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 how an argument of the given record type should be passed.
116 virtual RecordArgABI getRecordArgABI(const CXXRecordDecl *RD) const = 0;
118 /// Returns true if the implicit 'sret' parameter comes after the implicit
119 /// 'this' parameter of C++ instance methods.
120 virtual bool isSRetParameterAfterThis() const { return false; }
122 /// Find the LLVM type used to represent the given member pointer
125 ConvertMemberPointerType(const MemberPointerType *MPT);
127 /// Load a member function from an object and a member function
128 /// pointer. Apply the this-adjustment and set 'This' to the
130 virtual llvm::Value *EmitLoadOfMemberFunctionPointer(
131 CodeGenFunction &CGF, const Expr *E, llvm::Value *&This,
132 llvm::Value *MemPtr, const MemberPointerType *MPT);
134 /// Calculate an l-value from an object and a data member pointer.
135 virtual llvm::Value *
136 EmitMemberDataPointerAddress(CodeGenFunction &CGF, const Expr *E,
137 llvm::Value *Base, llvm::Value *MemPtr,
138 const MemberPointerType *MPT);
140 /// Perform a derived-to-base, base-to-derived, or bitcast member
141 /// pointer conversion.
142 virtual llvm::Value *EmitMemberPointerConversion(CodeGenFunction &CGF,
146 /// Perform a derived-to-base, base-to-derived, or bitcast member
147 /// pointer conversion on a constant value.
148 virtual llvm::Constant *EmitMemberPointerConversion(const CastExpr *E,
149 llvm::Constant *Src);
151 /// Return true if the given member pointer can be zero-initialized
152 /// (in the C++ sense) with an LLVM zeroinitializer.
153 virtual bool isZeroInitializable(const MemberPointerType *MPT);
155 /// Create a null member pointer of the given type.
156 virtual llvm::Constant *EmitNullMemberPointer(const MemberPointerType *MPT);
158 /// Create a member pointer for the given method.
159 virtual llvm::Constant *EmitMemberPointer(const CXXMethodDecl *MD);
161 /// Create a member pointer for the given field.
162 virtual llvm::Constant *EmitMemberDataPointer(const MemberPointerType *MPT,
165 /// Create a member pointer for the given member pointer constant.
166 virtual llvm::Constant *EmitMemberPointer(const APValue &MP, QualType MPT);
168 /// Emit a comparison between two member pointers. Returns an i1.
169 virtual llvm::Value *
170 EmitMemberPointerComparison(CodeGenFunction &CGF,
173 const MemberPointerType *MPT,
176 /// Determine if a member pointer is non-null. Returns an i1.
177 virtual llvm::Value *
178 EmitMemberPointerIsNotNull(CodeGenFunction &CGF,
180 const MemberPointerType *MPT);
183 /// A utility method for computing the offset required for the given
184 /// base-to-derived or derived-to-base member-pointer conversion.
185 /// Does not handle virtual conversions (in case we ever fully
186 /// support an ABI that allows this). Returns null if no adjustment
188 llvm::Constant *getMemberPointerAdjustment(const CastExpr *E);
190 /// \brief Computes the non-virtual adjustment needed for a member pointer
191 /// conversion along an inheritance path stored in an APValue. Unlike
192 /// getMemberPointerAdjustment(), the adjustment can be negative if the path
193 /// is from a derived type to a base type.
194 CharUnits getMemberPointerPathAdjustment(const APValue &MP);
197 /// Adjust the given non-null pointer to an object of polymorphic
198 /// type to point to the complete object.
200 /// The IR type of the result should be a pointer but is otherwise
202 virtual llvm::Value *adjustToCompleteObject(CodeGenFunction &CGF,
206 virtual llvm::Value *GetVirtualBaseClassOffset(CodeGenFunction &CGF,
208 const CXXRecordDecl *ClassDecl,
209 const CXXRecordDecl *BaseClassDecl) = 0;
211 /// Build the signature of the given constructor variant by adding
212 /// any required parameters. For convenience, ArgTys has been initialized
213 /// with the type of 'this' and ResTy has been initialized with the type of
214 /// 'this' if HasThisReturn(GlobalDecl(Ctor, T)) is true or 'void' otherwise
215 /// (although both may be changed by the ABI).
217 /// If there are ever any ABIs where the implicit parameters are
218 /// intermixed with the formal parameters, we can address those
220 virtual void BuildConstructorSignature(const CXXConstructorDecl *Ctor,
223 SmallVectorImpl<CanQualType> &ArgTys) = 0;
225 virtual llvm::BasicBlock *EmitCtorCompleteObjectHandler(CodeGenFunction &CGF,
226 const CXXRecordDecl *RD);
228 /// Emit the code to initialize hidden members required
229 /// to handle virtual inheritance, if needed by the ABI.
231 initializeHiddenVirtualInheritanceMembers(CodeGenFunction &CGF,
232 const CXXRecordDecl *RD) {}
234 /// Emit constructor variants required by this ABI.
235 virtual void EmitCXXConstructors(const CXXConstructorDecl *D) = 0;
237 /// Build the signature of the given destructor 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(Dtor, T)) is true or 'void' otherwise
241 /// (although both may be changed by the ABI).
242 virtual void BuildDestructorSignature(const CXXDestructorDecl *Dtor,
245 SmallVectorImpl<CanQualType> &ArgTys) = 0;
247 /// Returns true if the given destructor type should be emitted as a linkonce
248 /// delegating thunk, regardless of whether the dtor is defined in this TU or
250 virtual bool useThunkForDtorVariant(const CXXDestructorDecl *Dtor,
251 CXXDtorType DT) const = 0;
253 /// Emit destructor variants required by this ABI.
254 virtual void EmitCXXDestructors(const CXXDestructorDecl *D) = 0;
256 /// Get the type of the implicit "this" parameter used by a method. May return
257 /// zero if no specific type is applicable, e.g. if the ABI expects the "this"
258 /// parameter to point to some artificial offset in a complete object due to
259 /// vbases being reordered.
260 virtual const CXXRecordDecl *
261 getThisArgumentTypeForMethod(const CXXMethodDecl *MD) {
262 return MD->getParent();
265 /// Perform ABI-specific "this" argument adjustment required prior to
266 /// a call of a virtual function.
267 /// The "VirtualCall" argument is true iff the call itself is virtual.
268 virtual llvm::Value *
269 adjustThisArgumentForVirtualFunctionCall(CodeGenFunction &CGF, GlobalDecl GD,
275 /// Build a parameter variable suitable for 'this'.
276 void buildThisParam(CodeGenFunction &CGF, FunctionArgList &Params);
278 /// Insert any ABI-specific implicit parameters into the parameter list for a
279 /// function. This generally involves extra data for constructors and
282 /// ABIs may also choose to override the return type, which has been
283 /// initialized with the type of 'this' if HasThisReturn(CGF.CurGD) is true or
284 /// the formal return type of the function otherwise.
285 virtual void addImplicitStructorParams(CodeGenFunction &CGF, QualType &ResTy,
286 FunctionArgList &Params) = 0;
288 /// Perform ABI-specific "this" parameter adjustment in a virtual function
290 virtual llvm::Value *adjustThisParameterInVirtualFunctionPrologue(
291 CodeGenFunction &CGF, GlobalDecl GD, llvm::Value *This) {
295 /// Emit the ABI-specific prolog for the function.
296 virtual void EmitInstanceFunctionProlog(CodeGenFunction &CGF) = 0;
298 /// Add any ABI-specific implicit arguments needed to call a constructor.
300 /// \return The number of args added to the call, which is typically zero or
303 addImplicitConstructorArgs(CodeGenFunction &CGF, const CXXConstructorDecl *D,
304 CXXCtorType Type, bool ForVirtualBase,
305 bool Delegating, CallArgList &Args) = 0;
307 /// Emit the destructor call.
308 virtual void EmitDestructorCall(CodeGenFunction &CGF,
309 const CXXDestructorDecl *DD, CXXDtorType Type,
310 bool ForVirtualBase, bool Delegating,
311 llvm::Value *This) = 0;
313 /// Emits the VTable definitions required for the given record type.
314 virtual void emitVTableDefinitions(CodeGenVTables &CGVT,
315 const CXXRecordDecl *RD) = 0;
317 /// Get the address point of the vtable for the given base subobject while
318 /// building a constructor or a destructor. On return, NeedsVirtualOffset
319 /// tells if a virtual base adjustment is needed in order to get the offset
320 /// of the base subobject.
321 virtual llvm::Value *getVTableAddressPointInStructor(
322 CodeGenFunction &CGF, const CXXRecordDecl *RD, BaseSubobject Base,
323 const CXXRecordDecl *NearestVBase, bool &NeedsVirtualOffset) = 0;
325 /// Get the address point of the vtable for the given base subobject while
326 /// building a constexpr.
327 virtual llvm::Constant *
328 getVTableAddressPointForConstExpr(BaseSubobject Base,
329 const CXXRecordDecl *VTableClass) = 0;
331 /// Get the address of the vtable for the given record decl which should be
332 /// used for the vptr at the given offset in RD.
333 virtual llvm::GlobalVariable *getAddrOfVTable(const CXXRecordDecl *RD,
334 CharUnits VPtrOffset) = 0;
336 /// Build a virtual function pointer in the ABI-specific way.
337 virtual llvm::Value *getVirtualFunctionPointer(CodeGenFunction &CGF,
342 /// Emit the ABI-specific virtual destructor call.
343 virtual void EmitVirtualDestructorCall(CodeGenFunction &CGF,
344 const CXXDestructorDecl *Dtor,
345 CXXDtorType DtorType,
346 SourceLocation CallLoc,
347 llvm::Value *This) = 0;
349 virtual void adjustCallArgsForDestructorThunk(CodeGenFunction &CGF,
351 CallArgList &CallArgs) {}
353 /// Emit any tables needed to implement virtual inheritance. For Itanium,
354 /// this emits virtual table tables. For the MSVC++ ABI, this emits virtual
356 virtual void emitVirtualInheritanceTables(const CXXRecordDecl *RD) = 0;
358 virtual void setThunkLinkage(llvm::Function *Thunk, bool ForVTable) = 0;
360 virtual llvm::Value *performThisAdjustment(CodeGenFunction &CGF,
362 const ThisAdjustment &TA) = 0;
364 virtual llvm::Value *performReturnAdjustment(CodeGenFunction &CGF,
366 const ReturnAdjustment &RA) = 0;
368 virtual void EmitReturnFromThunk(CodeGenFunction &CGF,
369 RValue RV, QualType ResultType);
371 /// Gets the pure virtual member call function.
372 virtual StringRef GetPureVirtualCallName() = 0;
374 /// Gets the deleted virtual member call name.
375 virtual StringRef GetDeletedVirtualCallName() = 0;
377 /// \brief Returns true iff static data members that are initialized in the
378 /// class definition should have linkonce linkage.
379 virtual bool isInlineInitializedStaticDataMemberLinkOnce() { return false; }
381 /**************************** Array cookies ******************************/
383 /// Returns the extra size required in order to store the array
384 /// cookie for the given new-expression. May return 0 to indicate that no
385 /// array cookie is required.
387 /// Several cases are filtered out before this method is called:
388 /// - non-array allocations never need a cookie
389 /// - calls to \::operator new(size_t, void*) never need a cookie
391 /// \param expr - the new-expression being allocated.
392 virtual CharUnits GetArrayCookieSize(const CXXNewExpr *expr);
394 /// Initialize the array cookie for the given allocation.
396 /// \param NewPtr - a char* which is the presumed-non-null
397 /// return value of the allocation function
398 /// \param NumElements - the computed number of elements,
399 /// potentially collapsed from the multidimensional array case;
401 /// \param ElementType - the base element allocated type,
402 /// i.e. the allocated type after stripping all array types
403 virtual llvm::Value *InitializeArrayCookie(CodeGenFunction &CGF,
405 llvm::Value *NumElements,
406 const CXXNewExpr *expr,
407 QualType ElementType);
409 /// Reads the array cookie associated with the given pointer,
412 /// \param Ptr - a pointer to the first element in the array
413 /// \param ElementType - the base element type of elements of the array
414 /// \param NumElements - an out parameter which will be initialized
415 /// with the number of elements allocated, or zero if there is no
417 /// \param AllocPtr - an out parameter which will be initialized
418 /// with a char* pointing to the address returned by the allocation
420 /// \param CookieSize - an out parameter which will be initialized
421 /// with the size of the cookie, or zero if there is no cookie
422 virtual void ReadArrayCookie(CodeGenFunction &CGF, llvm::Value *Ptr,
423 const CXXDeleteExpr *expr,
424 QualType ElementType, llvm::Value *&NumElements,
425 llvm::Value *&AllocPtr, CharUnits &CookieSize);
427 /// Return whether the given global decl needs a VTT parameter.
428 virtual bool NeedsVTTParameter(GlobalDecl GD);
431 /// Returns the extra size required in order to store the array
432 /// cookie for the given type. Assumes that an array cookie is
434 virtual CharUnits getArrayCookieSizeImpl(QualType elementType);
436 /// Reads the array cookie for an allocation which is known to have one.
437 /// This is called by the standard implementation of ReadArrayCookie.
439 /// \param ptr - a pointer to the allocation made for an array, as a char*
440 /// \param cookieSize - the computed cookie size of an array
442 /// Other parameters are as above.
445 virtual llvm::Value *readArrayCookieImpl(CodeGenFunction &IGF,
447 CharUnits cookieSize);
451 /*************************** Static local guards ****************************/
453 /// Emits the guarded initializer and destructor setup for the given
454 /// variable, given that it couldn't be emitted as a constant.
455 /// If \p PerformInit is false, the initialization has been folded to a
456 /// constant and should not be performed.
458 /// The variable may be:
459 /// - a static local variable
460 /// - a static data member of a class template instantiation
461 virtual void EmitGuardedInit(CodeGenFunction &CGF, const VarDecl &D,
462 llvm::GlobalVariable *DeclPtr,
463 bool PerformInit) = 0;
465 /// Emit code to force the execution of a destructor during global
466 /// teardown. The default implementation of this uses atexit.
468 /// \param dtor - a function taking a single pointer argument
469 /// \param addr - a pointer to pass to the destructor function.
470 virtual void registerGlobalDtor(CodeGenFunction &CGF, const VarDecl &D,
471 llvm::Constant *dtor, llvm::Constant *addr);
473 /*************************** thread_local initialization ********************/
475 /// Emits ABI-required functions necessary to initialize thread_local
476 /// variables in this translation unit.
478 /// \param Decls The thread_local declarations in this translation unit.
479 /// \param InitFunc If this translation unit contains any non-constant
480 /// initialization or non-trivial destruction for thread_local
481 /// variables, a function to perform the initialization. Otherwise, 0.
482 virtual void EmitThreadLocalInitFuncs(
483 llvm::ArrayRef<std::pair<const VarDecl *, llvm::GlobalVariable *> > Decls,
484 llvm::Function *InitFunc);
486 /// Emit a reference to a non-local thread_local variable (including
487 /// triggering the initialization of all thread_local variables in its
488 /// translation unit).
489 virtual LValue EmitThreadLocalVarDeclLValue(CodeGenFunction &CGF,
493 /**************************** RTTI Uniqueness ******************************/
496 /// Returns true if the ABI requires RTTI type_info objects to be unique
497 /// across a program.
498 virtual bool shouldRTTIBeUnique() { return true; }
501 /// What sort of unique-RTTI behavior should we use?
502 enum RTTIUniquenessKind {
503 /// We are guaranteeing, or need to guarantee, that the RTTI string
507 /// We are not guaranteeing uniqueness for the RTTI string, so we
508 /// can demote to hidden visibility but must use string comparisons.
511 /// We are not guaranteeing uniqueness for the RTTI string, so we
512 /// have to use string comparisons, but we also have to emit it with
513 /// non-hidden visibility.
517 /// Return the required visibility status for the given type and linkage in
520 classifyRTTIUniqueness(QualType CanTy,
521 llvm::GlobalValue::LinkageTypes Linkage);
524 // Create an instance of a C++ ABI class:
526 /// Creates an Itanium-family ABI.
527 CGCXXABI *CreateItaniumCXXABI(CodeGenModule &CGM);
529 /// Creates a Microsoft-family ABI.
530 CGCXXABI *CreateMicrosoftCXXABI(CodeGenModule &CGM);