| //===--- 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 "CGCXXABI.h" |
| #include "CodeGenFunction.h" |
| #include "CodeGenModule.h" |
| #include "clang/AST/CXXInheritance.h" |
| #include "clang/AST/RecordLayout.h" |
| #include "clang/CodeGen/CGFunctionInfo.h" |
| #include "clang/CodeGen/ConstantInitBuilder.h" |
| #include "clang/Frontend/CodeGenOptions.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(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); |
| |
| 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, ForDefinition); |
| } |
| |
| 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. |
| const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl()); |
| setThunkVisibility(CGM, MD, Thunk, ThunkFn); |
| |
| 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, 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->getBasicBlockList()) { |
| for (auto &I : BB) { |
| if (auto *DII = dyn_cast<llvm::DbgInfoIntrinsic>(&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()->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; |
| |
| // 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(&*AI, CGM.getClassPointerAlignment(MD->getParent())); |
| llvm::BasicBlock *EntryBB = &Fn->front(); |
| llvm::BasicBlock::iterator ThisStore = |
| std::find_if(EntryBB->begin(), EntryBB->end(), [&](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); |
| 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) { |
| 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. |
| 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::Constant *CalleePtr, |
| 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, LoadCXXThisAddress(), 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, CalleePtr); |
| 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); |
| |
| #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()->getAs<FunctionProtoType>(); |
| |
| #ifndef NDEBUG |
| const CGFunctionInfo &CallFnInfo = CGM.getTypes().arrangeCXXMethodCall( |
| CallArgs, FPT, RequiredArgs::forPrototypePlus(FPT, 1, MD), 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 && |
| !hasScalarEvaluationKind(CurFnInfo->getReturnType())) |
| Slot = ReturnValueSlot(ReturnValue, ResultType.isVolatileQualified()); |
| |
| // Now emit our call. |
| llvm::Instruction *CallOrInvoke; |
| CGCallee Callee = CGCallee::forDirect(CalleePtr, MD); |
| RValue RV = EmitCall(*CurFnInfo, Callee, 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(const CXXMethodDecl *MD, |
| llvm::Value *AdjustedThisPtr, |
| llvm::Value *CalleePtr) { |
| // 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"); |
| 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(CalleePtr, Args); |
| Call->setTailCallKind(llvm::CallInst::TCK_MustTail); |
| |
| // Apply the standard set of call attributes. |
| unsigned CallingConv; |
| llvm::AttributeList Attrs; |
| CGM.ConstructAttributeList(CalleePtr->getName(), *CurFnInfo, MD, Attrs, |
| CallingConv, /*AttrOnCallSite=*/true); |
| 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); |
| // Create a scope with an artificial location for the body of this function. |
| auto AL = ApplyDebugLocation::CreateArtificial(*this); |
| |
| // Get our callee. |
| llvm::Type *Ty = |
| CGM.getTypes().GetFunctionType(CGM.getTypes().arrangeGlobalDeclaration(GD)); |
| llvm::Constant *Callee = CGM.GetAddrOfFunction(GD, Ty, /*ForVTable=*/true); |
| |
| // Make the call and return the result. |
| EmitCallAndReturnForThunk(Callee, &Thunk); |
| } |
| |
| 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; |
| } |
| |
| setThunkProperties(CGM, Thunk, ThunkFn, ForVTable, GD); |
| 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) |
| return; |
| ThunkFn = |
| CodeGenFunction(CGM).GenerateVarArgsThunk(ThunkFn, FnInfo, GD, Thunk); |
| } else { |
| // Normal thunk body generation. |
| CodeGenFunction(CGM).generateThunk(ThunkFn, FnInfo, GD, Thunk); |
| } |
| |
| setThunkProperties(CGM, Thunk, ThunkFn, ForVTable, GD); |
| } |
| |
| 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 (const ThunkInfo& Thunk : *ThunkInfoVector) |
| emitThunk(GD, Thunk, /*ForVTable=*/false); |
| } |
| |
| void CodeGenVTables::addVTableComponent( |
| ConstantArrayBuilder &builder, const VTableLayout &layout, |
| unsigned idx, llvm::Constant *rtti, unsigned &nextVTableThunkIndex) { |
| auto &component = layout.vtable_components()[idx]; |
| |
| auto addOffsetConstant = [&](CharUnits offset) { |
| builder.add(llvm::ConstantExpr::getIntToPtr( |
| llvm::ConstantInt::get(CGM.PtrDiffTy, offset.getQuantity()), |
| CGM.Int8PtrTy)); |
| }; |
| |
| switch (component.getKind()) { |
| case VTableComponent::CK_VCallOffset: |
| return addOffsetConstant(component.getVCallOffset()); |
| |
| case VTableComponent::CK_VBaseOffset: |
| return addOffsetConstant(component.getVBaseOffset()); |
| |
| case VTableComponent::CK_OffsetToTop: |
| return addOffsetConstant(component.getOffsetToTop()); |
| |
| case VTableComponent::CK_RTTI: |
| return builder.add(llvm::ConstantExpr::getBitCast(rtti, CGM.Int8PtrTy)); |
| |
| 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 (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.addNullPointer(CGM.Int8PtrTy); |
| // Method is acceptable, continue processing as usual. |
| } |
| |
| auto getSpecialVirtualFn = [&](StringRef name) { |
| llvm::FunctionType *fnTy = |
| llvm::FunctionType::get(CGM.VoidTy, /*isVarArg=*/false); |
| llvm::Constant *fn = CGM.CreateRuntimeFunction(fnTy, name); |
| 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 == idx) { |
| auto &thunkInfo = layout.vtable_thunks()[nextVTableThunkIndex].second; |
| |
| maybeEmitThunkForVTable(GD, thunkInfo); |
| nextVTableThunkIndex++; |
| fnPtr = CGM.GetAddrOfThunk(GD, thunkInfo); |
| |
| // Otherwise we can use the method definition directly. |
| } else { |
| llvm::Type *fnTy = CGM.getTypes().GetFunctionTypeForVTable(GD); |
| fnPtr = CGM.GetAddrOfFunction(GD, fnTy, /*ForVTable=*/true); |
| } |
| |
| fnPtr = llvm::ConstantExpr::getBitCast(fnPtr, CGM.Int8PtrTy); |
| builder.add(fnPtr); |
| return; |
| } |
| |
| case VTableComponent::CK_UnusedFunctionPointer: |
| return builder.addNullPointer(CGM.Int8PtrTy); |
| } |
| |
| llvm_unreachable("Unexpected vtable component kind"); |
| } |
| |
| llvm::Type *CodeGenVTables::getVTableType(const VTableLayout &layout) { |
| SmallVector<llvm::Type *, 4> tys; |
| for (unsigned i = 0, e = layout.getNumVTables(); i != e; ++i) { |
| tys.push_back(llvm::ArrayType::get(CGM.Int8PtrTy, layout.getVTableSize(i))); |
| } |
| |
| return llvm::StructType::get(CGM.getLLVMContext(), tys); |
| } |
| |
| void CodeGenVTables::createVTableInitializer(ConstantStructBuilder &builder, |
| const VTableLayout &layout, |
| llvm::Constant *rtti) { |
| unsigned nextVTableThunkIndex = 0; |
| for (unsigned i = 0, e = layout.getNumVTables(); i != e; ++i) { |
| auto vtableElem = builder.beginArray(CGM.Int8PtrTy); |
| size_t thisIndex = layout.getVTableOffset(i); |
| size_t nextIndex = thisIndex + layout.getVTableSize(i); |
| for (unsigned i = thisIndex; i != nextIndex; ++i) { |
| addVTableComponent(vtableElem, layout, i, rtti, nextVTableThunkIndex); |
| } |
| 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); |
| StringRef Name = OutName.str(); |
| |
| 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; |
| |
| // Create the variable that will hold the construction vtable. |
| llvm::GlobalVariable *VTable = |
| CGM.CreateOrReplaceCXXRuntimeVariable(Name, VTType, Linkage); |
| CGM.setGlobalVisibility(VTable, RD, ForDefinition); |
| |
| // 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); |
| components.finishAndSetAsInitializer(VTable); |
| |
| CGM.EmitVTableTypeMetadata(VTable, *VTLayout.get()); |
| |
| return 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 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::HasHiddenLTOVisibility(const CXXRecordDecl *RD) { |
| LinkageInfo LV = RD->getLinkageAndVisibility(); |
| if (!isExternallyVisible(LV.getLinkage())) |
| return true; |
| |
| if (RD->hasAttr<LTOVisibilityPublicAttr>() || RD->hasAttr<UuidAttr>()) |
| return false; |
| |
| if (getTriple().isOSBinFormatCOFF()) { |
| if (RD->hasAttr<DLLExportAttr>() || RD->hasAttr<DLLImportAttr>()) |
| return false; |
| } else { |
| if (LV.getVisibility() != HiddenVisibility) |
| return false; |
| } |
| |
| if (getCodeGenOpts().LTOVisibilityPublicStd) { |
| const DeclContext *DC = RD; |
| while (1) { |
| 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 false; |
| break; |
| } |
| } |
| } |
| |
| return true; |
| } |
| |
| void CodeGenModule::EmitVTableTypeMetadata(llvm::GlobalVariable *VTable, |
| const VTableLayout &VTLayout) { |
| if (!getCodeGenOpts().LTOUnit) |
| return; |
| |
| CharUnits PointerWidth = |
| Context.toCharUnitsFromBits(Context.getTargetInfo().getPointerWidth(0)); |
| |
| typedef std::pair<const CXXRecordDecl *, unsigned> BSEntry; |
| std::vector<BSEntry> BitsetEntries; |
| // Create a bit set entry for each address point. |
| for (auto &&AP : VTLayout.getAddressPoints()) |
| BitsetEntries.push_back( |
| std::make_pair(AP.first.getBase(), |
| VTLayout.getVTableOffset(AP.second.VTableIndex) + |
| AP.second.AddressPointIndex)); |
| |
| // Sort the bit set entries for determinism. |
| std::sort(BitsetEntries.begin(), BitsetEntries.end(), |
| [this](const BSEntry &E1, const BSEntry &E2) { |
| if (&E1 == &E2) |
| return false; |
| |
| std::string S1; |
| llvm::raw_string_ostream O1(S1); |
| getCXXABI().getMangleContext().mangleTypeName( |
| QualType(E1.first->getTypeForDecl(), 0), O1); |
| O1.flush(); |
| |
| std::string S2; |
| llvm::raw_string_ostream O2(S2); |
| getCXXABI().getMangleContext().mangleTypeName( |
| QualType(E2.first->getTypeForDecl(), 0), O2); |
| O2.flush(); |
| |
| if (S1 < S2) |
| return true; |
| if (S1 != S2) |
| return false; |
| |
| return E1.second < E2.second; |
| }); |
| |
| for (auto BitsetEntry : BitsetEntries) |
| AddVTableTypeMetadata(VTable, PointerWidth * BitsetEntry.second, |
| BitsetEntry.first); |
| } |