clang/lib/CodeGen/CGCXXABI.h

   1 //===----- CGCXXABI.h - Interface to C++ ABIs -------------------*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This provides an abstract class for C++ code generation. Concrete subclasses
  10 // of this implement code generation for specific C++ ABIs.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #ifndef LLVM_CLANG_LIB_CODEGEN_CGCXXABI_H
  15 #define LLVM_CLANG_LIB_CODEGEN_CGCXXABI_H
  16
  17 #include "CodeGenFunction.h"
  18 #include "clang/Basic/LLVM.h"
  19 #include "clang/CodeGen/CodeGenABITypes.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 MangleContext;
  35
  36 namespace CodeGen {
  37 class CGCallee;
  38 class CodeGenFunction;
  39 class CodeGenModule;
  40 struct CatchTypeInfo;
  41
  42 /// Implements C++ ABI-specific code generation functions.
  43 class CGCXXABI {
  44   friend class CodeGenModule;
  45
  46 protected:
  47   CodeGenModule &CGM;
  48   std::unique_ptr<MangleContext> MangleCtx;
  49
  50   CGCXXABI(CodeGenModule &CGM)
  51     : CGM(CGM), MangleCtx(CGM.getContext().createMangleContext()) {}
  52
  53 protected:
  54   ImplicitParamDecl *getThisDecl(CodeGenFunction &CGF) {
  55     return CGF.CXXABIThisDecl;
  56   }
  57   llvm::Value *getThisValue(CodeGenFunction &CGF) {
  58     return CGF.CXXABIThisValue;
  59   }
  60   Address getThisAddress(CodeGenFunction &CGF) {
  61     return Address(
  62         CGF.CXXABIThisValue,
  63         CGF.ConvertTypeForMem(CGF.CXXABIThisDecl->getType()->getPointeeType()),
  64         CGF.CXXABIThisAlignment);
  65   }
  66
  67   /// Issue a diagnostic about unsupported features in the ABI.
  68   void ErrorUnsupportedABI(CodeGenFunction &CGF, StringRef S);
  69
  70   /// Get a null value for unsupported member pointers.
  71   llvm::Constant *GetBogusMemberPointer(QualType T);
  72
  73   ImplicitParamDecl *&getStructorImplicitParamDecl(CodeGenFunction &CGF) {
  74     return CGF.CXXStructorImplicitParamDecl;
  75   }
  76   llvm::Value *&getStructorImplicitParamValue(CodeGenFunction &CGF) {
  77     return CGF.CXXStructorImplicitParamValue;
  78   }
  79
  80   /// Loads the incoming C++ this pointer as it was passed by the caller.
  81   llvm::Value *loadIncomingCXXThis(CodeGenFunction &CGF);
  82
  83   void setCXXABIThisValue(CodeGenFunction &CGF, llvm::Value *ThisPtr);
  84
  85   ASTContext &getContext() const { return CGM.getContext(); }
  86
  87   bool mayNeedDestruction(const VarDecl *VD) const;
  88
  89   /// Determine whether we will definitely emit this variable with a constant
  90   /// initializer, either because the language semantics demand it or because
  91   /// we know that the initializer is a constant.
  92   // For weak definitions, any initializer available in the current translation
  93   // is not necessarily reflective of the initializer used; such initializers
  94   // are ignored unless if InspectInitForWeakDef is true.
  95   bool
  96   isEmittedWithConstantInitializer(const VarDecl *VD,
  97                                    bool InspectInitForWeakDef = false) const;
  98
  99   virtual bool requiresArrayCookie(const CXXDeleteExpr *E, QualType eltType);
 100   virtual bool requiresArrayCookie(const CXXNewExpr *E);
 101
 102   /// Determine whether there's something special about the rules of
 103   /// the ABI tell us that 'this' is a complete object within the
 104   /// given function.  Obvious common logic like being defined on a
 105   /// final class will have been taken care of by the caller.
 106   virtual bool isThisCompleteObject(GlobalDecl GD) const = 0;
 107
 108   virtual bool constructorsAndDestructorsReturnThis() const {
 109     return CGM.getCodeGenOpts().CtorDtorReturnThis;
 110   }
 111
 112 public:
 113
 114   virtual ~CGCXXABI();
 115
 116   /// Gets the mangle context.
 117   MangleContext &getMangleContext() {
 118     return *MangleCtx;
 119   }
 120
 121   /// Returns true if the given constructor or destructor is one of the
 122   /// kinds that the ABI says returns 'this' (only applies when called
 123   /// non-virtually for destructors).
 124   ///
 125   /// There currently is no way to indicate if a destructor returns 'this'
 126   /// when called virtually, and code generation does not support the case.
 127   virtual bool HasThisReturn(GlobalDecl GD) const {
 128     if (isa<CXXConstructorDecl>(GD.getDecl()) ||
 129         (isa<CXXDestructorDecl>(GD.getDecl()) &&
 130          GD.getDtorType() != Dtor_Deleting))
 131       return constructorsAndDestructorsReturnThis();
 132     return false;
 133   }
 134
 135   virtual bool hasMostDerivedReturn(GlobalDecl GD) const { return false; }
 136
 137   virtual bool useSinitAndSterm() const { return false; }
 138
 139   /// Returns true if the target allows calling a function through a pointer
 140   /// with a different signature than the actual function (or equivalently,
 141   /// bitcasting a function or function pointer to a different function type).
 142   /// In principle in the most general case this could depend on the target, the
 143   /// calling convention, and the actual types of the arguments and return
 144   /// value. Here it just means whether the signature mismatch could *ever* be
 145   /// allowed; in other words, does the target do strict checking of signatures
 146   /// for all calls.
 147   virtual bool canCallMismatchedFunctionType() const { return true; }
 148
 149   /// If the C++ ABI requires the given type be returned in a particular way,
 150   /// this method sets RetAI and returns true.
 151   virtual bool classifyReturnType(CGFunctionInfo &FI) const = 0;
 152
 153   /// Specify how one should pass an argument of a record type.
 154   enum RecordArgABI {
 155     /// Pass it using the normal C aggregate rules for the ABI, potentially
 156     /// introducing extra copies and passing some or all of it in registers.
 157     RAA_Default = 0,
 158
 159     /// Pass it on the stack using its defined layout.  The argument must be
 160     /// evaluated directly into the correct stack position in the arguments area,
 161     /// and the call machinery must not move it or introduce extra copies.
 162     RAA_DirectInMemory,
 163
 164     /// Pass it as a pointer to temporary memory.
 165     RAA_Indirect
 166   };
 167
 168   /// Returns how an argument of the given record type should be passed.
 169   virtual RecordArgABI getRecordArgABI(const CXXRecordDecl *RD) const = 0;
 170
 171   /// Returns true if the implicit 'sret' parameter comes after the implicit
 172   /// 'this' parameter of C++ instance methods.
 173   virtual bool isSRetParameterAfterThis() const { return false; }
 174
 175   /// Returns true if the ABI permits the argument to be a homogeneous
 176   /// aggregate.
 177   virtual bool
 178   isPermittedToBeHomogeneousAggregate(const CXXRecordDecl *RD) const {
 179     return true;
 180   };
 181
 182   /// Find the LLVM type used to represent the given member pointer
 183   /// type.
 184   virtual llvm::Type *
 185   ConvertMemberPointerType(const MemberPointerType *MPT);
 186
 187   /// Load a member function from an object and a member function
 188   /// pointer.  Apply the this-adjustment and set 'This' to the
 189   /// adjusted value.
 190   virtual CGCallee EmitLoadOfMemberFunctionPointer(
 191       CodeGenFunction &CGF, const Expr *E, Address This,
 192       llvm::Value *&ThisPtrForCall, llvm::Value *MemPtr,
 193       const MemberPointerType *MPT);
 194
 195   /// Calculate an l-value from an object and a data member pointer.
 196   virtual llvm::Value *
 197   EmitMemberDataPointerAddress(CodeGenFunction &CGF, const Expr *E,
 198                                Address Base, llvm::Value *MemPtr,
 199                                const MemberPointerType *MPT);
 200
 201   /// Perform a derived-to-base, base-to-derived, or bitcast member
 202   /// pointer conversion.
 203   virtual llvm::Value *EmitMemberPointerConversion(CodeGenFunction &CGF,
 204                                                    const CastExpr *E,
 205                                                    llvm::Value *Src);
 206
 207   /// Perform a derived-to-base, base-to-derived, or bitcast member
 208   /// pointer conversion on a constant value.
 209   virtual llvm::Constant *EmitMemberPointerConversion(const CastExpr *E,
 210                                                       llvm::Constant *Src);
 211
 212   /// Return true if the given member pointer can be zero-initialized
 213   /// (in the C++ sense) with an LLVM zeroinitializer.
 214   virtual bool isZeroInitializable(const MemberPointerType *MPT);
 215
 216   /// Return whether or not a member pointers type is convertible to an IR type.
 217   virtual bool isMemberPointerConvertible(const MemberPointerType *MPT) const {
 218     return true;
 219   }
 220
 221   /// Create a null member pointer of the given type.
 222   virtual llvm::Constant *EmitNullMemberPointer(const MemberPointerType *MPT);
 223
 224   /// Create a member pointer for the given method.
 225   virtual llvm::Constant *EmitMemberFunctionPointer(const CXXMethodDecl *MD);
 226
 227   /// Create a member pointer for the given field.
 228   virtual llvm::Constant *EmitMemberDataPointer(const MemberPointerType *MPT,
 229                                                 CharUnits offset);
 230
 231   /// Create a member pointer for the given member pointer constant.
 232   virtual llvm::Constant *EmitMemberPointer(const APValue &MP, QualType MPT);
 233
 234   /// Emit a comparison between two member pointers.  Returns an i1.
 235   virtual llvm::Value *
 236   EmitMemberPointerComparison(CodeGenFunction &CGF,
 237                               llvm::Value *L,
 238                               llvm::Value *R,
 239                               const MemberPointerType *MPT,
 240                               bool Inequality);
 241
 242   /// Determine if a member pointer is non-null.  Returns an i1.
 243   virtual llvm::Value *
 244   EmitMemberPointerIsNotNull(CodeGenFunction &CGF,
 245                              llvm::Value *MemPtr,
 246                              const MemberPointerType *MPT);
 247
 248 protected:
 249   /// A utility method for computing the offset required for the given
 250   /// base-to-derived or derived-to-base member-pointer conversion.
 251   /// Does not handle virtual conversions (in case we ever fully
 252   /// support an ABI that allows this).  Returns null if no adjustment
 253   /// is required.
 254   llvm::Constant *getMemberPointerAdjustment(const CastExpr *E);
 255
 256 public:
 257   virtual void emitVirtualObjectDelete(CodeGenFunction &CGF,
 258                                        const CXXDeleteExpr *DE,
 259                                        Address Ptr, QualType ElementType,
 260                                        const CXXDestructorDecl *Dtor) = 0;
 261   virtual void emitRethrow(CodeGenFunction &CGF, bool isNoReturn) = 0;
 262   virtual void emitThrow(CodeGenFunction &CGF, const CXXThrowExpr *E) = 0;
 263   virtual llvm::GlobalVariable *getThrowInfo(QualType T) { return nullptr; }
 264
 265   /// Determine whether it's possible to emit a vtable for \p RD, even
 266   /// though we do not know that the vtable has been marked as used by semantic
 267   /// analysis.
 268   virtual bool canSpeculativelyEmitVTable(const CXXRecordDecl *RD) const = 0;
 269
 270   virtual void emitBeginCatch(CodeGenFunction &CGF, const CXXCatchStmt *C) = 0;
 271
 272   virtual llvm::CallInst *
 273   emitTerminateForUnexpectedException(CodeGenFunction &CGF,
 274                                       llvm::Value *Exn);
 275
 276   virtual llvm::Constant *getAddrOfRTTIDescriptor(QualType Ty) = 0;
 277   virtual CatchTypeInfo
 278   getAddrOfCXXCatchHandlerType(QualType Ty, QualType CatchHandlerType) = 0;
 279   virtual CatchTypeInfo getCatchAllTypeInfo();
 280
 281   virtual bool shouldTypeidBeNullChecked(bool IsDeref,
 282                                          QualType SrcRecordTy) = 0;
 283   virtual void EmitBadTypeidCall(CodeGenFunction &CGF) = 0;
 284   virtual llvm::Value *EmitTypeid(CodeGenFunction &CGF, QualType SrcRecordTy,
 285                                   Address ThisPtr,
 286                                   llvm::Type *StdTypeInfoPtrTy) = 0;
 287
 288   virtual bool shouldDynamicCastCallBeNullChecked(bool SrcIsPtr,
 289                                                   QualType SrcRecordTy) = 0;
 290
 291   virtual llvm::Value *
 292   EmitDynamicCastCall(CodeGenFunction &CGF, Address Value,
 293                       QualType SrcRecordTy, QualType DestTy,
 294                       QualType DestRecordTy, llvm::BasicBlock *CastEnd) = 0;
 295
 296   virtual llvm::Value *EmitDynamicCastToVoid(CodeGenFunction &CGF,
 297                                              Address Value,
 298                                              QualType SrcRecordTy,
 299                                              QualType DestTy) = 0;
 300
 301   virtual bool EmitBadCastCall(CodeGenFunction &CGF) = 0;
 302
 303   virtual llvm::Value *GetVirtualBaseClassOffset(CodeGenFunction &CGF,
 304                                                  Address This,
 305                                                  const CXXRecordDecl *ClassDecl,
 306                                         const CXXRecordDecl *BaseClassDecl) = 0;
 307
 308   virtual llvm::BasicBlock *EmitCtorCompleteObjectHandler(CodeGenFunction &CGF,
 309                                                           const CXXRecordDecl *RD);
 310
 311   /// Emit the code to initialize hidden members required
 312   /// to handle virtual inheritance, if needed by the ABI.
 313   virtual void
 314   initializeHiddenVirtualInheritanceMembers(CodeGenFunction &CGF,
 315                                             const CXXRecordDecl *RD) {}
 316
 317   /// Emit constructor variants required by this ABI.
 318   virtual void EmitCXXConstructors(const CXXConstructorDecl *D) = 0;
 319
 320   /// Additional implicit arguments to add to the beginning (Prefix) and end
 321   /// (Suffix) of a constructor / destructor arg list.
 322   ///
 323   /// Note that Prefix should actually be inserted *after* the first existing
 324   /// arg; `this` arguments always come first.
 325   struct AddedStructorArgs {
 326     struct Arg {
 327       llvm::Value *Value;
 328       QualType Type;
 329     };
 330     SmallVector<Arg, 1> Prefix;
 331     SmallVector<Arg, 1> Suffix;
 332     AddedStructorArgs() = default;
 333     AddedStructorArgs(SmallVector<Arg, 1> P, SmallVector<Arg, 1> S)
 334         : Prefix(std::move(P)), Suffix(std::move(S)) {}
 335     static AddedStructorArgs prefix(SmallVector<Arg, 1> Args) {
 336       return {std::move(Args), {}};
 337     }
 338     static AddedStructorArgs suffix(SmallVector<Arg, 1> Args) {
 339       return {{}, std::move(Args)};
 340     }
 341   };
 342
 343   /// Similar to AddedStructorArgs, but only notes the number of additional
 344   /// arguments.
 345   struct AddedStructorArgCounts {
 346     unsigned Prefix = 0;
 347     unsigned Suffix = 0;
 348     AddedStructorArgCounts() = default;
 349     AddedStructorArgCounts(unsigned P, unsigned S) : Prefix(P), Suffix(S) {}
 350     static AddedStructorArgCounts prefix(unsigned N) { return {N, 0}; }
 351     static AddedStructorArgCounts suffix(unsigned N) { return {0, N}; }
 352   };
 353
 354   /// Build the signature of the given constructor or destructor variant by
 355   /// adding any required parameters.  For convenience, ArgTys has been
 356   /// initialized with the type of 'this'.
 357   virtual AddedStructorArgCounts
 358   buildStructorSignature(GlobalDecl GD,
 359                          SmallVectorImpl<CanQualType> &ArgTys) = 0;
 360
 361   /// Returns true if the given destructor type should be emitted as a linkonce
 362   /// delegating thunk, regardless of whether the dtor is defined in this TU or
 363   /// not.
 364   virtual bool useThunkForDtorVariant(const CXXDestructorDecl *Dtor,
 365                                       CXXDtorType DT) const = 0;
 366
 367   virtual void setCXXDestructorDLLStorage(llvm::GlobalValue *GV,
 368                                           const CXXDestructorDecl *Dtor,
 369                                           CXXDtorType DT) const;
 370
 371   virtual llvm::GlobalValue::LinkageTypes
 372   getCXXDestructorLinkage(GVALinkage Linkage, const CXXDestructorDecl *Dtor,
 373                           CXXDtorType DT) const;
 374
 375   /// Emit destructor variants required by this ABI.
 376   virtual void EmitCXXDestructors(const CXXDestructorDecl *D) = 0;
 377
 378   /// Get the type of the implicit "this" parameter used by a method. May return
 379   /// zero if no specific type is applicable, e.g. if the ABI expects the "this"
 380   /// parameter to point to some artificial offset in a complete object due to
 381   /// vbases being reordered.
 382   virtual const CXXRecordDecl *getThisArgumentTypeForMethod(GlobalDecl GD) {
 383     return cast<CXXMethodDecl>(GD.getDecl())->getParent();
 384   }
 385
 386   /// Perform ABI-specific "this" argument adjustment required prior to
 387   /// a call of a virtual function.
 388   /// The "VirtualCall" argument is true iff the call itself is virtual.
 389   virtual Address
 390   adjustThisArgumentForVirtualFunctionCall(CodeGenFunction &CGF, GlobalDecl GD,
 391                                            Address This, bool VirtualCall) {
 392     return This;
 393   }
 394
 395   /// Build a parameter variable suitable for 'this'.
 396   void buildThisParam(CodeGenFunction &CGF, FunctionArgList &Params);
 397
 398   /// Insert any ABI-specific implicit parameters into the parameter list for a
 399   /// function.  This generally involves extra data for constructors and
 400   /// destructors.
 401   ///
 402   /// ABIs may also choose to override the return type, which has been
 403   /// initialized with the type of 'this' if HasThisReturn(CGF.CurGD) is true or
 404   /// the formal return type of the function otherwise.
 405   virtual void addImplicitStructorParams(CodeGenFunction &CGF, QualType &ResTy,
 406                                          FunctionArgList &Params) = 0;
 407
 408   /// Get the ABI-specific "this" parameter adjustment to apply in the prologue
 409   /// of a virtual function.
 410   virtual CharUnits getVirtualFunctionPrologueThisAdjustment(GlobalDecl GD) {
 411     return CharUnits::Zero();
 412   }
 413
 414   /// Emit the ABI-specific prolog for the function.
 415   virtual void EmitInstanceFunctionProlog(CodeGenFunction &CGF) = 0;
 416
 417   virtual AddedStructorArgs
 418   getImplicitConstructorArgs(CodeGenFunction &CGF, const CXXConstructorDecl *D,
 419                              CXXCtorType Type, bool ForVirtualBase,
 420                              bool Delegating) = 0;
 421
 422   /// Add any ABI-specific implicit arguments needed to call a constructor.
 423   ///
 424   /// \return The number of arguments added at the beginning and end of the
 425   /// call, which is typically zero or one.
 426   AddedStructorArgCounts
 427   addImplicitConstructorArgs(CodeGenFunction &CGF, const CXXConstructorDecl *D,
 428                              CXXCtorType Type, bool ForVirtualBase,
 429                              bool Delegating, CallArgList &Args);
 430
 431   /// Get the implicit (second) parameter that comes after the "this" pointer,
 432   /// or nullptr if there is isn't one.
 433   virtual llvm::Value *
 434   getCXXDestructorImplicitParam(CodeGenFunction &CGF,
 435                                 const CXXDestructorDecl *DD, CXXDtorType Type,
 436                                 bool ForVirtualBase, bool Delegating) = 0;
 437
 438   /// Emit the destructor call.
 439   virtual void EmitDestructorCall(CodeGenFunction &CGF,
 440                                   const CXXDestructorDecl *DD, CXXDtorType Type,
 441                                   bool ForVirtualBase, bool Delegating,
 442                                   Address This, QualType ThisTy) = 0;
 443
 444   /// Emits the VTable definitions required for the given record type.
 445   virtual void emitVTableDefinitions(CodeGenVTables &CGVT,
 446                                      const CXXRecordDecl *RD) = 0;
 447
 448   /// Checks if ABI requires extra virtual offset for vtable field.
 449   virtual bool
 450   isVirtualOffsetNeededForVTableField(CodeGenFunction &CGF,
 451                                       CodeGenFunction::VPtr Vptr) = 0;
 452
 453   /// Checks if ABI requires to initialize vptrs for given dynamic class.
 454   virtual bool doStructorsInitializeVPtrs(const CXXRecordDecl *VTableClass) = 0;
 455
 456   /// Get the address point of the vtable for the given base subobject.
 457   virtual llvm::Constant *
 458   getVTableAddressPoint(BaseSubobject Base,
 459                         const CXXRecordDecl *VTableClass) = 0;
 460
 461   /// Get the address point of the vtable for the given base subobject while
 462   /// building a constructor or a destructor.
 463   virtual llvm::Value *
 464   getVTableAddressPointInStructor(CodeGenFunction &CGF, const CXXRecordDecl *RD,
 465                                   BaseSubobject Base,
 466                                   const CXXRecordDecl *NearestVBase) = 0;
 467
 468   /// Get the address point of the vtable for the given base subobject while
 469   /// building a constexpr.
 470   virtual llvm::Constant *
 471   getVTableAddressPointForConstExpr(BaseSubobject Base,
 472                                     const CXXRecordDecl *VTableClass) = 0;
 473
 474   /// Get the address of the vtable for the given record decl which should be
 475   /// used for the vptr at the given offset in RD.
 476   virtual llvm::GlobalVariable *getAddrOfVTable(const CXXRecordDecl *RD,
 477                                                 CharUnits VPtrOffset) = 0;
 478
 479   /// Build a virtual function pointer in the ABI-specific way.
 480   virtual CGCallee getVirtualFunctionPointer(CodeGenFunction &CGF,
 481                                              GlobalDecl GD, Address This,
 482                                              llvm::Type *Ty,
 483                                              SourceLocation Loc) = 0;
 484
 485   using DeleteOrMemberCallExpr =
 486       llvm::PointerUnion<const CXXDeleteExpr *, const CXXMemberCallExpr *>;
 487
 488   /// Emit the ABI-specific virtual destructor call.
 489   virtual llvm::Value *EmitVirtualDestructorCall(CodeGenFunction &CGF,
 490                                                  const CXXDestructorDecl *Dtor,
 491                                                  CXXDtorType DtorType,
 492                                                  Address This,
 493                                                  DeleteOrMemberCallExpr E) = 0;
 494
 495   virtual void adjustCallArgsForDestructorThunk(CodeGenFunction &CGF,
 496                                                 GlobalDecl GD,
 497                                                 CallArgList &CallArgs) {}
 498
 499   /// Emit any tables needed to implement virtual inheritance.  For Itanium,
 500   /// this emits virtual table tables.  For the MSVC++ ABI, this emits virtual
 501   /// base tables.
 502   virtual void emitVirtualInheritanceTables(const CXXRecordDecl *RD) = 0;
 503
 504   virtual bool exportThunk() = 0;
 505   virtual void setThunkLinkage(llvm::Function *Thunk, bool ForVTable,
 506                                GlobalDecl GD, bool ReturnAdjustment) = 0;
 507
 508   virtual llvm::Value *performThisAdjustment(CodeGenFunction &CGF,
 509                                              Address This,
 510                                              const ThisAdjustment &TA) = 0;
 511
 512   virtual llvm::Value *performReturnAdjustment(CodeGenFunction &CGF,
 513                                                Address Ret,
 514                                                const ReturnAdjustment &RA) = 0;
 515
 516   virtual void EmitReturnFromThunk(CodeGenFunction &CGF,
 517                                    RValue RV, QualType ResultType);
 518
 519   virtual size_t getSrcArgforCopyCtor(const CXXConstructorDecl *,
 520                                       FunctionArgList &Args) const = 0;
 521
 522   /// Gets the offsets of all the virtual base pointers in a given class.
 523   virtual std::vector<CharUnits> getVBPtrOffsets(const CXXRecordDecl *RD);
 524
 525   /// Gets the pure virtual member call function.
 526   virtual StringRef GetPureVirtualCallName() = 0;
 527
 528   /// Gets the deleted virtual member call name.
 529   virtual StringRef GetDeletedVirtualCallName() = 0;
 530
 531   /**************************** Array cookies ******************************/
 532
 533   /// Returns the extra size required in order to store the array
 534   /// cookie for the given new-expression.  May return 0 to indicate that no
 535   /// array cookie is required.
 536   ///
 537   /// Several cases are filtered out before this method is called:
 538   ///   - non-array allocations never need a cookie
 539   ///   - calls to \::operator new(size_t, void*) never need a cookie
 540   ///
 541   /// \param expr - the new-expression being allocated.
 542   virtual CharUnits GetArrayCookieSize(const CXXNewExpr *expr);
 543
 544   /// Initialize the array cookie for the given allocation.
 545   ///
 546   /// \param NewPtr - a char* which is the presumed-non-null
 547   ///   return value of the allocation function
 548   /// \param NumElements - the computed number of elements,
 549   ///   potentially collapsed from the multidimensional array case;
 550   ///   always a size_t
 551   /// \param ElementType - the base element allocated type,
 552   ///   i.e. the allocated type after stripping all array types
 553   virtual Address InitializeArrayCookie(CodeGenFunction &CGF,
 554                                         Address NewPtr,
 555                                         llvm::Value *NumElements,
 556                                         const CXXNewExpr *expr,
 557                                         QualType ElementType);
 558
 559   /// Reads the array cookie associated with the given pointer,
 560   /// if it has one.
 561   ///
 562   /// \param Ptr - a pointer to the first element in the array
 563   /// \param ElementType - the base element type of elements of the array
 564   /// \param NumElements - an out parameter which will be initialized
 565   ///   with the number of elements allocated, or zero if there is no
 566   ///   cookie
 567   /// \param AllocPtr - an out parameter which will be initialized
 568   ///   with a char* pointing to the address returned by the allocation
 569   ///   function
 570   /// \param CookieSize - an out parameter which will be initialized
 571   ///   with the size of the cookie, or zero if there is no cookie
 572   virtual void ReadArrayCookie(CodeGenFunction &CGF, Address Ptr,
 573                                const CXXDeleteExpr *expr,
 574                                QualType ElementType, llvm::Value *&NumElements,
 575                                llvm::Value *&AllocPtr, CharUnits &CookieSize);
 576
 577   /// Return whether the given global decl needs a VTT parameter.
 578   virtual bool NeedsVTTParameter(GlobalDecl GD);
 579
 580 protected:
 581   /// Returns the extra size required in order to store the array
 582   /// cookie for the given type.  Assumes that an array cookie is
 583   /// required.
 584   virtual CharUnits getArrayCookieSizeImpl(QualType elementType);
 585
 586   /// Reads the array cookie for an allocation which is known to have one.
 587   /// This is called by the standard implementation of ReadArrayCookie.
 588   ///
 589   /// \param ptr - a pointer to the allocation made for an array, as a char*
 590   /// \param cookieSize - the computed cookie size of an array
 591   ///
 592   /// Other parameters are as above.
 593   ///
 594   /// \return a size_t
 595   virtual llvm::Value *readArrayCookieImpl(CodeGenFunction &IGF, Address ptr,
 596                                            CharUnits cookieSize);
 597
 598 public:
 599
 600   /*************************** Static local guards ****************************/
 601
 602   /// Emits the guarded initializer and destructor setup for the given
 603   /// variable, given that it couldn't be emitted as a constant.
 604   /// If \p PerformInit is false, the initialization has been folded to a
 605   /// constant and should not be performed.
 606   ///
 607   /// The variable may be:
 608   ///   - a static local variable
 609   ///   - a static data member of a class template instantiation
 610   virtual void EmitGuardedInit(CodeGenFunction &CGF, const VarDecl &D,
 611                                llvm::GlobalVariable *DeclPtr,
 612                                bool PerformInit) = 0;
 613
 614   /// Emit code to force the execution of a destructor during global
 615   /// teardown.  The default implementation of this uses atexit.
 616   ///
 617   /// \param Dtor - a function taking a single pointer argument
 618   /// \param Addr - a pointer to pass to the destructor function.
 619   virtual void registerGlobalDtor(CodeGenFunction &CGF, const VarDecl &D,
 620                                   llvm::FunctionCallee Dtor,
 621                                   llvm::Constant *Addr) = 0;
 622
 623   /*************************** thread_local initialization ********************/
 624
 625   /// Emits ABI-required functions necessary to initialize thread_local
 626   /// variables in this translation unit.
 627   ///
 628   /// \param CXXThreadLocals - The thread_local declarations in this translation
 629   ///        unit.
 630   /// \param CXXThreadLocalInits - If this translation unit contains any
 631   ///        non-constant initialization or non-trivial destruction for
 632   ///        thread_local variables, a list of functions to perform the
 633   ///        initialization.
 634   virtual void EmitThreadLocalInitFuncs(
 635       CodeGenModule &CGM, ArrayRef<const VarDecl *> CXXThreadLocals,
 636       ArrayRef<llvm::Function *> CXXThreadLocalInits,
 637       ArrayRef<const VarDecl *> CXXThreadLocalInitVars) = 0;
 638
 639   // Determine if references to thread_local global variables can be made
 640   // directly or require access through a thread wrapper function.
 641   virtual bool usesThreadWrapperFunction(const VarDecl *VD) const = 0;
 642
 643   /// Emit a reference to a non-local thread_local variable (including
 644   /// triggering the initialization of all thread_local variables in its
 645   /// translation unit).
 646   virtual LValue EmitThreadLocalVarDeclLValue(CodeGenFunction &CGF,
 647                                               const VarDecl *VD,
 648                                               QualType LValType) = 0;
 649
 650   /// Emit a single constructor/destructor with the given type from a C++
 651   /// constructor Decl.
 652   virtual void emitCXXStructor(GlobalDecl GD) = 0;
 653
 654   /// Load a vtable from This, an object of polymorphic type RD, or from one of
 655   /// its virtual bases if it does not have its own vtable. Returns the vtable
 656   /// and the class from which the vtable was loaded.
 657   virtual std::pair<llvm::Value *, const CXXRecordDecl *>
 658   LoadVTablePtr(CodeGenFunction &CGF, Address This,
 659                 const CXXRecordDecl *RD) = 0;
 660 };
 661
 662 // Create an instance of a C++ ABI class:
 663
 664 /// Creates an Itanium-family ABI.
 665 CGCXXABI *CreateItaniumCXXABI(CodeGenModule &CGM);
 666
 667 /// Creates a Microsoft-family ABI.
 668 CGCXXABI *CreateMicrosoftCXXABI(CodeGenModule &CGM);
 669
 670 struct CatchRetScope final : EHScopeStack::Cleanup {
 671   llvm::CatchPadInst *CPI;
 672
 673   CatchRetScope(llvm::CatchPadInst *CPI) : CPI(CPI) {}
 674
 675   void Emit(CodeGenFunction &CGF, Flags flags) override {
 676     llvm::BasicBlock *BB = CGF.createBasicBlock("catchret.dest");
 677     CGF.Builder.CreateCatchRet(CPI, BB);
 678     CGF.EmitBlock(BB);
 679   }
 680 };
 681 }
 682 }
 683
 684 #endif