1 //===-- llvm/MC/MCInstrItineraries.h - Scheduling ---------------*- C++ -*-===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // This file describes the structures used for instruction 11 // itineraries, stages, and operand reads/writes. This is used by 12 // schedulers to determine instruction stages and latencies. 13 // 14 //===----------------------------------------------------------------------===// 15 16 #ifndef LLVM_MC_MCINSTRITINERARIES_H 17 #define LLVM_MC_MCINSTRITINERARIES_H 18 19 #include "llvm/MC/MCSchedule.h" 20 #include <algorithm> 21 22 namespace llvm { 23 24 //===----------------------------------------------------------------------===// 25 /// Instruction stage - These values represent a non-pipelined step in 26 /// the execution of an instruction. Cycles represents the number of 27 /// discrete time slots needed to complete the stage. Units represent 28 /// the choice of functional units that can be used to complete the 29 /// stage. Eg. IntUnit1, IntUnit2. NextCycles indicates how many 30 /// cycles should elapse from the start of this stage to the start of 31 /// the next stage in the itinerary. A value of -1 indicates that the 32 /// next stage should start immediately after the current one. 33 /// For example: 34 /// 35 /// { 1, x, -1 } 36 /// indicates that the stage occupies FU x for 1 cycle and that 37 /// the next stage starts immediately after this one. 38 /// 39 /// { 2, x|y, 1 } 40 /// indicates that the stage occupies either FU x or FU y for 2 41 /// consecuative cycles and that the next stage starts one cycle 42 /// after this stage starts. That is, the stage requirements 43 /// overlap in time. 44 /// 45 /// { 1, x, 0 } 46 /// indicates that the stage occupies FU x for 1 cycle and that 47 /// the next stage starts in this same cycle. This can be used to 48 /// indicate that the instruction requires multiple stages at the 49 /// same time. 50 /// 51 /// FU reservation can be of two different kinds: 52 /// - FUs which instruction actually requires 53 /// - FUs which instruction just reserves. Reserved unit is not available for 54 /// execution of other instruction. However, several instructions can reserve 55 /// the same unit several times. 56 /// Such two types of units reservation is used to model instruction domain 57 /// change stalls, FUs using the same resource (e.g. same register file), etc. 58 59 struct InstrStage { 60 enum ReservationKinds { 61 Required = 0, 62 Reserved = 1 63 }; 64 65 unsigned Cycles_; ///< Length of stage in machine cycles 66 unsigned Units_; ///< Choice of functional units 67 int NextCycles_; ///< Number of machine cycles to next stage 68 ReservationKinds Kind_; ///< Kind of the FU reservation 69 70 /// getCycles - returns the number of cycles the stage is occupied 71 unsigned getCycles() const { 72 return Cycles_; 73 } 74 75 /// getUnits - returns the choice of FUs 76 unsigned getUnits() const { 77 return Units_; 78 } 79 80 ReservationKinds getReservationKind() const { 81 return Kind_; 82 } 83 84 /// getNextCycles - returns the number of cycles from the start of 85 /// this stage to the start of the next stage in the itinerary 86 unsigned getNextCycles() const { 87 return (NextCycles_ >= 0) ? (unsigned)NextCycles_ : Cycles_; 88 } 89 }; 90 91 92 //===----------------------------------------------------------------------===// 93 /// Instruction itinerary - An itinerary represents the scheduling 94 /// information for an instruction. This includes a set of stages 95 /// occupies by the instruction, and the pipeline cycle in which 96 /// operands are read and written. 97 /// 98 struct InstrItinerary { 99 int NumMicroOps; ///< # of micro-ops, -1 means it's variable 100 unsigned FirstStage; ///< Index of first stage in itinerary 101 unsigned LastStage; ///< Index of last + 1 stage in itinerary 102 unsigned FirstOperandCycle; ///< Index of first operand rd/wr 103 unsigned LastOperandCycle; ///< Index of last + 1 operand rd/wr 104 }; 105 106 107 //===----------------------------------------------------------------------===// 108 /// Instruction itinerary Data - Itinerary data supplied by a subtarget to be 109 /// used by a target. 110 /// 111 class InstrItineraryData { 112 public: 113 const MCSchedModel *SchedModel; ///< Basic machine properties. 114 const InstrStage *Stages; ///< Array of stages selected 115 const unsigned *OperandCycles; ///< Array of operand cycles selected 116 const unsigned *Forwardings; ///< Array of pipeline forwarding pathes 117 const InstrItinerary *Itineraries; ///< Array of itineraries selected 118 119 /// Ctors. 120 /// 121 InstrItineraryData() : SchedModel(&MCSchedModel::DefaultSchedModel), 122 Stages(nullptr), OperandCycles(nullptr), 123 Forwardings(nullptr), Itineraries(nullptr) {} 124 125 InstrItineraryData(const MCSchedModel *SM, const InstrStage *S, 126 const unsigned *OS, const unsigned *F) 127 : SchedModel(SM), Stages(S), OperandCycles(OS), Forwardings(F), 128 Itineraries(SchedModel->InstrItineraries) {} 129 130 /// isEmpty - Returns true if there are no itineraries. 131 /// 132 bool isEmpty() const { return Itineraries == nullptr; } 133 134 /// isEndMarker - Returns true if the index is for the end marker 135 /// itinerary. 136 /// 137 bool isEndMarker(unsigned ItinClassIndx) const { 138 return ((Itineraries[ItinClassIndx].FirstStage == ~0U) && 139 (Itineraries[ItinClassIndx].LastStage == ~0U)); 140 } 141 142 /// beginStage - Return the first stage of the itinerary. 143 /// 144 const InstrStage *beginStage(unsigned ItinClassIndx) const { 145 unsigned StageIdx = Itineraries[ItinClassIndx].FirstStage; 146 return Stages + StageIdx; 147 } 148 149 /// endStage - Return the last+1 stage of the itinerary. 150 /// 151 const InstrStage *endStage(unsigned ItinClassIndx) const { 152 unsigned StageIdx = Itineraries[ItinClassIndx].LastStage; 153 return Stages + StageIdx; 154 } 155 156 /// getStageLatency - Return the total stage latency of the given 157 /// class. The latency is the maximum completion time for any stage 158 /// in the itinerary. 159 /// 160 /// If no stages exist, it defaults to one cycle. 161 unsigned getStageLatency(unsigned ItinClassIndx) const { 162 // If the target doesn't provide itinerary information, use a simple 163 // non-zero default value for all instructions. 164 if (isEmpty()) 165 return 1; 166 167 // Calculate the maximum completion time for any stage. 168 unsigned Latency = 0, StartCycle = 0; 169 for (const InstrStage *IS = beginStage(ItinClassIndx), 170 *E = endStage(ItinClassIndx); IS != E; ++IS) { 171 Latency = std::max(Latency, StartCycle + IS->getCycles()); 172 StartCycle += IS->getNextCycles(); 173 } 174 return Latency; 175 } 176 177 /// getOperandCycle - Return the cycle for the given class and 178 /// operand. Return -1 if no cycle is specified for the operand. 179 /// 180 int getOperandCycle(unsigned ItinClassIndx, unsigned OperandIdx) const { 181 if (isEmpty()) 182 return -1; 183 184 unsigned FirstIdx = Itineraries[ItinClassIndx].FirstOperandCycle; 185 unsigned LastIdx = Itineraries[ItinClassIndx].LastOperandCycle; 186 if ((FirstIdx + OperandIdx) >= LastIdx) 187 return -1; 188 189 return (int)OperandCycles[FirstIdx + OperandIdx]; 190 } 191 192 /// hasPipelineForwarding - Return true if there is a pipeline forwarding 193 /// between instructions of itinerary classes DefClass and UseClasses so that 194 /// value produced by an instruction of itinerary class DefClass, operand 195 /// index DefIdx can be bypassed when it's read by an instruction of 196 /// itinerary class UseClass, operand index UseIdx. 197 bool hasPipelineForwarding(unsigned DefClass, unsigned DefIdx, 198 unsigned UseClass, unsigned UseIdx) const { 199 unsigned FirstDefIdx = Itineraries[DefClass].FirstOperandCycle; 200 unsigned LastDefIdx = Itineraries[DefClass].LastOperandCycle; 201 if ((FirstDefIdx + DefIdx) >= LastDefIdx) 202 return false; 203 if (Forwardings[FirstDefIdx + DefIdx] == 0) 204 return false; 205 206 unsigned FirstUseIdx = Itineraries[UseClass].FirstOperandCycle; 207 unsigned LastUseIdx = Itineraries[UseClass].LastOperandCycle; 208 if ((FirstUseIdx + UseIdx) >= LastUseIdx) 209 return false; 210 211 return Forwardings[FirstDefIdx + DefIdx] == 212 Forwardings[FirstUseIdx + UseIdx]; 213 } 214 215 /// getOperandLatency - Compute and return the use operand latency of a given 216 /// itinerary class and operand index if the value is produced by an 217 /// instruction of the specified itinerary class and def operand index. 218 int getOperandLatency(unsigned DefClass, unsigned DefIdx, 219 unsigned UseClass, unsigned UseIdx) const { 220 if (isEmpty()) 221 return -1; 222 223 int DefCycle = getOperandCycle(DefClass, DefIdx); 224 if (DefCycle == -1) 225 return -1; 226 227 int UseCycle = getOperandCycle(UseClass, UseIdx); 228 if (UseCycle == -1) 229 return -1; 230 231 UseCycle = DefCycle - UseCycle + 1; 232 if (UseCycle > 0 && 233 hasPipelineForwarding(DefClass, DefIdx, UseClass, UseIdx)) 234 // FIXME: This assumes one cycle benefit for every pipeline forwarding. 235 --UseCycle; 236 return UseCycle; 237 } 238 239 /// getNumMicroOps - Return the number of micro-ops that the given class 240 /// decodes to. Return -1 for classes that require dynamic lookup via 241 /// TargetInstrInfo. 242 int getNumMicroOps(unsigned ItinClassIndx) const { 243 if (isEmpty()) 244 return 1; 245 return Itineraries[ItinClassIndx].NumMicroOps; 246 } 247 }; 248 249 } // End llvm namespace 250 251 #endif 252
