//===- CallGraph.cpp - AST-based Call graph -------------------------------===//

//

// 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 defines the AST-based CallGraph.

//

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

#include "clang/Analysis/CallGraph.h"

#include "clang/AST/Decl.h"

#include "clang/AST/DeclBase.h"

#include "clang/AST/DeclObjC.h"

#include "clang/AST/Expr.h"

#include "clang/AST/ExprObjC.h"

#include "clang/AST/Stmt.h"

#include "clang/AST/StmtVisitor.h"

#include "clang/Basic/IdentifierTable.h"

#include "clang/Basic/LLVM.h"

#include "llvm/ADT/PostOrderIterator.h"

#include "llvm/ADT/STLExtras.h"

#include "llvm/ADT/Statistic.h"

#include "llvm/Support/Casting.h"

#include "llvm/Support/Compiler.h"

#include "llvm/Support/DOTGraphTraits.h"

#include "llvm/Support/GraphWriter.h"

#include "llvm/Support/raw_ostream.h"

#include <cassert>

#include <memory>

#include <string>

using namespace clang;

#define DEBUG_TYPE "CallGraph"

STATISTIC(NumObjCCallEdges, "Number of Objective-C method call edges");

STATISTIC(NumBlockCallEdges, "Number of block call edges");

namespace {

/// A helper class, which walks the AST and locates all the call sites in the

/// given function body.

class CGBuilder : public StmtVisitor<CGBuilder> {

  CallGraph *G;

  CallGraphNode *CallerNode;

public:

  CGBuilder(CallGraph *g, CallGraphNode *N) : G(g), CallerNode(N) {}

  void VisitStmt(Stmt *S) { VisitChildren(S); }

  Decl *getDeclFromCall(CallExpr *CE) {

    if (FunctionDecl *CalleeDecl = CE->getDirectCallee())

      return CalleeDecl;

    // Simple detection of a call through a block.

    Expr *CEE = CE->getCallee()->IgnoreParenImpCasts();

    if (BlockExpr *Block = dyn_cast<BlockExpr>(CEE)) {

      NumBlockCallEdges++;

      return Block->getBlockDecl();

    }

    return nullptr;

  }

  void addCalledDecl(Decl *D, Expr *CallExpr) {

    if (G->includeInGraph(D)) {

      CallGraphNode *CalleeNode = G->getOrInsertNode(D);

      CallerNode->addCallee({CalleeNode, CallExpr});

    }

  }

  void VisitCallExpr(CallExpr *CE) {

    if (Decl *D = getDeclFromCall(CE))

      addCalledDecl(D, CE);

    VisitChildren(CE);

  }

  void VisitLambdaExpr(LambdaExpr *LE) {

    if (FunctionTemplateDecl *FTD = LE->getDependentCallOperator())

      for (FunctionDecl *FD : FTD->specializations())

        G->VisitFunctionDecl(FD);

    else if (CXXMethodDecl *MD = LE->getCallOperator())

      G->VisitFunctionDecl(MD);

  }

  void VisitCXXNewExpr(CXXNewExpr *E) {

    if (FunctionDecl *FD = E->getOperatorNew())

      addCalledDecl(FD, E);

    VisitChildren(E);

  }

  void VisitCXXConstructExpr(CXXConstructExpr *E) {

    CXXConstructorDecl *Ctor = E->getConstructor();

    if (FunctionDecl *Def = Ctor->getDefinition())

      addCalledDecl(Def, E);

    VisitChildren(E);

  }

  // Include the evaluation of the default argument.

  void VisitCXXDefaultArgExpr(CXXDefaultArgExpr *E) {

    Visit(E->getExpr());

  }

  // Include the evaluation of the default initializers in a class.

  void VisitCXXDefaultInitExpr(CXXDefaultInitExpr *E) {

    Visit(E->getExpr());

  }

  // Adds may-call edges for the ObjC message sends.

  void VisitObjCMessageExpr(ObjCMessageExpr *ME) {

    if (ObjCInterfaceDecl *IDecl = ME->getReceiverInterface()) {

      Selector Sel = ME->getSelector();

      // Find the callee definition within the same translation unit.

      Decl *D = nullptr;

      if (ME->isInstanceMessage())

        D = IDecl->lookupPrivateMethod(Sel);

      else

        D = IDecl->lookupPrivateClassMethod(Sel);

      if (D) {

        addCalledDecl(D, ME);

        NumObjCCallEdges++;

      }

    }

  }

  void VisitChildren(Stmt *S) {

    for (Stmt *SubStmt : S->children())

      if (SubStmt)

        this->Visit(SubStmt);

  }

};

} // namespace

void CallGraph::addNodesForBlocks(DeclContext *D) {

  if (BlockDecl *BD = dyn_cast<BlockDecl>(D))

    addNodeForDecl(BD, true);

  for (auto *I : D->decls())

    if (auto *DC = dyn_cast<DeclContext>(I))

      addNodesForBlocks(DC);

}

CallGraph::CallGraph() {

  Root = getOrInsertNode(nullptr);

}

CallGraph::~CallGraph() = default;

bool CallGraph::includeInGraph(const Decl *D) {

  assert(D);

  if (!D->hasBody())

    return false;

  if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {

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

    // only determined when they are instantiated.

    if (FD->isDependentContext())

      return false;

    IdentifierInfo *II = FD->getIdentifier();

    if (II && 
II->getName().startswith("__inline")19.2k
)

      return false;

  }

  return true;

}

void CallGraph::addNodeForDecl(Decl* D, bool IsGlobal) {

  assert(D);

  // Allocate a new node, mark it as root, and process its calls.

  CallGraphNode *Node = getOrInsertNode(D);

  // Process all the calls by this function as well.

  CGBuilder builder(this, Node);

  if (Stmt *Body = D->getBody())

    builder.Visit(Body);

  // Include C++ constructor member initializers.

  if (auto constructor = dyn_cast<CXXConstructorDecl>(D)) {

    for (CXXCtorInitializer *init : constructor->inits()) {

      builder.Visit(init->getInit());

    }

  }

}

CallGraphNode *CallGraph::getNode(const Decl *F) const {

  FunctionMapTy::const_iterator I = FunctionMap.find(F);

  if (I == FunctionMap.end()) return nullptr;

  return I->second.get();

}

CallGraphNode *CallGraph::getOrInsertNode(Decl *F) {

  if (F && 
!isa<ObjCMethodDecl>(F)36.4k
)

    F = F->getCanonicalDecl();

  std::unique_ptr<CallGraphNode> &Node = FunctionMap[F];

  if (Node)

    return Node.get();

  Node = std::make_unique<CallGraphNode>(F);

  // Make Root node a parent of all functions to make sure all are reachable.

  if (F)

    Root->addCallee({Node.get(), /*Call=*/nullptr});

  return Node.get();

}

void CallGraph::print(raw_ostream &OS) const {

  OS << " --- Call graph Dump --- \n";

  // We are going to print the graph in reverse post order, partially, to make

  // sure the output is deterministic.

  llvm::ReversePostOrderTraversal<const CallGraph *> RPOT(this);

  for (llvm::ReversePostOrderTraversal<const CallGraph *>::rpo_iterator

         I = RPOT.begin(), E = RPOT.end(); I != E; 
++I27
) {

    const CallGraphNode *N = *I;

    OS << "  Function: ";

    if (N == Root)

      OS << "< root >";

    else

      N->print(OS);

    OS << " calls: ";

    for (CallGraphNode::const_iterator CI = N->begin(),

                                       CE = N->end(); CI != CE; 
++CI47
) {

      assert(CI->Callee != Root && "No one can call the root node.");

      CI->Callee->print(OS);

      OS << " ";

    }

    OS << '\n';

  }

  OS.flush();

}

LLVM_DUMP_METHOD void CallGraph::dump() const {

  print(llvm::errs());

}

void CallGraph::viewGraph() const {

  llvm::ViewGraph(this, "CallGraph");

}

void CallGraphNode::print(raw_ostream &os) const {

  if (const NamedDecl *ND = dyn_cast_or_null<NamedDecl>(FD))

      return ND->printQualifiedName(os);

  os << "< >";

}

LLVM_DUMP_METHOD void CallGraphNode::dump() const {

  print(llvm::errs());

}

namespace llvm {

template <>

struct DOTGraphTraits<const CallGraph*> : public DefaultDOTGraphTraits {

  DOTGraphTraits (bool isSimple = false) : DefaultDOTGraphTraits(isSimple) {}

  static std::string getNodeLabel(const CallGraphNode *Node,

                                  const CallGraph *CG) {

    if (CG->getRoot() == Node) {

      return "< root >";

    }

    if (const NamedDecl *ND = dyn_cast_or_null<NamedDecl>(Node->getDecl()))

      return ND->getNameAsString();

    else

      return "< >";

  }

};

} // namespace llvm