X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=include%2Fllvm%2FADT%2FPostOrderIterator.h;h=7f6350e4443e1567cc712b1e8b6d872bd9bb207a;hb=e19f11215d8fa29635b28317dd1cfd1915d048d4;hp=bf7ce9d0bb6aa0feb522605613bc9d7fe511e286;hpb=a2769a33c94f021a609a462b28ebea069eba6f74;p=oota-llvm.git

diff --git a/include/llvm/ADT/PostOrderIterator.h b/include/llvm/ADT/PostOrderIterator.h
index bf7ce9d0bb6..7f6350e4443 100644
--- a/include/llvm/ADT/PostOrderIterator.h
+++ b/include/llvm/ADT/PostOrderIterator.h
@@ -17,69 +17,116 @@
 #define LLVM_ADT_POSTORDERITERATOR_H
 
 #include "llvm/ADT/GraphTraits.h"
-#include "llvm/ADT/iterator.h"
+#include "llvm/ADT/SmallPtrSet.h"
 #include <set>
-#include <stack>
 #include <vector>
 
 namespace llvm {
 
-template<class SetType, bool External>   // Non-external set
+// The po_iterator_storage template provides access to the set of already
+// visited nodes during the po_iterator's depth-first traversal.
+//
+// The default implementation simply contains a set of visited nodes, while
+// the Extended=true version uses a reference to an external set.
+//
+// It is possible to prune the depth-first traversal in several ways:
+//
+// - When providing an external set that already contains some graph nodes,
+//   those nodes won't be visited again. This is useful for restarting a
+//   post-order traversal on a graph with nodes that aren't dominated by a
+//   single node.
+//
+// - By providing a custom SetType class, unwanted graph nodes can be excluded
+//   by having the insert() function return false. This could for example
+//   confine a CFG traversal to blocks in a specific loop.
+//
+// - Finally, by specializing the po_iterator_storage template itself, graph
+//   edges can be pruned by returning false in the insertEdge() function. This
+//   could be used to remove loop back-edges from the CFG seen by po_iterator.
+//
+// A specialized po_iterator_storage class can observe both the pre-order and
+// the post-order. The insertEdge() function is called in a pre-order, while
+// the finishPostorder() function is called just before the po_iterator moves
+// on to the next node.
+
+/// Default po_iterator_storage implementation with an internal set object.
+template<class SetType, bool External>
 class po_iterator_storage {
-public:
   SetType Visited;
+public:
+  // Return true if edge destination should be visited.
+  template<typename NodeType>
+  bool insertEdge(NodeType *From, NodeType *To) {
+    return Visited.insert(To);
+  }
+
+  // Called after all children of BB have been visited.
+  template<typename NodeType>
+  void finishPostorder(NodeType *BB) {}
 };
 
+/// Specialization of po_iterator_storage that references an external set.
 template<class SetType>
 class po_iterator_storage<SetType, true> {
+  SetType &Visited;
 public:
   po_iterator_storage(SetType &VSet) : Visited(VSet) {}
   po_iterator_storage(const po_iterator_storage &S) : Visited(S.Visited) {}
-  SetType &Visited;
+
+  // Return true if edge destination should be visited, called with From = 0 for
+  // the root node.
+  // Graph edges can be pruned by specializing this function.
+  template<class NodeType>
+  bool insertEdge(NodeType *From, NodeType *To) { return Visited.insert(To); }
+
+  // Called after all children of BB have been visited.
+  template<class NodeType>
+  void finishPostorder(NodeType *BB) {}
 };
 
 template<class GraphT,
-         class SetType = std::set<typename GraphTraits<GraphT>::NodeType*>,
-         bool ExtStorage = false,
-         class GT = GraphTraits<GraphT> >
-class po_iterator : public forward_iterator<typename GT::NodeType, ptrdiff_t>,
+  class SetType = llvm::SmallPtrSet<typename GraphTraits<GraphT>::NodeType*, 8>,
+  bool ExtStorage = false,
+  class GT = GraphTraits<GraphT> >
+class po_iterator : public std::iterator<std::forward_iterator_tag,
+                                         typename GT::NodeType, ptrdiff_t>,
                     public po_iterator_storage<SetType, ExtStorage> {
-  typedef forward_iterator<typename GT::NodeType, ptrdiff_t> super;
+  typedef std::iterator<std::forward_iterator_tag,
+                        typename GT::NodeType, ptrdiff_t> super;
   typedef typename GT::NodeType          NodeType;
   typedef typename GT::ChildIteratorType ChildItTy;
 
   // 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;
 
   void traverseChild() {
-    while (VisitStack.top().second != GT::child_end(VisitStack.top().first)) {
-      NodeType *BB = *VisitStack.top().second++;
-      if (!this->Visited.count(BB)) {  // If the block is not visited...
-        this->Visited.insert(BB);
-        VisitStack.push(std::make_pair(BB, GT::child_begin(BB)));
+    while (VisitStack.back().second != GT::child_end(VisitStack.back().first)) {
+      NodeType *BB = *VisitStack.back().second++;
+      if (this->insertEdge(VisitStack.back().first, BB)) {
+        // If the block is not visited...
+        VisitStack.push_back(std::make_pair(BB, GT::child_begin(BB)));
       }
     }
   }
 
   inline po_iterator(NodeType *BB) {
-    this->Visited.insert(BB);
-    VisitStack.push(std::make_pair(BB, GT::child_begin(BB)));
+    this->insertEdge((NodeType*)0, BB);
+    VisitStack.push_back(std::make_pair(BB, GT::child_begin(BB)));
     traverseChild();
   }
   inline po_iterator() {} // End is when stack is empty.
 
   inline po_iterator(NodeType *BB, SetType &S) :
-    po_iterator_storage<SetType, ExtStorage>(&S) {
-    if(!S.count(BB)) {
-      this->Visited.insert(BB);
-      VisitStack.push(std::make_pair(BB, GT::child_begin(BB)));
+    po_iterator_storage<SetType, ExtStorage>(S) {
+    if (this->insertEdge((NodeType*)0, BB)) {
+      VisitStack.push_back(std::make_pair(BB, GT::child_begin(BB)));
       traverseChild();
     }
   }
 
   inline po_iterator(SetType &S) :
-      po_iterator_storage<SetType, ExtStorage>(&S) {
+      po_iterator_storage<SetType, ExtStorage>(S) {
   } // End is when stack is empty.
 public:
   typedef typename super::pointer pointer;
@@ -100,7 +147,7 @@ public:
   inline bool operator!=(const _Self& x) const { return !operator==(x); }
 
   inline pointer operator*() const {
-    return VisitStack.top().first;
+    return VisitStack.back().first;
   }
 
   // This is a nonstandard operator-> that dereferences the pointer an extra
@@ -110,7 +157,8 @@ public:
   inline NodeType *operator->() const { return operator*(); }
 
   inline _Self& operator++() {   // Preincrement
-    VisitStack.pop();
+    this->finishPostorder(VisitStack.back().first);
+    VisitStack.pop_back();
     if (!VisitStack.empty())
       traverseChild();
     return *this;
@@ -164,14 +212,14 @@ ipo_iterator<T> ipo_end(T G){
   return ipo_iterator<T>::end(G);
 }
 
-//Provide global definitions of external inverse postorder iterators...
+// Provide global definitions of external inverse postorder iterators...
 template <class T,
           class SetType = std::set<typename GraphTraits<T>::NodeType*> >
 struct ipo_ext_iterator : public ipo_iterator<T, SetType, true> {
   ipo_ext_iterator(const ipo_iterator<T, SetType, true> &V) :
-    ipo_iterator<T, SetType, true>(&V) {}
+    ipo_iterator<T, SetType, true>(V) {}
   ipo_ext_iterator(const po_iterator<Inverse<T>, SetType, true> &V) :
-    ipo_iterator<T, SetType, true>(&V) {}
+    ipo_iterator<T, SetType, true>(V) {}
 };
 
 template <class T, class SetType>