// Copyright 2015 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
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// found in the LICENSE file.
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#include "src/address-map.h"
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#include "src/heap/heap.h"
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#include "src/isolate.h"
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#include "src/objects-inl.h"
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namespace v8 {
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namespace internal {
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RootIndexMap::RootIndexMap(Isolate* isolate) {
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map_ = isolate->root_index_map();
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if (map_ != nullptr) return;
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map_ = new HeapObjectToIndexHashMap();
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for (uint32_t i = 0; i < Heap::kStrongRootListLength; i++) {
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Heap::RootListIndex root_index = static_cast<Heap::RootListIndex>(i);
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Object* root = isolate->heap()->root(root_index);
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if (!root->IsHeapObject()) continue;
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// Omit root entries that can be written after initialization. They must
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// not be referenced through the root list in the snapshot.
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// Since we map the raw address of an root item to its root list index, the
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// raw address must be constant, i.e. the object must be immovable.
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if (isolate->heap()->RootCanBeTreatedAsConstant(root_index)) {
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HeapObject* heap_object = HeapObject::cast(root);
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Maybe<uint32_t> maybe_index = map_->Get(heap_object);
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if (maybe_index.IsJust()) {
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// Some are initialized to a previous value in the root list.
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DCHECK_LT(maybe_index.FromJust(), i);
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} else {
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map_->Set(heap_object, i);
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}
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} else {
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// Immortal immovable root objects are constant and allocated on the first
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// page of old space. Non-constant roots cannot be immortal immovable. The
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// root index map contains all immortal immmovable root objects.
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CHECK(!Heap::RootIsImmortalImmovable(root_index));
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}
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}
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isolate->set_root_index_map(map_);
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}
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} // namespace internal
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} // namespace v8
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