1//===- CallGraph.cpp - AST-based Call graph -------------------------------===// 2// 3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4// See https://llvm.org/LICENSE.txt for license information. 5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6// 7//===----------------------------------------------------------------------===// 8// 9// This file defines the AST-based CallGraph. 10// 11//===----------------------------------------------------------------------===// 12 13#include "clang/Analysis/CallGraph.h" 14#include "clang/AST/Decl.h" 15#include "clang/AST/DeclBase.h" 16#include "clang/AST/DeclObjC.h" 17#include "clang/AST/Expr.h" 18#include "clang/AST/ExprObjC.h" 19#include "clang/AST/Stmt.h" 20#include "clang/AST/StmtVisitor.h" 21#include "clang/Basic/IdentifierTable.h" 22#include "clang/Basic/LLVM.h" 23#include "llvm/ADT/PostOrderIterator.h" 24#include "llvm/ADT/STLExtras.h" 25#include "llvm/ADT/Statistic.h" 26#include "llvm/Support/Casting.h" 27#include "llvm/Support/Compiler.h" 28#include "llvm/Support/DOTGraphTraits.h" 29#include "llvm/Support/GraphWriter.h" 30#include "llvm/Support/raw_ostream.h" 31#include <cassert> 32#include <memory> 33#include <string> 34 35using namespace clang; 36 37#define DEBUG_TYPE "CallGraph" 38 39STATISTIC(NumObjCCallEdges, "Number of Objective-C method call edges"); 40STATISTIC(NumBlockCallEdges, "Number of block call edges"); 41 42namespace { 43 44/// A helper class, which walks the AST and locates all the call sites in the 45/// given function body. 46class CGBuilder : public StmtVisitor<CGBuilder> { 47 CallGraph *G; 48 CallGraphNode *CallerNode; 49 50public: 51 CGBuilder(CallGraph *g, CallGraphNode *N) : G(g), CallerNode(N) {} 52 53 void VisitStmt(Stmt *S) { VisitChildren(S); } 54 55 Decl *getDeclFromCall(CallExpr *CE) { 56 if (FunctionDecl *CalleeDecl = CE->getDirectCallee()) 57 return CalleeDecl; 58 59 // Simple detection of a call through a block. 60 Expr *CEE = CE->getCallee()->IgnoreParenImpCasts(); 61 if (BlockExpr *Block = dyn_cast<BlockExpr>(CEE)) { 62 NumBlockCallEdges++; 63 return Block->getBlockDecl(); 64 } 65 66 return nullptr; 67 } 68 69 void addCalledDecl(Decl *D) { 70 if (G->includeInGraph(D)) { 71 CallGraphNode *CalleeNode = G->getOrInsertNode(D); 72 CallerNode->addCallee(CalleeNode); 73 } 74 } 75 76 void VisitCallExpr(CallExpr *CE) { 77 if (Decl *D = getDeclFromCall(CE)) 78 addCalledDecl(D); 79 VisitChildren(CE); 80 } 81 82 void VisitLambdaExpr(LambdaExpr *LE) { 83 if (FunctionTemplateDecl *FTD = LE->getDependentCallOperator()) 84 for (FunctionDecl *FD : FTD->specializations()) 85 G->VisitFunctionDecl(FD); 86 else if (CXXMethodDecl *MD = LE->getCallOperator()) 87 G->VisitFunctionDecl(MD); 88 } 89 90 void VisitCXXNewExpr(CXXNewExpr *E) { 91 if (FunctionDecl *FD = E->getOperatorNew()) 92 addCalledDecl(FD); 93 VisitChildren(E); 94 } 95 96 void VisitCXXConstructExpr(CXXConstructExpr *E) { 97 CXXConstructorDecl *Ctor = E->getConstructor(); 98 if (FunctionDecl *Def = Ctor->getDefinition()) 99 addCalledDecl(Def); 100 VisitChildren(E); 101 } 102 103 // Include the evaluation of the default argument. 104 void VisitCXXDefaultArgExpr(CXXDefaultArgExpr *E) { 105 Visit(E->getExpr()); 106 } 107 108 // Include the evaluation of the default initializers in a class. 109 void VisitCXXDefaultInitExpr(CXXDefaultInitExpr *E) { 110 Visit(E->getExpr()); 111 } 112 113 // Adds may-call edges for the ObjC message sends. 114 void VisitObjCMessageExpr(ObjCMessageExpr *ME) { 115 if (ObjCInterfaceDecl *IDecl = ME->getReceiverInterface()) { 116 Selector Sel = ME->getSelector(); 117 118 // Find the callee definition within the same translation unit. 119 Decl *D = nullptr; 120 if (ME->isInstanceMessage()) 121 D = IDecl->lookupPrivateMethod(Sel); 122 else 123 D = IDecl->lookupPrivateClassMethod(Sel); 124 if (D) { 125 addCalledDecl(D); 126 NumObjCCallEdges++; 127 } 128 } 129 } 130 131 void VisitChildren(Stmt *S) { 132 for (Stmt *SubStmt : S->children()) 133 if (SubStmt) 134 this->Visit(SubStmt); 135 } 136}; 137 138} // namespace 139 140void CallGraph::addNodesForBlocks(DeclContext *D) { 141 if (BlockDecl *BD = dyn_cast<BlockDecl>(D)) 142 addNodeForDecl(BD, true); 143 144 for (auto *I : D->decls()) 145 if (auto *DC = dyn_cast<DeclContext>(I)) 146 addNodesForBlocks(DC); 147} 148 149CallGraph::CallGraph() { 150 Root = getOrInsertNode(nullptr); 151} 152 153CallGraph::~CallGraph() = default; 154 155bool CallGraph::includeInGraph(const Decl *D) { 156 assert(D); 157 if (!D->hasBody()) 158 return false; 159 160 if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) { 161 // We skip function template definitions, as their semantics is 162 // only determined when they are instantiated. 163 if (FD->isDependentContext()) 164 return false; 165 166 IdentifierInfo *II = FD->getIdentifier(); 167 if (II && II->getName().startswith("__inline")) 168 return false; 169 } 170 171 return true; 172} 173 174void CallGraph::addNodeForDecl(Decl* D, bool IsGlobal) { 175 assert(D); 176 177 // Allocate a new node, mark it as root, and process its calls. 178 CallGraphNode *Node = getOrInsertNode(D); 179 180 // Process all the calls by this function as well. 181 CGBuilder builder(this, Node); 182 if (Stmt *Body = D->getBody()) 183 builder.Visit(Body); 184 185 // Include C++ constructor member initializers. 186 if (auto constructor = dyn_cast<CXXConstructorDecl>(D)) { 187 for (CXXCtorInitializer *init : constructor->inits()) { 188 builder.Visit(init->getInit()); 189 } 190 } 191} 192 193CallGraphNode *CallGraph::getNode(const Decl *F) const { 194 FunctionMapTy::const_iterator I = FunctionMap.find(F); 195 if (I == FunctionMap.end()) return nullptr; 196 return I->second.get(); 197} 198 199CallGraphNode *CallGraph::getOrInsertNode(Decl *F) { 200 if (F && !isa<ObjCMethodDecl>(F)) 201 F = F->getCanonicalDecl(); 202 203 std::unique_ptr<CallGraphNode> &Node = FunctionMap[F]; 204 if (Node) 205 return Node.get(); 206 207 Node = std::make_unique<CallGraphNode>(F); 208 // Make Root node a parent of all functions to make sure all are reachable. 209 if (F) 210 Root->addCallee(Node.get()); 211 return Node.get(); 212} 213 214void CallGraph::print(raw_ostream &OS) const { 215 OS << " --- Call graph Dump --- \n"; 216 217 // We are going to print the graph in reverse post order, partially, to make 218 // sure the output is deterministic. 219 llvm::ReversePostOrderTraversal<const CallGraph *> RPOT(this); 220 for (llvm::ReversePostOrderTraversal<const CallGraph *>::rpo_iterator 221 I = RPOT.begin(), E = RPOT.end(); I != E; ++I) { 222 const CallGraphNode *N = *I; 223 224 OS << " Function: "; 225 if (N == Root) 226 OS << "< root >"; 227 else 228 N->print(OS); 229 230 OS << " calls: "; 231 for (CallGraphNode::const_iterator CI = N->begin(), 232 CE = N->end(); CI != CE; ++CI) { 233 assert(*CI != Root && "No one can call the root node."); 234 (*CI)->print(OS); 235 OS << " "; 236 } 237 OS << '\n'; 238 } 239 OS.flush(); 240} 241 242LLVM_DUMP_METHOD void CallGraph::dump() const { 243 print(llvm::errs()); 244} 245 246void CallGraph::viewGraph() const { 247 llvm::ViewGraph(this, "CallGraph"); 248} 249 250void CallGraphNode::print(raw_ostream &os) const { 251 if (const NamedDecl *ND = dyn_cast_or_null<NamedDecl>(FD)) 252 return ND->printQualifiedName(os); 253 os << "< >"; 254} 255 256LLVM_DUMP_METHOD void CallGraphNode::dump() const { 257 print(llvm::errs()); 258} 259 260namespace llvm { 261 262template <> 263struct DOTGraphTraits<const CallGraph*> : public DefaultDOTGraphTraits { 264 DOTGraphTraits (bool isSimple = false) : DefaultDOTGraphTraits(isSimple) {} 265 266 static std::string getNodeLabel(const CallGraphNode *Node, 267 const CallGraph *CG) { 268 if (CG->getRoot() == Node) { 269 return "< root >"; 270 } 271 if (const NamedDecl *ND = dyn_cast_or_null<NamedDecl>(Node->getDecl())) 272 return ND->getNameAsString(); 273 else 274 return "< >"; 275 } 276}; 277 278} // namespace llvm 279