1 //===- llvm/ADT/PostOrderIterator.h - PostOrder 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 a generic graph
11 // post order iterator. This should work over any graph type that has a
12 // GraphTraits specialization.
14 //===----------------------------------------------------------------------===//
16 #ifndef LLVM_ADT_POSTORDERITERATOR_H
17 #define LLVM_ADT_POSTORDERITERATOR_H
19 #include "llvm/ADT/GraphTraits.h"
20 #include "llvm/ADT/SmallPtrSet.h"
27 template<class SetType, bool External> // Non-external set
28 class po_iterator_storage {
33 template<class SetType>
34 class po_iterator_storage<SetType, true> {
36 po_iterator_storage(SetType &VSet) : Visited(VSet) {}
37 po_iterator_storage(const po_iterator_storage &S) : Visited(S.Visited) {}
41 template<class GraphT,
42 class SetType = llvm::SmallPtrSet<typename GraphTraits<GraphT>::NodeType*, 8>,
43 bool ExtStorage = false,
44 class GT = GraphTraits<GraphT> >
45 class po_iterator : public std::iterator<std::forward_iterator_tag,
46 typename GT::NodeType, ptrdiff_t>,
47 public po_iterator_storage<SetType, ExtStorage> {
48 typedef std::iterator<std::forward_iterator_tag,
49 typename GT::NodeType, ptrdiff_t> super;
50 typedef typename GT::NodeType NodeType;
51 typedef typename GT::ChildIteratorType ChildItTy;
53 // VisitStack - Used to maintain the ordering. Top = current block
54 // First element is basic block pointer, second is the 'next child' to visit
55 std::stack<std::pair<NodeType *, ChildItTy> > VisitStack;
57 void traverseChild() {
58 while (VisitStack.top().second != GT::child_end(VisitStack.top().first)) {
59 NodeType *BB = *VisitStack.top().second++;
60 if (!this->Visited.count(BB)) { // If the block is not visited...
61 this->Visited.insert(BB);
62 VisitStack.push(std::make_pair(BB, GT::child_begin(BB)));
67 inline po_iterator(NodeType *BB) {
68 this->Visited.insert(BB);
69 VisitStack.push(std::make_pair(BB, GT::child_begin(BB)));
72 inline po_iterator() {} // End is when stack is empty.
74 inline po_iterator(NodeType *BB, SetType &S) :
75 po_iterator_storage<SetType, ExtStorage>(S) {
77 this->Visited.insert(BB);
78 VisitStack.push(std::make_pair(BB, GT::child_begin(BB)));
83 inline po_iterator(SetType &S) :
84 po_iterator_storage<SetType, ExtStorage>(S) {
85 } // End is when stack is empty.
87 typedef typename super::pointer pointer;
88 typedef po_iterator<GraphT, SetType, ExtStorage, GT> _Self;
90 // Provide static "constructors"...
91 static inline _Self begin(GraphT G) { return _Self(GT::getEntryNode(G)); }
92 static inline _Self end (GraphT G) { return _Self(); }
94 static inline _Self begin(GraphT G, SetType &S) {
95 return _Self(GT::getEntryNode(G), S);
97 static inline _Self end (GraphT G, SetType &S) { return _Self(S); }
99 inline bool operator==(const _Self& x) const {
100 return VisitStack == x.VisitStack;
102 inline bool operator!=(const _Self& x) const { return !operator==(x); }
104 inline pointer operator*() const {
105 return VisitStack.top().first;
108 // This is a nonstandard operator-> that dereferences the pointer an extra
109 // time... so that you can actually call methods ON the BasicBlock, because
110 // the contained type is a pointer. This allows BBIt->getTerminator() f.e.
112 inline NodeType *operator->() const { return operator*(); }
114 inline _Self& operator++() { // Preincrement
116 if (!VisitStack.empty())
121 inline _Self operator++(int) { // Postincrement
122 _Self tmp = *this; ++*this; return tmp;
126 // Provide global constructors that automatically figure out correct types...
129 po_iterator<T> po_begin(T G) { return po_iterator<T>::begin(G); }
131 po_iterator<T> po_end (T G) { return po_iterator<T>::end(G); }
133 // Provide global definitions of external postorder iterators...
134 template<class T, class SetType=std::set<typename GraphTraits<T>::NodeType*> >
135 struct po_ext_iterator : public po_iterator<T, SetType, true> {
136 po_ext_iterator(const po_iterator<T, SetType, true> &V) :
137 po_iterator<T, SetType, true>(V) {}
140 template<class T, class SetType>
141 po_ext_iterator<T, SetType> po_ext_begin(T G, SetType &S) {
142 return po_ext_iterator<T, SetType>::begin(G, S);
145 template<class T, class SetType>
146 po_ext_iterator<T, SetType> po_ext_end(T G, SetType &S) {
147 return po_ext_iterator<T, SetType>::end(G, S);
150 // Provide global definitions of inverse post order iterators...
152 class SetType = std::set<typename GraphTraits<T>::NodeType*>,
153 bool External = false>
154 struct ipo_iterator : public po_iterator<Inverse<T>, SetType, External > {
155 ipo_iterator(const po_iterator<Inverse<T>, SetType, External> &V) :
156 po_iterator<Inverse<T>, SetType, External> (V) {}
160 ipo_iterator<T> ipo_begin(T G, bool Reverse = false) {
161 return ipo_iterator<T>::begin(G, Reverse);
165 ipo_iterator<T> ipo_end(T G){
166 return ipo_iterator<T>::end(G);
169 //Provide global definitions of external inverse postorder iterators...
171 class SetType = std::set<typename GraphTraits<T>::NodeType*> >
172 struct ipo_ext_iterator : public ipo_iterator<T, SetType, true> {
173 ipo_ext_iterator(const ipo_iterator<T, SetType, true> &V) :
174 ipo_iterator<T, SetType, true>(&V) {}
175 ipo_ext_iterator(const po_iterator<Inverse<T>, SetType, true> &V) :
176 ipo_iterator<T, SetType, true>(&V) {}
179 template <class T, class SetType>
180 ipo_ext_iterator<T, SetType> ipo_ext_begin(T G, SetType &S) {
181 return ipo_ext_iterator<T, SetType>::begin(G, S);
184 template <class T, class SetType>
185 ipo_ext_iterator<T, SetType> ipo_ext_end(T G, SetType &S) {
186 return ipo_ext_iterator<T, SetType>::end(G, S);
189 //===--------------------------------------------------------------------===//
190 // Reverse Post Order CFG iterator code
191 //===--------------------------------------------------------------------===//
193 // This is used to visit basic blocks in a method in reverse post order. This
194 // class is awkward to use because I don't know a good incremental algorithm to
195 // computer RPO from a graph. Because of this, the construction of the
196 // ReversePostOrderTraversal object is expensive (it must walk the entire graph
197 // with a postorder iterator to build the data structures). The moral of this
198 // story is: Don't create more ReversePostOrderTraversal classes than necessary.
200 // This class should be used like this:
202 // ReversePostOrderTraversal<Function*> RPOT(FuncPtr); // Expensive to create
203 // for (rpo_iterator I = RPOT.begin(); I != RPOT.end(); ++I) {
206 // for (rpo_iterator I = RPOT.begin(); I != RPOT.end(); ++I) {
212 template<class GraphT, class GT = GraphTraits<GraphT> >
213 class ReversePostOrderTraversal {
214 typedef typename GT::NodeType NodeType;
215 std::vector<NodeType*> Blocks; // Block list in normal PO order
216 inline void Initialize(NodeType *BB) {
217 copy(po_begin(BB), po_end(BB), back_inserter(Blocks));
220 typedef typename std::vector<NodeType*>::reverse_iterator rpo_iterator;
222 inline ReversePostOrderTraversal(GraphT G) {
223 Initialize(GT::getEntryNode(G));
226 // Because we want a reverse post order, use reverse iterators from the vector
227 inline rpo_iterator begin() { return Blocks.rbegin(); }
228 inline rpo_iterator end() { return Blocks.rend(); }
231 } // End llvm namespace