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//===---- ScheduleDAG.cpp - Implement the ScheduleDAG class ---------------===//
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// The LLVM Compiler Infrastructure
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//===----------------------------------------------------------------------===//
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// This implements the ScheduleDAG class, which is a base class used by
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// scheduling implementation classes.
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "pre-RA-sched"
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#include "llvm/CodeGen/ScheduleDAG.h"
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#include "llvm/CodeGen/ScheduleHazardRecognizer.h"
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#include "llvm/Target/TargetMachine.h"
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#include "llvm/Target/TargetInstrInfo.h"
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#include "llvm/Target/TargetRegisterInfo.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/raw_ostream.h"
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ScheduleDAG::ScheduleDAG(MachineFunction &mf)
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TII(TM.getInstrInfo()),
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TRI(TM.getRegisterInfo()),
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MF(mf), MRI(mf.getRegInfo()),
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ScheduleDAG::~ScheduleDAG() {}
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/// dump - dump the schedule.
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void ScheduleDAG::dumpSchedule() const {
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for (unsigned i = 0, e = Sequence.size(); i != e; i++) {
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if (SUnit *SU = Sequence[i])
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dbgs() << "**** NOOP ****\n";
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/// Run - perform scheduling.
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void ScheduleDAG::Run(MachineBasicBlock *bb,
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MachineBasicBlock::iterator insertPos) {
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InsertPos = insertPos;
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dbgs() << "*** Final schedule ***\n";
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/// addPred - This adds the specified edge as a pred of the current node if
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/// not already. It also adds the current node as a successor of the
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void SUnit::addPred(const SDep &D) {
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// If this node already has this depenence, don't add a redundant one.
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for (SmallVector<SDep, 4>::const_iterator I = Preds.begin(), E = Preds.end();
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// Now add a corresponding succ to N.
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SUnit *N = D.getSUnit();
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// Update the bookkeeping.
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if (D.getKind() == SDep::Data) {
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assert(NumPreds < UINT_MAX && "NumPreds will overflow!");
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assert(N->NumSuccs < UINT_MAX && "NumSuccs will overflow!");
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if (!N->isScheduled) {
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assert(NumPredsLeft < UINT_MAX && "NumPredsLeft will overflow!");
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assert(N->NumSuccsLeft < UINT_MAX && "NumSuccsLeft will overflow!");
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N->Succs.push_back(P);
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if (P.getLatency() != 0) {
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this->setDepthDirty();
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/// removePred - This removes the specified edge as a pred of the current
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/// node if it exists. It also removes the current node as a successor of
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/// the specified node.
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void SUnit::removePred(const SDep &D) {
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// Find the matching predecessor.
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for (SmallVector<SDep, 4>::iterator I = Preds.begin(), E = Preds.end();
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bool FoundSucc = false;
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// Find the corresponding successor in N.
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SUnit *N = D.getSUnit();
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for (SmallVector<SDep, 4>::iterator II = N->Succs.begin(),
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EE = N->Succs.end(); II != EE; ++II)
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assert(FoundSucc && "Mismatching preds / succs lists!");
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// Update the bookkeeping.
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if (P.getKind() == SDep::Data) {
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assert(NumPreds > 0 && "NumPreds will underflow!");
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assert(N->NumSuccs > 0 && "NumSuccs will underflow!");
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if (!N->isScheduled) {
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assert(NumPredsLeft > 0 && "NumPredsLeft will underflow!");
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assert(N->NumSuccsLeft > 0 && "NumSuccsLeft will underflow!");
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if (P.getLatency() != 0) {
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this->setDepthDirty();
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void SUnit::setDepthDirty() {
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if (!isDepthCurrent) return;
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SmallVector<SUnit*, 8> WorkList;
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WorkList.push_back(this);
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SUnit *SU = WorkList.pop_back_val();
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SU->isDepthCurrent = false;
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for (SUnit::const_succ_iterator I = SU->Succs.begin(),
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E = SU->Succs.end(); I != E; ++I) {
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SUnit *SuccSU = I->getSUnit();
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if (SuccSU->isDepthCurrent)
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WorkList.push_back(SuccSU);
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} while (!WorkList.empty());
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void SUnit::setHeightDirty() {
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if (!isHeightCurrent) return;
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SmallVector<SUnit*, 8> WorkList;
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WorkList.push_back(this);
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SUnit *SU = WorkList.pop_back_val();
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SU->isHeightCurrent = false;
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for (SUnit::const_pred_iterator I = SU->Preds.begin(),
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E = SU->Preds.end(); I != E; ++I) {
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SUnit *PredSU = I->getSUnit();
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if (PredSU->isHeightCurrent)
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WorkList.push_back(PredSU);
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} while (!WorkList.empty());
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/// setDepthToAtLeast - Update this node's successors to reflect the
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/// fact that this node's depth just increased.
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void SUnit::setDepthToAtLeast(unsigned NewDepth) {
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if (NewDepth <= getDepth())
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isDepthCurrent = true;
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/// setHeightToAtLeast - Update this node's predecessors to reflect the
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/// fact that this node's height just increased.
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void SUnit::setHeightToAtLeast(unsigned NewHeight) {
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if (NewHeight <= getHeight())
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isHeightCurrent = true;
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/// ComputeDepth - Calculate the maximal path from the node to the exit.
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void SUnit::ComputeDepth() {
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SmallVector<SUnit*, 8> WorkList;
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WorkList.push_back(this);
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SUnit *Cur = WorkList.back();
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unsigned MaxPredDepth = 0;
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for (SUnit::const_pred_iterator I = Cur->Preds.begin(),
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E = Cur->Preds.end(); I != E; ++I) {
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SUnit *PredSU = I->getSUnit();
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if (PredSU->isDepthCurrent)
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MaxPredDepth = std::max(MaxPredDepth,
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PredSU->Depth + I->getLatency());
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WorkList.push_back(PredSU);
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if (MaxPredDepth != Cur->Depth) {
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Cur->setDepthDirty();
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Cur->Depth = MaxPredDepth;
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Cur->isDepthCurrent = true;
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} while (!WorkList.empty());
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/// ComputeHeight - Calculate the maximal path from the node to the entry.
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void SUnit::ComputeHeight() {
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SmallVector<SUnit*, 8> WorkList;
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WorkList.push_back(this);
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SUnit *Cur = WorkList.back();
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unsigned MaxSuccHeight = 0;
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for (SUnit::const_succ_iterator I = Cur->Succs.begin(),
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E = Cur->Succs.end(); I != E; ++I) {
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SUnit *SuccSU = I->getSUnit();
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if (SuccSU->isHeightCurrent)
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MaxSuccHeight = std::max(MaxSuccHeight,
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SuccSU->Height + I->getLatency());
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WorkList.push_back(SuccSU);
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if (MaxSuccHeight != Cur->Height) {
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Cur->setHeightDirty();
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Cur->Height = MaxSuccHeight;
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Cur->isHeightCurrent = true;
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} while (!WorkList.empty());
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/// SUnit - Scheduling unit. It's an wrapper around either a single SDNode or
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/// a group of nodes flagged together.
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void SUnit::dump(const ScheduleDAG *G) const {
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dbgs() << "SU(" << NodeNum << "): ";
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void SUnit::dumpAll(const ScheduleDAG *G) const {
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dbgs() << " # preds left : " << NumPredsLeft << "\n";
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dbgs() << " # succs left : " << NumSuccsLeft << "\n";
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dbgs() << " Latency : " << Latency << "\n";
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dbgs() << " Depth : " << Depth << "\n";
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dbgs() << " Height : " << Height << "\n";
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if (Preds.size() != 0) {
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dbgs() << " Predecessors:\n";
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for (SUnit::const_succ_iterator I = Preds.begin(), E = Preds.end();
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switch (I->getKind()) {
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case SDep::Data: dbgs() << "val "; break;
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case SDep::Anti: dbgs() << "anti"; break;
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case SDep::Output: dbgs() << "out "; break;
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case SDep::Order: dbgs() << "ch "; break;
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dbgs() << I->getSUnit() << " - SU(" << I->getSUnit()->NodeNum << ")";
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if (I->isArtificial())
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dbgs() << ": Latency=" << I->getLatency();
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if (Succs.size() != 0) {
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dbgs() << " Successors:\n";
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for (SUnit::const_succ_iterator I = Succs.begin(), E = Succs.end();
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switch (I->getKind()) {
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case SDep::Data: dbgs() << "val "; break;
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case SDep::Anti: dbgs() << "anti"; break;
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case SDep::Output: dbgs() << "out "; break;
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case SDep::Order: dbgs() << "ch "; break;
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dbgs() << I->getSUnit() << " - SU(" << I->getSUnit()->NodeNum << ")";
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if (I->isArtificial())
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dbgs() << ": Latency=" << I->getLatency();
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/// VerifySchedule - Verify that all SUnits were scheduled and that
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/// their state is consistent.
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void ScheduleDAG::VerifySchedule(bool isBottomUp) {
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bool AnyNotSched = false;
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unsigned DeadNodes = 0;
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for (unsigned i = 0, e = SUnits.size(); i != e; ++i) {
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if (!SUnits[i].isScheduled) {
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if (SUnits[i].NumPreds == 0 && SUnits[i].NumSuccs == 0) {
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dbgs() << "*** Scheduling failed! ***\n";
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SUnits[i].dump(this);
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dbgs() << "has not been scheduled!\n";
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if (SUnits[i].isScheduled &&
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(isBottomUp ? SUnits[i].getHeight() : SUnits[i].getDepth()) >
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dbgs() << "*** Scheduling failed! ***\n";
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SUnits[i].dump(this);
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dbgs() << "has an unexpected "
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<< (isBottomUp ? "Height" : "Depth") << " value!\n";
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if (SUnits[i].NumSuccsLeft != 0) {
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dbgs() << "*** Scheduling failed! ***\n";
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SUnits[i].dump(this);
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dbgs() << "has successors left!\n";
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if (SUnits[i].NumPredsLeft != 0) {
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dbgs() << "*** Scheduling failed! ***\n";
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SUnits[i].dump(this);
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dbgs() << "has predecessors left!\n";
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for (unsigned i = 0, e = Sequence.size(); i != e; ++i)
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assert(!AnyNotSched);
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assert(Sequence.size() + DeadNodes - Noops == SUnits.size() &&
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"The number of nodes scheduled doesn't match the expected number!");
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/// InitDAGTopologicalSorting - create the initial topological
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/// ordering from the DAG to be scheduled.
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/// The idea of the algorithm is taken from
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/// "Online algorithms for managing the topological order of
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/// a directed acyclic graph" by David J. Pearce and Paul H.J. Kelly
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/// This is the MNR algorithm, which was first introduced by
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/// A. Marchetti-Spaccamela, U. Nanni and H. Rohnert in
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/// "Maintaining a topological order under edge insertions".
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/// Short description of the algorithm:
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/// Topological ordering, ord, of a DAG maps each node to a topological
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/// index so that for all edges X->Y it is the case that ord(X) < ord(Y).
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/// This means that if there is a path from the node X to the node Z,
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/// then ord(X) < ord(Z).
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/// This property can be used to check for reachability of nodes:
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/// if Z is reachable from X, then an insertion of the edge Z->X would
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/// The algorithm first computes a topological ordering for the DAG by
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/// initializing the Index2Node and Node2Index arrays and then tries to keep
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/// the ordering up-to-date after edge insertions by reordering the DAG.
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/// On insertion of the edge X->Y, the algorithm first marks by calling DFS
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/// the nodes reachable from Y, and then shifts them using Shift to lie
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/// immediately after X in Index2Node.
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void ScheduleDAGTopologicalSort::InitDAGTopologicalSorting() {
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unsigned DAGSize = SUnits.size();
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std::vector<SUnit*> WorkList;
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WorkList.reserve(DAGSize);
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Index2Node.resize(DAGSize);
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Node2Index.resize(DAGSize);
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// Initialize the data structures.
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for (unsigned i = 0, e = DAGSize; i != e; ++i) {
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SUnit *SU = &SUnits[i];
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int NodeNum = SU->NodeNum;
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unsigned Degree = SU->Succs.size();
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// Temporarily use the Node2Index array as scratch space for degree counts.
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Node2Index[NodeNum] = Degree;
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// Is it a node without dependencies?
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assert(SU->Succs.empty() && "SUnit should have no successors");
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// Collect leaf nodes.
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WorkList.push_back(SU);
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while (!WorkList.empty()) {
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SUnit *SU = WorkList.back();
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Allocate(SU->NodeNum, --Id);
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for (SUnit::const_pred_iterator I = SU->Preds.begin(), E = SU->Preds.end();
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SUnit *SU = I->getSUnit();
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if (!--Node2Index[SU->NodeNum])
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// If all dependencies of the node are processed already,
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// then the node can be computed now.
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WorkList.push_back(SU);
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Visited.resize(DAGSize);
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// Check correctness of the ordering
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for (unsigned i = 0, e = DAGSize; i != e; ++i) {
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SUnit *SU = &SUnits[i];
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for (SUnit::const_pred_iterator I = SU->Preds.begin(), E = SU->Preds.end();
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assert(Node2Index[SU->NodeNum] > Node2Index[I->getSUnit()->NodeNum] &&
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"Wrong topological sorting");
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/// AddPred - Updates the topological ordering to accomodate an edge
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/// to be added from SUnit X to SUnit Y.
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void ScheduleDAGTopologicalSort::AddPred(SUnit *Y, SUnit *X) {
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int UpperBound, LowerBound;
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LowerBound = Node2Index[Y->NodeNum];
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UpperBound = Node2Index[X->NodeNum];
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bool HasLoop = false;
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// Is Ord(X) < Ord(Y) ?
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if (LowerBound < UpperBound) {
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// Update the topological order.
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DFS(Y, UpperBound, HasLoop);
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assert(!HasLoop && "Inserted edge creates a loop!");
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// Recompute topological indexes.
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Shift(Visited, LowerBound, UpperBound);
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/// RemovePred - Updates the topological ordering to accomodate an
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/// an edge to be removed from the specified node N from the predecessors
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/// of the current node M.
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void ScheduleDAGTopologicalSort::RemovePred(SUnit *M, SUnit *N) {
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// InitDAGTopologicalSorting();
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/// DFS - Make a DFS traversal to mark all nodes reachable from SU and mark
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/// all nodes affected by the edge insertion. These nodes will later get new
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/// topological indexes by means of the Shift method.
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void ScheduleDAGTopologicalSort::DFS(const SUnit *SU, int UpperBound,
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std::vector<const SUnit*> WorkList;
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WorkList.reserve(SUnits.size());
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WorkList.push_back(SU);
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SU = WorkList.back();
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Visited.set(SU->NodeNum);
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for (int I = SU->Succs.size()-1; I >= 0; --I) {
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int s = SU->Succs[I].getSUnit()->NodeNum;
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if (Node2Index[s] == UpperBound) {
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// Visit successors if not already and in affected region.
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if (!Visited.test(s) && Node2Index[s] < UpperBound) {
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WorkList.push_back(SU->Succs[I].getSUnit());
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} while (!WorkList.empty());
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/// Shift - Renumber the nodes so that the topological ordering is
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void ScheduleDAGTopologicalSort::Shift(BitVector& Visited, int LowerBound,
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for (i = LowerBound; i <= UpperBound; ++i) {
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// w is node at topological index i.
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int w = Index2Node[i];
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if (Visited.test(w)) {
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Allocate(w, i - shift);
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for (unsigned j = 0; j < L.size(); ++j) {
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Allocate(L[j], i - shift);
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/// WillCreateCycle - Returns true if adding an edge from SU to TargetSU will
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bool ScheduleDAGTopologicalSort::WillCreateCycle(SUnit *SU, SUnit *TargetSU) {
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if (IsReachable(TargetSU, SU))
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for (SUnit::pred_iterator I = SU->Preds.begin(), E = SU->Preds.end();
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if (I->isAssignedRegDep() &&
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IsReachable(TargetSU, I->getSUnit()))
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/// IsReachable - Checks if SU is reachable from TargetSU.
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bool ScheduleDAGTopologicalSort::IsReachable(const SUnit *SU,
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const SUnit *TargetSU) {
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// If insertion of the edge SU->TargetSU would create a cycle
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// then there is a path from TargetSU to SU.
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int UpperBound, LowerBound;
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LowerBound = Node2Index[TargetSU->NodeNum];
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UpperBound = Node2Index[SU->NodeNum];
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bool HasLoop = false;
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// Is Ord(TargetSU) < Ord(SU) ?
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if (LowerBound < UpperBound) {
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// There may be a path from TargetSU to SU. Check for it.
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DFS(TargetSU, UpperBound, HasLoop);
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/// Allocate - assign the topological index to the node n.
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void ScheduleDAGTopologicalSort::Allocate(int n, int index) {
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Node2Index[n] = index;
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Index2Node[index] = n;
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ScheduleDAGTopologicalSort::
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ScheduleDAGTopologicalSort(std::vector<SUnit> &sunits) : SUnits(sunits) {}
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ScheduleHazardRecognizer::~ScheduleHazardRecognizer() {}
added
removed
libclamav/c++/llvm/lib/CodeGen/ScheduleDAG.cpp
