1 //===--- CGDeclCXX.cpp - Emit LLVM Code for C++ declarations --------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This contains code dealing with code generation of C++ declarations
12 //===----------------------------------------------------------------------===//
14 #include "CodeGenFunction.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"
23 using namespace clang;
24 using namespace CodeGen;
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!");
32 ASTContext &Context = CGF.getContext();
34 CharUnits alignment = Context.getDeclAlign(&D);
35 QualType type = D.getType();
36 LValue lv = CGF.MakeAddrLValue(DeclPtr, type, alignment);
38 const Expr *Init = D.getInit();
39 switch (CGF.getEvaluationKind(type)) {
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),
49 CGF.EmitScalarInit(Init, &D, lv, false);
53 CGF.EmitComplexExprIntoLValue(Init, lv, /*isInit*/ true);
56 CGF.EmitAggExpr(Init, AggValueSlot::forLValue(lv,AggValueSlot::IsDestructed,
57 AggValueSlot::DoesNotNeedGCBarriers,
58 AggValueSlot::IsNotAliased));
61 llvm_unreachable("bad evaluation kind");
64 /// Emit code to cause the destruction of the given variable with
65 /// static storage duration.
66 static void EmitDeclDestroy(CodeGenFunction &CGF, const VarDecl &D,
67 llvm::Constant *addr) {
68 CodeGenModule &CGM = CGF.CGM;
70 // FIXME: __attribute__((cleanup)) ?
72 QualType type = D.getType();
73 QualType::DestructionKind dtorKind = type.isDestructedType();
76 case QualType::DK_none:
79 case QualType::DK_cxx_destructor:
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");
89 llvm::Constant *function;
90 llvm::Constant *argument;
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();
100 function = CGM.getAddrOfCXXStructor(dtor, StructorType::Complete);
101 argument = llvm::ConstantExpr::getBitCast(
102 addr, CGF.getTypes().ConvertType(type)->getPointerTo());
104 // Otherwise, the standard logic requires a helper function.
106 function = CodeGenFunction(CGM)
107 .generateDestroyHelper(addr, type, CGF.getDestroyer(dtorKind),
108 CGF.needsEHCleanup(dtorKind), &D);
109 argument = llvm::Constant::getNullValue(CGF.Int8PtrTy);
112 CGM.getCXXABI().registerGlobalDtor(CGF, D, function, argument);
115 /// Emit code to cause the variable at the given address to be considered as
116 /// constant from this point onwards.
117 static void EmitDeclInvariant(CodeGenFunction &CGF, const VarDecl &D,
118 llvm::Constant *Addr) {
119 // Don't emit the intrinsic if we're not optimizing.
120 if (!CGF.CGM.getCodeGenOpts().OptimizationLevel)
123 // Grab the llvm.invariant.start intrinsic.
124 llvm::Intrinsic::ID InvStartID = llvm::Intrinsic::invariant_start;
125 llvm::Constant *InvariantStart = CGF.CGM.getIntrinsic(InvStartID);
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);
135 void CodeGenFunction::EmitCXXGlobalVarDeclInit(const VarDecl &D,
136 llvm::Constant *DeclPtr,
139 const Expr *Init = D.getInit();
140 QualType T = D.getType();
142 if (!T->isReferenceType()) {
143 if (getLangOpts().OpenMP && D.hasAttr<OMPThreadPrivateDeclAttr>())
144 (void)CGM.getOpenMPRuntime().EmitOMPThreadPrivateVarDefinition(
145 &D, DeclPtr, D.getAttr<OMPThreadPrivateDeclAttr>()->getLocation(),
148 EmitDeclInit(*this, D, DeclPtr);
149 if (CGM.isTypeConstant(D.getType(), true))
150 EmitDeclInvariant(*this, D, DeclPtr);
152 EmitDeclDestroy(*this, D, DeclPtr);
156 assert(PerformInit && "cannot have constant initializer which needs "
157 "destruction for reference");
158 unsigned Alignment = getContext().getDeclAlign(&D).getQuantity();
159 RValue RV = EmitReferenceBindingToExpr(Init);
160 EmitStoreOfScalar(RV.getScalarVal(), DeclPtr, false, Alignment, T);
163 /// Create a stub function, suitable for being passed to atexit,
164 /// which passes the given address to the given destructor function.
165 llvm::Constant *CodeGenFunction::createAtExitStub(const VarDecl &VD,
166 llvm::Constant *dtor,
167 llvm::Constant *addr) {
168 // Get the destructor function type, void(*)(void).
169 llvm::FunctionType *ty = llvm::FunctionType::get(CGM.VoidTy, false);
170 SmallString<256> FnName;
172 llvm::raw_svector_ostream Out(FnName);
173 CGM.getCXXABI().getMangleContext().mangleDynamicAtExitDestructor(&VD, Out);
175 llvm::Function *fn = CGM.CreateGlobalInitOrDestructFunction(ty, FnName.str(),
178 CodeGenFunction CGF(CGM);
180 CGF.StartFunction(&VD, CGM.getContext().VoidTy, fn,
181 CGM.getTypes().arrangeNullaryFunction(), FunctionArgList());
183 llvm::CallInst *call = CGF.Builder.CreateCall(dtor, addr);
185 // Make sure the call and the callee agree on calling convention.
186 if (llvm::Function *dtorFn =
187 dyn_cast<llvm::Function>(dtor->stripPointerCasts()))
188 call->setCallingConv(dtorFn->getCallingConv());
190 CGF.FinishFunction();
195 /// Register a global destructor using the C atexit runtime function.
196 void CodeGenFunction::registerGlobalDtorWithAtExit(const VarDecl &VD,
197 llvm::Constant *dtor,
198 llvm::Constant *addr) {
199 // Create a function which calls the destructor.
200 llvm::Constant *dtorStub = createAtExitStub(VD, dtor, addr);
202 // extern "C" int atexit(void (*f)(void));
203 llvm::FunctionType *atexitTy =
204 llvm::FunctionType::get(IntTy, dtorStub->getType(), false);
206 llvm::Constant *atexit =
207 CGM.CreateRuntimeFunction(atexitTy, "atexit");
208 if (llvm::Function *atexitFn = dyn_cast<llvm::Function>(atexit))
209 atexitFn->setDoesNotThrow();
211 EmitNounwindRuntimeCall(atexit, dtorStub);
214 void CodeGenFunction::EmitCXXGuardedInit(const VarDecl &D,
215 llvm::GlobalVariable *DeclPtr,
217 // If we've been asked to forbid guard variables, emit an error now.
218 // This diagnostic is hard-coded for Darwin's use case; we can find
219 // better phrasing if someone else needs it.
220 if (CGM.getCodeGenOpts().ForbidGuardVariables)
221 CGM.Error(D.getLocation(),
222 "this initialization requires a guard variable, which "
223 "the kernel does not support");
225 CGM.getCXXABI().EmitGuardedInit(*this, D, DeclPtr, PerformInit);
228 llvm::Function *CodeGenModule::CreateGlobalInitOrDestructFunction(
229 llvm::FunctionType *FTy, const Twine &Name, SourceLocation Loc, bool TLS) {
231 llvm::Function::Create(FTy, llvm::GlobalValue::InternalLinkage,
233 if (!getLangOpts().AppleKext && !TLS) {
234 // Set the section if needed.
235 if (const char *Section = getTarget().getStaticInitSectionSpecifier())
236 Fn->setSection(Section);
239 Fn->setCallingConv(getRuntimeCC());
241 if (!getLangOpts().Exceptions)
242 Fn->setDoesNotThrow();
244 if (!isInSanitizerBlacklist(Fn, Loc)) {
245 if (getLangOpts().Sanitize.has(SanitizerKind::Address))
246 Fn->addFnAttr(llvm::Attribute::SanitizeAddress);
247 if (getLangOpts().Sanitize.has(SanitizerKind::Thread))
248 Fn->addFnAttr(llvm::Attribute::SanitizeThread);
249 if (getLangOpts().Sanitize.has(SanitizerKind::Memory))
250 Fn->addFnAttr(llvm::Attribute::SanitizeMemory);
256 /// Create a global pointer to a function that will initialize a global
257 /// variable. The user has requested that this pointer be emitted in a specific
259 void CodeGenModule::EmitPointerToInitFunc(const VarDecl *D,
260 llvm::GlobalVariable *GV,
261 llvm::Function *InitFunc,
263 llvm::GlobalVariable *PtrArray = new llvm::GlobalVariable(
264 TheModule, InitFunc->getType(), /*isConstant=*/true,
265 llvm::GlobalValue::PrivateLinkage, InitFunc, "__cxx_init_fn_ptr");
266 PtrArray->setSection(ISA->getSection());
267 addUsedGlobal(PtrArray);
269 // If the GV is already in a comdat group, then we have to join it.
270 llvm::Comdat *C = GV->getComdat();
272 // LinkOnce and Weak linkage are lowered down to a single-member comdat group.
273 // Make an explicit group so we can join it.
274 if (!C && (GV->hasWeakLinkage() || GV->hasLinkOnceLinkage())) {
275 C = TheModule.getOrInsertComdat(GV->getName());
279 PtrArray->setComdat(C);
283 CodeGenModule::EmitCXXGlobalVarDeclInitFunc(const VarDecl *D,
284 llvm::GlobalVariable *Addr,
286 llvm::FunctionType *FTy = llvm::FunctionType::get(VoidTy, false);
287 SmallString<256> FnName;
289 llvm::raw_svector_ostream Out(FnName);
290 getCXXABI().getMangleContext().mangleDynamicInitializer(D, Out);
293 // Create a variable initialization function.
295 CreateGlobalInitOrDestructFunction(FTy, FnName.str(), D->getLocation());
297 auto *ISA = D->getAttr<InitSegAttr>();
298 CodeGenFunction(*this).GenerateCXXGlobalVarDeclInitFunc(Fn, D, Addr,
301 llvm::GlobalVariable *COMDATKey =
302 supportsCOMDAT() && D->isExternallyVisible() ? Addr : nullptr;
304 if (D->getTLSKind()) {
305 // FIXME: Should we support init_priority for thread_local?
306 // FIXME: Ideally, initialization of instantiated thread_local static data
307 // members of class templates should not trigger initialization of other
308 // entities in the TU.
309 // FIXME: We only need to register one __cxa_thread_atexit function for the
311 CXXThreadLocalInits.push_back(Fn);
312 CXXThreadLocalInitVars.push_back(Addr);
313 } else if (PerformInit && ISA) {
314 EmitPointerToInitFunc(D, Addr, Fn, ISA);
315 DelayedCXXInitPosition.erase(D);
316 } else if (auto *IPA = D->getAttr<InitPriorityAttr>()) {
317 OrderGlobalInits Key(IPA->getPriority(), PrioritizedCXXGlobalInits.size());
318 PrioritizedCXXGlobalInits.push_back(std::make_pair(Key, Fn));
319 DelayedCXXInitPosition.erase(D);
320 } else if (isTemplateInstantiation(D->getTemplateSpecializationKind())) {
321 // C++ [basic.start.init]p2:
322 // Definitions of explicitly specialized class template static data
323 // members have ordered initialization. Other class template static data
324 // members (i.e., implicitly or explicitly instantiated specializations)
325 // have unordered initialization.
327 // As a consequence, we can put them into their own llvm.global_ctors entry.
329 // If the global is externally visible, put the initializer into a COMDAT
330 // group with the global being initialized. On most platforms, this is a
331 // minor startup time optimization. In the MS C++ ABI, there are no guard
332 // variables, so this COMDAT key is required for correctness.
333 AddGlobalCtor(Fn, 65535, COMDATKey);
334 DelayedCXXInitPosition.erase(D);
335 } else if (D->hasAttr<SelectAnyAttr>()) {
336 // SelectAny globals will be comdat-folded. Put the initializer into a
337 // COMDAT group associated with the global, so the initializers get folded
339 AddGlobalCtor(Fn, 65535, COMDATKey);
340 DelayedCXXInitPosition.erase(D);
342 llvm::DenseMap<const Decl *, unsigned>::iterator I =
343 DelayedCXXInitPosition.find(D);
344 if (I == DelayedCXXInitPosition.end()) {
345 CXXGlobalInits.push_back(Fn);
347 assert(CXXGlobalInits[I->second] == nullptr);
348 CXXGlobalInits[I->second] = Fn;
349 DelayedCXXInitPosition.erase(I);
354 void CodeGenModule::EmitCXXThreadLocalInitFunc() {
355 getCXXABI().EmitThreadLocalInitFuncs(
356 *this, CXXThreadLocals, CXXThreadLocalInits, CXXThreadLocalInitVars);
358 CXXThreadLocalInits.clear();
359 CXXThreadLocalInitVars.clear();
360 CXXThreadLocals.clear();
364 CodeGenModule::EmitCXXGlobalInitFunc() {
365 while (!CXXGlobalInits.empty() && !CXXGlobalInits.back())
366 CXXGlobalInits.pop_back();
368 if (CXXGlobalInits.empty() && PrioritizedCXXGlobalInits.empty())
371 llvm::FunctionType *FTy = llvm::FunctionType::get(VoidTy, false);
374 // Create our global initialization function.
375 if (!PrioritizedCXXGlobalInits.empty()) {
376 SmallVector<llvm::Function *, 8> LocalCXXGlobalInits;
377 llvm::array_pod_sort(PrioritizedCXXGlobalInits.begin(),
378 PrioritizedCXXGlobalInits.end());
379 // Iterate over "chunks" of ctors with same priority and emit each chunk
380 // into separate function. Note - everything is sorted first by priority,
381 // second - by lex order, so we emit ctor functions in proper order.
382 for (SmallVectorImpl<GlobalInitData >::iterator
383 I = PrioritizedCXXGlobalInits.begin(),
384 E = PrioritizedCXXGlobalInits.end(); I != E; ) {
385 SmallVectorImpl<GlobalInitData >::iterator
386 PrioE = std::upper_bound(I + 1, E, *I, GlobalInitPriorityCmp());
388 LocalCXXGlobalInits.clear();
389 unsigned Priority = I->first.priority;
390 // Compute the function suffix from priority. Prepend with zeroes to make
391 // sure the function names are also ordered as priorities.
392 std::string PrioritySuffix = llvm::utostr(Priority);
393 // Priority is always <= 65535 (enforced by sema).
394 PrioritySuffix = std::string(6-PrioritySuffix.size(), '0')+PrioritySuffix;
395 llvm::Function *Fn = CreateGlobalInitOrDestructFunction(
396 FTy, "_GLOBAL__I_" + PrioritySuffix);
398 for (; I < PrioE; ++I)
399 LocalCXXGlobalInits.push_back(I->second);
401 CodeGenFunction(*this).GenerateCXXGlobalInitFunc(Fn, LocalCXXGlobalInits);
402 AddGlobalCtor(Fn, Priority);
406 SmallString<128> FileName;
407 SourceManager &SM = Context.getSourceManager();
408 if (const FileEntry *MainFile = SM.getFileEntryForID(SM.getMainFileID())) {
409 // Include the filename in the symbol name. Including "sub_" matches gcc and
410 // makes sure these symbols appear lexicographically behind the symbols with
411 // priority emitted above.
412 FileName = llvm::sys::path::filename(MainFile->getName());
414 FileName = SmallString<128>("<null>");
417 for (size_t i = 0; i < FileName.size(); ++i) {
418 // Replace everything that's not [a-zA-Z0-9._] with a _. This set happens
419 // to be the set of C preprocessing numbers.
420 if (!isPreprocessingNumberBody(FileName[i]))
424 llvm::Function *Fn = CreateGlobalInitOrDestructFunction(
425 FTy, llvm::Twine("_GLOBAL__sub_I_", FileName));
427 CodeGenFunction(*this).GenerateCXXGlobalInitFunc(Fn, CXXGlobalInits);
430 CXXGlobalInits.clear();
431 PrioritizedCXXGlobalInits.clear();
434 void CodeGenModule::EmitCXXGlobalDtorFunc() {
435 if (CXXGlobalDtors.empty())
438 llvm::FunctionType *FTy = llvm::FunctionType::get(VoidTy, false);
440 // Create our global destructor function.
441 llvm::Function *Fn = CreateGlobalInitOrDestructFunction(FTy, "_GLOBAL__D_a");
443 CodeGenFunction(*this).GenerateCXXGlobalDtorsFunc(Fn, CXXGlobalDtors);
447 /// Emit the code necessary to initialize the given global variable.
448 void CodeGenFunction::GenerateCXXGlobalVarDeclInitFunc(llvm::Function *Fn,
450 llvm::GlobalVariable *Addr,
452 // Check if we need to emit debug info for variable initializer.
453 if (D->hasAttr<NoDebugAttr>())
454 DebugInfo = nullptr; // disable debug info indefinitely for this function
456 CurEHLocation = D->getLocStart();
458 StartFunction(GlobalDecl(D), getContext().VoidTy, Fn,
459 getTypes().arrangeNullaryFunction(),
460 FunctionArgList(), D->getLocation(),
461 D->getInit()->getExprLoc());
463 // Use guarded initialization if the global variable is weak. This
464 // occurs for, e.g., instantiated static data members and
465 // definitions explicitly marked weak.
466 if (Addr->hasWeakLinkage() || Addr->hasLinkOnceLinkage()) {
467 EmitCXXGuardedInit(*D, Addr, PerformInit);
469 EmitCXXGlobalVarDeclInit(*D, Addr, PerformInit);
476 CodeGenFunction::GenerateCXXGlobalInitFunc(llvm::Function *Fn,
477 ArrayRef<llvm::Function *> Decls,
478 llvm::GlobalVariable *Guard) {
480 ApplyDebugLocation NL(*this);
481 StartFunction(GlobalDecl(), getContext().VoidTy, Fn,
482 getTypes().arrangeNullaryFunction(), FunctionArgList());
483 // Emit an artificial location for this function.
484 ArtificialLocation AL(*this);
486 llvm::BasicBlock *ExitBlock = nullptr;
488 // If we have a guard variable, check whether we've already performed
489 // these initializations. This happens for TLS initialization functions.
490 llvm::Value *GuardVal = Builder.CreateLoad(Guard);
491 llvm::Value *Uninit = Builder.CreateIsNull(GuardVal,
492 "guard.uninitialized");
493 // Mark as initialized before initializing anything else. If the
494 // initializers use previously-initialized thread_local vars, that's
495 // probably supposed to be OK, but the standard doesn't say.
496 Builder.CreateStore(llvm::ConstantInt::get(GuardVal->getType(),1), Guard);
497 llvm::BasicBlock *InitBlock = createBasicBlock("init");
498 ExitBlock = createBasicBlock("exit");
499 Builder.CreateCondBr(Uninit, InitBlock, ExitBlock);
500 EmitBlock(InitBlock);
503 RunCleanupsScope Scope(*this);
505 // When building in Objective-C++ ARC mode, create an autorelease pool
506 // around the global initializers.
507 if (getLangOpts().ObjCAutoRefCount && getLangOpts().CPlusPlus) {
508 llvm::Value *token = EmitObjCAutoreleasePoolPush();
509 EmitObjCAutoreleasePoolCleanup(token);
512 for (unsigned i = 0, e = Decls.size(); i != e; ++i)
514 EmitRuntimeCall(Decls[i]);
516 Scope.ForceCleanup();
519 Builder.CreateBr(ExitBlock);
520 EmitBlock(ExitBlock);
527 void CodeGenFunction::GenerateCXXGlobalDtorsFunc(llvm::Function *Fn,
528 const std::vector<std::pair<llvm::WeakVH, llvm::Constant*> >
531 ApplyDebugLocation NL(*this);
532 StartFunction(GlobalDecl(), getContext().VoidTy, Fn,
533 getTypes().arrangeNullaryFunction(), FunctionArgList());
534 // Emit an artificial location for this function.
535 ArtificialLocation AL(*this);
537 // Emit the dtors, in reverse order from construction.
538 for (unsigned i = 0, e = DtorsAndObjects.size(); i != e; ++i) {
539 llvm::Value *Callee = DtorsAndObjects[e - i - 1].first;
540 llvm::CallInst *CI = Builder.CreateCall(Callee,
541 DtorsAndObjects[e - i - 1].second);
542 // Make sure the call and the callee agree on calling convention.
543 if (llvm::Function *F = dyn_cast<llvm::Function>(Callee))
544 CI->setCallingConv(F->getCallingConv());
551 /// generateDestroyHelper - Generates a helper function which, when
552 /// invoked, destroys the given object.
553 llvm::Function *CodeGenFunction::generateDestroyHelper(
554 llvm::Constant *addr, QualType type, Destroyer *destroyer,
555 bool useEHCleanupForArray, const VarDecl *VD) {
556 FunctionArgList args;
557 ImplicitParamDecl dst(getContext(), nullptr, SourceLocation(), nullptr,
558 getContext().VoidPtrTy);
559 args.push_back(&dst);
561 const CGFunctionInfo &FI = CGM.getTypes().arrangeFreeFunctionDeclaration(
562 getContext().VoidTy, args, FunctionType::ExtInfo(), /*variadic=*/false);
563 llvm::FunctionType *FTy = CGM.getTypes().GetFunctionType(FI);
564 llvm::Function *fn = CGM.CreateGlobalInitOrDestructFunction(
565 FTy, "__cxx_global_array_dtor", VD->getLocation());
567 CurEHLocation = VD->getLocStart();
569 StartFunction(VD, getContext().VoidTy, fn, FI, args);
571 emitDestroy(addr, type, destroyer, useEHCleanupForArray);