LLVM API Documentation

PostOrderIterator.h

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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 #include <vector>
00024 
00025 namespace llvm {
00026 
00027 template<class SetType, bool External>   // Non-external set 
00028 class po_iterator_storage { 
00029 public: 
00030   SetType Visited; 
00031 }; 
00032 
00033 template<class SetType> 
00034 class po_iterator_storage<SetType, true> { 
00035 public: 
00036   po_iterator_storage(SetType &VSet) : Visited(VSet) {} 
00037   po_iterator_storage(const po_iterator_storage &S) : Visited(S.Visited) {} 
00038   SetType &Visited; 
00039 }; 
00040 
00041 template<class GraphT, 
00042         class SetType = std::set<typename GraphTraits<GraphT>::NodeType*>, 
00043         bool ExtStorage = false, 
00044         class GT = GraphTraits<GraphT> > 
00045 class po_iterator : public forward_iterator<typename GT::NodeType, ptrdiff_t>, 
00046                     public po_iterator_storage<SetType, ExtStorage> { 
00047   typedef forward_iterator<typename GT::NodeType, ptrdiff_t> super;
00048   typedef typename GT::NodeType          NodeType;
00049   typedef typename GT::ChildIteratorType ChildItTy;
00050   
00051   // VisitStack - Used to maintain the ordering.  Top = current block
00052   // First element is basic block pointer, second is the 'next child' to visit
00053   std::stack<std::pair<NodeType *, ChildItTy> > VisitStack;
00054 
00055   void traverseChild() {
00056     while (VisitStack.top().second != GT::child_end(VisitStack.top().first)) {
00057       NodeType *BB = *VisitStack.top().second++;
00058       if (!this->Visited.count(BB)) {  // If the block is not visited...
00059         this->Visited.insert(BB);
00060         VisitStack.push(std::make_pair(BB, GT::child_begin(BB)));
00061       }
00062     }
00063   }
00064 
00065   inline po_iterator(NodeType *BB) {
00066     this->Visited.insert(BB);
00067     VisitStack.push(std::make_pair(BB, GT::child_begin(BB)));
00068     traverseChild();
00069   }
00070   inline po_iterator() {} // End is when stack is empty. 
00071      
00072   inline po_iterator(NodeType *BB, SetType &S) : 
00073     po_iterator_storage<SetType, ExtStorage>(&S) { 
00074     if(!S.count(BB)) { 
00075       this->Visited.insert(BB); 
00076       VisitStack.push(std::make_pair(BB, GT::child_begin(BB))); 
00077       traverseChild(); 
00078     } 
00079   } 
00080  
00081   inline po_iterator(SetType &S) : 
00082       po_iterator_storage<SetType, ExtStorage>(&S) {
00083   } // End is when stack is empty. 
00084 public:
00085   typedef typename super::pointer pointer;
00086   typedef po_iterator<GraphT, SetType, ExtStorage, GT> _Self; 
00087 
00088   // Provide static "constructors"...
00089   static inline _Self begin(GraphT G) { return _Self(GT::getEntryNode(G)); }
00090   static inline _Self end  (GraphT G) { return _Self(); }
00091 
00092   static inline _Self begin(GraphT G, SetType &S) { 
00093     return _Self(GT::getEntryNode(G), S); 
00094   } 
00095   static inline _Self end  (GraphT G, SetType &S) { return _Self(S); } 
00096   
00097   inline bool operator==(const _Self& x) const {
00098     return VisitStack == x.VisitStack;
00099   }
00100   inline bool operator!=(const _Self& x) const { return !operator==(x); }
00101 
00102   inline pointer operator*() const {
00103     return VisitStack.top().first;
00104   }
00105 
00106   // This is a nonstandard operator-> that dereferences the pointer an extra
00107   // time... so that you can actually call methods ON the BasicBlock, because
00108   // the contained type is a pointer.  This allows BBIt->getTerminator() f.e.
00109   //
00110   inline NodeType *operator->() const { return operator*(); }
00111 
00112   inline _Self& operator++() {   // Preincrement
00113     VisitStack.pop();
00114     if (!VisitStack.empty())
00115       traverseChild();
00116     return *this;
00117   }
00118 
00119   inline _Self operator++(int) { // Postincrement
00120     _Self tmp = *this; ++*this; return tmp;
00121   }
00122 };
00123 
00124 // Provide global constructors that automatically figure out correct types...
00125 //
00126 template <class T>
00127 po_iterator<T> po_begin(T G) { return po_iterator<T>::begin(G); }
00128 template <class T>
00129 po_iterator<T> po_end  (T G) { return po_iterator<T>::end(G); }
00130 
00131 // Provide global definitions of external postorder iterators... 
00132 template<class T, class SetType=std::set<typename GraphTraits<T>::NodeType*> > 
00133 struct po_ext_iterator : public po_iterator<T, SetType, true> { 
00134   po_ext_iterator(const po_iterator<T, SetType, true> &V) :  
00135   po_iterator<T, SetType, true>(V) {} 
00136 }; 
00137  
00138 template<class T, class SetType> 
00139 po_ext_iterator<T, SetType> po_ext_begin(T G, SetType &S) { 
00140   return po_ext_iterator<T, SetType>::begin(G, S); 
00141 } 
00142 
00143 template<class T, class SetType> 
00144 po_ext_iterator<T, SetType> po_ext_end(T G, SetType &S) { 
00145   return po_ext_iterator<T, SetType>::end(G, S); 
00146 } 
00147 
00148 // Provide global definitions of inverse post order iterators...
00149 template <class T, 
00150           class SetType = std::set<typename GraphTraits<T>::NoddeType*>,  
00151           bool External = false> 
00152 struct ipo_iterator : public po_iterator<Inverse<T>, SetType, External > { 
00153   ipo_iterator(const po_iterator<Inverse<T>, SetType, External> &V) : 
00154      po_iterator<Inverse<T>, SetType, External> (V) {} 
00155 };
00156 
00157 template <class T>
00158 ipo_iterator<T> ipo_begin(T G, bool Reverse = false) {
00159   return ipo_iterator<T>::begin(G, Reverse);
00160 }
00161 
00162 template <class T>
00163 ipo_iterator<T> ipo_end(T G){
00164   return ipo_iterator<T>::end(G);
00165 }
00166 
00167 //Provide global definitions of external inverse postorder iterators... 
00168 template <class T, class SetType = std::set<typename GraphTraits<T>::NodeType*> > 
00169 struct ipo_ext_iterator : public ipo_iterator<T, SetType, true> { 
00170   ipo_ext_iterator(const ipo_iterator<T, SetType, true> &V) : 
00171     ipo_iterator<T, SetType, true>(&V) {} 
00172   ipo_ext_iterator(const po_iterator<Inverse<T>, SetType, true> &V) : 
00173     ipo_iterator<T, SetType, true>(&V) {} 
00174 }; 
00175 
00176 template <class T, class SetType> 
00177 ipo_ext_iterator<T, SetType> ipo_ext_begin(T G, SetType &S) { 
00178   return ipo_ext_iterator<T, SetType>::begin(G, S); 
00179 } 
00180 
00181 template <class T, class SetType> 
00182 ipo_ext_iterator<T, SetType> ipo_ext_end(T G, SetType &S) { 
00183   return ipo_ext_iterator<T, SetType>::end(G, S); 
00184 } 
00185 
00186 //===--------------------------------------------------------------------===//
00187 // Reverse Post Order CFG iterator code
00188 //===--------------------------------------------------------------------===//
00189 //
00190 // This is used to visit basic blocks in a method in reverse post order.  This
00191 // class is awkward to use because I don't know a good incremental algorithm to
00192 // computer RPO from a graph.  Because of this, the construction of the
00193 // ReversePostOrderTraversal object is expensive (it must walk the entire graph
00194 // with a postorder iterator to build the data structures).  The moral of this
00195 // story is: Don't create more ReversePostOrderTraversal classes than necessary.
00196 //
00197 // This class should be used like this:
00198 // {
00199 //   ReversePostOrderTraversal<Function*> RPOT(FuncPtr); // Expensive to create
00200 //   for (rpo_iterator I = RPOT.begin(); I != RPOT.end(); ++I) {
00201 //      ...
00202 //   }
00203 //   for (rpo_iterator I = RPOT.begin(); I != RPOT.end(); ++I) {
00204 //      ...
00205 //   }
00206 // }
00207 //
00208 
00209 template<class GraphT, class GT = GraphTraits<GraphT> >
00210 class ReversePostOrderTraversal {
00211   typedef typename GT::NodeType NodeType;
00212   std::vector<NodeType*> Blocks;       // Block list in normal PO order
00213   inline void Initialize(NodeType *BB) {
00214     copy(po_begin(BB), po_end(BB), back_inserter(Blocks));
00215   }
00216 public:
00217   typedef typename std::vector<NodeType*>::reverse_iterator rpo_iterator;
00218 
00219   inline ReversePostOrderTraversal(GraphT G) {
00220     Initialize(GT::getEntryNode(G));
00221   }
00222 
00223   // Because we want a reverse post order, use reverse iterators from the vector
00224   inline rpo_iterator begin() { return Blocks.rbegin(); }
00225   inline rpo_iterator end()   { return Blocks.rend(); }
00226 };
00227 
00228 } // End llvm namespace
00229 
00230 #endif