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[PM] [cleanup] Update doxygen comments to use the new style, add some
doxygen comments, make existing comments doxygen comments etc. Also, switch commented-out debug helpers to #if-0-ed out debug helpers. No functionality changed. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@195783 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chandler Carruth
parent
46f89920ce
commit
aba7b68814
@ -6,16 +6,18 @@
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This builds on the llvm/ADT/GraphTraits.h file to find the strongly connected
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// components (SCCs) of a graph in O(N+E) time using Tarjan's DFS algorithm.
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//
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// The SCC iterator has the important property that if a node in SCC S1 has an
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// edge to a node in SCC S2, then it visits S1 *after* S2.
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//
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// To visit S1 *before* S2, use the scc_iterator on the Inverse graph.
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// (NOTE: This requires some simple wrappers and is not supported yet.)
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//
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/// \file
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///
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/// This builds on the llvm/ADT/GraphTraits.h file to find the strongly
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/// connected components (SCCs) of a graph in O(N+E) time using Tarjan's DFS
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/// algorithm.
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///
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/// The SCC iterator has the important property that if a node in SCC S1 has an
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/// edge to a node in SCC S2, then it visits S1 *after* S2.
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///
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/// To visit S1 *before* S2, use the scc_iterator on the Inverse graph. (NOTE:
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/// This requires some simple wrappers and is not supported yet.)
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///
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_ADT_SCCITERATOR_H
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@ -27,11 +29,12 @@
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namespace llvm {
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//===----------------------------------------------------------------------===//
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///
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/// scc_iterator - Enumerate the SCCs of a directed graph, in
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/// reverse topological order of the SCC DAG.
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/// \brief Enumerate the SCCs of a directed graph in reverse topological order
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/// of the SCC DAG.
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///
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/// This is implemented using Tarjan's DFS algorithm using an internal stack to
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/// build up a vector of nodes in a particular SCC. Note that it is a forward
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/// iterator and thus you cannot backtrack or re-visit nodes.
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template<class GraphT, class GT = GraphTraits<GraphT> >
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class scc_iterator
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: public std::iterator<std::forward_iterator_tag,
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@ -50,30 +53,32 @@ class scc_iterator
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unsigned visitNum;
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DenseMap<NodeType *, unsigned> nodeVisitNumbers;
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// SCCNodeStack - Stack holding nodes of the SCC.
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// Stack holding nodes of the SCC.
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std::vector<NodeType *> SCCNodeStack;
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// CurrentSCC - The current SCC, retrieved using operator*().
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// The current SCC, retrieved using operator*().
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SccTy CurrentSCC;
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// VisitStack - Used to maintain the ordering. Top = current block
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// First element is basic block pointer, second is the 'next child' to visit
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// Used to maintain the ordering. The top is the current block, the first
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// element is basic block pointer, second is the 'next child' to visit.
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std::vector<std::pair<NodeType *, ChildItTy> > VisitStack;
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// MinVisitNumStack - Stack holding the "min" values for each node in the DFS.
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// This is used to track the minimum uplink values for all children of
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// the corresponding node on the VisitStack.
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// Stack holding the "min" values for each node in the DFS. This is used to
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// track the minimum uplink values for all children of the corresponding node
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// on the VisitStack.
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std::vector<unsigned> MinVisitNumStack;
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// A single "visit" within the non-recursive DFS traversal.
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void DFSVisitOne(NodeType *N) {
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++visitNum; // Global counter for the visit order
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++visitNum;
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nodeVisitNumbers[N] = visitNum;
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SCCNodeStack.push_back(N);
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MinVisitNumStack.push_back(visitNum);
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VisitStack.push_back(std::make_pair(N, GT::child_begin(N)));
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//dbgs() << "TarjanSCC: Node " << N <<
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// " : visitNum = " << visitNum << "\n";
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#if 0 // Enable if needed when debugging.
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dbgs() << "TarjanSCC: Node " << N <<
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" : visitNum = " << visitNum << "\n";
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#endif
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}
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// The stack-based DFS traversal; defined below.
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@ -108,9 +113,11 @@ class scc_iterator
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if (!MinVisitNumStack.empty() && MinVisitNumStack.back() > minVisitNum)
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MinVisitNumStack.back() = minVisitNum;
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//dbgs() << "TarjanSCC: Popped node " << visitingN <<
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// " : minVisitNum = " << minVisitNum << "; Node visit num = " <<
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// nodeVisitNumbers[visitingN] << "\n";
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#if 0 // Enable if needed when debugging.
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dbgs() << "TarjanSCC: Popped node " << visitingN <<
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" : minVisitNum = " << minVisitNum << "; Node visit num = " <<
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nodeVisitNumbers[visitingN] << "\n";
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#endif
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if (minVisitNum != nodeVisitNumbers[visitingN])
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continue;
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@ -137,11 +144,11 @@ class scc_iterator
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public:
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typedef scc_iterator<GraphT, GT> _Self;
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// Provide static "constructors"...
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static inline _Self begin(const GraphT &G){return _Self(GT::getEntryNode(G));}
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static inline _Self end (const GraphT &) { return _Self(); }
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// Direct loop termination test: I.isAtEnd() is more efficient than I == end()
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/// \brief Direct loop termination test which is more efficient than
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/// comparison with \c end().
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inline bool isAtEnd() const {
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assert(!CurrentSCC.empty() || VisitStack.empty());
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return CurrentSCC.empty();
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@ -152,16 +159,14 @@ public:
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}
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inline bool operator!=(const _Self& x) const { return !operator==(x); }
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// Iterator traversal: forward iteration only
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inline _Self& operator++() { // Preincrement
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inline _Self& operator++() {
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GetNextSCC();
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return *this;
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}
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inline _Self operator++(int) { // Postincrement
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inline _Self operator++(int) {
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_Self tmp = *this; ++*this; return tmp;
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}
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// Retrieve a reference to the current SCC
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inline const SccTy &operator*() const {
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assert(!CurrentSCC.empty() && "Dereferencing END SCC iterator!");
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return CurrentSCC;
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@ -171,9 +176,10 @@ public:
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return CurrentSCC;
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}
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// hasLoop() -- Test if the current SCC has a loop. If it has more than one
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// node, this is trivially true. If not, it may still contain a loop if the
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// node has an edge back to itself.
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/// \brief Test if the current SCC has a loop.
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///
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/// If the SCC has more than one node, this is trivially true. If not, it may
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/// still contain a loop if the node has an edge back to itself.
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bool hasLoop() const {
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assert(!CurrentSCC.empty() && "Dereferencing END SCC iterator!");
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if (CurrentSCC.size() > 1) return true;
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@ -184,8 +190,8 @@ public:
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return false;
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}
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/// ReplaceNode - This informs the scc_iterator that the specified Old node
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/// has been deleted, and New is to be used in its place.
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/// This informs the \c scc_iterator that the specified \c Old node
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/// has been deleted, and \c New is to be used in its place.
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void ReplaceNode(NodeType *Old, NodeType *New) {
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assert(nodeVisitNumbers.count(Old) && "Old not in scc_iterator?");
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nodeVisitNumbers[New] = nodeVisitNumbers[Old];
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@ -194,22 +200,25 @@ public:
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};
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// Global constructor for the SCC iterator.
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/// \brief Construct the begin iterator for a deduced graph type T.
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template <class T>
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scc_iterator<T> scc_begin(const T &G) {
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return scc_iterator<T>::begin(G);
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}
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/// \brief Construct the end iterator for a deduced graph type T.
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template <class T>
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scc_iterator<T> scc_end(const T &G) {
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return scc_iterator<T>::end(G);
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}
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/// \brief Construct the begin iterator for a deduced graph type T's Inverse<T>.
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template <class T>
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scc_iterator<Inverse<T> > scc_begin(const Inverse<T> &G) {
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return scc_iterator<Inverse<T> >::begin(G);
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}
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/// \brief Construct the end iterator for a deduced graph type T's Inverse<T>.
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template <class T>
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scc_iterator<Inverse<T> > scc_end(const Inverse<T> &G) {
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return scc_iterator<Inverse<T> >::end(G);
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