X-Git-Url: http://plrg.eecs.uci.edu/git/?a=blobdiff_plain;f=include%2Fllvm%2FADT%2FSCCIterator.h;h=bc74416ac88baa468cfe1d544c5c5355d7bbd594;hb=5e7bb43066143d35d57dee88a113d56bdc9375c8;hp=f21c7d162e5129fa713ad291e21080acb30e8d81;hpb=d0fde30ce850b78371fd1386338350591f9ff494;p=oota-llvm.git diff --git a/include/llvm/ADT/SCCIterator.h b/include/llvm/ADT/SCCIterator.h index f21c7d162e5..bc74416ac88 100644 --- a/include/llvm/ADT/SCCIterator.h +++ b/include/llvm/ADT/SCCIterator.h @@ -1,204 +1,245 @@ -//===-- Support/SCCIterator.h - SCC iterator --------------------*- C++ -*-===// -// -// The LLVM Compiler Infrastructure -// -// This file was developed by the LLVM research group and is distributed under -// the University of Illinois Open Source License. See LICENSE.TXT for details. -// -//===----------------------------------------------------------------------===// +//===---- ADT/SCCIterator.h - Strongly Connected Comp. Iter. ----*- C++ -*-===// // -// This builds on the Support/GraphTraits.h file to find the strongly connected -// components (SCCs) of a graph in O(N+E) time using Tarjan's DFS algorithm. +// The LLVM Compiler Infrastructure // -// The SCC iterator has the important property that if a node in SCC S1 has an -// edge to a node in SCC S2, then it visits S1 *after* S2. -// -// To visit S1 *before* S2, use the scc_iterator on the Inverse graph. -// (NOTE: This requires some simple wrappers and is not supported yet.) +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// +/// \file +/// +/// This builds on the llvm/ADT/GraphTraits.h file to find the strongly +/// connected components (SCCs) of a graph in O(N+E) time using Tarjan's DFS +/// algorithm. +/// +/// The SCC iterator has the important property that if a node in SCC S1 has an +/// edge to a node in SCC S2, then it visits S1 *after* S2. +/// +/// To visit S1 *before* S2, use the scc_iterator on the Inverse graph. (NOTE: +/// This requires some simple wrappers and is not supported yet.) +/// +//===----------------------------------------------------------------------===// -#ifndef SUPPORT_SCCITERATOR_H -#define SUPPORT_SCCITERATOR_H +#ifndef LLVM_ADT_SCCITERATOR_H +#define LLVM_ADT_SCCITERATOR_H -#include "Support/GraphTraits.h" -#include "Support/iterator" +#include "llvm/ADT/DenseMap.h" +#include "llvm/ADT/GraphTraits.h" +#include "llvm/ADT/iterator.h" #include -#include namespace llvm { -//===----------------------------------------------------------------------===// +/// \brief Enumerate the SCCs of a directed graph in reverse topological order +/// of the SCC DAG. /// -/// scc_iterator - Enumerate the SCCs of a directed graph, in -/// reverse topological order of the SCC DAG. -/// -template > +/// This is implemented using Tarjan's DFS algorithm using an internal stack to +/// build up a vector of nodes in a particular SCC. Note that it is a forward +/// iterator and thus you cannot backtrack or re-visit nodes. +template > class scc_iterator - : public forward_iterator, ptrdiff_t> { - typedef typename GT::NodeType NodeType; + : public iterator_facade_base< + scc_iterator, std::forward_iterator_tag, + const std::vector, ptrdiff_t> { + typedef typename GT::NodeType NodeType; typedef typename GT::ChildIteratorType ChildItTy; - typedef std::vector SccTy; - typedef forward_iterator super; - typedef typename super::reference reference; - typedef typename super::pointer pointer; - - // The visit counters used to detect when a complete SCC is on the stack. - // visitNum is the global counter. - // nodeVisitNumbers are per-node visit numbers, also used as DFS flags. + typedef std::vector SccTy; + typedef typename scc_iterator::reference reference; + + /// Element of VisitStack during DFS. + struct StackElement { + NodeType *Node; ///< The current node pointer. + ChildItTy NextChild; ///< The next child, modified inplace during DFS. + unsigned MinVisited; ///< Minimum uplink value of all children of Node. + + StackElement(NodeType *Node, const ChildItTy &Child, unsigned Min) + : Node(Node), NextChild(Child), MinVisited(Min) {} + + bool operator==(const StackElement &Other) const { + return Node == Other.Node && + NextChild == Other.NextChild && + MinVisited == Other.MinVisited; + } + }; + + /// The visit counters used to detect when a complete SCC is on the stack. + /// visitNum is the global counter. + /// + /// nodeVisitNumbers are per-node visit numbers, also used as DFS flags. unsigned visitNum; - std::map nodeVisitNumbers; + DenseMap nodeVisitNumbers; - // SCCNodeStack - Stack holding nodes of the SCC. + /// Stack holding nodes of the SCC. std::vector SCCNodeStack; - // CurrentSCC - The current SCC, retrieved using operator*(). + /// The current SCC, retrieved using operator*(). SccTy CurrentSCC; - // VisitStack - Used to maintain the ordering. Top = current block - // First element is basic block pointer, second is the 'next child' to visit - std::vector > VisitStack; - - // MinVistNumStack - Stack holding the "min" values for each node in the DFS. - // This is used to track the minimum uplink values for all children of - // the corresponding node on the VisitStack. - std::vector MinVisitNumStack; - - // A single "visit" within the non-recursive DFS traversal. - void DFSVisitOne(NodeType* N) { - ++visitNum; // Global counter for the visit order - nodeVisitNumbers[N] = visitNum; - SCCNodeStack.push_back(N); - MinVisitNumStack.push_back(visitNum); - VisitStack.push_back(make_pair(N, GT::child_begin(N))); - //DEBUG(std::cerr << "TarjanSCC: Node " << N << - // " : visitNum = " << visitNum << "\n"); - } + /// DFS stack, Used to maintain the ordering. The top contains the current + /// node, the next child to visit, and the minimum uplink value of all child + std::vector VisitStack; - // The stack-based DFS traversal; defined below. - void DFSVisitChildren() { - assert(!VisitStack.empty()); - while (VisitStack.back().second != GT::child_end(VisitStack.back().first)) - { // TOS has at least one more child so continue DFS - NodeType *childN = *VisitStack.back().second++; - if (nodeVisitNumbers.find(childN) == nodeVisitNumbers.end()) - { // this node has never been seen - DFSVisitOne(childN); - } - else - { - unsigned childNum = nodeVisitNumbers[childN]; - if (MinVisitNumStack.back() > childNum) - MinVisitNumStack.back() = childNum; - } - } - } + /// A single "visit" within the non-recursive DFS traversal. + void DFSVisitOne(NodeType *N); - // Compute the next SCC using the DFS traversal. - void GetNextSCC() { - assert(VisitStack.size() == MinVisitNumStack.size()); - CurrentSCC.clear(); // Prepare to compute the next SCC - while (! VisitStack.empty()) - { - DFSVisitChildren(); - - assert(VisitStack.back().second == - GT::child_end(VisitStack.back().first)); - NodeType* visitingN = VisitStack.back().first; - unsigned minVisitNum = MinVisitNumStack.back(); - VisitStack.pop_back(); - MinVisitNumStack.pop_back(); - if (! MinVisitNumStack.empty() && MinVisitNumStack.back() > minVisitNum) - MinVisitNumStack.back() = minVisitNum; - - //DEBUG(std::cerr << "TarjanSCC: Popped node " << visitingN << - // " : minVisitNum = " << minVisitNum << "; Node visit num = " << - // nodeVisitNumbers[visitingN] << "\n"); - - if (minVisitNum == nodeVisitNumbers[visitingN]) - { // A full SCC is on the SCCNodeStack! It includes all nodes below - // visitingN on the stack. Copy those nodes to CurrentSCC, - // reset their minVisit values, and return (this suspends - // the DFS traversal till the next ++). - do { - CurrentSCC.push_back(SCCNodeStack.back()); - SCCNodeStack.pop_back(); - nodeVisitNumbers[CurrentSCC.back()] = ~0UL; - } while (CurrentSCC.back() != visitingN); - return; - } - } - } + /// The stack-based DFS traversal; defined below. + void DFSVisitChildren(); + + /// Compute the next SCC using the DFS traversal. + void GetNextSCC(); - inline scc_iterator(NodeType *entryN) : visitNum(0) { + scc_iterator(NodeType *entryN) : visitNum(0) { DFSVisitOne(entryN); GetNextSCC(); } - inline scc_iterator() { /* End is when DFS stack is empty */ } -public: - typedef scc_iterator _Self; + /// End is when the DFS stack is empty. + scc_iterator() {} - // Provide static "constructors"... - static inline _Self begin(GraphT& G) { return _Self(GT::getEntryNode(G)); } - static inline _Self end (GraphT& G) { return _Self(); } +public: + static scc_iterator begin(const GraphT &G) { + return scc_iterator(GT::getEntryNode(G)); + } + static scc_iterator end(const GraphT &) { return scc_iterator(); } - // Direct loop termination test (I.fini() is more efficient than I == end()) - inline bool fini() const { + /// \brief Direct loop termination test which is more efficient than + /// comparison with \c end(). + bool isAtEnd() const { assert(!CurrentSCC.empty() || VisitStack.empty()); return CurrentSCC.empty(); } - inline bool operator==(const _Self& x) const { + bool operator==(const scc_iterator &x) const { return VisitStack == x.VisitStack && CurrentSCC == x.CurrentSCC; } - inline bool operator!=(const _Self& x) const { return !operator==(x); } - // Iterator traversal: forward iteration only - inline _Self& operator++() { // Preincrement + scc_iterator &operator++() { GetNextSCC(); - return *this; - } - inline _Self operator++(int) { // Postincrement - _Self tmp = *this; ++*this; return tmp; + return *this; } - // Retrieve a reference to the current SCC - inline const SccTy &operator*() const { + reference operator*() const { assert(!CurrentSCC.empty() && "Dereferencing END SCC iterator!"); return CurrentSCC; } - inline SccTy &operator*() { - assert(!CurrentSCC.empty() && "Dereferencing END SCC iterator!"); - return CurrentSCC; + + /// \brief Test if the current SCC has a loop. + /// + /// If the SCC has more than one node, this is trivially true. If not, it may + /// still contain a loop if the node has an edge back to itself. + bool hasLoop() const; + + /// This informs the \c scc_iterator that the specified \c Old node + /// has been deleted, and \c New is to be used in its place. + void ReplaceNode(NodeType *Old, NodeType *New) { + assert(nodeVisitNumbers.count(Old) && "Old not in scc_iterator?"); + nodeVisitNumbers[New] = nodeVisitNumbers[Old]; + nodeVisitNumbers.erase(Old); + } +}; + +template +void scc_iterator::DFSVisitOne(NodeType *N) { + ++visitNum; + nodeVisitNumbers[N] = visitNum; + SCCNodeStack.push_back(N); + VisitStack.push_back(StackElement(N, GT::child_begin(N), visitNum)); +#if 0 // Enable if needed when debugging. + dbgs() << "TarjanSCC: Node " << N << + " : visitNum = " << visitNum << "\n"; +#endif +} + +template +void scc_iterator::DFSVisitChildren() { + assert(!VisitStack.empty()); + while (VisitStack.back().NextChild != GT::child_end(VisitStack.back().Node)) { + // TOS has at least one more child so continue DFS + NodeType *childN = *VisitStack.back().NextChild++; + typename DenseMap::iterator Visited = + nodeVisitNumbers.find(childN); + if (Visited == nodeVisitNumbers.end()) { + // this node has never been seen. + DFSVisitOne(childN); + continue; + } + + unsigned childNum = Visited->second; + if (VisitStack.back().MinVisited > childNum) + VisitStack.back().MinVisited = childNum; + } +} + +template void scc_iterator::GetNextSCC() { + CurrentSCC.clear(); // Prepare to compute the next SCC + while (!VisitStack.empty()) { + DFSVisitChildren(); + + // Pop the leaf on top of the VisitStack. + NodeType *visitingN = VisitStack.back().Node; + unsigned minVisitNum = VisitStack.back().MinVisited; + assert(VisitStack.back().NextChild == GT::child_end(visitingN)); + VisitStack.pop_back(); + + // Propagate MinVisitNum to parent so we can detect the SCC starting node. + if (!VisitStack.empty() && VisitStack.back().MinVisited > minVisitNum) + VisitStack.back().MinVisited = minVisitNum; + +#if 0 // Enable if needed when debugging. + dbgs() << "TarjanSCC: Popped node " << visitingN << + " : minVisitNum = " << minVisitNum << "; Node visit num = " << + nodeVisitNumbers[visitingN] << "\n"; +#endif + + if (minVisitNum != nodeVisitNumbers[visitingN]) + continue; + + // A full SCC is on the SCCNodeStack! It includes all nodes below + // visitingN on the stack. Copy those nodes to CurrentSCC, + // reset their minVisit values, and return (this suspends + // the DFS traversal till the next ++). + do { + CurrentSCC.push_back(SCCNodeStack.back()); + SCCNodeStack.pop_back(); + nodeVisitNumbers[CurrentSCC.back()] = ~0U; + } while (CurrentSCC.back() != visitingN); + return; } +} - // hasLoop() -- Test if the current SCC has a loop. If it has more than one - // node, this is trivially true. If not, it may still contain a loop if the - // node has an edge back to itself. - bool hasLoop() const { +template +bool scc_iterator::hasLoop() const { assert(!CurrentSCC.empty() && "Dereferencing END SCC iterator!"); - if (CurrentSCC.size() > 1) return true; + if (CurrentSCC.size() > 1) + return true; NodeType *N = CurrentSCC.front(); - for (ChildItTy CI = GT::child_begin(N), CE=GT::child_end(N); CI != CE; ++CI) + for (ChildItTy CI = GT::child_begin(N), CE = GT::child_end(N); CI != CE; + ++CI) if (*CI == N) return true; return false; } -}; - -// Global constructor for the SCC iterator. -template -scc_iterator scc_begin(T G) { +/// \brief Construct the begin iterator for a deduced graph type T. +template scc_iterator scc_begin(const T &G) { return scc_iterator::begin(G); } -template -scc_iterator scc_end(T G) { +/// \brief Construct the end iterator for a deduced graph type T. +template scc_iterator scc_end(const T &G) { return scc_iterator::end(G); } +/// \brief Construct the begin iterator for a deduced graph type T's Inverse. +template scc_iterator > scc_begin(const Inverse &G) { + return scc_iterator >::begin(G); +} + +/// \brief Construct the end iterator for a deduced graph type T's Inverse. +template scc_iterator > scc_end(const Inverse &G) { + return scc_iterator >::end(G); +} + } // End llvm namespace #endif