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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206142 91177308-0d34-0410-b5e6-96231b3b80d8
280 lines
10 KiB
C++
280 lines
10 KiB
C++
//===- llvm/ADT/PostOrderIterator.h - PostOrder iterator --------*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file builds on the ADT/GraphTraits.h file to build a generic graph
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// post order iterator. This should work over any graph type that has a
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// GraphTraits specialization.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_ADT_POSTORDERITERATOR_H
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#define LLVM_ADT_POSTORDERITERATOR_H
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#include "llvm/ADT/GraphTraits.h"
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#include "llvm/ADT/SmallPtrSet.h"
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#include <set>
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#include <vector>
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namespace llvm {
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// The po_iterator_storage template provides access to the set of already
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// visited nodes during the po_iterator's depth-first traversal.
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//
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// The default implementation simply contains a set of visited nodes, while
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// the Extended=true version uses a reference to an external set.
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//
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// It is possible to prune the depth-first traversal in several ways:
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//
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// - When providing an external set that already contains some graph nodes,
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// those nodes won't be visited again. This is useful for restarting a
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// post-order traversal on a graph with nodes that aren't dominated by a
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// single node.
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//
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// - By providing a custom SetType class, unwanted graph nodes can be excluded
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// by having the insert() function return false. This could for example
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// confine a CFG traversal to blocks in a specific loop.
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//
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// - Finally, by specializing the po_iterator_storage template itself, graph
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// edges can be pruned by returning false in the insertEdge() function. This
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// could be used to remove loop back-edges from the CFG seen by po_iterator.
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//
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// A specialized po_iterator_storage class can observe both the pre-order and
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// the post-order. The insertEdge() function is called in a pre-order, while
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// the finishPostorder() function is called just before the po_iterator moves
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// on to the next node.
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/// Default po_iterator_storage implementation with an internal set object.
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template<class SetType, bool External>
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class po_iterator_storage {
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SetType Visited;
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public:
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// Return true if edge destination should be visited.
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template<typename NodeType>
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bool insertEdge(NodeType *From, NodeType *To) {
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return Visited.insert(To);
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}
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// Called after all children of BB have been visited.
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template<typename NodeType>
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void finishPostorder(NodeType *BB) {}
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};
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/// Specialization of po_iterator_storage that references an external set.
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template<class SetType>
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class po_iterator_storage<SetType, true> {
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SetType &Visited;
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public:
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po_iterator_storage(SetType &VSet) : Visited(VSet) {}
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po_iterator_storage(const po_iterator_storage &S) : Visited(S.Visited) {}
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// Return true if edge destination should be visited, called with From = 0 for
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// the root node.
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// Graph edges can be pruned by specializing this function.
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template<class NodeType>
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bool insertEdge(NodeType *From, NodeType *To) { return Visited.insert(To); }
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// Called after all children of BB have been visited.
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template<class NodeType>
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void finishPostorder(NodeType *BB) {}
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};
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template<class GraphT,
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class SetType = llvm::SmallPtrSet<typename GraphTraits<GraphT>::NodeType*, 8>,
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bool ExtStorage = false,
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class GT = GraphTraits<GraphT> >
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class po_iterator : public std::iterator<std::forward_iterator_tag,
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typename GT::NodeType, ptrdiff_t>,
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public po_iterator_storage<SetType, ExtStorage> {
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typedef std::iterator<std::forward_iterator_tag,
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typename GT::NodeType, ptrdiff_t> super;
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typedef typename GT::NodeType NodeType;
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typedef typename GT::ChildIteratorType ChildItTy;
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// VisitStack - Used to maintain the ordering. Top = current block
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// First element is basic block pointer, second is the 'next child' to visit
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std::vector<std::pair<NodeType *, ChildItTy> > VisitStack;
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void traverseChild() {
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while (VisitStack.back().second != GT::child_end(VisitStack.back().first)) {
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NodeType *BB = *VisitStack.back().second++;
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if (this->insertEdge(VisitStack.back().first, BB)) {
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// If the block is not visited...
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VisitStack.push_back(std::make_pair(BB, GT::child_begin(BB)));
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}
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}
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}
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inline po_iterator(NodeType *BB) {
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this->insertEdge((NodeType*)nullptr, BB);
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VisitStack.push_back(std::make_pair(BB, GT::child_begin(BB)));
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traverseChild();
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}
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inline po_iterator() {} // End is when stack is empty.
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inline po_iterator(NodeType *BB, SetType &S) :
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po_iterator_storage<SetType, ExtStorage>(S) {
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if (this->insertEdge((NodeType*)nullptr, BB)) {
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VisitStack.push_back(std::make_pair(BB, GT::child_begin(BB)));
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traverseChild();
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}
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}
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inline po_iterator(SetType &S) :
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po_iterator_storage<SetType, ExtStorage>(S) {
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} // End is when stack is empty.
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public:
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typedef typename super::pointer pointer;
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typedef po_iterator<GraphT, SetType, ExtStorage, GT> _Self;
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// Provide static "constructors"...
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static inline _Self begin(GraphT G) { return _Self(GT::getEntryNode(G)); }
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static inline _Self end (GraphT G) { return _Self(); }
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static inline _Self begin(GraphT G, SetType &S) {
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return _Self(GT::getEntryNode(G), S);
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}
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static inline _Self end (GraphT G, SetType &S) { return _Self(S); }
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inline bool operator==(const _Self& x) const {
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return VisitStack == x.VisitStack;
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}
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inline bool operator!=(const _Self& x) const { return !operator==(x); }
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inline pointer operator*() const {
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return VisitStack.back().first;
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}
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// This is a nonstandard operator-> that dereferences the pointer an extra
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// time... so that you can actually call methods ON the BasicBlock, because
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// the contained type is a pointer. This allows BBIt->getTerminator() f.e.
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//
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inline NodeType *operator->() const { return operator*(); }
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inline _Self& operator++() { // Preincrement
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this->finishPostorder(VisitStack.back().first);
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VisitStack.pop_back();
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if (!VisitStack.empty())
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traverseChild();
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return *this;
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}
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inline _Self operator++(int) { // Postincrement
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_Self tmp = *this; ++*this; return tmp;
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}
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};
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// Provide global constructors that automatically figure out correct types...
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//
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template <class T>
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po_iterator<T> po_begin(T G) { return po_iterator<T>::begin(G); }
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template <class T>
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po_iterator<T> po_end (T G) { return po_iterator<T>::end(G); }
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// Provide global definitions of external postorder iterators...
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template<class T, class SetType=std::set<typename GraphTraits<T>::NodeType*> >
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struct po_ext_iterator : public po_iterator<T, SetType, true> {
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po_ext_iterator(const po_iterator<T, SetType, true> &V) :
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po_iterator<T, SetType, true>(V) {}
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};
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template<class T, class SetType>
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po_ext_iterator<T, SetType> po_ext_begin(T G, SetType &S) {
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return po_ext_iterator<T, SetType>::begin(G, S);
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}
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template<class T, class SetType>
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po_ext_iterator<T, SetType> po_ext_end(T G, SetType &S) {
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return po_ext_iterator<T, SetType>::end(G, S);
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}
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// Provide global definitions of inverse post order iterators...
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template <class T,
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class SetType = std::set<typename GraphTraits<T>::NodeType*>,
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bool External = false>
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struct ipo_iterator : public po_iterator<Inverse<T>, SetType, External > {
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ipo_iterator(const po_iterator<Inverse<T>, SetType, External> &V) :
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po_iterator<Inverse<T>, SetType, External> (V) {}
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};
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template <class T>
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ipo_iterator<T> ipo_begin(T G, bool Reverse = false) {
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return ipo_iterator<T>::begin(G, Reverse);
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}
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template <class T>
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ipo_iterator<T> ipo_end(T G){
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return ipo_iterator<T>::end(G);
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}
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// Provide global definitions of external inverse postorder iterators...
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template <class T,
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class SetType = std::set<typename GraphTraits<T>::NodeType*> >
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struct ipo_ext_iterator : public ipo_iterator<T, SetType, true> {
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ipo_ext_iterator(const ipo_iterator<T, SetType, true> &V) :
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ipo_iterator<T, SetType, true>(V) {}
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ipo_ext_iterator(const po_iterator<Inverse<T>, SetType, true> &V) :
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ipo_iterator<T, SetType, true>(V) {}
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};
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template <class T, class SetType>
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ipo_ext_iterator<T, SetType> ipo_ext_begin(T G, SetType &S) {
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return ipo_ext_iterator<T, SetType>::begin(G, S);
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}
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template <class T, class SetType>
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ipo_ext_iterator<T, SetType> ipo_ext_end(T G, SetType &S) {
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return ipo_ext_iterator<T, SetType>::end(G, S);
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}
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//===--------------------------------------------------------------------===//
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// Reverse Post Order CFG iterator code
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//===--------------------------------------------------------------------===//
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//
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// This is used to visit basic blocks in a method in reverse post order. This
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// class is awkward to use because I don't know a good incremental algorithm to
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// computer RPO from a graph. Because of this, the construction of the
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// ReversePostOrderTraversal object is expensive (it must walk the entire graph
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// with a postorder iterator to build the data structures). The moral of this
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// story is: Don't create more ReversePostOrderTraversal classes than necessary.
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//
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// This class should be used like this:
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// {
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// ReversePostOrderTraversal<Function*> RPOT(FuncPtr); // Expensive to create
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// for (rpo_iterator I = RPOT.begin(); I != RPOT.end(); ++I) {
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// ...
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// }
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// for (rpo_iterator I = RPOT.begin(); I != RPOT.end(); ++I) {
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// ...
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// }
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// }
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//
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template<class GraphT, class GT = GraphTraits<GraphT> >
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class ReversePostOrderTraversal {
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typedef typename GT::NodeType NodeType;
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std::vector<NodeType*> Blocks; // Block list in normal PO order
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inline void Initialize(NodeType *BB) {
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std::copy(po_begin(BB), po_end(BB), std::back_inserter(Blocks));
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}
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public:
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typedef typename std::vector<NodeType*>::reverse_iterator rpo_iterator;
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inline ReversePostOrderTraversal(GraphT G) {
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Initialize(GT::getEntryNode(G));
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}
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// Because we want a reverse post order, use reverse iterators from the vector
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inline rpo_iterator begin() { return Blocks.rbegin(); }
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inline rpo_iterator end() { return Blocks.rend(); }
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};
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} // End llvm namespace
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#endif
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