src/third_party/v8/src/snapshot/startup-deserializer.cc

// Copyright 2017 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "src/snapshot/startup-deserializer.h"

#include "src/api/api.h"
#include "src/codegen/assembler-inl.h"
#include "src/execution/v8threads.h"
#include "src/heap/heap-inl.h"
#include "src/logging/log.h"
#include "src/snapshot/snapshot.h"

namespace v8 {
namespace internal {

void StartupDeserializer::DeserializeIntoIsolate() {
  HandleScope scope(isolate());

  // No active threads.
  DCHECK_NULL(isolate()->thread_manager()->FirstThreadStateInUse());
  // No active handles.
  DCHECK(isolate()->handle_scope_implementer()->blocks()->empty());
  // Startup object cache is not yet populated.
  DCHECK(isolate()->startup_object_cache()->empty());
  // Builtins are not yet created.
  DCHECK(!isolate()->builtins()->is_initialized());

  {
    isolate()->heap()->IterateSmiRoots(this);
    isolate()->heap()->IterateRoots(
        this,
        base::EnumSet<SkipRoot>{SkipRoot::kUnserializable, SkipRoot::kWeak});
    Iterate(isolate(), this);
    DeserializeStringTable();

    isolate()->heap()->IterateWeakRoots(
        this, base::EnumSet<SkipRoot>{SkipRoot::kUnserializable});
    DeserializeDeferredObjects();
    for (Handle<AccessorInfo> info : accessor_infos()) {
      RestoreExternalReferenceRedirector(isolate(), info);
    }
    for (Handle<CallHandlerInfo> info : call_handler_infos()) {
      RestoreExternalReferenceRedirector(isolate(), info);
    }

    // Flush the instruction cache for the entire code-space. Must happen after
    // builtins deserialization.
    FlushICache();
  }

  CheckNoArrayBufferBackingStores();

  isolate()->heap()->set_native_contexts_list(
      ReadOnlyRoots(isolate()).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::zero()) {
    isolate()->heap()->set_allocation_sites_list(
        ReadOnlyRoots(isolate()).undefined_value());
  }
  isolate()->heap()->set_dirty_js_finalization_registries_list(
      ReadOnlyRoots(isolate()).undefined_value());
  isolate()->heap()->set_dirty_js_finalization_registries_list_tail(
      ReadOnlyRoots(isolate()).undefined_value());

  isolate()->builtins()->MarkInitialized();

  LogNewMapEvents();
  WeakenDescriptorArrays();

  if (FLAG_rehash_snapshot && can_rehash()) {
    // Hash seed was initalized in ReadOnlyDeserializer.
    Rehash();
  }
}

void StartupDeserializer::DeserializeStringTable() {
  // See StartupSerializer::SerializeStringTable.

  // Get the string table size.
  int string_table_size = source()->GetInt();

  // Add each string to the Isolate's string table.
  // TODO(leszeks): Consider pre-sizing the string table.
  for (int i = 0; i < string_table_size; ++i) {
    Handle<String> string = Handle<String>::cast(ReadObject());
    StringTableInsertionKey key(string);
    Handle<String> result =
        isolate()->string_table()->LookupKey(isolate(), &key);
    USE(result);

    // This is startup, so there should be no duplicate entries in the string
    // table, and the lookup should unconditionally add the given string.
    DCHECK_EQ(*result, *string);
  }

  DCHECK_EQ(string_table_size, isolate()->string_table()->NumberOfElements());
}

void StartupDeserializer::LogNewMapEvents() {
  if (FLAG_trace_maps) LOG(isolate(), LogAllMaps());
}

void StartupDeserializer::FlushICache() {
  DCHECK(!deserializing_user_code());
  // The entire isolate is newly deserialized. Simply flush all code pages.
  for (Page* p : *isolate()->heap()->code_space()) {
    FlushInstructionCache(p->area_start(), p->area_end() - p->area_start());
  }
}

}  // namespace internal
}  // namespace v8