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Diffstat (limited to 'contrib/llvm-project/clang/lib/CodeGen/CGVTables.cpp')
| -rw-r--r-- | contrib/llvm-project/clang/lib/CodeGen/CGVTables.cpp | 1355 |
1 files changed, 1355 insertions, 0 deletions
diff --git a/contrib/llvm-project/clang/lib/CodeGen/CGVTables.cpp b/contrib/llvm-project/clang/lib/CodeGen/CGVTables.cpp new file mode 100644 index 000000000000..a0b5d9e4b096 --- /dev/null +++ b/contrib/llvm-project/clang/lib/CodeGen/CGVTables.cpp @@ -0,0 +1,1355 @@ +//===--- CGVTables.cpp - Emit LLVM Code for C++ vtables -------------------===// +// +// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. +// See https://llvm.org/LICENSE.txt for license information. +// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception +// +//===----------------------------------------------------------------------===// +// +// This contains code dealing with C++ code generation of virtual tables. +// +//===----------------------------------------------------------------------===// + +#include "CGCXXABI.h" +#include "CodeGenFunction.h" +#include "CodeGenModule.h" +#include "clang/AST/Attr.h" +#include "clang/AST/CXXInheritance.h" +#include "clang/AST/RecordLayout.h" +#include "clang/Basic/CodeGenOptions.h" +#include "clang/CodeGen/CGFunctionInfo.h" +#include "clang/CodeGen/ConstantInitBuilder.h" +#include "llvm/IR/IntrinsicInst.h" +#include "llvm/Support/Format.h" +#include "llvm/Transforms/Utils/Cloning.h" +#include <algorithm> +#include <cstdio> + +using namespace clang; +using namespace CodeGen; + +CodeGenVTables::CodeGenVTables(CodeGenModule &CGM) + : CGM(CGM), VTContext(CGM.getContext().getVTableContext()) {} + +llvm::Constant *CodeGenModule::GetAddrOfThunk(StringRef Name, llvm::Type *FnTy, + GlobalDecl GD) { + return GetOrCreateLLVMFunction(Name, FnTy, GD, /*ForVTable=*/true, + /*DontDefer=*/true, /*IsThunk=*/true); +} + +static void setThunkProperties(CodeGenModule &CGM, const ThunkInfo &Thunk, + llvm::Function *ThunkFn, bool ForVTable, + GlobalDecl GD) { + CGM.setFunctionLinkage(GD, ThunkFn); + CGM.getCXXABI().setThunkLinkage(ThunkFn, ForVTable, GD, + !Thunk.Return.isEmpty()); + + // Set the right visibility. + CGM.setGVProperties(ThunkFn, GD); + + if (!CGM.getCXXABI().exportThunk()) { + ThunkFn->setDLLStorageClass(llvm::GlobalValue::DefaultStorageClass); + ThunkFn->setDSOLocal(true); + } + + if (CGM.supportsCOMDAT() && ThunkFn->isWeakForLinker()) + ThunkFn->setComdat(CGM.getModule().getOrInsertComdat(ThunkFn->getName())); +} + +#ifndef NDEBUG +static bool similar(const ABIArgInfo &infoL, CanQualType typeL, + const ABIArgInfo &infoR, CanQualType typeR) { + return (infoL.getKind() == infoR.getKind() && + (typeL == typeR || + (isa<PointerType>(typeL) && isa<PointerType>(typeR)) || + (isa<ReferenceType>(typeL) && isa<ReferenceType>(typeR)))); +} +#endif + +static RValue PerformReturnAdjustment(CodeGenFunction &CGF, + QualType ResultType, RValue RV, + const ThunkInfo &Thunk) { + // Emit the return adjustment. + bool NullCheckValue = !ResultType->isReferenceType(); + + llvm::BasicBlock *AdjustNull = nullptr; + llvm::BasicBlock *AdjustNotNull = nullptr; + llvm::BasicBlock *AdjustEnd = nullptr; + + llvm::Value *ReturnValue = RV.getScalarVal(); + + if (NullCheckValue) { + AdjustNull = CGF.createBasicBlock("adjust.null"); + AdjustNotNull = CGF.createBasicBlock("adjust.notnull"); + AdjustEnd = CGF.createBasicBlock("adjust.end"); + + llvm::Value *IsNull = CGF.Builder.CreateIsNull(ReturnValue); + CGF.Builder.CreateCondBr(IsNull, AdjustNull, AdjustNotNull); + CGF.EmitBlock(AdjustNotNull); + } + + auto ClassDecl = ResultType->getPointeeType()->getAsCXXRecordDecl(); + auto ClassAlign = CGF.CGM.getClassPointerAlignment(ClassDecl); + ReturnValue = CGF.CGM.getCXXABI().performReturnAdjustment( + CGF, + Address(ReturnValue, CGF.ConvertTypeForMem(ResultType->getPointeeType()), + ClassAlign), + Thunk.Return); + + if (NullCheckValue) { + CGF.Builder.CreateBr(AdjustEnd); + CGF.EmitBlock(AdjustNull); + CGF.Builder.CreateBr(AdjustEnd); + CGF.EmitBlock(AdjustEnd); + + llvm::PHINode *PHI = CGF.Builder.CreatePHI(ReturnValue->getType(), 2); + PHI->addIncoming(ReturnValue, AdjustNotNull); + PHI->addIncoming(llvm::Constant::getNullValue(ReturnValue->getType()), + AdjustNull); + ReturnValue = PHI; + } + + return RValue::get(ReturnValue); +} + +/// This function clones a function's DISubprogram node and enters it into +/// a value map with the intent that the map can be utilized by the cloner +/// to short-circuit Metadata node mapping. +/// Furthermore, the function resolves any DILocalVariable nodes referenced +/// by dbg.value intrinsics so they can be properly mapped during cloning. +static void resolveTopLevelMetadata(llvm::Function *Fn, + llvm::ValueToValueMapTy &VMap) { + // Clone the DISubprogram node and put it into the Value map. + auto *DIS = Fn->getSubprogram(); + if (!DIS) + return; + auto *NewDIS = DIS->replaceWithDistinct(DIS->clone()); + VMap.MD()[DIS].reset(NewDIS); + + // Find all llvm.dbg.declare intrinsics and resolve the DILocalVariable nodes + // they are referencing. + for (auto &BB : *Fn) { + for (auto &I : BB) { + if (auto *DII = dyn_cast<llvm::DbgVariableIntrinsic>(&I)) { + auto *DILocal = DII->getVariable(); + if (!DILocal->isResolved()) + DILocal->resolve(); + } + } + } +} + +// This function does roughly the same thing as GenerateThunk, but in a +// very different way, so that va_start and va_end work correctly. +// FIXME: This function assumes "this" is the first non-sret LLVM argument of +// a function, and that there is an alloca built in the entry block +// for all accesses to "this". +// FIXME: This function assumes there is only one "ret" statement per function. +// FIXME: Cloning isn't correct in the presence of indirect goto! +// FIXME: This implementation of thunks bloats codesize by duplicating the +// function definition. There are alternatives: +// 1. Add some sort of stub support to LLVM for cases where we can +// do a this adjustment, then a sibcall. +// 2. We could transform the definition to take a va_list instead of an +// actual variable argument list, then have the thunks (including a +// no-op thunk for the regular definition) call va_start/va_end. +// There's a bit of per-call overhead for this solution, but it's +// better for codesize if the definition is long. +llvm::Function * +CodeGenFunction::GenerateVarArgsThunk(llvm::Function *Fn, + const CGFunctionInfo &FnInfo, + GlobalDecl GD, const ThunkInfo &Thunk) { + const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl()); + const FunctionProtoType *FPT = MD->getType()->castAs<FunctionProtoType>(); + QualType ResultType = FPT->getReturnType(); + + // Get the original function + assert(FnInfo.isVariadic()); + llvm::Type *Ty = CGM.getTypes().GetFunctionType(FnInfo); + llvm::Value *Callee = CGM.GetAddrOfFunction(GD, Ty, /*ForVTable=*/true); + llvm::Function *BaseFn = cast<llvm::Function>(Callee); + + // Cloning can't work if we don't have a definition. The Microsoft ABI may + // require thunks when a definition is not available. Emit an error in these + // cases. + if (!MD->isDefined()) { + CGM.ErrorUnsupported(MD, "return-adjusting thunk with variadic arguments"); + return Fn; + } + assert(!BaseFn->isDeclaration() && "cannot clone undefined variadic method"); + + // Clone to thunk. + llvm::ValueToValueMapTy VMap; + + // We are cloning a function while some Metadata nodes are still unresolved. + // Ensure that the value mapper does not encounter any of them. + resolveTopLevelMetadata(BaseFn, VMap); + llvm::Function *NewFn = llvm::CloneFunction(BaseFn, VMap); + Fn->replaceAllUsesWith(NewFn); + NewFn->takeName(Fn); + Fn->eraseFromParent(); + Fn = NewFn; + + // "Initialize" CGF (minimally). + CurFn = Fn; + + // Get the "this" value + llvm::Function::arg_iterator AI = Fn->arg_begin(); + if (CGM.ReturnTypeUsesSRet(FnInfo)) + ++AI; + + // Find the first store of "this", which will be to the alloca associated + // with "this". + Address ThisPtr = + Address(&*AI, ConvertTypeForMem(MD->getThisType()->getPointeeType()), + CGM.getClassPointerAlignment(MD->getParent())); + llvm::BasicBlock *EntryBB = &Fn->front(); + llvm::BasicBlock::iterator ThisStore = + llvm::find_if(*EntryBB, [&](llvm::Instruction &I) { + return isa<llvm::StoreInst>(I) && + I.getOperand(0) == ThisPtr.getPointer(); + }); + assert(ThisStore != EntryBB->end() && + "Store of this should be in entry block?"); + // Adjust "this", if necessary. + Builder.SetInsertPoint(&*ThisStore); + llvm::Value *AdjustedThisPtr = + CGM.getCXXABI().performThisAdjustment(*this, ThisPtr, Thunk.This); + AdjustedThisPtr = Builder.CreateBitCast(AdjustedThisPtr, + ThisStore->getOperand(0)->getType()); + ThisStore->setOperand(0, AdjustedThisPtr); + + if (!Thunk.Return.isEmpty()) { + // Fix up the returned value, if necessary. + for (llvm::BasicBlock &BB : *Fn) { + llvm::Instruction *T = BB.getTerminator(); + if (isa<llvm::ReturnInst>(T)) { + RValue RV = RValue::get(T->getOperand(0)); + T->eraseFromParent(); + Builder.SetInsertPoint(&BB); + RV = PerformReturnAdjustment(*this, ResultType, RV, Thunk); + Builder.CreateRet(RV.getScalarVal()); + break; + } + } + } + + return Fn; +} + +void CodeGenFunction::StartThunk(llvm::Function *Fn, GlobalDecl GD, + const CGFunctionInfo &FnInfo, + bool IsUnprototyped) { + assert(!CurGD.getDecl() && "CurGD was already set!"); + CurGD = GD; + CurFuncIsThunk = true; + + // Build FunctionArgs. + const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl()); + QualType ThisType = MD->getThisType(); + QualType ResultType; + if (IsUnprototyped) + ResultType = CGM.getContext().VoidTy; + else if (CGM.getCXXABI().HasThisReturn(GD)) + ResultType = ThisType; + else if (CGM.getCXXABI().hasMostDerivedReturn(GD)) + ResultType = CGM.getContext().VoidPtrTy; + else + ResultType = MD->getType()->castAs<FunctionProtoType>()->getReturnType(); + FunctionArgList FunctionArgs; + + // Create the implicit 'this' parameter declaration. + CGM.getCXXABI().buildThisParam(*this, FunctionArgs); + + // Add the rest of the parameters, if we have a prototype to work with. + if (!IsUnprototyped) { + FunctionArgs.append(MD->param_begin(), MD->param_end()); + + if (isa<CXXDestructorDecl>(MD)) + CGM.getCXXABI().addImplicitStructorParams(*this, ResultType, + FunctionArgs); + } + + // Start defining the function. + auto NL = ApplyDebugLocation::CreateEmpty(*this); + StartFunction(GlobalDecl(), ResultType, Fn, FnInfo, FunctionArgs, + MD->getLocation()); + // Create a scope with an artificial location for the body of this function. + auto AL = ApplyDebugLocation::CreateArtificial(*this); + + // Since we didn't pass a GlobalDecl to StartFunction, do this ourselves. + CGM.getCXXABI().EmitInstanceFunctionProlog(*this); + CXXThisValue = CXXABIThisValue; + CurCodeDecl = MD; + CurFuncDecl = MD; +} + +void CodeGenFunction::FinishThunk() { + // Clear these to restore the invariants expected by + // StartFunction/FinishFunction. + CurCodeDecl = nullptr; + CurFuncDecl = nullptr; + + FinishFunction(); +} + +void CodeGenFunction::EmitCallAndReturnForThunk(llvm::FunctionCallee Callee, + const ThunkInfo *Thunk, + bool IsUnprototyped) { + assert(isa<CXXMethodDecl>(CurGD.getDecl()) && + "Please use a new CGF for this thunk"); + const CXXMethodDecl *MD = cast<CXXMethodDecl>(CurGD.getDecl()); + + // Adjust the 'this' pointer if necessary + llvm::Value *AdjustedThisPtr = + Thunk ? CGM.getCXXABI().performThisAdjustment( + *this, LoadCXXThisAddress(), Thunk->This) + : LoadCXXThis(); + + // If perfect forwarding is required a variadic method, a method using + // inalloca, or an unprototyped thunk, use musttail. Emit an error if this + // thunk requires a return adjustment, since that is impossible with musttail. + if (CurFnInfo->usesInAlloca() || CurFnInfo->isVariadic() || IsUnprototyped) { + if (Thunk && !Thunk->Return.isEmpty()) { + if (IsUnprototyped) + CGM.ErrorUnsupported( + MD, "return-adjusting thunk with incomplete parameter type"); + else if (CurFnInfo->isVariadic()) + llvm_unreachable("shouldn't try to emit musttail return-adjusting " + "thunks for variadic functions"); + else + CGM.ErrorUnsupported( + MD, "non-trivial argument copy for return-adjusting thunk"); + } + EmitMustTailThunk(CurGD, AdjustedThisPtr, Callee); + return; + } + + // Start building CallArgs. + CallArgList CallArgs; + QualType ThisType = MD->getThisType(); + CallArgs.add(RValue::get(AdjustedThisPtr), ThisType); + + if (isa<CXXDestructorDecl>(MD)) + CGM.getCXXABI().adjustCallArgsForDestructorThunk(*this, CurGD, CallArgs); + +#ifndef NDEBUG + unsigned PrefixArgs = CallArgs.size() - 1; +#endif + // Add the rest of the arguments. + for (const ParmVarDecl *PD : MD->parameters()) + EmitDelegateCallArg(CallArgs, PD, SourceLocation()); + + const FunctionProtoType *FPT = MD->getType()->castAs<FunctionProtoType>(); + +#ifndef NDEBUG + const CGFunctionInfo &CallFnInfo = CGM.getTypes().arrangeCXXMethodCall( + CallArgs, FPT, RequiredArgs::forPrototypePlus(FPT, 1), PrefixArgs); + assert(CallFnInfo.getRegParm() == CurFnInfo->getRegParm() && + CallFnInfo.isNoReturn() == CurFnInfo->isNoReturn() && + CallFnInfo.getCallingConvention() == CurFnInfo->getCallingConvention()); + assert(isa<CXXDestructorDecl>(MD) || // ignore dtor return types + similar(CallFnInfo.getReturnInfo(), CallFnInfo.getReturnType(), + CurFnInfo->getReturnInfo(), CurFnInfo->getReturnType())); + assert(CallFnInfo.arg_size() == CurFnInfo->arg_size()); + for (unsigned i = 0, e = CurFnInfo->arg_size(); i != e; ++i) + assert(similar(CallFnInfo.arg_begin()[i].info, + CallFnInfo.arg_begin()[i].type, + CurFnInfo->arg_begin()[i].info, + CurFnInfo->arg_begin()[i].type)); +#endif + + // Determine whether we have a return value slot to use. + QualType ResultType = CGM.getCXXABI().HasThisReturn(CurGD) + ? ThisType + : CGM.getCXXABI().hasMostDerivedReturn(CurGD) + ? CGM.getContext().VoidPtrTy + : FPT->getReturnType(); + ReturnValueSlot Slot; + if (!ResultType->isVoidType() && + (CurFnInfo->getReturnInfo().getKind() == ABIArgInfo::Indirect || + hasAggregateEvaluationKind(ResultType))) + Slot = ReturnValueSlot(ReturnValue, ResultType.isVolatileQualified(), + /*IsUnused=*/false, /*IsExternallyDestructed=*/true); + + // Now emit our call. + llvm::CallBase *CallOrInvoke; + RValue RV = EmitCall(*CurFnInfo, CGCallee::forDirect(Callee, CurGD), Slot, + CallArgs, &CallOrInvoke); + + // Consider return adjustment if we have ThunkInfo. + if (Thunk && !Thunk->Return.isEmpty()) + RV = PerformReturnAdjustment(*this, ResultType, RV, *Thunk); + else if (llvm::CallInst* Call = dyn_cast<llvm::CallInst>(CallOrInvoke)) + Call->setTailCallKind(llvm::CallInst::TCK_Tail); + + // Emit return. + if (!ResultType->isVoidType() && Slot.isNull()) + CGM.getCXXABI().EmitReturnFromThunk(*this, RV, ResultType); + + // Disable the final ARC autorelease. + AutoreleaseResult = false; + + FinishThunk(); +} + +void CodeGenFunction::EmitMustTailThunk(GlobalDecl GD, + llvm::Value *AdjustedThisPtr, + llvm::FunctionCallee Callee) { + // Emitting a musttail call thunk doesn't use any of the CGCall.cpp machinery + // to translate AST arguments into LLVM IR arguments. For thunks, we know + // that the caller prototype more or less matches the callee prototype with + // the exception of 'this'. + SmallVector<llvm::Value *, 8> Args(llvm::make_pointer_range(CurFn->args())); + + // Set the adjusted 'this' pointer. + const ABIArgInfo &ThisAI = CurFnInfo->arg_begin()->info; + if (ThisAI.isDirect()) { + const ABIArgInfo &RetAI = CurFnInfo->getReturnInfo(); + int ThisArgNo = RetAI.isIndirect() && !RetAI.isSRetAfterThis() ? 1 : 0; + llvm::Type *ThisType = Args[ThisArgNo]->getType(); + if (ThisType != AdjustedThisPtr->getType()) + AdjustedThisPtr = Builder.CreateBitCast(AdjustedThisPtr, ThisType); + Args[ThisArgNo] = AdjustedThisPtr; + } else { + assert(ThisAI.isInAlloca() && "this is passed directly or inalloca"); + Address ThisAddr = GetAddrOfLocalVar(CXXABIThisDecl); + llvm::Type *ThisType = ThisAddr.getElementType(); + if (ThisType != AdjustedThisPtr->getType()) + AdjustedThisPtr = Builder.CreateBitCast(AdjustedThisPtr, ThisType); + Builder.CreateStore(AdjustedThisPtr, ThisAddr); + } + + // Emit the musttail call manually. Even if the prologue pushed cleanups, we + // don't actually want to run them. + llvm::CallInst *Call = Builder.CreateCall(Callee, Args); + Call->setTailCallKind(llvm::CallInst::TCK_MustTail); + + // Apply the standard set of call attributes. + unsigned CallingConv; + llvm::AttributeList Attrs; + CGM.ConstructAttributeList(Callee.getCallee()->getName(), *CurFnInfo, GD, + Attrs, CallingConv, /*AttrOnCallSite=*/true, + /*IsThunk=*/false); + Call->setAttributes(Attrs); + Call->setCallingConv(static_cast<llvm::CallingConv::ID>(CallingConv)); + + if (Call->getType()->isVoidTy()) + Builder.CreateRetVoid(); + else + Builder.CreateRet(Call); + + // Finish the function to maintain CodeGenFunction invariants. + // FIXME: Don't emit unreachable code. + EmitBlock(createBasicBlock()); + + FinishThunk(); +} + +void CodeGenFunction::generateThunk(llvm::Function *Fn, + const CGFunctionInfo &FnInfo, GlobalDecl GD, + const ThunkInfo &Thunk, + bool IsUnprototyped) { + StartThunk(Fn, GD, FnInfo, IsUnprototyped); + // Create a scope with an artificial location for the body of this function. + auto AL = ApplyDebugLocation::CreateArtificial(*this); + + // Get our callee. Use a placeholder type if this method is unprototyped so + // that CodeGenModule doesn't try to set attributes. + llvm::Type *Ty; + if (IsUnprototyped) + Ty = llvm::StructType::get(getLLVMContext()); + else + Ty = CGM.getTypes().GetFunctionType(FnInfo); + + llvm::Constant *Callee = CGM.GetAddrOfFunction(GD, Ty, /*ForVTable=*/true); + + // Fix up the function type for an unprototyped musttail call. + if (IsUnprototyped) + Callee = llvm::ConstantExpr::getBitCast(Callee, Fn->getType()); + + // Make the call and return the result. + EmitCallAndReturnForThunk(llvm::FunctionCallee(Fn->getFunctionType(), Callee), + &Thunk, IsUnprototyped); +} + +static bool shouldEmitVTableThunk(CodeGenModule &CGM, const CXXMethodDecl *MD, + bool IsUnprototyped, bool ForVTable) { + // Always emit thunks in the MS C++ ABI. We cannot rely on other TUs to + // provide thunks for us. + if (CGM.getTarget().getCXXABI().isMicrosoft()) + return true; + + // In the Itanium C++ ABI, vtable thunks are provided by TUs that provide + // definitions of the main method. Therefore, emitting thunks with the vtable + // is purely an optimization. Emit the thunk if optimizations are enabled and + // all of the parameter types are complete. + if (ForVTable) + return CGM.getCodeGenOpts().OptimizationLevel && !IsUnprototyped; + + // Always emit thunks along with the method definition. + return true; +} + +llvm::Constant *CodeGenVTables::maybeEmitThunk(GlobalDecl GD, + const ThunkInfo &TI, + bool ForVTable) { + const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl()); + + // First, get a declaration. Compute the mangled name. Don't worry about + // getting the function prototype right, since we may only need this + // declaration to fill in a vtable slot. + SmallString<256> Name; + MangleContext &MCtx = CGM.getCXXABI().getMangleContext(); + llvm::raw_svector_ostream Out(Name); + if (const CXXDestructorDecl *DD = dyn_cast<CXXDestructorDecl>(MD)) + MCtx.mangleCXXDtorThunk(DD, GD.getDtorType(), TI.This, Out); + else + MCtx.mangleThunk(MD, TI, Out); + llvm::Type *ThunkVTableTy = CGM.getTypes().GetFunctionTypeForVTable(GD); + llvm::Constant *Thunk = CGM.GetAddrOfThunk(Name, ThunkVTableTy, GD); + + // If we don't need to emit a definition, return this declaration as is. + bool IsUnprototyped = !CGM.getTypes().isFuncTypeConvertible( + MD->getType()->castAs<FunctionType>()); + if (!shouldEmitVTableThunk(CGM, MD, IsUnprototyped, ForVTable)) + return Thunk; + + // Arrange a function prototype appropriate for a function definition. In some + // cases in the MS ABI, we may need to build an unprototyped musttail thunk. + const CGFunctionInfo &FnInfo = + IsUnprototyped ? CGM.getTypes().arrangeUnprototypedMustTailThunk(MD) + : CGM.getTypes().arrangeGlobalDeclaration(GD); + llvm::FunctionType *ThunkFnTy = CGM.getTypes().GetFunctionType(FnInfo); + + // If the type of the underlying GlobalValue is wrong, we'll have to replace + // it. It should be a declaration. + llvm::Function *ThunkFn = cast<llvm::Function>(Thunk->stripPointerCasts()); + if (ThunkFn->getFunctionType() != ThunkFnTy) { + llvm::GlobalValue *OldThunkFn = ThunkFn; + + assert(OldThunkFn->isDeclaration() && "Shouldn't replace non-declaration"); + + // Remove the name from the old thunk function and get a new thunk. + OldThunkFn->setName(StringRef()); + ThunkFn = llvm::Function::Create(ThunkFnTy, llvm::Function::ExternalLinkage, + Name.str(), &CGM.getModule()); + CGM.SetLLVMFunctionAttributes(MD, FnInfo, ThunkFn, /*IsThunk=*/false); + + // If needed, replace the old thunk with a bitcast. + if (!OldThunkFn->use_empty()) { + llvm::Constant *NewPtrForOldDecl = + llvm::ConstantExpr::getBitCast(ThunkFn, OldThunkFn->getType()); + OldThunkFn->replaceAllUsesWith(NewPtrForOldDecl); + } + + // Remove the old thunk. + OldThunkFn->eraseFromParent(); + } + + bool ABIHasKeyFunctions = CGM.getTarget().getCXXABI().hasKeyFunctions(); + bool UseAvailableExternallyLinkage = ForVTable && ABIHasKeyFunctions; + + if (!ThunkFn->isDeclaration()) { + if (!ABIHasKeyFunctions || UseAvailableExternallyLinkage) { + // There is already a thunk emitted for this function, do nothing. + return ThunkFn; + } + + setThunkProperties(CGM, TI, ThunkFn, ForVTable, GD); + return ThunkFn; + } + + // If this will be unprototyped, add the "thunk" attribute so that LLVM knows + // that the return type is meaningless. These thunks can be used to call + // functions with differing return types, and the caller is required to cast + // the prototype appropriately to extract the correct value. + if (IsUnprototyped) + ThunkFn->addFnAttr("thunk"); + + CGM.SetLLVMFunctionAttributesForDefinition(GD.getDecl(), ThunkFn); + + // Thunks for variadic methods are special because in general variadic + // arguments cannot be perfectly forwarded. In the general case, clang + // implements such thunks by cloning the original function body. However, for + // thunks with no return adjustment on targets that support musttail, we can + // use musttail to perfectly forward the variadic arguments. + bool ShouldCloneVarArgs = false; + if (!IsUnprototyped && ThunkFn->isVarArg()) { + ShouldCloneVarArgs = true; + if (TI.Return.isEmpty()) { + switch (CGM.getTriple().getArch()) { + case llvm::Triple::x86_64: + case llvm::Triple::x86: + case llvm::Triple::aarch64: + ShouldCloneVarArgs = false; + break; + default: + break; + } + } + } + + if (ShouldCloneVarArgs) { + if (UseAvailableExternallyLinkage) + return ThunkFn; + ThunkFn = + CodeGenFunction(CGM).GenerateVarArgsThunk(ThunkFn, FnInfo, GD, TI); + } else { + // Normal thunk body generation. + CodeGenFunction(CGM).generateThunk(ThunkFn, FnInfo, GD, TI, IsUnprototyped); + } + + setThunkProperties(CGM, TI, ThunkFn, ForVTable, GD); + return ThunkFn; +} + +void CodeGenVTables::EmitThunks(GlobalDecl GD) { + const CXXMethodDecl *MD = + cast<CXXMethodDecl>(GD.getDecl())->getCanonicalDecl(); + + // We don't need to generate thunks for the base destructor. + if (isa<CXXDestructorDecl>(MD) && GD.getDtorType() == Dtor_Base) + return; + + const VTableContextBase::ThunkInfoVectorTy *ThunkInfoVector = + VTContext->getThunkInfo(GD); + + if (!ThunkInfoVector) + return; + + for (const ThunkInfo& Thunk : *ThunkInfoVector) + maybeEmitThunk(GD, Thunk, /*ForVTable=*/false); +} + +void CodeGenVTables::addRelativeComponent(ConstantArrayBuilder &builder, + llvm::Constant *component, + unsigned vtableAddressPoint, + bool vtableHasLocalLinkage, + bool isCompleteDtor) const { + // No need to get the offset of a nullptr. + if (component->isNullValue()) + return builder.add(llvm::ConstantInt::get(CGM.Int32Ty, 0)); + + auto *globalVal = + cast<llvm::GlobalValue>(component->stripPointerCastsAndAliases()); + llvm::Module &module = CGM.getModule(); + + // We don't want to copy the linkage of the vtable exactly because we still + // want the stub/proxy to be emitted for properly calculating the offset. + // Examples where there would be no symbol emitted are available_externally + // and private linkages. + auto stubLinkage = vtableHasLocalLinkage ? llvm::GlobalValue::InternalLinkage + : llvm::GlobalValue::ExternalLinkage; + + llvm::Constant *target; + if (auto *func = dyn_cast<llvm::Function>(globalVal)) { + target = llvm::DSOLocalEquivalent::get(func); + } else { + llvm::SmallString<16> rttiProxyName(globalVal->getName()); + rttiProxyName.append(".rtti_proxy"); + + // The RTTI component may not always be emitted in the same linkage unit as + // the vtable. As a general case, we can make a dso_local proxy to the RTTI + // that points to the actual RTTI struct somewhere. This will result in a + // GOTPCREL relocation when taking the relative offset to the proxy. + llvm::GlobalVariable *proxy = module.getNamedGlobal(rttiProxyName); + if (!proxy) { + proxy = new llvm::GlobalVariable(module, globalVal->getType(), + /*isConstant=*/true, stubLinkage, + globalVal, rttiProxyName); + proxy->setDSOLocal(true); + proxy->setUnnamedAddr(llvm::GlobalValue::UnnamedAddr::Global); + if (!proxy->hasLocalLinkage()) { + proxy->setVisibility(llvm::GlobalValue::HiddenVisibility); + proxy->setComdat(module.getOrInsertComdat(rttiProxyName)); + } + // Do not instrument the rtti proxies with hwasan to avoid a duplicate + // symbol error. Aliases generated by hwasan will retain the same namebut + // the addresses they are set to may have different tags from different + // compilation units. We don't run into this without hwasan because the + // proxies are in comdat groups, but those aren't propagated to the alias. + RemoveHwasanMetadata(proxy); + } + target = proxy; + } + + builder.addRelativeOffsetToPosition(CGM.Int32Ty, target, + /*position=*/vtableAddressPoint); +} + +static bool UseRelativeLayout(const CodeGenModule &CGM) { + return CGM.getTarget().getCXXABI().isItaniumFamily() && + CGM.getItaniumVTableContext().isRelativeLayout(); +} + +bool CodeGenVTables::useRelativeLayout() const { + return UseRelativeLayout(CGM); +} + +llvm::Type *CodeGenModule::getVTableComponentType() const { + if (UseRelativeLayout(*this)) + return Int32Ty; + return Int8PtrTy; +} + +llvm::Type *CodeGenVTables::getVTableComponentType() const { + return CGM.getVTableComponentType(); +} + +static void AddPointerLayoutOffset(const CodeGenModule &CGM, + ConstantArrayBuilder &builder, + CharUnits offset) { + builder.add(llvm::ConstantExpr::getIntToPtr( + llvm::ConstantInt::get(CGM.PtrDiffTy, offset.getQuantity()), + CGM.Int8PtrTy)); +} + +static void AddRelativeLayoutOffset(const CodeGenModule &CGM, + ConstantArrayBuilder &builder, + CharUnits offset) { + builder.add(llvm::ConstantInt::get(CGM.Int32Ty, offset.getQuantity())); +} + +void CodeGenVTables::addVTableComponent(ConstantArrayBuilder &builder, + const VTableLayout &layout, + unsigned componentIndex, + llvm::Constant *rtti, + unsigned &nextVTableThunkIndex, + unsigned vtableAddressPoint, + bool vtableHasLocalLinkage) { + auto &component = layout.vtable_components()[componentIndex]; + + auto addOffsetConstant = + useRelativeLayout() ? AddRelativeLayoutOffset : AddPointerLayoutOffset; + + switch (component.getKind()) { + case VTableComponent::CK_VCallOffset: + return addOffsetConstant(CGM, builder, component.getVCallOffset()); + + case VTableComponent::CK_VBaseOffset: + return addOffsetConstant(CGM, builder, component.getVBaseOffset()); + + case VTableComponent::CK_OffsetToTop: + return addOffsetConstant(CGM, builder, component.getOffsetToTop()); + + case VTableComponent::CK_RTTI: + if (useRelativeLayout()) + return addRelativeComponent(builder, rtti, vtableAddressPoint, + vtableHasLocalLinkage, + /*isCompleteDtor=*/false); + else + return builder.add(llvm::ConstantExpr::getBitCast(rtti, CGM.Int8PtrTy)); + + case VTableComponent::CK_FunctionPointer: + case VTableComponent::CK_CompleteDtorPointer: + case VTableComponent::CK_DeletingDtorPointer: { + GlobalDecl GD = component.getGlobalDecl(); + + if (CGM.getLangOpts().CUDA) { + // Emit NULL for methods we can't codegen on this + // side. Otherwise we'd end up with vtable with unresolved + // references. + const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl()); + // OK on device side: functions w/ __device__ attribute + // OK on host side: anything except __device__-only functions. + bool CanEmitMethod = + CGM.getLangOpts().CUDAIsDevice + ? MD->hasAttr<CUDADeviceAttr>() + : (MD->hasAttr<CUDAHostAttr>() || !MD->hasAttr<CUDADeviceAttr>()); + if (!CanEmitMethod) + return builder.add(llvm::ConstantExpr::getNullValue(CGM.Int8PtrTy)); + // Method is acceptable, continue processing as usual. + } + + auto getSpecialVirtualFn = [&](StringRef name) -> llvm::Constant * { + // FIXME(PR43094): When merging comdat groups, lld can select a local + // symbol as the signature symbol even though it cannot be accessed + // outside that symbol's TU. The relative vtables ABI would make + // __cxa_pure_virtual and __cxa_deleted_virtual local symbols, and + // depending on link order, the comdat groups could resolve to the one + // with the local symbol. As a temporary solution, fill these components + // with zero. We shouldn't be calling these in the first place anyway. + if (useRelativeLayout()) + return llvm::ConstantPointerNull::get(CGM.Int8PtrTy); + + // For NVPTX devices in OpenMP emit special functon as null pointers, + // otherwise linking ends up with unresolved references. + if (CGM.getLangOpts().OpenMP && CGM.getLangOpts().OpenMPIsDevice && + CGM.getTriple().isNVPTX()) + return llvm::ConstantPointerNull::get(CGM.Int8PtrTy); + llvm::FunctionType *fnTy = + llvm::FunctionType::get(CGM.VoidTy, /*isVarArg=*/false); + llvm::Constant *fn = cast<llvm::Constant>( + CGM.CreateRuntimeFunction(fnTy, name).getCallee()); + if (auto f = dyn_cast<llvm::Function>(fn)) + f->setUnnamedAddr(llvm::GlobalValue::UnnamedAddr::Global); + return llvm::ConstantExpr::getBitCast(fn, CGM.Int8PtrTy); + }; + + llvm::Constant *fnPtr; + + // Pure virtual member functions. + if (cast<CXXMethodDecl>(GD.getDecl())->isPure()) { + if (!PureVirtualFn) + PureVirtualFn = + getSpecialVirtualFn(CGM.getCXXABI().GetPureVirtualCallName()); + fnPtr = PureVirtualFn; + + // Deleted virtual member functions. + } else if (cast<CXXMethodDecl>(GD.getDecl())->isDeleted()) { + if (!DeletedVirtualFn) + DeletedVirtualFn = + getSpecialVirtualFn(CGM.getCXXABI().GetDeletedVirtualCallName()); + fnPtr = DeletedVirtualFn; + + // Thunks. + } else if (nextVTableThunkIndex < layout.vtable_thunks().size() && + layout.vtable_thunks()[nextVTableThunkIndex].first == + componentIndex) { + auto &thunkInfo = layout.vtable_thunks()[nextVTableThunkIndex].second; + + nextVTableThunkIndex++; + fnPtr = maybeEmitThunk(GD, thunkInfo, /*ForVTable=*/true); + + // Otherwise we can use the method definition directly. + } else { + llvm::Type *fnTy = CGM.getTypes().GetFunctionTypeForVTable(GD); + fnPtr = CGM.GetAddrOfFunction(GD, fnTy, /*ForVTable=*/true); + } + + if (useRelativeLayout()) { + return addRelativeComponent( + builder, fnPtr, vtableAddressPoint, vtableHasLocalLinkage, + component.getKind() == VTableComponent::CK_CompleteDtorPointer); + } else + return builder.add(llvm::ConstantExpr::getBitCast(fnPtr, CGM.Int8PtrTy)); + } + + case VTableComponent::CK_UnusedFunctionPointer: + if (useRelativeLayout()) + return builder.add(llvm::ConstantExpr::getNullValue(CGM.Int32Ty)); + else + return builder.addNullPointer(CGM.Int8PtrTy); + } + + llvm_unreachable("Unexpected vtable component kind"); +} + +llvm::Type *CodeGenVTables::getVTableType(const VTableLayout &layout) { + SmallVector<llvm::Type *, 4> tys; + llvm::Type *componentType = getVTableComponentType(); + for (unsigned i = 0, e = layout.getNumVTables(); i != e; ++i) + tys.push_back(llvm::ArrayType::get(componentType, layout.getVTableSize(i))); + + return llvm::StructType::get(CGM.getLLVMContext(), tys); +} + +void CodeGenVTables::createVTableInitializer(ConstantStructBuilder &builder, + const VTableLayout &layout, + llvm::Constant *rtti, + bool vtableHasLocalLinkage) { + llvm::Type *componentType = getVTableComponentType(); + + const auto &addressPoints = layout.getAddressPointIndices(); + unsigned nextVTableThunkIndex = 0; + for (unsigned vtableIndex = 0, endIndex = layout.getNumVTables(); + vtableIndex != endIndex; ++vtableIndex) { + auto vtableElem = builder.beginArray(componentType); + + size_t vtableStart = layout.getVTableOffset(vtableIndex); + size_t vtableEnd = vtableStart + layout.getVTableSize(vtableIndex); + for (size_t componentIndex = vtableStart; componentIndex < vtableEnd; + ++componentIndex) { + addVTableComponent(vtableElem, layout, componentIndex, rtti, + nextVTableThunkIndex, addressPoints[vtableIndex], + vtableHasLocalLinkage); + } + vtableElem.finishAndAddTo(builder); + } +} + +llvm::GlobalVariable *CodeGenVTables::GenerateConstructionVTable( + const CXXRecordDecl *RD, const BaseSubobject &Base, bool BaseIsVirtual, + llvm::GlobalVariable::LinkageTypes Linkage, + VTableAddressPointsMapTy &AddressPoints) { + if (CGDebugInfo *DI = CGM.getModuleDebugInfo()) + DI->completeClassData(Base.getBase()); + + std::unique_ptr<VTableLayout> VTLayout( + getItaniumVTableContext().createConstructionVTableLayout( + Base.getBase(), Base.getBaseOffset(), BaseIsVirtual, RD)); + + // Add the address points. + AddressPoints = VTLayout->getAddressPoints(); + + // Get the mangled construction vtable name. + SmallString<256> OutName; + llvm::raw_svector_ostream Out(OutName); + cast<ItaniumMangleContext>(CGM.getCXXABI().getMangleContext()) + .mangleCXXCtorVTable(RD, Base.getBaseOffset().getQuantity(), + Base.getBase(), Out); + SmallString<256> Name(OutName); + + bool UsingRelativeLayout = getItaniumVTableContext().isRelativeLayout(); + bool VTableAliasExists = + UsingRelativeLayout && CGM.getModule().getNamedAlias(Name); + if (VTableAliasExists) { + // We previously made the vtable hidden and changed its name. + Name.append(".local"); + } + + llvm::Type *VTType = getVTableType(*VTLayout); + + // Construction vtable symbols are not part of the Itanium ABI, so we cannot + // guarantee that they actually will be available externally. Instead, when + // emitting an available_externally VTT, we provide references to an internal + // linkage construction vtable. The ABI only requires complete-object vtables + // to be the same for all instances of a type, not construction vtables. + if (Linkage == llvm::GlobalVariable::AvailableExternallyLinkage) + Linkage = llvm::GlobalVariable::InternalLinkage; + + llvm::Align Align = CGM.getDataLayout().getABITypeAlign(VTType); + + // Create the variable that will hold the construction vtable. + llvm::GlobalVariable *VTable = + CGM.CreateOrReplaceCXXRuntimeVariable(Name, VTType, Linkage, Align); + + // V-tables are always unnamed_addr. + VTable->setUnnamedAddr(llvm::GlobalValue::UnnamedAddr::Global); + + llvm::Constant *RTTI = CGM.GetAddrOfRTTIDescriptor( + CGM.getContext().getTagDeclType(Base.getBase())); + + // Create and set the initializer. + ConstantInitBuilder builder(CGM); + auto components = builder.beginStruct(); + createVTableInitializer(components, *VTLayout, RTTI, + VTable->hasLocalLinkage()); + components.finishAndSetAsInitializer(VTable); + + // Set properties only after the initializer has been set to ensure that the + // GV is treated as definition and not declaration. + assert(!VTable->isDeclaration() && "Shouldn't set properties on declaration"); + CGM.setGVProperties(VTable, RD); + + CGM.EmitVTableTypeMetadata(RD, VTable, *VTLayout.get()); + + if (UsingRelativeLayout) { + RemoveHwasanMetadata(VTable); + if (!VTable->isDSOLocal()) + GenerateRelativeVTableAlias(VTable, OutName); + } + + return VTable; +} + +// Ensure this vtable is not instrumented by hwasan. That is, a global alias is +// not generated for it. This is mainly used by the relative-vtables ABI where +// vtables instead contain 32-bit offsets between the vtable and function +// pointers. Hwasan is disabled for these vtables for now because the tag in a +// vtable pointer may fail the overflow check when resolving 32-bit PLT +// relocations. A future alternative for this would be finding which usages of +// the vtable can continue to use the untagged hwasan value without any loss of +// value in hwasan. +void CodeGenVTables::RemoveHwasanMetadata(llvm::GlobalValue *GV) const { + if (CGM.getLangOpts().Sanitize.has(SanitizerKind::HWAddress)) { + llvm::GlobalValue::SanitizerMetadata Meta; + if (GV->hasSanitizerMetadata()) + Meta = GV->getSanitizerMetadata(); + Meta.NoHWAddress = true; + GV->setSanitizerMetadata(Meta); + } +} + +// If the VTable is not dso_local, then we will not be able to indicate that +// the VTable does not need a relocation and move into rodata. A frequent +// time this can occur is for classes that should be made public from a DSO +// (like in libc++). For cases like these, we can make the vtable hidden or +// private and create a public alias with the same visibility and linkage as +// the original vtable type. +void CodeGenVTables::GenerateRelativeVTableAlias(llvm::GlobalVariable *VTable, + llvm::StringRef AliasNameRef) { + assert(getItaniumVTableContext().isRelativeLayout() && + "Can only use this if the relative vtable ABI is used"); + assert(!VTable->isDSOLocal() && "This should be called only if the vtable is " + "not guaranteed to be dso_local"); + + // If the vtable is available_externally, we shouldn't (or need to) generate + // an alias for it in the first place since the vtable won't actually by + // emitted in this compilation unit. + if (VTable->hasAvailableExternallyLinkage()) + return; + + // Create a new string in the event the alias is already the name of the + // vtable. Using the reference directly could lead to use of an inititialized + // value in the module's StringMap. + llvm::SmallString<256> AliasName(AliasNameRef); + VTable->setName(AliasName + ".local"); + + auto Linkage = VTable->getLinkage(); + assert(llvm::GlobalAlias::isValidLinkage(Linkage) && + "Invalid vtable alias linkage"); + + llvm::GlobalAlias *VTableAlias = CGM.getModule().getNamedAlias(AliasName); + if (!VTableAlias) { + VTableAlias = llvm::GlobalAlias::create(VTable->getValueType(), + VTable->getAddressSpace(), Linkage, + AliasName, &CGM.getModule()); + } else { + assert(VTableAlias->getValueType() == VTable->getValueType()); + assert(VTableAlias->getLinkage() == Linkage); + } + VTableAlias->setVisibility(VTable->getVisibility()); + VTableAlias->setUnnamedAddr(VTable->getUnnamedAddr()); + + // Both of these imply dso_local for the vtable. + if (!VTable->hasComdat()) { + // If this is in a comdat, then we shouldn't make the linkage private due to + // an issue in lld where private symbols can be used as the key symbol when + // choosing the prevelant group. This leads to "relocation refers to a + // symbol in a discarded section". + VTable->setLinkage(llvm::GlobalValue::PrivateLinkage); + } else { + // We should at least make this hidden since we don't want to expose it. + VTable->setVisibility(llvm::GlobalValue::HiddenVisibility); + } + + VTableAlias->setAliasee(VTable); +} + +static bool shouldEmitAvailableExternallyVTable(const CodeGenModule &CGM, + const CXXRecordDecl *RD) { + return CGM.getCodeGenOpts().OptimizationLevel > 0 && + CGM.getCXXABI().canSpeculativelyEmitVTable(RD); +} + +/// Compute the required linkage of the vtable for the given class. +/// +/// Note that we only call this at the end of the translation unit. +llvm::GlobalVariable::LinkageTypes +CodeGenModule::getVTableLinkage(const CXXRecordDecl *RD) { + if (!RD->isExternallyVisible()) + return llvm::GlobalVariable::InternalLinkage; + + // We're at the end of the translation unit, so the current key + // function is fully correct. + const CXXMethodDecl *keyFunction = Context.getCurrentKeyFunction(RD); + if (keyFunction && !RD->hasAttr<DLLImportAttr>()) { + // If this class has a key function, use that to determine the + // linkage of the vtable. + const FunctionDecl *def = nullptr; + if (keyFunction->hasBody(def)) + keyFunction = cast<CXXMethodDecl>(def); + + switch (keyFunction->getTemplateSpecializationKind()) { + case TSK_Undeclared: + case TSK_ExplicitSpecialization: + assert((def || CodeGenOpts.OptimizationLevel > 0 || + CodeGenOpts.getDebugInfo() != codegenoptions::NoDebugInfo) && + "Shouldn't query vtable linkage without key function, " + "optimizations, or debug info"); + if (!def && CodeGenOpts.OptimizationLevel > 0) + return llvm::GlobalVariable::AvailableExternallyLinkage; + + if (keyFunction->isInlined()) + return !Context.getLangOpts().AppleKext ? + llvm::GlobalVariable::LinkOnceODRLinkage : + llvm::Function::InternalLinkage; + + return llvm::GlobalVariable::ExternalLinkage; + + case TSK_ImplicitInstantiation: + return !Context.getLangOpts().AppleKext ? + llvm::GlobalVariable::LinkOnceODRLinkage : + llvm::Function::InternalLinkage; + + case TSK_ExplicitInstantiationDefinition: + return !Context.getLangOpts().AppleKext ? + llvm::GlobalVariable::WeakODRLinkage : + llvm::Function::InternalLinkage; + + case TSK_ExplicitInstantiationDeclaration: + llvm_unreachable("Should not have been asked to emit this"); + } + } + + // -fapple-kext mode does not support weak linkage, so we must use + // internal linkage. + if (Context.getLangOpts().AppleKext) + return llvm::Function::InternalLinkage; + + llvm::GlobalVariable::LinkageTypes DiscardableODRLinkage = + llvm::GlobalValue::LinkOnceODRLinkage; + llvm::GlobalVariable::LinkageTypes NonDiscardableODRLinkage = + llvm::GlobalValue::WeakODRLinkage; + if (RD->hasAttr<DLLExportAttr>()) { + // Cannot discard exported vtables. + DiscardableODRLinkage = NonDiscardableODRLinkage; + } else if (RD->hasAttr<DLLImportAttr>()) { + // Imported vtables are available externally. + DiscardableODRLinkage = llvm::GlobalVariable::AvailableExternallyLinkage; + NonDiscardableODRLinkage = llvm::GlobalVariable::AvailableExternallyLinkage; + } + + switch (RD->getTemplateSpecializationKind()) { + case TSK_Undeclared: + case TSK_ExplicitSpecialization: + case TSK_ImplicitInstantiation: + return DiscardableODRLinkage; + + case TSK_ExplicitInstantiationDeclaration: + // Explicit instantiations in MSVC do not provide vtables, so we must emit + // our own. + if (getTarget().getCXXABI().isMicrosoft()) + return DiscardableODRLinkage; + return shouldEmitAvailableExternallyVTable(*this, RD) + ? llvm::GlobalVariable::AvailableExternallyLinkage + : llvm::GlobalVariable::ExternalLinkage; + + case TSK_ExplicitInstantiationDefinition: + return NonDiscardableODRLinkage; + } + + llvm_unreachable("Invalid TemplateSpecializationKind!"); +} + +/// This is a callback from Sema to tell us that a particular vtable is +/// required to be emitted in this translation unit. +/// +/// This is only called for vtables that _must_ be emitted (mainly due to key +/// functions). For weak vtables, CodeGen tracks when they are needed and +/// emits them as-needed. +void CodeGenModule::EmitVTable(CXXRecordDecl *theClass) { + VTables.GenerateClassData(theClass); +} + +void +CodeGenVTables::GenerateClassData(const CXXRecordDecl *RD) { + if (CGDebugInfo *DI = CGM.getModuleDebugInfo()) + DI->completeClassData(RD); + + if (RD->getNumVBases()) + CGM.getCXXABI().emitVirtualInheritanceTables(RD); + + CGM.getCXXABI().emitVTableDefinitions(*this, RD); +} + +/// At this point in the translation unit, does it appear that can we +/// rely on the vtable being defined elsewhere in the program? +/// +/// The response is really only definitive when called at the end of +/// the translation unit. +/// +/// The only semantic restriction here is that the object file should +/// not contain a vtable definition when that vtable is defined +/// strongly elsewhere. Otherwise, we'd just like to avoid emitting +/// vtables when unnecessary. +bool CodeGenVTables::isVTableExternal(const CXXRecordDecl *RD) { + assert(RD->isDynamicClass() && "Non-dynamic classes have no VTable."); + + // We always synthesize vtables if they are needed in the MS ABI. MSVC doesn't + // emit them even if there is an explicit template instantiation. + if (CGM.getTarget().getCXXABI().isMicrosoft()) + return false; + + // If we have an explicit instantiation declaration (and not a + // definition), the vtable is defined elsewhere. + TemplateSpecializationKind TSK = RD->getTemplateSpecializationKind(); + if (TSK == TSK_ExplicitInstantiationDeclaration) + return true; + + // Otherwise, if the class is an instantiated template, the + // vtable must be defined here. + if (TSK == TSK_ImplicitInstantiation || + TSK == TSK_ExplicitInstantiationDefinition) + return false; + + // Otherwise, if the class doesn't have a key function (possibly + // anymore), the vtable must be defined here. + const CXXMethodDecl *keyFunction = CGM.getContext().getCurrentKeyFunction(RD); + if (!keyFunction) + return false; + + // Otherwise, if we don't have a definition of the key function, the + // vtable must be defined somewhere else. + return !keyFunction->hasBody(); +} + +/// Given that we're currently at the end of the translation unit, and +/// we've emitted a reference to the vtable for this class, should +/// we define that vtable? +static bool shouldEmitVTableAtEndOfTranslationUnit(CodeGenModule &CGM, + const CXXRecordDecl *RD) { + // If vtable is internal then it has to be done. + if (!CGM.getVTables().isVTableExternal(RD)) + return true; + + // If it's external then maybe we will need it as available_externally. + return shouldEmitAvailableExternallyVTable(CGM, RD); +} + +/// Given that at some point we emitted a reference to one or more +/// vtables, and that we are now at the end of the translation unit, +/// decide whether we should emit them. +void CodeGenModule::EmitDeferredVTables() { +#ifndef NDEBUG + // Remember the size of DeferredVTables, because we're going to assume + // that this entire operation doesn't modify it. + size_t savedSize = DeferredVTables.size(); +#endif + + for (const CXXRecordDecl *RD : DeferredVTables) + if (shouldEmitVTableAtEndOfTranslationUnit(*this, RD)) + VTables.GenerateClassData(RD); + else if (shouldOpportunisticallyEmitVTables()) + OpportunisticVTables.push_back(RD); + + assert(savedSize == DeferredVTables.size() && + "deferred extra vtables during vtable emission?"); + DeferredVTables.clear(); +} + +bool CodeGenModule::AlwaysHasLTOVisibilityPublic(const CXXRecordDecl *RD) { + if (RD->hasAttr<LTOVisibilityPublicAttr>() || RD->hasAttr<UuidAttr>()) + return true; + + if (!getCodeGenOpts().LTOVisibilityPublicStd) + return false; + + const DeclContext *DC = RD; + while (true) { + auto *D = cast<Decl>(DC); + DC = DC->getParent(); + if (isa<TranslationUnitDecl>(DC->getRedeclContext())) { + if (auto *ND = dyn_cast<NamespaceDecl>(D)) + if (const IdentifierInfo *II = ND->getIdentifier()) + if (II->isStr("std") || II->isStr("stdext")) + return true; + break; + } + } + + return false; +} + +bool CodeGenModule::HasHiddenLTOVisibility(const CXXRecordDecl *RD) { + LinkageInfo LV = RD->getLinkageAndVisibility(); + if (!isExternallyVisible(LV.getLinkage())) + return true; + + if (getTriple().isOSBinFormatCOFF()) { + if (RD->hasAttr<DLLExportAttr>() || RD->hasAttr<DLLImportAttr>()) + return false; + } else { + if (LV.getVisibility() != HiddenVisibility) + return false; + } + + return !AlwaysHasLTOVisibilityPublic(RD); +} + +llvm::GlobalObject::VCallVisibility CodeGenModule::GetVCallVisibilityLevel( + const CXXRecordDecl *RD, llvm::DenseSet<const CXXRecordDecl *> &Visited) { + // If we have already visited this RD (which means this is a recursive call + // since the initial call should have an empty Visited set), return the max + // visibility. The recursive calls below compute the min between the result + // of the recursive call and the current TypeVis, so returning the max here + // ensures that it will have no effect on the current TypeVis. + if (!Visited.insert(RD).second) + return llvm::GlobalObject::VCallVisibilityTranslationUnit; + + LinkageInfo LV = RD->getLinkageAndVisibility(); + llvm::GlobalObject::VCallVisibility TypeVis; + if (!isExternallyVisible(LV.getLinkage())) + TypeVis = llvm::GlobalObject::VCallVisibilityTranslationUnit; + else if (HasHiddenLTOVisibility(RD)) + TypeVis = llvm::GlobalObject::VCallVisibilityLinkageUnit; + else + TypeVis = llvm::GlobalObject::VCallVisibilityPublic; + + for (auto B : RD->bases()) + if (B.getType()->getAsCXXRecordDecl()->isDynamicClass()) + TypeVis = std::min( + TypeVis, + GetVCallVisibilityLevel(B.getType()->getAsCXXRecordDecl(), Visited)); + + for (auto B : RD->vbases()) + if (B.getType()->getAsCXXRecordDecl()->isDynamicClass()) + TypeVis = std::min( + TypeVis, + GetVCallVisibilityLevel(B.getType()->getAsCXXRecordDecl(), Visited)); + + return TypeVis; +} + +void CodeGenModule::EmitVTableTypeMetadata(const CXXRecordDecl *RD, + llvm::GlobalVariable *VTable, + const VTableLayout &VTLayout) { + if (!getCodeGenOpts().LTOUnit) + return; + + CharUnits ComponentWidth = GetTargetTypeStoreSize(getVTableComponentType()); + + typedef std::pair<const CXXRecordDecl *, unsigned> AddressPoint; + std::vector<AddressPoint> AddressPoints; + for (auto &&AP : VTLayout.getAddressPoints()) + AddressPoints.push_back(std::make_pair( + AP.first.getBase(), VTLayout.getVTableOffset(AP.second.VTableIndex) + + AP.second.AddressPointIndex)); + + // Sort the address points for determinism. + llvm::sort(AddressPoints, [this](const AddressPoint &AP1, + const AddressPoint &AP2) { + if (&AP1 == &AP2) + return false; + + std::string S1; + llvm::raw_string_ostream O1(S1); + getCXXABI().getMangleContext().mangleTypeName( + QualType(AP1.first->getTypeForDecl(), 0), O1); + O1.flush(); + + std::string S2; + llvm::raw_string_ostream O2(S2); + getCXXABI().getMangleContext().mangleTypeName( + QualType(AP2.first->getTypeForDecl(), 0), O2); + O2.flush(); + + if (S1 < S2) + return true; + if (S1 != S2) + return false; + + return AP1.second < AP2.second; + }); + + ArrayRef<VTableComponent> Comps = VTLayout.vtable_components(); + for (auto AP : AddressPoints) { + // Create type metadata for the address point. + AddVTableTypeMetadata(VTable, ComponentWidth * AP.second, AP.first); + + // The class associated with each address point could also potentially be + // used for indirect calls via a member function pointer, so we need to + // annotate the address of each function pointer with the appropriate member + // function pointer type. + for (unsigned I = 0; I != Comps.size(); ++I) { + if (Comps[I].getKind() != VTableComponent::CK_FunctionPointer) + continue; + llvm::Metadata *MD = CreateMetadataIdentifierForVirtualMemPtrType( + Context.getMemberPointerType( + Comps[I].getFunctionDecl()->getType(), + Context.getRecordType(AP.first).getTypePtr())); + VTable->addTypeMetadata((ComponentWidth * I).getQuantity(), MD); + } + } + + if (getCodeGenOpts().VirtualFunctionElimination || + getCodeGenOpts().WholeProgramVTables) { + llvm::DenseSet<const CXXRecordDecl *> Visited; + llvm::GlobalObject::VCallVisibility TypeVis = + GetVCallVisibilityLevel(RD, Visited); + if (TypeVis != llvm::GlobalObject::VCallVisibilityPublic) + VTable->setVCallVisibilityMetadata(TypeVis); + } +} |