1 //== BodyFarm.cpp - Factory for conjuring up fake bodies ----------*- 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 // BodyFarm is a factory for creating faux implementations for functions/methods
11 // for analysis purposes.
12 //
13 //===----------------------------------------------------------------------===//
14
15 #include "BodyFarm.h"
16 #include "clang/AST/ASTContext.h"
17 #include "clang/AST/Decl.h"
18 #include "clang/AST/Expr.h"
19 #include "clang/AST/ExprObjC.h"
20 #include "llvm/ADT/StringSwitch.h"
21
22 using namespace clang;
23
24 //===----------------------------------------------------------------------===//
25 // Helper creation functions for constructing faux ASTs.
26 //===----------------------------------------------------------------------===//
27
isDispatchBlock(QualType Ty)28 static bool isDispatchBlock(QualType Ty) {
29 // Is it a block pointer?
30 const BlockPointerType *BPT = Ty->getAs<BlockPointerType>();
31 if (!BPT)
32 return false;
33
34 // Check if the block pointer type takes no arguments and
35 // returns void.
36 const FunctionProtoType *FT =
37 BPT->getPointeeType()->getAs<FunctionProtoType>();
38 if (!FT || !FT->getResultType()->isVoidType() ||
39 FT->getNumArgs() != 0)
40 return false;
41
42 return true;
43 }
44
45 namespace {
46 class ASTMaker {
47 public:
ASTMaker(ASTContext & C)48 ASTMaker(ASTContext &C) : C(C) {}
49
50 /// Create a new BinaryOperator representing a simple assignment.
51 BinaryOperator *makeAssignment(const Expr *LHS, const Expr *RHS, QualType Ty);
52
53 /// Create a new BinaryOperator representing a comparison.
54 BinaryOperator *makeComparison(const Expr *LHS, const Expr *RHS,
55 BinaryOperator::Opcode Op);
56
57 /// Create a new compound stmt using the provided statements.
58 CompoundStmt *makeCompound(ArrayRef<Stmt*>);
59
60 /// Create a new DeclRefExpr for the referenced variable.
61 DeclRefExpr *makeDeclRefExpr(const VarDecl *D);
62
63 /// Create a new UnaryOperator representing a dereference.
64 UnaryOperator *makeDereference(const Expr *Arg, QualType Ty);
65
66 /// Create an implicit cast for an integer conversion.
67 Expr *makeIntegralCast(const Expr *Arg, QualType Ty);
68
69 /// Create an implicit cast to a builtin boolean type.
70 ImplicitCastExpr *makeIntegralCastToBoolean(const Expr *Arg);
71
72 // Create an implicit cast for lvalue-to-rvaluate conversions.
73 ImplicitCastExpr *makeLvalueToRvalue(const Expr *Arg, QualType Ty);
74
75 /// Create an Objective-C bool literal.
76 ObjCBoolLiteralExpr *makeObjCBool(bool Val);
77
78 /// Create a Return statement.
79 ReturnStmt *makeReturn(const Expr *RetVal);
80
81 private:
82 ASTContext &C;
83 };
84 }
85
makeAssignment(const Expr * LHS,const Expr * RHS,QualType Ty)86 BinaryOperator *ASTMaker::makeAssignment(const Expr *LHS, const Expr *RHS,
87 QualType Ty) {
88 return new (C) BinaryOperator(const_cast<Expr*>(LHS), const_cast<Expr*>(RHS),
89 BO_Assign, Ty, VK_RValue,
90 OK_Ordinary, SourceLocation(), false);
91 }
92
makeComparison(const Expr * LHS,const Expr * RHS,BinaryOperator::Opcode Op)93 BinaryOperator *ASTMaker::makeComparison(const Expr *LHS, const Expr *RHS,
94 BinaryOperator::Opcode Op) {
95 assert(BinaryOperator::isLogicalOp(Op) ||
96 BinaryOperator::isComparisonOp(Op));
97 return new (C) BinaryOperator(const_cast<Expr*>(LHS),
98 const_cast<Expr*>(RHS),
99 Op,
100 C.getLogicalOperationType(),
101 VK_RValue,
102 OK_Ordinary, SourceLocation(), false);
103 }
104
makeCompound(ArrayRef<Stmt * > Stmts)105 CompoundStmt *ASTMaker::makeCompound(ArrayRef<Stmt *> Stmts) {
106 return new (C) CompoundStmt(C, Stmts, SourceLocation(), SourceLocation());
107 }
108
makeDeclRefExpr(const VarDecl * D)109 DeclRefExpr *ASTMaker::makeDeclRefExpr(const VarDecl *D) {
110 DeclRefExpr *DR =
111 DeclRefExpr::Create(/* Ctx = */ C,
112 /* QualifierLoc = */ NestedNameSpecifierLoc(),
113 /* TemplateKWLoc = */ SourceLocation(),
114 /* D = */ const_cast<VarDecl*>(D),
115 /* isEnclosingLocal = */ false,
116 /* NameLoc = */ SourceLocation(),
117 /* T = */ D->getType(),
118 /* VK = */ VK_LValue);
119 return DR;
120 }
121
makeDereference(const Expr * Arg,QualType Ty)122 UnaryOperator *ASTMaker::makeDereference(const Expr *Arg, QualType Ty) {
123 return new (C) UnaryOperator(const_cast<Expr*>(Arg), UO_Deref, Ty,
124 VK_LValue, OK_Ordinary, SourceLocation());
125 }
126
makeLvalueToRvalue(const Expr * Arg,QualType Ty)127 ImplicitCastExpr *ASTMaker::makeLvalueToRvalue(const Expr *Arg, QualType Ty) {
128 return ImplicitCastExpr::Create(C, Ty, CK_LValueToRValue,
129 const_cast<Expr*>(Arg), 0, VK_RValue);
130 }
131
makeIntegralCast(const Expr * Arg,QualType Ty)132 Expr *ASTMaker::makeIntegralCast(const Expr *Arg, QualType Ty) {
133 if (Arg->getType() == Ty)
134 return const_cast<Expr*>(Arg);
135
136 return ImplicitCastExpr::Create(C, Ty, CK_IntegralCast,
137 const_cast<Expr*>(Arg), 0, VK_RValue);
138 }
139
makeIntegralCastToBoolean(const Expr * Arg)140 ImplicitCastExpr *ASTMaker::makeIntegralCastToBoolean(const Expr *Arg) {
141 return ImplicitCastExpr::Create(C, C.BoolTy, CK_IntegralToBoolean,
142 const_cast<Expr*>(Arg), 0, VK_RValue);
143 }
144
makeObjCBool(bool Val)145 ObjCBoolLiteralExpr *ASTMaker::makeObjCBool(bool Val) {
146 QualType Ty = C.getBOOLDecl() ? C.getBOOLType() : C.ObjCBuiltinBoolTy;
147 return new (C) ObjCBoolLiteralExpr(Val, Ty, SourceLocation());
148 }
149
makeReturn(const Expr * RetVal)150 ReturnStmt *ASTMaker::makeReturn(const Expr *RetVal) {
151 return new (C) ReturnStmt(SourceLocation(), const_cast<Expr*>(RetVal), 0);
152 }
153
154 //===----------------------------------------------------------------------===//
155 // Creation functions for faux ASTs.
156 //===----------------------------------------------------------------------===//
157
158 typedef Stmt *(*FunctionFarmer)(ASTContext &C, const FunctionDecl *D);
159
160 /// Create a fake body for dispatch_once.
create_dispatch_once(ASTContext & C,const FunctionDecl * D)161 static Stmt *create_dispatch_once(ASTContext &C, const FunctionDecl *D) {
162 // Check if we have at least two parameters.
163 if (D->param_size() != 2)
164 return 0;
165
166 // Check if the first parameter is a pointer to integer type.
167 const ParmVarDecl *Predicate = D->getParamDecl(0);
168 QualType PredicateQPtrTy = Predicate->getType();
169 const PointerType *PredicatePtrTy = PredicateQPtrTy->getAs<PointerType>();
170 if (!PredicatePtrTy)
171 return 0;
172 QualType PredicateTy = PredicatePtrTy->getPointeeType();
173 if (!PredicateTy->isIntegerType())
174 return 0;
175
176 // Check if the second parameter is the proper block type.
177 const ParmVarDecl *Block = D->getParamDecl(1);
178 QualType Ty = Block->getType();
179 if (!isDispatchBlock(Ty))
180 return 0;
181
182 // Everything checks out. Create a fakse body that checks the predicate,
183 // sets it, and calls the block. Basically, an AST dump of:
184 //
185 // void dispatch_once(dispatch_once_t *predicate, dispatch_block_t block) {
186 // if (!*predicate) {
187 // *predicate = 1;
188 // block();
189 // }
190 // }
191
192 ASTMaker M(C);
193
194 // (1) Create the call.
195 DeclRefExpr *DR = M.makeDeclRefExpr(Block);
196 ImplicitCastExpr *ICE = M.makeLvalueToRvalue(DR, Ty);
197 CallExpr *CE = new (C) CallExpr(C, ICE, None, C.VoidTy, VK_RValue,
198 SourceLocation());
199
200 // (2) Create the assignment to the predicate.
201 IntegerLiteral *IL =
202 IntegerLiteral::Create(C, llvm::APInt(C.getTypeSize(C.IntTy), (uint64_t) 1),
203 C.IntTy, SourceLocation());
204 BinaryOperator *B =
205 M.makeAssignment(
206 M.makeDereference(
207 M.makeLvalueToRvalue(
208 M.makeDeclRefExpr(Predicate), PredicateQPtrTy),
209 PredicateTy),
210 M.makeIntegralCast(IL, PredicateTy),
211 PredicateTy);
212
213 // (3) Create the compound statement.
214 Stmt *Stmts[2];
215 Stmts[0] = B;
216 Stmts[1] = CE;
217 CompoundStmt *CS = M.makeCompound(ArrayRef<Stmt*>(Stmts, 2));
218
219 // (4) Create the 'if' condition.
220 ImplicitCastExpr *LValToRval =
221 M.makeLvalueToRvalue(
222 M.makeDereference(
223 M.makeLvalueToRvalue(
224 M.makeDeclRefExpr(Predicate),
225 PredicateQPtrTy),
226 PredicateTy),
227 PredicateTy);
228
229 UnaryOperator *UO = new (C) UnaryOperator(LValToRval, UO_LNot, C.IntTy,
230 VK_RValue, OK_Ordinary,
231 SourceLocation());
232
233 // (5) Create the 'if' statement.
234 IfStmt *If = new (C) IfStmt(C, SourceLocation(), 0, UO, CS);
235 return If;
236 }
237
238 /// Create a fake body for dispatch_sync.
create_dispatch_sync(ASTContext & C,const FunctionDecl * D)239 static Stmt *create_dispatch_sync(ASTContext &C, const FunctionDecl *D) {
240 // Check if we have at least two parameters.
241 if (D->param_size() != 2)
242 return 0;
243
244 // Check if the second parameter is a block.
245 const ParmVarDecl *PV = D->getParamDecl(1);
246 QualType Ty = PV->getType();
247 if (!isDispatchBlock(Ty))
248 return 0;
249
250 // Everything checks out. Create a fake body that just calls the block.
251 // This is basically just an AST dump of:
252 //
253 // void dispatch_sync(dispatch_queue_t queue, void (^block)(void)) {
254 // block();
255 // }
256 //
257 ASTMaker M(C);
258 DeclRefExpr *DR = M.makeDeclRefExpr(PV);
259 ImplicitCastExpr *ICE = M.makeLvalueToRvalue(DR, Ty);
260 CallExpr *CE = new (C) CallExpr(C, ICE, None, C.VoidTy, VK_RValue,
261 SourceLocation());
262 return CE;
263 }
264
create_OSAtomicCompareAndSwap(ASTContext & C,const FunctionDecl * D)265 static Stmt *create_OSAtomicCompareAndSwap(ASTContext &C, const FunctionDecl *D)
266 {
267 // There are exactly 3 arguments.
268 if (D->param_size() != 3)
269 return 0;
270
271 // Signature:
272 // _Bool OSAtomicCompareAndSwapPtr(void *__oldValue,
273 // void *__newValue,
274 // void * volatile *__theValue)
275 // Generate body:
276 // if (oldValue == *theValue) {
277 // *theValue = newValue;
278 // return YES;
279 // }
280 // else return NO;
281
282 QualType ResultTy = D->getResultType();
283 bool isBoolean = ResultTy->isBooleanType();
284 if (!isBoolean && !ResultTy->isIntegralType(C))
285 return 0;
286
287 const ParmVarDecl *OldValue = D->getParamDecl(0);
288 QualType OldValueTy = OldValue->getType();
289
290 const ParmVarDecl *NewValue = D->getParamDecl(1);
291 QualType NewValueTy = NewValue->getType();
292
293 assert(OldValueTy == NewValueTy);
294
295 const ParmVarDecl *TheValue = D->getParamDecl(2);
296 QualType TheValueTy = TheValue->getType();
297 const PointerType *PT = TheValueTy->getAs<PointerType>();
298 if (!PT)
299 return 0;
300 QualType PointeeTy = PT->getPointeeType();
301
302 ASTMaker M(C);
303 // Construct the comparison.
304 Expr *Comparison =
305 M.makeComparison(
306 M.makeLvalueToRvalue(M.makeDeclRefExpr(OldValue), OldValueTy),
307 M.makeLvalueToRvalue(
308 M.makeDereference(
309 M.makeLvalueToRvalue(M.makeDeclRefExpr(TheValue), TheValueTy),
310 PointeeTy),
311 PointeeTy),
312 BO_EQ);
313
314 // Construct the body of the IfStmt.
315 Stmt *Stmts[2];
316 Stmts[0] =
317 M.makeAssignment(
318 M.makeDereference(
319 M.makeLvalueToRvalue(M.makeDeclRefExpr(TheValue), TheValueTy),
320 PointeeTy),
321 M.makeLvalueToRvalue(M.makeDeclRefExpr(NewValue), NewValueTy),
322 NewValueTy);
323
324 Expr *BoolVal = M.makeObjCBool(true);
325 Expr *RetVal = isBoolean ? M.makeIntegralCastToBoolean(BoolVal)
326 : M.makeIntegralCast(BoolVal, ResultTy);
327 Stmts[1] = M.makeReturn(RetVal);
328 CompoundStmt *Body = M.makeCompound(ArrayRef<Stmt*>(Stmts, 2));
329
330 // Construct the else clause.
331 BoolVal = M.makeObjCBool(false);
332 RetVal = isBoolean ? M.makeIntegralCastToBoolean(BoolVal)
333 : M.makeIntegralCast(BoolVal, ResultTy);
334 Stmt *Else = M.makeReturn(RetVal);
335
336 /// Construct the If.
337 Stmt *If =
338 new (C) IfStmt(C, SourceLocation(), 0, Comparison, Body,
339 SourceLocation(), Else);
340
341 return If;
342 }
343
getBody(const FunctionDecl * D)344 Stmt *BodyFarm::getBody(const FunctionDecl *D) {
345 D = D->getCanonicalDecl();
346
347 Optional<Stmt *> &Val = Bodies[D];
348 if (Val.hasValue())
349 return Val.getValue();
350
351 Val = 0;
352
353 if (D->getIdentifier() == 0)
354 return 0;
355
356 StringRef Name = D->getName();
357 if (Name.empty())
358 return 0;
359
360 FunctionFarmer FF;
361
362 if (Name.startswith("OSAtomicCompareAndSwap") ||
363 Name.startswith("objc_atomicCompareAndSwap")) {
364 FF = create_OSAtomicCompareAndSwap;
365 }
366 else {
367 FF = llvm::StringSwitch<FunctionFarmer>(Name)
368 .Case("dispatch_sync", create_dispatch_sync)
369 .Case("dispatch_once", create_dispatch_once)
370 .Default(NULL);
371 }
372
373 if (FF) { Val = FF(C, D); }
374 return Val.getValue();
375 }
376
377