clang  14.0.0git
ASTDiff.cpp
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1 //===- ASTDiff.cpp - AST differencing implementation-----------*- C++ -*- -===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file contains definitons for the AST differencing interface.
10 //
11 //===----------------------------------------------------------------------===//
12 
17 #include "clang/Lex/Lexer.h"
18 #include "llvm/ADT/PriorityQueue.h"
19 
20 #include <limits>
21 #include <memory>
22 #include <unordered_set>
23 
24 using namespace llvm;
25 using namespace clang;
26 
27 namespace clang {
28 namespace diff {
29 
30 namespace {
31 /// Maps nodes of the left tree to ones on the right, and vice versa.
32 class Mapping {
33 public:
34  Mapping() = default;
35  Mapping(Mapping &&Other) = default;
36  Mapping &operator=(Mapping &&Other) = default;
37 
38  Mapping(size_t Size) {
39  SrcToDst = std::make_unique<NodeId[]>(Size);
40  DstToSrc = std::make_unique<NodeId[]>(Size);
41  }
42 
43  void link(NodeId Src, NodeId Dst) {
44  SrcToDst[Src] = Dst, DstToSrc[Dst] = Src;
45  }
46 
47  NodeId getDst(NodeId Src) const { return SrcToDst[Src]; }
48  NodeId getSrc(NodeId Dst) const { return DstToSrc[Dst]; }
49  bool hasSrc(NodeId Src) const { return getDst(Src).isValid(); }
50  bool hasDst(NodeId Dst) const { return getSrc(Dst).isValid(); }
51 
52 private:
53  std::unique_ptr<NodeId[]> SrcToDst, DstToSrc;
54 };
55 } // end anonymous namespace
56 
58 public:
60  Mapping TheMapping;
61 
63  const ComparisonOptions &Options);
64 
65  /// Matches nodes one-by-one based on their similarity.
66  void computeMapping();
67 
68  // Compute Change for each node based on similarity.
69  void computeChangeKinds(Mapping &M);
70 
71  NodeId getMapped(const std::unique_ptr<SyntaxTree::Impl> &Tree,
72  NodeId Id) const {
73  if (&*Tree == &T1)
74  return TheMapping.getDst(Id);
75  assert(&*Tree == &T2 && "Invalid tree.");
76  return TheMapping.getSrc(Id);
77  }
78 
79 private:
80  // Returns true if the two subtrees are identical.
81  bool identical(NodeId Id1, NodeId Id2) const;
82 
83  // Returns false if the nodes must not be mached.
84  bool isMatchingPossible(NodeId Id1, NodeId Id2) const;
85 
86  // Returns true if the nodes' parents are matched.
87  bool haveSameParents(const Mapping &M, NodeId Id1, NodeId Id2) const;
88 
89  // Uses an optimal albeit slow algorithm to compute a mapping between two
90  // subtrees, but only if both have fewer nodes than MaxSize.
91  void addOptimalMapping(Mapping &M, NodeId Id1, NodeId Id2) const;
92 
93  // Computes the ratio of common descendants between the two nodes.
94  // Descendants are only considered to be equal when they are mapped in M.
95  double getJaccardSimilarity(const Mapping &M, NodeId Id1, NodeId Id2) const;
96 
97  // Returns the node that has the highest degree of similarity.
98  NodeId findCandidate(const Mapping &M, NodeId Id1) const;
99 
100  // Returns a mapping of identical subtrees.
101  Mapping matchTopDown() const;
102 
103  // Tries to match any yet unmapped nodes, in a bottom-up fashion.
104  void matchBottomUp(Mapping &M) const;
105 
106  const ComparisonOptions &Options;
107 
108  friend class ZhangShashaMatcher;
109 };
110 
111 /// Represents the AST of a TranslationUnit.
113 public:
115  /// Constructs a tree from an AST node.
116  Impl(SyntaxTree *Parent, Decl *N, ASTContext &AST);
117  Impl(SyntaxTree *Parent, Stmt *N, ASTContext &AST);
118  template <class T>
120  std::enable_if_t<std::is_base_of<Stmt, T>::value, T> *Node,
121  ASTContext &AST)
122  : Impl(Parent, dyn_cast<Stmt>(Node), AST) {}
123  template <class T>
125  std::enable_if_t<std::is_base_of<Decl, T>::value, T> *Node,
126  ASTContext &AST)
127  : Impl(Parent, dyn_cast<Decl>(Node), AST) {}
128 
132  /// Nodes in preorder.
133  std::vector<Node> Nodes;
134  std::vector<NodeId> Leaves;
135  // Maps preorder indices to postorder ones.
136  std::vector<int> PostorderIds;
137  std::vector<NodeId> NodesBfs;
138 
139  int getSize() const { return Nodes.size(); }
140  NodeId getRootId() const { return 0; }
141  PreorderIterator begin() const { return getRootId(); }
142  PreorderIterator end() const { return getSize(); }
143 
144  const Node &getNode(NodeId Id) const { return Nodes[Id]; }
146  bool isValidNodeId(NodeId Id) const { return Id >= 0 && Id < getSize(); }
147  void addNode(Node &N) { Nodes.push_back(N); }
148  int getNumberOfDescendants(NodeId Id) const;
149  bool isInSubtree(NodeId Id, NodeId SubtreeRoot) const;
150  int findPositionInParent(NodeId Id, bool Shifted = false) const;
151 
152  std::string getRelativeName(const NamedDecl *ND,
153  const DeclContext *Context) const;
154  std::string getRelativeName(const NamedDecl *ND) const;
155 
156  std::string getNodeValue(NodeId Id) const;
157  std::string getNodeValue(const Node &Node) const;
158  std::string getDeclValue(const Decl *D) const;
159  std::string getStmtValue(const Stmt *S) const;
160 
161 private:
162  void initTree();
163  void setLeftMostDescendants();
164 };
165 
166 static bool isSpecializedNodeExcluded(const Decl *D) { return D->isImplicit(); }
167 static bool isSpecializedNodeExcluded(const Stmt *S) { return false; }
169  return !I->isWritten();
170 }
171 
172 template <class T>
173 static bool isNodeExcluded(const SourceManager &SrcMgr, T *N) {
174  if (!N)
175  return true;
176  SourceLocation SLoc = N->getSourceRange().getBegin();
177  if (SLoc.isValid()) {
178  // Ignore everything from other files.
179  if (!SrcMgr.isInMainFile(SLoc))
180  return true;
181  // Ignore macros.
182  if (SLoc != SrcMgr.getSpellingLoc(SLoc))
183  return true;
184  }
185  return isSpecializedNodeExcluded(N);
186 }
187 
188 namespace {
189 // Sets Height, Parent and Children for each node.
190 struct PreorderVisitor : public RecursiveASTVisitor<PreorderVisitor> {
191  int Id = 0, Depth = 0;
192  NodeId Parent;
193  SyntaxTree::Impl &Tree;
194 
195  PreorderVisitor(SyntaxTree::Impl &Tree) : Tree(Tree) {}
196 
197  template <class T> std::tuple<NodeId, NodeId> PreTraverse(T *ASTNode) {
198  NodeId MyId = Id;
199  Tree.Nodes.emplace_back();
200  Node &N = Tree.getMutableNode(MyId);
201  N.Parent = Parent;
202  N.Depth = Depth;
203  N.ASTNode = DynTypedNode::create(*ASTNode);
204  assert(!N.ASTNode.getNodeKind().isNone() &&
205  "Expected nodes to have a valid kind.");
206  if (Parent.isValid()) {
207  Node &P = Tree.getMutableNode(Parent);
208  P.Children.push_back(MyId);
209  }
210  Parent = MyId;
211  ++Id;
212  ++Depth;
213  return std::make_tuple(MyId, Tree.getNode(MyId).Parent);
214  }
215  void PostTraverse(std::tuple<NodeId, NodeId> State) {
216  NodeId MyId, PreviousParent;
217  std::tie(MyId, PreviousParent) = State;
218  assert(MyId.isValid() && "Expecting to only traverse valid nodes.");
219  Parent = PreviousParent;
220  --Depth;
221  Node &N = Tree.getMutableNode(MyId);
222  N.RightMostDescendant = Id - 1;
223  assert(N.RightMostDescendant >= 0 &&
224  N.RightMostDescendant < Tree.getSize() &&
225  "Rightmost descendant must be a valid tree node.");
226  if (N.isLeaf())
227  Tree.Leaves.push_back(MyId);
228  N.Height = 1;
229  for (NodeId Child : N.Children)
230  N.Height = std::max(N.Height, 1 + Tree.getNode(Child).Height);
231  }
232  bool TraverseDecl(Decl *D) {
233  if (isNodeExcluded(Tree.AST.getSourceManager(), D))
234  return true;
235  auto SavedState = PreTraverse(D);
237  PostTraverse(SavedState);
238  return true;
239  }
240  bool TraverseStmt(Stmt *S) {
241  if (auto *E = dyn_cast_or_null<Expr>(S))
242  S = E->IgnoreImplicit();
243  if (isNodeExcluded(Tree.AST.getSourceManager(), S))
244  return true;
245  auto SavedState = PreTraverse(S);
247  PostTraverse(SavedState);
248  return true;
249  }
250  bool TraverseType(QualType T) { return true; }
251  bool TraverseConstructorInitializer(CXXCtorInitializer *Init) {
252  if (isNodeExcluded(Tree.AST.getSourceManager(), Init))
253  return true;
254  auto SavedState = PreTraverse(Init);
256  PostTraverse(SavedState);
257  return true;
258  }
259 };
260 } // end anonymous namespace
261 
262 SyntaxTree::Impl::Impl(SyntaxTree *Parent, ASTContext &AST)
263  : Parent(Parent), AST(AST), TypePP(AST.getLangOpts()) {
265 }
266 
268  : Impl(Parent, AST) {
269  PreorderVisitor PreorderWalker(*this);
270  PreorderWalker.TraverseDecl(N);
271  initTree();
272 }
273 
275  : Impl(Parent, AST) {
276  PreorderVisitor PreorderWalker(*this);
277  PreorderWalker.TraverseStmt(N);
278  initTree();
279 }
280 
281 static std::vector<NodeId> getSubtreePostorder(const SyntaxTree::Impl &Tree,
282  NodeId Root) {
283  std::vector<NodeId> Postorder;
284  std::function<void(NodeId)> Traverse = [&](NodeId Id) {
285  const Node &N = Tree.getNode(Id);
286  for (NodeId Child : N.Children)
287  Traverse(Child);
288  Postorder.push_back(Id);
289  };
290  Traverse(Root);
291  return Postorder;
292 }
293 
294 static std::vector<NodeId> getSubtreeBfs(const SyntaxTree::Impl &Tree,
295  NodeId Root) {
296  std::vector<NodeId> Ids;
297  size_t Expanded = 0;
298  Ids.push_back(Root);
299  while (Expanded < Ids.size())
300  for (NodeId Child : Tree.getNode(Ids[Expanded++]).Children)
301  Ids.push_back(Child);
302  return Ids;
303 }
304 
305 void SyntaxTree::Impl::initTree() {
306  setLeftMostDescendants();
307  int PostorderId = 0;
308  PostorderIds.resize(getSize());
309  std::function<void(NodeId)> PostorderTraverse = [&](NodeId Id) {
310  for (NodeId Child : getNode(Id).Children)
311  PostorderTraverse(Child);
312  PostorderIds[Id] = PostorderId;
313  ++PostorderId;
314  };
315  PostorderTraverse(getRootId());
316  NodesBfs = getSubtreeBfs(*this, getRootId());
317 }
318 
319 void SyntaxTree::Impl::setLeftMostDescendants() {
320  for (NodeId Leaf : Leaves) {
321  getMutableNode(Leaf).LeftMostDescendant = Leaf;
322  NodeId Parent, Cur = Leaf;
323  while ((Parent = getNode(Cur).Parent).isValid() &&
324  getNode(Parent).Children[0] == Cur) {
325  Cur = Parent;
326  getMutableNode(Cur).LeftMostDescendant = Leaf;
327  }
328  }
329 }
330 
332  return getNode(Id).RightMostDescendant - Id + 1;
333 }
334 
335 bool SyntaxTree::Impl::isInSubtree(NodeId Id, NodeId SubtreeRoot) const {
336  return Id >= SubtreeRoot && Id <= getNode(SubtreeRoot).RightMostDescendant;
337 }
338 
341  if (Parent.isInvalid())
342  return 0;
343  const auto &Siblings = getNode(Parent).Children;
344  int Position = 0;
345  for (size_t I = 0, E = Siblings.size(); I < E; ++I) {
346  if (Shifted)
347  Position += getNode(Siblings[I]).Shift;
348  if (Siblings[I] == Id) {
349  Position += I;
350  return Position;
351  }
352  }
353  llvm_unreachable("Node not found in parent's children.");
354 }
355 
356 // Returns the qualified name of ND. If it is subordinate to Context,
357 // then the prefix of the latter is removed from the returned value.
360  const DeclContext *Context) const {
362  std::string ContextPrefix;
363  if (!Context)
364  return Val;
365  if (auto *Namespace = dyn_cast<NamespaceDecl>(Context))
366  ContextPrefix = Namespace->getQualifiedNameAsString();
367  else if (auto *Record = dyn_cast<RecordDecl>(Context))
368  ContextPrefix = Record->getQualifiedNameAsString();
369  else if (AST.getLangOpts().CPlusPlus11)
370  if (auto *Tag = dyn_cast<TagDecl>(Context))
371  ContextPrefix = Tag->getQualifiedNameAsString();
372  // Strip the qualifier, if Val refers to something in the current scope.
373  // But leave one leading ':' in place, so that we know that this is a
374  // relative path.
375  if (!ContextPrefix.empty() && StringRef(Val).startswith(ContextPrefix))
376  Val = Val.substr(ContextPrefix.size() + 1);
377  return Val;
378 }
379 
381  return getRelativeName(ND, ND->getDeclContext());
382 }
383 
385  const Stmt *S) {
386  while (S) {
387  const auto &Parents = AST.getParents(*S);
388  if (Parents.empty())
389  return nullptr;
390  const auto &P = Parents[0];
391  if (const auto *D = P.get<Decl>())
392  return D->getDeclContext();
393  S = P.get<Stmt>();
394  }
395  return nullptr;
396 }
397 
399  const PrintingPolicy &TypePP) {
400  if (Init->isAnyMemberInitializer())
401  return std::string(Init->getAnyMember()->getName());
402  if (Init->isBaseInitializer())
403  return QualType(Init->getBaseClass(), 0).getAsString(TypePP);
404  if (Init->isDelegatingInitializer())
405  return Init->getTypeSourceInfo()->getType().getAsString(TypePP);
406  llvm_unreachable("Unknown initializer type");
407 }
408 
410  return getNodeValue(getNode(Id));
411 }
412 
414  const DynTypedNode &DTN = N.ASTNode;
415  if (auto *S = DTN.get<Stmt>())
416  return getStmtValue(S);
417  if (auto *D = DTN.get<Decl>())
418  return getDeclValue(D);
419  if (auto *Init = DTN.get<CXXCtorInitializer>())
420  return getInitializerValue(Init, TypePP);
421  llvm_unreachable("Fatal: unhandled AST node.\n");
422 }
423 
426  if (auto *V = dyn_cast<ValueDecl>(D))
427  return getRelativeName(V) + "(" + V->getType().getAsString(TypePP) + ")";
428  if (auto *N = dyn_cast<NamedDecl>(D))
429  Value += getRelativeName(N) + ";";
430  if (auto *T = dyn_cast<TypedefNameDecl>(D))
431  return Value + T->getUnderlyingType().getAsString(TypePP) + ";";
432  if (auto *T = dyn_cast<TypeDecl>(D))
433  if (T->getTypeForDecl())
434  Value +=
435  T->getTypeForDecl()->getCanonicalTypeInternal().getAsString(TypePP) +
436  ";";
437  if (auto *U = dyn_cast<UsingDirectiveDecl>(D))
438  return std::string(U->getNominatedNamespace()->getName());
439  if (auto *A = dyn_cast<AccessSpecDecl>(D)) {
440  CharSourceRange Range(A->getSourceRange(), false);
441  return std::string(
442  Lexer::getSourceText(Range, AST.getSourceManager(), AST.getLangOpts()));
443  }
444  return Value;
445 }
446 
448  if (auto *U = dyn_cast<UnaryOperator>(S))
449  return std::string(UnaryOperator::getOpcodeStr(U->getOpcode()));
450  if (auto *B = dyn_cast<BinaryOperator>(S))
451  return std::string(B->getOpcodeStr());
452  if (auto *M = dyn_cast<MemberExpr>(S))
453  return getRelativeName(M->getMemberDecl());
454  if (auto *I = dyn_cast<IntegerLiteral>(S)) {
455  SmallString<256> Str;
456  I->getValue().toString(Str, /*Radix=*/10, /*Signed=*/false);
457  return std::string(Str.str());
458  }
459  if (auto *F = dyn_cast<FloatingLiteral>(S)) {
460  SmallString<256> Str;
461  F->getValue().toString(Str);
462  return std::string(Str.str());
463  }
464  if (auto *D = dyn_cast<DeclRefExpr>(S))
465  return getRelativeName(D->getDecl(), getEnclosingDeclContext(AST, S));
466  if (auto *String = dyn_cast<StringLiteral>(S))
467  return std::string(String->getString());
468  if (auto *B = dyn_cast<CXXBoolLiteralExpr>(S))
469  return B->getValue() ? "true" : "false";
470  return "";
471 }
472 
473 /// Identifies a node in a subtree by its postorder offset, starting at 1.
474 struct SNodeId {
475  int Id = 0;
476 
477  explicit SNodeId(int Id) : Id(Id) {}
478  explicit SNodeId() = default;
479 
480  operator int() const { return Id; }
481  SNodeId &operator++() { return ++Id, *this; }
482  SNodeId &operator--() { return --Id, *this; }
483  SNodeId operator+(int Other) const { return SNodeId(Id + Other); }
484 };
485 
486 class Subtree {
487 private:
488  /// The parent tree.
489  const SyntaxTree::Impl &Tree;
490  /// Maps SNodeIds to original ids.
491  std::vector<NodeId> RootIds;
492  /// Maps subtree nodes to their leftmost descendants wtihin the subtree.
493  std::vector<SNodeId> LeftMostDescendants;
494 
495 public:
496  std::vector<SNodeId> KeyRoots;
497 
498  Subtree(const SyntaxTree::Impl &Tree, NodeId SubtreeRoot) : Tree(Tree) {
499  RootIds = getSubtreePostorder(Tree, SubtreeRoot);
500  int NumLeaves = setLeftMostDescendants();
501  computeKeyRoots(NumLeaves);
502  }
503  int getSize() const { return RootIds.size(); }
505  assert(Id > 0 && Id <= getSize() && "Invalid subtree node index.");
506  return RootIds[Id - 1];
507  }
508  const Node &getNode(SNodeId Id) const {
509  return Tree.getNode(getIdInRoot(Id));
510  }
512  assert(Id > 0 && Id <= getSize() && "Invalid subtree node index.");
513  return LeftMostDescendants[Id - 1];
514  }
515  /// Returns the postorder index of the leftmost descendant in the subtree.
517  return Tree.PostorderIds[getIdInRoot(SNodeId(1))];
518  }
520  return Tree.getNodeValue(getIdInRoot(Id));
521  }
522 
523 private:
524  /// Returns the number of leafs in the subtree.
525  int setLeftMostDescendants() {
526  int NumLeaves = 0;
527  LeftMostDescendants.resize(getSize());
528  for (int I = 0; I < getSize(); ++I) {
529  SNodeId SI(I + 1);
530  const Node &N = getNode(SI);
531  NumLeaves += N.isLeaf();
532  assert(I == Tree.PostorderIds[getIdInRoot(SI)] - getPostorderOffset() &&
533  "Postorder traversal in subtree should correspond to traversal in "
534  "the root tree by a constant offset.");
535  LeftMostDescendants[I] = SNodeId(Tree.PostorderIds[N.LeftMostDescendant] -
536  getPostorderOffset());
537  }
538  return NumLeaves;
539  }
540  void computeKeyRoots(int Leaves) {
541  KeyRoots.resize(Leaves);
542  std::unordered_set<int> Visited;
543  int K = Leaves - 1;
544  for (SNodeId I(getSize()); I > 0; --I) {
545  SNodeId LeftDesc = getLeftMostDescendant(I);
546  if (Visited.count(LeftDesc))
547  continue;
548  assert(K >= 0 && "K should be non-negative");
549  KeyRoots[K] = I;
550  Visited.insert(LeftDesc);
551  --K;
552  }
553  }
554 };
555 
556 /// Implementation of Zhang and Shasha's Algorithm for tree edit distance.
557 /// Computes an optimal mapping between two trees using only insertion,
558 /// deletion and update as edit actions (similar to the Levenshtein distance).
560  const ASTDiff::Impl &DiffImpl;
561  Subtree S1;
562  Subtree S2;
563  std::unique_ptr<std::unique_ptr<double[]>[]> TreeDist, ForestDist;
564 
565 public:
567  const SyntaxTree::Impl &T2, NodeId Id1, NodeId Id2)
568  : DiffImpl(DiffImpl), S1(T1, Id1), S2(T2, Id2) {
569  TreeDist = std::make_unique<std::unique_ptr<double[]>[]>(
570  size_t(S1.getSize()) + 1);
571  ForestDist = std::make_unique<std::unique_ptr<double[]>[]>(
572  size_t(S1.getSize()) + 1);
573  for (int I = 0, E = S1.getSize() + 1; I < E; ++I) {
574  TreeDist[I] = std::make_unique<double[]>(size_t(S2.getSize()) + 1);
575  ForestDist[I] = std::make_unique<double[]>(size_t(S2.getSize()) + 1);
576  }
577  }
578 
579  std::vector<std::pair<NodeId, NodeId>> getMatchingNodes() {
580  std::vector<std::pair<NodeId, NodeId>> Matches;
581  std::vector<std::pair<SNodeId, SNodeId>> TreePairs;
582 
583  computeTreeDist();
584 
585  bool RootNodePair = true;
586 
587  TreePairs.emplace_back(SNodeId(S1.getSize()), SNodeId(S2.getSize()));
588 
589  while (!TreePairs.empty()) {
590  SNodeId LastRow, LastCol, FirstRow, FirstCol, Row, Col;
591  std::tie(LastRow, LastCol) = TreePairs.back();
592  TreePairs.pop_back();
593 
594  if (!RootNodePair) {
595  computeForestDist(LastRow, LastCol);
596  }
597 
598  RootNodePair = false;
599 
600  FirstRow = S1.getLeftMostDescendant(LastRow);
601  FirstCol = S2.getLeftMostDescendant(LastCol);
602 
603  Row = LastRow;
604  Col = LastCol;
605 
606  while (Row > FirstRow || Col > FirstCol) {
607  if (Row > FirstRow &&
608  ForestDist[Row - 1][Col] + 1 == ForestDist[Row][Col]) {
609  --Row;
610  } else if (Col > FirstCol &&
611  ForestDist[Row][Col - 1] + 1 == ForestDist[Row][Col]) {
612  --Col;
613  } else {
614  SNodeId LMD1 = S1.getLeftMostDescendant(Row);
615  SNodeId LMD2 = S2.getLeftMostDescendant(Col);
616  if (LMD1 == S1.getLeftMostDescendant(LastRow) &&
617  LMD2 == S2.getLeftMostDescendant(LastCol)) {
618  NodeId Id1 = S1.getIdInRoot(Row);
619  NodeId Id2 = S2.getIdInRoot(Col);
620  assert(DiffImpl.isMatchingPossible(Id1, Id2) &&
621  "These nodes must not be matched.");
622  Matches.emplace_back(Id1, Id2);
623  --Row;
624  --Col;
625  } else {
626  TreePairs.emplace_back(Row, Col);
627  Row = LMD1;
628  Col = LMD2;
629  }
630  }
631  }
632  }
633  return Matches;
634  }
635 
636 private:
637  /// We use a simple cost model for edit actions, which seems good enough.
638  /// Simple cost model for edit actions. This seems to make the matching
639  /// algorithm perform reasonably well.
640  /// The values range between 0 and 1, or infinity if this edit action should
641  /// always be avoided.
642  static constexpr double DeletionCost = 1;
643  static constexpr double InsertionCost = 1;
644 
645  double getUpdateCost(SNodeId Id1, SNodeId Id2) {
646  if (!DiffImpl.isMatchingPossible(S1.getIdInRoot(Id1), S2.getIdInRoot(Id2)))
648  return S1.getNodeValue(Id1) != S2.getNodeValue(Id2);
649  }
650 
651  void computeTreeDist() {
652  for (SNodeId Id1 : S1.KeyRoots)
653  for (SNodeId Id2 : S2.KeyRoots)
654  computeForestDist(Id1, Id2);
655  }
656 
657  void computeForestDist(SNodeId Id1, SNodeId Id2) {
658  assert(Id1 > 0 && Id2 > 0 && "Expecting offsets greater than 0.");
659  SNodeId LMD1 = S1.getLeftMostDescendant(Id1);
660  SNodeId LMD2 = S2.getLeftMostDescendant(Id2);
661 
662  ForestDist[LMD1][LMD2] = 0;
663  for (SNodeId D1 = LMD1 + 1; D1 <= Id1; ++D1) {
664  ForestDist[D1][LMD2] = ForestDist[D1 - 1][LMD2] + DeletionCost;
665  for (SNodeId D2 = LMD2 + 1; D2 <= Id2; ++D2) {
666  ForestDist[LMD1][D2] = ForestDist[LMD1][D2 - 1] + InsertionCost;
667  SNodeId DLMD1 = S1.getLeftMostDescendant(D1);
668  SNodeId DLMD2 = S2.getLeftMostDescendant(D2);
669  if (DLMD1 == LMD1 && DLMD2 == LMD2) {
670  double UpdateCost = getUpdateCost(D1, D2);
671  ForestDist[D1][D2] =
672  std::min({ForestDist[D1 - 1][D2] + DeletionCost,
673  ForestDist[D1][D2 - 1] + InsertionCost,
674  ForestDist[D1 - 1][D2 - 1] + UpdateCost});
675  TreeDist[D1][D2] = ForestDist[D1][D2];
676  } else {
677  ForestDist[D1][D2] =
678  std::min({ForestDist[D1 - 1][D2] + DeletionCost,
679  ForestDist[D1][D2 - 1] + InsertionCost,
680  ForestDist[DLMD1][DLMD2] + TreeDist[D1][D2]});
681  }
682  }
683  }
684  }
685 };
686 
687 ASTNodeKind Node::getType() const { return ASTNode.getNodeKind(); }
688 
689 StringRef Node::getTypeLabel() const { return getType().asStringRef(); }
690 
692  if (auto *ND = ASTNode.get<NamedDecl>()) {
693  if (ND->getDeclName().isIdentifier())
694  return ND->getQualifiedNameAsString();
695  }
696  return llvm::None;
697 }
698 
700  if (auto *ND = ASTNode.get<NamedDecl>()) {
701  if (ND->getDeclName().isIdentifier())
702  return ND->getName();
703  }
704  return llvm::None;
705 }
706 
707 namespace {
708 // Compares nodes by their depth.
709 struct HeightLess {
710  const SyntaxTree::Impl &Tree;
711  HeightLess(const SyntaxTree::Impl &Tree) : Tree(Tree) {}
712  bool operator()(NodeId Id1, NodeId Id2) const {
713  return Tree.getNode(Id1).Height < Tree.getNode(Id2).Height;
714  }
715 };
716 } // end anonymous namespace
717 
718 namespace {
719 // Priority queue for nodes, sorted descendingly by their height.
720 class PriorityList {
721  const SyntaxTree::Impl &Tree;
722  HeightLess Cmp;
723  std::vector<NodeId> Container;
724  PriorityQueue<NodeId, std::vector<NodeId>, HeightLess> List;
725 
726 public:
727  PriorityList(const SyntaxTree::Impl &Tree)
728  : Tree(Tree), Cmp(Tree), List(Cmp, Container) {}
729 
730  void push(NodeId id) { List.push(id); }
731 
732  std::vector<NodeId> pop() {
733  int Max = peekMax();
734  std::vector<NodeId> Result;
735  if (Max == 0)
736  return Result;
737  while (peekMax() == Max) {
738  Result.push_back(List.top());
739  List.pop();
740  }
741  // TODO this is here to get a stable output, not a good heuristic
742  llvm::sort(Result);
743  return Result;
744  }
745  int peekMax() const {
746  if (List.empty())
747  return 0;
748  return Tree.getNode(List.top()).Height;
749  }
750  void open(NodeId Id) {
751  for (NodeId Child : Tree.getNode(Id).Children)
752  push(Child);
753  }
754 };
755 } // end anonymous namespace
756 
757 bool ASTDiff::Impl::identical(NodeId Id1, NodeId Id2) const {
758  const Node &N1 = T1.getNode(Id1);
759  const Node &N2 = T2.getNode(Id2);
760  if (N1.Children.size() != N2.Children.size() ||
761  !isMatchingPossible(Id1, Id2) ||
762  T1.getNodeValue(Id1) != T2.getNodeValue(Id2))
763  return false;
764  for (size_t Id = 0, E = N1.Children.size(); Id < E; ++Id)
765  if (!identical(N1.Children[Id], N2.Children[Id]))
766  return false;
767  return true;
768 }
769 
770 bool ASTDiff::Impl::isMatchingPossible(NodeId Id1, NodeId Id2) const {
771  return Options.isMatchingAllowed(T1.getNode(Id1), T2.getNode(Id2));
772 }
773 
774 bool ASTDiff::Impl::haveSameParents(const Mapping &M, NodeId Id1,
775  NodeId Id2) const {
776  NodeId P1 = T1.getNode(Id1).Parent;
777  NodeId P2 = T2.getNode(Id2).Parent;
778  return (P1.isInvalid() && P2.isInvalid()) ||
779  (P1.isValid() && P2.isValid() && M.getDst(P1) == P2);
780 }
781 
782 void ASTDiff::Impl::addOptimalMapping(Mapping &M, NodeId Id1,
783  NodeId Id2) const {
784  if (std::max(T1.getNumberOfDescendants(Id1), T2.getNumberOfDescendants(Id2)) >
785  Options.MaxSize)
786  return;
787  ZhangShashaMatcher Matcher(*this, T1, T2, Id1, Id2);
788  std::vector<std::pair<NodeId, NodeId>> R = Matcher.getMatchingNodes();
789  for (const auto &Tuple : R) {
790  NodeId Src = Tuple.first;
791  NodeId Dst = Tuple.second;
792  if (!M.hasSrc(Src) && !M.hasDst(Dst))
793  M.link(Src, Dst);
794  }
795 }
796 
797 double ASTDiff::Impl::getJaccardSimilarity(const Mapping &M, NodeId Id1,
798  NodeId Id2) const {
799  int CommonDescendants = 0;
800  const Node &N1 = T1.getNode(Id1);
801  // Count the common descendants, excluding the subtree root.
802  for (NodeId Src = Id1 + 1; Src <= N1.RightMostDescendant; ++Src) {
803  NodeId Dst = M.getDst(Src);
804  CommonDescendants += int(Dst.isValid() && T2.isInSubtree(Dst, Id2));
805  }
806  // We need to subtract 1 to get the number of descendants excluding the root.
807  double Denominator = T1.getNumberOfDescendants(Id1) - 1 +
808  T2.getNumberOfDescendants(Id2) - 1 - CommonDescendants;
809  // CommonDescendants is less than the size of one subtree.
810  assert(Denominator >= 0 && "Expected non-negative denominator.");
811  if (Denominator == 0)
812  return 0;
813  return CommonDescendants / Denominator;
814 }
815 
816 NodeId ASTDiff::Impl::findCandidate(const Mapping &M, NodeId Id1) const {
817  NodeId Candidate;
818  double HighestSimilarity = 0.0;
819  for (NodeId Id2 : T2) {
820  if (!isMatchingPossible(Id1, Id2))
821  continue;
822  if (M.hasDst(Id2))
823  continue;
824  double Similarity = getJaccardSimilarity(M, Id1, Id2);
825  if (Similarity >= Options.MinSimilarity && Similarity > HighestSimilarity) {
826  HighestSimilarity = Similarity;
827  Candidate = Id2;
828  }
829  }
830  return Candidate;
831 }
832 
833 void ASTDiff::Impl::matchBottomUp(Mapping &M) const {
834  std::vector<NodeId> Postorder = getSubtreePostorder(T1, T1.getRootId());
835  for (NodeId Id1 : Postorder) {
836  if (Id1 == T1.getRootId() && !M.hasSrc(T1.getRootId()) &&
837  !M.hasDst(T2.getRootId())) {
838  if (isMatchingPossible(T1.getRootId(), T2.getRootId())) {
839  M.link(T1.getRootId(), T2.getRootId());
840  addOptimalMapping(M, T1.getRootId(), T2.getRootId());
841  }
842  break;
843  }
844  bool Matched = M.hasSrc(Id1);
845  const Node &N1 = T1.getNode(Id1);
846  bool MatchedChildren = llvm::any_of(
847  N1.Children, [&](NodeId Child) { return M.hasSrc(Child); });
848  if (Matched || !MatchedChildren)
849  continue;
850  NodeId Id2 = findCandidate(M, Id1);
851  if (Id2.isValid()) {
852  M.link(Id1, Id2);
853  addOptimalMapping(M, Id1, Id2);
854  }
855  }
856 }
857 
858 Mapping ASTDiff::Impl::matchTopDown() const {
859  PriorityList L1(T1);
860  PriorityList L2(T2);
861 
862  Mapping M(T1.getSize() + T2.getSize());
863 
864  L1.push(T1.getRootId());
865  L2.push(T2.getRootId());
866 
867  int Max1, Max2;
868  while (std::min(Max1 = L1.peekMax(), Max2 = L2.peekMax()) >
869  Options.MinHeight) {
870  if (Max1 > Max2) {
871  for (NodeId Id : L1.pop())
872  L1.open(Id);
873  continue;
874  }
875  if (Max2 > Max1) {
876  for (NodeId Id : L2.pop())
877  L2.open(Id);
878  continue;
879  }
880  std::vector<NodeId> H1, H2;
881  H1 = L1.pop();
882  H2 = L2.pop();
883  for (NodeId Id1 : H1) {
884  for (NodeId Id2 : H2) {
885  if (identical(Id1, Id2) && !M.hasSrc(Id1) && !M.hasDst(Id2)) {
886  for (int I = 0, E = T1.getNumberOfDescendants(Id1); I < E; ++I)
887  M.link(Id1 + I, Id2 + I);
888  }
889  }
890  }
891  for (NodeId Id1 : H1) {
892  if (!M.hasSrc(Id1))
893  L1.open(Id1);
894  }
895  for (NodeId Id2 : H2) {
896  if (!M.hasDst(Id2))
897  L2.open(Id2);
898  }
899  }
900  return M;
901 }
902 
904  const ComparisonOptions &Options)
905  : T1(T1), T2(T2), Options(Options) {
906  computeMapping();
908 }
909 
911  TheMapping = matchTopDown();
912  if (Options.StopAfterTopDown)
913  return;
914  matchBottomUp(TheMapping);
915 }
916 
918  for (NodeId Id1 : T1) {
919  if (!M.hasSrc(Id1)) {
920  T1.getMutableNode(Id1).Change = Delete;
921  T1.getMutableNode(Id1).Shift -= 1;
922  }
923  }
924  for (NodeId Id2 : T2) {
925  if (!M.hasDst(Id2)) {
926  T2.getMutableNode(Id2).Change = Insert;
927  T2.getMutableNode(Id2).Shift -= 1;
928  }
929  }
930  for (NodeId Id1 : T1.NodesBfs) {
931  NodeId Id2 = M.getDst(Id1);
932  if (Id2.isInvalid())
933  continue;
934  if (!haveSameParents(M, Id1, Id2) ||
935  T1.findPositionInParent(Id1, true) !=
936  T2.findPositionInParent(Id2, true)) {
937  T1.getMutableNode(Id1).Shift -= 1;
938  T2.getMutableNode(Id2).Shift -= 1;
939  }
940  }
941  for (NodeId Id2 : T2.NodesBfs) {
942  NodeId Id1 = M.getSrc(Id2);
943  if (Id1.isInvalid())
944  continue;
945  Node &N1 = T1.getMutableNode(Id1);
946  Node &N2 = T2.getMutableNode(Id2);
947  if (Id1.isInvalid())
948  continue;
949  if (!haveSameParents(M, Id1, Id2) ||
950  T1.findPositionInParent(Id1, true) !=
951  T2.findPositionInParent(Id2, true)) {
952  N1.Change = N2.Change = Move;
953  }
954  if (T1.getNodeValue(Id1) != T2.getNodeValue(Id2)) {
955  N1.Change = N2.Change = (N1.Change == Move ? UpdateMove : Update);
956  }
957  }
958 }
959 
961  const ComparisonOptions &Options)
962  : DiffImpl(std::make_unique<Impl>(*T1.TreeImpl, *T2.TreeImpl, Options)) {}
963 
964 ASTDiff::~ASTDiff() = default;
965 
966 NodeId ASTDiff::getMapped(const SyntaxTree &SourceTree, NodeId Id) const {
967  return DiffImpl->getMapped(SourceTree.TreeImpl, Id);
968 }
969 
971  : TreeImpl(std::make_unique<SyntaxTree::Impl>(
972  this, AST.getTranslationUnitDecl(), AST)) {}
973 
974 SyntaxTree::~SyntaxTree() = default;
975 
976 const ASTContext &SyntaxTree::getASTContext() const { return TreeImpl->AST; }
977 
979  return TreeImpl->getNode(Id);
980 }
981 
982 int SyntaxTree::getSize() const { return TreeImpl->getSize(); }
983 NodeId SyntaxTree::getRootId() const { return TreeImpl->getRootId(); }
985  return TreeImpl->begin();
986 }
988 
990  return TreeImpl->findPositionInParent(Id);
991 }
992 
993 std::pair<unsigned, unsigned>
995  const SourceManager &SrcMgr = TreeImpl->AST.getSourceManager();
996  SourceRange Range = N.ASTNode.getSourceRange();
997  SourceLocation BeginLoc = Range.getBegin();
999  Range.getEnd(), /*Offset=*/0, SrcMgr, TreeImpl->AST.getLangOpts());
1000  if (auto *ThisExpr = N.ASTNode.get<CXXThisExpr>()) {
1001  if (ThisExpr->isImplicit())
1002  EndLoc = BeginLoc;
1003  }
1004  unsigned Begin = SrcMgr.getFileOffset(SrcMgr.getExpansionLoc(BeginLoc));
1005  unsigned End = SrcMgr.getFileOffset(SrcMgr.getExpansionLoc(EndLoc));
1006  return {Begin, End};
1007 }
1008 
1010  return TreeImpl->getNodeValue(Id);
1011 }
1012 
1014  return TreeImpl->getNodeValue(N);
1015 }
1016 
1017 } // end namespace diff
1018 } // end namespace clang
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Represents the AST of a TranslationUnit.
Definition: ASTDiff.cpp:112
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Definition: ASTDiff.cpp:137
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Definition: SourceManager.h:1287
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Definition: SourceLocation.h:86
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__device__ int
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U
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Serialize the node attributes to a string representation.
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Definition: ASTDiff.cpp:447
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@ UpdateMove
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Definition: ASTDiff.cpp:519
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Definition: ASTDiff.h:40
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Definition: DeclBase.h:563
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Definition: ASTDiff.cpp:140
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@ Delete
Definition: ASTDiff.h:29
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Definition: ASTDiff.h:38
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Returns a DiagnosticConsumer that serializes diagnostics to a bitcode file.
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Definition: ASTDiff.cpp:60
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Definition: ASTDiff.cpp:124
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llvm::Optional< StringRef > getIdentifier() const
Definition: ASTDiff.cpp:699
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Definition: ASTDiffInternal.h:42
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LineState State
Definition: UnwrappedLineFormatter.cpp:987
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std::string getQualifiedNameAsString() const
Definition: Decl.cpp:1582
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Impl(SyntaxTree *Parent, std::enable_if_t< std::is_base_of< Stmt, T >::value, T > *Node, ASTContext &AST)
Definition: ASTDiff.cpp:119
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std::string getDeclValue(const Decl *D) const
Definition: ASTDiff.cpp:424
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unsigned AnonymousTagLocations
When printing an anonymous tag name, also print the location of that entity (e.g.,...
Definition: PrettyPrinter.h:175
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Definition: ASTDiff.cpp:917
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int getSize() const
Definition: ASTDiff.cpp:982
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Represents the this expression in C++.
Definition: ExprCXX.h:1142
std
Definition: Format.h:4125
ASTDiff.h
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Definition: ASTDiff.cpp:579
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Kind identifier.
Definition: ASTTypeTraits.h:51
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Nodes in preorder.
Definition: ASTDiff.cpp:133
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Definition: CalledOnceCheck.h:17
RecursiveASTVisitor.h
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Stmt - This represents one statement.
Definition: Stmt.h:69
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Definition: ASTDiff.cpp:139
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Represents a Clang AST node, alongside some additional information.
Definition: ASTDiff.h:37
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Definition: ASTDiff.h:42
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Definition: ASTDiff.cpp:339
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Return true if this is a valid SourceLocation object.
Definition: SourceLocation.h:110
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Definition: ASTDiff.cpp:984
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const Node & getNode(NodeId Id) const
Definition: ASTDiff.cpp:978
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Definition: ASTDiff.cpp:168
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Implementation of Zhang and Shasha's Algorithm for tree edit distance.
Definition: ASTDiff.cpp:559
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Definition: ASTDiff.cpp:59
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Definition: ASTDiff.cpp:192
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Definition: SourceManager.h:1158
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Definition: ASTDiff.cpp:131
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Definition: ASTDiff.cpp:193
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Computes the source location just past the end of the token at this source location.
Definition: Lexer.cpp:787
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Returns the postorder index of the leftmost descendant in the subtree.
Definition: ASTDiff.cpp:516
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Definition: ASTDiff.cpp:71
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Definition: ASTDiff.cpp:503
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Definition: ASTDiff.cpp:486
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Definition: ASTDiff.cpp:384
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Definition: ASTDiff.cpp:147
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Represents a C++ base or member initializer.
Definition: DeclCXX.h:2172
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@ Insert
Definition: ASTDiff.h:31
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Definition: ASTDiff.h:39
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Constructs a tree from a translation unit.
Definition: ASTDiff.cpp:970
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Definition: ASTDiff.cpp:281
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Definition: ASTDiff.h:38
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Definition: ASTDiff.cpp:483
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Definition: ASTDiff.h:46
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Definition: DeclBase.h:439
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Given a SourceLocation object, return the spelling location referenced by the ID.
Definition: SourceManager.h:1206