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Diffstat (limited to 'contrib/llvm/tools/clang/lib/CodeGen/CGVTables.cpp')
| -rw-r--r-- | contrib/llvm/tools/clang/lib/CodeGen/CGVTables.cpp | 906 |
1 files changed, 906 insertions, 0 deletions
diff --git a/contrib/llvm/tools/clang/lib/CodeGen/CGVTables.cpp b/contrib/llvm/tools/clang/lib/CodeGen/CGVTables.cpp new file mode 100644 index 0000000..57370a6 --- /dev/null +++ b/contrib/llvm/tools/clang/lib/CodeGen/CGVTables.cpp @@ -0,0 +1,906 @@ +//===--- CGVTables.cpp - Emit LLVM Code for C++ vtables -------------------===// +// +// 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 C++ code generation of virtual tables. +// +//===----------------------------------------------------------------------===// + +#include "CodeGenFunction.h" +#include "CGCXXABI.h" +#include "CodeGenModule.h" +#include "clang/AST/CXXInheritance.h" +#include "clang/AST/RecordLayout.h" +#include "clang/CodeGen/CGFunctionInfo.h" +#include "clang/Frontend/CodeGenOptions.h" +#include "llvm/ADT/DenseSet.h" +#include "llvm/ADT/SetVector.h" +#include "llvm/Support/Compiler.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(GlobalDecl GD, + const ThunkInfo &Thunk) { + const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl()); + + // Compute the mangled name. + SmallString<256> Name; + llvm::raw_svector_ostream Out(Name); + if (const CXXDestructorDecl* DD = dyn_cast<CXXDestructorDecl>(MD)) + getCXXABI().getMangleContext().mangleCXXDtorThunk(DD, GD.getDtorType(), + Thunk.This, Out); + else + getCXXABI().getMangleContext().mangleThunk(MD, Thunk, Out); + Out.flush(); + + llvm::Type *Ty = getTypes().GetFunctionTypeForVTable(GD); + return GetOrCreateLLVMFunction(Name, Ty, GD, /*ForVTable=*/true, + /*DontDefer=*/true, /*IsThunk=*/true); +} + +static void setThunkVisibility(CodeGenModule &CGM, const CXXMethodDecl *MD, + const ThunkInfo &Thunk, llvm::Function *Fn) { + CGM.setGlobalVisibility(Fn, MD); +} + +#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); + } + + ReturnValue = CGF.CGM.getCXXABI().performReturnAdjustment(CGF, ReturnValue, + 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 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. +void 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()->getAs<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); + + // Clone to thunk. + llvm::ValueToValueMapTy VMap; + llvm::Function *NewFn = llvm::CloneFunction(BaseFn, VMap, + /*ModuleLevelChanges=*/false); + CGM.getModule().getFunctionList().push_back(NewFn); + 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". + llvm::Value *ThisPtr = &*AI; + llvm::BasicBlock *EntryBB = Fn->begin(); + llvm::Instruction *ThisStore = + std::find_if(EntryBB->begin(), EntryBB->end(), [&](llvm::Instruction &I) { + return isa<llvm::StoreInst>(I) && I.getOperand(0) == ThisPtr; + }); + assert(ThisStore && "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); + ThisStore->setOperand(0, AdjustedThisPtr); + + if (!Thunk.Return.isEmpty()) { + // Fix up the returned value, if necessary. + for (llvm::Function::iterator I = Fn->begin(), E = Fn->end(); I != E; I++) { + llvm::Instruction *T = I->getTerminator(); + if (isa<llvm::ReturnInst>(T)) { + RValue RV = RValue::get(T->getOperand(0)); + T->eraseFromParent(); + Builder.SetInsertPoint(&*I); + RV = PerformReturnAdjustment(*this, ResultType, RV, Thunk); + Builder.CreateRet(RV.getScalarVal()); + break; + } + } + } +} + +void CodeGenFunction::StartThunk(llvm::Function *Fn, GlobalDecl GD, + const CGFunctionInfo &FnInfo) { + assert(!CurGD.getDecl() && "CurGD was already set!"); + CurGD = GD; + CurFuncIsThunk = true; + + // Build FunctionArgs. + const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl()); + QualType ThisType = MD->getThisType(getContext()); + const FunctionProtoType *FPT = MD->getType()->getAs<FunctionProtoType>(); + QualType ResultType = CGM.getCXXABI().HasThisReturn(GD) + ? ThisType + : CGM.getCXXABI().hasMostDerivedReturn(GD) + ? CGM.getContext().VoidPtrTy + : FPT->getReturnType(); + FunctionArgList FunctionArgs; + + // Create the implicit 'this' parameter declaration. + CGM.getCXXABI().buildThisParam(*this, FunctionArgs); + + // Add the rest of the parameters. + FunctionArgs.append(MD->param_begin(), MD->param_end()); + + if (isa<CXXDestructorDecl>(MD)) + CGM.getCXXABI().addImplicitStructorParams(*this, ResultType, FunctionArgs); + + // Start defining the function. + StartFunction(GlobalDecl(), ResultType, Fn, FnInfo, FunctionArgs, + MD->getLocation(), MD->getLocation()); + + // Since we didn't pass a GlobalDecl to StartFunction, do this ourselves. + CGM.getCXXABI().EmitInstanceFunctionProlog(*this); + CXXThisValue = CXXABIThisValue; +} + +void CodeGenFunction::EmitCallAndReturnForThunk(llvm::Value *Callee, + const ThunkInfo *Thunk) { + 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, LoadCXXThis(), Thunk->This) + : LoadCXXThis(); + + if (CurFnInfo->usesInAlloca()) { + // We don't handle return adjusting thunks, because they require us to call + // the copy constructor. For now, fall through and pretend the return + // adjustment was empty so we don't crash. + if (Thunk && !Thunk->Return.isEmpty()) { + CGM.ErrorUnsupported( + MD, "non-trivial argument copy for return-adjusting thunk"); + } + EmitMustTailThunk(MD, AdjustedThisPtr, Callee); + return; + } + + // Start building CallArgs. + CallArgList CallArgs; + QualType ThisType = MD->getThisType(getContext()); + CallArgs.add(RValue::get(AdjustedThisPtr), ThisType); + + if (isa<CXXDestructorDecl>(MD)) + CGM.getCXXABI().adjustCallArgsForDestructorThunk(*this, CurGD, CallArgs); + + // Add the rest of the arguments. + for (const ParmVarDecl *PD : MD->params()) + EmitDelegateCallArg(CallArgs, PD, PD->getLocStart()); + + const FunctionProtoType *FPT = MD->getType()->getAs<FunctionProtoType>(); + +#ifndef NDEBUG + const CGFunctionInfo &CallFnInfo = + CGM.getTypes().arrangeCXXMethodCall(CallArgs, FPT, + RequiredArgs::forPrototypePlus(FPT, 1)); + 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 && + !hasScalarEvaluationKind(CurFnInfo->getReturnType())) + Slot = ReturnValueSlot(ReturnValue, ResultType.isVolatileQualified()); + + // Now emit our call. + llvm::Instruction *CallOrInvoke; + RValue RV = EmitCall(*CurFnInfo, Callee, Slot, CallArgs, MD, &CallOrInvoke); + + // Consider return adjustment if we have ThunkInfo. + if (Thunk && !Thunk->Return.isEmpty()) + RV = PerformReturnAdjustment(*this, ResultType, RV, *Thunk); + + // Emit return. + if (!ResultType->isVoidType() && Slot.isNull()) + CGM.getCXXABI().EmitReturnFromThunk(*this, RV, ResultType); + + // Disable the final ARC autorelease. + AutoreleaseResult = false; + + FinishFunction(); +} + +void CodeGenFunction::EmitMustTailThunk(const CXXMethodDecl *MD, + llvm::Value *AdjustedThisPtr, + llvm::Value *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; + for (llvm::Argument &A : CurFn->args()) + Args.push_back(&A); + + // 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"); + llvm::Value *ThisAddr = GetAddrOfLocalVar(CXXABIThisDecl); + llvm::Type *ThisType = + cast<llvm::PointerType>(ThisAddr->getType())->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; + CodeGen::AttributeListType AttributeList; + CGM.ConstructAttributeList(*CurFnInfo, MD, AttributeList, CallingConv, + /*AttrOnCallSite=*/true); + llvm::AttributeSet Attrs = + llvm::AttributeSet::get(getLLVMContext(), AttributeList); + 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()); + FinishFunction(); +} + +void CodeGenFunction::GenerateThunk(llvm::Function *Fn, + const CGFunctionInfo &FnInfo, + GlobalDecl GD, const ThunkInfo &Thunk) { + StartThunk(Fn, GD, FnInfo); + + // Get our callee. + llvm::Type *Ty = + CGM.getTypes().GetFunctionType(CGM.getTypes().arrangeGlobalDeclaration(GD)); + llvm::Value *Callee = CGM.GetAddrOfFunction(GD, Ty, /*ForVTable=*/true); + + // Make the call and return the result. + EmitCallAndReturnForThunk(Callee, &Thunk); + + // Set the right linkage. + CGM.setFunctionLinkage(GD, Fn); + + if (CGM.supportsCOMDAT() && Fn->isWeakForLinker()) + Fn->setComdat(CGM.getModule().getOrInsertComdat(Fn->getName())); + + // Set the right visibility. + const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl()); + setThunkVisibility(CGM, MD, Thunk, Fn); +} + +void CodeGenVTables::emitThunk(GlobalDecl GD, const ThunkInfo &Thunk, + bool ForVTable) { + const CGFunctionInfo &FnInfo = CGM.getTypes().arrangeGlobalDeclaration(GD); + + // FIXME: re-use FnInfo in this computation. + llvm::Constant *C = CGM.GetAddrOfThunk(GD, Thunk); + llvm::GlobalValue *Entry; + + // Strip off a bitcast if we got one back. + if (llvm::ConstantExpr *CE = dyn_cast<llvm::ConstantExpr>(C)) { + assert(CE->getOpcode() == llvm::Instruction::BitCast); + Entry = cast<llvm::GlobalValue>(CE->getOperand(0)); + } else { + Entry = cast<llvm::GlobalValue>(C); + } + + // There's already a declaration with the same name, check if it has the same + // type or if we need to replace it. + if (Entry->getType()->getElementType() != + CGM.getTypes().GetFunctionTypeForVTable(GD)) { + llvm::GlobalValue *OldThunkFn = Entry; + + // If the types mismatch then we have to rewrite the definition. + assert(OldThunkFn->isDeclaration() && + "Shouldn't replace non-declaration"); + + // Remove the name from the old thunk function and get a new thunk. + OldThunkFn->setName(StringRef()); + Entry = cast<llvm::GlobalValue>(CGM.GetAddrOfThunk(GD, Thunk)); + + // If needed, replace the old thunk with a bitcast. + if (!OldThunkFn->use_empty()) { + llvm::Constant *NewPtrForOldDecl = + llvm::ConstantExpr::getBitCast(Entry, OldThunkFn->getType()); + OldThunkFn->replaceAllUsesWith(NewPtrForOldDecl); + } + + // Remove the old thunk. + OldThunkFn->eraseFromParent(); + } + + llvm::Function *ThunkFn = cast<llvm::Function>(Entry); + 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; + } + + // Change the linkage. + CGM.setFunctionLinkage(GD, ThunkFn); + return; + } + + CGM.SetLLVMFunctionAttributesForDefinition(GD.getDecl(), ThunkFn); + + if (ThunkFn->isVarArg()) { + // Varargs thunks are special; we can't just generate a call because + // we can't copy the varargs. Our implementation is rather + // expensive/sucky at the moment, so don't generate the thunk unless + // we have to. + // FIXME: Do something better here; GenerateVarArgsThunk is extremely ugly. + if (!UseAvailableExternallyLinkage) { + CodeGenFunction(CGM).GenerateVarArgsThunk(ThunkFn, FnInfo, GD, Thunk); + CGM.getCXXABI().setThunkLinkage(ThunkFn, ForVTable, GD, + !Thunk.Return.isEmpty()); + } + } else { + // Normal thunk body generation. + CodeGenFunction(CGM).GenerateThunk(ThunkFn, FnInfo, GD, Thunk); + CGM.getCXXABI().setThunkLinkage(ThunkFn, ForVTable, GD, + !Thunk.Return.isEmpty()); + } +} + +void CodeGenVTables::maybeEmitThunkForVTable(GlobalDecl GD, + const ThunkInfo &Thunk) { + // If the ABI has key functions, only the TU with the key function should emit + // the thunk. However, we can allow inlining of thunks if we emit them with + // available_externally linkage together with vtables when optimizations are + // enabled. + if (CGM.getTarget().getCXXABI().hasKeyFunctions() && + !CGM.getCodeGenOpts().OptimizationLevel) + return; + + // We can't emit thunks for member functions with incomplete types. + const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl()); + if (!CGM.getTypes().isFuncTypeConvertible( + MD->getType()->castAs<FunctionType>())) + return; + + emitThunk(GD, Thunk, /*ForVTable=*/true); +} + +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 (unsigned I = 0, E = ThunkInfoVector->size(); I != E; ++I) + emitThunk(GD, (*ThunkInfoVector)[I], /*ForVTable=*/false); +} + +llvm::Constant *CodeGenVTables::CreateVTableInitializer( + const CXXRecordDecl *RD, const VTableComponent *Components, + unsigned NumComponents, const VTableLayout::VTableThunkTy *VTableThunks, + unsigned NumVTableThunks, llvm::Constant *RTTI) { + SmallVector<llvm::Constant *, 64> Inits; + + llvm::Type *Int8PtrTy = CGM.Int8PtrTy; + + llvm::Type *PtrDiffTy = + CGM.getTypes().ConvertType(CGM.getContext().getPointerDiffType()); + + unsigned NextVTableThunkIndex = 0; + + llvm::Constant *PureVirtualFn = nullptr, *DeletedVirtualFn = nullptr; + + for (unsigned I = 0; I != NumComponents; ++I) { + VTableComponent Component = Components[I]; + + llvm::Constant *Init = nullptr; + + switch (Component.getKind()) { + case VTableComponent::CK_VCallOffset: + Init = llvm::ConstantInt::get(PtrDiffTy, + Component.getVCallOffset().getQuantity()); + Init = llvm::ConstantExpr::getIntToPtr(Init, Int8PtrTy); + break; + case VTableComponent::CK_VBaseOffset: + Init = llvm::ConstantInt::get(PtrDiffTy, + Component.getVBaseOffset().getQuantity()); + Init = llvm::ConstantExpr::getIntToPtr(Init, Int8PtrTy); + break; + case VTableComponent::CK_OffsetToTop: + Init = llvm::ConstantInt::get(PtrDiffTy, + Component.getOffsetToTop().getQuantity()); + Init = llvm::ConstantExpr::getIntToPtr(Init, Int8PtrTy); + break; + case VTableComponent::CK_RTTI: + Init = llvm::ConstantExpr::getBitCast(RTTI, Int8PtrTy); + break; + case VTableComponent::CK_FunctionPointer: + case VTableComponent::CK_CompleteDtorPointer: + case VTableComponent::CK_DeletingDtorPointer: { + GlobalDecl GD; + + // Get the right global decl. + switch (Component.getKind()) { + default: + llvm_unreachable("Unexpected vtable component kind"); + case VTableComponent::CK_FunctionPointer: + GD = Component.getFunctionDecl(); + break; + case VTableComponent::CK_CompleteDtorPointer: + GD = GlobalDecl(Component.getDestructorDecl(), Dtor_Complete); + break; + case VTableComponent::CK_DeletingDtorPointer: + GD = GlobalDecl(Component.getDestructorDecl(), Dtor_Deleting); + break; + } + + if (cast<CXXMethodDecl>(GD.getDecl())->isPure()) { + // We have a pure virtual member function. + if (!PureVirtualFn) { + llvm::FunctionType *Ty = + llvm::FunctionType::get(CGM.VoidTy, /*isVarArg=*/false); + StringRef PureCallName = CGM.getCXXABI().GetPureVirtualCallName(); + PureVirtualFn = CGM.CreateRuntimeFunction(Ty, PureCallName); + PureVirtualFn = llvm::ConstantExpr::getBitCast(PureVirtualFn, + CGM.Int8PtrTy); + } + Init = PureVirtualFn; + } else if (cast<CXXMethodDecl>(GD.getDecl())->isDeleted()) { + if (!DeletedVirtualFn) { + llvm::FunctionType *Ty = + llvm::FunctionType::get(CGM.VoidTy, /*isVarArg=*/false); + StringRef DeletedCallName = + CGM.getCXXABI().GetDeletedVirtualCallName(); + DeletedVirtualFn = CGM.CreateRuntimeFunction(Ty, DeletedCallName); + DeletedVirtualFn = llvm::ConstantExpr::getBitCast(DeletedVirtualFn, + CGM.Int8PtrTy); + } + Init = DeletedVirtualFn; + } else { + // Check if we should use a thunk. + if (NextVTableThunkIndex < NumVTableThunks && + VTableThunks[NextVTableThunkIndex].first == I) { + const ThunkInfo &Thunk = VTableThunks[NextVTableThunkIndex].second; + + maybeEmitThunkForVTable(GD, Thunk); + Init = CGM.GetAddrOfThunk(GD, Thunk); + + NextVTableThunkIndex++; + } else { + llvm::Type *Ty = CGM.getTypes().GetFunctionTypeForVTable(GD); + + Init = CGM.GetAddrOfFunction(GD, Ty, /*ForVTable=*/true); + } + + Init = llvm::ConstantExpr::getBitCast(Init, Int8PtrTy); + } + break; + } + + case VTableComponent::CK_UnusedFunctionPointer: + Init = llvm::ConstantExpr::getNullValue(Int8PtrTy); + break; + }; + + Inits.push_back(Init); + } + + llvm::ArrayType *ArrayType = llvm::ArrayType::get(Int8PtrTy, NumComponents); + return llvm::ConstantArray::get(ArrayType, Inits); +} + +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); + Out.flush(); + StringRef Name = OutName.str(); + + llvm::ArrayType *ArrayType = + llvm::ArrayType::get(CGM.Int8PtrTy, VTLayout->getNumVTableComponents()); + + // 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; + + // Create the variable that will hold the construction vtable. + llvm::GlobalVariable *VTable = + CGM.CreateOrReplaceCXXRuntimeVariable(Name, ArrayType, Linkage); + CGM.setGlobalVisibility(VTable, RD); + + // V-tables are always unnamed_addr. + VTable->setUnnamedAddr(true); + + llvm::Constant *RTTI = CGM.GetAddrOfRTTIDescriptor( + CGM.getContext().getTagDeclType(Base.getBase())); + + // Create and set the initializer. + llvm::Constant *Init = CreateVTableInitializer( + Base.getBase(), VTLayout->vtable_component_begin(), + VTLayout->getNumVTableComponents(), VTLayout->vtable_thunk_begin(), + VTLayout->getNumVTableThunks(), RTTI); + VTable->setInitializer(Init); + + CGM.EmitVTableBitSetEntries(VTable, *VTLayout.get()); + + return VTable; +} + +/// Compute the required linkage of the v-table 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 && "Should not have been asked to emit this"); + 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: + return llvm::GlobalVariable::ExternalLinkage; + + case TSK_ExplicitInstantiationDefinition: + return NonDiscardableODRLinkage; + } + + llvm_unreachable("Invalid TemplateSpecializationKind!"); +} + +/// This is a callback from Sema to tell us that that a particular v-table 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 v-table definition when that v-table is defined +/// strongly elsewhere. Otherwise, we'd just like to avoid emitting +/// v-tables when unnecessary. +bool CodeGenVTables::isVTableExternal(const CXXRecordDecl *RD) { + assert(RD->isDynamicClass() && "Non-dynamic classes have no VTable."); + + // If we have an explicit instantiation declaration (and not a + // definition), the v-table is defined elsewhere. + TemplateSpecializationKind TSK = RD->getTemplateSpecializationKind(); + if (TSK == TSK_ExplicitInstantiationDeclaration) + return true; + + // Otherwise, if the class is an instantiated template, the + // v-table 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 v-table 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 + // v-table 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 v-table for this class, should +/// we define that v-table? +static bool shouldEmitVTableAtEndOfTranslationUnit(CodeGenModule &CGM, + const CXXRecordDecl *RD) { + return !CGM.getVTables().isVTableExternal(RD); +} + +/// Given that at some point we emitted a reference to one or more +/// v-tables, 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 + + typedef std::vector<const CXXRecordDecl *>::const_iterator const_iterator; + for (const_iterator i = DeferredVTables.begin(), + e = DeferredVTables.end(); i != e; ++i) { + const CXXRecordDecl *RD = *i; + if (shouldEmitVTableAtEndOfTranslationUnit(*this, RD)) + VTables.GenerateClassData(RD); + } + + assert(savedSize == DeferredVTables.size() && + "deferred extra v-tables during v-table emission?"); + DeferredVTables.clear(); +} + +void CodeGenModule::EmitVTableBitSetEntries(llvm::GlobalVariable *VTable, + const VTableLayout &VTLayout) { + if (!LangOpts.Sanitize.has(SanitizerKind::CFIVCall) && + !LangOpts.Sanitize.has(SanitizerKind::CFINVCall) && + !LangOpts.Sanitize.has(SanitizerKind::CFIDerivedCast) && + !LangOpts.Sanitize.has(SanitizerKind::CFIUnrelatedCast)) + return; + + llvm::Metadata *VTableMD = llvm::ConstantAsMetadata::get(VTable); + + std::vector<llvm::MDTuple *> BitsetEntries; + // Create a bit set entry for each address point. + for (auto &&AP : VTLayout.getAddressPoints()) { + // FIXME: Add blacklisting scheme. + if (AP.first.getBase()->isInStdNamespace()) + continue; + + std::string OutName; + llvm::raw_string_ostream Out(OutName); + getCXXABI().getMangleContext().mangleCXXVTableBitSet(AP.first.getBase(), + Out); + + CharUnits PointerWidth = + Context.toCharUnitsFromBits(Context.getTargetInfo().getPointerWidth(0)); + uint64_t AddrPointOffset = AP.second * PointerWidth.getQuantity(); + + llvm::Metadata *BitsetOps[] = { + llvm::MDString::get(getLLVMContext(), Out.str()), + VTableMD, + llvm::ConstantAsMetadata::get( + llvm::ConstantInt::get(Int64Ty, AddrPointOffset))}; + llvm::MDTuple *BitsetEntry = + llvm::MDTuple::get(getLLVMContext(), BitsetOps); + BitsetEntries.push_back(BitsetEntry); + } + + // Sort the bit set entries for determinism. + std::sort(BitsetEntries.begin(), BitsetEntries.end(), [](llvm::MDTuple *T1, + llvm::MDTuple *T2) { + if (T1 == T2) + return false; + + StringRef S1 = cast<llvm::MDString>(T1->getOperand(0))->getString(); + StringRef S2 = cast<llvm::MDString>(T2->getOperand(0))->getString(); + if (S1 < S2) + return true; + if (S1 != S2) + return false; + + uint64_t Offset1 = cast<llvm::ConstantInt>( + cast<llvm::ConstantAsMetadata>(T1->getOperand(2)) + ->getValue())->getZExtValue(); + uint64_t Offset2 = cast<llvm::ConstantInt>( + cast<llvm::ConstantAsMetadata>(T2->getOperand(2)) + ->getValue())->getZExtValue(); + assert(Offset1 != Offset2); + return Offset1 < Offset2; + }); + + llvm::NamedMDNode *BitsetsMD = + getModule().getOrInsertNamedMetadata("llvm.bitsets"); + for (auto BitsetEntry : BitsetEntries) + BitsetsMD->addOperand(BitsetEntry); +} |
