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//===--- MicrosoftCXXABI.cpp - Emit LLVM Code from ASTs for a Module ------===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// This provides C++ code generation targeting the Microsoft Visual C++ ABI.
// The class in this file generates structures that follow the Microsoft
// Visual C++ ABI, which is actually not very well documented at all outside
// of Microsoft.
#include "CGCXXABI.h"
#include "CGCleanup.h"
#include "CGVTables.h"
#include "CodeGenModule.h"
#include "CodeGenTypes.h"
#include "TargetInfo.h"
#include "clang/AST/Attr.h"
#include "clang/AST/CXXInheritance.h"
#include "clang/AST/Decl.h"
#include "clang/AST/DeclCXX.h"
#include "clang/AST/StmtCXX.h"
#include "clang/AST/VTableBuilder.h"
#include "clang/CodeGen/ConstantInitBuilder.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/StringSet.h"
#include "llvm/IR/Intrinsics.h"
using namespace clang;
using namespace CodeGen;
namespace {
/// Holds all the vbtable globals for a given class.
struct VBTableGlobals {
const VPtrInfoVector *VBTables;
SmallVector<llvm::GlobalVariable *, 2> Globals;
class MicrosoftCXXABI : public CGCXXABI {
MicrosoftCXXABI(CodeGenModule &CGM)
: CGCXXABI(CGM), BaseClassDescriptorType(nullptr),
CompleteObjectLocatorType(nullptr), CatchableTypeType(nullptr),
ThrowInfoType(nullptr) {}
bool HasThisReturn(GlobalDecl GD) const override;
bool hasMostDerivedReturn(GlobalDecl GD) const override;
bool classifyReturnType(CGFunctionInfo &FI) const override;
RecordArgABI getRecordArgABI(const CXXRecordDecl *RD) const override;
bool isSRetParameterAfterThis() const override { return true; }
bool isThisCompleteObject(GlobalDecl GD) const override {
// The Microsoft ABI doesn't use separate complete-object vs.
// base-object variants of constructors, but it does of destructors.
if (isa<CXXDestructorDecl>(GD.getDecl())) {
switch (GD.getDtorType()) {
case Dtor_Complete:
case Dtor_Deleting:
return true;
case Dtor_Base:
return false;
case Dtor_Comdat: llvm_unreachable("emitting dtor comdat as function?");
llvm_unreachable("bad dtor kind");
// No other kinds.
return false;
size_t getSrcArgforCopyCtor(const CXXConstructorDecl *CD,
FunctionArgList &Args) const override {
assert(Args.size() >= 2 &&
"expected the arglist to have at least two args!");
// The 'most_derived' parameter goes second if the ctor is variadic and
// has v-bases.
if (CD->getParent()->getNumVBases() > 0 &&
return 2;
return 1;
std::vector<CharUnits> getVBPtrOffsets(const CXXRecordDecl *RD) override {
std::vector<CharUnits> VBPtrOffsets;
const ASTContext &Context = getContext();
const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
const VBTableGlobals &VBGlobals = enumerateVBTables(RD);
for (const std::unique_ptr<VPtrInfo> &VBT : *VBGlobals.VBTables) {
const ASTRecordLayout &SubobjectLayout =
CharUnits Offs = VBT->NonVirtualOffset;
Offs += SubobjectLayout.getVBPtrOffset();
if (VBT->getVBaseWithVPtr())
Offs += Layout.getVBaseClassOffset(VBT->getVBaseWithVPtr());
llvm::array_pod_sort(VBPtrOffsets.begin(), VBPtrOffsets.end());
return VBPtrOffsets;
StringRef GetPureVirtualCallName() override { return "_purecall"; }
StringRef GetDeletedVirtualCallName() override { return "_purecall"; }
void emitVirtualObjectDelete(CodeGenFunction &CGF, const CXXDeleteExpr *DE,
Address Ptr, QualType ElementType,
const CXXDestructorDecl *Dtor) override;
void emitRethrow(CodeGenFunction &CGF, bool isNoReturn) override;
void emitThrow(CodeGenFunction &CGF, const CXXThrowExpr *E) override;
void emitBeginCatch(CodeGenFunction &CGF, const CXXCatchStmt *C) override;
llvm::GlobalVariable *getMSCompleteObjectLocator(const CXXRecordDecl *RD,
const VPtrInfo &Info);
llvm::Constant *getAddrOfRTTIDescriptor(QualType Ty) override;
getAddrOfCXXCatchHandlerType(QualType Ty, QualType CatchHandlerType) override;
/// MSVC needs an extra flag to indicate a catchall.
CatchTypeInfo getCatchAllTypeInfo() override {
return CatchTypeInfo{nullptr, 0x40};
bool shouldTypeidBeNullChecked(bool IsDeref, QualType SrcRecordTy) override;
void EmitBadTypeidCall(CodeGenFunction &CGF) override;
llvm::Value *EmitTypeid(CodeGenFunction &CGF, QualType SrcRecordTy,
Address ThisPtr,
llvm::Type *StdTypeInfoPtrTy) override;
bool shouldDynamicCastCallBeNullChecked(bool SrcIsPtr,
QualType SrcRecordTy) override;
llvm::Value *EmitDynamicCastCall(CodeGenFunction &CGF, Address Value,
QualType SrcRecordTy, QualType DestTy,
QualType DestRecordTy,
llvm::BasicBlock *CastEnd) override;
llvm::Value *EmitDynamicCastToVoid(CodeGenFunction &CGF, Address Value,
QualType SrcRecordTy,
QualType DestTy) override;
bool EmitBadCastCall(CodeGenFunction &CGF) override;
bool canSpeculativelyEmitVTable(const CXXRecordDecl *RD) const override {
return false;
llvm::Value *
GetVirtualBaseClassOffset(CodeGenFunction &CGF, Address This,
const CXXRecordDecl *ClassDecl,
const CXXRecordDecl *BaseClassDecl) override;
llvm::BasicBlock *
EmitCtorCompleteObjectHandler(CodeGenFunction &CGF,
const CXXRecordDecl *RD) override;
llvm::BasicBlock *
EmitDtorCompleteObjectHandler(CodeGenFunction &CGF);
void initializeHiddenVirtualInheritanceMembers(CodeGenFunction &CGF,
const CXXRecordDecl *RD) override;
void EmitCXXConstructors(const CXXConstructorDecl *D) override;
// Background on MSVC destructors
// ==============================
// Both Itanium and MSVC ABIs have destructor variants. The variant names
// roughly correspond in the following way:
// Itanium Microsoft
// Base -> no name, just ~Class
// Complete -> vbase destructor
// Deleting -> scalar deleting destructor
// vector deleting destructor
// The base and complete destructors are the same as in Itanium, although the
// complete destructor does not accept a VTT parameter when there are virtual
// bases. A separate mechanism involving vtordisps is used to ensure that
// virtual methods of destroyed subobjects are not called.
// The deleting destructors accept an i32 bitfield as a second parameter. Bit
// 1 indicates if the memory should be deleted. Bit 2 indicates if the this
// pointer points to an array. The scalar deleting destructor assumes that
// bit 2 is zero, and therefore does not contain a loop.
// For virtual destructors, only one entry is reserved in the vftable, and it
// always points to the vector deleting destructor. The vector deleting
// destructor is the most general, so it can be used to destroy objects in
// place, delete single heap objects, or delete arrays.
// A TU defining a non-inline destructor is only guaranteed to emit a base
// destructor, and all of the other variants are emitted on an as-needed basis
// in COMDATs. Because a non-base destructor can be emitted in a TU that
// lacks a definition for the destructor, non-base destructors must always
// delegate to or alias the base destructor.
buildStructorSignature(GlobalDecl GD,
SmallVectorImpl<CanQualType> &ArgTys) override;
/// Non-base dtors should be emitted as delegating thunks in this ABI.
bool useThunkForDtorVariant(const CXXDestructorDecl *Dtor,
CXXDtorType DT) const override {
return DT != Dtor_Base;
void setCXXDestructorDLLStorage(llvm::GlobalValue *GV,
const CXXDestructorDecl *Dtor,
CXXDtorType DT) const override;
getCXXDestructorLinkage(GVALinkage Linkage, const CXXDestructorDecl *Dtor,
CXXDtorType DT) const override;
void EmitCXXDestructors(const CXXDestructorDecl *D) override;
const CXXRecordDecl *
getThisArgumentTypeForMethod(const CXXMethodDecl *MD) override {
if (MD->isVirtual() && !isa<CXXDestructorDecl>(MD)) {
MethodVFTableLocation ML =
// The vbases might be ordered differently in the final overrider object
// and the complete object, so the "this" argument may sometimes point to
// memory that has no particular type (e.g. past the complete object).
// In this case, we just use a generic pointer type.
// FIXME: might want to have a more precise type in the non-virtual
// multiple inheritance case.
if (ML.VBase || !ML.VFPtrOffset.isZero())
return nullptr;
return MD->getParent();
adjustThisArgumentForVirtualFunctionCall(CodeGenFunction &CGF, GlobalDecl GD,
Address This,
bool VirtualCall) override;
void addImplicitStructorParams(CodeGenFunction &CGF, QualType &ResTy,
FunctionArgList &Params) override;
void EmitInstanceFunctionProlog(CodeGenFunction &CGF) override;
AddedStructorArgs getImplicitConstructorArgs(CodeGenFunction &CGF,
const CXXConstructorDecl *D,
CXXCtorType Type,
bool ForVirtualBase,
bool Delegating) override;
llvm::Value *getCXXDestructorImplicitParam(CodeGenFunction &CGF,
const CXXDestructorDecl *DD,
CXXDtorType Type,
bool ForVirtualBase,
bool Delegating) override;
void EmitDestructorCall(CodeGenFunction &CGF, const CXXDestructorDecl *DD,
CXXDtorType Type, bool ForVirtualBase,
bool Delegating, Address This,
QualType ThisTy) override;
void emitVTableTypeMetadata(const VPtrInfo &Info, const CXXRecordDecl *RD,
llvm::GlobalVariable *VTable);
void emitVTableDefinitions(CodeGenVTables &CGVT,
const CXXRecordDecl *RD) override;
bool isVirtualOffsetNeededForVTableField(CodeGenFunction &CGF,
CodeGenFunction::VPtr Vptr) override;
/// Don't initialize vptrs if dynamic class
/// is marked with with the 'novtable' attribute.
bool doStructorsInitializeVPtrs(const CXXRecordDecl *VTableClass) override {
return !VTableClass->hasAttr<MSNoVTableAttr>();
llvm::Constant *
getVTableAddressPoint(BaseSubobject Base,
const CXXRecordDecl *VTableClass) override;
llvm::Value *getVTableAddressPointInStructor(
CodeGenFunction &CGF, const CXXRecordDecl *VTableClass,
BaseSubobject Base, const CXXRecordDecl *NearestVBase) override;
llvm::Constant *
getVTableAddressPointForConstExpr(BaseSubobject Base,
const CXXRecordDecl *VTableClass) override;
llvm::GlobalVariable *getAddrOfVTable(const CXXRecordDecl *RD,
CharUnits VPtrOffset) override;
CGCallee getVirtualFunctionPointer(CodeGenFunction &CGF, GlobalDecl GD,
Address This, llvm::Type *Ty,
SourceLocation Loc) override;
llvm::Value *EmitVirtualDestructorCall(CodeGenFunction &CGF,
const CXXDestructorDecl *Dtor,
CXXDtorType DtorType, Address This,
DeleteOrMemberCallExpr E) override;
void adjustCallArgsForDestructorThunk(CodeGenFunction &CGF, GlobalDecl GD,
CallArgList &CallArgs) override {
assert(GD.getDtorType() == Dtor_Deleting &&
"Only deleting destructor thunks are available in this ABI");
void emitVirtualInheritanceTables(const CXXRecordDecl *RD) override;
llvm::GlobalVariable *
getAddrOfVBTable(const VPtrInfo &VBT, const CXXRecordDecl *RD,
llvm::GlobalVariable::LinkageTypes Linkage);
llvm::GlobalVariable *
getAddrOfVirtualDisplacementMap(const CXXRecordDecl *SrcRD,
const CXXRecordDecl *DstRD) {
SmallString<256> OutName;
llvm::raw_svector_ostream Out(OutName);
getMangleContext().mangleCXXVirtualDisplacementMap(SrcRD, DstRD, Out);
StringRef MangledName = OutName.str();
if (auto *VDispMap = CGM.getModule().getNamedGlobal(MangledName))
return VDispMap;
MicrosoftVTableContext &VTContext = CGM.getMicrosoftVTableContext();
unsigned NumEntries = 1 + SrcRD->getNumVBases();
SmallVector<llvm::Constant *, 4> Map(NumEntries,
Map[0] = llvm::ConstantInt::get(CGM.IntTy, 0);
bool AnyDifferent = false;
for (const auto &I : SrcRD->vbases()) {
const CXXRecordDecl *VBase = I.getType()->getAsCXXRecordDecl();
if (!DstRD->isVirtuallyDerivedFrom(VBase))
unsigned SrcVBIndex = VTContext.getVBTableIndex(SrcRD, VBase);
unsigned DstVBIndex = VTContext.getVBTableIndex(DstRD, VBase);
Map[SrcVBIndex] = llvm::ConstantInt::get(CGM.IntTy, DstVBIndex * 4);
AnyDifferent |= SrcVBIndex != DstVBIndex;
// This map would be useless, don't use it.
if (!AnyDifferent)
return nullptr;
llvm::ArrayType *VDispMapTy = llvm::ArrayType::get(CGM.IntTy, Map.size());
llvm::Constant *Init = llvm::ConstantArray::get(VDispMapTy, Map);
llvm::GlobalValue::LinkageTypes Linkage =
SrcRD->isExternallyVisible() && DstRD->isExternallyVisible()
? llvm::GlobalValue::LinkOnceODRLinkage
: llvm::GlobalValue::InternalLinkage;
auto *VDispMap = new llvm::GlobalVariable(
CGM.getModule(), VDispMapTy, /*isConstant=*/true, Linkage,
/*Initializer=*/Init, MangledName);
return VDispMap;
void emitVBTableDefinition(const VPtrInfo &VBT, const CXXRecordDecl *RD,
llvm::GlobalVariable *GV) const;
void setThunkLinkage(llvm::Function *Thunk, bool ForVTable,
GlobalDecl GD, bool ReturnAdjustment) override {
GVALinkage Linkage =
if (Linkage == GVA_Internal)
else if (ReturnAdjustment)
bool exportThunk() override { return false; }
llvm::Value *performThisAdjustment(CodeGenFunction &CGF, Address This,
const ThisAdjustment &TA) override;
llvm::Value *performReturnAdjustment(CodeGenFunction &CGF, Address Ret,
const ReturnAdjustment &RA) override;
void EmitThreadLocalInitFuncs(
CodeGenModule &CGM, ArrayRef<const VarDecl *> CXXThreadLocals,
ArrayRef<llvm::Function *> CXXThreadLocalInits,
ArrayRef<const VarDecl *> CXXThreadLocalInitVars) override;
bool usesThreadWrapperFunction(const VarDecl *VD) const override {
return false;
LValue EmitThreadLocalVarDeclLValue(CodeGenFunction &CGF, const VarDecl *VD,
QualType LValType) override;
void EmitGuardedInit(CodeGenFunction &CGF, const VarDecl &D,
llvm::GlobalVariable *DeclPtr,
bool PerformInit) override;
void registerGlobalDtor(CodeGenFunction &CGF, const VarDecl &D,
llvm::FunctionCallee Dtor,
llvm::Constant *Addr) override;
// ==== Notes on array cookies =========
// MSVC seems to only use cookies when the class has a destructor; a
// two-argument usual array deallocation function isn't sufficient.
// For example, this code prints "100" and "1":
// struct A {
// char x;
// void *operator new[](size_t sz) {
// printf("%u\n", sz);
// return malloc(sz);
// }
// void operator delete[](void *p, size_t sz) {
// printf("%u\n", sz);
// free(p);
// }
// };
// int main() {
// A *p = new A[100];
// delete[] p;
// }
// Whereas it prints "104" and "104" if you give A a destructor.
bool requiresArrayCookie(const CXXDeleteExpr *expr,
QualType elementType) override;
bool requiresArrayCookie(const CXXNewExpr *expr) override;
CharUnits getArrayCookieSizeImpl(QualType type) override;
Address InitializeArrayCookie(CodeGenFunction &CGF,
Address NewPtr,
llvm::Value *NumElements,
const CXXNewExpr *expr,
QualType ElementType) override;
llvm::Value *readArrayCookieImpl(CodeGenFunction &CGF,
Address allocPtr,
CharUnits cookieSize) override;
friend struct MSRTTIBuilder;
bool isImageRelative() const {
return CGM.getTarget().getPointerWidth(/*AddrSpace=*/0) == 64;
// 5 routines for constructing the llvm types for MS RTTI structs.
llvm::StructType *getTypeDescriptorType(StringRef TypeInfoString) {
llvm::SmallString<32> TDTypeName("rtti.TypeDescriptor");
TDTypeName += llvm::utostr(TypeInfoString.size());
llvm::StructType *&TypeDescriptorType =
if (TypeDescriptorType)
return TypeDescriptorType;
llvm::Type *FieldTypes[] = {
llvm::ArrayType::get(CGM.Int8Ty, TypeInfoString.size() + 1)};
TypeDescriptorType =
llvm::StructType::create(CGM.getLLVMContext(), FieldTypes, TDTypeName);
return TypeDescriptorType;
llvm::Type *getImageRelativeType(llvm::Type *PtrType) {
if (!isImageRelative())
return PtrType;
return CGM.IntTy;
llvm::StructType *getBaseClassDescriptorType() {
if (BaseClassDescriptorType)
return BaseClassDescriptorType;
llvm::Type *FieldTypes[] = {
BaseClassDescriptorType = llvm::StructType::create(
CGM.getLLVMContext(), FieldTypes, "rtti.BaseClassDescriptor");
return BaseClassDescriptorType;
llvm::StructType *getClassHierarchyDescriptorType() {
if (ClassHierarchyDescriptorType)
return ClassHierarchyDescriptorType;
// Forward-declare RTTIClassHierarchyDescriptor to break a cycle.
ClassHierarchyDescriptorType = llvm::StructType::create(
CGM.getLLVMContext(), "rtti.ClassHierarchyDescriptor");
llvm::Type *FieldTypes[] = {
return ClassHierarchyDescriptorType;
llvm::StructType *getCompleteObjectLocatorType() {
if (CompleteObjectLocatorType)
return CompleteObjectLocatorType;
CompleteObjectLocatorType = llvm::StructType::create(
CGM.getLLVMContext(), "rtti.CompleteObjectLocator");
llvm::Type *FieldTypes[] = {
llvm::ArrayRef<llvm::Type *> FieldTypesRef(FieldTypes);
if (!isImageRelative())
FieldTypesRef = FieldTypesRef.drop_back();
return CompleteObjectLocatorType;
llvm::GlobalVariable *getImageBase() {
StringRef Name = "__ImageBase";
if (llvm::GlobalVariable *GV = CGM.getModule().getNamedGlobal(Name))
return GV;
auto *GV = new llvm::GlobalVariable(CGM.getModule(), CGM.Int8Ty,
/*Initializer=*/nullptr, Name);
return GV;
llvm::Constant *getImageRelativeConstant(llvm::Constant *PtrVal) {
if (!isImageRelative())
return PtrVal;
if (PtrVal->isNullValue())
return llvm::Constant::getNullValue(CGM.IntTy);
llvm::Constant *ImageBaseAsInt =
llvm::ConstantExpr::getPtrToInt(getImageBase(), CGM.IntPtrTy);
llvm::Constant *PtrValAsInt =
llvm::ConstantExpr::getPtrToInt(PtrVal, CGM.IntPtrTy);
llvm::Constant *Diff =
llvm::ConstantExpr::getSub(PtrValAsInt, ImageBaseAsInt,
/*HasNUW=*/true, /*HasNSW=*/true);
return llvm::ConstantExpr::getTrunc(Diff, CGM.IntTy);
MicrosoftMangleContext &getMangleContext() {
return cast<MicrosoftMangleContext>(CodeGen::CGCXXABI::getMangleContext());
llvm::Constant *getZeroInt() {
return llvm::ConstantInt::get(CGM.IntTy, 0);
llvm::Constant *getAllOnesInt() {
return llvm::Constant::getAllOnesValue(CGM.IntTy);
CharUnits getVirtualFunctionPrologueThisAdjustment(GlobalDecl GD) override;
GetNullMemberPointerFields(const MemberPointerType *MPT,
llvm::SmallVectorImpl<llvm::Constant *> &fields);
/// Shared code for virtual base adjustment. Returns the offset from
/// the vbptr to the virtual base. Optionally returns the address of the
/// vbptr itself.
llvm::Value *GetVBaseOffsetFromVBPtr(CodeGenFunction &CGF,
Address Base,
llvm::Value *VBPtrOffset,
llvm::Value *VBTableOffset,
llvm::Value **VBPtr = nullptr);
llvm::Value *GetVBaseOffsetFromVBPtr(CodeGenFunction &CGF,
Address Base,
int32_t VBPtrOffset,
int32_t VBTableOffset,
llvm::Value **VBPtr = nullptr) {
assert(VBTableOffset % 4 == 0 && "should be byte offset into table of i32s");
llvm::Value *VBPOffset = llvm::ConstantInt::get(CGM.IntTy, VBPtrOffset),
*VBTOffset = llvm::ConstantInt::get(CGM.IntTy, VBTableOffset);
return GetVBaseOffsetFromVBPtr(CGF, Base, VBPOffset, VBTOffset, VBPtr);
std::tuple<Address, llvm::Value *, const CXXRecordDecl *>
performBaseAdjustment(CodeGenFunction &CGF, Address Value,
QualType SrcRecordTy);
/// Performs a full virtual base adjustment. Used to dereference
/// pointers to members of virtual bases.
llvm::Value *AdjustVirtualBase(CodeGenFunction &CGF, const Expr *E,
const CXXRecordDecl *RD, Address Base,
llvm::Value *VirtualBaseAdjustmentOffset,
llvm::Value *VBPtrOffset /* optional */);
/// Emits a full member pointer with the fields common to data and
/// function member pointers.
llvm::Constant *EmitFullMemberPointer(llvm::Constant *FirstField,
bool IsMemberFunction,
const CXXRecordDecl *RD,
CharUnits NonVirtualBaseAdjustment,
unsigned VBTableIndex);
bool MemberPointerConstantIsNull(const MemberPointerType *MPT,
llvm::Constant *MP);
/// - Initialize all vbptrs of 'this' with RD as the complete type.
void EmitVBPtrStores(CodeGenFunction &CGF, const CXXRecordDecl *RD);
/// Caching wrapper around VBTableBuilder::enumerateVBTables().
const VBTableGlobals &enumerateVBTables(const CXXRecordDecl *RD);
/// Generate a thunk for calling a virtual member function MD.
llvm::Function *EmitVirtualMemPtrThunk(const CXXMethodDecl *MD,
const MethodVFTableLocation &ML);
llvm::Constant *EmitMemberDataPointer(const CXXRecordDecl *RD,
CharUnits offset);
llvm::Type *ConvertMemberPointerType(const MemberPointerType *MPT) override;
bool isZeroInitializable(const MemberPointerType *MPT) override;
bool isMemberPointerConvertible(const MemberPointerType *MPT) const override {
const CXXRecordDecl *RD = MPT->getMostRecentCXXRecordDecl();
return RD->hasAttr<MSInheritanceAttr>();
llvm::Constant *EmitNullMemberPointer(const MemberPointerType *MPT) override;
llvm::Constant *EmitMemberDataPointer(const MemberPointerType *MPT,
CharUnits offset) override;
llvm::Constant *EmitMemberFunctionPointer(const CXXMethodDecl *MD) override;
llvm::Constant *EmitMemberPointer(const APValue &MP, QualType MPT) override;
llvm::Value *EmitMemberPointerComparison(CodeGenFunction &CGF,
llvm::Value *L,
llvm::Value *R,
const MemberPointerType *MPT,
bool Inequality) override;
llvm::Value *EmitMemberPointerIsNotNull(CodeGenFunction &CGF,
llvm::Value *MemPtr,
const MemberPointerType *MPT) override;
llvm::Value *
EmitMemberDataPointerAddress(CodeGenFunction &CGF, const Expr *E,
Address Base, llvm::Value *MemPtr,
const MemberPointerType *MPT) override;
llvm::Value *EmitNonNullMemberPointerConversion(
const MemberPointerType *SrcTy, const MemberPointerType *DstTy,
CastKind CK, CastExpr::path_const_iterator PathBegin,
CastExpr::path_const_iterator PathEnd, llvm::Value *Src,
CGBuilderTy &Builder);
llvm::Value *EmitMemberPointerConversion(CodeGenFunction &CGF,
const CastExpr *E,
llvm::Value *Src) override;
llvm::Constant *EmitMemberPointerConversion(const CastExpr *E,
llvm::Constant *Src) override;
llvm::Constant *EmitMemberPointerConversion(
const MemberPointerType *SrcTy, const MemberPointerType *DstTy,
CastKind CK, CastExpr::path_const_iterator PathBegin,
CastExpr::path_const_iterator PathEnd, llvm::Constant *Src);
EmitLoadOfMemberFunctionPointer(CodeGenFunction &CGF, const Expr *E,
Address This, llvm::Value *&ThisPtrForCall,
llvm::Value *MemPtr,
const MemberPointerType *MPT) override;
void emitCXXStructor(GlobalDecl GD) override;
llvm::StructType *getCatchableTypeType() {
if (CatchableTypeType)
return CatchableTypeType;
llvm::Type *FieldTypes[] = {
CGM.IntTy, // Flags
getImageRelativeType(CGM.Int8PtrTy), // TypeDescriptor
CGM.IntTy, // NonVirtualAdjustment
CGM.IntTy, // OffsetToVBPtr
CGM.IntTy, // VBTableIndex
CGM.IntTy, // Size
getImageRelativeType(CGM.Int8PtrTy) // CopyCtor
CatchableTypeType = llvm::StructType::create(
CGM.getLLVMContext(), FieldTypes, "eh.CatchableType");
return CatchableTypeType;
llvm::StructType *getCatchableTypeArrayType(uint32_t NumEntries) {
llvm::StructType *&CatchableTypeArrayType =
if (CatchableTypeArrayType)
return CatchableTypeArrayType;
llvm::SmallString<23> CTATypeName("eh.CatchableTypeArray.");
CTATypeName += llvm::utostr(NumEntries);
llvm::Type *CTType =
llvm::Type *FieldTypes[] = {
CGM.IntTy, // NumEntries
llvm::ArrayType::get(CTType, NumEntries) // CatchableTypes
CatchableTypeArrayType =
llvm::StructType::create(CGM.getLLVMContext(), FieldTypes, CTATypeName);
return CatchableTypeArrayType;
llvm::StructType *getThrowInfoType() {
if (ThrowInfoType)
return ThrowInfoType;
llvm::Type *FieldTypes[] = {
CGM.IntTy, // Flags
getImageRelativeType(CGM.Int8PtrTy), // CleanupFn
getImageRelativeType(CGM.Int8PtrTy), // ForwardCompat
getImageRelativeType(CGM.Int8PtrTy) // CatchableTypeArray
ThrowInfoType = llvm::StructType::create(CGM.getLLVMContext(), FieldTypes,
return ThrowInfoType;
llvm::FunctionCallee getThrowFn() {
// _CxxThrowException is passed an exception object and a ThrowInfo object
// which describes the exception.
llvm::Type *Args[] = {CGM.Int8PtrTy, getThrowInfoType()->getPointerTo()};
llvm::FunctionType *FTy =
llvm::FunctionType::get(CGM.VoidTy, Args, /*isVarArg=*/false);
llvm::FunctionCallee Throw =
CGM.CreateRuntimeFunction(FTy, "_CxxThrowException");
// _CxxThrowException is stdcall on 32-bit x86 platforms.
if (CGM.getTarget().getTriple().getArch() == llvm::Triple::x86) {
if (auto *Fn = dyn_cast<llvm::Function>(Throw.getCallee()))
return Throw;
llvm::Function *getAddrOfCXXCtorClosure(const CXXConstructorDecl *CD,
CXXCtorType CT);
llvm::Constant *getCatchableType(QualType T,
uint32_t NVOffset = 0,
int32_t VBPtrOffset = -1,
uint32_t VBIndex = 0);
llvm::GlobalVariable *getCatchableTypeArray(QualType T);
llvm::GlobalVariable *getThrowInfo(QualType T) override;
std::pair<llvm::Value *, const CXXRecordDecl *>
LoadVTablePtr(CodeGenFunction &CGF, Address This,
const CXXRecordDecl *RD) override;
virtual bool
isPermittedToBeHomogeneousAggregate(const CXXRecordDecl *RD) const override;
typedef std::pair<const CXXRecordDecl *, CharUnits> VFTableIdTy;
typedef llvm::DenseMap<VFTableIdTy, llvm::GlobalVariable *> VTablesMapTy;
typedef llvm::DenseMap<VFTableIdTy, llvm::GlobalValue *> VFTablesMapTy;
/// All the vftables that have been referenced.
VFTablesMapTy VFTablesMap;
VTablesMapTy VTablesMap;
/// This set holds the record decls we've deferred vtable emission for.
llvm::SmallPtrSet<const CXXRecordDecl *, 4> DeferredVFTables;
/// All the vbtables which have been referenced.
llvm::DenseMap<const CXXRecordDecl *, VBTableGlobals> VBTablesMap;
/// Info on the global variable used to guard initialization of static locals.
/// The BitIndex field is only used for externally invisible declarations.
struct GuardInfo {
GuardInfo() : Guard(nullptr), BitIndex(0) {}
llvm::GlobalVariable *Guard;
unsigned BitIndex;
/// Map from DeclContext to the current guard variable. We assume that the
/// AST is visited in source code order.
llvm::DenseMap<const DeclContext *, GuardInfo> GuardVariableMap;
llvm::DenseMap<const DeclContext *, GuardInfo> ThreadLocalGuardVariableMap;
llvm::DenseMap<const DeclContext *, unsigned> ThreadSafeGuardNumMap;
llvm::DenseMap<size_t, llvm::StructType *> TypeDescriptorTypeMap;
llvm::StructType *BaseClassDescriptorType;
llvm::StructType *ClassHierarchyDescriptorType;
llvm::StructType *CompleteObjectLocatorType;
llvm::DenseMap<QualType, llvm::GlobalVariable *> CatchableTypeArrays;
llvm::StructType *CatchableTypeType;
llvm::DenseMap<uint32_t, llvm::StructType *> CatchableTypeArrayTypeMap;
llvm::StructType *ThrowInfoType;
MicrosoftCXXABI::getRecordArgABI(const CXXRecordDecl *RD) const {
// Use the default C calling convention rules for things that can be passed in
// registers, i.e. non-trivially copyable records or records marked with
// [[trivial_abi]].
if (RD->canPassInRegisters())
return RAA_Default;
switch (CGM.getTarget().getTriple().getArch()) {
// FIXME: Implement for other architectures.
return RAA_Indirect;
case llvm::Triple::thumb:
// Pass things indirectly for now because it is simple.
// FIXME: This is incompatible with MSVC for arguments with a dtor and no
// copy ctor.
return RAA_Indirect;
case llvm::Triple::x86: {
// If the argument has *required* alignment greater than four bytes, pass
// it indirectly. Prior to MSVC version 19.14, passing overaligned
// arguments was not supported and resulted in a compiler error. In 19.14
// and later versions, such arguments are now passed indirectly.
TypeInfo Info = getContext().getTypeInfo(RD->getTypeForDecl());
if (Info.AlignIsRequired && Info.Align > 4)
return RAA_Indirect;
// If C++ prohibits us from making a copy, construct the arguments directly
// into argument memory.
return RAA_DirectInMemory;
case llvm::Triple::x86_64:
case llvm::Triple::aarch64:
return RAA_Indirect;
llvm_unreachable("invalid enum");
void MicrosoftCXXABI::emitVirtualObjectDelete(CodeGenFunction &CGF,
const CXXDeleteExpr *DE,
Address Ptr,
QualType ElementType,
const CXXDestructorDecl *Dtor) {
// FIXME: Provide a source location here even though there's no
// CXXMemberCallExpr for dtor call.
bool UseGlobalDelete = DE->isGlobalDelete();
CXXDtorType DtorType = UseGlobalDelete ? Dtor_Complete : Dtor_Deleting;
llvm::Value *MDThis = EmitVirtualDestructorCall(CGF, Dtor, DtorType, Ptr, DE);
if (UseGlobalDelete)
CGF.EmitDeleteCall(DE->getOperatorDelete(), MDThis, ElementType);
void MicrosoftCXXABI::emitRethrow(CodeGenFunction &CGF, bool isNoReturn) {
llvm::Value *Args[] = {
llvm::FunctionCallee Fn = getThrowFn();
if (isNoReturn)
CGF.EmitNoreturnRuntimeCallOrInvoke(Fn, Args);
CGF.EmitRuntimeCallOrInvoke(Fn, Args);
void MicrosoftCXXABI::emitBeginCatch(CodeGenFunction &CGF,
const CXXCatchStmt *S) {
// In the MS ABI, the runtime handles the copy, and the catch handler is
// responsible for destruction.
VarDecl *CatchParam = S->getExceptionDecl();
llvm::BasicBlock *CatchPadBB = CGF.Builder.GetInsertBlock();
llvm::CatchPadInst *CPI =
CGF.CurrentFuncletPad = CPI;
// If this is a catch-all or the catch parameter is unnamed, we don't need to
// emit an alloca to the object.
if (!CatchParam || !CatchParam->getDeclName()) {
CGF.EHStack.pushCleanup<CatchRetScope>(NormalCleanup, CPI);
CodeGenFunction::AutoVarEmission var = CGF.EmitAutoVarAlloca(*CatchParam);
CPI->setArgOperand(2, var.getObjectAddress(CGF).getPointer());
CGF.EHStack.pushCleanup<CatchRetScope>(NormalCleanup, CPI);
/// We need to perform a generic polymorphic operation (like a typeid
/// or a cast), which requires an object with a vfptr. Adjust the
/// address to point to an object with a vfptr.
std::tuple<Address, llvm::Value *, const CXXRecordDecl *>
MicrosoftCXXABI::performBaseAdjustment(CodeGenFunction &CGF, Address Value,
QualType SrcRecordTy) {
Value = CGF.Builder.CreateBitCast(Value, CGF.Int8PtrTy);
const CXXRecordDecl *SrcDecl = SrcRecordTy->getAsCXXRecordDecl();
const ASTContext &Context = getContext();
// If the class itself has a vfptr, great. This check implicitly
// covers non-virtual base subobjects: a class with its own virtual
// functions would be a candidate to be a primary base.
if (Context.getASTRecordLayout(SrcDecl).hasExtendableVFPtr())
return std::make_tuple(Value, llvm::ConstantInt::get(CGF.Int32Ty, 0),
// Okay, one of the vbases must have a vfptr, or else this isn't
// actually a polymorphic class.
const CXXRecordDecl *PolymorphicBase = nullptr;
for (auto &Base : SrcDecl->vbases()) {
const CXXRecordDecl *BaseDecl = Base.getType()->getAsCXXRecordDecl();
if (Context.getASTRecordLayout(BaseDecl).hasExtendableVFPtr()) {
PolymorphicBase = BaseDecl;
assert(PolymorphicBase && "polymorphic class has no apparent vfptr?");
llvm::Value *Offset =
GetVirtualBaseClassOffset(CGF, Value, SrcDecl, PolymorphicBase);
llvm::Value *Ptr = CGF.Builder.CreateInBoundsGEP(
Value.getElementType(), Value.getPointer(), Offset);
CharUnits VBaseAlign =
CGF.CGM.getVBaseAlignment(Value.getAlignment(), SrcDecl, PolymorphicBase);
return std::make_tuple(Address(Ptr, VBaseAlign), Offset, PolymorphicBase);
bool MicrosoftCXXABI::shouldTypeidBeNullChecked(bool IsDeref,
QualType SrcRecordTy) {
const CXXRecordDecl *SrcDecl = SrcRecordTy->getAsCXXRecordDecl();
return IsDeref &&
static llvm::CallBase *emitRTtypeidCall(CodeGenFunction &CGF,
llvm::Value *Argument) {
llvm::Type *ArgTypes[] = {CGF.Int8PtrTy};
llvm::FunctionType *FTy =
llvm::FunctionType::get(CGF.Int8PtrTy, ArgTypes, false);
llvm::Value *Args[] = {Argument};
llvm::FunctionCallee Fn = CGF.CGM.CreateRuntimeFunction(FTy, "__RTtypeid");
return CGF.EmitRuntimeCallOrInvoke(Fn, Args);
void MicrosoftCXXABI::EmitBadTypeidCall(CodeGenFunction &CGF) {
llvm::CallBase *Call =
emitRTtypeidCall(CGF, llvm::Constant::getNullValue(CGM.VoidPtrTy));
llvm::Value *MicrosoftCXXABI::EmitTypeid(CodeGenFunction &CGF,
QualType SrcRecordTy,
Address ThisPtr,
llvm::Type *StdTypeInfoPtrTy) {
std::tie(ThisPtr, std::ignore, std::ignore) =
performBaseAdjustment(CGF, ThisPtr, SrcRecordTy);
llvm::CallBase *Typeid = emitRTtypeidCall(CGF, ThisPtr.getPointer());
return CGF.Builder.CreateBitCast(Typeid, StdTypeInfoPtrTy);
bool MicrosoftCXXABI::shouldDynamicCastCallBeNullChecked(bool SrcIsPtr,
QualType SrcRecordTy) {
const CXXRecordDecl *SrcDecl = SrcRecordTy->getAsCXXRecordDecl();
return SrcIsPtr &&
llvm::Value *MicrosoftCXXABI::EmitDynamicCastCall(
CodeGenFunction &CGF, Address This, QualType SrcRecordTy,
QualType DestTy, QualType DestRecordTy, llvm::BasicBlock *CastEnd) {
llvm::Type *DestLTy = CGF.ConvertType(DestTy);
llvm::Value *SrcRTTI =
llvm::Value *DestRTTI =
llvm::Value *Offset;
std::tie(This, Offset, std::ignore) =
performBaseAdjustment(CGF, This, SrcRecordTy);
llvm::Value *ThisPtr = This.getPointer();
Offset = CGF.Builder.CreateTrunc(Offset, CGF.Int32Ty);
// PVOID __RTDynamicCast(
// PVOID inptr,
// LONG VfDelta,
// PVOID SrcType,
// PVOID TargetType,
// BOOL isReference)
llvm::Type *ArgTypes[] = {CGF.Int8PtrTy, CGF.Int32Ty, CGF.Int8PtrTy,
CGF.Int8PtrTy, CGF.Int32Ty};
llvm::FunctionCallee Function = CGF.CGM.CreateRuntimeFunction(
llvm::FunctionType::get(CGF.Int8PtrTy, ArgTypes, false),
llvm::Value *Args[] = {
ThisPtr, Offset, SrcRTTI, DestRTTI,
llvm::ConstantInt::get(CGF.Int32Ty, DestTy->isReferenceType())};
ThisPtr = CGF.EmitRuntimeCallOrInvoke(Function, Args);
return CGF.Builder.CreateBitCast(ThisPtr, DestLTy);
llvm::Value *
MicrosoftCXXABI::EmitDynamicCastToVoid(CodeGenFunction &CGF, Address Value,
QualType SrcRecordTy,
QualType DestTy) {
std::tie(Value, std::ignore, std::ignore) =
performBaseAdjustment(CGF, Value, SrcRecordTy);
// PVOID __RTCastToVoid(
// PVOID inptr)
llvm::Type *ArgTypes[] = {CGF.Int8PtrTy};
llvm::FunctionCallee Function = CGF.CGM.CreateRuntimeFunction(
llvm::FunctionType::get(CGF.Int8PtrTy, ArgTypes, false),
llvm::Value *Args[] = {Value.getPointer()};
return CGF.EmitRuntimeCall(Function, Args);
bool MicrosoftCXXABI::EmitBadCastCall(CodeGenFunction &CGF) {
return false;
llvm::Value *MicrosoftCXXABI::GetVirtualBaseClassOffset(
CodeGenFunction &CGF, Address This, const CXXRecordDecl *ClassDecl,
const CXXRecordDecl *BaseClassDecl) {
const ASTContext &Context = getContext();
int64_t VBPtrChars =
llvm::Value *VBPtrOffset = llvm::ConstantInt::get(CGM.PtrDiffTy, VBPtrChars);
CharUnits IntSize = Context.getTypeSizeInChars(Context.IntTy);
CharUnits VBTableChars =
IntSize *
CGM.getMicrosoftVTableContext().getVBTableIndex(ClassDecl, BaseClassDecl);
llvm::Value *VBTableOffset =
llvm::ConstantInt::get(CGM.IntTy, VBTableChars.getQuantity());
llvm::Value *VBPtrToNewBase =
GetVBaseOffsetFromVBPtr(CGF, This, VBPtrOffset, VBTableOffset);
VBPtrToNewBase =
CGF.Builder.CreateSExtOrBitCast(VBPtrToNewBase, CGM.PtrDiffTy);
return CGF.Builder.CreateNSWAdd(VBPtrOffset, VBPtrToNewBase);
bool MicrosoftCXXABI::HasThisReturn(GlobalDecl GD) const {
return isa<CXXConstructorDecl>(GD.getDecl());
static bool isDeletingDtor(GlobalDecl GD) {
return isa<CXXDestructorDecl>(GD.getDecl()) &&
GD.getDtorType() == Dtor_Deleting;
bool MicrosoftCXXABI::hasMostDerivedReturn(GlobalDecl GD) const {
return isDeletingDtor(GD);
static bool isTrivialForAArch64MSVC(const CXXRecordDecl *RD) {
// For AArch64, we use the C++14 definition of an aggregate, so we also
// check for:
// No private or protected non static data members.
// No base classes
// No virtual functions
// Additionally, we need to ensure that there is a trivial copy assignment
// operator, a trivial destructor and no user-provided constructors.
if (RD->hasProtectedFields() || RD->hasPrivateFields())
return false;
if (RD->getNumBases() > 0)
return false;
if (RD->isPolymorphic())
return false;
if (RD->hasNonTrivialCopyAssignment())
return false;
for (const CXXConstructorDecl *Ctor : RD->ctors())
if (Ctor->isUserProvided())
return false;
if (RD->hasNonTrivialDestructor())
return false;
return true;
bool MicrosoftCXXABI::classifyReturnType(CGFunctionInfo &FI) const {
const CXXRecordDecl *RD = FI.getReturnType()->getAsCXXRecordDecl();
if (!RD)
return false;
// Normally, the C++ concept of "is trivially copyable" is used to determine
// if a struct can be returned directly. However, as MSVC and the language
// have evolved, the definition of "trivially copyable" has changed, while the
// ABI must remain stable. AArch64 uses the C++14 concept of an "aggregate",
// while other ISAs use the older concept of "plain old data".
bool isTrivialForABI = RD->isPOD();
bool isAArch64 = CGM.getTarget().getTriple().isAArch64();
if (isAArch64)
isTrivialForABI = RD->canPassInRegisters() && isTrivialForAArch64MSVC(RD);
// MSVC always returns structs indirectly from C++ instance methods.
bool isIndirectReturn = !isTrivialForABI || FI.isInstanceMethod();
if (isIndirectReturn) {
CharUnits Align = CGM.getContext().getTypeAlignInChars(FI.getReturnType());
FI.getReturnInfo() = ABIArgInfo::getIndirect(Align, /*ByVal=*/false);
// MSVC always passes `this` before the `sret` parameter.
// On AArch64, use the `inreg` attribute if the object is considered to not
// be trivially copyable, or if this is an instance method struct return.
return true;
// Otherwise, use the C ABI rules.
return false;
llvm::BasicBlock *
MicrosoftCXXABI::EmitCtorCompleteObjectHandler(CodeGenFunction &CGF,
const CXXRecordDecl *RD) {
llvm::Value *IsMostDerivedClass = getStructorImplicitParamValue(CGF);
assert(IsMostDerivedClass &&
"ctor for a class with virtual bases must have an implicit parameter");
llvm::Value *IsCompleteObject =
CGF.Builder.CreateIsNotNull(IsMostDerivedClass, "is_complete_object");
llvm::BasicBlock *CallVbaseCtorsBB = CGF.createBasicBlock("ctor.init_vbases");
llvm::BasicBlock *SkipVbaseCtorsBB = CGF.createBasicBlock("ctor.skip_vbases");
CallVbaseCtorsBB, SkipVbaseCtorsBB);
// Fill in the vbtable pointers here.
EmitVBPtrStores(CGF, RD);
// CGF will put the base ctor calls in this basic block for us later.
return SkipVbaseCtorsBB;
llvm::BasicBlock *
MicrosoftCXXABI::EmitDtorCompleteObjectHandler(CodeGenFunction &CGF) {
llvm::Value *IsMostDerivedClass = getStructorImplicitParamValue(CGF);
assert(IsMostDerivedClass &&
"ctor for a class with virtual bases must have an implicit parameter");
llvm::Value *IsCompleteObject =
CGF.Builder.CreateIsNotNull(IsMostDerivedClass, "is_complete_object");
llvm::BasicBlock *CallVbaseDtorsBB = CGF.createBasicBlock("Dtor.dtor_vbases");
llvm::BasicBlock *SkipVbaseDtorsBB = CGF.createBasicBlock("Dtor.skip_vbases");
CallVbaseDtorsBB, SkipVbaseDtorsBB);
// CGF will put the base dtor calls in this basic block for us later.
return SkipVbaseDtorsBB;
void MicrosoftCXXABI::initializeHiddenVirtualInheritanceMembers(
CodeGenFunction &CGF, const CXXRecordDecl *RD) {
// In most cases, an override for a vbase virtual method can adjust
// the "this" parameter by applying a constant offset.
// However, this is not enough while a constructor or a destructor of some
// class X is being executed if all the following conditions are met:
// - X has virtual bases, (1)
// - X overrides a virtual method M of a vbase Y, (2)
// - X itself is a vbase of the most derived class.
// If (1) and (2) are true, the vtorDisp for vbase Y is a hidden member of X
// which holds the extra amount of "this" adjustment we must do when we use
// the X vftables (i.e. during X ctor or dtor).
// Outside the ctors and dtors, the values of vtorDisps are zero.
const ASTRecordLayout &Layout = getContext().getASTRecordLayout(RD);
typedef ASTRecordLayout::VBaseOffsetsMapTy VBOffsets;
const VBOffsets &VBaseMap = Layout.getVBaseOffsetsMap();
CGBuilderTy &Builder = CGF.Builder;
unsigned AS = getThisAddress(CGF).getAddressSpace();
llvm::Value *Int8This = nullptr; // Initialize lazily.
for (const CXXBaseSpecifier &S : RD->vbases()) {
const CXXRecordDecl *VBase = S.getType()->getAsCXXRecordDecl();
auto I = VBaseMap.find(VBase);
assert(I != VBaseMap.end());
if (!I->second.hasVtorDisp())
llvm::Value *VBaseOffset =
GetVirtualBaseClassOffset(CGF, getThisAddress(CGF), RD, VBase);
uint64_t ConstantVBaseOffset = I->second.VBaseOffset.getQuantity();
// vtorDisp_for_vbase = vbptr[vbase_idx] - offsetof(RD, vbase).
llvm::Value *VtorDispValue = Builder.CreateSub(
VBaseOffset, llvm::ConstantInt::get(CGM.PtrDiffTy, ConstantVBaseOffset),
VtorDispValue = Builder.CreateTruncOrBitCast(VtorDispValue, CGF.Int32Ty);
if (!Int8This)
Int8This = Builder.CreateBitCast(getThisValue(CGF),
llvm::Value *VtorDispPtr =
Builder.CreateInBoundsGEP(CGF.Int8Ty, Int8This, VBaseOffset);
// vtorDisp is always the 32-bits before the vbase in the class layout.
VtorDispPtr = Builder.CreateConstGEP1_32(VtorDispPtr, -4);
VtorDispPtr = Builder.CreateBitCast(
VtorDispPtr, CGF.Int32Ty->getPointerTo(AS), "vtordisp.ptr");
Builder.CreateAlignedStore(VtorDispValue, VtorDispPtr,
static bool hasDefaultCXXMethodCC(ASTContext &Context,
const CXXMethodDecl *MD) {
CallingConv ExpectedCallingConv = Context.getDefaultCallingConvention(
/*IsVariadic=*/false, /*IsCXXMethod=*/true);
CallingConv ActualCallingConv =
return ExpectedCallingConv == ActualCallingConv;
void MicrosoftCXXABI::EmitCXXConstructors(const CXXConstructorDecl *D) {
// There's only one constructor type in this ABI.
CGM.EmitGlobal(GlobalDecl(D, Ctor_Complete));
// Exported default constructors either have a simple call-site where they use
// the typical calling convention and have a single 'this' pointer for an
// argument -or- they get a wrapper function which appropriately thunks to the
// real default constructor. This thunk is the default constructor closure.
if (D->hasAttr<DLLExportAttr>() && D->isDefaultConstructor() &&
D->isDefined()) {
if (!hasDefaultCXXMethodCC(getContext(), D) || D->getNumParams() != 0) {
llvm::Function *Fn = getAddrOfCXXCtorClosure(D, Ctor_DefaultClosure);
CGM.setGVProperties(Fn, D);
void MicrosoftCXXABI::EmitVBPtrStores(CodeGenFunction &CGF,
const CXXRecordDecl *RD) {
Address This = getThisAddress(CGF);
This = CGF.Builder.CreateElementBitCast(This, CGM.Int8Ty, "this.int8");
const ASTContext &Context = getContext();
const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
const VBTableGlobals &VBGlobals = enumerateVBTables(RD);
for (unsigned I = 0, E = VBGlobals.VBTables->size(); I != E; ++I) {
const std::unique_ptr<VPtrInfo> &VBT = (*VBGlobals.VBTables)[I];
llvm::GlobalVariable *GV = VBGlobals.Globals[I];
const ASTRecordLayout &SubobjectLayout =
CharUnits Offs = VBT->NonVirtualOffset;
Offs += SubobjectLayout.getVBPtrOffset();
if (VBT->getVBaseWithVPtr())
Offs += Layout.getVBaseClassOffset(VBT->getVBaseWithVPtr());
Address VBPtr = CGF.Builder.CreateConstInBoundsByteGEP(This, Offs);
llvm::Value *GVPtr =
CGF.Builder.CreateConstInBoundsGEP2_32(GV->getValueType(), GV, 0, 0);
VBPtr = CGF.Builder.CreateElementBitCast(VBPtr, GVPtr->getType(),
"vbptr." + VBT->ObjectWithVPtr->getName());
CGF.Builder.CreateStore(GVPtr, VBPtr);
MicrosoftCXXABI::buildStructorSignature(GlobalDecl GD,
SmallVectorImpl<CanQualType> &ArgTys) {
AddedStructorArgCounts Added;
// TODO: 'for base' flag
if (isa<CXXDestructorDecl>(GD.getDecl()) &&
GD.getDtorType() == Dtor_Deleting) {
// The scalar deleting destructor takes an implicit int parameter.
auto *CD = dyn_cast<CXXConstructorDecl>(GD.getDecl());
if (!CD)
return Added;
// All parameters are already in place except is_most_derived, which goes
// after 'this' if it's variadic and last if it's not.
const CXXRecordDecl *Class = CD->getParent();
const FunctionProtoType *FPT = CD->getType()->castAs<FunctionProtoType>();
if (Class->getNumVBases()) {
if (FPT->isVariadic()) {
ArgTys.insert(ArgTys.begin() + 1, getContext().IntTy);
} else {
return Added;
void MicrosoftCXXABI::setCXXDestructorDLLStorage(llvm::GlobalValue *GV,
const CXXDestructorDecl *Dtor,
CXXDtorType DT) const {
// Deleting destructor variants are never imported or exported. Give them the
// default storage class.
if (DT == Dtor_Deleting) {
} else {
const NamedDecl *ND = Dtor;
CGM.setDLLImportDLLExport(GV, ND);
llvm::GlobalValue::LinkageTypes MicrosoftCXXABI::getCXXDestructorLinkage(
GVALinkage Linkage, const CXXDestructorDecl *Dtor, CXXDtorType DT) const {
// Internal things are always internal, regardless of attributes. After this,
// we know the thunk is externally visible.
if (Linkage == GVA_Internal)
return llvm::GlobalValue::InternalLinkage;
switch (DT) {
case Dtor_Base:
// The base destructor most closely tracks the user-declared constructor, so
// we delegate back to the normal declarator case.
return CGM.getLLVMLinkageForDeclarator(Dtor, Linkage,
case Dtor_Complete:
// The complete destructor is like an inline function, but it may be
// imported and therefore must be exported as well. This requires changing
// the linkage if a DLL attribute is present.
if (Dtor->hasAttr<DLLExportAttr>())
return llvm::GlobalValue::WeakODRLinkage;
if (Dtor->hasAttr<DLLImportAttr>())
return llvm::GlobalValue::AvailableExternallyLinkage;
return llvm::GlobalValue::LinkOnceODRLinkage;
case Dtor_Deleting:
// Deleting destructors are like inline functions. They have vague linkage
// and are emitted everywhere they are used. They are internal if the class
// is internal.
return llvm::GlobalValue::LinkOnceODRLinkage;
case Dtor_Comdat:
llvm_unreachable("MS C++ ABI does not support comdat dtors");
llvm_unreachable("invalid dtor type");
void MicrosoftCXXABI::EmitCXXDestructors(const CXXDestructorDecl *D) {
// The TU defining a dtor is only guaranteed to emit a base destructor. All
// other destructor variants are delegating thunks.
CGM.EmitGlobal(GlobalDecl(D, Dtor_Base));
// If the class is dllexported, emit the complete (vbase) destructor wherever
// the base dtor is emitted.
// FIXME: To match MSVC, this should only be done when the class is exported
// with -fdllexport-inlines enabled.
if (D->getParent()->getNumVBases() > 0 && D->hasAttr<DLLExportAttr>())
CGM.EmitGlobal(GlobalDecl(D, Dtor_Complete));
MicrosoftCXXABI::getVirtualFunctionPrologueThisAdjustment(GlobalDecl GD) {
const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl());
if (const CXXDestructorDecl *DD = dyn_cast<CXXDestructorDecl>(MD)) {
// Complete destructors take a pointer to the complete object as a
// parameter, thus don't need this adjustment.
if (GD.getDtorType() == Dtor_Complete)
return CharUnits();
// There's no Dtor_Base in vftable but it shares the this adjustment with
// the deleting one, so look it up instead.
GD = GlobalDecl(DD, Dtor_Deleting);
MethodVFTableLocation ML =
CharUnits Adjustment = ML.VFPtrOffset;
// Normal virtual instance methods need to adjust from the vfptr that first
// defined the virtual method to the virtual base subobject, but destructors
// do not. The vector deleting destructor thunk applies this adjustment for
// us if necessary.
if (isa<CXXDestructorDecl>(MD))
Adjustment = CharUnits::Zero();
if (ML.VBase) {
const ASTRecordLayout &DerivedLayout =
Adjustment += DerivedLayout.getVBaseClassOffset(ML.VBase);
return Adjustment;
Address MicrosoftCXXABI::adjustThisArgumentForVirtualFunctionCall(
CodeGenFunction &CGF, GlobalDecl GD, Address This,
bool VirtualCall) {
if (!VirtualCall) {
// If the call of a virtual function is not virtual, we just have to
// compensate for the adjustment the virtual function does in its prologue.
CharUnits Adjustment = getVirtualFunctionPrologueThisAdjustment(GD);
if (Adjustment.isZero())
return This;
This = CGF.Builder.CreateElementBitCast(This, CGF.Int8Ty);
return CGF.Builder.CreateConstByteGEP(This, Adjustment);
const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl());
GlobalDecl LookupGD = GD;
if (const CXXDestructorDecl *DD = dyn_cast<CXXDestructorDecl>(MD)) {
// Complete dtors take a pointer to the complete object,
// thus don't need adjustment.
if (GD.getDtorType() == Dtor_Complete)
return This;
// There's only Dtor_Deleting in vftable but it shares the this adjustment
// with the base one, so look up the deleting one instead.
LookupGD = GlobalDecl(DD, Dtor_Deleting);
MethodVFTableLocation ML =
CharUnits StaticOffset = ML.VFPtrOffset;
// Base destructors expect 'this' to point to the beginning of the base
// subobject, not the first vfptr that happens to contain the virtual dtor.
// However, we still need to apply the virtual base adjustment.
if (isa<CXXDestructorDecl>(MD) && GD.getDtorType() == Dtor_Base)
StaticOffset = CharUnits::Zero();
Address Result = This;
if (ML.VBase) {
Result = CGF.Builder.CreateElementBitCast(Result, CGF.Int8Ty);
const CXXRecordDecl *Derived = MD->getParent();
const CXXRecordDecl *VBase = ML.VBase;
llvm::Value *VBaseOffset =
GetVirtualBaseClassOffset(CGF, Result, Derived, VBase);
llvm::Value *VBasePtr = CGF.Builder.CreateInBoundsGEP(
Result.getElementType(), Result.getPointer(), VBaseOffset);
CharUnits VBaseAlign =
CGF.CGM.getVBaseAlignment(Result.getAlignment(), Derived, VBase);
Result = Address(VBasePtr, VBaseAlign);
if (!StaticOffset.isZero()) {
Result = CGF.Builder.CreateElementBitCast(Result, CGF.Int8Ty);
if (ML.VBase) {
// Non-virtual adjustment might result in a pointer outside the allocated
// object, e.g. if the final overrider class is laid out after the virtual
// base that declares a method in the most derived class.
// FIXME: Update the code that emits this adjustment in thunks prologues.
Result = CGF.Builder.CreateConstByteGEP(Result, StaticOffset);
} else {
Result = CGF.Builder.CreateConstInBoundsByteGEP(Result, StaticOffset);
return Result;
void MicrosoftCXXABI::addImplicitStructorParams(CodeGenFunction &CGF,
QualType &ResTy,
FunctionArgList &Params) {
ASTContext &Context = getContext();
const CXXMethodDecl *MD = cast<CXXMethodDecl>(CGF.CurGD.getDecl());
assert(isa<CXXConstructorDecl>(MD) || isa<CXXDestructorDecl>(MD));
if (isa<CXXConstructorDecl>(MD) && MD->getParent()->getNumVBases()) {
auto *IsMostDerived = ImplicitParamDecl::Create(
Context, /*DC=*/nullptr, CGF.CurGD.getDecl()->getLocation(),
&Context.Idents.get("is_most_derived"), Context.IntTy,
// The 'most_derived' parameter goes second if the ctor is variadic and last
// if it's not. Dtors can't be variadic.
const FunctionProtoType *FPT = MD->getType()->castAs<FunctionProtoType>();
if (FPT->isVariadic())
Params.insert(Params.begin() + 1, IsMostDerived);
getStructorImplicitParamDecl(CGF) = IsMostDerived;
} else if (isDeletingDtor(CGF.CurGD)) {
auto *ShouldDelete = ImplicitParamDecl::Create(
Context, /*DC=*/nullptr, CGF.CurGD.getDecl()->getLocation(),
&Context.Idents.get("should_call_delete"), Context.IntTy,
getStructorImplicitParamDecl(CGF) = ShouldDelete;
void MicrosoftCXXABI::EmitInstanceFunctionProlog(CodeGenFunction &CGF) {
// Naked functions have no prolog.
if (CGF.CurFuncDecl && CGF.CurFuncDecl->hasAttr<NakedAttr>())
// Overridden virtual methods of non-primary bases need to adjust the incoming
// 'this' pointer in the prologue. In this hierarchy, C::b will subtract
// sizeof(void*) to adjust from B* to C*:
// struct A { virtual void a(); };
// struct B { virtual void b(); };
// struct C : A, B { virtual void b(); };
// Leave the value stored in the 'this' alloca unadjusted, so that the
// debugger sees the unadjusted value. Microsoft debuggers require this, and
// will apply the ThisAdjustment in the method type information.
// FIXME: Do something better for DWARF debuggers, which won't expect this,
// without making our codegen depend on debug info settings.
llvm::Value *This = loadIncomingCXXThis(CGF);
const CXXMethodDecl *MD = cast<CXXMethodDecl>(CGF.CurGD.getDecl());
if (!CGF.CurFuncIsThunk && MD->isVirtual()) {
CharUnits Adjustment = getVirtualFunctionPrologueThisAdjustment(CGF.CurGD);
if (!Adjustment.isZero()) {
unsigned AS = cast<llvm::PointerType>(This->getType())->getAddressSpace();
llvm::Type *charPtrTy = CGF.Int8Ty->getPointerTo(AS),
*thisTy = This->getType();
This = CGF.Builder.CreateBitCast(This, charPtrTy);
This = CGF.Builder.CreateConstInBoundsGEP1_32(CGF.Int8Ty, This,
This = CGF.Builder.CreateBitCast(This, thisTy, "this.adjusted");
setCXXABIThisValue(CGF, This);
// If this is a function that the ABI specifies returns 'this', initialize
// the return slot to 'this' at the start of the function.
// Unlike the setting of return types, this is done within the ABI
// implementation instead of by clients of CGCXXABI because:
// 1) getThisValue is currently protected
// 2) in theory, an ABI could implement 'this' returns some other way;
// HasThisReturn only specifies a contract, not the implementation
if (HasThisReturn(CGF.CurGD))
CGF.Builder.CreateStore(getThisValue(CGF), CGF.ReturnValue);
else if (hasMostDerivedReturn(CGF.CurGD))
if (isa<CXXConstructorDecl>(MD) && MD->getParent()->getNumVBases()) {
assert(getStructorImplicitParamDecl(CGF) &&
"no implicit parameter for a constructor with virtual bases?");
= CGF.Builder.CreateLoad(
if (isDeletingDtor(CGF.CurGD)) {
assert(getStructorImplicitParamDecl(CGF) &&
"no implicit parameter for a deleting destructor?");
= CGF.Builder.CreateLoad(
CGCXXABI::AddedStructorArgs MicrosoftCXXABI::getImplicitConstructorArgs(
CodeGenFunction &CGF, const CXXConstructorDecl *D, CXXCtorType Type,
bool ForVirtualBase, bool Delegating) {
assert(Type == Ctor_Complete || Type == Ctor_Base);
// Check if we need a 'most_derived' parameter.
if (!D->getParent()->getNumVBases())
return AddedStructorArgs{};
// Add the 'most_derived' argument second if we are variadic or last if not.
const FunctionProtoType *FPT = D->getType()->castAs<FunctionProtoType>();
llvm::Value *MostDerivedArg;
if (Delegating) {
MostDerivedArg = getStructorImplicitParamValue(CGF);
} else {
MostDerivedArg = llvm::ConstantInt::get(CGM.Int32Ty, Type == Ctor_Complete);
if (FPT->isVariadic()) {
return AddedStructorArgs::prefix({{MostDerivedArg, getContext().IntTy}});
return AddedStructorArgs::suffix({{MostDerivedArg, getContext().IntTy}});
llvm::Value *MicrosoftCXXABI::getCXXDestructorImplicitParam(
CodeGenFunction &CGF, const CXXDestructorDecl *DD, CXXDtorType Type,
bool ForVirtualBase, bool Delegating) {
return nullptr;
void MicrosoftCXXABI::EmitDestructorCall(CodeGenFunction &CGF,
const CXXDestructorDecl *DD,
CXXDtorType Type, bool ForVirtualBase,
bool Delegating, Address This,
QualType ThisTy) {
// Use the base destructor variant in place of the complete destructor variant
// if the class has no virtual bases. This effectively implements some of the
// -mconstructor-aliases optimization, but as part of the MS C++ ABI.
if (Type == Dtor_Complete && DD->getParent()->getNumVBases() == 0)
Type = Dtor_Base;
GlobalDecl GD(DD, Type);
CGCallee Callee = CGCallee::forDirect(CGM.getAddrOfCXXStructor(GD), GD);
if (DD->isVirtual()) {
assert(Type != CXXDtorType::Dtor_Deleting &&
"The deleting destructor should only be called via a virtual call");
This = adjustThisArgumentForVirtualFunctionCall(CGF, GlobalDecl(DD, Type),
This, false);
llvm::BasicBlock *BaseDtorEndBB = nullptr;
if (ForVirtualBase && isa<CXXConstructorDecl>(CGF.CurCodeDecl)) {
BaseDtorEndBB = EmitDtorCompleteObjectHandler(CGF);
llvm::Value *Implicit =
getCXXDestructorImplicitParam(CGF, DD, Type, ForVirtualBase,
Delegating); // = nullptr
CGF.EmitCXXDestructorCall(GD, Callee, This.getPointer(), ThisTy,
/*ImplicitParamTy=*/QualType(), nullptr);
if (BaseDtorEndBB) {
// Complete object handler should continue to be the remaining
void MicrosoftCXXABI::emitVTableTypeMetadata(const VPtrInfo &Info,
const CXXRecordDecl *RD,
llvm::GlobalVariable *VTable) {
if (!CGM.getCodeGenOpts().LTOUnit)
// TODO: Should VirtualFunctionElimination also be supported here?
// See similar handling in CodeGenModule::EmitVTableTypeMetadata.
if (CGM.getCodeGenOpts().WholeProgramVTables) {
llvm::DenseSet<const CXXRecordDecl *> Visited;
llvm::GlobalObject::VCallVisibility TypeVis =
CGM.GetVCallVisibilityLevel(RD, Visited);
if (TypeVis != llvm::GlobalObject::VCallVisibilityPublic)
// The location of the first virtual function pointer in the virtual table,
// aka the "address point" on Itanium. This is at offset 0 if RTTI is
// disabled, or sizeof(void*) if RTTI is enabled.
CharUnits AddressPoint =
? getContext().toCharUnitsFromBits(
: CharUnits::Zero();
if (Info.PathToIntroducingObject.empty()) {
CGM.AddVTableTypeMetadata(VTable, AddressPoint, RD);
// Add a bitset entry for the least derived base belonging to this vftable.
CGM.AddVTableTypeMetadata(VTable, AddressPoint,
// Add a bitset entry for each derived class that is laid out at the same
// offset as the least derived base.
for (unsigned I = Info.PathToIntroducingObject.size() - 1; I != 0; --I) {
const CXXRecordDecl *DerivedRD = Info.PathToIntroducingObject[I - 1];
const CXXRecordDecl *BaseRD = Info.PathToIntroducingObject[I];
const ASTRecordLayout &Layout =
CharUnits Offset;
auto VBI = Layout.getVBaseOffsetsMap().find(BaseRD);
if (VBI == Layout.getVBaseOffsetsMap().end())
Offset = Layout.getBaseClassOffset(BaseRD);
Offset = VBI->second.VBaseOffset;
if (!Offset.isZero())
CGM.AddVTableTypeMetadata(VTable, AddressPoint, DerivedRD);
// Finally do the same for the most derived class.
if (Info.FullOffsetInMDC.isZero())
CGM.AddVTableTypeMetadata(VTable, AddressPoint, RD);
void MicrosoftCXXABI::emitVTableDefinitions(CodeGenVTables &CGVT,
const CXXRecordDecl *RD) {
MicrosoftVTableContext &VFTContext = CGM.getMicrosoftVTableContext();
const VPtrInfoVector &VFPtrs = VFTContext.getVFPtrOffsets(RD);
for (const std::unique_ptr<VPtrInfo>& Info : VFPtrs) {
llvm::GlobalVariable *VTable = getAddrOfVTable(RD, Info->FullOffsetInMDC);
if (VTable->hasInitializer())
const VTableLayout &VTLayout =
VFTContext.getVFTableLayout(RD, Info->FullOffsetInMDC);
llvm::Constant *RTTI = nullptr;
if (any_of(VTLayout.vtable_components(),
[](const VTableComponent &VTC) { return VTC.isRTTIKind(); }))
RTTI = getMSCompleteObjectLocator(RD, *Info);
ConstantInitBuilder builder(CGM);
auto components = builder.beginStruct();
CGVT.createVTableInitializer(components, VTLayout, RTTI,
emitVTableTypeMetadata(*Info, RD, VTable);
bool MicrosoftCXXABI::isVirtualOffsetNeededForVTableField(
CodeGenFunction &CGF, CodeGenFunction::VPtr Vptr) {
return Vptr.NearestVBase != nullptr;
llvm::Value *MicrosoftCXXABI::getVTableAddressPointInStructor(
CodeGenFunction &CGF, const CXXRecordDecl *VTableClass, BaseSubobject Base,
const CXXRecordDecl *NearestVBase) {
llvm::Constant *VTableAddressPoint = getVTableAddressPoint(Base, VTableClass);
if (!VTableAddressPoint) {
assert(Base.getBase()->getNumVBases() &&
return VTableAddressPoint;
static void mangleVFTableName(MicrosoftMangleContext &MangleContext,
const CXXRecordDecl *RD, const VPtrInfo &VFPtr,
SmallString<256> &Name) {
llvm::raw_svector_ostream Out(Name);
MangleContext.mangleCXXVFTable(RD, VFPtr.MangledPath, Out);
llvm::Constant *
MicrosoftCXXABI::getVTableAddressPoint(BaseSubobject Base,
const CXXRecordDecl *VTableClass) {
(void)getAddrOfVTable(VTableClass, Base.getBaseOffset());
VFTableIdTy ID(VTableClass, Base.getBaseOffset());
return VFTablesMap[ID];
llvm::Constant *MicrosoftCXXABI::getVTableAddressPointForConstExpr(
BaseSubobject Base, const CXXRecordDecl *VTableClass) {
llvm::Constant *VFTable = getVTableAddressPoint(Base, VTableClass);
assert(VFTable && "Couldn't find a vftable for the given base?");
return VFTable;
llvm::GlobalVariable *MicrosoftCXXABI::getAddrOfVTable(const CXXRecordDecl *RD,
CharUnits VPtrOffset) {
// getAddrOfVTable may return 0 if asked to get an address of a vtable which
// shouldn't be used in the given record type. We want to cache this result in
// VFTablesMap, thus a simple zero check is not sufficient.
VFTableIdTy ID(RD, VPtrOffset);
VTablesMapTy::iterator I;
bool Inserted;
std::tie(I, Inserted) = VTablesMap.insert(std::make_pair(ID, nullptr));
if (!Inserted)
return I->second;
llvm::GlobalVariable *&VTable = I->second;
MicrosoftVTableContext &VTContext = CGM.getMicrosoftVTableContext();
const VPtrInfoVector &VFPtrs = VTContext.getVFPtrOffsets(RD);
if (DeferredVFTables.insert(RD).second) {
// We haven't processed this record type before.
// Queue up this vtable for possible deferred emission.
#ifndef NDEBUG
// Create all the vftables at once in order to make sure each vftable has
// a unique mangled name.
llvm::StringSet<> ObservedMangledNames;
for (size_t J = 0, F = VFPtrs.size(); J != F; ++J) {
SmallString<256> Name;
mangleVFTableName(getMangleContext(), RD, *VFPtrs[J], Name);
if (!ObservedMangledNames.insert(Name.str()).second)
llvm_unreachable("Already saw this mangling before?");
const std::unique_ptr<VPtrInfo> *VFPtrI = std::find_if(
VFPtrs.begin(), VFPtrs.end(), [&](const std::unique_ptr<VPtrInfo>& VPI) {
return VPI->FullOffsetInMDC == VPtrOffset;
if (VFPtrI == VFPtrs.end()) {
VFTablesMap[ID] = nullptr;
return nullptr;
const std::unique_ptr<VPtrInfo> &VFPtr = *VFPtrI;
SmallString<256> VFTableName;
mangleVFTableName(getMangleContext(), RD, *VFPtr, VFTableName);
// Classes marked __declspec(dllimport) need vftables generated on the
// import-side in order to support features like constexpr. No other
// translation unit relies on the emission of the local vftable, translation
// units are expected to generate them as needed.
// Because of this unique behavior, we maintain this logic here instead of
// getVTableLinkage.
llvm::GlobalValue::LinkageTypes VFTableLinkage =
RD->hasAttr<DLLImportAttr>() ? llvm::GlobalValue::LinkOnceODRLinkage
: CGM.getVTableLinkage(RD);
bool VFTableComesFromAnotherTU =
llvm::GlobalValue::isAvailableExternallyLinkage(VFTableLinkage) ||
bool VTableAliasIsRequred =
!VFTableComesFromAnotherTU && getContext().getLangOpts().RTTIData;
if (llvm::GlobalValue *VFTable =
CGM.getModule().getNamedGlobal(VFTableName)) {
VFTablesMap[ID] = VFTable;
VTable = VTableAliasIsRequred
? cast<llvm::GlobalVariable>(
: cast<llvm::GlobalVariable>(VFTable);
return VTable;
const VTableLayout &VTLayout =
VTContext.getVFTableLayout(RD, VFPtr->FullOffsetInMDC);
llvm::GlobalValue::LinkageTypes VTableLinkage =
VTableAliasIsRequred ? llvm::GlobalValue::PrivateLinkage : VFTableLinkage;
StringRef VTableName = VTableAliasIsRequred ? StringRef() : VFTableName.str();
llvm::Type *VTableType = CGM.getVTables().getVTableType(VTLayout);
// Create a backing variable for the contents of VTable. The VTable may
// or may not include space for a pointer to RTTI data.
llvm::GlobalValue *VFTable;
VTable = new llvm::GlobalVariable(CGM.getModule(), VTableType,
/*isConstant=*/true, VTableLinkage,
/*Initializer=*/nullptr, VTableName);
llvm::Comdat *C = nullptr;
if (!VFTableComesFromAnotherTU &&
(llvm::GlobalValue::isWeakForLinker(VFTableLinkage) ||
(llvm::GlobalValue::isLocalLinkage(VFTableLinkage) &&
C = CGM.getModule().getOrInsertComdat(VFTableName.str());
// Only insert a pointer into the VFTable for RTTI data if we are not
// importing it. We never reference the RTTI data directly so there is no
// need to make room for it.
if (VTableAliasIsRequred) {
llvm::Value *GEPIndices[] = {llvm::ConstantInt::get(CGM.Int32Ty, 0),
llvm::ConstantInt::get(CGM.Int32Ty, 0),
llvm::ConstantInt::get(CGM.Int32Ty, 1)};
// Create a GEP which points just after the first entry in the VFTable,
// this should be the location of the first virtual method.
llvm::Constant *VTableGEP = llvm::ConstantExpr::getInBoundsGetElementPtr(
VTable->getValueType(), VTable, GEPIndices);
if (llvm::GlobalValue::isWeakForLinker(VFTableLinkage)) {
VFTableLinkage = llvm::GlobalValue::ExternalLinkage;
if (C)
VFTable = llvm::GlobalAlias::create(CGM.Int8PtrTy,
/*AddressSpace=*/0, VFTableLinkage,
VFTableName.str(), VTableGEP,
} else {
// We don't need a GlobalAlias to be a symbol for the VTable if we won't
// be referencing any RTTI data.
// The GlobalVariable will end up being an appropriate definition of the
// VFTable.
VFTable = VTable;
if (C)
if (RD->hasAttr<DLLExportAttr>())
VFTablesMap[ID] = VFTable;
return VTable;
CGCallee MicrosoftCXXABI::getVirtualFunctionPointer(CodeGenFunction &CGF,
GlobalDecl GD,
Address This,
llvm::Type *Ty,
SourceLocation Loc) {
CGBuilderTy &Builder = CGF.Builder;
Ty = Ty->getPointerTo();
Address VPtr =
adjustThisArgumentForVirtualFunctionCall(CGF, GD, This, true);
auto *MethodDecl = cast<CXXMethodDecl>(GD.getDecl());
llvm::Value *VTable = CGF.GetVTablePtr(VPtr, Ty->getPointerTo(),
MicrosoftVTableContext &VFTContext = CGM.getMicrosoftVTableContext();
MethodVFTableLocation ML = VFTContext.getMethodVFTableLocation(GD);
// Compute the identity of the most derived class whose virtual table is
// located at the MethodVFTableLocation ML.
auto getObjectWithVPtr = [&] {
return llvm::find_if(VFTContext.getVFPtrOffsets(
ML.VBase ? ML.VBase : MethodDecl->getParent()),
[&](const std::unique_ptr<VPtrInfo> &Info) {
return Info->FullOffsetInMDC == ML.VFPtrOffset;
llvm::Value *VFunc;
if (CGF.ShouldEmitVTableTypeCheckedLoad(MethodDecl->getParent())) {
VFunc = CGF.EmitVTableTypeCheckedLoad(
getObjectWithVPtr(), VTable,
ML.Index * CGM.getContext().getTargetInfo().getPointerWidth(0) / 8);
} else {
if (CGM.getCodeGenOpts().PrepareForLTO)
CGF.EmitTypeMetadataCodeForVCall(getObjectWithVPtr(), VTable, Loc);
llvm::Value *VFuncPtr =
Builder.CreateConstInBoundsGEP1_64(VTable, ML.Index, "vfn");
VFunc = Builder.CreateAlignedLoad(Ty, VFuncPtr, CGF.getPointerAlign());
CGCallee Callee(GD, VFunc);
return Callee;
llvm::Value *MicrosoftCXXABI::EmitVirtualDestructorCall(
CodeGenFunction &CGF, const CXXDestructorDecl *Dtor, CXXDtorType DtorType,
Address This, DeleteOrMemberCallExpr E) {
auto *CE = E.dyn_cast<const CXXMemberCallExpr *>();
auto *D = E.dyn_cast<const CXXDeleteExpr *>();
assert((CE != nullptr) ^ (D != nullptr));
assert(CE == nullptr || CE->arg_begin() == CE->arg_end());
assert(DtorType == Dtor_Deleting || DtorType == Dtor_Complete);
// We have only one destructor in the vftable but can get both behaviors
// by passing an implicit int parameter.
GlobalDecl GD(Dtor, Dtor_Deleting);
const CGFunctionInfo *FInfo =
llvm::FunctionType *Ty = CGF.CGM.getTypes().GetFunctionType(*FInfo);
CGCallee Callee = CGCallee::forVirtual(CE, GD, This, Ty);
ASTContext &Context = getContext();
llvm::Value *ImplicitParam = llvm::ConstantInt::get(
DtorType == Dtor_Deleting);
QualType ThisTy;
if (CE) {
ThisTy = CE->getObjectType();
} else {
ThisTy = D->getDestroyedType();
This = adjustThisArgumentForVirtualFunctionCall(CGF, GD, This, true);
RValue RV = CGF.EmitCXXDestructorCall(GD, Callee, This.getPointer(), ThisTy,
ImplicitParam, Context.IntTy, CE);
return RV.getScalarVal();
const VBTableGlobals &
MicrosoftCXXABI::enumerateVBTables(const CXXRecordDecl *RD) {
// At this layer, we can key the cache off of a single class, which is much
// easier than caching each vbtable individually.
llvm::DenseMap<const CXXRecordDecl*, VBTableGlobals>::iterator Entry;
bool Added;
std::tie(Entry, Added) =
VBTablesMap.insert(std::make_pair(RD, VBTableGlobals()));
VBTableGlobals &VBGlobals = Entry->second;
if (!Added)
return VBGlobals;
MicrosoftVTableContext &Context = CGM.getMicrosoftVTableContext();
VBGlobals.VBTables = &Context.enumerateVBTables(RD);
// Cache the globals for all vbtables so we don't have to recompute the
// mangled names.
llvm::GlobalVariable::LinkageTypes Linkage = CGM.getVTableLinkage(RD);
for (VPtrInfoVector::const_iterator I = VBGlobals.VBTables->begin(),
E = VBGlobals.VBTables->end();
I != E; ++I) {
VBGlobals.Globals.push_back(getAddrOfVBTable(**I, RD, Linkage));
return VBGlobals;
llvm::Function *
MicrosoftCXXABI::EmitVirtualMemPtrThunk(const CXXMethodDecl *MD,
const MethodVFTableLocation &ML) {
assert(!isa<CXXConstructorDecl>(MD) && !isa<CXXDestructorDecl>(MD) &&
"can't form pointers to ctors or virtual dtors");
// Calculate the mangled name.
SmallString<256> ThunkName;
llvm::raw_svector_ostream Out(ThunkName);
getMangleContext().mangleVirtualMemPtrThunk(MD, ML, Out);
// If the thunk has been generated previously, just return it.
if (llvm::GlobalValue *GV = CGM.getModule().getNamedValue(ThunkName))
return cast<llvm::Function>(GV);
// Create the llvm::Function.
const CGFunctionInfo &FnInfo =
llvm::FunctionType *ThunkTy = CGM.getTypes().GetFunctionType(FnInfo);
llvm::Function *ThunkFn =
llvm::Function::Create(ThunkTy, llvm::Function::ExternalLinkage,
ThunkName.str(), &CGM.getModule());
assert(ThunkFn->getName() == ThunkName && "name was uniqued!");
? llvm::GlobalValue::LinkOnceODRLinkage
: llvm::GlobalValue::InternalLinkage);
if (MD->isExternallyVisible())
CGM.SetLLVMFunctionAttributes(MD, FnInfo, ThunkFn);
CGM.SetLLVMFunctionAttributesForDefinition(MD, ThunkFn);
// 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.
// These thunks can be compared, so they are not unnamed.
// Start codegen.
CodeGenFunction CGF(CGM);
CGF.CurGD = GlobalDecl(MD);
CGF.CurFuncIsThunk = true;
// Build FunctionArgs, but only include the implicit 'this' parameter
// declaration.
FunctionArgList FunctionArgs;
buildThisParam(CGF, FunctionArgs);
// Start defining the function.
CGF.StartFunction(GlobalDecl(), FnInfo.getReturnType(), ThunkFn, FnInfo,
FunctionArgs, MD->getLocation(), SourceLocation());
setCXXABIThisValue(CGF, loadIncomingCXXThis(CGF));
// Load the vfptr and then callee from the vftable. The callee should have
// adjusted 'this' so that the vfptr is at offset zero.
llvm::Value *VTable = CGF.GetVTablePtr(
getThisAddress(CGF), ThunkTy->getPointerTo()->getPointerTo(), MD->getParent());
llvm::Value *VFuncPtr =
CGF.Builder.CreateConstInBoundsGEP1_64(VTable, ML.Index, "vfn");
llvm::Value *Callee =
CGF.Builder.CreateAlignedLoad(ThunkTy->getPointerTo(), VFuncPtr,
CGF.EmitMustTailThunk(MD, getThisValue(CGF), {ThunkTy, Callee});
return ThunkFn;
void MicrosoftCXXABI::emitVirtualInheritanceTables(const CXXRecordDecl *RD) {
const VBTableGlobals &VBGlobals = enumerateVBTables(RD);
for (unsigned I = 0, E = VBGlobals.VBTables->size(); I != E; ++I) {
const std::unique_ptr<VPtrInfo>& VBT = (*VBGlobals.VBTables)[I];
llvm::GlobalVariable *GV = VBGlobals.Globals[I];
if (GV->isDeclaration())
emitVBTableDefinition(*VBT, RD, GV);
llvm::GlobalVariable *
MicrosoftCXXABI::getAddrOfVBTable(const VPtrInfo &VBT, const CXXRecordDecl *RD,
llvm::GlobalVariable::LinkageTypes Linkage) {
SmallString<256> OutName;
llvm::raw_svector_ostream Out(OutName);
getMangleContext().mangleCXXVBTable(RD, VBT.MangledPath, Out);
StringRef Name = OutName.str();
llvm::ArrayType *VBTableType =
llvm::ArrayType::get(CGM.IntTy, 1 + VBT.ObjectWithVPtr->getNumVBases());
assert(!CGM.getModule().getNamedGlobal(Name) &&
"vbtable with this name already exists: mangling bug?");
CharUnits Alignment =
llvm::GlobalVariable *GV = CGM.CreateOrReplaceCXXRuntimeVariable(
Name, VBTableType, Linkage, Alignment.getQuantity());
if (RD->hasAttr<DLLImportAttr>())
else if (RD->hasAttr<DLLExportAttr>())
if (!GV->hasExternalLinkage())
emitVBTableDefinition(VBT, RD, GV);
return GV;
void MicrosoftCXXABI::emitVBTableDefinition(const VPtrInfo &VBT,
const CXXRecordDecl *RD,
llvm::GlobalVariable *GV) const {
const CXXRecordDecl *ObjectWithVPtr = VBT.ObjectWithVPtr;
assert(RD->getNumVBases() && ObjectWithVPtr->getNumVBases() &&
"should only emit vbtables for classes with vbtables");
const ASTRecordLayout &BaseLayout =
const ASTRecordLayout &DerivedLayout = getContext().getASTRecordLayout(RD);
SmallVector<llvm::Constant *, 4> Offsets(1 + ObjectWithVPtr->getNumVBases(),
// The offset from ObjectWithVPtr's vbptr to itself always leads.
CharUnits VBPtrOffset = BaseLayout.getVBPtrOffset();
Offsets[0] = llvm::ConstantInt::get(CGM.IntTy, -VBPtrOffset.getQuantity());
MicrosoftVTableContext &Context = CGM.getMicrosoftVTableContext();
for (const auto &I : ObjectWithVPtr->vbases()) {
const CXXRecordDecl *VBase = I.getType()->getAsCXXRecordDecl();
CharUnits Offset = DerivedLayout.getVBaseClassOffset(VBase);
// Make it relative to the subobject vbptr.
CharUnits CompleteVBPtrOffset = VBT.NonVirtualOffset + VBPtrOffset;
if (VBT.getVBaseWithVPtr())
CompleteVBPtrOffset +=
Offset -= CompleteVBPtrOffset;
unsigned VBIndex = Context.getVBTableIndex(ObjectWithVPtr, VBase);
assert(Offsets[VBIndex] == nullptr && "The same vbindex seen twice?");
Offsets[VBIndex] = llvm::ConstantInt::get(CGM.IntTy, Offset.getQuantity());
assert(Offsets.size() ==
llvm::ArrayType *VBTableType =
llvm::ArrayType::get(CGM.IntTy, Offsets.size());
llvm::Constant *Init = llvm::ConstantArray::get(VBTableType, Offsets);
if (RD->hasAttr<DLLImportAttr>())
llvm::Value *MicrosoftCXXABI::performThisAdjustment(CodeGenFunction &CGF,
Address This,
const ThisAdjustment &TA) {
if (TA.isEmpty())
return This.getPointer();
This = CGF.Builder.CreateElementBitCast(This, CGF.Int8Ty);
llvm::Value *V;
if (TA.Virtual.isEmpty()) {
V = This.getPointer();
} else {
assert(TA.Virtual.Microsoft.VtordispOffset < 0);
// Adjust the this argument based on the vtordisp value.
Address VtorDispPtr =
VtorDispPtr = CGF.Builder.CreateElementBitCast(VtorDispPtr, CGF.Int32Ty);
llvm::Value *VtorDisp = CGF.Builder.CreateLoad(VtorDispPtr, "vtordisp");
V = CGF.Builder.CreateGEP(This.getPointer(),
// Unfortunately, having applied the vtordisp means that we no
// longer really have a known alignment for the vbptr step.
// We'll assume the vbptr is pointer-aligned.
if (TA.Virtual.Microsoft.VBPtrOffset) {
// If the final overrider is defined in a virtual base other than the one
// that holds the vfptr, we have to use a vtordispex thunk which looks up
// the vbtable of the derived class.
assert(TA.Virtual.Microsoft.VBPtrOffset > 0);
assert(TA.Virtual.Microsoft.VBOffsetOffset >= 0);
llvm::Value *VBPtr;
llvm::Value *VBaseOffset =
GetVBaseOffsetFromVBPtr(CGF, Address(V, CGF.getPointerAlign()),
TA.Virtual.Microsoft.VBOffsetOffset, &VBPtr);
V = CGF.Builder.CreateInBoundsGEP(CGF.Int8Ty, VBPtr, VBaseOffset);
if (TA.NonVirtual) {
// Non-virtual adjustment might result in a pointer outside the allocated
// object, e.g. if the final overrider class is laid out after the virtual
// base that declares a method in the most derived class.
V = CGF.Builder.CreateConstGEP1_32(V, TA.NonVirtual);
// Don't need to bitcast back, the call CodeGen will handle this.
return V;
llvm::Value *
MicrosoftCXXABI::performReturnAdjustment(CodeGenFunction &CGF, Address Ret,
const ReturnAdjustment &RA) {
if (RA.isEmpty())
return Ret.getPointer();
auto OrigTy = Ret.getType();
Ret = CGF.Builder.CreateElementBitCast(Ret, CGF.Int8Ty);
llvm::Value *V = Ret.getPointer();
if (RA.Virtual.Microsoft.VBIndex) {
assert(RA.Virtual.Microsoft.VBIndex > 0);
int32_t IntSize = CGF.getIntSize().getQuantity();
llvm::Value *VBPtr;
llvm::Value *VBaseOffset =
GetVBaseOffsetFromVBPtr(CGF, Ret, RA.Virtual.Microsoft.VBPtrOffset,
IntSize * RA.Virtual.Microsoft.VBIndex, &VBPtr);
V = CGF.Builder.CreateInBoundsGEP(CGF.Int8Ty, VBPtr, VBaseOffset);
if (RA.NonVirtual)
V = CGF.Builder.CreateConstInBoundsGEP1_32(CGF.Int8Ty, V, RA.NonVirtual);
// Cast back to the original type.
return CGF.Builder.CreateBitCast(V, OrigTy);
bool MicrosoftCXXABI::requiresArrayCookie(const CXXDeleteExpr *expr,
QualType elementType) {
// Microsoft seems to completely ignore the possibility of a
// two-argument usual deallocation function.
return elementType.isDestructedType();
bool MicrosoftCXXABI::requiresArrayCookie(const CXXNewExpr *expr) {
// Microsoft seems to completely ignore the possibility of a
// two-argument usual deallocation function.
return expr->getAllocatedType().isDestructedType();
CharUnits MicrosoftCXXABI::getArrayCookieSizeImpl(QualType type) {
// The array cookie is always a size_t; we then pad that out to the
// alignment of the element type.
ASTContext &Ctx = getContext();
return std::max(Ctx.getTypeSizeInChars(Ctx.getSizeType()),
llvm::Value *MicrosoftCXXABI::readArrayCookieImpl(CodeGenFunction &CGF,
Address allocPtr,
CharUnits cookieSize) {
Address numElementsPtr =
CGF.Builder.CreateElementBitCast(allocPtr, CGF.SizeTy);
return CGF.Builder.CreateLoad(numElementsPtr);
Address MicrosoftCXXABI::InitializeArrayCookie(CodeGenFunction &CGF,
Address newPtr,
llvm::Value *numElements,
const CXXNewExpr *expr,
QualType elementType) {
// The size of the cookie.
CharUnits cookieSize = getArrayCookieSizeImpl(elementType);
// Compute an offset to the cookie.
Address cookiePtr = newPtr;
// Write the number of elements into the appropriate slot.
Address numElementsPtr
= CGF.Builder.CreateElementBitCast(cookiePtr, CGF.SizeTy);
CGF.Builder.CreateStore(numElements, numElementsPtr);
// Finally, compute a pointer to the actual data buffer by skipping
// over the cookie completely.
return CGF.Builder.CreateConstInBoundsByteGEP(newPtr, cookieSize);
static void emitGlobalDtorWithTLRegDtor(CodeGenFunction &CGF, const VarDecl &VD,
llvm::FunctionCallee Dtor,
llvm::Constant *Addr) {
// Create a function which calls the destructor.
llvm::Constant *DtorStub = CGF.createAtExitStub(VD, Dtor, Addr);
// extern "C" int __tlregdtor(void (*f)(void));
llvm::FunctionType *TLRegDtorTy = llvm::FunctionType::get(
CGF.IntTy, DtorStub->getType(), /*isVarArg=*/false);
llvm::FunctionCallee TLRegDtor = CGF.CGM.CreateRuntimeFunction(
TLRegDtorTy, "__tlregdtor", llvm::AttributeList(), /*Local=*/true);
if (llvm::Function *TLRegDtorFn =
CGF.EmitNounwindRuntimeCall(TLRegDtor, DtorStub);
void MicrosoftCXXABI::registerGlobalDtor(CodeGenFunction &CGF, const VarDecl &D,
llvm::FunctionCallee Dtor,
llvm::Constant *Addr) {
if (D.isNoDestroy(CGM.getContext()))
if (D.getTLSKind())
return emitGlobalDtorWithTLRegDtor(CGF, D, Dtor, Addr);
// The default behavior is to use atexit.
CGF.registerGlobalDtorWithAtExit(D, Dtor, Addr);
void MicrosoftCXXABI::EmitThreadLocalInitFuncs(
CodeGenModule &CGM, ArrayRef<const VarDecl *> CXXThreadLocals,
ArrayRef<llvm::Function *> CXXThreadLocalInits,
ArrayRef<const VarDecl *> CXXThreadLocalInitVars) {
if (CXXThreadLocalInits.empty())
CGM.AppendLinkerOptions(CGM.getTarget().getTriple().getArch() ==
? "/include:___dyn_tls_init@12"
: "/include:__dyn_tls_init");
// This will create a GV in the .CRT$XDU section. It will point to our
// initialization function. The CRT will call all of these function
// pointers at start-up time and, eventually, at thread-creation time.
auto AddToXDU = [&CGM](llvm::Function *InitFunc) {
llvm::GlobalVariable *InitFuncPtr = new llvm::GlobalVariable(
CGM.getModule(), InitFunc->getType(), /*isConstant=*/true,
llvm::GlobalVariable::InternalLinkage, InitFunc,
Twine(InitFunc->getName(), "$initializer$"));
// This variable has discardable linkage, we have to add it to @llvm.used to
// ensure it won't get discarded.
return InitFuncPtr;
std::vector<llvm::Function *> NonComdatInits;
for (size_t I = 0, E = CXXThreadLocalInitVars.size(); I != E; ++I) {
llvm::GlobalVariable *GV = cast<llvm::GlobalVariable>(
llvm::Function *F = CXXThreadLocalInits[I];
// If the GV is already in a comdat group, then we have to join it.
if (llvm::Comdat *C = GV->getComdat())