CGDecl.cpp revision 19bd77c64937d6818c61f2aa9e6a9d51c65d0356
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 "clang/AST/ASTContext.h" 18#include "clang/AST/CharUnits.h" 19#include "clang/AST/Decl.h" 20#include "clang/AST/DeclObjC.h" 21#include "clang/Basic/SourceManager.h" 22#include "clang/Basic/TargetInfo.h" 23#include "clang/Frontend/CodeGenOptions.h" 24#include "llvm/GlobalVariable.h" 25#include "llvm/Intrinsics.h" 26#include "llvm/Target/TargetData.h" 27#include "llvm/Type.h" 28using namespace clang; 29using namespace CodeGen; 30 31 32void CodeGenFunction::EmitDecl(const Decl &D) { 33 switch (D.getKind()) { 34 case Decl::TranslationUnit: 35 case Decl::Namespace: 36 case Decl::UnresolvedUsingTypename: 37 case Decl::ClassTemplateSpecialization: 38 case Decl::ClassTemplatePartialSpecialization: 39 case Decl::TemplateTypeParm: 40 case Decl::UnresolvedUsingValue: 41 case Decl::NonTypeTemplateParm: 42 case Decl::CXXMethod: 43 case Decl::CXXConstructor: 44 case Decl::CXXDestructor: 45 case Decl::CXXConversion: 46 case Decl::Field: 47 case Decl::IndirectField: 48 case Decl::ObjCIvar: 49 case Decl::ObjCAtDefsField: 50 case Decl::ParmVar: 51 case Decl::ImplicitParam: 52 case Decl::ClassTemplate: 53 case Decl::FunctionTemplate: 54 case Decl::TypeAliasTemplate: 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 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 case Decl::TypeAlias: { // using X = int; [C++0x] 97 const TypedefNameDecl &TD = cast<TypedefNameDecl>(D); 98 QualType Ty = TD.getUnderlyingType(); 99 100 if (Ty->isVariablyModifiedType()) 101 EmitVLASize(Ty); 102 } 103 } 104} 105 106/// EmitVarDecl - This method handles emission of any variable declaration 107/// inside a function, including static vars etc. 108void CodeGenFunction::EmitVarDecl(const VarDecl &D) { 109 switch (D.getStorageClass()) { 110 case SC_None: 111 case SC_Auto: 112 case SC_Register: 113 return EmitAutoVarDecl(D); 114 case SC_Static: { 115 llvm::GlobalValue::LinkageTypes Linkage = 116 llvm::GlobalValue::InternalLinkage; 117 118 // If the function definition has some sort of weak linkage, its 119 // static variables should also be weak so that they get properly 120 // uniqued. We can't do this in C, though, because there's no 121 // standard way to agree on which variables are the same (i.e. 122 // there's no mangling). 123 if (getContext().getLangOptions().CPlusPlus) 124 if (llvm::GlobalValue::isWeakForLinker(CurFn->getLinkage())) 125 Linkage = CurFn->getLinkage(); 126 127 return EmitStaticVarDecl(D, Linkage); 128 } 129 case SC_Extern: 130 case SC_PrivateExtern: 131 // Don't emit it now, allow it to be emitted lazily on its first use. 132 return; 133 } 134 135 assert(0 && "Unknown storage class"); 136} 137 138static std::string GetStaticDeclName(CodeGenFunction &CGF, const VarDecl &D, 139 const char *Separator) { 140 CodeGenModule &CGM = CGF.CGM; 141 if (CGF.getContext().getLangOptions().CPlusPlus) { 142 llvm::StringRef Name = CGM.getMangledName(&D); 143 return Name.str(); 144 } 145 146 std::string ContextName; 147 if (!CGF.CurFuncDecl) { 148 // Better be in a block declared in global scope. 149 const NamedDecl *ND = cast<NamedDecl>(&D); 150 const DeclContext *DC = ND->getDeclContext(); 151 if (const BlockDecl *BD = dyn_cast<BlockDecl>(DC)) { 152 MangleBuffer Name; 153 CGM.getBlockMangledName(GlobalDecl(), Name, BD); 154 ContextName = Name.getString(); 155 } 156 else 157 assert(0 && "Unknown context for block static var decl"); 158 } else if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(CGF.CurFuncDecl)) { 159 llvm::StringRef Name = CGM.getMangledName(FD); 160 ContextName = Name.str(); 161 } else if (isa<ObjCMethodDecl>(CGF.CurFuncDecl)) 162 ContextName = CGF.CurFn->getName(); 163 else 164 assert(0 && "Unknown context for static var decl"); 165 166 return ContextName + Separator + D.getNameAsString(); 167} 168 169llvm::GlobalVariable * 170CodeGenFunction::CreateStaticVarDecl(const VarDecl &D, 171 const char *Separator, 172 llvm::GlobalValue::LinkageTypes Linkage) { 173 QualType Ty = D.getType(); 174 assert(Ty->isConstantSizeType() && "VLAs can't be static"); 175 176 std::string Name = GetStaticDeclName(*this, D, Separator); 177 178 const llvm::Type *LTy = CGM.getTypes().ConvertTypeForMem(Ty); 179 llvm::GlobalVariable *GV = 180 new llvm::GlobalVariable(CGM.getModule(), LTy, 181 Ty.isConstant(getContext()), Linkage, 182 CGM.EmitNullConstant(D.getType()), Name, 0, 183 D.isThreadSpecified(), 184 CGM.getContext().getTargetAddressSpace(Ty)); 185 GV->setAlignment(getContext().getDeclAlign(&D).getQuantity()); 186 if (Linkage != llvm::GlobalValue::InternalLinkage) 187 GV->setVisibility(CurFn->getVisibility()); 188 return GV; 189} 190 191/// AddInitializerToStaticVarDecl - Add the initializer for 'D' to the 192/// global variable that has already been created for it. If the initializer 193/// has a different type than GV does, this may free GV and return a different 194/// one. Otherwise it just returns GV. 195llvm::GlobalVariable * 196CodeGenFunction::AddInitializerToStaticVarDecl(const VarDecl &D, 197 llvm::GlobalVariable *GV) { 198 llvm::Constant *Init = CGM.EmitConstantExpr(D.getInit(), D.getType(), this); 199 200 // If constant emission failed, then this should be a C++ static 201 // initializer. 202 if (!Init) { 203 if (!getContext().getLangOptions().CPlusPlus) 204 CGM.ErrorUnsupported(D.getInit(), "constant l-value expression"); 205 else if (Builder.GetInsertBlock()) { 206 // Since we have a static initializer, this global variable can't 207 // be constant. 208 GV->setConstant(false); 209 210 EmitCXXGuardedInit(D, GV); 211 } 212 return GV; 213 } 214 215 // The initializer may differ in type from the global. Rewrite 216 // the global to match the initializer. (We have to do this 217 // because some types, like unions, can't be completely represented 218 // in the LLVM type system.) 219 if (GV->getType()->getElementType() != Init->getType()) { 220 llvm::GlobalVariable *OldGV = GV; 221 222 GV = new llvm::GlobalVariable(CGM.getModule(), Init->getType(), 223 OldGV->isConstant(), 224 OldGV->getLinkage(), Init, "", 225 /*InsertBefore*/ OldGV, 226 D.isThreadSpecified(), 227 CGM.getContext().getTargetAddressSpace(D.getType())); 228 GV->setVisibility(OldGV->getVisibility()); 229 230 // Steal the name of the old global 231 GV->takeName(OldGV); 232 233 // Replace all uses of the old global with the new global 234 llvm::Constant *NewPtrForOldDecl = 235 llvm::ConstantExpr::getBitCast(GV, OldGV->getType()); 236 OldGV->replaceAllUsesWith(NewPtrForOldDecl); 237 238 // Erase the old global, since it is no longer used. 239 OldGV->eraseFromParent(); 240 } 241 242 GV->setInitializer(Init); 243 return GV; 244} 245 246void CodeGenFunction::EmitStaticVarDecl(const VarDecl &D, 247 llvm::GlobalValue::LinkageTypes Linkage) { 248 llvm::Value *&DMEntry = LocalDeclMap[&D]; 249 assert(DMEntry == 0 && "Decl already exists in localdeclmap!"); 250 251 llvm::GlobalVariable *GV = CreateStaticVarDecl(D, ".", Linkage); 252 253 // Store into LocalDeclMap before generating initializer to handle 254 // circular references. 255 DMEntry = GV; 256 257 // We can't have a VLA here, but we can have a pointer to a VLA, 258 // even though that doesn't really make any sense. 259 // Make sure to evaluate VLA bounds now so that we have them for later. 260 if (D.getType()->isVariablyModifiedType()) 261 EmitVLASize(D.getType()); 262 263 // Local static block variables must be treated as globals as they may be 264 // referenced in their RHS initializer block-literal expresion. 265 CGM.setStaticLocalDeclAddress(&D, GV); 266 267 // If this value has an initializer, emit it. 268 if (D.getInit()) 269 GV = AddInitializerToStaticVarDecl(D, GV); 270 271 GV->setAlignment(getContext().getDeclAlign(&D).getQuantity()); 272 273 // FIXME: Merge attribute handling. 274 if (const AnnotateAttr *AA = D.getAttr<AnnotateAttr>()) { 275 SourceManager &SM = CGM.getContext().getSourceManager(); 276 llvm::Constant *Ann = 277 CGM.EmitAnnotateAttr(GV, AA, 278 SM.getInstantiationLineNumber(D.getLocation())); 279 CGM.AddAnnotation(Ann); 280 } 281 282 if (const SectionAttr *SA = D.getAttr<SectionAttr>()) 283 GV->setSection(SA->getName()); 284 285 if (D.hasAttr<UsedAttr>()) 286 CGM.AddUsedGlobal(GV); 287 288 // We may have to cast the constant because of the initializer 289 // mismatch above. 290 // 291 // FIXME: It is really dangerous to store this in the map; if anyone 292 // RAUW's the GV uses of this constant will be invalid. 293 const llvm::Type *LTy = CGM.getTypes().ConvertTypeForMem(D.getType()); 294 const llvm::Type *LPtrTy = 295 LTy->getPointerTo(CGM.getContext().getTargetAddressSpace(D.getType())); 296 DMEntry = llvm::ConstantExpr::getBitCast(GV, LPtrTy); 297 298 // Emit global variable debug descriptor for static vars. 299 CGDebugInfo *DI = getDebugInfo(); 300 if (DI) { 301 DI->setLocation(D.getLocation()); 302 DI->EmitGlobalVariable(static_cast<llvm::GlobalVariable *>(GV), &D); 303 } 304} 305 306namespace { 307 struct CallArrayDtor : EHScopeStack::Cleanup { 308 CallArrayDtor(const CXXDestructorDecl *Dtor, 309 const ConstantArrayType *Type, 310 llvm::Value *Loc) 311 : Dtor(Dtor), Type(Type), Loc(Loc) {} 312 313 const CXXDestructorDecl *Dtor; 314 const ConstantArrayType *Type; 315 llvm::Value *Loc; 316 317 void Emit(CodeGenFunction &CGF, bool IsForEH) { 318 QualType BaseElementTy = CGF.getContext().getBaseElementType(Type); 319 const llvm::Type *BasePtr = CGF.ConvertType(BaseElementTy); 320 BasePtr = llvm::PointerType::getUnqual(BasePtr); 321 llvm::Value *BaseAddrPtr = CGF.Builder.CreateBitCast(Loc, BasePtr); 322 CGF.EmitCXXAggrDestructorCall(Dtor, Type, BaseAddrPtr); 323 } 324 }; 325 326 struct CallVarDtor : EHScopeStack::Cleanup { 327 CallVarDtor(const CXXDestructorDecl *Dtor, 328 llvm::Value *NRVOFlag, 329 llvm::Value *Loc) 330 : Dtor(Dtor), NRVOFlag(NRVOFlag), Loc(Loc) {} 331 332 const CXXDestructorDecl *Dtor; 333 llvm::Value *NRVOFlag; 334 llvm::Value *Loc; 335 336 void Emit(CodeGenFunction &CGF, bool IsForEH) { 337 // Along the exceptions path we always execute the dtor. 338 bool NRVO = !IsForEH && NRVOFlag; 339 340 llvm::BasicBlock *SkipDtorBB = 0; 341 if (NRVO) { 342 // If we exited via NRVO, we skip the destructor call. 343 llvm::BasicBlock *RunDtorBB = CGF.createBasicBlock("nrvo.unused"); 344 SkipDtorBB = CGF.createBasicBlock("nrvo.skipdtor"); 345 llvm::Value *DidNRVO = CGF.Builder.CreateLoad(NRVOFlag, "nrvo.val"); 346 CGF.Builder.CreateCondBr(DidNRVO, SkipDtorBB, RunDtorBB); 347 CGF.EmitBlock(RunDtorBB); 348 } 349 350 CGF.EmitCXXDestructorCall(Dtor, Dtor_Complete, 351 /*ForVirtualBase=*/false, Loc); 352 353 if (NRVO) CGF.EmitBlock(SkipDtorBB); 354 } 355 }; 356 357 struct CallStackRestore : EHScopeStack::Cleanup { 358 llvm::Value *Stack; 359 CallStackRestore(llvm::Value *Stack) : Stack(Stack) {} 360 void Emit(CodeGenFunction &CGF, bool IsForEH) { 361 llvm::Value *V = CGF.Builder.CreateLoad(Stack, "tmp"); 362 llvm::Value *F = CGF.CGM.getIntrinsic(llvm::Intrinsic::stackrestore); 363 CGF.Builder.CreateCall(F, V); 364 } 365 }; 366 367 struct CallCleanupFunction : EHScopeStack::Cleanup { 368 llvm::Constant *CleanupFn; 369 const CGFunctionInfo &FnInfo; 370 const VarDecl &Var; 371 372 CallCleanupFunction(llvm::Constant *CleanupFn, const CGFunctionInfo *Info, 373 const VarDecl *Var) 374 : CleanupFn(CleanupFn), FnInfo(*Info), Var(*Var) {} 375 376 void Emit(CodeGenFunction &CGF, bool IsForEH) { 377 DeclRefExpr DRE(const_cast<VarDecl*>(&Var), Var.getType(), VK_LValue, 378 SourceLocation()); 379 // Compute the address of the local variable, in case it's a byref 380 // or something. 381 llvm::Value *Addr = CGF.EmitDeclRefLValue(&DRE).getAddress(); 382 383 // In some cases, the type of the function argument will be different from 384 // the type of the pointer. An example of this is 385 // void f(void* arg); 386 // __attribute__((cleanup(f))) void *g; 387 // 388 // To fix this we insert a bitcast here. 389 QualType ArgTy = FnInfo.arg_begin()->type; 390 llvm::Value *Arg = 391 CGF.Builder.CreateBitCast(Addr, CGF.ConvertType(ArgTy)); 392 393 CallArgList Args; 394 Args.add(RValue::get(Arg), 395 CGF.getContext().getPointerType(Var.getType())); 396 CGF.EmitCall(FnInfo, CleanupFn, ReturnValueSlot(), Args); 397 } 398 }; 399} 400 401/// EmitAutoVarWithLifetime - Does the setup required for an automatic 402/// variable with lifetime. 403static void EmitAutoVarWithLifetime(CodeGenFunction &CGF, const VarDecl &var, 404 llvm::Value *addr, 405 Qualifiers::ObjCLifetime lifetime) { 406 switch (lifetime) { 407 case Qualifiers::OCL_None: 408 llvm_unreachable("present but none"); 409 410 case Qualifiers::OCL_ExplicitNone: 411 // nothing to do 412 break; 413 414 case Qualifiers::OCL_Strong: { 415 CGF.PushARCReleaseCleanup(CGF.getARCCleanupKind(), 416 var.getType(), addr, 417 var.hasAttr<ObjCPreciseLifetimeAttr>()); 418 break; 419 } 420 case Qualifiers::OCL_Autoreleasing: 421 // nothing to do 422 break; 423 424 case Qualifiers::OCL_Weak: 425 // __weak objects always get EH cleanups; otherwise, exceptions 426 // could cause really nasty crashes instead of mere leaks. 427 CGF.PushARCWeakReleaseCleanup(NormalAndEHCleanup, var.getType(), addr); 428 break; 429 } 430} 431 432static bool isAccessedBy(const VarDecl &var, const Stmt *s) { 433 if (const Expr *e = dyn_cast<Expr>(s)) { 434 // Skip the most common kinds of expressions that make 435 // hierarchy-walking expensive. 436 s = e = e->IgnoreParenCasts(); 437 438 if (const DeclRefExpr *ref = dyn_cast<DeclRefExpr>(e)) 439 return (ref->getDecl() == &var); 440 } 441 442 for (Stmt::const_child_range children = s->children(); children; ++children) 443 if (isAccessedBy(var, *children)) 444 return true; 445 446 return false; 447} 448 449static bool isAccessedBy(const ValueDecl *decl, const Expr *e) { 450 if (!decl) return false; 451 if (!isa<VarDecl>(decl)) return false; 452 const VarDecl *var = cast<VarDecl>(decl); 453 return isAccessedBy(*var, e); 454} 455 456static void drillIntoBlockVariable(CodeGenFunction &CGF, 457 LValue &lvalue, 458 const VarDecl *var) { 459 lvalue.setAddress(CGF.BuildBlockByrefAddress(lvalue.getAddress(), var)); 460} 461 462void CodeGenFunction::EmitScalarInit(const Expr *init, 463 const ValueDecl *D, 464 LValue lvalue, 465 bool capturedByInit) { 466 Qualifiers::ObjCLifetime lifetime = lvalue.getObjCLifetime(); 467 if (!lifetime) { 468 llvm::Value *value = EmitScalarExpr(init); 469 if (capturedByInit) 470 drillIntoBlockVariable(*this, lvalue, cast<VarDecl>(D)); 471 EmitStoreThroughLValue(RValue::get(value), lvalue, lvalue.getType()); 472 return; 473 } 474 475 // If we're emitting a value with lifetime, we have to do the 476 // initialization *before* we leave the cleanup scopes. 477 CodeGenFunction::RunCleanupsScope Scope(*this); 478 if (const ExprWithCleanups *ewc = dyn_cast<ExprWithCleanups>(init)) 479 init = ewc->getSubExpr(); 480 481 // We have to maintain the illusion that the variable is 482 // zero-initialized. If the variable might be accessed in its 483 // initializer, zero-initialize before running the initializer, then 484 // actually perform the initialization with an assign. 485 bool accessedByInit = false; 486 if (lifetime != Qualifiers::OCL_ExplicitNone) 487 accessedByInit = isAccessedBy(D, init); 488 if (accessedByInit) { 489 LValue tempLV = lvalue; 490 // Drill down to the __block object if necessary. 491 if (capturedByInit) { 492 // We can use a simple GEP for this because it can't have been 493 // moved yet. 494 tempLV.setAddress(Builder.CreateStructGEP(tempLV.getAddress(), 495 getByRefValueLLVMField(cast<VarDecl>(D)))); 496 } 497 498 const llvm::PointerType *ty 499 = cast<llvm::PointerType>(tempLV.getAddress()->getType()); 500 ty = cast<llvm::PointerType>(ty->getElementType()); 501 502 llvm::Value *zero = llvm::ConstantPointerNull::get(ty); 503 504 // If __weak, we want to use a barrier under certain conditions. 505 if (lifetime == Qualifiers::OCL_Weak) 506 EmitARCInitWeak(tempLV.getAddress(), zero); 507 508 // Otherwise just do a simple store. 509 else 510 EmitStoreOfScalar(zero, tempLV); 511 } 512 513 // Emit the initializer. 514 llvm::Value *value = 0; 515 516 switch (lifetime) { 517 case Qualifiers::OCL_None: 518 llvm_unreachable("present but none"); 519 520 case Qualifiers::OCL_ExplicitNone: 521 // nothing to do 522 value = EmitScalarExpr(init); 523 break; 524 525 case Qualifiers::OCL_Strong: { 526 value = EmitARCRetainScalarExpr(init); 527 break; 528 } 529 530 case Qualifiers::OCL_Weak: { 531 // No way to optimize a producing initializer into this. It's not 532 // worth optimizing for, because the value will immediately 533 // disappear in the common case. 534 value = EmitScalarExpr(init); 535 536 if (capturedByInit) drillIntoBlockVariable(*this, lvalue, cast<VarDecl>(D)); 537 if (accessedByInit) 538 EmitARCStoreWeak(lvalue.getAddress(), value, /*ignored*/ true); 539 else 540 EmitARCInitWeak(lvalue.getAddress(), value); 541 return; 542 } 543 544 case Qualifiers::OCL_Autoreleasing: 545 value = EmitARCRetainAutoreleaseScalarExpr(init); 546 break; 547 } 548 549 if (capturedByInit) drillIntoBlockVariable(*this, lvalue, cast<VarDecl>(D)); 550 551 // If the variable might have been accessed by its initializer, we 552 // might have to initialize with a barrier. We have to do this for 553 // both __weak and __strong, but __weak got filtered out above. 554 if (accessedByInit && lifetime == Qualifiers::OCL_Strong) { 555 llvm::Value *oldValue = EmitLoadOfScalar(lvalue); 556 EmitStoreOfScalar(value, lvalue); 557 EmitARCRelease(oldValue, /*precise*/ false); 558 return; 559 } 560 561 EmitStoreOfScalar(value, lvalue); 562} 563 564/// EmitScalarInit - Initialize the given lvalue with the given object. 565void CodeGenFunction::EmitScalarInit(llvm::Value *init, LValue lvalue) { 566 Qualifiers::ObjCLifetime lifetime = lvalue.getObjCLifetime(); 567 if (!lifetime) 568 return EmitStoreThroughLValue(RValue::get(init), lvalue, lvalue.getType()); 569 570 switch (lifetime) { 571 case Qualifiers::OCL_None: 572 llvm_unreachable("present but none"); 573 574 case Qualifiers::OCL_ExplicitNone: 575 // nothing to do 576 break; 577 578 case Qualifiers::OCL_Strong: 579 init = EmitARCRetain(lvalue.getType(), init); 580 break; 581 582 case Qualifiers::OCL_Weak: 583 // Initialize and then skip the primitive store. 584 EmitARCInitWeak(lvalue.getAddress(), init); 585 return; 586 587 case Qualifiers::OCL_Autoreleasing: 588 init = EmitARCRetainAutorelease(lvalue.getType(), init); 589 break; 590 } 591 592 EmitStoreOfScalar(init, lvalue); 593} 594 595/// canEmitInitWithFewStoresAfterMemset - Decide whether we can emit the 596/// non-zero parts of the specified initializer with equal or fewer than 597/// NumStores scalar stores. 598static bool canEmitInitWithFewStoresAfterMemset(llvm::Constant *Init, 599 unsigned &NumStores) { 600 // Zero and Undef never requires any extra stores. 601 if (isa<llvm::ConstantAggregateZero>(Init) || 602 isa<llvm::ConstantPointerNull>(Init) || 603 isa<llvm::UndefValue>(Init)) 604 return true; 605 if (isa<llvm::ConstantInt>(Init) || isa<llvm::ConstantFP>(Init) || 606 isa<llvm::ConstantVector>(Init) || isa<llvm::BlockAddress>(Init) || 607 isa<llvm::ConstantExpr>(Init)) 608 return Init->isNullValue() || NumStores--; 609 610 // See if we can emit each element. 611 if (isa<llvm::ConstantArray>(Init) || isa<llvm::ConstantStruct>(Init)) { 612 for (unsigned i = 0, e = Init->getNumOperands(); i != e; ++i) { 613 llvm::Constant *Elt = cast<llvm::Constant>(Init->getOperand(i)); 614 if (!canEmitInitWithFewStoresAfterMemset(Elt, NumStores)) 615 return false; 616 } 617 return true; 618 } 619 620 // Anything else is hard and scary. 621 return false; 622} 623 624/// emitStoresForInitAfterMemset - For inits that 625/// canEmitInitWithFewStoresAfterMemset returned true for, emit the scalar 626/// stores that would be required. 627static void emitStoresForInitAfterMemset(llvm::Constant *Init, llvm::Value *Loc, 628 bool isVolatile, CGBuilderTy &Builder) { 629 // Zero doesn't require any stores. 630 if (isa<llvm::ConstantAggregateZero>(Init) || 631 isa<llvm::ConstantPointerNull>(Init) || 632 isa<llvm::UndefValue>(Init)) 633 return; 634 635 if (isa<llvm::ConstantInt>(Init) || isa<llvm::ConstantFP>(Init) || 636 isa<llvm::ConstantVector>(Init) || isa<llvm::BlockAddress>(Init) || 637 isa<llvm::ConstantExpr>(Init)) { 638 if (!Init->isNullValue()) 639 Builder.CreateStore(Init, Loc, isVolatile); 640 return; 641 } 642 643 assert((isa<llvm::ConstantStruct>(Init) || isa<llvm::ConstantArray>(Init)) && 644 "Unknown value type!"); 645 646 for (unsigned i = 0, e = Init->getNumOperands(); i != e; ++i) { 647 llvm::Constant *Elt = cast<llvm::Constant>(Init->getOperand(i)); 648 if (Elt->isNullValue()) continue; 649 650 // Otherwise, get a pointer to the element and emit it. 651 emitStoresForInitAfterMemset(Elt, Builder.CreateConstGEP2_32(Loc, 0, i), 652 isVolatile, Builder); 653 } 654} 655 656 657/// shouldUseMemSetPlusStoresToInitialize - Decide whether we should use memset 658/// plus some stores to initialize a local variable instead of using a memcpy 659/// from a constant global. It is beneficial to use memset if the global is all 660/// zeros, or mostly zeros and large. 661static bool shouldUseMemSetPlusStoresToInitialize(llvm::Constant *Init, 662 uint64_t GlobalSize) { 663 // If a global is all zeros, always use a memset. 664 if (isa<llvm::ConstantAggregateZero>(Init)) return true; 665 666 667 // If a non-zero global is <= 32 bytes, always use a memcpy. If it is large, 668 // do it if it will require 6 or fewer scalar stores. 669 // TODO: Should budget depends on the size? Avoiding a large global warrants 670 // plopping in more stores. 671 unsigned StoreBudget = 6; 672 uint64_t SizeLimit = 32; 673 674 return GlobalSize > SizeLimit && 675 canEmitInitWithFewStoresAfterMemset(Init, StoreBudget); 676} 677 678 679/// EmitAutoVarDecl - Emit code and set up an entry in LocalDeclMap for a 680/// variable declaration with auto, register, or no storage class specifier. 681/// These turn into simple stack objects, or GlobalValues depending on target. 682void CodeGenFunction::EmitAutoVarDecl(const VarDecl &D) { 683 AutoVarEmission emission = EmitAutoVarAlloca(D); 684 EmitAutoVarInit(emission); 685 EmitAutoVarCleanups(emission); 686} 687 688/// EmitAutoVarAlloca - Emit the alloca and debug information for a 689/// local variable. Does not emit initalization or destruction. 690CodeGenFunction::AutoVarEmission 691CodeGenFunction::EmitAutoVarAlloca(const VarDecl &D) { 692 QualType Ty = D.getType(); 693 694 AutoVarEmission emission(D); 695 696 bool isByRef = D.hasAttr<BlocksAttr>(); 697 emission.IsByRef = isByRef; 698 699 CharUnits alignment = getContext().getDeclAlign(&D); 700 emission.Alignment = alignment; 701 702 llvm::Value *DeclPtr; 703 if (Ty->isConstantSizeType()) { 704 if (!Target.useGlobalsForAutomaticVariables()) { 705 bool NRVO = getContext().getLangOptions().ElideConstructors && 706 D.isNRVOVariable(); 707 708 // If this value is a POD array or struct with a statically 709 // determinable constant initializer, there are optimizations we 710 // can do. 711 // TODO: we can potentially constant-evaluate non-POD structs and 712 // arrays as long as the initialization is trivial (e.g. if they 713 // have a non-trivial destructor, but not a non-trivial constructor). 714 if (D.getInit() && 715 (Ty->isArrayType() || Ty->isRecordType()) && 716 (Ty.isPODType(getContext()) || 717 getContext().getBaseElementType(Ty)->isObjCObjectPointerType()) && 718 D.getInit()->isConstantInitializer(getContext(), false)) { 719 720 // If the variable's a const type, and it's neither an NRVO 721 // candidate nor a __block variable, emit it as a global instead. 722 if (CGM.getCodeGenOpts().MergeAllConstants && Ty.isConstQualified() && 723 !NRVO && !isByRef) { 724 EmitStaticVarDecl(D, llvm::GlobalValue::InternalLinkage); 725 726 emission.Address = 0; // signal this condition to later callbacks 727 assert(emission.wasEmittedAsGlobal()); 728 return emission; 729 } 730 731 // Otherwise, tell the initialization code that we're in this case. 732 emission.IsConstantAggregate = true; 733 } 734 735 // A normal fixed sized variable becomes an alloca in the entry block, 736 // unless it's an NRVO variable. 737 const llvm::Type *LTy = ConvertTypeForMem(Ty); 738 739 if (NRVO) { 740 // The named return value optimization: allocate this variable in the 741 // return slot, so that we can elide the copy when returning this 742 // variable (C++0x [class.copy]p34). 743 DeclPtr = ReturnValue; 744 745 if (const RecordType *RecordTy = Ty->getAs<RecordType>()) { 746 if (!cast<CXXRecordDecl>(RecordTy->getDecl())->hasTrivialDestructor()) { 747 // Create a flag that is used to indicate when the NRVO was applied 748 // to this variable. Set it to zero to indicate that NRVO was not 749 // applied. 750 llvm::Value *Zero = Builder.getFalse(); 751 llvm::Value *NRVOFlag = CreateTempAlloca(Zero->getType(), "nrvo"); 752 EnsureInsertPoint(); 753 Builder.CreateStore(Zero, NRVOFlag); 754 755 // Record the NRVO flag for this variable. 756 NRVOFlags[&D] = NRVOFlag; 757 emission.NRVOFlag = NRVOFlag; 758 } 759 } 760 } else { 761 if (isByRef) 762 LTy = BuildByRefType(&D); 763 764 llvm::AllocaInst *Alloc = CreateTempAlloca(LTy); 765 Alloc->setName(D.getNameAsString()); 766 767 CharUnits allocaAlignment = alignment; 768 if (isByRef) 769 allocaAlignment = std::max(allocaAlignment, 770 getContext().toCharUnitsFromBits(Target.getPointerAlign(0))); 771 Alloc->setAlignment(allocaAlignment.getQuantity()); 772 DeclPtr = Alloc; 773 } 774 } else { 775 // Targets that don't support recursion emit locals as globals. 776 const char *Class = 777 D.getStorageClass() == SC_Register ? ".reg." : ".auto."; 778 DeclPtr = CreateStaticVarDecl(D, Class, 779 llvm::GlobalValue::InternalLinkage); 780 } 781 782 // FIXME: Can this happen? 783 if (Ty->isVariablyModifiedType()) 784 EmitVLASize(Ty); 785 } else { 786 EnsureInsertPoint(); 787 788 if (!DidCallStackSave) { 789 // Save the stack. 790 llvm::Value *Stack = CreateTempAlloca(Int8PtrTy, "saved_stack"); 791 792 llvm::Value *F = CGM.getIntrinsic(llvm::Intrinsic::stacksave); 793 llvm::Value *V = Builder.CreateCall(F); 794 795 Builder.CreateStore(V, Stack); 796 797 DidCallStackSave = true; 798 799 // Push a cleanup block and restore the stack there. 800 // FIXME: in general circumstances, this should be an EH cleanup. 801 EHStack.pushCleanup<CallStackRestore>(NormalCleanup, Stack); 802 } 803 804 // Get the element type. 805 const llvm::Type *LElemTy = ConvertTypeForMem(Ty); 806 const llvm::Type *LElemPtrTy = 807 LElemTy->getPointerTo(CGM.getContext().getTargetAddressSpace(Ty)); 808 809 llvm::Value *VLASize = EmitVLASize(Ty); 810 811 // Allocate memory for the array. 812 llvm::AllocaInst *VLA = 813 Builder.CreateAlloca(llvm::Type::getInt8Ty(getLLVMContext()), VLASize, "vla"); 814 VLA->setAlignment(alignment.getQuantity()); 815 816 DeclPtr = Builder.CreateBitCast(VLA, LElemPtrTy, "tmp"); 817 } 818 819 llvm::Value *&DMEntry = LocalDeclMap[&D]; 820 assert(DMEntry == 0 && "Decl already exists in localdeclmap!"); 821 DMEntry = DeclPtr; 822 emission.Address = DeclPtr; 823 824 // Emit debug info for local var declaration. 825 if (HaveInsertPoint()) 826 if (CGDebugInfo *DI = getDebugInfo()) { 827 DI->setLocation(D.getLocation()); 828 if (Target.useGlobalsForAutomaticVariables()) { 829 DI->EmitGlobalVariable(static_cast<llvm::GlobalVariable *>(DeclPtr), &D); 830 } else 831 DI->EmitDeclareOfAutoVariable(&D, DeclPtr, Builder); 832 } 833 834 return emission; 835} 836 837/// Determines whether the given __block variable is potentially 838/// captured by the given expression. 839static bool isCapturedBy(const VarDecl &var, const Expr *e) { 840 // Skip the most common kinds of expressions that make 841 // hierarchy-walking expensive. 842 e = e->IgnoreParenCasts(); 843 844 if (const BlockExpr *be = dyn_cast<BlockExpr>(e)) { 845 const BlockDecl *block = be->getBlockDecl(); 846 for (BlockDecl::capture_const_iterator i = block->capture_begin(), 847 e = block->capture_end(); i != e; ++i) { 848 if (i->getVariable() == &var) 849 return true; 850 } 851 852 // No need to walk into the subexpressions. 853 return false; 854 } 855 856 for (Stmt::const_child_range children = e->children(); children; ++children) 857 if (isCapturedBy(var, cast<Expr>(*children))) 858 return true; 859 860 return false; 861} 862 863void CodeGenFunction::EmitAutoVarInit(const AutoVarEmission &emission) { 864 assert(emission.Variable && "emission was not valid!"); 865 866 // If this was emitted as a global constant, we're done. 867 if (emission.wasEmittedAsGlobal()) return; 868 869 const VarDecl &D = *emission.Variable; 870 QualType type = D.getType(); 871 872 // If this local has an initializer, emit it now. 873 const Expr *Init = D.getInit(); 874 875 // If we are at an unreachable point, we don't need to emit the initializer 876 // unless it contains a label. 877 if (!HaveInsertPoint()) { 878 if (!Init || !ContainsLabel(Init)) return; 879 EnsureInsertPoint(); 880 } 881 882 // Initialize the structure of a __block variable. 883 if (emission.IsByRef) 884 emitByrefStructureInit(emission); 885 886 if (!Init) return; 887 888 CharUnits alignment = emission.Alignment; 889 890 // Check whether this is a byref variable that's potentially 891 // captured and moved by its own initializer. If so, we'll need to 892 // emit the initializer first, then copy into the variable. 893 bool capturedByInit = emission.IsByRef && isCapturedBy(D, Init); 894 895 llvm::Value *Loc = 896 capturedByInit ? emission.Address : emission.getObjectAddress(*this); 897 898 if (!emission.IsConstantAggregate) { 899 LValue lv = MakeAddrLValue(Loc, type, alignment.getQuantity()); 900 lv.setNonGC(true); 901 return EmitExprAsInit(Init, &D, lv, capturedByInit); 902 } 903 904 // If this is a simple aggregate initialization, we can optimize it 905 // in various ways. 906 assert(!capturedByInit && "constant init contains a capturing block?"); 907 908 bool isVolatile = type.isVolatileQualified(); 909 910 llvm::Constant *constant = CGM.EmitConstantExpr(D.getInit(), type, this); 911 assert(constant != 0 && "Wasn't a simple constant init?"); 912 913 llvm::Value *SizeVal = 914 llvm::ConstantInt::get(IntPtrTy, 915 getContext().getTypeSizeInChars(type).getQuantity()); 916 917 const llvm::Type *BP = Int8PtrTy; 918 if (Loc->getType() != BP) 919 Loc = Builder.CreateBitCast(Loc, BP, "tmp"); 920 921 // If the initializer is all or mostly zeros, codegen with memset then do 922 // a few stores afterward. 923 if (shouldUseMemSetPlusStoresToInitialize(constant, 924 CGM.getTargetData().getTypeAllocSize(constant->getType()))) { 925 Builder.CreateMemSet(Loc, llvm::ConstantInt::get(Int8Ty, 0), SizeVal, 926 alignment.getQuantity(), isVolatile); 927 if (!constant->isNullValue()) { 928 Loc = Builder.CreateBitCast(Loc, constant->getType()->getPointerTo()); 929 emitStoresForInitAfterMemset(constant, Loc, isVolatile, Builder); 930 } 931 } else { 932 // Otherwise, create a temporary global with the initializer then 933 // memcpy from the global to the alloca. 934 std::string Name = GetStaticDeclName(*this, D, "."); 935 llvm::GlobalVariable *GV = 936 new llvm::GlobalVariable(CGM.getModule(), constant->getType(), true, 937 llvm::GlobalValue::InternalLinkage, 938 constant, Name, 0, false, 0); 939 GV->setAlignment(alignment.getQuantity()); 940 GV->setUnnamedAddr(true); 941 942 llvm::Value *SrcPtr = GV; 943 if (SrcPtr->getType() != BP) 944 SrcPtr = Builder.CreateBitCast(SrcPtr, BP, "tmp"); 945 946 Builder.CreateMemCpy(Loc, SrcPtr, SizeVal, alignment.getQuantity(), 947 isVolatile); 948 } 949} 950 951/// Emit an expression as an initializer for a variable at the given 952/// location. The expression is not necessarily the normal 953/// initializer for the variable, and the address is not necessarily 954/// its normal location. 955/// 956/// \param init the initializing expression 957/// \param var the variable to act as if we're initializing 958/// \param loc the address to initialize; its type is a pointer 959/// to the LLVM mapping of the variable's type 960/// \param alignment the alignment of the address 961/// \param capturedByInit true if the variable is a __block variable 962/// whose address is potentially changed by the initializer 963void CodeGenFunction::EmitExprAsInit(const Expr *init, 964 const ValueDecl *D, 965 LValue lvalue, 966 bool capturedByInit) { 967 QualType type = D->getType(); 968 969 if (type->isReferenceType()) { 970 RValue rvalue = EmitReferenceBindingToExpr(init, D); 971 if (capturedByInit) 972 drillIntoBlockVariable(*this, lvalue, cast<VarDecl>(D)); 973 EmitStoreThroughLValue(rvalue, lvalue, type); 974 } else if (!hasAggregateLLVMType(type)) { 975 EmitScalarInit(init, D, lvalue, capturedByInit); 976 } else if (type->isAnyComplexType()) { 977 ComplexPairTy complex = EmitComplexExpr(init); 978 if (capturedByInit) 979 drillIntoBlockVariable(*this, lvalue, cast<VarDecl>(D)); 980 StoreComplexToAddr(complex, lvalue.getAddress(), lvalue.isVolatile()); 981 } else { 982 // TODO: how can we delay here if D is captured by its initializer? 983 EmitAggExpr(init, AggValueSlot::forLValue(lvalue, true, false)); 984 } 985} 986 987void CodeGenFunction::EmitAutoVarCleanups(const AutoVarEmission &emission) { 988 assert(emission.Variable && "emission was not valid!"); 989 990 // If this was emitted as a global constant, we're done. 991 if (emission.wasEmittedAsGlobal()) return; 992 993 const VarDecl &D = *emission.Variable; 994 995 // Handle C++ or ARC destruction of variables. 996 if (getLangOptions().CPlusPlus) { 997 QualType type = D.getType(); 998 QualType baseType = getContext().getBaseElementType(type); 999 if (const RecordType *RT = baseType->getAs<RecordType>()) { 1000 CXXRecordDecl *ClassDecl = cast<CXXRecordDecl>(RT->getDecl()); 1001 if (!ClassDecl->hasTrivialDestructor()) { 1002 // Note: We suppress the destructor call when the corresponding NRVO 1003 // flag has been set. 1004 1005 // Note that for __block variables, we want to destroy the 1006 // original stack object, not the possible forwarded object. 1007 llvm::Value *Loc = emission.getObjectAddress(*this); 1008 1009 const CXXDestructorDecl *D = ClassDecl->getDestructor(); 1010 assert(D && "EmitLocalBlockVarDecl - destructor is nul"); 1011 1012 if (type != baseType) { 1013 const ConstantArrayType *Array = 1014 getContext().getAsConstantArrayType(type); 1015 assert(Array && "types changed without array?"); 1016 EHStack.pushCleanup<CallArrayDtor>(NormalAndEHCleanup, 1017 D, Array, Loc); 1018 } else { 1019 EHStack.pushCleanup<CallVarDtor>(NormalAndEHCleanup, 1020 D, emission.NRVOFlag, Loc); 1021 } 1022 } 1023 } 1024 } 1025 1026 if (Qualifiers::ObjCLifetime lifetime 1027 = D.getType().getQualifiers().getObjCLifetime()) { 1028 if (!D.isARCPseudoStrong()) { 1029 llvm::Value *loc = emission.getObjectAddress(*this); 1030 EmitAutoVarWithLifetime(*this, D, loc, lifetime); 1031 } 1032 } 1033 1034 // Handle the cleanup attribute. 1035 if (const CleanupAttr *CA = D.getAttr<CleanupAttr>()) { 1036 const FunctionDecl *FD = CA->getFunctionDecl(); 1037 1038 llvm::Constant *F = CGM.GetAddrOfFunction(FD); 1039 assert(F && "Could not find function!"); 1040 1041 const CGFunctionInfo &Info = CGM.getTypes().getFunctionInfo(FD); 1042 EHStack.pushCleanup<CallCleanupFunction>(NormalAndEHCleanup, F, &Info, &D); 1043 } 1044 1045 // If this is a block variable, call _Block_object_destroy 1046 // (on the unforwarded address). 1047 if (emission.IsByRef) 1048 enterByrefCleanup(emission); 1049} 1050 1051namespace { 1052 /// A cleanup to perform a release of an object at the end of a 1053 /// function. This is used to balance out the incoming +1 of a 1054 /// ns_consumed argument when we can't reasonably do that just by 1055 /// not doing the initial retain for a __block argument. 1056 struct ConsumeARCParameter : EHScopeStack::Cleanup { 1057 ConsumeARCParameter(llvm::Value *param) : Param(param) {} 1058 1059 llvm::Value *Param; 1060 1061 void Emit(CodeGenFunction &CGF, bool IsForEH) { 1062 CGF.EmitARCRelease(Param, /*precise*/ false); 1063 } 1064 }; 1065} 1066 1067/// Emit an alloca (or GlobalValue depending on target) 1068/// for the specified parameter and set up LocalDeclMap. 1069void CodeGenFunction::EmitParmDecl(const VarDecl &D, llvm::Value *Arg, 1070 unsigned ArgNo) { 1071 // FIXME: Why isn't ImplicitParamDecl a ParmVarDecl? 1072 assert((isa<ParmVarDecl>(D) || isa<ImplicitParamDecl>(D)) && 1073 "Invalid argument to EmitParmDecl"); 1074 1075 Arg->setName(D.getName()); 1076 1077 // Use better IR generation for certain implicit parameters. 1078 if (isa<ImplicitParamDecl>(D)) { 1079 // The only implicit argument a block has is its literal. 1080 if (BlockInfo) { 1081 LocalDeclMap[&D] = Arg; 1082 1083 if (CGDebugInfo *DI = getDebugInfo()) { 1084 DI->setLocation(D.getLocation()); 1085 DI->EmitDeclareOfBlockLiteralArgVariable(*BlockInfo, Arg, Builder); 1086 } 1087 1088 return; 1089 } 1090 } 1091 1092 QualType Ty = D.getType(); 1093 1094 llvm::Value *DeclPtr; 1095 // If this is an aggregate or variable sized value, reuse the input pointer. 1096 if (!Ty->isConstantSizeType() || 1097 CodeGenFunction::hasAggregateLLVMType(Ty)) { 1098 DeclPtr = Arg; 1099 } else { 1100 // Otherwise, create a temporary to hold the value. 1101 DeclPtr = CreateMemTemp(Ty, D.getName() + ".addr"); 1102 1103 bool doStore = true; 1104 1105 Qualifiers qs = Ty.getQualifiers(); 1106 1107 if (Qualifiers::ObjCLifetime lt = qs.getObjCLifetime()) { 1108 // We honor __attribute__((ns_consumed)) for types with lifetime. 1109 // For __strong, it's handled by just skipping the initial retain; 1110 // otherwise we have to balance out the initial +1 with an extra 1111 // cleanup to do the release at the end of the function. 1112 bool isConsumed = D.hasAttr<NSConsumedAttr>(); 1113 1114 // 'self' is always formally __strong, but if this is not an 1115 // init method then we don't want to retain it. 1116 if (D.isARCPseudoStrong()) { 1117 const ObjCMethodDecl *method = cast<ObjCMethodDecl>(CurCodeDecl); 1118 assert(&D == method->getSelfDecl()); 1119 assert(lt == Qualifiers::OCL_Strong); 1120 assert(qs.hasConst()); 1121 assert(method->getMethodFamily() != OMF_init); 1122 (void) method; 1123 lt = Qualifiers::OCL_ExplicitNone; 1124 } 1125 1126 if (lt == Qualifiers::OCL_Strong) { 1127 if (!isConsumed) 1128 // Don't use objc_retainBlock for block pointers, because we 1129 // don't want to Block_copy something just because we got it 1130 // as a parameter. 1131 Arg = EmitARCRetainNonBlock(Arg); 1132 } else { 1133 // Push the cleanup for a consumed parameter. 1134 if (isConsumed) 1135 EHStack.pushCleanup<ConsumeARCParameter>(getARCCleanupKind(), Arg); 1136 1137 if (lt == Qualifiers::OCL_Weak) { 1138 EmitARCInitWeak(DeclPtr, Arg); 1139 doStore = false; // The weak init is a store, no need to do two 1140 } 1141 } 1142 1143 // Enter the cleanup scope. 1144 EmitAutoVarWithLifetime(*this, D, DeclPtr, lt); 1145 } 1146 1147 // Store the initial value into the alloca. 1148 if (doStore) 1149 EmitStoreOfScalar(Arg, DeclPtr, Ty.isVolatileQualified(), 1150 getContext().getDeclAlign(&D).getQuantity(), Ty, 1151 CGM.getTBAAInfo(Ty)); 1152 } 1153 1154 llvm::Value *&DMEntry = LocalDeclMap[&D]; 1155 assert(DMEntry == 0 && "Decl already exists in localdeclmap!"); 1156 DMEntry = DeclPtr; 1157 1158 // Emit debug info for param declaration. 1159 if (CGDebugInfo *DI = getDebugInfo()) 1160 DI->EmitDeclareOfArgVariable(&D, DeclPtr, ArgNo, Builder); 1161} 1162