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 CLANG_CODEGEN_CXXABI_H 16 #define CLANG_CODEGEN_CXXABI_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 } 26 27 namespace clang { 28 class CastExpr; 29 class CXXConstructorDecl; 30 class CXXDestructorDecl; 31 class CXXMethodDecl; 32 class CXXRecordDecl; 33 class FieldDecl; 34 class MangleContext; 35 36 namespace CodeGen { 37 class CodeGenFunction; 38 class CodeGenModule; 39 40 /// \brief Implements C++ ABI-specific code generation functions. 41 class CGCXXABI { 42 protected: 43 CodeGenModule &CGM; 44 std::unique_ptr<MangleContext> MangleCtx; 45 46 CGCXXABI(CodeGenModule &CGM) 47 : CGM(CGM), MangleCtx(CGM.getContext().createMangleContext()) {} 48 49 protected: 50 ImplicitParamDecl *&getThisDecl(CodeGenFunction &CGF) { 51 return CGF.CXXABIThisDecl; 52 } 53 llvm::Value *&getThisValue(CodeGenFunction &CGF) { 54 return CGF.CXXABIThisValue; 55 } 56 57 /// Issue a diagnostic about unsupported features in the ABI. 58 void ErrorUnsupportedABI(CodeGenFunction &CGF, StringRef S); 59 60 /// Get a null value for unsupported member pointers. 61 llvm::Constant *GetBogusMemberPointer(QualType T); 62 63 ImplicitParamDecl *&getStructorImplicitParamDecl(CodeGenFunction &CGF) { 64 return CGF.CXXStructorImplicitParamDecl; 65 } 66 llvm::Value *&getStructorImplicitParamValue(CodeGenFunction &CGF) { 67 return CGF.CXXStructorImplicitParamValue; 68 } 69 70 /// Perform prolog initialization of the parameter variable suitable 71 /// for 'this' emitted by buildThisParam. 72 void EmitThisParam(CodeGenFunction &CGF); 73 74 ASTContext &getContext() const { return CGM.getContext(); } 75 76 virtual bool requiresArrayCookie(const CXXDeleteExpr *E, QualType eltType); 77 virtual bool requiresArrayCookie(const CXXNewExpr *E); 78 79 public: 80 81 virtual ~CGCXXABI(); 82 83 /// Gets the mangle context. 84 MangleContext &getMangleContext() { 85 return *MangleCtx; 86 } 87 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). 91 /// 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; } 95 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; 99 100 /// Specify how one should pass an argument of a record type. 101 enum RecordArgABI { 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. 104 RAA_Default = 0, 105 106 /// 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. 109 RAA_DirectInMemory, 110 111 /// Pass it as a pointer to temporary memory. 112 RAA_Indirect 113 }; 114 115 /// 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; 118 119 /// Returns how an argument of the given record type should be passed. 120 virtual RecordArgABI getRecordArgABI(const CXXRecordDecl *RD) const = 0; 121 122 /// 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; } 125 126 /// Find the LLVM type used to represent the given member pointer 127 /// type. 128 virtual llvm::Type * 129 ConvertMemberPointerType(const MemberPointerType *MPT); 130 131 /// Load a member function from an object and a member function 132 /// pointer. Apply the this-adjustment and set 'This' to the 133 /// adjusted value. 134 virtual llvm::Value *EmitLoadOfMemberFunctionPointer( 135 CodeGenFunction &CGF, const Expr *E, llvm::Value *&This, 136 llvm::Value *MemPtr, const MemberPointerType *MPT); 137 138 /// 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); 143 144 /// Perform a derived-to-base, base-to-derived, or bitcast member 145 /// pointer conversion. 146 virtual llvm::Value *EmitMemberPointerConversion(CodeGenFunction &CGF, 147 const CastExpr *E, 148 llvm::Value *Src); 149 150 /// 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); 154 155 /// 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); 158 159 /// Create a null member pointer of the given type. 160 virtual llvm::Constant *EmitNullMemberPointer(const MemberPointerType *MPT); 161 162 /// Create a member pointer for the given method. 163 virtual llvm::Constant *EmitMemberPointer(const CXXMethodDecl *MD); 164 165 /// Create a member pointer for the given field. 166 virtual llvm::Constant *EmitMemberDataPointer(const MemberPointerType *MPT, 167 CharUnits offset); 168 169 /// Create a member pointer for the given member pointer constant. 170 virtual llvm::Constant *EmitMemberPointer(const APValue &MP, QualType MPT); 171 172 /// Emit a comparison between two member pointers. Returns an i1. 173 virtual llvm::Value * 174 EmitMemberPointerComparison(CodeGenFunction &CGF, 175 llvm::Value *L, 176 llvm::Value *R, 177 const MemberPointerType *MPT, 178 bool Inequality); 179 180 /// Determine if a member pointer is non-null. Returns an i1. 181 virtual llvm::Value * 182 EmitMemberPointerIsNotNull(CodeGenFunction &CGF, 183 llvm::Value *MemPtr, 184 const MemberPointerType *MPT); 185 186 protected: 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 191 /// is required. 192 llvm::Constant *getMemberPointerAdjustment(const CastExpr *E); 193 194 /// \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); 199 200 public: 201 /// Adjust the given non-null pointer to an object of polymorphic 202 /// type to point to the complete object. 203 /// 204 /// The IR type of the result should be a pointer but is otherwise 205 /// irrelevant. 206 virtual llvm::Value *adjustToCompleteObject(CodeGenFunction &CGF, 207 llvm::Value *ptr, 208 QualType type) = 0; 209 210 virtual llvm::Constant *getAddrOfRTTIDescriptor(QualType Ty) = 0; 211 212 virtual bool shouldTypeidBeNullChecked(bool IsDeref, 213 QualType SrcRecordTy) = 0; 214 virtual void EmitBadTypeidCall(CodeGenFunction &CGF) = 0; 215 virtual llvm::Value *EmitTypeid(CodeGenFunction &CGF, QualType SrcRecordTy, 216 llvm::Value *ThisPtr, 217 llvm::Type *StdTypeInfoPtrTy) = 0; 218 219 virtual bool shouldDynamicCastCallBeNullChecked(bool SrcIsPtr, 220 QualType SrcRecordTy) = 0; 221 222 virtual llvm::Value * 223 EmitDynamicCastCall(CodeGenFunction &CGF, llvm::Value *Value, 224 QualType SrcRecordTy, QualType DestTy, 225 QualType DestRecordTy, llvm::BasicBlock *CastEnd) = 0; 226 227 virtual llvm::Value *EmitDynamicCastToVoid(CodeGenFunction &CGF, 228 llvm::Value *Value, 229 QualType SrcRecordTy, 230 QualType DestTy) = 0; 231 232 virtual bool EmitBadCastCall(CodeGenFunction &CGF) = 0; 233 234 virtual llvm::Value *GetVirtualBaseClassOffset(CodeGenFunction &CGF, 235 llvm::Value *This, 236 const CXXRecordDecl *ClassDecl, 237 const CXXRecordDecl *BaseClassDecl) = 0; 238 239 /// Build the signature of the given constructor variant by adding 240 /// any required parameters. For convenience, ArgTys has been initialized 241 /// with the type of 'this' and ResTy has been initialized with the type of 242 /// 'this' if HasThisReturn(GlobalDecl(Ctor, T)) is true or 'void' otherwise 243 /// (although both may be changed by the ABI). 244 /// 245 /// If there are ever any ABIs where the implicit parameters are 246 /// intermixed with the formal parameters, we can address those 247 /// then. 248 virtual void BuildConstructorSignature(const CXXConstructorDecl *Ctor, 249 CXXCtorType T, 250 CanQualType &ResTy, 251 SmallVectorImpl<CanQualType> &ArgTys) = 0; 252 253 virtual llvm::BasicBlock *EmitCtorCompleteObjectHandler(CodeGenFunction &CGF, 254 const CXXRecordDecl *RD); 255 256 /// Emit the code to initialize hidden members required 257 /// to handle virtual inheritance, if needed by the ABI. 258 virtual void 259 initializeHiddenVirtualInheritanceMembers(CodeGenFunction &CGF, 260 const CXXRecordDecl *RD) {} 261 262 /// Emit constructor variants required by this ABI. 263 virtual void EmitCXXConstructors(const CXXConstructorDecl *D) = 0; 264 265 /// Build the signature of the given destructor variant by adding 266 /// any required parameters. For convenience, ArgTys has been initialized 267 /// with the type of 'this' and ResTy has been initialized with the type of 268 /// 'this' if HasThisReturn(GlobalDecl(Dtor, T)) is true or 'void' otherwise 269 /// (although both may be changed by the ABI). 270 virtual void BuildDestructorSignature(const CXXDestructorDecl *Dtor, 271 CXXDtorType T, 272 CanQualType &ResTy, 273 SmallVectorImpl<CanQualType> &ArgTys) = 0; 274 275 /// Returns true if the given destructor type should be emitted as a linkonce 276 /// delegating thunk, regardless of whether the dtor is defined in this TU or 277 /// not. 278 virtual bool useThunkForDtorVariant(const CXXDestructorDecl *Dtor, 279 CXXDtorType DT) const = 0; 280 281 /// Emit destructor variants required by this ABI. 282 virtual void EmitCXXDestructors(const CXXDestructorDecl *D) = 0; 283 284 /// Get the type of the implicit "this" parameter used by a method. May return 285 /// zero if no specific type is applicable, e.g. if the ABI expects the "this" 286 /// parameter to point to some artificial offset in a complete object due to 287 /// vbases being reordered. 288 virtual const CXXRecordDecl * 289 getThisArgumentTypeForMethod(const CXXMethodDecl *MD) { 290 return MD->getParent(); 291 } 292 293 /// Perform ABI-specific "this" argument adjustment required prior to 294 /// a call of a virtual function. 295 /// The "VirtualCall" argument is true iff the call itself is virtual. 296 virtual llvm::Value * 297 adjustThisArgumentForVirtualFunctionCall(CodeGenFunction &CGF, GlobalDecl GD, 298 llvm::Value *This, 299 bool VirtualCall) { 300 return This; 301 } 302 303 /// Build a parameter variable suitable for 'this'. 304 void buildThisParam(CodeGenFunction &CGF, FunctionArgList &Params); 305 306 /// Insert any ABI-specific implicit parameters into the parameter list for a 307 /// function. This generally involves extra data for constructors and 308 /// destructors. 309 /// 310 /// ABIs may also choose to override the return type, which has been 311 /// initialized with the type of 'this' if HasThisReturn(CGF.CurGD) is true or 312 /// the formal return type of the function otherwise. 313 virtual void addImplicitStructorParams(CodeGenFunction &CGF, QualType &ResTy, 314 FunctionArgList &Params) = 0; 315 316 /// Perform ABI-specific "this" parameter adjustment in a virtual function 317 /// prologue. 318 virtual llvm::Value *adjustThisParameterInVirtualFunctionPrologue( 319 CodeGenFunction &CGF, GlobalDecl GD, llvm::Value *This) { 320 return This; 321 } 322 323 /// Emit the ABI-specific prolog for the function. 324 virtual void EmitInstanceFunctionProlog(CodeGenFunction &CGF) = 0; 325 326 /// Add any ABI-specific implicit arguments needed to call a constructor. 327 /// 328 /// \return The number of args added to the call, which is typically zero or 329 /// one. 330 virtual unsigned 331 addImplicitConstructorArgs(CodeGenFunction &CGF, const CXXConstructorDecl *D, 332 CXXCtorType Type, bool ForVirtualBase, 333 bool Delegating, CallArgList &Args) = 0; 334 335 /// Emit the destructor call. 336 virtual void EmitDestructorCall(CodeGenFunction &CGF, 337 const CXXDestructorDecl *DD, CXXDtorType Type, 338 bool ForVirtualBase, bool Delegating, 339 llvm::Value *This) = 0; 340 341 /// Emits the VTable definitions required for the given record type. 342 virtual void emitVTableDefinitions(CodeGenVTables &CGVT, 343 const CXXRecordDecl *RD) = 0; 344 345 /// Get the address point of the vtable for the given base subobject while 346 /// building a constructor or a destructor. On return, NeedsVirtualOffset 347 /// tells if a virtual base adjustment is needed in order to get the offset 348 /// of the base subobject. 349 virtual llvm::Value *getVTableAddressPointInStructor( 350 CodeGenFunction &CGF, const CXXRecordDecl *RD, BaseSubobject Base, 351 const CXXRecordDecl *NearestVBase, bool &NeedsVirtualOffset) = 0; 352 353 /// Get the address point of the vtable for the given base subobject while 354 /// building a constexpr. 355 virtual llvm::Constant * 356 getVTableAddressPointForConstExpr(BaseSubobject Base, 357 const CXXRecordDecl *VTableClass) = 0; 358 359 /// Get the address of the vtable for the given record decl which should be 360 /// used for the vptr at the given offset in RD. 361 virtual llvm::GlobalVariable *getAddrOfVTable(const CXXRecordDecl *RD, 362 CharUnits VPtrOffset) = 0; 363 364 /// Build a virtual function pointer in the ABI-specific way. 365 virtual llvm::Value *getVirtualFunctionPointer(CodeGenFunction &CGF, 366 GlobalDecl GD, 367 llvm::Value *This, 368 llvm::Type *Ty) = 0; 369 370 /// Emit the ABI-specific virtual destructor call. 371 virtual void EmitVirtualDestructorCall(CodeGenFunction &CGF, 372 const CXXDestructorDecl *Dtor, 373 CXXDtorType DtorType, 374 SourceLocation CallLoc, 375 llvm::Value *This) = 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 /// Gets the pure virtual member call function. 401 virtual StringRef GetPureVirtualCallName() = 0; 402 403 /// Gets the deleted virtual member call name. 404 virtual StringRef GetDeletedVirtualCallName() = 0; 405 406 /// \brief Returns true iff static data members that are initialized in the 407 /// class definition should have linkonce linkage. 408 virtual bool isInlineInitializedStaticDataMemberLinkOnce() { return false; } 409 410 /**************************** Array cookies ******************************/ 411 412 /// Returns the extra size required in order to store the array 413 /// cookie for the given new-expression. May return 0 to indicate that no 414 /// array cookie is required. 415 /// 416 /// Several cases are filtered out before this method is called: 417 /// - non-array allocations never need a cookie 418 /// - calls to \::operator new(size_t, void*) never need a cookie 419 /// 420 /// \param expr - the new-expression being allocated. 421 virtual CharUnits GetArrayCookieSize(const CXXNewExpr *expr); 422 423 /// Initialize the array cookie for the given allocation. 424 /// 425 /// \param NewPtr - a char* which is the presumed-non-null 426 /// return value of the allocation function 427 /// \param NumElements - the computed number of elements, 428 /// potentially collapsed from the multidimensional array case; 429 /// always a size_t 430 /// \param ElementType - the base element allocated type, 431 /// i.e. the allocated type after stripping all array types 432 virtual llvm::Value *InitializeArrayCookie(CodeGenFunction &CGF, 433 llvm::Value *NewPtr, 434 llvm::Value *NumElements, 435 const CXXNewExpr *expr, 436 QualType ElementType); 437 438 /// Reads the array cookie associated with the given pointer, 439 /// if it has one. 440 /// 441 /// \param Ptr - a pointer to the first element in the array 442 /// \param ElementType - the base element type of elements of the array 443 /// \param NumElements - an out parameter which will be initialized 444 /// with the number of elements allocated, or zero if there is no 445 /// cookie 446 /// \param AllocPtr - an out parameter which will be initialized 447 /// with a char* pointing to the address returned by the allocation 448 /// function 449 /// \param CookieSize - an out parameter which will be initialized 450 /// with the size of the cookie, or zero if there is no cookie 451 virtual void ReadArrayCookie(CodeGenFunction &CGF, llvm::Value *Ptr, 452 const CXXDeleteExpr *expr, 453 QualType ElementType, llvm::Value *&NumElements, 454 llvm::Value *&AllocPtr, CharUnits &CookieSize); 455 456 /// Return whether the given global decl needs a VTT parameter. 457 virtual bool NeedsVTTParameter(GlobalDecl GD); 458 459 protected: 460 /// Returns the extra size required in order to store the array 461 /// cookie for the given type. Assumes that an array cookie is 462 /// required. 463 virtual CharUnits getArrayCookieSizeImpl(QualType elementType); 464 465 /// Reads the array cookie for an allocation which is known to have one. 466 /// This is called by the standard implementation of ReadArrayCookie. 467 /// 468 /// \param ptr - a pointer to the allocation made for an array, as a char* 469 /// \param cookieSize - the computed cookie size of an array 470 /// 471 /// Other parameters are as above. 472 /// 473 /// \return a size_t 474 virtual llvm::Value *readArrayCookieImpl(CodeGenFunction &IGF, 475 llvm::Value *ptr, 476 CharUnits cookieSize); 477 478 public: 479 480 /*************************** Static local guards ****************************/ 481 482 /// Emits the guarded initializer and destructor setup for the given 483 /// variable, given that it couldn't be emitted as a constant. 484 /// If \p PerformInit is false, the initialization has been folded to a 485 /// constant and should not be performed. 486 /// 487 /// The variable may be: 488 /// - a static local variable 489 /// - a static data member of a class template instantiation 490 virtual void EmitGuardedInit(CodeGenFunction &CGF, const VarDecl &D, 491 llvm::GlobalVariable *DeclPtr, 492 bool PerformInit) = 0; 493 494 /// Emit code to force the execution of a destructor during global 495 /// teardown. The default implementation of this uses atexit. 496 /// 497 /// \param dtor - a function taking a single pointer argument 498 /// \param addr - a pointer to pass to the destructor function. 499 virtual void registerGlobalDtor(CodeGenFunction &CGF, const VarDecl &D, 500 llvm::Constant *dtor, llvm::Constant *addr); 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 Decls The thread_local declarations in this translation unit. 508 /// \param InitFunc If this translation unit contains any non-constant 509 /// initialization or non-trivial destruction for thread_local 510 /// variables, a function to perform the initialization. Otherwise, 0. 511 virtual void EmitThreadLocalInitFuncs( 512 ArrayRef<std::pair<const VarDecl *, llvm::GlobalVariable *> > Decls, 513 llvm::Function *InitFunc); 514 515 /// Emit a reference to a non-local thread_local variable (including 516 /// triggering the initialization of all thread_local variables in its 517 /// translation unit). 518 virtual LValue EmitThreadLocalVarDeclLValue(CodeGenFunction &CGF, 519 const VarDecl *VD, 520 QualType LValType); 521 }; 522 523 // Create an instance of a C++ ABI class: 524 525 /// Creates an Itanium-family ABI. 526 CGCXXABI *CreateItaniumCXXABI(CodeGenModule &CGM); 527 528 /// Creates a Microsoft-family ABI. 529 CGCXXABI *CreateMicrosoftCXXABI(CodeGenModule &CGM); 530 531 } 532 } 533 534 #endif 535
