//===- CallGraph.h - AST-based Call graph -----------------------*- C++ -*-===//

//

// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.

// See https://llvm.org/LICENSE.txt for license information.

// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

//

//===----------------------------------------------------------------------===//

//

//  This file declares the AST-based CallGraph.

//

//  A call graph for functions whose definitions/bodies are available in the

//  current translation unit. The graph has a "virtual" root node that contains

//  edges to all externally available functions.

//

//===----------------------------------------------------------------------===//

#ifndef LLVM_CLANG_ANALYSIS_CALLGRAPH_H

#define LLVM_CLANG_ANALYSIS_CALLGRAPH_H

#include "clang/AST/Decl.h"

#include "clang/AST/RecursiveASTVisitor.h"

#include "llvm/ADT/DenseMap.h"

#include "llvm/ADT/GraphTraits.h"

#include "llvm/ADT/STLExtras.h"

#include "llvm/ADT/SetVector.h"

#include "llvm/ADT/SmallVector.h"

#include "llvm/ADT/iterator_range.h"

#include <memory>

namespace clang {

class CallGraphNode;

class Decl;

class DeclContext;

class Stmt;

/// The AST-based call graph.

///

/// The call graph extends itself with the given declarations by implementing

/// the recursive AST visitor, which constructs the graph by visiting the given

/// declarations.

class CallGraph : public RecursiveASTVisitor<CallGraph> {

  friend class CallGraphNode;

  using FunctionMapTy =

      llvm::DenseMap<const Decl *, std::unique_ptr<CallGraphNode>>;

  /// FunctionMap owns all CallGraphNodes.

  FunctionMapTy FunctionMap;

  /// This is a virtual root node that has edges to all the functions.

  CallGraphNode *Root;

public:

  CallGraph();

  ~CallGraph();

  /// Populate the call graph with the functions in the given

  /// declaration.

  ///

  /// Recursively walks the declaration to find all the dependent Decls as well.

  void addToCallGraph(Decl *D) {

    TraverseDecl(D);

  }

  /// Determine if a declaration should be included in the graph.

  static bool includeInGraph(const Decl *D);

  /// Determine if a declaration should be included in the graph for the 

  /// purposes of being a callee. This is similar to includeInGraph except

  /// it permits declarations, not just definitions.

  static bool includeCalleeInGraph(const Decl *D);

  /// Lookup the node for the given declaration.

  CallGraphNode *getNode(const Decl *) const;

  /// Lookup the node for the given declaration. If none found, insert

  /// one into the graph.

  CallGraphNode *getOrInsertNode(Decl *);

  using iterator = FunctionMapTy::iterator;

  using const_iterator = FunctionMapTy::const_iterator;

  /// Iterators through all the elements in the graph. Note, this gives

  /// non-deterministic order.

  iterator begin() { return FunctionMap.begin(); }

  iterator end()   { return FunctionMap.end();   }

  const_iterator begin() const { return FunctionMap.begin(); }

  const_iterator end()   const { return FunctionMap.end();   }

  /// Get the number of nodes in the graph.

  unsigned size() const { return FunctionMap.size(); }

  /// Get the virtual root of the graph, all the functions available externally

  /// are represented as callees of the node.

  CallGraphNode *getRoot() const { return Root; }

  /// Iterators through all the nodes of the graph that have no parent. These

  /// are the unreachable nodes, which are either unused or are due to us

  /// failing to add a call edge due to the analysis imprecision.

  using nodes_iterator = llvm::SetVector<CallGraphNode *>::iterator;

  using const_nodes_iterator = llvm::SetVector<CallGraphNode *>::const_iterator;

  void print(raw_ostream &os) const;

  void dump() const;

  void viewGraph() const;

  void addNodesForBlocks(DeclContext *D);

  /// Part of recursive declaration visitation. We recursively visit all the

  /// declarations to collect the root functions.

  bool VisitFunctionDecl(FunctionDecl *FD) {

    // We skip function template definitions, as their semantics is

    // only determined when they are instantiated.

    if (includeInGraph(FD) && 
FD->isThisDeclarationADefinition()22.6k
) {

      // Add all blocks declared inside this function to the graph.

      addNodesForBlocks(FD);

      // If this function has external linkage, anything could call it.

      // Note, we are not precise here. For example, the function could have

      // its address taken.

      addNodeForDecl(FD, FD->isGlobal());

    }

    return true;

  }

  /// Part of recursive declaration visitation.

  bool VisitObjCMethodDecl(ObjCMethodDecl *MD) {

    if (includeInGraph(MD)) {

      addNodesForBlocks(MD);

      addNodeForDecl(MD, true);

    }

    return true;

  }

  // We are only collecting the declarations, so do not step into the bodies.

  bool TraverseStmt(Stmt *S) { return true; }

  bool shouldWalkTypesOfTypeLocs() const { return false; }

  bool shouldVisitTemplateInstantiations() const { return true; }

  bool shouldVisitImplicitCode() const { return true; }

private:

  /// Add the given declaration to the call graph.

  void addNodeForDecl(Decl *D, bool IsGlobal);

};

class CallGraphNode {

public:

  struct CallRecord {

    CallGraphNode *Callee;

    Expr *CallExpr;

    CallRecord() = default;

    CallRecord(CallGraphNode *Callee_, Expr *CallExpr_)

        : Callee(Callee_), CallExpr(CallExpr_) {}

    // The call destination is the only important data here,

    // allow to transparently unwrap into it.

    operator CallGraphNode *() const { return Callee; }

  };

private:

  /// The function/method declaration.

  Decl *FD;

  /// The list of functions called from this node.

  SmallVector<CallRecord, 5> CalledFunctions;

public:

  CallGraphNode(Decl *D) : FD(D) {}

  using iterator = SmallVectorImpl<CallRecord>::iterator;

  using const_iterator = SmallVectorImpl<CallRecord>::const_iterator;

  /// Iterators through all the callees/children of the node.

  iterator begin() { return CalledFunctions.begin(); }

  iterator end() { return CalledFunctions.end(); }

  const_iterator begin() const { return CalledFunctions.begin(); }

  const_iterator end() const { return CalledFunctions.end(); }

  /// Iterator access to callees/children of the node.

  llvm::iterator_range<iterator> callees() {

    return llvm::make_range(begin(), end());

  }

  llvm::iterator_range<const_iterator> callees() const {

    return llvm::make_range(begin(), end());

  }

  bool empty() const { return CalledFunctions.empty(); }

  unsigned size() const { return CalledFunctions.size(); }

  void addCallee(CallRecord Call) { CalledFunctions.push_back(Call); }

  Decl *getDecl() const { return FD; }

  FunctionDecl *getDefinition() const {

    return getDecl()->getAsFunction()->getDefinition();

  }

  void print(raw_ostream &os) const;

  void dump() const;

};

// NOTE: we are comparing based on the callee only. So different call records

// (with different call expressions) to the same callee will compare equal!

inline bool operator==(const CallGraphNode::CallRecord &LHS,

                       const CallGraphNode::CallRecord &RHS) {

  return LHS.Callee == RHS.Callee;

}

} // namespace clang

namespace llvm {

// Specialize DenseMapInfo for clang::CallGraphNode::CallRecord.

template <> struct DenseMapInfo<clang::CallGraphNode::CallRecord> {

  static inline clang::CallGraphNode::CallRecord getEmptyKey() {

    return clang::CallGraphNode::CallRecord(

        DenseMapInfo<clang::CallGraphNode *>::getEmptyKey(),

        DenseMapInfo<clang::Expr *>::getEmptyKey());

  }

  static inline clang::CallGraphNode::CallRecord getTombstoneKey() {

    return clang::CallGraphNode::CallRecord(

        DenseMapInfo<clang::CallGraphNode *>::getTombstoneKey(),

        DenseMapInfo<clang::Expr *>::getTombstoneKey());

  }

  static unsigned getHashValue(const clang::CallGraphNode::CallRecord &Val) {

    // NOTE: we are comparing based on the callee only.

    // Different call records with the same callee will compare equal!

    return DenseMapInfo<clang::CallGraphNode *>::getHashValue(Val.Callee);

  }

  static bool isEqual(const clang::CallGraphNode::CallRecord &LHS,

                      const clang::CallGraphNode::CallRecord &RHS) {

    return LHS == RHS;

  }

};

// Graph traits for iteration, viewing.

template <> struct GraphTraits<clang::CallGraphNode*> {

  using NodeType = clang::CallGraphNode;

  using NodeRef = clang::CallGraphNode *;

  using ChildIteratorType = NodeType::iterator;

  static NodeType *getEntryNode(clang::CallGraphNode *CGN) { return CGN; }

  static ChildIteratorType child_begin(NodeType *N) { return N->begin();  }

  static ChildIteratorType child_end(NodeType *N) { return N->end(); }

};

template <> struct GraphTraits<const clang::CallGraphNode*> {

  using NodeType = const clang::CallGraphNode;

  using NodeRef = const clang::CallGraphNode *;

  using ChildIteratorType = NodeType::const_iterator;

  static NodeType *getEntryNode(const clang::CallGraphNode *CGN) { return CGN; }

  static ChildIteratorType child_begin(NodeType *N) { return N->begin();}

  static ChildIteratorType child_end(NodeType *N) { return N->end(); }

};

template <> struct GraphTraits<clang::CallGraph*>

  : public GraphTraits<clang::CallGraphNode*> {

  static NodeType *getEntryNode(clang::CallGraph *CGN) {

    return CGN->getRoot();  // Start at the external node!

  }

  static clang::CallGraphNode *

  CGGetValue(clang::CallGraph::const_iterator::value_type &P) {

    return P.second.get();

  }

  // nodes_iterator/begin/end - Allow iteration over all nodes in the graph

  using nodes_iterator =

      mapped_iterator<clang::CallGraph::iterator, decltype(&CGGetValue)>;

  static nodes_iterator nodes_begin(clang::CallGraph *CG) {

    return nodes_iterator(CG->begin(), &CGGetValue);

  }

  static nodes_iterator nodes_end  (clang::CallGraph *CG) {

    return nodes_iterator(CG->end(), &CGGetValue);

  }

  static unsigned size(clang::CallGraph *CG) { return CG->size(); }

};

template <> struct GraphTraits<const clang::CallGraph*> :

  public GraphTraits<const clang::CallGraphNode*> {

  static NodeType *getEntryNode(const clang::CallGraph *CGN) {

    return CGN->getRoot();

  }

  static clang::CallGraphNode *

  CGGetValue(clang::CallGraph::const_iterator::value_type &P) {

    return P.second.get();

  }

  // nodes_iterator/begin/end - Allow iteration over all nodes in the graph

  using nodes_iterator =

      mapped_iterator<clang::CallGraph::const_iterator, decltype(&CGGetValue)>;

  static nodes_iterator nodes_begin(const clang::CallGraph *CG) {

    return nodes_iterator(CG->begin(), &CGGetValue);

  }

  static nodes_iterator nodes_end(const clang::CallGraph *CG) {

    return nodes_iterator(CG->end(), &CGGetValue);

  }

  static unsigned size(const clang::CallGraph *CG) { return CG->size(); }

};

} // namespace llvm

#endif // LLVM_CLANG_ANALYSIS_CALLGRAPH_H