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/PointerIntPair.h"
38 #include "llvm/ADT/SmallPtrSet.h"
39 #include "llvm/ADT/iterator_range.h"
45 // df_iterator_storage - A private class which is used to figure out where to
46 // store the visited set.
47 template<class SetType, bool External> // Non-external set
48 class df_iterator_storage {
53 template<class SetType>
54 class df_iterator_storage<SetType, true> {
56 df_iterator_storage(SetType &VSet) : Visited(VSet) {}
57 df_iterator_storage(const df_iterator_storage &S) : Visited(S.Visited) {}
62 // Generic Depth First Iterator
63 template<class GraphT,
64 class SetType = llvm::SmallPtrSet<typename GraphTraits<GraphT>::NodeType*, 8>,
65 bool ExtStorage = false, class GT = GraphTraits<GraphT> >
66 class df_iterator : public std::iterator<std::forward_iterator_tag,
67 typename GT::NodeType, ptrdiff_t>,
68 public df_iterator_storage<SetType, ExtStorage> {
69 typedef std::iterator<std::forward_iterator_tag,
70 typename GT::NodeType, ptrdiff_t> super;
72 typedef typename GT::NodeType NodeType;
73 typedef typename GT::ChildIteratorType ChildItTy;
74 typedef PointerIntPair<NodeType*, 1> PointerIntTy;
76 // VisitStack - Used to maintain the ordering. Top = current block
77 // First element is node pointer, second is the 'next child' to visit
78 // if the int in PointerIntTy is 0, the 'next child' to visit is invalid
79 std::vector<std::pair<PointerIntTy, ChildItTy> > VisitStack;
81 inline df_iterator(NodeType *Node) {
82 this->Visited.insert(Node);
83 VisitStack.push_back(std::make_pair(PointerIntTy(Node, 0),
84 GT::child_begin(Node)));
86 inline df_iterator() {
87 // End is when stack is empty
89 inline df_iterator(NodeType *Node, SetType &S)
90 : df_iterator_storage<SetType, ExtStorage>(S) {
92 VisitStack.push_back(std::make_pair(PointerIntTy(Node, 0),
93 GT::child_begin(Node)));
94 this->Visited.insert(Node);
97 inline df_iterator(SetType &S)
98 : df_iterator_storage<SetType, ExtStorage>(S) {
99 // End is when stack is empty
102 inline void toNext() {
104 std::pair<PointerIntTy, ChildItTy> &Top = VisitStack.back();
105 NodeType *Node = Top.first.getPointer();
106 ChildItTy &It = Top.second;
107 if (!Top.first.getInt()) {
108 // now retrieve the real begin of the children before we dive in
109 It = GT::child_begin(Node);
113 while (It != GT::child_end(Node)) {
114 NodeType *Next = *It++;
115 // Has our next sibling been visited?
116 if (Next && this->Visited.insert(Next).second) {
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;
132 // Provide static begin and end methods as our public "constructors"
133 static df_iterator begin(const GraphT &G) {
134 return df_iterator(GT::getEntryNode(G));
136 static df_iterator end(const GraphT &G) { return df_iterator(); }
138 // Static begin and end methods as our public ctors for external iterators
139 static df_iterator begin(const GraphT &G, SetType &S) {
140 return df_iterator(GT::getEntryNode(G), S);
142 static df_iterator end(const GraphT &G, SetType &S) { return df_iterator(S); }
144 bool operator==(const df_iterator &x) const {
145 return VisitStack == x.VisitStack;
147 bool operator!=(const df_iterator &x) const { return !(*this == x); }
149 pointer operator*() const { return VisitStack.back().first.getPointer(); }
151 // This is a nonstandard operator-> that dereferences the pointer an extra
152 // time... so that you can actually call methods ON the Node, because
153 // the contained type is a pointer. This allows BBIt->getTerminator() f.e.
155 NodeType *operator->() const { return **this; }
157 df_iterator &operator++() { // Preincrement
162 // skips all children of the current node and traverses to next node
164 df_iterator &skipChildren() {
165 VisitStack.pop_back();
166 if (!VisitStack.empty())
171 df_iterator operator++(int) { // Postincrement
172 df_iterator tmp = *this;
177 // nodeVisited - return true if this iterator has already visited the
178 // specified node. This is public, and will probably be used to iterate over
179 // nodes that a depth first iteration did not find: ie unreachable nodes.
181 bool nodeVisited(NodeType *Node) const {
182 return this->Visited.count(Node) != 0;
185 /// getPathLength - Return the length of the path from the entry node to the
186 /// current node, counting both nodes.
187 unsigned getPathLength() const { return VisitStack.size(); }
189 /// getPath - Return the n'th node in the path from the entry node to the
191 NodeType *getPath(unsigned n) const {
192 return VisitStack[n].first.getPointer();
197 // Provide global constructors that automatically figure out correct types...
200 df_iterator<T> df_begin(const T& G) {
201 return df_iterator<T>::begin(G);
205 df_iterator<T> df_end(const T& G) {
206 return df_iterator<T>::end(G);
209 // Provide an accessor method to use them in range-based patterns.
211 iterator_range<df_iterator<T>> depth_first(const T& G) {
212 return iterator_range<df_iterator<T>>(df_begin(G), df_end(G));
215 // Provide global definitions of external depth first iterators...
216 template <class T, class SetTy = std::set<typename GraphTraits<T>::NodeType*> >
217 struct df_ext_iterator : public df_iterator<T, SetTy, true> {
218 df_ext_iterator(const df_iterator<T, SetTy, true> &V)
219 : df_iterator<T, SetTy, true>(V) {}
222 template <class T, class SetTy>
223 df_ext_iterator<T, SetTy> df_ext_begin(const T& G, SetTy &S) {
224 return df_ext_iterator<T, SetTy>::begin(G, S);
227 template <class T, class SetTy>
228 df_ext_iterator<T, SetTy> df_ext_end(const T& G, SetTy &S) {
229 return df_ext_iterator<T, SetTy>::end(G, S);
232 template <class T, class SetTy>
233 iterator_range<df_ext_iterator<T, SetTy>> depth_first_ext(const T& G,
235 return iterator_range<df_ext_iterator<T, SetTy>>(df_ext_begin(G, S),
240 // Provide global definitions of inverse depth first iterators...
242 class SetTy = llvm::SmallPtrSet<typename GraphTraits<T>::NodeType*, 8>,
243 bool External = false>
244 struct idf_iterator : public df_iterator<Inverse<T>, SetTy, External> {
245 idf_iterator(const df_iterator<Inverse<T>, SetTy, External> &V)
246 : df_iterator<Inverse<T>, SetTy, External>(V) {}
250 idf_iterator<T> idf_begin(const T& G) {
251 return idf_iterator<T>::begin(Inverse<T>(G));
255 idf_iterator<T> idf_end(const T& G){
256 return idf_iterator<T>::end(Inverse<T>(G));
259 // Provide an accessor method to use them in range-based patterns.
261 iterator_range<idf_iterator<T>> inverse_depth_first(const T& G) {
262 return iterator_range<idf_iterator<T>>(idf_begin(G), idf_end(G));
265 // Provide global definitions of external inverse depth first iterators...
266 template <class T, class SetTy = std::set<typename GraphTraits<T>::NodeType*> >
267 struct idf_ext_iterator : public idf_iterator<T, SetTy, true> {
268 idf_ext_iterator(const idf_iterator<T, SetTy, true> &V)
269 : idf_iterator<T, SetTy, true>(V) {}
270 idf_ext_iterator(const df_iterator<Inverse<T>, SetTy, true> &V)
271 : idf_iterator<T, SetTy, true>(V) {}
274 template <class T, class SetTy>
275 idf_ext_iterator<T, SetTy> idf_ext_begin(const T& G, SetTy &S) {
276 return idf_ext_iterator<T, SetTy>::begin(Inverse<T>(G), S);
279 template <class T, class SetTy>
280 idf_ext_iterator<T, SetTy> idf_ext_end(const T& G, SetTy &S) {
281 return idf_ext_iterator<T, SetTy>::end(Inverse<T>(G), S);
284 template <class T, class SetTy>
285 iterator_range<idf_ext_iterator<T, SetTy>> inverse_depth_first_ext(const T& G,
287 return iterator_range<idf_ext_iterator<T, SetTy>>(idf_ext_begin(G, S),
291 } // End llvm namespace