void SwiftAggLowering::addTypedData(const RecordDecl *record, CharUnits begin,
const ASTRecordLayout &layout) {
// Unions are a special case.
if (record->isUnion()) {
for (auto field : record->fields()) {
if (field->isBitField()) {
addBitFieldData(field, begin, 0);
} else {
addTypedData(field->getType(), begin);
}
}
return;
}
// Note that correctness does not rely on us adding things in
// their actual order of layout; it's just somewhat more efficient
// for the builder.
// With that in mind, add "early" C++ data.
auto cxxRecord = dyn_cast<CXXRecordDecl>(record);
if (cxxRecord) {
// - a v-table pointer, if the class adds its own
if (layout.hasOwnVFPtr()) {
addTypedData(CGM.Int8PtrTy, begin);
}
// - non-virtual bases
for (auto &baseSpecifier : cxxRecord->bases()) {
if (baseSpecifier.isVirtual()) continue;
auto baseRecord = baseSpecifier.getType()->getAsCXXRecordDecl();
addTypedData(baseRecord, begin + layout.getBaseClassOffset(baseRecord));
}
// - a vbptr if the class adds its own
if (layout.hasOwnVBPtr()) {
addTypedData(CGM.Int8PtrTy, begin + layout.getVBPtrOffset());
}
}
// Add fields.
for (auto field : record->fields()) {
auto fieldOffsetInBits = layout.getFieldOffset(field->getFieldIndex());
if (field->isBitField()) {
addBitFieldData(field, begin, fieldOffsetInBits);
} else {
addTypedData(field->getType(),
begin + CGM.getContext().toCharUnitsFromBits(fieldOffsetInBits));
}
}
// Add "late" C++ data:
if (cxxRecord) {
// - virtual bases
for (auto &vbaseSpecifier : cxxRecord->vbases()) {
auto baseRecord = vbaseSpecifier.getType()->getAsCXXRecordDecl();
addTypedData(baseRecord, begin + layout.getVBaseClassOffset(baseRecord));
}
}
}
/// \brief Layout the range of bitfields from BFI to BFE as contiguous storage.
bool CGRecordLayoutBuilder::LayoutBitfields(const ASTRecordLayout &Layout,
unsigned &FirstFieldNo,
RecordDecl::field_iterator &FI,
RecordDecl::field_iterator FE) {
assert(FI != FE);
uint64_t FirstFieldOffset = Layout.getFieldOffset(FirstFieldNo);
uint64_t NextFieldOffsetInBits = Types.getContext().toBits(NextFieldOffset);
unsigned CharAlign = Types.getTarget().getCharAlign();
assert(FirstFieldOffset % CharAlign == 0 &&
"First field offset is misaligned");
CharUnits FirstFieldOffsetInBytes
= Types.getContext().toCharUnitsFromBits(FirstFieldOffset);
unsigned StorageAlignment
= llvm::MinAlign(Alignment.getQuantity(),
FirstFieldOffsetInBytes.getQuantity());
if (FirstFieldOffset < NextFieldOffsetInBits) {
CharUnits FieldOffsetInCharUnits =
Types.getContext().toCharUnitsFromBits(FirstFieldOffset);
// Try to resize the last base field.
if (!ResizeLastBaseFieldIfNecessary(FieldOffsetInCharUnits))
llvm_unreachable("We must be able to resize the last base if we need to "
"pack bits into it.");
NextFieldOffsetInBits = Types.getContext().toBits(NextFieldOffset);
assert(FirstFieldOffset >= NextFieldOffsetInBits);
}
// Append padding if necessary.
AppendPadding(Types.getContext().toCharUnitsFromBits(FirstFieldOffset),
CharUnits::One());
// Find the last bitfield in a contiguous run of bitfields.
RecordDecl::field_iterator BFI = FI;
unsigned LastFieldNo = FirstFieldNo;
uint64_t NextContiguousFieldOffset = FirstFieldOffset;
for (RecordDecl::field_iterator FJ = FI;
(FJ != FE && (*FJ)->isBitField() &&
NextContiguousFieldOffset == Layout.getFieldOffset(LastFieldNo) &&
(*FJ)->getBitWidthValue(Types.getContext()) != 0); FI = FJ++) {
NextContiguousFieldOffset += (*FJ)->getBitWidthValue(Types.getContext());
++LastFieldNo;
// We must use packed structs for packed fields, and also unnamed bit
// fields since they don't affect the struct alignment.
if (!Packed && ((*FJ)->hasAttr<PackedAttr>() || !(*FJ)->getDeclName()))
return false;
}
RecordDecl::field_iterator BFE = llvm::next(FI);
--LastFieldNo;
assert(LastFieldNo >= FirstFieldNo && "Empty run of contiguous bitfields");
FieldDecl *LastFD = *FI;
// Find the last bitfield's offset, add its size, and round it up to the
// character alignment to compute the storage required.
uint64_t LastFieldOffset = Layout.getFieldOffset(LastFieldNo);
uint64_t LastFieldSize = LastFD->getBitWidthValue(Types.getContext());
uint64_t TotalBits = (LastFieldOffset + LastFieldSize) - FirstFieldOffset;
CharUnits StorageBytes = Types.getContext().toCharUnitsFromBits(
llvm::RoundUpToAlignment(TotalBits, CharAlign));
uint64_t StorageBits = Types.getContext().toBits(StorageBytes);
// Grow the storage to encompass any known padding in the layout when doing
// so will make the storage a power-of-two. There are two cases when we can
// do this. The first is when we have a subsequent field and can widen up to
// its offset. The second is when the data size of the AST record layout is
// past the end of the current storage. The latter is true when there is tail
// padding on a struct and no members of a super class can be packed into it.
//
// Note that we widen the storage as much as possible here to express the
// maximum latitude the language provides, and rely on the backend to lower
// these in conjunction with shifts and masks to narrower operations where
// beneficial.
uint64_t EndOffset = Types.getContext().toBits(Layout.getDataSize());
if (BFE != FE)
// If there are more fields to be laid out, the offset at the end of the
// bitfield is the offset of the next field in the record.
EndOffset = Layout.getFieldOffset(LastFieldNo + 1);
assert(EndOffset >= (FirstFieldOffset + TotalBits) &&
"End offset is not past the end of the known storage bits.");
uint64_t SpaceBits = EndOffset - FirstFieldOffset;
uint64_t LongBits = Types.getTarget().getLongWidth();
uint64_t WidenedBits = (StorageBits / LongBits) * LongBits +
llvm::NextPowerOf2(StorageBits % LongBits - 1);
assert(WidenedBits >= StorageBits && "Widening shrunk the bits!");
if (WidenedBits <= SpaceBits) {
StorageBits = WidenedBits;
StorageBytes = Types.getContext().toCharUnitsFromBits(StorageBits);
assert(StorageBits == (uint64_t)Types.getContext().toBits(StorageBytes));
}
unsigned FieldIndex = FieldTypes.size();
AppendBytes(StorageBytes);
// Now walk the bitfields associating them with this field of storage and
// building up the bitfield specific info.
unsigned FieldNo = FirstFieldNo;
for (; BFI != BFE; ++BFI, ++FieldNo) {
FieldDecl *FD = *BFI;
uint64_t FieldOffset = Layout.getFieldOffset(FieldNo) - FirstFieldOffset;
uint64_t FieldSize = FD->getBitWidthValue(Types.getContext());
Fields[FD] = FieldIndex;
BitFields[FD] = CGBitFieldInfo::MakeInfo(Types, FD, FieldOffset, FieldSize,
StorageBits, StorageAlignment);
}
FirstFieldNo = LastFieldNo;
return true;
}