//===- RecordLayout.h - Layout information for a struct/union ---*- 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 file defines the RecordLayout interface.

//

//===----------------------------------------------------------------------===//

#ifndef LLVM_CLANG_AST_RECORDLAYOUT_H

#define LLVM_CLANG_AST_RECORDLAYOUT_H

#include "clang/AST/ASTVector.h"

#include "clang/AST/CharUnits.h"

#include "clang/AST/DeclCXX.h"

#include "clang/Basic/LLVM.h"

#include "llvm/ADT/ArrayRef.h"

#include "llvm/ADT/DenseMap.h"

#include "llvm/ADT/PointerIntPair.h"

#include <cassert>

#include <cstdint>

namespace clang {

class ASTContext;

class CXXRecordDecl;

/// ASTRecordLayout -

/// This class contains layout information for one RecordDecl,

/// which is a struct/union/class.  The decl represented must be a definition,

/// not a forward declaration.

/// This class is also used to contain layout information for one

/// ObjCInterfaceDecl. FIXME - Find appropriate name.

/// These objects are managed by ASTContext.

class ASTRecordLayout {

public:

  struct VBaseInfo {

    /// The offset to this virtual base in the complete-object layout

    /// of this class.

    CharUnits VBaseOffset;

  private:

    /// Whether this virtual base requires a vtordisp field in the

    /// Microsoft ABI.  These fields are required for certain operations

    /// in constructors and destructors.

    bool HasVtorDisp = false;

  public:

    VBaseInfo() = default;

    VBaseInfo(CharUnits VBaseOffset, bool hasVtorDisp)

        : VBaseOffset(VBaseOffset), HasVtorDisp(hasVtorDisp) {}

    bool hasVtorDisp() const { return HasVtorDisp; }

  };

  using VBaseOffsetsMapTy = llvm::DenseMap<const CXXRecordDecl *, VBaseInfo>;

private:

  friend class ASTContext;

  /// Size - Size of record in characters.

  CharUnits Size;

  /// DataSize - Size of record in characters without tail padding.

  CharUnits DataSize;

  // Alignment - Alignment of record in characters.

  CharUnits Alignment;

  // PreferredAlignment - Preferred alignment of record in characters. This

  // can be different than Alignment in cases where it is beneficial for

  // performance or backwards compatibility preserving (e.g. AIX-ABI).

  CharUnits PreferredAlignment;

  // UnadjustedAlignment - Maximum of the alignments of the record members in

  // characters.

  CharUnits UnadjustedAlignment;

  /// RequiredAlignment - The required alignment of the object.  In the MS-ABI

  /// the __declspec(align()) trumps #pramga pack and must always be obeyed.

  CharUnits RequiredAlignment;

  /// FieldOffsets - Array of field offsets in bits.

  ASTVector<uint64_t> FieldOffsets;

  /// CXXRecordLayoutInfo - Contains C++ specific layout information.

  struct CXXRecordLayoutInfo {

    /// NonVirtualSize - The non-virtual size (in chars) of an object, which is

    /// the size of the object without virtual bases.

    CharUnits NonVirtualSize;

    /// NonVirtualAlignment - The non-virtual alignment (in chars) of an object,

    /// which is the alignment of the object without virtual bases.

    CharUnits NonVirtualAlignment;

    /// PreferredNVAlignment - The preferred non-virtual alignment (in chars) of

    /// an object, which is the preferred alignment of the object without

    /// virtual bases.

    CharUnits PreferredNVAlignment;

    /// SizeOfLargestEmptySubobject - The size of the largest empty subobject

    /// (either a base or a member). Will be zero if the class doesn't contain

    /// any empty subobjects.

    CharUnits SizeOfLargestEmptySubobject;

    /// VBPtrOffset - Virtual base table offset (Microsoft-only).

    CharUnits VBPtrOffset;

    /// HasOwnVFPtr - Does this class provide a virtual function table

    /// (vtable in Itanium, vftbl in Microsoft) that is independent from

    /// its base classes?

    bool HasOwnVFPtr : 1;

    /// HasVFPtr - Does this class have a vftable that could be extended by

    /// a derived class.  The class may have inherited this pointer from

    /// a primary base class.

    bool HasExtendableVFPtr : 1;

    /// EndsWithZeroSizedObject - True if this class contains a zero sized

    /// member or base or a base with a zero sized member or base.

    /// Only used for MS-ABI.

    bool EndsWithZeroSizedObject : 1;

    /// True if this class is zero sized or first base is zero sized or

    /// has this property.  Only used for MS-ABI.

    bool LeadsWithZeroSizedBase : 1;

    /// PrimaryBase - The primary base info for this record.

    llvm::PointerIntPair<const CXXRecordDecl *, 1, bool> PrimaryBase;

    /// BaseSharingVBPtr - The base we share vbptr with.

    const CXXRecordDecl *BaseSharingVBPtr;

    /// FIXME: This should really use a SmallPtrMap, once we have one in LLVM :)

    using BaseOffsetsMapTy = llvm::DenseMap<const CXXRecordDecl *, CharUnits>;

    /// BaseOffsets - Contains a map from base classes to their offset.

    BaseOffsetsMapTy BaseOffsets;

    /// VBaseOffsets - Contains a map from vbase classes to their offset.

    VBaseOffsetsMapTy VBaseOffsets;

  };

  /// CXXInfo - If the record layout is for a C++ record, this will have

  /// C++ specific information about the record.

  CXXRecordLayoutInfo *CXXInfo = nullptr;

  ASTRecordLayout(const ASTContext &Ctx, CharUnits size, CharUnits alignment,

                  CharUnits preferredAlignment, CharUnits unadjustedAlignment,

                  CharUnits requiredAlignment, CharUnits datasize,

                  ArrayRef<uint64_t> fieldoffsets);

  using BaseOffsetsMapTy = CXXRecordLayoutInfo::BaseOffsetsMapTy;

  // Constructor for C++ records.

  ASTRecordLayout(const ASTContext &Ctx, CharUnits size, CharUnits alignment,

                  CharUnits preferredAlignment, CharUnits unadjustedAlignment,

                  CharUnits requiredAlignment, bool hasOwnVFPtr,

                  bool hasExtendableVFPtr, CharUnits vbptroffset,

                  CharUnits datasize, ArrayRef<uint64_t> fieldoffsets,

                  CharUnits nonvirtualsize, CharUnits nonvirtualalignment,

                  CharUnits preferrednvalignment,

                  CharUnits SizeOfLargestEmptySubobject,

                  const CXXRecordDecl *PrimaryBase, bool IsPrimaryBaseVirtual,

                  const CXXRecordDecl *BaseSharingVBPtr,

                  bool EndsWithZeroSizedObject, bool LeadsWithZeroSizedBase,

                  const BaseOffsetsMapTy &BaseOffsets,

                  const VBaseOffsetsMapTy &VBaseOffsets);

  ~ASTRecordLayout() = default;

  void Destroy(ASTContext &Ctx);

public:

  ASTRecordLayout(const ASTRecordLayout &) = delete;

  ASTRecordLayout &operator=(const ASTRecordLayout &) = delete;

  /// getAlignment - Get the record alignment in characters.

  CharUnits getAlignment() const { return Alignment; }

  /// getPreferredFieldAlignment - Get the record preferred alignment in

  /// characters.

  CharUnits getPreferredAlignment() const { return PreferredAlignment; }

  /// getUnadjustedAlignment - Get the record alignment in characters, before

  /// alignment adjustement.

  CharUnits getUnadjustedAlignment() const { return UnadjustedAlignment; }

  /// getSize - Get the record size in characters.

  CharUnits getSize() const { return Size; }

  /// getFieldCount - Get the number of fields in the layout.

  unsigned getFieldCount() const { return FieldOffsets.size(); }

  /// getFieldOffset - Get the offset of the given field index, in

  /// bits.

  uint64_t getFieldOffset(unsigned FieldNo) const {

    return FieldOffsets[FieldNo];

  }

  /// getDataSize() - Get the record data size, which is the record size

  /// without tail padding, in characters.

  CharUnits getDataSize() const { return DataSize; }

  /// getNonVirtualSize - Get the non-virtual size (in chars) of an object,

  /// which is the size of the object without virtual bases.

  CharUnits getNonVirtualSize() const {

    assert(CXXInfo && "Record layout does not have C++ specific info!");

    return CXXInfo->NonVirtualSize;

  }

  /// getNonVirtualAlignment - Get the non-virtual alignment (in chars) of an

  /// object, which is the alignment of the object without virtual bases.

  CharUnits getNonVirtualAlignment() const {

    assert(CXXInfo && "Record layout does not have C++ specific info!");

    return CXXInfo->NonVirtualAlignment;

  }

  /// getPreferredNVAlignment - Get the preferred non-virtual alignment (in

  /// chars) of an object, which is the preferred alignment of the object

  /// without virtual bases.

  CharUnits getPreferredNVAlignment() const {

    assert(CXXInfo && "Record layout does not have C++ specific info!");

    return CXXInfo->PreferredNVAlignment;

  }

  /// getPrimaryBase - Get the primary base for this record.

  const CXXRecordDecl *getPrimaryBase() const {

    assert(CXXInfo && "Record layout does not have C++ specific info!");

    return CXXInfo->PrimaryBase.getPointer();

  }

  /// isPrimaryBaseVirtual - Get whether the primary base for this record

  /// is virtual or not.

  bool isPrimaryBaseVirtual() const {

    assert(CXXInfo && "Record layout does not have C++ specific info!");

    return CXXInfo->PrimaryBase.getInt();

  }

  /// getBaseClassOffset - Get the offset, in chars, for the given base class.

  CharUnits getBaseClassOffset(const CXXRecordDecl *Base) const {

    assert(CXXInfo && "Record layout does not have C++ specific info!");

    Base = Base->getDefinition();

    assert(CXXInfo->BaseOffsets.count(Base) && "Did not find base!");

    return CXXInfo->BaseOffsets[Base];

  }

  /// getVBaseClassOffset - Get the offset, in chars, for the given base class.

  CharUnits getVBaseClassOffset(const CXXRecordDecl *VBase) const {

    assert(CXXInfo && "Record layout does not have C++ specific info!");

    VBase = VBase->getDefinition();

    assert(CXXInfo->VBaseOffsets.count(VBase) && "Did not find base!");

    return CXXInfo->VBaseOffsets[VBase].VBaseOffset;

  }

  CharUnits getSizeOfLargestEmptySubobject() const {

    assert(CXXInfo && "Record layout does not have C++ specific info!");

    return CXXInfo->SizeOfLargestEmptySubobject;

  }

  /// hasOwnVFPtr - Does this class provide its own virtual-function

  /// table pointer, rather than inheriting one from a primary base

  /// class?  If so, it is at offset zero.

  ///

  /// This implies that the ABI has no primary base class, meaning

  /// that it has no base classes that are suitable under the conditions

  /// of the ABI.

  bool hasOwnVFPtr() const {

    assert(CXXInfo && "Record layout does not have C++ specific info!");

    return CXXInfo->HasOwnVFPtr;

  }

  /// hasVFPtr - Does this class have a virtual function table pointer

  /// that can be extended by a derived class?  This is synonymous with

  /// this class having a VFPtr at offset zero.

  bool hasExtendableVFPtr() const {

    assert(CXXInfo && "Record layout does not have C++ specific info!");

    return CXXInfo->HasExtendableVFPtr;

  }

  /// hasOwnVBPtr - Does this class provide its own virtual-base

  /// table pointer, rather than inheriting one from a primary base

  /// class?

  ///

  /// This implies that the ABI has no primary base class, meaning

  /// that it has no base classes that are suitable under the conditions

  /// of the ABI.

  bool hasOwnVBPtr() const {

    assert(CXXInfo && "Record layout does not have C++ specific info!");

    return hasVBPtr() && 
!CXXInfo->BaseSharingVBPtr1.81k
;

  }

  /// hasVBPtr - Does this class have a virtual function table pointer.

  bool hasVBPtr() const {

    assert(CXXInfo && "Record layout does not have C++ specific info!");

    return !CXXInfo->VBPtrOffset.isNegative();

  }

  CharUnits getRequiredAlignment() const { return RequiredAlignment; }

  bool endsWithZeroSizedObject() const {

    return CXXInfo && 
CXXInfo->EndsWithZeroSizedObject4.37k
;

  }

  bool leadsWithZeroSizedBase() const {

    assert(CXXInfo && "Record layout does not have C++ specific info!");

    return CXXInfo->LeadsWithZeroSizedBase;

  }

  /// getVBPtrOffset - Get the offset for virtual base table pointer.

  /// This is only meaningful with the Microsoft ABI.

  CharUnits getVBPtrOffset() const {

    assert(CXXInfo && "Record layout does not have C++ specific info!");

    return CXXInfo->VBPtrOffset;

  }

  const CXXRecordDecl *getBaseSharingVBPtr() const {

    assert(CXXInfo && "Record layout does not have C++ specific info!");

    return CXXInfo->BaseSharingVBPtr;

  }

  const VBaseOffsetsMapTy &getVBaseOffsetsMap() const {

    assert(CXXInfo && "Record layout does not have C++ specific info!");

    return CXXInfo->VBaseOffsets;

  }

};

} // namespace clang

#endif // LLVM_CLANG_AST_RECORDLAYOUT_H