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.begin(idx), *E = ItinData.end(idx);
37 if ((IS->getCycles() == 0) && (IS->getUnits() == 0))
40 unsigned ItinDepth = 0;
42 ItinDepth += IS->getCycles();
44 ScoreboardDepth = std::max(ScoreboardDepth, ItinDepth);
48 Scoreboard = new unsigned[ScoreboardDepth];
51 DEBUG(errs() << "Using exact hazard recognizer: ScoreboardDepth = "
52 << ScoreboardDepth << '\n');
55 ExactHazardRecognizer::~ExactHazardRecognizer() {
59 void ExactHazardRecognizer::Reset() {
60 memset(Scoreboard, 0, ScoreboardDepth * sizeof(unsigned));
64 unsigned ExactHazardRecognizer::getFutureIndex(unsigned offset) {
65 return (ScoreboardHead + offset) % ScoreboardDepth;
68 void ExactHazardRecognizer::dumpScoreboard() {
69 errs() << "Scoreboard:\n";
71 unsigned last = ScoreboardDepth - 1;
72 while ((last > 0) && (Scoreboard[getFutureIndex(last)] == 0))
75 for (unsigned i = 0; i <= last; i++) {
76 unsigned FUs = Scoreboard[getFutureIndex(i)];
78 for (int j = 31; j >= 0; j--)
79 errs() << ((FUs & (1 << j)) ? '1' : '0');
84 ExactHazardRecognizer::HazardType ExactHazardRecognizer::getHazardType(SUnit *SU) {
87 // Use the itinerary for the underlying instruction to check for
88 // free FU's in the scoreboard at the appropriate future cycles.
89 unsigned idx = SU->getInstr()->getDesc().getSchedClass();
90 for (const InstrStage *IS = ItinData.begin(idx), *E = ItinData.end(idx);
92 // We must find one of the stage's units free for every cycle the
93 // stage is occupied. FIXME it would be more accurate to find the
94 // same unit free in all the cycles.
95 for (unsigned int i = 0; i < IS->getCycles(); ++i) {
96 assert(((cycle + i) < ScoreboardDepth) &&
97 "Scoreboard depth exceeded!");
99 unsigned index = getFutureIndex(cycle + i);
100 unsigned freeUnits = IS->getUnits() & ~Scoreboard[index];
102 DEBUG(errs() << "*** Hazard in cycle " << (cycle + i) << ", ");
103 DEBUG(errs() << "SU(" << SU->NodeNum << "): ");
104 DEBUG(SU->getInstr()->dump());
109 // Advance the cycle to the next stage.
110 cycle += IS->getNextCycles();
116 void ExactHazardRecognizer::EmitInstruction(SUnit *SU) {
119 // Use the itinerary for the underlying instruction to reserve FU's
120 // in the scoreboard at the appropriate future cycles.
121 unsigned idx = SU->getInstr()->getDesc().getSchedClass();
122 for (const InstrStage *IS = ItinData.begin(idx), *E = ItinData.end(idx);
124 // We must reserve one of the stage's units for every cycle the
125 // stage is occupied. FIXME it would be more accurate to reserve
126 // the same unit free in all the cycles.
127 for (unsigned int i = 0; i < IS->getCycles(); ++i) {
128 assert(((cycle + i) < ScoreboardDepth) &&
129 "Scoreboard depth exceeded!");
131 unsigned index = getFutureIndex(cycle + i);
132 unsigned freeUnits = IS->getUnits() & ~Scoreboard[index];
134 // reduce to a single unit
135 unsigned freeUnit = 0;
137 freeUnit = freeUnits;
138 freeUnits = freeUnit & (freeUnit - 1);
141 assert(freeUnit && "No function unit available!");
142 Scoreboard[index] |= freeUnit;
145 // Advance the cycle to the next stage.
146 cycle += IS->getNextCycles();
149 DEBUG(dumpScoreboard());
152 void ExactHazardRecognizer::AdvanceCycle() {
153 Scoreboard[ScoreboardHead] = 0;
154 ScoreboardHead = getFutureIndex(1);
157 } /* namespace llvm */