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//===----- CGCXXABI.h - Interface to C++ ABIs -------------------*- C++ -*-===//
// 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 an abstract class for C++ code generation. Concrete subclasses
// of this implement code generation for specific C++ ABIs.
#include "CodeGenFunction.h"
#include "clang/Basic/LLVM.h"
namespace llvm {
class Constant;
class Type;
class Value;
class CallInst;
namespace clang {
class CastExpr;
class CXXConstructorDecl;
class CXXDestructorDecl;
class CXXMethodDecl;
class CXXRecordDecl;
class FieldDecl;
class MangleContext;
namespace CodeGen {
class CGCallee;
class CodeGenFunction;
class CodeGenModule;
struct CatchTypeInfo;
/// Implements C++ ABI-specific code generation functions.
class CGCXXABI {
CodeGenModule &CGM;
std::unique_ptr<MangleContext> MangleCtx;
CGCXXABI(CodeGenModule &CGM)
: CGM(CGM), MangleCtx(CGM.getContext().createMangleContext()) {}
ImplicitParamDecl *getThisDecl(CodeGenFunction &CGF) {
return CGF.CXXABIThisDecl;
llvm::Value *getThisValue(CodeGenFunction &CGF) {
return CGF.CXXABIThisValue;
Address getThisAddress(CodeGenFunction &CGF) {
return Address(CGF.CXXABIThisValue, CGF.CXXABIThisAlignment);
/// Issue a diagnostic about unsupported features in the ABI.
void ErrorUnsupportedABI(CodeGenFunction &CGF, StringRef S);
/// Get a null value for unsupported member pointers.
llvm::Constant *GetBogusMemberPointer(QualType T);
ImplicitParamDecl *&getStructorImplicitParamDecl(CodeGenFunction &CGF) {
return CGF.CXXStructorImplicitParamDecl;
llvm::Value *&getStructorImplicitParamValue(CodeGenFunction &CGF) {
return CGF.CXXStructorImplicitParamValue;
/// Loads the incoming C++ this pointer as it was passed by the caller.
llvm::Value *loadIncomingCXXThis(CodeGenFunction &CGF);
void setCXXABIThisValue(CodeGenFunction &CGF, llvm::Value *ThisPtr);
ASTContext &getContext() const { return CGM.getContext(); }
virtual bool requiresArrayCookie(const CXXDeleteExpr *E, QualType eltType);
virtual bool requiresArrayCookie(const CXXNewExpr *E);
/// Determine whether there's something special about the rules of
/// the ABI tell us that 'this' is a complete object within the
/// given function. Obvious common logic like being defined on a
/// final class will have been taken care of by the caller.
virtual bool isThisCompleteObject(GlobalDecl GD) const = 0;
virtual ~CGCXXABI();
/// Gets the mangle context.
MangleContext &getMangleContext() {
return *MangleCtx;
/// Returns true if the given constructor or destructor is one of the
/// kinds that the ABI says returns 'this' (only applies when called
/// non-virtually for destructors).
/// There currently is no way to indicate if a destructor returns 'this'
/// when called virtually, and code generation does not support the case.
virtual bool HasThisReturn(GlobalDecl GD) const { return false; }
virtual bool hasMostDerivedReturn(GlobalDecl GD) const { return false; }
/// Returns true if the target allows calling a function through a pointer
/// with a different signature than the actual function (or equivalently,
/// bitcasting a function or function pointer to a different function type).
/// In principle in the most general case this could depend on the target, the
/// calling convention, and the actual types of the arguments and return
/// value. Here it just means whether the signature mismatch could *ever* be
/// allowed; in other words, does the target do strict checking of signatures
/// for all calls.
virtual bool canCallMismatchedFunctionType() const { return true; }
/// If the C++ ABI requires the given type be returned in a particular way,
/// this method sets RetAI and returns true.
virtual bool classifyReturnType(CGFunctionInfo &FI) const = 0;
/// Specify how one should pass an argument of a record type.
enum RecordArgABI {
/// Pass it using the normal C aggregate rules for the ABI, potentially
/// introducing extra copies and passing some or all of it in registers.
RAA_Default = 0,
/// Pass it on the stack using its defined layout. The argument must be
/// evaluated directly into the correct stack position in the arguments area,
/// and the call machinery must not move it or introduce extra copies.
/// Pass it as a pointer to temporary memory.
/// Returns how an argument of the given record type should be passed.
virtual RecordArgABI getRecordArgABI(const CXXRecordDecl *RD) const = 0;
/// Returns true if the implicit 'sret' parameter comes after the implicit
/// 'this' parameter of C++ instance methods.
virtual bool isSRetParameterAfterThis() const { return false; }
/// Find the LLVM type used to represent the given member pointer
/// type.
virtual llvm::Type *
ConvertMemberPointerType(const MemberPointerType *MPT);
/// Load a member function from an object and a member function
/// pointer. Apply the this-adjustment and set 'This' to the
/// adjusted value.
virtual CGCallee EmitLoadOfMemberFunctionPointer(
CodeGenFunction &CGF, const Expr *E, Address This,
llvm::Value *&ThisPtrForCall, llvm::Value *MemPtr,
const MemberPointerType *MPT);
/// Calculate an l-value from an object and a data member pointer.
virtual llvm::Value *
EmitMemberDataPointerAddress(CodeGenFunction &CGF, const Expr *E,
Address Base, llvm::Value *MemPtr,
const MemberPointerType *MPT);
/// Perform a derived-to-base, base-to-derived, or bitcast member
/// pointer conversion.
virtual llvm::Value *EmitMemberPointerConversion(CodeGenFunction &CGF,
const CastExpr *E,
llvm::Value *Src);
/// Perform a derived-to-base, base-to-derived, or bitcast member
/// pointer conversion on a constant value.
virtual llvm::Constant *EmitMemberPointerConversion(const CastExpr *E,
llvm::Constant *Src);
/// Return true if the given member pointer can be zero-initialized
/// (in the C++ sense) with an LLVM zeroinitializer.
virtual bool isZeroInitializable(const MemberPointerType *MPT);
/// Return whether or not a member pointers type is convertible to an IR type.
virtual bool isMemberPointerConvertible(const MemberPointerType *MPT) const {
return true;
/// Create a null member pointer of the given type.
virtual llvm::Constant *EmitNullMemberPointer(const MemberPointerType *MPT);
/// Create a member pointer for the given method.
virtual llvm::Constant *EmitMemberFunctionPointer(const CXXMethodDecl *MD);
/// Create a member pointer for the given field.
virtual llvm::Constant *EmitMemberDataPointer(const MemberPointerType *MPT,
CharUnits offset);
/// Create a member pointer for the given member pointer constant.
virtual llvm::Constant *EmitMemberPointer(const APValue &MP, QualType MPT);
/// Emit a comparison between two member pointers. Returns an i1.
virtual llvm::Value *
EmitMemberPointerComparison(CodeGenFunction &CGF,
llvm::Value *L,
llvm::Value *R,
const MemberPointerType *MPT,
bool Inequality);
/// Determine if a member pointer is non-null. Returns an i1.
virtual llvm::Value *
EmitMemberPointerIsNotNull(CodeGenFunction &CGF,
llvm::Value *MemPtr,
const MemberPointerType *MPT);
/// A utility method for computing the offset required for the given
/// base-to-derived or derived-to-base member-pointer conversion.
/// Does not handle virtual conversions (in case we ever fully
/// support an ABI that allows this). Returns null if no adjustment
/// is required.
llvm::Constant *getMemberPointerAdjustment(const CastExpr *E);
/// Computes the non-virtual adjustment needed for a member pointer
/// conversion along an inheritance path stored in an APValue. Unlike
/// getMemberPointerAdjustment(), the adjustment can be negative if the path
/// is from a derived type to a base type.
CharUnits getMemberPointerPathAdjustment(const APValue &MP);
virtual void emitVirtualObjectDelete(CodeGenFunction &CGF,
const CXXDeleteExpr *DE,
Address Ptr, QualType ElementType,
const CXXDestructorDecl *Dtor) = 0;
virtual void emitRethrow(CodeGenFunction &CGF, bool isNoReturn) = 0;
virtual void emitThrow(CodeGenFunction &CGF, const CXXThrowExpr *E) = 0;
virtual llvm::GlobalVariable *getThrowInfo(QualType T) { return nullptr; }
/// Determine whether it's possible to emit a vtable for \p RD, even
/// though we do not know that the vtable has been marked as used by semantic
/// analysis.
virtual bool canSpeculativelyEmitVTable(const CXXRecordDecl *RD) const = 0;
virtual void emitBeginCatch(CodeGenFunction &CGF, const CXXCatchStmt *C) = 0;
virtual llvm::CallInst *
emitTerminateForUnexpectedException(CodeGenFunction &CGF,
llvm::Value *Exn);
virtual llvm::Constant *getAddrOfRTTIDescriptor(QualType Ty) = 0;
virtual CatchTypeInfo
getAddrOfCXXCatchHandlerType(QualType Ty, QualType CatchHandlerType) = 0;
virtual CatchTypeInfo getCatchAllTypeInfo();
virtual bool shouldTypeidBeNullChecked(bool IsDeref,
QualType SrcRecordTy) = 0;
virtual void EmitBadTypeidCall(CodeGenFunction &CGF) = 0;
virtual llvm::Value *EmitTypeid(CodeGenFunction &CGF, QualType SrcRecordTy,
Address ThisPtr,
llvm::Type *StdTypeInfoPtrTy) = 0;
virtual bool shouldDynamicCastCallBeNullChecked(bool SrcIsPtr,
QualType SrcRecordTy) = 0;
virtual llvm::Value *
EmitDynamicCastCall(CodeGenFunction &CGF, Address Value,
QualType SrcRecordTy, QualType DestTy,
QualType DestRecordTy, llvm::BasicBlock *CastEnd) = 0;
virtual llvm::Value *EmitDynamicCastToVoid(CodeGenFunction &CGF,
Address Value,
QualType SrcRecordTy,
QualType DestTy) = 0;
virtual bool EmitBadCastCall(CodeGenFunction &CGF) = 0;
virtual llvm::Value *GetVirtualBaseClassOffset(CodeGenFunction &CGF,
Address This,
const CXXRecordDecl *ClassDecl,
const CXXRecordDecl *BaseClassDecl) = 0;
virtual llvm::BasicBlock *EmitCtorCompleteObjectHandler(CodeGenFunction &CGF,
const CXXRecordDecl *RD);
/// Emit the code to initialize hidden members required
/// to handle virtual inheritance, if needed by the ABI.
virtual void
initializeHiddenVirtualInheritanceMembers(CodeGenFunction &CGF,
const CXXRecordDecl *RD) {}
/// Emit constructor variants required by this ABI.
virtual void EmitCXXConstructors(const CXXConstructorDecl *D) = 0;
/// Notes how many arguments were added to the beginning (Prefix) and ending
/// (Suffix) of an arg list.
/// Note that Prefix actually refers to the number of args *after* the first
/// one: `this` arguments always come first.
struct AddedStructorArgs {
unsigned Prefix = 0;
unsigned Suffix = 0;
AddedStructorArgs() = default;
AddedStructorArgs(unsigned P, unsigned S) : Prefix(P), Suffix(S) {}
static AddedStructorArgs prefix(unsigned N) { return {N, 0}; }
static AddedStructorArgs suffix(unsigned N) { return {0, N}; }
/// Build the signature of the given constructor or destructor variant by
/// adding any required parameters. For convenience, ArgTys has been
/// initialized with the type of 'this'.
virtual AddedStructorArgs
buildStructorSignature(GlobalDecl GD,
SmallVectorImpl<CanQualType> &ArgTys) = 0;
/// Returns true if the given destructor type should be emitted as a linkonce
/// delegating thunk, regardless of whether the dtor is defined in this TU or
/// not.
virtual bool useThunkForDtorVariant(const CXXDestructorDecl *Dtor,
CXXDtorType DT) const = 0;
virtual void setCXXDestructorDLLStorage(llvm::GlobalValue *GV,
const CXXDestructorDecl *Dtor,
CXXDtorType DT) const;
virtual llvm::GlobalValue::LinkageTypes
getCXXDestructorLinkage(GVALinkage Linkage, const CXXDestructorDecl *Dtor,
CXXDtorType DT) const;
/// Emit destructor variants required by this ABI.
virtual void EmitCXXDestructors(const CXXDestructorDecl *D) = 0;
/// Get the type of the implicit "this" parameter used by a method. May return
/// zero if no specific type is applicable, e.g. if the ABI expects the "this"
/// parameter to point to some artificial offset in a complete object due to
/// vbases being reordered.
virtual const CXXRecordDecl *
getThisArgumentTypeForMethod(const CXXMethodDecl *MD) {
return MD->getParent();
/// Perform ABI-specific "this" argument adjustment required prior to
/// a call of a virtual function.
/// The "VirtualCall" argument is true iff the call itself is virtual.
virtual Address
adjustThisArgumentForVirtualFunctionCall(CodeGenFunction &CGF, GlobalDecl GD,
Address This, bool VirtualCall) {
return This;
/// Build a parameter variable suitable for 'this'.
void buildThisParam(CodeGenFunction &CGF, FunctionArgList &Params);
/// Insert any ABI-specific implicit parameters into the parameter list for a
/// function. This generally involves extra data for constructors and
/// destructors.
/// ABIs may also choose to override the return type, which has been
/// initialized with the type of 'this' if HasThisReturn(CGF.CurGD) is true or
/// the formal return type of the function otherwise.
virtual void addImplicitStructorParams(CodeGenFunction &CGF, QualType &ResTy,
FunctionArgList &Params) = 0;
/// Get the ABI-specific "this" parameter adjustment to apply in the prologue
/// of a virtual function.
virtual CharUnits getVirtualFunctionPrologueThisAdjustment(GlobalDecl GD) {
return CharUnits::Zero();
/// Emit the ABI-specific prolog for the function.
virtual void EmitInstanceFunctionProlog(CodeGenFunction &CGF) = 0;
/// Add any ABI-specific implicit arguments needed to call a constructor.
/// \return The number of arguments added at the beginning and end of the
/// call, which is typically zero or one.
virtual AddedStructorArgs
addImplicitConstructorArgs(CodeGenFunction &CGF, const CXXConstructorDecl *D,
CXXCtorType Type, bool ForVirtualBase,
bool Delegating, CallArgList &Args) = 0;
/// Emit the destructor call.
virtual void EmitDestructorCall(CodeGenFunction &CGF,
const CXXDestructorDecl *DD, CXXDtorType Type,
bool ForVirtualBase, bool Delegating,
Address This, QualType ThisTy) = 0;
/// Emits the VTable definitions required for the given record type.
virtual void emitVTableDefinitions(CodeGenVTables &CGVT,
const CXXRecordDecl *RD) = 0;
/// Checks if ABI requires extra virtual offset for vtable field.
virtual bool
isVirtualOffsetNeededForVTableField(CodeGenFunction &CGF,
CodeGenFunction::VPtr Vptr) = 0;
/// Checks if ABI requires to initialize vptrs for given dynamic class.
virtual bool doStructorsInitializeVPtrs(const CXXRecordDecl *VTableClass) = 0;
/// Get the address point of the vtable for the given base subobject.
virtual llvm::Constant *
getVTableAddressPoint(BaseSubobject Base,
const CXXRecordDecl *VTableClass) = 0;
/// Get the address point of the vtable for the given base subobject while
/// building a constructor or a destructor.
virtual llvm::Value *
getVTableAddressPointInStructor(CodeGenFunction &CGF, const CXXRecordDecl *RD,
BaseSubobject Base,
const CXXRecordDecl *NearestVBase) = 0;
/// Get the address point of the vtable for the given base subobject while
/// building a constexpr.
virtual llvm::Constant *
getVTableAddressPointForConstExpr(BaseSubobject Base,
const CXXRecordDecl *VTableClass) = 0;
/// Get the address of the vtable for the given record decl which should be
/// used for the vptr at the given offset in RD.
virtual llvm::GlobalVariable *getAddrOfVTable(const CXXRecordDecl *RD,
CharUnits VPtrOffset) = 0;
/// Build a virtual function pointer in the ABI-specific way.
virtual CGCallee getVirtualFunctionPointer(CodeGenFunction &CGF,
GlobalDecl GD, Address This,
llvm::Type *Ty,
SourceLocation Loc) = 0;
using DeleteOrMemberCallExpr =
llvm::PointerUnion<const CXXDeleteExpr *, const CXXMemberCallExpr *>;
/// Emit the ABI-specific virtual destructor call.
virtual llvm::Value *EmitVirtualDestructorCall(CodeGenFunction &CGF,
const CXXDestructorDecl *Dtor,
CXXDtorType DtorType,
Address This,
DeleteOrMemberCallExpr E) = 0;
virtual void adjustCallArgsForDestructorThunk(CodeGenFunction &CGF,
GlobalDecl GD,
CallArgList &CallArgs) {}
/// Emit any tables needed to implement virtual inheritance. For Itanium,
/// this emits virtual table tables. For the MSVC++ ABI, this emits virtual
/// base tables.
virtual void emitVirtualInheritanceTables(const CXXRecordDecl *RD) = 0;
virtual bool exportThunk() = 0;
virtual void setThunkLinkage(llvm::Function *Thunk, bool ForVTable,
GlobalDecl GD, bool ReturnAdjustment) = 0;
virtual llvm::Value *performThisAdjustment(CodeGenFunction &CGF,
Address This,
const ThisAdjustment &TA) = 0;
virtual llvm::Value *performReturnAdjustment(CodeGenFunction &CGF,
Address Ret,
const ReturnAdjustment &RA) = 0;
virtual void EmitReturnFromThunk(CodeGenFunction &CGF,
RValue RV, QualType ResultType);
virtual size_t getSrcArgforCopyCtor(const CXXConstructorDecl *,
FunctionArgList &Args) const = 0;
/// Gets the offsets of all the virtual base pointers in a given class.
virtual std::vector<CharUnits> getVBPtrOffsets(const CXXRecordDecl *RD);
/// Gets the pure virtual member call function.
virtual StringRef GetPureVirtualCallName() = 0;
/// Gets the deleted virtual member call name.
virtual StringRef GetDeletedVirtualCallName() = 0;
/**************************** Array cookies ******************************/
/// Returns the extra size required in order to store the array
/// cookie for the given new-expression. May return 0 to indicate that no
/// array cookie is required.
/// Several cases are filtered out before this method is called:
/// - non-array allocations never need a cookie
/// - calls to \::operator new(size_t, void*) never need a cookie
/// \param expr - the new-expression being allocated.
virtual CharUnits GetArrayCookieSize(const CXXNewExpr *expr);
/// Initialize the array cookie for the given allocation.
/// \param NewPtr - a char* which is the presumed-non-null
/// return value of the allocation function
/// \param NumElements - the computed number of elements,
/// potentially collapsed from the multidimensional array case;
/// always a size_t
/// \param ElementType - the base element allocated type,
/// i.e. the allocated type after stripping all array types
virtual Address InitializeArrayCookie(CodeGenFunction &CGF,
Address NewPtr,
llvm::Value *NumElements,
const CXXNewExpr *expr,
QualType ElementType);
/// Reads the array cookie associated with the given pointer,
/// if it has one.
/// \param Ptr - a pointer to the first element in the array
/// \param ElementType - the base element type of elements of the array
/// \param NumElements - an out parameter which will be initialized
/// with the number of elements allocated, or zero if there is no
/// cookie
/// \param AllocPtr - an out parameter which will be initialized
/// with a char* pointing to the address returned by the allocation
/// function
/// \param CookieSize - an out parameter which will be initialized
/// with the size of the cookie, or zero if there is no cookie
virtual void ReadArrayCookie(CodeGenFunction &CGF, Address Ptr,
const CXXDeleteExpr *expr,
QualType ElementType, llvm::Value *&NumElements,
llvm::Value *&AllocPtr, CharUnits &CookieSize);
/// Return whether the given global decl needs a VTT parameter.
virtual bool NeedsVTTParameter(GlobalDecl GD);
/// Returns the extra size required in order to store the array
/// cookie for the given type. Assumes that an array cookie is
/// required.
virtual CharUnits getArrayCookieSizeImpl(QualType elementType);
/// Reads the array cookie for an allocation which is known to have one.
/// This is called by the standard implementation of ReadArrayCookie.
/// \param ptr - a pointer to the allocation made for an array, as a char*
/// \param cookieSize - the computed cookie size of an array
/// Other parameters are as above.
/// \return a size_t
virtual llvm::Value *readArrayCookieImpl(CodeGenFunction &IGF, Address ptr,
CharUnits cookieSize);
/*************************** Static local guards ****************************/
/// Emits the guarded initializer and destructor setup for the given
/// variable, given that it couldn't be emitted as a constant.
/// If \p PerformInit is false, the initialization has been folded to a
/// constant and should not be performed.
/// The variable may be:
/// - a static local variable
/// - a static data member of a class template instantiation
virtual void EmitGuardedInit(CodeGenFunction &CGF, const VarDecl &D,
llvm::GlobalVariable *DeclPtr,
bool PerformInit) = 0;
/// Emit code to force the execution of a destructor during global
/// teardown. The default implementation of this uses atexit.
/// \param Dtor - a function taking a single pointer argument
/// \param Addr - a pointer to pass to the destructor function.
virtual void registerGlobalDtor(CodeGenFunction &CGF, const VarDecl &D,
llvm::FunctionCallee Dtor,
llvm::Constant *Addr) = 0;
/*************************** thread_local initialization ********************/
/// Emits ABI-required functions necessary to initialize thread_local
/// variables in this translation unit.
/// \param CXXThreadLocals - The thread_local declarations in this translation
/// unit.
/// \param CXXThreadLocalInits - If this translation unit contains any
/// non-constant initialization or non-trivial destruction for
/// thread_local variables, a list of functions to perform the
/// initialization.
virtual void EmitThreadLocalInitFuncs(
CodeGenModule &CGM, ArrayRef<const VarDecl *> CXXThreadLocals,
ArrayRef<llvm::Function *> CXXThreadLocalInits,
ArrayRef<const VarDecl *> CXXThreadLocalInitVars) = 0;
// Determine if references to thread_local global variables can be made
// directly or require access through a thread wrapper function.
virtual bool usesThreadWrapperFunction(const VarDecl *VD) const = 0;
/// Emit a reference to a non-local thread_local variable (including
/// triggering the initialization of all thread_local variables in its
/// translation unit).
virtual LValue EmitThreadLocalVarDeclLValue(CodeGenFunction &CGF,
const VarDecl *VD,
QualType LValType) = 0;
/// Emit a single constructor/destructor with the given type from a C++
/// constructor Decl.
virtual void emitCXXStructor(GlobalDecl GD) = 0;
/// Load a vtable from This, an object of polymorphic type RD, or from one of
/// its virtual bases if it does not have its own vtable. Returns the vtable
/// and the class from which the vtable was loaded.
virtual std::pair<llvm::Value *, const CXXRecordDecl *>
LoadVTablePtr(CodeGenFunction &CGF, Address This,
const CXXRecordDecl *RD) = 0;
// Create an instance of a C++ ABI class:
/// Creates an Itanium-family ABI.
CGCXXABI *CreateItaniumCXXABI(CodeGenModule &CGM);
/// Creates a Microsoft-family ABI.
CGCXXABI *CreateMicrosoftCXXABI(CodeGenModule &CGM);
struct CatchRetScope final : EHScopeStack::Cleanup {
llvm::CatchPadInst *CPI;
CatchRetScope(llvm::CatchPadInst *CPI) : CPI(CPI) {}
void Emit(CodeGenFunction &CGF, Flags flags) override {
llvm::BasicBlock *BB = CGF.createBasicBlock("catchret.dest");
CGF.Builder.CreateCatchRet(CPI, BB);