clang/lib/CodeGen/CGCXXABI.cpp - llvm-project - Git at Google

 //===----- CGCXXABI.cpp - Interface to C++ ABIs ---------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 // This provides an abstract class for C++ code generation. Concrete subclasses
 // of this implement code generation for specific C++ ABIs.
 //
 //===----------------------------------------------------------------------===//

 #include "CGCXXABI.h"
 #include "CGCleanup.h"
 #include "clang/AST/Attr.h"

 using namespace clang;
 using namespace CodeGen;

 CGCXXABI::~CGCXXABI() { }

 void CGCXXABI::ErrorUnsupportedABI(CodeGenFunction &CGF, StringRef S) {
   DiagnosticsEngine &Diags = CGF.CGM.getDiags();
   unsigned DiagID = Diags.getCustomDiagID(DiagnosticsEngine::Error,
                                           "cannot yet compile %0 in this ABI");
   Diags.Report(CGF.getContext().getFullLoc(CGF.CurCodeDecl->getLocation()),
                DiagID)
     << S;
 }

 llvm::Constant *CGCXXABI::GetBogusMemberPointer(QualType T) {
   return llvm::Constant::getNullValue(CGM.getTypes().ConvertType(T));
 }

 llvm::Type *
 CGCXXABI::ConvertMemberPointerType(const MemberPointerType *MPT) {
   return CGM.getTypes().ConvertType(CGM.getContext().getPointerDiffType());
 }

 CGCallee CGCXXABI::EmitLoadOfMemberFunctionPointer(
     CodeGenFunction &CGF, const Expr *E, Address This,
     llvm::Value *&ThisPtrForCall,
     llvm::Value *MemPtr, const MemberPointerType *MPT) {
   ErrorUnsupportedABI(CGF, "calls through member pointers");

   ThisPtrForCall = This.getPointer();
   const FunctionProtoType *FPT =
     MPT->getPointeeType()->getAs<FunctionProtoType>();
   const auto *RD =
       cast<CXXRecordDecl>(MPT->getClass()->castAs<RecordType>()->getDecl());
   llvm::FunctionType *FTy = CGM.getTypes().GetFunctionType(
       CGM.getTypes().arrangeCXXMethodType(RD, FPT, /*FD=*/nullptr));
   llvm::Constant *FnPtr = llvm::Constant::getNullValue(FTy->getPointerTo());
   return CGCallee::forDirect(FnPtr, FPT);
 }

 llvm::Value *
 CGCXXABI::EmitMemberDataPointerAddress(CodeGenFunction &CGF, const Expr *E,
                                        Address Base, llvm::Value *MemPtr,
                                        const MemberPointerType *MPT) {
   ErrorUnsupportedABI(CGF, "loads of member pointers");
   llvm::Type *Ty = CGF.ConvertType(MPT->getPointeeType())
                          ->getPointerTo(Base.getAddressSpace());
   return llvm::Constant::getNullValue(Ty);
 }

 llvm::Value *CGCXXABI::EmitMemberPointerConversion(CodeGenFunction &CGF,
                                                    const CastExpr *E,
                                                    llvm::Value *Src) {
   ErrorUnsupportedABI(CGF, "member function pointer conversions");
   return GetBogusMemberPointer(E->getType());
 }

 llvm::Constant *CGCXXABI::EmitMemberPointerConversion(const CastExpr *E,
                                                       llvm::Constant *Src) {
   return GetBogusMemberPointer(E->getType());
 }

 llvm::Value *
 CGCXXABI::EmitMemberPointerComparison(CodeGenFunction &CGF,
                                       llvm::Value *L,
                                       llvm::Value *R,
                                       const MemberPointerType *MPT,
                                       bool Inequality) {
   ErrorUnsupportedABI(CGF, "member function pointer comparison");
   return CGF.Builder.getFalse();
 }

 llvm::Value *
 CGCXXABI::EmitMemberPointerIsNotNull(CodeGenFunction &CGF,
                                      llvm::Value *MemPtr,
                                      const MemberPointerType *MPT) {
   ErrorUnsupportedABI(CGF, "member function pointer null testing");
   return CGF.Builder.getFalse();
 }

 llvm::Constant *
 CGCXXABI::EmitNullMemberPointer(const MemberPointerType *MPT) {
   return GetBogusMemberPointer(QualType(MPT, 0));
 }

 llvm::Constant *CGCXXABI::EmitMemberFunctionPointer(const CXXMethodDecl *MD) {
   return GetBogusMemberPointer(CGM.getContext().getMemberPointerType(
       MD->getType(), MD->getParent()->getTypeForDecl()));
 }

 llvm::Constant *CGCXXABI::EmitMemberDataPointer(const MemberPointerType *MPT,
                                                 CharUnits offset) {
   return GetBogusMemberPointer(QualType(MPT, 0));
 }

 llvm::Constant *CGCXXABI::EmitMemberPointer(const APValue &MP, QualType MPT) {
   return GetBogusMemberPointer(MPT);
 }

 bool CGCXXABI::isZeroInitializable(const MemberPointerType *MPT) {
   // Fake answer.
   return true;
 }

 void CGCXXABI::buildThisParam(CodeGenFunction &CGF, FunctionArgList &params) {
   const CXXMethodDecl *MD = cast<CXXMethodDecl>(CGF.CurGD.getDecl());

   // FIXME: I'm not entirely sure I like using a fake decl just for code
   // generation. Maybe we can come up with a better way?
   auto *ThisDecl = ImplicitParamDecl::Create(
       CGM.getContext(), nullptr, MD->getLocation(),
       &CGM.getContext().Idents.get("this"), MD->getThisType(),
       ImplicitParamDecl::CXXThis);
   params.push_back(ThisDecl);
   CGF.CXXABIThisDecl = ThisDecl;

   // Compute the presumed alignment of 'this', which basically comes
   // down to whether we know it's a complete object or not.
   auto &Layout = CGF.getContext().getASTRecordLayout(MD->getParent());
   if (MD->getParent()->getNumVBases() == 0 || // avoid vcall in common case
       MD->getParent()->isEffectivelyFinal() ||
       isThisCompleteObject(CGF.CurGD)) {
     CGF.CXXABIThisAlignment = Layout.getAlignment();
   } else {
     CGF.CXXABIThisAlignment = Layout.getNonVirtualAlignment();
   }
 }

 llvm::Value *CGCXXABI::loadIncomingCXXThis(CodeGenFunction &CGF) {
   return CGF.Builder.CreateLoad(CGF.GetAddrOfLocalVar(getThisDecl(CGF)),
                                 "this");
 }

 void CGCXXABI::setCXXABIThisValue(CodeGenFunction &CGF, llvm::Value *ThisPtr) {
   /// Initialize the 'this' slot.
   assert(getThisDecl(CGF) && "no 'this' variable for function");
   CGF.CXXABIThisValue = ThisPtr;
 }

 void CGCXXABI::EmitReturnFromThunk(CodeGenFunction &CGF,
                                    RValue RV, QualType ResultType) {
   assert(!CGF.hasAggregateEvaluationKind(ResultType) &&
          "cannot handle aggregates");
   CGF.EmitReturnOfRValue(RV, ResultType);
 }

 CharUnits CGCXXABI::GetArrayCookieSize(const CXXNewExpr *expr) {
   if (!requiresArrayCookie(expr))
     return CharUnits::Zero();
   return getArrayCookieSizeImpl(expr->getAllocatedType());
 }

 CharUnits CGCXXABI::getArrayCookieSizeImpl(QualType elementType) {
   // BOGUS
   return CharUnits::Zero();
 }

 Address CGCXXABI::InitializeArrayCookie(CodeGenFunction &CGF,
                                         Address NewPtr,
                                         llvm::Value *NumElements,
                                         const CXXNewExpr *expr,
                                         QualType ElementType) {
   // Should never be called.
   ErrorUnsupportedABI(CGF, "array cookie initialization");
   return Address::invalid();
 }

 bool CGCXXABI::requiresArrayCookie(const CXXDeleteExpr *expr,
                                    QualType elementType) {
   // If the class's usual deallocation function takes two arguments,
   // it needs a cookie.
   if (expr->doesUsualArrayDeleteWantSize())
     return true;

   return elementType.isDestructedType();
 }

 bool CGCXXABI::requiresArrayCookie(const CXXNewExpr *expr) {
   // If the class's usual deallocation function takes two arguments,
   // it needs a cookie.
   if (expr->doesUsualArrayDeleteWantSize())
     return true;

   return expr->getAllocatedType().isDestructedType();
 }

 void CGCXXABI::ReadArrayCookie(CodeGenFunction &CGF, Address ptr,
                                const CXXDeleteExpr *expr, QualType eltTy,
                                llvm::Value *&numElements,
                                llvm::Value *&allocPtr, CharUnits &cookieSize) {
   // Derive a char* in the same address space as the pointer.
   ptr = CGF.Builder.CreateElementBitCast(ptr, CGF.Int8Ty);

   // If we don't need an array cookie, bail out early.
   if (!requiresArrayCookie(expr, eltTy)) {
     allocPtr = ptr.getPointer();
     numElements = nullptr;
     cookieSize = CharUnits::Zero();
     return;
   }

   cookieSize = getArrayCookieSizeImpl(eltTy);
   Address allocAddr =
     CGF.Builder.CreateConstInBoundsByteGEP(ptr, -cookieSize);
   allocPtr = allocAddr.getPointer();
   numElements = readArrayCookieImpl(CGF, allocAddr, cookieSize);
 }

 llvm::Value *CGCXXABI::readArrayCookieImpl(CodeGenFunction &CGF,
                                            Address ptr,
                                            CharUnits cookieSize) {
   ErrorUnsupportedABI(CGF, "reading a new[] cookie");
   return llvm::ConstantInt::get(CGF.SizeTy, 0);
 }

 /// Returns the adjustment, in bytes, required for the given
 /// member-pointer operation.  Returns null if no adjustment is
 /// required.
 llvm::Constant *CGCXXABI::getMemberPointerAdjustment(const CastExpr *E) {
   assert(E->getCastKind() == CK_DerivedToBaseMemberPointer ||
          E->getCastKind() == CK_BaseToDerivedMemberPointer);

   QualType derivedType;
   if (E->getCastKind() == CK_DerivedToBaseMemberPointer)
     derivedType = E->getSubExpr()->getType();
   else
     derivedType = E->getType();

   const CXXRecordDecl *derivedClass =
     derivedType->castAs<MemberPointerType>()->getClass()->getAsCXXRecordDecl();

   return CGM.GetNonVirtualBaseClassOffset(derivedClass,
                                           E->path_begin(),
                                           E->path_end());
 }

 llvm::BasicBlock *
 CGCXXABI::EmitCtorCompleteObjectHandler(CodeGenFunction &CGF,
                                         const CXXRecordDecl *RD) {
   if (CGM.getTarget().getCXXABI().hasConstructorVariants())
     llvm_unreachable("shouldn't be called in this ABI");

   ErrorUnsupportedABI(CGF, "complete object detection in ctor");
   return nullptr;
 }

 void CGCXXABI::setCXXDestructorDLLStorage(llvm::GlobalValue *GV,
                                           const CXXDestructorDecl *Dtor,
                                           CXXDtorType DT) const {
   // Assume the base C++ ABI has no special rules for destructor variants.
   CGM.setDLLImportDLLExport(GV, Dtor);
 }

 llvm::GlobalValue::LinkageTypes CGCXXABI::getCXXDestructorLinkage(
     GVALinkage Linkage, const CXXDestructorDecl *Dtor, CXXDtorType DT) const {
   // Delegate back to CGM by default.
   return CGM.getLLVMLinkageForDeclarator(Dtor, Linkage,
                                          /*IsConstantVariable=*/false);
 }

 bool CGCXXABI::NeedsVTTParameter(GlobalDecl GD) {
   return false;
 }

 llvm::CallInst *
 CGCXXABI::emitTerminateForUnexpectedException(CodeGenFunction &CGF,
                                               llvm::Value *Exn) {
   // Just call std::terminate and ignore the violating exception.
   return CGF.EmitNounwindRuntimeCall(CGF.CGM.getTerminateFn());
 }

 CatchTypeInfo CGCXXABI::getCatchAllTypeInfo() {
   return CatchTypeInfo{nullptr, 0};
 }

 std::vector<CharUnits> CGCXXABI::getVBPtrOffsets(const CXXRecordDecl *RD) {
   return std::vector<CharUnits>();
 }

 CGCXXABI::AddedStructorArgCounts CGCXXABI::addImplicitConstructorArgs(
     CodeGenFunction &CGF, const CXXConstructorDecl *D, CXXCtorType Type,
     bool ForVirtualBase, bool Delegating, CallArgList &Args) {
   AddedStructorArgs AddedArgs =
       getImplicitConstructorArgs(CGF, D, Type, ForVirtualBase, Delegating);
   for (size_t i = 0; i < AddedArgs.Prefix.size(); ++i) {
     Args.insert(Args.begin() + 1 + i,
                 CallArg(RValue::get(AddedArgs.Prefix[i].Value),
                         AddedArgs.Prefix[i].Type));
   }
   for (const auto &arg : AddedArgs.Suffix) {
     Args.add(RValue::get(arg.Value), arg.Type);
   }
   return AddedStructorArgCounts(AddedArgs.Prefix.size(),
                                 AddedArgs.Suffix.size());
 }
	//===----- CGCXXABI.cpp - Interface to C++ ABIs ---------------------------===//
	//
	// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
	// See https://llvm.org/LICENSE.txt for license information.
	// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
	//
	//===----------------------------------------------------------------------===//
	//
	// This provides an abstract class for C++ code generation. Concrete subclasses
	// of this implement code generation for specific C++ ABIs.
	//
	//===----------------------------------------------------------------------===//

	#include "CGCXXABI.h"
	#include "CGCleanup.h"
	#include "clang/AST/Attr.h"

	using namespace clang;
	using namespace CodeGen;

	CGCXXABI::~CGCXXABI() { }

	void CGCXXABI::ErrorUnsupportedABI(CodeGenFunction &CGF, StringRef S) {
	DiagnosticsEngine &Diags = CGF.CGM.getDiags();
	unsigned DiagID = Diags.getCustomDiagID(DiagnosticsEngine::Error,
	"cannot yet compile %0 in this ABI");
	Diags.Report(CGF.getContext().getFullLoc(CGF.CurCodeDecl->getLocation()),
	DiagID)
	<< S;
	}

	llvm::Constant *CGCXXABI::GetBogusMemberPointer(QualType T) {
	return llvm::Constant::getNullValue(CGM.getTypes().ConvertType(T));
	}

	llvm::Type *
	CGCXXABI::ConvertMemberPointerType(const MemberPointerType *MPT) {
	return CGM.getTypes().ConvertType(CGM.getContext().getPointerDiffType());
	}

	CGCallee CGCXXABI::EmitLoadOfMemberFunctionPointer(
	CodeGenFunction &CGF, const Expr *E, Address This,
	llvm::Value *&ThisPtrForCall,
	llvm::Value MemPtr, const MemberPointerType MPT) {
	ErrorUnsupportedABI(CGF, "calls through member pointers");

	ThisPtrForCall = This.getPointer();
	const FunctionProtoType *FPT =
	MPT->getPointeeType()->getAs<FunctionProtoType>();
	const auto *RD =
	cast<CXXRecordDecl>(MPT->getClass()->castAs<RecordType>()->getDecl());
	llvm::FunctionType *FTy = CGM.getTypes().GetFunctionType(
	CGM.getTypes().arrangeCXXMethodType(RD, FPT, /FD=/nullptr));
	llvm::Constant *FnPtr = llvm::Constant::getNullValue(FTy->getPointerTo());
	return CGCallee::forDirect(FnPtr, FPT);
	}

	llvm::Value *
	CGCXXABI::EmitMemberDataPointerAddress(CodeGenFunction &CGF, const Expr *E,
	Address Base, llvm::Value *MemPtr,
	const MemberPointerType *MPT) {
	ErrorUnsupportedABI(CGF, "loads of member pointers");
	llvm::Type *Ty = CGF.ConvertType(MPT->getPointeeType())
	->getPointerTo(Base.getAddressSpace());
	return llvm::Constant::getNullValue(Ty);
	}

	llvm::Value *CGCXXABI::EmitMemberPointerConversion(CodeGenFunction &CGF,
	const CastExpr *E,
	llvm::Value *Src) {
	ErrorUnsupportedABI(CGF, "member function pointer conversions");
	return GetBogusMemberPointer(E->getType());
	}

	llvm::Constant CGCXXABI::EmitMemberPointerConversion(const CastExpr E,
	llvm::Constant *Src) {
	return GetBogusMemberPointer(E->getType());
	}

	llvm::Value *
	CGCXXABI::EmitMemberPointerComparison(CodeGenFunction &CGF,
	llvm::Value *L,
	llvm::Value *R,
	const MemberPointerType *MPT,
	bool Inequality) {
	ErrorUnsupportedABI(CGF, "member function pointer comparison");
	return CGF.Builder.getFalse();
	}

	llvm::Value *
	CGCXXABI::EmitMemberPointerIsNotNull(CodeGenFunction &CGF,
	llvm::Value *MemPtr,
	const MemberPointerType *MPT) {
	ErrorUnsupportedABI(CGF, "member function pointer null testing");
	return CGF.Builder.getFalse();
	}

	llvm::Constant *
	CGCXXABI::EmitNullMemberPointer(const MemberPointerType *MPT) {
	return GetBogusMemberPointer(QualType(MPT, 0));
	}

	llvm::Constant CGCXXABI::EmitMemberFunctionPointer(const CXXMethodDecl MD) {
	return GetBogusMemberPointer(CGM.getContext().getMemberPointerType(
	MD->getType(), MD->getParent()->getTypeForDecl()));
	}

	llvm::Constant CGCXXABI::EmitMemberDataPointer(const MemberPointerType MPT,
	CharUnits offset) {
	return GetBogusMemberPointer(QualType(MPT, 0));
	}

	llvm::Constant *CGCXXABI::EmitMemberPointer(const APValue &MP, QualType MPT) {
	return GetBogusMemberPointer(MPT);
	}

	bool CGCXXABI::isZeroInitializable(const MemberPointerType *MPT) {
	// Fake answer.
	return true;
	}

	void CGCXXABI::buildThisParam(CodeGenFunction &CGF, FunctionArgList &params) {
	const CXXMethodDecl *MD = cast<CXXMethodDecl>(CGF.CurGD.getDecl());

	// FIXME: I'm not entirely sure I like using a fake decl just for code
	// generation. Maybe we can come up with a better way?
	auto *ThisDecl = ImplicitParamDecl::Create(
	CGM.getContext(), nullptr, MD->getLocation(),
	&CGM.getContext().Idents.get("this"), MD->getThisType(),
	ImplicitParamDecl::CXXThis);
	params.push_back(ThisDecl);
	CGF.CXXABIThisDecl = ThisDecl;

	// Compute the presumed alignment of 'this', which basically comes
	// down to whether we know it's a complete object or not.
	auto &Layout = CGF.getContext().getASTRecordLayout(MD->getParent());
	if (MD->getParent()->getNumVBases() == 0 \|\| // avoid vcall in common case
	MD->getParent()->isEffectivelyFinal() \|\|
	isThisCompleteObject(CGF.CurGD)) {
	CGF.CXXABIThisAlignment = Layout.getAlignment();
	} else {
	CGF.CXXABIThisAlignment = Layout.getNonVirtualAlignment();
	}
	}

	llvm::Value *CGCXXABI::loadIncomingCXXThis(CodeGenFunction &CGF) {
	return CGF.Builder.CreateLoad(CGF.GetAddrOfLocalVar(getThisDecl(CGF)),
	"this");
	}

	void CGCXXABI::setCXXABIThisValue(CodeGenFunction &CGF, llvm::Value *ThisPtr) {
	/// Initialize the 'this' slot.
	assert(getThisDecl(CGF) && "no 'this' variable for function");
	CGF.CXXABIThisValue = ThisPtr;
	}

	void CGCXXABI::EmitReturnFromThunk(CodeGenFunction &CGF,
	RValue RV, QualType ResultType) {
	assert(!CGF.hasAggregateEvaluationKind(ResultType) &&
	"cannot handle aggregates");
	CGF.EmitReturnOfRValue(RV, ResultType);
	}

	CharUnits CGCXXABI::GetArrayCookieSize(const CXXNewExpr *expr) {
	if (!requiresArrayCookie(expr))
	return CharUnits::Zero();
	return getArrayCookieSizeImpl(expr->getAllocatedType());
	}

	CharUnits CGCXXABI::getArrayCookieSizeImpl(QualType elementType) {
	// BOGUS
	return CharUnits::Zero();
	}

	Address CGCXXABI::InitializeArrayCookie(CodeGenFunction &CGF,
	Address NewPtr,
	llvm::Value *NumElements,
	const CXXNewExpr *expr,
	QualType ElementType) {
	// Should never be called.
	ErrorUnsupportedABI(CGF, "array cookie initialization");
	return Address::invalid();
	}

	bool CGCXXABI::requiresArrayCookie(const CXXDeleteExpr *expr,
	QualType elementType) {
	// If the class's usual deallocation function takes two arguments,
	// it needs a cookie.
	if (expr->doesUsualArrayDeleteWantSize())
	return true;

	return elementType.isDestructedType();
	}

	bool CGCXXABI::requiresArrayCookie(const CXXNewExpr *expr) {
	// If the class's usual deallocation function takes two arguments,
	// it needs a cookie.
	if (expr->doesUsualArrayDeleteWantSize())
	return true;

	return expr->getAllocatedType().isDestructedType();
	}

	void CGCXXABI::ReadArrayCookie(CodeGenFunction &CGF, Address ptr,
	const CXXDeleteExpr *expr, QualType eltTy,
	llvm::Value *&numElements,
	llvm::Value *&allocPtr, CharUnits &cookieSize) {
	// Derive a char* in the same address space as the pointer.
	ptr = CGF.Builder.CreateElementBitCast(ptr, CGF.Int8Ty);

	// If we don't need an array cookie, bail out early.
	if (!requiresArrayCookie(expr, eltTy)) {
	allocPtr = ptr.getPointer();
	numElements = nullptr;
	cookieSize = CharUnits::Zero();
	return;
	}

	cookieSize = getArrayCookieSizeImpl(eltTy);
	Address allocAddr =
	CGF.Builder.CreateConstInBoundsByteGEP(ptr, -cookieSize);
	allocPtr = allocAddr.getPointer();
	numElements = readArrayCookieImpl(CGF, allocAddr, cookieSize);
	}

	llvm::Value *CGCXXABI::readArrayCookieImpl(CodeGenFunction &CGF,
	Address ptr,
	CharUnits cookieSize) {
	ErrorUnsupportedABI(CGF, "reading a new[] cookie");
	return llvm::ConstantInt::get(CGF.SizeTy, 0);
	}

	/// Returns the adjustment, in bytes, required for the given
	/// member-pointer operation. Returns null if no adjustment is
	/// required.
	llvm::Constant CGCXXABI::getMemberPointerAdjustment(const CastExpr E) {
	assert(E->getCastKind() == CK_DerivedToBaseMemberPointer \|\|
	E->getCastKind() == CK_BaseToDerivedMemberPointer);

	QualType derivedType;
	if (E->getCastKind() == CK_DerivedToBaseMemberPointer)
	derivedType = E->getSubExpr()->getType();
	else
	derivedType = E->getType();

	const CXXRecordDecl *derivedClass =
	derivedType->castAs<MemberPointerType>()->getClass()->getAsCXXRecordDecl();

	return CGM.GetNonVirtualBaseClassOffset(derivedClass,
	E->path_begin(),
	E->path_end());
	}

	llvm::BasicBlock *
	CGCXXABI::EmitCtorCompleteObjectHandler(CodeGenFunction &CGF,
	const CXXRecordDecl *RD) {
	if (CGM.getTarget().getCXXABI().hasConstructorVariants())
	llvm_unreachable("shouldn't be called in this ABI");

	ErrorUnsupportedABI(CGF, "complete object detection in ctor");
	return nullptr;
	}

	void CGCXXABI::setCXXDestructorDLLStorage(llvm::GlobalValue *GV,
	const CXXDestructorDecl *Dtor,
	CXXDtorType DT) const {
	// Assume the base C++ ABI has no special rules for destructor variants.
	CGM.setDLLImportDLLExport(GV, Dtor);
	}

	llvm::GlobalValue::LinkageTypes CGCXXABI::getCXXDestructorLinkage(
	GVALinkage Linkage, const CXXDestructorDecl *Dtor, CXXDtorType DT) const {
	// Delegate back to CGM by default.
	return CGM.getLLVMLinkageForDeclarator(Dtor, Linkage,
	/IsConstantVariable=/false);
	}

	bool CGCXXABI::NeedsVTTParameter(GlobalDecl GD) {
	return false;
	}

	llvm::CallInst *
	CGCXXABI::emitTerminateForUnexpectedException(CodeGenFunction &CGF,
	llvm::Value *Exn) {
	// Just call std::terminate and ignore the violating exception.
	return CGF.EmitNounwindRuntimeCall(CGF.CGM.getTerminateFn());
	}

	CatchTypeInfo CGCXXABI::getCatchAllTypeInfo() {
	return CatchTypeInfo{nullptr, 0};
	}

	std::vector<CharUnits> CGCXXABI::getVBPtrOffsets(const CXXRecordDecl *RD) {
	return std::vector<CharUnits>();
	}

	CGCXXABI::AddedStructorArgCounts CGCXXABI::addImplicitConstructorArgs(
	CodeGenFunction &CGF, const CXXConstructorDecl *D, CXXCtorType Type,
	bool ForVirtualBase, bool Delegating, CallArgList &Args) {
	AddedStructorArgs AddedArgs =
	getImplicitConstructorArgs(CGF, D, Type, ForVirtualBase, Delegating);
	for (size_t i = 0; i < AddedArgs.Prefix.size(); ++i) {
	Args.insert(Args.begin() + 1 + i,
	CallArg(RValue::get(AddedArgs.Prefix[i].Value),
	AddedArgs.Prefix[i].Type));
	}
	for (const auto &arg : AddedArgs.Suffix) {
	Args.add(RValue::get(arg.Value), arg.Type);
	}
	return AddedStructorArgCounts(AddedArgs.Prefix.size(),
	AddedArgs.Suffix.size());
	}