1193323Sed//===- llvm/ADT/PostOrderIterator.h - PostOrder iterator --------*- C++ -*-===// 2193323Sed// 3193323Sed// The LLVM Compiler Infrastructure 4193323Sed// 5193323Sed// This file is distributed under the University of Illinois Open Source 6193323Sed// License. See LICENSE.TXT for details. 7193323Sed// 8193323Sed//===----------------------------------------------------------------------===// 9193323Sed// 10193323Sed// This file builds on the ADT/GraphTraits.h file to build a generic graph 11193323Sed// post order iterator. This should work over any graph type that has a 12193323Sed// GraphTraits specialization. 13193323Sed// 14193323Sed//===----------------------------------------------------------------------===// 15193323Sed 16193323Sed#ifndef LLVM_ADT_POSTORDERITERATOR_H 17193323Sed#define LLVM_ADT_POSTORDERITERATOR_H 18193323Sed 19193323Sed#include "llvm/ADT/GraphTraits.h" 20194612Sed#include "llvm/ADT/SmallPtrSet.h" 21193323Sed#include <set> 22193323Sed#include <vector> 23193323Sed 24193323Sednamespace llvm { 25193323Sed 26239462Sdim// The po_iterator_storage template provides access to the set of already 27239462Sdim// visited nodes during the po_iterator's depth-first traversal. 28239462Sdim// 29239462Sdim// The default implementation simply contains a set of visited nodes, while 30239462Sdim// the Extended=true version uses a reference to an external set. 31239462Sdim// 32239462Sdim// It is possible to prune the depth-first traversal in several ways: 33239462Sdim// 34239462Sdim// - When providing an external set that already contains some graph nodes, 35239462Sdim// those nodes won't be visited again. This is useful for restarting a 36239462Sdim// post-order traversal on a graph with nodes that aren't dominated by a 37239462Sdim// single node. 38239462Sdim// 39239462Sdim// - By providing a custom SetType class, unwanted graph nodes can be excluded 40239462Sdim// by having the insert() function return false. This could for example 41239462Sdim// confine a CFG traversal to blocks in a specific loop. 42239462Sdim// 43239462Sdim// - Finally, by specializing the po_iterator_storage template itself, graph 44239462Sdim// edges can be pruned by returning false in the insertEdge() function. This 45239462Sdim// could be used to remove loop back-edges from the CFG seen by po_iterator. 46239462Sdim// 47239462Sdim// A specialized po_iterator_storage class can observe both the pre-order and 48239462Sdim// the post-order. The insertEdge() function is called in a pre-order, while 49239462Sdim// the finishPostorder() function is called just before the po_iterator moves 50239462Sdim// on to the next node. 51239462Sdim 52239462Sdim/// Default po_iterator_storage implementation with an internal set object. 53239462Sdimtemplate<class SetType, bool External> 54193323Sedclass po_iterator_storage { 55239462Sdim SetType Visited; 56193323Sedpublic: 57239462Sdim // Return true if edge destination should be visited. 58239462Sdim template<typename NodeType> 59239462Sdim bool insertEdge(NodeType *From, NodeType *To) { 60239462Sdim return Visited.insert(To); 61239462Sdim } 62193323Sed 63239462Sdim // Called after all children of BB have been visited. 64239462Sdim template<typename NodeType> 65239462Sdim void finishPostorder(NodeType *BB) {} 66226633Sdim}; 67226633Sdim 68239462Sdim/// Specialization of po_iterator_storage that references an external set. 69226633Sdimtemplate<class SetType> 70193323Sedclass po_iterator_storage<SetType, true> { 71239462Sdim SetType &Visited; 72193323Sedpublic: 73193323Sed po_iterator_storage(SetType &VSet) : Visited(VSet) {} 74193323Sed po_iterator_storage(const po_iterator_storage &S) : Visited(S.Visited) {} 75239462Sdim 76239462Sdim // Return true if edge destination should be visited, called with From = 0 for 77239462Sdim // the root node. 78239462Sdim // Graph edges can be pruned by specializing this function. 79239462Sdim template<class NodeType> 80239462Sdim bool insertEdge(NodeType *From, NodeType *To) { return Visited.insert(To); } 81239462Sdim 82239462Sdim // Called after all children of BB have been visited. 83239462Sdim template<class NodeType> 84239462Sdim void finishPostorder(NodeType *BB) {} 85193323Sed}; 86193323Sed 87193323Sedtemplate<class GraphT, 88194612Sed class SetType = llvm::SmallPtrSet<typename GraphTraits<GraphT>::NodeType*, 8>, 89194612Sed bool ExtStorage = false, 90194612Sed class GT = GraphTraits<GraphT> > 91198090Srdivackyclass po_iterator : public std::iterator<std::forward_iterator_tag, 92198090Srdivacky typename GT::NodeType, ptrdiff_t>, 93193323Sed public po_iterator_storage<SetType, ExtStorage> { 94198090Srdivacky typedef std::iterator<std::forward_iterator_tag, 95198090Srdivacky typename GT::NodeType, ptrdiff_t> super; 96193323Sed typedef typename GT::NodeType NodeType; 97193323Sed typedef typename GT::ChildIteratorType ChildItTy; 98193323Sed 99193323Sed // VisitStack - Used to maintain the ordering. Top = current block 100193323Sed // First element is basic block pointer, second is the 'next child' to visit 101210299Sed std::vector<std::pair<NodeType *, ChildItTy> > VisitStack; 102193323Sed 103193323Sed void traverseChild() { 104210299Sed while (VisitStack.back().second != GT::child_end(VisitStack.back().first)) { 105210299Sed NodeType *BB = *VisitStack.back().second++; 106239462Sdim if (this->insertEdge(VisitStack.back().first, BB)) { 107239462Sdim // If the block is not visited... 108210299Sed VisitStack.push_back(std::make_pair(BB, GT::child_begin(BB))); 109193323Sed } 110193323Sed } 111193323Sed } 112193323Sed 113193323Sed inline po_iterator(NodeType *BB) { 114239462Sdim this->insertEdge((NodeType*)0, BB); 115210299Sed VisitStack.push_back(std::make_pair(BB, GT::child_begin(BB))); 116193323Sed traverseChild(); 117193323Sed } 118193323Sed inline po_iterator() {} // End is when stack is empty. 119193323Sed 120193323Sed inline po_iterator(NodeType *BB, SetType &S) : 121198090Srdivacky po_iterator_storage<SetType, ExtStorage>(S) { 122239462Sdim if (this->insertEdge((NodeType*)0, BB)) { 123210299Sed VisitStack.push_back(std::make_pair(BB, GT::child_begin(BB))); 124193323Sed traverseChild(); 125193323Sed } 126193323Sed } 127193323Sed 128193323Sed inline po_iterator(SetType &S) : 129198090Srdivacky po_iterator_storage<SetType, ExtStorage>(S) { 130193323Sed } // End is when stack is empty. 131193323Sedpublic: 132193323Sed typedef typename super::pointer pointer; 133193323Sed typedef po_iterator<GraphT, SetType, ExtStorage, GT> _Self; 134193323Sed 135193323Sed // Provide static "constructors"... 136193323Sed static inline _Self begin(GraphT G) { return _Self(GT::getEntryNode(G)); } 137193323Sed static inline _Self end (GraphT G) { return _Self(); } 138193323Sed 139193323Sed static inline _Self begin(GraphT G, SetType &S) { 140193323Sed return _Self(GT::getEntryNode(G), S); 141193323Sed } 142193323Sed static inline _Self end (GraphT G, SetType &S) { return _Self(S); } 143193323Sed 144193323Sed inline bool operator==(const _Self& x) const { 145193323Sed return VisitStack == x.VisitStack; 146193323Sed } 147193323Sed inline bool operator!=(const _Self& x) const { return !operator==(x); } 148193323Sed 149193323Sed inline pointer operator*() const { 150210299Sed return VisitStack.back().first; 151193323Sed } 152193323Sed 153193323Sed // This is a nonstandard operator-> that dereferences the pointer an extra 154193323Sed // time... so that you can actually call methods ON the BasicBlock, because 155193323Sed // the contained type is a pointer. This allows BBIt->getTerminator() f.e. 156193323Sed // 157193323Sed inline NodeType *operator->() const { return operator*(); } 158193323Sed 159193323Sed inline _Self& operator++() { // Preincrement 160239462Sdim this->finishPostorder(VisitStack.back().first); 161210299Sed VisitStack.pop_back(); 162193323Sed if (!VisitStack.empty()) 163193323Sed traverseChild(); 164193323Sed return *this; 165193323Sed } 166193323Sed 167193323Sed inline _Self operator++(int) { // Postincrement 168193323Sed _Self tmp = *this; ++*this; return tmp; 169193323Sed } 170193323Sed}; 171193323Sed 172193323Sed// Provide global constructors that automatically figure out correct types... 173193323Sed// 174193323Sedtemplate <class T> 175193323Sedpo_iterator<T> po_begin(T G) { return po_iterator<T>::begin(G); } 176193323Sedtemplate <class T> 177193323Sedpo_iterator<T> po_end (T G) { return po_iterator<T>::end(G); } 178193323Sed 179193323Sed// Provide global definitions of external postorder iterators... 180193323Sedtemplate<class T, class SetType=std::set<typename GraphTraits<T>::NodeType*> > 181193323Sedstruct po_ext_iterator : public po_iterator<T, SetType, true> { 182193323Sed po_ext_iterator(const po_iterator<T, SetType, true> &V) : 183193323Sed po_iterator<T, SetType, true>(V) {} 184193323Sed}; 185193323Sed 186193323Sedtemplate<class T, class SetType> 187193323Sedpo_ext_iterator<T, SetType> po_ext_begin(T G, SetType &S) { 188193323Sed return po_ext_iterator<T, SetType>::begin(G, S); 189193323Sed} 190193323Sed 191193323Sedtemplate<class T, class SetType> 192193323Sedpo_ext_iterator<T, SetType> po_ext_end(T G, SetType &S) { 193193323Sed return po_ext_iterator<T, SetType>::end(G, S); 194193323Sed} 195193323Sed 196193323Sed// Provide global definitions of inverse post order iterators... 197193323Sedtemplate <class T, 198193323Sed class SetType = std::set<typename GraphTraits<T>::NodeType*>, 199193323Sed bool External = false> 200193323Sedstruct ipo_iterator : public po_iterator<Inverse<T>, SetType, External > { 201193323Sed ipo_iterator(const po_iterator<Inverse<T>, SetType, External> &V) : 202193323Sed po_iterator<Inverse<T>, SetType, External> (V) {} 203193323Sed}; 204193323Sed 205193323Sedtemplate <class T> 206193323Sedipo_iterator<T> ipo_begin(T G, bool Reverse = false) { 207193323Sed return ipo_iterator<T>::begin(G, Reverse); 208193323Sed} 209193323Sed 210193323Sedtemplate <class T> 211193323Sedipo_iterator<T> ipo_end(T G){ 212193323Sed return ipo_iterator<T>::end(G); 213193323Sed} 214193323Sed 215239462Sdim// Provide global definitions of external inverse postorder iterators... 216193323Sedtemplate <class T, 217193323Sed class SetType = std::set<typename GraphTraits<T>::NodeType*> > 218193323Sedstruct ipo_ext_iterator : public ipo_iterator<T, SetType, true> { 219193323Sed ipo_ext_iterator(const ipo_iterator<T, SetType, true> &V) : 220239462Sdim ipo_iterator<T, SetType, true>(V) {} 221193323Sed ipo_ext_iterator(const po_iterator<Inverse<T>, SetType, true> &V) : 222239462Sdim ipo_iterator<T, SetType, true>(V) {} 223193323Sed}; 224193323Sed 225193323Sedtemplate <class T, class SetType> 226193323Sedipo_ext_iterator<T, SetType> ipo_ext_begin(T G, SetType &S) { 227193323Sed return ipo_ext_iterator<T, SetType>::begin(G, S); 228193323Sed} 229193323Sed 230193323Sedtemplate <class T, class SetType> 231193323Sedipo_ext_iterator<T, SetType> ipo_ext_end(T G, SetType &S) { 232193323Sed return ipo_ext_iterator<T, SetType>::end(G, S); 233193323Sed} 234193323Sed 235193323Sed//===--------------------------------------------------------------------===// 236193323Sed// Reverse Post Order CFG iterator code 237193323Sed//===--------------------------------------------------------------------===// 238193323Sed// 239193323Sed// This is used to visit basic blocks in a method in reverse post order. This 240193323Sed// class is awkward to use because I don't know a good incremental algorithm to 241193323Sed// computer RPO from a graph. Because of this, the construction of the 242193323Sed// ReversePostOrderTraversal object is expensive (it must walk the entire graph 243193323Sed// with a postorder iterator to build the data structures). The moral of this 244193323Sed// story is: Don't create more ReversePostOrderTraversal classes than necessary. 245193323Sed// 246193323Sed// This class should be used like this: 247193323Sed// { 248193323Sed// ReversePostOrderTraversal<Function*> RPOT(FuncPtr); // Expensive to create 249193323Sed// for (rpo_iterator I = RPOT.begin(); I != RPOT.end(); ++I) { 250193323Sed// ... 251193323Sed// } 252193323Sed// for (rpo_iterator I = RPOT.begin(); I != RPOT.end(); ++I) { 253193323Sed// ... 254193323Sed// } 255193323Sed// } 256193323Sed// 257193323Sed 258193323Sedtemplate<class GraphT, class GT = GraphTraits<GraphT> > 259193323Sedclass ReversePostOrderTraversal { 260193323Sed typedef typename GT::NodeType NodeType; 261193323Sed std::vector<NodeType*> Blocks; // Block list in normal PO order 262193323Sed inline void Initialize(NodeType *BB) { 263249423Sdim std::copy(po_begin(BB), po_end(BB), std::back_inserter(Blocks)); 264193323Sed } 265193323Sedpublic: 266193323Sed typedef typename std::vector<NodeType*>::reverse_iterator rpo_iterator; 267193323Sed 268193323Sed inline ReversePostOrderTraversal(GraphT G) { 269193323Sed Initialize(GT::getEntryNode(G)); 270193323Sed } 271193323Sed 272193323Sed // Because we want a reverse post order, use reverse iterators from the vector 273193323Sed inline rpo_iterator begin() { return Blocks.rbegin(); } 274193323Sed inline rpo_iterator end() { return Blocks.rend(); } 275193323Sed}; 276193323Sed 277193323Sed} // End llvm namespace 278193323Sed 279193323Sed#endif 280