r299653 - [analyzer] Reland r299544 "Add a modular constraint system to the CloneDetector"

Artem Dergachev via cfe-commits cfe-commits at lists.llvm.org
Thu Apr 6 07:34:07 PDT 2017


Author: dergachev
Date: Thu Apr  6 09:34:07 2017
New Revision: 299653

URL: http://llvm.org/viewvc/llvm-project?rev=299653&view=rev
Log:
[analyzer] Reland r299544 "Add a modular constraint system to the CloneDetector"

Hopefully fix crashes by unshadowing the variable.


Original commit message:

A big part of the clone detection code is functionality for filtering clones and
clone groups based on different criteria. So far this filtering process was
hardcoded into the CloneDetector class, which made it hard to understand and,
ultimately, to extend.

This patch splits the CloneDetector's logic into a sequence of reusable
constraints that are used for filtering clone groups. These constraints
can be turned on and off and reodreder at will, and new constraints are easy
to implement if necessary.

Unit tests are added for the new constraint interface.

This is a refactoring patch - no functional change intended.

Patch by Raphael Isemann!

Differential Revision: https://reviews.llvm.org/D23418

Added:
    cfe/trunk/unittests/Analysis/CloneDetectionTest.cpp
Modified:
    cfe/trunk/include/clang/Analysis/CloneDetection.h
    cfe/trunk/lib/Analysis/CloneDetection.cpp
    cfe/trunk/lib/StaticAnalyzer/Checkers/CloneChecker.cpp
    cfe/trunk/unittests/Analysis/CMakeLists.txt

Modified: cfe/trunk/include/clang/Analysis/CloneDetection.h
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Analysis/CloneDetection.h?rev=299653&r1=299652&r2=299653&view=diff
==============================================================================
--- cfe/trunk/include/clang/Analysis/CloneDetection.h (original)
+++ cfe/trunk/include/clang/Analysis/CloneDetection.h Thu Apr  6 09:34:07 2017
@@ -16,9 +16,7 @@
 #define LLVM_CLANG_AST_CLONEDETECTION_H
 
 #include "clang/Basic/SourceLocation.h"
-#include "llvm/ADT/Hashing.h"
-#include "llvm/ADT/StringMap.h"
-
+#include "llvm/ADT/SmallVector.h"
 #include <vector>
 
 namespace clang {
@@ -29,7 +27,7 @@ class VarDecl;
 class ASTContext;
 class CompoundStmt;
 
-/// \brief Identifies a list of statements.
+/// Identifies a list of statements.
 ///
 /// Can either identify a single arbitrary Stmt object, a continuous sequence of
 /// child statements inside a CompoundStmt or no statements at all.
@@ -39,8 +37,8 @@ class StmtSequence {
   /// Stmt, then S is a pointer to this Stmt.
   const Stmt *S;
 
-  /// The related ASTContext for S.
-  ASTContext *Context;
+  /// The declaration that contains the statements.
+  const Decl *D;
 
   /// If EndIndex is non-zero, then S is a CompoundStmt and this StmtSequence
   /// instance is representing the CompoundStmt children inside the array
@@ -49,7 +47,7 @@ class StmtSequence {
   unsigned EndIndex;
 
 public:
-  /// \brief Constructs a StmtSequence holding multiple statements.
+  /// Constructs a StmtSequence holding multiple statements.
   ///
   /// The resulting StmtSequence identifies a continuous sequence of statements
   /// in the body of the given CompoundStmt. Which statements of the body should
@@ -57,20 +55,20 @@ public:
   /// that describe a non-empty sub-array in the body of the given CompoundStmt.
   ///
   /// \param Stmt A CompoundStmt that contains all statements in its body.
-  /// \param Context The ASTContext for the given CompoundStmt.
+  /// \param Decl The Decl containing this Stmt.
   /// \param StartIndex The inclusive start index in the children array of
   ///                   \p Stmt
   /// \param EndIndex The exclusive end index in the children array of \p Stmt.
-  StmtSequence(const CompoundStmt *Stmt, ASTContext &Context,
-               unsigned StartIndex, unsigned EndIndex);
+  StmtSequence(const CompoundStmt *Stmt, const Decl *D, unsigned StartIndex,
+               unsigned EndIndex);
 
-  /// \brief Constructs a StmtSequence holding a single statement.
+  /// Constructs a StmtSequence holding a single statement.
   ///
   /// \param Stmt An arbitrary Stmt.
-  /// \param Context The ASTContext for the given Stmt.
-  StmtSequence(const Stmt *Stmt, ASTContext &Context);
+  /// \param Decl The Decl containing this Stmt.
+  StmtSequence(const Stmt *Stmt, const Decl *D);
 
-  /// \brief Constructs an empty StmtSequence.
+  /// Constructs an empty StmtSequence.
   StmtSequence();
 
   typedef const Stmt *const *iterator;
@@ -110,9 +108,12 @@ public:
   bool empty() const { return size() == 0; }
 
   /// Returns the related ASTContext for the stored Stmts.
-  ASTContext &getASTContext() const {
-    assert(Context);
-    return *Context;
+  ASTContext &getASTContext() const;
+
+  /// Returns the declaration that contains the stored Stmts.
+  const Decl *getContainingDecl() const {
+    assert(D);
+    return D;
   }
 
   /// Returns true if this objects holds a list of statements.
@@ -150,106 +151,214 @@ public:
   bool contains(const StmtSequence &Other) const;
 };
 
-/// \brief Searches for clones in source code.
+/// Searches for similar subtrees in the AST.
 ///
-/// First, this class needs a translation unit which is passed via
-/// \p analyzeTranslationUnit . It will then generate and store search data
-/// for all statements inside the given translation unit.
-/// Afterwards the generated data can be used to find code clones by calling
-/// \p findClones .
+/// First, this class needs several declarations with statement bodies which
+/// can be passed via analyzeCodeBody. Afterwards all statements can be
+/// searched for clones by calling findClones with a given list of constraints
+/// that should specify the wanted properties of the clones.
+///
+/// The result of findClones can be further constrained with the constrainClones
+/// method.
 ///
 /// This class only searches for clones in exectuable source code
 /// (e.g. function bodies). Other clones (e.g. cloned comments or declarations)
 /// are not supported.
 class CloneDetector {
+
 public:
-  typedef unsigned DataPiece;
+  /// A collection of StmtSequences that share an arbitrary property.
+  typedef llvm::SmallVector<StmtSequence, 8> CloneGroup;
 
-  /// Holds the data about a StmtSequence that is needed during the search for
-  /// code clones.
-  struct CloneSignature {
-    /// \brief The hash code of the StmtSequence.
-    ///
-    /// The initial clone groups that are formed during the search for clones
-    /// consist only of Sequences that share the same hash code. This makes this
-    /// value the central part of this heuristic that is needed to find clones
-    /// in a performant way. For this to work, the type of this variable
-    /// always needs to be small and fast to compare.
-    ///
-    /// Also, StmtSequences that are clones of each others have to share
-    /// the same hash code. StmtSequences that are not clones of each other
-    /// shouldn't share the same hash code, but if they do, it will only
-    /// degrade the performance of the hash search but doesn't influence
-    /// the correctness of the result.
-    size_t Hash;
-
-    /// \brief The complexity of the StmtSequence.
-    ///
-    /// This value gives an approximation on how many direct or indirect child
-    /// statements are contained in the related StmtSequence. In general, the
-    /// greater this value, the greater the amount of statements. However, this
-    /// is only an approximation and the actual amount of statements can be
-    /// higher or lower than this value. Statements that are generated by the
-    /// compiler (e.g. macro expansions) for example barely influence the
-    /// complexity value.
-    ///
-    /// The main purpose of this value is to filter clones that are too small
-    /// and therefore probably not interesting enough for the user.
-    unsigned Complexity;
+  /// Generates and stores search data for all statements in the body of
+  /// the given Decl.
+  void analyzeCodeBody(const Decl *D);
 
-    /// \brief Creates an empty CloneSignature without any data.
-    CloneSignature() : Complexity(1) {}
+  /// Constrains the given list of clone groups with the given constraint.
+  ///
+  /// The constraint is expected to have a method with the signature
+  ///     `void constrain(std::vector<CloneDetector::CloneGroup> &Sequences)`
+  /// as this is the interface that the CloneDetector uses for applying the
+  /// constraint. The constraint is supposed to directly modify the passed list
+  /// so that all clones in the list fulfill the specific property this
+  /// constraint ensures.
+  template <typename T>
+  static void constrainClones(std::vector<CloneGroup> &CloneGroups, T C) {
+    C.constrain(CloneGroups);
+  }
 
-    CloneSignature(llvm::hash_code Hash, unsigned Complexity)
-        : Hash(Hash), Complexity(Complexity) {}
-  };
+  /// Constrains the given list of clone groups with the given list of
+  /// constraints.
+  ///
+  /// The constraints are applied in sequence in the order in which they are
+  /// passed to this function.
+  template <typename T1, typename... Ts>
+  static void constrainClones(std::vector<CloneGroup> &CloneGroups, T1 C,
+                              Ts... ConstraintList) {
+    constrainClones(CloneGroups, C);
+    constrainClones(CloneGroups, ConstraintList...);
+  }
 
-  /// Holds group of StmtSequences that are clones of each other and the
-  /// complexity value (see CloneSignature::Complexity) that all stored
-  /// StmtSequences have in common.
-  struct CloneGroup {
-    std::vector<StmtSequence> Sequences;
-    CloneSignature Signature;
-
-    CloneGroup() {}
-
-    CloneGroup(const StmtSequence &Seq, CloneSignature Signature)
-        : Signature(Signature) {
-      Sequences.push_back(Seq);
+  /// Searches for clones in all previously passed statements.
+  /// \param Result Output parameter to which all created clone groups are
+  ///               added.
+  /// \param Passes The constraints that should be applied to the result.
+  template <typename... Ts>
+  void findClones(std::vector<CloneGroup> &Result, Ts... ConstraintList) {
+    // The initial assumption is that there is only one clone group and every
+    // statement is a clone of the others. This clone group will then be
+    // split up with the help of the constraints.
+    CloneGroup AllClones;
+    AllClones.reserve(Sequences.size());
+    for (const auto &C : Sequences) {
+      AllClones.push_back(C);
     }
 
-    /// \brief Returns false if and only if this group should be skipped when
-    ///        searching for clones.
-    bool isValid() const {
-      // A clone group with only one member makes no sense, so we skip them.
-      return Sequences.size() > 1;
-    }
-  };
+    Result.push_back(AllClones);
 
-  /// \brief Generates and stores search data for all statements in the body of
-  ///        the given Decl.
-  void analyzeCodeBody(const Decl *D);
+    constrainClones(Result, ConstraintList...);
+  }
 
-  /// \brief Stores the CloneSignature to allow future querying.
-  void add(const StmtSequence &S, const CloneSignature &Signature);
+private:
+  CloneGroup Sequences;
+};
+
+/// This class is a utility class that contains utility functions for building
+/// custom constraints.
+class CloneConstraint {
+public:
+  /// Removes all groups by using a filter function.
+  /// \param CloneGroups The list of CloneGroups that is supposed to be
+  ///                    filtered.
+  /// \param Filter The filter function that should return true for all groups
+  ///               that should be removed from the list.
+  static void
+  filterGroups(std::vector<CloneDetector::CloneGroup> &CloneGroups,
+               std::function<bool(const CloneDetector::CloneGroup &)> Filter) {
+    CloneGroups.erase(
+        std::remove_if(CloneGroups.begin(), CloneGroups.end(), Filter),
+        CloneGroups.end());
+  }
+
+  /// Splits the given CloneGroups until the given Compare function returns true
+  /// for all clones in a single group.
+  /// \param CloneGroups A list of CloneGroups that should be modified.
+  /// \param Compare The comparison function that all clones are supposed to
+  ///                pass. Should return true if and only if two clones belong
+  ///                to the same CloneGroup.
+  static void splitCloneGroups(
+      std::vector<CloneDetector::CloneGroup> &CloneGroups,
+      std::function<bool(const StmtSequence &, const StmtSequence &)> Compare);
+};
 
-  /// \brief Searches the provided statements for clones.
+/// Searches all children of the given clones for type II clones (i.e. they are
+/// identical in every aspect beside the used variable names).
+class RecursiveCloneTypeIIConstraint {
+
+  /// Generates and saves a hash code for the given Stmt.
+  /// \param S The given Stmt.
+  /// \param D The Decl containing S.
+  /// \param StmtsByHash Output parameter that will contain the hash codes for
+  ///                    each StmtSequence in the given Stmt.
+  /// \return The hash code of the given Stmt.
   ///
-  /// \param Result Output parameter that is filled with a list of found
-  ///               clone groups. Each group contains multiple StmtSequences
-  ///               that were identified to be clones of each other.
-  /// \param MinGroupComplexity Only return clones which have at least this
-  ///                           complexity value.
-  /// \param CheckPatterns Returns only clone groups in which the referenced
-  ///                      variables follow the same pattern.
-  void findClones(std::vector<CloneGroup> &Result, unsigned MinGroupComplexity,
-                  bool CheckPatterns = true);
+  /// If the given Stmt is a CompoundStmt, this method will also generate
+  /// hashes for all possible StmtSequences in the children of this Stmt.
+  size_t saveHash(const Stmt *S, const Decl *D,
+                  std::vector<std::pair<size_t, StmtSequence>> &StmtsByHash);
+
+public:
+  void constrain(std::vector<CloneDetector::CloneGroup> &Sequences);
+};
+
+/// Ensures that every clone has at least the given complexity.
+///
+/// Complexity is here defined as the total amount of children of a statement.
+/// This constraint assumes the first statement in the group is representative
+/// for all other statements in the group in terms of complexity.
+class MinComplexityConstraint {
+  unsigned MinComplexity;
+
+public:
+  MinComplexityConstraint(unsigned MinComplexity)
+      : MinComplexity(MinComplexity) {}
 
-  /// \brief Describes two clones that reference their variables in a different
-  ///        pattern which could indicate a programming error.
+  size_t calculateStmtComplexity(const StmtSequence &Seq,
+                                 const std::string &ParentMacroStack = "");
+
+  void constrain(std::vector<CloneDetector::CloneGroup> &CloneGroups) {
+    CloneConstraint::filterGroups(
+        CloneGroups, [this](const CloneDetector::CloneGroup &A) {
+          if (!A.empty())
+            return calculateStmtComplexity(A.front()) < MinComplexity;
+          else
+            return false;
+        });
+  }
+};
+
+/// Ensures that all clone groups contain at least the given amount of clones.
+class MinGroupSizeConstraint {
+  unsigned MinGroupSize;
+
+public:
+  MinGroupSizeConstraint(unsigned MinGroupSize = 2)
+      : MinGroupSize(MinGroupSize) {}
+
+  void constrain(std::vector<CloneDetector::CloneGroup> &CloneGroups) {
+    CloneConstraint::filterGroups(CloneGroups,
+                                  [this](const CloneDetector::CloneGroup &A) {
+                                    return A.size() < MinGroupSize;
+                                  });
+  }
+};
+
+/// Ensures that no clone group fully contains another clone group.
+struct OnlyLargestCloneConstraint {
+  void constrain(std::vector<CloneDetector::CloneGroup> &Result);
+};
+
+/// Analyzes the pattern of the referenced variables in a statement.
+class VariablePattern {
+
+  /// Describes an occurence of a variable reference in a statement.
+  struct VariableOccurence {
+    /// The index of the associated VarDecl in the Variables vector.
+    size_t KindID;
+    /// The statement in the code where the variable was referenced.
+    const Stmt *Mention;
+
+    VariableOccurence(size_t KindID, const Stmt *Mention)
+        : KindID(KindID), Mention(Mention) {}
+  };
+
+  /// All occurences of referenced variables in the order of appearance.
+  std::vector<VariableOccurence> Occurences;
+  /// List of referenced variables in the order of appearance.
+  /// Every item in this list is unique.
+  std::vector<const VarDecl *> Variables;
+
+  /// Adds a new variable referenced to this pattern.
+  /// \param VarDecl The declaration of the variable that is referenced.
+  /// \param Mention The SourceRange where this variable is referenced.
+  void addVariableOccurence(const VarDecl *VarDecl, const Stmt *Mention);
+
+  /// Adds each referenced variable from the given statement.
+  void addVariables(const Stmt *S);
+
+public:
+  /// Creates an VariablePattern object with information about the given
+  /// StmtSequence.
+  VariablePattern(const StmtSequence &Sequence) {
+    for (const Stmt *S : Sequence)
+      addVariables(S);
+  }
+
+  /// Describes two clones that reference their variables in a different pattern
+  /// which could indicate a programming error.
   struct SuspiciousClonePair {
-    /// \brief Utility class holding the relevant information about a single
-    ///        clone in this pair.
+    /// Utility class holding the relevant information about a single
+    /// clone in this pair.
     struct SuspiciousCloneInfo {
       /// The variable which referencing in this clone was against the pattern.
       const VarDecl *Variable;
@@ -270,17 +379,37 @@ public:
     SuspiciousCloneInfo SecondCloneInfo;
   };
 
-  /// \brief Searches the provided statements for pairs of clones that don't
-  ///        follow the same pattern when referencing variables.
-  /// \param Result Output parameter that will contain the clone pairs.
-  /// \param MinGroupComplexity Only clone pairs in which the clones have at
-  ///                           least this complexity value.
-  void findSuspiciousClones(std::vector<SuspiciousClonePair> &Result,
-                            unsigned MinGroupComplexity);
+  /// Counts the differences between this pattern and the given one.
+  /// \param Other The given VariablePattern to compare with.
+  /// \param FirstMismatch Output parameter that will be filled with information
+  ///        about the first difference between the two patterns. This parameter
+  ///        can be a nullptr, in which case it will be ignored.
+  /// \return Returns the number of differences between the pattern this object
+  ///         is following and the given VariablePattern.
+  ///
+  /// For example, the following statements all have the same pattern and this
+  /// function would return zero:
+  ///
+  ///   if (a < b) return a; return b;
+  ///   if (x < y) return x; return y;
+  ///   if (u2 < u1) return u2; return u1;
+  ///
+  /// But the following statement has a different pattern (note the changed
+  /// variables in the return statements) and would have two differences when
+  /// compared with one of the statements above.
+  ///
+  ///   if (a < b) return b; return a;
+  ///
+  /// This function should only be called if the related statements of the given
+  /// pattern and the statements of this objects are clones of each other.
+  unsigned countPatternDifferences(
+      const VariablePattern &Other,
+      VariablePattern::SuspiciousClonePair *FirstMismatch = nullptr);
+};
 
-private:
-  /// Stores all encountered StmtSequences alongside their CloneSignature.
-  std::vector<std::pair<CloneSignature, StmtSequence>> Sequences;
+/// Ensures that all clones reference variables in the same pattern.
+struct MatchingVariablePatternConstraint {
+  void constrain(std::vector<CloneDetector::CloneGroup> &CloneGroups);
 };
 
 } // end namespace clang

Modified: cfe/trunk/lib/Analysis/CloneDetection.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Analysis/CloneDetection.cpp?rev=299653&r1=299652&r2=299653&view=diff
==============================================================================
--- cfe/trunk/lib/Analysis/CloneDetection.cpp (original)
+++ cfe/trunk/lib/Analysis/CloneDetection.cpp Thu Apr  6 09:34:07 2017
@@ -24,27 +24,27 @@
 
 using namespace clang;
 
-StmtSequence::StmtSequence(const CompoundStmt *Stmt, ASTContext &Context,
+StmtSequence::StmtSequence(const CompoundStmt *Stmt, const Decl *D,
                            unsigned StartIndex, unsigned EndIndex)
-    : S(Stmt), Context(&Context), StartIndex(StartIndex), EndIndex(EndIndex) {
+    : S(Stmt), D(D), StartIndex(StartIndex), EndIndex(EndIndex) {
   assert(Stmt && "Stmt must not be a nullptr");
   assert(StartIndex < EndIndex && "Given array should not be empty");
   assert(EndIndex <= Stmt->size() && "Given array too big for this Stmt");
 }
 
-StmtSequence::StmtSequence(const Stmt *Stmt, ASTContext &Context)
-    : S(Stmt), Context(&Context), StartIndex(0), EndIndex(0) {}
+StmtSequence::StmtSequence(const Stmt *Stmt, const Decl *D)
+    : S(Stmt), D(D), StartIndex(0), EndIndex(0) {}
 
 StmtSequence::StmtSequence()
-    : S(nullptr), Context(nullptr), StartIndex(0), EndIndex(0) {}
+    : S(nullptr), D(nullptr), StartIndex(0), EndIndex(0) {}
 
 bool StmtSequence::contains(const StmtSequence &Other) const {
-  // If both sequences reside in different translation units, they can never
-  // contain each other.
-  if (Context != Other.Context)
+  // If both sequences reside in different declarations, they can never contain
+  // each other.
+  if (D != Other.D)
     return false;
 
-  const SourceManager &SM = Context->getSourceManager();
+  const SourceManager &SM = getASTContext().getSourceManager();
 
   // Otherwise check if the start and end locations of the current sequence
   // surround the other sequence.
@@ -76,6 +76,11 @@ StmtSequence::iterator StmtSequence::end
   return CS->body_begin() + EndIndex;
 }
 
+ASTContext &StmtSequence::getASTContext() const {
+  assert(D);
+  return D->getASTContext();
+}
+
 SourceLocation StmtSequence::getStartLoc() const {
   return front()->getLocStart();
 }
@@ -86,168 +91,8 @@ SourceRange StmtSequence::getSourceRange
   return SourceRange(getStartLoc(), getEndLoc());
 }
 
-namespace {
-
-/// \brief Analyzes the pattern of the referenced variables in a statement.
-class VariablePattern {
-
-  /// \brief Describes an occurence of a variable reference in a statement.
-  struct VariableOccurence {
-    /// The index of the associated VarDecl in the Variables vector.
-    size_t KindID;
-    /// The statement in the code where the variable was referenced.
-    const Stmt *Mention;
-
-    VariableOccurence(size_t KindID, const Stmt *Mention)
-        : KindID(KindID), Mention(Mention) {}
-  };
-
-  /// All occurences of referenced variables in the order of appearance.
-  std::vector<VariableOccurence> Occurences;
-  /// List of referenced variables in the order of appearance.
-  /// Every item in this list is unique.
-  std::vector<const VarDecl *> Variables;
-
-  /// \brief Adds a new variable referenced to this pattern.
-  /// \param VarDecl The declaration of the variable that is referenced.
-  /// \param Mention The SourceRange where this variable is referenced.
-  void addVariableOccurence(const VarDecl *VarDecl, const Stmt *Mention) {
-    // First check if we already reference this variable
-    for (size_t KindIndex = 0; KindIndex < Variables.size(); ++KindIndex) {
-      if (Variables[KindIndex] == VarDecl) {
-        // If yes, add a new occurence that points to the existing entry in
-        // the Variables vector.
-        Occurences.emplace_back(KindIndex, Mention);
-        return;
-      }
-    }
-    // If this variable wasn't already referenced, add it to the list of
-    // referenced variables and add a occurence that points to this new entry.
-    Occurences.emplace_back(Variables.size(), Mention);
-    Variables.push_back(VarDecl);
-  }
-
-  /// \brief Adds each referenced variable from the given statement.
-  void addVariables(const Stmt *S) {
-    // Sometimes we get a nullptr (such as from IfStmts which often have nullptr
-    // children). We skip such statements as they don't reference any
-    // variables.
-    if (!S)
-      return;
-
-    // Check if S is a reference to a variable. If yes, add it to the pattern.
-    if (auto D = dyn_cast<DeclRefExpr>(S)) {
-      if (auto VD = dyn_cast<VarDecl>(D->getDecl()->getCanonicalDecl()))
-        addVariableOccurence(VD, D);
-    }
-
-    // Recursively check all children of the given statement.
-    for (const Stmt *Child : S->children()) {
-      addVariables(Child);
-    }
-  }
-
-public:
-  /// \brief Creates an VariablePattern object with information about the given
-  ///        StmtSequence.
-  VariablePattern(const StmtSequence &Sequence) {
-    for (const Stmt *S : Sequence)
-      addVariables(S);
-  }
-
-  /// \brief Counts the differences between this pattern and the given one.
-  /// \param Other The given VariablePattern to compare with.
-  /// \param FirstMismatch Output parameter that will be filled with information
-  ///        about the first difference between the two patterns. This parameter
-  ///        can be a nullptr, in which case it will be ignored.
-  /// \return Returns the number of differences between the pattern this object
-  ///         is following and the given VariablePattern.
-  ///
-  /// For example, the following statements all have the same pattern and this
-  /// function would return zero:
-  ///
-  ///   if (a < b) return a; return b;
-  ///   if (x < y) return x; return y;
-  ///   if (u2 < u1) return u2; return u1;
-  ///
-  /// But the following statement has a different pattern (note the changed
-  /// variables in the return statements) and would have two differences when
-  /// compared with one of the statements above.
-  ///
-  ///   if (a < b) return b; return a;
-  ///
-  /// This function should only be called if the related statements of the given
-  /// pattern and the statements of this objects are clones of each other.
-  unsigned countPatternDifferences(
-      const VariablePattern &Other,
-      CloneDetector::SuspiciousClonePair *FirstMismatch = nullptr) {
-    unsigned NumberOfDifferences = 0;
-
-    assert(Other.Occurences.size() == Occurences.size());
-    for (unsigned i = 0; i < Occurences.size(); ++i) {
-      auto ThisOccurence = Occurences[i];
-      auto OtherOccurence = Other.Occurences[i];
-      if (ThisOccurence.KindID == OtherOccurence.KindID)
-        continue;
-
-      ++NumberOfDifferences;
-
-      // If FirstMismatch is not a nullptr, we need to store information about
-      // the first difference between the two patterns.
-      if (FirstMismatch == nullptr)
-        continue;
-
-      // Only proceed if we just found the first difference as we only store
-      // information about the first difference.
-      if (NumberOfDifferences != 1)
-        continue;
-
-      const VarDecl *FirstSuggestion = nullptr;
-      // If there is a variable available in the list of referenced variables
-      // which wouldn't break the pattern if it is used in place of the
-      // current variable, we provide this variable as the suggested fix.
-      if (OtherOccurence.KindID < Variables.size())
-        FirstSuggestion = Variables[OtherOccurence.KindID];
-
-      // Store information about the first clone.
-      FirstMismatch->FirstCloneInfo =
-          CloneDetector::SuspiciousClonePair::SuspiciousCloneInfo(
-              Variables[ThisOccurence.KindID], ThisOccurence.Mention,
-              FirstSuggestion);
-
-      // Same as above but with the other clone. We do this for both clones as
-      // we don't know which clone is the one containing the unintended
-      // pattern error.
-      const VarDecl *SecondSuggestion = nullptr;
-      if (ThisOccurence.KindID < Other.Variables.size())
-        SecondSuggestion = Other.Variables[ThisOccurence.KindID];
-
-      // Store information about the second clone.
-      FirstMismatch->SecondCloneInfo =
-          CloneDetector::SuspiciousClonePair::SuspiciousCloneInfo(
-              Other.Variables[OtherOccurence.KindID], OtherOccurence.Mention,
-              SecondSuggestion);
-
-      // SuspiciousClonePair guarantees that the first clone always has a
-      // suggested variable associated with it. As we know that one of the two
-      // clones in the pair always has suggestion, we swap the two clones
-      // in case the first clone has no suggested variable which means that
-      // the second clone has a suggested variable and should be first.
-      if (!FirstMismatch->FirstCloneInfo.Suggestion)
-        std::swap(FirstMismatch->FirstCloneInfo,
-                  FirstMismatch->SecondCloneInfo);
-
-      // This ensures that we always have at least one suggestion in a pair.
-      assert(FirstMismatch->FirstCloneInfo.Suggestion);
-    }
-
-    return NumberOfDifferences;
-  }
-};
-}
-
-/// \brief Prints the macro name that contains the given SourceLocation into
-///        the given raw_string_ostream.
+/// Prints the macro name that contains the given SourceLocation into the given
+/// raw_string_ostream.
 static void printMacroName(llvm::raw_string_ostream &MacroStack,
                            ASTContext &Context, SourceLocation Loc) {
   MacroStack << Lexer::getImmediateMacroName(Loc, Context.getSourceManager(),
@@ -258,8 +103,8 @@ static void printMacroName(llvm::raw_str
   MacroStack << " ";
 }
 
-/// \brief Returns a string that represents all macro expansions that
-///        expanded into the given SourceLocation.
+/// Returns a string that represents all macro expansions that expanded into the
+/// given SourceLocation.
 ///
 /// If 'getMacroStack(A) == getMacroStack(B)' is true, then the SourceLocations
 /// A and B are expanded from the same macros in the same order.
@@ -279,7 +124,9 @@ static std::string getMacroStack(SourceL
 }
 
 namespace {
-/// \brief Collects the data of a single Stmt.
+typedef unsigned DataPiece;
+
+/// Collects the data of a single Stmt.
 ///
 /// This class defines what a code clone is: If it collects for two statements
 /// the same data, then those two statements are considered to be clones of each
@@ -292,11 +139,11 @@ template <typename T>
 class StmtDataCollector : public ConstStmtVisitor<StmtDataCollector<T>> {
 
   ASTContext &Context;
-  /// \brief The data sink to which all data is forwarded.
+  /// The data sink to which all data is forwarded.
   T &DataConsumer;
 
 public:
-  /// \brief Collects data of the given Stmt.
+  /// Collects data of the given Stmt.
   /// \param S The given statement.
   /// \param Context The ASTContext of S.
   /// \param DataConsumer The data sink to which all data is forwarded.
@@ -307,7 +154,7 @@ public:
 
   // Below are utility methods for appending different data to the vector.
 
-  void addData(CloneDetector::DataPiece Integer) {
+  void addData(DataPiece Integer) {
     DataConsumer.update(
         StringRef(reinterpret_cast<char *>(&Integer), sizeof(Integer)));
   }
@@ -425,7 +272,7 @@ public:
   })
   DEF_ADD_DATA(DeclStmt, {
     auto numDecls = std::distance(S->decl_begin(), S->decl_end());
-    addData(static_cast<CloneDetector::DataPiece>(numDecls));
+    addData(static_cast<DataPiece>(numDecls));
     for (const Decl *D : S->decls()) {
       if (const VarDecl *VD = dyn_cast<VarDecl>(D)) {
         addData(VD->getType());
@@ -454,199 +301,131 @@ public:
 };
 } // end anonymous namespace
 
-namespace {
-/// Generates CloneSignatures for a set of statements and stores the results in
-/// a CloneDetector object.
-class CloneSignatureGenerator {
-
-  CloneDetector &CD;
-  ASTContext &Context;
-
-  /// \brief Generates CloneSignatures for all statements in the given statement
-  /// tree and stores them in the CloneDetector.
-  ///
-  /// \param S The root of the given statement tree.
-  /// \param ParentMacroStack A string representing the macros that generated
-  ///                         the parent statement or an empty string if no
-  ///                         macros generated the parent statement.
-  ///                         See getMacroStack() for generating such a string.
-  /// \return The CloneSignature of the root statement.
-  CloneDetector::CloneSignature
-  generateSignatures(const Stmt *S, const std::string &ParentMacroStack) {
-    // Create an empty signature that will be filled in this method.
-    CloneDetector::CloneSignature Signature;
-
-    llvm::MD5 Hash;
-
-    // Collect all relevant data from S and hash it.
-    StmtDataCollector<llvm::MD5>(S, Context, Hash);
-
-    // Look up what macros expanded into the current statement.
-    std::string StartMacroStack = getMacroStack(S->getLocStart(), Context);
-    std::string EndMacroStack = getMacroStack(S->getLocEnd(), Context);
-
-    // First, check if ParentMacroStack is not empty which means we are currently
-    // dealing with a parent statement which was expanded from a macro.
-    // If this parent statement was expanded from the same macros as this
-    // statement, we reduce the initial complexity of this statement to zero.
-    // This causes that a group of statements that were generated by a single
-    // macro expansion will only increase the total complexity by one.
-    // Note: This is not the final complexity of this statement as we still
-    // add the complexity of the child statements to the complexity value.
-    if (!ParentMacroStack.empty() && (StartMacroStack == ParentMacroStack &&
-                                      EndMacroStack == ParentMacroStack)) {
-      Signature.Complexity = 0;
-    }
-
-    // Storage for the signatures of the direct child statements. This is only
-    // needed if the current statement is a CompoundStmt.
-    std::vector<CloneDetector::CloneSignature> ChildSignatures;
-    const CompoundStmt *CS = dyn_cast<const CompoundStmt>(S);
-
-    // The signature of a statement includes the signatures of its children.
-    // Therefore we create the signatures for every child and add them to the
-    // current signature.
-    for (const Stmt *Child : S->children()) {
-      // Some statements like 'if' can have nullptr children that we will skip.
-      if (!Child)
-        continue;
-
-      // Recursive call to create the signature of the child statement. This
-      // will also create and store all clone groups in this child statement.
-      // We pass only the StartMacroStack along to keep things simple.
-      auto ChildSignature = generateSignatures(Child, StartMacroStack);
-
-      // Add the collected data to the signature of the current statement.
-      Signature.Complexity += ChildSignature.Complexity;
-      Hash.update(StringRef(reinterpret_cast<char *>(&ChildSignature.Hash),
-                            sizeof(ChildSignature.Hash)));
-
-      // If the current statement is a CompoundStatement, we need to store the
-      // signature for the generation of the sub-sequences.
-      if (CS)
-        ChildSignatures.push_back(ChildSignature);
-    }
-
-    // If the current statement is a CompoundStmt, we also need to create the
-    // clone groups from the sub-sequences inside the children.
-    if (CS)
-      handleSubSequences(CS, ChildSignatures);
-
-    // Create the final hash code for the current signature.
-    llvm::MD5::MD5Result HashResult;
-    Hash.final(HashResult);
-
-    // Copy as much of the generated hash code to the signature's hash code.
-    std::memcpy(&Signature.Hash, &HashResult,
-                std::min(sizeof(Signature.Hash), sizeof(HashResult)));
-
-    // Save the signature for the current statement in the CloneDetector object.
-    CD.add(StmtSequence(S, Context), Signature);
-
-    return Signature;
-  }
-
-  /// \brief Adds all possible sub-sequences in the child array of the given
-  ///        CompoundStmt to the CloneDetector.
-  /// \param CS The given CompoundStmt.
-  /// \param ChildSignatures A list of calculated signatures for each child in
-  ///                        the given CompoundStmt.
-  void handleSubSequences(
-      const CompoundStmt *CS,
-      const std::vector<CloneDetector::CloneSignature> &ChildSignatures) {
-
-    // FIXME: This function has quadratic runtime right now. Check if skipping
-    // this function for too long CompoundStmts is an option.
-
-    // The length of the sub-sequence. We don't need to handle sequences with
-    // the length 1 as they are already handled in CollectData().
-    for (unsigned Length = 2; Length <= CS->size(); ++Length) {
-      // The start index in the body of the CompoundStmt. We increase the
-      // position until the end of the sub-sequence reaches the end of the
-      // CompoundStmt body.
-      for (unsigned Pos = 0; Pos <= CS->size() - Length; ++Pos) {
-        // Create an empty signature and add the signatures of all selected
-        // child statements to it.
-        CloneDetector::CloneSignature SubSignature;
-        llvm::MD5 SubHash;
-
-        for (unsigned i = Pos; i < Pos + Length; ++i) {
-          SubSignature.Complexity += ChildSignatures[i].Complexity;
-          size_t ChildHash = ChildSignatures[i].Hash;
-
-          SubHash.update(StringRef(reinterpret_cast<char *>(&ChildHash),
-                                sizeof(ChildHash)));
-        }
-
-        // Create the final hash code for the current signature.
-        llvm::MD5::MD5Result HashResult;
-        SubHash.final(HashResult);
-
-        // Copy as much of the generated hash code to the signature's hash code.
-        std::memcpy(&SubSignature.Hash, &HashResult,
-                    std::min(sizeof(SubSignature.Hash), sizeof(HashResult)));
-
-        // Save the signature together with the information about what children
-        // sequence we selected.
-        CD.add(StmtSequence(CS, Context, Pos, Pos + Length), SubSignature);
-      }
-    }
-  }
-
-public:
-  explicit CloneSignatureGenerator(CloneDetector &CD, ASTContext &Context)
-      : CD(CD), Context(Context) {}
-
-  /// \brief Generates signatures for all statements in the given function body.
-  void consumeCodeBody(const Stmt *S) { generateSignatures(S, ""); }
-};
-} // end anonymous namespace
-
 void CloneDetector::analyzeCodeBody(const Decl *D) {
   assert(D);
   assert(D->hasBody());
-  CloneSignatureGenerator Generator(*this, D->getASTContext());
-  Generator.consumeCodeBody(D->getBody());
-}
 
-void CloneDetector::add(const StmtSequence &S,
-                        const CloneSignature &Signature) {
-  Sequences.push_back(std::make_pair(Signature, S));
+  Sequences.push_back(StmtSequence(D->getBody(), D));
 }
 
-namespace {
-/// \brief Returns true if and only if \p Stmt contains at least one other
+/// Returns true if and only if \p Stmt contains at least one other
 /// sequence in the \p Group.
-bool containsAnyInGroup(StmtSequence &Stmt, CloneDetector::CloneGroup &Group) {
-  for (StmtSequence &GroupStmt : Group.Sequences) {
-    if (Stmt.contains(GroupStmt))
+static bool containsAnyInGroup(StmtSequence &Seq,
+                               CloneDetector::CloneGroup &Group) {
+  for (StmtSequence &GroupSeq : Group) {
+    if (Seq.contains(GroupSeq))
       return true;
   }
   return false;
 }
 
-/// \brief Returns true if and only if all sequences in \p OtherGroup are
+/// Returns true if and only if all sequences in \p OtherGroup are
 /// contained by a sequence in \p Group.
-bool containsGroup(CloneDetector::CloneGroup &Group,
-                   CloneDetector::CloneGroup &OtherGroup) {
+static bool containsGroup(CloneDetector::CloneGroup &Group,
+                          CloneDetector::CloneGroup &OtherGroup) {
   // We have less sequences in the current group than we have in the other,
   // so we will never fulfill the requirement for returning true. This is only
   // possible because we know that a sequence in Group can contain at most
   // one sequence in OtherGroup.
-  if (Group.Sequences.size() < OtherGroup.Sequences.size())
+  if (Group.size() < OtherGroup.size())
     return false;
 
-  for (StmtSequence &Stmt : Group.Sequences) {
+  for (StmtSequence &Stmt : Group) {
     if (!containsAnyInGroup(Stmt, OtherGroup))
       return false;
   }
   return true;
 }
-} // end anonymous namespace
+
+void OnlyLargestCloneConstraint::constrain(
+    std::vector<CloneDetector::CloneGroup> &Result) {
+  std::vector<unsigned> IndexesToRemove;
+
+  // Compare every group in the result with the rest. If one groups contains
+  // another group, we only need to return the bigger group.
+  // Note: This doesn't scale well, so if possible avoid calling any heavy
+  // function from this loop to minimize the performance impact.
+  for (unsigned i = 0; i < Result.size(); ++i) {
+    for (unsigned j = 0; j < Result.size(); ++j) {
+      // Don't compare a group with itself.
+      if (i == j)
+        continue;
+
+      if (containsGroup(Result[j], Result[i])) {
+        IndexesToRemove.push_back(i);
+        break;
+      }
+    }
+  }
+
+  // Erasing a list of indexes from the vector should be done with decreasing
+  // indexes. As IndexesToRemove is constructed with increasing values, we just
+  // reverse iterate over it to get the desired order.
+  for (auto I = IndexesToRemove.rbegin(); I != IndexesToRemove.rend(); ++I) {
+    Result.erase(Result.begin() + *I);
+  }
+}
+
+static size_t createHash(llvm::MD5 &Hash) {
+  size_t HashCode;
+
+  // Create the final hash code for the current Stmt.
+  llvm::MD5::MD5Result HashResult;
+  Hash.final(HashResult);
+
+  // Copy as much as possible of the generated hash code to the Stmt's hash
+  // code.
+  std::memcpy(&HashCode, &HashResult,
+              std::min(sizeof(HashCode), sizeof(HashResult)));
+
+  return HashCode;
+}
+
+size_t RecursiveCloneTypeIIConstraint::saveHash(
+    const Stmt *S, const Decl *D,
+    std::vector<std::pair<size_t, StmtSequence>> &StmtsByHash) {
+  llvm::MD5 Hash;
+  ASTContext &Context = D->getASTContext();
+
+  StmtDataCollector<llvm::MD5>(S, Context, Hash);
+
+  auto CS = dyn_cast<CompoundStmt>(S);
+  SmallVector<size_t, 8> ChildHashes;
+
+  for (const Stmt *Child : S->children()) {
+    if (Child == nullptr) {
+      ChildHashes.push_back(0);
+      continue;
+    }
+    size_t ChildHash = saveHash(Child, D, StmtsByHash);
+    Hash.update(
+        StringRef(reinterpret_cast<char *>(&ChildHash), sizeof(ChildHash)));
+    ChildHashes.push_back(ChildHash);
+  }
+
+  if (CS) {
+    for (unsigned Length = 2; Length <= CS->size(); ++Length) {
+      for (unsigned Pos = 0; Pos <= CS->size() - Length; ++Pos) {
+        llvm::MD5 Hash;
+        for (unsigned i = Pos; i < Pos + Length; ++i) {
+          size_t ChildHash = ChildHashes[i];
+          Hash.update(StringRef(reinterpret_cast<char *>(&ChildHash),
+                                sizeof(ChildHash)));
+        }
+        StmtsByHash.push_back(std::make_pair(
+            createHash(Hash), StmtSequence(CS, D, Pos, Pos + Length)));
+      }
+    }
+  }
+
+  size_t HashCode = createHash(Hash);
+  StmtsByHash.push_back(std::make_pair(HashCode, StmtSequence(S, D)));
+  return HashCode;
+}
 
 namespace {
-/// \brief Wrapper around FoldingSetNodeID that it can be used as the template
-///        argument of the StmtDataCollector.
+/// Wrapper around FoldingSetNodeID that it can be used as the template
+/// argument of the StmtDataCollector.
 class FoldingSetNodeIDWrapper {
 
   llvm::FoldingSetNodeID &FS;
@@ -658,8 +437,8 @@ public:
 };
 } // end anonymous namespace
 
-/// \brief Writes the relevant data from all statements and child statements
-///        in the given StmtSequence into the given FoldingSetNodeID.
+/// Writes the relevant data from all statements and child statements
+/// in the given StmtSequence into the given FoldingSetNodeID.
 static void CollectStmtSequenceData(const StmtSequence &Sequence,
                                     FoldingSetNodeIDWrapper &OutputData) {
   for (const Stmt *S : Sequence) {
@@ -670,13 +449,13 @@ static void CollectStmtSequenceData(cons
       if (!Child)
         continue;
 
-      CollectStmtSequenceData(StmtSequence(Child, Sequence.getASTContext()),
+      CollectStmtSequenceData(StmtSequence(Child, Sequence.getContainingDecl()),
                               OutputData);
     }
   }
 }
 
-/// \brief Returns true if both sequences are clones of each other.
+/// Returns true if both sequences are clones of each other.
 static bool areSequencesClones(const StmtSequence &LHS,
                                const StmtSequence &RHS) {
   // We collect the data from all statements in the sequence as we did before
@@ -693,202 +472,272 @@ static bool areSequencesClones(const Stm
   return DataLHS == DataRHS;
 }
 
-/// \brief Finds all actual clone groups in a single group of presumed clones.
-/// \param Result Output parameter to which all found groups are added.
-/// \param Group A group of presumed clones. The clones are allowed to have a
-///              different variable pattern and may not be actual clones of each
-///              other.
-/// \param CheckVariablePattern If true, every clone in a group that was added
-///              to the output follows the same variable pattern as the other
-///              clones in its group.
-static void createCloneGroups(std::vector<CloneDetector::CloneGroup> &Result,
-                              const CloneDetector::CloneGroup &Group,
-                              bool CheckVariablePattern) {
-  // We remove the Sequences one by one, so a list is more appropriate.
-  std::list<StmtSequence> UnassignedSequences(Group.Sequences.begin(),
-                                              Group.Sequences.end());
-
-  // Search for clones as long as there could be clones in UnassignedSequences.
-  while (UnassignedSequences.size() > 1) {
-
-    // Pick the first Sequence as a protoype for a new clone group.
-    StmtSequence Prototype = UnassignedSequences.front();
-    UnassignedSequences.pop_front();
-
-    CloneDetector::CloneGroup FilteredGroup(Prototype, Group.Signature);
-
-    // Analyze the variable pattern of the prototype. Every other StmtSequence
-    // needs to have the same pattern to get into the new clone group.
-    VariablePattern PrototypeFeatures(Prototype);
-
-    // Search all remaining StmtSequences for an identical variable pattern
-    // and assign them to our new clone group.
-    auto I = UnassignedSequences.begin(), E = UnassignedSequences.end();
-    while (I != E) {
-      // If the sequence doesn't fit to the prototype, we have encountered
-      // an unintended hash code collision and we skip it.
-      if (!areSequencesClones(Prototype, *I)) {
-        ++I;
-        continue;
+void RecursiveCloneTypeIIConstraint::constrain(
+    std::vector<CloneDetector::CloneGroup> &Sequences) {
+  // FIXME: Maybe we can do this in-place and don't need this additional vector.
+  std::vector<CloneDetector::CloneGroup> Result;
+
+  for (CloneDetector::CloneGroup &Group : Sequences) {
+    // We assume in the following code that the Group is non-empty, so we
+    // skip all empty groups.
+    if (Group.empty())
+      continue;
+
+    std::vector<std::pair<size_t, StmtSequence>> StmtsByHash;
+
+    // Generate hash codes for all children of S and save them in StmtsByHash.
+    for (const StmtSequence &S : Group) {
+      saveHash(S.front(), S.getContainingDecl(), StmtsByHash);
+    }
+
+    // Sort hash_codes in StmtsByHash.
+    std::stable_sort(StmtsByHash.begin(), StmtsByHash.end(),
+                     [this](std::pair<size_t, StmtSequence> LHS,
+                            std::pair<size_t, StmtSequence> RHS) {
+                       return LHS.first < RHS.first;
+                     });
+
+    // Check for each StmtSequence if its successor has the same hash value.
+    // We don't check the last StmtSequence as it has no successor.
+    // Note: The 'size - 1 ' in the condition is safe because we check for an
+    // empty Group vector at the beginning of this function.
+    for (unsigned i = 0; i < StmtsByHash.size() - 1; ++i) {
+      const auto Current = StmtsByHash[i];
+
+      // It's likely that we just found an sequence of StmtSequences that
+      // represent a CloneGroup, so we create a new group and start checking and
+      // adding the StmtSequences in this sequence.
+      CloneDetector::CloneGroup NewGroup;
+
+      size_t PrototypeHash = Current.first;
+
+      for (; i < StmtsByHash.size(); ++i) {
+        // A different hash value means we have reached the end of the sequence.
+        if (PrototypeHash != StmtsByHash[i].first ||
+            !areSequencesClones(StmtsByHash[i].second, Current.second)) {
+          // The current sequence could be the start of a new CloneGroup. So we
+          // decrement i so that we visit it again in the outer loop.
+          // Note: i can never be 0 at this point because we are just comparing
+          // the hash of the Current StmtSequence with itself in the 'if' above.
+          assert(i != 0);
+          --i;
+          break;
+        }
+        // Same hash value means we should add the StmtSequence to the current
+        // group.
+        NewGroup.push_back(StmtsByHash[i].second);
       }
 
-      // If we weren't asked to check for a matching variable pattern in clone
-      // groups we can add the sequence now to the new clone group.
-      // If we were asked to check for matching variable pattern, we first have
-      // to check that there are no differences between the two patterns and
-      // only proceed if they match.
-      if (!CheckVariablePattern ||
-          VariablePattern(*I).countPatternDifferences(PrototypeFeatures) == 0) {
-        FilteredGroup.Sequences.push_back(*I);
-        I = UnassignedSequences.erase(I);
+      // We created a new clone group with matching hash codes and move it to
+      // the result vector.
+      Result.push_back(NewGroup);
+    }
+  }
+  // Sequences is the output parameter, so we copy our result into it.
+  Sequences = Result;
+}
+
+size_t MinComplexityConstraint::calculateStmtComplexity(
+    const StmtSequence &Seq, const std::string &ParentMacroStack) {
+  if (Seq.empty())
+    return 0;
+
+  size_t Complexity = 1;
+
+  ASTContext &Context = Seq.getASTContext();
+
+  // Look up what macros expanded into the current statement.
+  std::string StartMacroStack = getMacroStack(Seq.getStartLoc(), Context);
+  std::string EndMacroStack = getMacroStack(Seq.getEndLoc(), Context);
+
+  // First, check if ParentMacroStack is not empty which means we are currently
+  // dealing with a parent statement which was expanded from a macro.
+  // If this parent statement was expanded from the same macros as this
+  // statement, we reduce the initial complexity of this statement to zero.
+  // This causes that a group of statements that were generated by a single
+  // macro expansion will only increase the total complexity by one.
+  // Note: This is not the final complexity of this statement as we still
+  // add the complexity of the child statements to the complexity value.
+  if (!ParentMacroStack.empty() && (StartMacroStack == ParentMacroStack &&
+                                    EndMacroStack == ParentMacroStack)) {
+    Complexity = 0;
+  }
+
+  // Iterate over the Stmts in the StmtSequence and add their complexity values
+  // to the current complexity value.
+  if (Seq.holdsSequence()) {
+    for (const Stmt *S : Seq) {
+      Complexity += calculateStmtComplexity(
+          StmtSequence(S, Seq.getContainingDecl()), StartMacroStack);
+    }
+  } else {
+    for (const Stmt *S : Seq.front()->children()) {
+      Complexity += calculateStmtComplexity(
+          StmtSequence(S, Seq.getContainingDecl()), StartMacroStack);
+    }
+  }
+  return Complexity;
+}
+
+void MatchingVariablePatternConstraint::constrain(
+    std::vector<CloneDetector::CloneGroup> &CloneGroups) {
+  CloneConstraint::splitCloneGroups(
+      CloneGroups, [](const StmtSequence &A, const StmtSequence &B) {
+        VariablePattern PatternA(A);
+        VariablePattern PatternB(B);
+        return PatternA.countPatternDifferences(PatternB) == 0;
+      });
+}
+
+void CloneConstraint::splitCloneGroups(
+    std::vector<CloneDetector::CloneGroup> &CloneGroups,
+    std::function<bool(const StmtSequence &, const StmtSequence &)> Compare) {
+  std::vector<CloneDetector::CloneGroup> Result;
+  for (auto &HashGroup : CloneGroups) {
+    // Contains all indexes in HashGroup that were already added to a
+    // CloneGroup.
+    std::vector<char> Indexes;
+    Indexes.resize(HashGroup.size());
+
+    for (unsigned i = 0; i < HashGroup.size(); ++i) {
+      // Skip indexes that are already part of a CloneGroup.
+      if (Indexes[i])
         continue;
+
+      // Pick the first unhandled StmtSequence and consider it as the
+      // beginning
+      // of a new CloneGroup for now.
+      // We don't add i to Indexes because we never iterate back.
+      StmtSequence Prototype = HashGroup[i];
+      CloneDetector::CloneGroup PotentialGroup = {Prototype};
+      ++Indexes[i];
+
+      // Check all following StmtSequences for clones.
+      for (unsigned j = i + 1; j < HashGroup.size(); ++j) {
+        // Skip indexes that are already part of a CloneGroup.
+        if (Indexes[j])
+          continue;
+
+        // If a following StmtSequence belongs to our CloneGroup, we add it to
+        // it.
+        const StmtSequence &Candidate = HashGroup[j];
+
+        if (!Compare(Prototype, Candidate))
+          continue;
+
+        PotentialGroup.push_back(Candidate);
+        // Make sure we never visit this StmtSequence again.
+        ++Indexes[j];
       }
 
-      // We didn't found a matching variable pattern, so we continue with the
-      // next sequence.
-      ++I;
+      // Otherwise, add it to the result and continue searching for more
+      // groups.
+      Result.push_back(PotentialGroup);
     }
 
-    // Add a valid clone group to the list of found clone groups.
-    if (!FilteredGroup.isValid())
-      continue;
+    assert(std::all_of(Indexes.begin(), Indexes.end(),
+                       [](char c) { return c == 1; }));
+  }
+  CloneGroups = Result;
+}
 
-    Result.push_back(FilteredGroup);
+void VariablePattern::addVariableOccurence(const VarDecl *VarDecl,
+                                           const Stmt *Mention) {
+  // First check if we already reference this variable
+  for (size_t KindIndex = 0; KindIndex < Variables.size(); ++KindIndex) {
+    if (Variables[KindIndex] == VarDecl) {
+      // If yes, add a new occurence that points to the existing entry in
+      // the Variables vector.
+      Occurences.emplace_back(KindIndex, Mention);
+      return;
+    }
   }
+  // If this variable wasn't already referenced, add it to the list of
+  // referenced variables and add a occurence that points to this new entry.
+  Occurences.emplace_back(Variables.size(), Mention);
+  Variables.push_back(VarDecl);
 }
 
-void CloneDetector::findClones(std::vector<CloneGroup> &Result,
-                               unsigned MinGroupComplexity,
-                               bool CheckPatterns) {
-  // A shortcut (and necessary for the for-loop later in this function).
-  if (Sequences.empty())
+void VariablePattern::addVariables(const Stmt *S) {
+  // Sometimes we get a nullptr (such as from IfStmts which often have nullptr
+  // children). We skip such statements as they don't reference any
+  // variables.
+  if (!S)
     return;
 
-  // We need to search for groups of StmtSequences with the same hash code to
-  // create our initial clone groups. By sorting all known StmtSequences by
-  // their hash value we make sure that StmtSequences with the same hash code
-  // are grouped together in the Sequences vector.
-  // Note: We stable sort here because the StmtSequences are added in the order
-  // in which they appear in the source file. We want to preserve that order
-  // because we also want to report them in that order in the CloneChecker.
-  std::stable_sort(Sequences.begin(), Sequences.end(),
-                   [](std::pair<CloneSignature, StmtSequence> LHS,
-                      std::pair<CloneSignature, StmtSequence> RHS) {
-                     return LHS.first.Hash < RHS.first.Hash;
-                   });
-
-  std::vector<CloneGroup> CloneGroups;
-
-  // Check for each CloneSignature if its successor has the same hash value.
-  // We don't check the last CloneSignature as it has no successor.
-  // Note: The 'size - 1' in the condition is safe because we check for an empty
-  // Sequences vector at the beginning of this function.
-  for (unsigned i = 0; i < Sequences.size() - 1; ++i) {
-    const auto Current = Sequences[i];
-    const auto Next = Sequences[i + 1];
-
-    if (Current.first.Hash != Next.first.Hash)
-      continue;
-
-    // It's likely that we just found an sequence of CloneSignatures that
-    // represent a CloneGroup, so we create a new group and start checking and
-    // adding the CloneSignatures in this sequence.
-    CloneGroup Group;
-    Group.Signature = Current.first;
-
-    for (; i < Sequences.size(); ++i) {
-      const auto &Signature = Sequences[i];
-
-      // A different hash value means we have reached the end of the sequence.
-      if (Current.first.Hash != Signature.first.Hash) {
-        // The current Signature could be the start of a new CloneGroup. So we
-        // decrement i so that we visit it again in the outer loop.
-        // Note: i can never be 0 at this point because we are just comparing
-        // the hash of the Current CloneSignature with itself in the 'if' above.
-        assert(i != 0);
-        --i;
-        break;
-      }
+  // Check if S is a reference to a variable. If yes, add it to the pattern.
+  if (auto D = dyn_cast<DeclRefExpr>(S)) {
+    if (auto VD = dyn_cast<VarDecl>(D->getDecl()->getCanonicalDecl()))
+      addVariableOccurence(VD, D);
+  }
 
-      // Skip CloneSignatures that won't pass the complexity requirement.
-      if (Signature.first.Complexity < MinGroupComplexity)
-        continue;
+  // Recursively check all children of the given statement.
+  for (const Stmt *Child : S->children()) {
+    addVariables(Child);
+  }
+}
 
-      Group.Sequences.push_back(Signature.second);
-    }
+unsigned VariablePattern::countPatternDifferences(
+    const VariablePattern &Other,
+    VariablePattern::SuspiciousClonePair *FirstMismatch) {
+  unsigned NumberOfDifferences = 0;
 
-    // There is a chance that we haven't found more than two fitting
-    // CloneSignature because not enough CloneSignatures passed the complexity
-    // requirement. As a CloneGroup with less than two members makes no sense,
-    // we ignore this CloneGroup and won't add it to the result.
-    if (!Group.isValid())
+  assert(Other.Occurences.size() == Occurences.size());
+  for (unsigned i = 0; i < Occurences.size(); ++i) {
+    auto ThisOccurence = Occurences[i];
+    auto OtherOccurence = Other.Occurences[i];
+    if (ThisOccurence.KindID == OtherOccurence.KindID)
       continue;
 
-    CloneGroups.push_back(Group);
-  }
+    ++NumberOfDifferences;
 
-  // Add every valid clone group that fulfills the complexity requirement.
-  for (const CloneGroup &Group : CloneGroups) {
-    createCloneGroups(Result, Group, CheckPatterns);
-  }
-
-  std::vector<unsigned> IndexesToRemove;
+    // If FirstMismatch is not a nullptr, we need to store information about
+    // the first difference between the two patterns.
+    if (FirstMismatch == nullptr)
+      continue;
 
-  // Compare every group in the result with the rest. If one groups contains
-  // another group, we only need to return the bigger group.
-  // Note: This doesn't scale well, so if possible avoid calling any heavy
-  // function from this loop to minimize the performance impact.
-  for (unsigned i = 0; i < Result.size(); ++i) {
-    for (unsigned j = 0; j < Result.size(); ++j) {
-      // Don't compare a group with itself.
-      if (i == j)
-        continue;
+    // Only proceed if we just found the first difference as we only store
+    // information about the first difference.
+    if (NumberOfDifferences != 1)
+      continue;
 
-      if (containsGroup(Result[j], Result[i])) {
-        IndexesToRemove.push_back(i);
-        break;
-      }
-    }
-  }
+    const VarDecl *FirstSuggestion = nullptr;
+    // If there is a variable available in the list of referenced variables
+    // which wouldn't break the pattern if it is used in place of the
+    // current variable, we provide this variable as the suggested fix.
+    if (OtherOccurence.KindID < Variables.size())
+      FirstSuggestion = Variables[OtherOccurence.KindID];
+
+    // Store information about the first clone.
+    FirstMismatch->FirstCloneInfo =
+        VariablePattern::SuspiciousClonePair::SuspiciousCloneInfo(
+            Variables[ThisOccurence.KindID], ThisOccurence.Mention,
+            FirstSuggestion);
+
+    // Same as above but with the other clone. We do this for both clones as
+    // we don't know which clone is the one containing the unintended
+    // pattern error.
+    const VarDecl *SecondSuggestion = nullptr;
+    if (ThisOccurence.KindID < Other.Variables.size())
+      SecondSuggestion = Other.Variables[ThisOccurence.KindID];
+
+    // Store information about the second clone.
+    FirstMismatch->SecondCloneInfo =
+        VariablePattern::SuspiciousClonePair::SuspiciousCloneInfo(
+            Other.Variables[OtherOccurence.KindID], OtherOccurence.Mention,
+            SecondSuggestion);
+
+    // SuspiciousClonePair guarantees that the first clone always has a
+    // suggested variable associated with it. As we know that one of the two
+    // clones in the pair always has suggestion, we swap the two clones
+    // in case the first clone has no suggested variable which means that
+    // the second clone has a suggested variable and should be first.
+    if (!FirstMismatch->FirstCloneInfo.Suggestion)
+      std::swap(FirstMismatch->FirstCloneInfo, FirstMismatch->SecondCloneInfo);
 
-  // Erasing a list of indexes from the vector should be done with decreasing
-  // indexes. As IndexesToRemove is constructed with increasing values, we just
-  // reverse iterate over it to get the desired order.
-  for (auto I = IndexesToRemove.rbegin(); I != IndexesToRemove.rend(); ++I) {
-    Result.erase(Result.begin() + *I);
+    // This ensures that we always have at least one suggestion in a pair.
+    assert(FirstMismatch->FirstCloneInfo.Suggestion);
   }
-}
 
-void CloneDetector::findSuspiciousClones(
-    std::vector<CloneDetector::SuspiciousClonePair> &Result,
-    unsigned MinGroupComplexity) {
-  std::vector<CloneGroup> Clones;
-  // Reuse the normal search for clones but specify that the clone groups don't
-  // need to have a common referenced variable pattern so that we can manually
-  // search for the kind of pattern errors this function is supposed to find.
-  findClones(Clones, MinGroupComplexity, false);
-
-  for (const CloneGroup &Group : Clones) {
-    for (unsigned i = 0; i < Group.Sequences.size(); ++i) {
-      VariablePattern PatternA(Group.Sequences[i]);
-
-      for (unsigned j = i + 1; j < Group.Sequences.size(); ++j) {
-        VariablePattern PatternB(Group.Sequences[j]);
-
-        CloneDetector::SuspiciousClonePair ClonePair;
-        // For now, we only report clones which break the variable pattern just
-        // once because multiple differences in a pattern are an indicator that
-        // those differences are maybe intended (e.g. because it's actually
-        // a different algorithm).
-        // TODO: In very big clones even multiple variables can be unintended,
-        // so replacing this number with a percentage could better handle such
-        // cases. On the other hand it could increase the false-positive rate
-        // for all clones if the percentage is too high.
-        if (PatternA.countPatternDifferences(PatternB, &ClonePair) == 1) {
-          Result.push_back(ClonePair);
-          break;
-        }
-      }
-    }
-  }
+  return NumberOfDifferences;
 }

Modified: cfe/trunk/lib/StaticAnalyzer/Checkers/CloneChecker.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/StaticAnalyzer/Checkers/CloneChecker.cpp?rev=299653&r1=299652&r2=299653&view=diff
==============================================================================
--- cfe/trunk/lib/StaticAnalyzer/Checkers/CloneChecker.cpp (original)
+++ cfe/trunk/lib/StaticAnalyzer/Checkers/CloneChecker.cpp Thu Apr  6 09:34:07 2017
@@ -38,14 +38,15 @@ public:
   void checkEndOfTranslationUnit(const TranslationUnitDecl *TU,
                                  AnalysisManager &Mgr, BugReporter &BR) const;
 
-  /// \brief Reports all clones to the user.
+  /// Reports all clones to the user.
   void reportClones(BugReporter &BR, AnalysisManager &Mgr,
-                    int MinComplexity) const;
+                    std::vector<CloneDetector::CloneGroup> &CloneGroups) const;
 
-  /// \brief Reports only suspicious clones to the user along with informaton
-  ///        that explain why they are suspicious.
-  void reportSuspiciousClones(BugReporter &BR, AnalysisManager &Mgr,
-                              int MinComplexity) const;
+  /// Reports only suspicious clones to the user along with informaton
+  /// that explain why they are suspicious.
+  void reportSuspiciousClones(
+      BugReporter &BR, AnalysisManager &Mgr,
+      std::vector<CloneDetector::CloneGroup> &CloneGroups) const;
 };
 } // end anonymous namespace
 
@@ -72,11 +73,30 @@ void CloneChecker::checkEndOfTranslation
   bool ReportNormalClones = Mgr.getAnalyzerOptions().getBooleanOption(
       "ReportNormalClones", true, this);
 
+  // Let the CloneDetector create a list of clones from all the analyzed
+  // statements. We don't filter for matching variable patterns at this point
+  // because reportSuspiciousClones() wants to search them for errors.
+  std::vector<CloneDetector::CloneGroup> AllCloneGroups;
+
+  Detector.findClones(AllCloneGroups, RecursiveCloneTypeIIConstraint(),
+                      MinComplexityConstraint(MinComplexity),
+                      MinGroupSizeConstraint(2), OnlyLargestCloneConstraint());
+
   if (ReportSuspiciousClones)
-    reportSuspiciousClones(BR, Mgr, MinComplexity);
+    reportSuspiciousClones(BR, Mgr, AllCloneGroups);
+
+  // We are done for this translation unit unless we also need to report normal
+  // clones.
+  if (!ReportNormalClones)
+    return;
+
+  // Now that the suspicious clone detector has checked for pattern errors,
+  // we also filter all clones who don't have matching patterns
+  CloneDetector::constrainClones(AllCloneGroups,
+                                 MatchingVariablePatternConstraint(),
+                                 MinGroupSizeConstraint(2));
 
-  if (ReportNormalClones)
-    reportClones(BR, Mgr, MinComplexity);
+  reportClones(BR, Mgr, AllCloneGroups);
 }
 
 static PathDiagnosticLocation makeLocation(const StmtSequence &S,
@@ -87,37 +107,55 @@ static PathDiagnosticLocation makeLocati
       Mgr.getAnalysisDeclContext(ACtx.getTranslationUnitDecl()));
 }
 
-void CloneChecker::reportClones(BugReporter &BR, AnalysisManager &Mgr,
-                                int MinComplexity) const {
-
-  std::vector<CloneDetector::CloneGroup> CloneGroups;
-  Detector.findClones(CloneGroups, MinComplexity);
+void CloneChecker::reportClones(
+    BugReporter &BR, AnalysisManager &Mgr,
+    std::vector<CloneDetector::CloneGroup> &CloneGroups) const {
 
   if (!BT_Exact)
     BT_Exact.reset(new BugType(this, "Exact code clone", "Code clone"));
 
-  for (CloneDetector::CloneGroup &Group : CloneGroups) {
+  for (const CloneDetector::CloneGroup &Group : CloneGroups) {
     // We group the clones by printing the first as a warning and all others
     // as a note.
-    auto R = llvm::make_unique<BugReport>(
-        *BT_Exact, "Duplicate code detected",
-        makeLocation(Group.Sequences.front(), Mgr));
-    R->addRange(Group.Sequences.front().getSourceRange());
-
-    for (unsigned i = 1; i < Group.Sequences.size(); ++i)
-      R->addNote("Similar code here",
-                      makeLocation(Group.Sequences[i], Mgr),
-                      Group.Sequences[i].getSourceRange());
+    auto R = llvm::make_unique<BugReport>(*BT_Exact, "Duplicate code detected",
+                                          makeLocation(Group.front(), Mgr));
+    R->addRange(Group.front().getSourceRange());
+
+    for (unsigned i = 1; i < Group.size(); ++i)
+      R->addNote("Similar code here", makeLocation(Group[i], Mgr),
+                 Group[i].getSourceRange());
     BR.emitReport(std::move(R));
   }
 }
 
-void CloneChecker::reportSuspiciousClones(BugReporter &BR,
-                                          AnalysisManager &Mgr,
-                                          int MinComplexity) const {
-
-  std::vector<CloneDetector::SuspiciousClonePair> Clones;
-  Detector.findSuspiciousClones(Clones, MinComplexity);
+void CloneChecker::reportSuspiciousClones(
+    BugReporter &BR, AnalysisManager &Mgr,
+    std::vector<CloneDetector::CloneGroup> &CloneGroups) const {
+  std::vector<VariablePattern::SuspiciousClonePair> Pairs;
+
+  for (const CloneDetector::CloneGroup &Group : CloneGroups) {
+    for (unsigned i = 0; i < Group.size(); ++i) {
+      VariablePattern PatternA(Group[i]);
+
+      for (unsigned j = i + 1; j < Group.size(); ++j) {
+        VariablePattern PatternB(Group[j]);
+
+        VariablePattern::SuspiciousClonePair ClonePair;
+        // For now, we only report clones which break the variable pattern just
+        // once because multiple differences in a pattern are an indicator that
+        // those differences are maybe intended (e.g. because it's actually a
+        // different algorithm).
+        // FIXME: In very big clones even multiple variables can be unintended,
+        // so replacing this number with a percentage could better handle such
+        // cases. On the other hand it could increase the false-positive rate
+        // for all clones if the percentage is too high.
+        if (PatternA.countPatternDifferences(PatternB, &ClonePair) == 1) {
+          Pairs.push_back(ClonePair);
+          break;
+        }
+      }
+    }
+  }
 
   if (!BT_Suspicious)
     BT_Suspicious.reset(
@@ -128,7 +166,7 @@ void CloneChecker::reportSuspiciousClone
   AnalysisDeclContext *ADC =
       Mgr.getAnalysisDeclContext(ACtx.getTranslationUnitDecl());
 
-  for (CloneDetector::SuspiciousClonePair &Pair : Clones) {
+  for (VariablePattern::SuspiciousClonePair &Pair : Pairs) {
     // FIXME: We are ignoring the suggestions currently, because they are
     // only 50% accurate (even if the second suggestion is unavailable),
     // which may confuse the user.

Modified: cfe/trunk/unittests/Analysis/CMakeLists.txt
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/unittests/Analysis/CMakeLists.txt?rev=299653&r1=299652&r2=299653&view=diff
==============================================================================
--- cfe/trunk/unittests/Analysis/CMakeLists.txt (original)
+++ cfe/trunk/unittests/Analysis/CMakeLists.txt Thu Apr  6 09:34:07 2017
@@ -2,11 +2,12 @@ set(LLVM_LINK_COMPONENTS
   Support
   )
 
-add_clang_unittest(CFGTests
+add_clang_unittest(ClangAnalysisTests
   CFGTest.cpp
+  CloneDetectionTest.cpp
   )
 
-target_link_libraries(CFGTests
+target_link_libraries(ClangAnalysisTests
   clangAnalysis
   clangAST
   clangASTMatchers

Added: cfe/trunk/unittests/Analysis/CloneDetectionTest.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/unittests/Analysis/CloneDetectionTest.cpp?rev=299653&view=auto
==============================================================================
--- cfe/trunk/unittests/Analysis/CloneDetectionTest.cpp (added)
+++ cfe/trunk/unittests/Analysis/CloneDetectionTest.cpp Thu Apr  6 09:34:07 2017
@@ -0,0 +1,110 @@
+//===- unittests/Analysis/CloneDetectionTest.cpp - Clone detection tests --===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/AST/RecursiveASTVisitor.h"
+#include "clang/Analysis/CloneDetection.h"
+#include "clang/Tooling/Tooling.h"
+#include "gtest/gtest.h"
+
+namespace clang {
+namespace analysis {
+namespace {
+
+class CloneDetectionVisitor
+    : public RecursiveASTVisitor<CloneDetectionVisitor> {
+
+  CloneDetector &Detector;
+
+public:
+  explicit CloneDetectionVisitor(CloneDetector &D) : Detector(D) {}
+
+  bool VisitFunctionDecl(FunctionDecl *D) {
+    Detector.analyzeCodeBody(D);
+    return true;
+  }
+};
+
+/// Example constraint for testing purposes.
+/// Filters out all statements that are in a function which name starts with
+/// "bar".
+class NoBarFunctionConstraint {
+public:
+  void constrain(std::vector<CloneDetector::CloneGroup> &CloneGroups) {
+    CloneConstraint::splitCloneGroups(
+        CloneGroups, [](const StmtSequence &A, const StmtSequence &B) {
+          // Check if one of the sequences is in a function which name starts
+          // with "bar".
+          for (const StmtSequence &Arg : {A, B}) {
+            if (const auto *D =
+                    dyn_cast<const FunctionDecl>(Arg.getContainingDecl())) {
+              if (D->getNameAsString().find("bar") == 0)
+                return false;
+            }
+          }
+          return true;
+        });
+  }
+};
+
+TEST(CloneDetector, FilterFunctionsByName) {
+  auto ASTUnit =
+      clang::tooling::buildASTFromCode("void foo1(int &a1) { a1++; }\n"
+                                       "void foo2(int &a2) { a2++; }\n"
+                                       "void bar1(int &a3) { a3++; }\n"
+                                       "void bar2(int &a4) { a4++; }\n");
+  auto TU = ASTUnit->getASTContext().getTranslationUnitDecl();
+
+  CloneDetector Detector;
+  // Push all the function bodies into the detector.
+  CloneDetectionVisitor Visitor(Detector);
+  Visitor.TraverseTranslationUnitDecl(TU);
+
+  // Find clones with the usual settings, but but we want to filter out
+  // all statements from functions which names start with "bar".
+  std::vector<CloneDetector::CloneGroup> CloneGroups;
+  Detector.findClones(CloneGroups, NoBarFunctionConstraint(),
+                      RecursiveCloneTypeIIConstraint(),
+                      MinComplexityConstraint(2), MinGroupSizeConstraint(2),
+                      OnlyLargestCloneConstraint());
+
+  ASSERT_EQ(CloneGroups.size(), 1u);
+  ASSERT_EQ(CloneGroups.front().size(), 2u);
+
+  for (auto &Clone : CloneGroups.front()) {
+    const auto ND = dyn_cast<const FunctionDecl>(Clone.getContainingDecl());
+    ASSERT_TRUE(ND != nullptr);
+    // Check that no function name starting with "bar" is in the results...
+    ASSERT_TRUE(ND->getNameAsString().find("bar") != 0);
+  }
+
+  // Retry above's example without the filter...
+  CloneGroups.clear();
+
+  Detector.findClones(CloneGroups, RecursiveCloneTypeIIConstraint(),
+                      MinComplexityConstraint(2), MinGroupSizeConstraint(2),
+                      OnlyLargestCloneConstraint());
+  ASSERT_EQ(CloneGroups.size(), 1u);
+  ASSERT_EQ(CloneGroups.front().size(), 4u);
+
+  // Count how many functions with the bar prefix we have in the results.
+  int FoundFunctionsWithBarPrefix = 0;
+  for (auto &Clone : CloneGroups.front()) {
+    const auto ND = dyn_cast<const FunctionDecl>(Clone.getContainingDecl());
+    ASSERT_TRUE(ND != nullptr);
+    // This time check that we picked up the bar functions from above
+    if (ND->getNameAsString().find("bar") == 0) {
+      FoundFunctionsWithBarPrefix++;
+    }
+  }
+  // We should have found the two functions bar1 and bar2.
+  ASSERT_EQ(FoundFunctionsWithBarPrefix, 2);
+}
+} // namespace
+} // namespace analysis
+} // namespace clang




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