1 //===----- CGCXXABI.h - Interface to C++ ABIs -------------------*- C++ -*-===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // This provides an abstract class for C++ code generation. Concrete subclasses 11 // of this implement code generation for specific C++ ABIs. 12 // 13 //===----------------------------------------------------------------------===// 14 15 #ifndef LLVM_CLANG_LIB_CODEGEN_CGCXXABI_H 16 #define LLVM_CLANG_LIB_CODEGEN_CGCXXABI_H 17 18 #include "CodeGenFunction.h" 19 #include "clang/Basic/LLVM.h" 20 21 namespace llvm { 22 class Constant; 23 class Type; 24 class Value; 25 class CallInst; 26 } 27 28 namespace clang { 29 class CastExpr; 30 class CXXConstructorDecl; 31 class CXXDestructorDecl; 32 class CXXMethodDecl; 33 class CXXRecordDecl; 34 class FieldDecl; 35 class MangleContext; 36 37 namespace CodeGen { 38 class CodeGenFunction; 39 class CodeGenModule; 40 41 /// \brief Implements C++ ABI-specific code generation functions. 42 class CGCXXABI { 43 protected: 44 CodeGenModule &CGM; 45 std::unique_ptr<MangleContext> MangleCtx; 46 47 CGCXXABI(CodeGenModule &CGM) 48 : CGM(CGM), MangleCtx(CGM.getContext().createMangleContext()) {} 49 50 protected: 51 ImplicitParamDecl *&getThisDecl(CodeGenFunction &CGF) { 52 return CGF.CXXABIThisDecl; 53 } 54 llvm::Value *&getThisValue(CodeGenFunction &CGF) { 55 return CGF.CXXABIThisValue; 56 } 57 58 /// Issue a diagnostic about unsupported features in the ABI. 59 void ErrorUnsupportedABI(CodeGenFunction &CGF, StringRef S); 60 61 /// Get a null value for unsupported member pointers. 62 llvm::Constant *GetBogusMemberPointer(QualType T); 63 64 ImplicitParamDecl *&getStructorImplicitParamDecl(CodeGenFunction &CGF) { 65 return CGF.CXXStructorImplicitParamDecl; 66 } 67 llvm::Value *&getStructorImplicitParamValue(CodeGenFunction &CGF) { 68 return CGF.CXXStructorImplicitParamValue; 69 } 70 71 /// Perform prolog initialization of the parameter variable suitable 72 /// for 'this' emitted by buildThisParam. 73 void EmitThisParam(CodeGenFunction &CGF); 74 75 ASTContext &getContext() const { return CGM.getContext(); } 76 77 virtual bool requiresArrayCookie(const CXXDeleteExpr *E, QualType eltType); 78 virtual bool requiresArrayCookie(const CXXNewExpr *E); 79 80 public: 81 82 virtual ~CGCXXABI(); 83 84 /// Gets the mangle context. 85 MangleContext &getMangleContext() { 86 return *MangleCtx; 87 } 88 89 /// Returns true if the given constructor or destructor is one of the 90 /// kinds that the ABI says returns 'this' (only applies when called 91 /// non-virtually for destructors). 92 /// 93 /// There currently is no way to indicate if a destructor returns 'this' 94 /// when called virtually, and code generation does not support the case. 95 virtual bool HasThisReturn(GlobalDecl GD) const { return false; } 96 97 virtual bool hasMostDerivedReturn(GlobalDecl GD) const { return false; } 98 99 /// If the C++ ABI requires the given type be returned in a particular way, 100 /// this method sets RetAI and returns true. 101 virtual bool classifyReturnType(CGFunctionInfo &FI) const = 0; 102 103 /// Specify how one should pass an argument of a record type. 104 enum RecordArgABI { 105 /// Pass it using the normal C aggregate rules for the ABI, potentially 106 /// introducing extra copies and passing some or all of it in registers. 107 RAA_Default = 0, 108 109 /// Pass it on the stack using its defined layout. The argument must be 110 /// evaluated directly into the correct stack position in the arguments area, 111 /// and the call machinery must not move it or introduce extra copies. 112 RAA_DirectInMemory, 113 114 /// Pass it as a pointer to temporary memory. 115 RAA_Indirect 116 }; 117 118 /// Returns true if C++ allows us to copy the memory of an object of type RD 119 /// when it is passed as an argument. 120 bool canCopyArgument(const CXXRecordDecl *RD) const; 121 122 /// Returns how an argument of the given record type should be passed. 123 virtual RecordArgABI getRecordArgABI(const CXXRecordDecl *RD) const = 0; 124 125 /// Returns true if the implicit 'sret' parameter comes after the implicit 126 /// 'this' parameter of C++ instance methods. 127 virtual bool isSRetParameterAfterThis() const { return false; } 128 129 /// Find the LLVM type used to represent the given member pointer 130 /// type. 131 virtual llvm::Type * 132 ConvertMemberPointerType(const MemberPointerType *MPT); 133 134 /// Load a member function from an object and a member function 135 /// pointer. Apply the this-adjustment and set 'This' to the 136 /// adjusted value. 137 virtual llvm::Value *EmitLoadOfMemberFunctionPointer( 138 CodeGenFunction &CGF, const Expr *E, llvm::Value *&This, 139 llvm::Value *MemPtr, const MemberPointerType *MPT); 140 141 /// Calculate an l-value from an object and a data member pointer. 142 virtual llvm::Value * 143 EmitMemberDataPointerAddress(CodeGenFunction &CGF, const Expr *E, 144 llvm::Value *Base, llvm::Value *MemPtr, 145 const MemberPointerType *MPT); 146 147 /// Perform a derived-to-base, base-to-derived, or bitcast member 148 /// pointer conversion. 149 virtual llvm::Value *EmitMemberPointerConversion(CodeGenFunction &CGF, 150 const CastExpr *E, 151 llvm::Value *Src); 152 153 /// Perform a derived-to-base, base-to-derived, or bitcast member 154 /// pointer conversion on a constant value. 155 virtual llvm::Constant *EmitMemberPointerConversion(const CastExpr *E, 156 llvm::Constant *Src); 157 158 /// Return true if the given member pointer can be zero-initialized 159 /// (in the C++ sense) with an LLVM zeroinitializer. 160 virtual bool isZeroInitializable(const MemberPointerType *MPT); 161 162 /// Return whether or not a member pointers type is convertible to an IR type. 163 virtual bool isMemberPointerConvertible(const MemberPointerType *MPT) const { 164 return true; 165 } 166 167 virtual bool isTypeInfoCalculable(QualType Ty) const { 168 return !Ty->isIncompleteType(); 169 } 170 171 /// Create a null member pointer of the given type. 172 virtual llvm::Constant *EmitNullMemberPointer(const MemberPointerType *MPT); 173 174 /// Create a member pointer for the given method. 175 virtual llvm::Constant *EmitMemberPointer(const CXXMethodDecl *MD); 176 177 /// Create a member pointer for the given field. 178 virtual llvm::Constant *EmitMemberDataPointer(const MemberPointerType *MPT, 179 CharUnits offset); 180 181 /// Create a member pointer for the given member pointer constant. 182 virtual llvm::Constant *EmitMemberPointer(const APValue &MP, QualType MPT); 183 184 /// Emit a comparison between two member pointers. Returns an i1. 185 virtual llvm::Value * 186 EmitMemberPointerComparison(CodeGenFunction &CGF, 187 llvm::Value *L, 188 llvm::Value *R, 189 const MemberPointerType *MPT, 190 bool Inequality); 191 192 /// Determine if a member pointer is non-null. Returns an i1. 193 virtual llvm::Value * 194 EmitMemberPointerIsNotNull(CodeGenFunction &CGF, 195 llvm::Value *MemPtr, 196 const MemberPointerType *MPT); 197 198 protected: 199 /// A utility method for computing the offset required for the given 200 /// base-to-derived or derived-to-base member-pointer conversion. 201 /// Does not handle virtual conversions (in case we ever fully 202 /// support an ABI that allows this). Returns null if no adjustment 203 /// is required. 204 llvm::Constant *getMemberPointerAdjustment(const CastExpr *E); 205 206 /// \brief Computes the non-virtual adjustment needed for a member pointer 207 /// conversion along an inheritance path stored in an APValue. Unlike 208 /// getMemberPointerAdjustment(), the adjustment can be negative if the path 209 /// is from a derived type to a base type. 210 CharUnits getMemberPointerPathAdjustment(const APValue &MP); 211 212 public: 213 virtual void emitVirtualObjectDelete(CodeGenFunction &CGF, 214 const CXXDeleteExpr *DE, 215 llvm::Value *Ptr, QualType ElementType, 216 const CXXDestructorDecl *Dtor) = 0; 217 virtual void emitRethrow(CodeGenFunction &CGF, bool isNoReturn) = 0; 218 virtual void emitThrow(CodeGenFunction &CGF, const CXXThrowExpr *E) = 0; 219 virtual llvm::GlobalVariable *getThrowInfo(QualType T) { return nullptr; } 220 221 virtual void emitBeginCatch(CodeGenFunction &CGF, const CXXCatchStmt *C) = 0; 222 223 virtual llvm::CallInst * 224 emitTerminateForUnexpectedException(CodeGenFunction &CGF, 225 llvm::Value *Exn); 226 227 virtual llvm::Constant *getAddrOfRTTIDescriptor(QualType Ty) = 0; 228 virtual llvm::Constant * 229 getAddrOfCXXCatchHandlerType(QualType Ty, QualType CatchHandlerType) = 0; 230 231 virtual bool shouldTypeidBeNullChecked(bool IsDeref, 232 QualType SrcRecordTy) = 0; 233 virtual void EmitBadTypeidCall(CodeGenFunction &CGF) = 0; 234 virtual llvm::Value *EmitTypeid(CodeGenFunction &CGF, QualType SrcRecordTy, 235 llvm::Value *ThisPtr, 236 llvm::Type *StdTypeInfoPtrTy) = 0; 237 238 virtual bool shouldDynamicCastCallBeNullChecked(bool SrcIsPtr, 239 QualType SrcRecordTy) = 0; 240 241 virtual llvm::Value * 242 EmitDynamicCastCall(CodeGenFunction &CGF, llvm::Value *Value, 243 QualType SrcRecordTy, QualType DestTy, 244 QualType DestRecordTy, llvm::BasicBlock *CastEnd) = 0; 245 246 virtual llvm::Value *EmitDynamicCastToVoid(CodeGenFunction &CGF, 247 llvm::Value *Value, 248 QualType SrcRecordTy, 249 QualType DestTy) = 0; 250 251 virtual bool EmitBadCastCall(CodeGenFunction &CGF) = 0; 252 253 virtual llvm::Value *GetVirtualBaseClassOffset(CodeGenFunction &CGF, 254 llvm::Value *This, 255 const CXXRecordDecl *ClassDecl, 256 const CXXRecordDecl *BaseClassDecl) = 0; 257 258 virtual llvm::BasicBlock *EmitCtorCompleteObjectHandler(CodeGenFunction &CGF, 259 const CXXRecordDecl *RD); 260 261 /// Emit the code to initialize hidden members required 262 /// to handle virtual inheritance, if needed by the ABI. 263 virtual void 264 initializeHiddenVirtualInheritanceMembers(CodeGenFunction &CGF, 265 const CXXRecordDecl *RD) {} 266 267 /// Emit constructor variants required by this ABI. 268 virtual void EmitCXXConstructors(const CXXConstructorDecl *D) = 0; 269 270 /// Build the signature of the given constructor or destructor variant by 271 /// adding any required parameters. For convenience, ArgTys has been 272 /// initialized with the type of 'this'. 273 virtual void buildStructorSignature(const CXXMethodDecl *MD, StructorType T, 274 SmallVectorImpl<CanQualType> &ArgTys) = 0; 275 276 /// Returns true if the given destructor type should be emitted as a linkonce 277 /// delegating thunk, regardless of whether the dtor is defined in this TU or 278 /// not. 279 virtual bool useThunkForDtorVariant(const CXXDestructorDecl *Dtor, 280 CXXDtorType DT) const = 0; 281 282 /// Emit destructor variants required by this ABI. 283 virtual void EmitCXXDestructors(const CXXDestructorDecl *D) = 0; 284 285 /// Get the type of the implicit "this" parameter used by a method. May return 286 /// zero if no specific type is applicable, e.g. if the ABI expects the "this" 287 /// parameter to point to some artificial offset in a complete object due to 288 /// vbases being reordered. 289 virtual const CXXRecordDecl * 290 getThisArgumentTypeForMethod(const CXXMethodDecl *MD) { 291 return MD->getParent(); 292 } 293 294 /// Perform ABI-specific "this" argument adjustment required prior to 295 /// a call of a virtual function. 296 /// The "VirtualCall" argument is true iff the call itself is virtual. 297 virtual llvm::Value * 298 adjustThisArgumentForVirtualFunctionCall(CodeGenFunction &CGF, GlobalDecl GD, 299 llvm::Value *This, 300 bool VirtualCall) { 301 return This; 302 } 303 304 /// Build a parameter variable suitable for 'this'. 305 void buildThisParam(CodeGenFunction &CGF, FunctionArgList &Params); 306 307 /// Insert any ABI-specific implicit parameters into the parameter list for a 308 /// function. This generally involves extra data for constructors and 309 /// destructors. 310 /// 311 /// ABIs may also choose to override the return type, which has been 312 /// initialized with the type of 'this' if HasThisReturn(CGF.CurGD) is true or 313 /// the formal return type of the function otherwise. 314 virtual void addImplicitStructorParams(CodeGenFunction &CGF, QualType &ResTy, 315 FunctionArgList &Params) = 0; 316 317 /// Perform ABI-specific "this" parameter adjustment in a virtual function 318 /// prologue. 319 virtual llvm::Value *adjustThisParameterInVirtualFunctionPrologue( 320 CodeGenFunction &CGF, GlobalDecl GD, llvm::Value *This) { 321 return This; 322 } 323 324 /// Emit the ABI-specific prolog for the function. 325 virtual void EmitInstanceFunctionProlog(CodeGenFunction &CGF) = 0; 326 327 /// Add any ABI-specific implicit arguments needed to call a constructor. 328 /// 329 /// \return The number of args added to the call, which is typically zero or 330 /// one. 331 virtual unsigned 332 addImplicitConstructorArgs(CodeGenFunction &CGF, const CXXConstructorDecl *D, 333 CXXCtorType Type, bool ForVirtualBase, 334 bool Delegating, CallArgList &Args) = 0; 335 336 /// Emit the destructor call. 337 virtual void EmitDestructorCall(CodeGenFunction &CGF, 338 const CXXDestructorDecl *DD, CXXDtorType Type, 339 bool ForVirtualBase, bool Delegating, 340 llvm::Value *This) = 0; 341 342 /// Emits the VTable definitions required for the given record type. 343 virtual void emitVTableDefinitions(CodeGenVTables &CGVT, 344 const CXXRecordDecl *RD) = 0; 345 346 /// Get the address point of the vtable for the given base subobject while 347 /// building a constructor or a destructor. On return, NeedsVirtualOffset 348 /// tells if a virtual base adjustment is needed in order to get the offset 349 /// of the base subobject. 350 virtual llvm::Value *getVTableAddressPointInStructor( 351 CodeGenFunction &CGF, const CXXRecordDecl *RD, BaseSubobject Base, 352 const CXXRecordDecl *NearestVBase, bool &NeedsVirtualOffset) = 0; 353 354 /// Get the address point of the vtable for the given base subobject while 355 /// building a constexpr. 356 virtual llvm::Constant * 357 getVTableAddressPointForConstExpr(BaseSubobject Base, 358 const CXXRecordDecl *VTableClass) = 0; 359 360 /// Get the address of the vtable for the given record decl which should be 361 /// used for the vptr at the given offset in RD. 362 virtual llvm::GlobalVariable *getAddrOfVTable(const CXXRecordDecl *RD, 363 CharUnits VPtrOffset) = 0; 364 365 /// Build a virtual function pointer in the ABI-specific way. 366 virtual llvm::Value *getVirtualFunctionPointer(CodeGenFunction &CGF, 367 GlobalDecl GD, 368 llvm::Value *This, 369 llvm::Type *Ty) = 0; 370 371 /// Emit the ABI-specific virtual destructor call. 372 virtual llvm::Value * 373 EmitVirtualDestructorCall(CodeGenFunction &CGF, const CXXDestructorDecl *Dtor, 374 CXXDtorType DtorType, llvm::Value *This, 375 const CXXMemberCallExpr *CE) = 0; 376 377 virtual void adjustCallArgsForDestructorThunk(CodeGenFunction &CGF, 378 GlobalDecl GD, 379 CallArgList &CallArgs) {} 380 381 /// Emit any tables needed to implement virtual inheritance. For Itanium, 382 /// this emits virtual table tables. For the MSVC++ ABI, this emits virtual 383 /// base tables. 384 virtual void emitVirtualInheritanceTables(const CXXRecordDecl *RD) = 0; 385 386 virtual void setThunkLinkage(llvm::Function *Thunk, bool ForVTable, 387 GlobalDecl GD, bool ReturnAdjustment) = 0; 388 389 virtual llvm::Value *performThisAdjustment(CodeGenFunction &CGF, 390 llvm::Value *This, 391 const ThisAdjustment &TA) = 0; 392 393 virtual llvm::Value *performReturnAdjustment(CodeGenFunction &CGF, 394 llvm::Value *Ret, 395 const ReturnAdjustment &RA) = 0; 396 397 virtual void EmitReturnFromThunk(CodeGenFunction &CGF, 398 RValue RV, QualType ResultType); 399 400 virtual size_t getSrcArgforCopyCtor(const CXXConstructorDecl *, 401 FunctionArgList &Args) const = 0; 402 403 /// Gets the pure virtual member call function. 404 virtual StringRef GetPureVirtualCallName() = 0; 405 406 /// Gets the deleted virtual member call name. 407 virtual StringRef GetDeletedVirtualCallName() = 0; 408 409 /**************************** Array cookies ******************************/ 410 411 /// Returns the extra size required in order to store the array 412 /// cookie for the given new-expression. May return 0 to indicate that no 413 /// array cookie is required. 414 /// 415 /// Several cases are filtered out before this method is called: 416 /// - non-array allocations never need a cookie 417 /// - calls to \::operator new(size_t, void*) never need a cookie 418 /// 419 /// \param expr - the new-expression being allocated. 420 virtual CharUnits GetArrayCookieSize(const CXXNewExpr *expr); 421 422 /// Initialize the array cookie for the given allocation. 423 /// 424 /// \param NewPtr - a char* which is the presumed-non-null 425 /// return value of the allocation function 426 /// \param NumElements - the computed number of elements, 427 /// potentially collapsed from the multidimensional array case; 428 /// always a size_t 429 /// \param ElementType - the base element allocated type, 430 /// i.e. the allocated type after stripping all array types 431 virtual llvm::Value *InitializeArrayCookie(CodeGenFunction &CGF, 432 llvm::Value *NewPtr, 433 llvm::Value *NumElements, 434 const CXXNewExpr *expr, 435 QualType ElementType); 436 437 /// Reads the array cookie associated with the given pointer, 438 /// if it has one. 439 /// 440 /// \param Ptr - a pointer to the first element in the array 441 /// \param ElementType - the base element type of elements of the array 442 /// \param NumElements - an out parameter which will be initialized 443 /// with the number of elements allocated, or zero if there is no 444 /// cookie 445 /// \param AllocPtr - an out parameter which will be initialized 446 /// with a char* pointing to the address returned by the allocation 447 /// function 448 /// \param CookieSize - an out parameter which will be initialized 449 /// with the size of the cookie, or zero if there is no cookie 450 virtual void ReadArrayCookie(CodeGenFunction &CGF, llvm::Value *Ptr, 451 const CXXDeleteExpr *expr, 452 QualType ElementType, llvm::Value *&NumElements, 453 llvm::Value *&AllocPtr, CharUnits &CookieSize); 454 455 /// Return whether the given global decl needs a VTT parameter. 456 virtual bool NeedsVTTParameter(GlobalDecl GD); 457 458 protected: 459 /// Returns the extra size required in order to store the array 460 /// cookie for the given type. Assumes that an array cookie is 461 /// required. 462 virtual CharUnits getArrayCookieSizeImpl(QualType elementType); 463 464 /// Reads the array cookie for an allocation which is known to have one. 465 /// This is called by the standard implementation of ReadArrayCookie. 466 /// 467 /// \param ptr - a pointer to the allocation made for an array, as a char* 468 /// \param cookieSize - the computed cookie size of an array 469 /// 470 /// Other parameters are as above. 471 /// 472 /// \return a size_t 473 virtual llvm::Value *readArrayCookieImpl(CodeGenFunction &IGF, 474 llvm::Value *ptr, 475 CharUnits cookieSize); 476 477 public: 478 479 /*************************** Static local guards ****************************/ 480 481 /// Emits the guarded initializer and destructor setup for the given 482 /// variable, given that it couldn't be emitted as a constant. 483 /// If \p PerformInit is false, the initialization has been folded to a 484 /// constant and should not be performed. 485 /// 486 /// The variable may be: 487 /// - a static local variable 488 /// - a static data member of a class template instantiation 489 virtual void EmitGuardedInit(CodeGenFunction &CGF, const VarDecl &D, 490 llvm::GlobalVariable *DeclPtr, 491 bool PerformInit) = 0; 492 493 /// Emit code to force the execution of a destructor during global 494 /// teardown. The default implementation of this uses atexit. 495 /// 496 /// \param Dtor - a function taking a single pointer argument 497 /// \param Addr - a pointer to pass to the destructor function. 498 virtual void registerGlobalDtor(CodeGenFunction &CGF, const VarDecl &D, 499 llvm::Constant *Dtor, 500 llvm::Constant *Addr) = 0; 501 502 /*************************** thread_local initialization ********************/ 503 504 /// Emits ABI-required functions necessary to initialize thread_local 505 /// variables in this translation unit. 506 /// 507 /// \param CXXThreadLocals - The thread_local declarations in this translation 508 /// unit. 509 /// \param CXXThreadLocalInits - If this translation unit contains any 510 /// non-constant initialization or non-trivial destruction for 511 /// thread_local variables, a list of functions to perform the 512 /// initialization. 513 virtual void EmitThreadLocalInitFuncs( 514 CodeGenModule &CGM, 515 ArrayRef<std::pair<const VarDecl *, llvm::GlobalVariable *>> 516 CXXThreadLocals, 517 ArrayRef<llvm::Function *> CXXThreadLocalInits, 518 ArrayRef<llvm::GlobalVariable *> CXXThreadLocalInitVars) = 0; 519 520 // Determine if references to thread_local global variables can be made 521 // directly or require access through a thread wrapper function. 522 virtual bool usesThreadWrapperFunction() const = 0; 523 524 /// Emit a reference to a non-local thread_local variable (including 525 /// triggering the initialization of all thread_local variables in its 526 /// translation unit). 527 virtual LValue EmitThreadLocalVarDeclLValue(CodeGenFunction &CGF, 528 const VarDecl *VD, 529 QualType LValType) = 0; 530 531 /// Emit a single constructor/destructor with the given type from a C++ 532 /// constructor Decl. 533 virtual void emitCXXStructor(const CXXMethodDecl *MD, StructorType Type) = 0; 534 }; 535 536 // Create an instance of a C++ ABI class: 537 538 /// Creates an Itanium-family ABI. 539 CGCXXABI *CreateItaniumCXXABI(CodeGenModule &CGM); 540 541 /// Creates a Microsoft-family ABI. 542 CGCXXABI *CreateMicrosoftCXXABI(CodeGenModule &CGM); 543 544 } 545 } 546 547 #endif 548
