//===---- ScheduleDAG.cpp - Implement the ScheduleDAG class ---------------===// // // The LLVM Compiler Infrastructure // // This file is distributed under the University of Illinois Open Source // License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // // This implements the ScheduleDAG class, which is a base class used by // scheduling implementation classes. // //===----------------------------------------------------------------------===// #define DEBUG_TYPE "pre-RA-sched" #include "llvm/CodeGen/ScheduleDAG.h" #include "llvm/CodeGen/ScheduleHazardRecognizer.h" #include "llvm/CodeGen/SelectionDAGNodes.h" #include "llvm/Support/CommandLine.h" #include "llvm/Support/Debug.h" #include "llvm/Support/raw_ostream.h" #include "llvm/Target/TargetInstrInfo.h" #include "llvm/Target/TargetMachine.h" #include "llvm/Target/TargetRegisterInfo.h" #include <climits> using namespace llvm; #ifndef NDEBUG static cl::opt<bool> StressSchedOpt( "stress-sched", cl::Hidden, cl::init(false), cl::desc("Stress test instruction scheduling")); #endif void SchedulingPriorityQueue::anchor() { } ScheduleDAG::ScheduleDAG(MachineFunction &mf) : TM(mf.getTarget()), TII(TM.getInstrInfo()), TRI(TM.getRegisterInfo()), MF(mf), MRI(mf.getRegInfo()), EntrySU(), ExitSU() { #ifndef NDEBUG StressSched = StressSchedOpt; #endif } ScheduleDAG::~ScheduleDAG() {} /// Clear the DAG state (e.g. between scheduling regions). void ScheduleDAG::clearDAG() { SUnits.clear(); EntrySU = SUnit(); ExitSU = SUnit(); } /// getInstrDesc helper to handle SDNodes. const MCInstrDesc *ScheduleDAG::getNodeDesc(const SDNode *Node) const { if (!Node || !Node->isMachineOpcode()) return NULL; return &TII->get(Node->getMachineOpcode()); } /// addPred - This adds the specified edge as a pred of the current node if /// not already. It also adds the current node as a successor of the /// specified node. bool SUnit::addPred(const SDep &D, bool Required) { // If this node already has this dependence, don't add a redundant one. for (SmallVectorImpl<SDep>::iterator I = Preds.begin(), E = Preds.end(); I != E; ++I) { // Zero-latency weak edges may be added purely for heuristic ordering. Don't // add them if another kind of edge already exists. if (!Required && I->getSUnit() == D.getSUnit()) return false; if (I->overlaps(D)) { // Extend the latency if needed. Equivalent to removePred(I) + addPred(D). if (I->getLatency() < D.getLatency()) { SUnit *PredSU = I->getSUnit(); // Find the corresponding successor in N. SDep ForwardD = *I; ForwardD.setSUnit(this); for (SmallVectorImpl<SDep>::iterator II = PredSU->Succs.begin(), EE = PredSU->Succs.end(); II != EE; ++II) { if (*II == ForwardD) { II->setLatency(D.getLatency()); break; } } I->setLatency(D.getLatency()); } return false; } } // Now add a corresponding succ to N. SDep P = D; P.setSUnit(this); SUnit *N = D.getSUnit(); // Update the bookkeeping. if (D.getKind() == SDep::Data) { assert(NumPreds < UINT_MAX && "NumPreds will overflow!"); assert(N->NumSuccs < UINT_MAX && "NumSuccs will overflow!"); ++NumPreds; ++N->NumSuccs; } if (!N->isScheduled) { if (D.isWeak()) { ++WeakPredsLeft; } else { assert(NumPredsLeft < UINT_MAX && "NumPredsLeft will overflow!"); ++NumPredsLeft; } } if (!isScheduled) { if (D.isWeak()) { ++N->WeakSuccsLeft; } else { assert(N->NumSuccsLeft < UINT_MAX && "NumSuccsLeft will overflow!"); ++N->NumSuccsLeft; } } Preds.push_back(D); N->Succs.push_back(P); if (P.getLatency() != 0) { this->setDepthDirty(); N->setHeightDirty(); } return true; } /// removePred - This removes the specified edge as a pred of the current /// node if it exists. It also removes the current node as a successor of /// the specified node. void SUnit::removePred(const SDep &D) { // Find the matching predecessor. for (SmallVectorImpl<SDep>::iterator I = Preds.begin(), E = Preds.end(); I != E; ++I) if (*I == D) { // Find the corresponding successor in N. SDep P = D; P.setSUnit(this); SUnit *N = D.getSUnit(); SmallVectorImpl<SDep>::iterator Succ = std::find(N->Succs.begin(), N->Succs.end(), P); assert(Succ != N->Succs.end() && "Mismatching preds / succs lists!"); N->Succs.erase(Succ); Preds.erase(I); // Update the bookkeeping. if (P.getKind() == SDep::Data) { assert(NumPreds > 0 && "NumPreds will underflow!"); assert(N->NumSuccs > 0 && "NumSuccs will underflow!"); --NumPreds; --N->NumSuccs; } if (!N->isScheduled) { if (D.isWeak()) --WeakPredsLeft; else { assert(NumPredsLeft > 0 && "NumPredsLeft will underflow!"); --NumPredsLeft; } } if (!isScheduled) { if (D.isWeak()) --N->WeakSuccsLeft; else { assert(N->NumSuccsLeft > 0 && "NumSuccsLeft will underflow!"); --N->NumSuccsLeft; } } if (P.getLatency() != 0) { this->setDepthDirty(); N->setHeightDirty(); } return; } } void SUnit::setDepthDirty() { if (!isDepthCurrent) return; SmallVector<SUnit*, 8> WorkList; WorkList.push_back(this); do { SUnit *SU = WorkList.pop_back_val(); SU->isDepthCurrent = false; for (SUnit::const_succ_iterator I = SU->Succs.begin(), E = SU->Succs.end(); I != E; ++I) { SUnit *SuccSU = I->getSUnit(); if (SuccSU->isDepthCurrent) WorkList.push_back(SuccSU); } } while (!WorkList.empty()); } void SUnit::setHeightDirty() { if (!isHeightCurrent) return; SmallVector<SUnit*, 8> WorkList; WorkList.push_back(this); do { SUnit *SU = WorkList.pop_back_val(); SU->isHeightCurrent = false; for (SUnit::const_pred_iterator I = SU->Preds.begin(), E = SU->Preds.end(); I != E; ++I) { SUnit *PredSU = I->getSUnit(); if (PredSU->isHeightCurrent) WorkList.push_back(PredSU); } } while (!WorkList.empty()); } /// setDepthToAtLeast - Update this node's successors to reflect the /// fact that this node's depth just increased. /// void SUnit::setDepthToAtLeast(unsigned NewDepth) { if (NewDepth <= getDepth()) return; setDepthDirty(); Depth = NewDepth; isDepthCurrent = true; } /// setHeightToAtLeast - Update this node's predecessors to reflect the /// fact that this node's height just increased. /// void SUnit::setHeightToAtLeast(unsigned NewHeight) { if (NewHeight <= getHeight()) return; setHeightDirty(); Height = NewHeight; isHeightCurrent = true; } /// ComputeDepth - Calculate the maximal path from the node to the exit. /// void SUnit::ComputeDepth() { SmallVector<SUnit*, 8> WorkList; WorkList.push_back(this); do { SUnit *Cur = WorkList.back(); bool Done = true; unsigned MaxPredDepth = 0; for (SUnit::const_pred_iterator I = Cur->Preds.begin(), E = Cur->Preds.end(); I != E; ++I) { SUnit *PredSU = I->getSUnit(); if (PredSU->isDepthCurrent) MaxPredDepth = std::max(MaxPredDepth, PredSU->Depth + I->getLatency()); else { Done = false; WorkList.push_back(PredSU); } } if (Done) { WorkList.pop_back(); if (MaxPredDepth != Cur->Depth) { Cur->setDepthDirty(); Cur->Depth = MaxPredDepth; } Cur->isDepthCurrent = true; } } while (!WorkList.empty()); } /// ComputeHeight - Calculate the maximal path from the node to the entry. /// void SUnit::ComputeHeight() { SmallVector<SUnit*, 8> WorkList; WorkList.push_back(this); do { SUnit *Cur = WorkList.back(); bool Done = true; unsigned MaxSuccHeight = 0; for (SUnit::const_succ_iterator I = Cur->Succs.begin(), E = Cur->Succs.end(); I != E; ++I) { SUnit *SuccSU = I->getSUnit(); if (SuccSU->isHeightCurrent) MaxSuccHeight = std::max(MaxSuccHeight, SuccSU->Height + I->getLatency()); else { Done = false; WorkList.push_back(SuccSU); } } if (Done) { WorkList.pop_back(); if (MaxSuccHeight != Cur->Height) { Cur->setHeightDirty(); Cur->Height = MaxSuccHeight; } Cur->isHeightCurrent = true; } } while (!WorkList.empty()); } void SUnit::biasCriticalPath() { if (NumPreds < 2) return; SUnit::pred_iterator BestI = Preds.begin(); unsigned MaxDepth = BestI->getSUnit()->getDepth(); for (SUnit::pred_iterator I = std::next(BestI), E = Preds.end(); I != E; ++I) { if (I->getKind() == SDep::Data && I->getSUnit()->getDepth() > MaxDepth) BestI = I; } if (BestI != Preds.begin()) std::swap(*Preds.begin(), *BestI); } #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP) /// SUnit - Scheduling unit. It's an wrapper around either a single SDNode or /// a group of nodes flagged together. void SUnit::dump(const ScheduleDAG *G) const { dbgs() << "SU(" << NodeNum << "): "; G->dumpNode(this); } void SUnit::dumpAll(const ScheduleDAG *G) const { dump(G); dbgs() << " # preds left : " << NumPredsLeft << "\n"; dbgs() << " # succs left : " << NumSuccsLeft << "\n"; if (WeakPredsLeft) dbgs() << " # weak preds left : " << WeakPredsLeft << "\n"; if (WeakSuccsLeft) dbgs() << " # weak succs left : " << WeakSuccsLeft << "\n"; dbgs() << " # rdefs left : " << NumRegDefsLeft << "\n"; dbgs() << " Latency : " << Latency << "\n"; dbgs() << " Depth : " << getDepth() << "\n"; dbgs() << " Height : " << getHeight() << "\n"; if (Preds.size() != 0) { dbgs() << " Predecessors:\n"; for (SUnit::const_succ_iterator I = Preds.begin(), E = Preds.end(); I != E; ++I) { dbgs() << " "; switch (I->getKind()) { case SDep::Data: dbgs() << "val "; break; case SDep::Anti: dbgs() << "anti"; break; case SDep::Output: dbgs() << "out "; break; case SDep::Order: dbgs() << "ch "; break; } dbgs() << "SU(" << I->getSUnit()->NodeNum << ")"; if (I->isArtificial()) dbgs() << " *"; dbgs() << ": Latency=" << I->getLatency(); if (I->isAssignedRegDep()) dbgs() << " Reg=" << PrintReg(I->getReg(), G->TRI); dbgs() << "\n"; } } if (Succs.size() != 0) { dbgs() << " Successors:\n"; for (SUnit::const_succ_iterator I = Succs.begin(), E = Succs.end(); I != E; ++I) { dbgs() << " "; switch (I->getKind()) { case SDep::Data: dbgs() << "val "; break; case SDep::Anti: dbgs() << "anti"; break; case SDep::Output: dbgs() << "out "; break; case SDep::Order: dbgs() << "ch "; break; } dbgs() << "SU(" << I->getSUnit()->NodeNum << ")"; if (I->isArtificial()) dbgs() << " *"; dbgs() << ": Latency=" << I->getLatency(); if (I->isAssignedRegDep()) dbgs() << " Reg=" << PrintReg(I->getReg(), G->TRI); dbgs() << "\n"; } } dbgs() << "\n"; } #endif #ifndef NDEBUG /// VerifyScheduledDAG - Verify that all SUnits were scheduled and that /// their state is consistent. Return the number of scheduled nodes. /// unsigned ScheduleDAG::VerifyScheduledDAG(bool isBottomUp) { bool AnyNotSched = false; unsigned DeadNodes = 0; for (unsigned i = 0, e = SUnits.size(); i != e; ++i) { if (!SUnits[i].isScheduled) { if (SUnits[i].NumPreds == 0 && SUnits[i].NumSuccs == 0) { ++DeadNodes; continue; } if (!AnyNotSched) dbgs() << "*** Scheduling failed! ***\n"; SUnits[i].dump(this); dbgs() << "has not been scheduled!\n"; AnyNotSched = true; } if (SUnits[i].isScheduled && (isBottomUp ? SUnits[i].getHeight() : SUnits[i].getDepth()) > unsigned(INT_MAX)) { if (!AnyNotSched) dbgs() << "*** Scheduling failed! ***\n"; SUnits[i].dump(this); dbgs() << "has an unexpected " << (isBottomUp ? "Height" : "Depth") << " value!\n"; AnyNotSched = true; } if (isBottomUp) { if (SUnits[i].NumSuccsLeft != 0) { if (!AnyNotSched) dbgs() << "*** Scheduling failed! ***\n"; SUnits[i].dump(this); dbgs() << "has successors left!\n"; AnyNotSched = true; } } else { if (SUnits[i].NumPredsLeft != 0) { if (!AnyNotSched) dbgs() << "*** Scheduling failed! ***\n"; SUnits[i].dump(this); dbgs() << "has predecessors left!\n"; AnyNotSched = true; } } } assert(!AnyNotSched); return SUnits.size() - DeadNodes; } #endif /// InitDAGTopologicalSorting - create the initial topological /// ordering from the DAG to be scheduled. /// /// The idea of the algorithm is taken from /// "Online algorithms for managing the topological order of /// a directed acyclic graph" by David J. Pearce and Paul H.J. Kelly /// This is the MNR algorithm, which was first introduced by /// A. Marchetti-Spaccamela, U. Nanni and H. Rohnert in /// "Maintaining a topological order under edge insertions". /// /// Short description of the algorithm: /// /// Topological ordering, ord, of a DAG maps each node to a topological /// index so that for all edges X->Y it is the case that ord(X) < ord(Y). /// /// This means that if there is a path from the node X to the node Z, /// then ord(X) < ord(Z). /// /// This property can be used to check for reachability of nodes: /// if Z is reachable from X, then an insertion of the edge Z->X would /// create a cycle. /// /// The algorithm first computes a topological ordering for the DAG by /// initializing the Index2Node and Node2Index arrays and then tries to keep /// the ordering up-to-date after edge insertions by reordering the DAG. /// /// On insertion of the edge X->Y, the algorithm first marks by calling DFS /// the nodes reachable from Y, and then shifts them using Shift to lie /// immediately after X in Index2Node. void ScheduleDAGTopologicalSort::InitDAGTopologicalSorting() { unsigned DAGSize = SUnits.size(); std::vector<SUnit*> WorkList; WorkList.reserve(DAGSize); Index2Node.resize(DAGSize); Node2Index.resize(DAGSize); // Initialize the data structures. if (ExitSU) WorkList.push_back(ExitSU); for (unsigned i = 0, e = DAGSize; i != e; ++i) { SUnit *SU = &SUnits[i]; int NodeNum = SU->NodeNum; unsigned Degree = SU->Succs.size(); // Temporarily use the Node2Index array as scratch space for degree counts. Node2Index[NodeNum] = Degree; // Is it a node without dependencies? if (Degree == 0) { assert(SU->Succs.empty() && "SUnit should have no successors"); // Collect leaf nodes. WorkList.push_back(SU); } } int Id = DAGSize; while (!WorkList.empty()) { SUnit *SU = WorkList.back(); WorkList.pop_back(); if (SU->NodeNum < DAGSize) Allocate(SU->NodeNum, --Id); for (SUnit::const_pred_iterator I = SU->Preds.begin(), E = SU->Preds.end(); I != E; ++I) { SUnit *SU = I->getSUnit(); if (SU->NodeNum < DAGSize && !--Node2Index[SU->NodeNum]) // If all dependencies of the node are processed already, // then the node can be computed now. WorkList.push_back(SU); } } Visited.resize(DAGSize); #ifndef NDEBUG // Check correctness of the ordering for (unsigned i = 0, e = DAGSize; i != e; ++i) { SUnit *SU = &SUnits[i]; for (SUnit::const_pred_iterator I = SU->Preds.begin(), E = SU->Preds.end(); I != E; ++I) { assert(Node2Index[SU->NodeNum] > Node2Index[I->getSUnit()->NodeNum] && "Wrong topological sorting"); } } #endif } /// AddPred - Updates the topological ordering to accommodate an edge /// to be added from SUnit X to SUnit Y. void ScheduleDAGTopologicalSort::AddPred(SUnit *Y, SUnit *X) { int UpperBound, LowerBound; LowerBound = Node2Index[Y->NodeNum]; UpperBound = Node2Index[X->NodeNum]; bool HasLoop = false; // Is Ord(X) < Ord(Y) ? if (LowerBound < UpperBound) { // Update the topological order. Visited.reset(); DFS(Y, UpperBound, HasLoop); assert(!HasLoop && "Inserted edge creates a loop!"); // Recompute topological indexes. Shift(Visited, LowerBound, UpperBound); } } /// RemovePred - Updates the topological ordering to accommodate an /// an edge to be removed from the specified node N from the predecessors /// of the current node M. void ScheduleDAGTopologicalSort::RemovePred(SUnit *M, SUnit *N) { // InitDAGTopologicalSorting(); } /// DFS - Make a DFS traversal to mark all nodes reachable from SU and mark /// all nodes affected by the edge insertion. These nodes will later get new /// topological indexes by means of the Shift method. void ScheduleDAGTopologicalSort::DFS(const SUnit *SU, int UpperBound, bool &HasLoop) { std::vector<const SUnit*> WorkList; WorkList.reserve(SUnits.size()); WorkList.push_back(SU); do { SU = WorkList.back(); WorkList.pop_back(); Visited.set(SU->NodeNum); for (int I = SU->Succs.size()-1; I >= 0; --I) { unsigned s = SU->Succs[I].getSUnit()->NodeNum; // Edges to non-SUnits are allowed but ignored (e.g. ExitSU). if (s >= Node2Index.size()) continue; if (Node2Index[s] == UpperBound) { HasLoop = true; return; } // Visit successors if not already and in affected region. if (!Visited.test(s) && Node2Index[s] < UpperBound) { WorkList.push_back(SU->Succs[I].getSUnit()); } } } while (!WorkList.empty()); } /// Shift - Renumber the nodes so that the topological ordering is /// preserved. void ScheduleDAGTopologicalSort::Shift(BitVector& Visited, int LowerBound, int UpperBound) { std::vector<int> L; int shift = 0; int i; for (i = LowerBound; i <= UpperBound; ++i) { // w is node at topological index i. int w = Index2Node[i]; if (Visited.test(w)) { // Unmark. Visited.reset(w); L.push_back(w); shift = shift + 1; } else { Allocate(w, i - shift); } } for (unsigned j = 0; j < L.size(); ++j) { Allocate(L[j], i - shift); i = i + 1; } } /// WillCreateCycle - Returns true if adding an edge to TargetSU from SU will /// create a cycle. If so, it is not safe to call AddPred(TargetSU, SU). bool ScheduleDAGTopologicalSort::WillCreateCycle(SUnit *TargetSU, SUnit *SU) { // Is SU reachable from TargetSU via successor edges? if (IsReachable(SU, TargetSU)) return true; for (SUnit::pred_iterator I = TargetSU->Preds.begin(), E = TargetSU->Preds.end(); I != E; ++I) if (I->isAssignedRegDep() && IsReachable(SU, I->getSUnit())) return true; return false; } /// IsReachable - Checks if SU is reachable from TargetSU. bool ScheduleDAGTopologicalSort::IsReachable(const SUnit *SU, const SUnit *TargetSU) { // If insertion of the edge SU->TargetSU would create a cycle // then there is a path from TargetSU to SU. int UpperBound, LowerBound; LowerBound = Node2Index[TargetSU->NodeNum]; UpperBound = Node2Index[SU->NodeNum]; bool HasLoop = false; // Is Ord(TargetSU) < Ord(SU) ? if (LowerBound < UpperBound) { Visited.reset(); // There may be a path from TargetSU to SU. Check for it. DFS(TargetSU, UpperBound, HasLoop); } return HasLoop; } /// Allocate - assign the topological index to the node n. void ScheduleDAGTopologicalSort::Allocate(int n, int index) { Node2Index[n] = index; Index2Node[index] = n; } ScheduleDAGTopologicalSort:: ScheduleDAGTopologicalSort(std::vector<SUnit> &sunits, SUnit *exitsu) : SUnits(sunits), ExitSU(exitsu) {} ScheduleHazardRecognizer::~ScheduleHazardRecognizer() {}