1//===- llvm/ADT/DepthFirstIterator.h - Depth First 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 generic depth
11// first graph iterator.  This file exposes the following functions/types:
12//
13// df_begin/df_end/df_iterator
14//   * Normal depth-first iteration - visit a node and then all of its children.
15//
16// idf_begin/idf_end/idf_iterator
17//   * Depth-first iteration on the 'inverse' graph.
18//
19// df_ext_begin/df_ext_end/df_ext_iterator
20//   * Normal depth-first iteration - visit a node and then all of its children.
21//     This iterator stores the 'visited' set in an external set, which allows
22//     it to be more efficient, and allows external clients to use the set for
23//     other purposes.
24//
25// idf_ext_begin/idf_ext_end/idf_ext_iterator
26//   * Depth-first iteration on the 'inverse' graph.
27//     This iterator stores the 'visited' set in an external set, which allows
28//     it to be more efficient, and allows external clients to use the set for
29//     other purposes.
30//
31//===----------------------------------------------------------------------===//
32
33#ifndef LLVM_ADT_DEPTHFIRSTITERATOR_H
34#define LLVM_ADT_DEPTHFIRSTITERATOR_H
35
36#include "llvm/ADT/GraphTraits.h"
37#include "llvm/ADT/SmallPtrSet.h"
38#include "llvm/ADT/PointerIntPair.h"
39#include <set>
40#include <vector>
41
42namespace llvm {
43
44// df_iterator_storage - A private class which is used to figure out where to
45// store the visited set.
46template<class SetType, bool External>   // Non-external set
47class df_iterator_storage {
48public:
49  SetType Visited;
50};
51
52template<class SetType>
53class df_iterator_storage<SetType, true> {
54public:
55  df_iterator_storage(SetType &VSet) : Visited(VSet) {}
56  df_iterator_storage(const df_iterator_storage &S) : Visited(S.Visited) {}
57  SetType &Visited;
58};
59
60
61// Generic Depth First Iterator
62template<class GraphT,
63class SetType = llvm::SmallPtrSet<typename GraphTraits<GraphT>::NodeType*, 8>,
64         bool ExtStorage = false, class GT = GraphTraits<GraphT> >
65class df_iterator : public std::iterator<std::forward_iterator_tag,
66                                         typename GT::NodeType, ptrdiff_t>,
67                    public df_iterator_storage<SetType, ExtStorage> {
68  typedef std::iterator<std::forward_iterator_tag,
69                        typename GT::NodeType, ptrdiff_t> super;
70
71  typedef typename GT::NodeType          NodeType;
72  typedef typename GT::ChildIteratorType ChildItTy;
73  typedef PointerIntPair<NodeType*, 1>   PointerIntTy;
74
75  // VisitStack - Used to maintain the ordering.  Top = current block
76  // First element is node pointer, second is the 'next child' to visit
77  // if the int in PointerIntTy is 0, the 'next child' to visit is invalid
78  std::vector<std::pair<PointerIntTy, ChildItTy> > VisitStack;
79private:
80  inline df_iterator(NodeType *Node) {
81    this->Visited.insert(Node);
82    VisitStack.push_back(std::make_pair(PointerIntTy(Node, 0),
83                                        GT::child_begin(Node)));
84  }
85  inline df_iterator() {
86    // End is when stack is empty
87  }
88  inline df_iterator(NodeType *Node, SetType &S)
89    : df_iterator_storage<SetType, ExtStorage>(S) {
90    if (!S.count(Node)) {
91      VisitStack.push_back(std::make_pair(PointerIntTy(Node, 0),
92                                          GT::child_begin(Node)));
93      this->Visited.insert(Node);
94    }
95  }
96  inline df_iterator(SetType &S)
97    : df_iterator_storage<SetType, ExtStorage>(S) {
98    // End is when stack is empty
99  }
100
101  inline void toNext() {
102    do {
103      std::pair<PointerIntTy, ChildItTy> &Top = VisitStack.back();
104      NodeType *Node = Top.first.getPointer();
105      ChildItTy &It  = Top.second;
106      if (!Top.first.getInt()) {
107        // now retrieve the real begin of the children before we dive in
108        It = GT::child_begin(Node);
109        Top.first.setInt(1);
110      }
111
112      while (It != GT::child_end(Node)) {
113        NodeType *Next = *It++;
114        // Has our next sibling been visited?
115        if (Next && !this->Visited.count(Next)) {
116          // No, do it now.
117          this->Visited.insert(Next);
118          VisitStack.push_back(std::make_pair(PointerIntTy(Next, 0),
119                                              GT::child_begin(Next)));
120          return;
121        }
122      }
123
124      // Oops, ran out of successors... go up a level on the stack.
125      VisitStack.pop_back();
126    } while (!VisitStack.empty());
127  }
128
129public:
130  typedef typename super::pointer pointer;
131  typedef df_iterator<GraphT, SetType, ExtStorage, GT> _Self;
132
133  // Provide static begin and end methods as our public "constructors"
134  static inline _Self begin(const GraphT& G) {
135    return _Self(GT::getEntryNode(G));
136  }
137  static inline _Self end(const GraphT& G) { return _Self(); }
138
139  // Static begin and end methods as our public ctors for external iterators
140  static inline _Self begin(const GraphT& G, SetType &S) {
141    return _Self(GT::getEntryNode(G), S);
142  }
143  static inline _Self end(const GraphT& G, SetType &S) { return _Self(S); }
144
145  inline bool operator==(const _Self& x) const {
146    return VisitStack == x.VisitStack;
147  }
148  inline bool operator!=(const _Self& x) const { return !operator==(x); }
149
150  inline pointer operator*() const {
151    return VisitStack.back().first.getPointer();
152  }
153
154  // This is a nonstandard operator-> that dereferences the pointer an extra
155  // time... so that you can actually call methods ON the Node, because
156  // the contained type is a pointer.  This allows BBIt->getTerminator() f.e.
157  //
158  inline NodeType *operator->() const { return operator*(); }
159
160  inline _Self& operator++() {   // Preincrement
161    toNext();
162    return *this;
163  }
164
165  // skips all children of the current node and traverses to next node
166  //
167  inline _Self& skipChildren() {
168    VisitStack.pop_back();
169    if (!VisitStack.empty())
170      toNext();
171    return *this;
172  }
173
174  inline _Self operator++(int) { // Postincrement
175    _Self tmp = *this; ++*this; return tmp;
176  }
177
178  // nodeVisited - return true if this iterator has already visited the
179  // specified node.  This is public, and will probably be used to iterate over
180  // nodes that a depth first iteration did not find: ie unreachable nodes.
181  //
182  inline bool nodeVisited(NodeType *Node) const {
183    return this->Visited.count(Node) != 0;
184  }
185
186  /// getPathLength - Return the length of the path from the entry node to the
187  /// current node, counting both nodes.
188  unsigned getPathLength() const { return VisitStack.size(); }
189
190  /// getPath - Return the n'th node in the path from the entry node to the
191  /// current node.
192  NodeType *getPath(unsigned n) const {
193    return VisitStack[n].first.getPointer();
194  }
195};
196
197
198// Provide global constructors that automatically figure out correct types...
199//
200template <class T>
201df_iterator<T> df_begin(const T& G) {
202  return df_iterator<T>::begin(G);
203}
204
205template <class T>
206df_iterator<T> df_end(const T& G) {
207  return df_iterator<T>::end(G);
208}
209
210// Provide global definitions of external depth first iterators...
211template <class T, class SetTy = std::set<typename GraphTraits<T>::NodeType*> >
212struct df_ext_iterator : public df_iterator<T, SetTy, true> {
213  df_ext_iterator(const df_iterator<T, SetTy, true> &V)
214    : df_iterator<T, SetTy, true>(V) {}
215};
216
217template <class T, class SetTy>
218df_ext_iterator<T, SetTy> df_ext_begin(const T& G, SetTy &S) {
219  return df_ext_iterator<T, SetTy>::begin(G, S);
220}
221
222template <class T, class SetTy>
223df_ext_iterator<T, SetTy> df_ext_end(const T& G, SetTy &S) {
224  return df_ext_iterator<T, SetTy>::end(G, S);
225}
226
227
228// Provide global definitions of inverse depth first iterators...
229template <class T,
230  class SetTy = llvm::SmallPtrSet<typename GraphTraits<T>::NodeType*, 8>,
231          bool External = false>
232struct idf_iterator : public df_iterator<Inverse<T>, SetTy, External> {
233  idf_iterator(const df_iterator<Inverse<T>, SetTy, External> &V)
234    : df_iterator<Inverse<T>, SetTy, External>(V) {}
235};
236
237template <class T>
238idf_iterator<T> idf_begin(const T& G) {
239  return idf_iterator<T>::begin(Inverse<T>(G));
240}
241
242template <class T>
243idf_iterator<T> idf_end(const T& G){
244  return idf_iterator<T>::end(Inverse<T>(G));
245}
246
247// Provide global definitions of external inverse depth first iterators...
248template <class T, class SetTy = std::set<typename GraphTraits<T>::NodeType*> >
249struct idf_ext_iterator : public idf_iterator<T, SetTy, true> {
250  idf_ext_iterator(const idf_iterator<T, SetTy, true> &V)
251    : idf_iterator<T, SetTy, true>(V) {}
252  idf_ext_iterator(const df_iterator<Inverse<T>, SetTy, true> &V)
253    : idf_iterator<T, SetTy, true>(V) {}
254};
255
256template <class T, class SetTy>
257idf_ext_iterator<T, SetTy> idf_ext_begin(const T& G, SetTy &S) {
258  return idf_ext_iterator<T, SetTy>::begin(Inverse<T>(G), S);
259}
260
261template <class T, class SetTy>
262idf_ext_iterator<T, SetTy> idf_ext_end(const T& G, SetTy &S) {
263  return idf_ext_iterator<T, SetTy>::end(Inverse<T>(G), S);
264}
265
266} // End llvm namespace
267
268#endif
269