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 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(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 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) {
366 uint64_t fieldSize = D->getBitWidthValue(Types.getContext());
371 uint64_t nextFieldOffsetInBits = Types.getContext().toBits(NextFieldOffset);
372 CharUnits numBytesToAppend;
373 unsigned charAlign = Types.getContext().getTargetInfo().getCharAlign();
375 if (fieldOffset < nextFieldOffsetInBits && !BitsAvailableInLastField) {
376 assert(fieldOffset % charAlign == 0 &&
377 "Field offset not aligned correctly");
379 CharUnits fieldOffsetInCharUnits =
380 Types.getContext().toCharUnitsFromBits(fieldOffset);
382 // Try to resize the last base field.
383 if (ResizeLastBaseFieldIfNecessary(fieldOffsetInCharUnits))
384 nextFieldOffsetInBits = Types.getContext().toBits(NextFieldOffset);
387 if (fieldOffset < nextFieldOffsetInBits) {
388 assert(BitsAvailableInLastField && "Bitfield size mismatch!");
389 assert(!NextFieldOffset.isZero() && "Must have laid out at least one byte");
391 // The bitfield begins in the previous bit-field.
392 numBytesToAppend = Types.getContext().toCharUnitsFromBits(
393 llvm::RoundUpToAlignment(fieldSize - BitsAvailableInLastField,
396 assert(fieldOffset % charAlign == 0 &&
397 "Field offset not aligned correctly");
399 // Append padding if necessary.
400 AppendPadding(Types.getContext().toCharUnitsFromBits(fieldOffset),
403 numBytesToAppend = Types.getContext().toCharUnitsFromBits(
404 llvm::RoundUpToAlignment(fieldSize, charAlign));
406 assert(!numBytesToAppend.isZero() && "No bytes to append!");
409 // Add the bit field info.
410 BitFields.insert(std::make_pair(D,
411 CGBitFieldInfo::MakeInfo(Types, D, fieldOffset, fieldSize)));
413 AppendBytes(numBytesToAppend);
415 BitsAvailableInLastField =
416 Types.getContext().toBits(NextFieldOffset) - (fieldOffset + fieldSize);
419 bool CGRecordLayoutBuilder::LayoutField(const FieldDecl *D,
420 uint64_t fieldOffset) {
421 // If the field is packed, then we need a packed struct.
422 if (!Packed && D->hasAttr<PackedAttr>())
425 if (D->isBitField()) {
426 // We must use packed structs for unnamed bit fields since they
427 // don't affect the struct alignment.
428 if (!Packed && !D->getDeclName())
431 LayoutBitField(D, fieldOffset);
435 CheckZeroInitializable(D->getType());
437 assert(fieldOffset % Types.getTarget().getCharWidth() == 0
438 && "field offset is not on a byte boundary!");
439 CharUnits fieldOffsetInBytes
440 = Types.getContext().toCharUnitsFromBits(fieldOffset);
442 llvm::Type *Ty = Types.ConvertTypeForMem(D->getType());
443 CharUnits typeAlignment = getTypeAlignment(Ty);
445 // If the type alignment is larger then the struct alignment, we must use
447 if (typeAlignment > Alignment) {
448 assert(!Packed && "Alignment is wrong even with packed struct!");
453 if (const RecordType *RT = D->getType()->getAs<RecordType>()) {
454 const RecordDecl *RD = cast<RecordDecl>(RT->getDecl());
455 if (const MaxFieldAlignmentAttr *MFAA =
456 RD->getAttr<MaxFieldAlignmentAttr>()) {
457 if (MFAA->getAlignment() != Types.getContext().toBits(typeAlignment))
463 // Round up the field offset to the alignment of the field type.
464 CharUnits alignedNextFieldOffsetInBytes =
465 NextFieldOffset.RoundUpToAlignment(typeAlignment);
467 if (fieldOffsetInBytes < alignedNextFieldOffsetInBytes) {
468 // Try to resize the last base field.
469 if (ResizeLastBaseFieldIfNecessary(fieldOffsetInBytes)) {
470 alignedNextFieldOffsetInBytes =
471 NextFieldOffset.RoundUpToAlignment(typeAlignment);
475 if (fieldOffsetInBytes < alignedNextFieldOffsetInBytes) {
476 assert(!Packed && "Could not place field even with packed struct!");
480 AppendPadding(fieldOffsetInBytes, typeAlignment);
482 // Now append the field.
483 Fields[D] = FieldTypes.size();
484 AppendField(fieldOffsetInBytes, Ty);
486 LastLaidOutBase.invalidate();
491 CGRecordLayoutBuilder::LayoutUnionField(const FieldDecl *Field,
492 const ASTRecordLayout &Layout) {
493 if (Field->isBitField()) {
494 uint64_t FieldSize = Field->getBitWidthValue(Types.getContext());
496 // Ignore zero sized bit fields.
500 llvm::Type *FieldTy = llvm::Type::getInt8Ty(Types.getLLVMContext());
501 CharUnits NumBytesToAppend = Types.getContext().toCharUnitsFromBits(
502 llvm::RoundUpToAlignment(FieldSize,
503 Types.getContext().getTargetInfo().getCharAlign()));
505 if (NumBytesToAppend > CharUnits::One())
506 FieldTy = llvm::ArrayType::get(FieldTy, NumBytesToAppend.getQuantity());
508 // Add the bit field info.
509 BitFields.insert(std::make_pair(Field,
510 CGBitFieldInfo::MakeInfo(Types, Field, 0, FieldSize)));
514 // This is a regular union field.
516 return Types.ConvertTypeForMem(Field->getType());
519 void CGRecordLayoutBuilder::LayoutUnion(const RecordDecl *D) {
520 assert(D->isUnion() && "Can't call LayoutUnion on a non-union record!");
522 const ASTRecordLayout &layout = Types.getContext().getASTRecordLayout(D);
524 llvm::Type *unionType = 0;
525 CharUnits unionSize = CharUnits::Zero();
526 CharUnits unionAlign = CharUnits::Zero();
528 bool hasOnlyZeroSizedBitFields = true;
530 unsigned fieldNo = 0;
531 for (RecordDecl::field_iterator field = D->field_begin(),
532 fieldEnd = D->field_end(); field != fieldEnd; ++field, ++fieldNo) {
533 assert(layout.getFieldOffset(fieldNo) == 0 &&
534 "Union field offset did not start at the beginning of record!");
535 llvm::Type *fieldType = LayoutUnionField(*field, layout);
540 hasOnlyZeroSizedBitFields = false;
542 CharUnits fieldAlign = CharUnits::fromQuantity(
543 Types.getTargetData().getABITypeAlignment(fieldType));
544 CharUnits fieldSize = CharUnits::fromQuantity(
545 Types.getTargetData().getTypeAllocSize(fieldType));
547 if (fieldAlign < unionAlign)
550 if (fieldAlign > unionAlign || fieldSize > unionSize) {
551 unionType = fieldType;
552 unionAlign = fieldAlign;
553 unionSize = fieldSize;
557 // Now add our field.
559 AppendField(CharUnits::Zero(), unionType);
561 if (getTypeAlignment(unionType) > layout.getAlignment()) {
562 // We need a packed struct.
564 unionAlign = CharUnits::One();
567 if (unionAlign.isZero()) {
568 assert(hasOnlyZeroSizedBitFields &&
569 "0-align record did not have all zero-sized bit-fields!");
570 unionAlign = CharUnits::One();
573 // Append tail padding.
574 CharUnits recordSize = layout.getSize();
575 if (recordSize > unionSize)
576 AppendPadding(recordSize, unionAlign);
579 void CGRecordLayoutBuilder::LayoutBase(const CXXRecordDecl *base,
580 const CGRecordLayout &baseLayout,
581 CharUnits baseOffset) {
582 ResizeLastBaseFieldIfNecessary(baseOffset);
584 AppendPadding(baseOffset, CharUnits::One());
586 const ASTRecordLayout &baseASTLayout
587 = Types.getContext().getASTRecordLayout(base);
589 LastLaidOutBase.Offset = NextFieldOffset;
590 LastLaidOutBase.NonVirtualSize = baseASTLayout.getNonVirtualSize();
592 // Fields and bases can be laid out in the tail padding of previous
593 // bases. If this happens, we need to allocate the base as an i8
594 // array; otherwise, we can use the subobject type. However,
595 // actually doing that would require knowledge of what immediately
596 // follows this base in the layout, so instead we do a conservative
597 // approximation, which is to use the base subobject type if it
598 // has the same LLVM storage size as the nvsize.
600 llvm::StructType *subobjectType = baseLayout.getBaseSubobjectLLVMType();
601 AppendField(baseOffset, subobjectType);
604 void CGRecordLayoutBuilder::LayoutNonVirtualBase(const CXXRecordDecl *base,
605 CharUnits baseOffset) {
606 // Ignore empty bases.
607 if (base->isEmpty()) return;
609 const CGRecordLayout &baseLayout = Types.getCGRecordLayout(base);
610 if (IsZeroInitializableAsBase) {
611 assert(IsZeroInitializable &&
612 "class zero-initializable as base but not as complete object");
614 IsZeroInitializable = IsZeroInitializableAsBase =
615 baseLayout.isZeroInitializableAsBase();
618 LayoutBase(base, baseLayout, baseOffset);
619 NonVirtualBases[base] = (FieldTypes.size() - 1);
623 CGRecordLayoutBuilder::LayoutVirtualBase(const CXXRecordDecl *base,
624 CharUnits baseOffset) {
625 // Ignore empty bases.
626 if (base->isEmpty()) return;
628 const CGRecordLayout &baseLayout = Types.getCGRecordLayout(base);
629 if (IsZeroInitializable)
630 IsZeroInitializable = baseLayout.isZeroInitializableAsBase();
632 LayoutBase(base, baseLayout, baseOffset);
633 VirtualBases[base] = (FieldTypes.size() - 1);
636 /// LayoutVirtualBases - layout the non-virtual bases of a record decl.
638 CGRecordLayoutBuilder::LayoutVirtualBases(const CXXRecordDecl *RD,
639 const ASTRecordLayout &Layout) {
640 for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
641 E = RD->bases_end(); I != E; ++I) {
642 const CXXRecordDecl *BaseDecl =
643 cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
645 // We only want to lay out virtual bases that aren't indirect primary bases
646 // of some other base.
647 if (I->isVirtual() && !IndirectPrimaryBases.count(BaseDecl)) {
648 // Only lay out the base once.
649 if (!LaidOutVirtualBases.insert(BaseDecl))
652 CharUnits vbaseOffset = Layout.getVBaseClassOffset(BaseDecl);
653 LayoutVirtualBase(BaseDecl, vbaseOffset);
656 if (!BaseDecl->getNumVBases()) {
657 // This base isn't interesting since it doesn't have any virtual bases.
661 LayoutVirtualBases(BaseDecl, Layout);
666 CGRecordLayoutBuilder::LayoutNonVirtualBases(const CXXRecordDecl *RD,
667 const ASTRecordLayout &Layout) {
668 const CXXRecordDecl *PrimaryBase = Layout.getPrimaryBase();
670 // Check if we need to add a vtable pointer.
671 if (RD->isDynamicClass()) {
673 llvm::Type *FunctionType =
674 llvm::FunctionType::get(llvm::Type::getInt32Ty(Types.getLLVMContext()),
676 llvm::Type *VTableTy = FunctionType->getPointerTo();
678 assert(NextFieldOffset.isZero() &&
679 "VTable pointer must come first!");
680 AppendField(CharUnits::Zero(), VTableTy->getPointerTo());
682 if (!Layout.isPrimaryBaseVirtual())
683 LayoutNonVirtualBase(PrimaryBase, CharUnits::Zero());
685 LayoutVirtualBase(PrimaryBase, CharUnits::Zero());
689 // Layout the non-virtual bases.
690 for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
691 E = RD->bases_end(); I != E; ++I) {
695 const CXXRecordDecl *BaseDecl =
696 cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
698 // We've already laid out the primary base.
699 if (BaseDecl == PrimaryBase && !Layout.isPrimaryBaseVirtual())
702 LayoutNonVirtualBase(BaseDecl, Layout.getBaseClassOffset(BaseDecl));
707 CGRecordLayoutBuilder::ComputeNonVirtualBaseType(const CXXRecordDecl *RD) {
708 const ASTRecordLayout &Layout = Types.getContext().getASTRecordLayout(RD);
710 CharUnits NonVirtualSize = Layout.getNonVirtualSize();
711 CharUnits NonVirtualAlign = Layout.getNonVirtualAlign();
712 CharUnits AlignedNonVirtualTypeSize =
713 NonVirtualSize.RoundUpToAlignment(NonVirtualAlign);
715 // First check if we can use the same fields as for the complete class.
716 CharUnits RecordSize = Layout.getSize();
717 if (AlignedNonVirtualTypeSize == RecordSize)
720 // Check if we need padding.
721 CharUnits AlignedNextFieldOffset =
722 NextFieldOffset.RoundUpToAlignment(getAlignmentAsLLVMStruct());
724 if (AlignedNextFieldOffset > AlignedNonVirtualTypeSize) {
725 assert(!Packed && "cannot layout even as packed struct");
726 return false; // Needs packing.
729 bool needsPadding = (AlignedNonVirtualTypeSize != AlignedNextFieldOffset);
731 CharUnits NumBytes = AlignedNonVirtualTypeSize - AlignedNextFieldOffset;
732 FieldTypes.push_back(getByteArrayType(NumBytes));
736 BaseSubobjectType = llvm::StructType::create(Types.getLLVMContext(),
737 FieldTypes, "", Packed);
738 Types.addRecordTypeName(RD, BaseSubobjectType, ".base");
740 // Pull the padding back off.
742 FieldTypes.pop_back();
747 bool CGRecordLayoutBuilder::LayoutFields(const RecordDecl *D) {
748 assert(!D->isUnion() && "Can't call LayoutFields on a union!");
749 assert(!Alignment.isZero() && "Did not set alignment!");
751 const ASTRecordLayout &Layout = Types.getContext().getASTRecordLayout(D);
753 const CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(D);
755 LayoutNonVirtualBases(RD, Layout);
757 unsigned FieldNo = 0;
758 const FieldDecl *LastFD = 0;
760 for (RecordDecl::field_iterator Field = D->field_begin(),
761 FieldEnd = D->field_end(); Field != FieldEnd; ++Field, ++FieldNo) {
763 // Zero-length bitfields following non-bitfield members are
765 const FieldDecl *FD = (*Field);
766 if (Types.getContext().ZeroBitfieldFollowsNonBitfield(FD, LastFD)) {
773 if (!LayoutField(*Field, Layout.getFieldOffset(FieldNo))) {
775 "Could not layout fields even with a packed LLVM struct!");
781 // We've laid out the non-virtual bases and the fields, now compute the
782 // non-virtual base field types.
783 if (!ComputeNonVirtualBaseType(RD)) {
784 assert(!Packed && "Could not layout even with a packed LLVM struct!");
788 // And lay out the virtual bases.
789 RD->getIndirectPrimaryBases(IndirectPrimaryBases);
790 if (Layout.isPrimaryBaseVirtual())
791 IndirectPrimaryBases.insert(Layout.getPrimaryBase());
792 LayoutVirtualBases(RD, Layout);
795 // Append tail padding if necessary.
796 AppendTailPadding(Layout.getSize());
801 void CGRecordLayoutBuilder::AppendTailPadding(CharUnits RecordSize) {
802 ResizeLastBaseFieldIfNecessary(RecordSize);
804 assert(NextFieldOffset <= RecordSize && "Size mismatch!");
806 CharUnits AlignedNextFieldOffset =
807 NextFieldOffset.RoundUpToAlignment(getAlignmentAsLLVMStruct());
809 if (AlignedNextFieldOffset == RecordSize) {
810 // We don't need any padding.
814 CharUnits NumPadBytes = RecordSize - NextFieldOffset;
815 AppendBytes(NumPadBytes);
818 void CGRecordLayoutBuilder::AppendField(CharUnits fieldOffset,
819 llvm::Type *fieldType) {
820 CharUnits fieldSize =
821 CharUnits::fromQuantity(Types.getTargetData().getTypeAllocSize(fieldType));
823 FieldTypes.push_back(fieldType);
825 NextFieldOffset = fieldOffset + fieldSize;
826 BitsAvailableInLastField = 0;
829 void CGRecordLayoutBuilder::AppendPadding(CharUnits fieldOffset,
830 CharUnits fieldAlignment) {
831 assert(NextFieldOffset <= fieldOffset &&
832 "Incorrect field layout!");
834 // Round up the field offset to the alignment of the field type.
835 CharUnits alignedNextFieldOffset =
836 NextFieldOffset.RoundUpToAlignment(fieldAlignment);
838 if (alignedNextFieldOffset < fieldOffset) {
839 // Even with alignment, the field offset is not at the right place,
841 CharUnits padding = fieldOffset - NextFieldOffset;
843 AppendBytes(padding);
847 bool CGRecordLayoutBuilder::ResizeLastBaseFieldIfNecessary(CharUnits offset) {
848 // Check if we have a base to resize.
849 if (!LastLaidOutBase.isValid())
852 // This offset does not overlap with the tail padding.
853 if (offset >= NextFieldOffset)
856 // Restore the field offset and append an i8 array instead.
857 FieldTypes.pop_back();
858 NextFieldOffset = LastLaidOutBase.Offset;
859 AppendBytes(LastLaidOutBase.NonVirtualSize);
860 LastLaidOutBase.invalidate();
865 llvm::Type *CGRecordLayoutBuilder::getByteArrayType(CharUnits numBytes) {
866 assert(!numBytes.isZero() && "Empty byte arrays aren't allowed.");
868 llvm::Type *Ty = llvm::Type::getInt8Ty(Types.getLLVMContext());
869 if (numBytes > CharUnits::One())
870 Ty = llvm::ArrayType::get(Ty, numBytes.getQuantity());
875 void CGRecordLayoutBuilder::AppendBytes(CharUnits numBytes) {
876 if (numBytes.isZero())
879 // Append the padding field
880 AppendField(NextFieldOffset, getByteArrayType(numBytes));
883 CharUnits CGRecordLayoutBuilder::getTypeAlignment(llvm::Type *Ty) const {
885 return CharUnits::One();
887 return CharUnits::fromQuantity(Types.getTargetData().getABITypeAlignment(Ty));
890 CharUnits CGRecordLayoutBuilder::getAlignmentAsLLVMStruct() const {
892 return CharUnits::One();
894 CharUnits maxAlignment = CharUnits::One();
895 for (size_t i = 0; i != FieldTypes.size(); ++i)
896 maxAlignment = std::max(maxAlignment, getTypeAlignment(FieldTypes[i]));
901 /// Merge in whether a field of the given type is zero-initializable.
902 void CGRecordLayoutBuilder::CheckZeroInitializable(QualType T) {
903 // This record already contains a member pointer.
904 if (!IsZeroInitializableAsBase)
907 // Can only have member pointers if we're compiling C++.
908 if (!Types.getContext().getLangOptions().CPlusPlus)
911 const Type *elementType = T->getBaseElementTypeUnsafe();
913 if (const MemberPointerType *MPT = elementType->getAs<MemberPointerType>()) {
914 if (!Types.getCXXABI().isZeroInitializable(MPT))
915 IsZeroInitializable = IsZeroInitializableAsBase = false;
916 } else if (const RecordType *RT = elementType->getAs<RecordType>()) {
917 const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
918 const CGRecordLayout &Layout = Types.getCGRecordLayout(RD);
919 if (!Layout.isZeroInitializable())
920 IsZeroInitializable = IsZeroInitializableAsBase = false;
924 CGRecordLayout *CodeGenTypes::ComputeRecordLayout(const RecordDecl *D,
925 llvm::StructType *Ty) {
926 CGRecordLayoutBuilder Builder(*this);
930 Ty->setBody(Builder.FieldTypes, Builder.Packed);
932 // If we're in C++, compute the base subobject type.
933 llvm::StructType *BaseTy = 0;
934 if (isa<CXXRecordDecl>(D)) {
935 BaseTy = Builder.BaseSubobjectType;
936 if (!BaseTy) BaseTy = Ty;
940 new CGRecordLayout(Ty, BaseTy, Builder.IsZeroInitializable,
941 Builder.IsZeroInitializableAsBase);
943 RL->NonVirtualBases.swap(Builder.NonVirtualBases);
944 RL->CompleteObjectVirtualBases.swap(Builder.VirtualBases);
946 // Add all the field numbers.
947 RL->FieldInfo.swap(Builder.Fields);
949 // Add bitfield info.
950 RL->BitFields.swap(Builder.BitFields);
952 // Dump the layout, if requested.
953 if (getContext().getLangOptions().DumpRecordLayouts) {
954 llvm::errs() << "\n*** Dumping IRgen Record Layout\n";
955 llvm::errs() << "Record: ";
957 llvm::errs() << "\nLayout: ";
962 // Verify that the computed LLVM struct size matches the AST layout size.
963 const ASTRecordLayout &Layout = getContext().getASTRecordLayout(D);
965 uint64_t TypeSizeInBits = getContext().toBits(Layout.getSize());
966 assert(TypeSizeInBits == getTargetData().getTypeAllocSizeInBits(Ty) &&
967 "Type size mismatch!");
970 CharUnits NonVirtualSize = Layout.getNonVirtualSize();
971 CharUnits NonVirtualAlign = Layout.getNonVirtualAlign();
972 CharUnits AlignedNonVirtualTypeSize =
973 NonVirtualSize.RoundUpToAlignment(NonVirtualAlign);
975 uint64_t AlignedNonVirtualTypeSizeInBits =
976 getContext().toBits(AlignedNonVirtualTypeSize);
978 assert(AlignedNonVirtualTypeSizeInBits ==
979 getTargetData().getTypeAllocSizeInBits(BaseTy) &&
980 "Type size mismatch!");
983 // Verify that the LLVM and AST field offsets agree.
984 llvm::StructType *ST =
985 dyn_cast<llvm::StructType>(RL->getLLVMType());
986 const llvm::StructLayout *SL = getTargetData().getStructLayout(ST);
988 const ASTRecordLayout &AST_RL = getContext().getASTRecordLayout(D);
989 RecordDecl::field_iterator it = D->field_begin();
990 const FieldDecl *LastFD = 0;
991 bool IsMsStruct = D->hasAttr<MsStructAttr>();
992 for (unsigned i = 0, e = AST_RL.getFieldCount(); i != e; ++i, ++it) {
993 const FieldDecl *FD = *it;
995 // For non-bit-fields, just check that the LLVM struct offset matches the
997 if (!FD->isBitField()) {
998 unsigned FieldNo = RL->getLLVMFieldNo(FD);
999 assert(AST_RL.getFieldOffset(i) == SL->getElementOffsetInBits(FieldNo) &&
1000 "Invalid field offset!");
1006 // Zero-length bitfields following non-bitfield members are
1008 if (getContext().ZeroBitfieldFollowsNonBitfield(FD, LastFD)) {
1015 // Ignore unnamed bit-fields.
1016 if (!FD->getDeclName()) {
1021 const CGBitFieldInfo &Info = RL->getBitFieldInfo(FD);
1022 for (unsigned i = 0, e = Info.getNumComponents(); i != e; ++i) {
1023 const CGBitFieldInfo::AccessInfo &AI = Info.getComponent(i);
1025 // Verify that every component access is within the structure.
1026 uint64_t FieldOffset = SL->getElementOffsetInBits(AI.FieldIndex);
1027 uint64_t AccessBitOffset = FieldOffset +
1028 getContext().toBits(AI.FieldByteOffset);
1029 assert(AccessBitOffset + AI.AccessWidth <= TypeSizeInBits &&
1030 "Invalid bit-field access (out of range)!");
1038 void CGRecordLayout::print(raw_ostream &OS) const {
1039 OS << "<CGRecordLayout\n";
1040 OS << " LLVMType:" << *CompleteObjectType << "\n";
1041 if (BaseSubobjectType)
1042 OS << " NonVirtualBaseLLVMType:" << *BaseSubobjectType << "\n";
1043 OS << " IsZeroInitializable:" << IsZeroInitializable << "\n";
1044 OS << " BitFields:[\n";
1046 // Print bit-field infos in declaration order.
1047 std::vector<std::pair<unsigned, const CGBitFieldInfo*> > BFIs;
1048 for (llvm::DenseMap<const FieldDecl*, CGBitFieldInfo>::const_iterator
1049 it = BitFields.begin(), ie = BitFields.end();
1051 const RecordDecl *RD = it->first->getParent();
1053 for (RecordDecl::field_iterator
1054 it2 = RD->field_begin(); *it2 != it->first; ++it2)
1056 BFIs.push_back(std::make_pair(Index, &it->second));
1058 llvm::array_pod_sort(BFIs.begin(), BFIs.end());
1059 for (unsigned i = 0, e = BFIs.size(); i != e; ++i) {
1061 BFIs[i].second->print(OS);
1068 void CGRecordLayout::dump() const {
1069 print(llvm::errs());
1072 void CGBitFieldInfo::print(raw_ostream &OS) const {
1073 OS << "<CGBitFieldInfo";
1074 OS << " Size:" << Size;
1075 OS << " IsSigned:" << IsSigned << "\n";
1077 OS.indent(4 + strlen("<CGBitFieldInfo"));
1078 OS << " NumComponents:" << getNumComponents();
1079 OS << " Components: [";
1080 if (getNumComponents()) {
1082 for (unsigned i = 0, e = getNumComponents(); i != e; ++i) {
1083 const AccessInfo &AI = getComponent(i);
1086 << " FieldIndex:" << AI.FieldIndex
1087 << " FieldByteOffset:" << AI.FieldByteOffset.getQuantity()
1088 << " FieldBitStart:" << AI.FieldBitStart
1089 << " AccessWidth:" << AI.AccessWidth << "\n";
1090 OS.indent(8 + strlen("<AccessInfo"));
1091 OS << " AccessAlignment:" << AI.AccessAlignment.getQuantity()
1092 << " TargetBitOffset:" << AI.TargetBitOffset
1093 << " TargetBitWidth:" << AI.TargetBitWidth
1101 void CGBitFieldInfo::dump() const {
1102 print(llvm::errs());