1 //===- llvm/ADT/DepthFirstIterator.h - Depth First iterator -----*- 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 builds on the ADT/GraphTraits.h file to build generic depth
11 // first graph iterator. This file exposes the following functions/types:
13 // df_begin/df_end/df_iterator
14 // * Normal depth-first iteration - visit a node and then all of its children.
16 // idf_begin/idf_end/idf_iterator
17 // * Depth-first iteration on the 'inverse' graph.
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
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
31 //===----------------------------------------------------------------------===//
33 #ifndef LLVM_ADT_DEPTHFIRSTITERATOR_H
34 #define LLVM_ADT_DEPTHFIRSTITERATOR_H
36 #include "llvm/ADT/GraphTraits.h"
37 #include "llvm/ADT/SmallPtrSet.h"
38 #include "llvm/ADT/PointerIntPair.h"
44 // df_iterator_storage - A private class which is used to figure out where to
45 // store the visited set.
46 template<class SetType, bool External> // Non-external set
47 class df_iterator_storage {
52 template<class SetType>
53 class df_iterator_storage<SetType, true> {
55 df_iterator_storage(SetType &VSet) : Visited(VSet) {}
56 df_iterator_storage(const df_iterator_storage &S) : Visited(S.Visited) {}
61 // Generic Depth First Iterator
62 template<class GraphT,
63 class SetType = llvm::SmallPtrSet<typename GraphTraits<GraphT>::NodeType*, 8>,
64 bool ExtStorage = false, class GT = GraphTraits<GraphT> >
65 class 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;
71 typedef typename GT::NodeType NodeType;
72 typedef typename GT::ChildIteratorType ChildItTy;
73 typedef PointerIntPair<NodeType*, 1> PointerIntTy;
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;
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)));
85 inline df_iterator() {
86 // End is when stack is empty
88 inline df_iterator(NodeType *Node, SetType &S)
89 : df_iterator_storage<SetType, ExtStorage>(S) {
91 VisitStack.push_back(std::make_pair(PointerIntTy(Node, 0),
92 GT::child_begin(Node)));
93 this->Visited.insert(Node);
96 inline df_iterator(SetType &S)
97 : df_iterator_storage<SetType, ExtStorage>(S) {
98 // End is when stack is empty
101 inline void toNext() {
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);
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)) {
117 this->Visited.insert(Next);
118 VisitStack.push_back(std::make_pair(PointerIntTy(Next, 0),
119 GT::child_begin(Next)));
124 // Oops, ran out of successors... go up a level on the stack.
125 VisitStack.pop_back();
126 } while (!VisitStack.empty());
130 typedef typename super::pointer pointer;
131 typedef df_iterator<GraphT, SetType, ExtStorage, GT> _Self;
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));
137 static inline _Self end(const GraphT& G) { return _Self(); }
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);
143 static inline _Self end(const GraphT& G, SetType &S) { return _Self(S); }
145 inline bool operator==(const _Self& x) const {
146 return VisitStack.size() == x.VisitStack.size() &&
147 VisitStack == x.VisitStack;
149 inline bool operator!=(const _Self& x) const { return !operator==(x); }
151 inline pointer operator*() const {
152 return VisitStack.back().first.getPointer();
155 // This is a nonstandard operator-> that dereferences the pointer an extra
156 // time... so that you can actually call methods ON the Node, because
157 // the contained type is a pointer. This allows BBIt->getTerminator() f.e.
159 inline NodeType *operator->() const { return operator*(); }
161 inline _Self& operator++() { // Preincrement
166 // skips all children of the current node and traverses to next node
168 inline _Self& skipChildren() {
169 VisitStack.pop_back();
170 if (!VisitStack.empty())
175 inline _Self operator++(int) { // Postincrement
176 _Self tmp = *this; ++*this; return tmp;
179 // nodeVisited - return true if this iterator has already visited the
180 // specified node. This is public, and will probably be used to iterate over
181 // nodes that a depth first iteration did not find: ie unreachable nodes.
183 inline bool nodeVisited(NodeType *Node) const {
184 return this->Visited.count(Node) != 0;
189 // Provide global constructors that automatically figure out correct types...
192 df_iterator<T> df_begin(const T& G) {
193 return df_iterator<T>::begin(G);
197 df_iterator<T> df_end(const T& G) {
198 return df_iterator<T>::end(G);
201 // Provide global definitions of external depth first iterators...
202 template <class T, class SetTy = std::set<typename GraphTraits<T>::NodeType*> >
203 struct df_ext_iterator : public df_iterator<T, SetTy, true> {
204 df_ext_iterator(const df_iterator<T, SetTy, true> &V)
205 : df_iterator<T, SetTy, true>(V) {}
208 template <class T, class SetTy>
209 df_ext_iterator<T, SetTy> df_ext_begin(const T& G, SetTy &S) {
210 return df_ext_iterator<T, SetTy>::begin(G, S);
213 template <class T, class SetTy>
214 df_ext_iterator<T, SetTy> df_ext_end(const T& G, SetTy &S) {
215 return df_ext_iterator<T, SetTy>::end(G, S);
219 // Provide global definitions of inverse depth first iterators...
221 class SetTy = llvm::SmallPtrSet<typename GraphTraits<T>::NodeType*, 8>,
222 bool External = false>
223 struct idf_iterator : public df_iterator<Inverse<T>, SetTy, External> {
224 idf_iterator(const df_iterator<Inverse<T>, SetTy, External> &V)
225 : df_iterator<Inverse<T>, SetTy, External>(V) {}
229 idf_iterator<T> idf_begin(const T& G) {
230 return idf_iterator<T>::begin(Inverse<T>(G));
234 idf_iterator<T> idf_end(const T& G){
235 return idf_iterator<T>::end(Inverse<T>(G));
238 // Provide global definitions of external inverse depth first iterators...
239 template <class T, class SetTy = std::set<typename GraphTraits<T>::NodeType*> >
240 struct idf_ext_iterator : public idf_iterator<T, SetTy, true> {
241 idf_ext_iterator(const idf_iterator<T, SetTy, true> &V)
242 : idf_iterator<T, SetTy, true>(V) {}
243 idf_ext_iterator(const df_iterator<Inverse<T>, SetTy, true> &V)
244 : idf_iterator<T, SetTy, true>(V) {}
247 template <class T, class SetTy>
248 idf_ext_iterator<T, SetTy> idf_ext_begin(const T& G, SetTy &S) {
249 return idf_ext_iterator<T, SetTy>::begin(Inverse<T>(G), S);
252 template <class T, class SetTy>
253 idf_ext_iterator<T, SetTy> idf_ext_end(const T& G, SetTy &S) {
254 return idf_ext_iterator<T, SetTy>::end(Inverse<T>(G), S);
257 } // End llvm namespace