1 //===----- CGCXXABI.h - Interface to C++ ABIs -------------------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This provides an abstract class for C++ code generation. Concrete subclasses
11 // of this implement code generation for specific C++ ABIs.
13 //===----------------------------------------------------------------------===//
15 #ifndef CLANG_CODEGEN_CXXABI_H
16 #define CLANG_CODEGEN_CXXABI_H
18 #include "CodeGenFunction.h"
19 #include "clang/Basic/LLVM.h"
29 class CXXConstructorDecl;
30 class CXXDestructorDecl;
37 class CodeGenFunction;
40 /// \brief Implements C++ ABI-specific code generation functions.
44 std::unique_ptr<MangleContext> MangleCtx;
46 CGCXXABI(CodeGenModule &CGM)
47 : CGM(CGM), MangleCtx(CGM.getContext().createMangleContext()) {}
50 ImplicitParamDecl *&getThisDecl(CodeGenFunction &CGF) {
51 return CGF.CXXABIThisDecl;
53 llvm::Value *&getThisValue(CodeGenFunction &CGF) {
54 return CGF.CXXABIThisValue;
57 /// Issue a diagnostic about unsupported features in the ABI.
58 void ErrorUnsupportedABI(CodeGenFunction &CGF, StringRef S);
60 /// Get a null value for unsupported member pointers.
61 llvm::Constant *GetBogusMemberPointer(QualType T);
63 ImplicitParamDecl *&getStructorImplicitParamDecl(CodeGenFunction &CGF) {
64 return CGF.CXXStructorImplicitParamDecl;
66 llvm::Value *&getStructorImplicitParamValue(CodeGenFunction &CGF) {
67 return CGF.CXXStructorImplicitParamValue;
70 /// Perform prolog initialization of the parameter variable suitable
71 /// for 'this' emitted by buildThisParam.
72 void EmitThisParam(CodeGenFunction &CGF);
74 ASTContext &getContext() const { return CGM.getContext(); }
76 virtual bool requiresArrayCookie(const CXXDeleteExpr *E, QualType eltType);
77 virtual bool requiresArrayCookie(const CXXNewExpr *E);
83 /// Gets the mangle context.
84 MangleContext &getMangleContext() {
88 /// Returns true if the given constructor or destructor is one of the
89 /// kinds that the ABI says returns 'this' (only applies when called
90 /// non-virtually for destructors).
92 /// There currently is no way to indicate if a destructor returns 'this'
93 /// when called virtually, and code generation does not support the case.
94 virtual bool HasThisReturn(GlobalDecl GD) const { return false; }
96 /// If the C++ ABI requires the given type be returned in a particular way,
97 /// this method sets RetAI and returns true.
98 virtual bool classifyReturnType(CGFunctionInfo &FI) const = 0;
100 /// Specify how one should pass an argument of a record type.
102 /// Pass it using the normal C aggregate rules for the ABI, potentially
103 /// introducing extra copies and passing some or all of it in registers.
106 /// Pass it on the stack using its defined layout. The argument must be
107 /// evaluated directly into the correct stack position in the arguments area,
108 /// and the call machinery must not move it or introduce extra copies.
111 /// Pass it as a pointer to temporary memory.
115 /// Returns true if C++ allows us to copy the memory of an object of type RD
116 /// when it is passed as an argument.
117 bool canCopyArgument(const CXXRecordDecl *RD) const;
119 /// Returns how an argument of the given record type should be passed.
120 virtual RecordArgABI getRecordArgABI(const CXXRecordDecl *RD) const = 0;
122 /// Returns true if the implicit 'sret' parameter comes after the implicit
123 /// 'this' parameter of C++ instance methods.
124 virtual bool isSRetParameterAfterThis() const { return false; }
126 /// Find the LLVM type used to represent the given member pointer
129 ConvertMemberPointerType(const MemberPointerType *MPT);
131 /// Load a member function from an object and a member function
132 /// pointer. Apply the this-adjustment and set 'This' to the
134 virtual llvm::Value *EmitLoadOfMemberFunctionPointer(
135 CodeGenFunction &CGF, const Expr *E, llvm::Value *&This,
136 llvm::Value *MemPtr, const MemberPointerType *MPT);
138 /// Calculate an l-value from an object and a data member pointer.
139 virtual llvm::Value *
140 EmitMemberDataPointerAddress(CodeGenFunction &CGF, const Expr *E,
141 llvm::Value *Base, llvm::Value *MemPtr,
142 const MemberPointerType *MPT);
144 /// Perform a derived-to-base, base-to-derived, or bitcast member
145 /// pointer conversion.
146 virtual llvm::Value *EmitMemberPointerConversion(CodeGenFunction &CGF,
150 /// Perform a derived-to-base, base-to-derived, or bitcast member
151 /// pointer conversion on a constant value.
152 virtual llvm::Constant *EmitMemberPointerConversion(const CastExpr *E,
153 llvm::Constant *Src);
155 /// Return true if the given member pointer can be zero-initialized
156 /// (in the C++ sense) with an LLVM zeroinitializer.
157 virtual bool isZeroInitializable(const MemberPointerType *MPT);
159 /// Create a null member pointer of the given type.
160 virtual llvm::Constant *EmitNullMemberPointer(const MemberPointerType *MPT);
162 /// Create a member pointer for the given method.
163 virtual llvm::Constant *EmitMemberPointer(const CXXMethodDecl *MD);
165 /// Create a member pointer for the given field.
166 virtual llvm::Constant *EmitMemberDataPointer(const MemberPointerType *MPT,
169 /// Create a member pointer for the given member pointer constant.
170 virtual llvm::Constant *EmitMemberPointer(const APValue &MP, QualType MPT);
172 /// Emit a comparison between two member pointers. Returns an i1.
173 virtual llvm::Value *
174 EmitMemberPointerComparison(CodeGenFunction &CGF,
177 const MemberPointerType *MPT,
180 /// Determine if a member pointer is non-null. Returns an i1.
181 virtual llvm::Value *
182 EmitMemberPointerIsNotNull(CodeGenFunction &CGF,
184 const MemberPointerType *MPT);
187 /// A utility method for computing the offset required for the given
188 /// base-to-derived or derived-to-base member-pointer conversion.
189 /// Does not handle virtual conversions (in case we ever fully
190 /// support an ABI that allows this). Returns null if no adjustment
192 llvm::Constant *getMemberPointerAdjustment(const CastExpr *E);
194 /// \brief Computes the non-virtual adjustment needed for a member pointer
195 /// conversion along an inheritance path stored in an APValue. Unlike
196 /// getMemberPointerAdjustment(), the adjustment can be negative if the path
197 /// is from a derived type to a base type.
198 CharUnits getMemberPointerPathAdjustment(const APValue &MP);
201 /// Adjust the given non-null pointer to an object of polymorphic
202 /// type to point to the complete object.
204 /// The IR type of the result should be a pointer but is otherwise
206 virtual llvm::Value *adjustToCompleteObject(CodeGenFunction &CGF,
210 virtual bool shouldTypeidBeNullChecked(bool IsDeref,
211 QualType SrcRecordTy) = 0;
212 virtual void EmitBadTypeidCall(CodeGenFunction &CGF) = 0;
213 virtual llvm::Value *EmitTypeid(CodeGenFunction &CGF, QualType SrcRecordTy,
214 llvm::Value *ThisPtr,
215 llvm::Type *StdTypeInfoPtrTy) = 0;
217 virtual bool shouldDynamicCastCallBeNullChecked(bool SrcIsPtr,
218 QualType SrcRecordTy) = 0;
220 virtual llvm::Value *
221 EmitDynamicCastCall(CodeGenFunction &CGF, llvm::Value *Value,
222 QualType SrcRecordTy, QualType DestTy,
223 QualType DestRecordTy, llvm::BasicBlock *CastEnd) = 0;
225 virtual llvm::Value *EmitDynamicCastToVoid(CodeGenFunction &CGF,
227 QualType SrcRecordTy,
228 QualType DestTy) = 0;
230 virtual bool EmitBadCastCall(CodeGenFunction &CGF) = 0;
232 virtual llvm::Value *GetVirtualBaseClassOffset(CodeGenFunction &CGF,
234 const CXXRecordDecl *ClassDecl,
235 const CXXRecordDecl *BaseClassDecl) = 0;
237 /// Build the signature of the given constructor variant by adding
238 /// any required parameters. For convenience, ArgTys has been initialized
239 /// with the type of 'this' and ResTy has been initialized with the type of
240 /// 'this' if HasThisReturn(GlobalDecl(Ctor, T)) is true or 'void' otherwise
241 /// (although both may be changed by the ABI).
243 /// If there are ever any ABIs where the implicit parameters are
244 /// intermixed with the formal parameters, we can address those
246 virtual void BuildConstructorSignature(const CXXConstructorDecl *Ctor,
249 SmallVectorImpl<CanQualType> &ArgTys) = 0;
251 virtual llvm::BasicBlock *EmitCtorCompleteObjectHandler(CodeGenFunction &CGF,
252 const CXXRecordDecl *RD);
254 /// Emit the code to initialize hidden members required
255 /// to handle virtual inheritance, if needed by the ABI.
257 initializeHiddenVirtualInheritanceMembers(CodeGenFunction &CGF,
258 const CXXRecordDecl *RD) {}
260 /// Emit constructor variants required by this ABI.
261 virtual void EmitCXXConstructors(const CXXConstructorDecl *D) = 0;
263 /// Build the signature of the given destructor variant by adding
264 /// any required parameters. For convenience, ArgTys has been initialized
265 /// with the type of 'this' and ResTy has been initialized with the type of
266 /// 'this' if HasThisReturn(GlobalDecl(Dtor, T)) is true or 'void' otherwise
267 /// (although both may be changed by the ABI).
268 virtual void BuildDestructorSignature(const CXXDestructorDecl *Dtor,
271 SmallVectorImpl<CanQualType> &ArgTys) = 0;
273 /// Returns true if the given destructor type should be emitted as a linkonce
274 /// delegating thunk, regardless of whether the dtor is defined in this TU or
276 virtual bool useThunkForDtorVariant(const CXXDestructorDecl *Dtor,
277 CXXDtorType DT) const = 0;
279 /// Emit destructor variants required by this ABI.
280 virtual void EmitCXXDestructors(const CXXDestructorDecl *D) = 0;
282 /// Get the type of the implicit "this" parameter used by a method. May return
283 /// zero if no specific type is applicable, e.g. if the ABI expects the "this"
284 /// parameter to point to some artificial offset in a complete object due to
285 /// vbases being reordered.
286 virtual const CXXRecordDecl *
287 getThisArgumentTypeForMethod(const CXXMethodDecl *MD) {
288 return MD->getParent();
291 /// Perform ABI-specific "this" argument adjustment required prior to
292 /// a call of a virtual function.
293 /// The "VirtualCall" argument is true iff the call itself is virtual.
294 virtual llvm::Value *
295 adjustThisArgumentForVirtualFunctionCall(CodeGenFunction &CGF, GlobalDecl GD,
301 /// Build a parameter variable suitable for 'this'.
302 void buildThisParam(CodeGenFunction &CGF, FunctionArgList &Params);
304 /// Insert any ABI-specific implicit parameters into the parameter list for a
305 /// function. This generally involves extra data for constructors and
308 /// ABIs may also choose to override the return type, which has been
309 /// initialized with the type of 'this' if HasThisReturn(CGF.CurGD) is true or
310 /// the formal return type of the function otherwise.
311 virtual void addImplicitStructorParams(CodeGenFunction &CGF, QualType &ResTy,
312 FunctionArgList &Params) = 0;
314 /// Perform ABI-specific "this" parameter adjustment in a virtual function
316 virtual llvm::Value *adjustThisParameterInVirtualFunctionPrologue(
317 CodeGenFunction &CGF, GlobalDecl GD, llvm::Value *This) {
321 /// Emit the ABI-specific prolog for the function.
322 virtual void EmitInstanceFunctionProlog(CodeGenFunction &CGF) = 0;
324 /// Add any ABI-specific implicit arguments needed to call a constructor.
326 /// \return The number of args added to the call, which is typically zero or
329 addImplicitConstructorArgs(CodeGenFunction &CGF, const CXXConstructorDecl *D,
330 CXXCtorType Type, bool ForVirtualBase,
331 bool Delegating, CallArgList &Args) = 0;
333 /// Emit the destructor call.
334 virtual void EmitDestructorCall(CodeGenFunction &CGF,
335 const CXXDestructorDecl *DD, CXXDtorType Type,
336 bool ForVirtualBase, bool Delegating,
337 llvm::Value *This) = 0;
339 /// Emits the VTable definitions required for the given record type.
340 virtual void emitVTableDefinitions(CodeGenVTables &CGVT,
341 const CXXRecordDecl *RD) = 0;
343 /// Get the address point of the vtable for the given base subobject while
344 /// building a constructor or a destructor. On return, NeedsVirtualOffset
345 /// tells if a virtual base adjustment is needed in order to get the offset
346 /// of the base subobject.
347 virtual llvm::Value *getVTableAddressPointInStructor(
348 CodeGenFunction &CGF, const CXXRecordDecl *RD, BaseSubobject Base,
349 const CXXRecordDecl *NearestVBase, bool &NeedsVirtualOffset) = 0;
351 /// Get the address point of the vtable for the given base subobject while
352 /// building a constexpr.
353 virtual llvm::Constant *
354 getVTableAddressPointForConstExpr(BaseSubobject Base,
355 const CXXRecordDecl *VTableClass) = 0;
357 /// Get the address of the vtable for the given record decl which should be
358 /// used for the vptr at the given offset in RD.
359 virtual llvm::GlobalVariable *getAddrOfVTable(const CXXRecordDecl *RD,
360 CharUnits VPtrOffset) = 0;
362 /// Build a virtual function pointer in the ABI-specific way.
363 virtual llvm::Value *getVirtualFunctionPointer(CodeGenFunction &CGF,
368 /// Emit the ABI-specific virtual destructor call.
369 virtual void EmitVirtualDestructorCall(CodeGenFunction &CGF,
370 const CXXDestructorDecl *Dtor,
371 CXXDtorType DtorType,
372 SourceLocation CallLoc,
373 llvm::Value *This) = 0;
375 virtual void adjustCallArgsForDestructorThunk(CodeGenFunction &CGF,
377 CallArgList &CallArgs) {}
379 /// Emit any tables needed to implement virtual inheritance. For Itanium,
380 /// this emits virtual table tables. For the MSVC++ ABI, this emits virtual
382 virtual void emitVirtualInheritanceTables(const CXXRecordDecl *RD) = 0;
384 virtual void setThunkLinkage(llvm::Function *Thunk, bool ForVTable,
385 GlobalDecl GD, bool ReturnAdjustment) = 0;
387 virtual llvm::Value *performThisAdjustment(CodeGenFunction &CGF,
389 const ThisAdjustment &TA) = 0;
391 virtual llvm::Value *performReturnAdjustment(CodeGenFunction &CGF,
393 const ReturnAdjustment &RA) = 0;
395 virtual void EmitReturnFromThunk(CodeGenFunction &CGF,
396 RValue RV, QualType ResultType);
398 /// Gets the pure virtual member call function.
399 virtual StringRef GetPureVirtualCallName() = 0;
401 /// Gets the deleted virtual member call name.
402 virtual StringRef GetDeletedVirtualCallName() = 0;
404 /// \brief Returns true iff static data members that are initialized in the
405 /// class definition should have linkonce linkage.
406 virtual bool isInlineInitializedStaticDataMemberLinkOnce() { return false; }
408 /**************************** Array cookies ******************************/
410 /// Returns the extra size required in order to store the array
411 /// cookie for the given new-expression. May return 0 to indicate that no
412 /// array cookie is required.
414 /// Several cases are filtered out before this method is called:
415 /// - non-array allocations never need a cookie
416 /// - calls to \::operator new(size_t, void*) never need a cookie
418 /// \param expr - the new-expression being allocated.
419 virtual CharUnits GetArrayCookieSize(const CXXNewExpr *expr);
421 /// Initialize the array cookie for the given allocation.
423 /// \param NewPtr - a char* which is the presumed-non-null
424 /// return value of the allocation function
425 /// \param NumElements - the computed number of elements,
426 /// potentially collapsed from the multidimensional array case;
428 /// \param ElementType - the base element allocated type,
429 /// i.e. the allocated type after stripping all array types
430 virtual llvm::Value *InitializeArrayCookie(CodeGenFunction &CGF,
432 llvm::Value *NumElements,
433 const CXXNewExpr *expr,
434 QualType ElementType);
436 /// Reads the array cookie associated with the given pointer,
439 /// \param Ptr - a pointer to the first element in the array
440 /// \param ElementType - the base element type of elements of the array
441 /// \param NumElements - an out parameter which will be initialized
442 /// with the number of elements allocated, or zero if there is no
444 /// \param AllocPtr - an out parameter which will be initialized
445 /// with a char* pointing to the address returned by the allocation
447 /// \param CookieSize - an out parameter which will be initialized
448 /// with the size of the cookie, or zero if there is no cookie
449 virtual void ReadArrayCookie(CodeGenFunction &CGF, llvm::Value *Ptr,
450 const CXXDeleteExpr *expr,
451 QualType ElementType, llvm::Value *&NumElements,
452 llvm::Value *&AllocPtr, CharUnits &CookieSize);
454 /// Return whether the given global decl needs a VTT parameter.
455 virtual bool NeedsVTTParameter(GlobalDecl GD);
458 /// Returns the extra size required in order to store the array
459 /// cookie for the given type. Assumes that an array cookie is
461 virtual CharUnits getArrayCookieSizeImpl(QualType elementType);
463 /// Reads the array cookie for an allocation which is known to have one.
464 /// This is called by the standard implementation of ReadArrayCookie.
466 /// \param ptr - a pointer to the allocation made for an array, as a char*
467 /// \param cookieSize - the computed cookie size of an array
469 /// Other parameters are as above.
472 virtual llvm::Value *readArrayCookieImpl(CodeGenFunction &IGF,
474 CharUnits cookieSize);
478 /*************************** Static local guards ****************************/
480 /// Emits the guarded initializer and destructor setup for the given
481 /// variable, given that it couldn't be emitted as a constant.
482 /// If \p PerformInit is false, the initialization has been folded to a
483 /// constant and should not be performed.
485 /// The variable may be:
486 /// - a static local variable
487 /// - a static data member of a class template instantiation
488 virtual void EmitGuardedInit(CodeGenFunction &CGF, const VarDecl &D,
489 llvm::GlobalVariable *DeclPtr,
490 bool PerformInit) = 0;
492 /// Emit code to force the execution of a destructor during global
493 /// teardown. The default implementation of this uses atexit.
495 /// \param dtor - a function taking a single pointer argument
496 /// \param addr - a pointer to pass to the destructor function.
497 virtual void registerGlobalDtor(CodeGenFunction &CGF, const VarDecl &D,
498 llvm::Constant *dtor, llvm::Constant *addr);
500 /*************************** thread_local initialization ********************/
502 /// Emits ABI-required functions necessary to initialize thread_local
503 /// variables in this translation unit.
505 /// \param Decls The thread_local declarations in this translation unit.
506 /// \param InitFunc If this translation unit contains any non-constant
507 /// initialization or non-trivial destruction for thread_local
508 /// variables, a function to perform the initialization. Otherwise, 0.
509 virtual void EmitThreadLocalInitFuncs(
510 llvm::ArrayRef<std::pair<const VarDecl *, llvm::GlobalVariable *> > Decls,
511 llvm::Function *InitFunc);
513 /// Emit a reference to a non-local thread_local variable (including
514 /// triggering the initialization of all thread_local variables in its
515 /// translation unit).
516 virtual LValue EmitThreadLocalVarDeclLValue(CodeGenFunction &CGF,
520 /**************************** RTTI Uniqueness ******************************/
523 /// Returns true if the ABI requires RTTI type_info objects to be unique
524 /// across a program.
525 virtual bool shouldRTTIBeUnique() { return true; }
528 /// What sort of unique-RTTI behavior should we use?
529 enum RTTIUniquenessKind {
530 /// We are guaranteeing, or need to guarantee, that the RTTI string
534 /// We are not guaranteeing uniqueness for the RTTI string, so we
535 /// can demote to hidden visibility but must use string comparisons.
538 /// We are not guaranteeing uniqueness for the RTTI string, so we
539 /// have to use string comparisons, but we also have to emit it with
540 /// non-hidden visibility.
544 /// Return the required visibility status for the given type and linkage in
547 classifyRTTIUniqueness(QualType CanTy,
548 llvm::GlobalValue::LinkageTypes Linkage);
551 // Create an instance of a C++ ABI class:
553 /// Creates an Itanium-family ABI.
554 CGCXXABI *CreateItaniumCXXABI(CodeGenModule &CGM);
556 /// Creates a Microsoft-family ABI.
557 CGCXXABI *CreateMicrosoftCXXABI(CodeGenModule &CGM);