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 // Adds may-call edges for the ObjC message sends.
83 void VisitObjCMessageExpr(ObjCMessageExpr *ME) {
84 if (ObjCInterfaceDecl *IDecl = ME->getReceiverInterface()) {
85 Selector Sel = ME->getSelector();
86
87 // Find the callee definition within the same translation unit.
88 Decl *D = nullptr;
89 if (ME->isInstanceMessage())
90 D = IDecl->lookupPrivateMethod(Sel);
91 else
92 D = IDecl->lookupPrivateClassMethod(Sel);
93 if (D) {
94 addCalledDecl(D);
95 NumObjCCallEdges++;
96 }
97 }
98 }
99
100 void VisitChildren(Stmt *S) {
101 for (Stmt *SubStmt : S->children())
102 if (SubStmt)
103 this->Visit(SubStmt);
104 }
105};
106
107} // namespace
108
109void CallGraph::addNodesForBlocks(DeclContext *D) {
110 if (BlockDecl *BD = dyn_cast<BlockDecl>(D))
111 addNodeForDecl(BD, true);
112
113 for (auto *I : D->decls())
114 if (auto *DC = dyn_cast<DeclContext>(I))
115 addNodesForBlocks(DC);
116}
117
118CallGraph::CallGraph() {
119 Root = getOrInsertNode(nullptr);
120}
121
122CallGraph::~CallGraph() = default;
123
124bool CallGraph::includeInGraph(const Decl *D) {
125 assert(D);
126 if (!D->hasBody())
127 return false;
128
129 if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
130 // We skip function template definitions, as their semantics is
131 // only determined when they are instantiated.
132 if (FD->isDependentContext())
133 return false;
134
135 IdentifierInfo *II = FD->getIdentifier();
136 if (II && II->getName().startswith("__inline"))
137 return false;
138 }
139
140 return true;
141}
142
143void CallGraph::addNodeForDecl(Decl* D, bool IsGlobal) {
144 assert(D);
145
146 // Allocate a new node, mark it as root, and process it's calls.
147 CallGraphNode *Node = getOrInsertNode(D);
148
149 // Process all the calls by this function as well.
150 CGBuilder builder(this, Node);
151 if (Stmt *Body = D->getBody())
152 builder.Visit(Body);
153}
154
155CallGraphNode *CallGraph::getNode(const Decl *F) const {
156 FunctionMapTy::const_iterator I = FunctionMap.find(F);
157 if (I == FunctionMap.end()) return nullptr;
158 return I->second.get();
159}
160
161CallGraphNode *CallGraph::getOrInsertNode(Decl *F) {
162 if (F && !isa<ObjCMethodDecl>(F))
163 F = F->getCanonicalDecl();
164
165 std::unique_ptr<CallGraphNode> &Node = FunctionMap[F];
166 if (Node)
167 return Node.get();
168
169 Node = llvm::make_unique<CallGraphNode>(F);
170 // Make Root node a parent of all functions to make sure all are reachable.
171 if (F)
172 Root->addCallee(Node.get());
173 return Node.get();
174}
175
176void CallGraph::print(raw_ostream &OS) const {
177 OS << " --- Call graph Dump --- \n";
178
179 // We are going to print the graph in reverse post order, partially, to make
180 // sure the output is deterministic.
181 llvm::ReversePostOrderTraversal<const CallGraph *> RPOT(this);
182 for (llvm::ReversePostOrderTraversal<const CallGraph *>::rpo_iterator
183 I = RPOT.begin(), E = RPOT.end(); I != E; ++I) {
184 const CallGraphNode *N = *I;
185
186 OS << " Function: ";
187 if (N == Root)
188 OS << "< root >";
189 else
190 N->print(OS);
191
192 OS << " calls: ";
193 for (CallGraphNode::const_iterator CI = N->begin(),
194 CE = N->end(); CI != CE; ++CI) {
195 assert(*CI != Root && "No one can call the root node.");
196 (*CI)->print(OS);
197 OS << " ";
198 }
199 OS << '\n';
200 }
201 OS.flush();
202}
203
204LLVM_DUMP_METHOD void CallGraph::dump() const {
205 print(llvm::errs());
206}
207
208void CallGraph::viewGraph() const {
209 llvm::ViewGraph(this, "CallGraph");
210}
211
212void CallGraphNode::print(raw_ostream &os) const {
213 if (const NamedDecl *ND = dyn_cast_or_null<NamedDecl>(FD))
214 return ND->printQualifiedName(os);
215 os << "< >";
216}
217
218LLVM_DUMP_METHOD void CallGraphNode::dump() const {
219 print(llvm::errs());
220}
221
222namespace llvm {
223
224template <>
225struct DOTGraphTraits<const CallGraph*> : public DefaultDOTGraphTraits {
226 DOTGraphTraits (bool isSimple = false) : DefaultDOTGraphTraits(isSimple) {}
227
228 static std::string getNodeLabel(const CallGraphNode *Node,
229 const CallGraph *CG) {
230 if (CG->getRoot() == Node) {
231 return "< root >";
232 }
233 if (const NamedDecl *ND = dyn_cast_or_null<NamedDecl>(Node->getDecl()))
234 return ND->getNameAsString();
235 else
236 return "< >";
237 }
238};
239
240} // namespace llvm
241