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      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 "CGCXXABI.h"
     16 #include "CGObjCRuntime.h"
     17 #include "CGOpenMPRuntime.h"
     18 #include "clang/Frontend/CodeGenOptions.h"
     19 #include "llvm/ADT/StringExtras.h"
     20 #include "llvm/IR/Intrinsics.h"
     21 #include "llvm/Support/Path.h"
     22 
     23 using namespace clang;
     24 using namespace CodeGen;
     25 
     26 static void EmitDeclInit(CodeGenFunction &CGF, const VarDecl &D,
     27                          llvm::Constant *DeclPtr) {
     28   assert(D.hasGlobalStorage() && "VarDecl must have global storage!");
     29   assert(!D.getType()->isReferenceType() &&
     30          "Should not call EmitDeclInit on a reference!");
     31 
     32   ASTContext &Context = CGF.getContext();
     33 
     34   CharUnits alignment = Context.getDeclAlign(&D);
     35   QualType type = D.getType();
     36   LValue lv = CGF.MakeAddrLValue(DeclPtr, type, alignment);
     37 
     38   const Expr *Init = D.getInit();
     39   switch (CGF.getEvaluationKind(type)) {
     40   case TEK_Scalar: {
     41     CodeGenModule &CGM = CGF.CGM;
     42     if (lv.isObjCStrong())
     43       CGM.getObjCRuntime().EmitObjCGlobalAssign(CGF, CGF.EmitScalarExpr(Init),
     44                                                 DeclPtr, D.getTLSKind());
     45     else if (lv.isObjCWeak())
     46       CGM.getObjCRuntime().EmitObjCWeakAssign(CGF, CGF.EmitScalarExpr(Init),
     47                                               DeclPtr);
     48     else
     49       CGF.EmitScalarInit(Init, &D, lv, false);
     50     return;
     51   }
     52   case TEK_Complex:
     53     CGF.EmitComplexExprIntoLValue(Init, lv, /*isInit*/ true);
     54     return;
     55   case TEK_Aggregate:
     56     CGF.EmitAggExpr(Init, AggValueSlot::forLValue(lv,AggValueSlot::IsDestructed,
     57                                           AggValueSlot::DoesNotNeedGCBarriers,
     58                                                   AggValueSlot::IsNotAliased));
     59     return;
     60   }
     61   llvm_unreachable("bad evaluation kind");
     62 }
     63 
     64 /// Emit code to cause the destruction of the given variable with
     65 /// static storage duration.
     66 static void EmitDeclDestroy(CodeGenFunction &CGF, const VarDecl &D,
     67                             llvm::Constant *addr) {
     68   CodeGenModule &CGM = CGF.CGM;
     69 
     70   // FIXME:  __attribute__((cleanup)) ?
     71 
     72   QualType type = D.getType();
     73   QualType::DestructionKind dtorKind = type.isDestructedType();
     74 
     75   switch (dtorKind) {
     76   case QualType::DK_none:
     77     return;
     78 
     79   case QualType::DK_cxx_destructor:
     80     break;
     81 
     82   case QualType::DK_objc_strong_lifetime:
     83   case QualType::DK_objc_weak_lifetime:
     84     // We don't care about releasing objects during process teardown.
     85     assert(!D.getTLSKind() && "should have rejected this");
     86     return;
     87   }
     88 
     89   llvm::Constant *function;
     90   llvm::Constant *argument;
     91 
     92   // Special-case non-array C++ destructors, where there's a function
     93   // with the right signature that we can just call.
     94   const CXXRecordDecl *record = nullptr;
     95   if (dtorKind == QualType::DK_cxx_destructor &&
     96       (record = type->getAsCXXRecordDecl())) {
     97     assert(!record->hasTrivialDestructor());
     98     CXXDestructorDecl *dtor = record->getDestructor();
     99 
    100     function = CGM.getAddrOfCXXStructor(dtor, StructorType::Complete);
    101     argument = llvm::ConstantExpr::getBitCast(
    102         addr, CGF.getTypes().ConvertType(type)->getPointerTo());
    103 
    104   // Otherwise, the standard logic requires a helper function.
    105   } else {
    106     function = CodeGenFunction(CGM)
    107         .generateDestroyHelper(addr, type, CGF.getDestroyer(dtorKind),
    108                                CGF.needsEHCleanup(dtorKind), &D);
    109     argument = llvm::Constant::getNullValue(CGF.Int8PtrTy);
    110   }
    111 
    112   CGM.getCXXABI().registerGlobalDtor(CGF, D, function, argument);
    113 }
    114 
    115 /// Emit code to cause the variable at the given address to be considered as
    116 /// constant from this point onwards.
    117 static void EmitDeclInvariant(CodeGenFunction &CGF, const VarDecl &D,
    118                               llvm::Constant *Addr) {
    119   // Don't emit the intrinsic if we're not optimizing.
    120   if (!CGF.CGM.getCodeGenOpts().OptimizationLevel)
    121     return;
    122 
    123   // Grab the llvm.invariant.start intrinsic.
    124   llvm::Intrinsic::ID InvStartID = llvm::Intrinsic::invariant_start;
    125   llvm::Constant *InvariantStart = CGF.CGM.getIntrinsic(InvStartID);
    126 
    127   // Emit a call with the size in bytes of the object.
    128   CharUnits WidthChars = CGF.getContext().getTypeSizeInChars(D.getType());
    129   uint64_t Width = WidthChars.getQuantity();
    130   llvm::Value *Args[2] = { llvm::ConstantInt::getSigned(CGF.Int64Ty, Width),
    131                            llvm::ConstantExpr::getBitCast(Addr, CGF.Int8PtrTy)};
    132   CGF.Builder.CreateCall(InvariantStart, Args);
    133 }
    134 
    135 void CodeGenFunction::EmitCXXGlobalVarDeclInit(const VarDecl &D,
    136                                                llvm::Constant *DeclPtr,
    137                                                bool PerformInit) {
    138 
    139   const Expr *Init = D.getInit();
    140   QualType T = D.getType();
    141 
    142   // The address space of a static local variable (DeclPtr) may be different
    143   // from the address space of the "this" argument of the constructor. In that
    144   // case, we need an addrspacecast before calling the constructor.
    145   //
    146   // struct StructWithCtor {
    147   //   __device__ StructWithCtor() {...}
    148   // };
    149   // __device__ void foo() {
    150   //   __shared__ StructWithCtor s;
    151   //   ...
    152   // }
    153   //
    154   // For example, in the above CUDA code, the static local variable s has a
    155   // "shared" address space qualifier, but the constructor of StructWithCtor
    156   // expects "this" in the "generic" address space.
    157   unsigned ExpectedAddrSpace = getContext().getTargetAddressSpace(T);
    158   unsigned ActualAddrSpace = DeclPtr->getType()->getPointerAddressSpace();
    159   if (ActualAddrSpace != ExpectedAddrSpace) {
    160     llvm::Type *LTy = CGM.getTypes().ConvertTypeForMem(T);
    161     llvm::PointerType *PTy = llvm::PointerType::get(LTy, ExpectedAddrSpace);
    162     DeclPtr = llvm::ConstantExpr::getAddrSpaceCast(DeclPtr, PTy);
    163   }
    164 
    165   if (!T->isReferenceType()) {
    166     if (getLangOpts().OpenMP && D.hasAttr<OMPThreadPrivateDeclAttr>())
    167       (void)CGM.getOpenMPRuntime().emitThreadPrivateVarDefinition(
    168           &D, DeclPtr, D.getAttr<OMPThreadPrivateDeclAttr>()->getLocation(),
    169           PerformInit, this);
    170     if (PerformInit)
    171       EmitDeclInit(*this, D, DeclPtr);
    172     if (CGM.isTypeConstant(D.getType(), true))
    173       EmitDeclInvariant(*this, D, DeclPtr);
    174     else
    175       EmitDeclDestroy(*this, D, DeclPtr);
    176     return;
    177   }
    178 
    179   assert(PerformInit && "cannot have constant initializer which needs "
    180          "destruction for reference");
    181   unsigned Alignment = getContext().getDeclAlign(&D).getQuantity();
    182   RValue RV = EmitReferenceBindingToExpr(Init);
    183   EmitStoreOfScalar(RV.getScalarVal(), DeclPtr, false, Alignment, T);
    184 }
    185 
    186 /// Create a stub function, suitable for being passed to atexit,
    187 /// which passes the given address to the given destructor function.
    188 llvm::Constant *CodeGenFunction::createAtExitStub(const VarDecl &VD,
    189                                                   llvm::Constant *dtor,
    190                                                   llvm::Constant *addr) {
    191   // Get the destructor function type, void(*)(void).
    192   llvm::FunctionType *ty = llvm::FunctionType::get(CGM.VoidTy, false);
    193   SmallString<256> FnName;
    194   {
    195     llvm::raw_svector_ostream Out(FnName);
    196     CGM.getCXXABI().getMangleContext().mangleDynamicAtExitDestructor(&VD, Out);
    197   }
    198   llvm::Function *fn = CGM.CreateGlobalInitOrDestructFunction(ty, FnName.str(),
    199                                                               VD.getLocation());
    200 
    201   CodeGenFunction CGF(CGM);
    202 
    203   CGF.StartFunction(&VD, CGM.getContext().VoidTy, fn,
    204                     CGM.getTypes().arrangeNullaryFunction(), FunctionArgList());
    205 
    206   llvm::CallInst *call = CGF.Builder.CreateCall(dtor, addr);
    207 
    208  // Make sure the call and the callee agree on calling convention.
    209   if (llvm::Function *dtorFn =
    210         dyn_cast<llvm::Function>(dtor->stripPointerCasts()))
    211     call->setCallingConv(dtorFn->getCallingConv());
    212 
    213   CGF.FinishFunction();
    214 
    215   return fn;
    216 }
    217 
    218 /// Register a global destructor using the C atexit runtime function.
    219 void CodeGenFunction::registerGlobalDtorWithAtExit(const VarDecl &VD,
    220                                                    llvm::Constant *dtor,
    221                                                    llvm::Constant *addr) {
    222   // Create a function which calls the destructor.
    223   llvm::Constant *dtorStub = createAtExitStub(VD, dtor, addr);
    224 
    225   // extern "C" int atexit(void (*f)(void));
    226   llvm::FunctionType *atexitTy =
    227     llvm::FunctionType::get(IntTy, dtorStub->getType(), false);
    228 
    229   llvm::Constant *atexit =
    230     CGM.CreateRuntimeFunction(atexitTy, "atexit");
    231   if (llvm::Function *atexitFn = dyn_cast<llvm::Function>(atexit))
    232     atexitFn->setDoesNotThrow();
    233 
    234   EmitNounwindRuntimeCall(atexit, dtorStub);
    235 }
    236 
    237 void CodeGenFunction::EmitCXXGuardedInit(const VarDecl &D,
    238                                          llvm::GlobalVariable *DeclPtr,
    239                                          bool PerformInit) {
    240   // If we've been asked to forbid guard variables, emit an error now.
    241   // This diagnostic is hard-coded for Darwin's use case;  we can find
    242   // better phrasing if someone else needs it.
    243   if (CGM.getCodeGenOpts().ForbidGuardVariables)
    244     CGM.Error(D.getLocation(),
    245               "this initialization requires a guard variable, which "
    246               "the kernel does not support");
    247 
    248   CGM.getCXXABI().EmitGuardedInit(*this, D, DeclPtr, PerformInit);
    249 }
    250 
    251 llvm::Function *CodeGenModule::CreateGlobalInitOrDestructFunction(
    252     llvm::FunctionType *FTy, const Twine &Name, SourceLocation Loc, bool TLS) {
    253   llvm::Function *Fn =
    254     llvm::Function::Create(FTy, llvm::GlobalValue::InternalLinkage,
    255                            Name, &getModule());
    256   if (!getLangOpts().AppleKext && !TLS) {
    257     // Set the section if needed.
    258     if (const char *Section = getTarget().getStaticInitSectionSpecifier())
    259       Fn->setSection(Section);
    260   }
    261 
    262   Fn->setCallingConv(getRuntimeCC());
    263 
    264   if (!getLangOpts().Exceptions)
    265     Fn->setDoesNotThrow();
    266 
    267   if (!isInSanitizerBlacklist(Fn, Loc)) {
    268     if (getLangOpts().Sanitize.has(SanitizerKind::Address))
    269       Fn->addFnAttr(llvm::Attribute::SanitizeAddress);
    270     if (getLangOpts().Sanitize.has(SanitizerKind::Thread))
    271       Fn->addFnAttr(llvm::Attribute::SanitizeThread);
    272     if (getLangOpts().Sanitize.has(SanitizerKind::Memory))
    273       Fn->addFnAttr(llvm::Attribute::SanitizeMemory);
    274   }
    275 
    276   return Fn;
    277 }
    278 
    279 /// Create a global pointer to a function that will initialize a global
    280 /// variable.  The user has requested that this pointer be emitted in a specific
    281 /// section.
    282 void CodeGenModule::EmitPointerToInitFunc(const VarDecl *D,
    283                                           llvm::GlobalVariable *GV,
    284                                           llvm::Function *InitFunc,
    285                                           InitSegAttr *ISA) {
    286   llvm::GlobalVariable *PtrArray = new llvm::GlobalVariable(
    287       TheModule, InitFunc->getType(), /*isConstant=*/true,
    288       llvm::GlobalValue::PrivateLinkage, InitFunc, "__cxx_init_fn_ptr");
    289   PtrArray->setSection(ISA->getSection());
    290   addUsedGlobal(PtrArray);
    291 
    292   // If the GV is already in a comdat group, then we have to join it.
    293   if (llvm::Comdat *C = GV->getComdat())
    294     PtrArray->setComdat(C);
    295 }
    296 
    297 void
    298 CodeGenModule::EmitCXXGlobalVarDeclInitFunc(const VarDecl *D,
    299                                             llvm::GlobalVariable *Addr,
    300                                             bool PerformInit) {
    301   // Check if we've already initialized this decl.
    302   auto I = DelayedCXXInitPosition.find(D);
    303   if (I != DelayedCXXInitPosition.end() && I->second == ~0U)
    304     return;
    305 
    306   llvm::FunctionType *FTy = llvm::FunctionType::get(VoidTy, false);
    307   SmallString<256> FnName;
    308   {
    309     llvm::raw_svector_ostream Out(FnName);
    310     getCXXABI().getMangleContext().mangleDynamicInitializer(D, Out);
    311   }
    312 
    313   // Create a variable initialization function.
    314   llvm::Function *Fn =
    315       CreateGlobalInitOrDestructFunction(FTy, FnName.str(), D->getLocation());
    316 
    317   auto *ISA = D->getAttr<InitSegAttr>();
    318   CodeGenFunction(*this).GenerateCXXGlobalVarDeclInitFunc(Fn, D, Addr,
    319                                                           PerformInit);
    320 
    321   llvm::GlobalVariable *COMDATKey =
    322       supportsCOMDAT() && D->isExternallyVisible() ? Addr : nullptr;
    323 
    324   if (D->getTLSKind()) {
    325     // FIXME: Should we support init_priority for thread_local?
    326     // FIXME: Ideally, initialization of instantiated thread_local static data
    327     // members of class templates should not trigger initialization of other
    328     // entities in the TU.
    329     // FIXME: We only need to register one __cxa_thread_atexit function for the
    330     // entire TU.
    331     CXXThreadLocalInits.push_back(Fn);
    332     CXXThreadLocalInitVars.push_back(Addr);
    333   } else if (PerformInit && ISA) {
    334     EmitPointerToInitFunc(D, Addr, Fn, ISA);
    335   } else if (auto *IPA = D->getAttr<InitPriorityAttr>()) {
    336     OrderGlobalInits Key(IPA->getPriority(), PrioritizedCXXGlobalInits.size());
    337     PrioritizedCXXGlobalInits.push_back(std::make_pair(Key, Fn));
    338   } else if (isTemplateInstantiation(D->getTemplateSpecializationKind())) {
    339     // C++ [basic.start.init]p2:
    340     //   Definitions of explicitly specialized class template static data
    341     //   members have ordered initialization. Other class template static data
    342     //   members (i.e., implicitly or explicitly instantiated specializations)
    343     //   have unordered initialization.
    344     //
    345     // As a consequence, we can put them into their own llvm.global_ctors entry.
    346     //
    347     // If the global is externally visible, put the initializer into a COMDAT
    348     // group with the global being initialized.  On most platforms, this is a
    349     // minor startup time optimization.  In the MS C++ ABI, there are no guard
    350     // variables, so this COMDAT key is required for correctness.
    351     AddGlobalCtor(Fn, 65535, COMDATKey);
    352   } else if (D->hasAttr<SelectAnyAttr>()) {
    353     // SelectAny globals will be comdat-folded. Put the initializer into a
    354     // COMDAT group associated with the global, so the initializers get folded
    355     // too.
    356     AddGlobalCtor(Fn, 65535, COMDATKey);
    357   } else {
    358     I = DelayedCXXInitPosition.find(D); // Re-do lookup in case of re-hash.
    359     if (I == DelayedCXXInitPosition.end()) {
    360       CXXGlobalInits.push_back(Fn);
    361     } else if (I->second != ~0U) {
    362       assert(I->second < CXXGlobalInits.size() &&
    363              CXXGlobalInits[I->second] == nullptr);
    364       CXXGlobalInits[I->second] = Fn;
    365     }
    366   }
    367 
    368   // Remember that we already emitted the initializer for this global.
    369   DelayedCXXInitPosition[D] = ~0U;
    370 }
    371 
    372 void CodeGenModule::EmitCXXThreadLocalInitFunc() {
    373   getCXXABI().EmitThreadLocalInitFuncs(
    374       *this, CXXThreadLocals, CXXThreadLocalInits, CXXThreadLocalInitVars);
    375 
    376   CXXThreadLocalInits.clear();
    377   CXXThreadLocalInitVars.clear();
    378   CXXThreadLocals.clear();
    379 }
    380 
    381 void
    382 CodeGenModule::EmitCXXGlobalInitFunc() {
    383   while (!CXXGlobalInits.empty() && !CXXGlobalInits.back())
    384     CXXGlobalInits.pop_back();
    385 
    386   if (CXXGlobalInits.empty() && PrioritizedCXXGlobalInits.empty())
    387     return;
    388 
    389   llvm::FunctionType *FTy = llvm::FunctionType::get(VoidTy, false);
    390 
    391 
    392   // Create our global initialization function.
    393   if (!PrioritizedCXXGlobalInits.empty()) {
    394     SmallVector<llvm::Function *, 8> LocalCXXGlobalInits;
    395     llvm::array_pod_sort(PrioritizedCXXGlobalInits.begin(),
    396                          PrioritizedCXXGlobalInits.end());
    397     // Iterate over "chunks" of ctors with same priority and emit each chunk
    398     // into separate function. Note - everything is sorted first by priority,
    399     // second - by lex order, so we emit ctor functions in proper order.
    400     for (SmallVectorImpl<GlobalInitData >::iterator
    401            I = PrioritizedCXXGlobalInits.begin(),
    402            E = PrioritizedCXXGlobalInits.end(); I != E; ) {
    403       SmallVectorImpl<GlobalInitData >::iterator
    404         PrioE = std::upper_bound(I + 1, E, *I, GlobalInitPriorityCmp());
    405 
    406       LocalCXXGlobalInits.clear();
    407       unsigned Priority = I->first.priority;
    408       // Compute the function suffix from priority. Prepend with zeroes to make
    409       // sure the function names are also ordered as priorities.
    410       std::string PrioritySuffix = llvm::utostr(Priority);
    411       // Priority is always <= 65535 (enforced by sema).
    412       PrioritySuffix = std::string(6-PrioritySuffix.size(), '0')+PrioritySuffix;
    413       llvm::Function *Fn = CreateGlobalInitOrDestructFunction(
    414           FTy, "_GLOBAL__I_" + PrioritySuffix);
    415 
    416       for (; I < PrioE; ++I)
    417         LocalCXXGlobalInits.push_back(I->second);
    418 
    419       CodeGenFunction(*this).GenerateCXXGlobalInitFunc(Fn, LocalCXXGlobalInits);
    420       AddGlobalCtor(Fn, Priority);
    421     }
    422   }
    423 
    424   SmallString<128> FileName;
    425   SourceManager &SM = Context.getSourceManager();
    426   if (const FileEntry *MainFile = SM.getFileEntryForID(SM.getMainFileID())) {
    427     // Include the filename in the symbol name. Including "sub_" matches gcc and
    428     // makes sure these symbols appear lexicographically behind the symbols with
    429     // priority emitted above.
    430     FileName = llvm::sys::path::filename(MainFile->getName());
    431   } else {
    432     FileName = SmallString<128>("<null>");
    433   }
    434 
    435   for (size_t i = 0; i < FileName.size(); ++i) {
    436     // Replace everything that's not [a-zA-Z0-9._] with a _. This set happens
    437     // to be the set of C preprocessing numbers.
    438     if (!isPreprocessingNumberBody(FileName[i]))
    439       FileName[i] = '_';
    440   }
    441 
    442   llvm::Function *Fn = CreateGlobalInitOrDestructFunction(
    443       FTy, llvm::Twine("_GLOBAL__sub_I_", FileName));
    444 
    445   CodeGenFunction(*this).GenerateCXXGlobalInitFunc(Fn, CXXGlobalInits);
    446   AddGlobalCtor(Fn);
    447 
    448   CXXGlobalInits.clear();
    449   PrioritizedCXXGlobalInits.clear();
    450 }
    451 
    452 void CodeGenModule::EmitCXXGlobalDtorFunc() {
    453   if (CXXGlobalDtors.empty())
    454     return;
    455 
    456   llvm::FunctionType *FTy = llvm::FunctionType::get(VoidTy, false);
    457 
    458   // Create our global destructor function.
    459   llvm::Function *Fn = CreateGlobalInitOrDestructFunction(FTy, "_GLOBAL__D_a");
    460 
    461   CodeGenFunction(*this).GenerateCXXGlobalDtorsFunc(Fn, CXXGlobalDtors);
    462   AddGlobalDtor(Fn);
    463 }
    464 
    465 /// Emit the code necessary to initialize the given global variable.
    466 void CodeGenFunction::GenerateCXXGlobalVarDeclInitFunc(llvm::Function *Fn,
    467                                                        const VarDecl *D,
    468                                                  llvm::GlobalVariable *Addr,
    469                                                        bool PerformInit) {
    470   // Check if we need to emit debug info for variable initializer.
    471   if (D->hasAttr<NoDebugAttr>())
    472     DebugInfo = nullptr; // disable debug info indefinitely for this function
    473 
    474   CurEHLocation = D->getLocStart();
    475 
    476   StartFunction(GlobalDecl(D), getContext().VoidTy, Fn,
    477                 getTypes().arrangeNullaryFunction(),
    478                 FunctionArgList(), D->getLocation(),
    479                 D->getInit()->getExprLoc());
    480 
    481   // Use guarded initialization if the global variable is weak. This
    482   // occurs for, e.g., instantiated static data members and
    483   // definitions explicitly marked weak.
    484   if (Addr->hasWeakLinkage() || Addr->hasLinkOnceLinkage()) {
    485     EmitCXXGuardedInit(*D, Addr, PerformInit);
    486   } else {
    487     EmitCXXGlobalVarDeclInit(*D, Addr, PerformInit);
    488   }
    489 
    490   FinishFunction();
    491 }
    492 
    493 void
    494 CodeGenFunction::GenerateCXXGlobalInitFunc(llvm::Function *Fn,
    495                                            ArrayRef<llvm::Function *> Decls,
    496                                            llvm::GlobalVariable *Guard) {
    497   {
    498     auto NL = ApplyDebugLocation::CreateEmpty(*this);
    499     StartFunction(GlobalDecl(), getContext().VoidTy, Fn,
    500                   getTypes().arrangeNullaryFunction(), FunctionArgList());
    501     // Emit an artificial location for this function.
    502     auto AL = ApplyDebugLocation::CreateArtificial(*this);
    503 
    504     llvm::BasicBlock *ExitBlock = nullptr;
    505     if (Guard) {
    506       // If we have a guard variable, check whether we've already performed
    507       // these initializations. This happens for TLS initialization functions.
    508       llvm::Value *GuardVal = Builder.CreateLoad(Guard);
    509       llvm::Value *Uninit = Builder.CreateIsNull(GuardVal,
    510                                                  "guard.uninitialized");
    511       // Mark as initialized before initializing anything else. If the
    512       // initializers use previously-initialized thread_local vars, that's
    513       // probably supposed to be OK, but the standard doesn't say.
    514       Builder.CreateStore(llvm::ConstantInt::get(GuardVal->getType(),1), Guard);
    515       llvm::BasicBlock *InitBlock = createBasicBlock("init");
    516       ExitBlock = createBasicBlock("exit");
    517       Builder.CreateCondBr(Uninit, InitBlock, ExitBlock);
    518       EmitBlock(InitBlock);
    519     }
    520 
    521     RunCleanupsScope Scope(*this);
    522 
    523     // When building in Objective-C++ ARC mode, create an autorelease pool
    524     // around the global initializers.
    525     if (getLangOpts().ObjCAutoRefCount && getLangOpts().CPlusPlus) {
    526       llvm::Value *token = EmitObjCAutoreleasePoolPush();
    527       EmitObjCAutoreleasePoolCleanup(token);
    528     }
    529 
    530     for (unsigned i = 0, e = Decls.size(); i != e; ++i)
    531       if (Decls[i])
    532         EmitRuntimeCall(Decls[i]);
    533 
    534     Scope.ForceCleanup();
    535 
    536     if (ExitBlock) {
    537       Builder.CreateBr(ExitBlock);
    538       EmitBlock(ExitBlock);
    539     }
    540   }
    541 
    542   FinishFunction();
    543 }
    544 
    545 void CodeGenFunction::GenerateCXXGlobalDtorsFunc(llvm::Function *Fn,
    546                   const std::vector<std::pair<llvm::WeakVH, llvm::Constant*> >
    547                                                 &DtorsAndObjects) {
    548   {
    549     auto NL = ApplyDebugLocation::CreateEmpty(*this);
    550     StartFunction(GlobalDecl(), getContext().VoidTy, Fn,
    551                   getTypes().arrangeNullaryFunction(), FunctionArgList());
    552     // Emit an artificial location for this function.
    553     auto AL = ApplyDebugLocation::CreateArtificial(*this);
    554 
    555     // Emit the dtors, in reverse order from construction.
    556     for (unsigned i = 0, e = DtorsAndObjects.size(); i != e; ++i) {
    557       llvm::Value *Callee = DtorsAndObjects[e - i - 1].first;
    558       llvm::CallInst *CI = Builder.CreateCall(Callee,
    559                                           DtorsAndObjects[e - i - 1].second);
    560       // Make sure the call and the callee agree on calling convention.
    561       if (llvm::Function *F = dyn_cast<llvm::Function>(Callee))
    562         CI->setCallingConv(F->getCallingConv());
    563     }
    564   }
    565 
    566   FinishFunction();
    567 }
    568 
    569 /// generateDestroyHelper - Generates a helper function which, when
    570 /// invoked, destroys the given object.
    571 llvm::Function *CodeGenFunction::generateDestroyHelper(
    572     llvm::Constant *addr, QualType type, Destroyer *destroyer,
    573     bool useEHCleanupForArray, const VarDecl *VD) {
    574   FunctionArgList args;
    575   ImplicitParamDecl dst(getContext(), nullptr, SourceLocation(), nullptr,
    576                         getContext().VoidPtrTy);
    577   args.push_back(&dst);
    578 
    579   const CGFunctionInfo &FI = CGM.getTypes().arrangeFreeFunctionDeclaration(
    580       getContext().VoidTy, args, FunctionType::ExtInfo(), /*variadic=*/false);
    581   llvm::FunctionType *FTy = CGM.getTypes().GetFunctionType(FI);
    582   llvm::Function *fn = CGM.CreateGlobalInitOrDestructFunction(
    583       FTy, "__cxx_global_array_dtor", VD->getLocation());
    584 
    585   CurEHLocation = VD->getLocStart();
    586 
    587   StartFunction(VD, getContext().VoidTy, fn, FI, args);
    588 
    589   emitDestroy(addr, type, destroyer, useEHCleanupForArray);
    590 
    591   FinishFunction();
    592 
    593   return fn;
    594 }
    595