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 
EmitDeclInit(CodeGenFunction & CGF,const VarDecl & D,llvm::Constant * DeclPtr)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.
EmitDeclDestroy(CodeGenFunction & CGF,const VarDecl & D,llvm::Constant * addr)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.
EmitDeclInvariant(CodeGenFunction & CGF,const VarDecl & D,llvm::Constant * Addr)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 
EmitCXXGlobalVarDeclInit(const VarDecl & D,llvm::Constant * DeclPtr,bool PerformInit)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.
createAtExitStub(const VarDecl & VD,llvm::Constant * dtor,llvm::Constant * addr)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.
registerGlobalDtorWithAtExit(const VarDecl & VD,llvm::Constant * dtor,llvm::Constant * addr)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 
EmitCXXGuardedInit(const VarDecl & D,llvm::GlobalVariable * DeclPtr,bool PerformInit)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 
CreateGlobalInitOrDestructFunction(llvm::FunctionType * FTy,const Twine & Name,SourceLocation Loc,bool TLS)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.
EmitPointerToInitFunc(const VarDecl * D,llvm::GlobalVariable * GV,llvm::Function * InitFunc,InitSegAttr * ISA)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
EmitCXXGlobalVarDeclInitFunc(const VarDecl * D,llvm::GlobalVariable * Addr,bool PerformInit)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 
EmitCXXThreadLocalInitFunc()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
EmitCXXGlobalInitFunc()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 
EmitCXXGlobalDtorFunc()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.
GenerateCXXGlobalVarDeclInitFunc(llvm::Function * Fn,const VarDecl * D,llvm::GlobalVariable * Addr,bool PerformInit)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
GenerateCXXGlobalInitFunc(llvm::Function * Fn,ArrayRef<llvm::Function * > Decls,llvm::GlobalVariable * Guard)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 
GenerateCXXGlobalDtorsFunc(llvm::Function * Fn,const std::vector<std::pair<llvm::WeakVH,llvm::Constant * >> & DtorsAndObjects)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.
generateDestroyHelper(llvm::Constant * addr,QualType type,Destroyer * destroyer,bool useEHCleanupForArray,const VarDecl * VD)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