void CGRecordLowering::insertPadding() {
std::vector<std::pair<CharUnits, CharUnits> > Padding;
CharUnits Size = CharUnits::Zero();
for (std::vector<MemberInfo>::const_iterator Member = Members.begin(),
MemberEnd = Members.end();
Member != MemberEnd; ++Member) {
if (!Member->Data)
continue;
CharUnits Offset = Member->Offset;
assert(Offset >= Size);
// Insert padding if we need to.
if (Offset != Size.RoundUpToAlignment(Packed ? CharUnits::One() :
getAlignment(Member->Data)))
Padding.push_back(std::make_pair(Size, Offset - Size));
Size = Offset + getSize(Member->Data);
}
if (Padding.empty())
return;
// Add the padding to the Members list and sort it.
for (std::vector<std::pair<CharUnits, CharUnits> >::const_iterator
Pad = Padding.begin(), PadEnd = Padding.end();
Pad != PadEnd; ++Pad)
Members.push_back(StorageInfo(Pad->first, getByteArrayType(Pad->second)));
std::stable_sort(Members.begin(), Members.end());
}
bool
CGRecordLayoutBuilder::ComputeNonVirtualBaseType(const CXXRecordDecl *RD) {
const ASTRecordLayout &Layout = Types.getContext().getASTRecordLayout(RD);
CharUnits NonVirtualSize = Layout.getNonVirtualSize();
CharUnits NonVirtualAlign = Layout.getNonVirtualAlign();
CharUnits AlignedNonVirtualTypeSize =
NonVirtualSize.RoundUpToAlignment(NonVirtualAlign);
// First check if we can use the same fields as for the complete class.
CharUnits RecordSize = Layout.getSize();
if (AlignedNonVirtualTypeSize == RecordSize)
return true;
// Check if we need padding.
CharUnits AlignedNextFieldOffset =
NextFieldOffset.RoundUpToAlignment(getAlignmentAsLLVMStruct());
if (AlignedNextFieldOffset > AlignedNonVirtualTypeSize) {
assert(!Packed && "cannot layout even as packed struct");
return false; // Needs packing.
}
bool needsPadding = (AlignedNonVirtualTypeSize != AlignedNextFieldOffset);
if (needsPadding) {
CharUnits NumBytes = AlignedNonVirtualTypeSize - AlignedNextFieldOffset;
FieldTypes.push_back(getByteArrayType(NumBytes));
}
BaseSubobjectType = llvm::StructType::create(Types.getLLVMContext(),
FieldTypes, "", Packed);
Types.addRecordTypeName(RD, BaseSubobjectType, ".base");
// Pull the padding back off.
if (needsPadding)
FieldTypes.pop_back();
return true;
}
CGRecordLayout *CodeGenTypes::ComputeRecordLayout(const RecordDecl *D,
llvm::StructType *Ty) {
CGRecordLayoutBuilder Builder(*this);
Builder.Layout(D);
Ty->setBody(Builder.FieldTypes, Builder.Packed);
// If we're in C++, compute the base subobject type.
llvm::StructType *BaseTy = 0;
if (isa<CXXRecordDecl>(D) && !D->isUnion()) {
BaseTy = Builder.BaseSubobjectType;
if (!BaseTy) BaseTy = Ty;
}
CGRecordLayout *RL =
new CGRecordLayout(Ty, BaseTy, Builder.IsZeroInitializable,
Builder.IsZeroInitializableAsBase);
RL->NonVirtualBases.swap(Builder.NonVirtualBases);
RL->CompleteObjectVirtualBases.swap(Builder.VirtualBases);
// Add all the field numbers.
RL->FieldInfo.swap(Builder.Fields);
// Add bitfield info.
RL->BitFields.swap(Builder.BitFields);
// Dump the layout, if requested.
if (getContext().getLangOpts().DumpRecordLayouts) {
llvm::outs() << "\n*** Dumping IRgen Record Layout\n";
llvm::outs() << "Record: ";
D->dump(llvm::outs());
llvm::outs() << "\nLayout: ";
RL->print(llvm::outs());
}
#ifndef NDEBUG
// Verify that the computed LLVM struct size matches the AST layout size.
const ASTRecordLayout &Layout = getContext().getASTRecordLayout(D);
uint64_t TypeSizeInBits = getContext().toBits(Layout.getSize());
assert(TypeSizeInBits == getDataLayout().getTypeAllocSizeInBits(Ty) &&
"Type size mismatch!");
if (BaseTy) {
CharUnits NonVirtualSize = Layout.getNonVirtualSize();
CharUnits NonVirtualAlign = Layout.getNonVirtualAlign();
CharUnits AlignedNonVirtualTypeSize =
NonVirtualSize.RoundUpToAlignment(NonVirtualAlign);
uint64_t AlignedNonVirtualTypeSizeInBits =
getContext().toBits(AlignedNonVirtualTypeSize);
assert(AlignedNonVirtualTypeSizeInBits ==
getDataLayout().getTypeAllocSizeInBits(BaseTy) &&
"Type size mismatch!");
}
// Verify that the LLVM and AST field offsets agree.
llvm::StructType *ST =
dyn_cast<llvm::StructType>(RL->getLLVMType());
const llvm::StructLayout *SL = getDataLayout().getStructLayout(ST);
const ASTRecordLayout &AST_RL = getContext().getASTRecordLayout(D);
RecordDecl::field_iterator it = D->field_begin();
for (unsigned i = 0, e = AST_RL.getFieldCount(); i != e; ++i, ++it) {
const FieldDecl *FD = *it;
// For non-bit-fields, just check that the LLVM struct offset matches the
// AST offset.
if (!FD->isBitField()) {
unsigned FieldNo = RL->getLLVMFieldNo(FD);
assert(AST_RL.getFieldOffset(i) == SL->getElementOffsetInBits(FieldNo) &&
"Invalid field offset!");
continue;
}
// Ignore unnamed bit-fields.
if (!FD->getDeclName())
continue;
// Don't inspect zero-length bitfields.
if (FD->getBitWidthValue(getContext()) == 0)
continue;
const CGBitFieldInfo &Info = RL->getBitFieldInfo(FD);
llvm::Type *ElementTy = ST->getTypeAtIndex(RL->getLLVMFieldNo(FD));
// Unions have overlapping elements dictating their layout, but for
// non-unions we can verify that this section of the layout is the exact
// expected size.
if (D->isUnion()) {
// For unions we verify that the start is zero and the size
// is in-bounds. However, on BE systems, the offset may be non-zero, but
// the size + offset should match the storage size in that case as it
// "starts" at the back.
if (getDataLayout().isBigEndian())
assert(static_cast<unsigned>(Info.Offset + Info.Size) ==
Info.StorageSize &&
"Big endian union bitfield does not end at the back");
else
assert(Info.Offset == 0 &&
"Little endian union bitfield with a non-zero offset");
assert(Info.StorageSize <= SL->getSizeInBits() &&
"Union not large enough for bitfield storage");
} else {
assert(Info.StorageSize ==
getDataLayout().getTypeAllocSizeInBits(ElementTy) &&
"Storage size does not match the element type size");
}
assert(Info.Size > 0 && "Empty bitfield!");
assert(static_cast<unsigned>(Info.Offset) + Info.Size <= Info.StorageSize &&
"Bitfield outside of its allocated storage");
}
#endif
return RL;
}
