef V8_ENABLE_ALLOCATION_TIMEOUT
    if (FLAG_random_gc_interval > 0 || FLAG_gc_interval >= 0) {
      if (!always_allocate() && Heap::allocation_timeout_-- <= 0) {
        AllocationSpace space = FLAG_single_generation ? OLD_SPACE : NEW_SPACE;
        return AllocationResult::Retry(space);
      }
    }
  #endif
  #ifdef DEBUG
    IncrementObjectCounters();
  #endif
  
    if (CanSafepoint()) {
      main_thread_local_heap()->Safepoint();
    }
  
    size_t large_object_threshold = MaxRegularHeapObjectSize(type);
    bool large_object =
        static_cast<size_t>(size_in_bytes) > large_object_threshold;
  
    HeapObject object;
    AllocationResult allocation;
  
    if (FLAG_single_generation && type == AllocationType::kYoung) {
      type = AllocationType::kOld;
    }
  
    if (V8_ENABLE_THIRD_PARTY_HEAP_BOOL) {
      allocation = tp_heap_->Allocate(size_in_bytes, type, alignment);
    } else {
      if (AllocationType::kYoung == type) {
        if (large_object) {
          if (FLAG_young_generation_large_objects) {
            allocation = new_lo_space_->AllocateRaw(size_in_bytes);
          } else {
            // If young generation large objects are disalbed we have to tenure
            // the allocation and violate the given allocation type. This could be
            // dangerous. We may want to remove
            // FLAG_young_generation_large_objects and avoid patching.
            allocation = lo_space_->AllocateRaw(size_in_bytes);
          }
        } else {
          allocation = new_space_->AllocateRaw(size_in_bytes, alignment, origin);
        }
      } else if (AllocationType::kOld == type) {
        if (large_object) {
          allocation = lo_space_->AllocateRaw(size_in_bytes);
        } else {
          allocation = old_space_->AllocateRaw(size_in_bytes, alignment, origin);
        }
      } else if (AllocationType::kCode == type) {
        DCHECK(AllowCodeAllocation::IsAllowed());
        if (large_object) {
          allocation = code_lo_space_->AllocateRaw(size_in_bytes);
        } else {
          allocation = code_space_->AllocateRawUnaligned(size_in_bytes);
        }
      } else if (AllocationType::kMap == type) {
        allocation = map_space_->AllocateRawUnaligned(size_in_bytes);
      } else if (AllocationType::kReadOnly == type) {
        DCHECK(!large_object);
        DCHECK(CanAllocateInReadOnlySpace());
        DCHECK_EQ(AllocationOrigin::kRuntime, origin);
        allocation = read_only_space_->AllocateRaw(size_in_bytes, alignment);
      } else if (AllocationType::kSharedOld == type) {
        allocation =
            shared_old_allocator_->AllocateRaw(size_in_bytes, alignment, origin);
      } else if (AllocationType::kSharedMap == type) {
        allocation =
            shared_map_allocator_->AllocateRaw(size_in_bytes, alignment, origin);
      } else {
        UNREACHABLE();
      }
    }
  
    if (allocation.To(&object)) {
      if (AllocationType::kCode == type && !V8_ENABLE_THIRD_PARTY_HEAP_BOOL) {
        // Unprotect the memory chunk of the object if it was not unprotected
        // already.
        UnprotectAndRegisterMemoryChunk(object,
                                        UnprotectMemoryOrigin::kMainThread);
        ZapCodeObject(object.address(), size_in_bytes);
        if (!large_object) {
          MemoryChunk::FromHeapObject(object)
              ->GetCodeObjectRegistry()
              ->RegisterNewlyAllocatedCodeObject(object.address());
        }
      }
  
  #ifdef V8_ENABLE_CONSERVATIVE_STACK_SCANNING
      if (AllocationType::kReadOnly != type) {
        DCHECK_TAG_ALIGNED(object.address());
        Page::FromHeapObject(object)->object_start_bitmap()->SetBit(
            object.address());
      }
  #endif
  
      OnAllocationEvent(object, size_in_bytes);
    }
  
    return allocation;
  }
  
  template <Heap::AllocationRetryMode mode>
  HeapObject Heap::AllocateRawWith(int size, AllocationType allocation,
                                   AllocationOrigin origin,
                                   AllocationAlignment alignment) {
    DCHECK(AllowHandleAllocation::IsAllowed());
    DCHECK(AllowHeapAllocation::IsAllowed());
    DCHECK_EQ(gc_state(), NOT_IN_GC);
    Heap* heap = isolate()->heap();
    if (allocation == AllocationType::kYoung &&
        alignment == AllocationAlignment::kWordAligned &&
        size <= MaxRegularHeapObjectSize(allocation) &&
        V8_LIKELY(!FLAG_single_generation && FLAG_inline_new &&
                  FLAG_gc_interval == -1)) {
      Address* top = heap->NewSpaceAllocationTopAddress();
      Address* limit = heap->NewSpaceAllocationLimitAddress();
      if (*limit - *top >= static_cast<unsigned>(size)) {
        DCHECK(IsAligned(size, kTaggedSize));
        HeapObject obj = HeapObject::FromAddress(*top);
        *top += size;
        heap->CreateFillerObjectAt(obj.address(), size, ClearRecordedSlots::kNo);
        MSAN_ALLOCATED_UNINITIALIZED_MEMORY(obj.address(), size);
        return obj;
      }
    }
    switch (mode) {
      case kLightRetry:
        return AllocateRawWithLightRetrySlowPath(size, allocation, origin,
                                                 alignment);
      case kRetryOrFail:
        return AllocateRawWithRetryOrFailSlowPath(size, allocation, origin,
                                                  alignment);
    }
    UNREACHABLE();
  }
  
  Address Heap::AllocateRawOrFail(int size, AllocationType allocation,
                                  AllocationOrigin origin,
                                  AllocationAlignment alignment) {
    return AllocateRawWith<kRetryOrFail>(size, allocation, origin, alignment)
        .address();
  }
  
  void Heap::OnAllocationEvent(HeapObject object, int size_in_bytes) {
    for (auto& tracker : allocation_trackers_) {
      tracker->AllocationEvent(object.address(), size_in_bytes);
    }
  
    if (FLAG_verify_predictable) {
      ++allocations_count_;
      // Advance synthetic time by making a time request.
      MonotonicallyIncreasingTimeInMs();
  
      UpdateAllocationsHash(object);
      UpdateAllocationsHash(size_in_bytes);
  
      if (allocations_count_ % FLAG_dump_allocations_digest_at_alloc == 0) {
        PrintAllocationsHash();
      }
    } else if (FLAG_fuzzer_gc_analysis) {
      ++allocations_count_;
    } else if (FLAG_trace_allocation_stack_interval > 0) {
      ++allocations_count_;
      if (allocations_count_ % FLAG_trace_allocation_stack_interval == 0) {
        isolate()->PrintStack(stdout, Isolate::kPrintStackConcise);
      }
    }
  }
  
  bool Heap::CanAllocateInReadOnlySpace() {
    return read_only_space()->writable();
  }
  
  void Heap::UpdateAllocationsHash(HeapObject object) {
    Address object_address = object.address();
    MemoryChunk* memory_chunk = MemoryChunk::FromAddress(object_address);
    AllocationSpace allocation_space = memory_chunk->owner_identity();
  
    STATIC_ASSERT(kSpaceTagSize + kPageSizeBits <= 32);
    uint32_t value =
        static_cast<uint32_t>(object_address - memory_chunk->address()) |
        (static_cast<uint32_t>(allocation_space) << kPageSizeBits);
  
    UpdateAllocationsHash(value);
  }
  
  void Heap::UpdateAllocationsHash(uint32_t value) {
    uint16_t c1 = static_cast<uint16_t>(value);
    uint16_t c2 = static_cast<uint16_t>(value >> 16);
    raw_allocations_hash_ =
        StringHasher::AddCharacterCore(raw_allocations_hash_, c1);
    raw_allocations_hash_ =
        StringHasher::AddCharacterCore(raw_allocations_hash_, c2);
  }
  
  void Heap::RegisterExternalString(String string) {
    DCHECK(string.IsExternalString());
    DCHECK(!string.IsThinString());
    external_string_table_.AddString(string);
  }
  
  void Heap::FinalizeExternalString(String string) {
    DCHECK(string.IsExternalString());
    ExternalString ext_string = ExternalString::cast(string);
  
    if (!FLAG_enable_third_party_heap) {
      Page* page = Page::FromHeapObject(string);
      page->DecrementExternalBackingStoreBytes(
          ExternalBackingStoreType::kExternalString,
          ext_string.ExternalPayloadSize());
    }
  
    ext_string.DisposeResource(isolate());
  }
  
  Address Heap::NewSpaceTop() {
    return new_space_ ? new_space_->top() : kNullAddress;
  }
  
  bool Heap::InYoungGeneration(Object object) {
    DCHECK(!HasWeakHeapObjectTag(object));
    return object.IsHeapObject() && InYoungGeneration(HeapObject::cast(object));
  }
  
  // static
  bool Heap::InYoungGeneration(MaybeObject object) {
    HeapObject heap_object;
    return object->GetHeapObject(&heap_object) && InYoungGeneration(heap_object);
  }
  
  // static
  bool Heap::InYoungGeneration(HeapObject heap_object) {
    if (V8_ENABLE_THIRD_PARTY_HEAP_BOOL) return false;
    bool result =
        BasicMemoryChunk::FromHeapObject(heap_object)->InYoungGeneration();
  #ifdef DEBUG
    // If in the young generation, then check we're either not in the middle of
    // GC or the object is in to-space.
    if (result) {
      // If the object is in the young generation, then it's not in RO_SPACE so
      // this is safe.
      Heap* heap = Heap::FromWritableHeapObject(heap_object);
      DCHECK_IMPLIES(heap->gc_state() == NOT_IN_GC, InToPage(heap_object));
    }
  #endif
    return result;
  }
  
  // static
  bool Heap::InFromPage(Object object) {
    DCHECK(!HasWeakHeapObjectTag(object));
    return object.IsHeapObject() && InFromPage(HeapObject::cast(object));
  }
  
  // static
  bool Heap::InFromPage(MaybeObject object) {
    HeapObject heap_object;
    return object->GetHeapObject(&heap_object) && InFromPage(heap_object);
  }
  
  // static
  bool Heap::InFromPage(HeapObject heap_object) {
    return BasicMemoryChunk::FromHeapObject(heap_object)->IsFromPage();
  }
  
  // static
  bool Heap::InToPage(Object object) {
    DCHECK(!HasWeakHeapObjectTag(object));
    return object.IsHeapObject() && InToPage(HeapObject::cast(object));
  }
  
  // static
  bool Heap::InToPage(MaybeObject object) {
    HeapObject heap_object;
    return object->GetHeapObject(&heap_object) && InToPage(heap_object);
  }
  
  // static
  bool Heap::InToPage(HeapObject heap_object) {
    return BasicMemoryChunk::FromHeapObject(heap_object)->IsToPage();
  }
  
  bool Heap::InOldSpace(Object object) {
    if (V8_ENABLE_THIRD_PARTY_HEAP_BOOL) {
      return object.IsHeapObject() &&
             third_party_heap::Heap::InOldSpace(object.ptr());
    }
    return old_space_->Contains(object);
  }
  
  // static
  Heap* Heap::FromWritableHeapObject(HeapObject obj) {
    if (V8_ENABLE_THIRD_PARTY_HEAP_BOOL) {
      return Heap::GetIsolateFromWritableObject(obj)->heap();
    }
    BasicMemoryChunk* chunk = BasicMemoryChunk::FromHeapObject(obj);
    // RO_SPACE can be shared between heaps, so we can't use RO_SPACE objects to
    // find a heap. The exception is when the ReadOnlySpace is writeable, during
    // bootstrapping, so explicitly allow this case.
    SLOW_DCHECK(chunk->IsWritable());
    Heap* heap = chunk->heap();
    SLOW_DCHECK(heap != nullptr);
    return heap;
  }
  
  bool Heap::ShouldBePromoted(Address old_address) {
    Page* page = Page::FromAddress(old_address);
    Address age_mark = new_space_->age_mark();
    return page->IsFlagSet(MemoryChunk::NEW_SPACE_BELOW_AGE_MARK) &&
           (!page->ContainsLimit(age_mark) || old_address < age_mark);
  }
  
  void Heap::CopyBlock(Address dst, Address src, int byte_size) {
    DCHECK(IsAligned(byte_size, kTaggedSize));
    CopyTagged(dst, src, static_cast<size_t>(byte_size / kTaggedSize));
  }
  
  template <Heap::FindMementoMode mode>
  AllocationMemento Heap::FindAllocationMemento(Map map, HeapObject object) {
    Address object_address = object.address();
    Address memento_address = object_address + object.SizeFromMap(map);
    Address last_memento_word_address = memento_address + kTaggedSize;
    // If the memento would be on another page, bail out immediately.
    if (!Page::OnSamePage(object_address, last_memento_word_address)) {
      return AllocationMemento();
    }
    HeapObject candidate = HeapObject::FromAddress(memento_address);
    ObjectSlot candidate_map_slot = candidate.map_slot();
    // This fast check may peek at an uninitialized word. However, the slow check
    // below (memento_address == top) ensures that this is safe. Mark the word as
    // initialized to silence MemorySanitizer warnings.
    MSAN_MEMORY_IS_INITIALIZED(candidate_map_slot.address(), kTaggedSize);
    if (!candidate_map_slot.contains_map_value(
            ReadOnlyRoots(this).allocation_memento_map().ptr())) {
      return AllocationMemento();
    }
  
    // Bail out if the memento is below the age mark, which can happen when
    // mementos survived because a page got moved within new space.
    Page* object_page = Page::FromAddress(object_address);
    if (object_page->IsFlagSet(Page::NEW_SPACE_BELOW_AGE_MARK)) {
      Address age_mark =
          reinterpret_cast<SemiSpace*>(object_page->owner())->age_mark();
      if (!object_page->Contains(age_mark)) {
        return AllocationMemento();
      }
      // Do an exact check in the case where the age mark is on the same page.
      if (object_address < age_mark) {
        return AllocationMemento();
      }
    }
  
    AllocationMemento memento_candidate = AllocationMemento::cast(candidate);
  
    // Depending on what the memento is used for, we might need to perform
    // additional checks.
    Address top;
    switch (mode) {
      case Heap::kForGC:
        return memento_candidate;
      case Heap::kForRuntime:
        if (memento_candidate.is_null()) return AllocationMemento();
        // Either the object is the last object in the new space, or there is
        // another object of at least word size (the header map word) following
        // it, so suffices to compare ptr and top here.
        top = NewSpaceTop();
        DCHECK(memento_address == top ||
               memento_address + HeapObject::kHeaderSize <= top ||
               !Page::OnSamePage(memento_address, top - 1));
        if ((memento_address != top) && memento_candidate.IsValid()) {
          return memento_candidate;
        }
        return AllocationMemento();
      default:
        UNREACHABLE();
    }
    UNREACHABLE();
  }
  
  void Heap::UpdateAllocationSite(Map map, HeapObject object,
                                  PretenuringFeedbackMap* pretenuring_feedback) {
    DCHECK_NE(pretenuring_feedback, &global_pretenuring_feedback_);
  #ifdef DEBUG
    BasicMemoryChunk* chunk = BasicMemoryChunk::FromHeapObject(object);
    DCHECK_IMPLIES(chunk->IsToPage(),
                   chunk->IsFlagSet(MemoryChunk::PAGE_NEW_NEW_PROMOTION));
    DCHECK_IMPLIES(!chunk->InYoungGeneration(),
                   chunk->IsFlagSet(MemoryChunk::PAGE_NEW_OLD_PROMOTION));
  #endif
    if (!FLAG_allocation_site_pretenuring ||
        !AllocationSite::CanTrack(map.instance_type())) {
      return;
    }
    AllocationMemento memento_candidate =
        FindAllocationMemento<kForGC>(map, object);
    if (memento_candidate.is_null()) return;
  
    // Entering cached feedback is used in the parallel case. We are not allowed
    // to dereference the allocation site and rather have to postpone all checks
    // till actually merging the data.
    Address key = memento_candidate.GetAllocationSiteUnchecked();
    (*pretenuring_feedback)[AllocationSite::unchecked_cast(Object(key))]++;
  }
  
  bool Heap::IsPendingAllocationInternal(HeapObject object) {
    DCHECK(deserialization_complete());
  
    if (V8_ENABLE_THIRD_PARTY_HEAP_BOOL) {
      return tp_heap_->IsPendingAllocation(object);
    }
  
    BasicMemoryChunk* chunk = BasicMemoryChunk::FromHeapObject(object);
    if (chunk->InReadOnlySpace()) return false;
  
    BaseSpace* base_space = chunk->owner();
    Address addr = object.address();
  
    switch (base_space->identity()) {
      case NEW_SPACE: {
        base::SharedMutexGuard<base::kShared> guard(
            new_space_->pending_allocation_mutex());
        Address top = new_space_->original_top_acquire();
        Address limit = new_space_->original_limit_relaxed();
        DCHECK_LE(top, limit);
        return top && top <= addr && addr < limit;
      }
  
      case OLD_SPACE:
      case CODE_SPACE:
      case MAP_SPACE: {
        PagedSpace* paged_space = static_cast<PagedSpace*>(base_space);
        base::SharedMutexGuard<base::kShared> guard(
            paged_space->pending_allocation_mutex());
        Address top = paged_space->original_top();
        Address limit = paged_space->original_limit();
        DCHECK_LE(top, limit);
        return top && top <= addr && addr < limit;
      }
  
      case LO_SPACE:
      case CODE_LO_SPACE:
      case NEW_LO_SPACE: {
        LargeObjectSpace* large_space =
            static_cast<LargeObjectSpace*>(base_space);
        base::SharedMutexGuard<base::kShared> guard(
            large_space->pending_allocation_mutex());
        return addr == large_space->pending_object();
      }
  
      case RO_SPACE:
        UNREACHABLE();
    }
  
    UNREACHABLE();
  }
  
  bool Heap::IsPendingAllocation(HeapObject object) {
    bool result = IsPendingAllocationInternal(object);
    if (FLAG_trace_pending_allocations && result) {
      StdoutStream{} << "Pending allocation: " << std::hex << "0x" << object.ptr()
                     << "\n";
    }
    return result;
  }
  
  bool Heap::IsPendingAllocation(Object object) {
    return object.IsHeapObject() && IsPendingAllocation(HeapObject::cast(object));
  }
  
  void Heap::ExternalStringTable::AddString(String string) {
    DCHECK(string.IsExternalString());
    DCHECK(!Contains(string));
  
    if (InYoungGeneration(string)) {
      young_strings_.push_back(string);
    } else {
      old_strings_.push_back(string);
    }
  }
  
  Oddball Heap::ToBoolean(bool condition) {
    ReadOnlyRoots roots(this);
    return condition ? roots.true_value() : roots.false_value();
  }
  
  int Heap::NextScriptId() {
    FullObjectSlot last_script_id_slot(&roots_table()[RootIndex::kLastScriptId]);
    Smi last_id = Smi::cast(last_script_id_slot.Relaxed_Load());
    Smi new_id, last_id_before_cas;
    do {
      if (last_id.value() == Smi::kMaxValue) {
        STATIC_ASSERT(v8::UnboundScript::kNoScriptId == 0);
        new_id = Smi::FromInt(1);
      } else {
        new_id = Smi::FromInt(last_id.value() + 1);
      }
  
      // CAS returns the old value on success, and the current value in the slot
      // on failure. Therefore, we want to break if the returned value matches the
      // old value (last_id), and keep looping (with the new last_id value) if it
      // doesn't.
      last_id_before_cas = last_id;
      last_id =
          Smi::cast(last_script_id_slot.Relaxed_CompareAndSwap(last_id, new_id));
    } while (last_id != last_id_before_cas);
  
    return new_id.value();
  }
  
  int Heap::NextDebuggingId() {
    int last_id = last_debugging_id().value();
    if (last_id == DebugInfo::DebuggingIdBits::kMax) {
      last_id = DebugInfo::kNoDebuggingId;
    }
    last_id++;
    set_last_debugging_id(Smi::FromInt(last_id));
    return last_id;
  }
  
  int Heap::GetNextTemplateSerialNumber() {
    int next_serial_number = next_template_serial_number().value();
    set_next_template_serial_number(Smi::FromInt(next_serial_number + 1));
    return next_serial_number;
  }
  
  int Heap::MaxNumberToStringCacheSize() const {
    // Compute the size of the number string cache based on the max newspace size.
    // The number string cache has a minimum size based on twice the initial cache
    // size to ensure that it is bigger after being made 'full size'.
    size_t number_string_cache_size = max_semi_space_size_ / 512;
    number_string_cache_size =
        std::max(static_cast<size_t>(kInitialNumberStringCacheSize * 2),
                 std::min(static_cast<size_t>(0x4000), number_string_cache_size));
    // There is a string and a number per entry so the length is twice the number
    // of entries.
    return static_cast<int>(number_string_cache_size * 2);
  }
  
  void Heap::IncrementExternalBackingStoreBytes(ExternalBackingStoreType type,
                                                size_t amount) {
    base::CheckedIncrement(&backing_store_bytes_, static_cast<uint64_t>(amount),
                           std::memory_order_relaxed);
    // TODO(mlippautz): Implement interrupt for global memory allocations that can
    // trigger garbage collections.
  }
  
  void Heap::DecrementExternalBackingStoreBytes(ExternalBackingStoreType type,
                                                size_t amount) {
    base::CheckedDecrement(&backing_store_bytes_, static_cast<uint64_t>(amount),
                           std::memory_order_relaxed);
  }
  
  bool Heap::HasDirtyJSFinalizationRegistries() {
    return !dirty_js_finalization_registries_list().IsUndefined(isolate());
  }
  
  VerifyPointersVisitor::VerifyPointersVisitor(Heap* heap)
      : ObjectVisitorWithCageBases(heap), heap_(heap) {}
  
  AlwaysAllocateScope::AlwaysAllocateScope(Heap* heap) : heap_(heap) {
    heap_->always_allocate_scope_count_++;
  }
  
  AlwaysAllocateScope::~AlwaysAllocateScope() {
    heap_->always_allocate_scope_count_--;
  }
  
  OptionalAlwaysAllocateScope::OptionalAlwaysAllocateScope(Heap* heap)
      : heap_(heap) {
    if (heap_) heap_->always_allocate_scope_count_++;
  }
  
  OptionalAlwaysAllocateScope::~OptionalAlwaysAllocateScope() {
    if (heap_) heap_->always_allocate_scope_count_--;
  }
  
  AlwaysAllocateScopeForTesting::AlwaysAllocateScopeForTesting(Heap* heap)
      : scope_(heap) {}
  
  CodeSpaceMemoryModificationScope::CodeSpaceMemoryModificationScope(Heap* heap)
      : heap_(heap) {
    if (heap_->write_protect_code_memory()) {
      heap_->increment_code_space_memory_modification_scope_depth();
      heap_->code_space()->SetCodeModificationPermissions();
      LargePage* page = heap_->code_lo_space()->first_page();
      while (page != nullptr) {
        DCHECK(page->IsFlagSet(MemoryChunk::IS_EXECUTABLE));
        CHECK(heap_->memory_allocator()->IsMemoryChunkExecutable(page));
        page->SetCodeModificationPermissions();
        page = page->next_page();
      }
    }
  }
  
  CodeSpaceMemoryModificationScope::~CodeSpaceMemoryModificationScope() {
    if (heap_->write_protect_code_memory()) {
      heap_->decrement_code_space_memory_modification_scope_depth();
      heap_->code_space()->SetDefaultCodePermissions();
      LargePage* page = heap_->code_lo_space()->first_page();
      while (page != nullptr) {
        DCHECK(page->IsFlagSet(MemoryChunk::IS_EXECUTABLE));
        CHECK(heap_->memory_allocator()->IsMemoryChunkExecutable(page));
        page->SetDefaultCodePermissions();
        page = page->next_page();
      }
    }
  }
  
  CodePageCollectionMemoryModificationScope::
      CodePageCollectionMemoryModificationScope(Heap* heap)
      : heap_(heap) {
    if (heap_->write_protect_code_memory() &&
        !heap_->code_space_memory_modification_scope_depth()) {
      heap_->EnableUnprotectedMemoryChunksRegistry();
      heap_->IncrementCodePageCollectionMemoryModificationScopeDepth();
    }
  }
  
  CodePageCollectionMemoryModificationScope::
      ~CodePageCollectionMemoryModificationScope() {
    if (heap_->write_protect_code_memory() &&
        !heap_->code_space_memory_modification_scope_depth()) {
      heap_->DecrementCodePageCollectionMemoryModificationScopeDepth();
      if (heap_->code_page_collection_memory_modification_scope_depth() == 0) {
        heap_->ProtectUnprotectedMemoryChunks();
        heap_->DisableUnprotectedMemoryChunksRegistry();
      }
    }
  }
  
  #ifdef V8_ENABLE_THIRD_PARTY_HEAP
  CodePageMemoryModificationScope::CodePageMemoryModificationScope(Code code)
      : chunk_(nullptr), scope_active_(false) {}
  #else
  CodePageMemoryModificationScope::CodePageMemoryModificationScope(Code code)
      : CodePageMemoryModificationScope(BasicMemoryChunk::FromHeapObject(code)) {}
  #endif
  
  CodePageMemoryModificationScope::CodePageMemoryModificationScope(
      BasicMemoryChunk* chunk)
      : chunk_(chunk),
        scope_active_(chunk_->heap()->write_protect_code_memory() &&
                      chunk_->IsFlagSet(MemoryChunk::IS_EXECUTABLE)) {
    if (scope_active_) {
      DCHECK(chunk_->owner()->identity() == CODE_SPACE ||
             (chunk_->owner()->identity() == CODE_LO_SPACE));
      MemoryChunk::cast(chunk_)->SetCodeModificationPermissions();
    }
  }
  
  CodePageMemoryModificationScope::~CodePageMemoryModificationScope() {
    if (scope_active_) {
      MemoryChunk::cast(chunk_)->SetDefaultCodePermissions();
    }
  }
  
  }  // namespace internal
  }  // namespace v8
  
  #endif  // V8_HEAP_HEAP_INL_H_
  