xref: /freebsd/contrib/llvm-project/clang/lib/CodeGen/CGDeclCXX.cpp (revision ec0ea6efa1ad229d75c394c1a9b9cac33af2b1d3)
1 //===--- CGDeclCXX.cpp - Emit LLVM Code for C++ declarations --------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This contains code dealing with code generation of C++ declarations
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #include "CGCXXABI.h"
14 #include "CGObjCRuntime.h"
15 #include "CGOpenMPRuntime.h"
16 #include "CodeGenFunction.h"
17 #include "TargetInfo.h"
18 #include "clang/AST/Attr.h"
19 #include "clang/Basic/LangOptions.h"
20 #include "llvm/ADT/StringExtras.h"
21 #include "llvm/IR/Intrinsics.h"
22 #include "llvm/IR/MDBuilder.h"
23 #include "llvm/Support/Path.h"
24 
25 using namespace clang;
26 using namespace CodeGen;
27 
28 static void EmitDeclInit(CodeGenFunction &CGF, const VarDecl &D,
29                          ConstantAddress DeclPtr) {
30   assert(
31       (D.hasGlobalStorage() ||
32        (D.hasLocalStorage() && CGF.getContext().getLangOpts().OpenCLCPlusPlus)) &&
33       "VarDecl must have global or local (in the case of OpenCL) storage!");
34   assert(!D.getType()->isReferenceType() &&
35          "Should not call EmitDeclInit on a reference!");
36 
37   QualType type = D.getType();
38   LValue lv = CGF.MakeAddrLValue(DeclPtr, type);
39 
40   const Expr *Init = D.getInit();
41   switch (CGF.getEvaluationKind(type)) {
42   case TEK_Scalar: {
43     CodeGenModule &CGM = CGF.CGM;
44     if (lv.isObjCStrong())
45       CGM.getObjCRuntime().EmitObjCGlobalAssign(CGF, CGF.EmitScalarExpr(Init),
46                                                 DeclPtr, D.getTLSKind());
47     else if (lv.isObjCWeak())
48       CGM.getObjCRuntime().EmitObjCWeakAssign(CGF, CGF.EmitScalarExpr(Init),
49                                               DeclPtr);
50     else
51       CGF.EmitScalarInit(Init, &D, lv, false);
52     return;
53   }
54   case TEK_Complex:
55     CGF.EmitComplexExprIntoLValue(Init, lv, /*isInit*/ true);
56     return;
57   case TEK_Aggregate:
58     CGF.EmitAggExpr(Init,
59                     AggValueSlot::forLValue(lv, CGF, AggValueSlot::IsDestructed,
60                                             AggValueSlot::DoesNotNeedGCBarriers,
61                                             AggValueSlot::IsNotAliased,
62                                             AggValueSlot::DoesNotOverlap));
63     return;
64   }
65   llvm_unreachable("bad evaluation kind");
66 }
67 
68 /// Emit code to cause the destruction of the given variable with
69 /// static storage duration.
70 static void EmitDeclDestroy(CodeGenFunction &CGF, const VarDecl &D,
71                             ConstantAddress Addr) {
72   // Honor __attribute__((no_destroy)) and bail instead of attempting
73   // to emit a reference to a possibly nonexistent destructor, which
74   // in turn can cause a crash. This will result in a global constructor
75   // that isn't balanced out by a destructor call as intended by the
76   // attribute. This also checks for -fno-c++-static-destructors and
77   // bails even if the attribute is not present.
78   QualType::DestructionKind DtorKind = D.needsDestruction(CGF.getContext());
79 
80   // FIXME:  __attribute__((cleanup)) ?
81 
82   switch (DtorKind) {
83   case QualType::DK_none:
84     return;
85 
86   case QualType::DK_cxx_destructor:
87     break;
88 
89   case QualType::DK_objc_strong_lifetime:
90   case QualType::DK_objc_weak_lifetime:
91   case QualType::DK_nontrivial_c_struct:
92     // We don't care about releasing objects during process teardown.
93     assert(!D.getTLSKind() && "should have rejected this");
94     return;
95   }
96 
97   llvm::FunctionCallee Func;
98   llvm::Constant *Argument;
99 
100   CodeGenModule &CGM = CGF.CGM;
101   QualType Type = D.getType();
102 
103   // Special-case non-array C++ destructors, if they have the right signature.
104   // Under some ABIs, destructors return this instead of void, and cannot be
105   // passed directly to __cxa_atexit if the target does not allow this
106   // mismatch.
107   const CXXRecordDecl *Record = Type->getAsCXXRecordDecl();
108   bool CanRegisterDestructor =
109       Record && (!CGM.getCXXABI().HasThisReturn(
110                      GlobalDecl(Record->getDestructor(), Dtor_Complete)) ||
111                  CGM.getCXXABI().canCallMismatchedFunctionType());
112   // If __cxa_atexit is disabled via a flag, a different helper function is
113   // generated elsewhere which uses atexit instead, and it takes the destructor
114   // directly.
115   bool UsingExternalHelper = !CGM.getCodeGenOpts().CXAAtExit;
116   if (Record && (CanRegisterDestructor || UsingExternalHelper)) {
117     assert(!Record->hasTrivialDestructor());
118     CXXDestructorDecl *Dtor = Record->getDestructor();
119 
120     Func = CGM.getAddrAndTypeOfCXXStructor(GlobalDecl(Dtor, Dtor_Complete));
121     if (CGF.getContext().getLangOpts().OpenCL) {
122       auto DestAS =
123           CGM.getTargetCodeGenInfo().getAddrSpaceOfCxaAtexitPtrParam();
124       auto DestTy = CGF.getTypes().ConvertType(Type)->getPointerTo(
125           CGM.getContext().getTargetAddressSpace(DestAS));
126       auto SrcAS = D.getType().getQualifiers().getAddressSpace();
127       if (DestAS == SrcAS)
128         Argument = llvm::ConstantExpr::getBitCast(Addr.getPointer(), DestTy);
129       else
130         // FIXME: On addr space mismatch we are passing NULL. The generation
131         // of the global destructor function should be adjusted accordingly.
132         Argument = llvm::ConstantPointerNull::get(DestTy);
133     } else {
134       Argument = llvm::ConstantExpr::getBitCast(
135           Addr.getPointer(), CGF.getTypes().ConvertType(Type)->getPointerTo());
136     }
137   // Otherwise, the standard logic requires a helper function.
138   } else {
139     Func = CodeGenFunction(CGM)
140            .generateDestroyHelper(Addr, Type, CGF.getDestroyer(DtorKind),
141                                   CGF.needsEHCleanup(DtorKind), &D);
142     Argument = llvm::Constant::getNullValue(CGF.Int8PtrTy);
143   }
144 
145   CGM.getCXXABI().registerGlobalDtor(CGF, D, Func, Argument);
146 }
147 
148 /// Emit code to cause the variable at the given address to be considered as
149 /// constant from this point onwards.
150 static void EmitDeclInvariant(CodeGenFunction &CGF, const VarDecl &D,
151                               llvm::Constant *Addr) {
152   return CGF.EmitInvariantStart(
153       Addr, CGF.getContext().getTypeSizeInChars(D.getType()));
154 }
155 
156 void CodeGenFunction::EmitInvariantStart(llvm::Constant *Addr, CharUnits Size) {
157   // Do not emit the intrinsic if we're not optimizing.
158   if (!CGM.getCodeGenOpts().OptimizationLevel)
159     return;
160 
161   // Grab the llvm.invariant.start intrinsic.
162   llvm::Intrinsic::ID InvStartID = llvm::Intrinsic::invariant_start;
163   // Overloaded address space type.
164   llvm::Type *ObjectPtr[1] = {Int8PtrTy};
165   llvm::Function *InvariantStart = CGM.getIntrinsic(InvStartID, ObjectPtr);
166 
167   // Emit a call with the size in bytes of the object.
168   uint64_t Width = Size.getQuantity();
169   llvm::Value *Args[2] = { llvm::ConstantInt::getSigned(Int64Ty, Width),
170                            llvm::ConstantExpr::getBitCast(Addr, Int8PtrTy)};
171   Builder.CreateCall(InvariantStart, Args);
172 }
173 
174 void CodeGenFunction::EmitCXXGlobalVarDeclInit(const VarDecl &D,
175                                                llvm::Constant *DeclPtr,
176                                                bool PerformInit) {
177 
178   const Expr *Init = D.getInit();
179   QualType T = D.getType();
180 
181   // The address space of a static local variable (DeclPtr) may be different
182   // from the address space of the "this" argument of the constructor. In that
183   // case, we need an addrspacecast before calling the constructor.
184   //
185   // struct StructWithCtor {
186   //   __device__ StructWithCtor() {...}
187   // };
188   // __device__ void foo() {
189   //   __shared__ StructWithCtor s;
190   //   ...
191   // }
192   //
193   // For example, in the above CUDA code, the static local variable s has a
194   // "shared" address space qualifier, but the constructor of StructWithCtor
195   // expects "this" in the "generic" address space.
196   unsigned ExpectedAddrSpace = getContext().getTargetAddressSpace(T);
197   unsigned ActualAddrSpace = DeclPtr->getType()->getPointerAddressSpace();
198   if (ActualAddrSpace != ExpectedAddrSpace) {
199     llvm::Type *LTy = CGM.getTypes().ConvertTypeForMem(T);
200     llvm::PointerType *PTy = llvm::PointerType::get(LTy, ExpectedAddrSpace);
201     DeclPtr = llvm::ConstantExpr::getAddrSpaceCast(DeclPtr, PTy);
202   }
203 
204   ConstantAddress DeclAddr(DeclPtr, getContext().getDeclAlign(&D));
205 
206   if (!T->isReferenceType()) {
207     if (getLangOpts().OpenMP && !getLangOpts().OpenMPSimd &&
208         D.hasAttr<OMPThreadPrivateDeclAttr>()) {
209       (void)CGM.getOpenMPRuntime().emitThreadPrivateVarDefinition(
210           &D, DeclAddr, D.getAttr<OMPThreadPrivateDeclAttr>()->getLocation(),
211           PerformInit, this);
212     }
213     if (PerformInit)
214       EmitDeclInit(*this, D, DeclAddr);
215     if (CGM.isTypeConstant(D.getType(), true))
216       EmitDeclInvariant(*this, D, DeclPtr);
217     else
218       EmitDeclDestroy(*this, D, DeclAddr);
219     return;
220   }
221 
222   assert(PerformInit && "cannot have constant initializer which needs "
223          "destruction for reference");
224   RValue RV = EmitReferenceBindingToExpr(Init);
225   EmitStoreOfScalar(RV.getScalarVal(), DeclAddr, false, T);
226 }
227 
228 /// Create a stub function, suitable for being passed to atexit,
229 /// which passes the given address to the given destructor function.
230 llvm::Function *CodeGenFunction::createAtExitStub(const VarDecl &VD,
231                                                   llvm::FunctionCallee dtor,
232                                                   llvm::Constant *addr) {
233   // Get the destructor function type, void(*)(void).
234   llvm::FunctionType *ty = llvm::FunctionType::get(CGM.VoidTy, false);
235   SmallString<256> FnName;
236   {
237     llvm::raw_svector_ostream Out(FnName);
238     CGM.getCXXABI().getMangleContext().mangleDynamicAtExitDestructor(&VD, Out);
239   }
240 
241   const CGFunctionInfo &FI = CGM.getTypes().arrangeNullaryFunction();
242   llvm::Function *fn = CGM.CreateGlobalInitOrCleanUpFunction(
243       ty, FnName.str(), FI, VD.getLocation());
244 
245   CodeGenFunction CGF(CGM);
246 
247   CGF.StartFunction(GlobalDecl(&VD, DynamicInitKind::AtExit),
248                     CGM.getContext().VoidTy, fn, FI, FunctionArgList(),
249                     VD.getLocation(), VD.getInit()->getExprLoc());
250   // Emit an artificial location for this function.
251   auto AL = ApplyDebugLocation::CreateArtificial(CGF);
252 
253   llvm::CallInst *call = CGF.Builder.CreateCall(dtor, addr);
254 
255   // Make sure the call and the callee agree on calling convention.
256   if (auto *dtorFn = dyn_cast<llvm::Function>(
257           dtor.getCallee()->stripPointerCastsAndAliases()))
258     call->setCallingConv(dtorFn->getCallingConv());
259 
260   CGF.FinishFunction();
261 
262   return fn;
263 }
264 
265 /// Create a stub function, suitable for being passed to __pt_atexit_np,
266 /// which passes the given address to the given destructor function.
267 llvm::Function *CodeGenFunction::createTLSAtExitStub(
268     const VarDecl &D, llvm::FunctionCallee Dtor, llvm::Constant *Addr,
269     llvm::FunctionCallee &AtExit) {
270   SmallString<256> FnName;
271   {
272     llvm::raw_svector_ostream Out(FnName);
273     CGM.getCXXABI().getMangleContext().mangleDynamicAtExitDestructor(&D, Out);
274   }
275 
276   const CGFunctionInfo &FI = CGM.getTypes().arrangeLLVMFunctionInfo(
277       getContext().IntTy, /*instanceMethod=*/false, /*chainCall=*/false,
278       {getContext().IntTy}, FunctionType::ExtInfo(), {}, RequiredArgs::All);
279 
280   // Get the stub function type, int(*)(int,...).
281   llvm::FunctionType *StubTy =
282       llvm::FunctionType::get(CGM.IntTy, {CGM.IntTy}, true);
283 
284   llvm::Function *DtorStub = CGM.CreateGlobalInitOrCleanUpFunction(
285       StubTy, FnName.str(), FI, D.getLocation());
286 
287   CodeGenFunction CGF(CGM);
288 
289   FunctionArgList Args;
290   ImplicitParamDecl IPD(CGM.getContext(), CGM.getContext().IntTy,
291                         ImplicitParamDecl::Other);
292   Args.push_back(&IPD);
293   QualType ResTy = CGM.getContext().IntTy;
294 
295   CGF.StartFunction(GlobalDecl(&D, DynamicInitKind::AtExit), ResTy, DtorStub,
296                     FI, Args, D.getLocation(), D.getInit()->getExprLoc());
297 
298   // Emit an artificial location for this function.
299   auto AL = ApplyDebugLocation::CreateArtificial(CGF);
300 
301   llvm::CallInst *call = CGF.Builder.CreateCall(Dtor, Addr);
302 
303   // Make sure the call and the callee agree on calling convention.
304   if (auto *DtorFn = dyn_cast<llvm::Function>(
305           Dtor.getCallee()->stripPointerCastsAndAliases()))
306     call->setCallingConv(DtorFn->getCallingConv());
307 
308   // Return 0 from function
309   CGF.Builder.CreateStore(llvm::Constant::getNullValue(CGM.IntTy),
310                           CGF.ReturnValue);
311 
312   CGF.FinishFunction();
313 
314   return DtorStub;
315 }
316 
317 /// Register a global destructor using the C atexit runtime function.
318 void CodeGenFunction::registerGlobalDtorWithAtExit(const VarDecl &VD,
319                                                    llvm::FunctionCallee dtor,
320                                                    llvm::Constant *addr) {
321   // Create a function which calls the destructor.
322   llvm::Constant *dtorStub = createAtExitStub(VD, dtor, addr);
323   registerGlobalDtorWithAtExit(dtorStub);
324 }
325 
326 void CodeGenFunction::registerGlobalDtorWithAtExit(llvm::Constant *dtorStub) {
327   // extern "C" int atexit(void (*f)(void));
328   assert(dtorStub->getType() ==
329              llvm::PointerType::get(
330                  llvm::FunctionType::get(CGM.VoidTy, false),
331                  dtorStub->getType()->getPointerAddressSpace()) &&
332          "Argument to atexit has a wrong type.");
333 
334   llvm::FunctionType *atexitTy =
335       llvm::FunctionType::get(IntTy, dtorStub->getType(), false);
336 
337   llvm::FunctionCallee atexit =
338       CGM.CreateRuntimeFunction(atexitTy, "atexit", llvm::AttributeList(),
339                                 /*Local=*/true);
340   if (llvm::Function *atexitFn = dyn_cast<llvm::Function>(atexit.getCallee()))
341     atexitFn->setDoesNotThrow();
342 
343   EmitNounwindRuntimeCall(atexit, dtorStub);
344 }
345 
346 llvm::Value *
347 CodeGenFunction::unregisterGlobalDtorWithUnAtExit(llvm::Constant *dtorStub) {
348   // The unatexit subroutine unregisters __dtor functions that were previously
349   // registered by the atexit subroutine. If the referenced function is found,
350   // it is removed from the list of functions that are called at normal program
351   // termination and the unatexit returns a value of 0, otherwise a non-zero
352   // value is returned.
353   //
354   // extern "C" int unatexit(void (*f)(void));
355   assert(dtorStub->getType() ==
356              llvm::PointerType::get(
357                  llvm::FunctionType::get(CGM.VoidTy, false),
358                  dtorStub->getType()->getPointerAddressSpace()) &&
359          "Argument to unatexit has a wrong type.");
360 
361   llvm::FunctionType *unatexitTy =
362       llvm::FunctionType::get(IntTy, {dtorStub->getType()}, /*isVarArg=*/false);
363 
364   llvm::FunctionCallee unatexit =
365       CGM.CreateRuntimeFunction(unatexitTy, "unatexit", llvm::AttributeList());
366 
367   cast<llvm::Function>(unatexit.getCallee())->setDoesNotThrow();
368 
369   return EmitNounwindRuntimeCall(unatexit, dtorStub);
370 }
371 
372 void CodeGenFunction::EmitCXXGuardedInit(const VarDecl &D,
373                                          llvm::GlobalVariable *DeclPtr,
374                                          bool PerformInit) {
375   // If we've been asked to forbid guard variables, emit an error now.
376   // This diagnostic is hard-coded for Darwin's use case;  we can find
377   // better phrasing if someone else needs it.
378   if (CGM.getCodeGenOpts().ForbidGuardVariables)
379     CGM.Error(D.getLocation(),
380               "this initialization requires a guard variable, which "
381               "the kernel does not support");
382 
383   CGM.getCXXABI().EmitGuardedInit(*this, D, DeclPtr, PerformInit);
384 }
385 
386 void CodeGenFunction::EmitCXXGuardedInitBranch(llvm::Value *NeedsInit,
387                                                llvm::BasicBlock *InitBlock,
388                                                llvm::BasicBlock *NoInitBlock,
389                                                GuardKind Kind,
390                                                const VarDecl *D) {
391   assert((Kind == GuardKind::TlsGuard || D) && "no guarded variable");
392 
393   // A guess at how many times we will enter the initialization of a
394   // variable, depending on the kind of variable.
395   static const uint64_t InitsPerTLSVar = 1024;
396   static const uint64_t InitsPerLocalVar = 1024 * 1024;
397 
398   llvm::MDNode *Weights;
399   if (Kind == GuardKind::VariableGuard && !D->isLocalVarDecl()) {
400     // For non-local variables, don't apply any weighting for now. Due to our
401     // use of COMDATs, we expect there to be at most one initialization of the
402     // variable per DSO, but we have no way to know how many DSOs will try to
403     // initialize the variable.
404     Weights = nullptr;
405   } else {
406     uint64_t NumInits;
407     // FIXME: For the TLS case, collect and use profiling information to
408     // determine a more accurate brach weight.
409     if (Kind == GuardKind::TlsGuard || D->getTLSKind())
410       NumInits = InitsPerTLSVar;
411     else
412       NumInits = InitsPerLocalVar;
413 
414     // The probability of us entering the initializer is
415     //   1 / (total number of times we attempt to initialize the variable).
416     llvm::MDBuilder MDHelper(CGM.getLLVMContext());
417     Weights = MDHelper.createBranchWeights(1, NumInits - 1);
418   }
419 
420   Builder.CreateCondBr(NeedsInit, InitBlock, NoInitBlock, Weights);
421 }
422 
423 llvm::Function *CodeGenModule::CreateGlobalInitOrCleanUpFunction(
424     llvm::FunctionType *FTy, const Twine &Name, const CGFunctionInfo &FI,
425     SourceLocation Loc, bool TLS) {
426   llvm::Function *Fn = llvm::Function::Create(
427       FTy, llvm::GlobalValue::InternalLinkage, Name, &getModule());
428 
429   if (!getLangOpts().AppleKext && !TLS) {
430     // Set the section if needed.
431     if (const char *Section = getTarget().getStaticInitSectionSpecifier())
432       Fn->setSection(Section);
433   }
434 
435   SetInternalFunctionAttributes(GlobalDecl(), Fn, FI);
436 
437   Fn->setCallingConv(getRuntimeCC());
438 
439   if (!getLangOpts().Exceptions)
440     Fn->setDoesNotThrow();
441 
442   if (getLangOpts().Sanitize.has(SanitizerKind::Address) &&
443       !isInNoSanitizeList(SanitizerKind::Address, Fn, Loc))
444     Fn->addFnAttr(llvm::Attribute::SanitizeAddress);
445 
446   if (getLangOpts().Sanitize.has(SanitizerKind::KernelAddress) &&
447       !isInNoSanitizeList(SanitizerKind::KernelAddress, Fn, Loc))
448     Fn->addFnAttr(llvm::Attribute::SanitizeAddress);
449 
450   if (getLangOpts().Sanitize.has(SanitizerKind::HWAddress) &&
451       !isInNoSanitizeList(SanitizerKind::HWAddress, Fn, Loc))
452     Fn->addFnAttr(llvm::Attribute::SanitizeHWAddress);
453 
454   if (getLangOpts().Sanitize.has(SanitizerKind::KernelHWAddress) &&
455       !isInNoSanitizeList(SanitizerKind::KernelHWAddress, Fn, Loc))
456     Fn->addFnAttr(llvm::Attribute::SanitizeHWAddress);
457 
458   if (getLangOpts().Sanitize.has(SanitizerKind::MemTag) &&
459       !isInNoSanitizeList(SanitizerKind::MemTag, Fn, Loc))
460     Fn->addFnAttr(llvm::Attribute::SanitizeMemTag);
461 
462   if (getLangOpts().Sanitize.has(SanitizerKind::Thread) &&
463       !isInNoSanitizeList(SanitizerKind::Thread, Fn, Loc))
464     Fn->addFnAttr(llvm::Attribute::SanitizeThread);
465 
466   if (getLangOpts().Sanitize.has(SanitizerKind::Memory) &&
467       !isInNoSanitizeList(SanitizerKind::Memory, Fn, Loc))
468     Fn->addFnAttr(llvm::Attribute::SanitizeMemory);
469 
470   if (getLangOpts().Sanitize.has(SanitizerKind::KernelMemory) &&
471       !isInNoSanitizeList(SanitizerKind::KernelMemory, Fn, Loc))
472     Fn->addFnAttr(llvm::Attribute::SanitizeMemory);
473 
474   if (getLangOpts().Sanitize.has(SanitizerKind::SafeStack) &&
475       !isInNoSanitizeList(SanitizerKind::SafeStack, Fn, Loc))
476     Fn->addFnAttr(llvm::Attribute::SafeStack);
477 
478   if (getLangOpts().Sanitize.has(SanitizerKind::ShadowCallStack) &&
479       !isInNoSanitizeList(SanitizerKind::ShadowCallStack, Fn, Loc))
480     Fn->addFnAttr(llvm::Attribute::ShadowCallStack);
481 
482   return Fn;
483 }
484 
485 /// Create a global pointer to a function that will initialize a global
486 /// variable.  The user has requested that this pointer be emitted in a specific
487 /// section.
488 void CodeGenModule::EmitPointerToInitFunc(const VarDecl *D,
489                                           llvm::GlobalVariable *GV,
490                                           llvm::Function *InitFunc,
491                                           InitSegAttr *ISA) {
492   llvm::GlobalVariable *PtrArray = new llvm::GlobalVariable(
493       TheModule, InitFunc->getType(), /*isConstant=*/true,
494       llvm::GlobalValue::PrivateLinkage, InitFunc, "__cxx_init_fn_ptr");
495   PtrArray->setSection(ISA->getSection());
496   addUsedGlobal(PtrArray);
497 
498   // If the GV is already in a comdat group, then we have to join it.
499   if (llvm::Comdat *C = GV->getComdat())
500     PtrArray->setComdat(C);
501 }
502 
503 void
504 CodeGenModule::EmitCXXGlobalVarDeclInitFunc(const VarDecl *D,
505                                             llvm::GlobalVariable *Addr,
506                                             bool PerformInit) {
507 
508   // According to E.2.3.1 in CUDA-7.5 Programming guide: __device__,
509   // __constant__ and __shared__ variables defined in namespace scope,
510   // that are of class type, cannot have a non-empty constructor. All
511   // the checks have been done in Sema by now. Whatever initializers
512   // are allowed are empty and we just need to ignore them here.
513   if (getLangOpts().CUDAIsDevice && !getLangOpts().GPUAllowDeviceInit &&
514       (D->hasAttr<CUDADeviceAttr>() || D->hasAttr<CUDAConstantAttr>() ||
515        D->hasAttr<CUDASharedAttr>()))
516     return;
517 
518   if (getLangOpts().OpenMP &&
519       getOpenMPRuntime().emitDeclareTargetVarDefinition(D, Addr, PerformInit))
520     return;
521 
522   // Check if we've already initialized this decl.
523   auto I = DelayedCXXInitPosition.find(D);
524   if (I != DelayedCXXInitPosition.end() && I->second == ~0U)
525     return;
526 
527   llvm::FunctionType *FTy = llvm::FunctionType::get(VoidTy, false);
528   SmallString<256> FnName;
529   {
530     llvm::raw_svector_ostream Out(FnName);
531     getCXXABI().getMangleContext().mangleDynamicInitializer(D, Out);
532   }
533 
534   // Create a variable initialization function.
535   llvm::Function *Fn = CreateGlobalInitOrCleanUpFunction(
536       FTy, FnName.str(), getTypes().arrangeNullaryFunction(), D->getLocation());
537 
538   auto *ISA = D->getAttr<InitSegAttr>();
539   CodeGenFunction(*this).GenerateCXXGlobalVarDeclInitFunc(Fn, D, Addr,
540                                                           PerformInit);
541 
542   llvm::GlobalVariable *COMDATKey =
543       supportsCOMDAT() && D->isExternallyVisible() ? Addr : nullptr;
544 
545   if (D->getTLSKind()) {
546     // FIXME: Should we support init_priority for thread_local?
547     // FIXME: We only need to register one __cxa_thread_atexit function for the
548     // entire TU.
549     CXXThreadLocalInits.push_back(Fn);
550     CXXThreadLocalInitVars.push_back(D);
551   } else if (PerformInit && ISA) {
552     EmitPointerToInitFunc(D, Addr, Fn, ISA);
553   } else if (auto *IPA = D->getAttr<InitPriorityAttr>()) {
554     OrderGlobalInitsOrStermFinalizers Key(IPA->getPriority(),
555                                           PrioritizedCXXGlobalInits.size());
556     PrioritizedCXXGlobalInits.push_back(std::make_pair(Key, Fn));
557   } else if (isTemplateInstantiation(D->getTemplateSpecializationKind()) ||
558              getContext().GetGVALinkageForVariable(D) == GVA_DiscardableODR ||
559              D->hasAttr<SelectAnyAttr>()) {
560     // C++ [basic.start.init]p2:
561     //   Definitions of explicitly specialized class template static data
562     //   members have ordered initialization. Other class template static data
563     //   members (i.e., implicitly or explicitly instantiated specializations)
564     //   have unordered initialization.
565     //
566     // As a consequence, we can put them into their own llvm.global_ctors entry.
567     //
568     // If the global is externally visible, put the initializer into a COMDAT
569     // group with the global being initialized.  On most platforms, this is a
570     // minor startup time optimization.  In the MS C++ ABI, there are no guard
571     // variables, so this COMDAT key is required for correctness.
572     //
573     // SelectAny globals will be comdat-folded. Put the initializer into a
574     // COMDAT group associated with the global, so the initializers get folded
575     // too.
576 
577     AddGlobalCtor(Fn, 65535, COMDATKey);
578     if (COMDATKey && (getTriple().isOSBinFormatELF() ||
579                       getTarget().getCXXABI().isMicrosoft())) {
580       // When COMDAT is used on ELF or in the MS C++ ABI, the key must be in
581       // llvm.used to prevent linker GC.
582       addUsedGlobal(COMDATKey);
583     }
584   } else {
585     I = DelayedCXXInitPosition.find(D); // Re-do lookup in case of re-hash.
586     if (I == DelayedCXXInitPosition.end()) {
587       CXXGlobalInits.push_back(Fn);
588     } else if (I->second != ~0U) {
589       assert(I->second < CXXGlobalInits.size() &&
590              CXXGlobalInits[I->second] == nullptr);
591       CXXGlobalInits[I->second] = Fn;
592     }
593   }
594 
595   // Remember that we already emitted the initializer for this global.
596   DelayedCXXInitPosition[D] = ~0U;
597 }
598 
599 void CodeGenModule::EmitCXXThreadLocalInitFunc() {
600   getCXXABI().EmitThreadLocalInitFuncs(
601       *this, CXXThreadLocals, CXXThreadLocalInits, CXXThreadLocalInitVars);
602 
603   CXXThreadLocalInits.clear();
604   CXXThreadLocalInitVars.clear();
605   CXXThreadLocals.clear();
606 }
607 
608 static SmallString<128> getTransformedFileName(llvm::Module &M) {
609   SmallString<128> FileName = llvm::sys::path::filename(M.getName());
610 
611   if (FileName.empty())
612     FileName = "<null>";
613 
614   for (size_t i = 0; i < FileName.size(); ++i) {
615     // Replace everything that's not [a-zA-Z0-9._] with a _. This set happens
616     // to be the set of C preprocessing numbers.
617     if (!isPreprocessingNumberBody(FileName[i]))
618       FileName[i] = '_';
619   }
620 
621   return FileName;
622 }
623 
624 static std::string getPrioritySuffix(unsigned int Priority) {
625   assert(Priority <= 65535 && "Priority should always be <= 65535.");
626 
627   // Compute the function suffix from priority. Prepend with zeroes to make
628   // sure the function names are also ordered as priorities.
629   std::string PrioritySuffix = llvm::utostr(Priority);
630   PrioritySuffix = std::string(6 - PrioritySuffix.size(), '0') + PrioritySuffix;
631 
632   return PrioritySuffix;
633 }
634 
635 void
636 CodeGenModule::EmitCXXGlobalInitFunc() {
637   while (!CXXGlobalInits.empty() && !CXXGlobalInits.back())
638     CXXGlobalInits.pop_back();
639 
640   if (CXXGlobalInits.empty() && PrioritizedCXXGlobalInits.empty())
641     return;
642 
643   llvm::FunctionType *FTy = llvm::FunctionType::get(VoidTy, false);
644   const CGFunctionInfo &FI = getTypes().arrangeNullaryFunction();
645 
646   // Create our global prioritized initialization function.
647   if (!PrioritizedCXXGlobalInits.empty()) {
648     SmallVector<llvm::Function *, 8> LocalCXXGlobalInits;
649     llvm::array_pod_sort(PrioritizedCXXGlobalInits.begin(),
650                          PrioritizedCXXGlobalInits.end());
651     // Iterate over "chunks" of ctors with same priority and emit each chunk
652     // into separate function. Note - everything is sorted first by priority,
653     // second - by lex order, so we emit ctor functions in proper order.
654     for (SmallVectorImpl<GlobalInitData >::iterator
655            I = PrioritizedCXXGlobalInits.begin(),
656            E = PrioritizedCXXGlobalInits.end(); I != E; ) {
657       SmallVectorImpl<GlobalInitData >::iterator
658         PrioE = std::upper_bound(I + 1, E, *I, GlobalInitPriorityCmp());
659 
660       LocalCXXGlobalInits.clear();
661 
662       unsigned int Priority = I->first.priority;
663       llvm::Function *Fn = CreateGlobalInitOrCleanUpFunction(
664           FTy, "_GLOBAL__I_" + getPrioritySuffix(Priority), FI);
665 
666       for (; I < PrioE; ++I)
667         LocalCXXGlobalInits.push_back(I->second);
668 
669       CodeGenFunction(*this).GenerateCXXGlobalInitFunc(Fn, LocalCXXGlobalInits);
670       AddGlobalCtor(Fn, Priority);
671     }
672     PrioritizedCXXGlobalInits.clear();
673   }
674 
675   if (getCXXABI().useSinitAndSterm() && CXXGlobalInits.empty())
676     return;
677 
678   // Include the filename in the symbol name. Including "sub_" matches gcc
679   // and makes sure these symbols appear lexicographically behind the symbols
680   // with priority emitted above.
681   llvm::Function *Fn = CreateGlobalInitOrCleanUpFunction(
682       FTy, llvm::Twine("_GLOBAL__sub_I_", getTransformedFileName(getModule())),
683       FI);
684 
685   CodeGenFunction(*this).GenerateCXXGlobalInitFunc(Fn, CXXGlobalInits);
686   AddGlobalCtor(Fn);
687 
688   // In OpenCL global init functions must be converted to kernels in order to
689   // be able to launch them from the host.
690   // FIXME: Some more work might be needed to handle destructors correctly.
691   // Current initialization function makes use of function pointers callbacks.
692   // We can't support function pointers especially between host and device.
693   // However it seems global destruction has little meaning without any
694   // dynamic resource allocation on the device and program scope variables are
695   // destroyed by the runtime when program is released.
696   if (getLangOpts().OpenCL) {
697     GenOpenCLArgMetadata(Fn);
698     Fn->setCallingConv(llvm::CallingConv::SPIR_KERNEL);
699   }
700 
701   assert(!getLangOpts().CUDA || !getLangOpts().CUDAIsDevice ||
702          getLangOpts().GPUAllowDeviceInit);
703   if (getLangOpts().HIP && getLangOpts().CUDAIsDevice) {
704     Fn->setCallingConv(llvm::CallingConv::AMDGPU_KERNEL);
705     Fn->addFnAttr("device-init");
706   }
707 
708   CXXGlobalInits.clear();
709 }
710 
711 void CodeGenModule::EmitCXXGlobalCleanUpFunc() {
712   if (CXXGlobalDtorsOrStermFinalizers.empty() &&
713       PrioritizedCXXStermFinalizers.empty())
714     return;
715 
716   llvm::FunctionType *FTy = llvm::FunctionType::get(VoidTy, false);
717   const CGFunctionInfo &FI = getTypes().arrangeNullaryFunction();
718 
719   // Create our global prioritized cleanup function.
720   if (!PrioritizedCXXStermFinalizers.empty()) {
721     SmallVector<CXXGlobalDtorsOrStermFinalizer_t, 8> LocalCXXStermFinalizers;
722     llvm::array_pod_sort(PrioritizedCXXStermFinalizers.begin(),
723                          PrioritizedCXXStermFinalizers.end());
724     // Iterate over "chunks" of dtors with same priority and emit each chunk
725     // into separate function. Note - everything is sorted first by priority,
726     // second - by lex order, so we emit dtor functions in proper order.
727     for (SmallVectorImpl<StermFinalizerData>::iterator
728              I = PrioritizedCXXStermFinalizers.begin(),
729              E = PrioritizedCXXStermFinalizers.end();
730          I != E;) {
731       SmallVectorImpl<StermFinalizerData>::iterator PrioE =
732           std::upper_bound(I + 1, E, *I, StermFinalizerPriorityCmp());
733 
734       LocalCXXStermFinalizers.clear();
735 
736       unsigned int Priority = I->first.priority;
737       llvm::Function *Fn = CreateGlobalInitOrCleanUpFunction(
738           FTy, "_GLOBAL__a_" + getPrioritySuffix(Priority), FI);
739 
740       for (; I < PrioE; ++I) {
741         llvm::FunctionCallee DtorFn = I->second;
742         LocalCXXStermFinalizers.emplace_back(DtorFn.getFunctionType(),
743                                              DtorFn.getCallee(), nullptr);
744       }
745 
746       CodeGenFunction(*this).GenerateCXXGlobalCleanUpFunc(
747           Fn, LocalCXXStermFinalizers);
748       AddGlobalDtor(Fn, Priority);
749     }
750     PrioritizedCXXStermFinalizers.clear();
751   }
752 
753   if (CXXGlobalDtorsOrStermFinalizers.empty())
754     return;
755 
756   // Create our global cleanup function.
757   llvm::Function *Fn =
758       CreateGlobalInitOrCleanUpFunction(FTy, "_GLOBAL__D_a", FI);
759 
760   CodeGenFunction(*this).GenerateCXXGlobalCleanUpFunc(
761       Fn, CXXGlobalDtorsOrStermFinalizers);
762   AddGlobalDtor(Fn);
763   CXXGlobalDtorsOrStermFinalizers.clear();
764 }
765 
766 /// Emit the code necessary to initialize the given global variable.
767 void CodeGenFunction::GenerateCXXGlobalVarDeclInitFunc(llvm::Function *Fn,
768                                                        const VarDecl *D,
769                                                  llvm::GlobalVariable *Addr,
770                                                        bool PerformInit) {
771   // Check if we need to emit debug info for variable initializer.
772   if (D->hasAttr<NoDebugAttr>())
773     DebugInfo = nullptr; // disable debug info indefinitely for this function
774 
775   CurEHLocation = D->getBeginLoc();
776 
777   StartFunction(GlobalDecl(D, DynamicInitKind::Initializer),
778                 getContext().VoidTy, Fn, getTypes().arrangeNullaryFunction(),
779                 FunctionArgList());
780   // Emit an artificial location for this function.
781   auto AL = ApplyDebugLocation::CreateArtificial(*this);
782 
783   // Use guarded initialization if the global variable is weak. This
784   // occurs for, e.g., instantiated static data members and
785   // definitions explicitly marked weak.
786   //
787   // Also use guarded initialization for a variable with dynamic TLS and
788   // unordered initialization. (If the initialization is ordered, the ABI
789   // layer will guard the whole-TU initialization for us.)
790   if (Addr->hasWeakLinkage() || Addr->hasLinkOnceLinkage() ||
791       (D->getTLSKind() == VarDecl::TLS_Dynamic &&
792        isTemplateInstantiation(D->getTemplateSpecializationKind()))) {
793     EmitCXXGuardedInit(*D, Addr, PerformInit);
794   } else {
795     EmitCXXGlobalVarDeclInit(*D, Addr, PerformInit);
796   }
797 
798   FinishFunction();
799 }
800 
801 void
802 CodeGenFunction::GenerateCXXGlobalInitFunc(llvm::Function *Fn,
803                                            ArrayRef<llvm::Function *> Decls,
804                                            ConstantAddress Guard) {
805   {
806     auto NL = ApplyDebugLocation::CreateEmpty(*this);
807     StartFunction(GlobalDecl(), getContext().VoidTy, Fn,
808                   getTypes().arrangeNullaryFunction(), FunctionArgList());
809     // Emit an artificial location for this function.
810     auto AL = ApplyDebugLocation::CreateArtificial(*this);
811 
812     llvm::BasicBlock *ExitBlock = nullptr;
813     if (Guard.isValid()) {
814       // If we have a guard variable, check whether we've already performed
815       // these initializations. This happens for TLS initialization functions.
816       llvm::Value *GuardVal = Builder.CreateLoad(Guard);
817       llvm::Value *Uninit = Builder.CreateIsNull(GuardVal,
818                                                  "guard.uninitialized");
819       llvm::BasicBlock *InitBlock = createBasicBlock("init");
820       ExitBlock = createBasicBlock("exit");
821       EmitCXXGuardedInitBranch(Uninit, InitBlock, ExitBlock,
822                                GuardKind::TlsGuard, nullptr);
823       EmitBlock(InitBlock);
824       // Mark as initialized before initializing anything else. If the
825       // initializers use previously-initialized thread_local vars, that's
826       // probably supposed to be OK, but the standard doesn't say.
827       Builder.CreateStore(llvm::ConstantInt::get(GuardVal->getType(),1), Guard);
828 
829       // The guard variable can't ever change again.
830       EmitInvariantStart(
831           Guard.getPointer(),
832           CharUnits::fromQuantity(
833               CGM.getDataLayout().getTypeAllocSize(GuardVal->getType())));
834     }
835 
836     RunCleanupsScope Scope(*this);
837 
838     // When building in Objective-C++ ARC mode, create an autorelease pool
839     // around the global initializers.
840     if (getLangOpts().ObjCAutoRefCount && getLangOpts().CPlusPlus) {
841       llvm::Value *token = EmitObjCAutoreleasePoolPush();
842       EmitObjCAutoreleasePoolCleanup(token);
843     }
844 
845     for (unsigned i = 0, e = Decls.size(); i != e; ++i)
846       if (Decls[i])
847         EmitRuntimeCall(Decls[i]);
848 
849     Scope.ForceCleanup();
850 
851     if (ExitBlock) {
852       Builder.CreateBr(ExitBlock);
853       EmitBlock(ExitBlock);
854     }
855   }
856 
857   FinishFunction();
858 }
859 
860 void CodeGenFunction::GenerateCXXGlobalCleanUpFunc(
861     llvm::Function *Fn,
862     ArrayRef<std::tuple<llvm::FunctionType *, llvm::WeakTrackingVH,
863                         llvm::Constant *>>
864         DtorsOrStermFinalizers) {
865   {
866     auto NL = ApplyDebugLocation::CreateEmpty(*this);
867     StartFunction(GlobalDecl(), getContext().VoidTy, Fn,
868                   getTypes().arrangeNullaryFunction(), FunctionArgList());
869     // Emit an artificial location for this function.
870     auto AL = ApplyDebugLocation::CreateArtificial(*this);
871 
872     // Emit the cleanups, in reverse order from construction.
873     for (unsigned i = 0, e = DtorsOrStermFinalizers.size(); i != e; ++i) {
874       llvm::FunctionType *CalleeTy;
875       llvm::Value *Callee;
876       llvm::Constant *Arg;
877       std::tie(CalleeTy, Callee, Arg) = DtorsOrStermFinalizers[e - i - 1];
878 
879       llvm::CallInst *CI = nullptr;
880       if (Arg == nullptr) {
881         assert(
882             CGM.getCXXABI().useSinitAndSterm() &&
883             "Arg could not be nullptr unless using sinit and sterm functions.");
884         CI = Builder.CreateCall(CalleeTy, Callee);
885       } else
886         CI = Builder.CreateCall(CalleeTy, Callee, Arg);
887 
888       // Make sure the call and the callee agree on calling convention.
889       if (llvm::Function *F = dyn_cast<llvm::Function>(Callee))
890         CI->setCallingConv(F->getCallingConv());
891     }
892   }
893 
894   FinishFunction();
895 }
896 
897 /// generateDestroyHelper - Generates a helper function which, when
898 /// invoked, destroys the given object.  The address of the object
899 /// should be in global memory.
900 llvm::Function *CodeGenFunction::generateDestroyHelper(
901     Address addr, QualType type, Destroyer *destroyer,
902     bool useEHCleanupForArray, const VarDecl *VD) {
903   FunctionArgList args;
904   ImplicitParamDecl Dst(getContext(), getContext().VoidPtrTy,
905                         ImplicitParamDecl::Other);
906   args.push_back(&Dst);
907 
908   const CGFunctionInfo &FI =
909     CGM.getTypes().arrangeBuiltinFunctionDeclaration(getContext().VoidTy, args);
910   llvm::FunctionType *FTy = CGM.getTypes().GetFunctionType(FI);
911   llvm::Function *fn = CGM.CreateGlobalInitOrCleanUpFunction(
912       FTy, "__cxx_global_array_dtor", FI, VD->getLocation());
913 
914   CurEHLocation = VD->getBeginLoc();
915 
916   StartFunction(GlobalDecl(VD, DynamicInitKind::GlobalArrayDestructor),
917                 getContext().VoidTy, fn, FI, args);
918   // Emit an artificial location for this function.
919   auto AL = ApplyDebugLocation::CreateArtificial(*this);
920 
921   emitDestroy(addr, type, destroyer, useEHCleanupForArray);
922 
923   FinishFunction();
924 
925   return fn;
926 }
927