1 //===--- CGRecordLayoutBuilder.cpp - CGRecordLayout builder ----*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // Builder implementation for CGRecordLayout objects.
12 //===----------------------------------------------------------------------===//
14 #include "CGRecordLayout.h"
15 #include "clang/AST/ASTContext.h"
16 #include "clang/AST/Attr.h"
17 #include "clang/AST/CXXInheritance.h"
18 #include "clang/AST/DeclCXX.h"
19 #include "clang/AST/Expr.h"
20 #include "clang/AST/RecordLayout.h"
21 #include "clang/Frontend/CodeGenOptions.h"
22 #include "CodeGenTypes.h"
24 #include "llvm/DerivedTypes.h"
25 #include "llvm/Type.h"
26 #include "llvm/Support/Debug.h"
27 #include "llvm/Support/raw_ostream.h"
28 #include "llvm/Target/TargetData.h"
29 using namespace clang;
30 using namespace CodeGen;
34 class CGRecordLayoutBuilder {
36 /// FieldTypes - Holds the LLVM types that the struct is created from.
38 llvm::SmallVector<llvm::Type *, 16> FieldTypes;
40 /// BaseSubobjectType - Holds the LLVM type for the non-virtual part
41 /// of the struct. For example, consider:
43 /// struct A { int i; };
44 /// struct B { void *v; };
45 /// struct C : virtual A, B { };
47 /// The LLVM type of C will be
48 /// %struct.C = type { i32 (...)**, %struct.A, i32, %struct.B }
50 /// And the LLVM type of the non-virtual base struct will be
51 /// %struct.C.base = type { i32 (...)**, %struct.A, i32 }
53 /// This only gets initialized if the base subobject type is
54 /// different from the complete-object type.
55 llvm::StructType *BaseSubobjectType;
57 /// FieldInfo - Holds a field and its corresponding LLVM field number.
58 llvm::DenseMap<const FieldDecl *, unsigned> Fields;
60 /// BitFieldInfo - Holds location and size information about a bit field.
61 llvm::DenseMap<const FieldDecl *, CGBitFieldInfo> BitFields;
63 llvm::DenseMap<const CXXRecordDecl *, unsigned> NonVirtualBases;
64 llvm::DenseMap<const CXXRecordDecl *, unsigned> VirtualBases;
66 /// IndirectPrimaryBases - Virtual base classes, direct or indirect, that are
67 /// primary base classes for some other direct or indirect base class.
68 CXXIndirectPrimaryBaseSet IndirectPrimaryBases;
70 /// LaidOutVirtualBases - A set of all laid out virtual bases, used to avoid
71 /// avoid laying out virtual bases more than once.
72 llvm::SmallPtrSet<const CXXRecordDecl *, 4> LaidOutVirtualBases;
74 /// IsZeroInitializable - Whether this struct can be C++
75 /// zero-initialized with an LLVM zeroinitializer.
76 bool IsZeroInitializable;
77 bool IsZeroInitializableAsBase;
79 /// Packed - Whether the resulting LLVM struct will be packed or not.
82 /// IsMsStruct - Whether ms_struct is in effect or not
88 /// LastLaidOutBaseInfo - Contains the offset and non-virtual size of the
89 /// last base laid out. Used so that we can replace the last laid out base
90 /// type with an i8 array if needed.
91 struct LastLaidOutBaseInfo {
93 CharUnits NonVirtualSize;
95 bool isValid() const { return !NonVirtualSize.isZero(); }
96 void invalidate() { NonVirtualSize = CharUnits::Zero(); }
100 /// Alignment - Contains the alignment of the RecordDecl.
103 /// BitsAvailableInLastField - If a bit field spans only part of a LLVM field,
104 /// this will have the number of bits still available in the field.
105 char BitsAvailableInLastField;
107 /// NextFieldOffset - Holds the next field offset.
108 CharUnits NextFieldOffset;
110 /// LayoutUnionField - Will layout a field in an union and return the type
111 /// that the field will have.
112 llvm::Type *LayoutUnionField(const FieldDecl *Field,
113 const ASTRecordLayout &Layout);
115 /// LayoutUnion - Will layout a union RecordDecl.
116 void LayoutUnion(const RecordDecl *D);
118 /// LayoutField - try to layout all fields in the record decl.
119 /// Returns false if the operation failed because the struct is not packed.
120 bool LayoutFields(const RecordDecl *D);
122 /// Layout a single base, virtual or non-virtual
123 void LayoutBase(const CXXRecordDecl *base,
124 const CGRecordLayout &baseLayout,
125 CharUnits baseOffset);
127 /// LayoutVirtualBase - layout a single virtual base.
128 void LayoutVirtualBase(const CXXRecordDecl *base,
129 CharUnits baseOffset);
131 /// LayoutVirtualBases - layout the virtual bases of a record decl.
132 void LayoutVirtualBases(const CXXRecordDecl *RD,
133 const ASTRecordLayout &Layout);
135 /// LayoutNonVirtualBase - layout a single non-virtual base.
136 void LayoutNonVirtualBase(const CXXRecordDecl *base,
137 CharUnits baseOffset);
139 /// LayoutNonVirtualBases - layout the virtual bases of a record decl.
140 void LayoutNonVirtualBases(const CXXRecordDecl *RD,
141 const ASTRecordLayout &Layout);
143 /// ComputeNonVirtualBaseType - Compute the non-virtual base field types.
144 bool ComputeNonVirtualBaseType(const CXXRecordDecl *RD);
146 /// LayoutField - layout a single field. Returns false if the operation failed
147 /// because the current struct is not packed.
148 bool LayoutField(const FieldDecl *D, uint64_t FieldOffset);
150 /// LayoutBitField - layout a single bit field.
151 void LayoutBitField(const FieldDecl *D, uint64_t FieldOffset);
153 /// AppendField - Appends a field with the given offset and type.
154 void AppendField(CharUnits fieldOffset, llvm::Type *FieldTy);
156 /// AppendPadding - Appends enough padding bytes so that the total
157 /// struct size is a multiple of the field alignment.
158 void AppendPadding(CharUnits fieldOffset, CharUnits fieldAlignment);
160 /// ResizeLastBaseFieldIfNecessary - Fields and bases can be laid out in the
161 /// tail padding of a previous base. If this happens, the type of the previous
162 /// base needs to be changed to an array of i8. Returns true if the last
163 /// laid out base was resized.
164 bool ResizeLastBaseFieldIfNecessary(CharUnits offset);
166 /// getByteArrayType - Returns a byte array type with the given number of
168 llvm::Type *getByteArrayType(CharUnits NumBytes);
170 /// AppendBytes - Append a given number of bytes to the record.
171 void AppendBytes(CharUnits numBytes);
173 /// AppendTailPadding - Append enough tail padding so that the type will have
175 void AppendTailPadding(CharUnits RecordSize);
177 CharUnits getTypeAlignment(const llvm::Type *Ty) const;
179 /// getAlignmentAsLLVMStruct - Returns the maximum alignment of all the
180 /// LLVM element types.
181 CharUnits getAlignmentAsLLVMStruct() const;
183 /// CheckZeroInitializable - Check if the given type contains a pointer
185 void CheckZeroInitializable(QualType T);
188 CGRecordLayoutBuilder(CodeGenTypes &Types)
189 : BaseSubobjectType(0),
190 IsZeroInitializable(true), IsZeroInitializableAsBase(true),
191 Packed(false), IsMsStruct(false),
192 Types(Types), BitsAvailableInLastField(0) { }
194 /// Layout - Will layout a RecordDecl.
195 void Layout(const RecordDecl *D);
200 void CGRecordLayoutBuilder::Layout(const RecordDecl *D) {
201 Alignment = Types.getContext().getASTRecordLayout(D).getAlignment();
202 Packed = D->hasAttr<PackedAttr>();
204 IsMsStruct = D->hasAttr<MsStructAttr>();
214 // We weren't able to layout the struct. Try again with a packed struct
216 LastLaidOutBase.invalidate();
217 NextFieldOffset = CharUnits::Zero();
221 NonVirtualBases.clear();
222 VirtualBases.clear();
227 CGBitFieldInfo CGBitFieldInfo::MakeInfo(CodeGenTypes &Types,
229 uint64_t FieldOffset,
231 uint64_t ContainingTypeSizeInBits,
232 unsigned ContainingTypeAlign) {
233 const llvm::Type *Ty = Types.ConvertTypeForMem(FD->getType());
234 CharUnits TypeSizeInBytes =
235 CharUnits::fromQuantity(Types.getTargetData().getTypeAllocSize(Ty));
236 uint64_t TypeSizeInBits = Types.getContext().toBits(TypeSizeInBytes);
238 bool IsSigned = FD->getType()->isSignedIntegerOrEnumerationType();
240 if (FieldSize > TypeSizeInBits) {
241 // We have a wide bit-field. The extra bits are only used for padding, so
242 // if we have a bitfield of type T, with size N:
246 // We can just assume that it's:
250 FieldSize = TypeSizeInBits;
253 // in big-endian machines the first fields are in higher bit positions,
254 // so revert the offset. The byte offsets are reversed(back) later.
255 if (Types.getTargetData().isBigEndian()) {
256 FieldOffset = ((ContainingTypeSizeInBits)-FieldOffset-FieldSize);
259 // Compute the access components. The policy we use is to start by attempting
260 // to access using the width of the bit-field type itself and to always access
261 // at aligned indices of that type. If such an access would fail because it
262 // extends past the bound of the type, then we reduce size to the next smaller
263 // power of two and retry. The current algorithm assumes pow2 sized types,
264 // although this is easy to fix.
266 assert(llvm::isPowerOf2_32(TypeSizeInBits) && "Unexpected type size!");
267 CGBitFieldInfo::AccessInfo Components[3];
268 unsigned NumComponents = 0;
269 unsigned AccessedTargetBits = 0; // The number of target bits accessed.
270 unsigned AccessWidth = TypeSizeInBits; // The current access width to attempt.
272 // If requested, widen the initial bit-field access to be register sized. The
273 // theory is that this is most likely to allow multiple accesses into the same
274 // structure to be coalesced, and that the backend should be smart enough to
275 // narrow the store if no coalescing is ever done.
277 // The subsequent code will handle align these access to common boundaries and
278 // guaranteeing that we do not access past the end of the structure.
279 if (Types.getCodeGenOpts().UseRegisterSizedBitfieldAccess) {
280 if (AccessWidth < Types.getTarget().getRegisterWidth())
281 AccessWidth = Types.getTarget().getRegisterWidth();
284 // Round down from the field offset to find the first access position that is
285 // at an aligned offset of the initial access type.
286 uint64_t AccessStart = FieldOffset - (FieldOffset % AccessWidth);
288 // Adjust initial access size to fit within record.
289 while (AccessWidth > Types.getTarget().getCharWidth() &&
290 AccessStart + AccessWidth > ContainingTypeSizeInBits) {
292 AccessStart = FieldOffset - (FieldOffset % AccessWidth);
295 while (AccessedTargetBits < FieldSize) {
296 // Check that we can access using a type of this size, without reading off
297 // the end of the structure. This can occur with packed structures and
298 // -fno-bitfield-type-align, for example.
299 if (AccessStart + AccessWidth > ContainingTypeSizeInBits) {
300 // If so, reduce access size to the next smaller power-of-two and retry.
302 assert(AccessWidth >= Types.getTarget().getCharWidth()
303 && "Cannot access under byte size!");
307 // Otherwise, add an access component.
309 // First, compute the bits inside this access which are part of the
310 // target. We are reading bits [AccessStart, AccessStart + AccessWidth); the
311 // intersection with [FieldOffset, FieldOffset + FieldSize) gives the bits
312 // in the target that we are reading.
313 assert(FieldOffset < AccessStart + AccessWidth && "Invalid access start!");
314 assert(AccessStart < FieldOffset + FieldSize && "Invalid access start!");
315 uint64_t AccessBitsInFieldStart = std::max(AccessStart, FieldOffset);
316 uint64_t AccessBitsInFieldSize =
317 std::min(AccessWidth + AccessStart,
318 FieldOffset + FieldSize) - AccessBitsInFieldStart;
320 assert(NumComponents < 3 && "Unexpected number of components!");
321 CGBitFieldInfo::AccessInfo &AI = Components[NumComponents++];
323 // FIXME: We still follow the old access pattern of only using the field
324 // byte offset. We should switch this once we fix the struct layout to be
327 // on big-endian machines we reverted the bit offset because first fields are
328 // in higher bits. But this also reverts the bytes, so fix this here by reverting
329 // the byte offset on big-endian machines.
330 if (Types.getTargetData().isBigEndian()) {
331 AI.FieldByteOffset = Types.getContext().toCharUnitsFromBits(
332 ContainingTypeSizeInBits - AccessStart - AccessWidth);
334 AI.FieldByteOffset = Types.getContext().toCharUnitsFromBits(AccessStart);
336 AI.FieldBitStart = AccessBitsInFieldStart - AccessStart;
337 AI.AccessWidth = AccessWidth;
338 AI.AccessAlignment = Types.getContext().toCharUnitsFromBits(
339 llvm::MinAlign(ContainingTypeAlign, AccessStart));
340 AI.TargetBitOffset = AccessedTargetBits;
341 AI.TargetBitWidth = AccessBitsInFieldSize;
343 AccessStart += AccessWidth;
344 AccessedTargetBits += AI.TargetBitWidth;
347 assert(AccessedTargetBits == FieldSize && "Invalid bit-field access!");
348 return CGBitFieldInfo(FieldSize, NumComponents, Components, IsSigned);
351 CGBitFieldInfo CGBitFieldInfo::MakeInfo(CodeGenTypes &Types,
353 uint64_t FieldOffset,
354 uint64_t FieldSize) {
355 const RecordDecl *RD = FD->getParent();
356 const ASTRecordLayout &RL = Types.getContext().getASTRecordLayout(RD);
357 uint64_t ContainingTypeSizeInBits = Types.getContext().toBits(RL.getSize());
358 unsigned ContainingTypeAlign = Types.getContext().toBits(RL.getAlignment());
360 return MakeInfo(Types, FD, FieldOffset, FieldSize, ContainingTypeSizeInBits,
361 ContainingTypeAlign);
364 void CGRecordLayoutBuilder::LayoutBitField(const FieldDecl *D,
365 uint64_t fieldOffset) {
367 D->getBitWidth()->EvaluateAsInt(Types.getContext()).getZExtValue();
372 uint64_t nextFieldOffsetInBits = Types.getContext().toBits(NextFieldOffset);
373 CharUnits numBytesToAppend;
374 unsigned charAlign = Types.getContext().Target.getCharAlign();
376 if (fieldOffset < nextFieldOffsetInBits && !BitsAvailableInLastField) {
377 assert(fieldOffset % charAlign == 0 &&
378 "Field offset not aligned correctly");
380 CharUnits fieldOffsetInCharUnits =
381 Types.getContext().toCharUnitsFromBits(fieldOffset);
383 // Try to resize the last base field.
384 if (ResizeLastBaseFieldIfNecessary(fieldOffsetInCharUnits))
385 nextFieldOffsetInBits = Types.getContext().toBits(NextFieldOffset);
388 if (fieldOffset < nextFieldOffsetInBits) {
389 assert(BitsAvailableInLastField && "Bitfield size mismatch!");
390 assert(!NextFieldOffset.isZero() && "Must have laid out at least one byte");
392 // The bitfield begins in the previous bit-field.
393 numBytesToAppend = Types.getContext().toCharUnitsFromBits(
394 llvm::RoundUpToAlignment(fieldSize - BitsAvailableInLastField,
397 assert(fieldOffset % charAlign == 0 &&
398 "Field offset not aligned correctly");
400 // Append padding if necessary.
401 AppendPadding(Types.getContext().toCharUnitsFromBits(fieldOffset),
404 numBytesToAppend = Types.getContext().toCharUnitsFromBits(
405 llvm::RoundUpToAlignment(fieldSize, charAlign));
407 assert(!numBytesToAppend.isZero() && "No bytes to append!");
410 // Add the bit field info.
411 BitFields.insert(std::make_pair(D,
412 CGBitFieldInfo::MakeInfo(Types, D, fieldOffset, fieldSize)));
414 AppendBytes(numBytesToAppend);
416 BitsAvailableInLastField =
417 Types.getContext().toBits(NextFieldOffset) - (fieldOffset + fieldSize);
420 bool CGRecordLayoutBuilder::LayoutField(const FieldDecl *D,
421 uint64_t fieldOffset) {
422 // If the field is packed, then we need a packed struct.
423 if (!Packed && D->hasAttr<PackedAttr>())
426 if (D->isBitField()) {
427 // We must use packed structs for unnamed bit fields since they
428 // don't affect the struct alignment.
429 if (!Packed && !D->getDeclName())
432 LayoutBitField(D, fieldOffset);
436 CheckZeroInitializable(D->getType());
438 assert(fieldOffset % Types.getTarget().getCharWidth() == 0
439 && "field offset is not on a byte boundary!");
440 CharUnits fieldOffsetInBytes
441 = Types.getContext().toCharUnitsFromBits(fieldOffset);
443 llvm::Type *Ty = Types.ConvertTypeForMem(D->getType());
444 CharUnits typeAlignment = getTypeAlignment(Ty);
446 // If the type alignment is larger then the struct alignment, we must use
448 if (typeAlignment > Alignment) {
449 assert(!Packed && "Alignment is wrong even with packed struct!");
454 if (const RecordType *RT = D->getType()->getAs<RecordType>()) {
455 const RecordDecl *RD = cast<RecordDecl>(RT->getDecl());
456 if (const MaxFieldAlignmentAttr *MFAA =
457 RD->getAttr<MaxFieldAlignmentAttr>()) {
458 if (MFAA->getAlignment() != Types.getContext().toBits(typeAlignment))
464 // Round up the field offset to the alignment of the field type.
465 CharUnits alignedNextFieldOffsetInBytes =
466 NextFieldOffset.RoundUpToAlignment(typeAlignment);
468 if (fieldOffsetInBytes < alignedNextFieldOffsetInBytes) {
469 // Try to resize the last base field.
470 if (ResizeLastBaseFieldIfNecessary(fieldOffsetInBytes)) {
471 alignedNextFieldOffsetInBytes =
472 NextFieldOffset.RoundUpToAlignment(typeAlignment);
476 if (fieldOffsetInBytes < alignedNextFieldOffsetInBytes) {
477 assert(!Packed && "Could not place field even with packed struct!");
481 AppendPadding(fieldOffsetInBytes, typeAlignment);
483 // Now append the field.
484 Fields[D] = FieldTypes.size();
485 AppendField(fieldOffsetInBytes, Ty);
487 LastLaidOutBase.invalidate();
492 CGRecordLayoutBuilder::LayoutUnionField(const FieldDecl *Field,
493 const ASTRecordLayout &Layout) {
494 if (Field->isBitField()) {
496 Field->getBitWidth()->EvaluateAsInt(Types.getContext()).getZExtValue();
498 // Ignore zero sized bit fields.
502 llvm::Type *FieldTy = llvm::Type::getInt8Ty(Types.getLLVMContext());
503 CharUnits NumBytesToAppend = Types.getContext().toCharUnitsFromBits(
504 llvm::RoundUpToAlignment(FieldSize,
505 Types.getContext().Target.getCharAlign()));
507 if (NumBytesToAppend > CharUnits::One())
508 FieldTy = llvm::ArrayType::get(FieldTy, NumBytesToAppend.getQuantity());
510 // Add the bit field info.
511 BitFields.insert(std::make_pair(Field,
512 CGBitFieldInfo::MakeInfo(Types, Field, 0, FieldSize)));
516 // This is a regular union field.
518 return Types.ConvertTypeForMem(Field->getType());
521 void CGRecordLayoutBuilder::LayoutUnion(const RecordDecl *D) {
522 assert(D->isUnion() && "Can't call LayoutUnion on a non-union record!");
524 const ASTRecordLayout &layout = Types.getContext().getASTRecordLayout(D);
526 llvm::Type *unionType = 0;
527 CharUnits unionSize = CharUnits::Zero();
528 CharUnits unionAlign = CharUnits::Zero();
530 bool hasOnlyZeroSizedBitFields = true;
532 unsigned fieldNo = 0;
533 for (RecordDecl::field_iterator field = D->field_begin(),
534 fieldEnd = D->field_end(); field != fieldEnd; ++field, ++fieldNo) {
535 assert(layout.getFieldOffset(fieldNo) == 0 &&
536 "Union field offset did not start at the beginning of record!");
537 llvm::Type *fieldType = LayoutUnionField(*field, layout);
542 hasOnlyZeroSizedBitFields = false;
544 CharUnits fieldAlign = CharUnits::fromQuantity(
545 Types.getTargetData().getABITypeAlignment(fieldType));
546 CharUnits fieldSize = CharUnits::fromQuantity(
547 Types.getTargetData().getTypeAllocSize(fieldType));
549 if (fieldAlign < unionAlign)
552 if (fieldAlign > unionAlign || fieldSize > unionSize) {
553 unionType = fieldType;
554 unionAlign = fieldAlign;
555 unionSize = fieldSize;
559 // Now add our field.
561 AppendField(CharUnits::Zero(), unionType);
563 if (getTypeAlignment(unionType) > layout.getAlignment()) {
564 // We need a packed struct.
566 unionAlign = CharUnits::One();
569 if (unionAlign.isZero()) {
570 assert(hasOnlyZeroSizedBitFields &&
571 "0-align record did not have all zero-sized bit-fields!");
572 unionAlign = CharUnits::One();
575 // Append tail padding.
576 CharUnits recordSize = layout.getSize();
577 if (recordSize > unionSize)
578 AppendPadding(recordSize, unionAlign);
581 void CGRecordLayoutBuilder::LayoutBase(const CXXRecordDecl *base,
582 const CGRecordLayout &baseLayout,
583 CharUnits baseOffset) {
584 ResizeLastBaseFieldIfNecessary(baseOffset);
586 AppendPadding(baseOffset, CharUnits::One());
588 const ASTRecordLayout &baseASTLayout
589 = Types.getContext().getASTRecordLayout(base);
591 LastLaidOutBase.Offset = NextFieldOffset;
592 LastLaidOutBase.NonVirtualSize = baseASTLayout.getNonVirtualSize();
594 // Fields and bases can be laid out in the tail padding of previous
595 // bases. If this happens, we need to allocate the base as an i8
596 // array; otherwise, we can use the subobject type. However,
597 // actually doing that would require knowledge of what immediately
598 // follows this base in the layout, so instead we do a conservative
599 // approximation, which is to use the base subobject type if it
600 // has the same LLVM storage size as the nvsize.
602 llvm::StructType *subobjectType = baseLayout.getBaseSubobjectLLVMType();
603 AppendField(baseOffset, subobjectType);
606 void CGRecordLayoutBuilder::LayoutNonVirtualBase(const CXXRecordDecl *base,
607 CharUnits baseOffset) {
608 // Ignore empty bases.
609 if (base->isEmpty()) return;
611 const CGRecordLayout &baseLayout = Types.getCGRecordLayout(base);
612 if (IsZeroInitializableAsBase) {
613 assert(IsZeroInitializable &&
614 "class zero-initializable as base but not as complete object");
616 IsZeroInitializable = IsZeroInitializableAsBase =
617 baseLayout.isZeroInitializableAsBase();
620 LayoutBase(base, baseLayout, baseOffset);
621 NonVirtualBases[base] = (FieldTypes.size() - 1);
625 CGRecordLayoutBuilder::LayoutVirtualBase(const CXXRecordDecl *base,
626 CharUnits baseOffset) {
627 // Ignore empty bases.
628 if (base->isEmpty()) return;
630 const CGRecordLayout &baseLayout = Types.getCGRecordLayout(base);
631 if (IsZeroInitializable)
632 IsZeroInitializable = baseLayout.isZeroInitializableAsBase();
634 LayoutBase(base, baseLayout, baseOffset);
635 VirtualBases[base] = (FieldTypes.size() - 1);
638 /// LayoutVirtualBases - layout the non-virtual bases of a record decl.
640 CGRecordLayoutBuilder::LayoutVirtualBases(const CXXRecordDecl *RD,
641 const ASTRecordLayout &Layout) {
642 for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
643 E = RD->bases_end(); I != E; ++I) {
644 const CXXRecordDecl *BaseDecl =
645 cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
647 // We only want to lay out virtual bases that aren't indirect primary bases
648 // of some other base.
649 if (I->isVirtual() && !IndirectPrimaryBases.count(BaseDecl)) {
650 // Only lay out the base once.
651 if (!LaidOutVirtualBases.insert(BaseDecl))
654 CharUnits vbaseOffset = Layout.getVBaseClassOffset(BaseDecl);
655 LayoutVirtualBase(BaseDecl, vbaseOffset);
658 if (!BaseDecl->getNumVBases()) {
659 // This base isn't interesting since it doesn't have any virtual bases.
663 LayoutVirtualBases(BaseDecl, Layout);
668 CGRecordLayoutBuilder::LayoutNonVirtualBases(const CXXRecordDecl *RD,
669 const ASTRecordLayout &Layout) {
670 const CXXRecordDecl *PrimaryBase = Layout.getPrimaryBase();
672 // Check if we need to add a vtable pointer.
673 if (RD->isDynamicClass()) {
675 const llvm::Type *FunctionType =
676 llvm::FunctionType::get(llvm::Type::getInt32Ty(Types.getLLVMContext()),
678 const llvm::Type *VTableTy = FunctionType->getPointerTo();
680 assert(NextFieldOffset.isZero() &&
681 "VTable pointer must come first!");
682 AppendField(CharUnits::Zero(), VTableTy->getPointerTo());
684 if (!Layout.isPrimaryBaseVirtual())
685 LayoutNonVirtualBase(PrimaryBase, CharUnits::Zero());
687 LayoutVirtualBase(PrimaryBase, CharUnits::Zero());
691 // Layout the non-virtual bases.
692 for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
693 E = RD->bases_end(); I != E; ++I) {
697 const CXXRecordDecl *BaseDecl =
698 cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
700 // We've already laid out the primary base.
701 if (BaseDecl == PrimaryBase && !Layout.isPrimaryBaseVirtual())
704 LayoutNonVirtualBase(BaseDecl, Layout.getBaseClassOffset(BaseDecl));
709 CGRecordLayoutBuilder::ComputeNonVirtualBaseType(const CXXRecordDecl *RD) {
710 const ASTRecordLayout &Layout = Types.getContext().getASTRecordLayout(RD);
712 CharUnits NonVirtualSize = Layout.getNonVirtualSize();
713 CharUnits NonVirtualAlign = Layout.getNonVirtualAlign();
714 CharUnits AlignedNonVirtualTypeSize =
715 NonVirtualSize.RoundUpToAlignment(NonVirtualAlign);
717 // First check if we can use the same fields as for the complete class.
718 CharUnits RecordSize = Layout.getSize();
719 if (AlignedNonVirtualTypeSize == RecordSize)
722 // Check if we need padding.
723 CharUnits AlignedNextFieldOffset =
724 NextFieldOffset.RoundUpToAlignment(getAlignmentAsLLVMStruct());
726 if (AlignedNextFieldOffset > AlignedNonVirtualTypeSize) {
727 assert(!Packed && "cannot layout even as packed struct");
728 return false; // Needs packing.
731 bool needsPadding = (AlignedNonVirtualTypeSize != AlignedNextFieldOffset);
733 CharUnits NumBytes = AlignedNonVirtualTypeSize - AlignedNextFieldOffset;
734 FieldTypes.push_back(getByteArrayType(NumBytes));
738 BaseSubobjectType = llvm::StructType::createNamed(Types.getLLVMContext(), "",
740 Types.addRecordTypeName(RD, BaseSubobjectType, ".base");
742 // Pull the padding back off.
744 FieldTypes.pop_back();
749 bool CGRecordLayoutBuilder::LayoutFields(const RecordDecl *D) {
750 assert(!D->isUnion() && "Can't call LayoutFields on a union!");
751 assert(!Alignment.isZero() && "Did not set alignment!");
753 const ASTRecordLayout &Layout = Types.getContext().getASTRecordLayout(D);
755 const CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(D);
757 LayoutNonVirtualBases(RD, Layout);
759 unsigned FieldNo = 0;
760 const FieldDecl *LastFD = 0;
762 for (RecordDecl::field_iterator Field = D->field_begin(),
763 FieldEnd = D->field_end(); Field != FieldEnd; ++Field, ++FieldNo) {
765 // Zero-length bitfields following non-bitfield members are
767 const FieldDecl *FD = (*Field);
768 if (Types.getContext().ZeroBitfieldFollowsNonBitfield(FD, LastFD)) {
775 if (!LayoutField(*Field, Layout.getFieldOffset(FieldNo))) {
777 "Could not layout fields even with a packed LLVM struct!");
783 // We've laid out the non-virtual bases and the fields, now compute the
784 // non-virtual base field types.
785 if (!ComputeNonVirtualBaseType(RD)) {
786 assert(!Packed && "Could not layout even with a packed LLVM struct!");
790 // And lay out the virtual bases.
791 RD->getIndirectPrimaryBases(IndirectPrimaryBases);
792 if (Layout.isPrimaryBaseVirtual())
793 IndirectPrimaryBases.insert(Layout.getPrimaryBase());
794 LayoutVirtualBases(RD, Layout);
797 // Append tail padding if necessary.
798 AppendTailPadding(Layout.getSize());
803 void CGRecordLayoutBuilder::AppendTailPadding(CharUnits RecordSize) {
804 ResizeLastBaseFieldIfNecessary(RecordSize);
806 assert(NextFieldOffset <= RecordSize && "Size mismatch!");
808 CharUnits AlignedNextFieldOffset =
809 NextFieldOffset.RoundUpToAlignment(getAlignmentAsLLVMStruct());
811 if (AlignedNextFieldOffset == RecordSize) {
812 // We don't need any padding.
816 CharUnits NumPadBytes = RecordSize - NextFieldOffset;
817 AppendBytes(NumPadBytes);
820 void CGRecordLayoutBuilder::AppendField(CharUnits fieldOffset,
821 llvm::Type *fieldType) {
822 CharUnits fieldSize =
823 CharUnits::fromQuantity(Types.getTargetData().getTypeAllocSize(fieldType));
825 FieldTypes.push_back(fieldType);
827 NextFieldOffset = fieldOffset + fieldSize;
828 BitsAvailableInLastField = 0;
831 void CGRecordLayoutBuilder::AppendPadding(CharUnits fieldOffset,
832 CharUnits fieldAlignment) {
833 assert(NextFieldOffset <= fieldOffset &&
834 "Incorrect field layout!");
836 // Round up the field offset to the alignment of the field type.
837 CharUnits alignedNextFieldOffset =
838 NextFieldOffset.RoundUpToAlignment(fieldAlignment);
840 if (alignedNextFieldOffset < fieldOffset) {
841 // Even with alignment, the field offset is not at the right place,
843 CharUnits padding = fieldOffset - NextFieldOffset;
845 AppendBytes(padding);
849 bool CGRecordLayoutBuilder::ResizeLastBaseFieldIfNecessary(CharUnits offset) {
850 // Check if we have a base to resize.
851 if (!LastLaidOutBase.isValid())
854 // This offset does not overlap with the tail padding.
855 if (offset >= NextFieldOffset)
858 // Restore the field offset and append an i8 array instead.
859 FieldTypes.pop_back();
860 NextFieldOffset = LastLaidOutBase.Offset;
861 AppendBytes(LastLaidOutBase.NonVirtualSize);
862 LastLaidOutBase.invalidate();
867 llvm::Type *CGRecordLayoutBuilder::getByteArrayType(CharUnits numBytes) {
868 assert(!numBytes.isZero() && "Empty byte arrays aren't allowed.");
870 llvm::Type *Ty = llvm::Type::getInt8Ty(Types.getLLVMContext());
871 if (numBytes > CharUnits::One())
872 Ty = llvm::ArrayType::get(Ty, numBytes.getQuantity());
877 void CGRecordLayoutBuilder::AppendBytes(CharUnits numBytes) {
878 if (numBytes.isZero())
881 // Append the padding field
882 AppendField(NextFieldOffset, getByteArrayType(numBytes));
885 CharUnits CGRecordLayoutBuilder::getTypeAlignment(const llvm::Type *Ty) const {
887 return CharUnits::One();
889 return CharUnits::fromQuantity(Types.getTargetData().getABITypeAlignment(Ty));
892 CharUnits CGRecordLayoutBuilder::getAlignmentAsLLVMStruct() const {
894 return CharUnits::One();
896 CharUnits maxAlignment = CharUnits::One();
897 for (size_t i = 0; i != FieldTypes.size(); ++i)
898 maxAlignment = std::max(maxAlignment, getTypeAlignment(FieldTypes[i]));
903 /// Merge in whether a field of the given type is zero-initializable.
904 void CGRecordLayoutBuilder::CheckZeroInitializable(QualType T) {
905 // This record already contains a member pointer.
906 if (!IsZeroInitializableAsBase)
909 // Can only have member pointers if we're compiling C++.
910 if (!Types.getContext().getLangOptions().CPlusPlus)
913 const Type *elementType = T->getBaseElementTypeUnsafe();
915 if (const MemberPointerType *MPT = elementType->getAs<MemberPointerType>()) {
916 if (!Types.getCXXABI().isZeroInitializable(MPT))
917 IsZeroInitializable = IsZeroInitializableAsBase = false;
918 } else if (const RecordType *RT = elementType->getAs<RecordType>()) {
919 const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
920 const CGRecordLayout &Layout = Types.getCGRecordLayout(RD);
921 if (!Layout.isZeroInitializable())
922 IsZeroInitializable = IsZeroInitializableAsBase = false;
926 CGRecordLayout *CodeGenTypes::ComputeRecordLayout(const RecordDecl *D,
927 llvm::StructType *Ty) {
928 CGRecordLayoutBuilder Builder(*this);
932 Ty->setBody(Builder.FieldTypes, Builder.Packed);
934 // If we're in C++, compute the base subobject type.
935 llvm::StructType *BaseTy = 0;
936 if (isa<CXXRecordDecl>(D)) {
937 BaseTy = Builder.BaseSubobjectType;
938 if (!BaseTy) BaseTy = Ty;
942 new CGRecordLayout(Ty, BaseTy, Builder.IsZeroInitializable,
943 Builder.IsZeroInitializableAsBase);
945 RL->NonVirtualBases.swap(Builder.NonVirtualBases);
946 RL->CompleteObjectVirtualBases.swap(Builder.VirtualBases);
948 // Add all the field numbers.
949 RL->FieldInfo.swap(Builder.Fields);
951 // Add bitfield info.
952 RL->BitFields.swap(Builder.BitFields);
954 // Dump the layout, if requested.
955 if (getContext().getLangOptions().DumpRecordLayouts) {
956 llvm::errs() << "\n*** Dumping IRgen Record Layout\n";
957 llvm::errs() << "Record: ";
959 llvm::errs() << "\nLayout: ";
964 // Verify that the computed LLVM struct size matches the AST layout size.
965 const ASTRecordLayout &Layout = getContext().getASTRecordLayout(D);
967 uint64_t TypeSizeInBits = getContext().toBits(Layout.getSize());
968 assert(TypeSizeInBits == getTargetData().getTypeAllocSizeInBits(Ty) &&
969 "Type size mismatch!");
972 CharUnits NonVirtualSize = Layout.getNonVirtualSize();
973 CharUnits NonVirtualAlign = Layout.getNonVirtualAlign();
974 CharUnits AlignedNonVirtualTypeSize =
975 NonVirtualSize.RoundUpToAlignment(NonVirtualAlign);
977 uint64_t AlignedNonVirtualTypeSizeInBits =
978 getContext().toBits(AlignedNonVirtualTypeSize);
980 assert(AlignedNonVirtualTypeSizeInBits ==
981 getTargetData().getTypeAllocSizeInBits(BaseTy) &&
982 "Type size mismatch!");
985 // Verify that the LLVM and AST field offsets agree.
986 const llvm::StructType *ST =
987 dyn_cast<llvm::StructType>(RL->getLLVMType());
988 const llvm::StructLayout *SL = getTargetData().getStructLayout(ST);
990 const ASTRecordLayout &AST_RL = getContext().getASTRecordLayout(D);
991 RecordDecl::field_iterator it = D->field_begin();
992 const FieldDecl *LastFD = 0;
993 bool IsMsStruct = D->hasAttr<MsStructAttr>();
994 for (unsigned i = 0, e = AST_RL.getFieldCount(); i != e; ++i, ++it) {
995 const FieldDecl *FD = *it;
997 // For non-bit-fields, just check that the LLVM struct offset matches the
999 if (!FD->isBitField()) {
1000 unsigned FieldNo = RL->getLLVMFieldNo(FD);
1001 assert(AST_RL.getFieldOffset(i) == SL->getElementOffsetInBits(FieldNo) &&
1002 "Invalid field offset!");
1008 // Zero-length bitfields following non-bitfield members are
1010 if (getContext().ZeroBitfieldFollowsNonBitfield(FD, LastFD)) {
1017 // Ignore unnamed bit-fields.
1018 if (!FD->getDeclName()) {
1023 const CGBitFieldInfo &Info = RL->getBitFieldInfo(FD);
1024 for (unsigned i = 0, e = Info.getNumComponents(); i != e; ++i) {
1025 const CGBitFieldInfo::AccessInfo &AI = Info.getComponent(i);
1027 // Verify that every component access is within the structure.
1028 uint64_t FieldOffset = SL->getElementOffsetInBits(AI.FieldIndex);
1029 uint64_t AccessBitOffset = FieldOffset +
1030 getContext().toBits(AI.FieldByteOffset);
1031 assert(AccessBitOffset + AI.AccessWidth <= TypeSizeInBits &&
1032 "Invalid bit-field access (out of range)!");
1040 void CGRecordLayout::print(llvm::raw_ostream &OS) const {
1041 OS << "<CGRecordLayout\n";
1042 OS << " LLVMType:" << *CompleteObjectType << "\n";
1043 if (BaseSubobjectType)
1044 OS << " NonVirtualBaseLLVMType:" << *BaseSubobjectType << "\n";
1045 OS << " IsZeroInitializable:" << IsZeroInitializable << "\n";
1046 OS << " BitFields:[\n";
1048 // Print bit-field infos in declaration order.
1049 std::vector<std::pair<unsigned, const CGBitFieldInfo*> > BFIs;
1050 for (llvm::DenseMap<const FieldDecl*, CGBitFieldInfo>::const_iterator
1051 it = BitFields.begin(), ie = BitFields.end();
1053 const RecordDecl *RD = it->first->getParent();
1055 for (RecordDecl::field_iterator
1056 it2 = RD->field_begin(); *it2 != it->first; ++it2)
1058 BFIs.push_back(std::make_pair(Index, &it->second));
1060 llvm::array_pod_sort(BFIs.begin(), BFIs.end());
1061 for (unsigned i = 0, e = BFIs.size(); i != e; ++i) {
1063 BFIs[i].second->print(OS);
1070 void CGRecordLayout::dump() const {
1071 print(llvm::errs());
1074 void CGBitFieldInfo::print(llvm::raw_ostream &OS) const {
1075 OS << "<CGBitFieldInfo";
1076 OS << " Size:" << Size;
1077 OS << " IsSigned:" << IsSigned << "\n";
1079 OS.indent(4 + strlen("<CGBitFieldInfo"));
1080 OS << " NumComponents:" << getNumComponents();
1081 OS << " Components: [";
1082 if (getNumComponents()) {
1084 for (unsigned i = 0, e = getNumComponents(); i != e; ++i) {
1085 const AccessInfo &AI = getComponent(i);
1088 << " FieldIndex:" << AI.FieldIndex
1089 << " FieldByteOffset:" << AI.FieldByteOffset.getQuantity()
1090 << " FieldBitStart:" << AI.FieldBitStart
1091 << " AccessWidth:" << AI.AccessWidth << "\n";
1092 OS.indent(8 + strlen("<AccessInfo"));
1093 OS << " AccessAlignment:" << AI.AccessAlignment.getQuantity()
1094 << " TargetBitOffset:" << AI.TargetBitOffset
1095 << " TargetBitWidth:" << AI.TargetBitWidth
1103 void CGBitFieldInfo::dump() const {
1104 print(llvm::errs());