LLVM API Documentation
00001 //===- llvm/ADT/PostOrderIterator.h - PostOrder iterator --------*- C++ -*-===// 00002 // 00003 // The LLVM Compiler Infrastructure 00004 // 00005 // This file was developed by the LLVM research group and is distributed under 00006 // the University of Illinois Open Source License. See LICENSE.TXT for details. 00007 // 00008 //===----------------------------------------------------------------------===// 00009 // 00010 // This file builds on the ADT/GraphTraits.h file to build a generic graph 00011 // post order iterator. This should work over any graph type that has a 00012 // GraphTraits specialization. 00013 // 00014 //===----------------------------------------------------------------------===// 00015 00016 #ifndef LLVM_ADT_POSTORDERITERATOR_H 00017 #define LLVM_ADT_POSTORDERITERATOR_H 00018 00019 #include "llvm/ADT/GraphTraits.h" 00020 #include "llvm/ADT/iterator" 00021 #include <stack> 00022 #include <set> 00023 00024 namespace llvm { 00025 00026 template<class GraphT, class GT = GraphTraits<GraphT> > 00027 class po_iterator : public forward_iterator<typename GT::NodeType, ptrdiff_t> { 00028 typedef forward_iterator<typename GT::NodeType, ptrdiff_t> super; 00029 typedef typename GT::NodeType NodeType; 00030 typedef typename GT::ChildIteratorType ChildItTy; 00031 00032 std::set<NodeType *> Visited; // All of the blocks visited so far... 00033 // VisitStack - Used to maintain the ordering. Top = current block 00034 // First element is basic block pointer, second is the 'next child' to visit 00035 std::stack<std::pair<NodeType *, ChildItTy> > VisitStack; 00036 00037 void traverseChild() { 00038 while (VisitStack.top().second != GT::child_end(VisitStack.top().first)) { 00039 NodeType *BB = *VisitStack.top().second++; 00040 if (!Visited.count(BB)) { // If the block is not visited... 00041 Visited.insert(BB); 00042 VisitStack.push(std::make_pair(BB, GT::child_begin(BB))); 00043 } 00044 } 00045 } 00046 00047 inline po_iterator(NodeType *BB) { 00048 Visited.insert(BB); 00049 VisitStack.push(std::make_pair(BB, GT::child_begin(BB))); 00050 traverseChild(); 00051 } 00052 inline po_iterator() { /* End is when stack is empty */ } 00053 public: 00054 typedef typename super::pointer pointer; 00055 typedef po_iterator<GraphT, GT> _Self; 00056 00057 // Provide static "constructors"... 00058 static inline _Self begin(GraphT G) { return _Self(GT::getEntryNode(G)); } 00059 static inline _Self end (GraphT G) { return _Self(); } 00060 00061 inline bool operator==(const _Self& x) const { 00062 return VisitStack == x.VisitStack; 00063 } 00064 inline bool operator!=(const _Self& x) const { return !operator==(x); } 00065 00066 inline pointer operator*() const { 00067 return VisitStack.top().first; 00068 } 00069 00070 // This is a nonstandard operator-> that dereferences the pointer an extra 00071 // time... so that you can actually call methods ON the BasicBlock, because 00072 // the contained type is a pointer. This allows BBIt->getTerminator() f.e. 00073 // 00074 inline NodeType *operator->() const { return operator*(); } 00075 00076 inline _Self& operator++() { // Preincrement 00077 VisitStack.pop(); 00078 if (!VisitStack.empty()) 00079 traverseChild(); 00080 return *this; 00081 } 00082 00083 inline _Self operator++(int) { // Postincrement 00084 _Self tmp = *this; ++*this; return tmp; 00085 } 00086 }; 00087 00088 // Provide global constructors that automatically figure out correct types... 00089 // 00090 template <class T> 00091 po_iterator<T> po_begin(T G) { return po_iterator<T>::begin(G); } 00092 template <class T> 00093 po_iterator<T> po_end (T G) { return po_iterator<T>::end(G); } 00094 00095 // Provide global definitions of inverse post order iterators... 00096 template <class T> 00097 struct ipo_iterator : public po_iterator<Inverse<T> > { 00098 ipo_iterator(const po_iterator<Inverse<T> > &V) :po_iterator<Inverse<T> >(V){} 00099 }; 00100 00101 template <class T> 00102 ipo_iterator<T> ipo_begin(T G, bool Reverse = false) { 00103 return ipo_iterator<T>::begin(G, Reverse); 00104 } 00105 00106 template <class T> 00107 ipo_iterator<T> ipo_end(T G){ 00108 return ipo_iterator<T>::end(G); 00109 } 00110 00111 00112 //===--------------------------------------------------------------------===// 00113 // Reverse Post Order CFG iterator code 00114 //===--------------------------------------------------------------------===// 00115 // 00116 // This is used to visit basic blocks in a method in reverse post order. This 00117 // class is awkward to use because I don't know a good incremental algorithm to 00118 // computer RPO from a graph. Because of this, the construction of the 00119 // ReversePostOrderTraversal object is expensive (it must walk the entire graph 00120 // with a postorder iterator to build the data structures). The moral of this 00121 // story is: Don't create more ReversePostOrderTraversal classes than necessary. 00122 // 00123 // This class should be used like this: 00124 // { 00125 // ReversePostOrderTraversal<Function*> RPOT(FuncPtr); // Expensive to create 00126 // for (rpo_iterator I = RPOT.begin(); I != RPOT.end(); ++I) { 00127 // ... 00128 // } 00129 // for (rpo_iterator I = RPOT.begin(); I != RPOT.end(); ++I) { 00130 // ... 00131 // } 00132 // } 00133 // 00134 00135 template<class GraphT, class GT = GraphTraits<GraphT> > 00136 class ReversePostOrderTraversal { 00137 typedef typename GT::NodeType NodeType; 00138 std::vector<NodeType*> Blocks; // Block list in normal PO order 00139 inline void Initialize(NodeType *BB) { 00140 copy(po_begin(BB), po_end(BB), back_inserter(Blocks)); 00141 } 00142 public: 00143 typedef typename std::vector<NodeType*>::reverse_iterator rpo_iterator; 00144 00145 inline ReversePostOrderTraversal(GraphT G) { 00146 Initialize(GT::getEntryNode(G)); 00147 } 00148 00149 // Because we want a reverse post order, use reverse iterators from the vector 00150 inline rpo_iterator begin() { return Blocks.rbegin(); } 00151 inline rpo_iterator end() { return Blocks.rend(); } 00152 }; 00153 00154 } // End llvm namespace 00155 00156 #endif