1 // Copyright 2016 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_INTERPRETER_BYTECODE_REGISTER_OPTIMIZER_H_ 6 #define V8_INTERPRETER_BYTECODE_REGISTER_OPTIMIZER_H_ 7 8 #include "src/interpreter/bytecode-pipeline.h" 9 10 namespace v8 { 11 namespace internal { 12 namespace interpreter { 13 14 // An optimization stage for eliminating unnecessary transfers between 15 // registers. The bytecode generator uses temporary registers 16 // liberally for correctness and convenience and this stage removes 17 // transfers that are not required and preserves correctness. 18 class BytecodeRegisterOptimizer final : public BytecodePipelineStage, 19 public TemporaryRegisterObserver, 20 public ZoneObject { 21 public: 22 BytecodeRegisterOptimizer(Zone* zone, 23 TemporaryRegisterAllocator* register_allocator, 24 int parameter_count, 25 BytecodePipelineStage* next_stage); ~BytecodeRegisterOptimizer()26 virtual ~BytecodeRegisterOptimizer() {} 27 28 // BytecodePipelineStage interface. 29 void Write(BytecodeNode* node) override; 30 void WriteJump(BytecodeNode* node, BytecodeLabel* label) override; 31 void BindLabel(BytecodeLabel* label) override; 32 void BindLabel(const BytecodeLabel& target, BytecodeLabel* label) override; 33 Handle<BytecodeArray> ToBytecodeArray( 34 int fixed_register_count, int parameter_count, 35 Handle<FixedArray> handler_table) override; 36 37 private: 38 static const uint32_t kInvalidEquivalenceId = kMaxUInt32; 39 40 class RegisterInfo; 41 42 // TemporaryRegisterObserver interface. 43 void TemporaryRegisterFreeEvent(Register reg) override; 44 45 // Helpers for BytecodePipelineStage interface. 46 void FlushState(); 47 void WriteToNextStage(BytecodeNode* node) const; 48 void WriteToNextStage(BytecodeNode* node, 49 const BytecodeSourceInfo& output_info) const; 50 51 // Update internal state for register transfer from |input| to 52 // |output| using |source_info| as source position information if 53 // any bytecodes are emitted due to transfer. 54 void RegisterTransfer(RegisterInfo* input, RegisterInfo* output, 55 const BytecodeSourceInfo& source_info); 56 57 // Emit a register transfer bytecode from |input| to |output|. 58 void OutputRegisterTransfer( 59 RegisterInfo* input, RegisterInfo* output, 60 const BytecodeSourceInfo& source_info = BytecodeSourceInfo()); 61 62 // Emits a Nop to preserve source position information in the 63 // bytecode pipeline. 64 void EmitNopForSourceInfo(const BytecodeSourceInfo& source_info) const; 65 66 // Handlers for bytecode nodes for register to register transfers. 67 void DoLdar(const BytecodeNode* const node); 68 void DoMov(const BytecodeNode* const node); 69 void DoStar(const BytecodeNode* const node); 70 71 // Operand processing methods for bytecodes other than those 72 // performing register to register transfers. 73 void PrepareOperands(BytecodeNode* const node); 74 void PrepareAccumulator(BytecodeNode* const node); 75 void PrepareRegisterOperands(BytecodeNode* const node); 76 77 void PrepareRegisterOutputOperand(RegisterInfo* reg_info); 78 void PrepareRegisterRangeOutputOperand(Register start, int count); 79 void PrepareRegisterInputOperand(BytecodeNode* const node, Register reg, 80 int operand_index); 81 void PrepareRegisterRangeInputOperand(Register start, int count); 82 83 Register GetEquivalentRegisterForInputOperand(Register reg); 84 85 static Register GetRegisterInputOperand(int index, Bytecode bytecode, 86 const uint32_t* operands, 87 int operand_count); 88 static Register GetRegisterOutputOperand(int index, Bytecode bytecode, 89 const uint32_t* operands, 90 int operand_count); 91 92 void CreateMaterializedEquivalent(RegisterInfo* info); 93 RegisterInfo* GetMaterializedEquivalent(RegisterInfo* info); 94 RegisterInfo* GetMaterializedEquivalentNotAccumulator(RegisterInfo* info); 95 void Materialize(RegisterInfo* info); 96 void AddToEquivalenceSet(RegisterInfo* set_member, 97 RegisterInfo* non_set_member); 98 99 // Methods for finding and creating metadata for each register. 100 RegisterInfo* GetOrCreateRegisterInfo(Register reg); 101 RegisterInfo* GetRegisterInfo(Register reg); 102 RegisterInfo* NewRegisterInfo(Register reg); 103 void GrowRegisterMap(Register reg); 104 RegisterIsTemporary(Register reg)105 bool RegisterIsTemporary(Register reg) const { 106 return reg >= temporary_base_; 107 } 108 RegisterIsObservable(Register reg)109 bool RegisterIsObservable(Register reg) const { 110 return reg != accumulator_ && !RegisterIsTemporary(reg); 111 } 112 OperandToRegister(uint32_t operand)113 static Register OperandToRegister(uint32_t operand) { 114 return Register::FromOperand(static_cast<int32_t>(operand)); 115 } 116 GetRegisterInfoTableIndex(Register reg)117 size_t GetRegisterInfoTableIndex(Register reg) const { 118 return static_cast<size_t>(reg.index() + register_info_table_offset_); 119 } 120 RegisterFromRegisterInfoTableIndex(size_t index)121 Register RegisterFromRegisterInfoTableIndex(size_t index) const { 122 return Register(static_cast<int>(index) - register_info_table_offset_); 123 } 124 NextEquivalenceId()125 uint32_t NextEquivalenceId() { 126 equivalence_id_++; 127 CHECK_NE(equivalence_id_, kInvalidEquivalenceId); 128 return equivalence_id_; 129 } 130 zone()131 Zone* zone() { return zone_; } 132 133 const Register accumulator_; 134 RegisterInfo* accumulator_info_; 135 const Register temporary_base_; 136 137 // Direct mapping to register info. 138 ZoneVector<RegisterInfo*> register_info_table_; 139 int register_info_table_offset_; 140 141 // Counter for equivalence sets identifiers. 142 int equivalence_id_; 143 144 BytecodePipelineStage* next_stage_; 145 bool flush_required_; 146 Zone* zone_; 147 148 DISALLOW_COPY_AND_ASSIGN(BytecodeRegisterOptimizer); 149 }; 150 151 } // namespace interpreter 152 } // namespace internal 153 } // namespace v8 154 155 #endif // V8_INTERPRETER_BYTECODE_REGISTER_OPTIMIZER_H_ 156