llvm-6502/include/llvm/ADT/PostOrderIterator.h

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//===- 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*)0, 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*)0, 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) {
copy(po_begin(BB), po_end(BB), 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