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llvm-project/clang/lib/CodeGen/CGRecordLayoutBuilder.cpp

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//===--- 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/raw_ostream.h"
using namespace clang;
using namespace CodeGen;
namespace {
class CGRecordLayoutBuilder {
public:
/// FieldTypes - Holds the LLVM types that the struct is created from.
///
SmallVector<llvm::Type *, 16> FieldTypes;
/// BaseSubobjectType - Holds the LLVM type for the non-virtual part
/// of the struct. For example, consider:
///
/// struct A { int i; };
/// struct B { void *v; };
/// struct C : virtual A, B { };
///
/// The LLVM type of C will be
/// %struct.C = type { i32 (...)**, %struct.A, i32, %struct.B }
///
/// And the LLVM type of the non-virtual base struct will be
/// %struct.C.base = type { i32 (...)**, %struct.A, i32 }
///
/// This only gets initialized if the base subobject type is
/// different from the complete-object type.
llvm::StructType *BaseSubobjectType;
/// FieldInfo - Holds a field and its corresponding LLVM field number.
llvm::DenseMap<const FieldDecl *, unsigned> Fields;
/// BitFieldInfo - Holds location and size information about a bit field.
llvm::DenseMap<const FieldDecl *, CGBitFieldInfo> BitFields;
llvm::DenseMap<const CXXRecordDecl *, unsigned> NonVirtualBases;
llvm::DenseMap<const CXXRecordDecl *, unsigned> VirtualBases;
/// IndirectPrimaryBases - Virtual base classes, direct or indirect, that are
/// primary base classes for some other direct or indirect base class.
CXXIndirectPrimaryBaseSet IndirectPrimaryBases;
/// LaidOutVirtualBases - A set of all laid out virtual bases, used to avoid
/// avoid laying out virtual bases more than once.
llvm::SmallPtrSet<const CXXRecordDecl *, 4> LaidOutVirtualBases;
/// IsZeroInitializable - Whether this struct can be C++
/// zero-initialized with an LLVM zeroinitializer.
bool IsZeroInitializable;
bool IsZeroInitializableAsBase;
/// Packed - Whether the resulting LLVM struct will be packed or not.
bool Packed;
private:
CodeGenTypes &Types;
/// LastLaidOutBaseInfo - Contains the offset and non-virtual size of the
/// last base laid out. Used so that we can replace the last laid out base
/// type with an i8 array if needed.
struct LastLaidOutBaseInfo {
CharUnits Offset;
CharUnits NonVirtualSize;
bool isValid() const { return !NonVirtualSize.isZero(); }
void invalidate() { NonVirtualSize = CharUnits::Zero(); }
} LastLaidOutBase;
/// Alignment - Contains the alignment of the RecordDecl.
CharUnits Alignment;
/// NextFieldOffset - Holds the next field offset.
CharUnits NextFieldOffset;
/// LayoutUnionField - Will layout a field in an union and return the type
/// that the field will have.
llvm::Type *LayoutUnionField(const FieldDecl *Field,
const ASTRecordLayout &Layout);
/// LayoutUnion - Will layout a union RecordDecl.
void LayoutUnion(const RecordDecl *D);
/// Lay out a sequence of contiguous bitfields.
bool LayoutBitfields(const ASTRecordLayout &Layout,
unsigned &FirstFieldNo,
RecordDecl::field_iterator &FI,
RecordDecl::field_iterator FE);
/// LayoutField - try to layout all fields in the record decl.
/// Returns false if the operation failed because the struct is not packed.
bool LayoutFields(const RecordDecl *D);
/// Layout a single base, virtual or non-virtual
bool LayoutBase(const CXXRecordDecl *base,
const CGRecordLayout &baseLayout,
CharUnits baseOffset);
/// LayoutVirtualBase - layout a single virtual base.
bool LayoutVirtualBase(const CXXRecordDecl *base,
CharUnits baseOffset);
/// LayoutVirtualBases - layout the virtual bases of a record decl.
bool LayoutVirtualBases(const CXXRecordDecl *RD,
const ASTRecordLayout &Layout);
/// MSLayoutVirtualBases - layout the virtual bases of a record decl,
/// like MSVC.
bool MSLayoutVirtualBases(const CXXRecordDecl *RD,
const ASTRecordLayout &Layout);
/// LayoutNonVirtualBase - layout a single non-virtual base.
bool LayoutNonVirtualBase(const CXXRecordDecl *base,
CharUnits baseOffset);
/// LayoutNonVirtualBases - layout the virtual bases of a record decl.
bool LayoutNonVirtualBases(const CXXRecordDecl *RD,
const ASTRecordLayout &Layout);
/// ComputeNonVirtualBaseType - Compute the non-virtual base field types.
bool ComputeNonVirtualBaseType(const CXXRecordDecl *RD);
/// LayoutField - layout a single field. Returns false if the operation failed
/// because the current struct is not packed.
bool LayoutField(const FieldDecl *D, uint64_t FieldOffset);
/// LayoutBitField - layout a single bit field.
void LayoutBitField(const FieldDecl *D, uint64_t FieldOffset);
/// AppendField - Appends a field with the given offset and type.
void AppendField(CharUnits fieldOffset, llvm::Type *FieldTy);
/// AppendPadding - Appends enough padding bytes so that the total
/// struct size is a multiple of the field alignment.
void AppendPadding(CharUnits fieldOffset, CharUnits fieldAlignment);
/// ResizeLastBaseFieldIfNecessary - Fields and bases can be laid out in the
/// tail padding of a previous base. If this happens, the type of the previous
/// base needs to be changed to an array of i8. Returns true if the last
/// laid out base was resized.
bool ResizeLastBaseFieldIfNecessary(CharUnits offset);
/// getByteArrayType - Returns a byte array type with the given number of
/// elements.
llvm::Type *getByteArrayType(CharUnits NumBytes);
/// AppendBytes - Append a given number of bytes to the record.
void AppendBytes(CharUnits numBytes);
/// AppendTailPadding - Append enough tail padding so that the type will have
/// the passed size.
void AppendTailPadding(CharUnits RecordSize);
CharUnits getTypeAlignment(llvm::Type *Ty) const;
/// getAlignmentAsLLVMStruct - Returns the maximum alignment of all the
/// LLVM element types.
CharUnits getAlignmentAsLLVMStruct() const;
/// CheckZeroInitializable - Check if the given type contains a pointer
/// to data member.
void CheckZeroInitializable(QualType T);
public:
CGRecordLayoutBuilder(CodeGenTypes &Types)
: BaseSubobjectType(0),
IsZeroInitializable(true), IsZeroInitializableAsBase(true),
Packed(false), Types(Types) { }
/// Layout - Will layout a RecordDecl.
void Layout(const RecordDecl *D);
};
}
void CGRecordLayoutBuilder::Layout(const RecordDecl *D) {
Alignment = Types.getContext().getASTRecordLayout(D).getAlignment();
Packed = D->hasAttr<PackedAttr>();
if (D->isUnion()) {
LayoutUnion(D);
return;
}
if (LayoutFields(D))
return;
// We weren't able to layout the struct. Try again with a packed struct
Packed = true;
LastLaidOutBase.invalidate();
NextFieldOffset = CharUnits::Zero();
FieldTypes.clear();
Fields.clear();
BitFields.clear();
NonVirtualBases.clear();
VirtualBases.clear();
LayoutFields(D);
}
CGBitFieldInfo CGBitFieldInfo::MakeInfo(CodeGenTypes &Types,
const FieldDecl *FD,
uint64_t Offset, uint64_t Size,
uint64_t StorageSize,
uint64_t StorageAlignment) {
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, StorageAlignment);
}
/// \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;
}
bool CGRecordLayoutBuilder::LayoutField(const FieldDecl *D,
uint64_t fieldOffset) {
// If the field is packed, then we need a packed struct.
if (!Packed && D->hasAttr<PackedAttr>())
return false;
assert(!D->isBitField() && "Bitfields should be laid out seperately.");
CheckZeroInitializable(D->getType());
assert(fieldOffset % Types.getTarget().getCharWidth() == 0
&& "field offset is not on a byte boundary!");
CharUnits fieldOffsetInBytes
= Types.getContext().toCharUnitsFromBits(fieldOffset);
llvm::Type *Ty = Types.ConvertTypeForMem(D->getType());
CharUnits typeAlignment = getTypeAlignment(Ty);
// If the type alignment is larger then the struct alignment, we must use
// a packed struct.
if (typeAlignment > Alignment) {
assert(!Packed && "Alignment is wrong even with packed struct!");
return false;
}
if (!Packed) {
if (const RecordType *RT = D->getType()->getAs<RecordType>()) {
const RecordDecl *RD = cast<RecordDecl>(RT->getDecl());
if (const MaxFieldAlignmentAttr *MFAA =
RD->getAttr<MaxFieldAlignmentAttr>()) {
if (MFAA->getAlignment() != Types.getContext().toBits(typeAlignment))
return false;
}
}
}
// Round up the field offset to the alignment of the field type.
CharUnits alignedNextFieldOffsetInBytes =
NextFieldOffset.RoundUpToAlignment(typeAlignment);
if (fieldOffsetInBytes < alignedNextFieldOffsetInBytes) {
// Try to resize the last base field.
if (ResizeLastBaseFieldIfNecessary(fieldOffsetInBytes)) {
alignedNextFieldOffsetInBytes =
NextFieldOffset.RoundUpToAlignment(typeAlignment);
}
}
if (fieldOffsetInBytes < alignedNextFieldOffsetInBytes) {
assert(!Packed && "Could not place field even with packed struct!");
return false;
}
AppendPadding(fieldOffsetInBytes, typeAlignment);
// Now append the field.
Fields[D] = FieldTypes.size();
AppendField(fieldOffsetInBytes, Ty);
LastLaidOutBase.invalidate();
return true;
}
llvm::Type *
CGRecordLayoutBuilder::LayoutUnionField(const FieldDecl *Field,
const ASTRecordLayout &Layout) {
Fields[Field] = 0;
if (Field->isBitField()) {
uint64_t FieldSize = Field->getBitWidthValue(Types.getContext());
// Ignore zero sized bit fields.
if (FieldSize == 0)
return 0;
unsigned StorageBits = llvm::RoundUpToAlignment(
FieldSize, Types.getTarget().getCharAlign());
CharUnits NumBytesToAppend
= Types.getContext().toCharUnitsFromBits(StorageBits);
llvm::Type *FieldTy = llvm::Type::getInt8Ty(Types.getLLVMContext());
if (NumBytesToAppend > CharUnits::One())
FieldTy = llvm::ArrayType::get(FieldTy, NumBytesToAppend.getQuantity());
// Add the bit field info.
BitFields[Field] = CGBitFieldInfo::MakeInfo(Types, Field, 0, FieldSize,
StorageBits,
Alignment.getQuantity());
return FieldTy;
}
// This is a regular union field.
return Types.ConvertTypeForMem(Field->getType());
}
void CGRecordLayoutBuilder::LayoutUnion(const RecordDecl *D) {
assert(D->isUnion() && "Can't call LayoutUnion on a non-union record!");
const ASTRecordLayout &layout = Types.getContext().getASTRecordLayout(D);
llvm::Type *unionType = 0;
CharUnits unionSize = CharUnits::Zero();
CharUnits unionAlign = CharUnits::Zero();
bool hasOnlyZeroSizedBitFields = true;
bool checkedFirstFieldZeroInit = false;
unsigned fieldNo = 0;
for (RecordDecl::field_iterator field = D->field_begin(),
fieldEnd = D->field_end(); field != fieldEnd; ++field, ++fieldNo) {
assert(layout.getFieldOffset(fieldNo) == 0 &&
"Union field offset did not start at the beginning of record!");
llvm::Type *fieldType = LayoutUnionField(*field, layout);
if (!fieldType)
continue;
if (field->getDeclName() && !checkedFirstFieldZeroInit) {
CheckZeroInitializable(field->getType());
checkedFirstFieldZeroInit = true;
}
hasOnlyZeroSizedBitFields = false;
CharUnits fieldAlign = CharUnits::fromQuantity(
Types.getDataLayout().getABITypeAlignment(fieldType));
CharUnits fieldSize = CharUnits::fromQuantity(
Types.getDataLayout().getTypeAllocSize(fieldType));
if (fieldAlign < unionAlign)
continue;
if (fieldAlign > unionAlign || fieldSize > unionSize) {
unionType = fieldType;
unionAlign = fieldAlign;
unionSize = fieldSize;
}
}
// Now add our field.
if (unionType) {
AppendField(CharUnits::Zero(), unionType);
if (getTypeAlignment(unionType) > layout.getAlignment()) {
// We need a packed struct.
Packed = true;
unionAlign = CharUnits::One();
}
}
if (unionAlign.isZero()) {
(void)hasOnlyZeroSizedBitFields;
assert(hasOnlyZeroSizedBitFields &&
"0-align record did not have all zero-sized bit-fields!");
unionAlign = CharUnits::One();
}
// Append tail padding.
CharUnits recordSize = layout.getSize();
if (recordSize > unionSize)
AppendPadding(recordSize, unionAlign);
}
bool CGRecordLayoutBuilder::LayoutBase(const CXXRecordDecl *base,
const CGRecordLayout &baseLayout,
CharUnits baseOffset) {
ResizeLastBaseFieldIfNecessary(baseOffset);
AppendPadding(baseOffset, CharUnits::One());
const ASTRecordLayout &baseASTLayout
= Types.getContext().getASTRecordLayout(base);
LastLaidOutBase.Offset = NextFieldOffset;
LastLaidOutBase.NonVirtualSize = baseASTLayout.getNonVirtualSize();
llvm::StructType *subobjectType = baseLayout.getBaseSubobjectLLVMType();
if (getTypeAlignment(subobjectType) > Alignment)
return false;
AppendField(baseOffset, subobjectType);
return true;
}
bool CGRecordLayoutBuilder::LayoutNonVirtualBase(const CXXRecordDecl *base,
CharUnits baseOffset) {
// Ignore empty bases.
if (base->isEmpty()) return true;
const CGRecordLayout &baseLayout = Types.getCGRecordLayout(base);
if (IsZeroInitializableAsBase) {
assert(IsZeroInitializable &&
"class zero-initializable as base but not as complete object");
IsZeroInitializable = IsZeroInitializableAsBase =
baseLayout.isZeroInitializableAsBase();
}
if (!LayoutBase(base, baseLayout, baseOffset))
return false;
NonVirtualBases[base] = (FieldTypes.size() - 1);
return true;
}
bool
CGRecordLayoutBuilder::LayoutVirtualBase(const CXXRecordDecl *base,
CharUnits baseOffset) {
// Ignore empty bases.
if (base->isEmpty()) return true;
const CGRecordLayout &baseLayout = Types.getCGRecordLayout(base);
if (IsZeroInitializable)
IsZeroInitializable = baseLayout.isZeroInitializableAsBase();
if (!LayoutBase(base, baseLayout, baseOffset))
return false;
VirtualBases[base] = (FieldTypes.size() - 1);
return true;
}
bool
CGRecordLayoutBuilder::MSLayoutVirtualBases(const CXXRecordDecl *RD,
const ASTRecordLayout &Layout) {
if (!RD->getNumVBases())
return true;
// The vbases list is uniqued and ordered by a depth-first
// traversal, which is what we need here.
for (CXXRecordDecl::base_class_const_iterator I = RD->vbases_begin(),
E = RD->vbases_end(); I != E; ++I) {
const CXXRecordDecl *BaseDecl =
cast<CXXRecordDecl>(I->getType()->castAs<RecordType>()->getDecl());
CharUnits vbaseOffset = Layout.getVBaseClassOffset(BaseDecl);
if (!LayoutVirtualBase(BaseDecl, vbaseOffset))
return false;
}
return true;
}
/// LayoutVirtualBases - layout the non-virtual bases of a record decl.
bool
CGRecordLayoutBuilder::LayoutVirtualBases(const CXXRecordDecl *RD,
const ASTRecordLayout &Layout) {
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());
// We only want to lay out virtual bases that aren't indirect primary bases
// of some other base.
if (I->isVirtual() && !IndirectPrimaryBases.count(BaseDecl)) {
// Only lay out the base once.
if (!LaidOutVirtualBases.insert(BaseDecl))
continue;
CharUnits vbaseOffset = Layout.getVBaseClassOffset(BaseDecl);
if (!LayoutVirtualBase(BaseDecl, vbaseOffset))
return false;
}
if (!BaseDecl->getNumVBases()) {
// This base isn't interesting since it doesn't have any virtual bases.
continue;
}
if (!LayoutVirtualBases(BaseDecl, Layout))
return false;
}
return true;
}
bool
CGRecordLayoutBuilder::LayoutNonVirtualBases(const CXXRecordDecl *RD,
const ASTRecordLayout &Layout) {
const CXXRecordDecl *PrimaryBase = Layout.getPrimaryBase();
// If we have a primary base, lay it out first.
if (PrimaryBase) {
if (!Layout.isPrimaryBaseVirtual()) {
if (!LayoutNonVirtualBase(PrimaryBase, CharUnits::Zero()))
return false;
} else {
if (!LayoutVirtualBase(PrimaryBase, CharUnits::Zero()))
return false;
}
// Otherwise, add a vtable / vf-table if the layout says to do so.
} else if (Layout.hasOwnVFPtr()) {
llvm::Type *FunctionType =
llvm::FunctionType::get(llvm::Type::getInt32Ty(Types.getLLVMContext()),
/*isVarArg=*/true);
llvm::Type *VTableTy = FunctionType->getPointerTo();
if (getTypeAlignment(VTableTy) > Alignment) {
// FIXME: Should we allow this to happen in Sema?
assert(!Packed && "Alignment is wrong even with packed struct!");
return false;
}
assert(NextFieldOffset.isZero() &&
"VTable pointer must come first!");
AppendField(CharUnits::Zero(), VTableTy->getPointerTo());
}
// Layout the 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());
// We've already laid out the primary base.
if (BaseDecl == PrimaryBase && !Layout.isPrimaryBaseVirtual())
continue;
if (!LayoutNonVirtualBase(BaseDecl, Layout.getBaseClassOffset(BaseDecl)))
return false;
}
// Add a vb-table pointer if the layout insists.
if (Layout.getVBPtrOffset() != CharUnits::fromQuantity(-1)) {
CharUnits VBPtrOffset = Layout.getVBPtrOffset();
llvm::Type *Vbptr = llvm::Type::getInt32PtrTy(Types.getLLVMContext());
AppendPadding(VBPtrOffset, getTypeAlignment(Vbptr));
AppendField(VBPtrOffset, Vbptr);
}
return true;
}
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;
}
bool CGRecordLayoutBuilder::LayoutFields(const RecordDecl *D) {
assert(!D->isUnion() && "Can't call LayoutFields on a union!");
assert(!Alignment.isZero() && "Did not set alignment!");
const ASTRecordLayout &Layout = Types.getContext().getASTRecordLayout(D);
const CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(D);
if (RD)
if (!LayoutNonVirtualBases(RD, Layout))
return false;
unsigned FieldNo = 0;
for (RecordDecl::field_iterator FI = D->field_begin(), FE = D->field_end();
FI != FE; ++FI, ++FieldNo) {
FieldDecl *FD = *FI;
// If this field is a bitfield, layout all of the consecutive
// non-zero-length bitfields and the last zero-length bitfield; these will
// all share storage.
if (FD->isBitField()) {
// If all we have is a zero-width bitfield, skip it.
if (FD->getBitWidthValue(Types.getContext()) == 0)
continue;
// Layout this range of bitfields.
if (!LayoutBitfields(Layout, FieldNo, FI, FE)) {
assert(!Packed &&
"Could not layout bitfields even with a packed LLVM struct!");
return false;
}
assert(FI != FE && "Advanced past the last bitfield");
continue;
}
if (!LayoutField(FD, Layout.getFieldOffset(FieldNo))) {
assert(!Packed &&
"Could not layout fields even with a packed LLVM struct!");
return false;
}
}
if (RD) {
// We've laid out the non-virtual bases and the fields, now compute the
// non-virtual base field types.
if (!ComputeNonVirtualBaseType(RD)) {
assert(!Packed && "Could not layout even with a packed LLVM struct!");
return false;
}
// Lay out the virtual bases. The MS ABI uses a different
// algorithm here due to the lack of primary virtual bases.
if (Types.getTarget().getCXXABI().hasPrimaryVBases()) {
RD->getIndirectPrimaryBases(IndirectPrimaryBases);
if (Layout.isPrimaryBaseVirtual())
IndirectPrimaryBases.insert(Layout.getPrimaryBase());
if (!LayoutVirtualBases(RD, Layout))
return false;
} else {
if (!MSLayoutVirtualBases(RD, Layout))
return false;
}
}
// Append tail padding if necessary.
AppendTailPadding(Layout.getSize());
return true;
}
void CGRecordLayoutBuilder::AppendTailPadding(CharUnits RecordSize) {
ResizeLastBaseFieldIfNecessary(RecordSize);
assert(NextFieldOffset <= RecordSize && "Size mismatch!");
CharUnits AlignedNextFieldOffset =
NextFieldOffset.RoundUpToAlignment(getAlignmentAsLLVMStruct());
if (AlignedNextFieldOffset == RecordSize) {
// We don't need any padding.
return;
}
CharUnits NumPadBytes = RecordSize - NextFieldOffset;
AppendBytes(NumPadBytes);
}
void CGRecordLayoutBuilder::AppendField(CharUnits fieldOffset,
llvm::Type *fieldType) {
CharUnits fieldSize =
CharUnits::fromQuantity(Types.getDataLayout().getTypeAllocSize(fieldType));
FieldTypes.push_back(fieldType);
NextFieldOffset = fieldOffset + fieldSize;
}
void CGRecordLayoutBuilder::AppendPadding(CharUnits fieldOffset,
CharUnits fieldAlignment) {
assert(NextFieldOffset <= fieldOffset &&
"Incorrect field layout!");
// Do nothing if we're already at the right offset.
if (fieldOffset == NextFieldOffset) return;
// If we're not emitting a packed LLVM type, try to avoid adding
// unnecessary padding fields.
if (!Packed) {
// Round up the field offset to the alignment of the field type.
CharUnits alignedNextFieldOffset =
NextFieldOffset.RoundUpToAlignment(fieldAlignment);
assert(alignedNextFieldOffset <= fieldOffset);
// If that's the right offset, we're done.
if (alignedNextFieldOffset == fieldOffset) return;
}
// Otherwise we need explicit padding.
CharUnits padding = fieldOffset - NextFieldOffset;
AppendBytes(padding);
}
bool CGRecordLayoutBuilder::ResizeLastBaseFieldIfNecessary(CharUnits offset) {
// Check if we have a base to resize.
if (!LastLaidOutBase.isValid())
return false;
// This offset does not overlap with the tail padding.
if (offset >= NextFieldOffset)
return false;
// Restore the field offset and append an i8 array instead.
FieldTypes.pop_back();
NextFieldOffset = LastLaidOutBase.Offset;
AppendBytes(LastLaidOutBase.NonVirtualSize);
LastLaidOutBase.invalidate();
return true;
}
llvm::Type *CGRecordLayoutBuilder::getByteArrayType(CharUnits numBytes) {
assert(!numBytes.isZero() && "Empty byte arrays aren't allowed.");
llvm::Type *Ty = llvm::Type::getInt8Ty(Types.getLLVMContext());
if (numBytes > CharUnits::One())
Ty = llvm::ArrayType::get(Ty, numBytes.getQuantity());
return Ty;
}
void CGRecordLayoutBuilder::AppendBytes(CharUnits numBytes) {
if (numBytes.isZero())
return;
// Append the padding field
AppendField(NextFieldOffset, getByteArrayType(numBytes));
}
CharUnits CGRecordLayoutBuilder::getTypeAlignment(llvm::Type *Ty) const {
if (Packed)
return CharUnits::One();
return CharUnits::fromQuantity(Types.getDataLayout().getABITypeAlignment(Ty));
}
CharUnits CGRecordLayoutBuilder::getAlignmentAsLLVMStruct() const {
if (Packed)
return CharUnits::One();
CharUnits maxAlignment = CharUnits::One();
for (size_t i = 0; i != FieldTypes.size(); ++i)
maxAlignment = std::max(maxAlignment, getTypeAlignment(FieldTypes[i]));
return maxAlignment;
}
/// Merge in whether a field of the given type is zero-initializable.
void CGRecordLayoutBuilder::CheckZeroInitializable(QualType T) {
// This record already contains a member pointer.
if (!IsZeroInitializableAsBase)
return;
// Can only have member pointers if we're compiling C++.
if (!Types.getContext().getLangOpts().CPlusPlus)
return;
const Type *elementType = T->getBaseElementTypeUnsafe();
if (const MemberPointerType *MPT = elementType->getAs<MemberPointerType>()) {
if (!Types.getCXXABI().isZeroInitializable(MPT))
IsZeroInitializable = IsZeroInitializableAsBase = false;
} else if (const RecordType *RT = elementType->getAs<RecordType>()) {
const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
const CGRecordLayout &Layout = Types.getCGRecordLayout(RD);
if (!Layout.isZeroInitializable())
IsZeroInitializable = IsZeroInitializableAsBase = false;
}
}
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;
}
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";
}
void CGRecordLayout::dump() const {
print(llvm::errs());
}
void CGBitFieldInfo::print(raw_ostream &OS) const {
OS << "<CGBitFieldInfo"
<< " Offset:" << Offset
<< " Size:" << Size
<< " IsSigned:" << IsSigned
<< " StorageSize:" << StorageSize
<< " StorageAlignment:" << StorageAlignment << ">";
}
void CGBitFieldInfo::dump() const {
print(llvm::errs());
}
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