Import LLVM 10.0.0 release including clang, lld and lldb.

ok hackroom
tested by plenty

1 files changed, 1019 insertions, 0 deletions

diff --git a/gnu/llvm/clang/lib/Tooling/ASTDiff/ASTDiff.cpp b/gnu/llvm/clang/lib/Tooling/ASTDiff/ASTDiff.cpp
new file mode 100644
index 00000000000..4d495228cb5
--- /dev/null
+++ b/gnu/llvm/clang/lib/Tooling/ASTDiff/ASTDiff.cpp
@@ -0,0 +1,1019 @@
+//===- ASTDiff.cpp - AST differencing implementation-----------*- C++ -*- -===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file contains definitons for the AST differencing interface.
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/Tooling/ASTDiff/ASTDiff.h"
+
+#include "clang/AST/RecursiveASTVisitor.h"
+#include "clang/Lex/Lexer.h"
+#include "llvm/ADT/PriorityQueue.h"
+
+#include <limits>
+#include <memory>
+#include <unordered_set>
+
+using namespace llvm;
+using namespace clang;
+
+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(size_t Size) {
+    SrcToDst = std::make_unique<NodeId[]>(Size);
+    DstToSrc = std::make_unique<NodeId[]>(Size);
+  }
+
+  void link(NodeId Src, NodeId Dst) {
+    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<NodeId[]> SrcToDst, DstToSrc;
+};
+} // end anonymous namespace
+
+class ASTDiff::Impl {
+public:
+  SyntaxTree::Impl &T1, &T2;
+  Mapping TheMapping;
+
+  Impl(SyntaxTree::Impl &T1, SyntaxTree::Impl &T2,
+       const ComparisonOptions &Options);
+
+  /// Matches nodes one-by-one based on their similarity.
+  void computeMapping();
+
+  // Compute Change for each node based on similarity.
+  void computeChangeKinds(Mapping &M);
+
+  NodeId getMapped(const std::unique_ptr<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;
+
+  // Returns false if the nodes must not be mached.
+  bool isMatchingPossible(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.
+  void addOptimalMapping(Mapping &M, NodeId Id1, NodeId Id2) const;
+
+  // Computes the ratio of common descendants between the two nodes.
+  // Descendants are only considered to be equal when they are mapped in M.
+  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;
+
+  const ComparisonOptions &Options;
+
+  friend class ZhangShashaMatcher;
+};
+
+/// Represents the AST of a TranslationUnit.
+class SyntaxTree::Impl {
+public:
+  Impl(SyntaxTree *Parent, ASTContext &AST);
+  /// Constructs a tree from an AST node.
+  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,
+       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,
+       ASTContext &AST)
+      : Impl(Parent, dyn_cast<Decl>(Node), AST) {}
+
+  SyntaxTree *Parent;
+  ASTContext &AST;
+  PrintingPolicy TypePP;
+  /// Nodes in preorder.
+  std::vector<Node> Nodes;
+  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]; }
+  bool isValidNodeId(NodeId Id) const { return Id >= 0 && Id < getSize(); }
+  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 getRelativeName(const NamedDecl *ND,
+                              const DeclContext *Context) const;
+  std::string getRelativeName(const NamedDecl *ND) const;
+
+  std::string getNodeValue(NodeId Id) const;
+  std::string getNodeValue(const Node &Node) const;
+  std::string getDeclValue(const Decl *D) const;
+  std::string getStmtValue(const Stmt *S) const;
+
+private:
+  void initTree();
+  void setLeftMostDescendants();
+};
+
+static bool isSpecializedNodeExcluded(const Decl *D) { return D->isImplicit(); }
+static bool isSpecializedNodeExcluded(const Stmt *S) { return false; }
+static bool isSpecializedNodeExcluded(CXXCtorInitializer *I) {
+  return !I->isWritten();
+}
+
+template <class T>
+static bool isNodeExcluded(const SourceManager &SrcMgr, T *N) {
+  if (!N)
+    return true;
+  SourceLocation SLoc = N->getSourceRange().getBegin();
+  if (SLoc.isValid()) {
+    // Ignore everything from other files.
+    if (!SrcMgr.isInMainFile(SLoc))
+      return true;
+    // Ignore macros.
+    if (SLoc != SrcMgr.getSpellingLoc(SLoc))
+      return true;
+  }
+  return isSpecializedNodeExcluded(N);
+}
+
+namespace {
+// Sets Height, Parent and Children for each node.
+struct PreorderVisitor : public RecursiveASTVisitor<PreorderVisitor> {
+  int Id = 0, Depth = 0;
+  NodeId Parent;
+  SyntaxTree::Impl &Tree;
+
+  PreorderVisitor(SyntaxTree::Impl &Tree) : Tree(Tree) {}
+
+  template <class T> std::tuple<NodeId, NodeId> PreTraverse(T *ASTNode) {
+    NodeId MyId = Id;
+    Tree.Nodes.emplace_back();
+    Node &N = Tree.getMutableNode(MyId);
+    N.Parent = Parent;
+    N.Depth = Depth;
+    N.ASTNode = DynTypedNode::create(*ASTNode);
+    assert(!N.ASTNode.getNodeKind().isNone() &&
+           "Expected nodes to have a valid kind.");
+    if (Parent.isValid()) {
+      Node &P = Tree.getMutableNode(Parent);
+      P.Children.push_back(MyId);
+    }
+    Parent = MyId;
+    ++Id;
+    ++Depth;
+    return std::make_tuple(MyId, Tree.getNode(MyId).Parent);
+  }
+  void PostTraverse(std::tuple<NodeId, NodeId> State) {
+    NodeId MyId, PreviousParent;
+    std::tie(MyId, PreviousParent) = State;
+    assert(MyId.isValid() && "Expecting to only traverse valid nodes.");
+    Parent = PreviousParent;
+    --Depth;
+    Node &N = Tree.getMutableNode(MyId);
+    N.RightMostDescendant = Id - 1;
+    assert(N.RightMostDescendant >= 0 &&
+           N.RightMostDescendant < Tree.getSize() &&
+           "Rightmost descendant must be a valid tree node.");
+    if (N.isLeaf())
+      Tree.Leaves.push_back(MyId);
+    N.Height = 1;
+    for (NodeId Child : N.Children)
+      N.Height = std::max(N.Height, 1 + Tree.getNode(Child).Height);
+  }
+  bool TraverseDecl(Decl *D) {
+    if (isNodeExcluded(Tree.AST.getSourceManager(), D))
+      return true;
+    auto SavedState = PreTraverse(D);
+    RecursiveASTVisitor<PreorderVisitor>::TraverseDecl(D);
+    PostTraverse(SavedState);
+    return true;
+  }
+  bool TraverseStmt(Stmt *S) {
+    if (auto *E = dyn_cast_or_null<Expr>(S))
+      S = E->IgnoreImplicit();
+    if (isNodeExcluded(Tree.AST.getSourceManager(), S))
+      return true;
+    auto SavedState = PreTraverse(S);
+    RecursiveASTVisitor<PreorderVisitor>::TraverseStmt(S);
+    PostTraverse(SavedState);
+    return true;
+  }
+  bool TraverseType(QualType T) { return true; }
+  bool TraverseConstructorInitializer(CXXCtorInitializer *Init) {
+    if (isNodeExcluded(Tree.AST.getSourceManager(), Init))
+      return true;
+    auto SavedState = PreTraverse(Init);
+    RecursiveASTVisitor<PreorderVisitor>::TraverseConstructorInitializer(Init);
+    PostTraverse(SavedState);
+    return true;
+  }
+};
+} // end anonymous namespace
+
+SyntaxTree::Impl::Impl(SyntaxTree *Parent, ASTContext &AST)
+    : Parent(Parent), AST(AST), TypePP(AST.getLangOpts()) {
+  TypePP.AnonymousTagLocations = false;
+}
+
+SyntaxTree::Impl::Impl(SyntaxTree *Parent, Decl *N, ASTContext &AST)
+    : Impl(Parent, AST) {
+  PreorderVisitor PreorderWalker(*this);
+  PreorderWalker.TraverseDecl(N);
+  initTree();
+}
+
+SyntaxTree::Impl::Impl(SyntaxTree *Parent, Stmt *N, ASTContext &AST)
+    : Impl(Parent, AST) {
+  PreorderVisitor PreorderWalker(*this);
+  PreorderWalker.TraverseStmt(N);
+  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;
+  PostorderIds.resize(getSize());
+  std::function<void(NodeId)> PostorderTraverse = [&](NodeId Id) {
+    for (NodeId Child : getNode(Id).Children)
+      PostorderTraverse(Child);
+    PostorderIds[Id] = PostorderId;
+    ++PostorderId;
+  };
+  PostorderTraverse(getRootId());
+  NodesBfs = getSubtreeBfs(*this, getRootId());
+}
+
+void SyntaxTree::Impl::setLeftMostDescendants() {
+  for (NodeId Leaf : Leaves) {
+    getMutableNode(Leaf).LeftMostDescendant = Leaf;
+    NodeId Parent, Cur = Leaf;
+    while ((Parent = getNode(Cur).Parent).isValid() &&
+           getNode(Parent).Children[0] == Cur) {
+      Cur = Parent;
+      getMutableNode(Cur).LeftMostDescendant = Leaf;
+    }
+  }
+}
+
+int SyntaxTree::Impl::getNumberOfDescendants(NodeId Id) const {
+  return getNode(Id).RightMostDescendant - Id + 1;
+}
+
+bool SyntaxTree::Impl::isInSubtree(NodeId Id, NodeId SubtreeRoot) const {
+  return Id >= SubtreeRoot && Id <= getNode(SubtreeRoot).RightMostDescendant;
+}
+
+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.");
+}
+
+// Returns the qualified name of ND. If it is subordinate to Context,
+// then the prefix of the latter is removed from the returned value.
+std::string
+SyntaxTree::Impl::getRelativeName(const NamedDecl *ND,
+                                  const DeclContext *Context) const {
+  std::string Val = ND->getQualifiedNameAsString();
+  std::string ContextPrefix;
+  if (!Context)
+    return Val;
+  if (auto *Namespace = dyn_cast<NamespaceDecl>(Context))
+    ContextPrefix = Namespace->getQualifiedNameAsString();
+  else if (auto *Record = dyn_cast<RecordDecl>(Context))
+    ContextPrefix = Record->getQualifiedNameAsString();
+  else if (AST.getLangOpts().CPlusPlus11)
+    if (auto *Tag = dyn_cast<TagDecl>(Context))
+      ContextPrefix = Tag->getQualifiedNameAsString();
+  // Strip the qualifier, if Val refers to something in the current scope.
+  // But leave one leading ':' in place, so that we know that this is a
+  // relative path.
+  if (!ContextPrefix.empty() && StringRef(Val).startswith(ContextPrefix))
+    Val = Val.substr(ContextPrefix.size() + 1);
+  return Val;
+}
+
+std::string SyntaxTree::Impl::getRelativeName(const NamedDecl *ND) const {
+  return getRelativeName(ND, ND->getDeclContext());
+}
+
+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>();
+  }
+  return nullptr;
+}
+
+static std::string getInitializerValue(const CXXCtorInitializer *Init,
+                                       const PrintingPolicy &TypePP) {
+  if (Init->isAnyMemberInitializer())
+    return Init->getAnyMember()->getName();
+  if (Init->isBaseInitializer())
+    return QualType(Init->getBaseClass(), 0).getAsString(TypePP);
+  if (Init->isDelegatingInitializer())
+    return Init->getTypeSourceInfo()->getType().getAsString(TypePP);
+  llvm_unreachable("Unknown initializer type");
+}
+
+std::string SyntaxTree::Impl::getNodeValue(NodeId Id) const {
+  return getNodeValue(getNode(Id));
+}
+
+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);
+  if (auto *Init = DTN.get<CXXCtorInitializer>())
+    return getInitializerValue(Init, TypePP);
+  llvm_unreachable("Fatal: unhandled AST node.\n");
+}
+
+std::string SyntaxTree::Impl::getDeclValue(const Decl *D) const {
+  std::string Value;
+  if (auto *V = dyn_cast<ValueDecl>(D))
+    return getRelativeName(V) + "(" + V->getType().getAsString(TypePP) + ")";
+  if (auto *N = dyn_cast<NamedDecl>(D))
+    Value += getRelativeName(N) + ";";
+  if (auto *T = dyn_cast<TypedefNameDecl>(D))
+    return Value + T->getUnderlyingType().getAsString(TypePP) + ";";
+  if (auto *T = dyn_cast<TypeDecl>(D))
+    if (T->getTypeForDecl())
+      Value +=
+          T->getTypeForDecl()->getCanonicalTypeInternal().getAsString(TypePP) +
+          ";";
+  if (auto *U = dyn_cast<UsingDirectiveDecl>(D))
+    return U->getNominatedNamespace()->getName();
+  if (auto *A = dyn_cast<AccessSpecDecl>(D)) {
+    CharSourceRange Range(A->getSourceRange(), false);
+    return Lexer::getSourceText(Range, AST.getSourceManager(),
+                                AST.getLangOpts());
+  }
+  return Value;
+}
+
+std::string SyntaxTree::Impl::getStmtValue(const Stmt *S) const {
+  if (auto *U = dyn_cast<UnaryOperator>(S))
+    return UnaryOperator::getOpcodeStr(U->getOpcode());
+  if (auto *B = dyn_cast<BinaryOperator>(S))
+    return B->getOpcodeStr();
+  if (auto *M = dyn_cast<MemberExpr>(S))
+    return getRelativeName(M->getMemberDecl());
+  if (auto *I = dyn_cast<IntegerLiteral>(S)) {
+    SmallString<256> Str;
+    I->getValue().toString(Str, /*Radix=*/10, /*Signed=*/false);
+    return Str.str();
+  }
+  if (auto *F = dyn_cast<FloatingLiteral>(S)) {
+    SmallString<256> Str;
+    F->getValue().toString(Str);
+    return Str.str();
+  }
+  if (auto *D = dyn_cast<DeclRefExpr>(S))
+    return getRelativeName(D->getDecl(), getEnclosingDeclContext(AST, S));
+  if (auto *String = dyn_cast<StringLiteral>(S))
+    return String->getString();
+  if (auto *B = dyn_cast<CXXBoolLiteralExpr>(S))
+    return B->getValue() ? "true" : "false";
+  return "";
+}
+
+/// Identifies a node in a subtree by its postorder offset, starting at 1.
+struct SNodeId {
+  int Id = 0;
+
+  explicit SNodeId(int Id) : Id(Id) {}
+  explicit SNodeId() = default;
+
+  operator int() const { return Id; }
+  SNodeId &operator++() { return ++Id, *this; }
+  SNodeId &operator--() { return --Id, *this; }
+  SNodeId operator+(int Other) const { return SNodeId(Id + Other); }
+};
+
+class Subtree {
+private:
+  /// The parent tree.
+  const SyntaxTree::Impl &Tree;
+  /// Maps SNodeIds to original ids.
+  std::vector<NodeId> RootIds;
+  /// Maps subtree nodes to their leftmost descendants wtihin the subtree.
+  std::vector<SNodeId> LeftMostDescendants;
+
+public:
+  std::vector<SNodeId> KeyRoots;
+
+  Subtree(const SyntaxTree::Impl &Tree, NodeId SubtreeRoot) : Tree(Tree) {
+    RootIds = getSubtreePostorder(Tree, SubtreeRoot);
+    int NumLeaves = setLeftMostDescendants();
+    computeKeyRoots(NumLeaves);
+  }
+  int getSize() const { return RootIds.size(); }
+  NodeId getIdInRoot(SNodeId Id) const {
+    assert(Id > 0 && Id <= getSize() && "Invalid subtree node index.");
+    return RootIds[Id - 1];
+  }
+  const Node &getNode(SNodeId Id) const {
+    return Tree.getNode(getIdInRoot(Id));
+  }
+  SNodeId getLeftMostDescendant(SNodeId Id) const {
+    assert(Id > 0 && Id <= getSize() && "Invalid subtree node index.");
+    return LeftMostDescendants[Id - 1];
+  }
+  /// Returns the postorder index of the leftmost descendant in the subtree.
+  NodeId getPostorderOffset() const {
+    return Tree.PostorderIds[getIdInRoot(SNodeId(1))];
+  }
+  std::string getNodeValue(SNodeId Id) const {
+    return Tree.getNodeValue(getIdInRoot(Id));
+  }
+
+private:
+  /// Returns the number of leafs in the subtree.
+  int setLeftMostDescendants() {
+    int NumLeaves = 0;
+    LeftMostDescendants.resize(getSize());
+    for (int I = 0; I < getSize(); ++I) {
+      SNodeId SI(I + 1);
+      const Node &N = getNode(SI);
+      NumLeaves += N.isLeaf();
+      assert(I == Tree.PostorderIds[getIdInRoot(SI)] - getPostorderOffset() &&
+             "Postorder traversal in subtree should correspond to traversal in "
+             "the root tree by a constant offset.");
+      LeftMostDescendants[I] = SNodeId(Tree.PostorderIds[N.LeftMostDescendant] -
+                                       getPostorderOffset());
+    }
+    return NumLeaves;
+  }
+  void computeKeyRoots(int Leaves) {
+    KeyRoots.resize(Leaves);
+    std::unordered_set<int> Visited;
+    int K = Leaves - 1;
+    for (SNodeId I(getSize()); I > 0; --I) {
+      SNodeId LeftDesc = getLeftMostDescendant(I);
+      if (Visited.count(LeftDesc))
+        continue;
+      assert(K >= 0 && "K should be non-negative");
+      KeyRoots[K] = I;
+      Visited.insert(LeftDesc);
+      --K;
+    }
+  }
+};
+
+/// Implementation of Zhang and Shasha's Algorithm for tree edit distance.
+/// Computes an optimal mapping between two trees using only insertion,
+/// deletion and update as edit actions (similar to the Levenshtein distance).
+class ZhangShashaMatcher {
+  const ASTDiff::Impl &DiffImpl;
+  Subtree S1;
+  Subtree S2;
+  std::unique_ptr<std::unique_ptr<double[]>[]> TreeDist, ForestDist;
+
+public:
+  ZhangShashaMatcher(const ASTDiff::Impl &DiffImpl, const SyntaxTree::Impl &T1,
+                     const SyntaxTree::Impl &T2, NodeId Id1, NodeId Id2)
+      : DiffImpl(DiffImpl), S1(T1, Id1), S2(T2, Id2) {
+    TreeDist = std::make_unique<std::unique_ptr<double[]>[]>(
+        size_t(S1.getSize()) + 1);
+    ForestDist = std::make_unique<std::unique_ptr<double[]>[]>(
+        size_t(S1.getSize()) + 1);
+    for (int I = 0, E = S1.getSize() + 1; I < E; ++I) {
+      TreeDist[I] = std::make_unique<double[]>(size_t(S2.getSize()) + 1);
+      ForestDist[I] = std::make_unique<double[]>(size_t(S2.getSize()) + 1);
+    }
+  }
+
+  std::vector<std::pair<NodeId, NodeId>> getMatchingNodes() {
+    std::vector<std::pair<NodeId, NodeId>> Matches;
+    std::vector<std::pair<SNodeId, SNodeId>> TreePairs;
+
+    computeTreeDist();
+
+    bool RootNodePair = true;
+
+    TreePairs.emplace_back(SNodeId(S1.getSize()), SNodeId(S2.getSize()));
+
+    while (!TreePairs.empty()) {
+      SNodeId LastRow, LastCol, FirstRow, FirstCol, Row, Col;
+      std::tie(LastRow, LastCol) = TreePairs.back();
+      TreePairs.pop_back();
+
+      if (!RootNodePair) {
+        computeForestDist(LastRow, LastCol);
+      }
+
+      RootNodePair = false;
+
+      FirstRow = S1.getLeftMostDescendant(LastRow);
+      FirstCol = S2.getLeftMostDescendant(LastCol);
+
+      Row = LastRow;
+      Col = LastCol;
+
+      while (Row > FirstRow || Col > FirstCol) {
+        if (Row > FirstRow &&
+            ForestDist[Row - 1][Col] + 1 == ForestDist[Row][Col]) {
+          --Row;
+        } else if (Col > FirstCol &&
+                   ForestDist[Row][Col - 1] + 1 == ForestDist[Row][Col]) {
+          --Col;
+        } else {
+          SNodeId LMD1 = S1.getLeftMostDescendant(Row);
+          SNodeId LMD2 = S2.getLeftMostDescendant(Col);
+          if (LMD1 == S1.getLeftMostDescendant(LastRow) &&
+              LMD2 == S2.getLeftMostDescendant(LastCol)) {
+            NodeId Id1 = S1.getIdInRoot(Row);
+            NodeId Id2 = S2.getIdInRoot(Col);
+            assert(DiffImpl.isMatchingPossible(Id1, Id2) &&
+                   "These nodes must not be matched.");
+            Matches.emplace_back(Id1, Id2);
+            --Row;
+            --Col;
+          } else {
+            TreePairs.emplace_back(Row, Col);
+            Row = LMD1;
+            Col = LMD2;
+          }
+        }
+      }
+    }
+    return Matches;
+  }
+
+private:
+  /// 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.
+  static constexpr double DeletionCost = 1;
+  static constexpr double InsertionCost = 1;
+
+  double getUpdateCost(SNodeId Id1, SNodeId Id2) {
+    if (!DiffImpl.isMatchingPossible(S1.getIdInRoot(Id1), S2.getIdInRoot(Id2)))
+      return std::numeric_limits<double>::max();
+    return S1.getNodeValue(Id1) != S2.getNodeValue(Id2);
+  }
+
+  void computeTreeDist() {
+    for (SNodeId Id1 : S1.KeyRoots)
+      for (SNodeId Id2 : S2.KeyRoots)
+        computeForestDist(Id1, Id2);
+  }
+
+  void computeForestDist(SNodeId Id1, SNodeId Id2) {
+    assert(Id1 > 0 && Id2 > 0 && "Expecting offsets greater than 0.");
+    SNodeId LMD1 = S1.getLeftMostDescendant(Id1);
+    SNodeId LMD2 = S2.getLeftMostDescendant(Id2);
+
+    ForestDist[LMD1][LMD2] = 0;
+    for (SNodeId D1 = LMD1 + 1; D1 <= Id1; ++D1) {
+      ForestDist[D1][LMD2] = ForestDist[D1 - 1][LMD2] + DeletionCost;
+      for (SNodeId D2 = LMD2 + 1; D2 <= Id2; ++D2) {
+        ForestDist[LMD1][D2] = ForestDist[LMD1][D2 - 1] + InsertionCost;
+        SNodeId DLMD1 = S1.getLeftMostDescendant(D1);
+        SNodeId DLMD2 = S2.getLeftMostDescendant(D2);
+        if (DLMD1 == LMD1 && DLMD2 == LMD2) {
+          double UpdateCost = getUpdateCost(D1, D2);
+          ForestDist[D1][D2] =
+              std::min({ForestDist[D1 - 1][D2] + DeletionCost,
+                        ForestDist[D1][D2 - 1] + InsertionCost,
+                        ForestDist[D1 - 1][D2 - 1] + UpdateCost});
+          TreeDist[D1][D2] = ForestDist[D1][D2];
+        } else {
+          ForestDist[D1][D2] =
+              std::min({ForestDist[D1 - 1][D2] + DeletionCost,
+                        ForestDist[D1][D2 - 1] + InsertionCost,
+                        ForestDist[DLMD1][DLMD2] + TreeDist[D1][D2]});
+        }
+      }
+    }
+  }
+};
+
+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 {
+  const SyntaxTree::Impl &Tree;
+  HeightLess(const SyntaxTree::Impl &Tree) : Tree(Tree) {}
+  bool operator()(NodeId Id1, NodeId Id2) const {
+    return Tree.getNode(Id1).Height < Tree.getNode(Id2).Height;
+  }
+};
+} // end anonymous namespace
+
+namespace {
+// Priority queue for nodes, sorted descendingly by their height.
+class PriorityList {
+  const SyntaxTree::Impl &Tree;
+  HeightLess Cmp;
+  std::vector<NodeId> Container;
+  PriorityQueue<NodeId, std::vector<NodeId>, HeightLess> List;
+
+public:
+  PriorityList(const SyntaxTree::Impl &Tree)
+      : Tree(Tree), Cmp(Tree), List(Cmp, Container) {}
+
+  void push(NodeId id) { List.push(id); }
+
+  std::vector<NodeId> pop() {
+    int Max = peekMax();
+    std::vector<NodeId> Result;
+    if (Max == 0)
+      return Result;
+    while (peekMax() == Max) {
+      Result.push_back(List.top());
+      List.pop();
+    }
+    // TODO this is here to get a stable output, not a good heuristic
+    llvm::sort(Result);
+    return Result;
+  }
+  int peekMax() const {
+    if (List.empty())
+      return 0;
+    return Tree.getNode(List.top()).Height;
+  }
+  void open(NodeId Id) {
+    for (NodeId Child : Tree.getNode(Id).Children)
+      push(Child);
+  }
+};
+} // end anonymous namespace
+
+bool ASTDiff::Impl::identical(NodeId Id1, NodeId Id2) const {
+  const Node &N1 = T1.getNode(Id1);
+  const Node &N2 = T2.getNode(Id2);
+  if (N1.Children.size() != N2.Children.size() ||
+      !isMatchingPossible(Id1, Id2) ||
+      T1.getNodeValue(Id1) != T2.getNodeValue(Id2))
+    return false;
+  for (size_t Id = 0, E = N1.Children.size(); Id < E; ++Id)
+    if (!identical(N1.Children[Id], N2.Children[Id]))
+      return false;
+  return true;
+}
+
+bool ASTDiff::Impl::isMatchingPossible(NodeId Id1, NodeId Id2) const {
+  return Options.isMatchingAllowed(T1.getNode(Id1), T2.getNode(Id2));
+}
+
+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)
+    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 (!M.hasSrc(Src) && !M.hasDst(Dst))
+      M.link(Src, Dst);
+  }
+}
+
+double ASTDiff::Impl::getJaccardSimilarity(const Mapping &M, NodeId Id1,
+                                           NodeId Id2) const {
+  int CommonDescendants = 0;
+  const Node &N1 = T1.getNode(Id1);
+  // Count the common descendants, excluding the subtree root.
+  for (NodeId Src = Id1 + 1; Src <= N1.RightMostDescendant; ++Src) {
+    NodeId Dst = M.getDst(Src);
+    CommonDescendants += int(Dst.isValid() && T2.isInSubtree(Dst, Id2));
+  }
+  // We need to subtract 1 to get the number of descendants excluding the root.
+  double Denominator = T1.getNumberOfDescendants(Id1) - 1 +
+                       T2.getNumberOfDescendants(Id2) - 1 - CommonDescendants;
+  // CommonDescendants is less than the size of one subtree.
+  assert(Denominator >= 0 && "Expected non-negative denominator.");
+  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 : T2) {
+    if (!isMatchingPossible(Id1, Id2))
+      continue;
+    if (M.hasDst(Id2))
+      continue;
+    double Similarity = getJaccardSimilarity(M, Id1, Id2);
+    if (Similarity >= Options.MinSimilarity && Similarity > HighestSimilarity) {
+      HighestSimilarity = Similarity;
+      Candidate = Id2;
+    }
+  }
+  return Candidate;
+}
+
+void ASTDiff::Impl::matchBottomUp(Mapping &M) const {
+  std::vector<NodeId> Postorder = getSubtreePostorder(T1, T1.getRootId());
+  for (NodeId Id1 : Postorder) {
+    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;
+    }
+    bool Matched = M.hasSrc(Id1);
+    const Node &N1 = T1.getNode(Id1);
+    bool MatchedChildren = llvm::any_of(
+        N1.Children, [&](NodeId Child) { return M.hasSrc(Child); });
+    if (Matched || !MatchedChildren)
+      continue;
+    NodeId Id2 = findCandidate(M, Id1);
+    if (Id2.isValid()) {
+      M.link(Id1, Id2);
+      addOptimalMapping(M, Id1, Id2);
+    }
+  }
+}
+
+Mapping ASTDiff::Impl::matchTopDown() const {
+  PriorityList L1(T1);
+  PriorityList L2(T2);
+
+  Mapping M(T1.getSize() + T2.getSize());
+
+  L1.push(T1.getRootId());
+  L2.push(T2.getRootId());
+
+  int Max1, Max2;
+  while (std::min(Max1 = L1.peekMax(), Max2 = L2.peekMax()) >
+         Options.MinHeight) {
+    if (Max1 > Max2) {
+      for (NodeId Id : L1.pop())
+        L1.open(Id);
+      continue;
+    }
+    if (Max2 > Max1) {
+      for (NodeId Id : L2.pop())
+        L2.open(Id);
+      continue;
+    }
+    std::vector<NodeId> H1, H2;
+    H1 = L1.pop();
+    H2 = L2.pop();
+    for (NodeId Id1 : H1) {
+      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))
+        L1.open(Id1);
+    }
+    for (NodeId Id2 : H2) {
+      if (!M.hasDst(Id2))
+        L2.open(Id2);
+    }
+  }
+  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() {
+  TheMapping = matchTopDown();
+  if (Options.StopAfterTopDown)
+    return;
+  matchBottomUp(TheMapping);
+}
+
+void ASTDiff::Impl::computeChangeKinds(Mapping &M) {
+  for (NodeId Id1 : T1) {
+    if (!M.hasSrc(Id1)) {
+      T1.getMutableNode(Id1).Change = Delete;
+      T1.getMutableNode(Id1).Shift -= 1;
+    }
+  }
+  for (NodeId Id2 : T2) {
+    if (!M.hasDst(Id2)) {
+      T2.getMutableNode(Id2).Change = Insert;
+      T2.getMutableNode(Id2).Shift -= 1;
+    }
+  }
+  for (NodeId Id1 : T1.NodesBfs) {
+    NodeId Id2 = M.getDst(Id1);
+    if (Id2.isInvalid())
+      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.Change = N2.Change = Move;
+    }
+    if (T1.getNodeValue(Id1) != T2.getNodeValue(Id2)) {
+      N1.Change = N2.Change = (N1.Change == Move ? UpdateMove : Update);
+    }
+  }
+}
+
+ASTDiff::ASTDiff(SyntaxTree &T1, SyntaxTree &T2,
+                 const ComparisonOptions &Options)
+    : DiffImpl(std::make_unique<Impl>(*T1.TreeImpl, *T2.TreeImpl, Options)) {}
+
+ASTDiff::~ASTDiff() = default;
+
+NodeId ASTDiff::getMapped(const SyntaxTree &SourceTree, NodeId Id) const {
+  return DiffImpl->getMapped(SourceTree.TreeImpl, Id);
+}
+
+SyntaxTree::SyntaxTree(ASTContext &AST)
+    : TreeImpl(std::make_unique<SyntaxTree::Impl>(
+          this, AST.getTranslationUnitDecl(), AST)) {}
+
+SyntaxTree::~SyntaxTree() = default;
+
+const ASTContext &SyntaxTree::getASTContext() const { return TreeImpl->AST; }
+
+const Node &SyntaxTree::getNode(NodeId Id) const {
+  return TreeImpl->getNode(Id);
+}
+
+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(); }
+
+int SyntaxTree::findPositionInParent(NodeId Id) const {
+  return TreeImpl->findPositionInParent(Id);
+}
+
+std::pair<unsigned, unsigned>
+SyntaxTree::getSourceRangeOffsets(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};
+}
+
+std::string SyntaxTree::getNodeValue(NodeId Id) const {
+  return TreeImpl->getNodeValue(Id);
+}
+
+std::string SyntaxTree::getNodeValue(const Node &N) const {
+  return TreeImpl->getNodeValue(N);
+}
+
+} // end namespace diff
+} // end namespace clang