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Diffstat (limited to 'include/llvm/ADT/PostOrderIterator.h')
| -rw-r--r-- | include/llvm/ADT/PostOrderIterator.h | 279 |
1 files changed, 279 insertions, 0 deletions
diff --git a/include/llvm/ADT/PostOrderIterator.h b/include/llvm/ADT/PostOrderIterator.h new file mode 100644 index 0000000..dd8cc74 --- /dev/null +++ b/include/llvm/ADT/PostOrderIterator.h @@ -0,0 +1,279 @@ +//===- llvm/ADT/PostOrderIterator.h - PostOrder iterator --------*- C++ -*-===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +// +// This file builds on the ADT/GraphTraits.h file to build a generic graph +// post order iterator. This should work over any graph type that has a +// GraphTraits specialization. +// +//===----------------------------------------------------------------------===// + +#ifndef LLVM_ADT_POSTORDERITERATOR_H +#define LLVM_ADT_POSTORDERITERATOR_H + +#include "llvm/ADT/GraphTraits.h" +#include "llvm/ADT/SmallPtrSet.h" +#include <set> +#include <vector> + +namespace llvm { + +// The po_iterator_storage template provides access to the set of already +// visited nodes during the po_iterator's depth-first traversal. +// +// The default implementation simply contains a set of visited nodes, while +// the Extended=true version uses a reference to an external set. +// +// It is possible to prune the depth-first traversal in several ways: +// +// - When providing an external set that already contains some graph nodes, +// those nodes won't be visited again. This is useful for restarting a +// post-order traversal on a graph with nodes that aren't dominated by a +// single node. +// +// - By providing a custom SetType class, unwanted graph nodes can be excluded +// by having the insert() function return false. This could for example +// confine a CFG traversal to blocks in a specific loop. +// +// - Finally, by specializing the po_iterator_storage template itself, graph +// edges can be pruned by returning false in the insertEdge() function. This +// could be used to remove loop back-edges from the CFG seen by po_iterator. +// +// A specialized po_iterator_storage class can observe both the pre-order and +// the post-order. The insertEdge() function is called in a pre-order, while +// the finishPostorder() function is called just before the po_iterator moves +// on to the next node. + +/// Default po_iterator_storage implementation with an internal set object. +template<class SetType, bool External> +class po_iterator_storage { + SetType Visited; +public: + // Return true if edge destination should be visited. + template<typename NodeType> + bool insertEdge(NodeType *From, NodeType *To) { + return Visited.insert(To); + } + + // Called after all children of BB have been visited. + template<typename NodeType> + void finishPostorder(NodeType *BB) {} +}; + +/// Specialization of po_iterator_storage that references an external set. +template<class SetType> +class po_iterator_storage<SetType, true> { + SetType &Visited; +public: + po_iterator_storage(SetType &VSet) : Visited(VSet) {} + po_iterator_storage(const po_iterator_storage &S) : Visited(S.Visited) {} + + // Return true if edge destination should be visited, called with From = 0 for + // the root node. + // Graph edges can be pruned by specializing this function. + template<class NodeType> + bool insertEdge(NodeType *From, NodeType *To) { return Visited.insert(To); } + + // Called after all children of BB have been visited. + template<class NodeType> + void finishPostorder(NodeType *BB) {} +}; + +template<class GraphT, + class SetType = llvm::SmallPtrSet<typename GraphTraits<GraphT>::NodeType*, 8>, + bool ExtStorage = false, + class GT = GraphTraits<GraphT> > +class po_iterator : public std::iterator<std::forward_iterator_tag, + typename GT::NodeType, ptrdiff_t>, + public po_iterator_storage<SetType, ExtStorage> { + typedef std::iterator<std::forward_iterator_tag, + typename GT::NodeType, ptrdiff_t> super; + typedef typename GT::NodeType NodeType; + typedef typename GT::ChildIteratorType ChildItTy; + + // VisitStack - Used to maintain the ordering. Top = current block + // First element is basic block pointer, second is the 'next child' to visit + std::vector<std::pair<NodeType *, ChildItTy> > VisitStack; + + void traverseChild() { + while (VisitStack.back().second != GT::child_end(VisitStack.back().first)) { + NodeType *BB = *VisitStack.back().second++; + if (this->insertEdge(VisitStack.back().first, BB)) { + // If the block is not visited... + VisitStack.push_back(std::make_pair(BB, GT::child_begin(BB))); + } + } + } + + inline po_iterator(NodeType *BB) { + this->insertEdge((NodeType*)nullptr, BB); + VisitStack.push_back(std::make_pair(BB, GT::child_begin(BB))); + traverseChild(); + } + inline po_iterator() {} // End is when stack is empty. + + inline po_iterator(NodeType *BB, SetType &S) : + po_iterator_storage<SetType, ExtStorage>(S) { + if (this->insertEdge((NodeType*)nullptr, BB)) { + VisitStack.push_back(std::make_pair(BB, GT::child_begin(BB))); + traverseChild(); + } + } + + inline po_iterator(SetType &S) : + po_iterator_storage<SetType, ExtStorage>(S) { + } // End is when stack is empty. +public: + typedef typename super::pointer pointer; + typedef po_iterator<GraphT, SetType, ExtStorage, GT> _Self; + + // Provide static "constructors"... + static inline _Self begin(GraphT G) { return _Self(GT::getEntryNode(G)); } + static inline _Self end (GraphT G) { return _Self(); } + + static inline _Self begin(GraphT G, SetType &S) { + return _Self(GT::getEntryNode(G), S); + } + static inline _Self end (GraphT G, SetType &S) { return _Self(S); } + + inline bool operator==(const _Self& x) const { + return VisitStack == x.VisitStack; + } + inline bool operator!=(const _Self& x) const { return !operator==(x); } + + inline pointer operator*() const { + return VisitStack.back().first; + } + + // This is a nonstandard operator-> that dereferences the pointer an extra + // time... so that you can actually call methods ON the BasicBlock, because + // the contained type is a pointer. This allows BBIt->getTerminator() f.e. + // + inline NodeType *operator->() const { return operator*(); } + + inline _Self& operator++() { // Preincrement + this->finishPostorder(VisitStack.back().first); + VisitStack.pop_back(); + if (!VisitStack.empty()) + traverseChild(); + return *this; + } + + inline _Self operator++(int) { // Postincrement + _Self tmp = *this; ++*this; return tmp; + } +}; + +// Provide global constructors that automatically figure out correct types... +// +template <class T> +po_iterator<T> po_begin(T G) { return po_iterator<T>::begin(G); } +template <class T> +po_iterator<T> po_end (T G) { return po_iterator<T>::end(G); } + +// Provide global definitions of external postorder iterators... +template<class T, class SetType=std::set<typename GraphTraits<T>::NodeType*> > +struct po_ext_iterator : public po_iterator<T, SetType, true> { + po_ext_iterator(const po_iterator<T, SetType, true> &V) : + po_iterator<T, SetType, true>(V) {} +}; + +template<class T, class SetType> +po_ext_iterator<T, SetType> po_ext_begin(T G, SetType &S) { + return po_ext_iterator<T, SetType>::begin(G, S); +} + +template<class T, class SetType> +po_ext_iterator<T, SetType> po_ext_end(T G, SetType &S) { + return po_ext_iterator<T, SetType>::end(G, S); +} + +// Provide global definitions of inverse post order iterators... +template <class T, + class SetType = std::set<typename GraphTraits<T>::NodeType*>, + bool External = false> +struct ipo_iterator : public po_iterator<Inverse<T>, SetType, External > { + ipo_iterator(const po_iterator<Inverse<T>, SetType, External> &V) : + po_iterator<Inverse<T>, SetType, External> (V) {} +}; + +template <class T> +ipo_iterator<T> ipo_begin(T G, bool Reverse = false) { + return ipo_iterator<T>::begin(G, Reverse); +} + +template <class T> +ipo_iterator<T> ipo_end(T G){ + return ipo_iterator<T>::end(G); +} + +// Provide global definitions of external inverse postorder iterators... +template <class T, + class SetType = std::set<typename GraphTraits<T>::NodeType*> > +struct ipo_ext_iterator : public ipo_iterator<T, SetType, true> { + ipo_ext_iterator(const ipo_iterator<T, SetType, true> &V) : + ipo_iterator<T, SetType, true>(V) {} + ipo_ext_iterator(const po_iterator<Inverse<T>, SetType, true> &V) : + ipo_iterator<T, SetType, true>(V) {} +}; + +template <class T, class SetType> +ipo_ext_iterator<T, SetType> ipo_ext_begin(T G, SetType &S) { + return ipo_ext_iterator<T, SetType>::begin(G, S); +} + +template <class T, class SetType> +ipo_ext_iterator<T, SetType> ipo_ext_end(T G, SetType &S) { + return ipo_ext_iterator<T, SetType>::end(G, S); +} + +//===--------------------------------------------------------------------===// +// Reverse Post Order CFG iterator code +//===--------------------------------------------------------------------===// +// +// This is used to visit basic blocks in a method in reverse post order. This +// class is awkward to use because I don't know a good incremental algorithm to +// computer RPO from a graph. Because of this, the construction of the +// ReversePostOrderTraversal object is expensive (it must walk the entire graph +// with a postorder iterator to build the data structures). The moral of this +// story is: Don't create more ReversePostOrderTraversal classes than necessary. +// +// This class should be used like this: +// { +// ReversePostOrderTraversal<Function*> RPOT(FuncPtr); // Expensive to create +// for (rpo_iterator I = RPOT.begin(); I != RPOT.end(); ++I) { +// ... +// } +// for (rpo_iterator I = RPOT.begin(); I != RPOT.end(); ++I) { +// ... +// } +// } +// + +template<class GraphT, class GT = GraphTraits<GraphT> > +class ReversePostOrderTraversal { + typedef typename GT::NodeType NodeType; + std::vector<NodeType*> Blocks; // Block list in normal PO order + inline void Initialize(NodeType *BB) { + std::copy(po_begin(BB), po_end(BB), std::back_inserter(Blocks)); + } +public: + typedef typename std::vector<NodeType*>::reverse_iterator rpo_iterator; + + inline ReversePostOrderTraversal(GraphT G) { + Initialize(GT::getEntryNode(G)); + } + + // Because we want a reverse post order, use reverse iterators from the vector + inline rpo_iterator begin() { return Blocks.rbegin(); } + inline rpo_iterator end() { return Blocks.rend(); } +}; + +} // End llvm namespace + +#endif |