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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 #define DEBUG_TYPE "CallGraph"
     14 
     15 #include "clang/Analysis/CallGraph.h"
     16 #include "clang/AST/ASTContext.h"
     17 #include "clang/AST/Decl.h"
     18 #include "clang/AST/StmtVisitor.h"
     19 #include "llvm/ADT/PostOrderIterator.h"
     20 #include "llvm/ADT/Statistic.h"
     21 #include "llvm/Support/GraphWriter.h"
     22 
     23 using namespace clang;
     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 0;
     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 = 0;
     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 (DeclContext::decl_iterator I = D->decls_begin(), E = D->decls_end();
     99        I!=E; ++I)
    100     if (DeclContext *DC = dyn_cast<DeclContext>(*I))
    101       addNodesForBlocks(DC);
    102 }
    103 
    104 CallGraph::CallGraph() {
    105   Root = getOrInsertNode(0);
    106 }
    107 
    108 CallGraph::~CallGraph() {
    109   if (!FunctionMap.empty()) {
    110     for (FunctionMapTy::iterator I = FunctionMap.begin(), E = FunctionMap.end();
    111         I != E; ++I)
    112       delete I->second;
    113     FunctionMap.clear();
    114   }
    115 }
    116 
    117 bool CallGraph::includeInGraph(const Decl *D) {
    118   assert(D);
    119   if (!D->getBody())
    120     return false;
    121 
    122   if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
    123     // We skip function template definitions, as their semantics is
    124     // only determined when they are instantiated.
    125     if (!FD->isThisDeclarationADefinition() ||
    126         FD->isDependentContext())
    127       return false;
    128 
    129     IdentifierInfo *II = FD->getIdentifier();
    130     if (II && II->getName().startswith("__inline"))
    131       return false;
    132   }
    133 
    134   if (const ObjCMethodDecl *ID = dyn_cast<ObjCMethodDecl>(D)) {
    135     if (!ID->isThisDeclarationADefinition())
    136       return false;
    137   }
    138 
    139   return true;
    140 }
    141 
    142 void CallGraph::addNodeForDecl(Decl* D, bool IsGlobal) {
    143   assert(D);
    144 
    145   // Allocate a new node, mark it as root, and process it's calls.
    146   CallGraphNode *Node = getOrInsertNode(D);
    147 
    148   // Process all the calls by this function as well.
    149   CGBuilder builder(this, Node);
    150   if (Stmt *Body = D->getBody())
    151     builder.Visit(Body);
    152 }
    153 
    154 CallGraphNode *CallGraph::getNode(const Decl *F) const {
    155   FunctionMapTy::const_iterator I = FunctionMap.find(F);
    156   if (I == FunctionMap.end()) return 0;
    157   return I->second;
    158 }
    159 
    160 CallGraphNode *CallGraph::getOrInsertNode(Decl *F) {
    161   CallGraphNode *&Node = FunctionMap[F];
    162   if (Node)
    163     return Node;
    164 
    165   Node = new CallGraphNode(F);
    166   // Make Root node a parent of all functions to make sure all are reachable.
    167   if (F != 0)
    168     Root->addCallee(Node, this);
    169   return Node;
    170 }
    171 
    172 void CallGraph::print(raw_ostream &OS) const {
    173   OS << " --- Call graph Dump --- \n";
    174 
    175   // We are going to print the graph in reverse post order, partially, to make
    176   // sure the output is deterministic.
    177   llvm::ReversePostOrderTraversal<const clang::CallGraph*> RPOT(this);
    178   for (llvm::ReversePostOrderTraversal<const clang::CallGraph*>::rpo_iterator
    179          I = RPOT.begin(), E = RPOT.end(); I != E; ++I) {
    180     const CallGraphNode *N = *I;
    181 
    182     OS << "  Function: ";
    183     if (N == Root)
    184       OS << "< root >";
    185     else
    186       N->print(OS);
    187 
    188     OS << " calls: ";
    189     for (CallGraphNode::const_iterator CI = N->begin(),
    190                                        CE = N->end(); CI != CE; ++CI) {
    191       assert(*CI != Root && "No one can call the root node.");
    192       (*CI)->print(OS);
    193       OS << " ";
    194     }
    195     OS << '\n';
    196   }
    197   OS.flush();
    198 }
    199 
    200 void CallGraph::dump() const {
    201   print(llvm::errs());
    202 }
    203 
    204 void CallGraph::viewGraph() const {
    205   llvm::ViewGraph(this, "CallGraph");
    206 }
    207 
    208 void CallGraphNode::print(raw_ostream &os) const {
    209   if (const NamedDecl *ND = dyn_cast_or_null<NamedDecl>(FD))
    210       return ND->printName(os);
    211   os << "< >";
    212 }
    213 
    214 void CallGraphNode::dump() const {
    215   print(llvm::errs());
    216 }
    217 
    218 namespace llvm {
    219 
    220 template <>
    221 struct DOTGraphTraits<const CallGraph*> : public DefaultDOTGraphTraits {
    222 
    223   DOTGraphTraits (bool isSimple=false) : DefaultDOTGraphTraits(isSimple) {}
    224 
    225   static std::string getNodeLabel(const CallGraphNode *Node,
    226                                   const CallGraph *CG) {
    227     if (CG->getRoot() == Node) {
    228       return "< root >";
    229     }
    230     if (const NamedDecl *ND = dyn_cast_or_null<NamedDecl>(Node->getDecl()))
    231       return ND->getNameAsString();
    232     else
    233       return "< >";
    234   }
    235 
    236 };
    237 }
    238