Index: include/clang/Tooling/ASTDiff/ASTDiff.h
===================================================================
--- include/clang/Tooling/ASTDiff/ASTDiff.h
+++ include/clang/Tooling/ASTDiff/ASTDiff.h
@@ -25,41 +25,28 @@
 namespace clang {
 namespace diff {
 
-/// This represents a match between two nodes in the source and destination
-/// trees, meaning that they are likely to be related.
-struct Match {
-  NodeId Src, Dst;
-};
-
 enum ChangeKind {
-  Delete, // (Src): delete node Src.
-  Update, // (Src, Dst): update the value of node Src to match Dst.
-  Insert, // (Src, Dst, Pos): insert Src as child of Dst at offset Pos.
-  Move    // (Src, Dst, Pos): move Src to be a child of Dst at offset Pos.
-};
-
-struct Change {
-  ChangeKind Kind;
-  NodeId Src, Dst;
-  size_t Position;
-
-  Change(ChangeKind Kind, NodeId Src, NodeId Dst, size_t Position)
-      : Kind(Kind), Src(Src), Dst(Dst), Position(Position) {}
-  Change(ChangeKind Kind, NodeId Src) : Kind(Kind), Src(Src) {}
-  Change(ChangeKind Kind, NodeId Src, NodeId Dst)
-      : Kind(Kind), Src(Src), Dst(Dst) {}
+  None,
+  Delete,    // (Src): delete node Src.
+  Update,    // (Src, Dst): update the value of node Src to match Dst.
+  Insert,    // (Src, Dst, Pos): insert Src as child of Dst at offset Pos.
+  Move,      // (Src, Dst, Pos): move Src to be a child of Dst at offset Pos.
+  UpdateMove // Same as Move plus Update.
 };
 
 /// Represents a Clang AST node, alongside some additional information.
 struct Node {
   NodeId Parent, LeftMostDescendant, RightMostDescendant;
-  int Depth, Height;
+  int Depth, Height, Shift;
   ast_type_traits::DynTypedNode ASTNode;
   SmallVector<NodeId, 4> Children;
+  ChangeKind ChangeKind = None;
 
-  ast_type_traits::ASTNodeKind getType() const { return ASTNode.getNodeKind(); }
-  const StringRef getTypeLabel() const { return getType().asStringRef(); }
+  ast_type_traits::ASTNodeKind getType() const;
+  StringRef getTypeLabel() const;
   bool isLeaf() const { return Children.empty(); }
+  llvm::Optional<StringRef> getIdentifier() const;
+  llvm::Optional<std::string> getQualifiedIdentifier() const;
 };
 
 class ASTDiff {
@@ -67,15 +54,8 @@
   ASTDiff(SyntaxTree &Src, SyntaxTree &Dst, const ComparisonOptions &Options);
   ~ASTDiff();
 
-  // Returns a list of matches.
-  std::vector<Match> getMatches();
-  /// Returns an edit script.
-  std::vector<Change> getChanges();
-
-  // Prints an edit action.
-  void printChange(raw_ostream &OS, const Change &Chg) const;
-  // Prints a match between two nodes.
-  void printMatch(raw_ostream &OS, const Match &M) const;
+  // Returns the ID of the node that is mapped to the given node in SourceTree.
+  NodeId getMapped(const SyntaxTree &SourceTree, NodeId Id) const;
 
   class Impl;
 
@@ -88,21 +68,33 @@
 class SyntaxTree {
 public:
   /// Constructs a tree from a translation unit.
-  SyntaxTree(const ASTContext &AST);
+  SyntaxTree(ASTContext &AST);
   /// Constructs a tree from any AST node.
   template <class T>
-  SyntaxTree(T *Node, const ASTContext &AST)
+  SyntaxTree(T *Node, ASTContext &AST)
       : TreeImpl(llvm::make_unique<Impl>(this, Node, AST)) {}
+  SyntaxTree(const SyntaxTree &Tree) = delete;
   ~SyntaxTree();
 
+  ASTContext &getASTContext() const;
+  StringRef getFilename() const;
+
+  int getSize() const;
+  NodeId getRootId() const;
+  using PreorderIterator = NodeId;
+  PreorderIterator begin() const;
+  PreorderIterator end() const;
+
   const Node &getNode(NodeId Id) const;
+  int findPositionInParent(NodeId Id) const;
+
+  std::pair<unsigned, unsigned> getFileOffsets(const Node &N) const;
 
   /// Serialize the node attributes to a string representation. This should
   /// uniquely distinguish nodes of the same kind. Note that this function just
   /// returns a representation of the node value, not considering descendants.
-  std::string getNodeValue(const DynTypedNode &DTN) const;
-
-  void printAsJson(raw_ostream &OS);
+  std::string getNodeValue(NodeId Id) const;
+  std::string getNodeValue(const Node &Node) const;
 
   class Impl;
   std::unique_ptr<Impl> TreeImpl;
@@ -114,19 +106,17 @@
 
   /// During bottom-up matching, match only nodes with at least this value as
   /// the ratio of their common descendants.
-  double MinSimilarity = 0.2;
+  double MinSimilarity = 0.5;
 
   /// Whenever two subtrees are matched in the bottom-up phase, the optimal
   /// mapping is computed, unless the size of either subtrees exceeds this.
   int MaxSize = 100;
 
-  /// If this is set to true, nodes that have parents that must not be matched
-  /// (see NodeComparison) will be allowed to be matched.
-  bool EnableMatchingWithUnmatchableParents = false;
+  bool StopAfterTopDown = false;
 
   /// Returns false if the nodes should never be matched.
-  bool isMatchingAllowed(const DynTypedNode &N1, const DynTypedNode &N2) const {
-    return N1.getNodeKind().isSame(N2.getNodeKind());
+  bool isMatchingAllowed(const Node &N1, const Node &N2) const {
+    return N1.getType().isSame(N2.getType());
   }
 };
 
Index: include/clang/Tooling/ASTDiff/ASTDiffInternal.h
===================================================================
--- include/clang/Tooling/ASTDiff/ASTDiffInternal.h
+++ include/clang/Tooling/ASTDiff/ASTDiffInternal.h
@@ -11,8 +11,6 @@
 #ifndef LLVM_CLANG_TOOLING_ASTDIFF_ASTDIFFINTERNAL_H
 #define LLVM_CLANG_TOOLING_ASTDIFF_ASTDIFFINTERNAL_H
 
-#include <utility>
-
 #include "clang/AST/ASTTypeTraits.h"
 
 namespace clang {
@@ -38,6 +36,8 @@
   operator int() const { return Id; }
   NodeId &operator++() { return ++Id, *this; }
   NodeId &operator--() { return --Id, *this; }
+  // Support defining iterators on NodeId.
+  NodeId &operator*() { return *this; }
 
   bool isValid() const { return Id != InvalidNodeId; }
   bool isInvalid() const { return Id == InvalidNodeId; }
Index: include/clang/Tooling/CommonOptionsParser.h
===================================================================
--- include/clang/Tooling/CommonOptionsParser.h
+++ include/clang/Tooling/CommonOptionsParser.h
@@ -27,6 +27,7 @@
 #ifndef LLVM_CLANG_TOOLING_COMMONOPTIONSPARSER_H
 #define LLVM_CLANG_TOOLING_COMMONOPTIONSPARSER_H
 
+#include "clang/Tooling/ArgumentsAdjusters.h"
 #include "clang/Tooling/CompilationDatabase.h"
 #include "llvm/Support/CommandLine.h"
 
@@ -111,6 +112,29 @@
   std::vector<std::string> ExtraArgsAfter;
 };
 
+class ArgumentsAdjustingCompilations : public CompilationDatabase {
+public:
+  ArgumentsAdjustingCompilations(
+      std::unique_ptr<CompilationDatabase> Compilations)
+      : Compilations(std::move(Compilations)) {}
+
+  void appendArgumentsAdjuster(ArgumentsAdjuster Adjuster);
+
+  std::vector<CompileCommand>
+  getCompileCommands(StringRef FilePath) const override;
+
+  std::vector<std::string> getAllFiles() const override;
+
+  std::vector<CompileCommand> getAllCompileCommands() const override;
+
+private:
+  std::unique_ptr<CompilationDatabase> Compilations;
+  std::vector<ArgumentsAdjuster> Adjusters;
+
+  std::vector<CompileCommand>
+  adjustCommands(std::vector<CompileCommand> Commands) const;
+};
+
 }  // namespace tooling
 }  // namespace clang
 
Index: lib/Tooling/ASTDiff/ASTDiff.cpp
===================================================================
--- lib/Tooling/ASTDiff/ASTDiff.cpp
+++ lib/Tooling/ASTDiff/ASTDiff.cpp
@@ -27,92 +27,63 @@
 namespace clang {
 namespace diff {
 
+namespace {
 /// Maps nodes of the left tree to ones on the right, and vice versa.
 class Mapping {
 public:
   Mapping() = default;
   Mapping(Mapping &&Other) = default;
   Mapping &operator=(Mapping &&Other) = default;
-  Mapping(int Size1, int Size2) {
-    // Maximum possible size after patching one tree.
-    int Size = Size1 + Size2;
-    SrcToDst = llvm::make_unique<SmallVector<NodeId, 2>[]>(Size);
-    DstToSrc = llvm::make_unique<SmallVector<NodeId, 2>[]>(Size);
+
+  Mapping(size_t Size) {
+    SrcToDst = llvm::make_unique<NodeId[]>(Size);
+    DstToSrc = llvm::make_unique<NodeId[]>(Size);
   }
 
   void link(NodeId Src, NodeId Dst) {
-    SrcToDst[Src].push_back(Dst);
-    DstToSrc[Dst].push_back(Src);
-  }
-
-  NodeId getDst(NodeId Src) const {
-    if (hasSrc(Src))
-      return SrcToDst[Src][0];
-    return NodeId();
-  }
-  NodeId getSrc(NodeId Dst) const {
-    if (hasDst(Dst))
-      return DstToSrc[Dst][0];
-    return NodeId();
-  }
-  const SmallVector<NodeId, 2> &getAllDsts(NodeId Src) const {
-    return SrcToDst[Src];
-  }
-  const SmallVector<NodeId, 2> &getAllSrcs(NodeId Dst) const {
-    return DstToSrc[Dst];
-  }
-  bool hasSrc(NodeId Src) const { return !SrcToDst[Src].empty(); }
-  bool hasDst(NodeId Dst) const { return !DstToSrc[Dst].empty(); }
-  bool hasSrcDst(NodeId Src, NodeId Dst) const {
-    for (NodeId DstId : SrcToDst[Src])
-      if (DstId == Dst)
-        return true;
-    for (NodeId SrcId : DstToSrc[Dst])
-      if (SrcId == Src)
-        return true;
-    return false;
+    SrcToDst[Src] = Dst, DstToSrc[Dst] = Src;
   }
 
+  NodeId getDst(NodeId Src) const { return SrcToDst[Src]; }
+  NodeId getSrc(NodeId Dst) const { return DstToSrc[Dst]; }
+  bool hasSrc(NodeId Src) const { return getDst(Src).isValid(); }
+  bool hasDst(NodeId Dst) const { return getSrc(Dst).isValid(); }
+
 private:
-  std::unique_ptr<SmallVector<NodeId, 2>[]> SrcToDst, DstToSrc;
+  std::unique_ptr<NodeId[]> SrcToDst, DstToSrc;
 };
+} // end anonymous namespace
 
 class ASTDiff::Impl {
 public:
   SyntaxTree::Impl &T1, &T2;
-  bool IsMappingDone = false;
   Mapping TheMapping;
 
   Impl(SyntaxTree::Impl &T1, SyntaxTree::Impl &T2,
-       const ComparisonOptions &Options)
-      : T1(T1), T2(T2), Options(Options) {}
+       const ComparisonOptions &Options);
 
   /// Matches nodes one-by-one based on their similarity.
   void computeMapping();
 
-  std::vector<Match> getMatches(Mapping &M);
-
-  /// Finds an edit script that converts T1 to T2.
-  std::vector<Change> computeChanges(Mapping &M);
+  // Compute ChangeKind for each node based on similarity.
+  void computeChangeKinds(Mapping &M);
 
-  void printChangeImpl(raw_ostream &OS, const Change &Chg) const;
-  void printMatchImpl(raw_ostream &OS, const Match &M) const;
-
-  // Returns a mapping of identical subtrees.
-  Mapping matchTopDown() const;
+  NodeId getMapped(const SyntaxTree::Impl &Tree, NodeId Id) const {
+    if (&Tree == &T1)
+      return TheMapping.getDst(Id);
+    assert(&Tree == &T2 && "Invalid tree.");
+    return TheMapping.getSrc(Id);
+  }
 
 private:
   // Returns true if the two subtrees are identical.
   bool identical(NodeId Id1, NodeId Id2) const;
 
-  bool canBeAddedToMapping(const Mapping &M, NodeId Id1, NodeId Id2) const;
-
   // Returns false if the nodes must not be mached.
   bool isMatchingPossible(NodeId Id1, NodeId Id2) const;
 
-  // Adds all corresponding subtrees of the two nodes to the mapping.
-  // The two nodes must be identical.
-  void addIsomorphicSubTrees(Mapping &M, NodeId Id1, NodeId Id2) const;
+  // Returns true if the nodes' parents are matched.
+  bool haveSameParents(const Mapping &M, NodeId Id1, NodeId Id2) const;
 
   // Uses an optimal albeit slow algorithm to compute a mapping between two
   // subtrees, but only if both have fewer nodes than MaxSize.
@@ -120,11 +91,14 @@
 
   // Computes the ratio of common descendants between the two nodes.
   // Descendants are only considered to be equal when they are mapped in M.
-  double getSimilarity(const Mapping &M, NodeId Id1, NodeId Id2) const;
+  double getJaccardSimilarity(const Mapping &M, NodeId Id1, NodeId Id2) const;
 
   // Returns the node that has the highest degree of similarity.
   NodeId findCandidate(const Mapping &M, NodeId Id1) const;
 
+  // Returns a mapping of identical subtrees.
+  Mapping matchTopDown() const;
+
   // Tries to match any yet unmapped nodes, in a bottom-up fashion.
   void matchBottomUp(Mapping &M) const;
 
@@ -137,29 +111,32 @@
 class SyntaxTree::Impl {
 public:
   /// Constructs a tree from the entire translation unit.
-  Impl(SyntaxTree *Parent, const ASTContext &AST);
+  Impl(SyntaxTree *Parent, ASTContext &AST);
   /// Constructs a tree from an AST node.
-  Impl(SyntaxTree *Parent, Decl *N, const ASTContext &AST);
-  Impl(SyntaxTree *Parent, Stmt *N, const ASTContext &AST);
+  Impl(SyntaxTree *Parent, Decl *N, ASTContext &AST);
+  Impl(SyntaxTree *Parent, Stmt *N, ASTContext &AST);
   template <class T>
   Impl(SyntaxTree *Parent,
        typename std::enable_if<std::is_base_of<Stmt, T>::value, T>::type *Node,
-       const ASTContext &AST)
+       ASTContext &AST)
       : Impl(Parent, dyn_cast<Stmt>(Node), AST) {}
   template <class T>
   Impl(SyntaxTree *Parent,
        typename std::enable_if<std::is_base_of<Decl, T>::value, T>::type *Node,
-       const ASTContext &AST)
+       ASTContext &AST)
       : Impl(Parent, dyn_cast<Decl>(Node), AST) {}
 
   SyntaxTree *Parent;
-  const ASTContext &AST;
+  ASTContext &AST;
   std::vector<NodeId> Leaves;
   // Maps preorder indices to postorder ones.
   std::vector<int> PostorderIds;
+  std::vector<NodeId> NodesBfs;
 
   int getSize() const { return Nodes.size(); }
   NodeId getRootId() const { return 0; }
+  PreorderIterator begin() const { return getRootId(); }
+  PreorderIterator end() const { return getSize(); }
 
   const Node &getNode(NodeId Id) const { return Nodes[Id]; }
   Node &getMutableNode(NodeId Id) { return Nodes[Id]; }
@@ -167,19 +144,22 @@
   void addNode(Node &N) { Nodes.push_back(N); }
   int getNumberOfDescendants(NodeId Id) const;
   bool isInSubtree(NodeId Id, NodeId SubtreeRoot) const;
+  int findPositionInParent(NodeId Id, bool Shifted = false) const;
 
   std::string getNodeValue(NodeId Id) const;
-  std::string getNodeValue(const DynTypedNode &DTN) const;
-  /// Prints the node as "<type>[: <value>](<postorder-id)"
-  void printNode(NodeId Id) const { printNode(llvm::outs(), Id); }
-  void printNode(raw_ostream &OS, NodeId Id) const;
-
-  void printTree() const;
-  void printTree(NodeId Root) const;
-  void printTree(raw_ostream &OS, NodeId Root) const;
+  std::string getNodeValue(const Node &Node) const;
+  std::string getDeclValue(const Decl *D) const;
+  std::string getStmtValue(const Stmt *S) const;
+
+  struct SubtreeIterator {
+    NodeId Root, End;
+    SubtreeIterator(const SyntaxTree::Impl &Tree, NodeId Root)
+        : Root(Root), End(Tree.getNode(Root).RightMostDescendant + 1) {}
+    PreorderIterator begin() const { return Root; }
+    PreorderIterator end() const { return End; }
+  };
 
-  void printAsJsonImpl(raw_ostream &OS) const;
-  void printNodeAsJson(raw_ostream &OS, NodeId Id) const;
+  SubtreeIterator iteratePreorder(NodeId Root) const { return {*this, Root}; }
 
 private:
   /// Nodes in preorder.
@@ -194,9 +174,20 @@
   if (!N)
     return true;
   SourceLocation SLoc = N->getLocStart();
-  return SLoc.isValid() && SrcMgr.isInSystemHeader(SLoc);
+  if (!SLoc.isValid())
+    return false;
+  // Ignore everything from other files.
+  if (!SrcMgr.isInMainFile(SLoc))
+    return true;
+  // Ignore macros.
+  if (N->getLocStart() != SrcMgr.getSpellingLoc(N->getLocStart()))
+    return true;
+  return false;
 }
 
+static bool isDeclExcluded(const Decl *D) { return D->isImplicit(); }
+static bool isStmtExcluded(const Stmt *S) { return false; }
+
 namespace {
 /// Counts the number of nodes that will be compared.
 struct NodeCountVisitor : public RecursiveASTVisitor<NodeCountVisitor> {
@@ -204,14 +195,16 @@
   const SyntaxTree::Impl &Tree;
   NodeCountVisitor(const SyntaxTree::Impl &Tree) : Tree(Tree) {}
   bool TraverseDecl(Decl *D) {
-    if (isNodeExcluded(Tree.AST.getSourceManager(), D))
+    if (isNodeExcluded(Tree.AST.getSourceManager(), D) || isDeclExcluded(D))
       return true;
     ++Count;
     RecursiveASTVisitor<NodeCountVisitor>::TraverseDecl(D);
     return true;
   }
   bool TraverseStmt(Stmt *S) {
-    if (isNodeExcluded(Tree.AST.getSourceManager(), S))
+    if (S)
+      S = S->IgnoreImplicit();
+    if (isNodeExcluded(Tree.AST.getSourceManager(), S) || isStmtExcluded(S))
       return true;
     ++Count;
     RecursiveASTVisitor<NodeCountVisitor>::TraverseStmt(S);
@@ -254,7 +247,7 @@
     Parent = PreviousParent;
     --Depth;
     Node &N = Tree.getMutableNode(MyId);
-    N.RightMostDescendant = Id;
+    N.RightMostDescendant = Id - 1;
     if (N.isLeaf())
       Tree.Leaves.push_back(MyId);
     N.Height = 1;
@@ -262,7 +255,7 @@
       N.Height = std::max(N.Height, 1 + Tree.getNode(Child).Height);
   }
   bool TraverseDecl(Decl *D) {
-    if (isNodeExcluded(Tree.AST.getSourceManager(), D))
+    if (isNodeExcluded(Tree.AST.getSourceManager(), D) || isDeclExcluded(D))
       return true;
     auto SavedState = PreTraverse(D);
     RecursiveASTVisitor<PreorderVisitor>::TraverseDecl(D);
@@ -270,7 +263,9 @@
     return true;
   }
   bool TraverseStmt(Stmt *S) {
-    if (isNodeExcluded(Tree.AST.getSourceManager(), S))
+    if (S)
+      S = S->IgnoreImplicit();
+    if (isNodeExcluded(Tree.AST.getSourceManager(), S) || isStmtExcluded(S))
       return true;
     auto SavedState = PreTraverse(S);
     RecursiveASTVisitor<PreorderVisitor>::TraverseStmt(S);
@@ -281,10 +276,10 @@
 };
 } // end anonymous namespace
 
-SyntaxTree::Impl::Impl(SyntaxTree *Parent, const ASTContext &AST)
+SyntaxTree::Impl::Impl(SyntaxTree *Parent, ASTContext &AST)
     : Impl(Parent, AST.getTranslationUnitDecl(), AST) {}
 
-SyntaxTree::Impl::Impl(SyntaxTree *Parent, Decl *N, const ASTContext &AST)
+SyntaxTree::Impl::Impl(SyntaxTree *Parent, Decl *N, ASTContext &AST)
     : Parent(Parent), AST(AST) {
   NodeCountVisitor NodeCounter(*this);
   NodeCounter.TraverseDecl(N);
@@ -294,7 +289,7 @@
   initTree();
 }
 
-SyntaxTree::Impl::Impl(SyntaxTree *Parent, Stmt *N, const ASTContext &AST)
+SyntaxTree::Impl::Impl(SyntaxTree *Parent, Stmt *N, ASTContext &AST)
     : Parent(Parent), AST(AST) {
   NodeCountVisitor NodeCounter(*this);
   NodeCounter.TraverseStmt(N);
@@ -304,6 +299,30 @@
   initTree();
 }
 
+static std::vector<NodeId> getSubtreePostorder(const SyntaxTree::Impl &Tree,
+                                               NodeId Root) {
+  std::vector<NodeId> Postorder;
+  std::function<void(NodeId)> Traverse = [&](NodeId Id) {
+    const Node &N = Tree.getNode(Id);
+    for (NodeId Child : N.Children)
+      Traverse(Child);
+    Postorder.push_back(Id);
+  };
+  Traverse(Root);
+  return Postorder;
+}
+
+static std::vector<NodeId> getSubtreeBfs(const SyntaxTree::Impl &Tree,
+                                         NodeId Root) {
+  std::vector<NodeId> Ids;
+  size_t Expanded = 0;
+  Ids.push_back(Root);
+  while (Expanded < Ids.size())
+    for (NodeId Child : Tree.getNode(Ids[Expanded++]).Children)
+      Ids.push_back(Child);
+  return Ids;
+}
+
 void SyntaxTree::Impl::initTree() {
   setLeftMostDescendants();
   int PostorderId = 0;
@@ -315,6 +334,7 @@
     ++PostorderId;
   };
   PostorderTraverse(getRootId());
+  NodesBfs = getSubtreeBfs(*this, getRootId());
 }
 
 void SyntaxTree::Impl::setLeftMostDescendants() {
@@ -329,136 +349,149 @@
   }
 }
 
-static std::vector<NodeId> getSubtreePostorder(const SyntaxTree::Impl &Tree,
-                                               NodeId Root) {
-  std::vector<NodeId> Postorder;
-  std::function<void(NodeId)> Traverse = [&](NodeId Id) {
-    const Node &N = Tree.getNode(Id);
-    for (NodeId Child : N.Children)
-      Traverse(Child);
-    Postorder.push_back(Id);
-  };
-  Traverse(Root);
-  return Postorder;
+int SyntaxTree::Impl::getNumberOfDescendants(NodeId Id) const {
+  return getNode(Id).RightMostDescendant - Id + 1;
 }
 
-static std::vector<NodeId> getSubtreeBfs(const SyntaxTree::Impl &Tree,
-                                         NodeId Root) {
-  std::vector<NodeId> Ids;
-  size_t Expanded = 0;
-  Ids.push_back(Root);
-  while (Expanded < Ids.size())
-    for (NodeId Child : Tree.getNode(Ids[Expanded++]).Children)
-      Ids.push_back(Child);
-  return Ids;
+bool SyntaxTree::Impl::isInSubtree(NodeId Id, NodeId SubtreeRoot) const {
+  return Id >= SubtreeRoot && Id <= getNode(SubtreeRoot).RightMostDescendant;
 }
 
-int SyntaxTree::Impl::getNumberOfDescendants(NodeId Id) const {
-  return getNode(Id).RightMostDescendant - Id + 1;
+int SyntaxTree::Impl::findPositionInParent(NodeId Id, bool Shifted) const {
+  NodeId Parent = getNode(Id).Parent;
+  if (Parent.isInvalid())
+    return 0;
+  const auto &Siblings = getNode(Parent).Children;
+  int Position = 0;
+  for (size_t I = 0, E = Siblings.size(); I < E; ++I) {
+    if (Shifted)
+      Position += getNode(Siblings[I]).Shift;
+    if (Siblings[I] == Id) {
+      Position += I;
+      return Position;
+    }
+  }
+  llvm_unreachable("Node not found in parent's children.");
 }
 
-bool SyntaxTree::Impl::isInSubtree(NodeId Id, NodeId SubtreeRoot) const {
-  NodeId Lower = SubtreeRoot;
-  NodeId Upper = getNode(SubtreeRoot).RightMostDescendant;
-  return Id >= Lower && Id <= Upper;
+// Returns the qualified name of ND. If the is declared in Context then
+// the name is made relative with respect to the qualified name of Context.
+static std::string getRelativeName(const NamedDecl *ND,
+                                   const DeclContext *Context) {
+  std::string ContextPrefix;
+  if (auto *Namespace = dyn_cast<NamespaceDecl>(Context))
+    ContextPrefix = Namespace->getQualifiedNameAsString();
+  else if (auto *Tag = dyn_cast<TagDecl>(Context))
+    ContextPrefix = Tag->getQualifiedNameAsString();
+  std::string Val = ND->getQualifiedNameAsString();
+  // Strip the qualifier, if Val refers to somthing in the current scope.
+  // But leave one leading ':' in place, so that we know that this is a
+  // relative path.
+  if (!ContextPrefix.empty() &&
+      Val.substr(0, ContextPrefix.size()) == ContextPrefix)
+    Val = Val.substr(ContextPrefix.size() + 1);
+  return Val;
 }
 
-std::string SyntaxTree::Impl::getNodeValue(NodeId Id) const {
-  return getNodeValue(getNode(Id).ASTNode);
+static std::string getRelativeName(const NamedDecl *ND) {
+  return getRelativeName(ND, ND->getDeclContext());
 }
 
-std::string SyntaxTree::Impl::getNodeValue(const DynTypedNode &DTN) const {
-  if (auto *X = DTN.get<BinaryOperator>())
-    return X->getOpcodeStr();
-  if (auto *X = DTN.get<AccessSpecDecl>()) {
-    CharSourceRange Range(X->getSourceRange(), false);
-    return Lexer::getSourceText(Range, AST.getSourceManager(),
-                                AST.getLangOpts());
-  }
-  if (auto *X = DTN.get<IntegerLiteral>()) {
-    SmallString<256> Str;
-    X->getValue().toString(Str, /*Radix=*/10, /*Signed=*/false);
-    return Str.str();
+static const DeclContext *getEnclosingDeclContext(ASTContext &AST,
+                                                  const Stmt *S) {
+  while (S) {
+    const auto &Parents = AST.getParents(*S);
+    if (Parents.empty())
+      return nullptr;
+    const auto &P = Parents[0];
+    if (const auto *D = P.get<Decl>())
+      return D->getDeclContext();
+    S = P.get<Stmt>();
   }
-  if (auto *X = DTN.get<StringLiteral>())
-    return X->getString();
-  if (auto *X = DTN.get<ValueDecl>())
-    return X->getNameAsString() + "(" + X->getType().getAsString() + ")";
-  if (DTN.get<DeclStmt>() || DTN.get<TranslationUnitDecl>())
-    return "";
-  std::string Value;
-  if (auto *X = DTN.get<DeclRefExpr>()) {
-    if (X->hasQualifier()) {
-      llvm::raw_string_ostream OS(Value);
-      PrintingPolicy PP(AST.getLangOpts());
-      X->getQualifier()->print(OS, PP);
-    }
-    Value += X->getDecl()->getNameAsString();
-    return Value;
-  }
-  if (auto *X = DTN.get<NamedDecl>())
-    Value += X->getNameAsString() + ";";
-  if (auto *X = DTN.get<TypedefNameDecl>())
-    return Value + X->getUnderlyingType().getAsString() + ";";
-  if (DTN.get<NamespaceDecl>())
-    return Value;
-  if (auto *X = DTN.get<TypeDecl>())
-    if (X->getTypeForDecl())
-      Value +=
-          X->getTypeForDecl()->getCanonicalTypeInternal().getAsString() + ";";
-  if (DTN.get<Decl>())
-    return Value;
-  if (DTN.get<Stmt>())
-    return "";
-  llvm_unreachable("Fatal: unhandled AST node.\n");
+  llvm_unreachable("Could not find Decl ancestor.");
 }
 
-void SyntaxTree::Impl::printTree() const { printTree(getRootId()); }
-void SyntaxTree::Impl::printTree(NodeId Root) const {
-  printTree(llvm::outs(), Root);
+std::string SyntaxTree::Impl::getNodeValue(NodeId Id) const {
+  return getNodeValue(getNode(Id));
 }
 
-void SyntaxTree::Impl::printTree(raw_ostream &OS, NodeId Root) const {
-  const Node &N = getNode(Root);
-  for (int I = 0; I < N.Depth; ++I)
-    OS << " ";
-  printNode(OS, Root);
-  OS << "\n";
-  for (NodeId Child : N.Children)
-    printTree(OS, Child);
+std::string SyntaxTree::Impl::getNodeValue(const Node &N) const {
+  const DynTypedNode &DTN = N.ASTNode;
+  if (auto *S = DTN.get<Stmt>())
+    return getStmtValue(S);
+  if (auto *D = DTN.get<Decl>())
+    return getDeclValue(D);
+  llvm_unreachable("Fatal: unhandled AST node.\n");
 }
 
-void SyntaxTree::Impl::printNode(raw_ostream &OS, NodeId Id) const {
-  if (Id.isInvalid()) {
-    OS << "None";
-    return;
-  }
-  OS << getNode(Id).getTypeLabel();
-  if (getNodeValue(Id) != "")
-    OS << ": " << getNodeValue(Id);
-  OS << "(" << PostorderIds[Id] << ")";
-}
-
-void SyntaxTree::Impl::printNodeAsJson(raw_ostream &OS, NodeId Id) const {
-  auto N = getNode(Id);
-  OS << R"({"type":")" << N.getTypeLabel() << R"(")";
-  if (getNodeValue(Id) != "")
-    OS << R"(,"value":")" << getNodeValue(Id) << R"(")";
-  OS << R"(,"children":[)";
-  if (N.Children.size() > 0) {
-    printNodeAsJson(OS, N.Children[0]);
-    for (size_t I = 1, E = N.Children.size(); I < E; ++I) {
-      OS << ",";
-      printNodeAsJson(OS, N.Children[I]);
+std::string SyntaxTree::Impl::getDeclValue(const Decl *D) const {
+  std::string Value;
+  PrintingPolicy TypePP(AST.getLangOpts());
+  TypePP.AnonymousTagLocations = false;
+
+  if (auto *X = dyn_cast<ValueDecl>(D)) {
+    Value += getRelativeName(X) + "(" + X->getType().getAsString(TypePP) + ")";
+    if (auto *X = dyn_cast<CXXConstructorDecl>(D)) {
+      for (auto *Init : X->inits()) {
+        if (!Init->isWritten())
+          continue;
+        if (Init->isBaseInitializer()) {
+          Value += Init->getBaseClass()->getCanonicalTypeInternal().getAsString(
+                       TypePP) +
+                   ",";
+        } else if (Init->isDelegatingInitializer()) {
+          Value += X->getNameAsString() + ",";
+        } else {
+          assert(Init->isAnyMemberInitializer());
+          Value += getRelativeName(Init->getMember()) + ",";
+        }
+      }
     }
+    return Value;
   }
-  OS << "]}";
+  if (auto *X = dyn_cast<NamedDecl>(D))
+    Value += getRelativeName(X) + ";";
+  if (auto *X = dyn_cast<TypedefNameDecl>(D))
+    return Value + X->getUnderlyingType().getAsString(TypePP) + ";";
+  if (auto *X = dyn_cast<TypeDecl>(D))
+    if (X->getTypeForDecl())
+      Value +=
+          X->getTypeForDecl()->getCanonicalTypeInternal().getAsString(TypePP) +
+          ";";
+  if (auto *X = dyn_cast<UsingDirectiveDecl>(D))
+    return X->getNominatedNamespace()->getName();
+  if (auto *X = dyn_cast<AccessSpecDecl>(D)) {
+    CharSourceRange Range(X->getSourceRange(), false);
+    return Lexer::getSourceText(Range, AST.getSourceManager(),
+                                AST.getLangOpts());
+  }
+  return Value;
 }
 
-void SyntaxTree::Impl::printAsJsonImpl(raw_ostream &OS) const {
-  OS << R"({"root":)";
-  printNodeAsJson(OS, getRootId());
-  OS << "}\n";
+std::string SyntaxTree::Impl::getStmtValue(const Stmt *S) const {
+  if (auto *X = dyn_cast<UnaryOperator>(S))
+    return UnaryOperator::getOpcodeStr(X->getOpcode());
+  if (auto *X = dyn_cast<BinaryOperator>(S))
+    return X->getOpcodeStr();
+  if (auto *X = dyn_cast<MemberExpr>(S))
+    return getRelativeName(X->getMemberDecl());
+  if (auto *X = dyn_cast<IntegerLiteral>(S)) {
+    SmallString<256> Str;
+    X->getValue().toString(Str, /*Radix=*/10, /*Signed=*/false);
+    return Str.str();
+  }
+  if (auto *X = dyn_cast<FloatingLiteral>(S)) {
+    SmallString<256> Str;
+    X->getValue().toString(Str);
+    return Str.str();
+  }
+  if (auto *X = dyn_cast<DeclRefExpr>(S))
+    return getRelativeName(X->getDecl(), getEnclosingDeclContext(AST, S));
+  if (auto *X = dyn_cast<StringLiteral>(S))
+    return X->getString();
+  if (auto *X = dyn_cast<CXXBoolLiteralExpr>(S))
+    return X->getValue() ? "true" : "false";
+  return "";
 }
 
 /// Identifies a node in a subtree by its postorder offset, starting at 1.
@@ -625,12 +658,11 @@
   }
 
 private:
-  /// Simple cost model for edit actions.
+  /// We use a simple cost model for edit actions, which seems good enough.
+  /// Simple cost model for edit actions. This seems to make the matching
+  /// algorithm perform reasonably well.
   /// The values range between 0 and 1, or infinity if this edit action should
   /// always be avoided.
-
-  /// These costs could be modified to better model the estimated cost of /
-  /// inserting / deleting the current node.
   static constexpr double DeletionCost = 1;
   static constexpr double InsertionCost = 1;
 
@@ -676,6 +708,28 @@
   }
 };
 
+ast_type_traits::ASTNodeKind Node::getType() const {
+  return ASTNode.getNodeKind();
+}
+
+StringRef Node::getTypeLabel() const { return getType().asStringRef(); }
+
+llvm::Optional<std::string> Node::getQualifiedIdentifier() const {
+  if (auto *ND = ASTNode.get<NamedDecl>()) {
+    if (ND->getDeclName().isIdentifier())
+      return ND->getQualifiedNameAsString();
+  }
+  return llvm::None;
+}
+
+llvm::Optional<StringRef> Node::getIdentifier() const {
+  if (auto *ND = ASTNode.get<NamedDecl>()) {
+    if (ND->getDeclName().isIdentifier())
+      return ND->getName();
+  }
+  return llvm::None;
+}
+
 namespace {
 // Compares nodes by their depth.
 struct HeightLess {
@@ -687,6 +741,7 @@
 };
 } // end anonymous namespace
 
+namespace {
 // Priority queue for nodes, sorted descendingly by their height.
 class PriorityList {
   const SyntaxTree::Impl &Tree;
@@ -723,6 +778,7 @@
       push(Child);
   }
 };
+} // end anonymous namespace
 
 bool ASTDiff::Impl::identical(NodeId Id1, NodeId Id2) const {
   const Node &N1 = T1.getNode(Id1);
@@ -737,75 +793,58 @@
   return true;
 }
 
-bool ASTDiff::Impl::canBeAddedToMapping(const Mapping &M, NodeId Id1,
-                                        NodeId Id2) const {
-  assert(isMatchingPossible(Id1, Id2) &&
-         "Matching must be possible in the first place.");
-  if (M.hasSrcDst(Id1, Id2))
-    return false;
-  if (Options.EnableMatchingWithUnmatchableParents)
-    return true;
-  const Node &N1 = T1.getNode(Id1);
-  const Node &N2 = T2.getNode(Id2);
-  NodeId P1 = N1.Parent;
-  NodeId P2 = N2.Parent;
-  // Only allow matching if parents can be matched.
-  return (P1.isInvalid() && P2.isInvalid()) ||
-         (P1.isValid() && P2.isValid() && isMatchingPossible(P1, P2));
-}
-
 bool ASTDiff::Impl::isMatchingPossible(NodeId Id1, NodeId Id2) const {
-  return Options.isMatchingAllowed(T1.getNode(Id1).ASTNode,
-                                   T2.getNode(Id2).ASTNode);
+  return Options.isMatchingAllowed(T1.getNode(Id1), T2.getNode(Id2));
 }
 
-void ASTDiff::Impl::addIsomorphicSubTrees(Mapping &M, NodeId Id1,
-                                          NodeId Id2) const {
-  assert(identical(Id1, Id2) && "Can only be called on identical subtrees.");
-  M.link(Id1, Id2);
-  const Node &N1 = T1.getNode(Id1);
-  const Node &N2 = T2.getNode(Id2);
-  for (size_t Id = 0, E = N1.Children.size(); Id < E; ++Id)
-    addIsomorphicSubTrees(M, N1.Children[Id], N2.Children[Id]);
+bool ASTDiff::Impl::haveSameParents(const Mapping &M, NodeId Id1,
+                                    NodeId Id2) const {
+  NodeId P1 = T1.getNode(Id1).Parent;
+  NodeId P2 = T2.getNode(Id2).Parent;
+  return (P1.isInvalid() && P2.isInvalid()) ||
+         (P1.isValid() && P2.isValid() && M.getDst(P1) == P2);
 }
 
 void ASTDiff::Impl::addOptimalMapping(Mapping &M, NodeId Id1,
                                       NodeId Id2) const {
-  if (std::max(T1.getNumberOfDescendants(Id1),
-               T2.getNumberOfDescendants(Id2)) >= Options.MaxSize)
+  if (std::max(T1.getNumberOfDescendants(Id1), T2.getNumberOfDescendants(Id2)) >
+      Options.MaxSize)
     return;
   ZhangShashaMatcher Matcher(*this, T1, T2, Id1, Id2);
   std::vector<std::pair<NodeId, NodeId>> R = Matcher.getMatchingNodes();
   for (const auto Tuple : R) {
     NodeId Src = Tuple.first;
     NodeId Dst = Tuple.second;
-    if (canBeAddedToMapping(M, Src, Dst))
+    if (!M.hasSrc(Src) && !M.hasDst(Dst))
       M.link(Src, Dst);
   }
 }
 
-double ASTDiff::Impl::getSimilarity(const Mapping &M, NodeId Id1,
-                                    NodeId Id2) const {
-  if (Id1.isInvalid() || Id2.isInvalid())
-    return 0.0;
+double ASTDiff::Impl::getJaccardSimilarity(const Mapping &M, NodeId Id1,
+                                           NodeId Id2) const {
   int CommonDescendants = 0;
   const Node &N1 = T1.getNode(Id1);
-  for (NodeId Id = Id1 + 1; Id <= N1.RightMostDescendant; ++Id)
-    CommonDescendants += int(T2.isInSubtree(M.getDst(Id), Id2));
-  return 2.0 * CommonDescendants /
-         (T1.getNumberOfDescendants(Id1) + T2.getNumberOfDescendants(Id2));
+  for (NodeId Src = Id1 + 1; Src <= N1.RightMostDescendant; ++Src) {
+    NodeId Dst = M.getDst(Src);
+    CommonDescendants += int(Dst.isValid() && T2.isInSubtree(Dst, Id2));
+  }
+  double Denominator = T1.getNumberOfDescendants(Id1) - 1 +
+                       T2.getNumberOfDescendants(Id2) - 1 - CommonDescendants;
+  if (Denominator == 0)
+    return 0;
+  return CommonDescendants / Denominator;
 }
 
 NodeId ASTDiff::Impl::findCandidate(const Mapping &M, NodeId Id1) const {
   NodeId Candidate;
   double HighestSimilarity = 0.0;
-  for (NodeId Id2 = 0, E = T2.getSize(); Id2 < E; ++Id2) {
+  for (NodeId Id2 : T2) {
     if (!isMatchingPossible(Id1, Id2))
       continue;
     if (M.hasDst(Id2))
       continue;
-    double Similarity = getSimilarity(M, Id1, Id2);
-    if (Similarity > HighestSimilarity) {
+    double Similarity = getJaccardSimilarity(M, Id1, Id2);
+    if (Similarity >= Options.MinSimilarity && Similarity > HighestSimilarity) {
       HighestSimilarity = Similarity;
       Candidate = Id2;
     }
@@ -816,26 +855,22 @@
 void ASTDiff::Impl::matchBottomUp(Mapping &M) const {
   std::vector<NodeId> Postorder = getSubtreePostorder(T1, T1.getRootId());
   for (NodeId Id1 : Postorder) {
-    if (Id1 == T1.getRootId()) {
+    if (Id1 == T1.getRootId() && !M.hasSrc(T1.getRootId()) &&
+        !M.hasDst(T2.getRootId())) {
       if (isMatchingPossible(T1.getRootId(), T2.getRootId())) {
         M.link(T1.getRootId(), T2.getRootId());
         addOptimalMapping(M, T1.getRootId(), T2.getRootId());
       }
       break;
     }
-    const Node &N1 = T1.getNode(Id1);
     bool Matched = M.hasSrc(Id1);
-    bool MatchedChildren =
-        std::any_of(N1.Children.begin(), N1.Children.end(),
-                    [&](NodeId Child) { return M.hasSrc(Child); });
-    if (Matched || !MatchedChildren)
+    if (Matched)
       continue;
     NodeId Id2 = findCandidate(M, Id1);
-    if (Id2.isInvalid() || !canBeAddedToMapping(M, Id1, Id2) ||
-        getSimilarity(M, Id1, Id2) < Options.MinSimilarity)
-      continue;
-    M.link(Id1, Id2);
-    addOptimalMapping(M, Id1, Id2);
+    if (Id2.isValid()) {
+      M.link(Id1, Id2);
+      addOptimalMapping(M, Id1, Id2);
+    }
   }
 }
 
@@ -843,7 +878,7 @@
   PriorityList L1(T1);
   PriorityList L2(T2);
 
-  Mapping M(T1.getSize(), T2.getSize());
+  Mapping M(T1.getSize() + T2.getSize());
 
   L1.push(T1.getRootId());
   L2.push(T2.getRootId());
@@ -865,9 +900,12 @@
     H1 = L1.pop();
     H2 = L2.pop();
     for (NodeId Id1 : H1) {
-      for (NodeId Id2 : H2)
-        if (identical(Id1, Id2) && canBeAddedToMapping(M, Id1, Id2))
-          addIsomorphicSubTrees(M, Id1, Id2);
+      for (NodeId Id2 : H2) {
+        if (identical(Id1, Id2) && !M.hasSrc(Id1) && !M.hasDst(Id2)) {
+          for (int I = 0, E = T1.getNumberOfDescendants(Id1); I < E; ++I)
+            M.link(Id1 + I, Id2 + I);
+        }
+      }
     }
     for (NodeId Id1 : H1) {
       if (!M.hasSrc(Id1))
@@ -881,99 +919,62 @@
   return M;
 }
 
+ASTDiff::Impl::Impl(SyntaxTree::Impl &T1, SyntaxTree::Impl &T2,
+                    const ComparisonOptions &Options)
+    : T1(T1), T2(T2), Options(Options) {
+  computeMapping();
+  computeChangeKinds(TheMapping);
+}
+
 void ASTDiff::Impl::computeMapping() {
-  if (IsMappingDone)
-    return;
   TheMapping = matchTopDown();
+  if (Options.StopAfterTopDown)
+    return;
   matchBottomUp(TheMapping);
-  IsMappingDone = true;
-}
-
-std::vector<Match> ASTDiff::Impl::getMatches(Mapping &M) {
-  std::vector<Match> Matches;
-  for (NodeId Id1 = 0, Id2, E = T1.getSize(); Id1 < E; ++Id1)
-    if ((Id2 = M.getDst(Id1)).isValid())
-      Matches.push_back({Id1, Id2});
-  return Matches;
 }
 
-std::vector<Change> ASTDiff::Impl::computeChanges(Mapping &M) {
-  std::vector<Change> Changes;
-  for (NodeId Id2 : getSubtreeBfs(T2, T2.getRootId())) {
-    const Node &N2 = T2.getNode(Id2);
-    NodeId Id1 = M.getSrc(Id2);
-    if (Id1.isValid()) {
-      assert(isMatchingPossible(Id1, Id2) && "Invalid matching.");
-      if (T1.getNodeValue(Id1) != T2.getNodeValue(Id2)) {
-        Changes.emplace_back(Update, Id1, Id2);
-      }
-      continue;
+void ASTDiff::Impl::computeChangeKinds(Mapping &M) {
+  for (NodeId Id1 : T1) {
+    if (!M.hasSrc(Id1)) {
+      T1.getMutableNode(Id1).ChangeKind = Delete;
+      T1.getMutableNode(Id1).Shift -= 1;
+    }
+  }
+  for (NodeId Id2 : T2) {
+    if (!M.hasDst(Id2)) {
+      T2.getMutableNode(Id2).ChangeKind = Insert;
+      T2.getMutableNode(Id2).Shift -= 1;
     }
-    NodeId P2 = N2.Parent;
-    NodeId P1 = M.getSrc(P2);
-    assert(P1.isValid() &&
-           "Parents must be matched for determining the change type.");
-    Node &Parent1 = T1.getMutableNode(P1);
-    const Node &Parent2 = T2.getNode(P2);
-    auto &Siblings1 = Parent1.Children;
-    const auto &Siblings2 = Parent2.Children;
-    size_t Position;
-    for (Position = 0; Position < Siblings2.size(); ++Position)
-      if (Siblings2[Position] == Id2 || Position >= Siblings1.size())
-        break;
-    Changes.emplace_back(Insert, Id2, P2, Position);
-    Node PatchNode;
-    PatchNode.Parent = P1;
-    PatchNode.LeftMostDescendant = N2.LeftMostDescendant;
-    PatchNode.RightMostDescendant = N2.RightMostDescendant;
-    PatchNode.Depth = N2.Depth;
-    PatchNode.ASTNode = N2.ASTNode;
-    // TODO update Depth if needed
-    NodeId PatchNodeId = T1.getSize();
-    // TODO maybe choose a different data structure for Children.
-    Siblings1.insert(Siblings1.begin() + Position, PatchNodeId);
-    T1.addNode(PatchNode);
-    M.link(PatchNodeId, Id2);
-  }
-  for (NodeId Id1 = 0; Id1 < T1.getSize(); ++Id1) {
+  }
+  for (NodeId Id1 : T1.NodesBfs) {
     NodeId Id2 = M.getDst(Id1);
     if (Id2.isInvalid())
-      Changes.emplace_back(Delete, Id1, Id2);
-  }
-  return Changes;
-}
-
-void ASTDiff::Impl::printChangeImpl(raw_ostream &OS, const Change &Chg) const {
-  switch (Chg.Kind) {
-  case Delete:
-    OS << "Delete ";
-    T1.printNode(OS, Chg.Src);
-    OS << "\n";
-    break;
-  case Update:
-    OS << "Update ";
-    T1.printNode(OS, Chg.Src);
-    OS << " to " << T2.getNodeValue(Chg.Dst) << "\n";
-    break;
-  case Insert:
-    OS << "Insert ";
-    T2.printNode(OS, Chg.Src);
-    OS << " into ";
-    T2.printNode(OS, Chg.Dst);
-    OS << " at " << Chg.Position << "\n";
-    break;
-  case Move:
-    llvm_unreachable("TODO");
-    break;
-  };
-}
-
-void ASTDiff::Impl::printMatchImpl(raw_ostream &OS, const Match &M) const {
-  OS << "Match ";
-  T1.printNode(OS, M.Src);
-  OS << " to ";
-  T2.printNode(OS, M.Dst);
-  OS << "\n";
+      continue;
+    if (!haveSameParents(M, Id1, Id2) ||
+        T1.findPositionInParent(Id1, true) !=
+            T2.findPositionInParent(Id2, true)) {
+      T1.getMutableNode(Id1).Shift -= 1;
+      T2.getMutableNode(Id2).Shift -= 1;
+    }
+  }
+  for (NodeId Id2 : T2.NodesBfs) {
+    NodeId Id1 = M.getSrc(Id2);
+    if (Id1.isInvalid())
+      continue;
+    Node &N1 = T1.getMutableNode(Id1);
+    Node &N2 = T2.getMutableNode(Id2);
+    if (Id1.isInvalid())
+      continue;
+    if (!haveSameParents(M, Id1, Id2) ||
+        T1.findPositionInParent(Id1, true) !=
+            T2.findPositionInParent(Id2, true)) {
+      N1.ChangeKind = N2.ChangeKind = Move;
+    }
+    if (T1.getNodeValue(Id1) != T2.getNodeValue(Id2)) {
+      N1.ChangeKind = N2.ChangeKind =
+          (N1.ChangeKind == Move ? UpdateMove : Update);
+    }
+  }
 }
 
 ASTDiff::ASTDiff(SyntaxTree &T1, SyntaxTree &T2,
@@ -982,34 +983,54 @@
 
 ASTDiff::~ASTDiff() = default;
 
-SyntaxTree::SyntaxTree(const ASTContext &AST)
+NodeId ASTDiff::getMapped(const SyntaxTree &SourceTree, NodeId Id) const {
+  return DiffImpl->getMapped(*SourceTree.TreeImpl, Id);
+}
+
+SyntaxTree::SyntaxTree(ASTContext &AST)
     : TreeImpl(llvm::make_unique<SyntaxTree::Impl>(
           this, AST.getTranslationUnitDecl(), AST)) {}
 
-std::vector<Match> ASTDiff::getMatches() {
-  DiffImpl->computeMapping();
-  return DiffImpl->getMatches(DiffImpl->TheMapping);
-}
+SyntaxTree::~SyntaxTree() = default;
 
-std::vector<Change> ASTDiff::getChanges() {
-  DiffImpl->computeMapping();
-  return DiffImpl->computeChanges(DiffImpl->TheMapping);
+ASTContext &SyntaxTree::getASTContext() const { return TreeImpl->AST; }
+
+const Node &SyntaxTree::getNode(NodeId Id) const {
+  return TreeImpl->getNode(Id);
 }
 
-void ASTDiff::printChange(raw_ostream &OS, const Change &Chg) const {
-  DiffImpl->printChangeImpl(OS, Chg);
+int SyntaxTree::getSize() const { return TreeImpl->getSize(); }
+NodeId SyntaxTree::getRootId() const { return TreeImpl->getRootId(); }
+SyntaxTree::PreorderIterator SyntaxTree::begin() const {
+  return TreeImpl->begin();
 }
+SyntaxTree::PreorderIterator SyntaxTree::end() const { return TreeImpl->end(); }
 
-void ASTDiff::printMatch(raw_ostream &OS, const Match &M) const {
-  DiffImpl->printMatchImpl(OS, M);
+int SyntaxTree::findPositionInParent(NodeId Id) const {
+  return TreeImpl->findPositionInParent(Id);
 }
 
-SyntaxTree::~SyntaxTree() = default;
+std::pair<unsigned, unsigned> SyntaxTree::getFileOffsets(const Node &N) const {
+  const SourceManager &SrcMgr = TreeImpl->AST.getSourceManager();
+  SourceRange Range = N.ASTNode.getSourceRange();
+  SourceLocation BeginLoc = Range.getBegin();
+  SourceLocation EndLoc = Lexer::getLocForEndOfToken(
+      Range.getEnd(), /*Offset=*/0, SrcMgr, TreeImpl->AST.getLangOpts());
+  if (auto *ThisExpr = N.ASTNode.get<CXXThisExpr>()) {
+    if (ThisExpr->isImplicit())
+      EndLoc = BeginLoc;
+  }
+  unsigned Begin = SrcMgr.getFileOffset(SrcMgr.getExpansionLoc(BeginLoc));
+  unsigned End = SrcMgr.getFileOffset(SrcMgr.getExpansionLoc(EndLoc));
+  return {Begin, End};
+}
 
-void SyntaxTree::printAsJson(raw_ostream &OS) { TreeImpl->printAsJsonImpl(OS); }
+std::string SyntaxTree::getNodeValue(NodeId Id) const {
+  return TreeImpl->getNodeValue(Id);
+}
 
-std::string SyntaxTree::getNodeValue(const DynTypedNode &DTN) const {
-  return TreeImpl->getNodeValue(DTN);
+std::string SyntaxTree::getNodeValue(const Node &N) const {
+  return TreeImpl->getNodeValue(N);
 }
 
 } // end namespace diff
Index: lib/Tooling/CommonOptionsParser.cpp
===================================================================
--- lib/Tooling/CommonOptionsParser.cpp
+++ lib/Tooling/CommonOptionsParser.cpp
@@ -25,7 +25,6 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Support/CommandLine.h"
-#include "clang/Tooling/ArgumentsAdjusters.h"
 #include "clang/Tooling/CommonOptionsParser.h"
 #include "clang/Tooling/Tooling.h"
 
@@ -54,43 +53,33 @@
     "\tsuffix of a path in the compile command database.\n"
     "\n";
 
-namespace {
-class ArgumentsAdjustingCompilations : public CompilationDatabase {
-public:
-  ArgumentsAdjustingCompilations(
-      std::unique_ptr<CompilationDatabase> Compilations)
-      : Compilations(std::move(Compilations)) {}
-
-  void appendArgumentsAdjuster(ArgumentsAdjuster Adjuster) {
-    Adjusters.push_back(std::move(Adjuster));
-  }
-
-  std::vector<CompileCommand>
-  getCompileCommands(StringRef FilePath) const override {
-    return adjustCommands(Compilations->getCompileCommands(FilePath));
-  }
+void ArgumentsAdjustingCompilations::appendArgumentsAdjuster(
+    ArgumentsAdjuster Adjuster) {
+  Adjusters.push_back(std::move(Adjuster));
+}
 
-  std::vector<std::string> getAllFiles() const override {
-    return Compilations->getAllFiles();
-  }
+std::vector<CompileCommand> ArgumentsAdjustingCompilations::getCompileCommands(
+    StringRef FilePath) const {
+  return adjustCommands(Compilations->getCompileCommands(FilePath));
+}
 
-  std::vector<CompileCommand> getAllCompileCommands() const override {
-    return adjustCommands(Compilations->getAllCompileCommands());
-  }
+std::vector<std::string>
+ArgumentsAdjustingCompilations::getAllFiles() const {
+  return Compilations->getAllFiles();
+}
 
-private:
-  std::unique_ptr<CompilationDatabase> Compilations;
-  std::vector<ArgumentsAdjuster> Adjusters;
+std::vector<CompileCommand>
+ArgumentsAdjustingCompilations::getAllCompileCommands() const {
+  return adjustCommands(Compilations->getAllCompileCommands());
+}
 
-  std::vector<CompileCommand>
-  adjustCommands(std::vector<CompileCommand> Commands) const {
-    for (CompileCommand &Command : Commands)
-      for (const auto &Adjuster : Adjusters)
-        Command.CommandLine = Adjuster(Command.CommandLine, Command.Filename);
-    return Commands;
-  }
-};
-} // namespace
+std::vector<CompileCommand> ArgumentsAdjustingCompilations::adjustCommands(
+    std::vector<CompileCommand> Commands) const {
+  for (CompileCommand &Command : Commands)
+    for (const auto &Adjuster : Adjusters)
+      Command.CommandLine = Adjuster(Command.CommandLine, Command.Filename);
+  return Commands;
+}
 
 CommonOptionsParser::CommonOptionsParser(
     int &argc, const char **argv, cl::OptionCategory &Category,
Index: test/Tooling/clang-diff-ast.cpp
===================================================================
--- /dev/null
+++ test/Tooling/clang-diff-ast.cpp
@@ -0,0 +1,59 @@
+// RUN: clang-diff -no-compilation-database -ast-dump %s -extra-arg='-std=c++11' | FileCheck %s
+//
+// This tests the getNodeValue function from Tooling/ASTDiff/ASTDiff.h
+
+// CHECK: NamespaceDecl: test;(
+namespace test {
+
+// CHECK: FunctionDecl: :f(
+// CHECK: CompoundStmt(
+void f() {
+  // CHECK: VarDecl: i(int)(
+  // CHECK: IntegerLiteral: 1
+  auto i = 1;
+  // CHECK: FloatingLiteral: 1.5(
+  auto r = 1.5;
+  // CHECK: CXXBoolLiteralExpr: true(
+  auto b = true;
+  // CHECK: CallExpr(
+  // CHECK: DeclRefExpr: :f(
+  f();
+  // CHECK: UnaryOperator: ++(
+  ++i;
+  // CHECK: BinaryOperator: =(
+  i = i;
+}
+
+} // end namespace test
+
+// CHECK: UsingDirectiveDecl: test(
+using namespace test;
+
+// CHECK: TypedefDecl: nat;unsigned int;(
+typedef unsigned nat;
+// CHECK: TypeAliasDecl: real;double;(
+using real = double;
+
+class Base {
+};
+
+// CHECK: CXXRecordDecl: X;X;(
+class X : Base {
+  int m;
+  // CHECK: CXXMethodDecl: :foo(const char *(int))(
+  // CHECK: ParmVarDecl: i(int)(
+  const char *foo(int i) {
+    if (i == 0)
+      // CHECK: StringLiteral: foo(
+      return "foo";
+    return 0;
+  }
+
+  // CHECK: AccessSpecDecl: public(
+public:
+  // CHECK: CXXConstructorDecl: :X(void (char, int))Base,:m,(
+  X(char, int) : Base(), m(0) {
+    // CHECK: MemberExpr: :m(
+    int x = m;
+  }
+};
Index: test/Tooling/clang-diff-basic.cpp
===================================================================
--- test/Tooling/clang-diff-basic.cpp
+++ test/Tooling/clang-diff-basic.cpp
@@ -1,6 +1,6 @@
-// RUN: %clang_cc1 -E %s > %T/src.cpp
-// RUN: %clang_cc1 -E %s > %T/dst.cpp -DDEST
-// RUN: clang-diff -no-compilation-database %T/src.cpp %T/dst.cpp | FileCheck %s
+// RUN: %clang_cc1 -E %s > %t.src.cpp
+// RUN: %clang_cc1 -E %s > %t.dst.cpp -DDEST
+// RUN: clang-diff -m -no-compilation-database %t.src.cpp %t.dst.cpp | FileCheck %s
 
 #ifndef DEST
 namespace src {
@@ -31,6 +31,8 @@
   int id(int i) { return i; }
 };
 }
+
+void f1() {{ (void) __func__;;; }}
 #else
 // CHECK: Match TranslationUnitDecl{{.*}} to TranslationUnitDecl
 // CHECK: Match NamespaceDecl: src{{.*}} to NamespaceDecl: dst
@@ -43,19 +45,19 @@
 }
 }
 
-// CHECK: Match DeclRefExpr: foo{{.*}} to DeclRefExpr: inner::foo
+// CHECK: Match DeclRefExpr: :foo{{.*}} to DeclRefExpr: :inner::foo
 void main() { inner::foo(); }
 
 // CHECK: Match StringLiteral: foo{{.*}} to StringLiteral: foo
 const char *b = "f" "o" "o";
 
 // unsigned is canonicalized to unsigned int
-// CHECK: Match TypedefDecl: nat;unsigned int;{{.*}} to TypedefDecl: nat;unsigned int;
+// CHECK: Match TypedefDecl: :nat;unsigned int;{{.*}} to TypedefDecl: :nat;unsigned int;
 typedef unsigned nat;
 
-// CHECK: Match VarDecl: p(int){{.*}} to VarDecl: prod(double)
+// CHECK: Match VarDecl: :p(int){{.*}} to VarDecl: :prod(double)
+// CHECK: Update VarDecl: :p(int){{.*}} to :prod(double)
 // CHECK: Match BinaryOperator: *{{.*}} to BinaryOperator: *
-// CHECK: Update VarDecl: p(int){{.*}} to prod(double)
 double prod = 1 * 2 * 10;
 // CHECK: Update DeclRefExpr
 int squared = prod * prod;
@@ -70,9 +72,15 @@
       return "foo";
     return 0;
   }
-  // CHECK: Delete AccessSpecDecl: public
   X(){};
-  // CHECK: Delete CXXMethodDecl
 };
 }
+
+namespace {
+// match with parents of different type
+// CHECK: Match FunctionDecl: f1{{.*}} to FunctionDecl: (anonymous namespace)::f1
+void f1() {{ (void) __func__;;; }}
+}
 #endif
+// CHECK: Delete AccessSpecDecl: public
+// CHECK: Delete CXXMethodDecl
Index: test/Tooling/clang-diff-bottomup.cpp
===================================================================
--- /dev/null
+++ test/Tooling/clang-diff-bottomup.cpp
@@ -0,0 +1,39 @@
+// RUN: %clang_cc1 -E %s > %t.src.cpp
+// RUN: %clang_cc1 -E %s > %t.dst.cpp -DDEST
+// RUN: clang-diff -m -no-compilation-database -s=0 %t.src.cpp %t.dst.cpp | FileCheck %s
+//
+// Test the bottom-up matching, with maxsize set to 0, so that the optimal matching will never be applied.
+
+#ifndef DEST
+
+void f1() { ; {{;}} }
+void f2() { ;; {{;}} }
+
+#else
+
+// Jaccard similarity threshold is 0.5.
+
+void f1() {
+// CompoundStmt: 3 matched descendants, subtree sizes 4 and 5
+// Jaccard similarity = 3 / (4 + 5 - 3) = 3 / 6 >= 0.5
+// CHECK: Match FunctionDecl: f1(void ())(1) to FunctionDecl: f1(void ())(1)
+// CHECK: Match CompoundStmt(2) to CompoundStmt(2)
+// CHECK: Match CompoundStmt(4) to CompoundStmt(3)
+// CHECK: Match CompoundStmt(5) to CompoundStmt(4)
+// CHECK: Match NullStmt(6) to NullStmt(5)
+  {{;}} ;;
+}
+
+void f2() {
+// CompoundStmt: 3 matched descendants, subtree sizes 4 and 5
+// Jaccard similarity = 3 / (5 + 6 - 3) = 3 / 8 < 0.5
+// CHECK-NOT: Match FunctionDecl(9)
+// CHECK-NOT: Match CompoundStmt(10)
+// CHECK: Match CompoundStmt(11) to CompoundStmt(10)
+// CHECK: Match CompoundStmt(12) to CompoundStmt(11)
+// CHECK: Match NullStmt(13) to NullStmt(12)
+// CHECK-NOT: Match NullStmt(13)
+  {{;}} ;;;
+}
+ 
+#endif
Index: test/Tooling/clang-diff-opt.cpp
===================================================================
--- /dev/null
+++ test/Tooling/clang-diff-opt.cpp
@@ -0,0 +1,38 @@
+// RUN: %clang_cc1 -E %s > %t.src.cpp
+// RUN: %clang_cc1 -E %s > %t.dst.cpp -DDEST
+// RUN: clang-diff -m -no-compilation-database %t.src.cpp %t.dst.cpp | FileCheck %s
+//
+// Test the behaviour of the matching according to the optimal tree edit
+// distance, implemented with Zhang and Shasha's algorithm.
+
+#ifndef DEST
+
+void f1() { {;} {{;}} }
+
+class A { int x; void f() { int a1 = x; } };
+
+#else
+
+void f1() {
+// Jaccard similarity = 3 / (5 + 4 - 3) = 3 / 6 >= 0.5
+// The optimal matching algorithm should move the ; into the outer block
+// CHECK: Match CompoundStmt(2) to CompoundStmt(2)
+// CHECK-NOT: Match CompoundStmt(3)
+// CHECK: Match NullStmt(4) to NullStmt(3)
+  ; {{;}}
+}
+
+class B {
+  // Only the class name changed; it is not included in the field value,
+  // therefore there is no update.
+  // CHECK: Match FieldDecl: :x(int)(9) to FieldDecl: :x(int)(8)
+  // CHECK-NOT: Update FieldDecl: :x(int)(9)
+  int x;
+  void f() {
+    // CHECK: Match MemberExpr: :x(14) to MemberExpr: :x(13)
+    // CHECK-NOT: Update MemberExpr: :x(14)
+    int b2 = B::x;
+  }
+};
+ 
+#endif
Index: test/Tooling/clang-diff-topdown.cpp
===================================================================
--- /dev/null
+++ test/Tooling/clang-diff-topdown.cpp
@@ -0,0 +1,66 @@
+// RUN: %clang_cc1 -E %s > %t.src.cpp
+// RUN: %clang_cc1 -E %s > %t.dst.cpp -DDEST
+// RUN: clang-diff -m -no-compilation-database -stop-after=topdown %t.src.cpp %t.dst.cpp | FileCheck %s
+//
+// Test the top-down matching of identical subtrees only.
+
+#ifndef DEST
+
+void f1()
+{
+  // Match some subtree of height greater than 2.
+  // CHECK: Match CompoundStmt(3) to CompoundStmt(3)
+  // CHECK: Match CompoundStmt(4) to CompoundStmt(4)
+  // CHECK: Match NullStmt(5) to NullStmt(5)
+  {{;}}
+
+  // Don't match subtrees that are smaller.
+  // CHECK-NOT: Match CompoundStmt(6)
+  // CHECK-NOT: Match NullStmt(7)
+  {;}
+
+  // Greedy approach - use the first matching subtree when there are multiple
+  // identical subtrees.
+  // CHECK: Match CompoundStmt(8) to CompoundStmt(8)
+  // CHECK: Match CompoundStmt(9) to CompoundStmt(9)
+  // CHECK: Match NullStmt(10) to NullStmt(10)
+  {{;;}}
+}
+
+int x;
+
+namespace src {
+  int x;
+  int x1 = x + 1;
+  int x2 = ::x + 1;
+}
+
+#else
+
+void f1() {
+
+  {{;}}
+
+  {;}
+
+  {{;;}}
+  // CHECK-NOT: Match {{.*}} to CompoundStmt(11)
+  // CHECK-NOT: Match {{.*}} to CompoundStmt(12)
+  // CHECK-NOT: Match {{.*}} to NullStmt(13)
+  {{;;}}
+
+  // CHECK-NOT: Match {{.*}} to NullStmt(14)
+  ;
+}
+
+int x;
+
+namespace dst {
+  int x;
+  // CHECK: Match DeclRefExpr: :x(17) to DeclRefExpr: :x(22)
+  int x1 = x + 1;
+  // CHECK: Match DeclRefExpr: x(21) to DeclRefExpr: x(26)
+  int x2 = ::x + 1;
+}
+
+#endif
Index: tools/clang-diff/CMakeLists.txt
===================================================================
--- tools/clang-diff/CMakeLists.txt
+++ tools/clang-diff/CMakeLists.txt
@@ -7,6 +7,7 @@
   )
 
 target_link_libraries(clang-diff
+  clangBasic
   clangFrontend
   clangTooling
   clangToolingASTDiff
Index: tools/clang-diff/ClangDiff.cpp
===================================================================
--- tools/clang-diff/ClangDiff.cpp
+++ tools/clang-diff/ClangDiff.cpp
@@ -25,15 +25,28 @@
 
 static cl::opt<bool>
     ASTDump("ast-dump",
-            cl::desc("Print the internal representation of the AST as JSON."),
+            cl::desc("Print the internal representation of the AST."),
             cl::init(false), cl::cat(ClangDiffCategory));
 
+static cl::opt<bool> ASTDumpJson(
+    "ast-dump-json",
+    cl::desc("Print the internal representation of the AST as JSON."),
+    cl::init(false), cl::cat(ClangDiffCategory));
+
+static cl::opt<bool>
+    PrintMatches("m", cl::desc("Print the matched nodes (verbose)."),
+                 cl::init(false), cl::cat(ClangDiffCategory));
+
 static cl::opt<bool> NoCompilationDatabase(
     "no-compilation-database",
     cl::desc(
         "Do not attempt to load build settings from a compilation database"),
     cl::init(false), cl::cat(ClangDiffCategory));
 
+static cl::opt<bool> HtmlDiff("html",
+                              cl::desc("Output a side-by-side diff in HTML."),
+                              cl::init(false), cl::cat(ClangDiffCategory));
+
 static cl::opt<std::string> SourcePath(cl::Positional, cl::desc("<source>"),
                                        cl::Required,
                                        cl::cat(ClangDiffCategory));
@@ -43,12 +56,33 @@
                                             cl::Optional,
                                             cl::cat(ClangDiffCategory));
 
+static cl::opt<std::string> StopAfter("stop-after",
+                                      cl::desc("<topdown|bottomup>"),
+                                      cl::Optional, cl::init(""),
+                                      cl::cat(ClangDiffCategory));
+
+static cl::opt<int> MaxSize("s", cl::desc("<maxsize>"), cl::Optional,
+                            cl::init(-1), cl::cat(ClangDiffCategory));
+
+static cl::opt<std::string> BuildPath("p", cl::desc("Build path"), cl::init(""),
+                                      cl::Optional, cl::cat(ClangDiffCategory));
+
+static cl::list<std::string> ArgsAfter(
+    "extra-arg",
+    cl::desc("Additional argument to append to the compiler command line"),
+    cl::cat(ClangDiffCategory));
+
+static cl::list<std::string> ArgsBefore(
+    "extra-arg-before",
+    cl::desc("Additional argument to prepend to the compiler command line"),
+    cl::cat(ClangDiffCategory));
+
 static std::unique_ptr<ASTUnit> getAST(const StringRef Filename) {
   std::string ErrorMessage;
   std::unique_ptr<CompilationDatabase> Compilations;
   if (!NoCompilationDatabase)
-    Compilations =
-        CompilationDatabase::autoDetectFromSource(Filename, ErrorMessage);
+    Compilations = CompilationDatabase::autoDetectFromSource(
+        BuildPath.empty() ? Filename : BuildPath, ErrorMessage);
   if (!Compilations) {
     if (!NoCompilationDatabase)
       llvm::errs()
@@ -58,6 +92,14 @@
     Compilations = llvm::make_unique<clang::tooling::FixedCompilationDatabase>(
         ".", std::vector<std::string>());
   }
+  auto AdjustingCompilations =
+      llvm::make_unique<ArgumentsAdjustingCompilations>(
+          std::move(Compilations));
+  AdjustingCompilations->appendArgumentsAdjuster(
+      getInsertArgumentAdjuster(ArgsBefore, ArgumentInsertPosition::BEGIN));
+  AdjustingCompilations->appendArgumentsAdjuster(
+      getInsertArgumentAdjuster(ArgsAfter, ArgumentInsertPosition::END));
+  Compilations = std::move(AdjustingCompilations);
   std::array<std::string, 1> Files = {{Filename}};
   ClangTool Tool(*Compilations, Files);
   std::vector<std::unique_ptr<ASTUnit>> ASTs;
@@ -67,6 +109,287 @@
   return std::move(ASTs[0]);
 }
 
+static char hexdigit(int N) { return N &= 0xf, N + (N < 10 ? '0' : 'a' - 10); }
+
+static const char HtmlDiffHeader[] = R"(
+<html>
+<head>
+<meta charset='utf-8'/>
+<style>
+span.d { color: red; }
+span.u { color: #cc00cc; }
+span.i { color: green; }
+span.m { font-weight: bold; }
+span   { font-weight: normal; color: black; }
+div.code {
+  width: 48%;
+  height: 98%;
+  overflow: scroll;
+  float: left;
+  padding: 0 0 0.5% 0.5%;
+  border: solid 2px LightGrey;
+  border-radius: 5px;
+}
+</style>
+</head>
+<script type='text/javascript'>
+highlightStack = []
+function clearHighlight() {
+  while (highlightStack.length) {
+    let [l, r] = highlightStack.pop()
+    document.getElementById(l).style.backgroundColor = 'white'
+    document.getElementById(r).style.backgroundColor = 'white'
+  }
+}
+function highlight(event) {
+  id = event.target['id']
+  doHighlight(id)
+}
+function doHighlight(id) {
+  clearHighlight()
+  source = document.getElementById(id)
+  if (!source.attributes['tid'])
+    return
+  tid = source.attributes['tid'].value
+  target = document.getElementById(tid)
+  if (!target || source.parentElement && source.parentElement.classList.contains('code'))
+    return
+  source.style.backgroundColor = target.style.backgroundColor = 'lightgrey'
+  highlightStack.push([id, tid])
+  source.scrollIntoView()
+  target.scrollIntoView()
+  location.hash = '#' + id
+}
+function scrollToBoth() {
+  doHighlight(location.hash.substr(1))
+}
+window.onload = scrollToBoth
+</script>
+<body>
+<div onclick='highlight(event)'>
+)";
+
+static void printHtml(raw_ostream &OS, char C) {
+  switch (C) {
+  case '&':
+    OS << "&amp;";
+    break;
+  case '<':
+    OS << "&lt;";
+    break;
+  case '>':
+    OS << "&gt;";
+    break;
+  case '\'':
+    OS << "&#x27;";
+    break;
+  case '"':
+    OS << "&quot;";
+    break;
+  default:
+    OS << C;
+  }
+}
+
+static void printHtml(raw_ostream &OS, const StringRef Str) {
+  for (char C : Str)
+    printHtml(OS, C);
+}
+
+static std::string getChangeKindAbbr(diff::ChangeKind Kind) {
+  switch (Kind) {
+  case diff::None:
+    return "";
+  case diff::Delete:
+    return "d";
+  case diff::Update:
+    return "u";
+  case diff::Insert:
+    return "i";
+  case diff::Move:
+    return "m";
+  case diff::UpdateMove:
+    return "u m";
+  }
+}
+
+static unsigned printHtmlForNode(raw_ostream &OS, const diff::ASTDiff &Diff,
+                                 diff::SyntaxTree &Tree, bool IsLeft,
+                                 diff::NodeId Id, unsigned Offset) {
+  const diff::Node &Node = Tree.getNode(Id);
+  char MyTag, OtherTag;
+  diff::NodeId LeftId, RightId;
+  diff::NodeId TargetId = Diff.getMapped(Tree, Id);
+  if (IsLeft) {
+    MyTag = 'L';
+    OtherTag = 'R';
+    LeftId = Id;
+    RightId = TargetId;
+  } else {
+    MyTag = 'R';
+    OtherTag = 'L';
+    LeftId = TargetId;
+    RightId = Id;
+  }
+  unsigned Begin, End;
+  std::tie(Begin, End) = Tree.getFileOffsets(Node);
+  const SourceManager &SrcMgr = Tree.getASTContext().getSourceManager();
+  auto Code = SrcMgr.getBuffer(SrcMgr.getMainFileID())->getBuffer();
+  for (; Offset < Begin; ++Offset)
+    printHtml(OS, Code[Offset]);
+  OS << "<span id='" << MyTag << Id << "' "
+     << "tid='" << OtherTag << TargetId << "' ";
+  OS << "title='";
+  printHtml(OS, Node.getTypeLabel());
+  OS << "\n" << LeftId << " -> " << RightId;
+  std::string Value = Tree.getNodeValue(Node);
+  if (!Value.empty()) {
+    OS << "\n";
+    printHtml(OS, Value);
+  }
+  OS << "'";
+  if (Node.ChangeKind != diff::None)
+    OS << " class='" << getChangeKindAbbr(Node.ChangeKind) << "'";
+  OS << ">";
+
+  for (diff::NodeId Child : Node.Children)
+    Offset = printHtmlForNode(OS, Diff, Tree, IsLeft, Child, Offset);
+
+  for (; Offset < End; ++Offset)
+    printHtml(OS, Code[Offset]);
+  if (Id == Tree.getRootId()) {
+    End = Code.size();
+    for (; Offset < End; ++Offset)
+      printHtml(OS, Code[Offset]);
+  }
+  OS << "</span>";
+  return Offset;
+}
+
+static void printJsonString(raw_ostream &OS, const StringRef Str) {
+  for (char C : Str) {
+    switch (C) {
+    case '"':
+      OS << R"(\")";
+      break;
+    case '\\':
+      OS << R"(\\)";
+      break;
+    case '\n':
+      OS << R"(\n)";
+      break;
+    case '\t':
+      OS << R"(\t)";
+      break;
+    default:
+      if ('\x00' <= C && C <= '\x1f') {
+        OS << R"(\u00)" << hexdigit(C >> 4) << hexdigit(C);
+      } else {
+        OS << C;
+      }
+    }
+  }
+}
+
+static void printNodeAttributes(raw_ostream &OS, diff::SyntaxTree &Tree,
+                                diff::NodeId Id) {
+  const diff::Node &N = Tree.getNode(Id);
+  OS << R"("id":)" << int(Id);
+  OS << R"(,"type":")" << N.getTypeLabel() << '"';
+  auto Offsets = Tree.getFileOffsets(N);
+  OS << R"(,"begin":)" << Offsets.first;
+  OS << R"(,"end":)" << Offsets.second;
+  std::string Value = Tree.getNodeValue(N);
+  if (!Value.empty()) {
+    OS << R"(,"value":")";
+    printJsonString(OS, Value);
+    OS << '"';
+  }
+}
+
+static void printNodeAsJson(raw_ostream &OS, diff::SyntaxTree &Tree,
+                            diff::NodeId Id) {
+  const diff::Node &N = Tree.getNode(Id);
+  OS << "{";
+  printNodeAttributes(OS, Tree, Id);
+  auto Identifier = N.getIdentifier();
+  auto QualifiedIdentifier = N.getQualifiedIdentifier();
+  if (Identifier) {
+    OS << R"(,"identifier":")";
+    printJsonString(OS, *Identifier);
+    OS << R"(")";
+    if (QualifiedIdentifier && *Identifier != *QualifiedIdentifier) {
+      OS << R"(,"qualified_identifier":")";
+      printJsonString(OS, *QualifiedIdentifier);
+      OS << R"(")";
+    }
+  }
+  OS << R"(,"children":[)";
+  if (N.Children.size() > 0) {
+    printNodeAsJson(OS, Tree, N.Children[0]);
+    for (size_t I = 1, E = N.Children.size(); I < E; ++I) {
+      OS << ",";
+      printNodeAsJson(OS, Tree, N.Children[I]);
+    }
+  }
+  OS << "]}";
+}
+
+static void printNode(raw_ostream &OS, diff::SyntaxTree &Tree,
+                      diff::NodeId Id) {
+  if (Id.isInvalid()) {
+    OS << "None";
+    return;
+  }
+  OS << Tree.getNode(Id).getTypeLabel();
+  std::string Value = Tree.getNodeValue(Id);
+  if (!Value.empty())
+    OS << ": " << Value;
+  OS << "(" << Id << ")";
+}
+
+static void printTree(raw_ostream &OS, diff::SyntaxTree &Tree) {
+  for (diff::NodeId Id : Tree) {
+    for (int I = 0; I < Tree.getNode(Id).Depth; ++I)
+      OS << " ";
+    printNode(OS, Tree, Id);
+    OS << "\n";
+  }
+}
+
+static void printDstChange(raw_ostream &OS, diff::ASTDiff &Diff,
+                           diff::SyntaxTree &SrcTree, diff::SyntaxTree &DstTree,
+                           diff::NodeId Dst) {
+  const diff::Node &DstNode = DstTree.getNode(Dst);
+  diff::NodeId Src = Diff.getMapped(DstTree, Dst);
+  switch (DstNode.ChangeKind) {
+  case diff::None:
+    break;
+  case diff::Delete:
+    llvm_unreachable("The destination tree can't have deletions.");
+  case diff::Update:
+    OS << "Update ";
+    printNode(OS, SrcTree, Src);
+    OS << " to " << DstTree.getNodeValue(Dst) << "\n";
+    break;
+  case diff::Insert:
+  case diff::Move:
+  case diff::UpdateMove:
+    if (DstNode.ChangeKind == diff::Insert)
+      OS << "Insert";
+    else if (DstNode.ChangeKind == diff::Move)
+      OS << "Move";
+    else if (DstNode.ChangeKind == diff::UpdateMove)
+      OS << "Update and Move";
+    OS << " ";
+    printNode(OS, DstTree, Dst);
+    OS << " into ";
+    printNode(OS, DstTree, DstNode.Parent);
+    OS << " at " << DstTree.findPositionInParent(Dst) << "\n";
+    break;
+  }
+}
+
 int main(int argc, const char **argv) {
   cl::HideUnrelatedOptions(ClangDiffCategory);
   if (!cl::ParseCommandLineOptions(argc, argv)) {
@@ -74,7 +397,7 @@
     return 1;
   }
 
-  if (ASTDump) {
+  if (ASTDump || ASTDumpJson) {
     if (!DestinationPath.empty()) {
       llvm::errs() << "Error: Please specify exactly one filename.\n";
       return 1;
@@ -83,7 +406,15 @@
     if (!AST)
       return 1;
     diff::SyntaxTree Tree(AST->getASTContext());
-    Tree.printAsJson(llvm::outs());
+    if (ASTDump) {
+      printTree(llvm::outs(), Tree);
+      return 0;
+    }
+    llvm::outs() << R"({"filename":")";
+    printJsonString(llvm::outs(), SourcePath);
+    llvm::outs() << R"(","root":)";
+    printNodeAsJson(llvm::outs(), Tree, Tree.getRootId());
+    llvm::outs() << "}\n";
     return 0;
   }
 
@@ -98,13 +429,51 @@
     return 1;
 
   diff::ComparisonOptions Options;
+  if (MaxSize != -1)
+    Options.MaxSize = MaxSize;
+  if (!StopAfter.empty()) {
+    if (StopAfter == "topdown")
+      Options.StopAfterTopDown = true;
+    else if (StopAfter != "bottomup") {
+      llvm::errs() << "Error: Invalid argument for -stop-after";
+      return 1;
+    }
+  }
   diff::SyntaxTree SrcTree(Src->getASTContext());
   diff::SyntaxTree DstTree(Dst->getASTContext());
-  diff::ASTDiff DiffTool(SrcTree, DstTree, Options);
-  for (const auto &Match : DiffTool.getMatches())
-    DiffTool.printMatch(llvm::outs(), Match);
-  for (const auto &Change : DiffTool.getChanges())
-    DiffTool.printChange(llvm::outs(), Change);
+  diff::ASTDiff Diff(SrcTree, DstTree, Options);
+
+  if (HtmlDiff) {
+    llvm::outs() << HtmlDiffHeader << "<pre>";
+    llvm::outs() << "<div id='L' class='code'>";
+    printHtmlForNode(llvm::outs(), Diff, SrcTree, true, SrcTree.getRootId(), 0);
+    llvm::outs() << "</div>";
+    llvm::outs() << "<div id='R' class='code'>";
+    printHtmlForNode(llvm::outs(), Diff, DstTree, false, DstTree.getRootId(),
+                     0);
+    llvm::outs() << "</div>";
+    llvm::outs() << "</pre></div></body></html>\n";
+    return 0;
+  }
+
+  for (diff::NodeId Dst : DstTree) {
+    diff::NodeId Src = Diff.getMapped(DstTree, Dst);
+    if (PrintMatches && Src.isValid()) {
+      llvm::outs() << "Match ";
+      printNode(llvm::outs(), SrcTree, Src);
+      llvm::outs() << " to ";
+      printNode(llvm::outs(), DstTree, Dst);
+      llvm::outs() << "\n";
+    }
+    printDstChange(llvm::outs(), Diff, SrcTree, DstTree, Dst);
+  }
+  for (diff::NodeId Src : SrcTree) {
+    if (Diff.getMapped(SrcTree, Src).isInvalid()) {
+      llvm::outs() << "Delete ";
+      printNode(llvm::outs(), SrcTree, Src);
+      llvm::outs() << "\n";
+    }
+  }
 
   return 0;
 }