-//===-- Support/TarjanSCCIterator.h - Tarjan SCC iterator -------*- C++ -*-===//
+//===-- Support/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 TarjanSCCIterator on the Inverse graph.
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// 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_TARJANSCCITERATOR_H
-#define SUPPORT_TARJANSCCITERATOR_H
+#ifndef LLVM_ADT_SCCITERATOR_H
+#define LLVM_ADT_SCCITERATOR_H
-#include "Support/GraphTraits.h"
-#include "Support/Debug.h"
-#include "Support/iterator"
+#include "llvm/ADT/GraphTraits.h"
+#include "llvm/ADT/iterator.h"
#include <vector>
-#include <stack>
#include <map>
-//--------------------------------------------------------------------------
-// class SCC : A simple representation of an SCC in a generic Graph.
-//--------------------------------------------------------------------------
+namespace llvm {
+//===----------------------------------------------------------------------===//
+///
+/// scc_iterator - Enumerate the SCCs of a directed graph, in
+/// reverse topological order of the SCC DAG.
+///
template<class GraphT, class GT = GraphTraits<GraphT> >
-struct SCC: public std::vector<typename GT::NodeType*> {
-
- typedef typename GT::NodeType NodeType;
+class scc_iterator
+ : public forward_iterator<std::vector<typename GT::NodeType>, ptrdiff_t> {
+ 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.
-//--------------------------------------------------------------------------
-
-template<class GraphT, class GT = GraphTraits<GraphT> >
-class TarjanSCC_iterator : public forward_iterator<SCC<GraphT, GT>, ptrdiff_t>
-{
- typedef SCC<GraphT, GT> SccTy;
+ typedef std::vector<NodeType*> 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;
+ unsigned visitNum;
+ std::map<NodeType *, unsigned> nodeVisitNumbers;
// SCCNodeStack - Stack holding nodes of the SCC.
- std::stack<NodeType *> SCCNodeStack;
+ std::vector<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;
+ std::vector<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;
+ std::vector<unsigned> 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");
+ SCCNodeStack.push_back(N);
+ MinVisitNumStack.push_back(visitNum);
+ VisitStack.push_back(std::make_pair(N, GT::child_begin(N)));
+ //DOUT << "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;
- }
+ 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.count(childN)) {
+ // this node has never been seen
+ DFSVisitOne(childN);
+ } else {
+ unsigned childNum = nodeVisitNumbers[childN];
+ if (MinVisitNumStack.back() > childNum)
+ MinVisitNumStack.back() = 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()] = ~0UL;
- } while (CurrentSCC.back() != visitingN);
- return;
- }
- }
+ 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;
+
+ //DOUT << "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()] = ~0U;
+ } while (CurrentSCC.back() != visitingN);
+ return;
+ }
+ }
}
- inline TarjanSCC_iterator(NodeType *entryN) : visitNum(0) {
+ inline scc_iterator(NodeType *entryN) : visitNum(0) {
DFSVisitOne(entryN);
GetNextSCC();
}
- inline TarjanSCC_iterator() { /* End is when DFS stack is empty */ }
+ inline scc_iterator() { /* End is when DFS stack is empty */ }
public:
- typedef TarjanSCC_iterator<GraphT, GT> _Self;
+ typedef scc_iterator<GraphT, GT> _Self;
// Provide static "constructors"...
static inline _Self begin(GraphT& G) { return _Self(GT::getEntryNode(G)); }
return CurrentSCC.empty();
}
- inline bool operator==(const _Self& x) const {
+ inline bool operator==(const _Self& 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
GetNextSCC();
- return *this;
+ return *this;
}
inline _Self operator++(int) { // Postincrement
- _Self tmp = *this; ++*this; return tmp;
+ _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() || VisitStack.empty());
- return CurrentSCC.empty()? NULL : &CurrentSCC;
+ // Retrieve a reference to the current SCC
+ inline const SccTy &operator*() const {
+ assert(!CurrentSCC.empty() && "Dereferencing END SCC iterator!");
+ return CurrentSCC;
}
- inline SccTy* operator*() {
- assert(!CurrentSCC.empty() || VisitStack.empty());
- return CurrentSCC.empty()? NULL : &CurrentSCC;
+ inline SccTy &operator*() {
+ assert(!CurrentSCC.empty() && "Dereferencing END SCC iterator!");
+ return CurrentSCC;
+ }
+
+ // 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 {
+ assert(!CurrentSCC.empty() && "Dereferencing END SCC iterator!");
+ 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)
+ if (*CI == N)
+ return true;
+ return false;
}
};
-// Global constructor for the Tarjan SCC iterator. Use *I == NULL or I.fini()
-// to test termination efficiently, instead of I == the "end" iterator.
+// Global constructor for the SCC iterator.
template <class T>
-TarjanSCC_iterator<T> tarj_begin(T G)
-{
- return TarjanSCC_iterator<T>::begin(G);
+scc_iterator<T> scc_begin(T G) {
+ return scc_iterator<T>::begin(G);
}
template <class T>
-TarjanSCC_iterator<T> tarj_end(T G)
-{
- return TarjanSCC_iterator<T>::end(G);
+scc_iterator<T> scc_end(T G) {
+ return scc_iterator<T>::end(G);
}
-//===----------------------------------------------------------------------===//
+} // End llvm namespace
#endif
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