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diff --git a/clang/lib/CodeGen/CGVTables.h b/clang/lib/CodeGen/CGVTables.h
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+++ b/clang/lib/CodeGen/CGVTables.h
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+//===--- CGVTables.h - Emit LLVM Code for C++ vtables -----------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This contains code dealing with C++ code generation of virtual tables.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_LIB_CODEGEN_CGVTABLES_H
+#define LLVM_CLANG_LIB_CODEGEN_CGVTABLES_H
+
+#include "clang/AST/BaseSubobject.h"
+#include "clang/AST/CharUnits.h"
+#include "clang/AST/GlobalDecl.h"
+#include "clang/AST/VTableBuilder.h"
+#include "clang/Basic/ABI.h"
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/IR/GlobalVariable.h"
+
+namespace clang {
+  class CXXRecordDecl;
+
+namespace CodeGen {
+  class CodeGenModule;
+  class ConstantArrayBuilder;
+  class ConstantStructBuilder;
+
+class CodeGenVTables {
+  CodeGenModule &CGM;
+
+  VTableContextBase *VTContext;
+
+  /// VTableAddressPointsMapTy - Address points for a single vtable.
+  typedef VTableLayout::AddressPointsMapTy VTableAddressPointsMapTy;
+
+  typedef std::pair<const CXXRecordDecl *, BaseSubobject> BaseSubobjectPairTy;
+  typedef llvm::DenseMap<BaseSubobjectPairTy, uint64_t> SubVTTIndiciesMapTy;
+
+  /// SubVTTIndicies - Contains indices into the various sub-VTTs.
+  SubVTTIndiciesMapTy SubVTTIndicies;
+
+  typedef llvm::DenseMap<BaseSubobjectPairTy, uint64_t>
+    SecondaryVirtualPointerIndicesMapTy;
+
+  /// SecondaryVirtualPointerIndices - Contains the secondary virtual pointer
+  /// indices.
+  SecondaryVirtualPointerIndicesMapTy SecondaryVirtualPointerIndices;
+
+  /// Cache for the pure virtual member call function.
+  llvm::Constant *PureVirtualFn = nullptr;
+
+  /// Cache for the deleted virtual member call function.
+  llvm::Constant *DeletedVirtualFn = nullptr;
+
+  /// Get the address of a thunk and emit it if necessary.
+  llvm::Constant *maybeEmitThunk(GlobalDecl GD,
+                                 const ThunkInfo &ThunkAdjustments,
+                                 bool ForVTable);
+
+  void addVTableComponent(ConstantArrayBuilder &builder,
+                          const VTableLayout &layout, unsigned idx,
+                          llvm::Constant *rtti,
+                          unsigned &nextVTableThunkIndex);
+
+public:
+  /// Add vtable components for the given vtable layout to the given
+  /// global initializer.
+  void createVTableInitializer(ConstantStructBuilder &builder,
+                               const VTableLayout &layout,
+                               llvm::Constant *rtti);
+
+  CodeGenVTables(CodeGenModule &CGM);
+
+  ItaniumVTableContext &getItaniumVTableContext() {
+    return *cast<ItaniumVTableContext>(VTContext);
+  }
+
+  MicrosoftVTableContext &getMicrosoftVTableContext() {
+    return *cast<MicrosoftVTableContext>(VTContext);
+  }
+
+  /// getSubVTTIndex - Return the index of the sub-VTT for the base class of the
+  /// given record decl.
+  uint64_t getSubVTTIndex(const CXXRecordDecl *RD, BaseSubobject Base);
+
+  /// getSecondaryVirtualPointerIndex - Return the index in the VTT where the
+  /// virtual pointer for the given subobject is located.
+  uint64_t getSecondaryVirtualPointerIndex(const CXXRecordDecl *RD,
+                                           BaseSubobject Base);
+
+  /// GenerateConstructionVTable - Generate a construction vtable for the given
+  /// base subobject.
+  llvm::GlobalVariable *
+  GenerateConstructionVTable(const CXXRecordDecl *RD, const BaseSubobject &Base,
+                             bool BaseIsVirtual,
+                             llvm::GlobalVariable::LinkageTypes Linkage,
+                             VTableAddressPointsMapTy& AddressPoints);
+
+
+  /// GetAddrOfVTT - Get the address of the VTT for the given record decl.
+  llvm::GlobalVariable *GetAddrOfVTT(const CXXRecordDecl *RD);
+
+  /// EmitVTTDefinition - Emit the definition of the given vtable.
+  void EmitVTTDefinition(llvm::GlobalVariable *VTT,
+                         llvm::GlobalVariable::LinkageTypes Linkage,
+                         const CXXRecordDecl *RD);
+
+  /// EmitThunks - Emit the associated thunks for the given global decl.
+  void EmitThunks(GlobalDecl GD);
+
+  /// GenerateClassData - Generate all the class data required to be
+  /// generated upon definition of a KeyFunction.  This includes the
+  /// vtable, the RTTI data structure (if RTTI is enabled) and the VTT
+  /// (if the class has virtual bases).
+  void GenerateClassData(const CXXRecordDecl *RD);
+
+  bool isVTableExternal(const CXXRecordDecl *RD);
+
+  /// Returns the type of a vtable with the given layout. Normally a struct of
+  /// arrays of pointers, with one struct element for each vtable in the vtable
+  /// group.
+  llvm::Type *getVTableType(const VTableLayout &layout);
+};
+
+} // end namespace CodeGen
+} // end namespace clang
+#endif