1 //===----- ExactHazardRecognizer.cpp - hazard recognizer -------- ---------===//
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 implements a a hazard recognizer using the instructions itineraries
11 // defined for the current target.
13 //===----------------------------------------------------------------------===//
15 #define DEBUG_TYPE "exact-hazards"
16 #include "ExactHazardRecognizer.h"
17 #include "llvm/CodeGen/ScheduleHazardRecognizer.h"
18 #include "llvm/Support/Debug.h"
19 #include "llvm/Support/ErrorHandling.h"
20 #include "llvm/Support/raw_ostream.h"
21 #include "llvm/Target/TargetInstrItineraries.h"
25 ExactHazardRecognizer::ExactHazardRecognizer(const InstrItineraryData &LItinData) :
26 ScheduleHazardRecognizer(), ItinData(LItinData)
28 // Determine the maximum depth of any itinerary. This determines the
29 // depth of the scoreboard. We always make the scoreboard at least 1
30 // cycle deep to avoid dealing with the boundary condition.
32 if (!ItinData.isEmpty()) {
33 for (unsigned idx = 0; ; ++idx) {
34 // If the begin stage of an itinerary has 0 cycles and units,
35 // then we have reached the end of the itineraries.
36 const InstrStage *IS = ItinData.beginStage(idx);
37 const InstrStage *E = ItinData.endStage(idx);
38 if ((IS->getCycles() == 0) && (IS->getUnits() == 0))
41 unsigned ItinDepth = 0;
43 ItinDepth += IS->getCycles();
45 ScoreboardDepth = std::max(ScoreboardDepth, ItinDepth);
49 Scoreboard = new unsigned[ScoreboardDepth];
52 DEBUG(errs() << "Using exact hazard recognizer: ScoreboardDepth = "
53 << ScoreboardDepth << '\n');
56 ExactHazardRecognizer::~ExactHazardRecognizer() {
60 void ExactHazardRecognizer::Reset() {
61 memset(Scoreboard, 0, ScoreboardDepth * sizeof(unsigned));
65 unsigned ExactHazardRecognizer::getFutureIndex(unsigned offset) {
66 return (ScoreboardHead + offset) % ScoreboardDepth;
69 void ExactHazardRecognizer::dumpScoreboard() {
70 errs() << "Scoreboard:\n";
72 unsigned last = ScoreboardDepth - 1;
73 while ((last > 0) && (Scoreboard[getFutureIndex(last)] == 0))
76 for (unsigned i = 0; i <= last; i++) {
77 unsigned FUs = Scoreboard[getFutureIndex(i)];
79 for (int j = 31; j >= 0; j--)
80 errs() << ((FUs & (1 << j)) ? '1' : '0');
85 ExactHazardRecognizer::HazardType ExactHazardRecognizer::getHazardType(SUnit *SU) {
88 // Use the itinerary for the underlying instruction to check for
89 // free FU's in the scoreboard at the appropriate future cycles.
90 unsigned idx = SU->getInstr()->getDesc().getSchedClass();
91 for (const InstrStage *IS = ItinData.beginStage(idx),
92 *E = ItinData.endStage(idx); IS != E; ++IS) {
93 // We must find one of the stage's units free for every cycle the
94 // stage is occupied. FIXME it would be more accurate to find the
95 // same unit free in all the cycles.
96 for (unsigned int i = 0; i < IS->getCycles(); ++i) {
97 assert(((cycle + i) < ScoreboardDepth) &&
98 "Scoreboard depth exceeded!");
100 unsigned index = getFutureIndex(cycle + i);
101 unsigned freeUnits = IS->getUnits() & ~Scoreboard[index];
103 DEBUG(errs() << "*** Hazard in cycle " << (cycle + i) << ", ");
104 DEBUG(errs() << "SU(" << SU->NodeNum << "): ");
105 DEBUG(SU->getInstr()->dump());
110 // Advance the cycle to the next stage.
111 cycle += IS->getNextCycles();
117 void ExactHazardRecognizer::EmitInstruction(SUnit *SU) {
120 // Use the itinerary for the underlying instruction to reserve FU's
121 // in the scoreboard at the appropriate future cycles.
122 unsigned idx = SU->getInstr()->getDesc().getSchedClass();
123 for (const InstrStage *IS = ItinData.beginStage(idx),
124 *E = ItinData.endStage(idx); IS != E; ++IS) {
125 // We must reserve one of the stage's units for every cycle the
126 // stage is occupied. FIXME it would be more accurate to reserve
127 // the same unit free in all the cycles.
128 for (unsigned int i = 0; i < IS->getCycles(); ++i) {
129 assert(((cycle + i) < ScoreboardDepth) &&
130 "Scoreboard depth exceeded!");
132 unsigned index = getFutureIndex(cycle + i);
133 unsigned freeUnits = IS->getUnits() & ~Scoreboard[index];
135 // reduce to a single unit
136 unsigned freeUnit = 0;
138 freeUnit = freeUnits;
139 freeUnits = freeUnit & (freeUnit - 1);
142 assert(freeUnit && "No function unit available!");
143 Scoreboard[index] |= freeUnit;
146 // Advance the cycle to the next stage.
147 cycle += IS->getNextCycles();
150 DEBUG(dumpScoreboard());
153 void ExactHazardRecognizer::AdvanceCycle() {
154 Scoreboard[ScoreboardHead] = 0;
155 ScoreboardHead = getFutureIndex(1);