//===- 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->BaseSharingVBPtr;
}
/// 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->EndsWithZeroSizedObject;
}
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