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//===----- CGCXXABI.h - Interface to C++ ABIs -------------------*- C++ -*-===//
// The LLVM Compiler Infrastructure
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
// 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;
namespace clang {
class CastExpr;
class CXXConstructorDecl;
class CXXDestructorDecl;
class CXXMethodDecl;
class CXXRecordDecl;
class FieldDecl;
class MangleContext;
namespace CodeGen {
class CodeGenFunction;
class CodeGenModule;
/// \brief 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;
/// 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;
/// Perform prolog initialization of the parameter variable suitable
/// for 'this' emitted by buildThisParam.
void EmitThisParam(CodeGenFunction &CGF);
ASTContext &getContext() const { return CGM.getContext(); }
virtual bool requiresArrayCookie(const CXXDeleteExpr *E, QualType eltType);
virtual bool requiresArrayCookie(const CXXNewExpr *E);
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; }
/// Returns true if the given record type should be returned indirectly.
virtual bool isReturnTypeIndirect(const CXXRecordDecl *RD) 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;
/// 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 llvm::Value *EmitLoadOfMemberFunctionPointer(
CodeGenFunction &CGF, const Expr *E, llvm::Value *&This,
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,
llvm::Value *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);
/// 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 *EmitMemberPointer(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);
/// \brief 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);
/// Adjust the given non-null pointer to an object of polymorphic
/// type to point to the complete object.
/// The IR type of the result should be a pointer but is otherwise
/// irrelevant.
virtual llvm::Value *adjustToCompleteObject(CodeGenFunction &CGF,
llvm::Value *ptr,
QualType type) = 0;
virtual llvm::Value *GetVirtualBaseClassOffset(CodeGenFunction &CGF,
llvm::Value *This,
const CXXRecordDecl *ClassDecl,
const CXXRecordDecl *BaseClassDecl) = 0;
/// Build the signature of the given constructor variant by adding
/// any required parameters. For convenience, ArgTys has been initialized
/// with the type of 'this' and ResTy has been initialized with the type of
/// 'this' if HasThisReturn(GlobalDecl(Ctor, T)) is true or 'void' otherwise
/// (although both may be changed by the ABI).
/// If there are ever any ABIs where the implicit parameters are
/// intermixed with the formal parameters, we can address those
/// then.
virtual void BuildConstructorSignature(const CXXConstructorDecl *Ctor,
CXXCtorType T,
CanQualType &ResTy,
SmallVectorImpl<CanQualType> &ArgTys) = 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;
/// Build the signature of the given destructor variant by adding
/// any required parameters. For convenience, ArgTys has been initialized
/// with the type of 'this' and ResTy has been initialized with the type of
/// 'this' if HasThisReturn(GlobalDecl(Dtor, T)) is true or 'void' otherwise
/// (although both may be changed by the ABI).
virtual void BuildDestructorSignature(const CXXDestructorDecl *Dtor,
CXXDtorType T,
CanQualType &ResTy,
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;
/// 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 llvm::Value *
adjustThisArgumentForVirtualFunctionCall(CodeGenFunction &CGF, GlobalDecl GD,
llvm::Value *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;
/// Perform ABI-specific "this" parameter adjustment in a virtual function
/// prologue.
virtual llvm::Value *adjustThisParameterInVirtualFunctionPrologue(
CodeGenFunction &CGF, GlobalDecl GD, llvm::Value *This) {
return This;
/// 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 args added to the call, which is typically zero or
/// one.
virtual unsigned
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,
llvm::Value *This) = 0;
/// Emits the VTable definitions required for the given record type.
virtual void emitVTableDefinitions(CodeGenVTables &CGVT,
const CXXRecordDecl *RD) = 0;
/// Get the address point of the vtable for the given base subobject while
/// building a constructor or a destructor. On return, NeedsVirtualOffset
/// tells if a virtual base adjustment is needed in order to get the offset
/// of the base subobject.
virtual llvm::Value *getVTableAddressPointInStructor(
CodeGenFunction &CGF, const CXXRecordDecl *RD, BaseSubobject Base,
const CXXRecordDecl *NearestVBase, bool &NeedsVirtualOffset) = 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 llvm::Value *getVirtualFunctionPointer(CodeGenFunction &CGF,
GlobalDecl GD,
llvm::Value *This,
llvm::Type *Ty) = 0;
/// Emit the ABI-specific virtual destructor call.
virtual void EmitVirtualDestructorCall(CodeGenFunction &CGF,
const CXXDestructorDecl *Dtor,
CXXDtorType DtorType,
SourceLocation CallLoc,
llvm::Value *This) = 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 void setThunkLinkage(llvm::Function *Thunk, bool ForVTable) = 0;
virtual llvm::Value *performThisAdjustment(CodeGenFunction &CGF,
llvm::Value *This,
const ThisAdjustment &TA) = 0;
virtual llvm::Value *performReturnAdjustment(CodeGenFunction &CGF,
llvm::Value *Ret,
const ReturnAdjustment &RA) = 0;
virtual void EmitReturnFromThunk(CodeGenFunction &CGF,
RValue RV, QualType ResultType);
/// Gets the pure virtual member call function.
virtual StringRef GetPureVirtualCallName() = 0;
/// Gets the deleted virtual member call name.
virtual StringRef GetDeletedVirtualCallName() = 0;
/// \brief Returns true iff static data members that are initialized in the
/// class definition should have linkonce linkage.
virtual bool isInlineInitializedStaticDataMemberLinkOnce() { return false; }
/**************************** 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 llvm::Value *InitializeArrayCookie(CodeGenFunction &CGF,
llvm::Value *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, llvm::Value *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,
llvm::Value *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::Constant *dtor, llvm::Constant *addr);
/*************************** thread_local initialization ********************/
/// Emits ABI-required functions necessary to initialize thread_local
/// variables in this translation unit.
/// \param Decls The thread_local declarations in this translation unit.
/// \param InitFunc If this translation unit contains any non-constant
/// initialization or non-trivial destruction for thread_local
/// variables, a function to perform the initialization. Otherwise, 0.
virtual void EmitThreadLocalInitFuncs(
llvm::ArrayRef<std::pair<const VarDecl *, llvm::GlobalVariable *> > Decls,
llvm::Function *InitFunc);
/// 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);
/**************************** RTTI Uniqueness ******************************/
/// Returns true if the ABI requires RTTI type_info objects to be unique
/// across a program.
virtual bool shouldRTTIBeUnique() { return true; }
/// What sort of unique-RTTI behavior should we use?
enum RTTIUniquenessKind {
/// We are guaranteeing, or need to guarantee, that the RTTI string
/// is unique.
/// We are not guaranteeing uniqueness for the RTTI string, so we
/// can demote to hidden visibility but must use string comparisons.
/// We are not guaranteeing uniqueness for the RTTI string, so we
/// have to use string comparisons, but we also have to emit it with
/// non-hidden visibility.
/// Return the required visibility status for the given type and linkage in
/// the current ABI.
classifyRTTIUniqueness(QualType CanTy,
llvm::GlobalValue::LinkageTypes Linkage);
// 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);