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

1003 lines
33 KiB
C++

//=== ASTRecordLayoutBuilder.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 "RecordLayoutBuilder.h"
#include "clang/AST/Attr.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 "llvm/Support/Format.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/Support/MathExtras.h"
using namespace clang;
ASTRecordLayoutBuilder::ASTRecordLayoutBuilder(ASTContext &Context)
: Context(Context), Size(0), Alignment(8), Packed(false),
UnfilledBitsInLastByte(0), MaxFieldAlignment(0), DataSize(0), IsUnion(false),
NonVirtualSize(0), NonVirtualAlignment(8), FirstNearlyEmptyVBase(0) { }
/// IsNearlyEmpty - Indicates when a class has a vtable pointer, but
/// no other data.
bool ASTRecordLayoutBuilder::IsNearlyEmpty(const CXXRecordDecl *RD) const {
// FIXME: Audit the corners
if (!RD->isDynamicClass())
return false;
const ASTRecordLayout &BaseInfo = Context.getASTRecordLayout(RD);
if (BaseInfo.getNonVirtualSize() == Context.Target.getPointerWidth(0))
return true;
return false;
}
void ASTRecordLayoutBuilder::IdentifyPrimaryBases(const CXXRecordDecl *RD) {
const ASTRecordLayout::PrimaryBaseInfo &BaseInfo =
Context.getASTRecordLayout(RD).getPrimaryBaseInfo();
// If the record has a primary base class that is virtual, add it to the set
// of primary bases.
if (BaseInfo.isVirtual())
IndirectPrimaryBases.insert(BaseInfo.getBase());
// Now traverse all bases and find primary bases for them.
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());
// Only bases with virtual bases participate in computing the
// indirect primary virtual base classes.
if (Base->getNumVBases())
IdentifyPrimaryBases(Base);
}
}
void
ASTRecordLayoutBuilder::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() && IsNearlyEmpty(Base)) {
// If it's not an indirect primary base, then we've found our primary
// base.
if (!IndirectPrimaryBases.count(Base)) {
PrimaryBase = ASTRecordLayout::PrimaryBaseInfo(Base,
/*IsVirtual=*/true);
return;
}
// Is this the first nearly empty virtual base?
if (!FirstNearlyEmptyVBase)
FirstNearlyEmptyVBase = Base;
}
SelectPrimaryVBase(Base);
if (PrimaryBase.getBase())
return;
}
}
/// DeterminePrimaryBase - Determine the primary base of the given class.
void ASTRecordLayoutBuilder::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.
for (CXXRecordDecl::base_class_const_iterator i = RD->bases_begin(),
e = RD->bases_end(); i != e; ++i) {
assert(!i->getType()->isDependentType() &&
"Cannot lay out class with dependent bases.");
const CXXRecordDecl *Base =
cast<CXXRecordDecl>(i->getType()->getAs<RecordType>()->getDecl());
IdentifyPrimaryBases(Base);
}
// 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 = ASTRecordLayout::PrimaryBaseInfo(Base, /*IsVirtual=*/false);
return;
}
}
// Otherwise, it 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.getBase())
return;
}
// Otherwise, it is the first nearly empty virtual base that is not an
// indirect primary virtual base class, if one exists.
if (FirstNearlyEmptyVBase) {
PrimaryBase = ASTRecordLayout::PrimaryBaseInfo(FirstNearlyEmptyVBase,
/*IsVirtual=*/true);
return;
}
// Otherwise there is no primary base class.
assert(!PrimaryBase.getBase() && "Should not get here with a primary base!");
// Allocate the virtual table pointer at offset zero.
assert(DataSize == 0 && "Vtable pointer must be at offset zero!");
// Update the size.
Size += Context.Target.getPointerWidth(0);
DataSize = Size;
// Update the alignment.
UpdateAlignment(Context.Target.getPointerAlign(0));
}
void
ASTRecordLayoutBuilder::LayoutNonVirtualBases(const CXXRecordDecl *RD) {
// First, determine the primary base class.
DeterminePrimaryBase(RD);
// If we have a primary base class, lay it out.
if (const CXXRecordDecl *Base = PrimaryBase.getBase()) {
if (PrimaryBase.isVirtual()) {
// We have a virtual primary base, insert it as an indirect primary base.
IndirectPrimaryBases.insert(Base);
assert(!VisitedVirtualBases.count(Base) && "vbase already visited!");
VisitedVirtualBases.insert(Base);
LayoutVirtualBase(Base);
} else
LayoutNonVirtualBase(Base);
}
// 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 *Base =
cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
// Skip the primary base.
if (Base == PrimaryBase.getBase() && !PrimaryBase.isVirtual())
continue;
// Lay out the base.
LayoutNonVirtualBase(Base);
}
}
void ASTRecordLayoutBuilder::LayoutNonVirtualBase(const CXXRecordDecl *RD) {
// Layout the base.
uint64_t Offset = LayoutBase(RD);
// Add its base class offset.
if (!Bases.insert(std::make_pair(RD, Offset)).second)
assert(false && "Added same base offset more than once!");
}
void
ASTRecordLayoutBuilder::AddPrimaryVirtualBaseOffsets(const CXXRecordDecl *RD,
uint64_t Offset,
const CXXRecordDecl *MostDerivedClass) {
// We already have the offset for the primary base of the most derived class.
if (RD != MostDerivedClass) {
const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
const CXXRecordDecl *PrimaryBase = Layout.getPrimaryBase();
// If this is a primary virtual base and we haven't seen it before, add it.
if (PrimaryBase && Layout.getPrimaryBaseWasVirtual() &&
!VBases.count(PrimaryBase))
VBases.insert(std::make_pair(PrimaryBase, Offset));
}
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 =
cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
if (!BaseDecl->getNumVBases()) {
// This base isn't interesting since it doesn't have any virtual bases.
continue;
}
// Compute the offset of this base.
uint64_t BaseOffset;
if (I->isVirtual()) {
// If we don't know this vbase yet, don't visit it. It will be visited
// later.
if (!VBases.count(BaseDecl)) {
continue;
}
// Check if we've already visited this base.
if (!VisitedVirtualBases.insert(BaseDecl))
continue;
// We want the vbase offset from the class we're currently laying out.
BaseOffset = VBases[BaseDecl];
} else if (RD == MostDerivedClass) {
// We want the base offset from the class we're currently laying out.
assert(Bases.count(BaseDecl) && "Did not find base!");
BaseOffset = Bases[BaseDecl];
} else {
const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
BaseOffset = Offset + Layout.getBaseClassOffset(BaseDecl);
}
AddPrimaryVirtualBaseOffsets(BaseDecl, BaseOffset, MostDerivedClass);
}
}
void
ASTRecordLayoutBuilder::LayoutVirtualBases(const CXXRecordDecl *RD,
const CXXRecordDecl *MostDerivedClass) {
const CXXRecordDecl *PrimaryBase;
bool PrimaryBaseIsVirtual;
if (MostDerivedClass == RD) {
PrimaryBase = this->PrimaryBase.getBase();
PrimaryBaseIsVirtual = this->PrimaryBase.isVirtual();
} else {
const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
PrimaryBase = Layout.getPrimaryBase();
PrimaryBaseIsVirtual = Layout.getPrimaryBaseWasVirtual();
}
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());
if (I->isVirtual()) {
if (PrimaryBase != Base || !PrimaryBaseIsVirtual) {
bool IndirectPrimaryBase = IndirectPrimaryBases.count(Base);
// Only lay out the virtual base if it's not an indirect primary base.
if (!IndirectPrimaryBase) {
// Only visit virtual bases once.
if (!VisitedVirtualBases.insert(Base))
continue;
LayoutVirtualBase(Base);
}
}
}
if (!Base->getNumVBases()) {
// This base isn't interesting since it doesn't have any virtual bases.
continue;
}
LayoutVirtualBases(Base, MostDerivedClass);
}
}
void ASTRecordLayoutBuilder::LayoutVirtualBase(const CXXRecordDecl *RD) {
// Layout the base.
uint64_t Offset = LayoutBase(RD);
// Add its base class offset.
if (!VBases.insert(std::make_pair(RD, Offset)).second)
assert(false && "Added same vbase offset more than once!");
}
uint64_t ASTRecordLayoutBuilder::LayoutBase(const CXXRecordDecl *RD) {
const ASTRecordLayout &BaseInfo = Context.getASTRecordLayout(RD);
// If we have an empty base class, try to place it at offset 0.
if (RD->isEmpty() && canPlaceRecordAtOffset(RD, 0)) {
// We were able to place the class at offset 0.
UpdateEmptyClassOffsets(RD, 0);
Size = std::max(Size, BaseInfo.getSize());
return 0;
}
unsigned BaseAlign = BaseInfo.getNonVirtualAlign();
// Round up the current record size to the base's alignment boundary.
uint64_t Offset = llvm::RoundUpToAlignment(DataSize, BaseAlign);
// Try to place the base.
while (true) {
if (canPlaceRecordAtOffset(RD, Offset))
break;
Offset += BaseAlign;
}
if (!RD->isEmpty()) {
// Update the data size.
DataSize = Offset + BaseInfo.getNonVirtualSize();
Size = std::max(Size, DataSize);
} else
Size = std::max(Size, Offset + BaseInfo.getSize());
// Remember max struct/class alignment.
UpdateAlignment(BaseAlign);
UpdateEmptyClassOffsets(RD, Offset);
return Offset;
}
bool ASTRecordLayoutBuilder::canPlaceRecordAtOffset(const CXXRecordDecl *RD,
uint64_t Offset) const {
// Look for an empty class with the same type at the same offset.
for (EmptyClassOffsetsTy::const_iterator I =
EmptyClassOffsets.lower_bound(Offset),
E = EmptyClassOffsets.upper_bound(Offset); I != E; ++I) {
if (I->second == RD)
return false;
}
const ASTRecordLayout &Info = Context.getASTRecordLayout(RD);
// Check 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());
uint64_t BaseClassOffset = Info.getBaseClassOffset(Base);
if (!canPlaceRecordAtOffset(Base, Offset + BaseClassOffset))
return false;
}
// Check fields.
unsigned FieldNo = 0;
for (CXXRecordDecl::field_iterator I = RD->field_begin(), E = RD->field_end();
I != E; ++I, ++FieldNo) {
const FieldDecl *FD = *I;
uint64_t FieldOffset = Info.getFieldOffset(FieldNo);
if (!canPlaceFieldAtOffset(FD, Offset + FieldOffset))
return false;
}
// FIXME: virtual bases.
return true;
}
bool ASTRecordLayoutBuilder::canPlaceFieldAtOffset(const FieldDecl *FD,
uint64_t Offset) const {
QualType T = FD->getType();
if (const RecordType *RT = T->getAs<RecordType>()) {
if (const CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(RT->getDecl()))
return canPlaceRecordAtOffset(RD, Offset);
}
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 = dyn_cast<CXXRecordDecl>(RT->getDecl());
if (!RD)
return true;
const ASTRecordLayout &Info = Context.getASTRecordLayout(RD);
uint64_t NumElements = Context.getConstantArrayElementCount(AT);
uint64_t ElementOffset = Offset;
for (uint64_t I = 0; I != NumElements; ++I) {
if (!canPlaceRecordAtOffset(RD, ElementOffset))
return false;
ElementOffset += Info.getSize();
}
}
return true;
}
void ASTRecordLayoutBuilder::UpdateEmptyClassOffsets(const CXXRecordDecl *RD,
uint64_t Offset) {
if (RD->isEmpty())
EmptyClassOffsets.insert(std::make_pair(Offset, RD));
const ASTRecordLayout &Info = Context.getASTRecordLayout(RD);
// Update 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());
uint64_t BaseClassOffset = Info.getBaseClassOffset(Base);
UpdateEmptyClassOffsets(Base, Offset + BaseClassOffset);
}
// Update fields.
unsigned FieldNo = 0;
for (CXXRecordDecl::field_iterator I = RD->field_begin(), E = RD->field_end();
I != E; ++I, ++FieldNo) {
const FieldDecl *FD = *I;
uint64_t FieldOffset = Info.getFieldOffset(FieldNo);
UpdateEmptyClassOffsets(FD, Offset + FieldOffset);
}
// FIXME: Update virtual bases.
}
void
ASTRecordLayoutBuilder::UpdateEmptyClassOffsets(const FieldDecl *FD,
uint64_t Offset) {
QualType T = FD->getType();
if (const RecordType *RT = T->getAs<RecordType>()) {
if (const CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(RT->getDecl())) {
UpdateEmptyClassOffsets(RD, Offset);
return;
}
}
if (const ConstantArrayType *AT = Context.getAsConstantArrayType(T)) {
QualType ElemTy = Context.getBaseElementType(AT);
const RecordType *RT = ElemTy->getAs<RecordType>();
if (!RT)
return;
const CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(RT->getDecl());
if (!RD)
return;
const ASTRecordLayout &Info = Context.getASTRecordLayout(RD);
uint64_t NumElements = Context.getConstantArrayElementCount(AT);
uint64_t ElementOffset = Offset;
for (uint64_t I = 0; I != NumElements; ++I) {
UpdateEmptyClassOffsets(RD, ElementOffset);
ElementOffset += Info.getSize();
}
}
}
void ASTRecordLayoutBuilder::Layout(const RecordDecl *D) {
IsUnion = D->isUnion();
Packed = D->hasAttr<PackedAttr>();
// The #pragma pack attribute specifies the maximum field alignment.
if (const PragmaPackAttr *PPA = D->getAttr<PragmaPackAttr>())
MaxFieldAlignment = PPA->getAlignment();
if (const AlignedAttr *AA = D->getAttr<AlignedAttr>())
UpdateAlignment(AA->getMaxAlignment());
// If this is a C++ class, lay out the vtable and the non-virtual bases.
const CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(D);
if (RD)
LayoutNonVirtualBases(RD);
LayoutFields(D);
NonVirtualSize = Size;
NonVirtualAlignment = Alignment;
// If this is a C++ class, lay out its virtual bases and add its primary
// virtual base offsets.
if (RD) {
LayoutVirtualBases(RD, RD);
VisitedVirtualBases.clear();
AddPrimaryVirtualBaseOffsets(RD, 0, RD);
}
// Finally, round the size of the total struct up to the alignment of the
// struct itself.
FinishLayout();
#ifndef NDEBUG
if (RD) {
// 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
}
// FIXME. Impl is no longer needed.
void ASTRecordLayoutBuilder::Layout(const ObjCInterfaceDecl *D,
const ObjCImplementationDecl *Impl) {
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.
Size = llvm::RoundUpToAlignment(SL.getDataSize(), 8);
DataSize = Size;
}
Packed = D->hasAttr<PackedAttr>();
// The #pragma pack attribute specifies the maximum field alignment.
if (const PragmaPackAttr *PPA = D->getAttr<PragmaPackAttr>())
MaxFieldAlignment = PPA->getAlignment();
if (const AlignedAttr *AA = D->getAttr<AlignedAttr>())
UpdateAlignment(AA->getMaxAlignment());
// Layout each ivar sequentially.
llvm::SmallVector<ObjCIvarDecl*, 16> Ivars;
Context.ShallowCollectObjCIvars(D, Ivars);
for (unsigned i = 0, e = Ivars.size(); i != e; ++i)
LayoutField(Ivars[i]);
// Finally, round the size of the total struct up to the alignment of the
// struct itself.
FinishLayout();
}
void ASTRecordLayoutBuilder::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 ASTRecordLayoutBuilder::LayoutWideBitField(uint64_t FieldSize,
uint64_t TypeSize) {
assert(Context.getLangOptions().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!");
unsigned TypeAlign = Context.getTypeAlign(Type);
// We're not going to use any of the unfilled bits in the last byte.
UnfilledBitsInLastByte = 0;
// The bitfield is allocated starting at the next offset aligned appropriately
// for T', with length n bits.
uint64_t FieldOffset = llvm::RoundUpToAlignment(DataSize, TypeAlign);
if (IsUnion) {
DataSize = std::max(DataSize, FieldSize);
} else {
uint64_t NewSizeInBits = FieldOffset + FieldSize;
DataSize = llvm::RoundUpToAlignment(NewSizeInBits, 8);
UnfilledBitsInLastByte = DataSize - NewSizeInBits;
}
// Place this field at the current location.
FieldOffsets.push_back(FieldOffset);
// Update the size.
Size = std::max(Size, DataSize);
// Remember max struct/class alignment.
UpdateAlignment(TypeAlign);
}
void ASTRecordLayoutBuilder::LayoutBitField(const FieldDecl *D) {
bool FieldPacked = Packed || D->hasAttr<PackedAttr>();
uint64_t FieldOffset = IsUnion ? 0 : (DataSize - UnfilledBitsInLastByte);
uint64_t FieldSize = D->getBitWidth()->EvaluateAsInt(Context).getZExtValue();
std::pair<uint64_t, unsigned> FieldInfo = Context.getTypeInfo(D->getType());
uint64_t TypeSize = FieldInfo.first;
unsigned FieldAlign = FieldInfo.second;
if (FieldSize > TypeSize) {
LayoutWideBitField(FieldSize, TypeSize);
return;
}
if (FieldPacked || !Context.Target.useBitFieldTypeAlignment())
FieldAlign = 1;
if (const AlignedAttr *AA = D->getAttr<AlignedAttr>())
FieldAlign = std::max(FieldAlign, AA->getMaxAlignment());
// The maximum field alignment overrides the aligned attribute.
if (MaxFieldAlignment)
FieldAlign = std::min(FieldAlign, MaxFieldAlignment);
// Check if we need to add padding to give the field the correct alignment.
if (FieldSize == 0 || (FieldOffset & (FieldAlign-1)) + FieldSize > TypeSize)
FieldOffset = (FieldOffset + (FieldAlign-1)) & ~(FieldAlign-1);
// Padding members don't affect overall alignment.
if (!D->getIdentifier())
FieldAlign = 1;
// Place this field at the current location.
FieldOffsets.push_back(FieldOffset);
// Update DataSize to include the last byte containing (part of) the bitfield.
if (IsUnion) {
// FIXME: I think FieldSize should be TypeSize here.
DataSize = std::max(DataSize, FieldSize);
} else {
uint64_t NewSizeInBits = FieldOffset + FieldSize;
DataSize = llvm::RoundUpToAlignment(NewSizeInBits, 8);
UnfilledBitsInLastByte = DataSize - NewSizeInBits;
}
// Update the size.
Size = std::max(Size, DataSize);
// Remember max struct/class alignment.
UpdateAlignment(FieldAlign);
}
void ASTRecordLayoutBuilder::LayoutField(const FieldDecl *D) {
if (D->isBitField()) {
LayoutBitField(D);
return;
}
// Reset the unfilled bits.
UnfilledBitsInLastByte = 0;
bool FieldPacked = Packed || D->hasAttr<PackedAttr>();
uint64_t FieldOffset = IsUnion ? 0 : DataSize;
uint64_t FieldSize;
unsigned 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 = 0;
const ArrayType* ATy = Context.getAsArrayType(D->getType());
FieldAlign = Context.getTypeAlign(ATy->getElementType());
} else if (const ReferenceType *RT = D->getType()->getAs<ReferenceType>()) {
unsigned AS = RT->getPointeeType().getAddressSpace();
FieldSize = Context.Target.getPointerWidth(AS);
FieldAlign = Context.Target.getPointerAlign(AS);
} else {
std::pair<uint64_t, unsigned> FieldInfo = Context.getTypeInfo(D->getType());
FieldSize = FieldInfo.first;
FieldAlign = FieldInfo.second;
}
if (FieldPacked)
FieldAlign = 8;
if (const AlignedAttr *AA = D->getAttr<AlignedAttr>())
FieldAlign = std::max(FieldAlign, AA->getMaxAlignment());
// The maximum field alignment overrides the aligned attribute.
if (MaxFieldAlignment)
FieldAlign = std::min(FieldAlign, MaxFieldAlignment);
// Round up the current record size to the field's alignment boundary.
FieldOffset = llvm::RoundUpToAlignment(FieldOffset, FieldAlign);
if (!IsUnion) {
while (true) {
// Check if we can place the field at this offset.
if (canPlaceFieldAtOffset(D, FieldOffset))
break;
// We couldn't place the field at the offset. Try again at a new offset.
FieldOffset += FieldAlign;
}
UpdateEmptyClassOffsets(D, FieldOffset);
}
// Place this field at the current location.
FieldOffsets.push_back(FieldOffset);
// Reserve space for this field.
if (IsUnion)
Size = std::max(Size, FieldSize);
else
Size = FieldOffset + FieldSize;
// Update the data size.
DataSize = Size;
// Remember max struct/class alignment.
UpdateAlignment(FieldAlign);
}
void ASTRecordLayoutBuilder::FinishLayout() {
// In C++, records cannot be of size 0.
if (Context.getLangOptions().CPlusPlus && Size == 0)
Size = 8;
// Finally, round the size of the record up to the alignment of the
// record itself.
Size = llvm::RoundUpToAlignment(Size, Alignment);
}
void ASTRecordLayoutBuilder::UpdateAlignment(unsigned NewAlignment) {
if (NewAlignment <= Alignment)
return;
assert(llvm::isPowerOf2_32(NewAlignment && "Alignment not a power of 2"));
Alignment = NewAlignment;
}
const ASTRecordLayout *
ASTRecordLayoutBuilder::ComputeLayout(ASTContext &Ctx,
const RecordDecl *D) {
ASTRecordLayoutBuilder Builder(Ctx);
Builder.Layout(D);
if (!isa<CXXRecordDecl>(D))
return new (Ctx) ASTRecordLayout(Ctx, Builder.Size, Builder.Alignment,
Builder.Size,
Builder.FieldOffsets.data(),
Builder.FieldOffsets.size());
// FIXME: This is not always correct. See the part about bitfields at
// http://www.codesourcery.com/public/cxx-abi/abi.html#POD for more info.
// FIXME: IsPODForThePurposeOfLayout should be stored in the record layout.
bool IsPODForThePurposeOfLayout = cast<CXXRecordDecl>(D)->isPOD();
// FIXME: This should be done in FinalizeLayout.
uint64_t DataSize =
IsPODForThePurposeOfLayout ? Builder.Size : Builder.DataSize;
uint64_t NonVirtualSize =
IsPODForThePurposeOfLayout ? DataSize : Builder.NonVirtualSize;
return new (Ctx) ASTRecordLayout(Ctx, Builder.Size, Builder.Alignment,
DataSize, Builder.FieldOffsets.data(),
Builder.FieldOffsets.size(),
NonVirtualSize,
Builder.NonVirtualAlignment,
Builder.PrimaryBase,
Builder.Bases, Builder.VBases);
}
const ASTRecordLayout *
ASTRecordLayoutBuilder::ComputeLayout(ASTContext &Ctx,
const ObjCInterfaceDecl *D,
const ObjCImplementationDecl *Impl) {
ASTRecordLayoutBuilder Builder(Ctx);
Builder.Layout(D, Impl);
return new (Ctx) ASTRecordLayout(Ctx, Builder.Size, Builder.Alignment,
Builder.DataSize,
Builder.FieldOffsets.data(),
Builder.FieldOffsets.size());
}
const CXXMethodDecl *
ASTRecordLayoutBuilder::ComputeKeyFunction(const CXXRecordDecl *RD) {
assert(RD->isDynamicClass() && "Class does not have any virtual methods!");
// If a class isnt' polymorphic it doesn't have a key function.
if (!RD->isPolymorphic())
return 0;
// A class inside an anonymous namespace 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->isInAnonymousNamespace())
return 0;
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;
// We found it.
return MD;
}
return 0;
}
static void PrintOffset(llvm::raw_ostream &OS,
uint64_t Offset, unsigned IndentLevel) {
OS << llvm::format("%4d | ", Offset);
OS.indent(IndentLevel * 2);
}
static void DumpCXXRecordLayout(llvm::raw_ostream &OS,
const CXXRecordDecl *RD, ASTContext &C,
uint64_t Offset,
unsigned IndentLevel,
const char* Description,
bool IncludeVirtualBases) {
const ASTRecordLayout &Info = C.getASTRecordLayout(RD);
PrintOffset(OS, Offset, IndentLevel);
OS << C.getTypeDeclType((CXXRecordDecl *)RD).getAsString();
if (Description)
OS << ' ' << Description;
if (RD->isEmpty())
OS << " (empty)";
OS << '\n';
IndentLevel++;
const CXXRecordDecl *PrimaryBase = Info.getPrimaryBase();
// Vtable pointer.
if (RD->isDynamicClass() && !PrimaryBase) {
PrintOffset(OS, Offset, IndentLevel);
OS << '(' << RD->getNameAsString() << " vtable 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());
uint64_t BaseOffset = Offset + Info.getBaseClassOffset(Base) / 8;
DumpCXXRecordLayout(OS, Base, C, BaseOffset, IndentLevel,
Base == PrimaryBase ? "(primary base)" : "(base)",
/*IncludeVirtualBases=*/false);
}
// 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;
uint64_t FieldOffset = Offset + Info.getFieldOffset(FieldNo) / 8;
if (const RecordType *RT = Field->getType()->getAs<RecordType>()) {
if (const CXXRecordDecl *D = dyn_cast<CXXRecordDecl>(RT->getDecl())) {
DumpCXXRecordLayout(OS, D, C, FieldOffset, IndentLevel,
Field->getNameAsCString(),
/*IncludeVirtualBases=*/true);
continue;
}
}
PrintOffset(OS, FieldOffset, IndentLevel);
OS << Field->getType().getAsString() << ' ';
OS << Field->getNameAsString() << '\n';
}
if (!IncludeVirtualBases)
return;
// Dump virtual bases.
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());
uint64_t VBaseOffset = Offset + Info.getVBaseClassOffset(VBase) / 8;
DumpCXXRecordLayout(OS, VBase, C, VBaseOffset, IndentLevel,
VBase == PrimaryBase ?
"(primary virtual base)" : "(virtual base)",
/*IncludeVirtualBases=*/false);
}
}
void ASTContext::DumpRecordLayout(const RecordDecl *RD,
llvm::raw_ostream &OS) {
const ASTRecordLayout &Info = getASTRecordLayout(RD);
if (const CXXRecordDecl *CXXRD = dyn_cast<CXXRecordDecl>(RD))
DumpCXXRecordLayout(OS, CXXRD, *this, 0, 0, 0,
/*IncludeVirtualBases=*/true);
else
OS << getTypeDeclType(RD).getAsString();
OS << " sizeof=" << Info.getSize() / 8;
OS << ", dsize=" << Info.getDataSize() / 8;
OS << ", align=" << Info.getAlignment() / 8 << '\n';
OS << " nvsize=" << Info.getNonVirtualSize() / 8;
OS << ", nvalign=" << Info.getNonVirtualAlign() / 8 << '\n';
OS << '\n';
}