PostOrderIterator.h revision 194612 
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/iterator.h"
21#include "llvm/ADT/SmallPtrSet.h"
22#include <set>
23#include <stack>
24#include <vector>
25
26namespace llvm {
27
28template<class SetType, bool External>   // Non-external set
29class po_iterator_storage {
30public:
31  SetType Visited;
32};
33
34template<class SetType>
35class po_iterator_storage<SetType, true> {
36public:
37  po_iterator_storage(SetType &VSet) : Visited(VSet) {}
38  po_iterator_storage(const po_iterator_storage &S) : Visited(S.Visited) {}
39  SetType &Visited;
40};
41
42template<class GraphT,
43  class SetType = llvm::SmallPtrSet<typename GraphTraits<GraphT>::NodeType*, 8>,
44  bool ExtStorage = false,
45  class GT = GraphTraits<GraphT> >
46class po_iterator : public forward_iterator<typename GT::NodeType, ptrdiff_t>,
47                    public po_iterator_storage<SetType, ExtStorage> {
48  typedef forward_iterator<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::stack<std::pair<NodeType *, ChildItTy> > VisitStack;
55
56  void traverseChild() {
57    while (VisitStack.top().second != GT::child_end(VisitStack.top().first)) {
58      NodeType *BB = *VisitStack.top().second++;
59      if (!this->Visited.count(BB)) {  // If the block is not visited...
60        this->Visited.insert(BB);
61        VisitStack.push(std::make_pair(BB, GT::child_begin(BB)));
62      }
63    }
64  }
65
66  inline po_iterator(NodeType *BB) {
67    this->Visited.insert(BB);
68    VisitStack.push(std::make_pair(BB, GT::child_begin(BB)));
69    traverseChild();
70  }
71  inline po_iterator() {} // End is when stack is empty.
72
73  inline po_iterator(NodeType *BB, SetType &S) :
74    po_iterator_storage<SetType, ExtStorage>(&S) {
75    if(!S.count(BB)) {
76      this->Visited.insert(BB);
77      VisitStack.push(std::make_pair(BB, GT::child_begin(BB)));
78      traverseChild();
79    }
80  }
81
82  inline po_iterator(SetType &S) :
83      po_iterator_storage<SetType, ExtStorage>(&S) {
84  } // End is when stack is empty.
85public:
86  typedef typename super::pointer pointer;
87  typedef po_iterator<GraphT, SetType, ExtStorage, GT> _Self;
88
89  // Provide static "constructors"...
90  static inline _Self begin(GraphT G) { return _Self(GT::getEntryNode(G)); }
91  static inline _Self end  (GraphT G) { return _Self(); }
92
93  static inline _Self begin(GraphT G, SetType &S) {
94    return _Self(GT::getEntryNode(G), S);
95  }
96  static inline _Self end  (GraphT G, SetType &S) { return _Self(S); }
97
98  inline bool operator==(const _Self& x) const {
99    return VisitStack == x.VisitStack;
100  }
101  inline bool operator!=(const _Self& x) const { return !operator==(x); }
102
103  inline pointer operator*() const {
104    return VisitStack.top().first;
105  }
106
107  // This is a nonstandard operator-> that dereferences the pointer an extra
108  // time... so that you can actually call methods ON the BasicBlock, because
109  // the contained type is a pointer.  This allows BBIt->getTerminator() f.e.
110  //
111  inline NodeType *operator->() const { return operator*(); }
112
113  inline _Self& operator++() {   // Preincrement
114    VisitStack.pop();
115    if (!VisitStack.empty())
116      traverseChild();
117    return *this;
118  }
119
120  inline _Self operator++(int) { // Postincrement
121    _Self tmp = *this; ++*this; return tmp;
122  }
123};
124
125// Provide global constructors that automatically figure out correct types...
126//
127template <class T>
128po_iterator<T> po_begin(T G) { return po_iterator<T>::begin(G); }
129template <class T>
130po_iterator<T> po_end  (T G) { return po_iterator<T>::end(G); }
131
132// Provide global definitions of external postorder iterators...
133template<class T, class SetType=std::set<typename GraphTraits<T>::NodeType*> >
134struct po_ext_iterator : public po_iterator<T, SetType, true> {
135  po_ext_iterator(const po_iterator<T, SetType, true> &V) :
136  po_iterator<T, SetType, true>(V) {}
137};
138
139template<class T, class SetType>
140po_ext_iterator<T, SetType> po_ext_begin(T G, SetType &S) {
141  return po_ext_iterator<T, SetType>::begin(G, S);
142}
143
144template<class T, class SetType>
145po_ext_iterator<T, SetType> po_ext_end(T G, SetType &S) {
146  return po_ext_iterator<T, SetType>::end(G, S);
147}
148
149// Provide global definitions of inverse post order iterators...
150template <class T,
151          class SetType = std::set<typename GraphTraits<T>::NodeType*>,
152          bool External = false>
153struct ipo_iterator : public po_iterator<Inverse<T>, SetType, External > {
154  ipo_iterator(const po_iterator<Inverse<T>, SetType, External> &V) :
155     po_iterator<Inverse<T>, SetType, External> (V) {}
156};
157
158template <class T>
159ipo_iterator<T> ipo_begin(T G, bool Reverse = false) {
160  return ipo_iterator<T>::begin(G, Reverse);
161}
162
163template <class T>
164ipo_iterator<T> ipo_end(T G){
165  return ipo_iterator<T>::end(G);
166}
167
168//Provide global definitions of external inverse postorder iterators...
169template <class T,
170          class SetType = std::set<typename GraphTraits<T>::NodeType*> >
171struct ipo_ext_iterator : public ipo_iterator<T, SetType, true> {
172  ipo_ext_iterator(const ipo_iterator<T, SetType, true> &V) :
173    ipo_iterator<T, SetType, true>(&V) {}
174  ipo_ext_iterator(const po_iterator<Inverse<T>, SetType, true> &V) :
175    ipo_iterator<T, SetType, true>(&V) {}
176};
177
178template <class T, class SetType>
179ipo_ext_iterator<T, SetType> ipo_ext_begin(T G, SetType &S) {
180  return ipo_ext_iterator<T, SetType>::begin(G, S);
181}
182
183template <class T, class SetType>
184ipo_ext_iterator<T, SetType> ipo_ext_end(T G, SetType &S) {
185  return ipo_ext_iterator<T, SetType>::end(G, S);
186}
187
188//===--------------------------------------------------------------------===//
189// Reverse Post Order CFG iterator code
190//===--------------------------------------------------------------------===//
191//
192// This is used to visit basic blocks in a method in reverse post order.  This
193// class is awkward to use because I don't know a good incremental algorithm to
194// computer RPO from a graph.  Because of this, the construction of the
195// ReversePostOrderTraversal object is expensive (it must walk the entire graph
196// with a postorder iterator to build the data structures).  The moral of this
197// story is: Don't create more ReversePostOrderTraversal classes than necessary.
198//
199// This class should be used like this:
200// {
201//   ReversePostOrderTraversal<Function*> RPOT(FuncPtr); // Expensive to create
202//   for (rpo_iterator I = RPOT.begin(); I != RPOT.end(); ++I) {
203//      ...
204//   }
205//   for (rpo_iterator I = RPOT.begin(); I != RPOT.end(); ++I) {
206//      ...
207//   }
208// }
209//
210
211template<class GraphT, class GT = GraphTraits<GraphT> >
212class ReversePostOrderTraversal {
213  typedef typename GT::NodeType NodeType;
214  std::vector<NodeType*> Blocks;       // Block list in normal PO order
215  inline void Initialize(NodeType *BB) {
216    copy(po_begin(BB), po_end(BB), back_inserter(Blocks));
217  }
218public:
219  typedef typename std::vector<NodeType*>::reverse_iterator rpo_iterator;
220
221  inline ReversePostOrderTraversal(GraphT G) {
222    Initialize(GT::getEntryNode(G));
223  }
224
225  // Because we want a reverse post order, use reverse iterators from the vector
226  inline rpo_iterator begin() { return Blocks.rbegin(); }
227  inline rpo_iterator end()   { return Blocks.rend(); }
228};
229
230} // End llvm namespace
231
232#endif
233