1 //===- llvm/MC/MCInstrItineraries.h - Scheduling ----------------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
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.
14 //===----------------------------------------------------------------------===//
16 #ifndef LLVM_MC_MCINSTRITINERARIES_H
17 #define LLVM_MC_MCINSTRITINERARIES_H
19 #include "llvm/MC/MCSchedule.h"
24 //===----------------------------------------------------------------------===//
25 /// 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.
36 /// indicates that the stage occupies FU x for 1 cycle and that
37 /// the next stage starts immediately after this one.
40 /// indicates that the stage occupies either FU x or FU y for 2
41 /// consecutive cycles and that the next stage starts one cycle
42 /// after this stage starts. That is, the stage requirements
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
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.
60 enum ReservationKinds {
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
70 /// \brief Returns the number of cycles the stage is occupied.
71 unsigned getCycles() const {
75 /// \brief Returns the choice of FUs.
76 unsigned getUnits() const {
80 ReservationKinds getReservationKind() const {
84 /// \brief Returns the number of cycles from the start of this stage to the
85 /// start of the next stage in the itinerary
86 unsigned getNextCycles() const {
87 return (NextCycles_ >= 0) ? (unsigned)NextCycles_ : Cycles_;
91 //===----------------------------------------------------------------------===//
92 /// An itinerary represents the scheduling information for an instruction.
93 /// This includes a set of stages occupied by the instruction and the pipeline
94 /// cycle in which operands are read and written.
96 struct InstrItinerary {
97 int NumMicroOps; ///< # of micro-ops, -1 means it's variable
98 unsigned FirstStage; ///< Index of first stage in itinerary
99 unsigned LastStage; ///< Index of last + 1 stage in itinerary
100 unsigned FirstOperandCycle; ///< Index of first operand rd/wr
101 unsigned LastOperandCycle; ///< Index of last + 1 operand rd/wr
104 //===----------------------------------------------------------------------===//
105 /// Itinerary data supplied by a subtarget to be used by a target.
107 class InstrItineraryData {
109 MCSchedModel SchedModel =
110 MCSchedModel::GetDefaultSchedModel(); ///< Basic machine properties.
111 const InstrStage *Stages = nullptr; ///< Array of stages selected
112 const unsigned *OperandCycles = nullptr; ///< Array of operand cycles selected
113 const unsigned *Forwardings = nullptr; ///< Array of pipeline forwarding paths
114 const InstrItinerary *Itineraries =
115 nullptr; ///< Array of itineraries selected
117 InstrItineraryData() = default;
118 InstrItineraryData(const MCSchedModel &SM, const InstrStage *S,
119 const unsigned *OS, const unsigned *F)
120 : SchedModel(SM), Stages(S), OperandCycles(OS), Forwardings(F),
121 Itineraries(SchedModel.InstrItineraries) {}
123 /// \brief Returns true if there are no itineraries.
124 bool isEmpty() const { return Itineraries == nullptr; }
126 /// \brief Returns true if the index is for the end marker itinerary.
127 bool isEndMarker(unsigned ItinClassIndx) const {
128 return ((Itineraries[ItinClassIndx].FirstStage == ~0U) &&
129 (Itineraries[ItinClassIndx].LastStage == ~0U));
132 /// \brief Return the first stage of the itinerary.
133 const InstrStage *beginStage(unsigned ItinClassIndx) const {
134 unsigned StageIdx = Itineraries[ItinClassIndx].FirstStage;
135 return Stages + StageIdx;
138 /// \brief Return the last+1 stage of the itinerary.
139 const InstrStage *endStage(unsigned ItinClassIndx) const {
140 unsigned StageIdx = Itineraries[ItinClassIndx].LastStage;
141 return Stages + StageIdx;
144 /// \brief Return the total stage latency of the given class. The latency is
145 /// the maximum completion time for any stage in the itinerary. If no stages
146 /// exist, it defaults to one cycle.
147 unsigned getStageLatency(unsigned ItinClassIndx) const {
148 // If the target doesn't provide itinerary information, use a simple
149 // non-zero default value for all instructions.
153 // Calculate the maximum completion time for any stage.
154 unsigned Latency = 0, StartCycle = 0;
155 for (const InstrStage *IS = beginStage(ItinClassIndx),
156 *E = endStage(ItinClassIndx); IS != E; ++IS) {
157 Latency = std::max(Latency, StartCycle + IS->getCycles());
158 StartCycle += IS->getNextCycles();
163 /// \brief Return the cycle for the given class and operand. Return -1 if no
164 /// cycle is specified for the operand.
165 int getOperandCycle(unsigned ItinClassIndx, unsigned OperandIdx) const {
169 unsigned FirstIdx = Itineraries[ItinClassIndx].FirstOperandCycle;
170 unsigned LastIdx = Itineraries[ItinClassIndx].LastOperandCycle;
171 if ((FirstIdx + OperandIdx) >= LastIdx)
174 return (int)OperandCycles[FirstIdx + OperandIdx];
177 /// \brief Return true if there is a pipeline forwarding between instructions
178 /// of itinerary classes DefClass and UseClasses so that value produced by an
179 /// instruction of itinerary class DefClass, operand index DefIdx can be
180 /// bypassed when it's read by an instruction of itinerary class UseClass,
181 /// operand index UseIdx.
182 bool hasPipelineForwarding(unsigned DefClass, unsigned DefIdx,
183 unsigned UseClass, unsigned UseIdx) const {
184 unsigned FirstDefIdx = Itineraries[DefClass].FirstOperandCycle;
185 unsigned LastDefIdx = Itineraries[DefClass].LastOperandCycle;
186 if ((FirstDefIdx + DefIdx) >= LastDefIdx)
188 if (Forwardings[FirstDefIdx + DefIdx] == 0)
191 unsigned FirstUseIdx = Itineraries[UseClass].FirstOperandCycle;
192 unsigned LastUseIdx = Itineraries[UseClass].LastOperandCycle;
193 if ((FirstUseIdx + UseIdx) >= LastUseIdx)
196 return Forwardings[FirstDefIdx + DefIdx] ==
197 Forwardings[FirstUseIdx + UseIdx];
200 /// \brief Compute and return the use operand latency of a given itinerary
201 /// class and operand index if the value is produced by an instruction of the
202 /// specified itinerary class and def operand index.
203 int getOperandLatency(unsigned DefClass, unsigned DefIdx,
204 unsigned UseClass, unsigned UseIdx) const {
208 int DefCycle = getOperandCycle(DefClass, DefIdx);
212 int UseCycle = getOperandCycle(UseClass, UseIdx);
216 UseCycle = DefCycle - UseCycle + 1;
218 hasPipelineForwarding(DefClass, DefIdx, UseClass, UseIdx))
219 // FIXME: This assumes one cycle benefit for every pipeline forwarding.
224 /// \brief Return the number of micro-ops that the given class decodes to.
225 /// Return -1 for classes that require dynamic lookup via TargetInstrInfo.
226 int getNumMicroOps(unsigned ItinClassIndx) const {
229 return Itineraries[ItinClassIndx].NumMicroOps;
233 } // end namespace llvm
235 #endif // LLVM_MC_MCINSTRITINERARIES_H