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 /// consecuative 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 /// Returns the number of cycles the stage is occupied.
71 unsigned getCycles() const {
75 /// Returns the choice of FUs.
76 unsigned getUnits() const {
80 ReservationKinds getReservationKind() const {
84 /// 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_;
92 //===----------------------------------------------------------------------===//
93 /// An itinerary represents the scheduling information for an instruction.
94 /// This includes a set of stages occupied by the instruction and the pipeline
95 /// cycle in which operands are read and written.
97 struct InstrItinerary {
98 int NumMicroOps; ///< # of micro-ops, -1 means it's variable
99 unsigned FirstStage; ///< Index of first stage in itinerary
100 unsigned LastStage; ///< Index of last + 1 stage in itinerary
101 unsigned FirstOperandCycle; ///< Index of first operand rd/wr
102 unsigned LastOperandCycle; ///< Index of last + 1 operand rd/wr
106 //===----------------------------------------------------------------------===//
107 /// Itinerary data supplied by a subtarget to be used by a target.
109 class InstrItineraryData {
111 MCSchedModel SchedModel; ///< Basic machine properties.
112 const InstrStage *Stages; ///< Array of stages selected
113 const unsigned *OperandCycles; ///< Array of operand cycles selected
114 const unsigned *Forwardings; ///< Array of pipeline forwarding pathes
115 const InstrItinerary *Itineraries; ///< Array of itineraries selected
119 InstrItineraryData() : SchedModel(MCSchedModel::GetDefaultSchedModel()),
120 Stages(nullptr), OperandCycles(nullptr),
121 Forwardings(nullptr), Itineraries(nullptr) {}
123 InstrItineraryData(const MCSchedModel &SM, const InstrStage *S,
124 const unsigned *OS, const unsigned *F)
125 : SchedModel(SM), Stages(S), OperandCycles(OS), Forwardings(F),
126 Itineraries(SchedModel.InstrItineraries) {}
128 /// Returns true if there are no itineraries.
129 bool isEmpty() const { return Itineraries == nullptr; }
131 /// Returns true if the index is for the end marker itinerary.
132 bool isEndMarker(unsigned ItinClassIndx) const {
133 return ((Itineraries[ItinClassIndx].FirstStage == ~0U) &&
134 (Itineraries[ItinClassIndx].LastStage == ~0U));
137 /// Return the first stage of the itinerary.
138 const InstrStage *beginStage(unsigned ItinClassIndx) const {
139 unsigned StageIdx = Itineraries[ItinClassIndx].FirstStage;
140 return Stages + StageIdx;
143 /// Return the last+1 stage of the itinerary.
144 const InstrStage *endStage(unsigned ItinClassIndx) const {
145 unsigned StageIdx = Itineraries[ItinClassIndx].LastStage;
146 return Stages + StageIdx;
149 /// Return the total stage latency of the given class.
150 /// The latency is the maximum completion time for any stage in the itinerary.
151 /// If no stages exist, it defaults to one cycle.
152 unsigned getStageLatency(unsigned ItinClassIndx) const {
153 // If the target doesn't provide itinerary information, use a simple
154 // non-zero default value for all instructions.
158 // Calculate the maximum completion time for any stage.
159 unsigned Latency = 0, StartCycle = 0;
160 for (const InstrStage *IS = beginStage(ItinClassIndx),
161 *E = endStage(ItinClassIndx); IS != E; ++IS) {
162 Latency = std::max(Latency, StartCycle + IS->getCycles());
163 StartCycle += IS->getNextCycles();
168 /// Return the cycle for the given class and operand.
169 /// Return -1 if no cycle is specified for the operand.
170 int getOperandCycle(unsigned ItinClassIndx, unsigned OperandIdx) const {
174 unsigned FirstIdx = Itineraries[ItinClassIndx].FirstOperandCycle;
175 unsigned LastIdx = Itineraries[ItinClassIndx].LastOperandCycle;
176 if ((FirstIdx + OperandIdx) >= LastIdx)
179 return (int)OperandCycles[FirstIdx + OperandIdx];
182 /// Return true if there is a pipeline forwarding
183 /// between instructions of itinerary classes DefClass and UseClasses so that
184 /// value produced by an instruction of itinerary class DefClass, operand
185 /// index DefIdx can be bypassed when it's read by an instruction of
186 /// itinerary class UseClass, operand index UseIdx.
187 bool hasPipelineForwarding(unsigned DefClass, unsigned DefIdx,
188 unsigned UseClass, unsigned UseIdx) const {
189 unsigned FirstDefIdx = Itineraries[DefClass].FirstOperandCycle;
190 unsigned LastDefIdx = Itineraries[DefClass].LastOperandCycle;
191 if ((FirstDefIdx + DefIdx) >= LastDefIdx)
193 if (Forwardings[FirstDefIdx + DefIdx] == 0)
196 unsigned FirstUseIdx = Itineraries[UseClass].FirstOperandCycle;
197 unsigned LastUseIdx = Itineraries[UseClass].LastOperandCycle;
198 if ((FirstUseIdx + UseIdx) >= LastUseIdx)
201 return Forwardings[FirstDefIdx + DefIdx] ==
202 Forwardings[FirstUseIdx + UseIdx];
205 /// Compute and return the use operand latency of a given
206 /// itinerary class and operand index if the value is produced by an
207 /// instruction of the specified itinerary class and def operand index.
208 int getOperandLatency(unsigned DefClass, unsigned DefIdx,
209 unsigned UseClass, unsigned UseIdx) const {
213 int DefCycle = getOperandCycle(DefClass, DefIdx);
217 int UseCycle = getOperandCycle(UseClass, UseIdx);
221 UseCycle = DefCycle - UseCycle + 1;
223 hasPipelineForwarding(DefClass, DefIdx, UseClass, UseIdx))
224 // FIXME: This assumes one cycle benefit for every pipeline forwarding.
229 /// Return the number of micro-ops that the given class decodes to.
230 /// Return -1 for classes that require dynamic lookup via TargetInstrInfo.
231 int getNumMicroOps(unsigned ItinClassIndx) const {
234 return Itineraries[ItinClassIndx].NumMicroOps;
238 } // End llvm namespace