address-map.cc

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// Copyright 2015 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/utils/address-map.h"
 
#include "src/execution/isolate.h"
#include "src/roots/roots-inl.h"
 
namespace v8 {
namespace internal {
 
RootIndexMap::RootIndexMap(Isolate* isolate) {
  map_ = isolate->root_index_map();
  if (map_ != nullptr) return;
  map_ = new HeapObjectToIndexHashMap();
  for (RootIndex root_index = RootIndex::kFirstStrongOrReadOnlyRoot;
       root_index <= RootIndex::kLastStrongOrReadOnlyRoot; ++root_index) {
    Tagged<Object> root = isolate->root(root_index);
    if (!IsHeapObject(root)) continue;
    // Omit root entries that can be written after initialization. They must
    // not be referenced through the root list in the snapshot.
    // Since we map the raw address of an root item to its root list index, the
    // raw address must be constant, i.e. the object must be immovable.
    if (RootsTable::IsImmortalImmovable(root_index)) {
      Tagged<HeapObject> heap_object = Cast<HeapObject>(root);
      Maybe<uint32_t> maybe_index = map_->Get(heap_object);
      uint32_t index = static_cast<uint32_t>(root_index);
      if (maybe_index.IsJust()) {
        // Some are initialized to a previous value in the root list.
        DCHECK_LT(maybe_index.FromJust(), index);
      } else {
        map_->Set(heap_object, index);
      }
    }
  }
  isolate->set_root_index_map(map_);
}
 
}  // namespace internal
}  // namespace v8