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      1 //== CallGraph.cpp - AST-based Call graph  ----------------------*- C++ -*--==//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 //
     10 //  This file defines the AST-based CallGraph.
     11 //
     12 //===----------------------------------------------------------------------===//
     13 #include "clang/Analysis/CallGraph.h"
     14 #include "clang/AST/ASTContext.h"
     15 #include "clang/AST/Decl.h"
     16 #include "clang/AST/StmtVisitor.h"
     17 #include "llvm/ADT/PostOrderIterator.h"
     18 #include "llvm/ADT/Statistic.h"
     19 #include "llvm/Support/GraphWriter.h"
     20 
     21 using namespace clang;
     22 
     23 #define DEBUG_TYPE "CallGraph"
     24 
     25 STATISTIC(NumObjCCallEdges, "Number of Objective-C method call edges");
     26 STATISTIC(NumBlockCallEdges, "Number of block call edges");
     27 
     28 namespace {
     29 /// A helper class, which walks the AST and locates all the call sites in the
     30 /// given function body.
     31 class CGBuilder : public StmtVisitor<CGBuilder> {
     32   CallGraph *G;
     33   CallGraphNode *CallerNode;
     34 
     35 public:
     36   CGBuilder(CallGraph *g, CallGraphNode *N)
     37     : G(g), CallerNode(N) {}
     38 
     39   void VisitStmt(Stmt *S) { VisitChildren(S); }
     40 
     41   Decl *getDeclFromCall(CallExpr *CE) {
     42     if (FunctionDecl *CalleeDecl = CE->getDirectCallee())
     43       return CalleeDecl;
     44 
     45     // Simple detection of a call through a block.
     46     Expr *CEE = CE->getCallee()->IgnoreParenImpCasts();
     47     if (BlockExpr *Block = dyn_cast<BlockExpr>(CEE)) {
     48       NumBlockCallEdges++;
     49       return Block->getBlockDecl();
     50     }
     51 
     52     return nullptr;
     53   }
     54 
     55   void addCalledDecl(Decl *D) {
     56     if (G->includeInGraph(D)) {
     57       CallGraphNode *CalleeNode = G->getOrInsertNode(D);
     58       CallerNode->addCallee(CalleeNode, G);
     59     }
     60   }
     61 
     62   void VisitCallExpr(CallExpr *CE) {
     63     if (Decl *D = getDeclFromCall(CE))
     64       addCalledDecl(D);
     65   }
     66 
     67   // Adds may-call edges for the ObjC message sends.
     68   void VisitObjCMessageExpr(ObjCMessageExpr *ME) {
     69     if (ObjCInterfaceDecl *IDecl = ME->getReceiverInterface()) {
     70       Selector Sel = ME->getSelector();
     71 
     72       // Find the callee definition within the same translation unit.
     73       Decl *D = nullptr;
     74       if (ME->isInstanceMessage())
     75         D = IDecl->lookupPrivateMethod(Sel);
     76       else
     77         D = IDecl->lookupPrivateClassMethod(Sel);
     78       if (D) {
     79         addCalledDecl(D);
     80         NumObjCCallEdges++;
     81       }
     82     }
     83   }
     84 
     85   void VisitChildren(Stmt *S) {
     86     for (Stmt::child_range I = S->children(); I; ++I)
     87       if (*I)
     88         static_cast<CGBuilder*>(this)->Visit(*I);
     89   }
     90 };
     91 
     92 } // end anonymous namespace
     93 
     94 void CallGraph::addNodesForBlocks(DeclContext *D) {
     95   if (BlockDecl *BD = dyn_cast<BlockDecl>(D))
     96     addNodeForDecl(BD, true);
     97 
     98   for (auto *I : D->decls())
     99     if (auto *DC = dyn_cast<DeclContext>(I))
    100       addNodesForBlocks(DC);
    101 }
    102 
    103 CallGraph::CallGraph() {
    104   Root = getOrInsertNode(nullptr);
    105 }
    106 
    107 CallGraph::~CallGraph() {
    108   llvm::DeleteContainerSeconds(FunctionMap);
    109 }
    110 
    111 bool CallGraph::includeInGraph(const Decl *D) {
    112   assert(D);
    113   if (!D->getBody())
    114     return false;
    115 
    116   if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
    117     // We skip function template definitions, as their semantics is
    118     // only determined when they are instantiated.
    119     if (!FD->isThisDeclarationADefinition() ||
    120         FD->isDependentContext())
    121       return false;
    122 
    123     IdentifierInfo *II = FD->getIdentifier();
    124     if (II && II->getName().startswith("__inline"))
    125       return false;
    126   }
    127 
    128   if (const ObjCMethodDecl *ID = dyn_cast<ObjCMethodDecl>(D)) {
    129     if (!ID->isThisDeclarationADefinition())
    130       return false;
    131   }
    132 
    133   return true;
    134 }
    135 
    136 void CallGraph::addNodeForDecl(Decl* D, bool IsGlobal) {
    137   assert(D);
    138 
    139   // Allocate a new node, mark it as root, and process it's calls.
    140   CallGraphNode *Node = getOrInsertNode(D);
    141 
    142   // Process all the calls by this function as well.
    143   CGBuilder builder(this, Node);
    144   if (Stmt *Body = D->getBody())
    145     builder.Visit(Body);
    146 }
    147 
    148 CallGraphNode *CallGraph::getNode(const Decl *F) const {
    149   FunctionMapTy::const_iterator I = FunctionMap.find(F);
    150   if (I == FunctionMap.end()) return nullptr;
    151   return I->second;
    152 }
    153 
    154 CallGraphNode *CallGraph::getOrInsertNode(Decl *F) {
    155   CallGraphNode *&Node = FunctionMap[F];
    156   if (Node)
    157     return Node;
    158 
    159   Node = new CallGraphNode(F);
    160   // Make Root node a parent of all functions to make sure all are reachable.
    161   if (F)
    162     Root->addCallee(Node, this);
    163   return Node;
    164 }
    165 
    166 void CallGraph::print(raw_ostream &OS) const {
    167   OS << " --- Call graph Dump --- \n";
    168 
    169   // We are going to print the graph in reverse post order, partially, to make
    170   // sure the output is deterministic.
    171   llvm::ReversePostOrderTraversal<const clang::CallGraph*> RPOT(this);
    172   for (llvm::ReversePostOrderTraversal<const clang::CallGraph*>::rpo_iterator
    173          I = RPOT.begin(), E = RPOT.end(); I != E; ++I) {
    174     const CallGraphNode *N = *I;
    175 
    176     OS << "  Function: ";
    177     if (N == Root)
    178       OS << "< root >";
    179     else
    180       N->print(OS);
    181 
    182     OS << " calls: ";
    183     for (CallGraphNode::const_iterator CI = N->begin(),
    184                                        CE = N->end(); CI != CE; ++CI) {
    185       assert(*CI != Root && "No one can call the root node.");
    186       (*CI)->print(OS);
    187       OS << " ";
    188     }
    189     OS << '\n';
    190   }
    191   OS.flush();
    192 }
    193 
    194 void CallGraph::dump() const {
    195   print(llvm::errs());
    196 }
    197 
    198 void CallGraph::viewGraph() const {
    199   llvm::ViewGraph(this, "CallGraph");
    200 }
    201 
    202 void CallGraphNode::print(raw_ostream &os) const {
    203   if (const NamedDecl *ND = dyn_cast_or_null<NamedDecl>(FD))
    204       return ND->printName(os);
    205   os << "< >";
    206 }
    207 
    208 void CallGraphNode::dump() const {
    209   print(llvm::errs());
    210 }
    211 
    212 namespace llvm {
    213 
    214 template <>
    215 struct DOTGraphTraits<const CallGraph*> : public DefaultDOTGraphTraits {
    216 
    217   DOTGraphTraits (bool isSimple=false) : DefaultDOTGraphTraits(isSimple) {}
    218 
    219   static std::string getNodeLabel(const CallGraphNode *Node,
    220                                   const CallGraph *CG) {
    221     if (CG->getRoot() == Node) {
    222       return "< root >";
    223     }
    224     if (const NamedDecl *ND = dyn_cast_or_null<NamedDecl>(Node->getDecl()))
    225       return ND->getNameAsString();
    226     else
    227       return "< >";
    228   }
    229 
    230 };
    231 }
    232