1 // Copyright 2018 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 #ifndef V8_BUILTINS_CONSTANTS_TABLE_BUILDER_H_ 6 #define V8_BUILTINS_CONSTANTS_TABLE_BUILDER_H_ 7 8 #include "src/base/macros.h" 9 #include "src/utils/allocation.h" 10 #include "src/utils/identity-map.h" 11 #include "src/handles/handles.h" 12 13 namespace v8 { 14 namespace internal { 15 16 class Isolate; 17 class Object; 18 19 // Utility class to build the builtins constants table and store it on the root 20 // list. The constants table contains constants used by builtins, and is there 21 // to avoid directly embedding them into code objects, which would not be 22 // possible for off-heap (and thus immutable) code objects. 23 class BuiltinsConstantsTableBuilder final { 24 public: 25 explicit BuiltinsConstantsTableBuilder(Isolate* isolate); 26 27 // Returns the index within the builtins constants table for the given 28 // object, possibly adding the object to the table. Objects are deduplicated. 29 uint32_t AddObject(Handle<Object> object); 30 31 // Self-references during code generation start out by referencing a handle 32 // with a temporary dummy object. Once the final Code object exists, such 33 // entries in the constants map must be patched up. 34 void PatchSelfReference(Handle<Object> self_reference, 35 Handle<Code> code_object); 36 37 // References to the array that stores basic block usage counters start out as 38 // references to a unique oddball. Once the actual array has been allocated, 39 // such entries in the constants map must be patched up. 40 void PatchBasicBlockCountersReference(Handle<ByteArray> counters); 41 42 // Should be called after all affected code (e.g. builtins and bytecode 43 // handlers) has been generated. 44 void Finalize(); 45 46 private: 47 Isolate* isolate_; 48 49 // Maps objects to corresponding indices within the constants list. 50 using ConstantsMap = IdentityMap<uint32_t, FreeStoreAllocationPolicy>; 51 ConstantsMap map_; 52 53 DISALLOW_COPY_AND_ASSIGN(BuiltinsConstantsTableBuilder); 54 }; 55 56 } // namespace internal 57 } // namespace v8 58 59 #endif // V8_BUILTINS_CONSTANTS_TABLE_BUILDER_H_ 60