861 lines
36 KiB
C++
861 lines
36 KiB
C++
//===--- CGRecordLayoutBuilder.cpp - CGRecordLayout builder ----*- C++ -*-===//
|
|
//
|
|
// The LLVM Compiler Infrastructure
|
|
//
|
|
// This file is distributed under the University of Illinois Open Source
|
|
// License. See LICENSE.TXT for details.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
//
|
|
// Builder implementation for CGRecordLayout objects.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#include "CGRecordLayout.h"
|
|
#include "CGCXXABI.h"
|
|
#include "CodeGenTypes.h"
|
|
#include "clang/AST/ASTContext.h"
|
|
#include "clang/AST/Attr.h"
|
|
#include "clang/AST/CXXInheritance.h"
|
|
#include "clang/AST/DeclCXX.h"
|
|
#include "clang/AST/Expr.h"
|
|
#include "clang/AST/RecordLayout.h"
|
|
#include "clang/Frontend/CodeGenOptions.h"
|
|
#include "llvm/IR/DataLayout.h"
|
|
#include "llvm/IR/DerivedTypes.h"
|
|
#include "llvm/IR/Type.h"
|
|
#include "llvm/Support/Debug.h"
|
|
#include "llvm/Support/MathExtras.h"
|
|
#include "llvm/Support/raw_ostream.h"
|
|
using namespace clang;
|
|
using namespace CodeGen;
|
|
|
|
namespace {
|
|
/// The CGRecordLowering is responsible for lowering an ASTRecordLayout to an
|
|
/// llvm::Type. Some of the lowering is straightforward, some is not. Here we
|
|
/// detail some of the complexities and weirdnesses here.
|
|
/// * LLVM does not have unions - Unions can, in theory be represented by any
|
|
/// llvm::Type with correct size. We choose a field via a specific heuristic
|
|
/// and add padding if necessary.
|
|
/// * LLVM does not have bitfields - Bitfields are collected into contiguous
|
|
/// runs and allocated as a single storage type for the run. ASTRecordLayout
|
|
/// contains enough information to determine where the runs break. Microsoft
|
|
/// and Itanium follow different rules and use different codepaths.
|
|
/// * It is desired that, when possible, bitfields use the appropriate iN type
|
|
/// when lowered to llvm types. For example unsigned x : 24 gets lowered to
|
|
/// i24. This isn't always possible because i24 has storage size of 32 bit
|
|
/// and if it is possible to use that extra byte of padding we must use
|
|
/// [i8 x 3] instead of i24. The function clipTailPadding does this.
|
|
/// C++ examples that require clipping:
|
|
/// struct { int a : 24; char b; }; // a must be clipped, b goes at offset 3
|
|
/// struct A { int a : 24; }; // a must be clipped because a struct like B
|
|
// could exist: struct B : A { char b; }; // b goes at offset 3
|
|
/// * Clang ignores 0 sized bitfields and 0 sized bases but *not* zero sized
|
|
/// fields. The existing asserts suggest that LLVM assumes that *every* field
|
|
/// has an underlying storage type. Therefore empty structures containing
|
|
/// zero sized subobjects such as empty records or zero sized arrays still get
|
|
/// a zero sized (empty struct) storage type.
|
|
/// * Clang reads the complete type rather than the base type when generating
|
|
/// code to access fields. Bitfields in tail position with tail padding may
|
|
/// be clipped in the base class but not the complete class (we may discover
|
|
/// that the tail padding is not used in the complete class.) However,
|
|
/// because LLVM reads from the complete type it can generate incorrect code
|
|
/// if we do not clip the tail padding off of the bitfield in the complete
|
|
/// layout. This introduces a somewhat awkward extra unnecessary clip stage.
|
|
/// The location of the clip is stored internally as a sentinal of type
|
|
/// SCISSOR. If LLVM were updated to read base types (which it probably
|
|
/// should because locations of things such as VBases are bogus in the llvm
|
|
/// type anyway) then we could eliminate the SCISSOR.
|
|
/// * Itanium allows nearly empty primary virtual bases. These bases don't get
|
|
/// get their own storage because they're laid out as part of another base
|
|
/// or at the beginning of the structure. Determining if a VBase actually
|
|
/// gets storage awkwardly involves a walk of all bases.
|
|
/// * VFPtrs and VBPtrs do *not* make a record NotZeroInitializable.
|
|
struct CGRecordLowering {
|
|
// MemberInfo is a helper structure that contains information about a record
|
|
// member. In additional to the standard member types, there exists a
|
|
// sentinal member type that ensures correct rounding.
|
|
struct MemberInfo {
|
|
CharUnits Offset;
|
|
enum InfoKind { VFPtr, VBPtr, Field, Base, VBase, Scissor } Kind;
|
|
llvm::Type *Data;
|
|
union {
|
|
const FieldDecl *FD;
|
|
const CXXRecordDecl *RD;
|
|
};
|
|
MemberInfo(CharUnits Offset, InfoKind Kind, llvm::Type *Data,
|
|
const FieldDecl *FD = nullptr)
|
|
: Offset(Offset), Kind(Kind), Data(Data), FD(FD) {}
|
|
MemberInfo(CharUnits Offset, InfoKind Kind, llvm::Type *Data,
|
|
const CXXRecordDecl *RD)
|
|
: Offset(Offset), Kind(Kind), Data(Data), RD(RD) {}
|
|
// MemberInfos are sorted so we define a < operator.
|
|
bool operator <(const MemberInfo& a) const { return Offset < a.Offset; }
|
|
};
|
|
// The constructor.
|
|
CGRecordLowering(CodeGenTypes &Types, const RecordDecl *D, bool Packed);
|
|
// Short helper routines.
|
|
/// \brief Constructs a MemberInfo instance from an offset and llvm::Type *.
|
|
MemberInfo StorageInfo(CharUnits Offset, llvm::Type *Data) {
|
|
return MemberInfo(Offset, MemberInfo::Field, Data);
|
|
}
|
|
|
|
/// The Microsoft bitfield layout rule allocates discrete storage
|
|
/// units of the field's formal type and only combines adjacent
|
|
/// fields of the same formal type. We want to emit a layout with
|
|
/// these discrete storage units instead of combining them into a
|
|
/// continuous run.
|
|
bool isDiscreteBitFieldABI() {
|
|
return Context.getTargetInfo().getCXXABI().isMicrosoft() ||
|
|
D->isMsStruct(Context);
|
|
}
|
|
|
|
/// The Itanium base layout rule allows virtual bases to overlap
|
|
/// other bases, which complicates layout in specific ways.
|
|
///
|
|
/// Note specifically that the ms_struct attribute doesn't change this.
|
|
bool isOverlappingVBaseABI() {
|
|
return !Context.getTargetInfo().getCXXABI().isMicrosoft();
|
|
}
|
|
|
|
/// \brief Wraps llvm::Type::getIntNTy with some implicit arguments.
|
|
llvm::Type *getIntNType(uint64_t NumBits) {
|
|
return llvm::Type::getIntNTy(Types.getLLVMContext(),
|
|
(unsigned)llvm::alignTo(NumBits, 8));
|
|
}
|
|
/// \brief Gets an llvm type of size NumBytes and alignment 1.
|
|
llvm::Type *getByteArrayType(CharUnits NumBytes) {
|
|
assert(!NumBytes.isZero() && "Empty byte arrays aren't allowed.");
|
|
llvm::Type *Type = llvm::Type::getInt8Ty(Types.getLLVMContext());
|
|
return NumBytes == CharUnits::One() ? Type :
|
|
(llvm::Type *)llvm::ArrayType::get(Type, NumBytes.getQuantity());
|
|
}
|
|
/// \brief Gets the storage type for a field decl and handles storage
|
|
/// for itanium bitfields that are smaller than their declared type.
|
|
llvm::Type *getStorageType(const FieldDecl *FD) {
|
|
llvm::Type *Type = Types.ConvertTypeForMem(FD->getType());
|
|
if (!FD->isBitField()) return Type;
|
|
if (isDiscreteBitFieldABI()) return Type;
|
|
return getIntNType(std::min(FD->getBitWidthValue(Context),
|
|
(unsigned)Context.toBits(getSize(Type))));
|
|
}
|
|
/// \brief Gets the llvm Basesubobject type from a CXXRecordDecl.
|
|
llvm::Type *getStorageType(const CXXRecordDecl *RD) {
|
|
return Types.getCGRecordLayout(RD).getBaseSubobjectLLVMType();
|
|
}
|
|
CharUnits bitsToCharUnits(uint64_t BitOffset) {
|
|
return Context.toCharUnitsFromBits(BitOffset);
|
|
}
|
|
CharUnits getSize(llvm::Type *Type) {
|
|
return CharUnits::fromQuantity(DataLayout.getTypeAllocSize(Type));
|
|
}
|
|
CharUnits getAlignment(llvm::Type *Type) {
|
|
return CharUnits::fromQuantity(DataLayout.getABITypeAlignment(Type));
|
|
}
|
|
bool isZeroInitializable(const FieldDecl *FD) {
|
|
return Types.isZeroInitializable(FD->getType());
|
|
}
|
|
bool isZeroInitializable(const RecordDecl *RD) {
|
|
return Types.isZeroInitializable(RD);
|
|
}
|
|
void appendPaddingBytes(CharUnits Size) {
|
|
if (!Size.isZero())
|
|
FieldTypes.push_back(getByteArrayType(Size));
|
|
}
|
|
uint64_t getFieldBitOffset(const FieldDecl *FD) {
|
|
return Layout.getFieldOffset(FD->getFieldIndex());
|
|
}
|
|
// Layout routines.
|
|
void setBitFieldInfo(const FieldDecl *FD, CharUnits StartOffset,
|
|
llvm::Type *StorageType);
|
|
/// \brief Lowers an ASTRecordLayout to a llvm type.
|
|
void lower(bool NonVirtualBaseType);
|
|
void lowerUnion();
|
|
void accumulateFields();
|
|
void accumulateBitFields(RecordDecl::field_iterator Field,
|
|
RecordDecl::field_iterator FieldEnd);
|
|
void accumulateBases();
|
|
void accumulateVPtrs();
|
|
void accumulateVBases();
|
|
/// \brief Recursively searches all of the bases to find out if a vbase is
|
|
/// not the primary vbase of some base class.
|
|
bool hasOwnStorage(const CXXRecordDecl *Decl, const CXXRecordDecl *Query);
|
|
void calculateZeroInit();
|
|
/// \brief Lowers bitfield storage types to I8 arrays for bitfields with tail
|
|
/// padding that is or can potentially be used.
|
|
void clipTailPadding();
|
|
/// \brief Determines if we need a packed llvm struct.
|
|
void determinePacked(bool NVBaseType);
|
|
/// \brief Inserts padding everwhere it's needed.
|
|
void insertPadding();
|
|
/// \brief Fills out the structures that are ultimately consumed.
|
|
void fillOutputFields();
|
|
// Input memoization fields.
|
|
CodeGenTypes &Types;
|
|
const ASTContext &Context;
|
|
const RecordDecl *D;
|
|
const CXXRecordDecl *RD;
|
|
const ASTRecordLayout &Layout;
|
|
const llvm::DataLayout &DataLayout;
|
|
// Helpful intermediate data-structures.
|
|
std::vector<MemberInfo> Members;
|
|
// Output fields, consumed by CodeGenTypes::ComputeRecordLayout.
|
|
SmallVector<llvm::Type *, 16> FieldTypes;
|
|
llvm::DenseMap<const FieldDecl *, unsigned> Fields;
|
|
llvm::DenseMap<const FieldDecl *, CGBitFieldInfo> BitFields;
|
|
llvm::DenseMap<const CXXRecordDecl *, unsigned> NonVirtualBases;
|
|
llvm::DenseMap<const CXXRecordDecl *, unsigned> VirtualBases;
|
|
bool IsZeroInitializable : 1;
|
|
bool IsZeroInitializableAsBase : 1;
|
|
bool Packed : 1;
|
|
private:
|
|
CGRecordLowering(const CGRecordLowering &) = delete;
|
|
void operator =(const CGRecordLowering &) = delete;
|
|
};
|
|
} // namespace {
|
|
|
|
CGRecordLowering::CGRecordLowering(CodeGenTypes &Types, const RecordDecl *D, bool Packed)
|
|
: Types(Types), Context(Types.getContext()), D(D),
|
|
RD(dyn_cast<CXXRecordDecl>(D)),
|
|
Layout(Types.getContext().getASTRecordLayout(D)),
|
|
DataLayout(Types.getDataLayout()), IsZeroInitializable(true),
|
|
IsZeroInitializableAsBase(true), Packed(Packed) {}
|
|
|
|
void CGRecordLowering::setBitFieldInfo(
|
|
const FieldDecl *FD, CharUnits StartOffset, llvm::Type *StorageType) {
|
|
CGBitFieldInfo &Info = BitFields[FD->getCanonicalDecl()];
|
|
Info.IsSigned = FD->getType()->isSignedIntegerOrEnumerationType();
|
|
Info.Offset = (unsigned)(getFieldBitOffset(FD) - Context.toBits(StartOffset));
|
|
Info.Size = FD->getBitWidthValue(Context);
|
|
Info.StorageSize = (unsigned)DataLayout.getTypeAllocSizeInBits(StorageType);
|
|
Info.StorageOffset = StartOffset;
|
|
if (Info.Size > Info.StorageSize)
|
|
Info.Size = Info.StorageSize;
|
|
// Reverse the bit offsets for big endian machines. Because we represent
|
|
// a bitfield as a single large integer load, we can imagine the bits
|
|
// counting from the most-significant-bit instead of the
|
|
// least-significant-bit.
|
|
if (DataLayout.isBigEndian())
|
|
Info.Offset = Info.StorageSize - (Info.Offset + Info.Size);
|
|
}
|
|
|
|
void CGRecordLowering::lower(bool NVBaseType) {
|
|
// The lowering process implemented in this function takes a variety of
|
|
// carefully ordered phases.
|
|
// 1) Store all members (fields and bases) in a list and sort them by offset.
|
|
// 2) Add a 1-byte capstone member at the Size of the structure.
|
|
// 3) Clip bitfield storages members if their tail padding is or might be
|
|
// used by another field or base. The clipping process uses the capstone
|
|
// by treating it as another object that occurs after the record.
|
|
// 4) Determine if the llvm-struct requires packing. It's important that this
|
|
// phase occur after clipping, because clipping changes the llvm type.
|
|
// This phase reads the offset of the capstone when determining packedness
|
|
// and updates the alignment of the capstone to be equal of the alignment
|
|
// of the record after doing so.
|
|
// 5) Insert padding everywhere it is needed. This phase requires 'Packed' to
|
|
// have been computed and needs to know the alignment of the record in
|
|
// order to understand if explicit tail padding is needed.
|
|
// 6) Remove the capstone, we don't need it anymore.
|
|
// 7) Determine if this record can be zero-initialized. This phase could have
|
|
// been placed anywhere after phase 1.
|
|
// 8) Format the complete list of members in a way that can be consumed by
|
|
// CodeGenTypes::ComputeRecordLayout.
|
|
CharUnits Size = NVBaseType ? Layout.getNonVirtualSize() : Layout.getSize();
|
|
if (D->isUnion())
|
|
return lowerUnion();
|
|
accumulateFields();
|
|
// RD implies C++.
|
|
if (RD) {
|
|
accumulateVPtrs();
|
|
accumulateBases();
|
|
if (Members.empty())
|
|
return appendPaddingBytes(Size);
|
|
if (!NVBaseType)
|
|
accumulateVBases();
|
|
}
|
|
std::stable_sort(Members.begin(), Members.end());
|
|
Members.push_back(StorageInfo(Size, getIntNType(8)));
|
|
clipTailPadding();
|
|
determinePacked(NVBaseType);
|
|
insertPadding();
|
|
Members.pop_back();
|
|
calculateZeroInit();
|
|
fillOutputFields();
|
|
}
|
|
|
|
void CGRecordLowering::lowerUnion() {
|
|
CharUnits LayoutSize = Layout.getSize();
|
|
llvm::Type *StorageType = nullptr;
|
|
bool SeenNamedMember = false;
|
|
// Iterate through the fields setting bitFieldInfo and the Fields array. Also
|
|
// locate the "most appropriate" storage type. The heuristic for finding the
|
|
// storage type isn't necessary, the first (non-0-length-bitfield) field's
|
|
// type would work fine and be simpler but would be different than what we've
|
|
// been doing and cause lit tests to change.
|
|
for (const auto *Field : D->fields()) {
|
|
if (Field->isBitField()) {
|
|
// Skip 0 sized bitfields.
|
|
if (Field->getBitWidthValue(Context) == 0)
|
|
continue;
|
|
llvm::Type *FieldType = getStorageType(Field);
|
|
if (LayoutSize < getSize(FieldType))
|
|
FieldType = getByteArrayType(LayoutSize);
|
|
setBitFieldInfo(Field, CharUnits::Zero(), FieldType);
|
|
}
|
|
Fields[Field->getCanonicalDecl()] = 0;
|
|
llvm::Type *FieldType = getStorageType(Field);
|
|
// Compute zero-initializable status.
|
|
// This union might not be zero initialized: it may contain a pointer to
|
|
// data member which might have some exotic initialization sequence.
|
|
// If this is the case, then we aught not to try and come up with a "better"
|
|
// type, it might not be very easy to come up with a Constant which
|
|
// correctly initializes it.
|
|
if (!SeenNamedMember) {
|
|
SeenNamedMember = Field->getIdentifier();
|
|
if (!SeenNamedMember)
|
|
if (const auto *FieldRD =
|
|
dyn_cast_or_null<RecordDecl>(Field->getType()->getAsTagDecl()))
|
|
SeenNamedMember = FieldRD->findFirstNamedDataMember();
|
|
if (SeenNamedMember && !isZeroInitializable(Field)) {
|
|
IsZeroInitializable = IsZeroInitializableAsBase = false;
|
|
StorageType = FieldType;
|
|
}
|
|
}
|
|
// Because our union isn't zero initializable, we won't be getting a better
|
|
// storage type.
|
|
if (!IsZeroInitializable)
|
|
continue;
|
|
// Conditionally update our storage type if we've got a new "better" one.
|
|
if (!StorageType ||
|
|
getAlignment(FieldType) > getAlignment(StorageType) ||
|
|
(getAlignment(FieldType) == getAlignment(StorageType) &&
|
|
getSize(FieldType) > getSize(StorageType)))
|
|
StorageType = FieldType;
|
|
}
|
|
// If we have no storage type just pad to the appropriate size and return.
|
|
if (!StorageType)
|
|
return appendPaddingBytes(LayoutSize);
|
|
// If our storage size was bigger than our required size (can happen in the
|
|
// case of packed bitfields on Itanium) then just use an I8 array.
|
|
if (LayoutSize < getSize(StorageType))
|
|
StorageType = getByteArrayType(LayoutSize);
|
|
FieldTypes.push_back(StorageType);
|
|
appendPaddingBytes(LayoutSize - getSize(StorageType));
|
|
// Set packed if we need it.
|
|
if (LayoutSize % getAlignment(StorageType))
|
|
Packed = true;
|
|
}
|
|
|
|
void CGRecordLowering::accumulateFields() {
|
|
for (RecordDecl::field_iterator Field = D->field_begin(),
|
|
FieldEnd = D->field_end();
|
|
Field != FieldEnd;)
|
|
if (Field->isBitField()) {
|
|
RecordDecl::field_iterator Start = Field;
|
|
// Iterate to gather the list of bitfields.
|
|
for (++Field; Field != FieldEnd && Field->isBitField(); ++Field);
|
|
accumulateBitFields(Start, Field);
|
|
} else {
|
|
Members.push_back(MemberInfo(
|
|
bitsToCharUnits(getFieldBitOffset(*Field)), MemberInfo::Field,
|
|
getStorageType(*Field), *Field));
|
|
++Field;
|
|
}
|
|
}
|
|
|
|
void
|
|
CGRecordLowering::accumulateBitFields(RecordDecl::field_iterator Field,
|
|
RecordDecl::field_iterator FieldEnd) {
|
|
// Run stores the first element of the current run of bitfields. FieldEnd is
|
|
// used as a special value to note that we don't have a current run. A
|
|
// bitfield run is a contiguous collection of bitfields that can be stored in
|
|
// the same storage block. Zero-sized bitfields and bitfields that would
|
|
// cross an alignment boundary break a run and start a new one.
|
|
RecordDecl::field_iterator Run = FieldEnd;
|
|
// Tail is the offset of the first bit off the end of the current run. It's
|
|
// used to determine if the ASTRecordLayout is treating these two bitfields as
|
|
// contiguous. StartBitOffset is offset of the beginning of the Run.
|
|
uint64_t StartBitOffset, Tail = 0;
|
|
if (isDiscreteBitFieldABI()) {
|
|
for (; Field != FieldEnd; ++Field) {
|
|
uint64_t BitOffset = getFieldBitOffset(*Field);
|
|
// Zero-width bitfields end runs.
|
|
if (Field->getBitWidthValue(Context) == 0) {
|
|
Run = FieldEnd;
|
|
continue;
|
|
}
|
|
llvm::Type *Type = Types.ConvertTypeForMem(Field->getType());
|
|
// If we don't have a run yet, or don't live within the previous run's
|
|
// allocated storage then we allocate some storage and start a new run.
|
|
if (Run == FieldEnd || BitOffset >= Tail) {
|
|
Run = Field;
|
|
StartBitOffset = BitOffset;
|
|
Tail = StartBitOffset + DataLayout.getTypeAllocSizeInBits(Type);
|
|
// Add the storage member to the record. This must be added to the
|
|
// record before the bitfield members so that it gets laid out before
|
|
// the bitfields it contains get laid out.
|
|
Members.push_back(StorageInfo(bitsToCharUnits(StartBitOffset), Type));
|
|
}
|
|
// Bitfields get the offset of their storage but come afterward and remain
|
|
// there after a stable sort.
|
|
Members.push_back(MemberInfo(bitsToCharUnits(StartBitOffset),
|
|
MemberInfo::Field, nullptr, *Field));
|
|
}
|
|
return;
|
|
}
|
|
for (;;) {
|
|
// Check to see if we need to start a new run.
|
|
if (Run == FieldEnd) {
|
|
// If we're out of fields, return.
|
|
if (Field == FieldEnd)
|
|
break;
|
|
// Any non-zero-length bitfield can start a new run.
|
|
if (Field->getBitWidthValue(Context) != 0) {
|
|
Run = Field;
|
|
StartBitOffset = getFieldBitOffset(*Field);
|
|
Tail = StartBitOffset + Field->getBitWidthValue(Context);
|
|
}
|
|
++Field;
|
|
continue;
|
|
}
|
|
// Add bitfields to the run as long as they qualify.
|
|
if (Field != FieldEnd && Field->getBitWidthValue(Context) != 0 &&
|
|
Tail == getFieldBitOffset(*Field)) {
|
|
Tail += Field->getBitWidthValue(Context);
|
|
++Field;
|
|
continue;
|
|
}
|
|
// We've hit a break-point in the run and need to emit a storage field.
|
|
llvm::Type *Type = getIntNType(Tail - StartBitOffset);
|
|
// Add the storage member to the record and set the bitfield info for all of
|
|
// the bitfields in the run. Bitfields get the offset of their storage but
|
|
// come afterward and remain there after a stable sort.
|
|
Members.push_back(StorageInfo(bitsToCharUnits(StartBitOffset), Type));
|
|
for (; Run != Field; ++Run)
|
|
Members.push_back(MemberInfo(bitsToCharUnits(StartBitOffset),
|
|
MemberInfo::Field, nullptr, *Run));
|
|
Run = FieldEnd;
|
|
}
|
|
}
|
|
|
|
void CGRecordLowering::accumulateBases() {
|
|
// If we've got a primary virtual base, we need to add it with the bases.
|
|
if (Layout.isPrimaryBaseVirtual()) {
|
|
const CXXRecordDecl *BaseDecl = Layout.getPrimaryBase();
|
|
Members.push_back(MemberInfo(CharUnits::Zero(), MemberInfo::Base,
|
|
getStorageType(BaseDecl), BaseDecl));
|
|
}
|
|
// Accumulate the non-virtual bases.
|
|
for (const auto &Base : RD->bases()) {
|
|
if (Base.isVirtual())
|
|
continue;
|
|
|
|
// Bases can be zero-sized even if not technically empty if they
|
|
// contain only a trailing array member.
|
|
const CXXRecordDecl *BaseDecl = Base.getType()->getAsCXXRecordDecl();
|
|
if (!BaseDecl->isEmpty() &&
|
|
!Context.getASTRecordLayout(BaseDecl).getNonVirtualSize().isZero())
|
|
Members.push_back(MemberInfo(Layout.getBaseClassOffset(BaseDecl),
|
|
MemberInfo::Base, getStorageType(BaseDecl), BaseDecl));
|
|
}
|
|
}
|
|
|
|
void CGRecordLowering::accumulateVPtrs() {
|
|
if (Layout.hasOwnVFPtr())
|
|
Members.push_back(MemberInfo(CharUnits::Zero(), MemberInfo::VFPtr,
|
|
llvm::FunctionType::get(getIntNType(32), /*isVarArg=*/true)->
|
|
getPointerTo()->getPointerTo()));
|
|
if (Layout.hasOwnVBPtr())
|
|
Members.push_back(MemberInfo(Layout.getVBPtrOffset(), MemberInfo::VBPtr,
|
|
llvm::Type::getInt32PtrTy(Types.getLLVMContext())));
|
|
}
|
|
|
|
void CGRecordLowering::accumulateVBases() {
|
|
CharUnits ScissorOffset = Layout.getNonVirtualSize();
|
|
// In the itanium ABI, it's possible to place a vbase at a dsize that is
|
|
// smaller than the nvsize. Here we check to see if such a base is placed
|
|
// before the nvsize and set the scissor offset to that, instead of the
|
|
// nvsize.
|
|
if (isOverlappingVBaseABI())
|
|
for (const auto &Base : RD->vbases()) {
|
|
const CXXRecordDecl *BaseDecl = Base.getType()->getAsCXXRecordDecl();
|
|
if (BaseDecl->isEmpty())
|
|
continue;
|
|
// If the vbase is a primary virtual base of some base, then it doesn't
|
|
// get its own storage location but instead lives inside of that base.
|
|
if (Context.isNearlyEmpty(BaseDecl) && !hasOwnStorage(RD, BaseDecl))
|
|
continue;
|
|
ScissorOffset = std::min(ScissorOffset,
|
|
Layout.getVBaseClassOffset(BaseDecl));
|
|
}
|
|
Members.push_back(MemberInfo(ScissorOffset, MemberInfo::Scissor, nullptr,
|
|
RD));
|
|
for (const auto &Base : RD->vbases()) {
|
|
const CXXRecordDecl *BaseDecl = Base.getType()->getAsCXXRecordDecl();
|
|
if (BaseDecl->isEmpty())
|
|
continue;
|
|
CharUnits Offset = Layout.getVBaseClassOffset(BaseDecl);
|
|
// If the vbase is a primary virtual base of some base, then it doesn't
|
|
// get its own storage location but instead lives inside of that base.
|
|
if (isOverlappingVBaseABI() &&
|
|
Context.isNearlyEmpty(BaseDecl) &&
|
|
!hasOwnStorage(RD, BaseDecl)) {
|
|
Members.push_back(MemberInfo(Offset, MemberInfo::VBase, nullptr,
|
|
BaseDecl));
|
|
continue;
|
|
}
|
|
// If we've got a vtordisp, add it as a storage type.
|
|
if (Layout.getVBaseOffsetsMap().find(BaseDecl)->second.hasVtorDisp())
|
|
Members.push_back(StorageInfo(Offset - CharUnits::fromQuantity(4),
|
|
getIntNType(32)));
|
|
Members.push_back(MemberInfo(Offset, MemberInfo::VBase,
|
|
getStorageType(BaseDecl), BaseDecl));
|
|
}
|
|
}
|
|
|
|
bool CGRecordLowering::hasOwnStorage(const CXXRecordDecl *Decl,
|
|
const CXXRecordDecl *Query) {
|
|
const ASTRecordLayout &DeclLayout = Context.getASTRecordLayout(Decl);
|
|
if (DeclLayout.isPrimaryBaseVirtual() && DeclLayout.getPrimaryBase() == Query)
|
|
return false;
|
|
for (const auto &Base : Decl->bases())
|
|
if (!hasOwnStorage(Base.getType()->getAsCXXRecordDecl(), Query))
|
|
return false;
|
|
return true;
|
|
}
|
|
|
|
void CGRecordLowering::calculateZeroInit() {
|
|
for (std::vector<MemberInfo>::const_iterator Member = Members.begin(),
|
|
MemberEnd = Members.end();
|
|
IsZeroInitializableAsBase && Member != MemberEnd; ++Member) {
|
|
if (Member->Kind == MemberInfo::Field) {
|
|
if (!Member->FD || isZeroInitializable(Member->FD))
|
|
continue;
|
|
IsZeroInitializable = IsZeroInitializableAsBase = false;
|
|
} else if (Member->Kind == MemberInfo::Base ||
|
|
Member->Kind == MemberInfo::VBase) {
|
|
if (isZeroInitializable(Member->RD))
|
|
continue;
|
|
IsZeroInitializable = false;
|
|
if (Member->Kind == MemberInfo::Base)
|
|
IsZeroInitializableAsBase = false;
|
|
}
|
|
}
|
|
}
|
|
|
|
void CGRecordLowering::clipTailPadding() {
|
|
std::vector<MemberInfo>::iterator Prior = Members.begin();
|
|
CharUnits Tail = getSize(Prior->Data);
|
|
for (std::vector<MemberInfo>::iterator Member = Prior + 1,
|
|
MemberEnd = Members.end();
|
|
Member != MemberEnd; ++Member) {
|
|
// Only members with data and the scissor can cut into tail padding.
|
|
if (!Member->Data && Member->Kind != MemberInfo::Scissor)
|
|
continue;
|
|
if (Member->Offset < Tail) {
|
|
assert(Prior->Kind == MemberInfo::Field && !Prior->FD &&
|
|
"Only storage fields have tail padding!");
|
|
Prior->Data = getByteArrayType(bitsToCharUnits(llvm::alignTo(
|
|
cast<llvm::IntegerType>(Prior->Data)->getIntegerBitWidth(), 8)));
|
|
}
|
|
if (Member->Data)
|
|
Prior = Member;
|
|
Tail = Prior->Offset + getSize(Prior->Data);
|
|
}
|
|
}
|
|
|
|
void CGRecordLowering::determinePacked(bool NVBaseType) {
|
|
if (Packed)
|
|
return;
|
|
CharUnits Alignment = CharUnits::One();
|
|
CharUnits NVAlignment = CharUnits::One();
|
|
CharUnits NVSize =
|
|
!NVBaseType && RD ? Layout.getNonVirtualSize() : CharUnits::Zero();
|
|
for (std::vector<MemberInfo>::const_iterator Member = Members.begin(),
|
|
MemberEnd = Members.end();
|
|
Member != MemberEnd; ++Member) {
|
|
if (!Member->Data)
|
|
continue;
|
|
// If any member falls at an offset that it not a multiple of its alignment,
|
|
// then the entire record must be packed.
|
|
if (Member->Offset % getAlignment(Member->Data))
|
|
Packed = true;
|
|
if (Member->Offset < NVSize)
|
|
NVAlignment = std::max(NVAlignment, getAlignment(Member->Data));
|
|
Alignment = std::max(Alignment, getAlignment(Member->Data));
|
|
}
|
|
// If the size of the record (the capstone's offset) is not a multiple of the
|
|
// record's alignment, it must be packed.
|
|
if (Members.back().Offset % Alignment)
|
|
Packed = true;
|
|
// If the non-virtual sub-object is not a multiple of the non-virtual
|
|
// sub-object's alignment, it must be packed. We cannot have a packed
|
|
// non-virtual sub-object and an unpacked complete object or vise versa.
|
|
if (NVSize % NVAlignment)
|
|
Packed = true;
|
|
// Update the alignment of the sentinal.
|
|
if (!Packed)
|
|
Members.back().Data = getIntNType(Context.toBits(Alignment));
|
|
}
|
|
|
|
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.alignTo(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());
|
|
}
|
|
|
|
void CGRecordLowering::fillOutputFields() {
|
|
for (std::vector<MemberInfo>::const_iterator Member = Members.begin(),
|
|
MemberEnd = Members.end();
|
|
Member != MemberEnd; ++Member) {
|
|
if (Member->Data)
|
|
FieldTypes.push_back(Member->Data);
|
|
if (Member->Kind == MemberInfo::Field) {
|
|
if (Member->FD)
|
|
Fields[Member->FD->getCanonicalDecl()] = FieldTypes.size() - 1;
|
|
// A field without storage must be a bitfield.
|
|
if (!Member->Data)
|
|
setBitFieldInfo(Member->FD, Member->Offset, FieldTypes.back());
|
|
} else if (Member->Kind == MemberInfo::Base)
|
|
NonVirtualBases[Member->RD] = FieldTypes.size() - 1;
|
|
else if (Member->Kind == MemberInfo::VBase)
|
|
VirtualBases[Member->RD] = FieldTypes.size() - 1;
|
|
}
|
|
}
|
|
|
|
CGBitFieldInfo CGBitFieldInfo::MakeInfo(CodeGenTypes &Types,
|
|
const FieldDecl *FD,
|
|
uint64_t Offset, uint64_t Size,
|
|
uint64_t StorageSize,
|
|
CharUnits StorageOffset) {
|
|
// This function is vestigial from CGRecordLayoutBuilder days but is still
|
|
// used in GCObjCRuntime.cpp. That usage has a "fixme" attached to it that
|
|
// when addressed will allow for the removal of this function.
|
|
llvm::Type *Ty = Types.ConvertTypeForMem(FD->getType());
|
|
CharUnits TypeSizeInBytes =
|
|
CharUnits::fromQuantity(Types.getDataLayout().getTypeAllocSize(Ty));
|
|
uint64_t TypeSizeInBits = Types.getContext().toBits(TypeSizeInBytes);
|
|
|
|
bool IsSigned = FD->getType()->isSignedIntegerOrEnumerationType();
|
|
|
|
if (Size > TypeSizeInBits) {
|
|
// We have a wide bit-field. The extra bits are only used for padding, so
|
|
// if we have a bitfield of type T, with size N:
|
|
//
|
|
// T t : N;
|
|
//
|
|
// We can just assume that it's:
|
|
//
|
|
// T t : sizeof(T);
|
|
//
|
|
Size = TypeSizeInBits;
|
|
}
|
|
|
|
// Reverse the bit offsets for big endian machines. Because we represent
|
|
// a bitfield as a single large integer load, we can imagine the bits
|
|
// counting from the most-significant-bit instead of the
|
|
// least-significant-bit.
|
|
if (Types.getDataLayout().isBigEndian()) {
|
|
Offset = StorageSize - (Offset + Size);
|
|
}
|
|
|
|
return CGBitFieldInfo(Offset, Size, IsSigned, StorageSize, StorageOffset);
|
|
}
|
|
|
|
CGRecordLayout *CodeGenTypes::ComputeRecordLayout(const RecordDecl *D,
|
|
llvm::StructType *Ty) {
|
|
CGRecordLowering Builder(*this, D, /*Packed=*/false);
|
|
|
|
Builder.lower(/*NonVirtualBaseType=*/false);
|
|
|
|
// If we're in C++, compute the base subobject type.
|
|
llvm::StructType *BaseTy = nullptr;
|
|
if (isa<CXXRecordDecl>(D) && !D->isUnion() && !D->hasAttr<FinalAttr>()) {
|
|
BaseTy = Ty;
|
|
if (Builder.Layout.getNonVirtualSize() != Builder.Layout.getSize()) {
|
|
CGRecordLowering BaseBuilder(*this, D, /*Packed=*/Builder.Packed);
|
|
BaseBuilder.lower(/*NonVirtualBaseType=*/true);
|
|
BaseTy = llvm::StructType::create(
|
|
getLLVMContext(), BaseBuilder.FieldTypes, "", BaseBuilder.Packed);
|
|
addRecordTypeName(D, BaseTy, ".base");
|
|
// BaseTy and Ty must agree on their packedness for getLLVMFieldNo to work
|
|
// on both of them with the same index.
|
|
assert(Builder.Packed == BaseBuilder.Packed &&
|
|
"Non-virtual and complete types must agree on packedness");
|
|
}
|
|
}
|
|
|
|
// Fill in the struct *after* computing the base type. Filling in the body
|
|
// signifies that the type is no longer opaque and record layout is complete,
|
|
// but we may need to recursively layout D while laying D out as a base type.
|
|
Ty->setBody(Builder.FieldTypes, Builder.Packed);
|
|
|
|
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();
|
|
|
|
uint64_t AlignedNonVirtualTypeSizeInBits =
|
|
getContext().toBits(NonVirtualSize);
|
|
|
|
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;
|
|
}
|
|
|
|
void CGRecordLayout::print(raw_ostream &OS) const {
|
|
OS << "<CGRecordLayout\n";
|
|
OS << " LLVMType:" << *CompleteObjectType << "\n";
|
|
if (BaseSubobjectType)
|
|
OS << " NonVirtualBaseLLVMType:" << *BaseSubobjectType << "\n";
|
|
OS << " IsZeroInitializable:" << IsZeroInitializable << "\n";
|
|
OS << " BitFields:[\n";
|
|
|
|
// Print bit-field infos in declaration order.
|
|
std::vector<std::pair<unsigned, const CGBitFieldInfo*> > BFIs;
|
|
for (llvm::DenseMap<const FieldDecl*, CGBitFieldInfo>::const_iterator
|
|
it = BitFields.begin(), ie = BitFields.end();
|
|
it != ie; ++it) {
|
|
const RecordDecl *RD = it->first->getParent();
|
|
unsigned Index = 0;
|
|
for (RecordDecl::field_iterator
|
|
it2 = RD->field_begin(); *it2 != it->first; ++it2)
|
|
++Index;
|
|
BFIs.push_back(std::make_pair(Index, &it->second));
|
|
}
|
|
llvm::array_pod_sort(BFIs.begin(), BFIs.end());
|
|
for (unsigned i = 0, e = BFIs.size(); i != e; ++i) {
|
|
OS.indent(4);
|
|
BFIs[i].second->print(OS);
|
|
OS << "\n";
|
|
}
|
|
|
|
OS << "]>\n";
|
|
}
|
|
|
|
LLVM_DUMP_METHOD void CGRecordLayout::dump() const {
|
|
print(llvm::errs());
|
|
}
|
|
|
|
void CGBitFieldInfo::print(raw_ostream &OS) const {
|
|
OS << "<CGBitFieldInfo"
|
|
<< " Offset:" << Offset
|
|
<< " Size:" << Size
|
|
<< " IsSigned:" << IsSigned
|
|
<< " StorageSize:" << StorageSize
|
|
<< " StorageOffset:" << StorageOffset.getQuantity() << ">";
|
|
}
|
|
|
|
LLVM_DUMP_METHOD void CGBitFieldInfo::dump() const {
|
|
print(llvm::errs());
|
|
}
|