[serializer] split up src/snapshot/serialize.*

src/snapshot/deserializer.cc

+// Copyright 2016 the V8 project authors. All rights reserved.

[Michael Achenbach, 2016/03/01 20:02:03]

This has no proper license header and blocks the current roll:
https://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium...

Please fix asap, or is this easy revertable?

+
+#include "src/snapshot/deserializer.h"
+
+#include "src/bootstrapper.h"
+#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_) {
+    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());
+
+  {
+    DisallowHeapAllocation no_gc;
+    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());
+  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();
+
+  // 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));
+    }
+    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 (FLAG_log_snapshot_positions) {
+    LOG(isolate_, SnapshotPositionEvent(address, source_.position()));
+  }
+
+  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
+    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)
+#if defined(V8_TARGET_ARCH_MIPS) || defined(V8_TARGET_ARCH_MIPS64) || \
+    defined(V8_TARGET_ARCH_PPC) || V8_EMBEDDED_CONSTANT_POOL
+      // Deserialize a new object from pointer found in code and write
+      // a pointer to it to the current object. Required only for MIPS, PPC or
+      // ARM with embedded constant pool, and omitted on the other architectures
+      // because it is fully unrolled and would cause bloat.
+      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
+      // object. Required only for MIPS, PPC or ARM with embedded constant pool.
+      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)
+#if defined(V8_TARGET_ARCH_MIPS) || defined(V8_TARGET_ARCH_MIPS64) || \
+    defined(V8_TARGET_ARCH_PPC) || V8_EMBEDDED_CONSTANT_POOL
+      // 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