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 LLVM_CLANG_LIB_CODEGEN_CGCXXABI_H
16 #define LLVM_CLANG_LIB_CODEGEN_CGCXXABI_H
18 #include "CodeGenFunction.h"
19 #include "clang/Basic/LLVM.h"
30 class CXXConstructorDecl;
31 class CXXDestructorDecl;
39 class CodeGenFunction;
43 /// \brief Implements C++ ABI-specific code generation functions.
47 std::unique_ptr<MangleContext> MangleCtx;
49 CGCXXABI(CodeGenModule &CGM)
50 : CGM(CGM), MangleCtx(CGM.getContext().createMangleContext()) {}
53 ImplicitParamDecl *getThisDecl(CodeGenFunction &CGF) {
54 return CGF.CXXABIThisDecl;
56 llvm::Value *getThisValue(CodeGenFunction &CGF) {
57 return CGF.CXXABIThisValue;
59 Address getThisAddress(CodeGenFunction &CGF) {
60 return Address(CGF.CXXABIThisValue, CGF.CXXABIThisAlignment);
63 /// Issue a diagnostic about unsupported features in the ABI.
64 void ErrorUnsupportedABI(CodeGenFunction &CGF, StringRef S);
66 /// Get a null value for unsupported member pointers.
67 llvm::Constant *GetBogusMemberPointer(QualType T);
69 ImplicitParamDecl *&getStructorImplicitParamDecl(CodeGenFunction &CGF) {
70 return CGF.CXXStructorImplicitParamDecl;
72 llvm::Value *&getStructorImplicitParamValue(CodeGenFunction &CGF) {
73 return CGF.CXXStructorImplicitParamValue;
76 /// Perform prolog initialization of the parameter variable suitable
77 /// for 'this' emitted by buildThisParam.
78 void EmitThisParam(CodeGenFunction &CGF);
80 ASTContext &getContext() const { return CGM.getContext(); }
82 virtual bool requiresArrayCookie(const CXXDeleteExpr *E, QualType eltType);
83 virtual bool requiresArrayCookie(const CXXNewExpr *E);
85 /// Determine whether there's something special about the rules of
86 /// the ABI tell us that 'this' is a complete object within the
87 /// given function. Obvious common logic like being defined on a
88 /// final class will have been taken care of by the caller.
89 virtual bool isThisCompleteObject(GlobalDecl GD) const = 0;
95 /// Gets the mangle context.
96 MangleContext &getMangleContext() {
100 /// Returns true if the given constructor or destructor is one of the
101 /// kinds that the ABI says returns 'this' (only applies when called
102 /// non-virtually for destructors).
104 /// There currently is no way to indicate if a destructor returns 'this'
105 /// when called virtually, and code generation does not support the case.
106 virtual bool HasThisReturn(GlobalDecl GD) const { return false; }
108 virtual bool hasMostDerivedReturn(GlobalDecl GD) const { return false; }
110 /// Returns true if the target allows calling a function through a pointer
111 /// with a different signature than the actual function (or equivalently,
112 /// bitcasting a function or function pointer to a different function type).
113 /// In principle in the most general case this could depend on the target, the
114 /// calling convention, and the actual types of the arguments and return
115 /// value. Here it just means whether the signature mismatch could *ever* be
116 /// allowed; in other words, does the target do strict checking of signatures
118 virtual bool canCallMismatchedFunctionType() const { return true; }
120 /// If the C++ ABI requires the given type be returned in a particular way,
121 /// this method sets RetAI and returns true.
122 virtual bool classifyReturnType(CGFunctionInfo &FI) const = 0;
124 /// Specify how one should pass an argument of a record type.
126 /// Pass it using the normal C aggregate rules for the ABI, potentially
127 /// introducing extra copies and passing some or all of it in registers.
130 /// Pass it on the stack using its defined layout. The argument must be
131 /// evaluated directly into the correct stack position in the arguments area,
132 /// and the call machinery must not move it or introduce extra copies.
135 /// Pass it as a pointer to temporary memory.
139 /// Returns true if C++ allows us to copy the memory of an object of type RD
140 /// when it is passed as an argument.
141 bool canCopyArgument(const CXXRecordDecl *RD) const;
143 /// Returns how an argument of the given record type should be passed.
144 virtual RecordArgABI getRecordArgABI(const CXXRecordDecl *RD) const = 0;
146 /// Returns true if the implicit 'sret' parameter comes after the implicit
147 /// 'this' parameter of C++ instance methods.
148 virtual bool isSRetParameterAfterThis() const { return false; }
150 /// Find the LLVM type used to represent the given member pointer
153 ConvertMemberPointerType(const MemberPointerType *MPT);
155 /// Load a member function from an object and a member function
156 /// pointer. Apply the this-adjustment and set 'This' to the
158 virtual CGCallee EmitLoadOfMemberFunctionPointer(
159 CodeGenFunction &CGF, const Expr *E, Address This,
160 llvm::Value *&ThisPtrForCall, llvm::Value *MemPtr,
161 const MemberPointerType *MPT);
163 /// Calculate an l-value from an object and a data member pointer.
164 virtual llvm::Value *
165 EmitMemberDataPointerAddress(CodeGenFunction &CGF, const Expr *E,
166 Address Base, llvm::Value *MemPtr,
167 const MemberPointerType *MPT);
169 /// Perform a derived-to-base, base-to-derived, or bitcast member
170 /// pointer conversion.
171 virtual llvm::Value *EmitMemberPointerConversion(CodeGenFunction &CGF,
175 /// Perform a derived-to-base, base-to-derived, or bitcast member
176 /// pointer conversion on a constant value.
177 virtual llvm::Constant *EmitMemberPointerConversion(const CastExpr *E,
178 llvm::Constant *Src);
180 /// Return true if the given member pointer can be zero-initialized
181 /// (in the C++ sense) with an LLVM zeroinitializer.
182 virtual bool isZeroInitializable(const MemberPointerType *MPT);
184 /// Return whether or not a member pointers type is convertible to an IR type.
185 virtual bool isMemberPointerConvertible(const MemberPointerType *MPT) const {
189 /// Create a null member pointer of the given type.
190 virtual llvm::Constant *EmitNullMemberPointer(const MemberPointerType *MPT);
192 /// Create a member pointer for the given method.
193 virtual llvm::Constant *EmitMemberFunctionPointer(const CXXMethodDecl *MD);
195 /// Create a member pointer for the given field.
196 virtual llvm::Constant *EmitMemberDataPointer(const MemberPointerType *MPT,
199 /// Create a member pointer for the given member pointer constant.
200 virtual llvm::Constant *EmitMemberPointer(const APValue &MP, QualType MPT);
202 /// Emit a comparison between two member pointers. Returns an i1.
203 virtual llvm::Value *
204 EmitMemberPointerComparison(CodeGenFunction &CGF,
207 const MemberPointerType *MPT,
210 /// Determine if a member pointer is non-null. Returns an i1.
211 virtual llvm::Value *
212 EmitMemberPointerIsNotNull(CodeGenFunction &CGF,
214 const MemberPointerType *MPT);
217 /// A utility method for computing the offset required for the given
218 /// base-to-derived or derived-to-base member-pointer conversion.
219 /// Does not handle virtual conversions (in case we ever fully
220 /// support an ABI that allows this). Returns null if no adjustment
222 llvm::Constant *getMemberPointerAdjustment(const CastExpr *E);
224 /// \brief Computes the non-virtual adjustment needed for a member pointer
225 /// conversion along an inheritance path stored in an APValue. Unlike
226 /// getMemberPointerAdjustment(), the adjustment can be negative if the path
227 /// is from a derived type to a base type.
228 CharUnits getMemberPointerPathAdjustment(const APValue &MP);
231 virtual void emitVirtualObjectDelete(CodeGenFunction &CGF,
232 const CXXDeleteExpr *DE,
233 Address Ptr, QualType ElementType,
234 const CXXDestructorDecl *Dtor) = 0;
235 virtual void emitRethrow(CodeGenFunction &CGF, bool isNoReturn) = 0;
236 virtual void emitThrow(CodeGenFunction &CGF, const CXXThrowExpr *E) = 0;
237 virtual llvm::GlobalVariable *getThrowInfo(QualType T) { return nullptr; }
239 /// \brief Determine whether it's possible to emit a vtable for \p RD, even
240 /// though we do not know that the vtable has been marked as used by semantic
242 virtual bool canSpeculativelyEmitVTable(const CXXRecordDecl *RD) const = 0;
244 virtual void emitBeginCatch(CodeGenFunction &CGF, const CXXCatchStmt *C) = 0;
246 virtual llvm::CallInst *
247 emitTerminateForUnexpectedException(CodeGenFunction &CGF,
250 virtual llvm::Constant *getAddrOfRTTIDescriptor(QualType Ty) = 0;
251 virtual CatchTypeInfo
252 getAddrOfCXXCatchHandlerType(QualType Ty, QualType CatchHandlerType) = 0;
253 virtual CatchTypeInfo getCatchAllTypeInfo();
255 virtual bool shouldTypeidBeNullChecked(bool IsDeref,
256 QualType SrcRecordTy) = 0;
257 virtual void EmitBadTypeidCall(CodeGenFunction &CGF) = 0;
258 virtual llvm::Value *EmitTypeid(CodeGenFunction &CGF, QualType SrcRecordTy,
260 llvm::Type *StdTypeInfoPtrTy) = 0;
262 virtual bool shouldDynamicCastCallBeNullChecked(bool SrcIsPtr,
263 QualType SrcRecordTy) = 0;
265 virtual llvm::Value *
266 EmitDynamicCastCall(CodeGenFunction &CGF, Address Value,
267 QualType SrcRecordTy, QualType DestTy,
268 QualType DestRecordTy, llvm::BasicBlock *CastEnd) = 0;
270 virtual llvm::Value *EmitDynamicCastToVoid(CodeGenFunction &CGF,
272 QualType SrcRecordTy,
273 QualType DestTy) = 0;
275 virtual bool EmitBadCastCall(CodeGenFunction &CGF) = 0;
277 virtual llvm::Value *GetVirtualBaseClassOffset(CodeGenFunction &CGF,
279 const CXXRecordDecl *ClassDecl,
280 const CXXRecordDecl *BaseClassDecl) = 0;
282 virtual llvm::BasicBlock *EmitCtorCompleteObjectHandler(CodeGenFunction &CGF,
283 const CXXRecordDecl *RD);
285 /// Emit the code to initialize hidden members required
286 /// to handle virtual inheritance, if needed by the ABI.
288 initializeHiddenVirtualInheritanceMembers(CodeGenFunction &CGF,
289 const CXXRecordDecl *RD) {}
291 /// Emit constructor variants required by this ABI.
292 virtual void EmitCXXConstructors(const CXXConstructorDecl *D) = 0;
294 /// Notes how many arguments were added to the beginning (Prefix) and ending
295 /// (Suffix) of an arg list.
297 /// Note that Prefix actually refers to the number of args *after* the first
298 /// one: `this` arguments always come first.
299 struct AddedStructorArgs {
302 AddedStructorArgs() = default;
303 AddedStructorArgs(unsigned P, unsigned S) : Prefix(P), Suffix(S) {}
304 static AddedStructorArgs prefix(unsigned N) { return {N, 0}; }
305 static AddedStructorArgs suffix(unsigned N) { return {0, N}; }
308 /// Build the signature of the given constructor or destructor variant by
309 /// adding any required parameters. For convenience, ArgTys has been
310 /// initialized with the type of 'this'.
311 virtual AddedStructorArgs
312 buildStructorSignature(const CXXMethodDecl *MD, StructorType T,
313 SmallVectorImpl<CanQualType> &ArgTys) = 0;
315 /// Returns true if the given destructor type should be emitted as a linkonce
316 /// delegating thunk, regardless of whether the dtor is defined in this TU or
318 virtual bool useThunkForDtorVariant(const CXXDestructorDecl *Dtor,
319 CXXDtorType DT) const = 0;
321 /// Emit destructor variants required by this ABI.
322 virtual void EmitCXXDestructors(const CXXDestructorDecl *D) = 0;
324 /// Get the type of the implicit "this" parameter used by a method. May return
325 /// zero if no specific type is applicable, e.g. if the ABI expects the "this"
326 /// parameter to point to some artificial offset in a complete object due to
327 /// vbases being reordered.
328 virtual const CXXRecordDecl *
329 getThisArgumentTypeForMethod(const CXXMethodDecl *MD) {
330 return MD->getParent();
333 /// Perform ABI-specific "this" argument adjustment required prior to
334 /// a call of a virtual function.
335 /// The "VirtualCall" argument is true iff the call itself is virtual.
337 adjustThisArgumentForVirtualFunctionCall(CodeGenFunction &CGF, GlobalDecl GD,
338 Address This, bool VirtualCall) {
342 /// Build a parameter variable suitable for 'this'.
343 void buildThisParam(CodeGenFunction &CGF, FunctionArgList &Params);
345 /// Insert any ABI-specific implicit parameters into the parameter list for a
346 /// function. This generally involves extra data for constructors and
349 /// ABIs may also choose to override the return type, which has been
350 /// initialized with the type of 'this' if HasThisReturn(CGF.CurGD) is true or
351 /// the formal return type of the function otherwise.
352 virtual void addImplicitStructorParams(CodeGenFunction &CGF, QualType &ResTy,
353 FunctionArgList &Params) = 0;
355 /// Get the ABI-specific "this" parameter adjustment to apply in the prologue
356 /// of a virtual function.
357 virtual CharUnits getVirtualFunctionPrologueThisAdjustment(GlobalDecl GD) {
358 return CharUnits::Zero();
361 /// Perform ABI-specific "this" parameter adjustment in a virtual function
363 virtual llvm::Value *adjustThisParameterInVirtualFunctionPrologue(
364 CodeGenFunction &CGF, GlobalDecl GD, llvm::Value *This) {
368 /// Emit the ABI-specific prolog for the function.
369 virtual void EmitInstanceFunctionProlog(CodeGenFunction &CGF) = 0;
371 /// Add any ABI-specific implicit arguments needed to call a constructor.
373 /// \return The number of arguments added at the beginning and end of the
374 /// call, which is typically zero or one.
375 virtual AddedStructorArgs
376 addImplicitConstructorArgs(CodeGenFunction &CGF, const CXXConstructorDecl *D,
377 CXXCtorType Type, bool ForVirtualBase,
378 bool Delegating, CallArgList &Args) = 0;
380 /// Emit the destructor call.
381 virtual void EmitDestructorCall(CodeGenFunction &CGF,
382 const CXXDestructorDecl *DD, CXXDtorType Type,
383 bool ForVirtualBase, bool Delegating,
386 /// Emits the VTable definitions required for the given record type.
387 virtual void emitVTableDefinitions(CodeGenVTables &CGVT,
388 const CXXRecordDecl *RD) = 0;
390 /// Checks if ABI requires extra virtual offset for vtable field.
392 isVirtualOffsetNeededForVTableField(CodeGenFunction &CGF,
393 CodeGenFunction::VPtr Vptr) = 0;
395 /// Checks if ABI requires to initialize vptrs for given dynamic class.
396 virtual bool doStructorsInitializeVPtrs(const CXXRecordDecl *VTableClass) = 0;
398 /// Get the address point of the vtable for the given base subobject.
399 virtual llvm::Constant *
400 getVTableAddressPoint(BaseSubobject Base,
401 const CXXRecordDecl *VTableClass) = 0;
403 /// Get the address point of the vtable for the given base subobject while
404 /// building a constructor or a destructor.
405 virtual llvm::Value *
406 getVTableAddressPointInStructor(CodeGenFunction &CGF, const CXXRecordDecl *RD,
408 const CXXRecordDecl *NearestVBase) = 0;
410 /// Get the address point of the vtable for the given base subobject while
411 /// building a constexpr.
412 virtual llvm::Constant *
413 getVTableAddressPointForConstExpr(BaseSubobject Base,
414 const CXXRecordDecl *VTableClass) = 0;
416 /// Get the address of the vtable for the given record decl which should be
417 /// used for the vptr at the given offset in RD.
418 virtual llvm::GlobalVariable *getAddrOfVTable(const CXXRecordDecl *RD,
419 CharUnits VPtrOffset) = 0;
421 /// Build a virtual function pointer in the ABI-specific way.
422 virtual CGCallee getVirtualFunctionPointer(CodeGenFunction &CGF,
426 SourceLocation Loc) = 0;
428 /// Emit the ABI-specific virtual destructor call.
429 virtual llvm::Value *
430 EmitVirtualDestructorCall(CodeGenFunction &CGF, const CXXDestructorDecl *Dtor,
431 CXXDtorType DtorType, Address This,
432 const CXXMemberCallExpr *CE) = 0;
434 virtual void adjustCallArgsForDestructorThunk(CodeGenFunction &CGF,
436 CallArgList &CallArgs) {}
438 /// Emit any tables needed to implement virtual inheritance. For Itanium,
439 /// this emits virtual table tables. For the MSVC++ ABI, this emits virtual
441 virtual void emitVirtualInheritanceTables(const CXXRecordDecl *RD) = 0;
443 virtual void setThunkLinkage(llvm::Function *Thunk, bool ForVTable,
444 GlobalDecl GD, bool ReturnAdjustment) = 0;
446 virtual llvm::Value *performThisAdjustment(CodeGenFunction &CGF,
448 const ThisAdjustment &TA) = 0;
450 virtual llvm::Value *performReturnAdjustment(CodeGenFunction &CGF,
452 const ReturnAdjustment &RA) = 0;
454 virtual void EmitReturnFromThunk(CodeGenFunction &CGF,
455 RValue RV, QualType ResultType);
457 virtual size_t getSrcArgforCopyCtor(const CXXConstructorDecl *,
458 FunctionArgList &Args) const = 0;
460 /// Gets the offsets of all the virtual base pointers in a given class.
461 virtual std::vector<CharUnits> getVBPtrOffsets(const CXXRecordDecl *RD);
463 /// Gets the pure virtual member call function.
464 virtual StringRef GetPureVirtualCallName() = 0;
466 /// Gets the deleted virtual member call name.
467 virtual StringRef GetDeletedVirtualCallName() = 0;
469 /**************************** Array cookies ******************************/
471 /// Returns the extra size required in order to store the array
472 /// cookie for the given new-expression. May return 0 to indicate that no
473 /// array cookie is required.
475 /// Several cases are filtered out before this method is called:
476 /// - non-array allocations never need a cookie
477 /// - calls to \::operator new(size_t, void*) never need a cookie
479 /// \param expr - the new-expression being allocated.
480 virtual CharUnits GetArrayCookieSize(const CXXNewExpr *expr);
482 /// Initialize the array cookie for the given allocation.
484 /// \param NewPtr - a char* which is the presumed-non-null
485 /// return value of the allocation function
486 /// \param NumElements - the computed number of elements,
487 /// potentially collapsed from the multidimensional array case;
489 /// \param ElementType - the base element allocated type,
490 /// i.e. the allocated type after stripping all array types
491 virtual Address InitializeArrayCookie(CodeGenFunction &CGF,
493 llvm::Value *NumElements,
494 const CXXNewExpr *expr,
495 QualType ElementType);
497 /// Reads the array cookie associated with the given pointer,
500 /// \param Ptr - a pointer to the first element in the array
501 /// \param ElementType - the base element type of elements of the array
502 /// \param NumElements - an out parameter which will be initialized
503 /// with the number of elements allocated, or zero if there is no
505 /// \param AllocPtr - an out parameter which will be initialized
506 /// with a char* pointing to the address returned by the allocation
508 /// \param CookieSize - an out parameter which will be initialized
509 /// with the size of the cookie, or zero if there is no cookie
510 virtual void ReadArrayCookie(CodeGenFunction &CGF, Address Ptr,
511 const CXXDeleteExpr *expr,
512 QualType ElementType, llvm::Value *&NumElements,
513 llvm::Value *&AllocPtr, CharUnits &CookieSize);
515 /// Return whether the given global decl needs a VTT parameter.
516 virtual bool NeedsVTTParameter(GlobalDecl GD);
519 /// Returns the extra size required in order to store the array
520 /// cookie for the given type. Assumes that an array cookie is
522 virtual CharUnits getArrayCookieSizeImpl(QualType elementType);
524 /// Reads the array cookie for an allocation which is known to have one.
525 /// This is called by the standard implementation of ReadArrayCookie.
527 /// \param ptr - a pointer to the allocation made for an array, as a char*
528 /// \param cookieSize - the computed cookie size of an array
530 /// Other parameters are as above.
533 virtual llvm::Value *readArrayCookieImpl(CodeGenFunction &IGF, Address ptr,
534 CharUnits cookieSize);
538 /*************************** Static local guards ****************************/
540 /// Emits the guarded initializer and destructor setup for the given
541 /// variable, given that it couldn't be emitted as a constant.
542 /// If \p PerformInit is false, the initialization has been folded to a
543 /// constant and should not be performed.
545 /// The variable may be:
546 /// - a static local variable
547 /// - a static data member of a class template instantiation
548 virtual void EmitGuardedInit(CodeGenFunction &CGF, const VarDecl &D,
549 llvm::GlobalVariable *DeclPtr,
550 bool PerformInit) = 0;
552 /// Emit code to force the execution of a destructor during global
553 /// teardown. The default implementation of this uses atexit.
555 /// \param Dtor - a function taking a single pointer argument
556 /// \param Addr - a pointer to pass to the destructor function.
557 virtual void registerGlobalDtor(CodeGenFunction &CGF, const VarDecl &D,
558 llvm::Constant *Dtor,
559 llvm::Constant *Addr) = 0;
561 /*************************** thread_local initialization ********************/
563 /// Emits ABI-required functions necessary to initialize thread_local
564 /// variables in this translation unit.
566 /// \param CXXThreadLocals - The thread_local declarations in this translation
568 /// \param CXXThreadLocalInits - If this translation unit contains any
569 /// non-constant initialization or non-trivial destruction for
570 /// thread_local variables, a list of functions to perform the
572 virtual void EmitThreadLocalInitFuncs(
573 CodeGenModule &CGM, ArrayRef<const VarDecl *> CXXThreadLocals,
574 ArrayRef<llvm::Function *> CXXThreadLocalInits,
575 ArrayRef<const VarDecl *> CXXThreadLocalInitVars) = 0;
577 // Determine if references to thread_local global variables can be made
578 // directly or require access through a thread wrapper function.
579 virtual bool usesThreadWrapperFunction() const = 0;
581 /// Emit a reference to a non-local thread_local variable (including
582 /// triggering the initialization of all thread_local variables in its
583 /// translation unit).
584 virtual LValue EmitThreadLocalVarDeclLValue(CodeGenFunction &CGF,
586 QualType LValType) = 0;
588 /// Emit a single constructor/destructor with the given type from a C++
589 /// constructor Decl.
590 virtual void emitCXXStructor(const CXXMethodDecl *MD, StructorType Type) = 0;
593 // Create an instance of a C++ ABI class:
595 /// Creates an Itanium-family ABI.
596 CGCXXABI *CreateItaniumCXXABI(CodeGenModule &CGM);
598 /// Creates a Microsoft-family ABI.
599 CGCXXABI *CreateMicrosoftCXXABI(CodeGenModule &CGM);