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
24 namespace llvm {
25
26 template<class SetType, bool External> // Non-external set
27 class po_iterator_storage {
28 public:
29 SetType Visited;
30 };
31
32 template<class SetType>
33 class po_iterator_storage<SetType, true> {
34 public:
po_iterator_storage(SetType & VSet)35 po_iterator_storage(SetType &VSet) : Visited(VSet) {}
po_iterator_storage(const po_iterator_storage & S)36 po_iterator_storage(const po_iterator_storage &S) : Visited(S.Visited) {}
37 SetType &Visited;
38 };
39
40 template<class GraphT,
41 class SetType = llvm::SmallPtrSet<typename GraphTraits<GraphT>::NodeType*, 8>,
42 bool ExtStorage = false,
43 class GT = GraphTraits<GraphT> >
44 class po_iterator : public std::iterator<std::forward_iterator_tag,
45 typename GT::NodeType, ptrdiff_t>,
46 public po_iterator_storage<SetType, ExtStorage> {
47 typedef std::iterator<std::forward_iterator_tag,
48 typename GT::NodeType, ptrdiff_t> super;
49 typedef typename GT::NodeType NodeType;
50 typedef typename GT::ChildIteratorType ChildItTy;
51
52 // VisitStack - Used to maintain the ordering. Top = current block
53 // First element is basic block pointer, second is the 'next child' to visit
54 std::vector<std::pair<NodeType *, ChildItTy> > VisitStack;
55
traverseChild()56 void traverseChild() {
57 while (VisitStack.back().second != GT::child_end(VisitStack.back().first)) {
58 NodeType *BB = *VisitStack.back().second++;
59 if (this->Visited.insert(BB)) { // If the block is not visited...
60 VisitStack.push_back(std::make_pair(BB, GT::child_begin(BB)));
61 }
62 }
63 }
64
po_iterator(NodeType * BB)65 inline po_iterator(NodeType *BB) {
66 this->Visited.insert(BB);
67 VisitStack.push_back(std::make_pair(BB, GT::child_begin(BB)));
68 traverseChild();
69 }
po_iterator()70 inline po_iterator() {} // End is when stack is empty.
71
po_iterator(NodeType * BB,SetType & S)72 inline po_iterator(NodeType *BB, SetType &S) :
73 po_iterator_storage<SetType, ExtStorage>(S) {
74 if (this->Visited.insert(BB)) {
75 VisitStack.push_back(std::make_pair(BB, GT::child_begin(BB)));
76 traverseChild();
77 }
78 }
79
po_iterator(SetType & S)80 inline po_iterator(SetType &S) :
81 po_iterator_storage<SetType, ExtStorage>(S) {
82 } // End is when stack is empty.
83 public:
84 typedef typename super::pointer pointer;
85 typedef po_iterator<GraphT, SetType, ExtStorage, GT> _Self;
86
87 // Provide static "constructors"...
begin(GraphT G)88 static inline _Self begin(GraphT G) { return _Self(GT::getEntryNode(G)); }
end(GraphT G)89 static inline _Self end (GraphT G) { return _Self(); }
90
begin(GraphT G,SetType & S)91 static inline _Self begin(GraphT G, SetType &S) {
92 return _Self(GT::getEntryNode(G), S);
93 }
end(GraphT G,SetType & S)94 static inline _Self end (GraphT G, SetType &S) { return _Self(S); }
95
96 inline bool operator==(const _Self& x) const {
97 return VisitStack == x.VisitStack;
98 }
99 inline bool operator!=(const _Self& x) const { return !operator==(x); }
100
101 inline pointer operator*() const {
102 return VisitStack.back().first;
103 }
104
105 // This is a nonstandard operator-> that dereferences the pointer an extra
106 // time... so that you can actually call methods ON the BasicBlock, because
107 // the contained type is a pointer. This allows BBIt->getTerminator() f.e.
108 //
109 inline NodeType *operator->() const { return operator*(); }
110
111 inline _Self& operator++() { // Preincrement
112 VisitStack.pop_back();
113 if (!VisitStack.empty())
114 traverseChild();
115 return *this;
116 }
117
118 inline _Self operator++(int) { // Postincrement
119 _Self tmp = *this; ++*this; return tmp;
120 }
121 };
122
123 // Provide global constructors that automatically figure out correct types...
124 //
125 template <class T>
po_begin(T G)126 po_iterator<T> po_begin(T G) { return po_iterator<T>::begin(G); }
127 template <class T>
po_end(T G)128 po_iterator<T> po_end (T G) { return po_iterator<T>::end(G); }
129
130 // Provide global definitions of external postorder iterators...
131 template<class T, class SetType=std::set<typename GraphTraits<T>::NodeType*> >
132 struct po_ext_iterator : public po_iterator<T, SetType, true> {
po_ext_iteratorpo_ext_iterator133 po_ext_iterator(const po_iterator<T, SetType, true> &V) :
134 po_iterator<T, SetType, true>(V) {}
135 };
136
137 template<class T, class SetType>
po_ext_begin(T G,SetType & S)138 po_ext_iterator<T, SetType> po_ext_begin(T G, SetType &S) {
139 return po_ext_iterator<T, SetType>::begin(G, S);
140 }
141
142 template<class T, class SetType>
po_ext_end(T G,SetType & S)143 po_ext_iterator<T, SetType> po_ext_end(T G, SetType &S) {
144 return po_ext_iterator<T, SetType>::end(G, S);
145 }
146
147 // Provide global definitions of inverse post order iterators...
148 template <class T,
149 class SetType = std::set<typename GraphTraits<T>::NodeType*>,
150 bool External = false>
151 struct ipo_iterator : public po_iterator<Inverse<T>, SetType, External > {
ipo_iteratoripo_iterator152 ipo_iterator(const po_iterator<Inverse<T>, SetType, External> &V) :
153 po_iterator<Inverse<T>, SetType, External> (V) {}
154 };
155
156 template <class T>
157 ipo_iterator<T> ipo_begin(T G, bool Reverse = false) {
158 return ipo_iterator<T>::begin(G, Reverse);
159 }
160
161 template <class T>
ipo_end(T G)162 ipo_iterator<T> ipo_end(T G){
163 return ipo_iterator<T>::end(G);
164 }
165
166 //Provide global definitions of external inverse postorder iterators...
167 template <class T,
168 class SetType = std::set<typename GraphTraits<T>::NodeType*> >
169 struct ipo_ext_iterator : public ipo_iterator<T, SetType, true> {
ipo_ext_iteratoripo_ext_iterator170 ipo_ext_iterator(const ipo_iterator<T, SetType, true> &V) :
171 ipo_iterator<T, SetType, true>(&V) {}
ipo_ext_iteratoripo_ext_iterator172 ipo_ext_iterator(const po_iterator<Inverse<T>, SetType, true> &V) :
173 ipo_iterator<T, SetType, true>(&V) {}
174 };
175
176 template <class T, class SetType>
ipo_ext_begin(T G,SetType & S)177 ipo_ext_iterator<T, SetType> ipo_ext_begin(T G, SetType &S) {
178 return ipo_ext_iterator<T, SetType>::begin(G, S);
179 }
180
181 template <class T, class SetType>
ipo_ext_end(T G,SetType & S)182 ipo_ext_iterator<T, SetType> ipo_ext_end(T G, SetType &S) {
183 return ipo_ext_iterator<T, SetType>::end(G, S);
184 }
185
186 //===--------------------------------------------------------------------===//
187 // Reverse Post Order CFG iterator code
188 //===--------------------------------------------------------------------===//
189 //
190 // This is used to visit basic blocks in a method in reverse post order. This
191 // class is awkward to use because I don't know a good incremental algorithm to
192 // computer RPO from a graph. Because of this, the construction of the
193 // ReversePostOrderTraversal object is expensive (it must walk the entire graph
194 // with a postorder iterator to build the data structures). The moral of this
195 // story is: Don't create more ReversePostOrderTraversal classes than necessary.
196 //
197 // This class should be used like this:
198 // {
199 // ReversePostOrderTraversal<Function*> RPOT(FuncPtr); // Expensive to create
200 // for (rpo_iterator I = RPOT.begin(); I != RPOT.end(); ++I) {
201 // ...
202 // }
203 // for (rpo_iterator I = RPOT.begin(); I != RPOT.end(); ++I) {
204 // ...
205 // }
206 // }
207 //
208
209 template<class GraphT, class GT = GraphTraits<GraphT> >
210 class ReversePostOrderTraversal {
211 typedef typename GT::NodeType NodeType;
212 std::vector<NodeType*> Blocks; // Block list in normal PO order
Initialize(NodeType * BB)213 inline void Initialize(NodeType *BB) {
214 copy(po_begin(BB), po_end(BB), back_inserter(Blocks));
215 }
216 public:
217 typedef typename std::vector<NodeType*>::reverse_iterator rpo_iterator;
218
ReversePostOrderTraversal(GraphT G)219 inline ReversePostOrderTraversal(GraphT G) {
220 Initialize(GT::getEntryNode(G));
221 }
222
223 // Because we want a reverse post order, use reverse iterators from the vector
begin()224 inline rpo_iterator begin() { return Blocks.rbegin(); }
end()225 inline rpo_iterator end() { return Blocks.rend(); }
226 };
227
228 } // End llvm namespace
229
230 #endif
231