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 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: 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 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 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 } 104 105 CompoundStmt *ASTMaker::makeCompound(ArrayRef<Stmt *> Stmts) { 106 return new (C) CompoundStmt(C, Stmts, SourceLocation(), SourceLocation()); 107 } 108 109 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 } 121 122 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 } 126 127 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 } 131 132 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 } 139 140 ImplicitCastExpr *ASTMaker::makeIntegralCastToBoolean(const Expr *Arg) { 141 return ImplicitCastExpr::Create(C, C.BoolTy, CK_IntegralToBoolean, 142 const_cast<Expr*>(Arg), 0, VK_RValue); 143 } 144 145 ObjCBoolLiteralExpr *ASTMaker::makeObjCBool(bool Val) { 146 QualType Ty = C.getBOOLDecl() ? C.getBOOLType() : C.ObjCBuiltinBoolTy; 147 return new (C) ObjCBoolLiteralExpr(Val, Ty, SourceLocation()); 148 } 149 150 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. 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. 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 } 264 265 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 } 343 344 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