deserializer.cc 35.1 KB
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// Copyright 2016 the V8 project authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
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#include "src/snapshot/deserializer.h"

#include "src/bootstrapper.h"
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#include "src/external-reference-table.h"
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#include "src/heap/heap.h"
#include "src/isolate.h"
#include "src/macro-assembler.h"
#include "src/snapshot/natives.h"
#include "src/v8.h"

namespace v8 {
namespace internal {

void Deserializer::DecodeReservation(
    Vector<const SerializedData::Reservation> res) {
  DCHECK_EQ(0, reservations_[NEW_SPACE].length());
  STATIC_ASSERT(NEW_SPACE == 0);
  int current_space = NEW_SPACE;
  for (auto& r : res) {
    reservations_[current_space].Add({r.chunk_size(), NULL, NULL});
    if (r.is_last()) current_space++;
  }
  DCHECK_EQ(kNumberOfSpaces, current_space);
  for (int i = 0; i < kNumberOfPreallocatedSpaces; i++) current_chunk_[i] = 0;
}

void Deserializer::FlushICacheForNewIsolate() {
  DCHECK(!deserializing_user_code_);
  // The entire isolate is newly deserialized. Simply flush all code pages.
  PageIterator it(isolate_->heap()->code_space());
  while (it.has_next()) {
    Page* p = it.next();
    Assembler::FlushICache(isolate_, p->area_start(),
                           p->area_end() - p->area_start());
  }
}

void Deserializer::FlushICacheForNewCodeObjects() {
  DCHECK(deserializing_user_code_);
  for (Code* code : new_code_objects_) {
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    if (FLAG_serialize_age_code) code->PreAge(isolate_);
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    Assembler::FlushICache(isolate_, code->instruction_start(),
                           code->instruction_size());
  }
}

bool Deserializer::ReserveSpace() {
#ifdef DEBUG
  for (int i = NEW_SPACE; i < kNumberOfSpaces; ++i) {
    CHECK(reservations_[i].length() > 0);
  }
#endif  // DEBUG
  if (!isolate_->heap()->ReserveSpace(reservations_)) return false;
  for (int i = 0; i < kNumberOfPreallocatedSpaces; i++) {
    high_water_[i] = reservations_[i][0].start;
  }
  return true;
}

void Deserializer::Initialize(Isolate* isolate) {
  DCHECK_NULL(isolate_);
  DCHECK_NOT_NULL(isolate);
  isolate_ = isolate;
  DCHECK_NULL(external_reference_table_);
  external_reference_table_ = ExternalReferenceTable::instance(isolate);
  CHECK_EQ(magic_number_,
           SerializedData::ComputeMagicNumber(external_reference_table_));
}

void Deserializer::Deserialize(Isolate* isolate) {
  Initialize(isolate);
  if (!ReserveSpace()) V8::FatalProcessOutOfMemory("deserializing context");
  // No active threads.
  DCHECK_NULL(isolate_->thread_manager()->FirstThreadStateInUse());
  // No active handles.
  DCHECK(isolate_->handle_scope_implementer()->blocks()->is_empty());
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  // Partial snapshot cache is not yet populated.
  DCHECK(isolate_->partial_snapshot_cache()->is_empty());
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  {
    DisallowHeapAllocation no_gc;
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    isolate_->heap()->IterateStrongRoots(this, VISIT_ONLY_STRONG_ROOT_LIST);
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    isolate_->heap()->IterateSmiRoots(this);
    isolate_->heap()->IterateStrongRoots(this, VISIT_ONLY_STRONG);
    isolate_->heap()->RepairFreeListsAfterDeserialization();
    isolate_->heap()->IterateWeakRoots(this, VISIT_ALL);
    DeserializeDeferredObjects();
    FlushICacheForNewIsolate();
  }

  isolate_->heap()->set_native_contexts_list(
      isolate_->heap()->undefined_value());
  // The allocation site list is build during root iteration, but if no sites
  // were encountered then it needs to be initialized to undefined.
  if (isolate_->heap()->allocation_sites_list() == Smi::FromInt(0)) {
    isolate_->heap()->set_allocation_sites_list(
        isolate_->heap()->undefined_value());
  }

  // Update data pointers to the external strings containing natives sources.
  Natives::UpdateSourceCache(isolate_->heap());
  ExtraNatives::UpdateSourceCache(isolate_->heap());

  // Issue code events for newly deserialized code objects.
  LOG_CODE_EVENT(isolate_, LogCodeObjects());
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  LOG_CODE_EVENT(isolate_, LogBytecodeHandlers());
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  LOG_CODE_EVENT(isolate_, LogCompiledFunctions());
}

MaybeHandle<Object> Deserializer::DeserializePartial(
    Isolate* isolate, Handle<JSGlobalProxy> global_proxy) {
  Initialize(isolate);
  if (!ReserveSpace()) {
    V8::FatalProcessOutOfMemory("deserialize context");
    return MaybeHandle<Object>();
  }

  Vector<Handle<Object> > attached_objects = Vector<Handle<Object> >::New(1);
  attached_objects[kGlobalProxyReference] = global_proxy;
  SetAttachedObjects(attached_objects);

  DisallowHeapAllocation no_gc;
  // Keep track of the code space start and end pointers in case new
  // code objects were unserialized
  OldSpace* code_space = isolate_->heap()->code_space();
  Address start_address = code_space->top();
  Object* root;
  VisitPointer(&root);
  DeserializeDeferredObjects();

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  isolate->heap()->RegisterReservationsForBlackAllocation(reservations_);

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  // There's no code deserialized here. If this assert fires then that's
  // changed and logging should be added to notify the profiler et al of the
  // new code, which also has to be flushed from instruction cache.
  CHECK_EQ(start_address, code_space->top());
  return Handle<Object>(root, isolate);
}

MaybeHandle<SharedFunctionInfo> Deserializer::DeserializeCode(
    Isolate* isolate) {
  Initialize(isolate);
  if (!ReserveSpace()) {
    return Handle<SharedFunctionInfo>();
  } else {
    deserializing_user_code_ = true;
    HandleScope scope(isolate);
    Handle<SharedFunctionInfo> result;
    {
      DisallowHeapAllocation no_gc;
      Object* root;
      VisitPointer(&root);
      DeserializeDeferredObjects();
      FlushICacheForNewCodeObjects();
      result = Handle<SharedFunctionInfo>(SharedFunctionInfo::cast(root));
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      isolate->heap()->RegisterReservationsForBlackAllocation(reservations_);
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    }
    CommitPostProcessedObjects(isolate);
    return scope.CloseAndEscape(result);
  }
}

Deserializer::~Deserializer() {
  // TODO(svenpanne) Re-enable this assertion when v8 initialization is fixed.
  // DCHECK(source_.AtEOF());
  attached_objects_.Dispose();
}

// This is called on the roots.  It is the driver of the deserialization
// process.  It is also called on the body of each function.
void Deserializer::VisitPointers(Object** start, Object** end) {
  // The space must be new space.  Any other space would cause ReadChunk to try
  // to update the remembered using NULL as the address.
  ReadData(start, end, NEW_SPACE, NULL);
}

void Deserializer::Synchronize(VisitorSynchronization::SyncTag tag) {
  static const byte expected = kSynchronize;
  CHECK_EQ(expected, source_.Get());
}

void Deserializer::DeserializeDeferredObjects() {
  for (int code = source_.Get(); code != kSynchronize; code = source_.Get()) {
    switch (code) {
      case kAlignmentPrefix:
      case kAlignmentPrefix + 1:
      case kAlignmentPrefix + 2:
        SetAlignment(code);
        break;
      default: {
        int space = code & kSpaceMask;
        DCHECK(space <= kNumberOfSpaces);
        DCHECK(code - space == kNewObject);
        HeapObject* object = GetBackReferencedObject(space);
        int size = source_.GetInt() << kPointerSizeLog2;
        Address obj_address = object->address();
        Object** start = reinterpret_cast<Object**>(obj_address + kPointerSize);
        Object** end = reinterpret_cast<Object**>(obj_address + size);
        bool filled = ReadData(start, end, space, obj_address);
        CHECK(filled);
        DCHECK(CanBeDeferred(object));
        PostProcessNewObject(object, space);
      }
    }
  }
}

// Used to insert a deserialized internalized string into the string table.
class StringTableInsertionKey : public HashTableKey {
 public:
  explicit StringTableInsertionKey(String* string)
      : string_(string), hash_(HashForObject(string)) {
    DCHECK(string->IsInternalizedString());
  }

  bool IsMatch(Object* string) override {
    // We know that all entries in a hash table had their hash keys created.
    // Use that knowledge to have fast failure.
    if (hash_ != HashForObject(string)) return false;
    // We want to compare the content of two internalized strings here.
    return string_->SlowEquals(String::cast(string));
  }

  uint32_t Hash() override { return hash_; }

  uint32_t HashForObject(Object* key) override {
    return String::cast(key)->Hash();
  }

  MUST_USE_RESULT Handle<Object> AsHandle(Isolate* isolate) override {
    return handle(string_, isolate);
  }

 private:
  String* string_;
  uint32_t hash_;
  DisallowHeapAllocation no_gc;
};

HeapObject* Deserializer::PostProcessNewObject(HeapObject* obj, int space) {
  if (deserializing_user_code()) {
    if (obj->IsString()) {
      String* string = String::cast(obj);
      // Uninitialize hash field as the hash seed may have changed.
      string->set_hash_field(String::kEmptyHashField);
      if (string->IsInternalizedString()) {
        // Canonicalize the internalized string. If it already exists in the
        // string table, set it to forward to the existing one.
        StringTableInsertionKey key(string);
        String* canonical = StringTable::LookupKeyIfExists(isolate_, &key);
        if (canonical == NULL) {
          new_internalized_strings_.Add(handle(string));
          return string;
        } else {
          string->SetForwardedInternalizedString(canonical);
          return canonical;
        }
      }
    } else if (obj->IsScript()) {
      new_scripts_.Add(handle(Script::cast(obj)));
    } else {
      DCHECK(CanBeDeferred(obj));
    }
  }
  if (obj->IsAllocationSite()) {
    DCHECK(obj->IsAllocationSite());
    // Allocation sites are present in the snapshot, and must be linked into
    // a list at deserialization time.
    AllocationSite* site = AllocationSite::cast(obj);
    // TODO(mvstanton): consider treating the heap()->allocation_sites_list()
    // as a (weak) root. If this root is relocated correctly, this becomes
    // unnecessary.
    if (isolate_->heap()->allocation_sites_list() == Smi::FromInt(0)) {
      site->set_weak_next(isolate_->heap()->undefined_value());
    } else {
      site->set_weak_next(isolate_->heap()->allocation_sites_list());
    }
    isolate_->heap()->set_allocation_sites_list(site);
  } else if (obj->IsCode()) {
    // We flush all code pages after deserializing the startup snapshot. In that
    // case, we only need to remember code objects in the large object space.
    // When deserializing user code, remember each individual code object.
    if (deserializing_user_code() || space == LO_SPACE) {
      new_code_objects_.Add(Code::cast(obj));
    }
  }
  // Check alignment.
  DCHECK_EQ(0, Heap::GetFillToAlign(obj->address(), obj->RequiredAlignment()));
  return obj;
}

void Deserializer::CommitPostProcessedObjects(Isolate* isolate) {
  StringTable::EnsureCapacityForDeserialization(
      isolate, new_internalized_strings_.length());
  for (Handle<String> string : new_internalized_strings_) {
    StringTableInsertionKey key(*string);
    DCHECK_NULL(StringTable::LookupKeyIfExists(isolate, &key));
    StringTable::LookupKey(isolate, &key);
  }

  Heap* heap = isolate->heap();
  Factory* factory = isolate->factory();
  for (Handle<Script> script : new_scripts_) {
    // Assign a new script id to avoid collision.
    script->set_id(isolate_->heap()->NextScriptId());
    // Add script to list.
    Handle<Object> list = WeakFixedArray::Add(factory->script_list(), script);
    heap->SetRootScriptList(*list);
  }
}

HeapObject* Deserializer::GetBackReferencedObject(int space) {
  HeapObject* obj;
  BackReference back_reference(source_.GetInt());
  if (space == LO_SPACE) {
    CHECK(back_reference.chunk_index() == 0);
    uint32_t index = back_reference.large_object_index();
    obj = deserialized_large_objects_[index];
  } else {
    DCHECK(space < kNumberOfPreallocatedSpaces);
    uint32_t chunk_index = back_reference.chunk_index();
    DCHECK_LE(chunk_index, current_chunk_[space]);
    uint32_t chunk_offset = back_reference.chunk_offset();
    Address address = reservations_[space][chunk_index].start + chunk_offset;
    if (next_alignment_ != kWordAligned) {
      int padding = Heap::GetFillToAlign(address, next_alignment_);
      next_alignment_ = kWordAligned;
      DCHECK(padding == 0 || HeapObject::FromAddress(address)->IsFiller());
      address += padding;
    }
    obj = HeapObject::FromAddress(address);
  }
  if (deserializing_user_code() && obj->IsInternalizedString()) {
    obj = String::cast(obj)->GetForwardedInternalizedString();
  }
  hot_objects_.Add(obj);
  return obj;
}

// This routine writes the new object into the pointer provided and then
// returns true if the new object was in young space and false otherwise.
// The reason for this strange interface is that otherwise the object is
// written very late, which means the FreeSpace map is not set up by the
// time we need to use it to mark the space at the end of a page free.
void Deserializer::ReadObject(int space_number, Object** write_back) {
  Address address;
  HeapObject* obj;
  int size = source_.GetInt() << kObjectAlignmentBits;

  if (next_alignment_ != kWordAligned) {
    int reserved = size + Heap::GetMaximumFillToAlign(next_alignment_);
    address = Allocate(space_number, reserved);
    obj = HeapObject::FromAddress(address);
    // If one of the following assertions fails, then we are deserializing an
    // aligned object when the filler maps have not been deserialized yet.
    // We require filler maps as padding to align the object.
    Heap* heap = isolate_->heap();
    DCHECK(heap->free_space_map()->IsMap());
    DCHECK(heap->one_pointer_filler_map()->IsMap());
    DCHECK(heap->two_pointer_filler_map()->IsMap());
    obj = heap->AlignWithFiller(obj, size, reserved, next_alignment_);
    address = obj->address();
    next_alignment_ = kWordAligned;
  } else {
    address = Allocate(space_number, size);
    obj = HeapObject::FromAddress(address);
  }

  isolate_->heap()->OnAllocationEvent(obj, size);
  Object** current = reinterpret_cast<Object**>(address);
  Object** limit = current + (size >> kPointerSizeLog2);

  if (ReadData(current, limit, space_number, address)) {
    // Only post process if object content has not been deferred.
    obj = PostProcessNewObject(obj, space_number);
  }

  Object* write_back_obj = obj;
  UnalignedCopy(write_back, &write_back_obj);
#ifdef DEBUG
  if (obj->IsCode()) {
    DCHECK(space_number == CODE_SPACE || space_number == LO_SPACE);
  } else {
    DCHECK(space_number != CODE_SPACE);
  }
#endif  // DEBUG
}

// We know the space requirements before deserialization and can
// pre-allocate that reserved space. During deserialization, all we need
// to do is to bump up the pointer for each space in the reserved
// space. This is also used for fixing back references.
// We may have to split up the pre-allocation into several chunks
// because it would not fit onto a single page. We do not have to keep
// track of when to move to the next chunk. An opcode will signal this.
// Since multiple large objects cannot be folded into one large object
// space allocation, we have to do an actual allocation when deserializing
// each large object. Instead of tracking offset for back references, we
// reference large objects by index.
Address Deserializer::Allocate(int space_index, int size) {
  if (space_index == LO_SPACE) {
    AlwaysAllocateScope scope(isolate_);
    LargeObjectSpace* lo_space = isolate_->heap()->lo_space();
    Executability exec = static_cast<Executability>(source_.Get());
    AllocationResult result = lo_space->AllocateRaw(size, exec);
    HeapObject* obj = HeapObject::cast(result.ToObjectChecked());
    deserialized_large_objects_.Add(obj);
    return obj->address();
  } else {
    DCHECK(space_index < kNumberOfPreallocatedSpaces);
    Address address = high_water_[space_index];
    DCHECK_NOT_NULL(address);
    high_water_[space_index] += size;
#ifdef DEBUG
    // Assert that the current reserved chunk is still big enough.
    const Heap::Reservation& reservation = reservations_[space_index];
    int chunk_index = current_chunk_[space_index];
    CHECK_LE(high_water_[space_index], reservation[chunk_index].end);
#endif
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    if (space_index == CODE_SPACE) SkipList::Update(address, size);
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    return address;
  }
}

Object** Deserializer::CopyInNativesSource(Vector<const char> source_vector,
                                           Object** current) {
  DCHECK(!isolate_->heap()->deserialization_complete());
  NativesExternalStringResource* resource = new NativesExternalStringResource(
      source_vector.start(), source_vector.length());
  Object* resource_obj = reinterpret_cast<Object*>(resource);
  UnalignedCopy(current++, &resource_obj);
  return current;
}

bool Deserializer::ReadData(Object** current, Object** limit, int source_space,
                            Address current_object_address) {
  Isolate* const isolate = isolate_;
  // Write barrier support costs around 1% in startup time.  In fact there
  // are no new space objects in current boot snapshots, so it's not needed,
  // but that may change.
  bool write_barrier_needed =
      (current_object_address != NULL && source_space != NEW_SPACE &&
       source_space != CODE_SPACE);
  while (current < limit) {
    byte data = source_.Get();
    switch (data) {
#define CASE_STATEMENT(where, how, within, space_number) \
  case where + how + within + space_number:              \
    STATIC_ASSERT((where & ~kWhereMask) == 0);           \
    STATIC_ASSERT((how & ~kHowToCodeMask) == 0);         \
    STATIC_ASSERT((within & ~kWhereToPointMask) == 0);   \
    STATIC_ASSERT((space_number & ~kSpaceMask) == 0);

#define CASE_BODY(where, how, within, space_number_if_any)                     \
  {                                                                            \
    bool emit_write_barrier = false;                                           \
    bool current_was_incremented = false;                                      \
    int space_number = space_number_if_any == kAnyOldSpace                     \
                           ? (data & kSpaceMask)                               \
                           : space_number_if_any;                              \
    if (where == kNewObject && how == kPlain && within == kStartOfObject) {    \
      ReadObject(space_number, current);                                       \
      emit_write_barrier = (space_number == NEW_SPACE);                        \
    } else {                                                                   \
      Object* new_object = NULL; /* May not be a real Object pointer. */       \
      if (where == kNewObject) {                                               \
        ReadObject(space_number, &new_object);                                 \
      } else if (where == kBackref) {                                          \
        emit_write_barrier = (space_number == NEW_SPACE);                      \
        new_object = GetBackReferencedObject(data & kSpaceMask);               \
      } else if (where == kBackrefWithSkip) {                                  \
        int skip = source_.GetInt();                                           \
        current = reinterpret_cast<Object**>(                                  \
            reinterpret_cast<Address>(current) + skip);                        \
        emit_write_barrier = (space_number == NEW_SPACE);                      \
        new_object = GetBackReferencedObject(data & kSpaceMask);               \
      } else if (where == kRootArray) {                                        \
        int id = source_.GetInt();                                             \
        Heap::RootListIndex root_index = static_cast<Heap::RootListIndex>(id); \
        new_object = isolate->heap()->root(root_index);                        \
        emit_write_barrier = isolate->heap()->InNewSpace(new_object);          \
      } else if (where == kPartialSnapshotCache) {                             \
        int cache_index = source_.GetInt();                                    \
        new_object = isolate->partial_snapshot_cache()->at(cache_index);       \
        emit_write_barrier = isolate->heap()->InNewSpace(new_object);          \
      } else if (where == kExternalReference) {                                \
        int skip = source_.GetInt();                                           \
        current = reinterpret_cast<Object**>(                                  \
            reinterpret_cast<Address>(current) + skip);                        \
        int reference_id = source_.GetInt();                                   \
        Address address = external_reference_table_->address(reference_id);    \
        new_object = reinterpret_cast<Object*>(address);                       \
      } else if (where == kAttachedReference) {                                \
        int index = source_.GetInt();                                          \
        DCHECK(deserializing_user_code() || index == kGlobalProxyReference);   \
        new_object = *attached_objects_[index];                                \
        emit_write_barrier = isolate->heap()->InNewSpace(new_object);          \
      } else {                                                                 \
        DCHECK(where == kBuiltin);                                             \
        DCHECK(deserializing_user_code());                                     \
        int builtin_id = source_.GetInt();                                     \
        DCHECK_LE(0, builtin_id);                                              \
        DCHECK_LT(builtin_id, Builtins::builtin_count);                        \
        Builtins::Name name = static_cast<Builtins::Name>(builtin_id);         \
        new_object = isolate->builtins()->builtin(name);                       \
        emit_write_barrier = false;                                            \
      }                                                                        \
      if (within == kInnerPointer) {                                           \
        if (space_number != CODE_SPACE || new_object->IsCode()) {              \
          Code* new_code_object = reinterpret_cast<Code*>(new_object);         \
          new_object =                                                         \
              reinterpret_cast<Object*>(new_code_object->instruction_start()); \
        } else {                                                               \
          DCHECK(space_number == CODE_SPACE);                                  \
          Cell* cell = Cell::cast(new_object);                                 \
          new_object = reinterpret_cast<Object*>(cell->ValueAddress());        \
        }                                                                      \
      }                                                                        \
      if (how == kFromCode) {                                                  \
        Address location_of_branch_data = reinterpret_cast<Address>(current);  \
        Assembler::deserialization_set_special_target_at(                      \
            isolate, location_of_branch_data,                                  \
            Code::cast(HeapObject::FromAddress(current_object_address)),       \
            reinterpret_cast<Address>(new_object));                            \
        location_of_branch_data += Assembler::kSpecialTargetSize;              \
        current = reinterpret_cast<Object**>(location_of_branch_data);         \
        current_was_incremented = true;                                        \
      } else {                                                                 \
        UnalignedCopy(current, &new_object);                                   \
      }                                                                        \
    }                                                                          \
    if (emit_write_barrier && write_barrier_needed) {                          \
      Address current_address = reinterpret_cast<Address>(current);            \
      SLOW_DCHECK(isolate->heap()->ContainsSlow(current_object_address));      \
      isolate->heap()->RecordWrite(                                            \
          HeapObject::FromAddress(current_object_address),                     \
          static_cast<int>(current_address - current_object_address),          \
          *reinterpret_cast<Object**>(current_address));                       \
    }                                                                          \
    if (!current_was_incremented) {                                            \
      current++;                                                               \
    }                                                                          \
    break;                                                                     \
  }

// This generates a case and a body for the new space (which has to do extra
// write barrier handling) and handles the other spaces with fall-through cases
// and one body.
#define ALL_SPACES(where, how, within)           \
  CASE_STATEMENT(where, how, within, NEW_SPACE)  \
  CASE_BODY(where, how, within, NEW_SPACE)       \
  CASE_STATEMENT(where, how, within, OLD_SPACE)  \
  CASE_STATEMENT(where, how, within, CODE_SPACE) \
  CASE_STATEMENT(where, how, within, MAP_SPACE)  \
  CASE_STATEMENT(where, how, within, LO_SPACE)   \
  CASE_BODY(where, how, within, kAnyOldSpace)

#define FOUR_CASES(byte_code) \
  case byte_code:             \
  case byte_code + 1:         \
  case byte_code + 2:         \
  case byte_code + 3:

#define SIXTEEN_CASES(byte_code) \
  FOUR_CASES(byte_code)          \
  FOUR_CASES(byte_code + 4)      \
  FOUR_CASES(byte_code + 8)      \
  FOUR_CASES(byte_code + 12)

#define SINGLE_CASE(where, how, within, space) \
  CASE_STATEMENT(where, how, within, space)    \
  CASE_BODY(where, how, within, space)

      // Deserialize a new object and write a pointer to it to the current
      // object.
      ALL_SPACES(kNewObject, kPlain, kStartOfObject)
      // Support for direct instruction pointers in functions.  It's an inner
      // pointer because it points at the entry point, not at the start of the
      // code object.
      SINGLE_CASE(kNewObject, kPlain, kInnerPointer, CODE_SPACE)
      // Deserialize a new code object and write a pointer to its first
      // instruction to the current code object.
      ALL_SPACES(kNewObject, kFromCode, kInnerPointer)
      // Find a recently deserialized object using its offset from the current
      // allocation point and write a pointer to it to the current object.
      ALL_SPACES(kBackref, kPlain, kStartOfObject)
      ALL_SPACES(kBackrefWithSkip, kPlain, kStartOfObject)
592
#if V8_CODE_EMBEDS_OBJECT_POINTER
593
      // Deserialize a new object from pointer found in code and write
594 595 596
      // a pointer to it to the current object. Required only for MIPS, PPC, ARM
      // or S390 with embedded constant pool, and omitted on the other
      // architectures because it is fully unrolled and would cause bloat.
597 598 599
      ALL_SPACES(kNewObject, kFromCode, kStartOfObject)
      // Find a recently deserialized code object using its offset from the
      // current allocation point and write a pointer to it to the current
600 601
      // object. Required only for MIPS, PPC, ARM or S390 with embedded
      // constant pool.
602 603 604 605 606 607 608 609 610 611 612 613 614 615
      ALL_SPACES(kBackref, kFromCode, kStartOfObject)
      ALL_SPACES(kBackrefWithSkip, kFromCode, kStartOfObject)
#endif
      // Find a recently deserialized code object using its offset from the
      // current allocation point and write a pointer to its first instruction
      // to the current code object or the instruction pointer in a function
      // object.
      ALL_SPACES(kBackref, kFromCode, kInnerPointer)
      ALL_SPACES(kBackrefWithSkip, kFromCode, kInnerPointer)
      ALL_SPACES(kBackref, kPlain, kInnerPointer)
      ALL_SPACES(kBackrefWithSkip, kPlain, kInnerPointer)
      // Find an object in the roots array and write a pointer to it to the
      // current object.
      SINGLE_CASE(kRootArray, kPlain, kStartOfObject, 0)
616
#if V8_CODE_EMBEDS_OBJECT_POINTER
617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818
      // Find an object in the roots array and write a pointer to it to in code.
      SINGLE_CASE(kRootArray, kFromCode, kStartOfObject, 0)
#endif
      // Find an object in the partial snapshots cache and write a pointer to it
      // to the current object.
      SINGLE_CASE(kPartialSnapshotCache, kPlain, kStartOfObject, 0)
      // Find an code entry in the partial snapshots cache and
      // write a pointer to it to the current object.
      SINGLE_CASE(kPartialSnapshotCache, kPlain, kInnerPointer, 0)
      // Find an external reference and write a pointer to it to the current
      // object.
      SINGLE_CASE(kExternalReference, kPlain, kStartOfObject, 0)
      // Find an external reference and write a pointer to it in the current
      // code object.
      SINGLE_CASE(kExternalReference, kFromCode, kStartOfObject, 0)
      // Find an object in the attached references and write a pointer to it to
      // the current object.
      SINGLE_CASE(kAttachedReference, kPlain, kStartOfObject, 0)
      SINGLE_CASE(kAttachedReference, kPlain, kInnerPointer, 0)
      SINGLE_CASE(kAttachedReference, kFromCode, kInnerPointer, 0)
      // Find a builtin and write a pointer to it to the current object.
      SINGLE_CASE(kBuiltin, kPlain, kStartOfObject, 0)
      SINGLE_CASE(kBuiltin, kPlain, kInnerPointer, 0)
      SINGLE_CASE(kBuiltin, kFromCode, kInnerPointer, 0)

#undef CASE_STATEMENT
#undef CASE_BODY
#undef ALL_SPACES

      case kSkip: {
        int size = source_.GetInt();
        current = reinterpret_cast<Object**>(
            reinterpret_cast<intptr_t>(current) + size);
        break;
      }

      case kInternalReferenceEncoded:
      case kInternalReference: {
        // Internal reference address is not encoded via skip, but by offset
        // from code entry.
        int pc_offset = source_.GetInt();
        int target_offset = source_.GetInt();
        Code* code =
            Code::cast(HeapObject::FromAddress(current_object_address));
        DCHECK(0 <= pc_offset && pc_offset <= code->instruction_size());
        DCHECK(0 <= target_offset && target_offset <= code->instruction_size());
        Address pc = code->entry() + pc_offset;
        Address target = code->entry() + target_offset;
        Assembler::deserialization_set_target_internal_reference_at(
            isolate, pc, target, data == kInternalReference
                                     ? RelocInfo::INTERNAL_REFERENCE
                                     : RelocInfo::INTERNAL_REFERENCE_ENCODED);
        break;
      }

      case kNop:
        break;

      case kNextChunk: {
        int space = source_.Get();
        DCHECK(space < kNumberOfPreallocatedSpaces);
        int chunk_index = current_chunk_[space];
        const Heap::Reservation& reservation = reservations_[space];
        // Make sure the current chunk is indeed exhausted.
        CHECK_EQ(reservation[chunk_index].end, high_water_[space]);
        // Move to next reserved chunk.
        chunk_index = ++current_chunk_[space];
        CHECK_LT(chunk_index, reservation.length());
        high_water_[space] = reservation[chunk_index].start;
        break;
      }

      case kDeferred: {
        // Deferred can only occur right after the heap object header.
        DCHECK(current == reinterpret_cast<Object**>(current_object_address +
                                                     kPointerSize));
        HeapObject* obj = HeapObject::FromAddress(current_object_address);
        // If the deferred object is a map, its instance type may be used
        // during deserialization. Initialize it with a temporary value.
        if (obj->IsMap()) Map::cast(obj)->set_instance_type(FILLER_TYPE);
        current = limit;
        return false;
      }

      case kSynchronize:
        // If we get here then that indicates that you have a mismatch between
        // the number of GC roots when serializing and deserializing.
        CHECK(false);
        break;

      case kNativesStringResource:
        current = CopyInNativesSource(Natives::GetScriptSource(source_.Get()),
                                      current);
        break;

      case kExtraNativesStringResource:
        current = CopyInNativesSource(
            ExtraNatives::GetScriptSource(source_.Get()), current);
        break;

      // Deserialize raw data of variable length.
      case kVariableRawData: {
        int size_in_bytes = source_.GetInt();
        byte* raw_data_out = reinterpret_cast<byte*>(current);
        source_.CopyRaw(raw_data_out, size_in_bytes);
        break;
      }

      case kVariableRepeat: {
        int repeats = source_.GetInt();
        Object* object = current[-1];
        DCHECK(!isolate->heap()->InNewSpace(object));
        for (int i = 0; i < repeats; i++) UnalignedCopy(current++, &object);
        break;
      }

      case kAlignmentPrefix:
      case kAlignmentPrefix + 1:
      case kAlignmentPrefix + 2:
        SetAlignment(data);
        break;

      STATIC_ASSERT(kNumberOfRootArrayConstants == Heap::kOldSpaceRoots);
      STATIC_ASSERT(kNumberOfRootArrayConstants == 32);
      SIXTEEN_CASES(kRootArrayConstantsWithSkip)
      SIXTEEN_CASES(kRootArrayConstantsWithSkip + 16) {
        int skip = source_.GetInt();
        current = reinterpret_cast<Object**>(
            reinterpret_cast<intptr_t>(current) + skip);
        // Fall through.
      }

      SIXTEEN_CASES(kRootArrayConstants)
      SIXTEEN_CASES(kRootArrayConstants + 16) {
        int id = data & kRootArrayConstantsMask;
        Heap::RootListIndex root_index = static_cast<Heap::RootListIndex>(id);
        Object* object = isolate->heap()->root(root_index);
        DCHECK(!isolate->heap()->InNewSpace(object));
        UnalignedCopy(current++, &object);
        break;
      }

      STATIC_ASSERT(kNumberOfHotObjects == 8);
      FOUR_CASES(kHotObjectWithSkip)
      FOUR_CASES(kHotObjectWithSkip + 4) {
        int skip = source_.GetInt();
        current = reinterpret_cast<Object**>(
            reinterpret_cast<Address>(current) + skip);
        // Fall through.
      }

      FOUR_CASES(kHotObject)
      FOUR_CASES(kHotObject + 4) {
        int index = data & kHotObjectMask;
        Object* hot_object = hot_objects_.Get(index);
        UnalignedCopy(current, &hot_object);
        if (write_barrier_needed) {
          Address current_address = reinterpret_cast<Address>(current);
          SLOW_DCHECK(isolate->heap()->ContainsSlow(current_object_address));
          isolate->heap()->RecordWrite(
              HeapObject::FromAddress(current_object_address),
              static_cast<int>(current_address - current_object_address),
              hot_object);
        }
        current++;
        break;
      }

      // Deserialize raw data of fixed length from 1 to 32 words.
      STATIC_ASSERT(kNumberOfFixedRawData == 32);
      SIXTEEN_CASES(kFixedRawData)
      SIXTEEN_CASES(kFixedRawData + 16) {
        byte* raw_data_out = reinterpret_cast<byte*>(current);
        int size_in_bytes = (data - kFixedRawDataStart) << kPointerSizeLog2;
        source_.CopyRaw(raw_data_out, size_in_bytes);
        current = reinterpret_cast<Object**>(raw_data_out + size_in_bytes);
        break;
      }

      STATIC_ASSERT(kNumberOfFixedRepeat == 16);
      SIXTEEN_CASES(kFixedRepeat) {
        int repeats = data - kFixedRepeatStart;
        Object* object;
        UnalignedCopy(&object, current - 1);
        DCHECK(!isolate->heap()->InNewSpace(object));
        for (int i = 0; i < repeats; i++) UnalignedCopy(current++, &object);
        break;
      }

#undef SIXTEEN_CASES
#undef FOUR_CASES
#undef SINGLE_CASE

      default:
        CHECK(false);
    }
  }
  CHECK_EQ(limit, current);
  return true;
}
}  // namespace internal
}  // namespace v8