mirror of
https://github.com/RPCS3/llvm-mirror.git
synced 2024-11-25 04:02:41 +01:00
226 lines
8.1 KiB
C++
226 lines
8.1 KiB
C++
//===-- 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.
|
|
//--------------------------------------------------------------------------
|
|
|
|
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()] = ~0UL;
|
|
} 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 {
|
|
assert(!CurrentSCC.empty() || VisitStack.empty());
|
|
return CurrentSCC.empty();
|
|
}
|
|
|
|
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;
|
|
}
|
|
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() || VisitStack.empty());
|
|
return CurrentSCC.empty()? NULL : &CurrentSCC;
|
|
}
|
|
inline SccTy* operator*() {
|
|
assert(!CurrentSCC.empty() || VisitStack.empty());
|
|
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);
|
|
}
|
|
|
|
template <class T>
|
|
TarjanSCC_iterator<T> tarj_end(T G)
|
|
{
|
|
return TarjanSCC_iterator<T>::end(G);
|
|
}
|
|
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#endif
|