1 //===- ASTDiff.cpp - AST differencing implementation-----------*- C++ -*- -===//
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
7 //===----------------------------------------------------------------------===//
9 // This file contains definitons for the AST differencing interface.
11 //===----------------------------------------------------------------------===//
13 #include "clang/Tooling/ASTDiff/ASTDiff.h"
15 #include "clang/AST/RecursiveASTVisitor.h"
16 #include "clang/Lex/Lexer.h"
17 #include "llvm/ADT/PriorityQueue.h"
21 #include <unordered_set>
24 using namespace clang;
30 /// Maps nodes of the left tree to ones on the right, and vice versa.
34 Mapping(Mapping &&Other) = default;
35 Mapping &operator=(Mapping &&Other) = default;
37 Mapping(size_t Size) {
38 SrcToDst = std::make_unique<NodeId[]>(Size);
39 DstToSrc = std::make_unique<NodeId[]>(Size);
42 void link(NodeId Src, NodeId Dst) {
43 SrcToDst[Src] = Dst, DstToSrc[Dst] = Src;
46 NodeId getDst(NodeId Src) const { return SrcToDst[Src]; }
47 NodeId getSrc(NodeId Dst) const { return DstToSrc[Dst]; }
48 bool hasSrc(NodeId Src) const { return getDst(Src).isValid(); }
49 bool hasDst(NodeId Dst) const { return getSrc(Dst).isValid(); }
52 std::unique_ptr<NodeId[]> SrcToDst, DstToSrc;
54 } // end anonymous namespace
58 SyntaxTree::Impl &T1, &T2;
61 Impl(SyntaxTree::Impl &T1, SyntaxTree::Impl &T2,
62 const ComparisonOptions &Options);
64 /// Matches nodes one-by-one based on their similarity.
65 void computeMapping();
67 // Compute Change for each node based on similarity.
68 void computeChangeKinds(Mapping &M);
70 NodeId getMapped(const std::unique_ptr<SyntaxTree::Impl> &Tree,
73 return TheMapping.getDst(Id);
74 assert(&*Tree == &T2 && "Invalid tree.");
75 return TheMapping.getSrc(Id);
79 // Returns true if the two subtrees are identical.
80 bool identical(NodeId Id1, NodeId Id2) const;
82 // Returns false if the nodes must not be mached.
83 bool isMatchingPossible(NodeId Id1, NodeId Id2) const;
85 // Returns true if the nodes' parents are matched.
86 bool haveSameParents(const Mapping &M, NodeId Id1, NodeId Id2) const;
88 // Uses an optimal albeit slow algorithm to compute a mapping between two
89 // subtrees, but only if both have fewer nodes than MaxSize.
90 void addOptimalMapping(Mapping &M, NodeId Id1, NodeId Id2) const;
92 // Computes the ratio of common descendants between the two nodes.
93 // Descendants are only considered to be equal when they are mapped in M.
94 double getJaccardSimilarity(const Mapping &M, NodeId Id1, NodeId Id2) const;
96 // Returns the node that has the highest degree of similarity.
97 NodeId findCandidate(const Mapping &M, NodeId Id1) const;
99 // Returns a mapping of identical subtrees.
100 Mapping matchTopDown() const;
102 // Tries to match any yet unmapped nodes, in a bottom-up fashion.
103 void matchBottomUp(Mapping &M) const;
105 const ComparisonOptions &Options;
107 friend class ZhangShashaMatcher;
110 /// Represents the AST of a TranslationUnit.
111 class SyntaxTree::Impl {
113 Impl(SyntaxTree *Parent, ASTContext &AST);
114 /// Constructs a tree from an AST node.
115 Impl(SyntaxTree *Parent, Decl *N, ASTContext &AST);
116 Impl(SyntaxTree *Parent, Stmt *N, ASTContext &AST);
118 Impl(SyntaxTree *Parent,
119 typename std::enable_if<std::is_base_of<Stmt, T>::value, T>::type *Node,
121 : Impl(Parent, dyn_cast<Stmt>(Node), AST) {}
123 Impl(SyntaxTree *Parent,
124 typename std::enable_if<std::is_base_of<Decl, T>::value, T>::type *Node,
126 : Impl(Parent, dyn_cast<Decl>(Node), AST) {}
130 PrintingPolicy TypePP;
131 /// Nodes in preorder.
132 std::vector<Node> Nodes;
133 std::vector<NodeId> Leaves;
134 // Maps preorder indices to postorder ones.
135 std::vector<int> PostorderIds;
136 std::vector<NodeId> NodesBfs;
138 int getSize() const { return Nodes.size(); }
139 NodeId getRootId() const { return 0; }
140 PreorderIterator begin() const { return getRootId(); }
141 PreorderIterator end() const { return getSize(); }
143 const Node &getNode(NodeId Id) const { return Nodes[Id]; }
144 Node &getMutableNode(NodeId Id) { return Nodes[Id]; }
145 bool isValidNodeId(NodeId Id) const { return Id >= 0 && Id < getSize(); }
146 void addNode(Node &N) { Nodes.push_back(N); }
147 int getNumberOfDescendants(NodeId Id) const;
148 bool isInSubtree(NodeId Id, NodeId SubtreeRoot) const;
149 int findPositionInParent(NodeId Id, bool Shifted = false) const;
151 std::string getRelativeName(const NamedDecl *ND,
152 const DeclContext *Context) const;
153 std::string getRelativeName(const NamedDecl *ND) const;
155 std::string getNodeValue(NodeId Id) const;
156 std::string getNodeValue(const Node &Node) const;
157 std::string getDeclValue(const Decl *D) const;
158 std::string getStmtValue(const Stmt *S) const;
162 void setLeftMostDescendants();
165 static bool isSpecializedNodeExcluded(const Decl *D) { return D->isImplicit(); }
166 static bool isSpecializedNodeExcluded(const Stmt *S) { return false; }
167 static bool isSpecializedNodeExcluded(CXXCtorInitializer *I) {
168 return !I->isWritten();
172 static bool isNodeExcluded(const SourceManager &SrcMgr, T *N) {
175 SourceLocation SLoc = N->getSourceRange().getBegin();
176 if (SLoc.isValid()) {
177 // Ignore everything from other files.
178 if (!SrcMgr.isInMainFile(SLoc))
181 if (SLoc != SrcMgr.getSpellingLoc(SLoc))
184 return isSpecializedNodeExcluded(N);
188 // Sets Height, Parent and Children for each node.
189 struct PreorderVisitor : public RecursiveASTVisitor<PreorderVisitor> {
190 int Id = 0, Depth = 0;
192 SyntaxTree::Impl &Tree;
194 PreorderVisitor(SyntaxTree::Impl &Tree) : Tree(Tree) {}
196 template <class T> std::tuple<NodeId, NodeId> PreTraverse(T *ASTNode) {
198 Tree.Nodes.emplace_back();
199 Node &N = Tree.getMutableNode(MyId);
202 N.ASTNode = DynTypedNode::create(*ASTNode);
203 assert(!N.ASTNode.getNodeKind().isNone() &&
204 "Expected nodes to have a valid kind.");
205 if (Parent.isValid()) {
206 Node &P = Tree.getMutableNode(Parent);
207 P.Children.push_back(MyId);
212 return std::make_tuple(MyId, Tree.getNode(MyId).Parent);
214 void PostTraverse(std::tuple<NodeId, NodeId> State) {
215 NodeId MyId, PreviousParent;
216 std::tie(MyId, PreviousParent) = State;
217 assert(MyId.isValid() && "Expecting to only traverse valid nodes.");
218 Parent = PreviousParent;
220 Node &N = Tree.getMutableNode(MyId);
221 N.RightMostDescendant = Id - 1;
222 assert(N.RightMostDescendant >= 0 &&
223 N.RightMostDescendant < Tree.getSize() &&
224 "Rightmost descendant must be a valid tree node.");
226 Tree.Leaves.push_back(MyId);
228 for (NodeId Child : N.Children)
229 N.Height = std::max(N.Height, 1 + Tree.getNode(Child).Height);
231 bool TraverseDecl(Decl *D) {
232 if (isNodeExcluded(Tree.AST.getSourceManager(), D))
234 auto SavedState = PreTraverse(D);
235 RecursiveASTVisitor<PreorderVisitor>::TraverseDecl(D);
236 PostTraverse(SavedState);
239 bool TraverseStmt(Stmt *S) {
240 if (auto *E = dyn_cast_or_null<Expr>(S))
241 S = E->IgnoreImplicit();
242 if (isNodeExcluded(Tree.AST.getSourceManager(), S))
244 auto SavedState = PreTraverse(S);
245 RecursiveASTVisitor<PreorderVisitor>::TraverseStmt(S);
246 PostTraverse(SavedState);
249 bool TraverseType(QualType T) { return true; }
250 bool TraverseConstructorInitializer(CXXCtorInitializer *Init) {
251 if (isNodeExcluded(Tree.AST.getSourceManager(), Init))
253 auto SavedState = PreTraverse(Init);
254 RecursiveASTVisitor<PreorderVisitor>::TraverseConstructorInitializer(Init);
255 PostTraverse(SavedState);
259 } // end anonymous namespace
261 SyntaxTree::Impl::Impl(SyntaxTree *Parent, ASTContext &AST)
262 : Parent(Parent), AST(AST), TypePP(AST.getLangOpts()) {
263 TypePP.AnonymousTagLocations = false;
266 SyntaxTree::Impl::Impl(SyntaxTree *Parent, Decl *N, ASTContext &AST)
267 : Impl(Parent, AST) {
268 PreorderVisitor PreorderWalker(*this);
269 PreorderWalker.TraverseDecl(N);
273 SyntaxTree::Impl::Impl(SyntaxTree *Parent, Stmt *N, ASTContext &AST)
274 : Impl(Parent, AST) {
275 PreorderVisitor PreorderWalker(*this);
276 PreorderWalker.TraverseStmt(N);
280 static std::vector<NodeId> getSubtreePostorder(const SyntaxTree::Impl &Tree,
282 std::vector<NodeId> Postorder;
283 std::function<void(NodeId)> Traverse = [&](NodeId Id) {
284 const Node &N = Tree.getNode(Id);
285 for (NodeId Child : N.Children)
287 Postorder.push_back(Id);
293 static std::vector<NodeId> getSubtreeBfs(const SyntaxTree::Impl &Tree,
295 std::vector<NodeId> Ids;
298 while (Expanded < Ids.size())
299 for (NodeId Child : Tree.getNode(Ids[Expanded++]).Children)
300 Ids.push_back(Child);
304 void SyntaxTree::Impl::initTree() {
305 setLeftMostDescendants();
307 PostorderIds.resize(getSize());
308 std::function<void(NodeId)> PostorderTraverse = [&](NodeId Id) {
309 for (NodeId Child : getNode(Id).Children)
310 PostorderTraverse(Child);
311 PostorderIds[Id] = PostorderId;
314 PostorderTraverse(getRootId());
315 NodesBfs = getSubtreeBfs(*this, getRootId());
318 void SyntaxTree::Impl::setLeftMostDescendants() {
319 for (NodeId Leaf : Leaves) {
320 getMutableNode(Leaf).LeftMostDescendant = Leaf;
321 NodeId Parent, Cur = Leaf;
322 while ((Parent = getNode(Cur).Parent).isValid() &&
323 getNode(Parent).Children[0] == Cur) {
325 getMutableNode(Cur).LeftMostDescendant = Leaf;
330 int SyntaxTree::Impl::getNumberOfDescendants(NodeId Id) const {
331 return getNode(Id).RightMostDescendant - Id + 1;
334 bool SyntaxTree::Impl::isInSubtree(NodeId Id, NodeId SubtreeRoot) const {
335 return Id >= SubtreeRoot && Id <= getNode(SubtreeRoot).RightMostDescendant;
338 int SyntaxTree::Impl::findPositionInParent(NodeId Id, bool Shifted) const {
339 NodeId Parent = getNode(Id).Parent;
340 if (Parent.isInvalid())
342 const auto &Siblings = getNode(Parent).Children;
344 for (size_t I = 0, E = Siblings.size(); I < E; ++I) {
346 Position += getNode(Siblings[I]).Shift;
347 if (Siblings[I] == Id) {
352 llvm_unreachable("Node not found in parent's children.");
355 // Returns the qualified name of ND. If it is subordinate to Context,
356 // then the prefix of the latter is removed from the returned value.
358 SyntaxTree::Impl::getRelativeName(const NamedDecl *ND,
359 const DeclContext *Context) const {
360 std::string Val = ND->getQualifiedNameAsString();
361 std::string ContextPrefix;
364 if (auto *Namespace = dyn_cast<NamespaceDecl>(Context))
365 ContextPrefix = Namespace->getQualifiedNameAsString();
366 else if (auto *Record = dyn_cast<RecordDecl>(Context))
367 ContextPrefix = Record->getQualifiedNameAsString();
368 else if (AST.getLangOpts().CPlusPlus11)
369 if (auto *Tag = dyn_cast<TagDecl>(Context))
370 ContextPrefix = Tag->getQualifiedNameAsString();
371 // Strip the qualifier, if Val refers to something in the current scope.
372 // But leave one leading ':' in place, so that we know that this is a
374 if (!ContextPrefix.empty() && StringRef(Val).startswith(ContextPrefix))
375 Val = Val.substr(ContextPrefix.size() + 1);
379 std::string SyntaxTree::Impl::getRelativeName(const NamedDecl *ND) const {
380 return getRelativeName(ND, ND->getDeclContext());
383 static const DeclContext *getEnclosingDeclContext(ASTContext &AST,
386 const auto &Parents = AST.getParents(*S);
389 const auto &P = Parents[0];
390 if (const auto *D = P.get<Decl>())
391 return D->getDeclContext();
397 static std::string getInitializerValue(const CXXCtorInitializer *Init,
398 const PrintingPolicy &TypePP) {
399 if (Init->isAnyMemberInitializer())
400 return Init->getAnyMember()->getName();
401 if (Init->isBaseInitializer())
402 return QualType(Init->getBaseClass(), 0).getAsString(TypePP);
403 if (Init->isDelegatingInitializer())
404 return Init->getTypeSourceInfo()->getType().getAsString(TypePP);
405 llvm_unreachable("Unknown initializer type");
408 std::string SyntaxTree::Impl::getNodeValue(NodeId Id) const {
409 return getNodeValue(getNode(Id));
412 std::string SyntaxTree::Impl::getNodeValue(const Node &N) const {
413 const DynTypedNode &DTN = N.ASTNode;
414 if (auto *S = DTN.get<Stmt>())
415 return getStmtValue(S);
416 if (auto *D = DTN.get<Decl>())
417 return getDeclValue(D);
418 if (auto *Init = DTN.get<CXXCtorInitializer>())
419 return getInitializerValue(Init, TypePP);
420 llvm_unreachable("Fatal: unhandled AST node.\n");
423 std::string SyntaxTree::Impl::getDeclValue(const Decl *D) const {
425 if (auto *V = dyn_cast<ValueDecl>(D))
426 return getRelativeName(V) + "(" + V->getType().getAsString(TypePP) + ")";
427 if (auto *N = dyn_cast<NamedDecl>(D))
428 Value += getRelativeName(N) + ";";
429 if (auto *T = dyn_cast<TypedefNameDecl>(D))
430 return Value + T->getUnderlyingType().getAsString(TypePP) + ";";
431 if (auto *T = dyn_cast<TypeDecl>(D))
432 if (T->getTypeForDecl())
434 T->getTypeForDecl()->getCanonicalTypeInternal().getAsString(TypePP) +
436 if (auto *U = dyn_cast<UsingDirectiveDecl>(D))
437 return U->getNominatedNamespace()->getName();
438 if (auto *A = dyn_cast<AccessSpecDecl>(D)) {
439 CharSourceRange Range(A->getSourceRange(), false);
440 return Lexer::getSourceText(Range, AST.getSourceManager(),
446 std::string SyntaxTree::Impl::getStmtValue(const Stmt *S) const {
447 if (auto *U = dyn_cast<UnaryOperator>(S))
448 return UnaryOperator::getOpcodeStr(U->getOpcode());
449 if (auto *B = dyn_cast<BinaryOperator>(S))
450 return B->getOpcodeStr();
451 if (auto *M = dyn_cast<MemberExpr>(S))
452 return getRelativeName(M->getMemberDecl());
453 if (auto *I = dyn_cast<IntegerLiteral>(S)) {
454 SmallString<256> Str;
455 I->getValue().toString(Str, /*Radix=*/10, /*Signed=*/false);
458 if (auto *F = dyn_cast<FloatingLiteral>(S)) {
459 SmallString<256> Str;
460 F->getValue().toString(Str);
463 if (auto *D = dyn_cast<DeclRefExpr>(S))
464 return getRelativeName(D->getDecl(), getEnclosingDeclContext(AST, S));
465 if (auto *String = dyn_cast<StringLiteral>(S))
466 return String->getString();
467 if (auto *B = dyn_cast<CXXBoolLiteralExpr>(S))
468 return B->getValue() ? "true" : "false";
472 /// Identifies a node in a subtree by its postorder offset, starting at 1.
476 explicit SNodeId(int Id) : Id(Id) {}
477 explicit SNodeId() = default;
479 operator int() const { return Id; }
480 SNodeId &operator++() { return ++Id, *this; }
481 SNodeId &operator--() { return --Id, *this; }
482 SNodeId operator+(int Other) const { return SNodeId(Id + Other); }
488 const SyntaxTree::Impl &Tree;
489 /// Maps SNodeIds to original ids.
490 std::vector<NodeId> RootIds;
491 /// Maps subtree nodes to their leftmost descendants wtihin the subtree.
492 std::vector<SNodeId> LeftMostDescendants;
495 std::vector<SNodeId> KeyRoots;
497 Subtree(const SyntaxTree::Impl &Tree, NodeId SubtreeRoot) : Tree(Tree) {
498 RootIds = getSubtreePostorder(Tree, SubtreeRoot);
499 int NumLeaves = setLeftMostDescendants();
500 computeKeyRoots(NumLeaves);
502 int getSize() const { return RootIds.size(); }
503 NodeId getIdInRoot(SNodeId Id) const {
504 assert(Id > 0 && Id <= getSize() && "Invalid subtree node index.");
505 return RootIds[Id - 1];
507 const Node &getNode(SNodeId Id) const {
508 return Tree.getNode(getIdInRoot(Id));
510 SNodeId getLeftMostDescendant(SNodeId Id) const {
511 assert(Id > 0 && Id <= getSize() && "Invalid subtree node index.");
512 return LeftMostDescendants[Id - 1];
514 /// Returns the postorder index of the leftmost descendant in the subtree.
515 NodeId getPostorderOffset() const {
516 return Tree.PostorderIds[getIdInRoot(SNodeId(1))];
518 std::string getNodeValue(SNodeId Id) const {
519 return Tree.getNodeValue(getIdInRoot(Id));
523 /// Returns the number of leafs in the subtree.
524 int setLeftMostDescendants() {
526 LeftMostDescendants.resize(getSize());
527 for (int I = 0; I < getSize(); ++I) {
529 const Node &N = getNode(SI);
530 NumLeaves += N.isLeaf();
531 assert(I == Tree.PostorderIds[getIdInRoot(SI)] - getPostorderOffset() &&
532 "Postorder traversal in subtree should correspond to traversal in "
533 "the root tree by a constant offset.");
534 LeftMostDescendants[I] = SNodeId(Tree.PostorderIds[N.LeftMostDescendant] -
535 getPostorderOffset());
539 void computeKeyRoots(int Leaves) {
540 KeyRoots.resize(Leaves);
541 std::unordered_set<int> Visited;
543 for (SNodeId I(getSize()); I > 0; --I) {
544 SNodeId LeftDesc = getLeftMostDescendant(I);
545 if (Visited.count(LeftDesc))
547 assert(K >= 0 && "K should be non-negative");
549 Visited.insert(LeftDesc);
555 /// Implementation of Zhang and Shasha's Algorithm for tree edit distance.
556 /// Computes an optimal mapping between two trees using only insertion,
557 /// deletion and update as edit actions (similar to the Levenshtein distance).
558 class ZhangShashaMatcher {
559 const ASTDiff::Impl &DiffImpl;
562 std::unique_ptr<std::unique_ptr<double[]>[]> TreeDist, ForestDist;
565 ZhangShashaMatcher(const ASTDiff::Impl &DiffImpl, const SyntaxTree::Impl &T1,
566 const SyntaxTree::Impl &T2, NodeId Id1, NodeId Id2)
567 : DiffImpl(DiffImpl), S1(T1, Id1), S2(T2, Id2) {
568 TreeDist = std::make_unique<std::unique_ptr<double[]>[]>(
569 size_t(S1.getSize()) + 1);
570 ForestDist = std::make_unique<std::unique_ptr<double[]>[]>(
571 size_t(S1.getSize()) + 1);
572 for (int I = 0, E = S1.getSize() + 1; I < E; ++I) {
573 TreeDist[I] = std::make_unique<double[]>(size_t(S2.getSize()) + 1);
574 ForestDist[I] = std::make_unique<double[]>(size_t(S2.getSize()) + 1);
578 std::vector<std::pair<NodeId, NodeId>> getMatchingNodes() {
579 std::vector<std::pair<NodeId, NodeId>> Matches;
580 std::vector<std::pair<SNodeId, SNodeId>> TreePairs;
584 bool RootNodePair = true;
586 TreePairs.emplace_back(SNodeId(S1.getSize()), SNodeId(S2.getSize()));
588 while (!TreePairs.empty()) {
589 SNodeId LastRow, LastCol, FirstRow, FirstCol, Row, Col;
590 std::tie(LastRow, LastCol) = TreePairs.back();
591 TreePairs.pop_back();
594 computeForestDist(LastRow, LastCol);
597 RootNodePair = false;
599 FirstRow = S1.getLeftMostDescendant(LastRow);
600 FirstCol = S2.getLeftMostDescendant(LastCol);
605 while (Row > FirstRow || Col > FirstCol) {
606 if (Row > FirstRow &&
607 ForestDist[Row - 1][Col] + 1 == ForestDist[Row][Col]) {
609 } else if (Col > FirstCol &&
610 ForestDist[Row][Col - 1] + 1 == ForestDist[Row][Col]) {
613 SNodeId LMD1 = S1.getLeftMostDescendant(Row);
614 SNodeId LMD2 = S2.getLeftMostDescendant(Col);
615 if (LMD1 == S1.getLeftMostDescendant(LastRow) &&
616 LMD2 == S2.getLeftMostDescendant(LastCol)) {
617 NodeId Id1 = S1.getIdInRoot(Row);
618 NodeId Id2 = S2.getIdInRoot(Col);
619 assert(DiffImpl.isMatchingPossible(Id1, Id2) &&
620 "These nodes must not be matched.");
621 Matches.emplace_back(Id1, Id2);
625 TreePairs.emplace_back(Row, Col);
636 /// We use a simple cost model for edit actions, which seems good enough.
637 /// Simple cost model for edit actions. This seems to make the matching
638 /// algorithm perform reasonably well.
639 /// The values range between 0 and 1, or infinity if this edit action should
640 /// always be avoided.
641 static constexpr double DeletionCost = 1;
642 static constexpr double InsertionCost = 1;
644 double getUpdateCost(SNodeId Id1, SNodeId Id2) {
645 if (!DiffImpl.isMatchingPossible(S1.getIdInRoot(Id1), S2.getIdInRoot(Id2)))
646 return std::numeric_limits<double>::max();
647 return S1.getNodeValue(Id1) != S2.getNodeValue(Id2);
650 void computeTreeDist() {
651 for (SNodeId Id1 : S1.KeyRoots)
652 for (SNodeId Id2 : S2.KeyRoots)
653 computeForestDist(Id1, Id2);
656 void computeForestDist(SNodeId Id1, SNodeId Id2) {
657 assert(Id1 > 0 && Id2 > 0 && "Expecting offsets greater than 0.");
658 SNodeId LMD1 = S1.getLeftMostDescendant(Id1);
659 SNodeId LMD2 = S2.getLeftMostDescendant(Id2);
661 ForestDist[LMD1][LMD2] = 0;
662 for (SNodeId D1 = LMD1 + 1; D1 <= Id1; ++D1) {
663 ForestDist[D1][LMD2] = ForestDist[D1 - 1][LMD2] + DeletionCost;
664 for (SNodeId D2 = LMD2 + 1; D2 <= Id2; ++D2) {
665 ForestDist[LMD1][D2] = ForestDist[LMD1][D2 - 1] + InsertionCost;
666 SNodeId DLMD1 = S1.getLeftMostDescendant(D1);
667 SNodeId DLMD2 = S2.getLeftMostDescendant(D2);
668 if (DLMD1 == LMD1 && DLMD2 == LMD2) {
669 double UpdateCost = getUpdateCost(D1, D2);
671 std::min({ForestDist[D1 - 1][D2] + DeletionCost,
672 ForestDist[D1][D2 - 1] + InsertionCost,
673 ForestDist[D1 - 1][D2 - 1] + UpdateCost});
674 TreeDist[D1][D2] = ForestDist[D1][D2];
677 std::min({ForestDist[D1 - 1][D2] + DeletionCost,
678 ForestDist[D1][D2 - 1] + InsertionCost,
679 ForestDist[DLMD1][DLMD2] + TreeDist[D1][D2]});
686 ast_type_traits::ASTNodeKind Node::getType() const {
687 return ASTNode.getNodeKind();
690 StringRef Node::getTypeLabel() const { return getType().asStringRef(); }
692 llvm::Optional<std::string> Node::getQualifiedIdentifier() const {
693 if (auto *ND = ASTNode.get<NamedDecl>()) {
694 if (ND->getDeclName().isIdentifier())
695 return ND->getQualifiedNameAsString();
700 llvm::Optional<StringRef> Node::getIdentifier() const {
701 if (auto *ND = ASTNode.get<NamedDecl>()) {
702 if (ND->getDeclName().isIdentifier())
703 return ND->getName();
709 // Compares nodes by their depth.
711 const SyntaxTree::Impl &Tree;
712 HeightLess(const SyntaxTree::Impl &Tree) : Tree(Tree) {}
713 bool operator()(NodeId Id1, NodeId Id2) const {
714 return Tree.getNode(Id1).Height < Tree.getNode(Id2).Height;
717 } // end anonymous namespace
720 // Priority queue for nodes, sorted descendingly by their height.
722 const SyntaxTree::Impl &Tree;
724 std::vector<NodeId> Container;
725 PriorityQueue<NodeId, std::vector<NodeId>, HeightLess> List;
728 PriorityList(const SyntaxTree::Impl &Tree)
729 : Tree(Tree), Cmp(Tree), List(Cmp, Container) {}
731 void push(NodeId id) { List.push(id); }
733 std::vector<NodeId> pop() {
735 std::vector<NodeId> Result;
738 while (peekMax() == Max) {
739 Result.push_back(List.top());
742 // TODO this is here to get a stable output, not a good heuristic
746 int peekMax() const {
749 return Tree.getNode(List.top()).Height;
751 void open(NodeId Id) {
752 for (NodeId Child : Tree.getNode(Id).Children)
756 } // end anonymous namespace
758 bool ASTDiff::Impl::identical(NodeId Id1, NodeId Id2) const {
759 const Node &N1 = T1.getNode(Id1);
760 const Node &N2 = T2.getNode(Id2);
761 if (N1.Children.size() != N2.Children.size() ||
762 !isMatchingPossible(Id1, Id2) ||
763 T1.getNodeValue(Id1) != T2.getNodeValue(Id2))
765 for (size_t Id = 0, E = N1.Children.size(); Id < E; ++Id)
766 if (!identical(N1.Children[Id], N2.Children[Id]))
771 bool ASTDiff::Impl::isMatchingPossible(NodeId Id1, NodeId Id2) const {
772 return Options.isMatchingAllowed(T1.getNode(Id1), T2.getNode(Id2));
775 bool ASTDiff::Impl::haveSameParents(const Mapping &M, NodeId Id1,
777 NodeId P1 = T1.getNode(Id1).Parent;
778 NodeId P2 = T2.getNode(Id2).Parent;
779 return (P1.isInvalid() && P2.isInvalid()) ||
780 (P1.isValid() && P2.isValid() && M.getDst(P1) == P2);
783 void ASTDiff::Impl::addOptimalMapping(Mapping &M, NodeId Id1,
785 if (std::max(T1.getNumberOfDescendants(Id1), T2.getNumberOfDescendants(Id2)) >
788 ZhangShashaMatcher Matcher(*this, T1, T2, Id1, Id2);
789 std::vector<std::pair<NodeId, NodeId>> R = Matcher.getMatchingNodes();
790 for (const auto Tuple : R) {
791 NodeId Src = Tuple.first;
792 NodeId Dst = Tuple.second;
793 if (!M.hasSrc(Src) && !M.hasDst(Dst))
798 double ASTDiff::Impl::getJaccardSimilarity(const Mapping &M, NodeId Id1,
800 int CommonDescendants = 0;
801 const Node &N1 = T1.getNode(Id1);
802 // Count the common descendants, excluding the subtree root.
803 for (NodeId Src = Id1 + 1; Src <= N1.RightMostDescendant; ++Src) {
804 NodeId Dst = M.getDst(Src);
805 CommonDescendants += int(Dst.isValid() && T2.isInSubtree(Dst, Id2));
807 // We need to subtract 1 to get the number of descendants excluding the root.
808 double Denominator = T1.getNumberOfDescendants(Id1) - 1 +
809 T2.getNumberOfDescendants(Id2) - 1 - CommonDescendants;
810 // CommonDescendants is less than the size of one subtree.
811 assert(Denominator >= 0 && "Expected non-negative denominator.");
812 if (Denominator == 0)
814 return CommonDescendants / Denominator;
817 NodeId ASTDiff::Impl::findCandidate(const Mapping &M, NodeId Id1) const {
819 double HighestSimilarity = 0.0;
820 for (NodeId Id2 : T2) {
821 if (!isMatchingPossible(Id1, Id2))
825 double Similarity = getJaccardSimilarity(M, Id1, Id2);
826 if (Similarity >= Options.MinSimilarity && Similarity > HighestSimilarity) {
827 HighestSimilarity = Similarity;
834 void ASTDiff::Impl::matchBottomUp(Mapping &M) const {
835 std::vector<NodeId> Postorder = getSubtreePostorder(T1, T1.getRootId());
836 for (NodeId Id1 : Postorder) {
837 if (Id1 == T1.getRootId() && !M.hasSrc(T1.getRootId()) &&
838 !M.hasDst(T2.getRootId())) {
839 if (isMatchingPossible(T1.getRootId(), T2.getRootId())) {
840 M.link(T1.getRootId(), T2.getRootId());
841 addOptimalMapping(M, T1.getRootId(), T2.getRootId());
845 bool Matched = M.hasSrc(Id1);
846 const Node &N1 = T1.getNode(Id1);
847 bool MatchedChildren = llvm::any_of(
848 N1.Children, [&](NodeId Child) { return M.hasSrc(Child); });
849 if (Matched || !MatchedChildren)
851 NodeId Id2 = findCandidate(M, Id1);
854 addOptimalMapping(M, Id1, Id2);
859 Mapping ASTDiff::Impl::matchTopDown() const {
863 Mapping M(T1.getSize() + T2.getSize());
865 L1.push(T1.getRootId());
866 L2.push(T2.getRootId());
869 while (std::min(Max1 = L1.peekMax(), Max2 = L2.peekMax()) >
872 for (NodeId Id : L1.pop())
877 for (NodeId Id : L2.pop())
881 std::vector<NodeId> H1, H2;
884 for (NodeId Id1 : H1) {
885 for (NodeId Id2 : H2) {
886 if (identical(Id1, Id2) && !M.hasSrc(Id1) && !M.hasDst(Id2)) {
887 for (int I = 0, E = T1.getNumberOfDescendants(Id1); I < E; ++I)
888 M.link(Id1 + I, Id2 + I);
892 for (NodeId Id1 : H1) {
896 for (NodeId Id2 : H2) {
904 ASTDiff::Impl::Impl(SyntaxTree::Impl &T1, SyntaxTree::Impl &T2,
905 const ComparisonOptions &Options)
906 : T1(T1), T2(T2), Options(Options) {
908 computeChangeKinds(TheMapping);
911 void ASTDiff::Impl::computeMapping() {
912 TheMapping = matchTopDown();
913 if (Options.StopAfterTopDown)
915 matchBottomUp(TheMapping);
918 void ASTDiff::Impl::computeChangeKinds(Mapping &M) {
919 for (NodeId Id1 : T1) {
920 if (!M.hasSrc(Id1)) {
921 T1.getMutableNode(Id1).Change = Delete;
922 T1.getMutableNode(Id1).Shift -= 1;
925 for (NodeId Id2 : T2) {
926 if (!M.hasDst(Id2)) {
927 T2.getMutableNode(Id2).Change = Insert;
928 T2.getMutableNode(Id2).Shift -= 1;
931 for (NodeId Id1 : T1.NodesBfs) {
932 NodeId Id2 = M.getDst(Id1);
935 if (!haveSameParents(M, Id1, Id2) ||
936 T1.findPositionInParent(Id1, true) !=
937 T2.findPositionInParent(Id2, true)) {
938 T1.getMutableNode(Id1).Shift -= 1;
939 T2.getMutableNode(Id2).Shift -= 1;
942 for (NodeId Id2 : T2.NodesBfs) {
943 NodeId Id1 = M.getSrc(Id2);
946 Node &N1 = T1.getMutableNode(Id1);
947 Node &N2 = T2.getMutableNode(Id2);
950 if (!haveSameParents(M, Id1, Id2) ||
951 T1.findPositionInParent(Id1, true) !=
952 T2.findPositionInParent(Id2, true)) {
953 N1.Change = N2.Change = Move;
955 if (T1.getNodeValue(Id1) != T2.getNodeValue(Id2)) {
956 N1.Change = N2.Change = (N1.Change == Move ? UpdateMove : Update);
961 ASTDiff::ASTDiff(SyntaxTree &T1, SyntaxTree &T2,
962 const ComparisonOptions &Options)
963 : DiffImpl(std::make_unique<Impl>(*T1.TreeImpl, *T2.TreeImpl, Options)) {}
965 ASTDiff::~ASTDiff() = default;
967 NodeId ASTDiff::getMapped(const SyntaxTree &SourceTree, NodeId Id) const {
968 return DiffImpl->getMapped(SourceTree.TreeImpl, Id);
971 SyntaxTree::SyntaxTree(ASTContext &AST)
972 : TreeImpl(std::make_unique<SyntaxTree::Impl>(
973 this, AST.getTranslationUnitDecl(), AST)) {}
975 SyntaxTree::~SyntaxTree() = default;
977 const ASTContext &SyntaxTree::getASTContext() const { return TreeImpl->AST; }
979 const Node &SyntaxTree::getNode(NodeId Id) const {
980 return TreeImpl->getNode(Id);
983 int SyntaxTree::getSize() const { return TreeImpl->getSize(); }
984 NodeId SyntaxTree::getRootId() const { return TreeImpl->getRootId(); }
985 SyntaxTree::PreorderIterator SyntaxTree::begin() const {
986 return TreeImpl->begin();
988 SyntaxTree::PreorderIterator SyntaxTree::end() const { return TreeImpl->end(); }
990 int SyntaxTree::findPositionInParent(NodeId Id) const {
991 return TreeImpl->findPositionInParent(Id);
994 std::pair<unsigned, unsigned>
995 SyntaxTree::getSourceRangeOffsets(const Node &N) const {
996 const SourceManager &SrcMgr = TreeImpl->AST.getSourceManager();
997 SourceRange Range = N.ASTNode.getSourceRange();
998 SourceLocation BeginLoc = Range.getBegin();
999 SourceLocation EndLoc = Lexer::getLocForEndOfToken(
1000 Range.getEnd(), /*Offset=*/0, SrcMgr, TreeImpl->AST.getLangOpts());
1001 if (auto *ThisExpr = N.ASTNode.get<CXXThisExpr>()) {
1002 if (ThisExpr->isImplicit())
1005 unsigned Begin = SrcMgr.getFileOffset(SrcMgr.getExpansionLoc(BeginLoc));
1006 unsigned End = SrcMgr.getFileOffset(SrcMgr.getExpansionLoc(EndLoc));
1007 return {Begin, End};
1010 std::string SyntaxTree::getNodeValue(NodeId Id) const {
1011 return TreeImpl->getNodeValue(Id);
1014 std::string SyntaxTree::getNodeValue(const Node &N) const {
1015 return TreeImpl->getNodeValue(N);
1018 } // end namespace diff
1019 } // end namespace clang