PostOrderIterator.h revision 5207936a24ab9e0bfaa10e798625df65143e3716 
1//===- llvm/ADT/PostOrderIterator.h - PostOrder iterator --------*- C++ -*-===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file builds on the ADT/GraphTraits.h file to build a generic graph
11// post order iterator.  This should work over any graph type that has a
12// GraphTraits specialization.
13//
14//===----------------------------------------------------------------------===//
15
16#ifndef LLVM_ADT_POSTORDERITERATOR_H
17#define LLVM_ADT_POSTORDERITERATOR_H
18
19#include "llvm/ADT/GraphTraits.h"
20#include "llvm/ADT/SmallPtrSet.h"
21#include <set>
22#include <vector>
23
24namespace llvm {
25
26template<class SetType, bool External>   // Non-external set
27class po_iterator_storage {
28public:
29  SetType Visited;
30};
31
32/// DFSetTraits - Allow the SetType used to record depth-first search results to
33/// optionally record node postorder.
34template<class SetType>
35struct DFSetTraits {
36  static void finishPostorder(
37    typename SetType::iterator::value_type, SetType &) {}
38};
39
40template<class SetType>
41class po_iterator_storage<SetType, true> {
42public:
43  po_iterator_storage(SetType &VSet) : Visited(VSet) {}
44  po_iterator_storage(const po_iterator_storage &S) : Visited(S.Visited) {}
45  SetType &Visited;
46};
47
48template<class GraphT,
49  class SetType = llvm::SmallPtrSet<typename GraphTraits<GraphT>::NodeType*, 8>,
50  bool ExtStorage = false,
51  class GT = GraphTraits<GraphT> >
52class po_iterator : public std::iterator<std::forward_iterator_tag,
53                                         typename GT::NodeType, ptrdiff_t>,
54                    public po_iterator_storage<SetType, ExtStorage> {
55  typedef std::iterator<std::forward_iterator_tag,
56                        typename GT::NodeType, ptrdiff_t> super;
57  typedef typename GT::NodeType          NodeType;
58  typedef typename GT::ChildIteratorType ChildItTy;
59
60  // VisitStack - Used to maintain the ordering.  Top = current block
61  // First element is basic block pointer, second is the 'next child' to visit
62  std::vector<std::pair<NodeType *, ChildItTy> > VisitStack;
63
64  void traverseChild() {
65    while (VisitStack.back().second != GT::child_end(VisitStack.back().first)) {
66      NodeType *BB = *VisitStack.back().second++;
67      if (this->Visited.insert(BB)) {  // If the block is not visited...
68        VisitStack.push_back(std::make_pair(BB, GT::child_begin(BB)));
69      }
70    }
71  }
72
73  inline po_iterator(NodeType *BB) {
74    this->Visited.insert(BB);
75    VisitStack.push_back(std::make_pair(BB, GT::child_begin(BB)));
76    traverseChild();
77  }
78  inline po_iterator() {} // End is when stack is empty.
79
80  inline po_iterator(NodeType *BB, SetType &S) :
81    po_iterator_storage<SetType, ExtStorage>(S) {
82    if (this->Visited.insert(BB)) {
83      VisitStack.push_back(std::make_pair(BB, GT::child_begin(BB)));
84      traverseChild();
85    }
86  }
87
88  inline po_iterator(SetType &S) :
89      po_iterator_storage<SetType, ExtStorage>(S) {
90  } // End is when stack is empty.
91public:
92  typedef typename super::pointer pointer;
93  typedef po_iterator<GraphT, SetType, ExtStorage, GT> _Self;
94
95  // Provide static "constructors"...
96  static inline _Self begin(GraphT G) { return _Self(GT::getEntryNode(G)); }
97  static inline _Self end  (GraphT G) { return _Self(); }
98
99  static inline _Self begin(GraphT G, SetType &S) {
100    return _Self(GT::getEntryNode(G), S);
101  }
102  static inline _Self end  (GraphT G, SetType &S) { return _Self(S); }
103
104  inline bool operator==(const _Self& x) const {
105    return VisitStack == x.VisitStack;
106  }
107  inline bool operator!=(const _Self& x) const { return !operator==(x); }
108
109  inline pointer operator*() const {
110    return VisitStack.back().first;
111  }
112
113  // This is a nonstandard operator-> that dereferences the pointer an extra
114  // time... so that you can actually call methods ON the BasicBlock, because
115  // the contained type is a pointer.  This allows BBIt->getTerminator() f.e.
116  //
117  inline NodeType *operator->() const { return operator*(); }
118
119  inline _Self& operator++() {   // Preincrement
120    DFSetTraits<SetType>::finishPostorder(VisitStack.back().first,
121                                          this->Visited);
122    VisitStack.pop_back();
123    if (!VisitStack.empty())
124      traverseChild();
125    return *this;
126  }
127
128  inline _Self operator++(int) { // Postincrement
129    _Self tmp = *this; ++*this; return tmp;
130  }
131};
132
133// Provide global constructors that automatically figure out correct types...
134//
135template <class T>
136po_iterator<T> po_begin(T G) { return po_iterator<T>::begin(G); }
137template <class T>
138po_iterator<T> po_end  (T G) { return po_iterator<T>::end(G); }
139
140// Provide global definitions of external postorder iterators...
141template<class T, class SetType=std::set<typename GraphTraits<T>::NodeType*> >
142struct po_ext_iterator : public po_iterator<T, SetType, true> {
143  po_ext_iterator(const po_iterator<T, SetType, true> &V) :
144  po_iterator<T, SetType, true>(V) {}
145};
146
147template<class T, class SetType>
148po_ext_iterator<T, SetType> po_ext_begin(T G, SetType &S) {
149  return po_ext_iterator<T, SetType>::begin(G, S);
150}
151
152template<class T, class SetType>
153po_ext_iterator<T, SetType> po_ext_end(T G, SetType &S) {
154  return po_ext_iterator<T, SetType>::end(G, S);
155}
156
157// Provide global definitions of inverse post order iterators...
158template <class T,
159          class SetType = std::set<typename GraphTraits<T>::NodeType*>,
160          bool External = false>
161struct ipo_iterator : public po_iterator<Inverse<T>, SetType, External > {
162  ipo_iterator(const po_iterator<Inverse<T>, SetType, External> &V) :
163     po_iterator<Inverse<T>, SetType, External> (V) {}
164};
165
166template <class T>
167ipo_iterator<T> ipo_begin(T G, bool Reverse = false) {
168  return ipo_iterator<T>::begin(G, Reverse);
169}
170
171template <class T>
172ipo_iterator<T> ipo_end(T G){
173  return ipo_iterator<T>::end(G);
174}
175
176//Provide global definitions of external inverse postorder iterators...
177template <class T,
178          class SetType = std::set<typename GraphTraits<T>::NodeType*> >
179struct ipo_ext_iterator : public ipo_iterator<T, SetType, true> {
180  ipo_ext_iterator(const ipo_iterator<T, SetType, true> &V) :
181    ipo_iterator<T, SetType, true>(&V) {}
182  ipo_ext_iterator(const po_iterator<Inverse<T>, SetType, true> &V) :
183    ipo_iterator<T, SetType, true>(&V) {}
184};
185
186template <class T, class SetType>
187ipo_ext_iterator<T, SetType> ipo_ext_begin(T G, SetType &S) {
188  return ipo_ext_iterator<T, SetType>::begin(G, S);
189}
190
191template <class T, class SetType>
192ipo_ext_iterator<T, SetType> ipo_ext_end(T G, SetType &S) {
193  return ipo_ext_iterator<T, SetType>::end(G, S);
194}
195
196//===--------------------------------------------------------------------===//
197// Reverse Post Order CFG iterator code
198//===--------------------------------------------------------------------===//
199//
200// This is used to visit basic blocks in a method in reverse post order.  This
201// class is awkward to use because I don't know a good incremental algorithm to
202// computer RPO from a graph.  Because of this, the construction of the
203// ReversePostOrderTraversal object is expensive (it must walk the entire graph
204// with a postorder iterator to build the data structures).  The moral of this
205// story is: Don't create more ReversePostOrderTraversal classes than necessary.
206//
207// This class should be used like this:
208// {
209//   ReversePostOrderTraversal<Function*> RPOT(FuncPtr); // Expensive to create
210//   for (rpo_iterator I = RPOT.begin(); I != RPOT.end(); ++I) {
211//      ...
212//   }
213//   for (rpo_iterator I = RPOT.begin(); I != RPOT.end(); ++I) {
214//      ...
215//   }
216// }
217//
218
219template<class GraphT, class GT = GraphTraits<GraphT> >
220class ReversePostOrderTraversal {
221  typedef typename GT::NodeType NodeType;
222  std::vector<NodeType*> Blocks;       // Block list in normal PO order
223  inline void Initialize(NodeType *BB) {
224    copy(po_begin(BB), po_end(BB), back_inserter(Blocks));
225  }
226public:
227  typedef typename std::vector<NodeType*>::reverse_iterator rpo_iterator;
228
229  inline ReversePostOrderTraversal(GraphT G) {
230    Initialize(GT::getEntryNode(G));
231  }
232
233  // Because we want a reverse post order, use reverse iterators from the vector
234  inline rpo_iterator begin() { return Blocks.rbegin(); }
235  inline rpo_iterator end()   { return Blocks.rend(); }
236};
237
238} // End llvm namespace
239
240#endif
241