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diff --git a/clang-tools-extra/clang-move/HelperDeclRefGraph.h b/clang-tools-extra/clang-move/HelperDeclRefGraph.h
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+//===-- UsedHelperDeclFinder.h - AST-based call graph for helper decls ----===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANG_MOVE_USED_HELPER_DECL_FINDER_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_MOVE_USED_HELPER_DECL_FINDER_H
+
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Analysis/CallGraph.h"
+#include "llvm/ADT/DenseSet.h"
+#include <memory>
+#include <vector>
+
+namespace clang {
+namespace move {
+
+// A reference graph for finding used/unused helper declarations in a single
+// translation unit (e.g. old.cc). We don't reuse CallGraph in clang/Analysis
+// because that CallGraph only supports function declarations.
+//
+// Helper declarations include following types:
+//   * function/variable/class definitions in an anonymous namespace.
+//   * static function/variable definitions in a global/named namespace.
+//
+// The reference graph is a directed graph. Each node in the graph represents a
+// helper declaration in old.cc or a non-moved/moved declaration (e.g. class,
+// function) in old.h, which means each node is associated with a Decl.
+//
+// To construct the graph, we use AST matcher to find interesting Decls (usually
+// a pair of Caller and Callee), and add an edge from the Caller node to the
+// Callee node.
+//
+// Specially, for a class, it might have multiple declarations such methods
+// and member variables. We only use a single node to present this class, and
+// this node is associated with the class declaration (CXXRecordDecl).
+//
+// The graph has 3 types of edges:
+//   1. moved_decl => helper_decl
+//   2. non_moved_decl => helper_decl
+//   3. helper_decl => helper_decl
+class HelperDeclRefGraph {
+public:
+  HelperDeclRefGraph() = default;
+  ~HelperDeclRefGraph() = default;
+
+  // Add a directed edge from the caller node to the callee node.
+  // A new node will be created if the node for Caller/Callee doesn't exist.
+  //
+  // Note that, all class member declarations are represented by a single node
+  // in the graph. The corresponding Decl of this node is the class declaration.
+  void addEdge(const Decl *Caller, const Decl *Callee);
+  CallGraphNode *getNode(const Decl *D) const;
+
+  // Get all reachable nodes in the graph from the given declaration D's node,
+  // including D.
+  llvm::DenseSet<const CallGraphNode *> getReachableNodes(const Decl *D) const;
+
+  // Dump the call graph for debug purpose.
+  void dump() const;
+
+private:
+  void print(raw_ostream &OS) const;
+  // Lookup a node for the given declaration D. If not found, insert a new
+  // node into the graph.
+  CallGraphNode *getOrInsertNode(Decl *D);
+
+  typedef llvm::DenseMap<const Decl *, std::unique_ptr<CallGraphNode>>
+      DeclMapTy;
+
+  // DeclMap owns all CallGraphNodes.
+  DeclMapTy DeclMap;
+};
+
+// A builder helps to construct a call graph of helper declarations.
+class HelperDeclRGBuilder : public ast_matchers::MatchFinder::MatchCallback {
+public:
+  HelperDeclRGBuilder() : RG(new HelperDeclRefGraph) {}
+  void run(const ast_matchers::MatchFinder::MatchResult &Result) override;
+  const HelperDeclRefGraph *getGraph() const { return RG.get(); }
+
+  // Find out the outmost enclosing class/function declaration of a given D.
+  // For a CXXMethodDecl, get its CXXRecordDecl; For a VarDecl/FunctionDecl, get
+  // its outmost enclosing FunctionDecl or CXXRecordDecl.
+  // Return D if not found.
+  static const Decl *getOutmostClassOrFunDecl(const Decl *D);
+
+private:
+  std::unique_ptr<HelperDeclRefGraph> RG;
+};
+
+} // namespace move
+} // namespace clang
+
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_MOVE_USED_HELPER_DECL_FINDER_H