1 //===--- CGDeclCXX.cpp - Emit LLVM Code for C++ declarations --------------===// 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 // This contains code dealing with code generation of C++ declarations 11 // 12 //===----------------------------------------------------------------------===// 13 14 #include "CodeGenFunction.h" 15 #include "CGObjCRuntime.h" 16 #include "CGCXXABI.h" 17 #include "clang/Frontend/CodeGenOptions.h" 18 #include "llvm/Intrinsics.h" 19 20 using namespace clang; 21 using namespace CodeGen; 22 23 static void EmitDeclInit(CodeGenFunction &CGF, const VarDecl &D, 24 llvm::Constant *DeclPtr) { 25 assert(D.hasGlobalStorage() && "VarDecl must have global storage!"); 26 assert(!D.getType()->isReferenceType() && 27 "Should not call EmitDeclInit on a reference!"); 28 29 ASTContext &Context = CGF.getContext(); 30 31 CharUnits alignment = Context.getDeclAlign(&D); 32 QualType type = D.getType(); 33 LValue lv = CGF.MakeAddrLValue(DeclPtr, type, alignment); 34 35 const Expr *Init = D.getInit(); 36 if (!CGF.hasAggregateLLVMType(type)) { 37 CodeGenModule &CGM = CGF.CGM; 38 if (lv.isObjCStrong()) 39 CGM.getObjCRuntime().EmitObjCGlobalAssign(CGF, CGF.EmitScalarExpr(Init), 40 DeclPtr, D.isThreadSpecified()); 41 else if (lv.isObjCWeak()) 42 CGM.getObjCRuntime().EmitObjCWeakAssign(CGF, CGF.EmitScalarExpr(Init), 43 DeclPtr); 44 else 45 CGF.EmitScalarInit(Init, &D, lv, false); 46 } else if (type->isAnyComplexType()) { 47 CGF.EmitComplexExprIntoAddr(Init, DeclPtr, lv.isVolatile()); 48 } else { 49 CGF.EmitAggExpr(Init, AggValueSlot::forLValue(lv,AggValueSlot::IsDestructed, 50 AggValueSlot::DoesNotNeedGCBarriers, 51 AggValueSlot::IsNotAliased)); 52 } 53 } 54 55 /// Emit code to cause the destruction of the given variable with 56 /// static storage duration. 57 static void EmitDeclDestroy(CodeGenFunction &CGF, const VarDecl &D, 58 llvm::Constant *addr) { 59 CodeGenModule &CGM = CGF.CGM; 60 61 // FIXME: __attribute__((cleanup)) ? 62 63 QualType type = D.getType(); 64 QualType::DestructionKind dtorKind = type.isDestructedType(); 65 66 switch (dtorKind) { 67 case QualType::DK_none: 68 return; 69 70 case QualType::DK_cxx_destructor: 71 break; 72 73 case QualType::DK_objc_strong_lifetime: 74 case QualType::DK_objc_weak_lifetime: 75 // We don't care about releasing objects during process teardown. 76 return; 77 } 78 79 llvm::Constant *function; 80 llvm::Constant *argument; 81 82 // Special-case non-array C++ destructors, where there's a function 83 // with the right signature that we can just call. 84 const CXXRecordDecl *record = 0; 85 if (dtorKind == QualType::DK_cxx_destructor && 86 (record = type->getAsCXXRecordDecl())) { 87 assert(!record->hasTrivialDestructor()); 88 CXXDestructorDecl *dtor = record->getDestructor(); 89 90 function = CGM.GetAddrOfCXXDestructor(dtor, Dtor_Complete); 91 argument = addr; 92 93 // Otherwise, the standard logic requires a helper function. 94 } else { 95 function = CodeGenFunction(CGM).generateDestroyHelper(addr, type, 96 CGF.getDestroyer(dtorKind), 97 CGF.needsEHCleanup(dtorKind)); 98 argument = llvm::Constant::getNullValue(CGF.Int8PtrTy); 99 } 100 101 CGM.getCXXABI().registerGlobalDtor(CGF, function, argument); 102 } 103 104 /// Emit code to cause the variable at the given address to be considered as 105 /// constant from this point onwards. 106 static void EmitDeclInvariant(CodeGenFunction &CGF, const VarDecl &D, 107 llvm::Constant *Addr) { 108 // Don't emit the intrinsic if we're not optimizing. 109 if (!CGF.CGM.getCodeGenOpts().OptimizationLevel) 110 return; 111 112 // Grab the llvm.invariant.start intrinsic. 113 llvm::Intrinsic::ID InvStartID = llvm::Intrinsic::invariant_start; 114 llvm::Constant *InvariantStart = CGF.CGM.getIntrinsic(InvStartID); 115 116 // Emit a call with the size in bytes of the object. 117 CharUnits WidthChars = CGF.getContext().getTypeSizeInChars(D.getType()); 118 uint64_t Width = WidthChars.getQuantity(); 119 llvm::Value *Args[2] = { llvm::ConstantInt::getSigned(CGF.Int64Ty, Width), 120 llvm::ConstantExpr::getBitCast(Addr, CGF.Int8PtrTy)}; 121 CGF.Builder.CreateCall(InvariantStart, Args); 122 } 123 124 void CodeGenFunction::EmitCXXGlobalVarDeclInit(const VarDecl &D, 125 llvm::Constant *DeclPtr, 126 bool PerformInit) { 127 128 const Expr *Init = D.getInit(); 129 QualType T = D.getType(); 130 131 if (!T->isReferenceType()) { 132 if (PerformInit) 133 EmitDeclInit(*this, D, DeclPtr); 134 if (CGM.isTypeConstant(D.getType(), true)) 135 EmitDeclInvariant(*this, D, DeclPtr); 136 else 137 EmitDeclDestroy(*this, D, DeclPtr); 138 return; 139 } 140 141 assert(PerformInit && "cannot have constant initializer which needs " 142 "destruction for reference"); 143 unsigned Alignment = getContext().getDeclAlign(&D).getQuantity(); 144 RValue RV = EmitReferenceBindingToExpr(Init, &D); 145 EmitStoreOfScalar(RV.getScalarVal(), DeclPtr, false, Alignment, T); 146 } 147 148 static llvm::Function * 149 CreateGlobalInitOrDestructFunction(CodeGenModule &CGM, 150 llvm::FunctionType *ty, 151 const Twine &name); 152 153 /// Create a stub function, suitable for being passed to atexit, 154 /// which passes the given address to the given destructor function. 155 static llvm::Constant *createAtExitStub(CodeGenModule &CGM, 156 llvm::Constant *dtor, 157 llvm::Constant *addr) { 158 // Get the destructor function type, void(*)(void). 159 llvm::FunctionType *ty = llvm::FunctionType::get(CGM.VoidTy, false); 160 llvm::Function *fn = 161 CreateGlobalInitOrDestructFunction(CGM, ty, 162 Twine("__dtor_", addr->getName())); 163 164 CodeGenFunction CGF(CGM); 165 166 CGF.StartFunction(GlobalDecl(), CGM.getContext().VoidTy, fn, 167 CGM.getTypes().arrangeNullaryFunction(), 168 FunctionArgList(), SourceLocation()); 169 170 llvm::CallInst *call = CGF.Builder.CreateCall(dtor, addr); 171 172 // Make sure the call and the callee agree on calling convention. 173 if (llvm::Function *dtorFn = 174 dyn_cast<llvm::Function>(dtor->stripPointerCasts())) 175 call->setCallingConv(dtorFn->getCallingConv()); 176 177 CGF.FinishFunction(); 178 179 return fn; 180 } 181 182 /// Register a global destructor using the C atexit runtime function. 183 void CodeGenFunction::registerGlobalDtorWithAtExit(llvm::Constant *dtor, 184 llvm::Constant *addr) { 185 // Create a function which calls the destructor. 186 llvm::Constant *dtorStub = createAtExitStub(CGM, dtor, addr); 187 188 // extern "C" int atexit(void (*f)(void)); 189 llvm::FunctionType *atexitTy = 190 llvm::FunctionType::get(IntTy, dtorStub->getType(), false); 191 192 llvm::Constant *atexit = 193 CGM.CreateRuntimeFunction(atexitTy, "atexit"); 194 if (llvm::Function *atexitFn = dyn_cast<llvm::Function>(atexit)) 195 atexitFn->setDoesNotThrow(); 196 197 Builder.CreateCall(atexit, dtorStub)->setDoesNotThrow(); 198 } 199 200 void CodeGenFunction::EmitCXXGuardedInit(const VarDecl &D, 201 llvm::GlobalVariable *DeclPtr, 202 bool PerformInit) { 203 // If we've been asked to forbid guard variables, emit an error now. 204 // This diagnostic is hard-coded for Darwin's use case; we can find 205 // better phrasing if someone else needs it. 206 if (CGM.getCodeGenOpts().ForbidGuardVariables) 207 CGM.Error(D.getLocation(), 208 "this initialization requires a guard variable, which " 209 "the kernel does not support"); 210 211 CGM.getCXXABI().EmitGuardedInit(*this, D, DeclPtr, PerformInit); 212 } 213 214 static llvm::Function * 215 CreateGlobalInitOrDestructFunction(CodeGenModule &CGM, 216 llvm::FunctionType *FTy, 217 const Twine &Name) { 218 llvm::Function *Fn = 219 llvm::Function::Create(FTy, llvm::GlobalValue::InternalLinkage, 220 Name, &CGM.getModule()); 221 if (!CGM.getContext().getLangOpts().AppleKext) { 222 // Set the section if needed. 223 if (const char *Section = 224 CGM.getContext().getTargetInfo().getStaticInitSectionSpecifier()) 225 Fn->setSection(Section); 226 } 227 228 if (!CGM.getLangOpts().Exceptions) 229 Fn->setDoesNotThrow(); 230 231 if (CGM.getLangOpts().AddressSanitizer) 232 Fn->addFnAttr(llvm::Attribute::AddressSafety); 233 234 return Fn; 235 } 236 237 void 238 CodeGenModule::EmitCXXGlobalVarDeclInitFunc(const VarDecl *D, 239 llvm::GlobalVariable *Addr, 240 bool PerformInit) { 241 llvm::FunctionType *FTy = llvm::FunctionType::get(VoidTy, false); 242 243 // Create a variable initialization function. 244 llvm::Function *Fn = 245 CreateGlobalInitOrDestructFunction(*this, FTy, "__cxx_global_var_init"); 246 247 CodeGenFunction(*this).GenerateCXXGlobalVarDeclInitFunc(Fn, D, Addr, 248 PerformInit); 249 250 if (D->hasAttr<InitPriorityAttr>()) { 251 unsigned int order = D->getAttr<InitPriorityAttr>()->getPriority(); 252 OrderGlobalInits Key(order, PrioritizedCXXGlobalInits.size()); 253 PrioritizedCXXGlobalInits.push_back(std::make_pair(Key, Fn)); 254 DelayedCXXInitPosition.erase(D); 255 } 256 else { 257 llvm::DenseMap<const Decl *, unsigned>::iterator I = 258 DelayedCXXInitPosition.find(D); 259 if (I == DelayedCXXInitPosition.end()) { 260 CXXGlobalInits.push_back(Fn); 261 } else { 262 assert(CXXGlobalInits[I->second] == 0); 263 CXXGlobalInits[I->second] = Fn; 264 DelayedCXXInitPosition.erase(I); 265 } 266 } 267 } 268 269 void 270 CodeGenModule::EmitCXXGlobalInitFunc() { 271 while (!CXXGlobalInits.empty() && !CXXGlobalInits.back()) 272 CXXGlobalInits.pop_back(); 273 274 if (CXXGlobalInits.empty() && PrioritizedCXXGlobalInits.empty()) 275 return; 276 277 llvm::FunctionType *FTy = llvm::FunctionType::get(VoidTy, false); 278 279 // Create our global initialization function. 280 llvm::Function *Fn = 281 CreateGlobalInitOrDestructFunction(*this, FTy, "_GLOBAL__I_a"); 282 283 if (!PrioritizedCXXGlobalInits.empty()) { 284 SmallVector<llvm::Constant*, 8> LocalCXXGlobalInits; 285 llvm::array_pod_sort(PrioritizedCXXGlobalInits.begin(), 286 PrioritizedCXXGlobalInits.end()); 287 for (unsigned i = 0; i < PrioritizedCXXGlobalInits.size(); i++) { 288 llvm::Function *Fn = PrioritizedCXXGlobalInits[i].second; 289 LocalCXXGlobalInits.push_back(Fn); 290 } 291 LocalCXXGlobalInits.append(CXXGlobalInits.begin(), CXXGlobalInits.end()); 292 CodeGenFunction(*this).GenerateCXXGlobalInitFunc(Fn, 293 &LocalCXXGlobalInits[0], 294 LocalCXXGlobalInits.size()); 295 } 296 else 297 CodeGenFunction(*this).GenerateCXXGlobalInitFunc(Fn, 298 &CXXGlobalInits[0], 299 CXXGlobalInits.size()); 300 AddGlobalCtor(Fn); 301 CXXGlobalInits.clear(); 302 PrioritizedCXXGlobalInits.clear(); 303 } 304 305 void CodeGenModule::EmitCXXGlobalDtorFunc() { 306 if (CXXGlobalDtors.empty()) 307 return; 308 309 llvm::FunctionType *FTy = llvm::FunctionType::get(VoidTy, false); 310 311 // Create our global destructor function. 312 llvm::Function *Fn = 313 CreateGlobalInitOrDestructFunction(*this, FTy, "_GLOBAL__D_a"); 314 315 CodeGenFunction(*this).GenerateCXXGlobalDtorsFunc(Fn, CXXGlobalDtors); 316 AddGlobalDtor(Fn); 317 } 318 319 /// Emit the code necessary to initialize the given global variable. 320 void CodeGenFunction::GenerateCXXGlobalVarDeclInitFunc(llvm::Function *Fn, 321 const VarDecl *D, 322 llvm::GlobalVariable *Addr, 323 bool PerformInit) { 324 if (CGM.getModuleDebugInfo() && !D->hasAttr<NoDebugAttr>()) 325 DebugInfo = CGM.getModuleDebugInfo(); 326 327 StartFunction(GlobalDecl(D), getContext().VoidTy, Fn, 328 getTypes().arrangeNullaryFunction(), 329 FunctionArgList(), D->getInit()->getExprLoc()); 330 331 // Use guarded initialization if the global variable is weak. This 332 // occurs for, e.g., instantiated static data members and 333 // definitions explicitly marked weak. 334 if (Addr->getLinkage() == llvm::GlobalValue::WeakODRLinkage || 335 Addr->getLinkage() == llvm::GlobalValue::WeakAnyLinkage) { 336 EmitCXXGuardedInit(*D, Addr, PerformInit); 337 } else { 338 EmitCXXGlobalVarDeclInit(*D, Addr, PerformInit); 339 } 340 341 FinishFunction(); 342 } 343 344 void CodeGenFunction::GenerateCXXGlobalInitFunc(llvm::Function *Fn, 345 llvm::Constant **Decls, 346 unsigned NumDecls) { 347 StartFunction(GlobalDecl(), getContext().VoidTy, Fn, 348 getTypes().arrangeNullaryFunction(), 349 FunctionArgList(), SourceLocation()); 350 351 RunCleanupsScope Scope(*this); 352 353 // When building in Objective-C++ ARC mode, create an autorelease pool 354 // around the global initializers. 355 if (getLangOpts().ObjCAutoRefCount && getLangOpts().CPlusPlus) { 356 llvm::Value *token = EmitObjCAutoreleasePoolPush(); 357 EmitObjCAutoreleasePoolCleanup(token); 358 } 359 360 for (unsigned i = 0; i != NumDecls; ++i) 361 if (Decls[i]) 362 Builder.CreateCall(Decls[i]); 363 364 Scope.ForceCleanup(); 365 366 FinishFunction(); 367 } 368 369 void CodeGenFunction::GenerateCXXGlobalDtorsFunc(llvm::Function *Fn, 370 const std::vector<std::pair<llvm::WeakVH, llvm::Constant*> > 371 &DtorsAndObjects) { 372 StartFunction(GlobalDecl(), getContext().VoidTy, Fn, 373 getTypes().arrangeNullaryFunction(), 374 FunctionArgList(), SourceLocation()); 375 376 // Emit the dtors, in reverse order from construction. 377 for (unsigned i = 0, e = DtorsAndObjects.size(); i != e; ++i) { 378 llvm::Value *Callee = DtorsAndObjects[e - i - 1].first; 379 llvm::CallInst *CI = Builder.CreateCall(Callee, 380 DtorsAndObjects[e - i - 1].second); 381 // Make sure the call and the callee agree on calling convention. 382 if (llvm::Function *F = dyn_cast<llvm::Function>(Callee)) 383 CI->setCallingConv(F->getCallingConv()); 384 } 385 386 FinishFunction(); 387 } 388 389 /// generateDestroyHelper - Generates a helper function which, when 390 /// invoked, destroys the given object. 391 llvm::Function * 392 CodeGenFunction::generateDestroyHelper(llvm::Constant *addr, 393 QualType type, 394 Destroyer *destroyer, 395 bool useEHCleanupForArray) { 396 FunctionArgList args; 397 ImplicitParamDecl dst(0, SourceLocation(), 0, getContext().VoidPtrTy); 398 args.push_back(&dst); 399 400 const CGFunctionInfo &FI = 401 CGM.getTypes().arrangeFunctionDeclaration(getContext().VoidTy, args, 402 FunctionType::ExtInfo(), 403 /*variadic*/ false); 404 llvm::FunctionType *FTy = CGM.getTypes().GetFunctionType(FI); 405 llvm::Function *fn = 406 CreateGlobalInitOrDestructFunction(CGM, FTy, "__cxx_global_array_dtor"); 407 408 StartFunction(GlobalDecl(), getContext().VoidTy, fn, FI, args, 409 SourceLocation()); 410 411 emitDestroy(addr, type, destroyer, useEHCleanupForArray); 412 413 FinishFunction(); 414 415 return fn; 416 } 417