lib/CodeGen/ScheduleDAG.cpp - platform/external/llvm - Git at Google

 //===---- 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 depenence, don't add a redundant one.
   for (SmallVector<SDep, 4>::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 (SmallVector<SDep, 4>::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 (SmallVector<SDep, 4>::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 = llvm::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              : " << 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() << "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();
       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() {}
	//===---- 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 depenence, don't add a redundant one.
	for (SmallVector<SDep, 4>::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 (SmallVector<SDep, 4>::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 (SmallVector<SDep, 4>::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 = llvm::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 : " << 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() << "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();
	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() {}