--- /dev/null
+//===-- Support/TarjanSCCIterator.h -Generic Tarjan SCC iterator -*- 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 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 TarjanSCCIterator on the Inverse graph.
+// (NOTE: This requires some simple wrappers and is not supported yet.)
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_SUPPORT_TARJANSCC_ITERATOR_H
+#define LLVM_SUPPORT_TARJANSCC_ITERATOR_H
+
+#include "Support/GraphTraits.h"
+#include <Support/Statistic.h>
+#include <Support/iterator>
+#include <vector>
+#include <stack>
+#include <map>
+
+
+//--------------------------------------------------------------------------
+// class SCC : A simple representation of an SCC in a generic Graph.
+//--------------------------------------------------------------------------
+
+template<class GraphT, class GT = GraphTraits<GraphT> >
+struct SCC: public std::vector<typename GT::NodeType*> {
+
+ typedef typename GT::NodeType NodeType;
+ typedef typename GT::ChildIteratorType ChildItTy;
+
+ typedef std::vector<typename GT::NodeType*> super;
+ typedef typename super::iterator iterator;
+ typedef typename super::const_iterator const_iterator;
+ typedef typename super::reverse_iterator reverse_iterator;
+ typedef typename super::const_reverse_iterator const_reverse_iterator;
+
+ // HasLoop() -- Test if this 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 {
+ if (size() > 1) return true;
+ NodeType* N = front();
+ for (ChildItTy CI=GT::child_begin(N), CE=GT::child_end(N); CI != CE; ++CI)
+ if (*CI == N)
+ return true;
+ return false;
+ }
+};
+
+//--------------------------------------------------------------------------
+// class TarjanSCC_iterator: Enumerate the SCCs of a directed graph, in
+// reverse topological order of the SCC DAG.
+//--------------------------------------------------------------------------
+
+const unsigned long MAXLONG = (1 << (8 * sizeof(unsigned long) - 1));
+
+namespace {
+ Statistic<> NumSCCs("NumSCCs", "Number of Strongly Connected Components");
+ Statistic<> MaxSCCSize("MaxSCCSize", "Size of largest Strongly Connected Component");
+}
+
+template<class GraphT, class GT = GraphTraits<GraphT> >
+class TarjanSCC_iterator : public forward_iterator<SCC<GraphT, GT>, ptrdiff_t>
+{
+ typedef SCC<GraphT, GT> SccTy;
+ typedef forward_iterator<SccTy, ptrdiff_t> super;
+ typedef typename super::reference reference;
+ typedef typename super::pointer pointer;
+ typedef typename GT::NodeType NodeType;
+ typedef typename GT::ChildIteratorType ChildItTy;
+
+ // 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 long visitNum;
+ std::map<NodeType *, unsigned long> nodeVisitNumbers;
+
+ // SCCNodeStack - Stack holding nodes of the SCC.
+ std::stack<NodeType *> SCCNodeStack;
+
+ // CurrentSCC - 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::stack<std::pair<NodeType *, ChildItTy> > 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::stack<unsigned long> 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(N);
+ MinVisitNumStack.push(visitNum);
+ VisitStack.push(make_pair(N, GT::child_begin(N)));
+ DEBUG(std::cerr << "TarjanSCC: Node " << N <<
+ " : visitNum = " << visitNum << "\n");
+ }
+
+ // The stack-based DFS traversal; defined below.
+ void DFSVisitChildren() {
+ assert(!VisitStack.empty());
+ while (VisitStack.top().second != GT::child_end(VisitStack.top().first))
+ { // TOS has at least one more child so continue DFS
+ NodeType *childN = *VisitStack.top().second++;
+ if (nodeVisitNumbers.find(childN) == nodeVisitNumbers.end())
+ { // this node has never been seen
+ DFSVisitOne(childN);
+ }
+ else
+ {
+ unsigned long childNum = nodeVisitNumbers[childN];
+ if (MinVisitNumStack.top() > childNum)
+ MinVisitNumStack.top() = childNum;
+ }
+ }
+ }
+
+ // 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.top().second==GT::child_end(VisitStack.top().first));
+ NodeType* visitingN = VisitStack.top().first;
+ unsigned long minVisitNum = MinVisitNumStack.top();
+ VisitStack.pop();
+ MinVisitNumStack.pop();
+ if (! MinVisitNumStack.empty() && MinVisitNumStack.top() > minVisitNum)
+ MinVisitNumStack.top() = 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.top());
+ SCCNodeStack.pop();
+ nodeVisitNumbers[CurrentSCC.back()] = MAXLONG;
+ } while (CurrentSCC.back() != visitingN);
+
+ ++NumSCCs;
+ if (CurrentSCC.size() > MaxSCCSize) MaxSCCSize = CurrentSCC.size();
+
+ return;
+ }
+ }
+ }
+
+ inline TarjanSCC_iterator(NodeType *entryN) : visitNum(0) {
+ DFSVisitOne(entryN);
+ GetNextSCC();
+ }
+ inline TarjanSCC_iterator() { /* End is when DFS stack is empty */ }
+
+public:
+ typedef TarjanSCC_iterator<GraphT, GT> _Self;
+
+ // Provide static "constructors"...
+ static inline _Self begin(GraphT& G) { return _Self(GT::getEntryNode(G)); }
+ static inline _Self end (GraphT& G) { return _Self(); }
+
+ // Direct loop termination test (I.fini() is more efficient than I == end())
+ inline bool fini() const {
+ return VisitStack.empty();
+ }
+
+ inline bool operator==(const _Self& x) const {
+ return VisitStack == x.VisitStack;
+ }
+ inline bool operator!=(const _Self& x) const { return !operator==(x); }
+
+ // Iterator traversal: forward iteration only
+ inline _Self& operator++() { // Preincrement
+ GetNextSCC();
+ return *this;
+ }
+ inline _Self operator++(int) { // Postincrement
+ _Self tmp = *this; ++*this; return tmp;
+ }
+
+ // Retrieve a pointer to the current SCC. Returns NULL when done.
+ inline const SccTy* operator*() const {
+ assert(!CurrentSCC.empty() || fini());
+ return CurrentSCC.empty()? NULL : &CurrentSCC;
+ }
+ inline SccTy* operator*() {
+ assert(!CurrentSCC.empty() || fini());
+ return CurrentSCC.empty()? NULL : &CurrentSCC;
+ }
+};
+
+
+// Global constructor for the Tarjan SCC iterator. Use *I == NULL or I.fini()
+// to test termination efficiently, instead of I == the "end" iterator.
+template <class T>
+TarjanSCC_iterator<T> tarj_begin(T G)
+{
+ return TarjanSCC_iterator<T>::begin(G);
+}
+
+
+//===----------------------------------------------------------------------===//
+
+#endif
--- /dev/null
+//===-- Support/TarjanSCCIterator.h -Generic Tarjan SCC iterator -*- 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 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 TarjanSCCIterator on the Inverse graph.
+// (NOTE: This requires some simple wrappers and is not supported yet.)
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_SUPPORT_TARJANSCC_ITERATOR_H
+#define LLVM_SUPPORT_TARJANSCC_ITERATOR_H
+
+#include "Support/GraphTraits.h"
+#include <Support/Statistic.h>
+#include <Support/iterator>
+#include <vector>
+#include <stack>
+#include <map>
+
+
+//--------------------------------------------------------------------------
+// class SCC : A simple representation of an SCC in a generic Graph.
+//--------------------------------------------------------------------------
+
+template<class GraphT, class GT = GraphTraits<GraphT> >
+struct SCC: public std::vector<typename GT::NodeType*> {
+
+ typedef typename GT::NodeType NodeType;
+ typedef typename GT::ChildIteratorType ChildItTy;
+
+ typedef std::vector<typename GT::NodeType*> super;
+ typedef typename super::iterator iterator;
+ typedef typename super::const_iterator const_iterator;
+ typedef typename super::reverse_iterator reverse_iterator;
+ typedef typename super::const_reverse_iterator const_reverse_iterator;
+
+ // HasLoop() -- Test if this 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 {
+ if (size() > 1) return true;
+ NodeType* N = front();
+ for (ChildItTy CI=GT::child_begin(N), CE=GT::child_end(N); CI != CE; ++CI)
+ if (*CI == N)
+ return true;
+ return false;
+ }
+};
+
+//--------------------------------------------------------------------------
+// class TarjanSCC_iterator: Enumerate the SCCs of a directed graph, in
+// reverse topological order of the SCC DAG.
+//--------------------------------------------------------------------------
+
+const unsigned long MAXLONG = (1 << (8 * sizeof(unsigned long) - 1));
+
+namespace {
+ Statistic<> NumSCCs("NumSCCs", "Number of Strongly Connected Components");
+ Statistic<> MaxSCCSize("MaxSCCSize", "Size of largest Strongly Connected Component");
+}
+
+template<class GraphT, class GT = GraphTraits<GraphT> >
+class TarjanSCC_iterator : public forward_iterator<SCC<GraphT, GT>, ptrdiff_t>
+{
+ typedef SCC<GraphT, GT> SccTy;
+ typedef forward_iterator<SccTy, ptrdiff_t> super;
+ typedef typename super::reference reference;
+ typedef typename super::pointer pointer;
+ typedef typename GT::NodeType NodeType;
+ typedef typename GT::ChildIteratorType ChildItTy;
+
+ // 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 long visitNum;
+ std::map<NodeType *, unsigned long> nodeVisitNumbers;
+
+ // SCCNodeStack - Stack holding nodes of the SCC.
+ std::stack<NodeType *> SCCNodeStack;
+
+ // CurrentSCC - 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::stack<std::pair<NodeType *, ChildItTy> > 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::stack<unsigned long> 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(N);
+ MinVisitNumStack.push(visitNum);
+ VisitStack.push(make_pair(N, GT::child_begin(N)));
+ DEBUG(std::cerr << "TarjanSCC: Node " << N <<
+ " : visitNum = " << visitNum << "\n");
+ }
+
+ // The stack-based DFS traversal; defined below.
+ void DFSVisitChildren() {
+ assert(!VisitStack.empty());
+ while (VisitStack.top().second != GT::child_end(VisitStack.top().first))
+ { // TOS has at least one more child so continue DFS
+ NodeType *childN = *VisitStack.top().second++;
+ if (nodeVisitNumbers.find(childN) == nodeVisitNumbers.end())
+ { // this node has never been seen
+ DFSVisitOne(childN);
+ }
+ else
+ {
+ unsigned long childNum = nodeVisitNumbers[childN];
+ if (MinVisitNumStack.top() > childNum)
+ MinVisitNumStack.top() = childNum;
+ }
+ }
+ }
+
+ // 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.top().second==GT::child_end(VisitStack.top().first));
+ NodeType* visitingN = VisitStack.top().first;
+ unsigned long minVisitNum = MinVisitNumStack.top();
+ VisitStack.pop();
+ MinVisitNumStack.pop();
+ if (! MinVisitNumStack.empty() && MinVisitNumStack.top() > minVisitNum)
+ MinVisitNumStack.top() = 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.top());
+ SCCNodeStack.pop();
+ nodeVisitNumbers[CurrentSCC.back()] = MAXLONG;
+ } while (CurrentSCC.back() != visitingN);
+
+ ++NumSCCs;
+ if (CurrentSCC.size() > MaxSCCSize) MaxSCCSize = CurrentSCC.size();
+
+ return;
+ }
+ }
+ }
+
+ inline TarjanSCC_iterator(NodeType *entryN) : visitNum(0) {
+ DFSVisitOne(entryN);
+ GetNextSCC();
+ }
+ inline TarjanSCC_iterator() { /* End is when DFS stack is empty */ }
+
+public:
+ typedef TarjanSCC_iterator<GraphT, GT> _Self;
+
+ // Provide static "constructors"...
+ static inline _Self begin(GraphT& G) { return _Self(GT::getEntryNode(G)); }
+ static inline _Self end (GraphT& G) { return _Self(); }
+
+ // Direct loop termination test (I.fini() is more efficient than I == end())
+ inline bool fini() const {
+ return VisitStack.empty();
+ }
+
+ inline bool operator==(const _Self& x) const {
+ return VisitStack == x.VisitStack;
+ }
+ inline bool operator!=(const _Self& x) const { return !operator==(x); }
+
+ // Iterator traversal: forward iteration only
+ inline _Self& operator++() { // Preincrement
+ GetNextSCC();
+ return *this;
+ }
+ inline _Self operator++(int) { // Postincrement
+ _Self tmp = *this; ++*this; return tmp;
+ }
+
+ // Retrieve a pointer to the current SCC. Returns NULL when done.
+ inline const SccTy* operator*() const {
+ assert(!CurrentSCC.empty() || fini());
+ return CurrentSCC.empty()? NULL : &CurrentSCC;
+ }
+ inline SccTy* operator*() {
+ assert(!CurrentSCC.empty() || fini());
+ return CurrentSCC.empty()? NULL : &CurrentSCC;
+ }
+};
+
+
+// Global constructor for the Tarjan SCC iterator. Use *I == NULL or I.fini()
+// to test termination efficiently, instead of I == the "end" iterator.
+template <class T>
+TarjanSCC_iterator<T> tarj_begin(T G)
+{
+ return TarjanSCC_iterator<T>::begin(G);
+}
+
+
+//===----------------------------------------------------------------------===//
+
+#endif
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