//===--- CGDeclCXX.cpp - Emit LLVM Code for C++ declarations --------------===// // // The LLVM Compiler Infrastructure // // This file is distributed under the University of Illinois Open Source // License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // // This contains code dealing with code generation of C++ declarations // //===----------------------------------------------------------------------===// #include "CodeGenFunction.h" #include "CGCXXABI.h" #include "CGObjCRuntime.h" #include "CGOpenMPRuntime.h" #include "clang/Frontend/CodeGenOptions.h" #include "llvm/ADT/StringExtras.h" #include "llvm/IR/Intrinsics.h" #include "llvm/Support/Path.h" using namespace clang; using namespace CodeGen; static void EmitDeclInit(CodeGenFunction &CGF, const VarDecl &D, ConstantAddress DeclPtr) { assert(D.hasGlobalStorage() && "VarDecl must have global storage!"); assert(!D.getType()->isReferenceType() && "Should not call EmitDeclInit on a reference!"); QualType type = D.getType(); LValue lv = CGF.MakeAddrLValue(DeclPtr, type); const Expr *Init = D.getInit(); switch (CGF.getEvaluationKind(type)) { case TEK_Scalar: { CodeGenModule &CGM = CGF.CGM; if (lv.isObjCStrong()) CGM.getObjCRuntime().EmitObjCGlobalAssign(CGF, CGF.EmitScalarExpr(Init), DeclPtr, D.getTLSKind()); else if (lv.isObjCWeak()) CGM.getObjCRuntime().EmitObjCWeakAssign(CGF, CGF.EmitScalarExpr(Init), DeclPtr); else CGF.EmitScalarInit(Init, &D, lv, false); return; } case TEK_Complex: CGF.EmitComplexExprIntoLValue(Init, lv, /*isInit*/ true); return; case TEK_Aggregate: CGF.EmitAggExpr(Init, AggValueSlot::forLValue(lv,AggValueSlot::IsDestructed, AggValueSlot::DoesNotNeedGCBarriers, AggValueSlot::IsNotAliased)); return; } llvm_unreachable("bad evaluation kind"); } /// Emit code to cause the destruction of the given variable with /// static storage duration. static void EmitDeclDestroy(CodeGenFunction &CGF, const VarDecl &D, ConstantAddress addr) { CodeGenModule &CGM = CGF.CGM; // FIXME: __attribute__((cleanup)) ? QualType type = D.getType(); QualType::DestructionKind dtorKind = type.isDestructedType(); switch (dtorKind) { case QualType::DK_none: return; case QualType::DK_cxx_destructor: break; case QualType::DK_objc_strong_lifetime: case QualType::DK_objc_weak_lifetime: // We don't care about releasing objects during process teardown. assert(!D.getTLSKind() && "should have rejected this"); return; } llvm::Constant *function; llvm::Constant *argument; // Special-case non-array C++ destructors, if they have the right signature. // Under some ABIs, destructors return this instead of void, and cannot be // passed directly to __cxa_atexit if the target does not allow this mismatch. const CXXRecordDecl *Record = type->getAsCXXRecordDecl(); bool CanRegisterDestructor = Record && (!CGM.getCXXABI().HasThisReturn( GlobalDecl(Record->getDestructor(), Dtor_Complete)) || CGM.getCXXABI().canCallMismatchedFunctionType()); // If __cxa_atexit is disabled via a flag, a different helper function is // generated elsewhere which uses atexit instead, and it takes the destructor // directly. bool UsingExternalHelper = !CGM.getCodeGenOpts().CXAAtExit; if (Record && (CanRegisterDestructor || UsingExternalHelper)) { assert(!Record->hasTrivialDestructor()); CXXDestructorDecl *dtor = Record->getDestructor(); function = CGM.getAddrOfCXXStructor(dtor, StructorType::Complete); argument = llvm::ConstantExpr::getBitCast( addr.getPointer(), CGF.getTypes().ConvertType(type)->getPointerTo()); // Otherwise, the standard logic requires a helper function. } else { function = CodeGenFunction(CGM) .generateDestroyHelper(addr, type, CGF.getDestroyer(dtorKind), CGF.needsEHCleanup(dtorKind), &D); argument = llvm::Constant::getNullValue(CGF.Int8PtrTy); } CGM.getCXXABI().registerGlobalDtor(CGF, D, function, argument); } /// Emit code to cause the variable at the given address to be considered as /// constant from this point onwards. static void EmitDeclInvariant(CodeGenFunction &CGF, const VarDecl &D, llvm::Constant *Addr) { // Don't emit the intrinsic if we're not optimizing. if (!CGF.CGM.getCodeGenOpts().OptimizationLevel) return; // Grab the llvm.invariant.start intrinsic. llvm::Intrinsic::ID InvStartID = llvm::Intrinsic::invariant_start; llvm::Constant *InvariantStart = CGF.CGM.getIntrinsic(InvStartID); // Emit a call with the size in bytes of the object. CharUnits WidthChars = CGF.getContext().getTypeSizeInChars(D.getType()); uint64_t Width = WidthChars.getQuantity(); llvm::Value *Args[2] = { llvm::ConstantInt::getSigned(CGF.Int64Ty, Width), llvm::ConstantExpr::getBitCast(Addr, CGF.Int8PtrTy)}; CGF.Builder.CreateCall(InvariantStart, Args); } void CodeGenFunction::EmitCXXGlobalVarDeclInit(const VarDecl &D, llvm::Constant *DeclPtr, bool PerformInit) { const Expr *Init = D.getInit(); QualType T = D.getType(); // The address space of a static local variable (DeclPtr) may be different // from the address space of the "this" argument of the constructor. In that // case, we need an addrspacecast before calling the constructor. // // struct StructWithCtor { // __device__ StructWithCtor() {...} // }; // __device__ void foo() { // __shared__ StructWithCtor s; // ... // } // // For example, in the above CUDA code, the static local variable s has a // "shared" address space qualifier, but the constructor of StructWithCtor // expects "this" in the "generic" address space. unsigned ExpectedAddrSpace = getContext().getTargetAddressSpace(T); unsigned ActualAddrSpace = DeclPtr->getType()->getPointerAddressSpace(); if (ActualAddrSpace != ExpectedAddrSpace) { llvm::Type *LTy = CGM.getTypes().ConvertTypeForMem(T); llvm::PointerType *PTy = llvm::PointerType::get(LTy, ExpectedAddrSpace); DeclPtr = llvm::ConstantExpr::getAddrSpaceCast(DeclPtr, PTy); } ConstantAddress DeclAddr(DeclPtr, getContext().getDeclAlign(&D)); if (!T->isReferenceType()) { if (getLangOpts().OpenMP && D.hasAttr<OMPThreadPrivateDeclAttr>()) (void)CGM.getOpenMPRuntime().emitThreadPrivateVarDefinition( &D, DeclAddr, D.getAttr<OMPThreadPrivateDeclAttr>()->getLocation(), PerformInit, this); if (PerformInit) EmitDeclInit(*this, D, DeclAddr); if (CGM.isTypeConstant(D.getType(), true)) EmitDeclInvariant(*this, D, DeclPtr); else EmitDeclDestroy(*this, D, DeclAddr); return; } assert(PerformInit && "cannot have constant initializer which needs " "destruction for reference"); RValue RV = EmitReferenceBindingToExpr(Init); EmitStoreOfScalar(RV.getScalarVal(), DeclAddr, false, T); } /// Create a stub function, suitable for being passed to atexit, /// which passes the given address to the given destructor function. llvm::Constant *CodeGenFunction::createAtExitStub(const VarDecl &VD, llvm::Constant *dtor, llvm::Constant *addr) { // Get the destructor function type, void(*)(void). llvm::FunctionType *ty = llvm::FunctionType::get(CGM.VoidTy, false); SmallString<256> FnName; { llvm::raw_svector_ostream Out(FnName); CGM.getCXXABI().getMangleContext().mangleDynamicAtExitDestructor(&VD, Out); } const CGFunctionInfo &FI = CGM.getTypes().arrangeNullaryFunction(); llvm::Function *fn = CGM.CreateGlobalInitOrDestructFunction(ty, FnName.str(), FI, VD.getLocation()); CodeGenFunction CGF(CGM); CGF.StartFunction(&VD, CGM.getContext().VoidTy, fn, FI, FunctionArgList()); llvm::CallInst *call = CGF.Builder.CreateCall(dtor, addr); // Make sure the call and the callee agree on calling convention. if (llvm::Function *dtorFn = dyn_cast<llvm::Function>(dtor->stripPointerCasts())) call->setCallingConv(dtorFn->getCallingConv()); CGF.FinishFunction(); return fn; } /// Register a global destructor using the C atexit runtime function. void CodeGenFunction::registerGlobalDtorWithAtExit(const VarDecl &VD, llvm::Constant *dtor, llvm::Constant *addr) { // Create a function which calls the destructor. llvm::Constant *dtorStub = createAtExitStub(VD, dtor, addr); // extern "C" int atexit(void (*f)(void)); llvm::FunctionType *atexitTy = llvm::FunctionType::get(IntTy, dtorStub->getType(), false); llvm::Constant *atexit = CGM.CreateRuntimeFunction(atexitTy, "atexit"); if (llvm::Function *atexitFn = dyn_cast<llvm::Function>(atexit)) atexitFn->setDoesNotThrow(); EmitNounwindRuntimeCall(atexit, dtorStub); } void CodeGenFunction::EmitCXXGuardedInit(const VarDecl &D, llvm::GlobalVariable *DeclPtr, bool PerformInit) { // If we've been asked to forbid guard variables, emit an error now. // This diagnostic is hard-coded for Darwin's use case; we can find // better phrasing if someone else needs it. if (CGM.getCodeGenOpts().ForbidGuardVariables) CGM.Error(D.getLocation(), "this initialization requires a guard variable, which " "the kernel does not support"); CGM.getCXXABI().EmitGuardedInit(*this, D, DeclPtr, PerformInit); } llvm::Function *CodeGenModule::CreateGlobalInitOrDestructFunction( llvm::FunctionType *FTy, const Twine &Name, const CGFunctionInfo &FI, SourceLocation Loc, bool TLS) { llvm::Function *Fn = llvm::Function::Create(FTy, llvm::GlobalValue::InternalLinkage, Name, &getModule()); if (!getLangOpts().AppleKext && !TLS) { // Set the section if needed. if (const char *Section = getTarget().getStaticInitSectionSpecifier()) Fn->setSection(Section); } SetInternalFunctionAttributes(nullptr, Fn, FI); Fn->setCallingConv(getRuntimeCC()); if (!getLangOpts().Exceptions) Fn->setDoesNotThrow(); if (!isInSanitizerBlacklist(Fn, Loc)) { if (getLangOpts().Sanitize.hasOneOf(SanitizerKind::Address | SanitizerKind::KernelAddress)) Fn->addFnAttr(llvm::Attribute::SanitizeAddress); if (getLangOpts().Sanitize.has(SanitizerKind::Thread)) Fn->addFnAttr(llvm::Attribute::SanitizeThread); if (getLangOpts().Sanitize.has(SanitizerKind::Memory)) Fn->addFnAttr(llvm::Attribute::SanitizeMemory); if (getLangOpts().Sanitize.has(SanitizerKind::SafeStack)) Fn->addFnAttr(llvm::Attribute::SafeStack); } return Fn; } /// Create a global pointer to a function that will initialize a global /// variable. The user has requested that this pointer be emitted in a specific /// section. void CodeGenModule::EmitPointerToInitFunc(const VarDecl *D, llvm::GlobalVariable *GV, llvm::Function *InitFunc, InitSegAttr *ISA) { llvm::GlobalVariable *PtrArray = new llvm::GlobalVariable( TheModule, InitFunc->getType(), /*isConstant=*/true, llvm::GlobalValue::PrivateLinkage, InitFunc, "__cxx_init_fn_ptr"); PtrArray->setSection(ISA->getSection()); addUsedGlobal(PtrArray); // If the GV is already in a comdat group, then we have to join it. if (llvm::Comdat *C = GV->getComdat()) PtrArray->setComdat(C); } void CodeGenModule::EmitCXXGlobalVarDeclInitFunc(const VarDecl *D, llvm::GlobalVariable *Addr, bool PerformInit) { // According to E.2.3.1 in CUDA-7.5 Programming guide: __device__, // __constant__ and __shared__ variables defined in namespace scope, // that are of class type, cannot have a non-empty constructor. All // the checks have been done in Sema by now. Whatever initializers // are allowed are empty and we just need to ignore them here. if (getLangOpts().CUDA && getLangOpts().CUDAIsDevice && (D->hasAttr<CUDADeviceAttr>() || D->hasAttr<CUDAConstantAttr>() || D->hasAttr<CUDASharedAttr>())) return; // Check if we've already initialized this decl. auto I = DelayedCXXInitPosition.find(D); if (I != DelayedCXXInitPosition.end() && I->second == ~0U) return; llvm::FunctionType *FTy = llvm::FunctionType::get(VoidTy, false); SmallString<256> FnName; { llvm::raw_svector_ostream Out(FnName); getCXXABI().getMangleContext().mangleDynamicInitializer(D, Out); } // Create a variable initialization function. llvm::Function *Fn = CreateGlobalInitOrDestructFunction(FTy, FnName.str(), getTypes().arrangeNullaryFunction(), D->getLocation()); auto *ISA = D->getAttr<InitSegAttr>(); CodeGenFunction(*this).GenerateCXXGlobalVarDeclInitFunc(Fn, D, Addr, PerformInit); llvm::GlobalVariable *COMDATKey = supportsCOMDAT() && D->isExternallyVisible() ? Addr : nullptr; if (D->getTLSKind()) { // FIXME: Should we support init_priority for thread_local? // FIXME: Ideally, initialization of instantiated thread_local static data // members of class templates should not trigger initialization of other // entities in the TU. // FIXME: We only need to register one __cxa_thread_atexit function for the // entire TU. CXXThreadLocalInits.push_back(Fn); CXXThreadLocalInitVars.push_back(D); } else if (PerformInit && ISA) { EmitPointerToInitFunc(D, Addr, Fn, ISA); } else if (auto *IPA = D->getAttr<InitPriorityAttr>()) { OrderGlobalInits Key(IPA->getPriority(), PrioritizedCXXGlobalInits.size()); PrioritizedCXXGlobalInits.push_back(std::make_pair(Key, Fn)); } else if (isTemplateInstantiation(D->getTemplateSpecializationKind())) { // C++ [basic.start.init]p2: // Definitions of explicitly specialized class template static data // members have ordered initialization. Other class template static data // members (i.e., implicitly or explicitly instantiated specializations) // have unordered initialization. // // As a consequence, we can put them into their own llvm.global_ctors entry. // // If the global is externally visible, put the initializer into a COMDAT // group with the global being initialized. On most platforms, this is a // minor startup time optimization. In the MS C++ ABI, there are no guard // variables, so this COMDAT key is required for correctness. AddGlobalCtor(Fn, 65535, COMDATKey); } else if (D->hasAttr<SelectAnyAttr>()) { // SelectAny globals will be comdat-folded. Put the initializer into a // COMDAT group associated with the global, so the initializers get folded // too. AddGlobalCtor(Fn, 65535, COMDATKey); } else { I = DelayedCXXInitPosition.find(D); // Re-do lookup in case of re-hash. if (I == DelayedCXXInitPosition.end()) { CXXGlobalInits.push_back(Fn); } else if (I->second != ~0U) { assert(I->second < CXXGlobalInits.size() && CXXGlobalInits[I->second] == nullptr); CXXGlobalInits[I->second] = Fn; } } // Remember that we already emitted the initializer for this global. DelayedCXXInitPosition[D] = ~0U; } void CodeGenModule::EmitCXXThreadLocalInitFunc() { getCXXABI().EmitThreadLocalInitFuncs( *this, CXXThreadLocals, CXXThreadLocalInits, CXXThreadLocalInitVars); CXXThreadLocalInits.clear(); CXXThreadLocalInitVars.clear(); CXXThreadLocals.clear(); } void CodeGenModule::EmitCXXGlobalInitFunc() { while (!CXXGlobalInits.empty() && !CXXGlobalInits.back()) CXXGlobalInits.pop_back(); if (CXXGlobalInits.empty() && PrioritizedCXXGlobalInits.empty()) return; llvm::FunctionType *FTy = llvm::FunctionType::get(VoidTy, false); const CGFunctionInfo &FI = getTypes().arrangeNullaryFunction(); // Create our global initialization function. if (!PrioritizedCXXGlobalInits.empty()) { SmallVector<llvm::Function *, 8> LocalCXXGlobalInits; llvm::array_pod_sort(PrioritizedCXXGlobalInits.begin(), PrioritizedCXXGlobalInits.end()); // Iterate over "chunks" of ctors with same priority and emit each chunk // into separate function. Note - everything is sorted first by priority, // second - by lex order, so we emit ctor functions in proper order. for (SmallVectorImpl<GlobalInitData >::iterator I = PrioritizedCXXGlobalInits.begin(), E = PrioritizedCXXGlobalInits.end(); I != E; ) { SmallVectorImpl<GlobalInitData >::iterator PrioE = std::upper_bound(I + 1, E, *I, GlobalInitPriorityCmp()); LocalCXXGlobalInits.clear(); unsigned Priority = I->first.priority; // Compute the function suffix from priority. Prepend with zeroes to make // sure the function names are also ordered as priorities. std::string PrioritySuffix = llvm::utostr(Priority); // Priority is always <= 65535 (enforced by sema). PrioritySuffix = std::string(6-PrioritySuffix.size(), '0')+PrioritySuffix; llvm::Function *Fn = CreateGlobalInitOrDestructFunction( FTy, "_GLOBAL__I_" + PrioritySuffix, FI); for (; I < PrioE; ++I) LocalCXXGlobalInits.push_back(I->second); CodeGenFunction(*this).GenerateCXXGlobalInitFunc(Fn, LocalCXXGlobalInits); AddGlobalCtor(Fn, Priority); } PrioritizedCXXGlobalInits.clear(); } SmallString<128> FileName; SourceManager &SM = Context.getSourceManager(); if (const FileEntry *MainFile = SM.getFileEntryForID(SM.getMainFileID())) { // Include the filename in the symbol name. Including "sub_" matches gcc and // makes sure these symbols appear lexicographically behind the symbols with // priority emitted above. FileName = llvm::sys::path::filename(MainFile->getName()); } else { FileName = "<null>"; } for (size_t i = 0; i < FileName.size(); ++i) { // Replace everything that's not [a-zA-Z0-9._] with a _. This set happens // to be the set of C preprocessing numbers. if (!isPreprocessingNumberBody(FileName[i])) FileName[i] = '_'; } llvm::Function *Fn = CreateGlobalInitOrDestructFunction( FTy, llvm::Twine("_GLOBAL__sub_I_", FileName), FI); CodeGenFunction(*this).GenerateCXXGlobalInitFunc(Fn, CXXGlobalInits); AddGlobalCtor(Fn); CXXGlobalInits.clear(); } void CodeGenModule::EmitCXXGlobalDtorFunc() { if (CXXGlobalDtors.empty()) return; llvm::FunctionType *FTy = llvm::FunctionType::get(VoidTy, false); // Create our global destructor function. const CGFunctionInfo &FI = getTypes().arrangeNullaryFunction(); llvm::Function *Fn = CreateGlobalInitOrDestructFunction(FTy, "_GLOBAL__D_a", FI); CodeGenFunction(*this).GenerateCXXGlobalDtorsFunc(Fn, CXXGlobalDtors); AddGlobalDtor(Fn); } /// Emit the code necessary to initialize the given global variable. void CodeGenFunction::GenerateCXXGlobalVarDeclInitFunc(llvm::Function *Fn, const VarDecl *D, llvm::GlobalVariable *Addr, bool PerformInit) { // Check if we need to emit debug info for variable initializer. if (D->hasAttr<NoDebugAttr>()) DebugInfo = nullptr; // disable debug info indefinitely for this function CurEHLocation = D->getLocStart(); StartFunction(GlobalDecl(D), getContext().VoidTy, Fn, getTypes().arrangeNullaryFunction(), FunctionArgList(), D->getLocation(), D->getInit()->getExprLoc()); // Use guarded initialization if the global variable is weak. This // occurs for, e.g., instantiated static data members and // definitions explicitly marked weak. if (Addr->hasWeakLinkage() || Addr->hasLinkOnceLinkage()) { EmitCXXGuardedInit(*D, Addr, PerformInit); } else { EmitCXXGlobalVarDeclInit(*D, Addr, PerformInit); } FinishFunction(); } void CodeGenFunction::GenerateCXXGlobalInitFunc(llvm::Function *Fn, ArrayRef<llvm::Function *> Decls, Address Guard) { { auto NL = ApplyDebugLocation::CreateEmpty(*this); StartFunction(GlobalDecl(), getContext().VoidTy, Fn, getTypes().arrangeNullaryFunction(), FunctionArgList()); // Emit an artificial location for this function. auto AL = ApplyDebugLocation::CreateArtificial(*this); llvm::BasicBlock *ExitBlock = nullptr; if (Guard.isValid()) { // If we have a guard variable, check whether we've already performed // these initializations. This happens for TLS initialization functions. llvm::Value *GuardVal = Builder.CreateLoad(Guard); llvm::Value *Uninit = Builder.CreateIsNull(GuardVal, "guard.uninitialized"); llvm::BasicBlock *InitBlock = createBasicBlock("init"); ExitBlock = createBasicBlock("exit"); Builder.CreateCondBr(Uninit, InitBlock, ExitBlock); EmitBlock(InitBlock); // Mark as initialized before initializing anything else. If the // initializers use previously-initialized thread_local vars, that's // probably supposed to be OK, but the standard doesn't say. Builder.CreateStore(llvm::ConstantInt::get(GuardVal->getType(),1), Guard); } RunCleanupsScope Scope(*this); // When building in Objective-C++ ARC mode, create an autorelease pool // around the global initializers. if (getLangOpts().ObjCAutoRefCount && getLangOpts().CPlusPlus) { llvm::Value *token = EmitObjCAutoreleasePoolPush(); EmitObjCAutoreleasePoolCleanup(token); } for (unsigned i = 0, e = Decls.size(); i != e; ++i) if (Decls[i]) EmitRuntimeCall(Decls[i]); Scope.ForceCleanup(); if (ExitBlock) { Builder.CreateBr(ExitBlock); EmitBlock(ExitBlock); } } FinishFunction(); } void CodeGenFunction::GenerateCXXGlobalDtorsFunc(llvm::Function *Fn, const std::vector<std::pair<llvm::WeakVH, llvm::Constant*> > &DtorsAndObjects) { { auto NL = ApplyDebugLocation::CreateEmpty(*this); StartFunction(GlobalDecl(), getContext().VoidTy, Fn, getTypes().arrangeNullaryFunction(), FunctionArgList()); // Emit an artificial location for this function. auto AL = ApplyDebugLocation::CreateArtificial(*this); // Emit the dtors, in reverse order from construction. for (unsigned i = 0, e = DtorsAndObjects.size(); i != e; ++i) { llvm::Value *Callee = DtorsAndObjects[e - i - 1].first; llvm::CallInst *CI = Builder.CreateCall(Callee, DtorsAndObjects[e - i - 1].second); // Make sure the call and the callee agree on calling convention. if (llvm::Function *F = dyn_cast<llvm::Function>(Callee)) CI->setCallingConv(F->getCallingConv()); } } FinishFunction(); } /// generateDestroyHelper - Generates a helper function which, when /// invoked, destroys the given object. The address of the object /// should be in global memory. llvm::Function *CodeGenFunction::generateDestroyHelper( Address addr, QualType type, Destroyer *destroyer, bool useEHCleanupForArray, const VarDecl *VD) { FunctionArgList args; ImplicitParamDecl dst(getContext(), nullptr, SourceLocation(), nullptr, getContext().VoidPtrTy); args.push_back(&dst); const CGFunctionInfo &FI = CGM.getTypes().arrangeBuiltinFunctionDeclaration(getContext().VoidTy, args); llvm::FunctionType *FTy = CGM.getTypes().GetFunctionType(FI); llvm::Function *fn = CGM.CreateGlobalInitOrDestructFunction( FTy, "__cxx_global_array_dtor", FI, VD->getLocation()); CurEHLocation = VD->getLocStart(); StartFunction(VD, getContext().VoidTy, fn, FI, args); emitDestroy(addr, type, destroyer, useEHCleanupForArray); FinishFunction(); return fn; }