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, Expr *CallExpr) {
70 if (G->includeCalleeInGraph(D)) {
71 CallGraphNode *CalleeNode = G->getOrInsertNode(D);
72 CallerNode->addCallee({CalleeNode, CallExpr});
73 }
74 }
75
76 void VisitCallExpr(CallExpr *CE) {
77 if (Decl *D = getDeclFromCall(CE))
78 addCalledDecl(D, CE);
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, E);
93 VisitChildren(E);
94 }
95
96 void VisitCXXConstructExpr(CXXConstructExpr *E) {
97 CXXConstructorDecl *Ctor = E->getConstructor();
98 if (FunctionDecl *Def = Ctor->getDefinition())
99 addCalledDecl(Def, E);
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, ME);
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 return includeCalleeInGraph(D);
161}
162
163bool CallGraph::includeCalleeInGraph(const Decl *D) {
164 if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
165 // We skip function template definitions, as their semantics is
166 // only determined when they are instantiated.
167 if (FD->isDependentContext())
168 return false;
169
170 IdentifierInfo *II = FD->getIdentifier();
171 if (II && II->getName().startswith("__inline"))
172 return false;
173 }
174
175 return true;
176}
177
178void CallGraph::addNodeForDecl(Decl* D, bool IsGlobal) {
179 assert(D);
180
181 // Allocate a new node, mark it as root, and process its calls.
182 CallGraphNode *Node = getOrInsertNode(D);
183
184 // Process all the calls by this function as well.
185 CGBuilder builder(this, Node);
186 if (Stmt *Body = D->getBody())
187 builder.Visit(Body);
188
189 // Include C++ constructor member initializers.
190 if (auto constructor = dyn_cast<CXXConstructorDecl>(D)) {
191 for (CXXCtorInitializer *init : constructor->inits()) {
192 builder.Visit(init->getInit());
193 }
194 }
195}
196
197CallGraphNode *CallGraph::getNode(const Decl *F) const {
198 FunctionMapTy::const_iterator I = FunctionMap.find(F);
199 if (I == FunctionMap.end()) return nullptr;
200 return I->second.get();
201}
202
203CallGraphNode *CallGraph::getOrInsertNode(Decl *F) {
204 if (F && !isa<ObjCMethodDecl>(F))
205 F = F->getCanonicalDecl();
206
207 std::unique_ptr<CallGraphNode> &Node = FunctionMap[F];
208 if (Node)
209 return Node.get();
210
211 Node = std::make_unique<CallGraphNode>(F);
212 // Make Root node a parent of all functions to make sure all are reachable.
213 if (F)
214 Root->addCallee({Node.get(), /*Call=*/nullptr});
215 return Node.get();
216}
217
218void CallGraph::print(raw_ostream &OS) const {
219 OS << " --- Call graph Dump --- \n";
220
221 // We are going to print the graph in reverse post order, partially, to make
222 // sure the output is deterministic.
223 llvm::ReversePostOrderTraversal<const CallGraph *> RPOT(this);
224 for (llvm::ReversePostOrderTraversal<const CallGraph *>::rpo_iterator
225 I = RPOT.begin(), E = RPOT.end(); I != E; ++I) {
226 const CallGraphNode *N = *I;
227
228 OS << " Function: ";
229 if (N == Root)
230 OS << "< root >";
231 else
232 N->print(OS);
233
234 OS << " calls: ";
235 for (CallGraphNode::const_iterator CI = N->begin(),
236 CE = N->end(); CI != CE; ++CI) {
237 assert(CI->Callee != Root && "No one can call the root node.");
238 CI->Callee->print(OS);
239 OS << " ";
240 }
241 OS << '\n';
242 }
243 OS.flush();
244}
245
246LLVM_DUMP_METHOD void CallGraph::dump() const {
247 print(llvm::errs());
248}
249
250void CallGraph::viewGraph() const {
251 llvm::ViewGraph(this, "CallGraph");
252}
253
254void CallGraphNode::print(raw_ostream &os) const {
255 if (const NamedDecl *ND = dyn_cast_or_null<NamedDecl>(FD))
256 return ND->printQualifiedName(os);
257 os << "< >";
258}
259
260LLVM_DUMP_METHOD void CallGraphNode::dump() const {
261 print(llvm::errs());
262}
263
264namespace llvm {
265
266template <>
267struct DOTGraphTraits<const CallGraph*> : public DefaultDOTGraphTraits {
268 DOTGraphTraits (bool isSimple = false) : DefaultDOTGraphTraits(isSimple) {}
269
270 static std::string getNodeLabel(const CallGraphNode *Node,
271 const CallGraph *CG) {
272 if (CG->getRoot() == Node) {
273 return "< root >";
274 }
275 if (const NamedDecl *ND = dyn_cast_or_null<NamedDecl>(Node->getDecl()))
276 return ND->getNameAsString();
277 else
278 return "< >";
279 }
280};
281
282} // namespace llvm
283