CGDecl.cpp revision 4707b9acf75c68c90278757ffd6a05b2544bc1eb
1//===--- CGDecl.cpp - Emit LLVM Code for 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 to emit Decl nodes as LLVM code. 11// 12//===----------------------------------------------------------------------===// 13 14#include "CGDebugInfo.h" 15#include "CodeGenFunction.h" 16#include "CodeGenModule.h" 17#include "CGBlocks.h" 18#include "clang/AST/ASTContext.h" 19#include "clang/AST/CharUnits.h" 20#include "clang/AST/Decl.h" 21#include "clang/AST/DeclObjC.h" 22#include "clang/Basic/SourceManager.h" 23#include "clang/Basic/TargetInfo.h" 24#include "clang/Frontend/CodeGenOptions.h" 25#include "llvm/GlobalVariable.h" 26#include "llvm/Intrinsics.h" 27#include "llvm/Target/TargetData.h" 28#include "llvm/Type.h" 29using namespace clang; 30using namespace CodeGen; 31 32 33void CodeGenFunction::EmitDecl(const Decl &D) { 34 switch (D.getKind()) { 35 case Decl::TranslationUnit: 36 case Decl::Namespace: 37 case Decl::UnresolvedUsingTypename: 38 case Decl::ClassTemplateSpecialization: 39 case Decl::ClassTemplatePartialSpecialization: 40 case Decl::TemplateTypeParm: 41 case Decl::UnresolvedUsingValue: 42 case Decl::NonTypeTemplateParm: 43 case Decl::CXXMethod: 44 case Decl::CXXConstructor: 45 case Decl::CXXDestructor: 46 case Decl::CXXConversion: 47 case Decl::Field: 48 case Decl::IndirectField: 49 case Decl::ObjCIvar: 50 case Decl::ObjCAtDefsField: 51 case Decl::ParmVar: 52 case Decl::ImplicitParam: 53 case Decl::ClassTemplate: 54 case Decl::FunctionTemplate: 55 case Decl::TemplateTemplateParm: 56 case Decl::ObjCMethod: 57 case Decl::ObjCCategory: 58 case Decl::ObjCProtocol: 59 case Decl::ObjCInterface: 60 case Decl::ObjCCategoryImpl: 61 case Decl::ObjCImplementation: 62 case Decl::ObjCProperty: 63 case Decl::ObjCCompatibleAlias: 64 case Decl::AccessSpec: 65 case Decl::LinkageSpec: 66 case Decl::ObjCPropertyImpl: 67 case Decl::ObjCClass: 68 case Decl::ObjCForwardProtocol: 69 case Decl::FileScopeAsm: 70 case Decl::Friend: 71 case Decl::FriendTemplate: 72 case Decl::Block: 73 assert(0 && "Declaration not should not be in declstmts!"); 74 case Decl::Function: // void X(); 75 case Decl::Record: // struct/union/class X; 76 case Decl::Enum: // enum X; 77 case Decl::EnumConstant: // enum ? { X = ? } 78 case Decl::CXXRecord: // struct/union/class X; [C++] 79 case Decl::Using: // using X; [C++] 80 case Decl::UsingShadow: 81 case Decl::UsingDirective: // using namespace X; [C++] 82 case Decl::NamespaceAlias: 83 case Decl::StaticAssert: // static_assert(X, ""); [C++0x] 84 case Decl::Label: // __label__ x; 85 // None of these decls require codegen support. 86 return; 87 88 case Decl::Var: { 89 const VarDecl &VD = cast<VarDecl>(D); 90 assert(VD.isLocalVarDecl() && 91 "Should not see file-scope variables inside a function!"); 92 return EmitVarDecl(VD); 93 } 94 95 case Decl::Typedef: { // typedef int X; 96 const TypedefDecl &TD = cast<TypedefDecl>(D); 97 QualType Ty = TD.getUnderlyingType(); 98 99 if (Ty->isVariablyModifiedType()) 100 EmitVLASize(Ty); 101 } 102 } 103} 104 105/// EmitVarDecl - This method handles emission of any variable declaration 106/// inside a function, including static vars etc. 107void CodeGenFunction::EmitVarDecl(const VarDecl &D) { 108 switch (D.getStorageClass()) { 109 case SC_None: 110 case SC_Auto: 111 case SC_Register: 112 return EmitAutoVarDecl(D); 113 case SC_Static: { 114 llvm::GlobalValue::LinkageTypes Linkage = 115 llvm::GlobalValue::InternalLinkage; 116 117 // If the function definition has some sort of weak linkage, its 118 // static variables should also be weak so that they get properly 119 // uniqued. We can't do this in C, though, because there's no 120 // standard way to agree on which variables are the same (i.e. 121 // there's no mangling). 122 if (getContext().getLangOptions().CPlusPlus) 123 if (llvm::GlobalValue::isWeakForLinker(CurFn->getLinkage())) 124 Linkage = CurFn->getLinkage(); 125 126 return EmitStaticVarDecl(D, Linkage); 127 } 128 case SC_Extern: 129 case SC_PrivateExtern: 130 // Don't emit it now, allow it to be emitted lazily on its first use. 131 return; 132 } 133 134 assert(0 && "Unknown storage class"); 135} 136 137static std::string GetStaticDeclName(CodeGenFunction &CGF, const VarDecl &D, 138 const char *Separator) { 139 CodeGenModule &CGM = CGF.CGM; 140 if (CGF.getContext().getLangOptions().CPlusPlus) { 141 llvm::StringRef Name = CGM.getMangledName(&D); 142 return Name.str(); 143 } 144 145 std::string ContextName; 146 if (!CGF.CurFuncDecl) { 147 // Better be in a block declared in global scope. 148 const NamedDecl *ND = cast<NamedDecl>(&D); 149 const DeclContext *DC = ND->getDeclContext(); 150 if (const BlockDecl *BD = dyn_cast<BlockDecl>(DC)) { 151 MangleBuffer Name; 152 CGM.getBlockMangledName(GlobalDecl(), Name, BD); 153 ContextName = Name.getString(); 154 } 155 else 156 assert(0 && "Unknown context for block static var decl"); 157 } else if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(CGF.CurFuncDecl)) { 158 llvm::StringRef Name = CGM.getMangledName(FD); 159 ContextName = Name.str(); 160 } else if (isa<ObjCMethodDecl>(CGF.CurFuncDecl)) 161 ContextName = CGF.CurFn->getName(); 162 else 163 assert(0 && "Unknown context for static var decl"); 164 165 return ContextName + Separator + D.getNameAsString(); 166} 167 168llvm::GlobalVariable * 169CodeGenFunction::CreateStaticVarDecl(const VarDecl &D, 170 const char *Separator, 171 llvm::GlobalValue::LinkageTypes Linkage) { 172 QualType Ty = D.getType(); 173 assert(Ty->isConstantSizeType() && "VLAs can't be static"); 174 175 std::string Name = GetStaticDeclName(*this, D, Separator); 176 177 const llvm::Type *LTy = CGM.getTypes().ConvertTypeForMem(Ty); 178 llvm::GlobalVariable *GV = 179 new llvm::GlobalVariable(CGM.getModule(), LTy, 180 Ty.isConstant(getContext()), Linkage, 181 CGM.EmitNullConstant(D.getType()), Name, 0, 182 D.isThreadSpecified(), Ty.getAddressSpace()); 183 GV->setAlignment(getContext().getDeclAlign(&D).getQuantity()); 184 if (Linkage != llvm::GlobalValue::InternalLinkage) 185 GV->setVisibility(CurFn->getVisibility()); 186 return GV; 187} 188 189/// AddInitializerToStaticVarDecl - Add the initializer for 'D' to the 190/// global variable that has already been created for it. If the initializer 191/// has a different type than GV does, this may free GV and return a different 192/// one. Otherwise it just returns GV. 193llvm::GlobalVariable * 194CodeGenFunction::AddInitializerToStaticVarDecl(const VarDecl &D, 195 llvm::GlobalVariable *GV) { 196 llvm::Constant *Init = CGM.EmitConstantExpr(D.getInit(), D.getType(), this); 197 198 // If constant emission failed, then this should be a C++ static 199 // initializer. 200 if (!Init) { 201 if (!getContext().getLangOptions().CPlusPlus) 202 CGM.ErrorUnsupported(D.getInit(), "constant l-value expression"); 203 else if (Builder.GetInsertBlock()) { 204 // Since we have a static initializer, this global variable can't 205 // be constant. 206 GV->setConstant(false); 207 208 EmitCXXGuardedInit(D, GV); 209 } 210 return GV; 211 } 212 213 // The initializer may differ in type from the global. Rewrite 214 // the global to match the initializer. (We have to do this 215 // because some types, like unions, can't be completely represented 216 // in the LLVM type system.) 217 if (GV->getType()->getElementType() != Init->getType()) { 218 llvm::GlobalVariable *OldGV = GV; 219 220 GV = new llvm::GlobalVariable(CGM.getModule(), Init->getType(), 221 OldGV->isConstant(), 222 OldGV->getLinkage(), Init, "", 223 /*InsertBefore*/ OldGV, 224 D.isThreadSpecified(), 225 D.getType().getAddressSpace()); 226 GV->setVisibility(OldGV->getVisibility()); 227 228 // Steal the name of the old global 229 GV->takeName(OldGV); 230 231 // Replace all uses of the old global with the new global 232 llvm::Constant *NewPtrForOldDecl = 233 llvm::ConstantExpr::getBitCast(GV, OldGV->getType()); 234 OldGV->replaceAllUsesWith(NewPtrForOldDecl); 235 236 // Erase the old global, since it is no longer used. 237 OldGV->eraseFromParent(); 238 } 239 240 GV->setInitializer(Init); 241 return GV; 242} 243 244void CodeGenFunction::EmitStaticVarDecl(const VarDecl &D, 245 llvm::GlobalValue::LinkageTypes Linkage) { 246 llvm::Value *&DMEntry = LocalDeclMap[&D]; 247 assert(DMEntry == 0 && "Decl already exists in localdeclmap!"); 248 249 llvm::GlobalVariable *GV = CreateStaticVarDecl(D, ".", Linkage); 250 251 // Store into LocalDeclMap before generating initializer to handle 252 // circular references. 253 DMEntry = GV; 254 255 // We can't have a VLA here, but we can have a pointer to a VLA, 256 // even though that doesn't really make any sense. 257 // Make sure to evaluate VLA bounds now so that we have them for later. 258 if (D.getType()->isVariablyModifiedType()) 259 EmitVLASize(D.getType()); 260 261 // Local static block variables must be treated as globals as they may be 262 // referenced in their RHS initializer block-literal expresion. 263 CGM.setStaticLocalDeclAddress(&D, GV); 264 265 // If this value has an initializer, emit it. 266 if (D.getInit()) 267 GV = AddInitializerToStaticVarDecl(D, GV); 268 269 GV->setAlignment(getContext().getDeclAlign(&D).getQuantity()); 270 271 // FIXME: Merge attribute handling. 272 if (const AnnotateAttr *AA = D.getAttr<AnnotateAttr>()) { 273 SourceManager &SM = CGM.getContext().getSourceManager(); 274 llvm::Constant *Ann = 275 CGM.EmitAnnotateAttr(GV, AA, 276 SM.getInstantiationLineNumber(D.getLocation())); 277 CGM.AddAnnotation(Ann); 278 } 279 280 if (const SectionAttr *SA = D.getAttr<SectionAttr>()) 281 GV->setSection(SA->getName()); 282 283 if (D.hasAttr<UsedAttr>()) 284 CGM.AddUsedGlobal(GV); 285 286 // We may have to cast the constant because of the initializer 287 // mismatch above. 288 // 289 // FIXME: It is really dangerous to store this in the map; if anyone 290 // RAUW's the GV uses of this constant will be invalid. 291 const llvm::Type *LTy = CGM.getTypes().ConvertTypeForMem(D.getType()); 292 const llvm::Type *LPtrTy = LTy->getPointerTo(D.getType().getAddressSpace()); 293 DMEntry = llvm::ConstantExpr::getBitCast(GV, LPtrTy); 294 295 // Emit global variable debug descriptor for static vars. 296 CGDebugInfo *DI = getDebugInfo(); 297 if (DI) { 298 DI->setLocation(D.getLocation()); 299 DI->EmitGlobalVariable(static_cast<llvm::GlobalVariable *>(GV), &D); 300 } 301} 302 303unsigned CodeGenFunction::getByRefValueLLVMField(const ValueDecl *VD) const { 304 assert(ByRefValueInfo.count(VD) && "Did not find value!"); 305 306 return ByRefValueInfo.find(VD)->second.second; 307} 308 309llvm::Value *CodeGenFunction::BuildBlockByrefAddress(llvm::Value *BaseAddr, 310 const VarDecl *V) { 311 llvm::Value *Loc = Builder.CreateStructGEP(BaseAddr, 1, "forwarding"); 312 Loc = Builder.CreateLoad(Loc); 313 Loc = Builder.CreateStructGEP(Loc, getByRefValueLLVMField(V), 314 V->getNameAsString()); 315 return Loc; 316} 317 318/// BuildByRefType - This routine changes a __block variable declared as T x 319/// into: 320/// 321/// struct { 322/// void *__isa; 323/// void *__forwarding; 324/// int32_t __flags; 325/// int32_t __size; 326/// void *__copy_helper; // only if needed 327/// void *__destroy_helper; // only if needed 328/// char padding[X]; // only if needed 329/// T x; 330/// } x 331/// 332const llvm::Type *CodeGenFunction::BuildByRefType(const VarDecl *D) { 333 std::pair<const llvm::Type *, unsigned> &Info = ByRefValueInfo[D]; 334 if (Info.first) 335 return Info.first; 336 337 QualType Ty = D->getType(); 338 339 std::vector<const llvm::Type *> Types; 340 341 llvm::PATypeHolder ByRefTypeHolder = llvm::OpaqueType::get(getLLVMContext()); 342 343 // void *__isa; 344 Types.push_back(Int8PtrTy); 345 346 // void *__forwarding; 347 Types.push_back(llvm::PointerType::getUnqual(ByRefTypeHolder)); 348 349 // int32_t __flags; 350 Types.push_back(Int32Ty); 351 352 // int32_t __size; 353 Types.push_back(Int32Ty); 354 355 bool HasCopyAndDispose = getContext().BlockRequiresCopying(Ty); 356 if (HasCopyAndDispose) { 357 /// void *__copy_helper; 358 Types.push_back(Int8PtrTy); 359 360 /// void *__destroy_helper; 361 Types.push_back(Int8PtrTy); 362 } 363 364 bool Packed = false; 365 CharUnits Align = getContext().getDeclAlign(D); 366 if (Align > getContext().toCharUnitsFromBits(Target.getPointerAlign(0))) { 367 // We have to insert padding. 368 369 // The struct above has 2 32-bit integers. 370 unsigned CurrentOffsetInBytes = 4 * 2; 371 372 // And either 2 or 4 pointers. 373 CurrentOffsetInBytes += (HasCopyAndDispose ? 4 : 2) * 374 CGM.getTargetData().getTypeAllocSize(Int8PtrTy); 375 376 // Align the offset. 377 unsigned AlignedOffsetInBytes = 378 llvm::RoundUpToAlignment(CurrentOffsetInBytes, Align.getQuantity()); 379 380 unsigned NumPaddingBytes = AlignedOffsetInBytes - CurrentOffsetInBytes; 381 if (NumPaddingBytes > 0) { 382 const llvm::Type *Ty = llvm::Type::getInt8Ty(getLLVMContext()); 383 // FIXME: We need a sema error for alignment larger than the minimum of 384 // the maximal stack alignmint and the alignment of malloc on the system. 385 if (NumPaddingBytes > 1) 386 Ty = llvm::ArrayType::get(Ty, NumPaddingBytes); 387 388 Types.push_back(Ty); 389 390 // We want a packed struct. 391 Packed = true; 392 } 393 } 394 395 // T x; 396 Types.push_back(ConvertTypeForMem(Ty)); 397 398 const llvm::Type *T = llvm::StructType::get(getLLVMContext(), Types, Packed); 399 400 cast<llvm::OpaqueType>(ByRefTypeHolder.get())->refineAbstractTypeTo(T); 401 CGM.getModule().addTypeName("struct.__block_byref_" + D->getNameAsString(), 402 ByRefTypeHolder.get()); 403 404 Info.first = ByRefTypeHolder.get(); 405 406 Info.second = Types.size() - 1; 407 408 return Info.first; 409} 410 411namespace { 412 struct CallArrayDtor : EHScopeStack::Cleanup { 413 CallArrayDtor(const CXXDestructorDecl *Dtor, 414 const ConstantArrayType *Type, 415 llvm::Value *Loc) 416 : Dtor(Dtor), Type(Type), Loc(Loc) {} 417 418 const CXXDestructorDecl *Dtor; 419 const ConstantArrayType *Type; 420 llvm::Value *Loc; 421 422 void Emit(CodeGenFunction &CGF, bool IsForEH) { 423 QualType BaseElementTy = CGF.getContext().getBaseElementType(Type); 424 const llvm::Type *BasePtr = CGF.ConvertType(BaseElementTy); 425 BasePtr = llvm::PointerType::getUnqual(BasePtr); 426 llvm::Value *BaseAddrPtr = CGF.Builder.CreateBitCast(Loc, BasePtr); 427 CGF.EmitCXXAggrDestructorCall(Dtor, Type, BaseAddrPtr); 428 } 429 }; 430 431 struct CallVarDtor : EHScopeStack::Cleanup { 432 CallVarDtor(const CXXDestructorDecl *Dtor, 433 llvm::Value *NRVOFlag, 434 llvm::Value *Loc) 435 : Dtor(Dtor), NRVOFlag(NRVOFlag), Loc(Loc) {} 436 437 const CXXDestructorDecl *Dtor; 438 llvm::Value *NRVOFlag; 439 llvm::Value *Loc; 440 441 void Emit(CodeGenFunction &CGF, bool IsForEH) { 442 // Along the exceptions path we always execute the dtor. 443 bool NRVO = !IsForEH && NRVOFlag; 444 445 llvm::BasicBlock *SkipDtorBB = 0; 446 if (NRVO) { 447 // If we exited via NRVO, we skip the destructor call. 448 llvm::BasicBlock *RunDtorBB = CGF.createBasicBlock("nrvo.unused"); 449 SkipDtorBB = CGF.createBasicBlock("nrvo.skipdtor"); 450 llvm::Value *DidNRVO = CGF.Builder.CreateLoad(NRVOFlag, "nrvo.val"); 451 CGF.Builder.CreateCondBr(DidNRVO, SkipDtorBB, RunDtorBB); 452 CGF.EmitBlock(RunDtorBB); 453 } 454 455 CGF.EmitCXXDestructorCall(Dtor, Dtor_Complete, 456 /*ForVirtualBase=*/false, Loc); 457 458 if (NRVO) CGF.EmitBlock(SkipDtorBB); 459 } 460 }; 461} 462 463namespace { 464 struct CallStackRestore : EHScopeStack::Cleanup { 465 llvm::Value *Stack; 466 CallStackRestore(llvm::Value *Stack) : Stack(Stack) {} 467 void Emit(CodeGenFunction &CGF, bool IsForEH) { 468 llvm::Value *V = CGF.Builder.CreateLoad(Stack, "tmp"); 469 llvm::Value *F = CGF.CGM.getIntrinsic(llvm::Intrinsic::stackrestore); 470 CGF.Builder.CreateCall(F, V); 471 } 472 }; 473 474 struct CallCleanupFunction : EHScopeStack::Cleanup { 475 llvm::Constant *CleanupFn; 476 const CGFunctionInfo &FnInfo; 477 const VarDecl &Var; 478 479 CallCleanupFunction(llvm::Constant *CleanupFn, const CGFunctionInfo *Info, 480 const VarDecl *Var) 481 : CleanupFn(CleanupFn), FnInfo(*Info), Var(*Var) {} 482 483 void Emit(CodeGenFunction &CGF, bool IsForEH) { 484 DeclRefExpr DRE(const_cast<VarDecl*>(&Var), Var.getType(), VK_LValue, 485 SourceLocation()); 486 // Compute the address of the local variable, in case it's a byref 487 // or something. 488 llvm::Value *Addr = CGF.EmitDeclRefLValue(&DRE).getAddress(); 489 490 // In some cases, the type of the function argument will be different from 491 // the type of the pointer. An example of this is 492 // void f(void* arg); 493 // __attribute__((cleanup(f))) void *g; 494 // 495 // To fix this we insert a bitcast here. 496 QualType ArgTy = FnInfo.arg_begin()->type; 497 llvm::Value *Arg = 498 CGF.Builder.CreateBitCast(Addr, CGF.ConvertType(ArgTy)); 499 500 CallArgList Args; 501 Args.push_back(std::make_pair(RValue::get(Arg), 502 CGF.getContext().getPointerType(Var.getType()))); 503 CGF.EmitCall(FnInfo, CleanupFn, ReturnValueSlot(), Args); 504 } 505 }; 506 507 struct CallBlockRelease : EHScopeStack::Cleanup { 508 llvm::Value *Addr; 509 CallBlockRelease(llvm::Value *Addr) : Addr(Addr) {} 510 511 void Emit(CodeGenFunction &CGF, bool IsForEH) { 512 CGF.BuildBlockRelease(Addr, BLOCK_FIELD_IS_BYREF); 513 } 514 }; 515} 516 517 518/// canEmitInitWithFewStoresAfterMemset - Decide whether we can emit the 519/// non-zero parts of the specified initializer with equal or fewer than 520/// NumStores scalar stores. 521static bool canEmitInitWithFewStoresAfterMemset(llvm::Constant *Init, 522 unsigned &NumStores) { 523 // Zero and Undef never requires any extra stores. 524 if (isa<llvm::ConstantAggregateZero>(Init) || 525 isa<llvm::ConstantPointerNull>(Init) || 526 isa<llvm::UndefValue>(Init)) 527 return true; 528 if (isa<llvm::ConstantInt>(Init) || isa<llvm::ConstantFP>(Init) || 529 isa<llvm::ConstantVector>(Init) || isa<llvm::BlockAddress>(Init) || 530 isa<llvm::ConstantExpr>(Init)) 531 return Init->isNullValue() || NumStores--; 532 533 // See if we can emit each element. 534 if (isa<llvm::ConstantArray>(Init) || isa<llvm::ConstantStruct>(Init)) { 535 for (unsigned i = 0, e = Init->getNumOperands(); i != e; ++i) { 536 llvm::Constant *Elt = cast<llvm::Constant>(Init->getOperand(i)); 537 if (!canEmitInitWithFewStoresAfterMemset(Elt, NumStores)) 538 return false; 539 } 540 return true; 541 } 542 543 // Anything else is hard and scary. 544 return false; 545} 546 547/// emitStoresForInitAfterMemset - For inits that 548/// canEmitInitWithFewStoresAfterMemset returned true for, emit the scalar 549/// stores that would be required. 550static void emitStoresForInitAfterMemset(llvm::Constant *Init, llvm::Value *Loc, 551 bool isVolatile, CGBuilderTy &Builder) { 552 // Zero doesn't require any stores. 553 if (isa<llvm::ConstantAggregateZero>(Init) || 554 isa<llvm::ConstantPointerNull>(Init) || 555 isa<llvm::UndefValue>(Init)) 556 return; 557 558 if (isa<llvm::ConstantInt>(Init) || isa<llvm::ConstantFP>(Init) || 559 isa<llvm::ConstantVector>(Init) || isa<llvm::BlockAddress>(Init) || 560 isa<llvm::ConstantExpr>(Init)) { 561 if (!Init->isNullValue()) 562 Builder.CreateStore(Init, Loc, isVolatile); 563 return; 564 } 565 566 assert((isa<llvm::ConstantStruct>(Init) || isa<llvm::ConstantArray>(Init)) && 567 "Unknown value type!"); 568 569 for (unsigned i = 0, e = Init->getNumOperands(); i != e; ++i) { 570 llvm::Constant *Elt = cast<llvm::Constant>(Init->getOperand(i)); 571 if (Elt->isNullValue()) continue; 572 573 // Otherwise, get a pointer to the element and emit it. 574 emitStoresForInitAfterMemset(Elt, Builder.CreateConstGEP2_32(Loc, 0, i), 575 isVolatile, Builder); 576 } 577} 578 579 580/// shouldUseMemSetPlusStoresToInitialize - Decide whether we should use memset 581/// plus some stores to initialize a local variable instead of using a memcpy 582/// from a constant global. It is beneficial to use memset if the global is all 583/// zeros, or mostly zeros and large. 584static bool shouldUseMemSetPlusStoresToInitialize(llvm::Constant *Init, 585 uint64_t GlobalSize) { 586 // If a global is all zeros, always use a memset. 587 if (isa<llvm::ConstantAggregateZero>(Init)) return true; 588 589 590 // If a non-zero global is <= 32 bytes, always use a memcpy. If it is large, 591 // do it if it will require 6 or fewer scalar stores. 592 // TODO: Should budget depends on the size? Avoiding a large global warrants 593 // plopping in more stores. 594 unsigned StoreBudget = 6; 595 uint64_t SizeLimit = 32; 596 597 return GlobalSize > SizeLimit && 598 canEmitInitWithFewStoresAfterMemset(Init, StoreBudget); 599} 600 601 602/// EmitAutoVarDecl - Emit code and set up an entry in LocalDeclMap for a 603/// variable declaration with auto, register, or no storage class specifier. 604/// These turn into simple stack objects, or GlobalValues depending on target. 605void CodeGenFunction::EmitAutoVarDecl(const VarDecl &D) { 606 AutoVarEmission emission = EmitAutoVarAlloca(D); 607 EmitAutoVarInit(emission); 608 EmitAutoVarCleanups(emission); 609} 610 611/// EmitAutoVarAlloca - Emit the alloca and debug information for a 612/// local variable. Does not emit initalization or destruction. 613CodeGenFunction::AutoVarEmission 614CodeGenFunction::EmitAutoVarAlloca(const VarDecl &D) { 615 QualType Ty = D.getType(); 616 617 AutoVarEmission emission(D); 618 619 bool isByRef = D.hasAttr<BlocksAttr>(); 620 emission.IsByRef = isByRef; 621 622 CharUnits alignment = getContext().getDeclAlign(&D); 623 emission.Alignment = alignment; 624 625 llvm::Value *DeclPtr; 626 if (Ty->isConstantSizeType()) { 627 if (!Target.useGlobalsForAutomaticVariables()) { 628 bool NRVO = getContext().getLangOptions().ElideConstructors && 629 D.isNRVOVariable(); 630 631 // If this value is a POD array or struct with a statically 632 // determinable constant initializer, there are optimizations we 633 // can do. 634 // TODO: we can potentially constant-evaluate non-POD structs and 635 // arrays as long as the initialization is trivial (e.g. if they 636 // have a non-trivial destructor, but not a non-trivial constructor). 637 if (D.getInit() && 638 (Ty->isArrayType() || Ty->isRecordType()) && Ty->isPODType() && 639 D.getInit()->isConstantInitializer(getContext(), false)) { 640 641 // If the variable's a const type, and it's neither an NRVO 642 // candidate nor a __block variable, emit it as a global instead. 643 if (CGM.getCodeGenOpts().MergeAllConstants && Ty.isConstQualified() && 644 !NRVO && !isByRef) { 645 EmitStaticVarDecl(D, llvm::GlobalValue::InternalLinkage); 646 647 emission.Address = 0; // signal this condition to later callbacks 648 assert(emission.wasEmittedAsGlobal()); 649 return emission; 650 } 651 652 // Otherwise, tell the initialization code that we're in this case. 653 emission.IsConstantAggregate = true; 654 } 655 656 // A normal fixed sized variable becomes an alloca in the entry block, 657 // unless it's an NRVO variable. 658 const llvm::Type *LTy = ConvertTypeForMem(Ty); 659 660 if (NRVO) { 661 // The named return value optimization: allocate this variable in the 662 // return slot, so that we can elide the copy when returning this 663 // variable (C++0x [class.copy]p34). 664 DeclPtr = ReturnValue; 665 666 if (const RecordType *RecordTy = Ty->getAs<RecordType>()) { 667 if (!cast<CXXRecordDecl>(RecordTy->getDecl())->hasTrivialDestructor()) { 668 // Create a flag that is used to indicate when the NRVO was applied 669 // to this variable. Set it to zero to indicate that NRVO was not 670 // applied. 671 llvm::Value *Zero = Builder.getFalse(); 672 llvm::Value *NRVOFlag = CreateTempAlloca(Zero->getType(), "nrvo"); 673 EnsureInsertPoint(); 674 Builder.CreateStore(Zero, NRVOFlag); 675 676 // Record the NRVO flag for this variable. 677 NRVOFlags[&D] = NRVOFlag; 678 emission.NRVOFlag = NRVOFlag; 679 } 680 } 681 } else { 682 if (isByRef) 683 LTy = BuildByRefType(&D); 684 685 llvm::AllocaInst *Alloc = CreateTempAlloca(LTy); 686 Alloc->setName(D.getNameAsString()); 687 688 CharUnits allocaAlignment = alignment; 689 if (isByRef) 690 allocaAlignment = std::max(allocaAlignment, 691 getContext().toCharUnitsFromBits(Target.getPointerAlign(0))); 692 Alloc->setAlignment(allocaAlignment.getQuantity()); 693 DeclPtr = Alloc; 694 } 695 } else { 696 // Targets that don't support recursion emit locals as globals. 697 const char *Class = 698 D.getStorageClass() == SC_Register ? ".reg." : ".auto."; 699 DeclPtr = CreateStaticVarDecl(D, Class, 700 llvm::GlobalValue::InternalLinkage); 701 } 702 703 // FIXME: Can this happen? 704 if (Ty->isVariablyModifiedType()) 705 EmitVLASize(Ty); 706 } else { 707 EnsureInsertPoint(); 708 709 if (!DidCallStackSave) { 710 // Save the stack. 711 llvm::Value *Stack = CreateTempAlloca(Int8PtrTy, "saved_stack"); 712 713 llvm::Value *F = CGM.getIntrinsic(llvm::Intrinsic::stacksave); 714 llvm::Value *V = Builder.CreateCall(F); 715 716 Builder.CreateStore(V, Stack); 717 718 DidCallStackSave = true; 719 720 // Push a cleanup block and restore the stack there. 721 // FIXME: in general circumstances, this should be an EH cleanup. 722 EHStack.pushCleanup<CallStackRestore>(NormalCleanup, Stack); 723 } 724 725 // Get the element type. 726 const llvm::Type *LElemTy = ConvertTypeForMem(Ty); 727 const llvm::Type *LElemPtrTy = LElemTy->getPointerTo(Ty.getAddressSpace()); 728 729 llvm::Value *VLASize = EmitVLASize(Ty); 730 731 // Allocate memory for the array. 732 llvm::AllocaInst *VLA = 733 Builder.CreateAlloca(llvm::Type::getInt8Ty(getLLVMContext()), VLASize, "vla"); 734 VLA->setAlignment(alignment.getQuantity()); 735 736 DeclPtr = Builder.CreateBitCast(VLA, LElemPtrTy, "tmp"); 737 } 738 739 llvm::Value *&DMEntry = LocalDeclMap[&D]; 740 assert(DMEntry == 0 && "Decl already exists in localdeclmap!"); 741 DMEntry = DeclPtr; 742 emission.Address = DeclPtr; 743 744 // Emit debug info for local var declaration. 745 if (CGDebugInfo *DI = getDebugInfo()) { 746 assert(HaveInsertPoint() && "Unexpected unreachable point!"); 747 748 DI->setLocation(D.getLocation()); 749 if (Target.useGlobalsForAutomaticVariables()) { 750 DI->EmitGlobalVariable(static_cast<llvm::GlobalVariable *>(DeclPtr), &D); 751 } else 752 DI->EmitDeclareOfAutoVariable(&D, DeclPtr, Builder); 753 } 754 755 return emission; 756} 757 758/// Determines whether the given __block variable is potentially 759/// captured by the given expression. 760static bool isCapturedBy(const VarDecl &var, const Expr *e) { 761 // Skip the most common kinds of expressions that make 762 // hierarchy-walking expensive. 763 e = e->IgnoreParenCasts(); 764 765 if (const BlockExpr *be = dyn_cast<BlockExpr>(e)) { 766 const BlockDecl *block = be->getBlockDecl(); 767 for (BlockDecl::capture_const_iterator i = block->capture_begin(), 768 e = block->capture_end(); i != e; ++i) { 769 if (i->getVariable() == &var) 770 return true; 771 } 772 773 // No need to walk into the subexpressions. 774 return false; 775 } 776 777 for (Stmt::const_child_range children = e->children(); children; ++children) 778 if (isCapturedBy(var, cast<Expr>(*children))) 779 return true; 780 781 return false; 782} 783 784void CodeGenFunction::EmitAutoVarInit(const AutoVarEmission &emission) { 785 assert(emission.Variable && "emission was not valid!"); 786 787 // If this was emitted as a global constant, we're done. 788 if (emission.wasEmittedAsGlobal()) return; 789 790 const VarDecl &D = *emission.Variable; 791 QualType type = D.getType(); 792 793 // If this local has an initializer, emit it now. 794 const Expr *Init = D.getInit(); 795 796 // If we are at an unreachable point, we don't need to emit the initializer 797 // unless it contains a label. 798 if (!HaveInsertPoint()) { 799 if (!Init || !ContainsLabel(Init)) return; 800 EnsureInsertPoint(); 801 } 802 803 CharUnits alignment = emission.Alignment; 804 805 if (emission.IsByRef) { 806 llvm::Value *V; 807 808 BlockFieldFlags fieldFlags; 809 bool fieldNeedsCopyDispose = false; 810 811 if (type->isBlockPointerType()) { 812 fieldFlags |= BLOCK_FIELD_IS_BLOCK; 813 fieldNeedsCopyDispose = true; 814 } else if (getContext().isObjCNSObjectType(type) || 815 type->isObjCObjectPointerType()) { 816 fieldFlags |= BLOCK_FIELD_IS_OBJECT; 817 fieldNeedsCopyDispose = true; 818 } else if (getLangOptions().CPlusPlus) { 819 if (getContext().getBlockVarCopyInits(&D)) 820 fieldNeedsCopyDispose = true; 821 else if (const CXXRecordDecl *record = type->getAsCXXRecordDecl()) 822 fieldNeedsCopyDispose = !record->hasTrivialDestructor(); 823 } 824 825 llvm::Value *addr = emission.Address; 826 827 // FIXME: Someone double check this. 828 if (type.isObjCGCWeak()) 829 fieldFlags |= BLOCK_FIELD_IS_WEAK; 830 831 // Initialize the 'isa', which is just 0 or 1. 832 int isa = 0; 833 if (fieldFlags & BLOCK_FIELD_IS_WEAK) 834 isa = 1; 835 V = Builder.CreateIntToPtr(Builder.getInt32(isa), Int8PtrTy, "isa"); 836 Builder.CreateStore(V, Builder.CreateStructGEP(addr, 0, "byref.isa")); 837 838 // Store the address of the variable into its own forwarding pointer. 839 Builder.CreateStore(addr, 840 Builder.CreateStructGEP(addr, 1, "byref.forwarding")); 841 842 // Blocks ABI: 843 // c) the flags field is set to either 0 if no helper functions are 844 // needed or BLOCK_HAS_COPY_DISPOSE if they are, 845 BlockFlags flags; 846 if (fieldNeedsCopyDispose) flags |= BLOCK_HAS_COPY_DISPOSE; 847 Builder.CreateStore(llvm::ConstantInt::get(IntTy, flags.getBitMask()), 848 Builder.CreateStructGEP(addr, 2, "byref.flags")); 849 850 const llvm::Type *V1; 851 V1 = cast<llvm::PointerType>(addr->getType())->getElementType(); 852 V = llvm::ConstantInt::get(IntTy, CGM.GetTargetTypeStoreSize(V1).getQuantity()); 853 Builder.CreateStore(V, Builder.CreateStructGEP(addr, 3, "byref.size")); 854 855 if (fieldNeedsCopyDispose) { 856 llvm::Value *copy_helper = Builder.CreateStructGEP(addr, 4); 857 Builder.CreateStore(CGM.BuildbyrefCopyHelper(addr->getType(), fieldFlags, 858 alignment.getQuantity(), &D), 859 copy_helper); 860 861 llvm::Value *destroy_helper = Builder.CreateStructGEP(addr, 5); 862 Builder.CreateStore(CGM.BuildbyrefDestroyHelper(addr->getType(), 863 fieldFlags, 864 alignment.getQuantity(), 865 &D), 866 destroy_helper); 867 } 868 } 869 870 if (!Init) return; 871 872 // Check whether this is a byref variable that's potentially 873 // captured and moved by its own initializer. If so, we'll need to 874 // emit the initializer first, then copy into the variable. 875 bool capturedByInit = emission.IsByRef && isCapturedBy(D, Init); 876 877 llvm::Value *Loc = 878 capturedByInit ? emission.Address : emission.getObjectAddress(*this); 879 880 bool isVolatile = type.isVolatileQualified(); 881 882 // If this is a simple aggregate initialization, we can optimize it 883 // in various ways. 884 if (emission.IsConstantAggregate) { 885 assert(!capturedByInit && "constant init contains a capturing block?"); 886 887 llvm::Constant *Init = CGM.EmitConstantExpr(D.getInit(), type, this); 888 assert(Init != 0 && "Wasn't a simple constant init?"); 889 890 llvm::Value *SizeVal = 891 llvm::ConstantInt::get(IntPtrTy, 892 getContext().getTypeSizeInChars(type).getQuantity()); 893 894 const llvm::Type *BP = Int8PtrTy; 895 if (Loc->getType() != BP) 896 Loc = Builder.CreateBitCast(Loc, BP, "tmp"); 897 898 // If the initializer is all or mostly zeros, codegen with memset then do 899 // a few stores afterward. 900 if (shouldUseMemSetPlusStoresToInitialize(Init, 901 CGM.getTargetData().getTypeAllocSize(Init->getType()))) { 902 Builder.CreateMemSet(Loc, llvm::ConstantInt::get(Int8Ty, 0), SizeVal, 903 alignment.getQuantity(), isVolatile); 904 if (!Init->isNullValue()) { 905 Loc = Builder.CreateBitCast(Loc, Init->getType()->getPointerTo()); 906 emitStoresForInitAfterMemset(Init, Loc, isVolatile, Builder); 907 } 908 } else { 909 // Otherwise, create a temporary global with the initializer then 910 // memcpy from the global to the alloca. 911 std::string Name = GetStaticDeclName(*this, D, "."); 912 llvm::GlobalVariable *GV = 913 new llvm::GlobalVariable(CGM.getModule(), Init->getType(), true, 914 llvm::GlobalValue::InternalLinkage, 915 Init, Name, 0, false, 0); 916 GV->setAlignment(alignment.getQuantity()); 917 918 llvm::Value *SrcPtr = GV; 919 if (SrcPtr->getType() != BP) 920 SrcPtr = Builder.CreateBitCast(SrcPtr, BP, "tmp"); 921 922 Builder.CreateMemCpy(Loc, SrcPtr, SizeVal, alignment.getQuantity(), 923 isVolatile); 924 } 925 } else if (type->isReferenceType()) { 926 RValue RV = EmitReferenceBindingToExpr(Init, &D); 927 if (capturedByInit) Loc = BuildBlockByrefAddress(Loc, &D); 928 EmitStoreOfScalar(RV.getScalarVal(), Loc, false, alignment.getQuantity(), 929 type); 930 } else if (!hasAggregateLLVMType(type)) { 931 llvm::Value *V = EmitScalarExpr(Init); 932 if (capturedByInit) Loc = BuildBlockByrefAddress(Loc, &D); 933 EmitStoreOfScalar(V, Loc, isVolatile, alignment.getQuantity(), type); 934 } else if (type->isAnyComplexType()) { 935 ComplexPairTy complex = EmitComplexExpr(Init); 936 if (capturedByInit) Loc = BuildBlockByrefAddress(Loc, &D); 937 StoreComplexToAddr(complex, Loc, isVolatile); 938 } else { 939 // TODO: how can we delay here if D is captured by its initializer? 940 EmitAggExpr(Init, AggValueSlot::forAddr(Loc, isVolatile, true, false)); 941 } 942} 943 944void CodeGenFunction::EmitAutoVarCleanups(const AutoVarEmission &emission) { 945 assert(emission.Variable && "emission was not valid!"); 946 947 // If this was emitted as a global constant, we're done. 948 if (emission.wasEmittedAsGlobal()) return; 949 950 const VarDecl &D = *emission.Variable; 951 952 // Handle C++ destruction of variables. 953 if (getLangOptions().CPlusPlus) { 954 QualType type = D.getType(); 955 QualType baseType = getContext().getBaseElementType(type); 956 if (const RecordType *RT = baseType->getAs<RecordType>()) { 957 CXXRecordDecl *ClassDecl = cast<CXXRecordDecl>(RT->getDecl()); 958 if (!ClassDecl->hasTrivialDestructor()) { 959 // Note: We suppress the destructor call when the corresponding NRVO 960 // flag has been set. 961 962 // Note that for __block variables, we want to destroy the 963 // original stack object, not the possible forwarded object. 964 llvm::Value *Loc = emission.getObjectAddress(*this); 965 966 const CXXDestructorDecl *D = ClassDecl->getDestructor(); 967 assert(D && "EmitLocalBlockVarDecl - destructor is nul"); 968 969 if (type != baseType) { 970 const ConstantArrayType *Array = 971 getContext().getAsConstantArrayType(type); 972 assert(Array && "types changed without array?"); 973 EHStack.pushCleanup<CallArrayDtor>(NormalAndEHCleanup, 974 D, Array, Loc); 975 } else { 976 EHStack.pushCleanup<CallVarDtor>(NormalAndEHCleanup, 977 D, emission.NRVOFlag, Loc); 978 } 979 } 980 } 981 } 982 983 // Handle the cleanup attribute. 984 if (const CleanupAttr *CA = D.getAttr<CleanupAttr>()) { 985 const FunctionDecl *FD = CA->getFunctionDecl(); 986 987 llvm::Constant *F = CGM.GetAddrOfFunction(FD); 988 assert(F && "Could not find function!"); 989 990 const CGFunctionInfo &Info = CGM.getTypes().getFunctionInfo(FD); 991 EHStack.pushCleanup<CallCleanupFunction>(NormalAndEHCleanup, F, &Info, &D); 992 } 993 994 // If this is a block variable, call _Block_object_destroy 995 // (on the unforwarded address). 996 if (emission.IsByRef && 997 CGM.getLangOptions().getGCMode() != LangOptions::GCOnly) 998 EHStack.pushCleanup<CallBlockRelease>(NormalAndEHCleanup, emission.Address); 999} 1000 1001/// Emit an alloca (or GlobalValue depending on target) 1002/// for the specified parameter and set up LocalDeclMap. 1003void CodeGenFunction::EmitParmDecl(const VarDecl &D, llvm::Value *Arg, 1004 unsigned ArgNo) { 1005 // FIXME: Why isn't ImplicitParamDecl a ParmVarDecl? 1006 assert((isa<ParmVarDecl>(D) || isa<ImplicitParamDecl>(D)) && 1007 "Invalid argument to EmitParmDecl"); 1008 1009 Arg->setName(D.getName()); 1010 1011 // Use better IR generation for certain implicit parameters. 1012 if (isa<ImplicitParamDecl>(D)) { 1013 // The only implicit argument a block has is its literal. 1014 if (BlockInfo) { 1015 LocalDeclMap[&D] = Arg; 1016 1017 if (CGDebugInfo *DI = getDebugInfo()) { 1018 DI->setLocation(D.getLocation()); 1019 DI->EmitDeclareOfBlockLiteralArgVariable(*BlockInfo, Arg, Builder); 1020 } 1021 1022 return; 1023 } 1024 } 1025 1026 QualType Ty = D.getType(); 1027 1028 llvm::Value *DeclPtr; 1029 // If this is an aggregate or variable sized value, reuse the input pointer. 1030 if (!Ty->isConstantSizeType() || 1031 CodeGenFunction::hasAggregateLLVMType(Ty)) { 1032 DeclPtr = Arg; 1033 } else { 1034 // Otherwise, create a temporary to hold the value. 1035 DeclPtr = CreateMemTemp(Ty, D.getName() + ".addr"); 1036 1037 // Store the initial value into the alloca. 1038 EmitStoreOfScalar(Arg, DeclPtr, Ty.isVolatileQualified(), 1039 getContext().getDeclAlign(&D).getQuantity(), Ty, 1040 CGM.getTBAAInfo(Ty)); 1041 } 1042 1043 llvm::Value *&DMEntry = LocalDeclMap[&D]; 1044 assert(DMEntry == 0 && "Decl already exists in localdeclmap!"); 1045 DMEntry = DeclPtr; 1046 1047 // Emit debug info for param declaration. 1048 if (CGDebugInfo *DI = getDebugInfo()) { 1049 DI->setLocation(D.getLocation()); 1050 DI->EmitDeclareOfArgVariable(&D, DeclPtr, ArgNo, Builder); 1051 } 1052} 1053