1 //===----- ScoreboardHazardRecognizer.cpp - Scheduler Support -------------===//
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 implements the ScoreboardHazardRecognizer class, which
11 // encapsultes hazard-avoidance heuristics for scheduling, based on the
12 // scheduling itineraries specified for the target.
14 //===----------------------------------------------------------------------===//
16 #define DEBUG_TYPE ::llvm::ScoreboardHazardRecognizer::DebugType
17 #include "llvm/CodeGen/ScoreboardHazardRecognizer.h"
18 #include "llvm/CodeGen/ScheduleDAG.h"
19 #include "llvm/Support/Debug.h"
20 #include "llvm/Support/ErrorHandling.h"
21 #include "llvm/Support/raw_ostream.h"
22 #include "llvm/Target/TargetInstrInfo.h"
23 #include "llvm/Target/TargetInstrItineraries.h"
28 const char *ScoreboardHazardRecognizer::DebugType = "";
31 ScoreboardHazardRecognizer::
32 ScoreboardHazardRecognizer(const InstrItineraryData *II,
33 const ScheduleDAG *SchedDAG,
34 const char *ParentDebugType) :
35 ScheduleHazardRecognizer(), ItinData(II), DAG(SchedDAG), IssueWidth(0),
39 DebugType = ParentDebugType;
42 // Determine the maximum depth of any itinerary. This determines the
43 // depth of the scoreboard. We always make the scoreboard at least 1
44 // cycle deep to avoid dealing with the boundary condition.
45 unsigned ScoreboardDepth = 1;
46 if (ItinData && !ItinData->isEmpty()) {
47 IssueWidth = ItinData->IssueWidth;
49 for (unsigned idx = 0; ; ++idx) {
50 if (ItinData->isEndMarker(idx))
53 const InstrStage *IS = ItinData->beginStage(idx);
54 const InstrStage *E = ItinData->endStage(idx);
55 unsigned CurCycle = 0;
56 unsigned ItinDepth = 0;
57 for (; IS != E; ++IS) {
58 unsigned StageDepth = CurCycle + IS->getCycles();
59 if (ItinDepth < StageDepth) ItinDepth = StageDepth;
60 CurCycle += IS->getNextCycles();
63 // Find the next power-of-2 >= ItinDepth
64 while (ItinDepth > ScoreboardDepth) {
68 MaxLookAhead = ScoreboardDepth;
71 ReservedScoreboard.reset(ScoreboardDepth);
72 RequiredScoreboard.reset(ScoreboardDepth);
74 DEBUG(dbgs() << "Using scoreboard hazard recognizer: Depth = "
75 << ScoreboardDepth << '\n');
78 void ScoreboardHazardRecognizer::Reset() {
80 RequiredScoreboard.reset();
81 ReservedScoreboard.reset();
84 void ScoreboardHazardRecognizer::Scoreboard::dump() const {
85 dbgs() << "Scoreboard:\n";
87 unsigned last = Depth - 1;
88 while ((last > 0) && ((*this)[last] == 0))
91 for (unsigned i = 0; i <= last; i++) {
92 unsigned FUs = (*this)[i];
94 for (int j = 31; j >= 0; j--)
95 dbgs() << ((FUs & (1 << j)) ? '1' : '0');
100 bool ScoreboardHazardRecognizer::atIssueLimit() const {
104 return IssueCount == IssueWidth;
107 ScheduleHazardRecognizer::HazardType
108 ScoreboardHazardRecognizer::getHazardType(SUnit *SU, int Stalls) {
109 if (!ItinData || ItinData->isEmpty())
112 // Note that stalls will be negative for bottom-up scheduling.
115 // Use the itinerary for the underlying instruction to check for
116 // free FU's in the scoreboard at the appropriate future cycles.
118 const TargetInstrDesc *TID = DAG->getInstrDesc(SU);
120 // Don't check hazards for non-machineinstr Nodes.
123 unsigned idx = TID->getSchedClass();
124 for (const InstrStage *IS = ItinData->beginStage(idx),
125 *E = ItinData->endStage(idx); IS != E; ++IS) {
126 // We must find one of the stage's units free for every cycle the
127 // stage is occupied. FIXME it would be more accurate to find the
128 // same unit free in all the cycles.
129 for (unsigned int i = 0; i < IS->getCycles(); ++i) {
130 int StageCycle = cycle + (int)i;
134 if (StageCycle >= (int)RequiredScoreboard.getDepth()) {
135 assert((StageCycle - Stalls) < (int)RequiredScoreboard.getDepth() &&
136 "Scoreboard depth exceeded!");
137 // This stage was stalled beyond pipeline depth, so cannot conflict.
141 unsigned freeUnits = IS->getUnits();
142 switch (IS->getReservationKind()) {
144 assert(0 && "Invalid FU reservation");
145 case InstrStage::Required:
146 // Required FUs conflict with both reserved and required ones
147 freeUnits &= ~ReservedScoreboard[StageCycle];
149 case InstrStage::Reserved:
150 // Reserved FUs can conflict only with required ones.
151 freeUnits &= ~RequiredScoreboard[StageCycle];
156 DEBUG(dbgs() << "*** Hazard in cycle " << (cycle + i) << ", ");
157 DEBUG(dbgs() << "SU(" << SU->NodeNum << "): ");
158 DEBUG(DAG->dumpNode(SU));
163 // Advance the cycle to the next stage.
164 cycle += IS->getNextCycles();
170 void ScoreboardHazardRecognizer::EmitInstruction(SUnit *SU) {
171 if (!ItinData || ItinData->isEmpty())
174 // Use the itinerary for the underlying instruction to reserve FU's
175 // in the scoreboard at the appropriate future cycles.
176 const TargetInstrDesc *TID = DAG->getInstrDesc(SU);
177 assert(TID && "The scheduler must filter non-machineinstrs");
178 if (DAG->TII->isZeroCost(TID->Opcode))
185 unsigned idx = TID->getSchedClass();
186 for (const InstrStage *IS = ItinData->beginStage(idx),
187 *E = ItinData->endStage(idx); IS != E; ++IS) {
188 // We must reserve one of the stage's units for every cycle the
189 // stage is occupied. FIXME it would be more accurate to reserve
190 // the same unit free in all the cycles.
191 for (unsigned int i = 0; i < IS->getCycles(); ++i) {
192 assert(((cycle + i) < RequiredScoreboard.getDepth()) &&
193 "Scoreboard depth exceeded!");
195 unsigned freeUnits = IS->getUnits();
196 switch (IS->getReservationKind()) {
198 assert(0 && "Invalid FU reservation");
199 case InstrStage::Required:
200 // Required FUs conflict with both reserved and required ones
201 freeUnits &= ~ReservedScoreboard[cycle + i];
203 case InstrStage::Reserved:
204 // Reserved FUs can conflict only with required ones.
205 freeUnits &= ~RequiredScoreboard[cycle + i];
209 // reduce to a single unit
210 unsigned freeUnit = 0;
212 freeUnit = freeUnits;
213 freeUnits = freeUnit & (freeUnit - 1);
216 assert(freeUnit && "No function unit available!");
217 if (IS->getReservationKind() == InstrStage::Required)
218 RequiredScoreboard[cycle + i] |= freeUnit;
220 ReservedScoreboard[cycle + i] |= freeUnit;
223 // Advance the cycle to the next stage.
224 cycle += IS->getNextCycles();
227 DEBUG(ReservedScoreboard.dump());
228 DEBUG(RequiredScoreboard.dump());
231 void ScoreboardHazardRecognizer::AdvanceCycle() {
233 ReservedScoreboard[0] = 0; ReservedScoreboard.advance();
234 RequiredScoreboard[0] = 0; RequiredScoreboard.advance();
237 void ScoreboardHazardRecognizer::RecedeCycle() {
239 ReservedScoreboard[ReservedScoreboard.getDepth()-1] = 0;
240 ReservedScoreboard.recede();
241 RequiredScoreboard[RequiredScoreboard.getDepth()-1] = 0;
242 RequiredScoreboard.recede();