//===- ASTDiff.cpp - AST differencing implementation-----------*- C++ -*- -===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// 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 = llvm::make_unique<NodeId[]>(Size);
DstToSrc = llvm::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 (S)
S = S->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 = llvm::make_unique<std::unique_ptr<double[]>[]>(
size_t(S1.getSize()) + 1);
ForestDist = llvm::make_unique<std::unique_ptr<double[]>[]>(
size_t(S1.getSize()) + 1);
for (int I = 0, E = S1.getSize() + 1; I < E; ++I) {
TreeDist[I] = llvm::make_unique<double[]>(size_t(S2.getSize()) + 1);
ForestDist[I] = llvm::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(llvm::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(llvm::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
