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//===----- ExactHazardRecognizer.cpp - hazard recognizer -------- ---------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This implements a a hazard recognizer using the instructions itineraries
// defined for the current target.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "exact-hazards"
#include "ExactHazardRecognizer.h"
#include "llvm/CodeGen/ScheduleHazardRecognizer.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetInstrItineraries.h"
using namespace llvm;
ExactHazardRecognizer::ExactHazardRecognizer(const InstrItineraryData &LItinData) :
ScheduleHazardRecognizer(), ItinData(LItinData)
{
// Determine the maximum depth of any itinerary. This determines the
// depth of the scoreboard. We always make the scoreboard at least 1
// cycle deep to avoid dealing with the boundary condition.
ScoreboardDepth = 1;
if (!ItinData.isEmpty()) {
for (unsigned idx = 0; ; ++idx) {
if (ItinData.isEndMarker(idx))
break;
const InstrStage *IS = ItinData.beginStage(idx);
const InstrStage *E = ItinData.endStage(idx);
unsigned ItinDepth = 0;
for (; IS != E; ++IS)
ItinDepth += IS->getCycles();
ScoreboardDepth = std::max(ScoreboardDepth, ItinDepth);
}
}
Scoreboard = new unsigned[ScoreboardDepth];
ScoreboardHead = 0;
DEBUG(errs() << "Using exact hazard recognizer: ScoreboardDepth = "
<< ScoreboardDepth << '\n');
}
ExactHazardRecognizer::~ExactHazardRecognizer() {
delete [] Scoreboard;
}
void ExactHazardRecognizer::Reset() {
memset(Scoreboard, 0, ScoreboardDepth * sizeof(unsigned));
ScoreboardHead = 0;
}
unsigned ExactHazardRecognizer::getFutureIndex(unsigned offset) {
return (ScoreboardHead + offset) % ScoreboardDepth;
}
void ExactHazardRecognizer::dumpScoreboard() {
errs() << "Scoreboard:\n";
unsigned last = ScoreboardDepth - 1;
while ((last > 0) && (Scoreboard[getFutureIndex(last)] == 0))
last--;
for (unsigned i = 0; i <= last; i++) {
unsigned FUs = Scoreboard[getFutureIndex(i)];
errs() << "\t";
for (int j = 31; j >= 0; j--)
errs() << ((FUs & (1 << j)) ? '1' : '0');
errs() << '\n';
}
}
ExactHazardRecognizer::HazardType ExactHazardRecognizer::getHazardType(SUnit *SU) {
if (ItinData.isEmpty())
return NoHazard;
unsigned cycle = 0;
// Use the itinerary for the underlying instruction to check for
// free FU's in the scoreboard at the appropriate future cycles.
unsigned idx = SU->getInstr()->getDesc().getSchedClass();
for (const InstrStage *IS = ItinData.beginStage(idx),
*E = ItinData.endStage(idx); IS != E; ++IS) {
// We must find one of the stage's units free for every cycle the
// stage is occupied. FIXME it would be more accurate to find the
// same unit free in all the cycles.
for (unsigned int i = 0; i < IS->getCycles(); ++i) {
assert(((cycle + i) < ScoreboardDepth) &&
"Scoreboard depth exceeded!");
unsigned index = getFutureIndex(cycle + i);
unsigned freeUnits = IS->getUnits() & ~Scoreboard[index];
if (!freeUnits) {
DEBUG(errs() << "*** Hazard in cycle " << (cycle + i) << ", ");
DEBUG(errs() << "SU(" << SU->NodeNum << "): ");
DEBUG(SU->getInstr()->dump());
return Hazard;
}
}
// Advance the cycle to the next stage.
cycle += IS->getNextCycles();
}
return NoHazard;
}
void ExactHazardRecognizer::EmitInstruction(SUnit *SU) {
if (ItinData.isEmpty())
return;
unsigned cycle = 0;
// Use the itinerary for the underlying instruction to reserve FU's
// in the scoreboard at the appropriate future cycles.
unsigned idx = SU->getInstr()->getDesc().getSchedClass();
for (const InstrStage *IS = ItinData.beginStage(idx),
*E = ItinData.endStage(idx); IS != E; ++IS) {
// We must reserve one of the stage's units for every cycle the
// stage is occupied. FIXME it would be more accurate to reserve
// the same unit free in all the cycles.
for (unsigned int i = 0; i < IS->getCycles(); ++i) {
assert(((cycle + i) < ScoreboardDepth) &&
"Scoreboard depth exceeded!");
unsigned index = getFutureIndex(cycle + i);
unsigned freeUnits = IS->getUnits() & ~Scoreboard[index];
// reduce to a single unit
unsigned freeUnit = 0;
do {
freeUnit = freeUnits;
freeUnits = freeUnit & (freeUnit - 1);
} while (freeUnits);
assert(freeUnit && "No function unit available!");
Scoreboard[index] |= freeUnit;
}
// Advance the cycle to the next stage.
cycle += IS->getNextCycles();
}
DEBUG(dumpScoreboard());
}
void ExactHazardRecognizer::AdvanceCycle() {
Scoreboard[ScoreboardHead] = 0;
ScoreboardHead = getFutureIndex(1);
}
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