1 // Copyright 2015 the V8 project authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #include "src/address-map.h" 6 #include "src/heap/heap.h" 7 #include "src/isolate.h" 8 #include "src/objects-inl.h" 9 10 namespace v8 { 11 namespace internal { 12 13 RootIndexMap::RootIndexMap(Isolate* isolate) { 14 map_ = isolate->root_index_map(); 15 if (map_ != nullptr) return; 16 map_ = new HeapObjectToIndexHashMap(); 17 for (uint32_t i = 0; i < Heap::kStrongRootListLength; i++) { 18 Heap::RootListIndex root_index = static_cast<Heap::RootListIndex>(i); 19 Object* root = isolate->heap()->root(root_index); 20 if (!root->IsHeapObject()) continue; 21 // Omit root entries that can be written after initialization. They must 22 // not be referenced through the root list in the snapshot. 23 // Since we map the raw address of an root item to its root list index, the 24 // raw address must be constant, i.e. the object must be immovable. 25 if (isolate->heap()->RootCanBeTreatedAsConstant(root_index)) { 26 HeapObject* heap_object = HeapObject::cast(root); 27 Maybe<uint32_t> maybe_index = map_->Get(heap_object); 28 if (maybe_index.IsJust()) { 29 // Some are initialized to a previous value in the root list. 30 DCHECK_LT(maybe_index.FromJust(), i); 31 } else { 32 map_->Set(heap_object, i); 33 } 34 } else { 35 // Immortal immovable root objects are constant and allocated on the first 36 // page of old space. Non-constant roots cannot be immortal immovable. The 37 // root index map contains all immortal immmovable root objects. 38 CHECK(!Heap::RootIsImmortalImmovable(root_index)); 39 } 40 } 41 isolate->set_root_index_map(map_); 42 } 43 44 } // namespace internal 45 } // namespace v8 46
