llvm/lib/CodeGen/ScheduleDAG.cpp - toolchain/llvm-project - Gitiles

 //===---- 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/Target/TargetMachine.h"
 #include "llvm/Target/TargetInstrInfo.h"
 #include "llvm/Target/TargetRegisterInfo.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/raw_ostream.h"
 #include <climits>
 using namespace llvm;

 ScheduleDAG::ScheduleDAG(MachineFunction &mf)
   : TM(mf.getTarget()),
     TII(TM.getInstrInfo()),
     TRI(TM.getRegisterInfo()),
     TLI(TM.getTargetLowering()),
     MF(mf), MRI(mf.getRegInfo()),
     ConstPool(MF.getConstantPool()),
     EntrySU(), ExitSU() {
 }

 ScheduleDAG::~ScheduleDAG() {}

 /// dump - dump the schedule.
 void ScheduleDAG::dumpSchedule() const {
   for (unsigned i = 0, e = Sequence.size(); i != e; i++) {
     if (SUnit *SU = Sequence[i])
       SU->dump(this);
     else
       dbgs() << "**** NOOP ****\n";
   }
 }


 /// Run - perform scheduling.
 ///
 void ScheduleDAG::Run(MachineBasicBlock *bb,
                       MachineBasicBlock::iterator insertPos) {
   BB = bb;
   InsertPos = insertPos;

   SUnits.clear();
   Sequence.clear();
   EntrySU = SUnit();
   ExitSU = SUnit();

   Schedule();

   DEBUG({
       dbgs() << "*** Final schedule ***\n";
       dumpSchedule();
       dbgs() << '\n';
     });
 }

 /// 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.
 void SUnit::addPred(const SDep &D) {
   // If this node already has this depenence, don't add a redundant one.
   for (SmallVector<SDep, 4>::const_iterator I = Preds.begin(), E = Preds.end();
        I != E; ++I)
     if (*I == D)
       return;
   // 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) {
     assert(NumPredsLeft < UINT_MAX && "NumPredsLeft will overflow!");
     ++NumPredsLeft;
   }
   if (!isScheduled) {
     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();
   }
 }

 /// 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 (SmallVector<SDep, 4>::iterator I = Preds.begin(), E = Preds.end();
        I != E; ++I)
     if (*I == D) {
       bool FoundSucc = false;
       // Find the corresponding successor in N.
       SDep P = D;
       P.setSUnit(this);
       SUnit *N = D.getSUnit();
       for (SmallVector<SDep, 4>::iterator II = N->Succs.begin(),
              EE = N->Succs.end(); II != EE; ++II)
         if (*II == P) {
           FoundSucc = true;
           N->Succs.erase(II);
           break;
         }
       assert(FoundSucc && "Mismatching preds / succs lists!");
       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) {
         assert(NumPredsLeft > 0 && "NumPredsLeft will underflow!");
         --NumPredsLeft;
       }
       if (!isScheduled) {
         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());
 }

 /// 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";
   dbgs() << "  Latency            : " << Latency << "\n";
   dbgs() << "  Depth              : " << Depth << "\n";
   dbgs() << "  Height             : " << Height << "\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() << "#";
       dbgs() << I->getSUnit() << " - SU(" << I->getSUnit()->NodeNum << ")";
       if (I->isArtificial())
         dbgs() << " *";
       dbgs() << ": Latency=" << I->getLatency();
       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() << "#";
       dbgs() << I->getSUnit() << " - SU(" << I->getSUnit()->NodeNum << ")";
       if (I->isArtificial())
         dbgs() << " *";
       dbgs() << ": Latency=" << I->getLatency();
       dbgs() << "\n";
     }
   }
   dbgs() << "\n";
 }

 #ifndef NDEBUG
 /// VerifySchedule - Verify that all SUnits were scheduled and that
 /// their state is consistent.
 ///
 void ScheduleDAG::VerifySchedule(bool isBottomUp) {
   bool AnyNotSched = false;
   unsigned DeadNodes = 0;
   unsigned Noops = 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;
       }
     }
   }
   for (unsigned i = 0, e = Sequence.size(); i != e; ++i)
     if (!Sequence[i])
       ++Noops;
   assert(!AnyNotSched);
   assert(Sequence.size() + DeadNodes - Noops == SUnits.size() &&
          "The number of nodes scheduled doesn't match the expected number!");
 }
 #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.
   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();
     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 (!--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 accomodate 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 accomodate 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) {
       int s = SU->Succs[I].getSUnit()->NodeNum;
       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 from SU to TargetSU will
 /// create a cycle.
 bool ScheduleDAGTopologicalSort::WillCreateCycle(SUnit *SU, SUnit *TargetSU) {
   if (IsReachable(TargetSU, SU))
     return true;
   for (SUnit::pred_iterator I = SU->Preds.begin(), E = SU->Preds.end();
        I != E; ++I)
     if (I->isAssignedRegDep() &&
         IsReachable(TargetSU, 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)
  : SUnits(sunits) {}

 ScheduleHazardRecognizer::~ScheduleHazardRecognizer() {}
	//===---- 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/Target/TargetMachine.h"
	#include "llvm/Target/TargetInstrInfo.h"
	#include "llvm/Target/TargetRegisterInfo.h"
	#include "llvm/Support/Debug.h"
	#include "llvm/Support/raw_ostream.h"
	#include <climits>
	using namespace llvm;

	ScheduleDAG::ScheduleDAG(MachineFunction &mf)
	: TM(mf.getTarget()),
	TII(TM.getInstrInfo()),
	TRI(TM.getRegisterInfo()),
	TLI(TM.getTargetLowering()),
	MF(mf), MRI(mf.getRegInfo()),
	ConstPool(MF.getConstantPool()),
	EntrySU(), ExitSU() {
	}

	ScheduleDAG::~ScheduleDAG() {}

	/// dump - dump the schedule.
	void ScheduleDAG::dumpSchedule() const {
	for (unsigned i = 0, e = Sequence.size(); i != e; i++) {
	if (SUnit *SU = Sequence[i])
	SU->dump(this);
	else
	dbgs() << "** NOOP **\n";
	}
	}


	/// Run - perform scheduling.
	///
	void ScheduleDAG::Run(MachineBasicBlock *bb,
	MachineBasicBlock::iterator insertPos) {
	BB = bb;
	InsertPos = insertPos;

	SUnits.clear();
	Sequence.clear();
	EntrySU = SUnit();
	ExitSU = SUnit();

	Schedule();

	DEBUG({
	dbgs() << "* Final schedule *\n";
	dumpSchedule();
	dbgs() << '\n';
	});
	}

	/// 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.
	void SUnit::addPred(const SDep &D) {
	// If this node already has this depenence, don't add a redundant one.
	for (SmallVector<SDep, 4>::const_iterator I = Preds.begin(), E = Preds.end();
	I != E; ++I)
	if (*I == D)
	return;
	// 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) {
	assert(NumPredsLeft < UINT_MAX && "NumPredsLeft will overflow!");
	++NumPredsLeft;
	}
	if (!isScheduled) {
	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();
	}
	}

	/// 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 (SmallVector<SDep, 4>::iterator I = Preds.begin(), E = Preds.end();
	I != E; ++I)
	if (*I == D) {
	bool FoundSucc = false;
	// Find the corresponding successor in N.
	SDep P = D;
	P.setSUnit(this);
	SUnit *N = D.getSUnit();
	for (SmallVector<SDep, 4>::iterator II = N->Succs.begin(),
	EE = N->Succs.end(); II != EE; ++II)
	if (*II == P) {
	FoundSucc = true;
	N->Succs.erase(II);
	break;
	}
	assert(FoundSucc && "Mismatching preds / succs lists!");
	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) {
	assert(NumPredsLeft > 0 && "NumPredsLeft will underflow!");
	--NumPredsLeft;
	}
	if (!isScheduled) {
	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());
	}

	/// 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";
	dbgs() << " Latency : " << Latency << "\n";
	dbgs() << " Depth : " << Depth << "\n";
	dbgs() << " Height : " << Height << "\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() << "#";
	dbgs() << I->getSUnit() << " - SU(" << I->getSUnit()->NodeNum << ")";
	if (I->isArtificial())
	dbgs() << " *";
	dbgs() << ": Latency=" << I->getLatency();
	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() << "#";
	dbgs() << I->getSUnit() << " - SU(" << I->getSUnit()->NodeNum << ")";
	if (I->isArtificial())
	dbgs() << " *";
	dbgs() << ": Latency=" << I->getLatency();
	dbgs() << "\n";
	}
	}
	dbgs() << "\n";
	}

	#ifndef NDEBUG
	/// VerifySchedule - Verify that all SUnits were scheduled and that
	/// their state is consistent.
	///
	void ScheduleDAG::VerifySchedule(bool isBottomUp) {
	bool AnyNotSched = false;
	unsigned DeadNodes = 0;
	unsigned Noops = 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;
	}
	}
	}
	for (unsigned i = 0, e = Sequence.size(); i != e; ++i)
	if (!Sequence[i])
	++Noops;
	assert(!AnyNotSched);
	assert(Sequence.size() + DeadNodes - Noops == SUnits.size() &&
	"The number of nodes scheduled doesn't match the expected number!");
	}
	#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.
	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();
	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 (!--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 accomodate 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 accomodate 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) {
	int s = SU->Succs[I].getSUnit()->NodeNum;
	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 from SU to TargetSU will
	/// create a cycle.
	bool ScheduleDAGTopologicalSort::WillCreateCycle(SUnit SU, SUnit TargetSU) {
	if (IsReachable(TargetSU, SU))
	return true;
	for (SUnit::pred_iterator I = SU->Preds.begin(), E = SU->Preds.end();
	I != E; ++I)
	if (I->isAssignedRegDep() &&
	IsReachable(TargetSU, 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)
	: SUnits(sunits) {}

	ScheduleHazardRecognizer::~ScheduleHazardRecognizer() {}