//===-- llvm/MC/MCInstrItineraries.h - Scheduling ---------------*- C++ -*-===// // // The LLVM Compiler Infrastructure // // This file is distributed under the University of Illinois Open Source // License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // // This file describes the structures used for instruction // itineraries, stages, and operand reads/writes. This is used by // schedulers to determine instruction stages and latencies. // //===----------------------------------------------------------------------===// #ifndef LLVM_MC_MCINSTRITINERARIES_H #define LLVM_MC_MCINSTRITINERARIES_H #include "llvm/MC/MCSchedule.h" #include <algorithm> namespace llvm { //===----------------------------------------------------------------------===// /// These values represent a non-pipelined step in /// the execution of an instruction. Cycles represents the number of /// discrete time slots needed to complete the stage. Units represent /// the choice of functional units that can be used to complete the /// stage. Eg. IntUnit1, IntUnit2. NextCycles indicates how many /// cycles should elapse from the start of this stage to the start of /// the next stage in the itinerary. A value of -1 indicates that the /// next stage should start immediately after the current one. /// For example: /// /// { 1, x, -1 } /// indicates that the stage occupies FU x for 1 cycle and that /// the next stage starts immediately after this one. /// /// { 2, x|y, 1 } /// indicates that the stage occupies either FU x or FU y for 2 /// consecutive cycles and that the next stage starts one cycle /// after this stage starts. That is, the stage requirements /// overlap in time. /// /// { 1, x, 0 } /// indicates that the stage occupies FU x for 1 cycle and that /// the next stage starts in this same cycle. This can be used to /// indicate that the instruction requires multiple stages at the /// same time. /// /// FU reservation can be of two different kinds: /// - FUs which instruction actually requires /// - FUs which instruction just reserves. Reserved unit is not available for /// execution of other instruction. However, several instructions can reserve /// the same unit several times. /// Such two types of units reservation is used to model instruction domain /// change stalls, FUs using the same resource (e.g. same register file), etc. struct InstrStage { enum ReservationKinds { Required = 0, Reserved = 1 }; unsigned Cycles_; ///< Length of stage in machine cycles unsigned Units_; ///< Choice of functional units int NextCycles_; ///< Number of machine cycles to next stage ReservationKinds Kind_; ///< Kind of the FU reservation /// \brief Returns the number of cycles the stage is occupied. unsigned getCycles() const { return Cycles_; } /// \brief Returns the choice of FUs. unsigned getUnits() const { return Units_; } ReservationKinds getReservationKind() const { return Kind_; } /// \brief Returns the number of cycles from the start of this stage to the /// start of the next stage in the itinerary unsigned getNextCycles() const { return (NextCycles_ >= 0) ? (unsigned)NextCycles_ : Cycles_; } }; //===----------------------------------------------------------------------===// /// An itinerary represents the scheduling information for an instruction. /// This includes a set of stages occupied by the instruction and the pipeline /// cycle in which operands are read and written. /// struct InstrItinerary { int NumMicroOps; ///< # of micro-ops, -1 means it's variable unsigned FirstStage; ///< Index of first stage in itinerary unsigned LastStage; ///< Index of last + 1 stage in itinerary unsigned FirstOperandCycle; ///< Index of first operand rd/wr unsigned LastOperandCycle; ///< Index of last + 1 operand rd/wr }; //===----------------------------------------------------------------------===// /// Itinerary data supplied by a subtarget to be used by a target. /// class InstrItineraryData { public: MCSchedModel SchedModel; ///< Basic machine properties. const InstrStage *Stages; ///< Array of stages selected const unsigned *OperandCycles; ///< Array of operand cycles selected const unsigned *Forwardings; ///< Array of pipeline forwarding pathes const InstrItinerary *Itineraries; ///< Array of itineraries selected /// Ctors. InstrItineraryData() : SchedModel(MCSchedModel::GetDefaultSchedModel()), Stages(nullptr), OperandCycles(nullptr), Forwardings(nullptr), Itineraries(nullptr) {} InstrItineraryData(const MCSchedModel &SM, const InstrStage *S, const unsigned *OS, const unsigned *F) : SchedModel(SM), Stages(S), OperandCycles(OS), Forwardings(F), Itineraries(SchedModel.InstrItineraries) {} /// \brief Returns true if there are no itineraries. bool isEmpty() const { return Itineraries == nullptr; } /// \brief Returns true if the index is for the end marker itinerary. bool isEndMarker(unsigned ItinClassIndx) const { return ((Itineraries[ItinClassIndx].FirstStage == ~0U) && (Itineraries[ItinClassIndx].LastStage == ~0U)); } /// \brief Return the first stage of the itinerary. const InstrStage *beginStage(unsigned ItinClassIndx) const { unsigned StageIdx = Itineraries[ItinClassIndx].FirstStage; return Stages + StageIdx; } /// \brief Return the last+1 stage of the itinerary. const InstrStage *endStage(unsigned ItinClassIndx) const { unsigned StageIdx = Itineraries[ItinClassIndx].LastStage; return Stages + StageIdx; } /// \brief Return the total stage latency of the given class. The latency is /// the maximum completion time for any stage in the itinerary. If no stages /// exist, it defaults to one cycle. unsigned getStageLatency(unsigned ItinClassIndx) const { // If the target doesn't provide itinerary information, use a simple // non-zero default value for all instructions. if (isEmpty()) return 1; // Calculate the maximum completion time for any stage. unsigned Latency = 0, StartCycle = 0; for (const InstrStage *IS = beginStage(ItinClassIndx), *E = endStage(ItinClassIndx); IS != E; ++IS) { Latency = std::max(Latency, StartCycle + IS->getCycles()); StartCycle += IS->getNextCycles(); } return Latency; } /// \brief Return the cycle for the given class and operand. Return -1 if no /// cycle is specified for the operand. int getOperandCycle(unsigned ItinClassIndx, unsigned OperandIdx) const { if (isEmpty()) return -1; unsigned FirstIdx = Itineraries[ItinClassIndx].FirstOperandCycle; unsigned LastIdx = Itineraries[ItinClassIndx].LastOperandCycle; if ((FirstIdx + OperandIdx) >= LastIdx) return -1; return (int)OperandCycles[FirstIdx + OperandIdx]; } /// \brief Return true if there is a pipeline forwarding between instructions /// of itinerary classes DefClass and UseClasses so that value produced by an /// instruction of itinerary class DefClass, operand index DefIdx can be /// bypassed when it's read by an instruction of itinerary class UseClass, /// operand index UseIdx. bool hasPipelineForwarding(unsigned DefClass, unsigned DefIdx, unsigned UseClass, unsigned UseIdx) const { unsigned FirstDefIdx = Itineraries[DefClass].FirstOperandCycle; unsigned LastDefIdx = Itineraries[DefClass].LastOperandCycle; if ((FirstDefIdx + DefIdx) >= LastDefIdx) return false; if (Forwardings[FirstDefIdx + DefIdx] == 0) return false; unsigned FirstUseIdx = Itineraries[UseClass].FirstOperandCycle; unsigned LastUseIdx = Itineraries[UseClass].LastOperandCycle; if ((FirstUseIdx + UseIdx) >= LastUseIdx) return false; return Forwardings[FirstDefIdx + DefIdx] == Forwardings[FirstUseIdx + UseIdx]; } /// \brief Compute and return the use operand latency of a given itinerary /// class and operand index if the value is produced by an instruction of the /// specified itinerary class and def operand index. int getOperandLatency(unsigned DefClass, unsigned DefIdx, unsigned UseClass, unsigned UseIdx) const { if (isEmpty()) return -1; int DefCycle = getOperandCycle(DefClass, DefIdx); if (DefCycle == -1) return -1; int UseCycle = getOperandCycle(UseClass, UseIdx); if (UseCycle == -1) return -1; UseCycle = DefCycle - UseCycle + 1; if (UseCycle > 0 && hasPipelineForwarding(DefClass, DefIdx, UseClass, UseIdx)) // FIXME: This assumes one cycle benefit for every pipeline forwarding. --UseCycle; return UseCycle; } /// \brief Return the number of micro-ops that the given class decodes to. /// Return -1 for classes that require dynamic lookup via TargetInstrInfo. int getNumMicroOps(unsigned ItinClassIndx) const { if (isEmpty()) return 1; return Itineraries[ItinClassIndx].NumMicroOps; } }; } // End llvm namespace #endif