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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 
EmitDeclInit(CodeGenFunction & CGF,const VarDecl & D,ConstantAddress DeclPtr)26 static void EmitDeclInit(CodeGenFunction &CGF, const VarDecl &D,
27                          ConstantAddress 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   QualType type = D.getType();
33   LValue lv = CGF.MakeAddrLValue(DeclPtr, type);
34 
35   const Expr *Init = D.getInit();
36   switch (CGF.getEvaluationKind(type)) {
37   case TEK_Scalar: {
38     CodeGenModule &CGM = CGF.CGM;
39     if (lv.isObjCStrong())
40       CGM.getObjCRuntime().EmitObjCGlobalAssign(CGF, CGF.EmitScalarExpr(Init),
41                                                 DeclPtr, D.getTLSKind());
42     else if (lv.isObjCWeak())
43       CGM.getObjCRuntime().EmitObjCWeakAssign(CGF, CGF.EmitScalarExpr(Init),
44                                               DeclPtr);
45     else
46       CGF.EmitScalarInit(Init, &D, lv, false);
47     return;
48   }
49   case TEK_Complex:
50     CGF.EmitComplexExprIntoLValue(Init, lv, /*isInit*/ true);
51     return;
52   case TEK_Aggregate:
53     CGF.EmitAggExpr(Init, AggValueSlot::forLValue(lv,AggValueSlot::IsDestructed,
54                                           AggValueSlot::DoesNotNeedGCBarriers,
55                                                   AggValueSlot::IsNotAliased));
56     return;
57   }
58   llvm_unreachable("bad evaluation kind");
59 }
60 
61 /// Emit code to cause the destruction of the given variable with
62 /// static storage duration.
EmitDeclDestroy(CodeGenFunction & CGF,const VarDecl & D,ConstantAddress addr)63 static void EmitDeclDestroy(CodeGenFunction &CGF, const VarDecl &D,
64                             ConstantAddress addr) {
65   CodeGenModule &CGM = CGF.CGM;
66 
67   // FIXME:  __attribute__((cleanup)) ?
68 
69   QualType type = D.getType();
70   QualType::DestructionKind dtorKind = type.isDestructedType();
71 
72   switch (dtorKind) {
73   case QualType::DK_none:
74     return;
75 
76   case QualType::DK_cxx_destructor:
77     break;
78 
79   case QualType::DK_objc_strong_lifetime:
80   case QualType::DK_objc_weak_lifetime:
81     // We don't care about releasing objects during process teardown.
82     assert(!D.getTLSKind() && "should have rejected this");
83     return;
84   }
85 
86   llvm::Constant *function;
87   llvm::Constant *argument;
88 
89   // Special-case non-array C++ destructors, if they have the right signature.
90   // Under some ABIs, destructors return this instead of void, and cannot be
91   // passed directly to __cxa_atexit if the target does not allow this mismatch.
92   const CXXRecordDecl *Record = type->getAsCXXRecordDecl();
93   bool CanRegisterDestructor =
94       Record && (!CGM.getCXXABI().HasThisReturn(
95                      GlobalDecl(Record->getDestructor(), Dtor_Complete)) ||
96                  CGM.getCXXABI().canCallMismatchedFunctionType());
97   // If __cxa_atexit is disabled via a flag, a different helper function is
98   // generated elsewhere which uses atexit instead, and it takes the destructor
99   // directly.
100   bool UsingExternalHelper = !CGM.getCodeGenOpts().CXAAtExit;
101   if (Record && (CanRegisterDestructor || UsingExternalHelper)) {
102     assert(!Record->hasTrivialDestructor());
103     CXXDestructorDecl *dtor = Record->getDestructor();
104 
105     function = CGM.getAddrOfCXXStructor(dtor, StructorType::Complete);
106     argument = llvm::ConstantExpr::getBitCast(
107         addr.getPointer(), CGF.getTypes().ConvertType(type)->getPointerTo());
108 
109   // Otherwise, the standard logic requires a helper function.
110   } else {
111     function = CodeGenFunction(CGM)
112         .generateDestroyHelper(addr, type, CGF.getDestroyer(dtorKind),
113                                CGF.needsEHCleanup(dtorKind), &D);
114     argument = llvm::Constant::getNullValue(CGF.Int8PtrTy);
115   }
116 
117   CGM.getCXXABI().registerGlobalDtor(CGF, D, function, argument);
118 }
119 
120 /// Emit code to cause the variable at the given address to be considered as
121 /// constant from this point onwards.
EmitDeclInvariant(CodeGenFunction & CGF,const VarDecl & D,llvm::Constant * Addr)122 static void EmitDeclInvariant(CodeGenFunction &CGF, const VarDecl &D,
123                               llvm::Constant *Addr) {
124   // Don't emit the intrinsic if we're not optimizing.
125   if (!CGF.CGM.getCodeGenOpts().OptimizationLevel)
126     return;
127 
128   // Grab the llvm.invariant.start intrinsic.
129   llvm::Intrinsic::ID InvStartID = llvm::Intrinsic::invariant_start;
130   llvm::Constant *InvariantStart = CGF.CGM.getIntrinsic(InvStartID);
131 
132   // Emit a call with the size in bytes of the object.
133   CharUnits WidthChars = CGF.getContext().getTypeSizeInChars(D.getType());
134   uint64_t Width = WidthChars.getQuantity();
135   llvm::Value *Args[2] = { llvm::ConstantInt::getSigned(CGF.Int64Ty, Width),
136                            llvm::ConstantExpr::getBitCast(Addr, CGF.Int8PtrTy)};
137   CGF.Builder.CreateCall(InvariantStart, Args);
138 }
139 
EmitCXXGlobalVarDeclInit(const VarDecl & D,llvm::Constant * DeclPtr,bool PerformInit)140 void CodeGenFunction::EmitCXXGlobalVarDeclInit(const VarDecl &D,
141                                                llvm::Constant *DeclPtr,
142                                                bool PerformInit) {
143 
144   const Expr *Init = D.getInit();
145   QualType T = D.getType();
146 
147   // The address space of a static local variable (DeclPtr) may be different
148   // from the address space of the "this" argument of the constructor. In that
149   // case, we need an addrspacecast before calling the constructor.
150   //
151   // struct StructWithCtor {
152   //   __device__ StructWithCtor() {...}
153   // };
154   // __device__ void foo() {
155   //   __shared__ StructWithCtor s;
156   //   ...
157   // }
158   //
159   // For example, in the above CUDA code, the static local variable s has a
160   // "shared" address space qualifier, but the constructor of StructWithCtor
161   // expects "this" in the "generic" address space.
162   unsigned ExpectedAddrSpace = getContext().getTargetAddressSpace(T);
163   unsigned ActualAddrSpace = DeclPtr->getType()->getPointerAddressSpace();
164   if (ActualAddrSpace != ExpectedAddrSpace) {
165     llvm::Type *LTy = CGM.getTypes().ConvertTypeForMem(T);
166     llvm::PointerType *PTy = llvm::PointerType::get(LTy, ExpectedAddrSpace);
167     DeclPtr = llvm::ConstantExpr::getAddrSpaceCast(DeclPtr, PTy);
168   }
169 
170   ConstantAddress DeclAddr(DeclPtr, getContext().getDeclAlign(&D));
171 
172   if (!T->isReferenceType()) {
173     if (getLangOpts().OpenMP && D.hasAttr<OMPThreadPrivateDeclAttr>())
174       (void)CGM.getOpenMPRuntime().emitThreadPrivateVarDefinition(
175           &D, DeclAddr, D.getAttr<OMPThreadPrivateDeclAttr>()->getLocation(),
176           PerformInit, this);
177     if (PerformInit)
178       EmitDeclInit(*this, D, DeclAddr);
179     if (CGM.isTypeConstant(D.getType(), true))
180       EmitDeclInvariant(*this, D, DeclPtr);
181     else
182       EmitDeclDestroy(*this, D, DeclAddr);
183     return;
184   }
185 
186   assert(PerformInit && "cannot have constant initializer which needs "
187          "destruction for reference");
188   RValue RV = EmitReferenceBindingToExpr(Init);
189   EmitStoreOfScalar(RV.getScalarVal(), DeclAddr, false, T);
190 }
191 
192 /// Create a stub function, suitable for being passed to atexit,
193 /// which passes the given address to the given destructor function.
createAtExitStub(const VarDecl & VD,llvm::Constant * dtor,llvm::Constant * addr)194 llvm::Constant *CodeGenFunction::createAtExitStub(const VarDecl &VD,
195                                                   llvm::Constant *dtor,
196                                                   llvm::Constant *addr) {
197   // Get the destructor function type, void(*)(void).
198   llvm::FunctionType *ty = llvm::FunctionType::get(CGM.VoidTy, false);
199   SmallString<256> FnName;
200   {
201     llvm::raw_svector_ostream Out(FnName);
202     CGM.getCXXABI().getMangleContext().mangleDynamicAtExitDestructor(&VD, Out);
203   }
204 
205   const CGFunctionInfo &FI = CGM.getTypes().arrangeNullaryFunction();
206   llvm::Function *fn = CGM.CreateGlobalInitOrDestructFunction(ty, FnName.str(),
207                                                               FI,
208                                                               VD.getLocation());
209 
210   CodeGenFunction CGF(CGM);
211 
212   CGF.StartFunction(&VD, CGM.getContext().VoidTy, fn, FI, FunctionArgList());
213 
214   llvm::CallInst *call = CGF.Builder.CreateCall(dtor, addr);
215 
216  // Make sure the call and the callee agree on calling convention.
217   if (llvm::Function *dtorFn =
218         dyn_cast<llvm::Function>(dtor->stripPointerCasts()))
219     call->setCallingConv(dtorFn->getCallingConv());
220 
221   CGF.FinishFunction();
222 
223   return fn;
224 }
225 
226 /// Register a global destructor using the C atexit runtime function.
registerGlobalDtorWithAtExit(const VarDecl & VD,llvm::Constant * dtor,llvm::Constant * addr)227 void CodeGenFunction::registerGlobalDtorWithAtExit(const VarDecl &VD,
228                                                    llvm::Constant *dtor,
229                                                    llvm::Constant *addr) {
230   // Create a function which calls the destructor.
231   llvm::Constant *dtorStub = createAtExitStub(VD, dtor, addr);
232 
233   // extern "C" int atexit(void (*f)(void));
234   llvm::FunctionType *atexitTy =
235     llvm::FunctionType::get(IntTy, dtorStub->getType(), false);
236 
237   llvm::Constant *atexit =
238     CGM.CreateRuntimeFunction(atexitTy, "atexit");
239   if (llvm::Function *atexitFn = dyn_cast<llvm::Function>(atexit))
240     atexitFn->setDoesNotThrow();
241 
242   EmitNounwindRuntimeCall(atexit, dtorStub);
243 }
244 
EmitCXXGuardedInit(const VarDecl & D,llvm::GlobalVariable * DeclPtr,bool PerformInit)245 void CodeGenFunction::EmitCXXGuardedInit(const VarDecl &D,
246                                          llvm::GlobalVariable *DeclPtr,
247                                          bool PerformInit) {
248   // If we've been asked to forbid guard variables, emit an error now.
249   // This diagnostic is hard-coded for Darwin's use case;  we can find
250   // better phrasing if someone else needs it.
251   if (CGM.getCodeGenOpts().ForbidGuardVariables)
252     CGM.Error(D.getLocation(),
253               "this initialization requires a guard variable, which "
254               "the kernel does not support");
255 
256   CGM.getCXXABI().EmitGuardedInit(*this, D, DeclPtr, PerformInit);
257 }
258 
CreateGlobalInitOrDestructFunction(llvm::FunctionType * FTy,const Twine & Name,const CGFunctionInfo & FI,SourceLocation Loc,bool TLS)259 llvm::Function *CodeGenModule::CreateGlobalInitOrDestructFunction(
260     llvm::FunctionType *FTy, const Twine &Name, const CGFunctionInfo &FI,
261     SourceLocation Loc, bool TLS) {
262   llvm::Function *Fn =
263     llvm::Function::Create(FTy, llvm::GlobalValue::InternalLinkage,
264                            Name, &getModule());
265   if (!getLangOpts().AppleKext && !TLS) {
266     // Set the section if needed.
267     if (const char *Section = getTarget().getStaticInitSectionSpecifier())
268       Fn->setSection(Section);
269   }
270 
271   SetInternalFunctionAttributes(nullptr, Fn, FI);
272 
273   Fn->setCallingConv(getRuntimeCC());
274 
275   if (!getLangOpts().Exceptions)
276     Fn->setDoesNotThrow();
277 
278   if (!isInSanitizerBlacklist(Fn, Loc)) {
279     if (getLangOpts().Sanitize.hasOneOf(SanitizerKind::Address |
280                                         SanitizerKind::KernelAddress))
281       Fn->addFnAttr(llvm::Attribute::SanitizeAddress);
282     if (getLangOpts().Sanitize.has(SanitizerKind::Thread))
283       Fn->addFnAttr(llvm::Attribute::SanitizeThread);
284     if (getLangOpts().Sanitize.has(SanitizerKind::Memory))
285       Fn->addFnAttr(llvm::Attribute::SanitizeMemory);
286     if (getLangOpts().Sanitize.has(SanitizerKind::SafeStack))
287       Fn->addFnAttr(llvm::Attribute::SafeStack);
288   }
289 
290   return Fn;
291 }
292 
293 /// Create a global pointer to a function that will initialize a global
294 /// variable.  The user has requested that this pointer be emitted in a specific
295 /// section.
EmitPointerToInitFunc(const VarDecl * D,llvm::GlobalVariable * GV,llvm::Function * InitFunc,InitSegAttr * ISA)296 void CodeGenModule::EmitPointerToInitFunc(const VarDecl *D,
297                                           llvm::GlobalVariable *GV,
298                                           llvm::Function *InitFunc,
299                                           InitSegAttr *ISA) {
300   llvm::GlobalVariable *PtrArray = new llvm::GlobalVariable(
301       TheModule, InitFunc->getType(), /*isConstant=*/true,
302       llvm::GlobalValue::PrivateLinkage, InitFunc, "__cxx_init_fn_ptr");
303   PtrArray->setSection(ISA->getSection());
304   addUsedGlobal(PtrArray);
305 
306   // If the GV is already in a comdat group, then we have to join it.
307   if (llvm::Comdat *C = GV->getComdat())
308     PtrArray->setComdat(C);
309 }
310 
311 void
EmitCXXGlobalVarDeclInitFunc(const VarDecl * D,llvm::GlobalVariable * Addr,bool PerformInit)312 CodeGenModule::EmitCXXGlobalVarDeclInitFunc(const VarDecl *D,
313                                             llvm::GlobalVariable *Addr,
314                                             bool PerformInit) {
315 
316   // According to E.2.3.1 in CUDA-7.5 Programming guide: __device__,
317   // __constant__ and __shared__ variables defined in namespace scope,
318   // that are of class type, cannot have a non-empty constructor. All
319   // the checks have been done in Sema by now. Whatever initializers
320   // are allowed are empty and we just need to ignore them here.
321   if (getLangOpts().CUDA && getLangOpts().CUDAIsDevice &&
322       (D->hasAttr<CUDADeviceAttr>() || D->hasAttr<CUDAConstantAttr>() ||
323        D->hasAttr<CUDASharedAttr>()))
324     return;
325 
326   // Check if we've already initialized this decl.
327   auto I = DelayedCXXInitPosition.find(D);
328   if (I != DelayedCXXInitPosition.end() && I->second == ~0U)
329     return;
330 
331   llvm::FunctionType *FTy = llvm::FunctionType::get(VoidTy, false);
332   SmallString<256> FnName;
333   {
334     llvm::raw_svector_ostream Out(FnName);
335     getCXXABI().getMangleContext().mangleDynamicInitializer(D, Out);
336   }
337 
338   // Create a variable initialization function.
339   llvm::Function *Fn =
340       CreateGlobalInitOrDestructFunction(FTy, FnName.str(),
341                                          getTypes().arrangeNullaryFunction(),
342                                          D->getLocation());
343 
344   auto *ISA = D->getAttr<InitSegAttr>();
345   CodeGenFunction(*this).GenerateCXXGlobalVarDeclInitFunc(Fn, D, Addr,
346                                                           PerformInit);
347 
348   llvm::GlobalVariable *COMDATKey =
349       supportsCOMDAT() && D->isExternallyVisible() ? Addr : nullptr;
350 
351   if (D->getTLSKind()) {
352     // FIXME: Should we support init_priority for thread_local?
353     // FIXME: Ideally, initialization of instantiated thread_local static data
354     // members of class templates should not trigger initialization of other
355     // entities in the TU.
356     // FIXME: We only need to register one __cxa_thread_atexit function for the
357     // entire TU.
358     CXXThreadLocalInits.push_back(Fn);
359     CXXThreadLocalInitVars.push_back(D);
360   } else if (PerformInit && ISA) {
361     EmitPointerToInitFunc(D, Addr, Fn, ISA);
362   } else if (auto *IPA = D->getAttr<InitPriorityAttr>()) {
363     OrderGlobalInits Key(IPA->getPriority(), PrioritizedCXXGlobalInits.size());
364     PrioritizedCXXGlobalInits.push_back(std::make_pair(Key, Fn));
365   } else if (isTemplateInstantiation(D->getTemplateSpecializationKind())) {
366     // C++ [basic.start.init]p2:
367     //   Definitions of explicitly specialized class template static data
368     //   members have ordered initialization. Other class template static data
369     //   members (i.e., implicitly or explicitly instantiated specializations)
370     //   have unordered initialization.
371     //
372     // As a consequence, we can put them into their own llvm.global_ctors entry.
373     //
374     // If the global is externally visible, put the initializer into a COMDAT
375     // group with the global being initialized.  On most platforms, this is a
376     // minor startup time optimization.  In the MS C++ ABI, there are no guard
377     // variables, so this COMDAT key is required for correctness.
378     AddGlobalCtor(Fn, 65535, COMDATKey);
379   } else if (D->hasAttr<SelectAnyAttr>()) {
380     // SelectAny globals will be comdat-folded. Put the initializer into a
381     // COMDAT group associated with the global, so the initializers get folded
382     // too.
383     AddGlobalCtor(Fn, 65535, COMDATKey);
384   } else {
385     I = DelayedCXXInitPosition.find(D); // Re-do lookup in case of re-hash.
386     if (I == DelayedCXXInitPosition.end()) {
387       CXXGlobalInits.push_back(Fn);
388     } else if (I->second != ~0U) {
389       assert(I->second < CXXGlobalInits.size() &&
390              CXXGlobalInits[I->second] == nullptr);
391       CXXGlobalInits[I->second] = Fn;
392     }
393   }
394 
395   // Remember that we already emitted the initializer for this global.
396   DelayedCXXInitPosition[D] = ~0U;
397 }
398 
EmitCXXThreadLocalInitFunc()399 void CodeGenModule::EmitCXXThreadLocalInitFunc() {
400   getCXXABI().EmitThreadLocalInitFuncs(
401       *this, CXXThreadLocals, CXXThreadLocalInits, CXXThreadLocalInitVars);
402 
403   CXXThreadLocalInits.clear();
404   CXXThreadLocalInitVars.clear();
405   CXXThreadLocals.clear();
406 }
407 
408 void
EmitCXXGlobalInitFunc()409 CodeGenModule::EmitCXXGlobalInitFunc() {
410   while (!CXXGlobalInits.empty() && !CXXGlobalInits.back())
411     CXXGlobalInits.pop_back();
412 
413   if (CXXGlobalInits.empty() && PrioritizedCXXGlobalInits.empty())
414     return;
415 
416   llvm::FunctionType *FTy = llvm::FunctionType::get(VoidTy, false);
417   const CGFunctionInfo &FI = getTypes().arrangeNullaryFunction();
418 
419   // Create our global initialization function.
420   if (!PrioritizedCXXGlobalInits.empty()) {
421     SmallVector<llvm::Function *, 8> LocalCXXGlobalInits;
422     llvm::array_pod_sort(PrioritizedCXXGlobalInits.begin(),
423                          PrioritizedCXXGlobalInits.end());
424     // Iterate over "chunks" of ctors with same priority and emit each chunk
425     // into separate function. Note - everything is sorted first by priority,
426     // second - by lex order, so we emit ctor functions in proper order.
427     for (SmallVectorImpl<GlobalInitData >::iterator
428            I = PrioritizedCXXGlobalInits.begin(),
429            E = PrioritizedCXXGlobalInits.end(); I != E; ) {
430       SmallVectorImpl<GlobalInitData >::iterator
431         PrioE = std::upper_bound(I + 1, E, *I, GlobalInitPriorityCmp());
432 
433       LocalCXXGlobalInits.clear();
434       unsigned Priority = I->first.priority;
435       // Compute the function suffix from priority. Prepend with zeroes to make
436       // sure the function names are also ordered as priorities.
437       std::string PrioritySuffix = llvm::utostr(Priority);
438       // Priority is always <= 65535 (enforced by sema).
439       PrioritySuffix = std::string(6-PrioritySuffix.size(), '0')+PrioritySuffix;
440       llvm::Function *Fn = CreateGlobalInitOrDestructFunction(
441           FTy, "_GLOBAL__I_" + PrioritySuffix, FI);
442 
443       for (; I < PrioE; ++I)
444         LocalCXXGlobalInits.push_back(I->second);
445 
446       CodeGenFunction(*this).GenerateCXXGlobalInitFunc(Fn, LocalCXXGlobalInits);
447       AddGlobalCtor(Fn, Priority);
448     }
449     PrioritizedCXXGlobalInits.clear();
450   }
451 
452   SmallString<128> FileName;
453   SourceManager &SM = Context.getSourceManager();
454   if (const FileEntry *MainFile = SM.getFileEntryForID(SM.getMainFileID())) {
455     // Include the filename in the symbol name. Including "sub_" matches gcc and
456     // makes sure these symbols appear lexicographically behind the symbols with
457     // priority emitted above.
458     FileName = llvm::sys::path::filename(MainFile->getName());
459   } else {
460     FileName = "<null>";
461   }
462 
463   for (size_t i = 0; i < FileName.size(); ++i) {
464     // Replace everything that's not [a-zA-Z0-9._] with a _. This set happens
465     // to be the set of C preprocessing numbers.
466     if (!isPreprocessingNumberBody(FileName[i]))
467       FileName[i] = '_';
468   }
469 
470   llvm::Function *Fn = CreateGlobalInitOrDestructFunction(
471       FTy, llvm::Twine("_GLOBAL__sub_I_", FileName), FI);
472 
473   CodeGenFunction(*this).GenerateCXXGlobalInitFunc(Fn, CXXGlobalInits);
474   AddGlobalCtor(Fn);
475 
476   CXXGlobalInits.clear();
477 }
478 
EmitCXXGlobalDtorFunc()479 void CodeGenModule::EmitCXXGlobalDtorFunc() {
480   if (CXXGlobalDtors.empty())
481     return;
482 
483   llvm::FunctionType *FTy = llvm::FunctionType::get(VoidTy, false);
484 
485   // Create our global destructor function.
486   const CGFunctionInfo &FI = getTypes().arrangeNullaryFunction();
487   llvm::Function *Fn =
488       CreateGlobalInitOrDestructFunction(FTy, "_GLOBAL__D_a", FI);
489 
490   CodeGenFunction(*this).GenerateCXXGlobalDtorsFunc(Fn, CXXGlobalDtors);
491   AddGlobalDtor(Fn);
492 }
493 
494 /// Emit the code necessary to initialize the given global variable.
GenerateCXXGlobalVarDeclInitFunc(llvm::Function * Fn,const VarDecl * D,llvm::GlobalVariable * Addr,bool PerformInit)495 void CodeGenFunction::GenerateCXXGlobalVarDeclInitFunc(llvm::Function *Fn,
496                                                        const VarDecl *D,
497                                                  llvm::GlobalVariable *Addr,
498                                                        bool PerformInit) {
499   // Check if we need to emit debug info for variable initializer.
500   if (D->hasAttr<NoDebugAttr>())
501     DebugInfo = nullptr; // disable debug info indefinitely for this function
502 
503   CurEHLocation = D->getLocStart();
504 
505   StartFunction(GlobalDecl(D), getContext().VoidTy, Fn,
506                 getTypes().arrangeNullaryFunction(),
507                 FunctionArgList(), D->getLocation(),
508                 D->getInit()->getExprLoc());
509 
510   // Use guarded initialization if the global variable is weak. This
511   // occurs for, e.g., instantiated static data members and
512   // definitions explicitly marked weak.
513   if (Addr->hasWeakLinkage() || Addr->hasLinkOnceLinkage()) {
514     EmitCXXGuardedInit(*D, Addr, PerformInit);
515   } else {
516     EmitCXXGlobalVarDeclInit(*D, Addr, PerformInit);
517   }
518 
519   FinishFunction();
520 }
521 
522 void
GenerateCXXGlobalInitFunc(llvm::Function * Fn,ArrayRef<llvm::Function * > Decls,Address Guard)523 CodeGenFunction::GenerateCXXGlobalInitFunc(llvm::Function *Fn,
524                                            ArrayRef<llvm::Function *> Decls,
525                                            Address Guard) {
526   {
527     auto NL = ApplyDebugLocation::CreateEmpty(*this);
528     StartFunction(GlobalDecl(), getContext().VoidTy, Fn,
529                   getTypes().arrangeNullaryFunction(), FunctionArgList());
530     // Emit an artificial location for this function.
531     auto AL = ApplyDebugLocation::CreateArtificial(*this);
532 
533     llvm::BasicBlock *ExitBlock = nullptr;
534     if (Guard.isValid()) {
535       // If we have a guard variable, check whether we've already performed
536       // these initializations. This happens for TLS initialization functions.
537       llvm::Value *GuardVal = Builder.CreateLoad(Guard);
538       llvm::Value *Uninit = Builder.CreateIsNull(GuardVal,
539                                                  "guard.uninitialized");
540       llvm::BasicBlock *InitBlock = createBasicBlock("init");
541       ExitBlock = createBasicBlock("exit");
542       Builder.CreateCondBr(Uninit, InitBlock, ExitBlock);
543       EmitBlock(InitBlock);
544       // Mark as initialized before initializing anything else. If the
545       // initializers use previously-initialized thread_local vars, that's
546       // probably supposed to be OK, but the standard doesn't say.
547       Builder.CreateStore(llvm::ConstantInt::get(GuardVal->getType(),1), Guard);
548     }
549 
550     RunCleanupsScope Scope(*this);
551 
552     // When building in Objective-C++ ARC mode, create an autorelease pool
553     // around the global initializers.
554     if (getLangOpts().ObjCAutoRefCount && getLangOpts().CPlusPlus) {
555       llvm::Value *token = EmitObjCAutoreleasePoolPush();
556       EmitObjCAutoreleasePoolCleanup(token);
557     }
558 
559     for (unsigned i = 0, e = Decls.size(); i != e; ++i)
560       if (Decls[i])
561         EmitRuntimeCall(Decls[i]);
562 
563     Scope.ForceCleanup();
564 
565     if (ExitBlock) {
566       Builder.CreateBr(ExitBlock);
567       EmitBlock(ExitBlock);
568     }
569   }
570 
571   FinishFunction();
572 }
573 
GenerateCXXGlobalDtorsFunc(llvm::Function * Fn,const std::vector<std::pair<llvm::WeakVH,llvm::Constant * >> & DtorsAndObjects)574 void CodeGenFunction::GenerateCXXGlobalDtorsFunc(llvm::Function *Fn,
575                   const std::vector<std::pair<llvm::WeakVH, llvm::Constant*> >
576                                                 &DtorsAndObjects) {
577   {
578     auto NL = ApplyDebugLocation::CreateEmpty(*this);
579     StartFunction(GlobalDecl(), getContext().VoidTy, Fn,
580                   getTypes().arrangeNullaryFunction(), FunctionArgList());
581     // Emit an artificial location for this function.
582     auto AL = ApplyDebugLocation::CreateArtificial(*this);
583 
584     // Emit the dtors, in reverse order from construction.
585     for (unsigned i = 0, e = DtorsAndObjects.size(); i != e; ++i) {
586       llvm::Value *Callee = DtorsAndObjects[e - i - 1].first;
587       llvm::CallInst *CI = Builder.CreateCall(Callee,
588                                           DtorsAndObjects[e - i - 1].second);
589       // Make sure the call and the callee agree on calling convention.
590       if (llvm::Function *F = dyn_cast<llvm::Function>(Callee))
591         CI->setCallingConv(F->getCallingConv());
592     }
593   }
594 
595   FinishFunction();
596 }
597 
598 /// generateDestroyHelper - Generates a helper function which, when
599 /// invoked, destroys the given object.  The address of the object
600 /// should be in global memory.
generateDestroyHelper(Address addr,QualType type,Destroyer * destroyer,bool useEHCleanupForArray,const VarDecl * VD)601 llvm::Function *CodeGenFunction::generateDestroyHelper(
602     Address addr, QualType type, Destroyer *destroyer,
603     bool useEHCleanupForArray, const VarDecl *VD) {
604   FunctionArgList args;
605   ImplicitParamDecl dst(getContext(), nullptr, SourceLocation(), nullptr,
606                         getContext().VoidPtrTy);
607   args.push_back(&dst);
608 
609   const CGFunctionInfo &FI =
610     CGM.getTypes().arrangeBuiltinFunctionDeclaration(getContext().VoidTy, args);
611   llvm::FunctionType *FTy = CGM.getTypes().GetFunctionType(FI);
612   llvm::Function *fn = CGM.CreateGlobalInitOrDestructFunction(
613       FTy, "__cxx_global_array_dtor", FI, VD->getLocation());
614 
615   CurEHLocation = VD->getLocStart();
616 
617   StartFunction(VD, getContext().VoidTy, fn, FI, args);
618 
619   emitDestroy(addr, type, destroyer, useEHCleanupForArray);
620 
621   FinishFunction();
622 
623   return fn;
624 }
625