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/MC/MCInstrItineraries.h"
20 #include "llvm/Support/Debug.h"
21 #include "llvm/Support/ErrorHandling.h"
22 #include "llvm/Support/raw_ostream.h"
23 #include "llvm/Target/TargetInstrInfo.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 MCInstrDesc *MCID = DAG->getInstrDesc(SU);
120 // Don't check hazards for non-machineinstr Nodes.
123 unsigned idx = MCID->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()) {
143 case InstrStage::Required:
144 // Required FUs conflict with both reserved and required ones
145 freeUnits &= ~ReservedScoreboard[StageCycle];
147 case InstrStage::Reserved:
148 // Reserved FUs can conflict only with required ones.
149 freeUnits &= ~RequiredScoreboard[StageCycle];
154 DEBUG(dbgs() << "*** Hazard in cycle +" << StageCycle << ", ");
155 DEBUG(dbgs() << "SU(" << SU->NodeNum << "): ");
156 DEBUG(DAG->dumpNode(SU));
161 // Advance the cycle to the next stage.
162 cycle += IS->getNextCycles();
168 void ScoreboardHazardRecognizer::EmitInstruction(SUnit *SU) {
169 if (!ItinData || ItinData->isEmpty())
172 // Use the itinerary for the underlying instruction to reserve FU's
173 // in the scoreboard at the appropriate future cycles.
174 const MCInstrDesc *MCID = DAG->getInstrDesc(SU);
175 assert(MCID && "The scheduler must filter non-machineinstrs");
176 if (DAG->TII->isZeroCost(MCID->Opcode))
183 unsigned idx = MCID->getSchedClass();
184 for (const InstrStage *IS = ItinData->beginStage(idx),
185 *E = ItinData->endStage(idx); IS != E; ++IS) {
186 // We must reserve one of the stage's units for every cycle the
187 // stage is occupied. FIXME it would be more accurate to reserve
188 // the same unit free in all the cycles.
189 for (unsigned int i = 0; i < IS->getCycles(); ++i) {
190 assert(((cycle + i) < RequiredScoreboard.getDepth()) &&
191 "Scoreboard depth exceeded!");
193 unsigned freeUnits = IS->getUnits();
194 switch (IS->getReservationKind()) {
195 case InstrStage::Required:
196 // Required FUs conflict with both reserved and required ones
197 freeUnits &= ~ReservedScoreboard[cycle + i];
199 case InstrStage::Reserved:
200 // Reserved FUs can conflict only with required ones.
201 freeUnits &= ~RequiredScoreboard[cycle + i];
205 // reduce to a single unit
206 unsigned freeUnit = 0;
208 freeUnit = freeUnits;
209 freeUnits = freeUnit & (freeUnit - 1);
212 if (IS->getReservationKind() == InstrStage::Required)
213 RequiredScoreboard[cycle + i] |= freeUnit;
215 ReservedScoreboard[cycle + i] |= freeUnit;
218 // Advance the cycle to the next stage.
219 cycle += IS->getNextCycles();
222 DEBUG(ReservedScoreboard.dump());
223 DEBUG(RequiredScoreboard.dump());
226 void ScoreboardHazardRecognizer::AdvanceCycle() {
228 ReservedScoreboard[0] = 0; ReservedScoreboard.advance();
229 RequiredScoreboard[0] = 0; RequiredScoreboard.advance();
232 void ScoreboardHazardRecognizer::RecedeCycle() {
234 ReservedScoreboard[ReservedScoreboard.getDepth()-1] = 0;
235 ReservedScoreboard.recede();
236 RequiredScoreboard[RequiredScoreboard.getDepth()-1] = 0;
237 RequiredScoreboard.recede();