runtime/vm/clustered_snapshot.cc

// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

#include <memory>

#include "vm/clustered_snapshot.h"

#include "platform/assert.h"
#include "vm/bootstrap.h"
#include "vm/bss_relocs.h"
#include "vm/class_id.h"
#include "vm/code_observers.h"
#include "vm/compiler/api/print_filter.h"
#include "vm/compiler/assembler/disassembler.h"
#include "vm/dart.h"
#include "vm/dispatch_table.h"
#include "vm/flag_list.h"
#include "vm/growable_array.h"
#include "vm/heap/heap.h"
#include "vm/image_snapshot.h"
#include "vm/native_entry.h"
#include "vm/object.h"
#include "vm/object_store.h"
#include "vm/program_visitor.h"
#include "vm/stub_code.h"
#include "vm/symbols.h"
#include "vm/timeline.h"
#include "vm/version.h"
#include "vm/zone_text_buffer.h"

#if !defined(DART_PRECOMPILED_RUNTIME)
#include "vm/compiler/backend/code_statistics.h"
#include "vm/compiler/backend/il_printer.h"
#include "vm/compiler/relocation.h"
#endif  // !defined(DART_PRECOMPILED_RUNTIME)

namespace dart {

#if !defined(DART_PRECOMPILED_RUNTIME)
DEFINE_FLAG(bool,
            print_cluster_information,
            false,
            "Print information about clusters written to snapshot");
#endif

#if defined(DART_PRECOMPILER)
DEFINE_FLAG(charp,
            write_v8_snapshot_profile_to,
            NULL,
            "Write a snapshot profile in V8 format to a file.");
#endif  // defined(DART_PRECOMPILER)

#if defined(DART_PRECOMPILER) && !defined(TARGET_ARCH_IA32)

static void RelocateCodeObjects(
    bool is_vm,
    GrowableArray<CodePtr>* code_objects,
    GrowableArray<ImageWriterCommand>* image_writer_commands) {
  auto thread = Thread::Current();
  auto isolate = is_vm ? Dart::vm_isolate() : thread->isolate();

  WritableCodePages writable_code_pages(thread, isolate);
  CodeRelocator::Relocate(thread, code_objects, image_writer_commands, is_vm);
}

class CodePtrKeyValueTrait {
 public:
  // Typedefs needed for the DirectChainedHashMap template.
  typedef const CodePtr Key;
  typedef const CodePtr Value;
  typedef CodePtr Pair;

  static Key KeyOf(Pair kv) { return kv; }
  static Value ValueOf(Pair kv) { return kv; }
  static inline intptr_t Hashcode(Key key) {
    return static_cast<intptr_t>(key);
  }

  static inline bool IsKeyEqual(Pair pair, Key key) { return pair == key; }
};

typedef DirectChainedHashMap<CodePtrKeyValueTrait> RawCodeSet;

#endif  // defined(DART_PRECOMPILER) && !defined(TARGET_ARCH_IA32)

static ObjectPtr AllocateUninitialized(PageSpace* old_space, intptr_t size) {
  ASSERT(Utils::IsAligned(size, kObjectAlignment));
  uword address = old_space->TryAllocateDataBumpLocked(size);
  if (address == 0) {
    OUT_OF_MEMORY();
  }
  return ObjectLayout::FromAddr(address);
}

void Deserializer::InitializeHeader(ObjectPtr raw,
                                    intptr_t class_id,
                                    intptr_t size,
                                    bool is_canonical) {
  ASSERT(Utils::IsAligned(size, kObjectAlignment));
  uint32_t tags = 0;
  tags = ObjectLayout::ClassIdTag::update(class_id, tags);
  tags = ObjectLayout::SizeTag::update(size, tags);
  tags = ObjectLayout::CanonicalBit::update(is_canonical, tags);
  tags = ObjectLayout::OldBit::update(true, tags);
  tags = ObjectLayout::OldAndNotMarkedBit::update(true, tags);
  tags = ObjectLayout::OldAndNotRememberedBit::update(true, tags);
  tags = ObjectLayout::NewBit::update(false, tags);
  raw->ptr()->tags_ = tags;
#if defined(HASH_IN_OBJECT_HEADER)
  raw->ptr()->hash_ = 0;
#endif
}

#if !defined(DART_PRECOMPILED_RUNTIME)
void SerializationCluster::WriteAndMeasureAlloc(Serializer* serializer) {
  intptr_t start_size = serializer->bytes_written();
  intptr_t start_data = serializer->GetDataSize();
  intptr_t start_objects = serializer->next_ref_index();
  WriteAlloc(serializer);
  intptr_t stop_size = serializer->bytes_written();
  intptr_t stop_data = serializer->GetDataSize();
  intptr_t stop_objects = serializer->next_ref_index();
  if (FLAG_print_cluster_information) {
    OS::PrintErr("Snapshot 0x%" Pp " (%" Pd "), ", start_size,
                 stop_size - start_size);
    OS::PrintErr("Data 0x%" Pp " (%" Pd "): ", start_data,
                 stop_data - start_data);
    OS::PrintErr("Alloc %s (%" Pd ")\n", name(), stop_objects - start_objects);
  }
  size_ += (stop_size - start_size) + (stop_data - start_data);
  num_objects_ += (stop_objects - start_objects);
}

void SerializationCluster::WriteAndMeasureFill(Serializer* serializer) {
  intptr_t start = serializer->bytes_written();
  WriteFill(serializer);
  intptr_t stop = serializer->bytes_written();
  if (FLAG_print_cluster_information) {
    OS::PrintErr("Snapshot 0x%" Pp " (%" Pd "): Fill %s\n", start, stop - start,
                 name());
  }
  size_ += (stop - start);
}

class ClassSerializationCluster : public SerializationCluster {
 public:
  explicit ClassSerializationCluster(intptr_t num_cids)
      : SerializationCluster("Class"),
        predefined_(kNumPredefinedCids),
        objects_(num_cids) {}
  ~ClassSerializationCluster() {}

  void Trace(Serializer* s, ObjectPtr object) {
    ClassPtr cls = Class::RawCast(object);
    intptr_t class_id = cls->ptr()->id_;

    if (class_id == kIllegalCid) {
      // Classes expected to be dropped by the precompiler should not be traced.
      s->UnexpectedObject(cls, "Class with illegal cid");
    }
    if (class_id < kNumPredefinedCids) {
      // These classes are allocated by Object::Init or Object::InitOnce, so the
      // deserializer must find them in the class table instead of allocating
      // them.
      predefined_.Add(cls);
    } else {
      objects_.Add(cls);
    }

    PushFromTo(cls);
  }

  void WriteAlloc(Serializer* s) {
    s->WriteCid(kClassCid);
    intptr_t count = predefined_.length();
    s->WriteUnsigned(count);
    for (intptr_t i = 0; i < count; i++) {
      ClassPtr cls = predefined_[i];
      s->AssignRef(cls);
      AutoTraceObject(cls);
      intptr_t class_id = cls->ptr()->id_;
      s->WriteCid(class_id);
    }
    count = objects_.length();
    s->WriteUnsigned(count);
    for (intptr_t i = 0; i < count; i++) {
      ClassPtr cls = objects_[i];
      s->AssignRef(cls);
    }
  }

  void WriteFill(Serializer* s) {
    intptr_t count = predefined_.length();
    for (intptr_t i = 0; i < count; i++) {
      WriteClass(s, predefined_[i]);
    }
    count = objects_.length();
    for (intptr_t i = 0; i < count; i++) {
      WriteClass(s, objects_[i]);
    }
  }

 private:
  void WriteClass(Serializer* s, ClassPtr cls) {
    AutoTraceObjectName(cls, cls->ptr()->name_);
    WriteFromTo(cls);
    intptr_t class_id = cls->ptr()->id_;
    if (class_id == kIllegalCid) {
      s->UnexpectedObject(cls, "Class with illegal cid");
    }
    s->WriteCid(class_id);
    if (s->kind() == Snapshot::kFull && RequireLegacyErasureOfConstants(cls)) {
      s->UnexpectedObject(cls, "Class with non mode agnostic constants");
    }
    if (s->kind() != Snapshot::kFullAOT) {
      s->Write<uint32_t>(cls->ptr()->binary_declaration_);
    }
    s->Write<int32_t>(Class::target_instance_size_in_words(cls));
    s->Write<int32_t>(Class::target_next_field_offset_in_words(cls));
    s->Write<int32_t>(Class::target_type_arguments_field_offset_in_words(cls));
    s->Write<int16_t>(cls->ptr()->num_type_arguments_);
    s->Write<uint16_t>(cls->ptr()->num_native_fields_);
    s->WriteTokenPosition(cls->ptr()->token_pos_);
    s->WriteTokenPosition(cls->ptr()->end_token_pos_);
    s->Write<uint32_t>(cls->ptr()->state_bits_);

    // In AOT, the bitmap of unboxed fields should also be serialized
    if (FLAG_precompiled_mode && !ClassTable::IsTopLevelCid(class_id)) {
      s->WriteUnsigned64(
          CalculateTargetUnboxedFieldsBitmap(s, class_id).Value());
    }
  }

  GrowableArray<ClassPtr> predefined_;
  GrowableArray<ClassPtr> objects_;

  UnboxedFieldBitmap CalculateTargetUnboxedFieldsBitmap(Serializer* s,
                                                        intptr_t class_id) {
    const auto unboxed_fields_bitmap_host =
        s->isolate()->group()->shared_class_table()->GetUnboxedFieldsMapAt(
            class_id);

    UnboxedFieldBitmap unboxed_fields_bitmap;
    if (unboxed_fields_bitmap_host.IsEmpty() ||
        kWordSize == compiler::target::kWordSize) {
      unboxed_fields_bitmap = unboxed_fields_bitmap_host;
    } else {
      ASSERT(kWordSize == 8 && compiler::target::kWordSize == 4);
      // A new bitmap is built if the word sizes in the target and
      // host are different
      unboxed_fields_bitmap.Reset();
      intptr_t target_i = 0, host_i = 0;

      while (host_i < UnboxedFieldBitmap::Length()) {
        // Each unboxed field has constant length, therefore the number of
        // words used by it should double when compiling from 64-bit to 32-bit.
        if (unboxed_fields_bitmap_host.Get(host_i++)) {
          unboxed_fields_bitmap.Set(target_i++);
          unboxed_fields_bitmap.Set(target_i++);
        } else {
          // For object pointers, the field is always one word length
          target_i++;
        }
      }
    }

    return unboxed_fields_bitmap;
  }

  bool RequireLegacyErasureOfConstants(ClassPtr cls) {
    // Do not generate a core snapshot containing constants that would require
    // a legacy erasure of their types if loaded in an isolate running in weak
    // mode.
    if (cls->ptr()->host_type_arguments_field_offset_in_words_ ==
            Class::kNoTypeArguments ||
        cls->ptr()->constants_ == Object::empty_array().raw()) {
      return false;
    }
    Zone* zone = Thread::Current()->zone();
    const Class& clazz = Class::Handle(zone, cls);
    return clazz.RequireLegacyErasureOfConstants(zone);
  }
};
#endif  // !DART_PRECOMPILED_RUNTIME

class ClassDeserializationCluster : public DeserializationCluster {
 public:
  ClassDeserializationCluster() {}
  ~ClassDeserializationCluster() {}

  void ReadAlloc(Deserializer* d) {
    predefined_start_index_ = d->next_index();
    PageSpace* old_space = d->heap()->old_space();
    intptr_t count = d->ReadUnsigned();
    ClassTable* table = d->isolate()->class_table();
    for (intptr_t i = 0; i < count; i++) {
      intptr_t class_id = d->ReadCid();
      ASSERT(table->HasValidClassAt(class_id));
      ClassPtr cls = table->At(class_id);
      ASSERT(cls != nullptr);
      d->AssignRef(cls);
    }
    predefined_stop_index_ = d->next_index();

    start_index_ = d->next_index();
    count = d->ReadUnsigned();
    for (intptr_t i = 0; i < count; i++) {
      d->AssignRef(AllocateUninitialized(old_space, Class::InstanceSize()));
    }
    stop_index_ = d->next_index();
  }

  void ReadFill(Deserializer* d) {
    ClassTable* table = d->isolate()->class_table();

    for (intptr_t id = predefined_start_index_; id < predefined_stop_index_;
         id++) {
      ClassPtr cls = static_cast<ClassPtr>(d->Ref(id));
      ReadFromTo(cls);
      intptr_t class_id = d->ReadCid();
      cls->ptr()->id_ = class_id;
#if !defined(DART_PRECOMPILED_RUNTIME)
      if (d->kind() != Snapshot::kFullAOT) {
        cls->ptr()->binary_declaration_ = d->Read<uint32_t>();
      }
#endif
      if (!IsInternalVMdefinedClassId(class_id)) {
        cls->ptr()->host_instance_size_in_words_ = d->Read<int32_t>();
        cls->ptr()->host_next_field_offset_in_words_ = d->Read<int32_t>();
#if !defined(DART_PRECOMPILED_RUNTIME)
        // Only one pair is serialized. The target field only exists when
        // DART_PRECOMPILED_RUNTIME is not defined
        cls->ptr()->target_instance_size_in_words_ =
            cls->ptr()->host_instance_size_in_words_;
        cls->ptr()->target_next_field_offset_in_words_ =
            cls->ptr()->host_next_field_offset_in_words_;
#endif  //  !defined(DART_PRECOMPILED_RUNTIME)
      } else {
        d->Read<int32_t>();  // Skip.
        d->Read<int32_t>();  // Skip.
      }
      cls->ptr()->host_type_arguments_field_offset_in_words_ =
          d->Read<int32_t>();
#if !defined(DART_PRECOMPILED_RUNTIME)
      cls->ptr()->target_type_arguments_field_offset_in_words_ =
          cls->ptr()->host_type_arguments_field_offset_in_words_;
#endif  //  !defined(DART_PRECOMPILED_RUNTIME)
      cls->ptr()->num_type_arguments_ = d->Read<int16_t>();
      cls->ptr()->num_native_fields_ = d->Read<uint16_t>();
      cls->ptr()->token_pos_ = d->ReadTokenPosition();
      cls->ptr()->end_token_pos_ = d->ReadTokenPosition();
      cls->ptr()->state_bits_ = d->Read<uint32_t>();

      if (FLAG_precompiled_mode) {
        d->ReadUnsigned64();  // Skip unboxed fields bitmap.
      }
    }

    auto shared_class_table = d->isolate()->group()->shared_class_table();
    for (intptr_t id = start_index_; id < stop_index_; id++) {
      ClassPtr cls = static_cast<ClassPtr>(d->Ref(id));
      Deserializer::InitializeHeader(cls, kClassCid, Class::InstanceSize());
      ReadFromTo(cls);

      intptr_t class_id = d->ReadCid();
      ASSERT(class_id >= kNumPredefinedCids);
      cls->ptr()->id_ = class_id;

#if !defined(DART_PRECOMPILED_RUNTIME)
      if (d->kind() != Snapshot::kFullAOT) {
        cls->ptr()->binary_declaration_ = d->Read<uint32_t>();
      }
#endif
      cls->ptr()->host_instance_size_in_words_ = d->Read<int32_t>();
      cls->ptr()->host_next_field_offset_in_words_ = d->Read<int32_t>();
      cls->ptr()->host_type_arguments_field_offset_in_words_ =
          d->Read<int32_t>();
#if !defined(DART_PRECOMPILED_RUNTIME)
      cls->ptr()->target_instance_size_in_words_ =
          cls->ptr()->host_instance_size_in_words_;
      cls->ptr()->target_next_field_offset_in_words_ =
          cls->ptr()->host_next_field_offset_in_words_;
      cls->ptr()->target_type_arguments_field_offset_in_words_ =
          cls->ptr()->host_type_arguments_field_offset_in_words_;
#endif  //  !defined(DART_PRECOMPILED_RUNTIME)
      cls->ptr()->num_type_arguments_ = d->Read<int16_t>();
      cls->ptr()->num_native_fields_ = d->Read<uint16_t>();
      cls->ptr()->token_pos_ = d->ReadTokenPosition();
      cls->ptr()->end_token_pos_ = d->ReadTokenPosition();
      cls->ptr()->state_bits_ = d->Read<uint32_t>();

      table->AllocateIndex(class_id);
      table->SetAt(class_id, cls);

      if (FLAG_precompiled_mode && !ClassTable::IsTopLevelCid(class_id)) {
        const UnboxedFieldBitmap unboxed_fields_map(d->ReadUnsigned64());
        shared_class_table->SetUnboxedFieldsMapAt(class_id, unboxed_fields_map);
      }
    }
  }

 private:
  intptr_t predefined_start_index_;
  intptr_t predefined_stop_index_;
};

#if !defined(DART_PRECOMPILED_RUNTIME)
class TypeArgumentsSerializationCluster : public SerializationCluster {
 public:
  TypeArgumentsSerializationCluster() : SerializationCluster("TypeArguments") {}
  ~TypeArgumentsSerializationCluster() {}

  void Trace(Serializer* s, ObjectPtr object) {
    TypeArgumentsPtr type_args = TypeArguments::RawCast(object);
    objects_.Add(type_args);

    s->Push(type_args->ptr()->instantiations_);
    const intptr_t length = Smi::Value(type_args->ptr()->length_);
    for (intptr_t i = 0; i < length; i++) {
      s->Push(type_args->ptr()->types()[i]);
    }
  }

  void WriteAlloc(Serializer* s) {
    s->WriteCid(kTypeArgumentsCid);
    const intptr_t count = objects_.length();
    s->WriteUnsigned(count);
    for (intptr_t i = 0; i < count; i++) {
      TypeArgumentsPtr type_args = objects_[i];
      s->AssignRef(type_args);
      AutoTraceObject(type_args);
      const intptr_t length = Smi::Value(type_args->ptr()->length_);
      s->WriteUnsigned(length);
    }
  }

  void WriteFill(Serializer* s) {
    const intptr_t count = objects_.length();
    for (intptr_t i = 0; i < count; i++) {
      TypeArgumentsPtr type_args = objects_[i];
      AutoTraceObject(type_args);
      const intptr_t length = Smi::Value(type_args->ptr()->length_);
      s->WriteUnsigned(length);
      s->Write<bool>(type_args->ptr()->IsCanonical());
      intptr_t hash = Smi::Value(type_args->ptr()->hash_);
      s->Write<int32_t>(hash);
      const intptr_t nullability = Smi::Value(type_args->ptr()->nullability_);
      s->WriteUnsigned(nullability);
      WriteField(type_args, instantiations_);
      for (intptr_t j = 0; j < length; j++) {
        s->WriteElementRef(type_args->ptr()->types()[j], j);
      }
    }
  }

 private:
  GrowableArray<TypeArgumentsPtr> objects_;
};
#endif  // !DART_PRECOMPILED_RUNTIME

class TypeArgumentsDeserializationCluster : public DeserializationCluster {
 public:
  TypeArgumentsDeserializationCluster() {}
  ~TypeArgumentsDeserializationCluster() {}

  void ReadAlloc(Deserializer* d) {
    start_index_ = d->next_index();
    PageSpace* old_space = d->heap()->old_space();
    const intptr_t count = d->ReadUnsigned();
    for (intptr_t i = 0; i < count; i++) {
      const intptr_t length = d->ReadUnsigned();
      d->AssignRef(AllocateUninitialized(old_space,
                                         TypeArguments::InstanceSize(length)));
    }
    stop_index_ = d->next_index();
  }

  void ReadFill(Deserializer* d) {
    for (intptr_t id = start_index_; id < stop_index_; id++) {
      TypeArgumentsPtr type_args = static_cast<TypeArgumentsPtr>(d->Ref(id));
      const intptr_t length = d->ReadUnsigned();
      bool is_canonical = d->Read<bool>();
      Deserializer::InitializeHeader(type_args, kTypeArgumentsCid,
                                     TypeArguments::InstanceSize(length),
                                     is_canonical);
      type_args->ptr()->length_ = Smi::New(length);
      type_args->ptr()->hash_ = Smi::New(d->Read<int32_t>());
      type_args->ptr()->nullability_ = Smi::New(d->ReadUnsigned());
      type_args->ptr()->instantiations_ = static_cast<ArrayPtr>(d->ReadRef());
      for (intptr_t j = 0; j < length; j++) {
        type_args->ptr()->types()[j] =
            static_cast<AbstractTypePtr>(d->ReadRef());
      }
    }
  }
};

#if !defined(DART_PRECOMPILED_RUNTIME)
class PatchClassSerializationCluster : public SerializationCluster {
 public:
  PatchClassSerializationCluster() : SerializationCluster("PatchClass") {}
  ~PatchClassSerializationCluster() {}

  void Trace(Serializer* s, ObjectPtr object) {
    PatchClassPtr cls = PatchClass::RawCast(object);
    objects_.Add(cls);
    PushFromTo(cls);
  }

  void WriteAlloc(Serializer* s) {
    s->WriteCid(kPatchClassCid);
    const intptr_t count = objects_.length();
    s->WriteUnsigned(count);
    for (intptr_t i = 0; i < count; i++) {
      PatchClassPtr cls = objects_[i];
      s->AssignRef(cls);
    }
  }

  void WriteFill(Serializer* s) {
    const intptr_t count = objects_.length();
    for (intptr_t i = 0; i < count; i++) {
      PatchClassPtr cls = objects_[i];
      AutoTraceObject(cls);
      WriteFromTo(cls);
      if (s->kind() != Snapshot::kFullAOT) {
        s->Write<int32_t>(cls->ptr()->library_kernel_offset_);
      }
    }
  }

 private:
  GrowableArray<PatchClassPtr> objects_;
};
#endif  // !DART_PRECOMPILED_RUNTIME

class PatchClassDeserializationCluster : public DeserializationCluster {
 public:
  PatchClassDeserializationCluster() {}
  ~PatchClassDeserializationCluster() {}

  void ReadAlloc(Deserializer* d) {
    start_index_ = d->next_index();
    PageSpace* old_space = d->heap()->old_space();
    const intptr_t count = d->ReadUnsigned();
    for (intptr_t i = 0; i < count; i++) {
      d->AssignRef(
          AllocateUninitialized(old_space, PatchClass::InstanceSize()));
    }
    stop_index_ = d->next_index();
  }

  void ReadFill(Deserializer* d) {
    for (intptr_t id = start_index_; id < stop_index_; id++) {
      PatchClassPtr cls = static_cast<PatchClassPtr>(d->Ref(id));
      Deserializer::InitializeHeader(cls, kPatchClassCid,
                                     PatchClass::InstanceSize());
      ReadFromTo(cls);
#if !defined(DART_PRECOMPILED_RUNTIME)
      if (d->kind() != Snapshot::kFullAOT) {
        cls->ptr()->library_kernel_offset_ = d->Read<int32_t>();
      }
#endif
    }
  }
};

#if !defined(DART_PRECOMPILED_RUNTIME)
class FunctionSerializationCluster : public SerializationCluster {
 public:
  FunctionSerializationCluster() : SerializationCluster("Function") {}
  ~FunctionSerializationCluster() {}

  void Trace(Serializer* s, ObjectPtr object) {
    Snapshot::Kind kind = s->kind();
    FunctionPtr func = Function::RawCast(object);
    objects_.Add(func);

    PushFromTo(func);
    if (kind == Snapshot::kFull) {
      NOT_IN_PRECOMPILED(s->Push(func->ptr()->bytecode_));
    } else if (kind == Snapshot::kFullAOT) {
      s->Push(func->ptr()->code_);
    } else if (kind == Snapshot::kFullJIT) {
      NOT_IN_PRECOMPILED(s->Push(func->ptr()->unoptimized_code_));
      NOT_IN_PRECOMPILED(s->Push(func->ptr()->bytecode_));
      s->Push(func->ptr()->code_);
      s->Push(func->ptr()->ic_data_array_);
    }
  }

  void WriteAlloc(Serializer* s) {
    s->WriteCid(kFunctionCid);
    const intptr_t count = objects_.length();
    s->WriteUnsigned(count);
    for (intptr_t i = 0; i < count; i++) {
      FunctionPtr func = objects_[i];
      s->AssignRef(func);
    }
  }

  void WriteFill(Serializer* s) {
    Snapshot::Kind kind = s->kind();
    const intptr_t count = objects_.length();
    for (intptr_t i = 0; i < count; i++) {
      FunctionPtr func = objects_[i];
      AutoTraceObjectName(func, MakeDisambiguatedFunctionName(s, func));
      WriteFromTo(func);
      if (kind == Snapshot::kFull) {
        NOT_IN_PRECOMPILED(WriteField(func, bytecode_));
      } else if (kind == Snapshot::kFullAOT) {
        WriteField(func, code_);
      } else if (s->kind() == Snapshot::kFullJIT) {
        NOT_IN_PRECOMPILED(WriteField(func, unoptimized_code_));
        NOT_IN_PRECOMPILED(WriteField(func, bytecode_));
        WriteField(func, code_);
        WriteField(func, ic_data_array_);
      }

      if (kind != Snapshot::kFullAOT) {
        s->WriteTokenPosition(func->ptr()->token_pos_);
        s->WriteTokenPosition(func->ptr()->end_token_pos_);
        s->Write<uint32_t>(func->ptr()->binary_declaration_);
      }

      s->Write<uint32_t>(func->ptr()->packed_fields_);
      s->Write<uint32_t>(func->ptr()->kind_tag_);
    }
  }

  static const char* MakeDisambiguatedFunctionName(Serializer* s,
                                                   FunctionPtr f) {
    if (s->profile_writer() == nullptr) {
      return nullptr;
    }

    REUSABLE_FUNCTION_HANDLESCOPE(s->thread());
    Function& fun = reused_function_handle.Handle();
    fun = f;
    ZoneTextBuffer printer(s->thread()->zone());
    fun.PrintName(NameFormattingParams::DisambiguatedUnqualified(
                      Object::NameVisibility::kInternalName),
                  &printer);
    return printer.buffer();
  }

 private:
  GrowableArray<FunctionPtr> objects_;
};
#endif  // !DART_PRECOMPILED_RUNTIME

class FunctionDeserializationCluster : public DeserializationCluster {
 public:
  FunctionDeserializationCluster() {}
  ~FunctionDeserializationCluster() {}

  void ReadAlloc(Deserializer* d) {
    start_index_ = d->next_index();
    PageSpace* old_space = d->heap()->old_space();
    const intptr_t count = d->ReadUnsigned();
    for (intptr_t i = 0; i < count; i++) {
      d->AssignRef(AllocateUninitialized(old_space, Function::InstanceSize()));
    }
    stop_index_ = d->next_index();
  }

  void ReadFill(Deserializer* d) {
    Snapshot::Kind kind = d->kind();

    for (intptr_t id = start_index_; id < stop_index_; id++) {
      FunctionPtr func = static_cast<FunctionPtr>(d->Ref(id));
      Deserializer::InitializeHeader(func, kFunctionCid,
                                     Function::InstanceSize());
      ReadFromTo(func);

      if (kind == Snapshot::kFull) {
        NOT_IN_PRECOMPILED(func->ptr()->bytecode_ =
                               static_cast<BytecodePtr>(d->ReadRef()));
      } else if (kind == Snapshot::kFullAOT) {
        func->ptr()->code_ = static_cast<CodePtr>(d->ReadRef());
      } else if (kind == Snapshot::kFullJIT) {
        NOT_IN_PRECOMPILED(func->ptr()->unoptimized_code_ =
                               static_cast<CodePtr>(d->ReadRef()));
        NOT_IN_PRECOMPILED(func->ptr()->bytecode_ =
                               static_cast<BytecodePtr>(d->ReadRef()));
        func->ptr()->code_ = static_cast<CodePtr>(d->ReadRef());
        func->ptr()->ic_data_array_ = static_cast<ArrayPtr>(d->ReadRef());
      }

#if defined(DEBUG)
      func->ptr()->entry_point_ = 0;
      func->ptr()->unchecked_entry_point_ = 0;
#endif

#if !defined(DART_PRECOMPILED_RUNTIME)
      if (kind != Snapshot::kFullAOT) {
        func->ptr()->token_pos_ = d->ReadTokenPosition();
        func->ptr()->end_token_pos_ = d->ReadTokenPosition();
        func->ptr()->binary_declaration_ = d->Read<uint32_t>();
      }
      func->ptr()->unboxed_parameters_info_.Reset();
#endif
      func->ptr()->packed_fields_ = d->Read<uint32_t>();
      func->ptr()->kind_tag_ = d->Read<uint32_t>();
      if (kind == Snapshot::kFullAOT) {
        // Omit fields used to support de/reoptimization.
      } else {
#if !defined(DART_PRECOMPILED_RUNTIME)
        func->ptr()->usage_counter_ = 0;
        func->ptr()->optimized_instruction_count_ = 0;
        func->ptr()->optimized_call_site_count_ = 0;
        func->ptr()->deoptimization_counter_ = 0;
        func->ptr()->state_bits_ = 0;
        func->ptr()->inlining_depth_ = 0;
#endif
      }
    }
  }

  void PostLoad(Deserializer* d, const Array& refs) {
    if (d->kind() == Snapshot::kFullAOT) {
      Function& func = Function::Handle(d->zone());
      for (intptr_t i = start_index_; i < stop_index_; i++) {
        func ^= refs.At(i);
        ASSERT(func.raw()->ptr()->code_->IsCode());
        uword entry_point = func.raw()->ptr()->code_->ptr()->entry_point_;
        ASSERT(entry_point != 0);
        func.raw()->ptr()->entry_point_ = entry_point;
        uword unchecked_entry_point =
            func.raw()->ptr()->code_->ptr()->unchecked_entry_point_;
        ASSERT(unchecked_entry_point != 0);
        func.raw()->ptr()->unchecked_entry_point_ = unchecked_entry_point;
      }
    } else if (d->kind() == Snapshot::kFullJIT) {
      Function& func = Function::Handle(d->zone());
      Code& code = Code::Handle(d->zone());
      for (intptr_t i = start_index_; i < stop_index_; i++) {
        func ^= refs.At(i);
        code = func.CurrentCode();
        if (func.HasCode() && !code.IsDisabled()) {
          func.SetInstructions(code);  // Set entrypoint.
          func.SetWasCompiled(true);
        } else {
          func.ClearCode();  // Set code and entrypoint to lazy compile stub.
        }
      }
    } else {
      Function& func = Function::Handle(d->zone());
      for (intptr_t i = start_index_; i < stop_index_; i++) {
        func ^= refs.At(i);
        func.ClearCode();  // Set code and entrypoint to lazy compile stub.
      }
    }
  }
};

#if !defined(DART_PRECOMPILED_RUNTIME)
class ClosureDataSerializationCluster : public SerializationCluster {
 public:
  ClosureDataSerializationCluster() : SerializationCluster("ClosureData") {}
  ~ClosureDataSerializationCluster() {}

  void Trace(Serializer* s, ObjectPtr object) {
    ClosureDataPtr data = ClosureData::RawCast(object);
    objects_.Add(data);

    if (s->kind() != Snapshot::kFullAOT) {
      s->Push(data->ptr()->context_scope_);
    }
    s->Push(data->ptr()->parent_function_);
    s->Push(data->ptr()->signature_type_);
    s->Push(data->ptr()->closure_);
  }

  void WriteAlloc(Serializer* s) {
    s->WriteCid(kClosureDataCid);
    const intptr_t count = objects_.length();
    s->WriteUnsigned(count);
    for (intptr_t i = 0; i < count; i++) {
      ClosureDataPtr data = objects_[i];
      s->AssignRef(data);
    }
  }

  void WriteFill(Serializer* s) {
    const intptr_t count = objects_.length();
    for (intptr_t i = 0; i < count; i++) {
      ClosureDataPtr data = objects_[i];
      AutoTraceObject(data);
      if (s->kind() != Snapshot::kFullAOT) {
        WriteField(data, context_scope_);
      }
      WriteField(data, parent_function_);
      WriteField(data, signature_type_);
      WriteField(data, closure_);
    }
  }

 private:
  GrowableArray<ClosureDataPtr> objects_;
};
#endif  // !DART_PRECOMPILED_RUNTIME

class ClosureDataDeserializationCluster : public DeserializationCluster {
 public:
  ClosureDataDeserializationCluster() {}
  ~ClosureDataDeserializationCluster() {}

  void ReadAlloc(Deserializer* d) {
    start_index_ = d->next_index();
    PageSpace* old_space = d->heap()->old_space();
    const intptr_t count = d->ReadUnsigned();
    for (intptr_t i = 0; i < count; i++) {
      d->AssignRef(
          AllocateUninitialized(old_space, ClosureData::InstanceSize()));
    }
    stop_index_ = d->next_index();
  }

  void ReadFill(Deserializer* d) {
    for (intptr_t id = start_index_; id < stop_index_; id++) {
      ClosureDataPtr data = static_cast<ClosureDataPtr>(d->Ref(id));
      Deserializer::InitializeHeader(data, kClosureDataCid,
                                     ClosureData::InstanceSize());
      if (d->kind() == Snapshot::kFullAOT) {
        data->ptr()->context_scope_ = ContextScope::null();
      } else {
        data->ptr()->context_scope_ =
            static_cast<ContextScopePtr>(d->ReadRef());
      }
      data->ptr()->parent_function_ = static_cast<FunctionPtr>(d->ReadRef());
      data->ptr()->signature_type_ = static_cast<TypePtr>(d->ReadRef());
      data->ptr()->closure_ = static_cast<InstancePtr>(d->ReadRef());
    }
  }
};

#if !defined(DART_PRECOMPILED_RUNTIME)
class SignatureDataSerializationCluster : public SerializationCluster {
 public:
  SignatureDataSerializationCluster() : SerializationCluster("SignatureData") {}
  ~SignatureDataSerializationCluster() {}

  void Trace(Serializer* s, ObjectPtr object) {
    SignatureDataPtr data = SignatureData::RawCast(object);
    objects_.Add(data);
    PushFromTo(data);
  }

  void WriteAlloc(Serializer* s) {
    s->WriteCid(kSignatureDataCid);
    const intptr_t count = objects_.length();
    s->WriteUnsigned(count);
    for (intptr_t i = 0; i < count; i++) {
      SignatureDataPtr data = objects_[i];
      s->AssignRef(data);
    }
  }

  void WriteFill(Serializer* s) {
    const intptr_t count = objects_.length();
    for (intptr_t i = 0; i < count; i++) {
      SignatureDataPtr data = objects_[i];
      AutoTraceObject(data);
      WriteFromTo(data);
    }
  }

 private:
  GrowableArray<SignatureDataPtr> objects_;
};
#endif  // !DART_PRECOMPILED_RUNTIME

class SignatureDataDeserializationCluster : public DeserializationCluster {
 public:
  SignatureDataDeserializationCluster() {}
  ~SignatureDataDeserializationCluster() {}

  void ReadAlloc(Deserializer* d) {
    start_index_ = d->next_index();
    PageSpace* old_space = d->heap()->old_space();
    const intptr_t count = d->ReadUnsigned();
    for (intptr_t i = 0; i < count; i++) {
      d->AssignRef(
          AllocateUninitialized(old_space, SignatureData::InstanceSize()));
    }
    stop_index_ = d->next_index();
  }

  void ReadFill(Deserializer* d) {
    for (intptr_t id = start_index_; id < stop_index_; id++) {
      SignatureDataPtr data = static_cast<SignatureDataPtr>(d->Ref(id));
      Deserializer::InitializeHeader(data, kSignatureDataCid,
                                     SignatureData::InstanceSize());
      ReadFromTo(data);
    }
  }
};

#if !defined(DART_PRECOMPILED_RUNTIME)
class FfiTrampolineDataSerializationCluster : public SerializationCluster {
 public:
  FfiTrampolineDataSerializationCluster()
      : SerializationCluster("FfiTrampolineData") {}
  ~FfiTrampolineDataSerializationCluster() {}

  void Trace(Serializer* s, ObjectPtr object) {
    FfiTrampolineDataPtr data = FfiTrampolineData::RawCast(object);
    objects_.Add(data);
    PushFromTo(data);
  }

  void WriteAlloc(Serializer* s) {
    s->WriteCid(kFfiTrampolineDataCid);
    const intptr_t count = objects_.length();
    s->WriteUnsigned(count);
    for (intptr_t i = 0; i < count; i++) {
      s->AssignRef(objects_[i]);
    }
  }

  void WriteFill(Serializer* s) {
    const intptr_t count = objects_.length();
    for (intptr_t i = 0; i < count; i++) {
      FfiTrampolineDataPtr const data = objects_[i];
      AutoTraceObject(data);
      WriteFromTo(data);

      if (s->kind() == Snapshot::kFullAOT) {
        s->WriteUnsigned(data->ptr()->callback_id_);
      } else {
        // FFI callbacks can only be written to AOT snapshots.
        ASSERT(data->ptr()->callback_target_ == Object::null());
      }
    }
  }

 private:
  GrowableArray<FfiTrampolineDataPtr> objects_;
};
#endif  // !DART_PRECOMPILED_RUNTIME

class FfiTrampolineDataDeserializationCluster : public DeserializationCluster {
 public:
  FfiTrampolineDataDeserializationCluster() {}
  ~FfiTrampolineDataDeserializationCluster() {}

  void ReadAlloc(Deserializer* d) {
    start_index_ = d->next_index();
    PageSpace* old_space = d->heap()->old_space();
    const intptr_t count = d->ReadUnsigned();
    for (intptr_t i = 0; i < count; i++) {
      d->AssignRef(
          AllocateUninitialized(old_space, FfiTrampolineData::InstanceSize()));
    }
    stop_index_ = d->next_index();
  }

  void ReadFill(Deserializer* d) {
    for (intptr_t id = start_index_; id < stop_index_; id++) {
      FfiTrampolineDataPtr data = static_cast<FfiTrampolineDataPtr>(d->Ref(id));
      Deserializer::InitializeHeader(data, kFfiTrampolineDataCid,
                                     FfiTrampolineData::InstanceSize());
      ReadFromTo(data);
      data->ptr()->callback_id_ =
          d->kind() == Snapshot::kFullAOT ? d->ReadUnsigned() : 0;
    }
  }
};

#if !defined(DART_PRECOMPILED_RUNTIME)
class RedirectionDataSerializationCluster : public SerializationCluster {
 public:
  RedirectionDataSerializationCluster()
      : SerializationCluster("RedirectionData") {}
  ~RedirectionDataSerializationCluster() {}

  void Trace(Serializer* s, ObjectPtr object) {
    RedirectionDataPtr data = RedirectionData::RawCast(object);
    objects_.Add(data);
    PushFromTo(data);
  }

  void WriteAlloc(Serializer* s) {
    s->WriteCid(kRedirectionDataCid);
    const intptr_t count = objects_.length();
    s->WriteUnsigned(count);
    for (intptr_t i = 0; i < count; i++) {
      RedirectionDataPtr data = objects_[i];
      s->AssignRef(data);
    }
  }

  void WriteFill(Serializer* s) {
    const intptr_t count = objects_.length();
    for (intptr_t i = 0; i < count; i++) {
      RedirectionDataPtr data = objects_[i];
      AutoTraceObject(data);
      WriteFromTo(data);
    }
  }

 private:
  GrowableArray<RedirectionDataPtr> objects_;
};
#endif  // !DART_PRECOMPILED_RUNTIME

class RedirectionDataDeserializationCluster : public DeserializationCluster {
 public:
  RedirectionDataDeserializationCluster() {}
  ~RedirectionDataDeserializationCluster() {}

  void ReadAlloc(Deserializer* d) {
    start_index_ = d->next_index();
    PageSpace* old_space = d->heap()->old_space();
    const intptr_t count = d->ReadUnsigned();
    for (intptr_t i = 0; i < count; i++) {
      d->AssignRef(
          AllocateUninitialized(old_space, RedirectionData::InstanceSize()));
    }
    stop_index_ = d->next_index();
  }

  void ReadFill(Deserializer* d) {
    for (intptr_t id = start_index_; id < stop_index_; id++) {
      RedirectionDataPtr data = static_cast<RedirectionDataPtr>(d->Ref(id));
      Deserializer::InitializeHeader(data, kRedirectionDataCid,
                                     RedirectionData::InstanceSize());
      ReadFromTo(data);
    }
  }
};

#if !defined(DART_PRECOMPILED_RUNTIME)
class FieldSerializationCluster : public SerializationCluster {
 public:
  FieldSerializationCluster() : SerializationCluster("Field") {}
  ~FieldSerializationCluster() {}

  void Trace(Serializer* s, ObjectPtr object) {
    FieldPtr field = Field::RawCast(object);
    objects_.Add(field);

    Snapshot::Kind kind = s->kind();

    s->Push(field->ptr()->name_);
    s->Push(field->ptr()->owner_);
    s->Push(field->ptr()->type_);
    // Write out the initializer function
    s->Push(field->ptr()->initializer_function_);

    if (kind != Snapshot::kFullAOT) {
      s->Push(field->ptr()->saved_initial_value_);
      s->Push(field->ptr()->guarded_list_length_);
    }
    if (kind == Snapshot::kFullJIT) {
      s->Push(field->ptr()->dependent_code_);
    }
    // Write out either static value, initial value or field offset.
    if (Field::StaticBit::decode(field->ptr()->kind_bits_)) {
      if (
          // For precompiled static fields, the value was already reset and
          // initializer_ now contains a Function.
          kind == Snapshot::kFullAOT ||
          // Do not reset const fields.
          Field::ConstBit::decode(field->ptr()->kind_bits_)) {
        s->Push(s->field_table()->At(
            Smi::Value(field->ptr()->host_offset_or_field_id_)));
      } else {
        // Otherwise, for static fields we write out the initial static value.
        s->Push(field->ptr()->saved_initial_value_);
      }
    } else {
      s->Push(Smi::New(Field::TargetOffsetOf(field)));
    }
  }

  void WriteAlloc(Serializer* s) {
    s->WriteCid(kFieldCid);
    const intptr_t count = objects_.length();
    s->WriteUnsigned(count);
    for (intptr_t i = 0; i < count; i++) {
      FieldPtr field = objects_[i];
      s->AssignRef(field);
    }
  }

  void WriteFill(Serializer* s) {
    Snapshot::Kind kind = s->kind();
    const intptr_t count = objects_.length();
    for (intptr_t i = 0; i < count; i++) {
      FieldPtr field = objects_[i];
      AutoTraceObjectName(field, field->ptr()->name_);

      WriteField(field, name_);
      WriteField(field, owner_);
      WriteField(field, type_);
      // Write out the initializer function and initial value if not in AOT.
      WriteField(field, initializer_function_);
      if (kind != Snapshot::kFullAOT) {
        WriteField(field, saved_initial_value_);
        WriteField(field, guarded_list_length_);
      }
      if (kind == Snapshot::kFullJIT) {
        WriteField(field, dependent_code_);
      }

      if (kind != Snapshot::kFullAOT) {
        s->WriteTokenPosition(field->ptr()->token_pos_);
        s->WriteTokenPosition(field->ptr()->end_token_pos_);
        s->WriteCid(field->ptr()->guarded_cid_);
        s->WriteCid(field->ptr()->is_nullable_);
        s->Write<int8_t>(field->ptr()->static_type_exactness_state_);
        s->Write<uint32_t>(field->ptr()->binary_declaration_);
      }
      s->Write<uint16_t>(field->ptr()->kind_bits_);

      // Write out the initial static value or field offset.
      if (Field::StaticBit::decode(field->ptr()->kind_bits_)) {
        if (
            // For precompiled static fields, the value was already reset and
            // initializer_ now contains a Function.
            kind == Snapshot::kFullAOT ||
            // Do not reset const fields.
            Field::ConstBit::decode(field->ptr()->kind_bits_)) {
          WriteFieldValue("static value",
                          s->field_table()->At(Smi::Value(
                              field->ptr()->host_offset_or_field_id_)));
        } else {
          // Otherwise, for static fields we write out the initial static value.
          WriteFieldValue("static value", field->ptr()->saved_initial_value_);
        }
        s->WriteUnsigned(Smi::Value(field->ptr()->host_offset_or_field_id_));
      } else {
        WriteFieldValue("offset", Smi::New(Field::TargetOffsetOf(field)));
      }
    }
  }

 private:
  GrowableArray<FieldPtr> objects_;
};
#endif  // !DART_PRECOMPILED_RUNTIME

class FieldDeserializationCluster : public DeserializationCluster {
 public:
  FieldDeserializationCluster() {}
  ~FieldDeserializationCluster() {}

  void ReadAlloc(Deserializer* d) {
    start_index_ = d->next_index();
    PageSpace* old_space = d->heap()->old_space();
    const intptr_t count = d->ReadUnsigned();
    for (intptr_t i = 0; i < count; i++) {
      d->AssignRef(AllocateUninitialized(old_space, Field::InstanceSize()));
    }
    stop_index_ = d->next_index();
  }

  void ReadFill(Deserializer* d) {
    Snapshot::Kind kind = d->kind();

    for (intptr_t id = start_index_; id < stop_index_; id++) {
      FieldPtr field = static_cast<FieldPtr>(d->Ref(id));
      Deserializer::InitializeHeader(field, kFieldCid, Field::InstanceSize());
      ReadFromTo(field);
      if (kind != Snapshot::kFullAOT) {
#if !defined(DART_PRECOMPILED_RUNTIME)
        field->ptr()->saved_initial_value_ =
            static_cast<InstancePtr>(d->ReadRef());
#endif
        field->ptr()->guarded_list_length_ = static_cast<SmiPtr>(d->ReadRef());
      }
      if (kind == Snapshot::kFullJIT) {
        field->ptr()->dependent_code_ = static_cast<ArrayPtr>(d->ReadRef());
      }
      if (kind != Snapshot::kFullAOT) {
        field->ptr()->token_pos_ = d->ReadTokenPosition();
        field->ptr()->end_token_pos_ = d->ReadTokenPosition();
        field->ptr()->guarded_cid_ = d->ReadCid();
        field->ptr()->is_nullable_ = d->ReadCid();
        field->ptr()->static_type_exactness_state_ = d->Read<int8_t>();
#if !defined(DART_PRECOMPILED_RUNTIME)
        field->ptr()->binary_declaration_ = d->Read<uint32_t>();
#endif
      }
      field->ptr()->kind_bits_ = d->Read<uint16_t>();

      ObjectPtr value_or_offset = d->ReadRef();
      if (Field::StaticBit::decode(field->ptr()->kind_bits_)) {
        intptr_t field_id = d->ReadUnsigned();
        d->field_table()->SetAt(field_id,
                                static_cast<InstancePtr>(value_or_offset));
        field->ptr()->host_offset_or_field_id_ = Smi::New(field_id);
      } else {
        field->ptr()->host_offset_or_field_id_ = Smi::RawCast(value_or_offset);
#if !defined(DART_PRECOMPILED_RUNTIME)
        field->ptr()->target_offset_ =
            Smi::Value(field->ptr()->host_offset_or_field_id_);
#endif  //  !defined(DART_PRECOMPILED_RUNTIME)
      }
    }
  }

  void PostLoad(Deserializer* d, const Array& refs) {
    Field& field = Field::Handle(d->zone());
    if (!Isolate::Current()->use_field_guards()) {
      for (intptr_t i = start_index_; i < stop_index_; i++) {
        field ^= refs.At(i);
        field.set_guarded_cid(kDynamicCid);
        field.set_is_nullable(true);
        field.set_guarded_list_length(Field::kNoFixedLength);
        field.set_guarded_list_length_in_object_offset(
            Field::kUnknownLengthOffset);
        field.set_static_type_exactness_state(
            StaticTypeExactnessState::NotTracking());
      }
    } else {
      for (intptr_t i = start_index_; i < stop_index_; i++) {
        field ^= refs.At(i);
        field.InitializeGuardedListLengthInObjectOffset();
      }
    }
  }
};

#if !defined(DART_PRECOMPILED_RUNTIME)
class ScriptSerializationCluster : public SerializationCluster {
 public:
  ScriptSerializationCluster() : SerializationCluster("Script") {}
  ~ScriptSerializationCluster() {}

  void Trace(Serializer* s, ObjectPtr object) {
    ScriptPtr script = Script::RawCast(object);
    objects_.Add(script);
    PushFromTo(script);
  }

  void WriteAlloc(Serializer* s) {
    s->WriteCid(kScriptCid);
    const intptr_t count = objects_.length();
    s->WriteUnsigned(count);
    for (intptr_t i = 0; i < count; i++) {
      ScriptPtr script = objects_[i];
      s->AssignRef(script);
    }
  }

  void WriteFill(Serializer* s) {
    const intptr_t count = objects_.length();
    for (intptr_t i = 0; i < count; i++) {
      ScriptPtr script = objects_[i];
      AutoTraceObjectName(script, script->ptr()->url_);
      WriteFromTo(script);
      s->Write<int32_t>(script->ptr()->line_offset_);
      s->Write<int32_t>(script->ptr()->col_offset_);
      s->Write<uint8_t>(script->ptr()->flags_);
      s->Write<int32_t>(script->ptr()->kernel_script_index_);
    }
  }

 private:
  GrowableArray<ScriptPtr> objects_;
};
#endif  // !DART_PRECOMPILED_RUNTIME

class ScriptDeserializationCluster : public DeserializationCluster {
 public:
  ScriptDeserializationCluster() {}
  ~ScriptDeserializationCluster() {}

  void ReadAlloc(Deserializer* d) {
    start_index_ = d->next_index();
    PageSpace* old_space = d->heap()->old_space();
    const intptr_t count = d->ReadUnsigned();
    for (intptr_t i = 0; i < count; i++) {
      d->AssignRef(AllocateUninitialized(old_space, Script::InstanceSize()));
    }
    stop_index_ = d->next_index();
  }

  void ReadFill(Deserializer* d) {
    for (intptr_t id = start_index_; id < stop_index_; id++) {
      ScriptPtr script = static_cast<ScriptPtr>(d->Ref(id));
      Deserializer::InitializeHeader(script, kScriptCid,
                                     Script::InstanceSize());
      ReadFromTo(script);
      script->ptr()->line_offset_ = d->Read<int32_t>();
      script->ptr()->col_offset_ = d->Read<int32_t>();
      script->ptr()->flags_ = d->Read<uint8_t>();
      script->ptr()->kernel_script_index_ = d->Read<int32_t>();
      script->ptr()->load_timestamp_ = 0;
    }
  }
};

#if !defined(DART_PRECOMPILED_RUNTIME)
class LibrarySerializationCluster : public SerializationCluster {
 public:
  LibrarySerializationCluster() : SerializationCluster("Library") {}
  ~LibrarySerializationCluster() {}

  void Trace(Serializer* s, ObjectPtr object) {
    LibraryPtr lib = Library::RawCast(object);
    objects_.Add(lib);
    PushFromTo(lib);
  }

  void WriteAlloc(Serializer* s) {
    s->WriteCid(kLibraryCid);
    const intptr_t count = objects_.length();
    s->WriteUnsigned(count);
    for (intptr_t i = 0; i < count; i++) {
      LibraryPtr lib = objects_[i];
      s->AssignRef(lib);
    }
  }

  void WriteFill(Serializer* s) {
    const intptr_t count = objects_.length();
    for (intptr_t i = 0; i < count; i++) {
      LibraryPtr lib = objects_[i];
      AutoTraceObjectName(lib, lib->ptr()->url_);
      WriteFromTo(lib);
      s->Write<int32_t>(lib->ptr()->index_);
      s->Write<uint16_t>(lib->ptr()->num_imports_);
      s->Write<int8_t>(lib->ptr()->load_state_);
      s->Write<uint8_t>(lib->ptr()->flags_);
      if (s->kind() != Snapshot::kFullAOT) {
        s->Write<uint32_t>(lib->ptr()->binary_declaration_);
      }
    }
  }

 private:
  GrowableArray<LibraryPtr> objects_;
};
#endif  // !DART_PRECOMPILED_RUNTIME

class LibraryDeserializationCluster : public DeserializationCluster {
 public:
  LibraryDeserializationCluster() {}
  ~LibraryDeserializationCluster() {}

  void ReadAlloc(Deserializer* d) {
    start_index_ = d->next_index();
    PageSpace* old_space = d->heap()->old_space();
    const intptr_t count = d->ReadUnsigned();
    for (intptr_t i = 0; i < count; i++) {
      d->AssignRef(AllocateUninitialized(old_space, Library::InstanceSize()));
    }
    stop_index_ = d->next_index();
  }

  void ReadFill(Deserializer* d) {
    for (intptr_t id = start_index_; id < stop_index_; id++) {
      LibraryPtr lib = static_cast<LibraryPtr>(d->Ref(id));
      Deserializer::InitializeHeader(lib, kLibraryCid, Library::InstanceSize());
      ReadFromTo(lib);
      lib->ptr()->native_entry_resolver_ = NULL;
      lib->ptr()->native_entry_symbol_resolver_ = NULL;
      lib->ptr()->index_ = d->Read<int32_t>();
      lib->ptr()->num_imports_ = d->Read<uint16_t>();
      lib->ptr()->load_state_ = d->Read<int8_t>();
      lib->ptr()->flags_ =
          LibraryLayout::InFullSnapshotBit::update(true, d->Read<uint8_t>());
#if !defined(DART_PRECOMPILED_RUNTIME)
      if (d->kind() != Snapshot::kFullAOT) {
        lib->ptr()->binary_declaration_ = d->Read<uint32_t>();
      }
#endif
    }
  }
};

#if !defined(DART_PRECOMPILED_RUNTIME)
class NamespaceSerializationCluster : public SerializationCluster {
 public:
  NamespaceSerializationCluster() : SerializationCluster("Namespace") {}
  ~NamespaceSerializationCluster() {}

  void Trace(Serializer* s, ObjectPtr object) {
    NamespacePtr ns = Namespace::RawCast(object);
    objects_.Add(ns);
    PushFromTo(ns);
  }

  void WriteAlloc(Serializer* s) {
    s->WriteCid(kNamespaceCid);
    const intptr_t count = objects_.length();
    s->WriteUnsigned(count);
    for (intptr_t i = 0; i < count; i++) {
      NamespacePtr ns = objects_[i];
      s->AssignRef(ns);
    }
  }

  void WriteFill(Serializer* s) {
    const intptr_t count = objects_.length();
    for (intptr_t i = 0; i < count; i++) {
      NamespacePtr ns = objects_[i];
      AutoTraceObject(ns);
      WriteFromTo(ns);
    }
  }

 private:
  GrowableArray<NamespacePtr> objects_;
};
#endif  // !DART_PRECOMPILED_RUNTIME

class NamespaceDeserializationCluster : public DeserializationCluster {
 public:
  NamespaceDeserializationCluster() {}
  ~NamespaceDeserializationCluster() {}

  void ReadAlloc(Deserializer* d) {
    start_index_ = d->next_index();
    PageSpace* old_space = d->heap()->old_space();
    const intptr_t count = d->ReadUnsigned();
    for (intptr_t i = 0; i < count; i++) {
      d->AssignRef(AllocateUninitialized(old_space, Namespace::InstanceSize()));
    }
    stop_index_ = d->next_index();
  }

  void ReadFill(Deserializer* d) {
    for (intptr_t id = start_index_; id < stop_index_; id++) {
      NamespacePtr ns = static_cast<NamespacePtr>(d->Ref(id));
      Deserializer::InitializeHeader(ns, kNamespaceCid,
                                     Namespace::InstanceSize());
      ReadFromTo(ns);
    }
  }
};

#if !defined(DART_PRECOMPILED_RUNTIME)
// KernelProgramInfo objects are not written into a full AOT snapshot.
class KernelProgramInfoSerializationCluster : public SerializationCluster {
 public:
  KernelProgramInfoSerializationCluster()
      : SerializationCluster("KernelProgramInfo") {}
  ~KernelProgramInfoSerializationCluster() {}

  void Trace(Serializer* s, ObjectPtr object) {
    KernelProgramInfoPtr info = KernelProgramInfo::RawCast(object);
    objects_.Add(info);
    PushFromTo(info);
  }

  void WriteAlloc(Serializer* s) {
    s->WriteCid(kKernelProgramInfoCid);
    const intptr_t count = objects_.length();
    s->WriteUnsigned(count);
    for (intptr_t i = 0; i < count; i++) {
      KernelProgramInfoPtr info = objects_[i];
      s->AssignRef(info);
    }
  }

  void WriteFill(Serializer* s) {
    const intptr_t count = objects_.length();
    for (intptr_t i = 0; i < count; i++) {
      KernelProgramInfoPtr info = objects_[i];
      AutoTraceObject(info);
      WriteFromTo(info);
      s->Write<uint32_t>(info->ptr()->kernel_binary_version_);
    }
  }

 private:
  GrowableArray<KernelProgramInfoPtr> objects_;
};

// Since KernelProgramInfo objects are not written into full AOT snapshots,
// one will never need to read them from a full AOT snapshot.
class KernelProgramInfoDeserializationCluster : public DeserializationCluster {
 public:
  KernelProgramInfoDeserializationCluster() {}
  ~KernelProgramInfoDeserializationCluster() {}

  void ReadAlloc(Deserializer* d) {
    start_index_ = d->next_index();
    PageSpace* old_space = d->heap()->old_space();
    const intptr_t count = d->ReadUnsigned();
    for (intptr_t i = 0; i < count; i++) {
      d->AssignRef(
          AllocateUninitialized(old_space, KernelProgramInfo::InstanceSize()));
    }
    stop_index_ = d->next_index();
  }

  void ReadFill(Deserializer* d) {
    for (intptr_t id = start_index_; id < stop_index_; id++) {
      KernelProgramInfoPtr info = static_cast<KernelProgramInfoPtr>(d->Ref(id));
      Deserializer::InitializeHeader(info, kKernelProgramInfoCid,
                                     KernelProgramInfo::InstanceSize());
      ReadFromTo(info);
      info->ptr()->kernel_binary_version_ = d->Read<uint32_t>();
    }
  }

  void PostLoad(Deserializer* d, const Array& refs) {
    Array& array = Array::Handle(d->zone());
    KernelProgramInfo& info = KernelProgramInfo::Handle(d->zone());
    for (intptr_t id = start_index_; id < stop_index_; id++) {
      info ^= refs.At(id);
      array = HashTables::New<UnorderedHashMap<SmiTraits>>(16, Heap::kOld);
      info.set_libraries_cache(array);
      array = HashTables::New<UnorderedHashMap<SmiTraits>>(16, Heap::kOld);
      info.set_classes_cache(array);
    }
  }
};

class CodeSerializationCluster : public SerializationCluster {
 public:
  explicit CodeSerializationCluster(Heap* heap)
      : SerializationCluster("Code") {}
  ~CodeSerializationCluster() {}

  void Trace(Serializer* s, ObjectPtr object) {
    CodePtr code = Code::RawCast(object);

    if (s->InCurrentLoadingUnit(code, /*record*/ true)) {
      objects_.Add(code);
    }

    if (!(s->kind() == Snapshot::kFullAOT && FLAG_use_bare_instructions)) {
      s->Push(code->ptr()->object_pool_);
    }
    s->Push(code->ptr()->owner_);
    s->Push(code->ptr()->exception_handlers_);
    s->Push(code->ptr()->pc_descriptors_);
    s->Push(code->ptr()->catch_entry_);
    if (s->InCurrentLoadingUnit(code->ptr()->compressed_stackmaps_)) {
      s->Push(code->ptr()->compressed_stackmaps_);
    }
    if (!FLAG_precompiled_mode || !FLAG_dwarf_stack_traces_mode) {
      s->Push(code->ptr()->inlined_id_to_function_);
      if (s->InCurrentLoadingUnit(code->ptr()->code_source_map_)) {
        s->Push(code->ptr()->code_source_map_);
      }
    }
    if (s->kind() == Snapshot::kFullJIT) {
      s->Push(code->ptr()->deopt_info_array_);
      s->Push(code->ptr()->static_calls_target_table_);
    } else if (s->kind() == Snapshot::kFullAOT) {
#if defined(DART_PRECOMPILER)
      auto const calls_array = code->ptr()->static_calls_target_table_;
      if (calls_array != Array::null()) {
        // Some Code entries in the static calls target table may only be
        // accessible via here, so push the Code objects.
        auto const length = Smi::Value(calls_array->ptr()->length_);
        for (intptr_t i = 0; i < length; i++) {
          auto const object = calls_array->ptr()->data()[i];
          if (object->IsHeapObject() && object->IsCode()) {
            s->Push(object);
          }
        }
      }
#else
      UNREACHABLE();
#endif
    }
#if !defined(PRODUCT)
    s->Push(code->ptr()->return_address_metadata_);
    if (FLAG_code_comments) {
      s->Push(code->ptr()->comments_);
    }
#endif
  }

  struct CodeOrderInfo {
    CodePtr code;
    intptr_t order;
  };

  static int CompareCodeOrderInfo(CodeOrderInfo const* a,
                                  CodeOrderInfo const* b) {
    if (a->order < b->order) return -1;
    if (a->order > b->order) return 1;
    return 0;
  }

  static void Insert(GrowableArray<CodeOrderInfo>* order_list,
                     IntMap<intptr_t>* order_map,
                     CodePtr code) {
    InstructionsPtr instr = code->ptr()->instructions_;
    intptr_t key = static_cast<intptr_t>(instr);
    intptr_t order;
    if (order_map->HasKey(key)) {
      order = order_map->Lookup(key);
    } else {
      order = order_list->length() + 1;
      order_map->Insert(key, order);
    }
    CodeOrderInfo info;
    info.code = code;
    info.order = order;
    order_list->Add(info);
  }

  static void Sort(GrowableArray<CodePtr>* codes) {
    GrowableArray<CodeOrderInfo> order_list;
    IntMap<intptr_t> order_map;
    for (intptr_t i = 0; i < codes->length(); i++) {
      Insert(&order_list, &order_map, (*codes)[i]);
    }
    order_list.Sort(CompareCodeOrderInfo);
    ASSERT(order_list.length() == codes->length());
    for (intptr_t i = 0; i < order_list.length(); i++) {
      (*codes)[i] = order_list[i].code;
    }
  }

  static void Sort(GrowableArray<Code*>* codes) {
    GrowableArray<CodeOrderInfo> order_list;
    IntMap<intptr_t> order_map;
    for (intptr_t i = 0; i < codes->length(); i++) {
      Insert(&order_list, &order_map, (*codes)[i]->raw());
    }
    order_list.Sort(CompareCodeOrderInfo);
    ASSERT(order_list.length() == codes->length());
    for (intptr_t i = 0; i < order_list.length(); i++) {
      *(*codes)[i] = order_list[i].code;
    }
  }

  void WriteAlloc(Serializer* s) {
    Sort(&objects_);
    auto loading_units = s->loading_units();
    if (loading_units != nullptr) {
      for (intptr_t i = LoadingUnit::kRootId + 1; i < loading_units->length();
           i++) {
        auto unit_objects = loading_units->At(i)->deferred_objects();
        Sort(unit_objects);
        for (intptr_t j = 0; j < unit_objects->length(); j++) {
          deferred_objects_.Add(unit_objects->At(j)->raw());
        }
      }
    }
    s->PrepareInstructions(&objects_);

    s->WriteCid(kCodeCid);
    const intptr_t count = objects_.length();
    s->WriteUnsigned(count);
    for (intptr_t i = 0; i < count; i++) {
      CodePtr code = objects_[i];
      s->AssignRef(code);
    }
    const intptr_t deferred_count = deferred_objects_.length();
    s->WriteUnsigned(deferred_count);
    for (intptr_t i = 0; i < deferred_count; i++) {
      CodePtr code = deferred_objects_[i];
      s->AssignRef(code);
    }
  }

  void WriteFill(Serializer* s) {
    Snapshot::Kind kind = s->kind();
    const intptr_t count = objects_.length();
    for (intptr_t i = 0; i < count; i++) {
      CodePtr code = objects_[i];
      WriteFill(s, kind, code, false);
    }
    const intptr_t deferred_count = deferred_objects_.length();
    for (intptr_t i = 0; i < deferred_count; i++) {
      CodePtr code = deferred_objects_[i];
      WriteFill(s, kind, code, true);
    }
  }

  void WriteFill(Serializer* s,
                 Snapshot::Kind kind,
                 CodePtr code,
                 bool deferred) {
    AutoTraceObjectName(code, MakeDisambiguatedCodeName(s, code));

    intptr_t pointer_offsets_length =
        Code::PtrOffBits::decode(code->ptr()->state_bits_);
    if (pointer_offsets_length != 0) {
      FATAL("Cannot serialize code with embedded pointers");
    }
    if (kind == Snapshot::kFullAOT && Code::IsDisabled(code)) {
      // Disabled code is fatal in AOT since we cannot recompile.
      s->UnexpectedObject(code, "Disabled code");
    }

    s->WriteInstructions(code->ptr()->instructions_,
                         code->ptr()->unchecked_offset_, code, deferred);
    if (kind == Snapshot::kFullJIT) {
      // TODO(rmacnak): Fix references to disabled code before serializing.
      // For now, we may write the FixCallersTarget or equivalent stub. This
      // will cause a fixup if this code is called.
      const uint32_t active_unchecked_offset =
          code->ptr()->unchecked_entry_point_ - code->ptr()->entry_point_;
      s->WriteInstructions(code->ptr()->active_instructions_,
                           active_unchecked_offset, code, deferred);
    }

    // No need to write object pool out if we are producing full AOT
    // snapshot with bare instructions.
    if (!(kind == Snapshot::kFullAOT && FLAG_use_bare_instructions)) {
      WriteField(code, object_pool_);
#if defined(DART_PRECOMPILER)
    } else if (FLAG_write_v8_snapshot_profile_to != nullptr &&
               code->ptr()->object_pool_ != ObjectPool::null()) {
      // If we are writing V8 snapshot profile then attribute references
      // going through the object pool to the code object itself.
      ObjectPoolPtr pool = code->ptr()->object_pool_;

      for (intptr_t i = 0; i < pool->ptr()->length_; i++) {
        uint8_t bits = pool->ptr()->entry_bits()[i];
        if (ObjectPool::TypeBits::decode(bits) ==
            ObjectPool::EntryType::kTaggedObject) {
          s->AttributeElementRef(pool->ptr()->data()[i].raw_obj_, i);
        }
      }
#endif  // defined(DART_PRECOMPILER)
    }
    WriteField(code, owner_);
    WriteField(code, exception_handlers_);
    WriteField(code, pc_descriptors_);
    WriteField(code, catch_entry_);
    if (s->InCurrentLoadingUnit(code->ptr()->compressed_stackmaps_)) {
      WriteField(code, compressed_stackmaps_);
    } else {
      WriteFieldValue(compressed_stackmaps_, CompressedStackMaps::null());
    }
    if (FLAG_precompiled_mode && FLAG_dwarf_stack_traces_mode) {
      WriteFieldValue(inlined_id_to_function_, Array::null());
      WriteFieldValue(code_source_map_, CodeSourceMap::null());
    } else {
      WriteField(code, inlined_id_to_function_);
      if (s->InCurrentLoadingUnit(code->ptr()->code_source_map_)) {
        WriteField(code, code_source_map_);
      } else {
        WriteFieldValue(code_source_map_, CodeSourceMap::null());
      }
    }
    if (kind == Snapshot::kFullJIT) {
      WriteField(code, deopt_info_array_);
      WriteField(code, static_calls_target_table_);
    }
#if !defined(PRODUCT)
    WriteField(code, return_address_metadata_);
    if (FLAG_code_comments) {
      WriteField(code, comments_);
    }
#endif
    s->Write<int32_t>(code->ptr()->state_bits_);
  }

  GrowableArray<CodePtr>* discovered_objects() { return &objects_; }

  // Some code objects would have their owners dropped from the snapshot,
  // which makes it is impossible to recover program structure when
  // analysing snapshot profile. To facilitate analysis of snapshot profiles
  // we include artificial nodes into profile representing such dropped
  // owners.
  void WriteDroppedOwnersIntoProfile(Serializer* s) {
    ASSERT(s->profile_writer() != nullptr);

    for (auto code : objects_) {
      ObjectPtr owner = WeakSerializationReference::Unwrap(code->ptr()->owner_);
      if (s->CreateArtificalNodeIfNeeded(owner)) {
        AutoTraceObject(code);
        s->AttributePropertyRef(owner, ":owner_",
                                /*permit_artificial_ref=*/true);
      }
    }
  }

 private:
  static const char* MakeDisambiguatedCodeName(Serializer* s, CodePtr c) {
    if (s->profile_writer() == nullptr) {
      return nullptr;
    }

    REUSABLE_CODE_HANDLESCOPE(s->thread());
    Code& code = reused_code_handle.Handle();
    code = c;
    return code.QualifiedName(
        NameFormattingParams::DisambiguatedWithoutClassName(
            Object::NameVisibility::kInternalName));
  }

  GrowableArray<CodePtr> objects_;
  GrowableArray<CodePtr> deferred_objects_;
};
#endif  // !DART_PRECOMPILED_RUNTIME

class CodeDeserializationCluster : public DeserializationCluster {
 public:
  CodeDeserializationCluster() {}
  ~CodeDeserializationCluster() {}

  void ReadAlloc(Deserializer* d) {
    PageSpace* old_space = d->heap()->old_space();
    start_index_ = d->next_index();
    const intptr_t count = d->ReadUnsigned();
    for (intptr_t i = 0; i < count; i++) {
      auto code = AllocateUninitialized(old_space, Code::InstanceSize(0));
      d->AssignRef(code);
    }
    stop_index_ = d->next_index();
    deferred_start_index_ = d->next_index();
    const intptr_t deferred_count = d->ReadUnsigned();
    for (intptr_t i = 0; i < deferred_count; i++) {
      auto code = AllocateUninitialized(old_space, Code::InstanceSize(0));
      d->AssignRef(code);
    }
    deferred_stop_index_ = d->next_index();
  }

  void ReadFill(Deserializer* d) {
    for (intptr_t id = start_index_; id < stop_index_; id++) {
      ReadFill(d, id, false);
    }
    for (intptr_t id = deferred_start_index_; id < deferred_stop_index_; id++) {
      ReadFill(d, id, true);
    }
  }

  void ReadFill(Deserializer* d, intptr_t id, bool deferred) {
    auto const code = static_cast<CodePtr>(d->Ref(id));
    Deserializer::InitializeHeader(code, kCodeCid, Code::InstanceSize(0));

    d->ReadInstructions(code, deferred);

    // There would be a single global pool if this is a full AOT snapshot
    // with bare instructions.
    if (!(d->kind() == Snapshot::kFullAOT && FLAG_use_bare_instructions)) {
      code->ptr()->object_pool_ = static_cast<ObjectPoolPtr>(d->ReadRef());
    } else {
      code->ptr()->object_pool_ = ObjectPool::null();
    }
    code->ptr()->owner_ = d->ReadRef();
    code->ptr()->exception_handlers_ =
        static_cast<ExceptionHandlersPtr>(d->ReadRef());
    code->ptr()->pc_descriptors_ = static_cast<PcDescriptorsPtr>(d->ReadRef());
    code->ptr()->catch_entry_ = d->ReadRef();
    code->ptr()->compressed_stackmaps_ =
        static_cast<CompressedStackMapsPtr>(d->ReadRef());
    code->ptr()->inlined_id_to_function_ = static_cast<ArrayPtr>(d->ReadRef());
    code->ptr()->code_source_map_ = static_cast<CodeSourceMapPtr>(d->ReadRef());

#if !defined(DART_PRECOMPILED_RUNTIME)
      if (d->kind() == Snapshot::kFullJIT) {
        code->ptr()->deopt_info_array_ = static_cast<ArrayPtr>(d->ReadRef());
        code->ptr()->static_calls_target_table_ =
            static_cast<ArrayPtr>(d->ReadRef());
      }
#endif  // !DART_PRECOMPILED_RUNTIME

#if !defined(PRODUCT)
      code->ptr()->return_address_metadata_ = d->ReadRef();
      code->ptr()->var_descriptors_ = LocalVarDescriptors::null();
      code->ptr()->comments_ = FLAG_code_comments
                                   ? static_cast<ArrayPtr>(d->ReadRef())
                                   : Array::null();
      code->ptr()->compile_timestamp_ = 0;
#endif

      code->ptr()->state_bits_ = d->Read<int32_t>();
  }

  void PostLoad(Deserializer* d, const Array& refs) {
    d->EndInstructions(refs, start_index_, stop_index_);

#if !defined(PRODUCT)
    if (!CodeObservers::AreActive() && !FLAG_support_disassembler) return;
#endif
    Code& code = Code::Handle(d->zone());
#if !defined(PRODUCT) || defined(FORCE_INCLUDE_DISASSEMBLER)
    Object& owner = Object::Handle(d->zone());
#endif
    for (intptr_t id = start_index_; id < stop_index_; id++) {
      code ^= refs.At(id);
#if !defined(DART_PRECOMPILED_RUNTIME) && !defined(PRODUCT)
      if (CodeObservers::AreActive()) {
        Code::NotifyCodeObservers(code, code.is_optimized());
      }
#endif
#if !defined(PRODUCT) || defined(FORCE_INCLUDE_DISASSEMBLER)
      owner = code.owner();
      if (owner.IsFunction()) {
        if ((FLAG_disassemble ||
             (code.is_optimized() && FLAG_disassemble_optimized)) &&
            compiler::PrintFilter::ShouldPrint(Function::Cast(owner))) {
          Disassembler::DisassembleCode(Function::Cast(owner), code,
                                        code.is_optimized());
        }
      } else if (FLAG_disassemble_stubs) {
        Disassembler::DisassembleStub(code.Name(), code);
      }
#endif  // !defined(PRODUCT) || defined(FORCE_INCLUDE_DISASSEMBLER)
    }
  }

 private:
  intptr_t deferred_start_index_;
  intptr_t deferred_stop_index_;
};

#if !defined(DART_PRECOMPILED_RUNTIME)
class BytecodeSerializationCluster : public SerializationCluster {
 public:
  BytecodeSerializationCluster() : SerializationCluster("Bytecode") {}
  virtual ~BytecodeSerializationCluster() {}

  void Trace(Serializer* s, ObjectPtr object) {
    BytecodePtr bytecode = Bytecode::RawCast(object);
    objects_.Add(bytecode);
    PushFromTo(bytecode);
  }

  void WriteAlloc(Serializer* s) {
    s->WriteCid(kBytecodeCid);
    const intptr_t count = objects_.length();
    s->WriteUnsigned(count);
    for (intptr_t i = 0; i < count; i++) {
      BytecodePtr bytecode = objects_[i];
      s->AssignRef(bytecode);
    }
  }

  void WriteFill(Serializer* s) {
    ASSERT(s->kind() != Snapshot::kFullAOT);
    const intptr_t count = objects_.length();
    for (intptr_t i = 0; i < count; i++) {
      BytecodePtr bytecode = objects_[i];
      s->Write<int32_t>(bytecode->ptr()->instructions_size_);
      WriteFromTo(bytecode);
      s->Write<int32_t>(bytecode->ptr()->instructions_binary_offset_);
      s->Write<int32_t>(bytecode->ptr()->source_positions_binary_offset_);
      s->Write<int32_t>(bytecode->ptr()->local_variables_binary_offset_);
    }
  }

 private:
  GrowableArray<BytecodePtr> objects_;
};

class BytecodeDeserializationCluster : public DeserializationCluster {
 public:
  BytecodeDeserializationCluster() {}
  virtual ~BytecodeDeserializationCluster() {}

  void ReadAlloc(Deserializer* d) {
    start_index_ = d->next_index();
    PageSpace* old_space = d->heap()->old_space();
    const intptr_t count = d->ReadUnsigned();
    for (intptr_t i = 0; i < count; i++) {
      d->AssignRef(AllocateUninitialized(old_space, Bytecode::InstanceSize()));
    }
    stop_index_ = d->next_index();
  }

  void ReadFill(Deserializer* d) {
    ASSERT(d->kind() != Snapshot::kFullAOT);

    for (intptr_t id = start_index_; id < stop_index_; id++) {
      BytecodePtr bytecode = static_cast<BytecodePtr>(d->Ref(id));
      Deserializer::InitializeHeader(bytecode, kBytecodeCid,
                                     Bytecode::InstanceSize());
      bytecode->ptr()->instructions_ = 0;
      bytecode->ptr()->instructions_size_ = d->Read<int32_t>();
      ReadFromTo(bytecode);
      bytecode->ptr()->instructions_binary_offset_ = d->Read<int32_t>();
      bytecode->ptr()->source_positions_binary_offset_ = d->Read<int32_t>();
      bytecode->ptr()->local_variables_binary_offset_ = d->Read<int32_t>();
    }
  }

  void PostLoad(Deserializer* d, const Array& refs) {
    Bytecode& bytecode = Bytecode::Handle(d->zone());
    ExternalTypedData& binary = ExternalTypedData::Handle(d->zone());

    for (intptr_t i = start_index_; i < stop_index_; i++) {
      bytecode ^= refs.At(i);
      binary = bytecode.GetBinary(d->zone());
      bytecode.set_instructions(reinterpret_cast<uword>(
          binary.DataAddr(bytecode.instructions_binary_offset())));
    }
  }
};

class ObjectPoolSerializationCluster : public SerializationCluster {
 public:
  ObjectPoolSerializationCluster() : SerializationCluster("ObjectPool") {}
  ~ObjectPoolSerializationCluster() {}

  void Trace(Serializer* s, ObjectPtr object) {
    ObjectPoolPtr pool = ObjectPool::RawCast(object);
    objects_.Add(pool);

    const intptr_t length = pool->ptr()->length_;
    uint8_t* entry_bits = pool->ptr()->entry_bits();
    for (intptr_t i = 0; i < length; i++) {
      auto entry_type = ObjectPool::TypeBits::decode(entry_bits[i]);
      if ((entry_type == ObjectPool::EntryType::kTaggedObject) ||
          (entry_type == ObjectPool::EntryType::kNativeEntryData)) {
        s->Push(pool->ptr()->data()[i].raw_obj_);
      }
    }
  }

  void WriteAlloc(Serializer* s) {
    s->WriteCid(kObjectPoolCid);
    const intptr_t count = objects_.length();
    s->WriteUnsigned(count);
    for (intptr_t i = 0; i < count; i++) {
      ObjectPoolPtr pool = objects_[i];
      s->AssignRef(pool);
      AutoTraceObject(pool);
      const intptr_t length = pool->ptr()->length_;
      s->WriteUnsigned(length);
    }
  }

  void WriteFill(Serializer* s) {
    const intptr_t count = objects_.length();
    for (intptr_t i = 0; i < count; i++) {
      ObjectPoolPtr pool = objects_[i];
      AutoTraceObject(pool);
      const intptr_t length = pool->ptr()->length_;
      s->WriteUnsigned(length);
      uint8_t* entry_bits = pool->ptr()->entry_bits();
      for (intptr_t j = 0; j < length; j++) {
        s->Write<uint8_t>(entry_bits[j]);
        ObjectPoolLayout::Entry& entry = pool->ptr()->data()[j];
        switch (ObjectPool::TypeBits::decode(entry_bits[j])) {
          case ObjectPool::EntryType::kTaggedObject: {
            if ((entry.raw_obj_ == StubCode::CallNoScopeNative().raw()) ||
                (entry.raw_obj_ == StubCode::CallAutoScopeNative().raw())) {
              // Natives can run while precompiling, becoming linked and
              // switching their stub. Reset to the initial stub used for
              // lazy-linking.
              s->WriteElementRef(StubCode::CallBootstrapNative().raw(), j);
              break;
            }
            s->WriteElementRef(entry.raw_obj_, j);
            break;
          }
          case ObjectPool::EntryType::kImmediate: {
            s->Write<intptr_t>(entry.raw_value_);
            break;
          }
          case ObjectPool::EntryType::kNativeEntryData: {
            ObjectPtr raw = entry.raw_obj_;
            TypedDataPtr raw_data = static_cast<TypedDataPtr>(raw);
            // kNativeEntryData object pool entries are for linking natives for
            // the interpreter. Before writing these entries into the snapshot,
            // we need to unlink them by nulling out the 'trampoline' and
            // 'native_function' fields.
            NativeEntryData::Payload* payload =
                NativeEntryData::FromTypedArray(raw_data);
            if (payload->kind == MethodRecognizer::kUnknown) {
              payload->trampoline = NULL;
              payload->native_function = NULL;
            }
            s->WriteElementRef(raw, j);
            break;
          }
          case ObjectPool::EntryType::kNativeFunction:
          case ObjectPool::EntryType::kNativeFunctionWrapper: {
            // Write nothing. Will initialize with the lazy link entry.
            break;
          }
          default:
            UNREACHABLE();
        }
      }
    }
  }

 private:
  GrowableArray<ObjectPoolPtr> objects_;
};
#endif  // !DART_PRECOMPILED_RUNTIME

class ObjectPoolDeserializationCluster : public DeserializationCluster {
 public:
  ObjectPoolDeserializationCluster() {}
  ~ObjectPoolDeserializationCluster() {}

  void ReadAlloc(Deserializer* d) {
    start_index_ = d->next_index();
    PageSpace* old_space = d->heap()->old_space();
    const intptr_t count = d->ReadUnsigned();
    for (intptr_t i = 0; i < count; i++) {
      const intptr_t length = d->ReadUnsigned();
      d->AssignRef(
          AllocateUninitialized(old_space, ObjectPool::InstanceSize(length)));
    }
    stop_index_ = d->next_index();
  }

  void ReadFill(Deserializer* d) {
    for (intptr_t id = start_index_; id < stop_index_; id += 1) {
      const intptr_t length = d->ReadUnsigned();
      ObjectPoolPtr pool = static_cast<ObjectPoolPtr>(d->Ref(id + 0));
      Deserializer::InitializeHeader(pool, kObjectPoolCid,
                                     ObjectPool::InstanceSize(length));
      pool->ptr()->length_ = length;
      for (intptr_t j = 0; j < length; j++) {
        const uint8_t entry_bits = d->Read<uint8_t>();
        pool->ptr()->entry_bits()[j] = entry_bits;
        ObjectPoolLayout::Entry& entry = pool->ptr()->data()[j];
        switch (ObjectPool::TypeBits::decode(entry_bits)) {
          case ObjectPool::EntryType::kNativeEntryData:
          case ObjectPool::EntryType::kTaggedObject:
            entry.raw_obj_ = d->ReadRef();
            break;
          case ObjectPool::EntryType::kImmediate:
            entry.raw_value_ = d->Read<intptr_t>();
            break;
          case ObjectPool::EntryType::kNativeFunction: {
            // Read nothing. Initialize with the lazy link entry.
            uword new_entry = NativeEntry::LinkNativeCallEntry();
            entry.raw_value_ = static_cast<intptr_t>(new_entry);
            break;
          }
          default:
            UNREACHABLE();
        }
      }
    }
  }
};

#if defined(DART_PRECOMPILER)
class WeakSerializationReferenceSerializationCluster
    : public SerializationCluster {
 public:
  WeakSerializationReferenceSerializationCluster(Zone* zone, Heap* heap)
      : SerializationCluster("WeakSerializationReference"),
        heap_(ASSERT_NOTNULL(heap)),
        objects_(zone, 0),
        canonical_wsrs_(zone, 0),
        canonical_wsr_map_(zone) {}
  ~WeakSerializationReferenceSerializationCluster() {}

  void Trace(Serializer* s, ObjectPtr object) {
    ASSERT(s->kind() == Snapshot::kFullAOT);
    // Make sure we don't trace again after choosing canonical WSRs.
    ASSERT(!have_canonicalized_wsrs_);

    auto const ref = WeakSerializationReference::RawCast(object);
    objects_.Add(ref);
    // We do _not_ push the target, since this is not a strong reference.
  }

  void WriteAlloc(Serializer* s) {
    ASSERT(s->kind() == Snapshot::kFullAOT);
    ASSERT(have_canonicalized_wsrs_);

    s->WriteCid(kWeakSerializationReferenceCid);
    s->WriteUnsigned(WrittenCount());

    // Set up references for those objects that will be written.
    for (auto const ref : canonical_wsrs_) {
      s->AssignRef(ref);
    }

    // In precompiled mode, set the object ID of each non-canonical WSR to
    // its canonical counterpart's object ID. This ensures that any reference to
    // it is serialized as a reference to the canonicalized one.
    for (auto const ref : objects_) {
      ASSERT(Serializer::IsReachableReference(heap_->GetObjectId(ref)));
      if (ShouldDrop(ref)) {
        // For dropped references, reset their ID to be the unreachable
        // reference value, so RefId retrieves the target ID instead.
        heap_->SetObjectId(ref, Serializer::kUnreachableReference);
        continue;
      }
      // Skip if we've already allocated a reference (this is a canonical WSR).
      if (Serializer::IsAllocatedReference(heap_->GetObjectId(ref))) continue;
      auto const target_cid = WeakSerializationReference::TargetClassIdOf(ref);
      ASSERT(canonical_wsr_map_.HasKey(target_cid));
      auto const canonical_index = canonical_wsr_map_.Lookup(target_cid) - 1;
      auto const canonical_wsr = objects_[canonical_index];
      // Set the object ID of this non-canonical WSR to the same as its
      // canonical WSR entry, so we'll reference the canonical WSR when
      // serializing references to this object.
      auto const canonical_heap_id = heap_->GetObjectId(canonical_wsr);
      ASSERT(Serializer::IsAllocatedReference(canonical_heap_id));
      heap_->SetObjectId(ref, canonical_heap_id);
    }
  }

  void WriteFill(Serializer* s) {
    ASSERT(s->kind() == Snapshot::kFullAOT);
    for (auto const ref : canonical_wsrs_) {
      AutoTraceObject(ref);

      // In precompiled mode, we drop the reference to the target and only
      // keep the class ID.
      s->WriteCid(WeakSerializationReference::TargetClassIdOf(ref));
    }
  }

  // Picks a WSR for each target class ID to be canonical. Should only be run
  // after all objects have been traced.
  void CanonicalizeReferences() {
    ASSERT(!have_canonicalized_wsrs_);
    for (intptr_t i = 0; i < objects_.length(); i++) {
      auto const ref = objects_[i];
      if (ShouldDrop(ref)) continue;
      auto const target_cid = WeakSerializationReference::TargetClassIdOf(ref);
      if (canonical_wsr_map_.HasKey(target_cid)) continue;
      canonical_wsr_map_.Insert(target_cid, i + 1);
      canonical_wsrs_.Add(ref);
    }
    have_canonicalized_wsrs_ = true;
  }

  intptr_t WrittenCount() const {
    ASSERT(have_canonicalized_wsrs_);
    return canonical_wsrs_.length();
  }

  intptr_t DroppedCount() const { return TotalCount() - WrittenCount(); }

  intptr_t TotalCount() const { return objects_.length(); }

 private:
  // Returns whether a WSR should be dropped due to its target being reachable
  // via strong references. WSRs only wrap heap objects, so we can just retrieve
  // the object ID from the heap directly.
  bool ShouldDrop(WeakSerializationReferencePtr ref) const {
    auto const target = WeakSerializationReference::TargetOf(ref);
    return Serializer::IsReachableReference(heap_->GetObjectId(target));
  }

  Heap* const heap_;
  GrowableArray<WeakSerializationReferencePtr> objects_;
  GrowableArray<WeakSerializationReferencePtr> canonical_wsrs_;
  IntMap<intptr_t> canonical_wsr_map_;
  bool have_canonicalized_wsrs_ = false;
};
#endif

#if defined(DART_PRECOMPILED_RUNTIME)
class WeakSerializationReferenceDeserializationCluster
    : public DeserializationCluster {
 public:
  WeakSerializationReferenceDeserializationCluster() {}
  ~WeakSerializationReferenceDeserializationCluster() {}

  void ReadAlloc(Deserializer* d) {
    start_index_ = d->next_index();
    PageSpace* old_space = d->heap()->old_space();
    const intptr_t count = d->ReadUnsigned();

    for (intptr_t i = 0; i < count; i++) {
      auto ref = AllocateUninitialized(
          old_space, WeakSerializationReference::InstanceSize());
      d->AssignRef(ref);
    }

    stop_index_ = d->next_index();
  }

  void ReadFill(Deserializer* d) {
    for (intptr_t id = start_index_; id < stop_index_; id++) {
      auto const ref = static_cast<WeakSerializationReferencePtr>(d->Ref(id));
      Deserializer::InitializeHeader(
          ref, kWeakSerializationReferenceCid,
          WeakSerializationReference::InstanceSize());
      ref->ptr()->cid_ = d->ReadCid();
    }
  }
};
#endif

#if !defined(DART_PRECOMPILED_RUNTIME)
class PcDescriptorsSerializationCluster : public SerializationCluster {
 public:
  PcDescriptorsSerializationCluster() : SerializationCluster("PcDescriptors") {}
  ~PcDescriptorsSerializationCluster() {}

  void Trace(Serializer* s, ObjectPtr object) {
    PcDescriptorsPtr desc = PcDescriptors::RawCast(object);
    objects_.Add(desc);
  }

  void WriteAlloc(Serializer* s) {
    s->WriteCid(kPcDescriptorsCid);
    const intptr_t count = objects_.length();
    s->WriteUnsigned(count);
    for (intptr_t i = 0; i < count; i++) {
      PcDescriptorsPtr desc = objects_[i];
      s->AssignRef(desc);
      AutoTraceObject(desc);
      const intptr_t length = desc->ptr()->length_;
      s->WriteUnsigned(length);
    }
  }

  void WriteFill(Serializer* s) {
    const intptr_t count = objects_.length();
    for (intptr_t i = 0; i < count; i++) {
      PcDescriptorsPtr desc = objects_[i];
      AutoTraceObject(desc);
      const intptr_t length = desc->ptr()->length_;
      s->WriteUnsigned(length);
      uint8_t* cdata = reinterpret_cast<uint8_t*>(desc->ptr()->data());
      s->WriteBytes(cdata, length);
    }
  }

 private:
  GrowableArray<PcDescriptorsPtr> objects_;
};
#endif  // !DART_PRECOMPILED_RUNTIME

class PcDescriptorsDeserializationCluster : public DeserializationCluster {
 public:
  PcDescriptorsDeserializationCluster() {}
  ~PcDescriptorsDeserializationCluster() {}

  void ReadAlloc(Deserializer* d) {
    start_index_ = d->next_index();
    PageSpace* old_space = d->heap()->old_space();
    const intptr_t count = d->ReadUnsigned();
    for (intptr_t i = 0; i < count; i++) {
      const intptr_t length = d->ReadUnsigned();
      d->AssignRef(AllocateUninitialized(old_space,
                                         PcDescriptors::InstanceSize(length)));
    }
    stop_index_ = d->next_index();
  }

  void ReadFill(Deserializer* d) {
    for (intptr_t id = start_index_; id < stop_index_; id += 1) {
      const intptr_t length = d->ReadUnsigned();
      PcDescriptorsPtr desc = static_cast<PcDescriptorsPtr>(d->Ref(id));
      Deserializer::InitializeHeader(desc, kPcDescriptorsCid,
                                     PcDescriptors::InstanceSize(length));
      desc->ptr()->length_ = length;
      uint8_t* cdata = reinterpret_cast<uint8_t*>(desc->ptr()->data());
      d->ReadBytes(cdata, length);
    }
  }
};

#if !defined(DART_PRECOMPILED_RUNTIME)
// PcDescriptor, CompressedStackMaps, OneByteString, TwoByteString
class RODataSerializationCluster : public SerializationCluster {
 public:
  RODataSerializationCluster(Zone* zone, const char* type, intptr_t cid)
      : SerializationCluster(ImageWriter::TagObjectTypeAsReadOnly(zone, type)),
        cid_(cid),
        objects_(),
        type_(type) {}
  ~RODataSerializationCluster() {}

  void Trace(Serializer* s, ObjectPtr object) {
    // A string's hash must already be computed when we write it because it
    // will be loaded into read-only memory. Extra bytes due to allocation
    // rounding need to be deterministically set for reliable deduplication in
    // shared images.
    if (object->ptr()->InVMIsolateHeap() ||
        s->heap()->old_space()->IsObjectFromImagePages(object)) {
      // This object is already read-only.
    } else {
      Object::FinalizeReadOnlyObject(object);
    }

    objects_.Add(object);
  }

  void WriteAlloc(Serializer* s) {
    s->WriteCid(cid_);

    intptr_t count = objects_.length();
    s->WriteUnsigned(count);
    uint32_t running_offset = 0;
    for (intptr_t i = 0; i < count; i++) {
      ObjectPtr object = objects_[i];
      s->AssignRef(object);
      if (cid_ == kOneByteStringCid || cid_ == kTwoByteStringCid) {
        s->TraceStartWritingObject(type_, object, String::RawCast(object));
      } else {
        s->TraceStartWritingObject(type_, object, nullptr);
      }
      uint32_t offset = s->GetDataOffset(object);
      s->TraceDataOffset(offset);
      ASSERT(Utils::IsAligned(
          offset, compiler::target::ObjectAlignment::kObjectAlignment));
      ASSERT(offset > running_offset);
      s->WriteUnsigned((offset - running_offset) >>
                       compiler::target::ObjectAlignment::kObjectAlignmentLog2);
      running_offset = offset;
      s->TraceEndWritingObject();
    }
  }

  void WriteFill(Serializer* s) {
    // No-op.
  }

 private:
  const intptr_t cid_;
  GrowableArray<ObjectPtr> objects_;
  const char* const type_;
};
#endif  // !DART_PRECOMPILED_RUNTIME

class RODataDeserializationCluster : public DeserializationCluster {
 public:
  RODataDeserializationCluster() {}
  ~RODataDeserializationCluster() {}

  void ReadAlloc(Deserializer* d) {
    intptr_t count = d->ReadUnsigned();
    uint32_t running_offset = 0;
    for (intptr_t i = 0; i < count; i++) {
      running_offset += d->ReadUnsigned() << kObjectAlignmentLog2;
      d->AssignRef(d->GetObjectAt(running_offset));
    }
  }

  void ReadFill(Deserializer* d) {
    // No-op.
  }
};

#if !defined(DART_PRECOMPILED_RUNTIME)
class ExceptionHandlersSerializationCluster : public SerializationCluster {
 public:
  ExceptionHandlersSerializationCluster()
      : SerializationCluster("ExceptionHandlers") {}
  ~ExceptionHandlersSerializationCluster() {}

  void Trace(Serializer* s, ObjectPtr object) {
    ExceptionHandlersPtr handlers = ExceptionHandlers::RawCast(object);
    objects_.Add(handlers);

    s->Push(handlers->ptr()->handled_types_data_);
  }

  void WriteAlloc(Serializer* s) {
    s->WriteCid(kExceptionHandlersCid);
    const intptr_t count = objects_.length();
    s->WriteUnsigned(count);
    for (intptr_t i = 0; i < count; i++) {
      ExceptionHandlersPtr handlers = objects_[i];
      s->AssignRef(handlers);
      AutoTraceObject(handlers);
      const intptr_t length = handlers->ptr()->num_entries_;
      s->WriteUnsigned(length);
    }
  }

  void WriteFill(Serializer* s) {
    const intptr_t count = objects_.length();
    for (intptr_t i = 0; i < count; i++) {
      ExceptionHandlersPtr handlers = objects_[i];
      AutoTraceObject(handlers);
      const intptr_t length = handlers->ptr()->num_entries_;
      s->WriteUnsigned(length);
      WriteField(handlers, handled_types_data_);
      for (intptr_t j = 0; j < length; j++) {
        const ExceptionHandlerInfo& info = handlers->ptr()->data()[j];
        s->Write<uint32_t>(info.handler_pc_offset);
        s->Write<int16_t>(info.outer_try_index);
        s->Write<int8_t>(info.needs_stacktrace);
        s->Write<int8_t>(info.has_catch_all);
        s->Write<int8_t>(info.is_generated);
      }
    }
  }

 private:
  GrowableArray<ExceptionHandlersPtr> objects_;
};
#endif  // !DART_PRECOMPILED_RUNTIME

class ExceptionHandlersDeserializationCluster : public DeserializationCluster {
 public:
  ExceptionHandlersDeserializationCluster() {}
  ~ExceptionHandlersDeserializationCluster() {}

  void ReadAlloc(Deserializer* d) {
    start_index_ = d->next_index();
    PageSpace* old_space = d->heap()->old_space();
    const intptr_t count = d->ReadUnsigned();
    for (intptr_t i = 0; i < count; i++) {
      const intptr_t length = d->ReadUnsigned();
      d->AssignRef(AllocateUninitialized(
          old_space, ExceptionHandlers::InstanceSize(length)));
    }
    stop_index_ = d->next_index();
  }

  void ReadFill(Deserializer* d) {
    for (intptr_t id = start_index_; id < stop_index_; id++) {
      ExceptionHandlersPtr handlers =
          static_cast<ExceptionHandlersPtr>(d->Ref(id));
      const intptr_t length = d->ReadUnsigned();
      Deserializer::InitializeHeader(handlers, kExceptionHandlersCid,
                                     ExceptionHandlers::InstanceSize(length));
      handlers->ptr()->num_entries_ = length;
      handlers->ptr()->handled_types_data_ =
          static_cast<ArrayPtr>(d->ReadRef());
      for (intptr_t j = 0; j < length; j++) {
        ExceptionHandlerInfo& info = handlers->ptr()->data()[j];
        info.handler_pc_offset = d->Read<uint32_t>();
        info.outer_try_index = d->Read<int16_t>();
        info.needs_stacktrace = d->Read<int8_t>();
        info.has_catch_all = d->Read<int8_t>();
        info.is_generated = d->Read<int8_t>();
      }
    }
  }
};

#if !defined(DART_PRECOMPILED_RUNTIME)
class ContextSerializationCluster : public SerializationCluster {
 public:
  ContextSerializationCluster() : SerializationCluster("Context") {}
  ~ContextSerializationCluster() {}

  void Trace(Serializer* s, ObjectPtr object) {
    ContextPtr context = Context::RawCast(object);
    objects_.Add(context);

    s->Push(context->ptr()->parent_);
    const intptr_t length = context->ptr()->num_variables_;
    for (intptr_t i = 0; i < length; i++) {
      s->Push(context->ptr()->data()[i]);
    }
  }

  void WriteAlloc(Serializer* s) {
    s->WriteCid(kContextCid);
    const intptr_t count = objects_.length();
    s->WriteUnsigned(count);
    for (intptr_t i = 0; i < count; i++) {
      ContextPtr context = objects_[i];
      s->AssignRef(context);
      AutoTraceObject(context);
      const intptr_t length = context->ptr()->num_variables_;
      s->WriteUnsigned(length);
    }
  }

  void WriteFill(Serializer* s) {
    const intptr_t count = objects_.length();
    for (intptr_t i = 0; i < count; i++) {
      ContextPtr context = objects_[i];
      AutoTraceObject(context);
      const intptr_t length = context->ptr()->num_variables_;
      s->WriteUnsigned(length);
      WriteField(context, parent_);
      for (intptr_t j = 0; j < length; j++) {
        s->WriteElementRef(context->ptr()->data()[j], j);
      }
    }
  }

 private:
  GrowableArray<ContextPtr> objects_;
};
#endif  // !DART_PRECOMPILED_RUNTIME

class ContextDeserializationCluster : public DeserializationCluster {
 public:
  ContextDeserializationCluster() {}
  ~ContextDeserializationCluster() {}

  void ReadAlloc(Deserializer* d) {
    start_index_ = d->next_index();
    PageSpace* old_space = d->heap()->old_space();
    const intptr_t count = d->ReadUnsigned();
    for (intptr_t i = 0; i < count; i++) {
      const intptr_t length = d->ReadUnsigned();
      d->AssignRef(
          AllocateUninitialized(old_space, Context::InstanceSize(length)));
    }
    stop_index_ = d->next_index();
  }

  void ReadFill(Deserializer* d) {
    for (intptr_t id = start_index_; id < stop_index_; id++) {
      ContextPtr context = static_cast<ContextPtr>(d->Ref(id));
      const intptr_t length = d->ReadUnsigned();
      Deserializer::InitializeHeader(context, kContextCid,
                                     Context::InstanceSize(length));
      context->ptr()->num_variables_ = length;
      context->ptr()->parent_ = static_cast<ContextPtr>(d->ReadRef());
      for (intptr_t j = 0; j < length; j++) {
        context->ptr()->data()[j] = d->ReadRef();
      }
    }
  }
};

#if !defined(DART_PRECOMPILED_RUNTIME)
class ContextScopeSerializationCluster : public SerializationCluster {
 public:
  ContextScopeSerializationCluster() : SerializationCluster("ContextScope") {}
  ~ContextScopeSerializationCluster() {}

  void Trace(Serializer* s, ObjectPtr object) {
    ContextScopePtr scope = ContextScope::RawCast(object);
    objects_.Add(scope);

    const intptr_t length = scope->ptr()->num_variables_;
    PushFromTo(scope, length);
  }

  void WriteAlloc(Serializer* s) {
    s->WriteCid(kContextScopeCid);
    const intptr_t count = objects_.length();
    s->WriteUnsigned(count);
    for (intptr_t i = 0; i < count; i++) {
      ContextScopePtr scope = objects_[i];
      s->AssignRef(scope);
      AutoTraceObject(scope);
      const intptr_t length = scope->ptr()->num_variables_;
      s->WriteUnsigned(length);
    }
  }

  void WriteFill(Serializer* s) {
    const intptr_t count = objects_.length();
    for (intptr_t i = 0; i < count; i++) {
      ContextScopePtr scope = objects_[i];
      AutoTraceObject(scope);
      const intptr_t length = scope->ptr()->num_variables_;
      s->WriteUnsigned(length);
      s->Write<bool>(scope->ptr()->is_implicit_);
      WriteFromTo(scope, length);
    }
  }

 private:
  GrowableArray<ContextScopePtr> objects_;
};
#endif  // !DART_PRECOMPILED_RUNTIME

class ContextScopeDeserializationCluster : public DeserializationCluster {
 public:
  ContextScopeDeserializationCluster() {}
  ~ContextScopeDeserializationCluster() {}

  void ReadAlloc(Deserializer* d) {
    start_index_ = d->next_index();
    PageSpace* old_space = d->heap()->