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diff --git a/include/llvm/Support/GenericDomTreeConstruction.h b/include/llvm/Support/GenericDomTreeConstruction.h
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+//===- GenericDomTreeConstruction.h - Dominator Calculation ------*- C++ -*-==//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+/// \file
+///
+/// Generic dominator tree construction - This file provides routines to
+/// construct immediate dominator information for a flow-graph based on the
+/// algorithm described in this document:
+///
+///   A Fast Algorithm for Finding Dominators in a Flowgraph
+///   T. Lengauer & R. Tarjan, ACM TOPLAS July 1979, pgs 121-141.
+///
+/// This implements the O(n*log(n)) versions of EVAL and LINK, because it turns
+/// out that the theoretically slower O(n*log(n)) implementation is actually
+/// faster than the almost-linear O(n*alpha(n)) version, even for large CFGs.
+///
+//===----------------------------------------------------------------------===//
+
+
+#ifndef LLVM_SUPPORT_GENERIC_DOM_TREE_CONSTRUCTION_H
+#define LLVM_SUPPORT_GENERIC_DOM_TREE_CONSTRUCTION_H
+
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/Support/GenericDomTree.h"
+
+namespace llvm {
+
+template<class GraphT>
+unsigned DFSPass(DominatorTreeBase<typename GraphT::NodeType>& DT,
+                 typename GraphT::NodeType* V, unsigned N) {
+  // This is more understandable as a recursive algorithm, but we can't use the
+  // recursive algorithm due to stack depth issues.  Keep it here for
+  // documentation purposes.
+#if 0
+  InfoRec &VInfo = DT.Info[DT.Roots[i]];
+  VInfo.DFSNum = VInfo.Semi = ++N;
+  VInfo.Label = V;
+
+  Vertex.push_back(V);        // Vertex[n] = V;
+
+  for (succ_iterator SI = succ_begin(V), E = succ_end(V); SI != E; ++SI) {
+    InfoRec &SuccVInfo = DT.Info[*SI];
+    if (SuccVInfo.Semi == 0) {
+      SuccVInfo.Parent = V;
+      N = DTDFSPass(DT, *SI, N);
+    }
+  }
+#else
+  bool IsChildOfArtificialExit = (N != 0);
+
+  SmallVector<std::pair<typename GraphT::NodeType*,
+                        typename GraphT::ChildIteratorType>, 32> Worklist;
+  Worklist.push_back(std::make_pair(V, GraphT::child_begin(V)));
+  while (!Worklist.empty()) {
+    typename GraphT::NodeType* BB = Worklist.back().first;
+    typename GraphT::ChildIteratorType NextSucc = Worklist.back().second;
+
+    typename DominatorTreeBase<typename GraphT::NodeType>::InfoRec &BBInfo =
+                                                                    DT.Info[BB];
+
+    // First time we visited this BB?
+    if (NextSucc == GraphT::child_begin(BB)) {
+      BBInfo.DFSNum = BBInfo.Semi = ++N;
+      BBInfo.Label = BB;
+
+      DT.Vertex.push_back(BB);       // Vertex[n] = V;
+
+      if (IsChildOfArtificialExit)
+        BBInfo.Parent = 1;
+
+      IsChildOfArtificialExit = false;
+    }
+
+    // store the DFS number of the current BB - the reference to BBInfo might
+    // get invalidated when processing the successors.
+    unsigned BBDFSNum = BBInfo.DFSNum;
+
+    // If we are done with this block, remove it from the worklist.
+    if (NextSucc == GraphT::child_end(BB)) {
+      Worklist.pop_back();
+      continue;
+    }
+
+    // Increment the successor number for the next time we get to it.
+    ++Worklist.back().second;
+    
+    // Visit the successor next, if it isn't already visited.
+    typename GraphT::NodeType* Succ = *NextSucc;
+
+    typename DominatorTreeBase<typename GraphT::NodeType>::InfoRec &SuccVInfo =
+                                                                  DT.Info[Succ];
+    if (SuccVInfo.Semi == 0) {
+      SuccVInfo.Parent = BBDFSNum;
+      Worklist.push_back(std::make_pair(Succ, GraphT::child_begin(Succ)));
+    }
+  }
+#endif
+    return N;
+}
+
+template<class GraphT>
+typename GraphT::NodeType* 
+Eval(DominatorTreeBase<typename GraphT::NodeType>& DT,
+     typename GraphT::NodeType *VIn, unsigned LastLinked) {
+  typename DominatorTreeBase<typename GraphT::NodeType>::InfoRec &VInInfo =
+                                                                  DT.Info[VIn];
+  if (VInInfo.DFSNum < LastLinked)
+    return VIn;
+
+  SmallVector<typename GraphT::NodeType*, 32> Work;
+  SmallPtrSet<typename GraphT::NodeType*, 32> Visited;
+
+  if (VInInfo.Parent >= LastLinked)
+    Work.push_back(VIn);
+  
+  while (!Work.empty()) {
+    typename GraphT::NodeType* V = Work.back();
+    typename DominatorTreeBase<typename GraphT::NodeType>::InfoRec &VInfo =
+                                                                     DT.Info[V];
+    typename GraphT::NodeType* VAncestor = DT.Vertex[VInfo.Parent];
+
+    // Process Ancestor first
+    if (Visited.insert(VAncestor) && VInfo.Parent >= LastLinked) {
+      Work.push_back(VAncestor);
+      continue;
+    } 
+    Work.pop_back(); 
+
+    // Update VInfo based on Ancestor info
+    if (VInfo.Parent < LastLinked)
+      continue;
+
+    typename DominatorTreeBase<typename GraphT::NodeType>::InfoRec &VAInfo =
+                                                             DT.Info[VAncestor];
+    typename GraphT::NodeType* VAncestorLabel = VAInfo.Label;
+    typename GraphT::NodeType* VLabel = VInfo.Label;
+    if (DT.Info[VAncestorLabel].Semi < DT.Info[VLabel].Semi)
+      VInfo.Label = VAncestorLabel;
+    VInfo.Parent = VAInfo.Parent;
+  }
+
+  return VInInfo.Label;
+}
+
+template<class FuncT, class NodeT>
+void Calculate(DominatorTreeBase<typename GraphTraits<NodeT>::NodeType>& DT,
+               FuncT& F) {
+  typedef GraphTraits<NodeT> GraphT;
+
+  unsigned N = 0;
+  bool MultipleRoots = (DT.Roots.size() > 1);
+  if (MultipleRoots) {
+    typename DominatorTreeBase<typename GraphT::NodeType>::InfoRec &BBInfo =
+        DT.Info[NULL];
+    BBInfo.DFSNum = BBInfo.Semi = ++N;
+    BBInfo.Label = NULL;
+
+    DT.Vertex.push_back(NULL);       // Vertex[n] = V;
+  }
+
+  // Step #1: Number blocks in depth-first order and initialize variables used
+  // in later stages of the algorithm.
+  for (unsigned i = 0, e = static_cast<unsigned>(DT.Roots.size());
+       i != e; ++i)
+    N = DFSPass<GraphT>(DT, DT.Roots[i], N);
+
+  // it might be that some blocks did not get a DFS number (e.g., blocks of 
+  // infinite loops). In these cases an artificial exit node is required.
+  MultipleRoots |= (DT.isPostDominator() && N != GraphTraits<FuncT*>::size(&F));
+
+  // When naively implemented, the Lengauer-Tarjan algorithm requires a separate
+  // bucket for each vertex. However, this is unnecessary, because each vertex
+  // is only placed into a single bucket (that of its semidominator), and each
+  // vertex's bucket is processed before it is added to any bucket itself.
+  //
+  // Instead of using a bucket per vertex, we use a single array Buckets that
+  // has two purposes. Before the vertex V with preorder number i is processed,
+  // Buckets[i] stores the index of the first element in V's bucket. After V's
+  // bucket is processed, Buckets[i] stores the index of the next element in the
+  // bucket containing V, if any.
+  SmallVector<unsigned, 32> Buckets;
+  Buckets.resize(N + 1);
+  for (unsigned i = 1; i <= N; ++i)
+    Buckets[i] = i;
+
+  for (unsigned i = N; i >= 2; --i) {
+    typename GraphT::NodeType* W = DT.Vertex[i];
+    typename DominatorTreeBase<typename GraphT::NodeType>::InfoRec &WInfo =
+                                                                     DT.Info[W];
+
+    // Step #2: Implicitly define the immediate dominator of vertices
+    for (unsigned j = i; Buckets[j] != i; j = Buckets[j]) {
+      typename GraphT::NodeType* V = DT.Vertex[Buckets[j]];
+      typename GraphT::NodeType* U = Eval<GraphT>(DT, V, i + 1);
+      DT.IDoms[V] = DT.Info[U].Semi < i ? U : W;
+    }
+
+    // Step #3: Calculate the semidominators of all vertices
+
+    // initialize the semi dominator to point to the parent node
+    WInfo.Semi = WInfo.Parent;
+    typedef GraphTraits<Inverse<NodeT> > InvTraits;
+    for (typename InvTraits::ChildIteratorType CI =
+         InvTraits::child_begin(W),
+         E = InvTraits::child_end(W); CI != E; ++CI) {
+      typename InvTraits::NodeType *N = *CI;
+      if (DT.Info.count(N)) {  // Only if this predecessor is reachable!
+        unsigned SemiU = DT.Info[Eval<GraphT>(DT, N, i + 1)].Semi;
+        if (SemiU < WInfo.Semi)
+          WInfo.Semi = SemiU;
+      }
+    }
+
+    // If V is a non-root vertex and sdom(V) = parent(V), then idom(V) is
+    // necessarily parent(V). In this case, set idom(V) here and avoid placing
+    // V into a bucket.
+    if (WInfo.Semi == WInfo.Parent) {
+      DT.IDoms[W] = DT.Vertex[WInfo.Parent];
+    } else {
+      Buckets[i] = Buckets[WInfo.Semi];
+      Buckets[WInfo.Semi] = i;
+    }
+  }
+
+  if (N >= 1) {
+    typename GraphT::NodeType* Root = DT.Vertex[1];
+    for (unsigned j = 1; Buckets[j] != 1; j = Buckets[j]) {
+      typename GraphT::NodeType* V = DT.Vertex[Buckets[j]];
+      DT.IDoms[V] = Root;
+    }
+  }
+
+  // Step #4: Explicitly define the immediate dominator of each vertex
+  for (unsigned i = 2; i <= N; ++i) {
+    typename GraphT::NodeType* W = DT.Vertex[i];
+    typename GraphT::NodeType*& WIDom = DT.IDoms[W];
+    if (WIDom != DT.Vertex[DT.Info[W].Semi])
+      WIDom = DT.IDoms[WIDom];
+  }
+
+  if (DT.Roots.empty()) return;
+
+  // Add a node for the root.  This node might be the actual root, if there is
+  // one exit block, or it may be the virtual exit (denoted by (BasicBlock *)0)
+  // which postdominates all real exits if there are multiple exit blocks, or
+  // an infinite loop.
+  typename GraphT::NodeType* Root = !MultipleRoots ? DT.Roots[0] : 0;
+
+  DT.DomTreeNodes[Root] = DT.RootNode =
+                        new DomTreeNodeBase<typename GraphT::NodeType>(Root, 0);
+
+  // Loop over all of the reachable blocks in the function...
+  for (unsigned i = 2; i <= N; ++i) {
+    typename GraphT::NodeType* W = DT.Vertex[i];
+
+    DomTreeNodeBase<typename GraphT::NodeType> *BBNode = DT.DomTreeNodes[W];
+    if (BBNode) continue;  // Haven't calculated this node yet?
+
+    typename GraphT::NodeType* ImmDom = DT.getIDom(W);
+
+    assert(ImmDom || DT.DomTreeNodes[NULL]);
+
+    // Get or calculate the node for the immediate dominator
+    DomTreeNodeBase<typename GraphT::NodeType> *IDomNode =
+                                                     DT.getNodeForBlock(ImmDom);
+
+    // Add a new tree node for this BasicBlock, and link it as a child of
+    // IDomNode
+    DomTreeNodeBase<typename GraphT::NodeType> *C =
+                    new DomTreeNodeBase<typename GraphT::NodeType>(W, IDomNode);
+    DT.DomTreeNodes[W] = IDomNode->addChild(C);
+  }
+
+  // Free temporary memory used to construct idom's
+  DT.IDoms.clear();
+  DT.Info.clear();
+  std::vector<typename GraphT::NodeType*>().swap(DT.Vertex);
+
+  DT.updateDFSNumbers();
+}
+
+}
+
+#endif