ScheduleDAG: Cleanup; NFC

- Fix doxygen comments (do not repeat documented name, remove definition
    comment if there is already one at the declaration, add \p, ...)
- Add some const modifiers
- Use range based for

llvm-svn: 295688

1 files changed, 133 insertions, 184 deletions

diff --git a/llvm/lib/CodeGen/ScheduleDAG.cpp b/llvm/lib/CodeGen/ScheduleDAG.cpp
index 5c177463a5d..01c056caa62 100644
--- a/llvm/lib/CodeGen/ScheduleDAG.cpp
+++ b/llvm/lib/CodeGen/ScheduleDAG.cpp
@@ -7,8 +7,8 @@
 //
 //===----------------------------------------------------------------------===//
 //
-// This implements the ScheduleDAG class, which is a base class used by
-// scheduling implementation classes.
+/// \file Implements the ScheduleDAG class, which is a base class used by
+/// scheduling implementation classes.
 //
 //===----------------------------------------------------------------------===//
 
@@ -46,45 +46,39 @@ ScheduleDAG::ScheduleDAG(MachineFunction &mf)
 
 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 nullptr;
   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) {
+  for (SDep &PredDep : Preds) {
     // 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())
+    if (!Required && PredDep.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();
+    if (PredDep.overlaps(D)) {
+      // Extend the latency if needed. Equivalent to
+      // removePred(PredDep) + addPred(D).
+      if (PredDep.getLatency() < D.getLatency()) {
+        SUnit *PredSU = PredDep.getSUnit();
         // Find the corresponding successor in N.
-        SDep ForwardD = *I;
+        SDep ForwardD = PredDep;
         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());
+        for (SDep &SuccDep : PredSU->Succs) {
+          if (SuccDep == ForwardD) {
+            SuccDep.setLatency(D.getLatency());
             break;
           }
         }
-        I->setLatency(D.getLatency());
+        PredDep.setLatency(D.getLatency());
       }
       return false;
     }
@@ -127,51 +121,46 @@ bool SUnit::addPred(const SDep &D, bool Required) {
   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 = find(N->Succs, 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;
+  SmallVectorImpl<SDep>::iterator I = find(Preds, D);
+  if (I == Preds.end())
+    return;
+  // Find the corresponding successor in N.
+  SDep P = D;
+  P.setSUnit(this);
+  SUnit *N = D.getSUnit();
+  SmallVectorImpl<SDep>::iterator Succ = find(N->Succs, 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();
+  }
 }
 
 void SUnit::setDepthDirty() {
@@ -181,9 +170,8 @@ void SUnit::setDepthDirty() {
   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();
+    for (SDep &SuccDep : SU->Succs) {
+      SUnit *SuccSU = SuccDep.getSUnit();
       if (SuccSU->isDepthCurrent)
         WorkList.push_back(SuccSU);
     }
@@ -197,18 +185,14 @@ void SUnit::setHeightDirty() {
   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();
+    for (SDep &PredDep : SU->Preds) {
+      SUnit *PredSU = PredDep.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;
@@ -217,9 +201,6 @@ void SUnit::setDepthToAtLeast(unsigned 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;
@@ -228,8 +209,7 @@ void SUnit::setHeightToAtLeast(unsigned NewHeight) {
   isHeightCurrent = true;
 }
 
-/// ComputeDepth - Calculate the maximal path from the node to the exit.
-///
+/// Calculates the maximal path from the node to the exit.
 void SUnit::ComputeDepth() {
   SmallVector<SUnit*, 8> WorkList;
   WorkList.push_back(this);
@@ -238,12 +218,11 @@ void SUnit::ComputeDepth() {
 
     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();
+    for (const SDep &PredDep : Cur->Preds) {
+      SUnit *PredSU = PredDep.getSUnit();
       if (PredSU->isDepthCurrent)
         MaxPredDepth = std::max(MaxPredDepth,
-                                PredSU->Depth + I->getLatency());
+                                PredSU->Depth + PredDep.getLatency());
       else {
         Done = false;
         WorkList.push_back(PredSU);
@@ -261,8 +240,7 @@ void SUnit::ComputeDepth() {
   } while (!WorkList.empty());
 }
 
-/// ComputeHeight - Calculate the maximal path from the node to the entry.
-///
+/// Calculates the maximal path from the node to the entry.
 void SUnit::ComputeHeight() {
   SmallVector<SUnit*, 8> WorkList;
   WorkList.push_back(this);
@@ -271,12 +249,11 @@ void SUnit::ComputeHeight() {
 
     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();
+    for (const SDep &SuccDep : Cur->Succs) {
+      SUnit *SuccSU = SuccDep.getSUnit();
       if (SuccSU->isHeightCurrent)
         MaxSuccHeight = std::max(MaxSuccHeight,
-                                 SuccSU->Height + I->getLatency());
+                                 SuccSU->Height + SuccDep.getLatency());
       else {
         Done = false;
         WorkList.push_back(SuccSU);
@@ -320,8 +297,6 @@ void SUnit::print(raw_ostream &OS, const ScheduleDAG *DAG) const {
     OS << "SU(" << NodeNum << ")";
 }
 
-/// SUnit - Scheduling unit. It's an wrapper around either a single SDNode or
-/// a group of nodes flagged together.
 LLVM_DUMP_METHOD void SUnit::dump(const ScheduleDAG *G) const {
   print(dbgs(), G);
   dbgs() << ": ";
@@ -344,41 +319,39 @@ LLVM_DUMP_METHOD void SUnit::dumpAll(const ScheduleDAG *G) const {
 
   if (Preds.size() != 0) {
     dbgs() << "  Predecessors:\n";
-    for (SUnit::const_succ_iterator I = Preds.begin(), E = Preds.end();
-         I != E; ++I) {
+    for (const SDep &SuccDep : Preds) {
       dbgs() << "   ";
-      switch (I->getKind()) {
+      switch (SuccDep.getKind()) {
       case SDep::Data:   dbgs() << "data "; break;
       case SDep::Anti:   dbgs() << "anti "; break;
       case SDep::Output: dbgs() << "out  "; break;
       case SDep::Order:  dbgs() << "ord  "; break;
       }
-      I->getSUnit()->print(dbgs(), G);
-      if (I->isArtificial())
+      SuccDep.getSUnit()->print(dbgs(), G);
+      if (SuccDep.isArtificial())
         dbgs() << " *";
-      dbgs() << ": Latency=" << I->getLatency();
-      if (I->isAssignedRegDep())
-        dbgs() << " Reg=" << PrintReg(I->getReg(), G->TRI);
+      dbgs() << ": Latency=" << SuccDep.getLatency();
+      if (SuccDep.isAssignedRegDep())
+        dbgs() << " Reg=" << PrintReg(SuccDep.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) {
+    for (const SDep &SuccDep : Succs) {
       dbgs() << "   ";
-      switch (I->getKind()) {
+      switch (SuccDep.getKind()) {
       case SDep::Data:   dbgs() << "data "; break;
       case SDep::Anti:   dbgs() << "anti "; break;
       case SDep::Output: dbgs() << "out  "; break;
       case SDep::Order:  dbgs() << "ord  "; break;
       }
-      I->getSUnit()->print(dbgs(), G);
-      if (I->isArtificial())
+      SuccDep.getSUnit()->print(dbgs(), G);
+      if (SuccDep.isArtificial())
         dbgs() << " *";
-      dbgs() << ": Latency=" << I->getLatency();
-      if (I->isAssignedRegDep())
-        dbgs() << " Reg=" << PrintReg(I->getReg(), G->TRI);
+      dbgs() << ": Latency=" << SuccDep.getLatency();
+      if (SuccDep.isAssignedRegDep())
+        dbgs() << " Reg=" << PrintReg(SuccDep.getReg(), G->TRI);
       dbgs() << "\n";
     }
   }
@@ -386,47 +359,44 @@ LLVM_DUMP_METHOD void SUnit::dumpAll(const ScheduleDAG *G) const {
 #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) {
+  for (const SUnit &SUnit : SUnits) {
+    if (!SUnit.isScheduled) {
+      if (SUnit.NumPreds == 0 && SUnit.NumSuccs == 0) {
         ++DeadNodes;
         continue;
       }
       if (!AnyNotSched)
         dbgs() << "*** Scheduling failed! ***\n";
-      SUnits[i].dump(this);
+      SUnit.dump(this);
       dbgs() << "has not been scheduled!\n";
       AnyNotSched = true;
     }
-    if (SUnits[i].isScheduled &&
-        (isBottomUp ? SUnits[i].getHeight() : SUnits[i].getDepth()) >
+    if (SUnit.isScheduled &&
+        (isBottomUp ? SUnit.getHeight() : SUnit.getDepth()) >
           unsigned(INT_MAX)) {
       if (!AnyNotSched)
         dbgs() << "*** Scheduling failed! ***\n";
-      SUnits[i].dump(this);
+      SUnit.dump(this);
       dbgs() << "has an unexpected "
            << (isBottomUp ? "Height" : "Depth") << " value!\n";
       AnyNotSched = true;
     }
     if (isBottomUp) {
-      if (SUnits[i].NumSuccsLeft != 0) {
+      if (SUnit.NumSuccsLeft != 0) {
         if (!AnyNotSched)
           dbgs() << "*** Scheduling failed! ***\n";
-        SUnits[i].dump(this);
+        SUnit.dump(this);
         dbgs() << "has successors left!\n";
         AnyNotSched = true;
       }
     } else {
-      if (SUnits[i].NumPredsLeft != 0) {
+      if (SUnit.NumPredsLeft != 0) {
         if (!AnyNotSched)
           dbgs() << "*** Scheduling failed! ***\n";
-        SUnits[i].dump(this);
+        SUnit.dump(this);
         dbgs() << "has predecessors left!\n";
         AnyNotSched = true;
       }
@@ -437,36 +407,33 @@ unsigned ScheduleDAG::VerifyScheduledDAG(bool isBottomUp) {
 }
 #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() {
+  // 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.
   unsigned DAGSize = SUnits.size();
   std::vector<SUnit*> WorkList;
   WorkList.reserve(DAGSize);
@@ -477,18 +444,17 @@ void ScheduleDAGTopologicalSort::InitDAGTopologicalSorting() {
   // 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();
+  for (SUnit &SU : SUnits) {
+    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");
+      assert(SU.Succs.empty() && "SUnit should have no successors");
       // Collect leaf nodes.
-      WorkList.push_back(SU);
+      WorkList.push_back(&SU);
     }
   }
 
@@ -498,9 +464,8 @@ void ScheduleDAGTopologicalSort::InitDAGTopologicalSorting() {
     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();
+    for (const SDep &PredDep : SU->Preds) {
+      SUnit *SU = PredDep.getSUnit();
       if (SU->NodeNum < DAGSize && !--Node2Index[SU->NodeNum])
         // If all dependencies of the node are processed already,
         // then the node can be computed now.
@@ -512,19 +477,15 @@ void ScheduleDAGTopologicalSort::InitDAGTopologicalSorting() {
 
 #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] &&
+  for (SUnit &SU : SUnits)  {
+    for (const SDep &PD : SU.Preds) {
+      assert(Node2Index[SU.NodeNum] > Node2Index[PD.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];
@@ -541,16 +502,10 @@ void ScheduleDAGTopologicalSort::AddPred(SUnit *Y, SUnit *X) {
   }
 }
 
-/// 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;
@@ -561,8 +516,9 @@ void ScheduleDAGTopologicalSort::DFS(const SUnit *SU, int UpperBound,
     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;
+    for (const SDep &SuccDep
+         : make_range(SU->Succs.rbegin(), SU->Succs.rend())) {
+      unsigned s = SuccDep.getSUnit()->NodeNum;
       // Edges to non-SUnits are allowed but ignored (e.g. ExitSU).
       if (s >= Node2Index.size())
         continue;
@@ -572,14 +528,12 @@ void ScheduleDAGTopologicalSort::DFS(const SUnit *SU, int UpperBound,
       }
       // Visit successors if not already and in affected region.
       if (!Visited.test(s) && Node2Index[s] < UpperBound) {
-        WorkList.push_back(SU->Succs[I].getSUnit());
+        WorkList.push_back(SuccDep.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;
@@ -599,28 +553,24 @@ void ScheduleDAGTopologicalSort::Shift(BitVector& Visited, int LowerBound,
     }
   }
 
-  for (unsigned j = 0; j < L.size(); ++j) {
-    Allocate(L[j], i - shift);
+  for (unsigned LI : L) {
+    Allocate(LI, 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()))
+  for (const SDep &PredDep : TargetSU->Preds)
+    if (PredDep.isAssignedRegDep() &&
+        IsReachable(SU, PredDep.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
@@ -638,7 +588,6 @@ bool ScheduleDAGTopologicalSort::IsReachable(const SUnit *SU,
   return HasLoop;
 }
 
-/// Allocate - assign the topological index to the node n.
 void ScheduleDAGTopologicalSort::Allocate(int n, int index) {
   Node2Index[n] = index;
   Index2Node[index] = n;