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llvm-project/clang/lib/AST/RecordLayoutBuilder.cpp

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//=== RecordLayoutBuilder.cpp - Helper class for building record layouts ---==//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "clang/AST/RecordLayout.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/Attr.h"
#include "clang/AST/CXXInheritance.h"
#include "clang/AST/Decl.h"
#include "clang/AST/DeclCXX.h"
#include "clang/AST/DeclObjC.h"
#include "clang/AST/Expr.h"
#include "clang/Basic/TargetInfo.h"
#include "clang/Sema/SemaDiagnostic.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/Support/CrashRecoveryContext.h"
#include "llvm/Support/Format.h"
#include "llvm/Support/MathExtras.h"
using namespace clang;
namespace {
/// BaseSubobjectInfo - Represents a single base subobject in a complete class.
/// For a class hierarchy like
///
/// class A { };
/// class B : A { };
/// class C : A, B { };
///
/// The BaseSubobjectInfo graph for C will have three BaseSubobjectInfo
/// instances, one for B and two for A.
///
/// If a base is virtual, it will only have one BaseSubobjectInfo allocated.
struct BaseSubobjectInfo {
/// Class - The class for this base info.
const CXXRecordDecl *Class;
/// IsVirtual - Whether the BaseInfo represents a virtual base or not.
bool IsVirtual;
/// Bases - Information about the base subobjects.
SmallVector<BaseSubobjectInfo*, 4> Bases;
/// PrimaryVirtualBaseInfo - Holds the base info for the primary virtual base
/// of this base info (if one exists).
BaseSubobjectInfo *PrimaryVirtualBaseInfo;
// FIXME: Document.
const BaseSubobjectInfo *Derived;
};
/// EmptySubobjectMap - Keeps track of which empty subobjects exist at different
/// offsets while laying out a C++ class.
class EmptySubobjectMap {
const ASTContext &Context;
uint64_t CharWidth;
/// Class - The class whose empty entries we're keeping track of.
const CXXRecordDecl *Class;
/// EmptyClassOffsets - A map from offsets to empty record decls.
typedef SmallVector<const CXXRecordDecl *, 1> ClassVectorTy;
typedef llvm::DenseMap<CharUnits, ClassVectorTy> EmptyClassOffsetsMapTy;
EmptyClassOffsetsMapTy EmptyClassOffsets;
/// MaxEmptyClassOffset - The highest offset known to contain an empty
/// base subobject.
CharUnits MaxEmptyClassOffset;
/// ComputeEmptySubobjectSizes - Compute the size of the largest base or
/// member subobject that is empty.
void ComputeEmptySubobjectSizes();
void AddSubobjectAtOffset(const CXXRecordDecl *RD, CharUnits Offset);
void UpdateEmptyBaseSubobjects(const BaseSubobjectInfo *Info,
CharUnits Offset, bool PlacingEmptyBase);
void UpdateEmptyFieldSubobjects(const CXXRecordDecl *RD,
const CXXRecordDecl *Class,
CharUnits Offset);
void UpdateEmptyFieldSubobjects(const FieldDecl *FD, CharUnits Offset);
/// AnyEmptySubobjectsBeyondOffset - Returns whether there are any empty
/// subobjects beyond the given offset.
bool AnyEmptySubobjectsBeyondOffset(CharUnits Offset) const {
return Offset <= MaxEmptyClassOffset;
}
CharUnits
getFieldOffset(const ASTRecordLayout &Layout, unsigned FieldNo) const {
uint64_t FieldOffset = Layout.getFieldOffset(FieldNo);
assert(FieldOffset % CharWidth == 0 &&
"Field offset not at char boundary!");
return Context.toCharUnitsFromBits(FieldOffset);
}
protected:
bool CanPlaceSubobjectAtOffset(const CXXRecordDecl *RD,
CharUnits Offset) const;
bool CanPlaceBaseSubobjectAtOffset(const BaseSubobjectInfo *Info,
CharUnits Offset);
bool CanPlaceFieldSubobjectAtOffset(const CXXRecordDecl *RD,
const CXXRecordDecl *Class,
CharUnits Offset) const;
bool CanPlaceFieldSubobjectAtOffset(const FieldDecl *FD,
CharUnits Offset) const;
public:
/// This holds the size of the largest empty subobject (either a base
/// or a member). Will be zero if the record being built doesn't contain
/// any empty classes.
CharUnits SizeOfLargestEmptySubobject;
EmptySubobjectMap(const ASTContext &Context, const CXXRecordDecl *Class)
: Context(Context), CharWidth(Context.getCharWidth()), Class(Class) {
ComputeEmptySubobjectSizes();
}
/// CanPlaceBaseAtOffset - Return whether the given base class can be placed
/// at the given offset.
/// Returns false if placing the record will result in two components
/// (direct or indirect) of the same type having the same offset.
bool CanPlaceBaseAtOffset(const BaseSubobjectInfo *Info,
CharUnits Offset);
/// CanPlaceFieldAtOffset - Return whether a field can be placed at the given
/// offset.
bool CanPlaceFieldAtOffset(const FieldDecl *FD, CharUnits Offset);
};
void EmptySubobjectMap::ComputeEmptySubobjectSizes() {
// Check the bases.
for (CXXRecordDecl::base_class_const_iterator I = Class->bases_begin(),
E = Class->bases_end(); I != E; ++I) {
const CXXRecordDecl *BaseDecl =
cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
CharUnits EmptySize;
const ASTRecordLayout &Layout = Context.getASTRecordLayout(BaseDecl);
if (BaseDecl->isEmpty()) {
// If the class decl is empty, get its size.
EmptySize = Layout.getSize();
} else {
// Otherwise, we get the largest empty subobject for the decl.
EmptySize = Layout.getSizeOfLargestEmptySubobject();
}
if (EmptySize > SizeOfLargestEmptySubobject)
SizeOfLargestEmptySubobject = EmptySize;
}
// Check the fields.
for (CXXRecordDecl::field_iterator I = Class->field_begin(),
E = Class->field_end(); I != E; ++I) {
const RecordType *RT =
Context.getBaseElementType(I->getType())->getAs<RecordType>();
// We only care about record types.
if (!RT)
continue;
CharUnits EmptySize;
const CXXRecordDecl *MemberDecl = cast<CXXRecordDecl>(RT->getDecl());
const ASTRecordLayout &Layout = Context.getASTRecordLayout(MemberDecl);
if (MemberDecl->isEmpty()) {
// If the class decl is empty, get its size.
EmptySize = Layout.getSize();
} else {
// Otherwise, we get the largest empty subobject for the decl.
EmptySize = Layout.getSizeOfLargestEmptySubobject();
}
if (EmptySize > SizeOfLargestEmptySubobject)
SizeOfLargestEmptySubobject = EmptySize;
}
}
bool
EmptySubobjectMap::CanPlaceSubobjectAtOffset(const CXXRecordDecl *RD,
CharUnits Offset) const {
// We only need to check empty bases.
if (!RD->isEmpty())
return true;
EmptyClassOffsetsMapTy::const_iterator I = EmptyClassOffsets.find(Offset);
if (I == EmptyClassOffsets.end())
return true;
const ClassVectorTy& Classes = I->second;
if (std::find(Classes.begin(), Classes.end(), RD) == Classes.end())
return true;
// There is already an empty class of the same type at this offset.
return false;
}
void EmptySubobjectMap::AddSubobjectAtOffset(const CXXRecordDecl *RD,
CharUnits Offset) {
// We only care about empty bases.
if (!RD->isEmpty())
return;
// If we have empty structures inside a union, we can assign both
// the same offset. Just avoid pushing them twice in the list.
ClassVectorTy& Classes = EmptyClassOffsets[Offset];
if (std::find(Classes.begin(), Classes.end(), RD) != Classes.end())
return;
Classes.push_back(RD);
// Update the empty class offset.
if (Offset > MaxEmptyClassOffset)
MaxEmptyClassOffset = Offset;
}
bool
EmptySubobjectMap::CanPlaceBaseSubobjectAtOffset(const BaseSubobjectInfo *Info,
CharUnits Offset) {
// We don't have to keep looking past the maximum offset that's known to
// contain an empty class.
if (!AnyEmptySubobjectsBeyondOffset(Offset))
return true;
if (!CanPlaceSubobjectAtOffset(Info->Class, Offset))
return false;
// Traverse all non-virtual bases.
const ASTRecordLayout &Layout = Context.getASTRecordLayout(Info->Class);
for (unsigned I = 0, E = Info->Bases.size(); I != E; ++I) {
BaseSubobjectInfo* Base = Info->Bases[I];
if (Base->IsVirtual)
continue;
CharUnits BaseOffset = Offset + Layout.getBaseClassOffset(Base->Class);
if (!CanPlaceBaseSubobjectAtOffset(Base, BaseOffset))
return false;
}
if (Info->PrimaryVirtualBaseInfo) {
BaseSubobjectInfo *PrimaryVirtualBaseInfo = Info->PrimaryVirtualBaseInfo;
if (Info == PrimaryVirtualBaseInfo->Derived) {
if (!CanPlaceBaseSubobjectAtOffset(PrimaryVirtualBaseInfo, Offset))
return false;
}
}
// Traverse all member variables.
unsigned FieldNo = 0;
for (CXXRecordDecl::field_iterator I = Info->Class->field_begin(),
E = Info->Class->field_end(); I != E; ++I, ++FieldNo) {
if (I->isBitField())
continue;
CharUnits FieldOffset = Offset + getFieldOffset(Layout, FieldNo);
if (!CanPlaceFieldSubobjectAtOffset(*I, FieldOffset))
return false;
}
return true;
}
void EmptySubobjectMap::UpdateEmptyBaseSubobjects(const BaseSubobjectInfo *Info,
CharUnits Offset,
bool PlacingEmptyBase) {
if (!PlacingEmptyBase && Offset >= SizeOfLargestEmptySubobject) {
// We know that the only empty subobjects that can conflict with empty
// subobject of non-empty bases, are empty bases that can be placed at
// offset zero. Because of this, we only need to keep track of empty base
// subobjects with offsets less than the size of the largest empty
// subobject for our class.
return;
}
AddSubobjectAtOffset(Info->Class, Offset);
// Traverse all non-virtual bases.
const ASTRecordLayout &Layout = Context.getASTRecordLayout(Info->Class);
for (unsigned I = 0, E = Info->Bases.size(); I != E; ++I) {
BaseSubobjectInfo* Base = Info->Bases[I];
if (Base->IsVirtual)
continue;
CharUnits BaseOffset = Offset + Layout.getBaseClassOffset(Base->Class);
UpdateEmptyBaseSubobjects(Base, BaseOffset, PlacingEmptyBase);
}
if (Info->PrimaryVirtualBaseInfo) {
BaseSubobjectInfo *PrimaryVirtualBaseInfo = Info->PrimaryVirtualBaseInfo;
if (Info == PrimaryVirtualBaseInfo->Derived)
UpdateEmptyBaseSubobjects(PrimaryVirtualBaseInfo, Offset,
PlacingEmptyBase);
}
// Traverse all member variables.
unsigned FieldNo = 0;
for (CXXRecordDecl::field_iterator I = Info->Class->field_begin(),
E = Info->Class->field_end(); I != E; ++I, ++FieldNo) {
if (I->isBitField())
continue;
CharUnits FieldOffset = Offset + getFieldOffset(Layout, FieldNo);
UpdateEmptyFieldSubobjects(*I, FieldOffset);
}
}
bool EmptySubobjectMap::CanPlaceBaseAtOffset(const BaseSubobjectInfo *Info,
CharUnits Offset) {
// If we know this class doesn't have any empty subobjects we don't need to
// bother checking.
if (SizeOfLargestEmptySubobject.isZero())
return true;
if (!CanPlaceBaseSubobjectAtOffset(Info, Offset))
return false;
// We are able to place the base at this offset. Make sure to update the
// empty base subobject map.
UpdateEmptyBaseSubobjects(Info, Offset, Info->Class->isEmpty());
return true;
}
bool
EmptySubobjectMap::CanPlaceFieldSubobjectAtOffset(const CXXRecordDecl *RD,
const CXXRecordDecl *Class,
CharUnits Offset) const {
// We don't have to keep looking past the maximum offset that's known to
// contain an empty class.
if (!AnyEmptySubobjectsBeyondOffset(Offset))
return true;
if (!CanPlaceSubobjectAtOffset(RD, Offset))
return false;
const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
// Traverse all non-virtual bases.
for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
E = RD->bases_end(); I != E; ++I) {
if (I->isVirtual())
continue;
const CXXRecordDecl *BaseDecl =
cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
CharUnits BaseOffset = Offset + Layout.getBaseClassOffset(BaseDecl);
if (!CanPlaceFieldSubobjectAtOffset(BaseDecl, Class, BaseOffset))
return false;
}
if (RD == Class) {
// This is the most derived class, traverse virtual bases as well.
for (CXXRecordDecl::base_class_const_iterator I = RD->vbases_begin(),
E = RD->vbases_end(); I != E; ++I) {
const CXXRecordDecl *VBaseDecl =
cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
CharUnits VBaseOffset = Offset + Layout.getVBaseClassOffset(VBaseDecl);
if (!CanPlaceFieldSubobjectAtOffset(VBaseDecl, Class, VBaseOffset))
return false;
}
}
// Traverse all member variables.
unsigned FieldNo = 0;
for (CXXRecordDecl::field_iterator I = RD->field_begin(), E = RD->field_end();
I != E; ++I, ++FieldNo) {
if (I->isBitField())
continue;
CharUnits FieldOffset = Offset + getFieldOffset(Layout, FieldNo);
if (!CanPlaceFieldSubobjectAtOffset(*I, FieldOffset))
return false;
}
return true;
}
bool
EmptySubobjectMap::CanPlaceFieldSubobjectAtOffset(const FieldDecl *FD,
CharUnits Offset) const {
// We don't have to keep looking past the maximum offset that's known to
// contain an empty class.
if (!AnyEmptySubobjectsBeyondOffset(Offset))
return true;
QualType T = FD->getType();
if (const RecordType *RT = T->getAs<RecordType>()) {
const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
return CanPlaceFieldSubobjectAtOffset(RD, RD, Offset);
}
// If we have an array type we need to look at every element.
if (const ConstantArrayType *AT = Context.getAsConstantArrayType(T)) {
QualType ElemTy = Context.getBaseElementType(AT);
const RecordType *RT = ElemTy->getAs<RecordType>();
if (!RT)
return true;
const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
uint64_t NumElements = Context.getConstantArrayElementCount(AT);
CharUnits ElementOffset = Offset;
for (uint64_t I = 0; I != NumElements; ++I) {
// We don't have to keep looking past the maximum offset that's known to
// contain an empty class.
if (!AnyEmptySubobjectsBeyondOffset(ElementOffset))
return true;
if (!CanPlaceFieldSubobjectAtOffset(RD, RD, ElementOffset))
return false;
ElementOffset += Layout.getSize();
}
}
return true;
}
bool
EmptySubobjectMap::CanPlaceFieldAtOffset(const FieldDecl *FD,
CharUnits Offset) {
if (!CanPlaceFieldSubobjectAtOffset(FD, Offset))
return false;
// We are able to place the member variable at this offset.
// Make sure to update the empty base subobject map.
UpdateEmptyFieldSubobjects(FD, Offset);
return true;
}
void EmptySubobjectMap::UpdateEmptyFieldSubobjects(const CXXRecordDecl *RD,
const CXXRecordDecl *Class,
CharUnits Offset) {
// We know that the only empty subobjects that can conflict with empty
// field subobjects are subobjects of empty bases that can be placed at offset
// zero. Because of this, we only need to keep track of empty field
// subobjects with offsets less than the size of the largest empty
// subobject for our class.
if (Offset >= SizeOfLargestEmptySubobject)
return;
AddSubobjectAtOffset(RD, Offset);
const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
// Traverse all non-virtual bases.
for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
E = RD->bases_end(); I != E; ++I) {
if (I->isVirtual())
continue;
const CXXRecordDecl *BaseDecl =
cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
CharUnits BaseOffset = Offset + Layout.getBaseClassOffset(BaseDecl);
UpdateEmptyFieldSubobjects(BaseDecl, Class, BaseOffset);
}
if (RD == Class) {
// This is the most derived class, traverse virtual bases as well.
for (CXXRecordDecl::base_class_const_iterator I = RD->vbases_begin(),
E = RD->vbases_end(); I != E; ++I) {
const CXXRecordDecl *VBaseDecl =
cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
CharUnits VBaseOffset = Offset + Layout.getVBaseClassOffset(VBaseDecl);
UpdateEmptyFieldSubobjects(VBaseDecl, Class, VBaseOffset);
}
}
// Traverse all member variables.
unsigned FieldNo = 0;
for (CXXRecordDecl::field_iterator I = RD->field_begin(), E = RD->field_end();
I != E; ++I, ++FieldNo) {
if (I->isBitField())
continue;
CharUnits FieldOffset = Offset + getFieldOffset(Layout, FieldNo);
UpdateEmptyFieldSubobjects(*I, FieldOffset);
}
}
void EmptySubobjectMap::UpdateEmptyFieldSubobjects(const FieldDecl *FD,
CharUnits Offset) {
QualType T = FD->getType();
if (const RecordType *RT = T->getAs<RecordType>()) {
const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
UpdateEmptyFieldSubobjects(RD, RD, Offset);
return;
}
// If we have an array type we need to update every element.
if (const ConstantArrayType *AT = Context.getAsConstantArrayType(T)) {
QualType ElemTy = Context.getBaseElementType(AT);
const RecordType *RT = ElemTy->getAs<RecordType>();
if (!RT)
return;
const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
uint64_t NumElements = Context.getConstantArrayElementCount(AT);
CharUnits ElementOffset = Offset;
for (uint64_t I = 0; I != NumElements; ++I) {
// We know that the only empty subobjects that can conflict with empty
// field subobjects are subobjects of empty bases that can be placed at
// offset zero. Because of this, we only need to keep track of empty field
// subobjects with offsets less than the size of the largest empty
// subobject for our class.
if (ElementOffset >= SizeOfLargestEmptySubobject)
return;
UpdateEmptyFieldSubobjects(RD, RD, ElementOffset);
ElementOffset += Layout.getSize();
}
}
}
typedef llvm::SmallPtrSet<const CXXRecordDecl*, 4> ClassSetTy;
class RecordLayoutBuilder {
protected:
// FIXME: Remove this and make the appropriate fields public.
friend class clang::ASTContext;
const ASTContext &Context;
EmptySubobjectMap *EmptySubobjects;
/// Size - The current size of the record layout.
uint64_t Size;
/// Alignment - The current alignment of the record layout.
CharUnits Alignment;
/// \brief The alignment if attribute packed is not used.
CharUnits UnpackedAlignment;
SmallVector<uint64_t, 16> FieldOffsets;
/// \brief Whether the external AST source has provided a layout for this
/// record.
unsigned ExternalLayout : 1;
/// \brief Whether we need to infer alignment, even when we have an
/// externally-provided layout.
unsigned InferAlignment : 1;
/// Packed - Whether the record is packed or not.
unsigned Packed : 1;
unsigned IsUnion : 1;
unsigned IsMac68kAlign : 1;
unsigned IsMsStruct : 1;
/// UnfilledBitsInLastUnit - If the last field laid out was a bitfield,
/// this contains the number of bits in the last unit that can be used for
/// an adjacent bitfield if necessary. The unit in question is usually
/// a byte, but larger units are used if IsMsStruct.
unsigned char UnfilledBitsInLastUnit;
/// LastBitfieldTypeSize - If IsMsStruct, represents the size of the type
/// of the previous field if it was a bitfield.
unsigned char LastBitfieldTypeSize;
/// MaxFieldAlignment - The maximum allowed field alignment. This is set by
/// #pragma pack.
CharUnits MaxFieldAlignment;
/// DataSize - The data size of the record being laid out.
uint64_t DataSize;
CharUnits NonVirtualSize;
CharUnits NonVirtualAlignment;
/// PrimaryBase - the primary base class (if one exists) of the class
/// we're laying out.
const CXXRecordDecl *PrimaryBase;
/// PrimaryBaseIsVirtual - Whether the primary base of the class we're laying
/// out is virtual.
bool PrimaryBaseIsVirtual;
/// HasOwnVFPtr - Whether the class provides its own vtable/vftbl
/// pointer, as opposed to inheriting one from a primary base class.
bool HasOwnVFPtr;
typedef llvm::DenseMap<const CXXRecordDecl *, CharUnits> BaseOffsetsMapTy;
/// Bases - base classes and their offsets in the record.
BaseOffsetsMapTy Bases;
// VBases - virtual base classes and their offsets in the record.
ASTRecordLayout::VBaseOffsetsMapTy VBases;
/// IndirectPrimaryBases - Virtual base classes, direct or indirect, that are
/// primary base classes for some other direct or indirect base class.
CXXIndirectPrimaryBaseSet IndirectPrimaryBases;
/// FirstNearlyEmptyVBase - The first nearly empty virtual base class in
/// inheritance graph order. Used for determining the primary base class.
const CXXRecordDecl *FirstNearlyEmptyVBase;
/// VisitedVirtualBases - A set of all the visited virtual bases, used to
/// avoid visiting virtual bases more than once.
llvm::SmallPtrSet<const CXXRecordDecl *, 4> VisitedVirtualBases;
/// \brief Externally-provided size.
uint64_t ExternalSize;
/// \brief Externally-provided alignment.
uint64_t ExternalAlign;
/// \brief Externally-provided field offsets.
llvm::DenseMap<const FieldDecl *, uint64_t> ExternalFieldOffsets;
/// \brief Externally-provided direct, non-virtual base offsets.
llvm::DenseMap<const CXXRecordDecl *, CharUnits> ExternalBaseOffsets;
/// \brief Externally-provided virtual base offsets.
llvm::DenseMap<const CXXRecordDecl *, CharUnits> ExternalVirtualBaseOffsets;
RecordLayoutBuilder(const ASTContext &Context,
EmptySubobjectMap *EmptySubobjects)
: Context(Context), EmptySubobjects(EmptySubobjects), Size(0),
Alignment(CharUnits::One()), UnpackedAlignment(CharUnits::One()),
ExternalLayout(false), InferAlignment(false),
Packed(false), IsUnion(false), IsMac68kAlign(false), IsMsStruct(false),
UnfilledBitsInLastUnit(0), LastBitfieldTypeSize(0),
MaxFieldAlignment(CharUnits::Zero()),
DataSize(0), NonVirtualSize(CharUnits::Zero()),
NonVirtualAlignment(CharUnits::One()),
PrimaryBase(0), PrimaryBaseIsVirtual(false),
HasOwnVFPtr(false),
FirstNearlyEmptyVBase(0) { }
/// Reset this RecordLayoutBuilder to a fresh state, using the given
/// alignment as the initial alignment. This is used for the
/// correct layout of vb-table pointers in MSVC.
void resetWithTargetAlignment(CharUnits TargetAlignment) {
const ASTContext &Context = this->Context;
EmptySubobjectMap *EmptySubobjects = this->EmptySubobjects;
this->~RecordLayoutBuilder();
new (this) RecordLayoutBuilder(Context, EmptySubobjects);
Alignment = UnpackedAlignment = TargetAlignment;
}
void Layout(const RecordDecl *D);
void Layout(const CXXRecordDecl *D);
void Layout(const ObjCInterfaceDecl *D);
void LayoutFields(const RecordDecl *D);
void LayoutField(const FieldDecl *D);
void LayoutWideBitField(uint64_t FieldSize, uint64_t TypeSize,
bool FieldPacked, const FieldDecl *D);
void LayoutBitField(const FieldDecl *D);
TargetCXXABI getCXXABI() const {
return Context.getTargetInfo().getCXXABI();
}
/// BaseSubobjectInfoAllocator - Allocator for BaseSubobjectInfo objects.
llvm::SpecificBumpPtrAllocator<BaseSubobjectInfo> BaseSubobjectInfoAllocator;
typedef llvm::DenseMap<const CXXRecordDecl *, BaseSubobjectInfo *>
BaseSubobjectInfoMapTy;
/// VirtualBaseInfo - Map from all the (direct or indirect) virtual bases
/// of the class we're laying out to their base subobject info.
BaseSubobjectInfoMapTy VirtualBaseInfo;
/// NonVirtualBaseInfo - Map from all the direct non-virtual bases of the
/// class we're laying out to their base subobject info.
BaseSubobjectInfoMapTy NonVirtualBaseInfo;
/// ComputeBaseSubobjectInfo - Compute the base subobject information for the
/// bases of the given class.
void ComputeBaseSubobjectInfo(const CXXRecordDecl *RD);
/// ComputeBaseSubobjectInfo - Compute the base subobject information for a
/// single class and all of its base classes.
BaseSubobjectInfo *ComputeBaseSubobjectInfo(const CXXRecordDecl *RD,
bool IsVirtual,
BaseSubobjectInfo *Derived);
/// DeterminePrimaryBase - Determine the primary base of the given class.
void DeterminePrimaryBase(const CXXRecordDecl *RD);
void SelectPrimaryVBase(const CXXRecordDecl *RD);
void EnsureVTablePointerAlignment(CharUnits UnpackedBaseAlign);
/// LayoutNonVirtualBases - Determines the primary base class (if any) and
/// lays it out. Will then proceed to lay out all non-virtual base clasess.
void LayoutNonVirtualBases(const CXXRecordDecl *RD);
/// LayoutNonVirtualBase - Lays out a single non-virtual base.
void LayoutNonVirtualBase(const BaseSubobjectInfo *Base);
void AddPrimaryVirtualBaseOffsets(const BaseSubobjectInfo *Info,
CharUnits Offset);
/// LayoutVirtualBases - Lays out all the virtual bases.
void LayoutVirtualBases(const CXXRecordDecl *RD,
const CXXRecordDecl *MostDerivedClass);
/// LayoutVirtualBase - Lays out a single virtual base.
void LayoutVirtualBase(const BaseSubobjectInfo *Base);
/// LayoutBase - Will lay out a base and return the offset where it was
/// placed, in chars.
CharUnits LayoutBase(const BaseSubobjectInfo *Base);
/// InitializeLayout - Initialize record layout for the given record decl.
void InitializeLayout(const Decl *D);
/// FinishLayout - Finalize record layout. Adjust record size based on the
/// alignment.
void FinishLayout(const NamedDecl *D);
void UpdateAlignment(CharUnits NewAlignment, CharUnits UnpackedNewAlignment);
void UpdateAlignment(CharUnits NewAlignment) {
UpdateAlignment(NewAlignment, NewAlignment);
}
/// \brief Retrieve the externally-supplied field offset for the given
/// field.
///
/// \param Field The field whose offset is being queried.
/// \param ComputedOffset The offset that we've computed for this field.
uint64_t updateExternalFieldOffset(const FieldDecl *Field,
uint64_t ComputedOffset);
void CheckFieldPadding(uint64_t Offset, uint64_t UnpaddedOffset,
uint64_t UnpackedOffset, unsigned UnpackedAlign,
bool isPacked, const FieldDecl *D);
DiagnosticBuilder Diag(SourceLocation Loc, unsigned DiagID);
CharUnits getSize() const {
assert(Size % Context.getCharWidth() == 0);
return Context.toCharUnitsFromBits(Size);
}
uint64_t getSizeInBits() const { return Size; }
void setSize(CharUnits NewSize) { Size = Context.toBits(NewSize); }
void setSize(uint64_t NewSize) { Size = NewSize; }
CharUnits getAligment() const { return Alignment; }
CharUnits getDataSize() const {
assert(DataSize % Context.getCharWidth() == 0);
return Context.toCharUnitsFromBits(DataSize);
}
uint64_t getDataSizeInBits() const { return DataSize; }
void setDataSize(CharUnits NewSize) { DataSize = Context.toBits(NewSize); }
void setDataSize(uint64_t NewSize) { DataSize = NewSize; }
RecordLayoutBuilder(const RecordLayoutBuilder &) LLVM_DELETED_FUNCTION;
void operator=(const RecordLayoutBuilder &) LLVM_DELETED_FUNCTION;
};
} // end anonymous namespace
void
RecordLayoutBuilder::SelectPrimaryVBase(const CXXRecordDecl *RD) {
for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
E = RD->bases_end(); I != E; ++I) {
assert(!I->getType()->isDependentType() &&
"Cannot layout class with dependent bases.");
const CXXRecordDecl *Base =
cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
// Check if this is a nearly empty virtual base.
if (I->isVirtual() && Context.isNearlyEmpty(Base)) {
// If it's not an indirect primary base, then we've found our primary
// base.
if (!IndirectPrimaryBases.count(Base)) {
PrimaryBase = Base;
PrimaryBaseIsVirtual = true;
return;
}
// Is this the first nearly empty virtual base?
if (!FirstNearlyEmptyVBase)
FirstNearlyEmptyVBase = Base;
}
SelectPrimaryVBase(Base);
if (PrimaryBase)
return;
}
}
/// DeterminePrimaryBase - Determine the primary base of the given class.
void RecordLayoutBuilder::DeterminePrimaryBase(const CXXRecordDecl *RD) {
// If the class isn't dynamic, it won't have a primary base.
if (!RD->isDynamicClass())
return;
// Compute all the primary virtual bases for all of our direct and
// indirect bases, and record all their primary virtual base classes.
RD->getIndirectPrimaryBases(IndirectPrimaryBases);
// If the record has a dynamic base class, attempt to choose a primary base
// class. It is the first (in direct base class order) non-virtual dynamic
// base class, if one exists.
for (CXXRecordDecl::base_class_const_iterator i = RD->bases_begin(),
e = RD->bases_end(); i != e; ++i) {
// Ignore virtual bases.
if (i->isVirtual())
continue;
const CXXRecordDecl *Base =
cast<CXXRecordDecl>(i->getType()->getAs<RecordType>()->getDecl());
if (Base->isDynamicClass()) {
// We found it.
PrimaryBase = Base;
PrimaryBaseIsVirtual = false;
return;
}
}
// Under the Itanium ABI, if there is no non-virtual primary base class,
// try to compute the primary virtual base. The primary virtual base is
// the first nearly empty virtual base that is not an indirect primary
// virtual base class, if one exists.
if (RD->getNumVBases() != 0) {
SelectPrimaryVBase(RD);
if (PrimaryBase)
return;
}
// Otherwise, it is the first indirect primary base class, if one exists.
if (FirstNearlyEmptyVBase) {
PrimaryBase = FirstNearlyEmptyVBase;
PrimaryBaseIsVirtual = true;
return;
}
assert(!PrimaryBase && "Should not get here with a primary base!");
}
BaseSubobjectInfo *
RecordLayoutBuilder::ComputeBaseSubobjectInfo(const CXXRecordDecl *RD,
bool IsVirtual,
BaseSubobjectInfo *Derived) {
BaseSubobjectInfo *Info;
if (IsVirtual) {
// Check if we already have info about this virtual base.
BaseSubobjectInfo *&InfoSlot = VirtualBaseInfo[RD];
if (InfoSlot) {
assert(InfoSlot->Class == RD && "Wrong class for virtual base info!");
return InfoSlot;
}
// We don't, create it.
InfoSlot = new (BaseSubobjectInfoAllocator.Allocate()) BaseSubobjectInfo;
Info = InfoSlot;
} else {
Info = new (BaseSubobjectInfoAllocator.Allocate()) BaseSubobjectInfo;
}
Info->Class = RD;
Info->IsVirtual = IsVirtual;
Info->Derived = 0;
Info->PrimaryVirtualBaseInfo = 0;
const CXXRecordDecl *PrimaryVirtualBase = 0;
BaseSubobjectInfo *PrimaryVirtualBaseInfo = 0;
// Check if this base has a primary virtual base.
if (RD->getNumVBases()) {
const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
if (Layout.isPrimaryBaseVirtual()) {
// This base does have a primary virtual base.
PrimaryVirtualBase = Layout.getPrimaryBase();
assert(PrimaryVirtualBase && "Didn't have a primary virtual base!");
// Now check if we have base subobject info about this primary base.
PrimaryVirtualBaseInfo = VirtualBaseInfo.lookup(PrimaryVirtualBase);
if (PrimaryVirtualBaseInfo) {
if (PrimaryVirtualBaseInfo->Derived) {
// We did have info about this primary base, and it turns out that it
// has already been claimed as a primary virtual base for another
// base.
PrimaryVirtualBase = 0;
} else {
// We can claim this base as our primary base.
Info->PrimaryVirtualBaseInfo = PrimaryVirtualBaseInfo;
PrimaryVirtualBaseInfo->Derived = Info;
}
}
}
}
// Now go through all direct bases.
for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
E = RD->bases_end(); I != E; ++I) {
bool IsVirtual = I->isVirtual();
const CXXRecordDecl *BaseDecl =
cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
Info->Bases.push_back(ComputeBaseSubobjectInfo(BaseDecl, IsVirtual, Info));
}
if (PrimaryVirtualBase && !PrimaryVirtualBaseInfo) {
// Traversing the bases must have created the base info for our primary
// virtual base.
PrimaryVirtualBaseInfo = VirtualBaseInfo.lookup(PrimaryVirtualBase);
assert(PrimaryVirtualBaseInfo &&
"Did not create a primary virtual base!");
// Claim the primary virtual base as our primary virtual base.
Info->PrimaryVirtualBaseInfo = PrimaryVirtualBaseInfo;
PrimaryVirtualBaseInfo->Derived = Info;
}
return Info;
}
void RecordLayoutBuilder::ComputeBaseSubobjectInfo(const CXXRecordDecl *RD) {
for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
E = RD->bases_end(); I != E; ++I) {
bool IsVirtual = I->isVirtual();
const CXXRecordDecl *BaseDecl =
cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
// Compute the base subobject info for this base.
BaseSubobjectInfo *Info = ComputeBaseSubobjectInfo(BaseDecl, IsVirtual, 0);
if (IsVirtual) {
// ComputeBaseInfo has already added this base for us.
assert(VirtualBaseInfo.count(BaseDecl) &&
"Did not add virtual base!");
} else {
// Add the base info to the map of non-virtual bases.
assert(!NonVirtualBaseInfo.count(BaseDecl) &&
"Non-virtual base already exists!");
NonVirtualBaseInfo.insert(std::make_pair(BaseDecl, Info));
}
}
}
void
RecordLayoutBuilder::EnsureVTablePointerAlignment(CharUnits UnpackedBaseAlign) {
CharUnits BaseAlign = (Packed) ? CharUnits::One() : UnpackedBaseAlign;
// The maximum field alignment overrides base align.
if (!MaxFieldAlignment.isZero()) {
BaseAlign = std::min(BaseAlign, MaxFieldAlignment);
UnpackedBaseAlign = std::min(UnpackedBaseAlign, MaxFieldAlignment);
}
// Round up the current record size to pointer alignment.
setSize(getSize().RoundUpToAlignment(BaseAlign));
setDataSize(getSize());
// Update the alignment.
UpdateAlignment(BaseAlign, UnpackedBaseAlign);
}
void
RecordLayoutBuilder::LayoutNonVirtualBases(const CXXRecordDecl *RD) {
// Then, determine the primary base class.
DeterminePrimaryBase(RD);
// Compute base subobject info.
ComputeBaseSubobjectInfo(RD);
// If we have a primary base class, lay it out.
if (PrimaryBase) {
if (PrimaryBaseIsVirtual) {
// If the primary virtual base was a primary virtual base of some other
// base class we'll have to steal it.
BaseSubobjectInfo *PrimaryBaseInfo = VirtualBaseInfo.lookup(PrimaryBase);
PrimaryBaseInfo->Derived = 0;
// We have a virtual primary base, insert it as an indirect primary base.
IndirectPrimaryBases.insert(PrimaryBase);
assert(!VisitedVirtualBases.count(PrimaryBase) &&
"vbase already visited!");
VisitedVirtualBases.insert(PrimaryBase);
LayoutVirtualBase(PrimaryBaseInfo);
} else {
BaseSubobjectInfo *PrimaryBaseInfo =
NonVirtualBaseInfo.lookup(PrimaryBase);
assert(PrimaryBaseInfo &&
"Did not find base info for non-virtual primary base!");
LayoutNonVirtualBase(PrimaryBaseInfo);
}
// If this class needs a vtable/vf-table and didn't get one from a
// primary base, add it in now.
} else if (RD->isDynamicClass()) {
assert(DataSize == 0 && "Vtable pointer must be at offset zero!");
CharUnits PtrWidth =
Context.toCharUnitsFromBits(Context.getTargetInfo().getPointerWidth(0));
CharUnits PtrAlign =
Context.toCharUnitsFromBits(Context.getTargetInfo().getPointerAlign(0));
EnsureVTablePointerAlignment(PtrAlign);
HasOwnVFPtr = true;
setSize(getSize() + PtrWidth);
setDataSize(getSize());
}
// Now lay out the non-virtual bases.
for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
E = RD->bases_end(); I != E; ++I) {
// Ignore virtual bases.
if (I->isVirtual())
continue;
const CXXRecordDecl *BaseDecl = I->getType()->getAsCXXRecordDecl();
// Skip the primary base, because we've already laid it out. The
// !PrimaryBaseIsVirtual check is required because we might have a
// non-virtual base of the same type as a primary virtual base.
if (BaseDecl == PrimaryBase && !PrimaryBaseIsVirtual)
continue;
// Lay out the base.
BaseSubobjectInfo *BaseInfo = NonVirtualBaseInfo.lookup(BaseDecl);
assert(BaseInfo && "Did not find base info for non-virtual base!");
LayoutNonVirtualBase(BaseInfo);
}
}
void RecordLayoutBuilder::LayoutNonVirtualBase(const BaseSubobjectInfo *Base) {
// Layout the base.
CharUnits Offset = LayoutBase(Base);
// Add its base class offset.
assert(!Bases.count(Base->Class) && "base offset already exists!");
Bases.insert(std::make_pair(Base->Class, Offset));
AddPrimaryVirtualBaseOffsets(Base, Offset);
}
void
RecordLayoutBuilder::AddPrimaryVirtualBaseOffsets(const BaseSubobjectInfo *Info,
CharUnits Offset) {
// This base isn't interesting, it has no virtual bases.
if (!Info->Class->getNumVBases())
return;
// First, check if we have a virtual primary base to add offsets for.
if (Info->PrimaryVirtualBaseInfo) {
assert(Info->PrimaryVirtualBaseInfo->IsVirtual &&
"Primary virtual base is not virtual!");
if (Info->PrimaryVirtualBaseInfo->Derived == Info) {
// Add the offset.
assert(!VBases.count(Info->PrimaryVirtualBaseInfo->Class) &&
"primary vbase offset already exists!");
VBases.insert(std::make_pair(Info->PrimaryVirtualBaseInfo->Class,
ASTRecordLayout::VBaseInfo(Offset, false)));
// Traverse the primary virtual base.
AddPrimaryVirtualBaseOffsets(Info->PrimaryVirtualBaseInfo, Offset);
}
}
// Now go through all direct non-virtual bases.
const ASTRecordLayout &Layout = Context.getASTRecordLayout(Info->Class);
for (unsigned I = 0, E = Info->Bases.size(); I != E; ++I) {
const BaseSubobjectInfo *Base = Info->Bases[I];
if (Base->IsVirtual)
continue;
CharUnits BaseOffset = Offset + Layout.getBaseClassOffset(Base->Class);
AddPrimaryVirtualBaseOffsets(Base, BaseOffset);
}
}
void
RecordLayoutBuilder::LayoutVirtualBases(const CXXRecordDecl *RD,
const CXXRecordDecl *MostDerivedClass) {
const CXXRecordDecl *PrimaryBase;
bool PrimaryBaseIsVirtual;
if (MostDerivedClass == RD) {
PrimaryBase = this->PrimaryBase;
PrimaryBaseIsVirtual = this->PrimaryBaseIsVirtual;
} else {
const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
PrimaryBase = Layout.getPrimaryBase();
PrimaryBaseIsVirtual = Layout.isPrimaryBaseVirtual();
}
for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
E = RD->bases_end(); I != E; ++I) {
assert(!I->getType()->isDependentType() &&
"Cannot layout class with dependent bases.");
const CXXRecordDecl *BaseDecl = I->getType()->getAsCXXRecordDecl();
if (I->isVirtual()) {
if (PrimaryBase != BaseDecl || !PrimaryBaseIsVirtual) {
bool IndirectPrimaryBase = IndirectPrimaryBases.count(BaseDecl);
// Only lay out the virtual base if it's not an indirect primary base.
if (!IndirectPrimaryBase) {
// Only visit virtual bases once.
if (!VisitedVirtualBases.insert(BaseDecl))
continue;
const BaseSubobjectInfo *BaseInfo = VirtualBaseInfo.lookup(BaseDecl);
assert(BaseInfo && "Did not find virtual base info!");
LayoutVirtualBase(BaseInfo);
}
}
}
if (!BaseDecl->getNumVBases()) {
// This base isn't interesting since it doesn't have any virtual bases.
continue;
}
LayoutVirtualBases(BaseDecl, MostDerivedClass);
}
}
void RecordLayoutBuilder::LayoutVirtualBase(const BaseSubobjectInfo *Base) {
assert(!Base->Derived && "Trying to lay out a primary virtual base!");
// Layout the base.
CharUnits Offset = LayoutBase(Base);
// Add its base class offset.
assert(!VBases.count(Base->Class) && "vbase offset already exists!");
VBases.insert(std::make_pair(Base->Class,
ASTRecordLayout::VBaseInfo(Offset, false)));
AddPrimaryVirtualBaseOffsets(Base, Offset);
}
CharUnits RecordLayoutBuilder::LayoutBase(const BaseSubobjectInfo *Base) {
const ASTRecordLayout &Layout = Context.getASTRecordLayout(Base->Class);
CharUnits Offset;
// Query the external layout to see if it provides an offset.
bool HasExternalLayout = false;
if (ExternalLayout) {
llvm::DenseMap<const CXXRecordDecl *, CharUnits>::iterator Known;
if (Base->IsVirtual) {
Known = ExternalVirtualBaseOffsets.find(Base->Class);
if (Known != ExternalVirtualBaseOffsets.end()) {
Offset = Known->second;
HasExternalLayout = true;
}
} else {
Known = ExternalBaseOffsets.find(Base->Class);
if (Known != ExternalBaseOffsets.end()) {
Offset = Known->second;
HasExternalLayout = true;
}
}
}
CharUnits UnpackedBaseAlign = Layout.getNonVirtualAlignment();
CharUnits BaseAlign = (Packed) ? CharUnits::One() : UnpackedBaseAlign;
// If we have an empty base class, try to place it at offset 0.
if (Base->Class->isEmpty() &&
(!HasExternalLayout || Offset == CharUnits::Zero()) &&
EmptySubobjects->CanPlaceBaseAtOffset(Base, CharUnits::Zero())) {
setSize(std::max(getSize(), Layout.getSize()));
UpdateAlignment(BaseAlign, UnpackedBaseAlign);
return CharUnits::Zero();
}
// The maximum field alignment overrides base align.
if (!MaxFieldAlignment.isZero()) {
BaseAlign = std::min(BaseAlign, MaxFieldAlignment);
UnpackedBaseAlign = std::min(UnpackedBaseAlign, MaxFieldAlignment);
}
if (!HasExternalLayout) {
// Round up the current record size to the base's alignment boundary.
Offset = getDataSize().RoundUpToAlignment(BaseAlign);
// Try to place the base.
while (!EmptySubobjects->CanPlaceBaseAtOffset(Base, Offset))
Offset += BaseAlign;
} else {
bool Allowed = EmptySubobjects->CanPlaceBaseAtOffset(Base, Offset);
(void)Allowed;
assert(Allowed && "Base subobject externally placed at overlapping offset");
if (InferAlignment && Offset < getDataSize().RoundUpToAlignment(BaseAlign)){
// The externally-supplied base offset is before the base offset we
// computed. Assume that the structure is packed.
Alignment = CharUnits::One();
InferAlignment = false;
}
}
if (!Base->Class->isEmpty()) {
// Update the data size.
setDataSize(Offset + Layout.getNonVirtualSize());
setSize(std::max(getSize(), getDataSize()));
} else
setSize(std::max(getSize(), Offset + Layout.getSize()));
// Remember max struct/class alignment.
UpdateAlignment(BaseAlign, UnpackedBaseAlign);
return Offset;
}
void RecordLayoutBuilder::InitializeLayout(const Decl *D) {
if (const RecordDecl *RD = dyn_cast<RecordDecl>(D)) {
IsUnion = RD->isUnion();
IsMsStruct = RD->isMsStruct(Context);
}
Packed = D->hasAttr<PackedAttr>();
// Honor the default struct packing maximum alignment flag.
if (unsigned DefaultMaxFieldAlignment = Context.getLangOpts().PackStruct) {
MaxFieldAlignment = CharUnits::fromQuantity(DefaultMaxFieldAlignment);
}
// mac68k alignment supersedes maximum field alignment and attribute aligned,
// and forces all structures to have 2-byte alignment. The IBM docs on it
// allude to additional (more complicated) semantics, especially with regard
// to bit-fields, but gcc appears not to follow that.
if (D->hasAttr<AlignMac68kAttr>()) {
IsMac68kAlign = true;
MaxFieldAlignment = CharUnits::fromQuantity(2);
Alignment = CharUnits::fromQuantity(2);
} else {
if (const MaxFieldAlignmentAttr *MFAA = D->getAttr<MaxFieldAlignmentAttr>())
MaxFieldAlignment = Context.toCharUnitsFromBits(MFAA->getAlignment());
if (unsigned MaxAlign = D->getMaxAlignment())
UpdateAlignment(Context.toCharUnitsFromBits(MaxAlign));
}
// If there is an external AST source, ask it for the various offsets.
if (const RecordDecl *RD = dyn_cast<RecordDecl>(D))
if (ExternalASTSource *External = Context.getExternalSource()) {
ExternalLayout = External->layoutRecordType(RD,
ExternalSize,
ExternalAlign,
ExternalFieldOffsets,
ExternalBaseOffsets,
ExternalVirtualBaseOffsets);
// Update based on external alignment.
if (ExternalLayout) {
if (ExternalAlign > 0) {
Alignment = Context.toCharUnitsFromBits(ExternalAlign);
} else {
// The external source didn't have alignment information; infer it.
InferAlignment = true;
}
}
}
}
void RecordLayoutBuilder::Layout(const RecordDecl *D) {
InitializeLayout(D);
LayoutFields(D);
// Finally, round the size of the total struct up to the alignment of the
// struct itself.
FinishLayout(D);
}
void RecordLayoutBuilder::Layout(const CXXRecordDecl *RD) {
InitializeLayout(RD);
// Lay out the vtable and the non-virtual bases.
LayoutNonVirtualBases(RD);
LayoutFields(RD);
NonVirtualSize = Context.toCharUnitsFromBits(
llvm::RoundUpToAlignment(getSizeInBits(),
Context.getTargetInfo().getCharAlign()));
NonVirtualAlignment = Alignment;
// Lay out the virtual bases and add the primary virtual base offsets.
LayoutVirtualBases(RD, RD);
// Finally, round the size of the total struct up to the alignment
// of the struct itself.
FinishLayout(RD);
#ifndef NDEBUG
// Check that we have base offsets for all bases.
for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
E = RD->bases_end(); I != E; ++I) {
if (I->isVirtual())
continue;
const CXXRecordDecl *BaseDecl =
cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
assert(Bases.count(BaseDecl) && "Did not find base offset!");
}
// And all virtual bases.
for (CXXRecordDecl::base_class_const_iterator I = RD->vbases_begin(),
E = RD->vbases_end(); I != E; ++I) {
const CXXRecordDecl *BaseDecl =
cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
assert(VBases.count(BaseDecl) && "Did not find base offset!");
}
#endif
}
void RecordLayoutBuilder::Layout(const ObjCInterfaceDecl *D) {
if (ObjCInterfaceDecl *SD = D->getSuperClass()) {
const ASTRecordLayout &SL = Context.getASTObjCInterfaceLayout(SD);
UpdateAlignment(SL.getAlignment());
// We start laying out ivars not at the end of the superclass
// structure, but at the next byte following the last field.
setSize(SL.getDataSize());
setDataSize(getSize());
}
InitializeLayout(D);
// Layout each ivar sequentially.
for (const ObjCIvarDecl *IVD = D->all_declared_ivar_begin(); IVD;
IVD = IVD->getNextIvar())
LayoutField(IVD);
// Finally, round the size of the total struct up to the alignment of the
// struct itself.
FinishLayout(D);
}
void RecordLayoutBuilder::LayoutFields(const RecordDecl *D) {
// Layout each field, for now, just sequentially, respecting alignment. In
// the future, this will need to be tweakable by targets.
for (RecordDecl::field_iterator Field = D->field_begin(),
FieldEnd = D->field_end(); Field != FieldEnd; ++Field)
LayoutField(*Field);
}
void RecordLayoutBuilder::LayoutWideBitField(uint64_t FieldSize,
uint64_t TypeSize,
bool FieldPacked,
const FieldDecl *D) {
assert(Context.getLangOpts().CPlusPlus &&
"Can only have wide bit-fields in C++!");
// Itanium C++ ABI 2.4:
// If sizeof(T)*8 < n, let T' be the largest integral POD type with
// sizeof(T')*8 <= n.
QualType IntegralPODTypes[] = {
Context.UnsignedCharTy, Context.UnsignedShortTy, Context.UnsignedIntTy,
Context.UnsignedLongTy, Context.UnsignedLongLongTy
};
QualType Type;
for (unsigned I = 0, E = llvm::array_lengthof(IntegralPODTypes);
I != E; ++I) {
uint64_t Size = Context.getTypeSize(IntegralPODTypes[I]);
if (Size > FieldSize)
break;
Type = IntegralPODTypes[I];
}
assert(!Type.isNull() && "Did not find a type!");
CharUnits TypeAlign = Context.getTypeAlignInChars(Type);
// We're not going to use any of the unfilled bits in the last byte.
UnfilledBitsInLastUnit = 0;
LastBitfieldTypeSize = 0;
uint64_t FieldOffset;
uint64_t UnpaddedFieldOffset = getDataSizeInBits() - UnfilledBitsInLastUnit;
if (IsUnion) {
setDataSize(std::max(getDataSizeInBits(), FieldSize));
FieldOffset = 0;
} else {
// The bitfield is allocated starting at the next offset aligned
// appropriately for T', with length n bits.
FieldOffset = llvm::RoundUpToAlignment(getDataSizeInBits(),
Context.toBits(TypeAlign));
uint64_t NewSizeInBits = FieldOffset + FieldSize;
setDataSize(llvm::RoundUpToAlignment(NewSizeInBits,
Context.getTargetInfo().getCharAlign()));
UnfilledBitsInLastUnit = getDataSizeInBits() - NewSizeInBits;
}
// Place this field at the current location.
FieldOffsets.push_back(FieldOffset);
CheckFieldPadding(FieldOffset, UnpaddedFieldOffset, FieldOffset,
Context.toBits(TypeAlign), FieldPacked, D);
// Update the size.
setSize(std::max(getSizeInBits(), getDataSizeInBits()));
// Remember max struct/class alignment.
UpdateAlignment(TypeAlign);
}
void RecordLayoutBuilder::LayoutBitField(const FieldDecl *D) {
bool FieldPacked = Packed || D->hasAttr<PackedAttr>();
uint64_t FieldSize = D->getBitWidthValue(Context);
std::pair<uint64_t, unsigned> FieldInfo = Context.getTypeInfo(D->getType());
uint64_t TypeSize = FieldInfo.first;
unsigned FieldAlign = FieldInfo.second;
if (IsMsStruct) {
// The field alignment for integer types in ms_struct structs is
// always the size.
FieldAlign = TypeSize;
// Ignore zero-length bitfields after non-bitfields in ms_struct structs.
if (!FieldSize && !LastBitfieldTypeSize)
FieldAlign = 1;
// If a bitfield is followed by a bitfield of a different size, don't
// pack the bits together in ms_struct structs.
if (LastBitfieldTypeSize != TypeSize) {
UnfilledBitsInLastUnit = 0;
LastBitfieldTypeSize = 0;
}
}
uint64_t UnpaddedFieldOffset = getDataSizeInBits() - UnfilledBitsInLastUnit;
uint64_t FieldOffset = IsUnion ? 0 : UnpaddedFieldOffset;
bool ZeroLengthBitfield = false;
if (!Context.getTargetInfo().useBitFieldTypeAlignment() &&
Context.getTargetInfo().useZeroLengthBitfieldAlignment() &&
FieldSize == 0) {
// The alignment of a zero-length bitfield affects the alignment
// of the next member. The alignment is the max of the zero
// length bitfield's alignment and a target specific fixed value.
ZeroLengthBitfield = true;
unsigned ZeroLengthBitfieldBoundary =
Context.getTargetInfo().getZeroLengthBitfieldBoundary();
if (ZeroLengthBitfieldBoundary > FieldAlign)
FieldAlign = ZeroLengthBitfieldBoundary;
}
if (FieldSize > TypeSize) {
LayoutWideBitField(FieldSize, TypeSize, FieldPacked, D);
return;
}
// The align if the field is not packed. This is to check if the attribute
// was unnecessary (-Wpacked).
unsigned UnpackedFieldAlign = FieldAlign;
uint64_t UnpackedFieldOffset = FieldOffset;
if (!Context.getTargetInfo().useBitFieldTypeAlignment() && !ZeroLengthBitfield)
UnpackedFieldAlign = 1;
if (FieldPacked ||
(!Context.getTargetInfo().useBitFieldTypeAlignment() && !ZeroLengthBitfield))
FieldAlign = 1;
FieldAlign = std::max(FieldAlign, D->getMaxAlignment());
UnpackedFieldAlign = std::max(UnpackedFieldAlign, D->getMaxAlignment());
// The maximum field alignment overrides the aligned attribute.
if (!MaxFieldAlignment.isZero() && FieldSize != 0) {
unsigned MaxFieldAlignmentInBits = Context.toBits(MaxFieldAlignment);
FieldAlign = std::min(FieldAlign, MaxFieldAlignmentInBits);
UnpackedFieldAlign = std::min(UnpackedFieldAlign, MaxFieldAlignmentInBits);
}
// ms_struct bitfields always have to start at a round alignment.
if (IsMsStruct && !LastBitfieldTypeSize) {
FieldOffset = llvm::RoundUpToAlignment(FieldOffset, FieldAlign);
UnpackedFieldOffset = llvm::RoundUpToAlignment(UnpackedFieldOffset,
UnpackedFieldAlign);
}
// Check if we need to add padding to give the field the correct alignment.
if (FieldSize == 0 ||
(MaxFieldAlignment.isZero() &&
(FieldOffset & (FieldAlign-1)) + FieldSize > TypeSize))
FieldOffset = llvm::RoundUpToAlignment(FieldOffset, FieldAlign);
if (FieldSize == 0 ||
(MaxFieldAlignment.isZero() &&
(UnpackedFieldOffset & (UnpackedFieldAlign-1)) + FieldSize > TypeSize))
UnpackedFieldOffset = llvm::RoundUpToAlignment(UnpackedFieldOffset,
UnpackedFieldAlign);
// Padding members don't affect overall alignment, unless zero length bitfield
// alignment is enabled.
if (!D->getIdentifier() &&
!Context.getTargetInfo().useZeroLengthBitfieldAlignment() &&
!IsMsStruct)
FieldAlign = UnpackedFieldAlign = 1;
if (ExternalLayout)
FieldOffset = updateExternalFieldOffset(D, FieldOffset);
// Place this field at the current location.
FieldOffsets.push_back(FieldOffset);
if (!ExternalLayout)
CheckFieldPadding(FieldOffset, UnpaddedFieldOffset, UnpackedFieldOffset,
UnpackedFieldAlign, FieldPacked, D);
// Update DataSize to include the last byte containing (part of) the bitfield.
if (IsUnion) {
// FIXME: I think FieldSize should be TypeSize here.
setDataSize(std::max(getDataSizeInBits(), FieldSize));
} else {
if (IsMsStruct && FieldSize) {
// Under ms_struct, a bitfield always takes up space equal to the size
// of the type. We can't just change the alignment computation on the
// other codepath because of the way this interacts with #pragma pack:
// in a packed struct, we need to allocate misaligned space in the
// struct to hold the bitfield.
if (!UnfilledBitsInLastUnit) {
setDataSize(FieldOffset + TypeSize);
UnfilledBitsInLastUnit = TypeSize - FieldSize;
} else if (UnfilledBitsInLastUnit < FieldSize) {
setDataSize(getDataSizeInBits() + TypeSize);
UnfilledBitsInLastUnit = TypeSize - FieldSize;
} else {
UnfilledBitsInLastUnit -= FieldSize;
}
LastBitfieldTypeSize = TypeSize;
} else {
uint64_t NewSizeInBits = FieldOffset + FieldSize;
uint64_t BitfieldAlignment = Context.getTargetInfo().getCharAlign();
setDataSize(llvm::RoundUpToAlignment(NewSizeInBits, BitfieldAlignment));
UnfilledBitsInLastUnit = getDataSizeInBits() - NewSizeInBits;
LastBitfieldTypeSize = 0;
}
}
// Update the size.
setSize(std::max(getSizeInBits(), getDataSizeInBits()));
// Remember max struct/class alignment.
UpdateAlignment(Context.toCharUnitsFromBits(FieldAlign),
Context.toCharUnitsFromBits(UnpackedFieldAlign));
}
void RecordLayoutBuilder::LayoutField(const FieldDecl *D) {
if (D->isBitField()) {
LayoutBitField(D);
return;
}
uint64_t UnpaddedFieldOffset = getDataSizeInBits() - UnfilledBitsInLastUnit;
// Reset the unfilled bits.
UnfilledBitsInLastUnit = 0;
LastBitfieldTypeSize = 0;
bool FieldPacked = Packed || D->hasAttr<PackedAttr>();
CharUnits FieldOffset =
IsUnion ? CharUnits::Zero() : getDataSize();
CharUnits FieldSize;
CharUnits FieldAlign;
if (D->getType()->isIncompleteArrayType()) {
// This is a flexible array member; we can't directly
// query getTypeInfo about these, so we figure it out here.
// Flexible array members don't have any size, but they
// have to be aligned appropriately for their element type.
FieldSize = CharUnits::Zero();
const ArrayType* ATy = Context.getAsArrayType(D->getType());
FieldAlign = Context.getTypeAlignInChars(ATy->getElementType());
} else if (const ReferenceType *RT = D->getType()->getAs<ReferenceType>()) {
unsigned AS = RT->getPointeeType().getAddressSpace();
FieldSize =
Context.toCharUnitsFromBits(Context.getTargetInfo().getPointerWidth(AS));
FieldAlign =
Context.toCharUnitsFromBits(Context.getTargetInfo().getPointerAlign(AS));
} else {
std::pair<CharUnits, CharUnits> FieldInfo =
Context.getTypeInfoInChars(D->getType());
FieldSize = FieldInfo.first;
FieldAlign = FieldInfo.second;
if (IsMsStruct) {
// If MS bitfield layout is required, figure out what type is being
// laid out and align the field to the width of that type.
// Resolve all typedefs down to their base type and round up the field
// alignment if necessary.
QualType T = Context.getBaseElementType(D->getType());
if (const BuiltinType *BTy = T->getAs<BuiltinType>()) {
CharUnits TypeSize = Context.getTypeSizeInChars(BTy);
if (TypeSize > FieldAlign)
FieldAlign = TypeSize;
}
}
}
// The align if the field is not packed. This is to check if the attribute
// was unnecessary (-Wpacked).
CharUnits UnpackedFieldAlign = FieldAlign;
CharUnits UnpackedFieldOffset = FieldOffset;
if (FieldPacked)
FieldAlign = CharUnits::One();
CharUnits MaxAlignmentInChars =
Context.toCharUnitsFromBits(D->getMaxAlignment());
FieldAlign = std::max(FieldAlign, MaxAlignmentInChars);
UnpackedFieldAlign = std::max(UnpackedFieldAlign, MaxAlignmentInChars);
// The maximum field alignment overrides the aligned attribute.
if (!MaxFieldAlignment.isZero()) {
FieldAlign = std::min(FieldAlign, MaxFieldAlignment);
UnpackedFieldAlign = std::min(UnpackedFieldAlign, MaxFieldAlignment);
}
// Round up the current record size to the field's alignment boundary.
FieldOffset = FieldOffset.RoundUpToAlignment(FieldAlign);
UnpackedFieldOffset =
UnpackedFieldOffset.RoundUpToAlignment(UnpackedFieldAlign);
if (ExternalLayout) {
FieldOffset = Context.toCharUnitsFromBits(
updateExternalFieldOffset(D, Context.toBits(FieldOffset)));
if (!IsUnion && EmptySubobjects) {
// Record the fact that we're placing a field at this offset.
bool Allowed = EmptySubobjects->CanPlaceFieldAtOffset(D, FieldOffset);
(void)Allowed;
assert(Allowed && "Externally-placed field cannot be placed here");
}
} else {
if (!IsUnion && EmptySubobjects) {
// Check if we can place the field at this offset.
while (!EmptySubobjects->CanPlaceFieldAtOffset(D, FieldOffset)) {
// We couldn't place the field at the offset. Try again at a new offset.
FieldOffset += FieldAlign;
}
}
}
// Place this field at the current location.
FieldOffsets.push_back(Context.toBits(FieldOffset));
if (!ExternalLayout)
CheckFieldPadding(Context.toBits(FieldOffset), UnpaddedFieldOffset,
Context.toBits(UnpackedFieldOffset),
Context.toBits(UnpackedFieldAlign), FieldPacked, D);
// Reserve space for this field.
uint64_t FieldSizeInBits = Context.toBits(FieldSize);
if (IsUnion)
setDataSize(std::max(getDataSizeInBits(), FieldSizeInBits));
else
setDataSize(FieldOffset + FieldSize);
// Update the size.
setSize(std::max(getSizeInBits(), getDataSizeInBits()));
// Remember max struct/class alignment.
UpdateAlignment(FieldAlign, UnpackedFieldAlign);
}
void RecordLayoutBuilder::FinishLayout(const NamedDecl *D) {
// In C++, records cannot be of size 0.
if (Context.getLangOpts().CPlusPlus && getSizeInBits() == 0) {
if (const CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(D)) {
// Compatibility with gcc requires a class (pod or non-pod)
// which is not empty but of size 0; such as having fields of
// array of zero-length, remains of Size 0
if (RD->isEmpty())
setSize(CharUnits::One());
}
else
setSize(CharUnits::One());
}
// Finally, round the size of the record up to the alignment of the
// record itself.
uint64_t UnpaddedSize = getSizeInBits() - UnfilledBitsInLastUnit;
uint64_t UnpackedSizeInBits =
llvm::RoundUpToAlignment(getSizeInBits(),
Context.toBits(UnpackedAlignment));
CharUnits UnpackedSize = Context.toCharUnitsFromBits(UnpackedSizeInBits);
uint64_t RoundedSize
= llvm::RoundUpToAlignment(getSizeInBits(), Context.toBits(Alignment));
if (ExternalLayout) {
// If we're inferring alignment, and the external size is smaller than
// our size after we've rounded up to alignment, conservatively set the
// alignment to 1.
if (InferAlignment && ExternalSize < RoundedSize) {
Alignment = CharUnits::One();
InferAlignment = false;
}
setSize(ExternalSize);
return;
}
// Set the size to the final size.
setSize(RoundedSize);
unsigned CharBitNum = Context.getTargetInfo().getCharWidth();
if (const RecordDecl *RD = dyn_cast<RecordDecl>(D)) {
// Warn if padding was introduced to the struct/class/union.
if (getSizeInBits() > UnpaddedSize) {
unsigned PadSize = getSizeInBits() - UnpaddedSize;
bool InBits = true;
if (PadSize % CharBitNum == 0) {
PadSize = PadSize / CharBitNum;
InBits = false;
}
Diag(RD->getLocation(), diag::warn_padded_struct_size)
<< Context.getTypeDeclType(RD)
<< PadSize
<< (InBits ? 1 : 0) /*(byte|bit)*/ << (PadSize > 1); // plural or not
}
// Warn if we packed it unnecessarily. If the alignment is 1 byte don't
// bother since there won't be alignment issues.
if (Packed && UnpackedAlignment > CharUnits::One() &&
getSize() == UnpackedSize)
Diag(D->getLocation(), diag::warn_unnecessary_packed)
<< Context.getTypeDeclType(RD);
}
}
void RecordLayoutBuilder::UpdateAlignment(CharUnits NewAlignment,
CharUnits UnpackedNewAlignment) {
// The alignment is not modified when using 'mac68k' alignment or when
// we have an externally-supplied layout that also provides overall alignment.
if (IsMac68kAlign || (ExternalLayout && !InferAlignment))
return;
if (NewAlignment > Alignment) {
assert(llvm::isPowerOf2_32(NewAlignment.getQuantity() &&
"Alignment not a power of 2"));
Alignment = NewAlignment;
}
if (UnpackedNewAlignment > UnpackedAlignment) {
assert(llvm::isPowerOf2_32(UnpackedNewAlignment.getQuantity() &&
"Alignment not a power of 2"));
UnpackedAlignment = UnpackedNewAlignment;
}
}
uint64_t
RecordLayoutBuilder::updateExternalFieldOffset(const FieldDecl *Field,
uint64_t ComputedOffset) {
assert(ExternalFieldOffsets.find(Field) != ExternalFieldOffsets.end() &&
"Field does not have an external offset");
uint64_t ExternalFieldOffset = ExternalFieldOffsets[Field];
if (InferAlignment && ExternalFieldOffset < ComputedOffset) {
// The externally-supplied field offset is before the field offset we
// computed. Assume that the structure is packed.
Alignment = CharUnits::One();
InferAlignment = false;
}
// Use the externally-supplied field offset.
return ExternalFieldOffset;
}
/// \brief Get diagnostic %select index for tag kind for
/// field padding diagnostic message.
/// WARNING: Indexes apply to particular diagnostics only!
///
/// \returns diagnostic %select index.
static unsigned getPaddingDiagFromTagKind(TagTypeKind Tag) {
switch (Tag) {
case TTK_Struct: return 0;
case TTK_Interface: return 1;
case TTK_Class: return 2;
default: llvm_unreachable("Invalid tag kind for field padding diagnostic!");
}
}
void RecordLayoutBuilder::CheckFieldPadding(uint64_t Offset,
uint64_t UnpaddedOffset,
uint64_t UnpackedOffset,
unsigned UnpackedAlign,
bool isPacked,
const FieldDecl *D) {
// We let objc ivars without warning, objc interfaces generally are not used
// for padding tricks.
if (isa<ObjCIvarDecl>(D))
return;
// Don't warn about structs created without a SourceLocation. This can
// be done by clients of the AST, such as codegen.
if (D->getLocation().isInvalid())
return;
unsigned CharBitNum = Context.getTargetInfo().getCharWidth();
// Warn if padding was introduced to the struct/class.
if (!IsUnion && Offset > UnpaddedOffset) {
unsigned PadSize = Offset - UnpaddedOffset;
bool InBits = true;
if (PadSize % CharBitNum == 0) {
PadSize = PadSize / CharBitNum;
InBits = false;
}
if (D->getIdentifier())
Diag(D->getLocation(), diag::warn_padded_struct_field)
<< getPaddingDiagFromTagKind(D->getParent()->getTagKind())
<< Context.getTypeDeclType(D->getParent())
<< PadSize
<< (InBits ? 1 : 0) /*(byte|bit)*/ << (PadSize > 1) // plural or not
<< D->getIdentifier();
else
Diag(D->getLocation(), diag::warn_padded_struct_anon_field)
<< getPaddingDiagFromTagKind(D->getParent()->getTagKind())
<< Context.getTypeDeclType(D->getParent())
<< PadSize
<< (InBits ? 1 : 0) /*(byte|bit)*/ << (PadSize > 1); // plural or not
}
// Warn if we packed it unnecessarily. If the alignment is 1 byte don't
// bother since there won't be alignment issues.
if (isPacked && UnpackedAlign > CharBitNum && Offset == UnpackedOffset)
Diag(D->getLocation(), diag::warn_unnecessary_packed)
<< D->getIdentifier();
}
static const CXXMethodDecl *computeKeyFunction(ASTContext &Context,
const CXXRecordDecl *RD) {
// If a class isn't polymorphic it doesn't have a key function.
if (!RD->isPolymorphic())
return 0;
// A class that is not externally visible doesn't have a key function. (Or
// at least, there's no point to assigning a key function to such a class;
// this doesn't affect the ABI.)
if (!RD->isExternallyVisible())
return 0;
// Template instantiations don't have key functions,see Itanium C++ ABI 5.2.6.
// Same behavior as GCC.
TemplateSpecializationKind TSK = RD->getTemplateSpecializationKind();
if (TSK == TSK_ImplicitInstantiation ||
TSK == TSK_ExplicitInstantiationDefinition)
return 0;
bool allowInlineFunctions =
Context.getTargetInfo().getCXXABI().canKeyFunctionBeInline();
for (CXXRecordDecl::method_iterator I = RD->method_begin(),
E = RD->method_end(); I != E; ++I) {
const CXXMethodDecl *MD = *I;
if (!MD->isVirtual())
continue;
if (MD->isPure())
continue;
// Ignore implicit member functions, they are always marked as inline, but
// they don't have a body until they're defined.
if (MD->isImplicit())
continue;
if (MD->isInlineSpecified())
continue;
if (MD->hasInlineBody())
continue;
// Ignore inline deleted or defaulted functions.
if (!MD->isUserProvided())
continue;
// In certain ABIs, ignore functions with out-of-line inline definitions.
if (!allowInlineFunctions) {
const FunctionDecl *Def;
if (MD->hasBody(Def) && Def->isInlineSpecified())
continue;
}
// We found it.
return MD;
}
return 0;
}
DiagnosticBuilder
RecordLayoutBuilder::Diag(SourceLocation Loc, unsigned DiagID) {
return Context.getDiagnostics().Report(Loc, DiagID);
}
/// Does the target C++ ABI require us to skip over the tail-padding
/// of the given class (considering it as a base class) when allocating
/// objects?
static bool mustSkipTailPadding(TargetCXXABI ABI, const CXXRecordDecl *RD) {
switch (ABI.getTailPaddingUseRules()) {
case TargetCXXABI::AlwaysUseTailPadding:
return false;
case TargetCXXABI::UseTailPaddingUnlessPOD03:
// FIXME: To the extent that this is meant to cover the Itanium ABI
// rules, we should implement the restrictions about over-sized
// bitfields:
//
// http://mentorembedded.github.com/cxx-abi/abi.html#POD :
// In general, a type is considered a POD for the purposes of
// layout if it is a POD type (in the sense of ISO C++
// [basic.types]). However, a POD-struct or POD-union (in the
// sense of ISO C++ [class]) with a bitfield member whose
// declared width is wider than the declared type of the
// bitfield is not a POD for the purpose of layout. Similarly,
// an array type is not a POD for the purpose of layout if the
// element type of the array is not a POD for the purpose of
// layout.
//
// Where references to the ISO C++ are made in this paragraph,
// the Technical Corrigendum 1 version of the standard is
// intended.
return RD->isPOD();
case TargetCXXABI::UseTailPaddingUnlessPOD11:
// This is equivalent to RD->getTypeForDecl().isCXX11PODType(),
// but with a lot of abstraction penalty stripped off. This does
// assume that these properties are set correctly even in C++98
// mode; fortunately, that is true because we want to assign
// consistently semantics to the type-traits intrinsics (or at
// least as many of them as possible).
return RD->isTrivial() && RD->isStandardLayout();
}
llvm_unreachable("bad tail-padding use kind");
}
static bool isMsLayout(const RecordDecl* D) {
return D->getASTContext().getTargetInfo().getCXXABI().isMicrosoft();
}
// This section contains an implementation of struct layout that is, up to the
// included tests, compatible with cl.exe (2012). The layout produced is
// significantly different than those produced by the Itanium ABI. Here we note
// the most important differences.
//
// * The alignment of bitfields in unions is ignored when computing the
// alignment of the union.
// * The existence of zero-width bitfield that occurs after anything other than
// a non-zero length bitfield is ignored.
// * The Itanium equivalent vtable pointers are split into a vfptr (virtual
// function pointer) and a vbptr (virtual base pointer). They can each be
// shared with a, non-virtual bases. These bases need not be the same. vfptrs
// always occur at offset 0. vbptrs can occur at an
// arbitrary offset and are placed after non-virtual bases but before fields.
// * Virtual bases sometimes require a 'vtordisp' field that is laid out before
// the virtual base and is used in conjunction with virtual overrides during
// construction and destruction.
// * vfptrs are allocated in a block of memory equal to the alignment of the
// fields and non-virtual bases at offset 0 in 32 bit mode and in a pointer
// sized block of memory in 64 bit mode.
// * vbptrs are allocated in a block of memory equal to the alignment of the
// fields and non-virtual bases. This block is at a potentially unaligned
// offset. If the allocation slot is unaligned and the alignment is less than
// or equal to the pointer size, additional space is allocated so that the
// pointer can be aligned properly. This causes very strange effects on the
// placement of objects after the allocated block. (see the code).
// * vtordisps are allocated in a block of memory with size and alignment equal
// to the alignment of the completed structure (before applying __declspec(
// align())). The vtordisp always occur at the end of the allocation block,
// immediately prior to the virtual base.
// * The last zero sized non-virtual base is allocated after the placement of
// vbptr if one exists and can be placed at the end of the struct, potentially
// aliasing either the first member or another struct allocated after this
// one.
// * The last zero size virtual base may be placed at the end of the struct.
// and can potentially alias a zero sized type in the next struct.
// * If the last field is a non-zero length bitfield, all virtual bases will
// have extra padding added before them for no obvious reason. The padding
// has the same number of bits as the type of the bitfield.
// * When laying out empty non-virtual bases, an extra byte of padding is added
// if the non-virtual base before the empty non-virtual base has a vbptr.
// * The ABI attempts to avoid aliasing of zero sized bases by adding padding
// between bases or vbases with specific properties. The criteria for
// additional padding between two bases is that the first base is zero sized
// or has a zero sized subobject and the second base is zero sized or leads
// with a zero sized base (sharing of vfptrs can reorder the layout of the
// so the leading base is not always the first one declared). The padding
// added for bases is 1 byte. The padding added for vbases depends on the
// alignment of the object but is at least 4 bytes (in both 32 and 64 bit
// modes).
// * There is no concept of non-virtual alignment or any distinction between
// data size and non-virtual size.
// * __declspec(align) on bitfields has the effect of changing the bitfield's
// alignment instead of its required alignment. This has implications on how
// it interacts with pragam pack.
namespace {
struct MicrosoftRecordLayoutBuilder {
struct ElementInfo {
CharUnits Size;
CharUnits Alignment;
};
typedef llvm::DenseMap<const CXXRecordDecl *, CharUnits> BaseOffsetsMapTy;
MicrosoftRecordLayoutBuilder(const ASTContext &Context) : Context(Context) {}
private:
MicrosoftRecordLayoutBuilder(const MicrosoftRecordLayoutBuilder &)
LLVM_DELETED_FUNCTION;
void operator=(const MicrosoftRecordLayoutBuilder &) LLVM_DELETED_FUNCTION;
public:
void layout(const RecordDecl *RD);
void cxxLayout(const CXXRecordDecl *RD);
/// \brief Initializes size and alignment and honors some flags.
void initializeLayout(const RecordDecl *RD);
/// \brief Initialized C++ layout, compute alignment and virtual alignment and
/// existence of vfptrs and vbptrs. Alignment is needed before the vfptr is
/// laid out.
void initializeCXXLayout(const CXXRecordDecl *RD);
void layoutNonVirtualBases(const CXXRecordDecl *RD);
void layoutNonVirtualBase(const CXXRecordDecl *BaseDecl,
const ASTRecordLayout &BaseLayout,
const ASTRecordLayout *&PreviousBaseLayout);
void injectVFPtr(const CXXRecordDecl *RD);
void injectVBPtr(const CXXRecordDecl *RD);
void injectVPtrs(const CXXRecordDecl *RD);
/// \brief Lays out the fields of the record. Also rounds size up to
/// alignment.
void layoutFields(const RecordDecl *RD);
void layoutField(const FieldDecl *FD);
void layoutBitField(const FieldDecl *FD);
/// \brief Lays out a single zero-width bit-field in the record and handles
/// special cases associated with zero-width bit-fields.
void layoutZeroWidthBitField(const FieldDecl *FD);
void layoutVirtualBases(const CXXRecordDecl *RD);
void finalizeLayout(const RecordDecl *RD);
/// \brief Gets the size and alignment of a base taking pragma pack and
/// __declspec(align) into account.
ElementInfo getAdjustedElementInfo(const ASTRecordLayout &Layout);
/// \brief Gets the size and alignment of a field taking pragma pack and
/// __declspec(align) into account. It also updates RequiredAlignment as a
/// side effect because it is most convenient to do so here.
ElementInfo getAdjustedElementInfo(const FieldDecl *FD);
/// \brief Places a field at an offset in CharUnits.
void placeFieldAtOffset(CharUnits FieldOffset) {
FieldOffsets.push_back(Context.toBits(FieldOffset));
}
/// \brief Places a bitfield at a bit offset.
void placeFieldAtBitOffset(uint64_t FieldOffset) {
FieldOffsets.push_back(FieldOffset);
}
/// \brief Compute the set of virtual bases for which vtordisps are required.
llvm::SmallPtrSet<const CXXRecordDecl *, 2>
computeVtorDispSet(const CXXRecordDecl *RD);
const ASTContext &Context;
/// \brief The size of the record being laid out.
CharUnits Size;
/// \brief The data alignment of the record layout.
CharUnits DataSize;
/// \brief The current alignment of the record layout.
CharUnits Alignment;
/// \brief The maximum allowed field alignment. This is set by #pragma pack.
CharUnits MaxFieldAlignment;
/// \brief The alignment that this record must obey. This is imposed by
/// __declspec(align()) on the record itself or one of its fields or bases.
CharUnits RequiredAlignment;
/// \brief The size of the allocation of the currently active bitfield.
/// This value isn't meaningful unless LastFieldIsNonZeroWidthBitfield
/// is true.
CharUnits CurrentBitfieldSize;
/// \brief Offset to the virtual base table pointer (if one exists).
CharUnits VBPtrOffset;
/// \brief The size and alignment info of a pointer.
ElementInfo PointerInfo;
/// \brief The primary base class (if one exists).
const CXXRecordDecl *PrimaryBase;
/// \brief The class we share our vb-pointer with.
const CXXRecordDecl *SharedVBPtrBase;
/// \brief The collection of field offsets.
SmallVector<uint64_t, 16> FieldOffsets;
/// \brief Base classes and their offsets in the record.
BaseOffsetsMapTy Bases;
/// \brief virtual base classes and their offsets in the record.
ASTRecordLayout::VBaseOffsetsMapTy VBases;
/// \brief The number of remaining bits in our last bitfield allocation.
/// This value isn't meaningful unless LastFieldIsNonZeroWidthBitfield is
/// true.
unsigned RemainingBitsInField;
bool IsUnion : 1;
/// \brief True if the last field laid out was a bitfield and was not 0
/// width.
bool LastFieldIsNonZeroWidthBitfield : 1;
/// \brief True if the class has its own vftable pointer.
bool HasOwnVFPtr : 1;
/// \brief True if the class has a vbtable pointer.
bool HasVBPtr : 1;
/// \brief Lets us know if we're in 64-bit mode
bool Is64BitMode : 1;
/// \brief 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 HasZeroSizedSubObject : 1;
/// \brief 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;
};
} // namespace
MicrosoftRecordLayoutBuilder::ElementInfo
MicrosoftRecordLayoutBuilder::getAdjustedElementInfo(
const ASTRecordLayout &Layout) {
ElementInfo Info;
Info.Alignment = Layout.getAlignment();
// Respect pragma pack.
if (!MaxFieldAlignment.isZero())
Info.Alignment = std::min(Info.Alignment, MaxFieldAlignment);
// Track zero-sized subobjects here where it's already available.
if (Layout.hasZeroSizedSubObject())
HasZeroSizedSubObject = true;
// Respect required alignment, this is necessary because we may have adjusted
// the alignment in the case of pragam pack. Note that the required alignment
// doesn't actually apply to the struct alignment at this point.
Alignment = std::max(Alignment, Info.Alignment);
Info.Alignment = std::max(Info.Alignment, Layout.getRequiredAlignment());
Info.Size = Layout.getDataSize();
return Info;
}
MicrosoftRecordLayoutBuilder::ElementInfo
MicrosoftRecordLayoutBuilder::getAdjustedElementInfo(
const FieldDecl *FD) {
ElementInfo Info;
// Respect align attributes.
CharUnits FieldRequiredAlignment =
Context.toCharUnitsFromBits(FD->getMaxAlignment());
// Respect attributes applied to subobjects of the field.
if (const RecordType *RT =
FD->getType()->getBaseElementTypeUnsafe()->getAs<RecordType>()) {
const ASTRecordLayout &Layout = Context.getASTRecordLayout(RT->getDecl());
// Get the element info for a layout, respecting pack.
Info = getAdjustedElementInfo(Layout);
// Nomally getAdjustedElementInfo returns the non-virtual size, which is
// correct for bases but not for fields.
Info.Size = Context.getTypeInfoInChars(FD->getType()).first;
// Capture required alignment as a side-effect.
RequiredAlignment = std::max(RequiredAlignment,
Layout.getRequiredAlignment());
}
else {
llvm::tie(Info.Size, Info.Alignment) =
Context.getTypeInfoInChars(FD->getType());
if (FD->isBitField() && FD->getMaxAlignment() != 0)
Info.Alignment = std::max(Info.Alignment, FieldRequiredAlignment);
}
// Respect packed field attribute.
if (FD->hasAttr<PackedAttr>())
Info.Alignment = CharUnits::One();
// Take required alignment into account. __declspec(align) on bitfields
// impacts the alignment rather than the required alignment.
if (!FD->isBitField()) {
Info.Alignment = std::max(Info.Alignment, FieldRequiredAlignment);
// Capture required alignment as a side-effect.
RequiredAlignment = std::max(RequiredAlignment, FieldRequiredAlignment);
}
// Respect pragma pack.
if (!MaxFieldAlignment.isZero())
Info.Alignment = std::min(Info.Alignment, MaxFieldAlignment);
// TODO: Add a Sema warning that MS ignores bitfield alignment in unions.
if (!(FD->isBitField() && IsUnion))
Alignment = std::max(Alignment, Info.Alignment);
return Info;
}
void MicrosoftRecordLayoutBuilder::layout(const RecordDecl *RD) {
initializeLayout(RD);
layoutFields(RD);
DataSize = Size = Size.RoundUpToAlignment(Alignment);
finalizeLayout(RD);
}
void MicrosoftRecordLayoutBuilder::cxxLayout(const CXXRecordDecl *RD) {
initializeLayout(RD);
initializeCXXLayout(RD);
layoutNonVirtualBases(RD);
layoutFields(RD);
injectVPtrs(RD);
DataSize = Size = Size.RoundUpToAlignment(Alignment);
layoutVirtualBases(RD);
finalizeLayout(RD);
}
void MicrosoftRecordLayoutBuilder::initializeLayout(const RecordDecl *RD) {
IsUnion = RD->isUnion();
Is64BitMode = Context.getTargetInfo().getPointerWidth(0) == 64;
Size = CharUnits::Zero();
Alignment = CharUnits::One();
// In 64-bit mode we always perform an alignment step after laying out vbases.
// In 32-bit mode we do not. The check to see if we need to perform alignment
// checks the RequiredAlignment field and performs alignment if it isn't 0.
RequiredAlignment = Is64BitMode ? CharUnits::One() : CharUnits::Zero();
RequiredAlignment = std::max(RequiredAlignment,
Context.toCharUnitsFromBits(RD->getMaxAlignment()));
// Compute the maximum field alignment.
MaxFieldAlignment = CharUnits::Zero();
// Honor the default struct packing maximum alignment flag.
if (unsigned DefaultMaxFieldAlignment = Context.getLangOpts().PackStruct)
MaxFieldAlignment = CharUnits::fromQuantity(DefaultMaxFieldAlignment);
// Honor the packing attribute. The MS-ABI ignores pragma pack if its larger
// than the pointer size.
if (const MaxFieldAlignmentAttr *MFAA = RD->getAttr<MaxFieldAlignmentAttr>()){
unsigned PackedAlignment = MFAA->getAlignment();
if (PackedAlignment <= Context.getTargetInfo().getPointerWidth(0))
MaxFieldAlignment = Context.toCharUnitsFromBits(PackedAlignment);
}
// Packed attribute forces max field alignment to be 1.
if (RD->hasAttr<PackedAttr>())
MaxFieldAlignment = CharUnits::One();
}
void
MicrosoftRecordLayoutBuilder::initializeCXXLayout(const CXXRecordDecl *RD) {
HasZeroSizedSubObject = false;
LeadsWithZeroSizedBase = false;
HasOwnVFPtr = false;
HasVBPtr = false;
PrimaryBase = 0;
SharedVBPtrBase = 0;
// Calculate pointer size and alignment. These are used for vfptr and vbprt
// injection.
PointerInfo.Size =
Context.toCharUnitsFromBits(Context.getTargetInfo().getPointerWidth(0));
PointerInfo.Alignment = PointerInfo.Size;
// Respect pragma pack.
if (!MaxFieldAlignment.isZero())
PointerInfo.Alignment = std::min(PointerInfo.Alignment, MaxFieldAlignment);
}
void
MicrosoftRecordLayoutBuilder::layoutNonVirtualBases(const CXXRecordDecl *RD) {
// The MS-ABI lays out all bases that contain leading vfptrs before it lays
// out any bases that do not contain vfptrs. We implement this as two passes
// over the bases. This approach guarantees that the primary base is laid out
// first. We use these passes to calculate some additional aggregated
// information about the bases, such as reqruied alignment and the presence of
// zero sized members.
const ASTRecordLayout* PreviousBaseLayout = 0;
// Iterate through the bases and lay out the non-virtual ones.
for (CXXRecordDecl::base_class_const_iterator i = RD->bases_begin(),
e = RD->bases_end();
i != e; ++i) {
const CXXRecordDecl *BaseDecl = i->getType()->getAsCXXRecordDecl();
const ASTRecordLayout &BaseLayout = Context.getASTRecordLayout(BaseDecl);
// Track RequiredAlignment for all bases in this pass.
RequiredAlignment = std::max(RequiredAlignment,
BaseLayout.getRequiredAlignment());
// Mark and skip virtual bases.
if (i->isVirtual()) {
HasVBPtr = true;
continue;
}
// Check fo a base to share a VBPtr with.
if (!SharedVBPtrBase && BaseLayout.hasVBPtr()) {
SharedVBPtrBase = BaseDecl;
HasVBPtr = true;
}
// Only lay out bases with extendable VFPtrs on the first pass.
if (!BaseLayout.hasExtendableVFPtr())
continue;
// If we don't have a primary base, this one qualifies.
if (!PrimaryBase) {
PrimaryBase = BaseDecl;
LeadsWithZeroSizedBase = BaseLayout.leadsWithZeroSizedBase();
}
// Lay out the base.
layoutNonVirtualBase(BaseDecl, BaseLayout, PreviousBaseLayout);
}
// Figure out if we need a fresh VFPtr for this class.
if (!PrimaryBase && RD->isDynamicClass())
for (CXXRecordDecl::method_iterator i = RD->method_begin(),
e = RD->method_end();
!HasOwnVFPtr && i != e; ++i)
HasOwnVFPtr = i->isVirtual() && i->size_overridden_methods() == 0;
// If we don't have a primary base then we have a leading object that could
// itself lead with a zero-sized object, something we track.
bool CheckLeadingLayout = !PrimaryBase;
// Iterate through the bases and lay out the non-virtual ones.
for (CXXRecordDecl::base_class_const_iterator i = RD->bases_begin(),
e = RD->bases_end();
i != e; ++i) {
if (i->isVirtual())
continue;
const CXXRecordDecl *BaseDecl = i->getType()->getAsCXXRecordDecl();
const ASTRecordLayout &BaseLayout = Context.getASTRecordLayout(BaseDecl);
// Only lay out bases without extendable VFPtrs on the second pass.
if (BaseLayout.hasExtendableVFPtr())
continue;
// If this is the first layout, check to see if it leads with a zero sized
// object. If it does, so do we.
if (CheckLeadingLayout) {
CheckLeadingLayout = false;
LeadsWithZeroSizedBase = BaseLayout.leadsWithZeroSizedBase();
}
// Lay out the base.
layoutNonVirtualBase(BaseDecl, BaseLayout, PreviousBaseLayout);
}
// Set our VBPtroffset if we know it at this point.
if (!HasVBPtr)
VBPtrOffset = CharUnits::fromQuantity(-1);
}
void MicrosoftRecordLayoutBuilder::layoutNonVirtualBase(
const CXXRecordDecl *BaseDecl,
const ASTRecordLayout &BaseLayout,
const ASTRecordLayout *&PreviousBaseLayout) {
// Insert padding between two bases if the left first one is zero sized or
// contains a zero sized subobject and the right is zero sized or one leads
// with a zero sized base.
if (PreviousBaseLayout && PreviousBaseLayout->hasZeroSizedSubObject() &&
BaseLayout.leadsWithZeroSizedBase())
Size++;
ElementInfo Info = getAdjustedElementInfo(BaseLayout);
CharUnits BaseOffset = Size.RoundUpToAlignment(Info.Alignment);
Bases.insert(std::make_pair(BaseDecl, BaseOffset));
Size = BaseOffset + BaseLayout.getDataSize();
PreviousBaseLayout = &BaseLayout;
VBPtrOffset = Size;
}
void MicrosoftRecordLayoutBuilder::layoutFields(const RecordDecl *RD) {
LastFieldIsNonZeroWidthBitfield = false;
for (RecordDecl::field_iterator Field = RD->field_begin(),
FieldEnd = RD->field_end();
Field != FieldEnd; ++Field)
layoutField(*Field);
}
void MicrosoftRecordLayoutBuilder::layoutField(const FieldDecl *FD) {
if (FD->isBitField()) {
layoutBitField(FD);
return;
}
LastFieldIsNonZeroWidthBitfield = false;
ElementInfo Info = getAdjustedElementInfo(FD);
if (IsUnion) {
placeFieldAtOffset(CharUnits::Zero());
Size = std::max(Size, Info.Size);
} else {
CharUnits FieldOffset = Size.RoundUpToAlignment(Info.Alignment);
placeFieldAtOffset(FieldOffset);
Size = FieldOffset + Info.Size;
}
}
void MicrosoftRecordLayoutBuilder::layoutBitField(const FieldDecl *FD) {
unsigned Width = FD->getBitWidthValue(Context);
if (Width == 0) {
layoutZeroWidthBitField(FD);
return;
}
ElementInfo Info = getAdjustedElementInfo(FD);
// Clamp the bitfield to a containable size for the sake of being able
// to lay them out. Sema will throw an error.
if (Width > Context.toBits(Info.Size))
Width = Context.toBits(Info.Size);
// Check to see if this bitfield fits into an existing allocation. Note:
// MSVC refuses to pack bitfields of formal types with different sizes
// into the same allocation.
if (!IsUnion && LastFieldIsNonZeroWidthBitfield &&
CurrentBitfieldSize == Info.Size && Width <= RemainingBitsInField) {
placeFieldAtBitOffset(Context.toBits(Size) - RemainingBitsInField);
RemainingBitsInField -= Width;
return;
}
LastFieldIsNonZeroWidthBitfield = true;
CurrentBitfieldSize = Info.Size;
if (IsUnion) {
placeFieldAtOffset(CharUnits::Zero());
Size = std::max(Size, Info.Size);
} else {
// Allocate a new block of memory and place the bitfield in it.
CharUnits FieldOffset = Size.RoundUpToAlignment(Info.Alignment);
placeFieldAtOffset(FieldOffset);
Size = FieldOffset + Info.Size;
RemainingBitsInField = Context.toBits(Info.Size) - Width;
}
}
void
MicrosoftRecordLayoutBuilder::layoutZeroWidthBitField(const FieldDecl *FD) {
// Zero-width bitfields are ignored unless they follow a non-zero-width
// bitfield.
if (!LastFieldIsNonZeroWidthBitfield) {
placeFieldAtOffset(IsUnion ? CharUnits::Zero() : Size);
// TODO: Add a Sema warning that MS ignores alignment for zero
// sized bitfields that occur after zero-size bitfields or non-bitfields.
return;
}
LastFieldIsNonZeroWidthBitfield = false;
ElementInfo Info = getAdjustedElementInfo(FD);
if (IsUnion) {
placeFieldAtOffset(CharUnits::Zero());
Size = std::max(Size, Info.Size);
} else {
// Round up the current record size to the field's alignment boundary.
CharUnits FieldOffset = Size.RoundUpToAlignment(Info.Alignment);
placeFieldAtOffset(FieldOffset);
Size = FieldOffset;
}
}
void MicrosoftRecordLayoutBuilder::injectVBPtr(const CXXRecordDecl *RD) {
if (!HasVBPtr)
return;
if (SharedVBPtrBase) {
const ASTRecordLayout &Layout = Context.getASTRecordLayout(SharedVBPtrBase);
VBPtrOffset = Bases[SharedVBPtrBase] + Layout.getVBPtrOffset();
return;
}
// Inject the VBPointer at the injection site.
CharUnits InjectionSite = VBPtrOffset;
// But before we do, make sure it's properly aligned.
VBPtrOffset = VBPtrOffset.RoundUpToAlignment(PointerInfo.Alignment);
// Determine where the first field should be laid out after the vbptr.
CharUnits FieldStart = VBPtrOffset + PointerInfo.Size;
// Make sure that the amount we push the fields back by is a multiple of the
// alignment.
CharUnits Offset = (FieldStart - InjectionSite).RoundUpToAlignment(Alignment);
// Increase the size of the object and push back all fields by the offset
// amount.
Size += Offset;
for (SmallVector<uint64_t, 16>::iterator i = FieldOffsets.begin(),
e = FieldOffsets.end();
i != e; ++i)
*i += Context.toBits(Offset);
for (BaseOffsetsMapTy::iterator i = Bases.begin(), e = Bases.end();
i != e; ++i)
if (i->second >= InjectionSite)
i->second += Offset;
// The presence of a vbptr suppresses zero sized objects that are not in
// virtual bases.
HasZeroSizedSubObject = false;
}
void MicrosoftRecordLayoutBuilder::injectVFPtr(const CXXRecordDecl *RD) {
if (!HasOwnVFPtr)
return;
// Make sure that the amount we push the struct back by is a multiple of the
// alignment.
CharUnits Offset = PointerInfo.Size.RoundUpToAlignment(Alignment);
// Increase the size of the object and push back all fields, the vbptr and all
// bases by the offset amount.
Size += Offset;
for (SmallVector<uint64_t, 16>::iterator i = FieldOffsets.begin(),
e = FieldOffsets.end();
i != e; ++i)
*i += Context.toBits(Offset);
if (HasVBPtr)
VBPtrOffset += Offset;
for (BaseOffsetsMapTy::iterator i = Bases.begin(), e = Bases.end();
i != e; ++i)
i->second += Offset;
}
void MicrosoftRecordLayoutBuilder::injectVPtrs(const CXXRecordDecl *RD) {
if (!(HasOwnVFPtr || (HasVBPtr && !SharedVBPtrBase)))
return;
if (!Is64BitMode || RequiredAlignment <= CharUnits::fromQuantity(8)) {
// Note that the VBPtr is injected first. It depends on the alignment of
// the object *before* the alignment is updated by inserting a pointer into
// the record.
injectVBPtr(RD);
injectVFPtr(RD);
Alignment = std::max(Alignment, PointerInfo.Alignment);
return;
}
// In 64-bit mode, structs with RequiredAlignment greater than 8 get special
// layout rules. Likely this is to avoid excessive padding intruced around
// the vfptrs and vbptrs. The special rules involve re-laying out the struct
// and inserting the vfptr and vbptr as if they were fields/bases.
FieldOffsets.clear();
Bases.clear();
Size = CharUnits::Zero();
Alignment = std::max(Alignment, PointerInfo.Alignment);
if (HasOwnVFPtr)
Size = PointerInfo.Size;
layoutNonVirtualBases(RD);
if (HasVBPtr && !SharedVBPtrBase) {
const CXXRecordDecl *PenultBaseDecl = 0;
const CXXRecordDecl *LastBaseDecl = 0;
// Iterate through the bases and find the last two non-virtual bases.
for (CXXRecordDecl::base_class_const_iterator i = RD->bases_begin(),
e = RD->bases_end();
i != e; ++i) {
if (i->isVirtual())
continue;
const CXXRecordDecl *BaseDecl = i->getType()->getAsCXXRecordDecl();
if (!LastBaseDecl || Bases[BaseDecl] > Bases[LastBaseDecl]) {
PenultBaseDecl = LastBaseDecl;
LastBaseDecl = BaseDecl;
}
}
const ASTRecordLayout *PenultBaseLayout = PenultBaseDecl ?
&Context.getASTRecordLayout(PenultBaseDecl) : 0;
const ASTRecordLayout *LastBaseLayout = LastBaseDecl ?
&Context.getASTRecordLayout(LastBaseDecl) : 0;
// Calculate the vbptr offset. The rule is different than in the general
// case layout. Particularly, if the last two non-virtual bases are both
// zero sized, the site of the vbptr is *before* the padding that occurs
// between the two zero sized bases and the vbptr potentially aliases with
// the first of these two bases. We have no understanding of why this is
// different from the general case layout but it may have to do with lazy
// placement of zero sized bases.
VBPtrOffset = Size;
if (LastBaseLayout && LastBaseLayout->getDataSize().isZero()) {
VBPtrOffset = Bases[LastBaseDecl];
if (PenultBaseLayout && PenultBaseLayout->getDataSize().isZero())
VBPtrOffset = Bases[PenultBaseDecl];
}
// Once we've located a spot for the vbptr, place it.
VBPtrOffset = VBPtrOffset.RoundUpToAlignment(PointerInfo.Alignment);
Size = VBPtrOffset + PointerInfo.Size;
if (LastBaseLayout && LastBaseLayout->getDataSize().isZero()) {
// Add the padding between zero sized bases after the vbptr.
if (PenultBaseLayout && PenultBaseLayout->getDataSize().isZero())
Size += CharUnits::One();
Size = Size.RoundUpToAlignment(LastBaseLayout->getRequiredAlignment());
Bases[LastBaseDecl] = Size;
}
}
layoutFields(RD);
// The presence of a vbptr suppresses zero sized objects that are not in
// virtual bases.
HasZeroSizedSubObject = false;
}
void MicrosoftRecordLayoutBuilder::layoutVirtualBases(const CXXRecordDecl *RD) {
if (!HasVBPtr)
return;
// Vtordisps are always 4 bytes (even in 64-bit mode)
CharUnits VtorDispSize = CharUnits::fromQuantity(4);
CharUnits VtorDispAlignment = VtorDispSize;
// vtordisps respect pragma pack.
if (!MaxFieldAlignment.isZero())
VtorDispAlignment = std::min(VtorDispAlignment, MaxFieldAlignment);
// The alignment of the vtordisp is at least the required alignment of the
// entire record. This requirement may be present to support vtordisp
// injection.
VtorDispAlignment = std::max(VtorDispAlignment, RequiredAlignment);
// Compute the vtordisp set.
llvm::SmallPtrSet<const CXXRecordDecl *, 2> HasVtordispSet =
computeVtorDispSet(RD);
// Iterate through the virtual bases and lay them out.
const ASTRecordLayout* PreviousBaseLayout = 0;
for (CXXRecordDecl::base_class_const_iterator i = RD->vbases_begin(),
e = RD->vbases_end();
i != e; ++i) {
const CXXRecordDecl *BaseDecl = i->getType()->getAsCXXRecordDecl();
const ASTRecordLayout &BaseLayout = Context.getASTRecordLayout(BaseDecl);
bool HasVtordisp = HasVtordispSet.count(BaseDecl);
// If the last field we laid out was a non-zero length bitfield then add
// some extra padding for no obvious reason.
if (LastFieldIsNonZeroWidthBitfield)
Size += CurrentBitfieldSize;
// Insert padding between two bases if the left first one is zero sized or
// contains a zero sized subobject and the right is zero sized or one leads
// with a zero sized base. The padding between virtual bases is 4
// bytes (in both 32 and 64 bits modes) and always involves rounding up to
// the required alignment, we don't know why.
if (PreviousBaseLayout && PreviousBaseLayout->hasZeroSizedSubObject() &&
BaseLayout.leadsWithZeroSizedBase())
Size = Size.RoundUpToAlignment(VtorDispAlignment) + VtorDispSize;
// Insert the vtordisp.
if (HasVtordisp)
Size = Size.RoundUpToAlignment(VtorDispAlignment) + VtorDispSize;
// Insert the virtual base.
ElementInfo Info = getAdjustedElementInfo(BaseLayout);
CharUnits BaseOffset = Size.RoundUpToAlignment(Info.Alignment);
VBases.insert(std::make_pair(BaseDecl,
ASTRecordLayout::VBaseInfo(BaseOffset, HasVtordisp)));
Size = BaseOffset + BaseLayout.getDataSize();
PreviousBaseLayout = &BaseLayout;
}
}
void MicrosoftRecordLayoutBuilder::finalizeLayout(const RecordDecl *RD) {
// Respect required alignment. Note that in 32-bit mode Required alignment
// may be 0 nad cause size not to be updated.
if (!RequiredAlignment.isZero()) {
Alignment = std::max(Alignment, RequiredAlignment);
Size = Size.RoundUpToAlignment(Alignment);
}
// Zero-sized structures have size equal to their alignment.
if (Size.isZero()) {
HasZeroSizedSubObject = true;
LeadsWithZeroSizedBase = true;
Size = Alignment;
}
}
static bool
RequiresVtordisp(const llvm::SmallPtrSet<const CXXRecordDecl *, 2> &HasVtordisp,
const CXXRecordDecl *RD) {
if (HasVtordisp.count(RD))
return true;
// If any of a virtual bases non-virtual bases (recursively) requires a
// vtordisp than so does this virtual base.
for (CXXRecordDecl::base_class_const_iterator i = RD->bases_begin(),
e = RD->bases_end();
i != e; ++i)
if (!i->isVirtual() &&
RequiresVtordisp(
HasVtordisp,
cast<CXXRecordDecl>(i->getType()->getAs<RecordType>()->getDecl())))
return true;
return false;
}
llvm::SmallPtrSet<const CXXRecordDecl *, 2>
MicrosoftRecordLayoutBuilder::computeVtorDispSet(const CXXRecordDecl *RD) {
llvm::SmallPtrSet<const CXXRecordDecl *, 2> HasVtordispSet;
// If any of our bases need a vtordisp for this type, so do we. Check our
// direct bases for vtordisp requirements.
for (CXXRecordDecl::base_class_const_iterator i = RD->bases_begin(),
e = RD->bases_end();
i != e; ++i) {
const CXXRecordDecl *BaseDecl =
cast<CXXRecordDecl>(i->getType()->getAs<RecordType>()->getDecl());
const ASTRecordLayout &Layout = Context.getASTRecordLayout(BaseDecl);
for (ASTRecordLayout::VBaseOffsetsMapTy::const_iterator
bi = Layout.getVBaseOffsetsMap().begin(),
be = Layout.getVBaseOffsetsMap().end();
bi != be; ++bi)
if (bi->second.hasVtorDisp())
HasVtordispSet.insert(bi->first);
}
// If we define a constructor or destructor and override a function that is
// defined in a virtual base's vtable, that virtual bases need a vtordisp.
// Here we collect a list of classes with vtables for which our virtual bases
// actually live. The virtual bases with this property will require
// vtordisps. In addition, virtual bases that contain non-virtual bases that
// define functions we override also require vtordisps, this case is checked
// explicitly below.
if (RD->hasUserDeclaredConstructor() || RD->hasUserDeclaredDestructor()) {
llvm::SmallPtrSet<const CXXMethodDecl *, 8> Work;
// Seed the working set with our non-destructor virtual methods.
for (CXXRecordDecl::method_iterator i = RD->method_begin(),
e = RD->method_end();
i != e; ++i)
if ((*i)->isVirtual() && !isa<CXXDestructorDecl>(*i))
Work.insert(*i);
while (!Work.empty()) {
const CXXMethodDecl *MD = *Work.begin();
CXXMethodDecl::method_iterator i = MD->begin_overridden_methods(),
e = MD->end_overridden_methods();
if (i == e)
// If a virtual method has no-overrides it lives in its parent's vtable.
HasVtordispSet.insert(MD->getParent());
else
Work.insert(i, e);
// We've finished processing this element, remove it from the working set.
Work.erase(MD);
}
}
// Re-check all of our vbases for vtordisp requirements (in case their
// non-virtual bases have vtordisp requirements).
for (CXXRecordDecl::base_class_const_iterator i = RD->vbases_begin(),
e = RD->vbases_end();
i != e; ++i) {
const CXXRecordDecl *BaseDecl = i->getType()->getAsCXXRecordDecl();
if (!HasVtordispSet.count(BaseDecl) &&
RequiresVtordisp(HasVtordispSet, BaseDecl))
HasVtordispSet.insert(BaseDecl);
}
return HasVtordispSet;
}
/// \brief Get or compute information about the layout of the specified record
/// (struct/union/class), which indicates its size and field position
/// information.
const ASTRecordLayout *
ASTContext::BuildMicrosoftASTRecordLayout(const RecordDecl *D) const {
MicrosoftRecordLayoutBuilder Builder(*this);
if (const CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(D)) {
Builder.cxxLayout(RD);
return new (*this) ASTRecordLayout(
*this, Builder.Size, Builder.Alignment, Builder.RequiredAlignment,
Builder.HasOwnVFPtr,
Builder.HasOwnVFPtr || Builder.PrimaryBase,
Builder.VBPtrOffset, Builder.DataSize, Builder.FieldOffsets.data(),
Builder.FieldOffsets.size(), Builder.DataSize,
Builder.Alignment, CharUnits::Zero(), Builder.PrimaryBase,
false, Builder.SharedVBPtrBase,
Builder.HasZeroSizedSubObject, Builder.LeadsWithZeroSizedBase,
Builder.Bases, Builder.VBases);
} else {
Builder.layout(D);
return new (*this) ASTRecordLayout(
*this, Builder.Size, Builder.Alignment, Builder.RequiredAlignment,
Builder.Size, Builder.FieldOffsets.data(), Builder.FieldOffsets.size());
}
}
/// getASTRecordLayout - Get or compute information about the layout of the
/// specified record (struct/union/class), which indicates its size and field
/// position information.
const ASTRecordLayout &
ASTContext::getASTRecordLayout(const RecordDecl *D) const {
// These asserts test different things. A record has a definition
// as soon as we begin to parse the definition. That definition is
// not a complete definition (which is what isDefinition() tests)
// until we *finish* parsing the definition.
if (D->hasExternalLexicalStorage() && !D->getDefinition())
getExternalSource()->CompleteType(const_cast<RecordDecl*>(D));
D = D->getDefinition();
assert(D && "Cannot get layout of forward declarations!");
assert(!D->isInvalidDecl() && "Cannot get layout of invalid decl!");
assert(D->isCompleteDefinition() && "Cannot layout type before complete!");
// Look up this layout, if already laid out, return what we have.
// Note that we can't save a reference to the entry because this function
// is recursive.
const ASTRecordLayout *Entry = ASTRecordLayouts[D];
if (Entry) return *Entry;
const ASTRecordLayout *NewEntry = 0;
if (isMsLayout(D) && !D->getASTContext().getExternalSource()) {
NewEntry = BuildMicrosoftASTRecordLayout(D);
} else if (const CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(D)) {
EmptySubobjectMap EmptySubobjects(*this, RD);
RecordLayoutBuilder Builder(*this, &EmptySubobjects);
Builder.Layout(RD);
// In certain situations, we are allowed to lay out objects in the
// tail-padding of base classes. This is ABI-dependent.
// FIXME: this should be stored in the record layout.
bool skipTailPadding =
mustSkipTailPadding(getTargetInfo().getCXXABI(), cast<CXXRecordDecl>(D));
// FIXME: This should be done in FinalizeLayout.
CharUnits DataSize =
skipTailPadding ? Builder.getSize() : Builder.getDataSize();
CharUnits NonVirtualSize =
skipTailPadding ? DataSize : Builder.NonVirtualSize;
NewEntry =
new (*this) ASTRecordLayout(*this, Builder.getSize(),
Builder.Alignment,
/*RequiredAlignment : used by MS-ABI)*/
Builder.Alignment,
Builder.HasOwnVFPtr,
RD->isDynamicClass(),
CharUnits::fromQuantity(-1),
DataSize,
Builder.FieldOffsets.data(),
Builder.FieldOffsets.size(),
NonVirtualSize,
Builder.NonVirtualAlignment,
EmptySubobjects.SizeOfLargestEmptySubobject,
Builder.PrimaryBase,
Builder.PrimaryBaseIsVirtual,
0, false, false,
Builder.Bases, Builder.VBases);
} else {
RecordLayoutBuilder Builder(*this, /*EmptySubobjects=*/0);
Builder.Layout(D);
NewEntry =
new (*this) ASTRecordLayout(*this, Builder.getSize(),
Builder.Alignment,
/*RequiredAlignment : used by MS-ABI)*/
Builder.Alignment,
Builder.getSize(),
Builder.FieldOffsets.data(),
Builder.FieldOffsets.size());
}
ASTRecordLayouts[D] = NewEntry;
if (getLangOpts().DumpRecordLayouts) {
llvm::outs() << "\n*** Dumping AST Record Layout\n";
DumpRecordLayout(D, llvm::outs(), getLangOpts().DumpRecordLayoutsSimple);
}
return *NewEntry;
}
const CXXMethodDecl *ASTContext::getCurrentKeyFunction(const CXXRecordDecl *RD) {
if (!getTargetInfo().getCXXABI().hasKeyFunctions())
return 0;
assert(RD->getDefinition() && "Cannot get key function for forward decl!");
RD = cast<CXXRecordDecl>(RD->getDefinition());
LazyDeclPtr &Entry = KeyFunctions[RD];
if (!Entry)
Entry = const_cast<CXXMethodDecl*>(computeKeyFunction(*this, RD));
return cast_or_null<CXXMethodDecl>(Entry.get(getExternalSource()));
}
void ASTContext::setNonKeyFunction(const CXXMethodDecl *Method) {
assert(Method == Method->getFirstDecl() &&
"not working with method declaration from class definition");
// Look up the cache entry. Since we're working with the first
// declaration, its parent must be the class definition, which is
// the correct key for the KeyFunctions hash.
llvm::DenseMap<const CXXRecordDecl*, LazyDeclPtr>::iterator
I = KeyFunctions.find(Method->getParent());
// If it's not cached, there's nothing to do.
if (I == KeyFunctions.end()) return;
// If it is cached, check whether it's the target method, and if so,
// remove it from the cache.
if (I->second.get(getExternalSource()) == Method) {
// FIXME: remember that we did this for module / chained PCH state?
KeyFunctions.erase(I);
}
}
static uint64_t getFieldOffset(const ASTContext &C, const FieldDecl *FD) {
const ASTRecordLayout &Layout = C.getASTRecordLayout(FD->getParent());
return Layout.getFieldOffset(FD->getFieldIndex());
}
uint64_t ASTContext::getFieldOffset(const ValueDecl *VD) const {
uint64_t OffsetInBits;
if (const FieldDecl *FD = dyn_cast<FieldDecl>(VD)) {
OffsetInBits = ::getFieldOffset(*this, FD);
} else {
const IndirectFieldDecl *IFD = cast<IndirectFieldDecl>(VD);
OffsetInBits = 0;
for (IndirectFieldDecl::chain_iterator CI = IFD->chain_begin(),
CE = IFD->chain_end();
CI != CE; ++CI)
OffsetInBits += ::getFieldOffset(*this, cast<FieldDecl>(*CI));
}
return OffsetInBits;
}
/// getObjCLayout - Get or compute information about the layout of the
/// given interface.
///
/// \param Impl - If given, also include the layout of the interface's
/// implementation. This may differ by including synthesized ivars.
const ASTRecordLayout &
ASTContext::getObjCLayout(const ObjCInterfaceDecl *D,
const ObjCImplementationDecl *Impl) const {
// Retrieve the definition
if (D->hasExternalLexicalStorage() && !D->getDefinition())
getExternalSource()->CompleteType(const_cast<ObjCInterfaceDecl*>(D));
D = D->getDefinition();
assert(D && D->isThisDeclarationADefinition() && "Invalid interface decl!");
// Look up this layout, if already laid out, return what we have.
const ObjCContainerDecl *Key =
Impl ? (const ObjCContainerDecl*) Impl : (const ObjCContainerDecl*) D;
if (const ASTRecordLayout *Entry = ObjCLayouts[Key])
return *Entry;
// Add in synthesized ivar count if laying out an implementation.
if (Impl) {
unsigned SynthCount = CountNonClassIvars(D);
// If there aren't any sythesized ivars then reuse the interface
// entry. Note we can't cache this because we simply free all
// entries later; however we shouldn't look up implementations
// frequently.
if (SynthCount == 0)
return getObjCLayout(D, 0);
}
RecordLayoutBuilder Builder(*this, /*EmptySubobjects=*/0);
Builder.Layout(D);
const ASTRecordLayout *NewEntry =
new (*this) ASTRecordLayout(*this, Builder.getSize(),
Builder.Alignment,
/*RequiredAlignment : used by MS-ABI)*/
Builder.Alignment,
Builder.getDataSize(),
Builder.FieldOffsets.data(),
Builder.FieldOffsets.size());
ObjCLayouts[Key] = NewEntry;
return *NewEntry;
}
static void PrintOffset(raw_ostream &OS,
CharUnits Offset, unsigned IndentLevel) {
OS << llvm::format("%4" PRId64 " | ", (int64_t)Offset.getQuantity());
OS.indent(IndentLevel * 2);
}
static void PrintIndentNoOffset(raw_ostream &OS, unsigned IndentLevel) {
OS << " | ";
OS.indent(IndentLevel * 2);
}
static void DumpCXXRecordLayout(raw_ostream &OS,
const CXXRecordDecl *RD, const ASTContext &C,
CharUnits Offset,
unsigned IndentLevel,
const char* Description,
bool IncludeVirtualBases) {
const ASTRecordLayout &Layout = C.getASTRecordLayout(RD);
PrintOffset(OS, Offset, IndentLevel);
OS << C.getTypeDeclType(const_cast<CXXRecordDecl *>(RD)).getAsString();
if (Description)
OS << ' ' << Description;
if (RD->isEmpty())
OS << " (empty)";
OS << '\n';
IndentLevel++;
const CXXRecordDecl *PrimaryBase = Layout.getPrimaryBase();
bool HasOwnVFPtr = Layout.hasOwnVFPtr();
bool HasOwnVBPtr = Layout.hasOwnVBPtr();
// Vtable pointer.
if (RD->isDynamicClass() && !PrimaryBase && !isMsLayout(RD)) {
PrintOffset(OS, Offset, IndentLevel);
OS << '(' << *RD << " vtable pointer)\n";
} else if (HasOwnVFPtr) {
PrintOffset(OS, Offset, IndentLevel);
// vfptr (for Microsoft C++ ABI)
OS << '(' << *RD << " vftable pointer)\n";
}
// Dump (non-virtual) bases
for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
E = RD->bases_end(); I != E; ++I) {
assert(!I->getType()->isDependentType() &&
"Cannot layout class with dependent bases.");
if (I->isVirtual())
continue;
const CXXRecordDecl *Base =
cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
CharUnits BaseOffset = Offset + Layout.getBaseClassOffset(Base);
DumpCXXRecordLayout(OS, Base, C, BaseOffset, IndentLevel,
Base == PrimaryBase ? "(primary base)" : "(base)",
/*IncludeVirtualBases=*/false);
}
// vbptr (for Microsoft C++ ABI)
if (HasOwnVBPtr) {
PrintOffset(OS, Offset + Layout.getVBPtrOffset(), IndentLevel);
OS << '(' << *RD << " vbtable pointer)\n";
}
// Dump fields.
uint64_t FieldNo = 0;
for (CXXRecordDecl::field_iterator I = RD->field_begin(),
E = RD->field_end(); I != E; ++I, ++FieldNo) {
const FieldDecl &Field = **I;
CharUnits FieldOffset = Offset +
C.toCharUnitsFromBits(Layout.getFieldOffset(FieldNo));
if (const RecordType *RT = Field.getType()->getAs<RecordType>()) {
if (const CXXRecordDecl *D = dyn_cast<CXXRecordDecl>(RT->getDecl())) {
DumpCXXRecordLayout(OS, D, C, FieldOffset, IndentLevel,
Field.getName().data(),
/*IncludeVirtualBases=*/true);
continue;
}
}
PrintOffset(OS, FieldOffset, IndentLevel);
OS << Field.getType().getAsString() << ' ' << Field << '\n';
}
if (!IncludeVirtualBases)
return;
// Dump virtual bases.
const ASTRecordLayout::VBaseOffsetsMapTy &vtordisps =
Layout.getVBaseOffsetsMap();
for (CXXRecordDecl::base_class_const_iterator I = RD->vbases_begin(),
E = RD->vbases_end(); I != E; ++I) {
assert(I->isVirtual() && "Found non-virtual class!");
const CXXRecordDecl *VBase =
cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
CharUnits VBaseOffset = Offset + Layout.getVBaseClassOffset(VBase);
if (vtordisps.find(VBase)->second.hasVtorDisp()) {
PrintOffset(OS, VBaseOffset - CharUnits::fromQuantity(4), IndentLevel);
OS << "(vtordisp for vbase " << *VBase << ")\n";
}
DumpCXXRecordLayout(OS, VBase, C, VBaseOffset, IndentLevel,
VBase == PrimaryBase ?
"(primary virtual base)" : "(virtual base)",
/*IncludeVirtualBases=*/false);
}
PrintIndentNoOffset(OS, IndentLevel - 1);
OS << "[sizeof=" << Layout.getSize().getQuantity();
if (!isMsLayout(RD))
OS << ", dsize=" << Layout.getDataSize().getQuantity();
OS << ", align=" << Layout.getAlignment().getQuantity() << '\n';
PrintIndentNoOffset(OS, IndentLevel - 1);
OS << " nvsize=" << Layout.getNonVirtualSize().getQuantity();
OS << ", nvalign=" << Layout.getNonVirtualAlignment().getQuantity() << "]\n";
OS << '\n';
}
void ASTContext::DumpRecordLayout(const RecordDecl *RD,
raw_ostream &OS,
bool Simple) const {
const ASTRecordLayout &Info = getASTRecordLayout(RD);
if (const CXXRecordDecl *CXXRD = dyn_cast<CXXRecordDecl>(RD))
if (!Simple)
return DumpCXXRecordLayout(OS, CXXRD, *this, CharUnits(), 0, 0,
/*IncludeVirtualBases=*/true);
OS << "Type: " << getTypeDeclType(RD).getAsString() << "\n";
if (!Simple) {
OS << "Record: ";
RD->dump();
}
OS << "\nLayout: ";
OS << "<ASTRecordLayout\n";
OS << " Size:" << toBits(Info.getSize()) << "\n";
if (!isMsLayout(RD))
OS << " DataSize:" << toBits(Info.getDataSize()) << "\n";
OS << " Alignment:" << toBits(Info.getAlignment()) << "\n";
OS << " FieldOffsets: [";
for (unsigned i = 0, e = Info.getFieldCount(); i != e; ++i) {
if (i) OS << ", ";
OS << Info.getFieldOffset(i);
}
OS << "]>\n";
}
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