1 //===------- llvm/CodeGen/ScheduleDAG.h - Common Base Class------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements the ScheduleDAG class, which is used as the common
11 // base class for instruction schedulers.
13 //===----------------------------------------------------------------------===//
15 #ifndef LLVM_CODEGEN_SCHEDULEDAG_H
16 #define LLVM_CODEGEN_SCHEDULEDAG_H
18 #include "llvm/CodeGen/MachineBasicBlock.h"
19 #include "llvm/Target/TargetMachine.h"
20 #include "llvm/ADT/DenseMap.h"
21 #include "llvm/ADT/BitVector.h"
22 #include "llvm/ADT/GraphTraits.h"
23 #include "llvm/ADT/SmallVector.h"
24 #include "llvm/ADT/PointerIntPair.h"
29 class MachineConstantPool;
30 class MachineFunction;
31 class MachineRegisterInfo;
33 class TargetRegisterInfo;
36 class TargetInstrInfo;
37 class TargetInstrDesc;
39 class TargetRegisterClass;
40 template<class Graph> class GraphWriter;
42 /// SDep - Scheduling dependency. This represents one direction of an
43 /// edge in the scheduling DAG.
46 /// Kind - These are the different kinds of scheduling dependencies.
48 Data, ///< Regular data dependence (aka true-dependence).
49 Anti, ///< A register anti-dependedence (aka WAR).
50 Output, ///< A register output-dependence (aka WAW).
51 Order ///< Any other ordering dependency.
55 /// Dep - A pointer to the depending/depended-on SUnit, and an enum
56 /// indicating the kind of the dependency.
57 PointerIntPair<SUnit *, 2, Kind> Dep;
59 /// Contents - A union discriminated by the dependence kind.
61 /// Reg - For Data, Anti, and Output dependencies, the associated
62 /// register. For Data dependencies that don't currently have a register
63 /// assigned, this is set to zero.
66 /// Order - Additional information about Order dependencies.
68 /// isNormalMemory - True if both sides of the dependence
69 /// access memory in non-volatile and fully modeled ways.
70 bool isNormalMemory : 1;
72 /// isMustAlias - True if both sides of the dependence are known to
73 /// access the same memory.
76 /// isArtificial - True if this is an artificial dependency, meaning
77 /// it is not necessary for program correctness, and may be safely
78 /// deleted if necessary.
79 bool isArtificial : 1;
83 /// Latency - The time associated with this edge. Often this is just
84 /// the value of the Latency field of the predecessor, however advanced
85 /// models may provide additional information about specific edges.
89 /// SDep - Construct a null SDep. This is only for use by container
90 /// classes which require default constructors. SUnits may not
91 /// have null SDep edges.
92 SDep() : Dep(0, Data) {}
94 /// SDep - Construct an SDep with the specified values.
95 SDep(SUnit *S, Kind kind, unsigned latency = 1, unsigned Reg = 0,
96 bool isNormalMemory = false, bool isMustAlias = false,
97 bool isArtificial = false)
98 : Dep(S, kind), Contents(), Latency(latency) {
103 "SDep::Anti and SDep::Output must use a non-zero Reg!");
106 assert(!isMustAlias && "isMustAlias only applies with SDep::Order!");
107 assert(!isArtificial && "isArtificial only applies with SDep::Order!");
111 assert(Reg == 0 && "Reg given for non-register dependence!");
112 Contents.Order.isNormalMemory = isNormalMemory;
113 Contents.Order.isMustAlias = isMustAlias;
114 Contents.Order.isArtificial = isArtificial;
119 bool operator==(const SDep &Other) const {
120 if (Dep != Other.Dep || Latency != Other.Latency) return false;
121 switch (Dep.getInt()) {
125 return Contents.Reg == Other.Contents.Reg;
127 return Contents.Order.isNormalMemory ==
128 Other.Contents.Order.isNormalMemory &&
129 Contents.Order.isMustAlias == Other.Contents.Order.isMustAlias &&
130 Contents.Order.isArtificial == Other.Contents.Order.isArtificial;
132 assert(0 && "Invalid dependency kind!");
136 bool operator!=(const SDep &Other) const {
137 return !operator==(Other);
140 /// getLatency - Return the latency value for this edge, which roughly
141 /// means the minimum number of cycles that must elapse between the
142 /// predecessor and the successor, given that they have this edge
144 unsigned getLatency() const {
148 /// setLatency - Set the latency for this edge.
149 void setLatency(unsigned Lat) {
153 //// getSUnit - Return the SUnit to which this edge points.
154 SUnit *getSUnit() const {
155 return Dep.getPointer();
158 //// setSUnit - Assign the SUnit to which this edge points.
159 void setSUnit(SUnit *SU) {
163 /// getKind - Return an enum value representing the kind of the dependence.
164 Kind getKind() const {
168 /// isCtrl - Shorthand for getKind() != SDep::Data.
169 bool isCtrl() const {
170 return getKind() != Data;
173 /// isNormalMemory - Test if this is an Order dependence between two
174 /// memory accesses where both sides of the dependence access memory
175 /// in non-volatile and fully modeled ways.
176 bool isNormalMemory() const {
177 return getKind() == Order && Contents.Order.isNormalMemory;
180 /// isMustAlias - Test if this is an Order dependence that is marked
181 /// as "must alias", meaning that the SUnits at either end of the edge
182 /// have a memory dependence on a known memory location.
183 bool isMustAlias() const {
184 return getKind() == Order && Contents.Order.isMustAlias;
187 /// isArtificial - Test if this is an Order dependence that is marked
188 /// as "artificial", meaning it isn't necessary for correctness.
189 bool isArtificial() const {
190 return getKind() == Order && Contents.Order.isArtificial;
193 /// isAssignedRegDep - Test if this is a Data dependence that is
194 /// associated with a register.
195 bool isAssignedRegDep() const {
196 return getKind() == Data && Contents.Reg != 0;
199 /// getReg - Return the register associated with this edge. This is
200 /// only valid on Data, Anti, and Output edges. On Data edges, this
201 /// value may be zero, meaning there is no associated register.
202 unsigned getReg() const {
203 assert((getKind() == Data || getKind() == Anti || getKind() == Output) &&
204 "getReg called on non-register dependence edge!");
208 /// setReg - Assign the associated register for this edge. This is
209 /// only valid on Data, Anti, and Output edges. On Anti and Output
210 /// edges, this value must not be zero. On Data edges, the value may
211 /// be zero, which would mean that no specific register is associated
213 void setReg(unsigned Reg) {
214 assert((getKind() == Data || getKind() == Anti || getKind() == Output) &&
215 "setReg called on non-register dependence edge!");
216 assert((getKind() != Anti || Reg != 0) &&
217 "SDep::Anti edge cannot use the zero register!");
218 assert((getKind() != Output || Reg != 0) &&
219 "SDep::Output edge cannot use the zero register!");
225 struct isPodLike<SDep> { static const bool value = true; };
227 /// SUnit - Scheduling unit. This is a node in the scheduling DAG.
230 SDNode *Node; // Representative node.
231 MachineInstr *Instr; // Alternatively, a MachineInstr.
233 SUnit *OrigNode; // If not this, the node from which
234 // this node was cloned.
236 // Preds/Succs - The SUnits before/after us in the graph.
237 SmallVector<SDep, 4> Preds; // All sunit predecessors.
238 SmallVector<SDep, 4> Succs; // All sunit successors.
240 typedef SmallVector<SDep, 4>::iterator pred_iterator;
241 typedef SmallVector<SDep, 4>::iterator succ_iterator;
242 typedef SmallVector<SDep, 4>::const_iterator const_pred_iterator;
243 typedef SmallVector<SDep, 4>::const_iterator const_succ_iterator;
245 unsigned NodeNum; // Entry # of node in the node vector.
246 unsigned NodeQueueId; // Queue id of node.
247 unsigned NumPreds; // # of SDep::Data preds.
248 unsigned NumSuccs; // # of SDep::Data sucss.
249 unsigned NumPredsLeft; // # of preds not scheduled.
250 unsigned NumSuccsLeft; // # of succs not scheduled.
251 unsigned short Latency; // Node latency.
252 bool isCall : 1; // Is a function call.
253 bool isTwoAddress : 1; // Is a two-address instruction.
254 bool isCommutable : 1; // Is a commutable instruction.
255 bool hasPhysRegDefs : 1; // Has physreg defs that are being used.
256 bool hasPhysRegClobbers : 1; // Has any physreg defs, used or not.
257 bool isPending : 1; // True once pending.
258 bool isAvailable : 1; // True once available.
259 bool isScheduled : 1; // True once scheduled.
260 bool isScheduleHigh : 1; // True if preferable to schedule high.
261 bool isCloned : 1; // True if this node has been cloned.
262 Sched::Preference SchedulingPref; // Scheduling preference.
264 SmallVector<MachineInstr*, 4> DbgInstrList; // dbg_values referencing this.
266 bool isDepthCurrent : 1; // True if Depth is current.
267 bool isHeightCurrent : 1; // True if Height is current.
268 unsigned Depth; // Node depth.
269 unsigned Height; // Node height.
271 const TargetRegisterClass *CopyDstRC; // Is a special copy node if not null.
272 const TargetRegisterClass *CopySrcRC;
274 /// SUnit - Construct an SUnit for pre-regalloc scheduling to represent
275 /// an SDNode and any nodes flagged to it.
276 SUnit(SDNode *node, unsigned nodenum)
277 : Node(node), Instr(0), OrigNode(0), NodeNum(nodenum),
278 NodeQueueId(0), NumPreds(0), NumSuccs(0), NumPredsLeft(0),
279 NumSuccsLeft(0), Latency(0),
280 isCall(false), isTwoAddress(false), isCommutable(false),
281 hasPhysRegDefs(false), hasPhysRegClobbers(false),
282 isPending(false), isAvailable(false), isScheduled(false),
283 isScheduleHigh(false), isCloned(false),
284 SchedulingPref(Sched::None),
285 isDepthCurrent(false), isHeightCurrent(false), Depth(0), Height(0),
286 CopyDstRC(NULL), CopySrcRC(NULL) {}
288 /// SUnit - Construct an SUnit for post-regalloc scheduling to represent
290 SUnit(MachineInstr *instr, unsigned nodenum)
291 : Node(0), Instr(instr), OrigNode(0), NodeNum(nodenum),
292 NodeQueueId(0), NumPreds(0), NumSuccs(0), NumPredsLeft(0),
293 NumSuccsLeft(0), Latency(0),
294 isCall(false), isTwoAddress(false), isCommutable(false),
295 hasPhysRegDefs(false), hasPhysRegClobbers(false),
296 isPending(false), isAvailable(false), isScheduled(false),
297 isScheduleHigh(false), isCloned(false),
298 SchedulingPref(Sched::None),
299 isDepthCurrent(false), isHeightCurrent(false), Depth(0), Height(0),
300 CopyDstRC(NULL), CopySrcRC(NULL) {}
302 /// SUnit - Construct a placeholder SUnit.
304 : Node(0), Instr(0), OrigNode(0), NodeNum(~0u),
305 NodeQueueId(0), NumPreds(0), NumSuccs(0), NumPredsLeft(0),
306 NumSuccsLeft(0), Latency(0),
307 isCall(false), isTwoAddress(false), isCommutable(false),
308 hasPhysRegDefs(false), hasPhysRegClobbers(false),
309 isPending(false), isAvailable(false), isScheduled(false),
310 isScheduleHigh(false), isCloned(false),
311 SchedulingPref(Sched::None),
312 isDepthCurrent(false), isHeightCurrent(false), Depth(0), Height(0),
313 CopyDstRC(NULL), CopySrcRC(NULL) {}
315 /// setNode - Assign the representative SDNode for this SUnit.
316 /// This may be used during pre-regalloc scheduling.
317 void setNode(SDNode *N) {
318 assert(!Instr && "Setting SDNode of SUnit with MachineInstr!");
322 /// getNode - Return the representative SDNode for this SUnit.
323 /// This may be used during pre-regalloc scheduling.
324 SDNode *getNode() const {
325 assert(!Instr && "Reading SDNode of SUnit with MachineInstr!");
329 /// isInstr - Return true if this SUnit refers to a machine instruction as
330 /// opposed to an SDNode.
331 bool isInstr() const { return !Node; }
333 /// setInstr - Assign the instruction for the SUnit.
334 /// This may be used during post-regalloc scheduling.
335 void setInstr(MachineInstr *MI) {
336 assert(!Node && "Setting MachineInstr of SUnit with SDNode!");
340 /// getInstr - Return the representative MachineInstr for this SUnit.
341 /// This may be used during post-regalloc scheduling.
342 MachineInstr *getInstr() const {
343 assert(!Node && "Reading MachineInstr of SUnit with SDNode!");
347 /// addPred - This adds the specified edge as a pred of the current node if
348 /// not already. It also adds the current node as a successor of the
350 void addPred(const SDep &D);
352 /// removePred - This removes the specified edge as a pred of the current
353 /// node if it exists. It also removes the current node as a successor of
354 /// the specified node.
355 void removePred(const SDep &D);
357 /// getDepth - Return the depth of this node, which is the length of the
358 /// maximum path up to any node with has no predecessors.
359 unsigned getDepth() const {
361 const_cast<SUnit *>(this)->ComputeDepth();
365 /// getHeight - Return the height of this node, which is the length of the
366 /// maximum path down to any node with has no successors.
367 unsigned getHeight() const {
368 if (!isHeightCurrent)
369 const_cast<SUnit *>(this)->ComputeHeight();
373 /// setDepthToAtLeast - If NewDepth is greater than this node's
374 /// depth value, set it to be the new depth value. This also
375 /// recursively marks successor nodes dirty.
376 void setDepthToAtLeast(unsigned NewDepth);
378 /// setDepthToAtLeast - If NewDepth is greater than this node's
379 /// depth value, set it to be the new height value. This also
380 /// recursively marks predecessor nodes dirty.
381 void setHeightToAtLeast(unsigned NewHeight);
383 /// setDepthDirty - Set a flag in this node to indicate that its
384 /// stored Depth value will require recomputation the next time
385 /// getDepth() is called.
386 void setDepthDirty();
388 /// setHeightDirty - Set a flag in this node to indicate that its
389 /// stored Height value will require recomputation the next time
390 /// getHeight() is called.
391 void setHeightDirty();
393 /// isPred - Test if node N is a predecessor of this node.
394 bool isPred(SUnit *N) {
395 for (unsigned i = 0, e = (unsigned)Preds.size(); i != e; ++i)
396 if (Preds[i].getSUnit() == N)
401 /// isSucc - Test if node N is a successor of this node.
402 bool isSucc(SUnit *N) {
403 for (unsigned i = 0, e = (unsigned)Succs.size(); i != e; ++i)
404 if (Succs[i].getSUnit() == N)
409 void dump(const ScheduleDAG *G) const;
410 void dumpAll(const ScheduleDAG *G) const;
411 void print(raw_ostream &O, const ScheduleDAG *G) const;
415 void ComputeHeight();
418 //===--------------------------------------------------------------------===//
419 /// SchedulingPriorityQueue - This interface is used to plug different
420 /// priorities computation algorithms into the list scheduler. It implements
421 /// the interface of a standard priority queue, where nodes are inserted in
422 /// arbitrary order and returned in priority order. The computation of the
423 /// priority and the representation of the queue are totally up to the
424 /// implementation to decide.
426 class SchedulingPriorityQueue {
430 SchedulingPriorityQueue(bool rf = false):
431 CurCycle(0), HasReadyFilter(rf) {}
432 virtual ~SchedulingPriorityQueue() {}
434 virtual bool isBottomUp() const = 0;
436 virtual void initNodes(std::vector<SUnit> &SUnits) = 0;
437 virtual void addNode(const SUnit *SU) = 0;
438 virtual void updateNode(const SUnit *SU) = 0;
439 virtual void releaseState() = 0;
441 virtual bool empty() const = 0;
443 bool hasReadyFilter() const { return HasReadyFilter; }
445 virtual bool isReady(SUnit *U) const {
446 assert(!HasReadyFilter && "The ready filter must override isReady()");
449 virtual void push(SUnit *U) = 0;
451 void push_all(const std::vector<SUnit *> &Nodes) {
452 for (std::vector<SUnit *>::const_iterator I = Nodes.begin(),
453 E = Nodes.end(); I != E; ++I)
457 virtual SUnit *pop() = 0;
459 virtual void remove(SUnit *SU) = 0;
461 virtual void dump(ScheduleDAG *DAG) const {}
463 /// ScheduledNode - As each node is scheduled, this method is invoked. This
464 /// allows the priority function to adjust the priority of related
465 /// unscheduled nodes, for example.
467 virtual void ScheduledNode(SUnit *) {}
469 virtual void UnscheduledNode(SUnit *) {}
471 void setCurCycle(unsigned Cycle) {
475 unsigned getCurCycle() const {
482 MachineBasicBlock *BB; // The block in which to insert instructions
483 MachineBasicBlock::iterator InsertPos;// The position to insert instructions
484 const TargetMachine &TM; // Target processor
485 const TargetInstrInfo *TII; // Target instruction information
486 const TargetRegisterInfo *TRI; // Target processor register info
487 MachineFunction &MF; // Machine function
488 MachineRegisterInfo &MRI; // Virtual/real register map
489 std::vector<SUnit*> Sequence; // The schedule. Null SUnit*'s
490 // represent noop instructions.
491 std::vector<SUnit> SUnits; // The scheduling units.
492 SUnit EntrySU; // Special node for the region entry.
493 SUnit ExitSU; // Special node for the region exit.
495 explicit ScheduleDAG(MachineFunction &mf);
497 virtual ~ScheduleDAG();
499 /// getInstrDesc - Return the TargetInstrDesc of this SUnit.
500 /// Return NULL for SDNodes without a machine opcode.
501 const TargetInstrDesc *getInstrDesc(const SUnit *SU) const {
502 if (SU->isInstr()) return &SU->getInstr()->getDesc();
503 return getNodeDesc(SU->getNode());
506 /// viewGraph - Pop up a GraphViz/gv window with the ScheduleDAG rendered
511 /// EmitSchedule - Insert MachineInstrs into the MachineBasicBlock
512 /// according to the order specified in Sequence.
514 virtual MachineBasicBlock *EmitSchedule() = 0;
516 void dumpSchedule() const;
518 virtual void dumpNode(const SUnit *SU) const = 0;
520 /// getGraphNodeLabel - Return a label for an SUnit node in a visualization
521 /// of the ScheduleDAG.
522 virtual std::string getGraphNodeLabel(const SUnit *SU) const = 0;
524 /// addCustomGraphFeatures - Add custom features for a visualization of
526 virtual void addCustomGraphFeatures(GraphWriter<ScheduleDAG*> &) const {}
529 /// VerifySchedule - Verify that all SUnits were scheduled and that
530 /// their state is consistent.
531 void VerifySchedule(bool isBottomUp);
535 /// Run - perform scheduling.
537 void Run(MachineBasicBlock *bb, MachineBasicBlock::iterator insertPos);
539 /// BuildSchedGraph - Build SUnits and set up their Preds and Succs
540 /// to form the scheduling dependency graph.
542 virtual void BuildSchedGraph(AliasAnalysis *AA) = 0;
544 /// ComputeLatency - Compute node latency.
546 virtual void ComputeLatency(SUnit *SU) = 0;
548 /// ComputeOperandLatency - Override dependence edge latency using
549 /// operand use/def information
551 virtual void ComputeOperandLatency(SUnit *, SUnit *,
554 /// Schedule - Order nodes according to selected style, filling
555 /// in the Sequence member.
557 virtual void Schedule() = 0;
559 /// ForceUnitLatencies - Return true if all scheduling edges should be given
560 /// a latency value of one. The default is to return false; schedulers may
561 /// override this as needed.
562 virtual bool ForceUnitLatencies() const { return false; }
564 /// EmitNoop - Emit a noop instruction.
568 void EmitPhysRegCopy(SUnit *SU, DenseMap<SUnit*, unsigned> &VRBaseMap);
571 // Return the TargetInstrDesc of this SDNode or NULL.
572 const TargetInstrDesc *getNodeDesc(const SDNode *Node) const;
575 class SUnitIterator : public std::iterator<std::forward_iterator_tag,
580 SUnitIterator(SUnit *N, unsigned Op) : Node(N), Operand(Op) {}
582 bool operator==(const SUnitIterator& x) const {
583 return Operand == x.Operand;
585 bool operator!=(const SUnitIterator& x) const { return !operator==(x); }
587 const SUnitIterator &operator=(const SUnitIterator &I) {
588 assert(I.Node==Node && "Cannot assign iterators to two different nodes!");
593 pointer operator*() const {
594 return Node->Preds[Operand].getSUnit();
596 pointer operator->() const { return operator*(); }
598 SUnitIterator& operator++() { // Preincrement
602 SUnitIterator operator++(int) { // Postincrement
603 SUnitIterator tmp = *this; ++*this; return tmp;
606 static SUnitIterator begin(SUnit *N) { return SUnitIterator(N, 0); }
607 static SUnitIterator end (SUnit *N) {
608 return SUnitIterator(N, (unsigned)N->Preds.size());
611 unsigned getOperand() const { return Operand; }
612 const SUnit *getNode() const { return Node; }
613 /// isCtrlDep - Test if this is not an SDep::Data dependence.
614 bool isCtrlDep() const {
615 return getSDep().isCtrl();
617 bool isArtificialDep() const {
618 return getSDep().isArtificial();
620 const SDep &getSDep() const {
621 return Node->Preds[Operand];
625 template <> struct GraphTraits<SUnit*> {
626 typedef SUnit NodeType;
627 typedef SUnitIterator ChildIteratorType;
628 static inline NodeType *getEntryNode(SUnit *N) { return N; }
629 static inline ChildIteratorType child_begin(NodeType *N) {
630 return SUnitIterator::begin(N);
632 static inline ChildIteratorType child_end(NodeType *N) {
633 return SUnitIterator::end(N);
637 template <> struct GraphTraits<ScheduleDAG*> : public GraphTraits<SUnit*> {
638 typedef std::vector<SUnit>::iterator nodes_iterator;
639 static nodes_iterator nodes_begin(ScheduleDAG *G) {
640 return G->SUnits.begin();
642 static nodes_iterator nodes_end(ScheduleDAG *G) {
643 return G->SUnits.end();
647 /// ScheduleDAGTopologicalSort is a class that computes a topological
648 /// ordering for SUnits and provides methods for dynamically updating
649 /// the ordering as new edges are added.
651 /// This allows a very fast implementation of IsReachable, for example.
653 class ScheduleDAGTopologicalSort {
654 /// SUnits - A reference to the ScheduleDAG's SUnits.
655 std::vector<SUnit> &SUnits;
657 /// Index2Node - Maps topological index to the node number.
658 std::vector<int> Index2Node;
659 /// Node2Index - Maps the node number to its topological index.
660 std::vector<int> Node2Index;
661 /// Visited - a set of nodes visited during a DFS traversal.
664 /// DFS - make a DFS traversal and mark all nodes affected by the
665 /// edge insertion. These nodes will later get new topological indexes
666 /// by means of the Shift method.
667 void DFS(const SUnit *SU, int UpperBound, bool& HasLoop);
669 /// Shift - reassign topological indexes for the nodes in the DAG
670 /// to preserve the topological ordering.
671 void Shift(BitVector& Visited, int LowerBound, int UpperBound);
673 /// Allocate - assign the topological index to the node n.
674 void Allocate(int n, int index);
677 explicit ScheduleDAGTopologicalSort(std::vector<SUnit> &SUnits);
679 /// InitDAGTopologicalSorting - create the initial topological
680 /// ordering from the DAG to be scheduled.
681 void InitDAGTopologicalSorting();
683 /// IsReachable - Checks if SU is reachable from TargetSU.
684 bool IsReachable(const SUnit *SU, const SUnit *TargetSU);
686 /// WillCreateCycle - Returns true if adding an edge from SU to TargetSU
687 /// will create a cycle.
688 bool WillCreateCycle(SUnit *SU, SUnit *TargetSU);
690 /// AddPred - Updates the topological ordering to accomodate an edge
691 /// to be added from SUnit X to SUnit Y.
692 void AddPred(SUnit *Y, SUnit *X);
694 /// RemovePred - Updates the topological ordering to accomodate an
695 /// an edge to be removed from the specified node N from the predecessors
696 /// of the current node M.
697 void RemovePred(SUnit *M, SUnit *N);
699 typedef std::vector<int>::iterator iterator;
700 typedef std::vector<int>::const_iterator const_iterator;
701 iterator begin() { return Index2Node.begin(); }
702 const_iterator begin() const { return Index2Node.begin(); }
703 iterator end() { return Index2Node.end(); }
704 const_iterator end() const { return Index2Node.end(); }
706 typedef std::vector<int>::reverse_iterator reverse_iterator;
707 typedef std::vector<int>::const_reverse_iterator const_reverse_iterator;
708 reverse_iterator rbegin() { return Index2Node.rbegin(); }
709 const_reverse_iterator rbegin() const { return Index2Node.rbegin(); }
710 reverse_iterator rend() { return Index2Node.rend(); }
711 const_reverse_iterator rend() const { return Index2Node.rend(); }