clang-tools-extra/clang-move/HelperDeclRefGraph.h

   1 //===-- UsedHelperDeclFinder.h - AST-based call graph for helper decls ----===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #ifndef LLVM_CLANG_TOOLS_EXTRA_CLANG_MOVE_USED_HELPER_DECL_FINDER_H
  10 #define LLVM_CLANG_TOOLS_EXTRA_CLANG_MOVE_USED_HELPER_DECL_FINDER_H
  11
  12 #include "clang/ASTMatchers/ASTMatchFinder.h"
  13 #include "clang/Analysis/CallGraph.h"
  14 #include "llvm/ADT/DenseSet.h"
  15 #include <memory>
  16 #include <vector>
  17
  18 namespace clang {
  19 namespace move {
  20
  21 // A reference graph for finding used/unused helper declarations in a single
  22 // translation unit (e.g. old.cc). We don't reuse CallGraph in clang/Analysis
  23 // because that CallGraph only supports function declarations.
  24 //
  25 // Helper declarations include following types:
  26 //   * function/variable/class definitions in an anonymous namespace.
  27 //   * static function/variable definitions in a global/named namespace.
  28 //
  29 // The reference graph is a directed graph. Each node in the graph represents a
  30 // helper declaration in old.cc or a non-moved/moved declaration (e.g. class,
  31 // function) in old.h, which means each node is associated with a Decl.
  32 //
  33 // To construct the graph, we use AST matcher to find interesting Decls (usually
  34 // a pair of Caller and Callee), and add an edge from the Caller node to the
  35 // Callee node.
  36 //
  37 // Specially, for a class, it might have multiple declarations such methods
  38 // and member variables. We only use a single node to present this class, and
  39 // this node is associated with the class declaration (CXXRecordDecl).
  40 //
  41 // The graph has 3 types of edges:
  42 //   1. moved_decl => helper_decl
  43 //   2. non_moved_decl => helper_decl
  44 //   3. helper_decl => helper_decl
  45 class HelperDeclRefGraph {
  46 public:
  47   HelperDeclRefGraph() = default;
  48   ~HelperDeclRefGraph() = default;
  49
  50   // Add a directed edge from the caller node to the callee node.
  51   // A new node will be created if the node for Caller/Callee doesn't exist.
  52   //
  53   // Note that, all class member declarations are represented by a single node
  54   // in the graph. The corresponding Decl of this node is the class declaration.
  55   void addEdge(const Decl *Caller, const Decl *Callee);
  56   CallGraphNode *getNode(const Decl *D) const;
  57
  58   // Get all reachable nodes in the graph from the given declaration D's node,
  59   // including D.
  60   llvm::DenseSet<const CallGraphNode *> getReachableNodes(const Decl *D) const;
  61
  62   // Dump the call graph for debug purpose.
  63   void dump() const;
  64
  65 private:
  66   void print(raw_ostream &OS) const;
  67   // Lookup a node for the given declaration D. If not found, insert a new
  68   // node into the graph.
  69   CallGraphNode *getOrInsertNode(Decl *D);
  70
  71   typedef llvm::DenseMap<const Decl *, std::unique_ptr<CallGraphNode>>
  72       DeclMapTy;
  73
  74   // DeclMap owns all CallGraphNodes.
  75   DeclMapTy DeclMap;
  76 };
  77
  78 // A builder helps to construct a call graph of helper declarations.
  79 class HelperDeclRGBuilder : public ast_matchers::MatchFinder::MatchCallback {
  80 public:
  81   HelperDeclRGBuilder() : RG(new HelperDeclRefGraph) {}
  82   void run(const ast_matchers::MatchFinder::MatchResult &Result) override;
  83   const HelperDeclRefGraph *getGraph() const { return RG.get(); }
  84
  85   // Find out the outmost enclosing class/function declaration of a given D.
  86   // For a CXXMethodDecl, get its CXXRecordDecl; For a VarDecl/FunctionDecl, get
  87   // its outmost enclosing FunctionDecl or CXXRecordDecl.
  88   // Return D if not found.
  89   static const Decl *getOutmostClassOrFunDecl(const Decl *D);
  90
  91 private:
  92   std::unique_ptr<HelperDeclRefGraph> RG;
  93 };
  94
  95 } // namespace move
  96 } // namespace clang
  97
  98 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_MOVE_USED_HELPER_DECL_FINDER_H