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 *SubStmt : S->children())
87       if (SubStmt)
88         this->Visit(SubStmt);
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 
109 bool CallGraph::includeInGraph(const Decl *D) {
110   assert(D);
111   if (!D->hasBody())
112     return false;
113 
114   if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
115     // We skip function template definitions, as their semantics is
116     // only determined when they are instantiated.
117     if (FD->isDependentContext())
118       return false;
119 
120     IdentifierInfo *II = FD->getIdentifier();
121     if (II && II->getName().startswith("__inline"))
122       return false;
123   }
124 
125   return true;
126 }
127 
128 void CallGraph::addNodeForDecl(Decl* D, bool IsGlobal) {
129   assert(D);
130 
131   // Allocate a new node, mark it as root, and process it's calls.
132   CallGraphNode *Node = getOrInsertNode(D);
133 
134   // Process all the calls by this function as well.
135   CGBuilder builder(this, Node);
136   if (Stmt *Body = D->getBody())
137     builder.Visit(Body);
138 }
139 
140 CallGraphNode *CallGraph::getNode(const Decl *F) const {
141   FunctionMapTy::const_iterator I = FunctionMap.find(F);
142   if (I == FunctionMap.end()) return nullptr;
143   return I->second.get();
144 }
145 
146 CallGraphNode *CallGraph::getOrInsertNode(Decl *F) {
147   if (F && !isa<ObjCMethodDecl>(F))
148     F = F->getCanonicalDecl();
149 
150   std::unique_ptr<CallGraphNode> &Node = FunctionMap[F];
151   if (Node)
152     return Node.get();
153 
154   Node = llvm::make_unique<CallGraphNode>(F);
155   // Make Root node a parent of all functions to make sure all are reachable.
156   if (F)
157     Root->addCallee(Node.get(), this);
158   return Node.get();
159 }
160 
161 void CallGraph::print(raw_ostream &OS) const {
162   OS << " --- Call graph Dump --- \n";
163 
164   // We are going to print the graph in reverse post order, partially, to make
165   // sure the output is deterministic.
166   llvm::ReversePostOrderTraversal<const clang::CallGraph*> RPOT(this);
167   for (llvm::ReversePostOrderTraversal<const clang::CallGraph*>::rpo_iterator
168          I = RPOT.begin(), E = RPOT.end(); I != E; ++I) {
169     const CallGraphNode *N = *I;
170 
171     OS << "  Function: ";
172     if (N == Root)
173       OS << "< root >";
174     else
175       N->print(OS);
176 
177     OS << " calls: ";
178     for (CallGraphNode::const_iterator CI = N->begin(),
179                                        CE = N->end(); CI != CE; ++CI) {
180       assert(*CI != Root && "No one can call the root node.");
181       (*CI)->print(OS);
182       OS << " ";
183     }
184     OS << '\n';
185   }
186   OS.flush();
187 }
188 
189 LLVM_DUMP_METHOD void CallGraph::dump() const {
190   print(llvm::errs());
191 }
192 
193 void CallGraph::viewGraph() const {
194   llvm::ViewGraph(this, "CallGraph");
195 }
196 
197 void CallGraphNode::print(raw_ostream &os) const {
198   if (const NamedDecl *ND = dyn_cast_or_null<NamedDecl>(FD))
199       return ND->printName(os);
200   os << "< >";
201 }
202 
203 LLVM_DUMP_METHOD void CallGraphNode::dump() const {
204   print(llvm::errs());
205 }
206 
207 namespace llvm {
208 
209 template <>
210 struct DOTGraphTraits<const CallGraph*> : public DefaultDOTGraphTraits {
211 
212   DOTGraphTraits (bool isSimple=false) : DefaultDOTGraphTraits(isSimple) {}
213 
214   static std::string getNodeLabel(const CallGraphNode *Node,
215                                   const CallGraph *CG) {
216     if (CG->getRoot() == Node) {
217       return "< root >";
218     }
219     if (const NamedDecl *ND = dyn_cast_or_null<NamedDecl>(Node->getDecl()))
220       return ND->getNameAsString();
221     else
222       return "< >";
223   }
224 
225 };
226 }
227