1 files changed, 31 insertions, 22 deletions

diff --git a/include/llvm/Support/GenericDomTree.h b/include/llvm/Support/GenericDomTree.h
index 0998eb9..63678bb 100644
--- a/include/llvm/Support/GenericDomTree.h
+++ b/include/llvm/Support/GenericDomTree.h
@@ -243,6 +243,8 @@ protected:
     this->Roots.clear();
     Vertex.clear();
     RootNode = nullptr;
+    DFSInfoValid = false;
+    SlowQueries = 0;
   }
 
   // NewBB is split and now it has one successor. Update dominator tree to
@@ -637,9 +639,38 @@ protected:
   friend void
   Calculate(DominatorTreeBase<typename GraphTraits<N>::NodeType> &DT, FuncT &F);
 
+
+  DomTreeNodeBase<NodeT> *getNodeForBlock(NodeT *BB) {
+    if (DomTreeNodeBase<NodeT> *Node = getNode(BB))
+      return Node;
+
+    // Haven't calculated this node yet?  Get or calculate the node for the
+    // immediate dominator.
+    NodeT *IDom = getIDom(BB);
+
+    assert(IDom || this->DomTreeNodes[nullptr]);
+    DomTreeNodeBase<NodeT> *IDomNode = getNodeForBlock(IDom);
+
+    // Add a new tree node for this NodeT, and link it as a child of
+    // IDomNode
+    return (this->DomTreeNodes[BB] = IDomNode->addChild(
+                llvm::make_unique<DomTreeNodeBase<NodeT>>(BB, IDomNode))).get();
+  }
+
+  NodeT *getIDom(NodeT *BB) const { return IDoms.lookup(BB); }
+
+  void addRoot(NodeT *BB) { this->Roots.push_back(BB); }
+
+public:
   /// updateDFSNumbers - Assign In and Out numbers to the nodes while walking
   /// dominator tree in dfs order.
   void updateDFSNumbers() const {
+
+    if (DFSInfoValid) {
+      SlowQueries = 0;
+      return;
+    }
+
     unsigned DFSNum = 0;
 
     SmallVector<std::pair<const DomTreeNodeBase<NodeT> *,
@@ -682,28 +713,6 @@ protected:
     DFSInfoValid = true;
   }
 
-  DomTreeNodeBase<NodeT> *getNodeForBlock(NodeT *BB) {
-    if (DomTreeNodeBase<NodeT> *Node = getNode(BB))
-      return Node;
-
-    // Haven't calculated this node yet?  Get or calculate the node for the
-    // immediate dominator.
-    NodeT *IDom = getIDom(BB);
-
-    assert(IDom || this->DomTreeNodes[nullptr]);
-    DomTreeNodeBase<NodeT> *IDomNode = getNodeForBlock(IDom);
-
-    // Add a new tree node for this NodeT, and link it as a child of
-    // IDomNode
-    return (this->DomTreeNodes[BB] = IDomNode->addChild(
-                llvm::make_unique<DomTreeNodeBase<NodeT>>(BB, IDomNode))).get();
-  }
-
-  NodeT *getIDom(NodeT *BB) const { return IDoms.lookup(BB); }
-
-  void addRoot(NodeT *BB) { this->Roots.push_back(BB); }
-
-public:
   /// recalculate - compute a dominator tree for the given function
   template <class FT> void recalculate(FT &F) {
     typedef GraphTraits<FT *> TraitsTy;