serializer-deserializer.cc 2.39 KB
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// Copyright 2020 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/serializer-deserializer.h"

#include "src/objects/foreign-inl.h"
#include "src/objects/objects-inl.h"

namespace v8 {
namespace internal {

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// The startup object cache is terminated by undefined. We visit the context
// snapshot...
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//  - during deserialization to populate it.
//  - during normal GC to keep its content alive.
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//  - not during serialization. The context serializer adds to it explicitly.
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DISABLE_CFI_PERF
void SerializerDeserializer::Iterate(Isolate* isolate, RootVisitor* visitor) {
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  std::vector<Object>* cache = isolate->startup_object_cache();
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  for (size_t i = 0;; ++i) {
    // Extend the array ready to get a value when deserializing.
    if (cache->size() <= i) cache->push_back(Smi::zero());
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    // During deserialization, the visitor populates the startup object cache
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    // and eventually terminates the cache with undefined.
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    visitor->VisitRootPointer(Root::kStartupObjectCache, nullptr,
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                              FullObjectSlot(&cache->at(i)));
    if (cache->at(i).IsUndefined(isolate)) break;
  }
}

bool SerializerDeserializer::CanBeDeferred(HeapObject o) {
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  // Maps cannot be deferred as objects are expected to have a valid map
  // immediately. Internalized strings cannot be deferred as they might be
  // converted to thin strings during post processing, at which point forward
  // references to the now-thin string will already have been written.
  // TODO(leszeks): Could we defer string serialization if forward references
  // were resolved after object post processing?
  return !o.IsMap() && !o.IsInternalizedString();
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}

void SerializerDeserializer::RestoreExternalReferenceRedirectors(
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    Isolate* isolate, const std::vector<AccessorInfo>& accessor_infos) {
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  // Restore wiped accessor infos.
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  for (AccessorInfo info : accessor_infos) {
    Foreign::cast(info.js_getter())
        .set_foreign_address(isolate, info.redirected_getter());
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  }
}

void SerializerDeserializer::RestoreExternalReferenceRedirectors(
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    Isolate* isolate, const std::vector<CallHandlerInfo>& call_handler_infos) {
  for (CallHandlerInfo info : call_handler_infos) {
    Foreign::cast(info.js_callback())
        .set_foreign_address(isolate, info.redirected_callback());
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  }
}

}  // namespace internal
}  // namespace v8