1 //=== RecordLayoutBuilder.cpp - Helper class for building record layouts ---==//
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 #include "clang/AST/RecordLayout.h"
11 #include "clang/AST/ASTContext.h"
12 #include "clang/AST/Attr.h"
13 #include "clang/AST/CXXInheritance.h"
14 #include "clang/AST/Decl.h"
15 #include "clang/AST/DeclCXX.h"
16 #include "clang/AST/DeclObjC.h"
17 #include "clang/AST/Expr.h"
18 #include "clang/Basic/TargetInfo.h"
19 #include "clang/Sema/SemaDiagnostic.h"
20 #include "llvm/ADT/SmallSet.h"
21 #include "llvm/Support/Format.h"
22 #include "llvm/Support/MathExtras.h"
24 using namespace clang;
28 /// BaseSubobjectInfo - Represents a single base subobject in a complete class.
29 /// For a class hierarchy like
33 /// class C : A, B { };
35 /// The BaseSubobjectInfo graph for C will have three BaseSubobjectInfo
36 /// instances, one for B and two for A.
38 /// If a base is virtual, it will only have one BaseSubobjectInfo allocated.
39 struct BaseSubobjectInfo {
40 /// Class - The class for this base info.
41 const CXXRecordDecl *Class;
43 /// IsVirtual - Whether the BaseInfo represents a virtual base or not.
46 /// Bases - Information about the base subobjects.
47 SmallVector<BaseSubobjectInfo*, 4> Bases;
49 /// PrimaryVirtualBaseInfo - Holds the base info for the primary virtual base
50 /// of this base info (if one exists).
51 BaseSubobjectInfo *PrimaryVirtualBaseInfo;
54 const BaseSubobjectInfo *Derived;
57 /// \brief Externally provided layout. Typically used when the AST source, such
58 /// as DWARF, lacks all the information that was available at compile time, such
59 /// as alignment attributes on fields and pragmas in effect.
60 struct ExternalLayout {
61 ExternalLayout() : Size(0), Align(0) {}
63 /// \brief Overall record size in bits.
66 /// \brief Overall record alignment in bits.
69 /// \brief Record field offsets in bits.
70 llvm::DenseMap<const FieldDecl *, uint64_t> FieldOffsets;
72 /// \brief Direct, non-virtual base offsets.
73 llvm::DenseMap<const CXXRecordDecl *, CharUnits> BaseOffsets;
75 /// \brief Virtual base offsets.
76 llvm::DenseMap<const CXXRecordDecl *, CharUnits> VirtualBaseOffsets;
78 /// Get the offset of the given field. The external source must provide
79 /// entries for all fields in the record.
80 uint64_t getExternalFieldOffset(const FieldDecl *FD) {
81 assert(FieldOffsets.count(FD) &&
82 "Field does not have an external offset");
83 return FieldOffsets[FD];
86 bool getExternalNVBaseOffset(const CXXRecordDecl *RD, CharUnits &BaseOffset) {
87 auto Known = BaseOffsets.find(RD);
88 if (Known == BaseOffsets.end())
90 BaseOffset = Known->second;
94 bool getExternalVBaseOffset(const CXXRecordDecl *RD, CharUnits &BaseOffset) {
95 auto Known = VirtualBaseOffsets.find(RD);
96 if (Known == VirtualBaseOffsets.end())
98 BaseOffset = Known->second;
103 /// EmptySubobjectMap - Keeps track of which empty subobjects exist at different
104 /// offsets while laying out a C++ class.
105 class EmptySubobjectMap {
106 const ASTContext &Context;
109 /// Class - The class whose empty entries we're keeping track of.
110 const CXXRecordDecl *Class;
112 /// EmptyClassOffsets - A map from offsets to empty record decls.
113 typedef llvm::TinyPtrVector<const CXXRecordDecl *> ClassVectorTy;
114 typedef llvm::DenseMap<CharUnits, ClassVectorTy> EmptyClassOffsetsMapTy;
115 EmptyClassOffsetsMapTy EmptyClassOffsets;
117 /// MaxEmptyClassOffset - The highest offset known to contain an empty
119 CharUnits MaxEmptyClassOffset;
121 /// ComputeEmptySubobjectSizes - Compute the size of the largest base or
122 /// member subobject that is empty.
123 void ComputeEmptySubobjectSizes();
125 void AddSubobjectAtOffset(const CXXRecordDecl *RD, CharUnits Offset);
127 void UpdateEmptyBaseSubobjects(const BaseSubobjectInfo *Info,
128 CharUnits Offset, bool PlacingEmptyBase);
130 void UpdateEmptyFieldSubobjects(const CXXRecordDecl *RD,
131 const CXXRecordDecl *Class,
133 void UpdateEmptyFieldSubobjects(const FieldDecl *FD, CharUnits Offset);
135 /// AnyEmptySubobjectsBeyondOffset - Returns whether there are any empty
136 /// subobjects beyond the given offset.
137 bool AnyEmptySubobjectsBeyondOffset(CharUnits Offset) const {
138 return Offset <= MaxEmptyClassOffset;
142 getFieldOffset(const ASTRecordLayout &Layout, unsigned FieldNo) const {
143 uint64_t FieldOffset = Layout.getFieldOffset(FieldNo);
144 assert(FieldOffset % CharWidth == 0 &&
145 "Field offset not at char boundary!");
147 return Context.toCharUnitsFromBits(FieldOffset);
151 bool CanPlaceSubobjectAtOffset(const CXXRecordDecl *RD,
152 CharUnits Offset) const;
154 bool CanPlaceBaseSubobjectAtOffset(const BaseSubobjectInfo *Info,
157 bool CanPlaceFieldSubobjectAtOffset(const CXXRecordDecl *RD,
158 const CXXRecordDecl *Class,
159 CharUnits Offset) const;
160 bool CanPlaceFieldSubobjectAtOffset(const FieldDecl *FD,
161 CharUnits Offset) const;
164 /// This holds the size of the largest empty subobject (either a base
165 /// or a member). Will be zero if the record being built doesn't contain
166 /// any empty classes.
167 CharUnits SizeOfLargestEmptySubobject;
169 EmptySubobjectMap(const ASTContext &Context, const CXXRecordDecl *Class)
170 : Context(Context), CharWidth(Context.getCharWidth()), Class(Class) {
171 ComputeEmptySubobjectSizes();
174 /// CanPlaceBaseAtOffset - Return whether the given base class can be placed
175 /// at the given offset.
176 /// Returns false if placing the record will result in two components
177 /// (direct or indirect) of the same type having the same offset.
178 bool CanPlaceBaseAtOffset(const BaseSubobjectInfo *Info,
181 /// CanPlaceFieldAtOffset - Return whether a field can be placed at the given
183 bool CanPlaceFieldAtOffset(const FieldDecl *FD, CharUnits Offset);
186 void EmptySubobjectMap::ComputeEmptySubobjectSizes() {
188 for (const CXXBaseSpecifier &Base : Class->bases()) {
189 const CXXRecordDecl *BaseDecl = Base.getType()->getAsCXXRecordDecl();
192 const ASTRecordLayout &Layout = Context.getASTRecordLayout(BaseDecl);
193 if (BaseDecl->isEmpty()) {
194 // If the class decl is empty, get its size.
195 EmptySize = Layout.getSize();
197 // Otherwise, we get the largest empty subobject for the decl.
198 EmptySize = Layout.getSizeOfLargestEmptySubobject();
201 if (EmptySize > SizeOfLargestEmptySubobject)
202 SizeOfLargestEmptySubobject = EmptySize;
206 for (const FieldDecl *FD : Class->fields()) {
207 const RecordType *RT =
208 Context.getBaseElementType(FD->getType())->getAs<RecordType>();
210 // We only care about record types.
215 const CXXRecordDecl *MemberDecl = RT->getAsCXXRecordDecl();
216 const ASTRecordLayout &Layout = Context.getASTRecordLayout(MemberDecl);
217 if (MemberDecl->isEmpty()) {
218 // If the class decl is empty, get its size.
219 EmptySize = Layout.getSize();
221 // Otherwise, we get the largest empty subobject for the decl.
222 EmptySize = Layout.getSizeOfLargestEmptySubobject();
225 if (EmptySize > SizeOfLargestEmptySubobject)
226 SizeOfLargestEmptySubobject = EmptySize;
231 EmptySubobjectMap::CanPlaceSubobjectAtOffset(const CXXRecordDecl *RD,
232 CharUnits Offset) const {
233 // We only need to check empty bases.
237 EmptyClassOffsetsMapTy::const_iterator I = EmptyClassOffsets.find(Offset);
238 if (I == EmptyClassOffsets.end())
241 const ClassVectorTy &Classes = I->second;
242 if (std::find(Classes.begin(), Classes.end(), RD) == Classes.end())
245 // There is already an empty class of the same type at this offset.
249 void EmptySubobjectMap::AddSubobjectAtOffset(const CXXRecordDecl *RD,
251 // We only care about empty bases.
255 // If we have empty structures inside a union, we can assign both
256 // the same offset. Just avoid pushing them twice in the list.
257 ClassVectorTy &Classes = EmptyClassOffsets[Offset];
258 if (std::find(Classes.begin(), Classes.end(), RD) != Classes.end())
261 Classes.push_back(RD);
263 // Update the empty class offset.
264 if (Offset > MaxEmptyClassOffset)
265 MaxEmptyClassOffset = Offset;
269 EmptySubobjectMap::CanPlaceBaseSubobjectAtOffset(const BaseSubobjectInfo *Info,
271 // We don't have to keep looking past the maximum offset that's known to
272 // contain an empty class.
273 if (!AnyEmptySubobjectsBeyondOffset(Offset))
276 if (!CanPlaceSubobjectAtOffset(Info->Class, Offset))
279 // Traverse all non-virtual bases.
280 const ASTRecordLayout &Layout = Context.getASTRecordLayout(Info->Class);
281 for (const BaseSubobjectInfo *Base : Info->Bases) {
285 CharUnits BaseOffset = Offset + Layout.getBaseClassOffset(Base->Class);
287 if (!CanPlaceBaseSubobjectAtOffset(Base, BaseOffset))
291 if (Info->PrimaryVirtualBaseInfo) {
292 BaseSubobjectInfo *PrimaryVirtualBaseInfo = Info->PrimaryVirtualBaseInfo;
294 if (Info == PrimaryVirtualBaseInfo->Derived) {
295 if (!CanPlaceBaseSubobjectAtOffset(PrimaryVirtualBaseInfo, Offset))
300 // Traverse all member variables.
301 unsigned FieldNo = 0;
302 for (CXXRecordDecl::field_iterator I = Info->Class->field_begin(),
303 E = Info->Class->field_end(); I != E; ++I, ++FieldNo) {
307 CharUnits FieldOffset = Offset + getFieldOffset(Layout, FieldNo);
308 if (!CanPlaceFieldSubobjectAtOffset(*I, FieldOffset))
315 void EmptySubobjectMap::UpdateEmptyBaseSubobjects(const BaseSubobjectInfo *Info,
317 bool PlacingEmptyBase) {
318 if (!PlacingEmptyBase && Offset >= SizeOfLargestEmptySubobject) {
319 // We know that the only empty subobjects that can conflict with empty
320 // subobject of non-empty bases, are empty bases that can be placed at
321 // offset zero. Because of this, we only need to keep track of empty base
322 // subobjects with offsets less than the size of the largest empty
323 // subobject for our class.
327 AddSubobjectAtOffset(Info->Class, Offset);
329 // Traverse all non-virtual bases.
330 const ASTRecordLayout &Layout = Context.getASTRecordLayout(Info->Class);
331 for (const BaseSubobjectInfo *Base : Info->Bases) {
335 CharUnits BaseOffset = Offset + Layout.getBaseClassOffset(Base->Class);
336 UpdateEmptyBaseSubobjects(Base, BaseOffset, PlacingEmptyBase);
339 if (Info->PrimaryVirtualBaseInfo) {
340 BaseSubobjectInfo *PrimaryVirtualBaseInfo = Info->PrimaryVirtualBaseInfo;
342 if (Info == PrimaryVirtualBaseInfo->Derived)
343 UpdateEmptyBaseSubobjects(PrimaryVirtualBaseInfo, Offset,
347 // Traverse all member variables.
348 unsigned FieldNo = 0;
349 for (CXXRecordDecl::field_iterator I = Info->Class->field_begin(),
350 E = Info->Class->field_end(); I != E; ++I, ++FieldNo) {
354 CharUnits FieldOffset = Offset + getFieldOffset(Layout, FieldNo);
355 UpdateEmptyFieldSubobjects(*I, FieldOffset);
359 bool EmptySubobjectMap::CanPlaceBaseAtOffset(const BaseSubobjectInfo *Info,
361 // If we know this class doesn't have any empty subobjects we don't need to
363 if (SizeOfLargestEmptySubobject.isZero())
366 if (!CanPlaceBaseSubobjectAtOffset(Info, Offset))
369 // We are able to place the base at this offset. Make sure to update the
370 // empty base subobject map.
371 UpdateEmptyBaseSubobjects(Info, Offset, Info->Class->isEmpty());
376 EmptySubobjectMap::CanPlaceFieldSubobjectAtOffset(const CXXRecordDecl *RD,
377 const CXXRecordDecl *Class,
378 CharUnits Offset) const {
379 // We don't have to keep looking past the maximum offset that's known to
380 // contain an empty class.
381 if (!AnyEmptySubobjectsBeyondOffset(Offset))
384 if (!CanPlaceSubobjectAtOffset(RD, Offset))
387 const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
389 // Traverse all non-virtual bases.
390 for (const CXXBaseSpecifier &Base : RD->bases()) {
391 if (Base.isVirtual())
394 const CXXRecordDecl *BaseDecl = Base.getType()->getAsCXXRecordDecl();
396 CharUnits BaseOffset = Offset + Layout.getBaseClassOffset(BaseDecl);
397 if (!CanPlaceFieldSubobjectAtOffset(BaseDecl, Class, BaseOffset))
402 // This is the most derived class, traverse virtual bases as well.
403 for (const CXXBaseSpecifier &Base : RD->vbases()) {
404 const CXXRecordDecl *VBaseDecl = Base.getType()->getAsCXXRecordDecl();
406 CharUnits VBaseOffset = Offset + Layout.getVBaseClassOffset(VBaseDecl);
407 if (!CanPlaceFieldSubobjectAtOffset(VBaseDecl, Class, VBaseOffset))
412 // Traverse all member variables.
413 unsigned FieldNo = 0;
414 for (CXXRecordDecl::field_iterator I = RD->field_begin(), E = RD->field_end();
415 I != E; ++I, ++FieldNo) {
419 CharUnits FieldOffset = Offset + getFieldOffset(Layout, FieldNo);
421 if (!CanPlaceFieldSubobjectAtOffset(*I, FieldOffset))
429 EmptySubobjectMap::CanPlaceFieldSubobjectAtOffset(const FieldDecl *FD,
430 CharUnits Offset) const {
431 // We don't have to keep looking past the maximum offset that's known to
432 // contain an empty class.
433 if (!AnyEmptySubobjectsBeyondOffset(Offset))
436 QualType T = FD->getType();
437 if (const CXXRecordDecl *RD = T->getAsCXXRecordDecl())
438 return CanPlaceFieldSubobjectAtOffset(RD, RD, Offset);
440 // If we have an array type we need to look at every element.
441 if (const ConstantArrayType *AT = Context.getAsConstantArrayType(T)) {
442 QualType ElemTy = Context.getBaseElementType(AT);
443 const RecordType *RT = ElemTy->getAs<RecordType>();
447 const CXXRecordDecl *RD = RT->getAsCXXRecordDecl();
448 const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
450 uint64_t NumElements = Context.getConstantArrayElementCount(AT);
451 CharUnits ElementOffset = Offset;
452 for (uint64_t I = 0; I != NumElements; ++I) {
453 // We don't have to keep looking past the maximum offset that's known to
454 // contain an empty class.
455 if (!AnyEmptySubobjectsBeyondOffset(ElementOffset))
458 if (!CanPlaceFieldSubobjectAtOffset(RD, RD, ElementOffset))
461 ElementOffset += Layout.getSize();
469 EmptySubobjectMap::CanPlaceFieldAtOffset(const FieldDecl *FD,
471 if (!CanPlaceFieldSubobjectAtOffset(FD, Offset))
474 // We are able to place the member variable at this offset.
475 // Make sure to update the empty base subobject map.
476 UpdateEmptyFieldSubobjects(FD, Offset);
480 void EmptySubobjectMap::UpdateEmptyFieldSubobjects(const CXXRecordDecl *RD,
481 const CXXRecordDecl *Class,
483 // We know that the only empty subobjects that can conflict with empty
484 // field subobjects are subobjects of empty bases that can be placed at offset
485 // zero. Because of this, we only need to keep track of empty field
486 // subobjects with offsets less than the size of the largest empty
487 // subobject for our class.
488 if (Offset >= SizeOfLargestEmptySubobject)
491 AddSubobjectAtOffset(RD, Offset);
493 const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
495 // Traverse all non-virtual bases.
496 for (const CXXBaseSpecifier &Base : RD->bases()) {
497 if (Base.isVirtual())
500 const CXXRecordDecl *BaseDecl = Base.getType()->getAsCXXRecordDecl();
502 CharUnits BaseOffset = Offset + Layout.getBaseClassOffset(BaseDecl);
503 UpdateEmptyFieldSubobjects(BaseDecl, Class, BaseOffset);
507 // This is the most derived class, traverse virtual bases as well.
508 for (const CXXBaseSpecifier &Base : RD->vbases()) {
509 const CXXRecordDecl *VBaseDecl = Base.getType()->getAsCXXRecordDecl();
511 CharUnits VBaseOffset = Offset + Layout.getVBaseClassOffset(VBaseDecl);
512 UpdateEmptyFieldSubobjects(VBaseDecl, Class, VBaseOffset);
516 // Traverse all member variables.
517 unsigned FieldNo = 0;
518 for (CXXRecordDecl::field_iterator I = RD->field_begin(), E = RD->field_end();
519 I != E; ++I, ++FieldNo) {
523 CharUnits FieldOffset = Offset + getFieldOffset(Layout, FieldNo);
525 UpdateEmptyFieldSubobjects(*I, FieldOffset);
529 void EmptySubobjectMap::UpdateEmptyFieldSubobjects(const FieldDecl *FD,
531 QualType T = FD->getType();
532 if (const CXXRecordDecl *RD = T->getAsCXXRecordDecl()) {
533 UpdateEmptyFieldSubobjects(RD, RD, Offset);
537 // If we have an array type we need to update every element.
538 if (const ConstantArrayType *AT = Context.getAsConstantArrayType(T)) {
539 QualType ElemTy = Context.getBaseElementType(AT);
540 const RecordType *RT = ElemTy->getAs<RecordType>();
544 const CXXRecordDecl *RD = RT->getAsCXXRecordDecl();
545 const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
547 uint64_t NumElements = Context.getConstantArrayElementCount(AT);
548 CharUnits ElementOffset = Offset;
550 for (uint64_t I = 0; I != NumElements; ++I) {
551 // We know that the only empty subobjects that can conflict with empty
552 // field subobjects are subobjects of empty bases that can be placed at
553 // offset zero. Because of this, we only need to keep track of empty field
554 // subobjects with offsets less than the size of the largest empty
555 // subobject for our class.
556 if (ElementOffset >= SizeOfLargestEmptySubobject)
559 UpdateEmptyFieldSubobjects(RD, RD, ElementOffset);
560 ElementOffset += Layout.getSize();
565 typedef llvm::SmallPtrSet<const CXXRecordDecl*, 4> ClassSetTy;
567 class ItaniumRecordLayoutBuilder {
569 // FIXME: Remove this and make the appropriate fields public.
570 friend class clang::ASTContext;
572 const ASTContext &Context;
574 EmptySubobjectMap *EmptySubobjects;
576 /// Size - The current size of the record layout.
579 /// Alignment - The current alignment of the record layout.
582 /// \brief The alignment if attribute packed is not used.
583 CharUnits UnpackedAlignment;
585 SmallVector<uint64_t, 16> FieldOffsets;
587 /// \brief Whether the external AST source has provided a layout for this
589 unsigned UseExternalLayout : 1;
591 /// \brief Whether we need to infer alignment, even when we have an
592 /// externally-provided layout.
593 unsigned InferAlignment : 1;
595 /// Packed - Whether the record is packed or not.
598 unsigned IsUnion : 1;
600 unsigned IsMac68kAlign : 1;
602 unsigned IsMsStruct : 1;
604 /// UnfilledBitsInLastUnit - If the last field laid out was a bitfield,
605 /// this contains the number of bits in the last unit that can be used for
606 /// an adjacent bitfield if necessary. The unit in question is usually
607 /// a byte, but larger units are used if IsMsStruct.
608 unsigned char UnfilledBitsInLastUnit;
609 /// LastBitfieldTypeSize - If IsMsStruct, represents the size of the type
610 /// of the previous field if it was a bitfield.
611 unsigned char LastBitfieldTypeSize;
613 /// MaxFieldAlignment - The maximum allowed field alignment. This is set by
615 CharUnits MaxFieldAlignment;
617 /// DataSize - The data size of the record being laid out.
620 CharUnits NonVirtualSize;
621 CharUnits NonVirtualAlignment;
623 /// PrimaryBase - the primary base class (if one exists) of the class
624 /// we're laying out.
625 const CXXRecordDecl *PrimaryBase;
627 /// PrimaryBaseIsVirtual - Whether the primary base of the class we're laying
629 bool PrimaryBaseIsVirtual;
631 /// HasOwnVFPtr - Whether the class provides its own vtable/vftbl
632 /// pointer, as opposed to inheriting one from a primary base class.
635 /// \brief the flag of field offset changing due to packed attribute.
638 typedef llvm::DenseMap<const CXXRecordDecl *, CharUnits> BaseOffsetsMapTy;
640 /// Bases - base classes and their offsets in the record.
641 BaseOffsetsMapTy Bases;
643 // VBases - virtual base classes and their offsets in the record.
644 ASTRecordLayout::VBaseOffsetsMapTy VBases;
646 /// IndirectPrimaryBases - Virtual base classes, direct or indirect, that are
647 /// primary base classes for some other direct or indirect base class.
648 CXXIndirectPrimaryBaseSet IndirectPrimaryBases;
650 /// FirstNearlyEmptyVBase - The first nearly empty virtual base class in
651 /// inheritance graph order. Used for determining the primary base class.
652 const CXXRecordDecl *FirstNearlyEmptyVBase;
654 /// VisitedVirtualBases - A set of all the visited virtual bases, used to
655 /// avoid visiting virtual bases more than once.
656 llvm::SmallPtrSet<const CXXRecordDecl *, 4> VisitedVirtualBases;
658 /// Valid if UseExternalLayout is true.
659 ExternalLayout External;
661 ItaniumRecordLayoutBuilder(const ASTContext &Context,
662 EmptySubobjectMap *EmptySubobjects)
663 : Context(Context), EmptySubobjects(EmptySubobjects), Size(0),
664 Alignment(CharUnits::One()), UnpackedAlignment(CharUnits::One()),
665 UseExternalLayout(false), InferAlignment(false), Packed(false),
666 IsUnion(false), IsMac68kAlign(false), IsMsStruct(false),
667 UnfilledBitsInLastUnit(0), LastBitfieldTypeSize(0),
668 MaxFieldAlignment(CharUnits::Zero()), DataSize(0),
669 NonVirtualSize(CharUnits::Zero()),
670 NonVirtualAlignment(CharUnits::One()), PrimaryBase(nullptr),
671 PrimaryBaseIsVirtual(false), HasOwnVFPtr(false),
672 HasPackedField(false), FirstNearlyEmptyVBase(nullptr) {}
674 void Layout(const RecordDecl *D);
675 void Layout(const CXXRecordDecl *D);
676 void Layout(const ObjCInterfaceDecl *D);
678 void LayoutFields(const RecordDecl *D);
679 void LayoutField(const FieldDecl *D, bool InsertExtraPadding);
680 void LayoutWideBitField(uint64_t FieldSize, uint64_t TypeSize,
681 bool FieldPacked, const FieldDecl *D);
682 void LayoutBitField(const FieldDecl *D);
684 TargetCXXABI getCXXABI() const {
685 return Context.getTargetInfo().getCXXABI();
688 /// BaseSubobjectInfoAllocator - Allocator for BaseSubobjectInfo objects.
689 llvm::SpecificBumpPtrAllocator<BaseSubobjectInfo> BaseSubobjectInfoAllocator;
691 typedef llvm::DenseMap<const CXXRecordDecl *, BaseSubobjectInfo *>
692 BaseSubobjectInfoMapTy;
694 /// VirtualBaseInfo - Map from all the (direct or indirect) virtual bases
695 /// of the class we're laying out to their base subobject info.
696 BaseSubobjectInfoMapTy VirtualBaseInfo;
698 /// NonVirtualBaseInfo - Map from all the direct non-virtual bases of the
699 /// class we're laying out to their base subobject info.
700 BaseSubobjectInfoMapTy NonVirtualBaseInfo;
702 /// ComputeBaseSubobjectInfo - Compute the base subobject information for the
703 /// bases of the given class.
704 void ComputeBaseSubobjectInfo(const CXXRecordDecl *RD);
706 /// ComputeBaseSubobjectInfo - Compute the base subobject information for a
707 /// single class and all of its base classes.
708 BaseSubobjectInfo *ComputeBaseSubobjectInfo(const CXXRecordDecl *RD,
710 BaseSubobjectInfo *Derived);
712 /// DeterminePrimaryBase - Determine the primary base of the given class.
713 void DeterminePrimaryBase(const CXXRecordDecl *RD);
715 void SelectPrimaryVBase(const CXXRecordDecl *RD);
717 void EnsureVTablePointerAlignment(CharUnits UnpackedBaseAlign);
719 /// LayoutNonVirtualBases - Determines the primary base class (if any) and
720 /// lays it out. Will then proceed to lay out all non-virtual base clasess.
721 void LayoutNonVirtualBases(const CXXRecordDecl *RD);
723 /// LayoutNonVirtualBase - Lays out a single non-virtual base.
724 void LayoutNonVirtualBase(const BaseSubobjectInfo *Base);
726 void AddPrimaryVirtualBaseOffsets(const BaseSubobjectInfo *Info,
729 /// LayoutVirtualBases - Lays out all the virtual bases.
730 void LayoutVirtualBases(const CXXRecordDecl *RD,
731 const CXXRecordDecl *MostDerivedClass);
733 /// LayoutVirtualBase - Lays out a single virtual base.
734 void LayoutVirtualBase(const BaseSubobjectInfo *Base);
736 /// LayoutBase - Will lay out a base and return the offset where it was
737 /// placed, in chars.
738 CharUnits LayoutBase(const BaseSubobjectInfo *Base);
740 /// InitializeLayout - Initialize record layout for the given record decl.
741 void InitializeLayout(const Decl *D);
743 /// FinishLayout - Finalize record layout. Adjust record size based on the
745 void FinishLayout(const NamedDecl *D);
747 void UpdateAlignment(CharUnits NewAlignment, CharUnits UnpackedNewAlignment);
748 void UpdateAlignment(CharUnits NewAlignment) {
749 UpdateAlignment(NewAlignment, NewAlignment);
752 /// \brief Retrieve the externally-supplied field offset for the given
755 /// \param Field The field whose offset is being queried.
756 /// \param ComputedOffset The offset that we've computed for this field.
757 uint64_t updateExternalFieldOffset(const FieldDecl *Field,
758 uint64_t ComputedOffset);
760 void CheckFieldPadding(uint64_t Offset, uint64_t UnpaddedOffset,
761 uint64_t UnpackedOffset, unsigned UnpackedAlign,
762 bool isPacked, const FieldDecl *D);
764 DiagnosticBuilder Diag(SourceLocation Loc, unsigned DiagID);
766 CharUnits getSize() const {
767 assert(Size % Context.getCharWidth() == 0);
768 return Context.toCharUnitsFromBits(Size);
770 uint64_t getSizeInBits() const { return Size; }
772 void setSize(CharUnits NewSize) { Size = Context.toBits(NewSize); }
773 void setSize(uint64_t NewSize) { Size = NewSize; }
775 CharUnits getAligment() const { return Alignment; }
777 CharUnits getDataSize() const {
778 assert(DataSize % Context.getCharWidth() == 0);
779 return Context.toCharUnitsFromBits(DataSize);
781 uint64_t getDataSizeInBits() const { return DataSize; }
783 void setDataSize(CharUnits NewSize) { DataSize = Context.toBits(NewSize); }
784 void setDataSize(uint64_t NewSize) { DataSize = NewSize; }
786 ItaniumRecordLayoutBuilder(const ItaniumRecordLayoutBuilder &) = delete;
787 void operator=(const ItaniumRecordLayoutBuilder &) = delete;
789 } // end anonymous namespace
791 void ItaniumRecordLayoutBuilder::SelectPrimaryVBase(const CXXRecordDecl *RD) {
792 for (const auto &I : RD->bases()) {
793 assert(!I.getType()->isDependentType() &&
794 "Cannot layout class with dependent bases.");
796 const CXXRecordDecl *Base = I.getType()->getAsCXXRecordDecl();
798 // Check if this is a nearly empty virtual base.
799 if (I.isVirtual() && Context.isNearlyEmpty(Base)) {
800 // If it's not an indirect primary base, then we've found our primary
802 if (!IndirectPrimaryBases.count(Base)) {
804 PrimaryBaseIsVirtual = true;
808 // Is this the first nearly empty virtual base?
809 if (!FirstNearlyEmptyVBase)
810 FirstNearlyEmptyVBase = Base;
813 SelectPrimaryVBase(Base);
819 /// DeterminePrimaryBase - Determine the primary base of the given class.
820 void ItaniumRecordLayoutBuilder::DeterminePrimaryBase(const CXXRecordDecl *RD) {
821 // If the class isn't dynamic, it won't have a primary base.
822 if (!RD->isDynamicClass())
825 // Compute all the primary virtual bases for all of our direct and
826 // indirect bases, and record all their primary virtual base classes.
827 RD->getIndirectPrimaryBases(IndirectPrimaryBases);
829 // If the record has a dynamic base class, attempt to choose a primary base
830 // class. It is the first (in direct base class order) non-virtual dynamic
831 // base class, if one exists.
832 for (const auto &I : RD->bases()) {
833 // Ignore virtual bases.
837 const CXXRecordDecl *Base = I.getType()->getAsCXXRecordDecl();
839 if (Base->isDynamicClass()) {
842 PrimaryBaseIsVirtual = false;
847 // Under the Itanium ABI, if there is no non-virtual primary base class,
848 // try to compute the primary virtual base. The primary virtual base is
849 // the first nearly empty virtual base that is not an indirect primary
850 // virtual base class, if one exists.
851 if (RD->getNumVBases() != 0) {
852 SelectPrimaryVBase(RD);
857 // Otherwise, it is the first indirect primary base class, if one exists.
858 if (FirstNearlyEmptyVBase) {
859 PrimaryBase = FirstNearlyEmptyVBase;
860 PrimaryBaseIsVirtual = true;
864 assert(!PrimaryBase && "Should not get here with a primary base!");
867 BaseSubobjectInfo *ItaniumRecordLayoutBuilder::ComputeBaseSubobjectInfo(
868 const CXXRecordDecl *RD, bool IsVirtual, BaseSubobjectInfo *Derived) {
869 BaseSubobjectInfo *Info;
872 // Check if we already have info about this virtual base.
873 BaseSubobjectInfo *&InfoSlot = VirtualBaseInfo[RD];
875 assert(InfoSlot->Class == RD && "Wrong class for virtual base info!");
879 // We don't, create it.
880 InfoSlot = new (BaseSubobjectInfoAllocator.Allocate()) BaseSubobjectInfo;
883 Info = new (BaseSubobjectInfoAllocator.Allocate()) BaseSubobjectInfo;
887 Info->IsVirtual = IsVirtual;
888 Info->Derived = nullptr;
889 Info->PrimaryVirtualBaseInfo = nullptr;
891 const CXXRecordDecl *PrimaryVirtualBase = nullptr;
892 BaseSubobjectInfo *PrimaryVirtualBaseInfo = nullptr;
894 // Check if this base has a primary virtual base.
895 if (RD->getNumVBases()) {
896 const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
897 if (Layout.isPrimaryBaseVirtual()) {
898 // This base does have a primary virtual base.
899 PrimaryVirtualBase = Layout.getPrimaryBase();
900 assert(PrimaryVirtualBase && "Didn't have a primary virtual base!");
902 // Now check if we have base subobject info about this primary base.
903 PrimaryVirtualBaseInfo = VirtualBaseInfo.lookup(PrimaryVirtualBase);
905 if (PrimaryVirtualBaseInfo) {
906 if (PrimaryVirtualBaseInfo->Derived) {
907 // We did have info about this primary base, and it turns out that it
908 // has already been claimed as a primary virtual base for another
910 PrimaryVirtualBase = nullptr;
912 // We can claim this base as our primary base.
913 Info->PrimaryVirtualBaseInfo = PrimaryVirtualBaseInfo;
914 PrimaryVirtualBaseInfo->Derived = Info;
920 // Now go through all direct bases.
921 for (const auto &I : RD->bases()) {
922 bool IsVirtual = I.isVirtual();
924 const CXXRecordDecl *BaseDecl = I.getType()->getAsCXXRecordDecl();
926 Info->Bases.push_back(ComputeBaseSubobjectInfo(BaseDecl, IsVirtual, Info));
929 if (PrimaryVirtualBase && !PrimaryVirtualBaseInfo) {
930 // Traversing the bases must have created the base info for our primary
932 PrimaryVirtualBaseInfo = VirtualBaseInfo.lookup(PrimaryVirtualBase);
933 assert(PrimaryVirtualBaseInfo &&
934 "Did not create a primary virtual base!");
936 // Claim the primary virtual base as our primary virtual base.
937 Info->PrimaryVirtualBaseInfo = PrimaryVirtualBaseInfo;
938 PrimaryVirtualBaseInfo->Derived = Info;
944 void ItaniumRecordLayoutBuilder::ComputeBaseSubobjectInfo(
945 const CXXRecordDecl *RD) {
946 for (const auto &I : RD->bases()) {
947 bool IsVirtual = I.isVirtual();
949 const CXXRecordDecl *BaseDecl = I.getType()->getAsCXXRecordDecl();
951 // Compute the base subobject info for this base.
952 BaseSubobjectInfo *Info = ComputeBaseSubobjectInfo(BaseDecl, IsVirtual,
956 // ComputeBaseInfo has already added this base for us.
957 assert(VirtualBaseInfo.count(BaseDecl) &&
958 "Did not add virtual base!");
960 // Add the base info to the map of non-virtual bases.
961 assert(!NonVirtualBaseInfo.count(BaseDecl) &&
962 "Non-virtual base already exists!");
963 NonVirtualBaseInfo.insert(std::make_pair(BaseDecl, Info));
968 void ItaniumRecordLayoutBuilder::EnsureVTablePointerAlignment(
969 CharUnits UnpackedBaseAlign) {
970 CharUnits BaseAlign = (Packed) ? CharUnits::One() : UnpackedBaseAlign;
972 // The maximum field alignment overrides base align.
973 if (!MaxFieldAlignment.isZero()) {
974 BaseAlign = std::min(BaseAlign, MaxFieldAlignment);
975 UnpackedBaseAlign = std::min(UnpackedBaseAlign, MaxFieldAlignment);
978 // Round up the current record size to pointer alignment.
979 setSize(getSize().alignTo(BaseAlign));
980 setDataSize(getSize());
982 // Update the alignment.
983 UpdateAlignment(BaseAlign, UnpackedBaseAlign);
986 void ItaniumRecordLayoutBuilder::LayoutNonVirtualBases(
987 const CXXRecordDecl *RD) {
988 // Then, determine the primary base class.
989 DeterminePrimaryBase(RD);
991 // Compute base subobject info.
992 ComputeBaseSubobjectInfo(RD);
994 // If we have a primary base class, lay it out.
996 if (PrimaryBaseIsVirtual) {
997 // If the primary virtual base was a primary virtual base of some other
998 // base class we'll have to steal it.
999 BaseSubobjectInfo *PrimaryBaseInfo = VirtualBaseInfo.lookup(PrimaryBase);
1000 PrimaryBaseInfo->Derived = nullptr;
1002 // We have a virtual primary base, insert it as an indirect primary base.
1003 IndirectPrimaryBases.insert(PrimaryBase);
1005 assert(!VisitedVirtualBases.count(PrimaryBase) &&
1006 "vbase already visited!");
1007 VisitedVirtualBases.insert(PrimaryBase);
1009 LayoutVirtualBase(PrimaryBaseInfo);
1011 BaseSubobjectInfo *PrimaryBaseInfo =
1012 NonVirtualBaseInfo.lookup(PrimaryBase);
1013 assert(PrimaryBaseInfo &&
1014 "Did not find base info for non-virtual primary base!");
1016 LayoutNonVirtualBase(PrimaryBaseInfo);
1019 // If this class needs a vtable/vf-table and didn't get one from a
1020 // primary base, add it in now.
1021 } else if (RD->isDynamicClass()) {
1022 assert(DataSize == 0 && "Vtable pointer must be at offset zero!");
1023 CharUnits PtrWidth =
1024 Context.toCharUnitsFromBits(Context.getTargetInfo().getPointerWidth(0));
1025 CharUnits PtrAlign =
1026 Context.toCharUnitsFromBits(Context.getTargetInfo().getPointerAlign(0));
1027 EnsureVTablePointerAlignment(PtrAlign);
1029 setSize(getSize() + PtrWidth);
1030 setDataSize(getSize());
1033 // Now lay out the non-virtual bases.
1034 for (const auto &I : RD->bases()) {
1036 // Ignore virtual bases.
1040 const CXXRecordDecl *BaseDecl = I.getType()->getAsCXXRecordDecl();
1042 // Skip the primary base, because we've already laid it out. The
1043 // !PrimaryBaseIsVirtual check is required because we might have a
1044 // non-virtual base of the same type as a primary virtual base.
1045 if (BaseDecl == PrimaryBase && !PrimaryBaseIsVirtual)
1048 // Lay out the base.
1049 BaseSubobjectInfo *BaseInfo = NonVirtualBaseInfo.lookup(BaseDecl);
1050 assert(BaseInfo && "Did not find base info for non-virtual base!");
1052 LayoutNonVirtualBase(BaseInfo);
1056 void ItaniumRecordLayoutBuilder::LayoutNonVirtualBase(
1057 const BaseSubobjectInfo *Base) {
1059 CharUnits Offset = LayoutBase(Base);
1061 // Add its base class offset.
1062 assert(!Bases.count(Base->Class) && "base offset already exists!");
1063 Bases.insert(std::make_pair(Base->Class, Offset));
1065 AddPrimaryVirtualBaseOffsets(Base, Offset);
1068 void ItaniumRecordLayoutBuilder::AddPrimaryVirtualBaseOffsets(
1069 const BaseSubobjectInfo *Info, CharUnits Offset) {
1070 // This base isn't interesting, it has no virtual bases.
1071 if (!Info->Class->getNumVBases())
1074 // First, check if we have a virtual primary base to add offsets for.
1075 if (Info->PrimaryVirtualBaseInfo) {
1076 assert(Info->PrimaryVirtualBaseInfo->IsVirtual &&
1077 "Primary virtual base is not virtual!");
1078 if (Info->PrimaryVirtualBaseInfo->Derived == Info) {
1080 assert(!VBases.count(Info->PrimaryVirtualBaseInfo->Class) &&
1081 "primary vbase offset already exists!");
1082 VBases.insert(std::make_pair(Info->PrimaryVirtualBaseInfo->Class,
1083 ASTRecordLayout::VBaseInfo(Offset, false)));
1085 // Traverse the primary virtual base.
1086 AddPrimaryVirtualBaseOffsets(Info->PrimaryVirtualBaseInfo, Offset);
1090 // Now go through all direct non-virtual bases.
1091 const ASTRecordLayout &Layout = Context.getASTRecordLayout(Info->Class);
1092 for (const BaseSubobjectInfo *Base : Info->Bases) {
1093 if (Base->IsVirtual)
1096 CharUnits BaseOffset = Offset + Layout.getBaseClassOffset(Base->Class);
1097 AddPrimaryVirtualBaseOffsets(Base, BaseOffset);
1101 void ItaniumRecordLayoutBuilder::LayoutVirtualBases(
1102 const CXXRecordDecl *RD, const CXXRecordDecl *MostDerivedClass) {
1103 const CXXRecordDecl *PrimaryBase;
1104 bool PrimaryBaseIsVirtual;
1106 if (MostDerivedClass == RD) {
1107 PrimaryBase = this->PrimaryBase;
1108 PrimaryBaseIsVirtual = this->PrimaryBaseIsVirtual;
1110 const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
1111 PrimaryBase = Layout.getPrimaryBase();
1112 PrimaryBaseIsVirtual = Layout.isPrimaryBaseVirtual();
1115 for (const CXXBaseSpecifier &Base : RD->bases()) {
1116 assert(!Base.getType()->isDependentType() &&
1117 "Cannot layout class with dependent bases.");
1119 const CXXRecordDecl *BaseDecl = Base.getType()->getAsCXXRecordDecl();
1121 if (Base.isVirtual()) {
1122 if (PrimaryBase != BaseDecl || !PrimaryBaseIsVirtual) {
1123 bool IndirectPrimaryBase = IndirectPrimaryBases.count(BaseDecl);
1125 // Only lay out the virtual base if it's not an indirect primary base.
1126 if (!IndirectPrimaryBase) {
1127 // Only visit virtual bases once.
1128 if (!VisitedVirtualBases.insert(BaseDecl).second)
1131 const BaseSubobjectInfo *BaseInfo = VirtualBaseInfo.lookup(BaseDecl);
1132 assert(BaseInfo && "Did not find virtual base info!");
1133 LayoutVirtualBase(BaseInfo);
1138 if (!BaseDecl->getNumVBases()) {
1139 // This base isn't interesting since it doesn't have any virtual bases.
1143 LayoutVirtualBases(BaseDecl, MostDerivedClass);
1147 void ItaniumRecordLayoutBuilder::LayoutVirtualBase(
1148 const BaseSubobjectInfo *Base) {
1149 assert(!Base->Derived && "Trying to lay out a primary virtual base!");
1152 CharUnits Offset = LayoutBase(Base);
1154 // Add its base class offset.
1155 assert(!VBases.count(Base->Class) && "vbase offset already exists!");
1156 VBases.insert(std::make_pair(Base->Class,
1157 ASTRecordLayout::VBaseInfo(Offset, false)));
1159 AddPrimaryVirtualBaseOffsets(Base, Offset);
1163 ItaniumRecordLayoutBuilder::LayoutBase(const BaseSubobjectInfo *Base) {
1164 const ASTRecordLayout &Layout = Context.getASTRecordLayout(Base->Class);
1169 // Query the external layout to see if it provides an offset.
1170 bool HasExternalLayout = false;
1171 if (UseExternalLayout) {
1172 if (Base->IsVirtual)
1173 HasExternalLayout = External.getExternalNVBaseOffset(Base->Class, Offset);
1175 HasExternalLayout = External.getExternalVBaseOffset(Base->Class, Offset);
1178 CharUnits UnpackedBaseAlign = Layout.getNonVirtualAlignment();
1179 CharUnits BaseAlign = (Packed) ? CharUnits::One() : UnpackedBaseAlign;
1181 // If we have an empty base class, try to place it at offset 0.
1182 if (Base->Class->isEmpty() &&
1183 (!HasExternalLayout || Offset == CharUnits::Zero()) &&
1184 EmptySubobjects->CanPlaceBaseAtOffset(Base, CharUnits::Zero())) {
1185 setSize(std::max(getSize(), Layout.getSize()));
1186 UpdateAlignment(BaseAlign, UnpackedBaseAlign);
1188 return CharUnits::Zero();
1191 // The maximum field alignment overrides base align.
1192 if (!MaxFieldAlignment.isZero()) {
1193 BaseAlign = std::min(BaseAlign, MaxFieldAlignment);
1194 UnpackedBaseAlign = std::min(UnpackedBaseAlign, MaxFieldAlignment);
1197 if (!HasExternalLayout) {
1198 // Round up the current record size to the base's alignment boundary.
1199 Offset = getDataSize().alignTo(BaseAlign);
1201 // Try to place the base.
1202 while (!EmptySubobjects->CanPlaceBaseAtOffset(Base, Offset))
1203 Offset += BaseAlign;
1205 bool Allowed = EmptySubobjects->CanPlaceBaseAtOffset(Base, Offset);
1207 assert(Allowed && "Base subobject externally placed at overlapping offset");
1209 if (InferAlignment && Offset < getDataSize().alignTo(BaseAlign)) {
1210 // The externally-supplied base offset is before the base offset we
1211 // computed. Assume that the structure is packed.
1212 Alignment = CharUnits::One();
1213 InferAlignment = false;
1217 if (!Base->Class->isEmpty()) {
1218 // Update the data size.
1219 setDataSize(Offset + Layout.getNonVirtualSize());
1221 setSize(std::max(getSize(), getDataSize()));
1223 setSize(std::max(getSize(), Offset + Layout.getSize()));
1225 // Remember max struct/class alignment.
1226 UpdateAlignment(BaseAlign, UnpackedBaseAlign);
1231 void ItaniumRecordLayoutBuilder::InitializeLayout(const Decl *D) {
1232 if (const RecordDecl *RD = dyn_cast<RecordDecl>(D)) {
1233 IsUnion = RD->isUnion();
1234 IsMsStruct = RD->isMsStruct(Context);
1237 Packed = D->hasAttr<PackedAttr>();
1239 // Honor the default struct packing maximum alignment flag.
1240 if (unsigned DefaultMaxFieldAlignment = Context.getLangOpts().PackStruct) {
1241 MaxFieldAlignment = CharUnits::fromQuantity(DefaultMaxFieldAlignment);
1244 // mac68k alignment supersedes maximum field alignment and attribute aligned,
1245 // and forces all structures to have 2-byte alignment. The IBM docs on it
1246 // allude to additional (more complicated) semantics, especially with regard
1247 // to bit-fields, but gcc appears not to follow that.
1248 if (D->hasAttr<AlignMac68kAttr>()) {
1249 IsMac68kAlign = true;
1250 MaxFieldAlignment = CharUnits::fromQuantity(2);
1251 Alignment = CharUnits::fromQuantity(2);
1253 if (const MaxFieldAlignmentAttr *MFAA = D->getAttr<MaxFieldAlignmentAttr>())
1254 MaxFieldAlignment = Context.toCharUnitsFromBits(MFAA->getAlignment());
1256 if (unsigned MaxAlign = D->getMaxAlignment())
1257 UpdateAlignment(Context.toCharUnitsFromBits(MaxAlign));
1260 // If there is an external AST source, ask it for the various offsets.
1261 if (const RecordDecl *RD = dyn_cast<RecordDecl>(D))
1262 if (ExternalASTSource *Source = Context.getExternalSource()) {
1263 UseExternalLayout = Source->layoutRecordType(
1264 RD, External.Size, External.Align, External.FieldOffsets,
1265 External.BaseOffsets, External.VirtualBaseOffsets);
1267 // Update based on external alignment.
1268 if (UseExternalLayout) {
1269 if (External.Align > 0) {
1270 Alignment = Context.toCharUnitsFromBits(External.Align);
1272 // The external source didn't have alignment information; infer it.
1273 InferAlignment = true;
1279 void ItaniumRecordLayoutBuilder::Layout(const RecordDecl *D) {
1280 InitializeLayout(D);
1283 // Finally, round the size of the total struct up to the alignment of the
1288 void ItaniumRecordLayoutBuilder::Layout(const CXXRecordDecl *RD) {
1289 InitializeLayout(RD);
1291 // Lay out the vtable and the non-virtual bases.
1292 LayoutNonVirtualBases(RD);
1296 NonVirtualSize = Context.toCharUnitsFromBits(
1297 llvm::alignTo(getSizeInBits(), Context.getTargetInfo().getCharAlign()));
1298 NonVirtualAlignment = Alignment;
1300 // Lay out the virtual bases and add the primary virtual base offsets.
1301 LayoutVirtualBases(RD, RD);
1303 // Finally, round the size of the total struct up to the alignment
1304 // of the struct itself.
1308 // Check that we have base offsets for all bases.
1309 for (const CXXBaseSpecifier &Base : RD->bases()) {
1310 if (Base.isVirtual())
1313 const CXXRecordDecl *BaseDecl = Base.getType()->getAsCXXRecordDecl();
1315 assert(Bases.count(BaseDecl) && "Did not find base offset!");
1318 // And all virtual bases.
1319 for (const CXXBaseSpecifier &Base : RD->vbases()) {
1320 const CXXRecordDecl *BaseDecl = Base.getType()->getAsCXXRecordDecl();
1322 assert(VBases.count(BaseDecl) && "Did not find base offset!");
1327 void ItaniumRecordLayoutBuilder::Layout(const ObjCInterfaceDecl *D) {
1328 if (ObjCInterfaceDecl *SD = D->getSuperClass()) {
1329 const ASTRecordLayout &SL = Context.getASTObjCInterfaceLayout(SD);
1331 UpdateAlignment(SL.getAlignment());
1333 // We start laying out ivars not at the end of the superclass
1334 // structure, but at the next byte following the last field.
1335 setSize(SL.getDataSize());
1336 setDataSize(getSize());
1339 InitializeLayout(D);
1340 // Layout each ivar sequentially.
1341 for (const ObjCIvarDecl *IVD = D->all_declared_ivar_begin(); IVD;
1342 IVD = IVD->getNextIvar())
1343 LayoutField(IVD, false);
1345 // Finally, round the size of the total struct up to the alignment of the
1350 void ItaniumRecordLayoutBuilder::LayoutFields(const RecordDecl *D) {
1351 // Layout each field, for now, just sequentially, respecting alignment. In
1352 // the future, this will need to be tweakable by targets.
1353 bool InsertExtraPadding = D->mayInsertExtraPadding(/*EmitRemark=*/true);
1354 bool HasFlexibleArrayMember = D->hasFlexibleArrayMember();
1355 for (auto I = D->field_begin(), End = D->field_end(); I != End; ++I) {
1359 InsertExtraPadding && (Next != End || !HasFlexibleArrayMember));
1363 // Rounds the specified size to have it a multiple of the char size.
1365 roundUpSizeToCharAlignment(uint64_t Size,
1366 const ASTContext &Context) {
1367 uint64_t CharAlignment = Context.getTargetInfo().getCharAlign();
1368 return llvm::alignTo(Size, CharAlignment);
1371 void ItaniumRecordLayoutBuilder::LayoutWideBitField(uint64_t FieldSize,
1374 const FieldDecl *D) {
1375 assert(Context.getLangOpts().CPlusPlus &&
1376 "Can only have wide bit-fields in C++!");
1378 // Itanium C++ ABI 2.4:
1379 // If sizeof(T)*8 < n, let T' be the largest integral POD type with
1380 // sizeof(T')*8 <= n.
1382 QualType IntegralPODTypes[] = {
1383 Context.UnsignedCharTy, Context.UnsignedShortTy, Context.UnsignedIntTy,
1384 Context.UnsignedLongTy, Context.UnsignedLongLongTy
1388 for (const QualType &QT : IntegralPODTypes) {
1389 uint64_t Size = Context.getTypeSize(QT);
1391 if (Size > FieldSize)
1396 assert(!Type.isNull() && "Did not find a type!");
1398 CharUnits TypeAlign = Context.getTypeAlignInChars(Type);
1400 // We're not going to use any of the unfilled bits in the last byte.
1401 UnfilledBitsInLastUnit = 0;
1402 LastBitfieldTypeSize = 0;
1404 uint64_t FieldOffset;
1405 uint64_t UnpaddedFieldOffset = getDataSizeInBits() - UnfilledBitsInLastUnit;
1408 uint64_t RoundedFieldSize = roundUpSizeToCharAlignment(FieldSize,
1410 setDataSize(std::max(getDataSizeInBits(), RoundedFieldSize));
1413 // The bitfield is allocated starting at the next offset aligned
1414 // appropriately for T', with length n bits.
1415 FieldOffset = llvm::alignTo(getDataSizeInBits(), Context.toBits(TypeAlign));
1417 uint64_t NewSizeInBits = FieldOffset + FieldSize;
1420 llvm::alignTo(NewSizeInBits, Context.getTargetInfo().getCharAlign()));
1421 UnfilledBitsInLastUnit = getDataSizeInBits() - NewSizeInBits;
1424 // Place this field at the current location.
1425 FieldOffsets.push_back(FieldOffset);
1427 CheckFieldPadding(FieldOffset, UnpaddedFieldOffset, FieldOffset,
1428 Context.toBits(TypeAlign), FieldPacked, D);
1431 setSize(std::max(getSizeInBits(), getDataSizeInBits()));
1433 // Remember max struct/class alignment.
1434 UpdateAlignment(TypeAlign);
1437 void ItaniumRecordLayoutBuilder::LayoutBitField(const FieldDecl *D) {
1438 bool FieldPacked = Packed || D->hasAttr<PackedAttr>();
1439 uint64_t FieldSize = D->getBitWidthValue(Context);
1440 TypeInfo FieldInfo = Context.getTypeInfo(D->getType());
1441 uint64_t TypeSize = FieldInfo.Width;
1442 unsigned FieldAlign = FieldInfo.Align;
1444 // UnfilledBitsInLastUnit is the difference between the end of the
1445 // last allocated bitfield (i.e. the first bit offset available for
1446 // bitfields) and the end of the current data size in bits (i.e. the
1447 // first bit offset available for non-bitfields). The current data
1448 // size in bits is always a multiple of the char size; additionally,
1449 // for ms_struct records it's also a multiple of the
1450 // LastBitfieldTypeSize (if set).
1452 // The struct-layout algorithm is dictated by the platform ABI,
1453 // which in principle could use almost any rules it likes. In
1454 // practice, UNIXy targets tend to inherit the algorithm described
1455 // in the System V generic ABI. The basic bitfield layout rule in
1456 // System V is to place bitfields at the next available bit offset
1457 // where the entire bitfield would fit in an aligned storage unit of
1458 // the declared type; it's okay if an earlier or later non-bitfield
1459 // is allocated in the same storage unit. However, some targets
1460 // (those that !useBitFieldTypeAlignment(), e.g. ARM APCS) don't
1461 // require this storage unit to be aligned, and therefore always put
1462 // the bitfield at the next available bit offset.
1464 // ms_struct basically requests a complete replacement of the
1465 // platform ABI's struct-layout algorithm, with the high-level goal
1466 // of duplicating MSVC's layout. For non-bitfields, this follows
1467 // the standard algorithm. The basic bitfield layout rule is to
1468 // allocate an entire unit of the bitfield's declared type
1469 // (e.g. 'unsigned long'), then parcel it up among successive
1470 // bitfields whose declared types have the same size, making a new
1471 // unit as soon as the last can no longer store the whole value.
1472 // Since it completely replaces the platform ABI's algorithm,
1473 // settings like !useBitFieldTypeAlignment() do not apply.
1475 // A zero-width bitfield forces the use of a new storage unit for
1476 // later bitfields. In general, this occurs by rounding up the
1477 // current size of the struct as if the algorithm were about to
1478 // place a non-bitfield of the field's formal type. Usually this
1479 // does not change the alignment of the struct itself, but it does
1480 // on some targets (those that useZeroLengthBitfieldAlignment(),
1481 // e.g. ARM). In ms_struct layout, zero-width bitfields are
1482 // ignored unless they follow a non-zero-width bitfield.
1484 // A field alignment restriction (e.g. from #pragma pack) or
1485 // specification (e.g. from __attribute__((aligned))) changes the
1486 // formal alignment of the field. For System V, this alters the
1487 // required alignment of the notional storage unit that must contain
1488 // the bitfield. For ms_struct, this only affects the placement of
1489 // new storage units. In both cases, the effect of #pragma pack is
1490 // ignored on zero-width bitfields.
1492 // On System V, a packed field (e.g. from #pragma pack or
1493 // __attribute__((packed))) always uses the next available bit
1496 // In an ms_struct struct, the alignment of a fundamental type is
1497 // always equal to its size. This is necessary in order to mimic
1498 // the i386 alignment rules on targets which might not fully align
1499 // all types (e.g. Darwin PPC32, where alignof(long long) == 4).
1501 // First, some simple bookkeeping to perform for ms_struct structs.
1503 // The field alignment for integer types is always the size.
1504 FieldAlign = TypeSize;
1506 // If the previous field was not a bitfield, or was a bitfield
1507 // with a different storage unit size, we're done with that
1509 if (LastBitfieldTypeSize != TypeSize) {
1510 // Also, ignore zero-length bitfields after non-bitfields.
1511 if (!LastBitfieldTypeSize && !FieldSize)
1514 UnfilledBitsInLastUnit = 0;
1515 LastBitfieldTypeSize = 0;
1519 // If the field is wider than its declared type, it follows
1520 // different rules in all cases.
1521 if (FieldSize > TypeSize) {
1522 LayoutWideBitField(FieldSize, TypeSize, FieldPacked, D);
1526 // Compute the next available bit offset.
1527 uint64_t FieldOffset =
1528 IsUnion ? 0 : (getDataSizeInBits() - UnfilledBitsInLastUnit);
1530 // Handle targets that don't honor bitfield type alignment.
1531 if (!IsMsStruct && !Context.getTargetInfo().useBitFieldTypeAlignment()) {
1532 // Some such targets do honor it on zero-width bitfields.
1533 if (FieldSize == 0 &&
1534 Context.getTargetInfo().useZeroLengthBitfieldAlignment()) {
1535 // The alignment to round up to is the max of the field's natural
1536 // alignment and a target-specific fixed value (sometimes zero).
1537 unsigned ZeroLengthBitfieldBoundary =
1538 Context.getTargetInfo().getZeroLengthBitfieldBoundary();
1539 FieldAlign = std::max(FieldAlign, ZeroLengthBitfieldBoundary);
1541 // If that doesn't apply, just ignore the field alignment.
1547 // Remember the alignment we would have used if the field were not packed.
1548 unsigned UnpackedFieldAlign = FieldAlign;
1550 // Ignore the field alignment if the field is packed unless it has zero-size.
1551 if (!IsMsStruct && FieldPacked && FieldSize != 0)
1554 // But, if there's an 'aligned' attribute on the field, honor that.
1555 unsigned ExplicitFieldAlign = D->getMaxAlignment();
1556 if (ExplicitFieldAlign) {
1557 FieldAlign = std::max(FieldAlign, ExplicitFieldAlign);
1558 UnpackedFieldAlign = std::max(UnpackedFieldAlign, ExplicitFieldAlign);
1561 // But, if there's a #pragma pack in play, that takes precedent over
1562 // even the 'aligned' attribute, for non-zero-width bitfields.
1563 unsigned MaxFieldAlignmentInBits = Context.toBits(MaxFieldAlignment);
1564 if (!MaxFieldAlignment.isZero() && FieldSize) {
1565 UnpackedFieldAlign = std::min(UnpackedFieldAlign, MaxFieldAlignmentInBits);
1567 FieldAlign = UnpackedFieldAlign;
1569 FieldAlign = std::min(FieldAlign, MaxFieldAlignmentInBits);
1572 // But, ms_struct just ignores all of that in unions, even explicit
1573 // alignment attributes.
1574 if (IsMsStruct && IsUnion) {
1575 FieldAlign = UnpackedFieldAlign = 1;
1578 // For purposes of diagnostics, we're going to simultaneously
1579 // compute the field offsets that we would have used if we weren't
1580 // adding any alignment padding or if the field weren't packed.
1581 uint64_t UnpaddedFieldOffset = FieldOffset;
1582 uint64_t UnpackedFieldOffset = FieldOffset;
1584 // Check if we need to add padding to fit the bitfield within an
1585 // allocation unit with the right size and alignment. The rules are
1586 // somewhat different here for ms_struct structs.
1588 // If it's not a zero-width bitfield, and we can fit the bitfield
1589 // into the active storage unit (and we haven't already decided to
1590 // start a new storage unit), just do so, regardless of any other
1591 // other consideration. Otherwise, round up to the right alignment.
1592 if (FieldSize == 0 || FieldSize > UnfilledBitsInLastUnit) {
1593 FieldOffset = llvm::alignTo(FieldOffset, FieldAlign);
1594 UnpackedFieldOffset =
1595 llvm::alignTo(UnpackedFieldOffset, UnpackedFieldAlign);
1596 UnfilledBitsInLastUnit = 0;
1600 // #pragma pack, with any value, suppresses the insertion of padding.
1601 bool AllowPadding = MaxFieldAlignment.isZero();
1603 // Compute the real offset.
1604 if (FieldSize == 0 ||
1606 (FieldOffset & (FieldAlign-1)) + FieldSize > TypeSize)) {
1607 FieldOffset = llvm::alignTo(FieldOffset, FieldAlign);
1608 } else if (ExplicitFieldAlign &&
1609 (MaxFieldAlignmentInBits == 0 ||
1610 ExplicitFieldAlign <= MaxFieldAlignmentInBits) &&
1611 Context.getTargetInfo().useExplicitBitFieldAlignment()) {
1612 // TODO: figure it out what needs to be done on targets that don't honor
1613 // bit-field type alignment like ARM APCS ABI.
1614 FieldOffset = llvm::alignTo(FieldOffset, ExplicitFieldAlign);
1617 // Repeat the computation for diagnostic purposes.
1618 if (FieldSize == 0 ||
1620 (UnpackedFieldOffset & (UnpackedFieldAlign-1)) + FieldSize > TypeSize))
1621 UnpackedFieldOffset =
1622 llvm::alignTo(UnpackedFieldOffset, UnpackedFieldAlign);
1623 else if (ExplicitFieldAlign &&
1624 (MaxFieldAlignmentInBits == 0 ||
1625 ExplicitFieldAlign <= MaxFieldAlignmentInBits) &&
1626 Context.getTargetInfo().useExplicitBitFieldAlignment())
1627 UnpackedFieldOffset =
1628 llvm::alignTo(UnpackedFieldOffset, ExplicitFieldAlign);
1631 // If we're using external layout, give the external layout a chance
1632 // to override this information.
1633 if (UseExternalLayout)
1634 FieldOffset = updateExternalFieldOffset(D, FieldOffset);
1636 // Okay, place the bitfield at the calculated offset.
1637 FieldOffsets.push_back(FieldOffset);
1641 // Anonymous members don't affect the overall record alignment,
1642 // except on targets where they do.
1644 !Context.getTargetInfo().useZeroLengthBitfieldAlignment() &&
1645 !D->getIdentifier())
1646 FieldAlign = UnpackedFieldAlign = 1;
1648 // Diagnose differences in layout due to padding or packing.
1649 if (!UseExternalLayout)
1650 CheckFieldPadding(FieldOffset, UnpaddedFieldOffset, UnpackedFieldOffset,
1651 UnpackedFieldAlign, FieldPacked, D);
1653 // Update DataSize to include the last byte containing (part of) the bitfield.
1655 // For unions, this is just a max operation, as usual.
1657 // For ms_struct, allocate the entire storage unit --- unless this
1658 // is a zero-width bitfield, in which case just use a size of 1.
1659 uint64_t RoundedFieldSize;
1662 (FieldSize ? TypeSize : Context.getTargetInfo().getCharWidth());
1664 // Otherwise, allocate just the number of bytes required to store
1667 RoundedFieldSize = roundUpSizeToCharAlignment(FieldSize, Context);
1669 setDataSize(std::max(getDataSizeInBits(), RoundedFieldSize));
1671 // For non-zero-width bitfields in ms_struct structs, allocate a new
1672 // storage unit if necessary.
1673 } else if (IsMsStruct && FieldSize) {
1674 // We should have cleared UnfilledBitsInLastUnit in every case
1675 // where we changed storage units.
1676 if (!UnfilledBitsInLastUnit) {
1677 setDataSize(FieldOffset + TypeSize);
1678 UnfilledBitsInLastUnit = TypeSize;
1680 UnfilledBitsInLastUnit -= FieldSize;
1681 LastBitfieldTypeSize = TypeSize;
1683 // Otherwise, bump the data size up to include the bitfield,
1684 // including padding up to char alignment, and then remember how
1685 // bits we didn't use.
1687 uint64_t NewSizeInBits = FieldOffset + FieldSize;
1688 uint64_t CharAlignment = Context.getTargetInfo().getCharAlign();
1689 setDataSize(llvm::alignTo(NewSizeInBits, CharAlignment));
1690 UnfilledBitsInLastUnit = getDataSizeInBits() - NewSizeInBits;
1692 // The only time we can get here for an ms_struct is if this is a
1693 // zero-width bitfield, which doesn't count as anything for the
1694 // purposes of unfilled bits.
1695 LastBitfieldTypeSize = 0;
1699 setSize(std::max(getSizeInBits(), getDataSizeInBits()));
1701 // Remember max struct/class alignment.
1702 UpdateAlignment(Context.toCharUnitsFromBits(FieldAlign),
1703 Context.toCharUnitsFromBits(UnpackedFieldAlign));
1706 void ItaniumRecordLayoutBuilder::LayoutField(const FieldDecl *D,
1707 bool InsertExtraPadding) {
1708 if (D->isBitField()) {
1713 uint64_t UnpaddedFieldOffset = getDataSizeInBits() - UnfilledBitsInLastUnit;
1715 // Reset the unfilled bits.
1716 UnfilledBitsInLastUnit = 0;
1717 LastBitfieldTypeSize = 0;
1719 bool FieldPacked = Packed || D->hasAttr<PackedAttr>();
1720 CharUnits FieldOffset =
1721 IsUnion ? CharUnits::Zero() : getDataSize();
1722 CharUnits FieldSize;
1723 CharUnits FieldAlign;
1725 if (D->getType()->isIncompleteArrayType()) {
1726 // This is a flexible array member; we can't directly
1727 // query getTypeInfo about these, so we figure it out here.
1728 // Flexible array members don't have any size, but they
1729 // have to be aligned appropriately for their element type.
1730 FieldSize = CharUnits::Zero();
1731 const ArrayType* ATy = Context.getAsArrayType(D->getType());
1732 FieldAlign = Context.getTypeAlignInChars(ATy->getElementType());
1733 } else if (const ReferenceType *RT = D->getType()->getAs<ReferenceType>()) {
1734 unsigned AS = Context.getTargetAddressSpace(RT->getPointeeType());
1736 Context.toCharUnitsFromBits(Context.getTargetInfo().getPointerWidth(AS));
1738 Context.toCharUnitsFromBits(Context.getTargetInfo().getPointerAlign(AS));
1740 std::pair<CharUnits, CharUnits> FieldInfo =
1741 Context.getTypeInfoInChars(D->getType());
1742 FieldSize = FieldInfo.first;
1743 FieldAlign = FieldInfo.second;
1746 // If MS bitfield layout is required, figure out what type is being
1747 // laid out and align the field to the width of that type.
1749 // Resolve all typedefs down to their base type and round up the field
1750 // alignment if necessary.
1751 QualType T = Context.getBaseElementType(D->getType());
1752 if (const BuiltinType *BTy = T->getAs<BuiltinType>()) {
1753 CharUnits TypeSize = Context.getTypeSizeInChars(BTy);
1755 if (!llvm::isPowerOf2_64(TypeSize.getQuantity())) {
1757 !Context.getTargetInfo().getTriple().isWindowsMSVCEnvironment() &&
1758 "Non PowerOf2 size in MSVC mode");
1759 // Base types with sizes that aren't a power of two don't work
1760 // with the layout rules for MS structs. This isn't an issue in
1761 // MSVC itself since there are no such base data types there.
1762 // On e.g. x86_32 mingw and linux, long double is 12 bytes though.
1763 // Any structs involving that data type obviously can't be ABI
1764 // compatible with MSVC regardless of how it is laid out.
1766 // Since ms_struct can be mass enabled (via a pragma or via the
1767 // -mms-bitfields command line parameter), this can trigger for
1768 // structs that don't actually need MSVC compatibility, so we
1769 // need to be able to sidestep the ms_struct layout for these types.
1771 // Since the combination of -mms-bitfields together with structs
1772 // like max_align_t (which contains a long double) for mingw is
1773 // quite comon (and GCC handles it silently), just handle it
1774 // silently there. For other targets that have ms_struct enabled
1775 // (most probably via a pragma or attribute), trigger a diagnostic
1776 // that defaults to an error.
1777 if (!Context.getTargetInfo().getTriple().isWindowsGNUEnvironment())
1778 Diag(D->getLocation(), diag::warn_npot_ms_struct);
1780 if (TypeSize > FieldAlign &&
1781 llvm::isPowerOf2_64(TypeSize.getQuantity()))
1782 FieldAlign = TypeSize;
1787 // The align if the field is not packed. This is to check if the attribute
1788 // was unnecessary (-Wpacked).
1789 CharUnits UnpackedFieldAlign = FieldAlign;
1790 CharUnits UnpackedFieldOffset = FieldOffset;
1793 FieldAlign = CharUnits::One();
1794 CharUnits MaxAlignmentInChars =
1795 Context.toCharUnitsFromBits(D->getMaxAlignment());
1796 FieldAlign = std::max(FieldAlign, MaxAlignmentInChars);
1797 UnpackedFieldAlign = std::max(UnpackedFieldAlign, MaxAlignmentInChars);
1799 // The maximum field alignment overrides the aligned attribute.
1800 if (!MaxFieldAlignment.isZero()) {
1801 FieldAlign = std::min(FieldAlign, MaxFieldAlignment);
1802 UnpackedFieldAlign = std::min(UnpackedFieldAlign, MaxFieldAlignment);
1805 // Round up the current record size to the field's alignment boundary.
1806 FieldOffset = FieldOffset.alignTo(FieldAlign);
1807 UnpackedFieldOffset = UnpackedFieldOffset.alignTo(UnpackedFieldAlign);
1809 if (UseExternalLayout) {
1810 FieldOffset = Context.toCharUnitsFromBits(
1811 updateExternalFieldOffset(D, Context.toBits(FieldOffset)));
1813 if (!IsUnion && EmptySubobjects) {
1814 // Record the fact that we're placing a field at this offset.
1815 bool Allowed = EmptySubobjects->CanPlaceFieldAtOffset(D, FieldOffset);
1817 assert(Allowed && "Externally-placed field cannot be placed here");
1820 if (!IsUnion && EmptySubobjects) {
1821 // Check if we can place the field at this offset.
1822 while (!EmptySubobjects->CanPlaceFieldAtOffset(D, FieldOffset)) {
1823 // We couldn't place the field at the offset. Try again at a new offset.
1824 FieldOffset += FieldAlign;
1829 // Place this field at the current location.
1830 FieldOffsets.push_back(Context.toBits(FieldOffset));
1832 if (!UseExternalLayout)
1833 CheckFieldPadding(Context.toBits(FieldOffset), UnpaddedFieldOffset,
1834 Context.toBits(UnpackedFieldOffset),
1835 Context.toBits(UnpackedFieldAlign), FieldPacked, D);
1837 if (InsertExtraPadding) {
1838 CharUnits ASanAlignment = CharUnits::fromQuantity(8);
1839 CharUnits ExtraSizeForAsan = ASanAlignment;
1840 if (FieldSize % ASanAlignment)
1842 ASanAlignment - CharUnits::fromQuantity(FieldSize % ASanAlignment);
1843 FieldSize += ExtraSizeForAsan;
1846 // Reserve space for this field.
1847 uint64_t FieldSizeInBits = Context.toBits(FieldSize);
1849 setDataSize(std::max(getDataSizeInBits(), FieldSizeInBits));
1851 setDataSize(FieldOffset + FieldSize);
1854 setSize(std::max(getSizeInBits(), getDataSizeInBits()));
1856 // Remember max struct/class alignment.
1857 UpdateAlignment(FieldAlign, UnpackedFieldAlign);
1860 void ItaniumRecordLayoutBuilder::FinishLayout(const NamedDecl *D) {
1861 // In C++, records cannot be of size 0.
1862 if (Context.getLangOpts().CPlusPlus && getSizeInBits() == 0) {
1863 if (const CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(D)) {
1864 // Compatibility with gcc requires a class (pod or non-pod)
1865 // which is not empty but of size 0; such as having fields of
1866 // array of zero-length, remains of Size 0
1868 setSize(CharUnits::One());
1871 setSize(CharUnits::One());
1874 // Finally, round the size of the record up to the alignment of the
1876 uint64_t UnpaddedSize = getSizeInBits() - UnfilledBitsInLastUnit;
1877 uint64_t UnpackedSizeInBits =
1878 llvm::alignTo(getSizeInBits(), Context.toBits(UnpackedAlignment));
1879 uint64_t RoundedSize =
1880 llvm::alignTo(getSizeInBits(), Context.toBits(Alignment));
1882 if (UseExternalLayout) {
1883 // If we're inferring alignment, and the external size is smaller than
1884 // our size after we've rounded up to alignment, conservatively set the
1886 if (InferAlignment && External.Size < RoundedSize) {
1887 Alignment = CharUnits::One();
1888 InferAlignment = false;
1890 setSize(External.Size);
1894 // Set the size to the final size.
1895 setSize(RoundedSize);
1897 unsigned CharBitNum = Context.getTargetInfo().getCharWidth();
1898 if (const RecordDecl *RD = dyn_cast<RecordDecl>(D)) {
1899 // Warn if padding was introduced to the struct/class/union.
1900 if (getSizeInBits() > UnpaddedSize) {
1901 unsigned PadSize = getSizeInBits() - UnpaddedSize;
1903 if (PadSize % CharBitNum == 0) {
1904 PadSize = PadSize / CharBitNum;
1907 Diag(RD->getLocation(), diag::warn_padded_struct_size)
1908 << Context.getTypeDeclType(RD)
1910 << (InBits ? 1 : 0); // (byte|bit)
1913 // Warn if we packed it unnecessarily, when the unpacked alignment is not
1914 // greater than the one after packing, the size in bits doesn't change and
1915 // the offset of each field is identical.
1916 if (Packed && UnpackedAlignment <= Alignment &&
1917 UnpackedSizeInBits == getSizeInBits() && !HasPackedField)
1918 Diag(D->getLocation(), diag::warn_unnecessary_packed)
1919 << Context.getTypeDeclType(RD);
1923 void ItaniumRecordLayoutBuilder::UpdateAlignment(
1924 CharUnits NewAlignment, CharUnits UnpackedNewAlignment) {
1925 // The alignment is not modified when using 'mac68k' alignment or when
1926 // we have an externally-supplied layout that also provides overall alignment.
1927 if (IsMac68kAlign || (UseExternalLayout && !InferAlignment))
1930 if (NewAlignment > Alignment) {
1931 assert(llvm::isPowerOf2_64(NewAlignment.getQuantity()) &&
1932 "Alignment not a power of 2");
1933 Alignment = NewAlignment;
1936 if (UnpackedNewAlignment > UnpackedAlignment) {
1937 assert(llvm::isPowerOf2_64(UnpackedNewAlignment.getQuantity()) &&
1938 "Alignment not a power of 2");
1939 UnpackedAlignment = UnpackedNewAlignment;
1944 ItaniumRecordLayoutBuilder::updateExternalFieldOffset(const FieldDecl *Field,
1945 uint64_t ComputedOffset) {
1946 uint64_t ExternalFieldOffset = External.getExternalFieldOffset(Field);
1948 if (InferAlignment && ExternalFieldOffset < ComputedOffset) {
1949 // The externally-supplied field offset is before the field offset we
1950 // computed. Assume that the structure is packed.
1951 Alignment = CharUnits::One();
1952 InferAlignment = false;
1955 // Use the externally-supplied field offset.
1956 return ExternalFieldOffset;
1959 /// \brief Get diagnostic %select index for tag kind for
1960 /// field padding diagnostic message.
1961 /// WARNING: Indexes apply to particular diagnostics only!
1963 /// \returns diagnostic %select index.
1964 static unsigned getPaddingDiagFromTagKind(TagTypeKind Tag) {
1966 case TTK_Struct: return 0;
1967 case TTK_Interface: return 1;
1968 case TTK_Class: return 2;
1969 default: llvm_unreachable("Invalid tag kind for field padding diagnostic!");
1973 void ItaniumRecordLayoutBuilder::CheckFieldPadding(
1974 uint64_t Offset, uint64_t UnpaddedOffset, uint64_t UnpackedOffset,
1975 unsigned UnpackedAlign, bool isPacked, const FieldDecl *D) {
1976 // We let objc ivars without warning, objc interfaces generally are not used
1977 // for padding tricks.
1978 if (isa<ObjCIvarDecl>(D))
1981 // Don't warn about structs created without a SourceLocation. This can
1982 // be done by clients of the AST, such as codegen.
1983 if (D->getLocation().isInvalid())
1986 unsigned CharBitNum = Context.getTargetInfo().getCharWidth();
1988 // Warn if padding was introduced to the struct/class.
1989 if (!IsUnion && Offset > UnpaddedOffset) {
1990 unsigned PadSize = Offset - UnpaddedOffset;
1992 if (PadSize % CharBitNum == 0) {
1993 PadSize = PadSize / CharBitNum;
1996 if (D->getIdentifier())
1997 Diag(D->getLocation(), diag::warn_padded_struct_field)
1998 << getPaddingDiagFromTagKind(D->getParent()->getTagKind())
1999 << Context.getTypeDeclType(D->getParent())
2001 << (InBits ? 1 : 0) // (byte|bit)
2002 << D->getIdentifier();
2004 Diag(D->getLocation(), diag::warn_padded_struct_anon_field)
2005 << getPaddingDiagFromTagKind(D->getParent()->getTagKind())
2006 << Context.getTypeDeclType(D->getParent())
2008 << (InBits ? 1 : 0); // (byte|bit)
2010 if (isPacked && Offset != UnpackedOffset) {
2011 HasPackedField = true;
2015 static const CXXMethodDecl *computeKeyFunction(ASTContext &Context,
2016 const CXXRecordDecl *RD) {
2017 // If a class isn't polymorphic it doesn't have a key function.
2018 if (!RD->isPolymorphic())
2021 // A class that is not externally visible doesn't have a key function. (Or
2022 // at least, there's no point to assigning a key function to such a class;
2023 // this doesn't affect the ABI.)
2024 if (!RD->isExternallyVisible())
2027 // Template instantiations don't have key functions per Itanium C++ ABI 5.2.6.
2028 // Same behavior as GCC.
2029 TemplateSpecializationKind TSK = RD->getTemplateSpecializationKind();
2030 if (TSK == TSK_ImplicitInstantiation ||
2031 TSK == TSK_ExplicitInstantiationDeclaration ||
2032 TSK == TSK_ExplicitInstantiationDefinition)
2035 bool allowInlineFunctions =
2036 Context.getTargetInfo().getCXXABI().canKeyFunctionBeInline();
2038 for (const CXXMethodDecl *MD : RD->methods()) {
2039 if (!MD->isVirtual())
2045 // Ignore implicit member functions, they are always marked as inline, but
2046 // they don't have a body until they're defined.
2047 if (MD->isImplicit())
2050 if (MD->isInlineSpecified())
2053 if (MD->hasInlineBody())
2056 // Ignore inline deleted or defaulted functions.
2057 if (!MD->isUserProvided())
2060 // In certain ABIs, ignore functions with out-of-line inline definitions.
2061 if (!allowInlineFunctions) {
2062 const FunctionDecl *Def;
2063 if (MD->hasBody(Def) && Def->isInlineSpecified())
2067 if (Context.getLangOpts().CUDA) {
2068 // While compiler may see key method in this TU, during CUDA
2069 // compilation we should ignore methods that are not accessible
2070 // on this side of compilation.
2071 if (Context.getLangOpts().CUDAIsDevice) {
2072 // In device mode ignore methods without __device__ attribute.
2073 if (!MD->hasAttr<CUDADeviceAttr>())
2076 // In host mode ignore __device__-only methods.
2077 if (!MD->hasAttr<CUDAHostAttr>() && MD->hasAttr<CUDADeviceAttr>())
2082 // If the key function is dllimport but the class isn't, then the class has
2083 // no key function. The DLL that exports the key function won't export the
2084 // vtable in this case.
2085 if (MD->hasAttr<DLLImportAttr>() && !RD->hasAttr<DLLImportAttr>())
2095 DiagnosticBuilder ItaniumRecordLayoutBuilder::Diag(SourceLocation Loc,
2097 return Context.getDiagnostics().Report(Loc, DiagID);
2100 /// Does the target C++ ABI require us to skip over the tail-padding
2101 /// of the given class (considering it as a base class) when allocating
2103 static bool mustSkipTailPadding(TargetCXXABI ABI, const CXXRecordDecl *RD) {
2104 switch (ABI.getTailPaddingUseRules()) {
2105 case TargetCXXABI::AlwaysUseTailPadding:
2108 case TargetCXXABI::UseTailPaddingUnlessPOD03:
2109 // FIXME: To the extent that this is meant to cover the Itanium ABI
2110 // rules, we should implement the restrictions about over-sized
2113 // http://itanium-cxx-abi.github.io/cxx-abi/abi.html#POD :
2114 // In general, a type is considered a POD for the purposes of
2115 // layout if it is a POD type (in the sense of ISO C++
2116 // [basic.types]). However, a POD-struct or POD-union (in the
2117 // sense of ISO C++ [class]) with a bitfield member whose
2118 // declared width is wider than the declared type of the
2119 // bitfield is not a POD for the purpose of layout. Similarly,
2120 // an array type is not a POD for the purpose of layout if the
2121 // element type of the array is not a POD for the purpose of
2124 // Where references to the ISO C++ are made in this paragraph,
2125 // the Technical Corrigendum 1 version of the standard is
2129 case TargetCXXABI::UseTailPaddingUnlessPOD11:
2130 // This is equivalent to RD->getTypeForDecl().isCXX11PODType(),
2131 // but with a lot of abstraction penalty stripped off. This does
2132 // assume that these properties are set correctly even in C++98
2133 // mode; fortunately, that is true because we want to assign
2134 // consistently semantics to the type-traits intrinsics (or at
2135 // least as many of them as possible).
2136 return RD->isTrivial() && RD->isStandardLayout();
2139 llvm_unreachable("bad tail-padding use kind");
2142 static bool isMsLayout(const ASTContext &Context) {
2143 return Context.getTargetInfo().getCXXABI().isMicrosoft();
2146 // This section contains an implementation of struct layout that is, up to the
2147 // included tests, compatible with cl.exe (2013). The layout produced is
2148 // significantly different than those produced by the Itanium ABI. Here we note
2149 // the most important differences.
2151 // * The alignment of bitfields in unions is ignored when computing the
2152 // alignment of the union.
2153 // * The existence of zero-width bitfield that occurs after anything other than
2154 // a non-zero length bitfield is ignored.
2155 // * There is no explicit primary base for the purposes of layout. All bases
2156 // with vfptrs are laid out first, followed by all bases without vfptrs.
2157 // * The Itanium equivalent vtable pointers are split into a vfptr (virtual
2158 // function pointer) and a vbptr (virtual base pointer). They can each be
2159 // shared with a, non-virtual bases. These bases need not be the same. vfptrs
2160 // always occur at offset 0. vbptrs can occur at an arbitrary offset and are
2161 // placed after the lexicographically last non-virtual base. This placement
2162 // is always before fields but can be in the middle of the non-virtual bases
2163 // due to the two-pass layout scheme for non-virtual-bases.
2164 // * Virtual bases sometimes require a 'vtordisp' field that is laid out before
2165 // the virtual base and is used in conjunction with virtual overrides during
2166 // construction and destruction. This is always a 4 byte value and is used as
2167 // an alternative to constructor vtables.
2168 // * vtordisps are allocated in a block of memory with size and alignment equal
2169 // to the alignment of the completed structure (before applying __declspec(
2170 // align())). The vtordisp always occur at the end of the allocation block,
2171 // immediately prior to the virtual base.
2172 // * vfptrs are injected after all bases and fields have been laid out. In
2173 // order to guarantee proper alignment of all fields, the vfptr injection
2174 // pushes all bases and fields back by the alignment imposed by those bases
2175 // and fields. This can potentially add a significant amount of padding.
2176 // vfptrs are always injected at offset 0.
2177 // * vbptrs are injected after all bases and fields have been laid out. In
2178 // order to guarantee proper alignment of all fields, the vfptr injection
2179 // pushes all bases and fields back by the alignment imposed by those bases
2180 // and fields. This can potentially add a significant amount of padding.
2181 // vbptrs are injected immediately after the last non-virtual base as
2182 // lexicographically ordered in the code. If this site isn't pointer aligned
2183 // the vbptr is placed at the next properly aligned location. Enough padding
2184 // is added to guarantee a fit.
2185 // * The last zero sized non-virtual base can be placed at the end of the
2186 // struct (potentially aliasing another object), or may alias with the first
2187 // field, even if they are of the same type.
2188 // * The last zero size virtual base may be placed at the end of the struct
2189 // potentially aliasing another object.
2190 // * The ABI attempts to avoid aliasing of zero sized bases by adding padding
2191 // between bases or vbases with specific properties. The criteria for
2192 // additional padding between two bases is that the first base is zero sized
2193 // or ends with a zero sized subobject and the second base is zero sized or
2194 // trails with a zero sized base or field (sharing of vfptrs can reorder the
2195 // layout of the so the leading base is not always the first one declared).
2196 // This rule does take into account fields that are not records, so padding
2197 // will occur even if the last field is, e.g. an int. The padding added for
2198 // bases is 1 byte. The padding added between vbases depends on the alignment
2199 // of the object but is at least 4 bytes (in both 32 and 64 bit modes).
2200 // * There is no concept of non-virtual alignment, non-virtual alignment and
2201 // alignment are always identical.
2202 // * There is a distinction between alignment and required alignment.
2203 // __declspec(align) changes the required alignment of a struct. This
2204 // alignment is _always_ obeyed, even in the presence of #pragma pack. A
2205 // record inherits required alignment from all of its fields and bases.
2206 // * __declspec(align) on bitfields has the effect of changing the bitfield's
2207 // alignment instead of its required alignment. This is the only known way
2208 // to make the alignment of a struct bigger than 8. Interestingly enough
2209 // this alignment is also immune to the effects of #pragma pack and can be
2210 // used to create structures with large alignment under #pragma pack.
2211 // However, because it does not impact required alignment, such a structure,
2212 // when used as a field or base, will not be aligned if #pragma pack is
2213 // still active at the time of use.
2215 // Known incompatibilities:
2216 // * all: #pragma pack between fields in a record
2217 // * 2010 and back: If the last field in a record is a bitfield, every object
2218 // laid out after the record will have extra padding inserted before it. The
2219 // extra padding will have size equal to the size of the storage class of the
2220 // bitfield. 0 sized bitfields don't exhibit this behavior and the extra
2221 // padding can be avoided by adding a 0 sized bitfield after the non-zero-
2223 // * 2012 and back: In 64-bit mode, if the alignment of a record is 16 or
2224 // greater due to __declspec(align()) then a second layout phase occurs after
2225 // The locations of the vf and vb pointers are known. This layout phase
2226 // suffers from the "last field is a bitfield" bug in 2010 and results in
2227 // _every_ field getting padding put in front of it, potentially including the
2228 // vfptr, leaving the vfprt at a non-zero location which results in a fault if
2229 // anything tries to read the vftbl. The second layout phase also treats
2230 // bitfields as separate entities and gives them each storage rather than
2231 // packing them. Additionally, because this phase appears to perform a
2232 // (an unstable) sort on the members before laying them out and because merged
2233 // bitfields have the same address, the bitfields end up in whatever order
2234 // the sort left them in, a behavior we could never hope to replicate.
2237 struct MicrosoftRecordLayoutBuilder {
2238 struct ElementInfo {
2240 CharUnits Alignment;
2242 typedef llvm::DenseMap<const CXXRecordDecl *, CharUnits> BaseOffsetsMapTy;
2243 MicrosoftRecordLayoutBuilder(const ASTContext &Context) : Context(Context) {}
2245 MicrosoftRecordLayoutBuilder(const MicrosoftRecordLayoutBuilder &) = delete;
2246 void operator=(const MicrosoftRecordLayoutBuilder &) = delete;
2248 void layout(const RecordDecl *RD);
2249 void cxxLayout(const CXXRecordDecl *RD);
2250 /// \brief Initializes size and alignment and honors some flags.
2251 void initializeLayout(const RecordDecl *RD);
2252 /// \brief Initialized C++ layout, compute alignment and virtual alignment and
2253 /// existence of vfptrs and vbptrs. Alignment is needed before the vfptr is
2255 void initializeCXXLayout(const CXXRecordDecl *RD);
2256 void layoutNonVirtualBases(const CXXRecordDecl *RD);
2257 void layoutNonVirtualBase(const CXXRecordDecl *RD,
2258 const CXXRecordDecl *BaseDecl,
2259 const ASTRecordLayout &BaseLayout,
2260 const ASTRecordLayout *&PreviousBaseLayout);
2261 void injectVFPtr(const CXXRecordDecl *RD);
2262 void injectVBPtr(const CXXRecordDecl *RD);
2263 /// \brief Lays out the fields of the record. Also rounds size up to
2265 void layoutFields(const RecordDecl *RD);
2266 void layoutField(const FieldDecl *FD);
2267 void layoutBitField(const FieldDecl *FD);
2268 /// \brief Lays out a single zero-width bit-field in the record and handles
2269 /// special cases associated with zero-width bit-fields.
2270 void layoutZeroWidthBitField(const FieldDecl *FD);
2271 void layoutVirtualBases(const CXXRecordDecl *RD);
2272 void finalizeLayout(const RecordDecl *RD);
2273 /// \brief Gets the size and alignment of a base taking pragma pack and
2274 /// __declspec(align) into account.
2275 ElementInfo getAdjustedElementInfo(const ASTRecordLayout &Layout);
2276 /// \brief Gets the size and alignment of a field taking pragma pack and
2277 /// __declspec(align) into account. It also updates RequiredAlignment as a
2278 /// side effect because it is most convenient to do so here.
2279 ElementInfo getAdjustedElementInfo(const FieldDecl *FD);
2280 /// \brief Places a field at an offset in CharUnits.
2281 void placeFieldAtOffset(CharUnits FieldOffset) {
2282 FieldOffsets.push_back(Context.toBits(FieldOffset));
2284 /// \brief Places a bitfield at a bit offset.
2285 void placeFieldAtBitOffset(uint64_t FieldOffset) {
2286 FieldOffsets.push_back(FieldOffset);
2288 /// \brief Compute the set of virtual bases for which vtordisps are required.
2289 void computeVtorDispSet(
2290 llvm::SmallPtrSetImpl<const CXXRecordDecl *> &HasVtorDispSet,
2291 const CXXRecordDecl *RD) const;
2292 const ASTContext &Context;
2293 /// \brief The size of the record being laid out.
2295 /// \brief The non-virtual size of the record layout.
2296 CharUnits NonVirtualSize;
2297 /// \brief The data size of the record layout.
2299 /// \brief The current alignment of the record layout.
2300 CharUnits Alignment;
2301 /// \brief The maximum allowed field alignment. This is set by #pragma pack.
2302 CharUnits MaxFieldAlignment;
2303 /// \brief The alignment that this record must obey. This is imposed by
2304 /// __declspec(align()) on the record itself or one of its fields or bases.
2305 CharUnits RequiredAlignment;
2306 /// \brief The size of the allocation of the currently active bitfield.
2307 /// This value isn't meaningful unless LastFieldIsNonZeroWidthBitfield
2309 CharUnits CurrentBitfieldSize;
2310 /// \brief Offset to the virtual base table pointer (if one exists).
2311 CharUnits VBPtrOffset;
2312 /// \brief Minimum record size possible.
2313 CharUnits MinEmptyStructSize;
2314 /// \brief The size and alignment info of a pointer.
2315 ElementInfo PointerInfo;
2316 /// \brief The primary base class (if one exists).
2317 const CXXRecordDecl *PrimaryBase;
2318 /// \brief The class we share our vb-pointer with.
2319 const CXXRecordDecl *SharedVBPtrBase;
2320 /// \brief The collection of field offsets.
2321 SmallVector<uint64_t, 16> FieldOffsets;
2322 /// \brief Base classes and their offsets in the record.
2323 BaseOffsetsMapTy Bases;
2324 /// \brief virtual base classes and their offsets in the record.
2325 ASTRecordLayout::VBaseOffsetsMapTy VBases;
2326 /// \brief The number of remaining bits in our last bitfield allocation.
2327 /// This value isn't meaningful unless LastFieldIsNonZeroWidthBitfield is
2329 unsigned RemainingBitsInField;
2331 /// \brief True if the last field laid out was a bitfield and was not 0
2333 bool LastFieldIsNonZeroWidthBitfield : 1;
2334 /// \brief True if the class has its own vftable pointer.
2335 bool HasOwnVFPtr : 1;
2336 /// \brief True if the class has a vbtable pointer.
2338 /// \brief True if the last sub-object within the type is zero sized or the
2339 /// object itself is zero sized. This *does not* count members that are not
2340 /// records. Only used for MS-ABI.
2341 bool EndsWithZeroSizedObject : 1;
2342 /// \brief True if this class is zero sized or first base is zero sized or
2343 /// has this property. Only used for MS-ABI.
2344 bool LeadsWithZeroSizedBase : 1;
2346 /// \brief True if the external AST source provided a layout for this record.
2347 bool UseExternalLayout : 1;
2349 /// \brief The layout provided by the external AST source. Only active if
2350 /// UseExternalLayout is true.
2351 ExternalLayout External;
2355 MicrosoftRecordLayoutBuilder::ElementInfo
2356 MicrosoftRecordLayoutBuilder::getAdjustedElementInfo(
2357 const ASTRecordLayout &Layout) {
2359 Info.Alignment = Layout.getAlignment();
2360 // Respect pragma pack.
2361 if (!MaxFieldAlignment.isZero())
2362 Info.Alignment = std::min(Info.Alignment, MaxFieldAlignment);
2363 // Track zero-sized subobjects here where it's already available.
2364 EndsWithZeroSizedObject = Layout.endsWithZeroSizedObject();
2365 // Respect required alignment, this is necessary because we may have adjusted
2366 // the alignment in the case of pragam pack. Note that the required alignment
2367 // doesn't actually apply to the struct alignment at this point.
2368 Alignment = std::max(Alignment, Info.Alignment);
2369 RequiredAlignment = std::max(RequiredAlignment, Layout.getRequiredAlignment());
2370 Info.Alignment = std::max(Info.Alignment, Layout.getRequiredAlignment());
2371 Info.Size = Layout.getNonVirtualSize();
2375 MicrosoftRecordLayoutBuilder::ElementInfo
2376 MicrosoftRecordLayoutBuilder::getAdjustedElementInfo(
2377 const FieldDecl *FD) {
2378 // Get the alignment of the field type's natural alignment, ignore any
2379 // alignment attributes.
2381 std::tie(Info.Size, Info.Alignment) =
2382 Context.getTypeInfoInChars(FD->getType()->getUnqualifiedDesugaredType());
2383 // Respect align attributes on the field.
2384 CharUnits FieldRequiredAlignment =
2385 Context.toCharUnitsFromBits(FD->getMaxAlignment());
2386 // Respect align attributes on the type.
2387 if (Context.isAlignmentRequired(FD->getType()))
2388 FieldRequiredAlignment = std::max(
2389 Context.getTypeAlignInChars(FD->getType()), FieldRequiredAlignment);
2390 // Respect attributes applied to subobjects of the field.
2391 if (FD->isBitField())
2392 // For some reason __declspec align impacts alignment rather than required
2393 // alignment when it is applied to bitfields.
2394 Info.Alignment = std::max(Info.Alignment, FieldRequiredAlignment);
2397 FD->getType()->getBaseElementTypeUnsafe()->getAs<RecordType>()) {
2398 auto const &Layout = Context.getASTRecordLayout(RT->getDecl());
2399 EndsWithZeroSizedObject = Layout.endsWithZeroSizedObject();
2400 FieldRequiredAlignment = std::max(FieldRequiredAlignment,
2401 Layout.getRequiredAlignment());
2403 // Capture required alignment as a side-effect.
2404 RequiredAlignment = std::max(RequiredAlignment, FieldRequiredAlignment);
2406 // Respect pragma pack, attribute pack and declspec align
2407 if (!MaxFieldAlignment.isZero())
2408 Info.Alignment = std::min(Info.Alignment, MaxFieldAlignment);
2409 if (FD->hasAttr<PackedAttr>())
2410 Info.Alignment = CharUnits::One();
2411 Info.Alignment = std::max(Info.Alignment, FieldRequiredAlignment);
2415 void MicrosoftRecordLayoutBuilder::layout(const RecordDecl *RD) {
2416 // For C record layout, zero-sized records always have size 4.
2417 MinEmptyStructSize = CharUnits::fromQuantity(4);
2418 initializeLayout(RD);
2420 DataSize = Size = Size.alignTo(Alignment);
2421 RequiredAlignment = std::max(
2422 RequiredAlignment, Context.toCharUnitsFromBits(RD->getMaxAlignment()));
2426 void MicrosoftRecordLayoutBuilder::cxxLayout(const CXXRecordDecl *RD) {
2427 // The C++ standard says that empty structs have size 1.
2428 MinEmptyStructSize = CharUnits::One();
2429 initializeLayout(RD);
2430 initializeCXXLayout(RD);
2431 layoutNonVirtualBases(RD);
2435 if (HasOwnVFPtr || (HasVBPtr && !SharedVBPtrBase))
2436 Alignment = std::max(Alignment, PointerInfo.Alignment);
2437 auto RoundingAlignment = Alignment;
2438 if (!MaxFieldAlignment.isZero())
2439 RoundingAlignment = std::min(RoundingAlignment, MaxFieldAlignment);
2440 NonVirtualSize = Size = Size.alignTo(RoundingAlignment);
2441 RequiredAlignment = std::max(
2442 RequiredAlignment, Context.toCharUnitsFromBits(RD->getMaxAlignment()));
2443 layoutVirtualBases(RD);
2447 void MicrosoftRecordLayoutBuilder::initializeLayout(const RecordDecl *RD) {
2448 IsUnion = RD->isUnion();
2449 Size = CharUnits::Zero();
2450 Alignment = CharUnits::One();
2451 // In 64-bit mode we always perform an alignment step after laying out vbases.
2452 // In 32-bit mode we do not. The check to see if we need to perform alignment
2453 // checks the RequiredAlignment field and performs alignment if it isn't 0.
2454 RequiredAlignment = Context.getTargetInfo().getTriple().isArch64Bit()
2456 : CharUnits::Zero();
2457 // Compute the maximum field alignment.
2458 MaxFieldAlignment = CharUnits::Zero();
2459 // Honor the default struct packing maximum alignment flag.
2460 if (unsigned DefaultMaxFieldAlignment = Context.getLangOpts().PackStruct)
2461 MaxFieldAlignment = CharUnits::fromQuantity(DefaultMaxFieldAlignment);
2462 // Honor the packing attribute. The MS-ABI ignores pragma pack if its larger
2463 // than the pointer size.
2464 if (const MaxFieldAlignmentAttr *MFAA = RD->getAttr<MaxFieldAlignmentAttr>()){
2465 unsigned PackedAlignment = MFAA->getAlignment();
2466 if (PackedAlignment <= Context.getTargetInfo().getPointerWidth(0))
2467 MaxFieldAlignment = Context.toCharUnitsFromBits(PackedAlignment);
2469 // Packed attribute forces max field alignment to be 1.
2470 if (RD->hasAttr<PackedAttr>())
2471 MaxFieldAlignment = CharUnits::One();
2473 // Try to respect the external layout if present.
2474 UseExternalLayout = false;
2475 if (ExternalASTSource *Source = Context.getExternalSource())
2476 UseExternalLayout = Source->layoutRecordType(
2477 RD, External.Size, External.Align, External.FieldOffsets,
2478 External.BaseOffsets, External.VirtualBaseOffsets);
2482 MicrosoftRecordLayoutBuilder::initializeCXXLayout(const CXXRecordDecl *RD) {
2483 EndsWithZeroSizedObject = false;
2484 LeadsWithZeroSizedBase = false;
2485 HasOwnVFPtr = false;
2487 PrimaryBase = nullptr;
2488 SharedVBPtrBase = nullptr;
2489 // Calculate pointer size and alignment. These are used for vfptr and vbprt
2492 Context.toCharUnitsFromBits(Context.getTargetInfo().getPointerWidth(0));
2493 PointerInfo.Alignment =
2494 Context.toCharUnitsFromBits(Context.getTargetInfo().getPointerAlign(0));
2495 // Respect pragma pack.
2496 if (!MaxFieldAlignment.isZero())
2497 PointerInfo.Alignment = std::min(PointerInfo.Alignment, MaxFieldAlignment);
2501 MicrosoftRecordLayoutBuilder::layoutNonVirtualBases(const CXXRecordDecl *RD) {
2502 // The MS-ABI lays out all bases that contain leading vfptrs before it lays
2503 // out any bases that do not contain vfptrs. We implement this as two passes
2504 // over the bases. This approach guarantees that the primary base is laid out
2505 // first. We use these passes to calculate some additional aggregated
2506 // information about the bases, such as required alignment and the presence of
2507 // zero sized members.
2508 const ASTRecordLayout *PreviousBaseLayout = nullptr;
2509 // Iterate through the bases and lay out the non-virtual ones.
2510 for (const CXXBaseSpecifier &Base : RD->bases()) {
2511 const CXXRecordDecl *BaseDecl = Base.getType()->getAsCXXRecordDecl();
2512 const ASTRecordLayout &BaseLayout = Context.getASTRecordLayout(BaseDecl);
2513 // Mark and skip virtual bases.
2514 if (Base.isVirtual()) {
2518 // Check for a base to share a VBPtr with.
2519 if (!SharedVBPtrBase && BaseLayout.hasVBPtr()) {
2520 SharedVBPtrBase = BaseDecl;
2523 // Only lay out bases with extendable VFPtrs on the first pass.
2524 if (!BaseLayout.hasExtendableVFPtr())
2526 // If we don't have a primary base, this one qualifies.
2528 PrimaryBase = BaseDecl;
2529 LeadsWithZeroSizedBase = BaseLayout.leadsWithZeroSizedBase();
2531 // Lay out the base.
2532 layoutNonVirtualBase(RD, BaseDecl, BaseLayout, PreviousBaseLayout);
2534 // Figure out if we need a fresh VFPtr for this class.
2535 if (!PrimaryBase && RD->isDynamicClass())
2536 for (CXXRecordDecl::method_iterator i = RD->method_begin(),
2537 e = RD->method_end();
2538 !HasOwnVFPtr && i != e; ++i)
2539 HasOwnVFPtr = i->isVirtual() && i->size_overridden_methods() == 0;
2540 // If we don't have a primary base then we have a leading object that could
2541 // itself lead with a zero-sized object, something we track.
2542 bool CheckLeadingLayout = !PrimaryBase;
2543 // Iterate through the bases and lay out the non-virtual ones.
2544 for (const CXXBaseSpecifier &Base : RD->bases()) {
2545 if (Base.isVirtual())
2547 const CXXRecordDecl *BaseDecl = Base.getType()->getAsCXXRecordDecl();
2548 const ASTRecordLayout &BaseLayout = Context.getASTRecordLayout(BaseDecl);
2549 // Only lay out bases without extendable VFPtrs on the second pass.
2550 if (BaseLayout.hasExtendableVFPtr()) {
2551 VBPtrOffset = Bases[BaseDecl] + BaseLayout.getNonVirtualSize();
2554 // If this is the first layout, check to see if it leads with a zero sized
2555 // object. If it does, so do we.
2556 if (CheckLeadingLayout) {
2557 CheckLeadingLayout = false;
2558 LeadsWithZeroSizedBase = BaseLayout.leadsWithZeroSizedBase();
2560 // Lay out the base.
2561 layoutNonVirtualBase(RD, BaseDecl, BaseLayout, PreviousBaseLayout);
2562 VBPtrOffset = Bases[BaseDecl] + BaseLayout.getNonVirtualSize();
2564 // Set our VBPtroffset if we know it at this point.
2566 VBPtrOffset = CharUnits::fromQuantity(-1);
2567 else if (SharedVBPtrBase) {
2568 const ASTRecordLayout &Layout = Context.getASTRecordLayout(SharedVBPtrBase);
2569 VBPtrOffset = Bases[SharedVBPtrBase] + Layout.getVBPtrOffset();
2573 static bool recordUsesEBO(const RecordDecl *RD) {
2574 if (!isa<CXXRecordDecl>(RD))
2576 if (RD->hasAttr<EmptyBasesAttr>())
2578 if (auto *LVA = RD->getAttr<LayoutVersionAttr>())
2579 // TODO: Double check with the next version of MSVC.
2580 if (LVA->getVersion() <= LangOptions::MSVC2015)
2582 // TODO: Some later version of MSVC will change the default behavior of the
2583 // compiler to enable EBO by default. When this happens, we will need an
2584 // additional isCompatibleWithMSVC check.
2588 void MicrosoftRecordLayoutBuilder::layoutNonVirtualBase(
2589 const CXXRecordDecl *RD,
2590 const CXXRecordDecl *BaseDecl,
2591 const ASTRecordLayout &BaseLayout,
2592 const ASTRecordLayout *&PreviousBaseLayout) {
2593 // Insert padding between two bases if the left first one is zero sized or
2594 // contains a zero sized subobject and the right is zero sized or one leads
2595 // with a zero sized base.
2596 bool MDCUsesEBO = recordUsesEBO(RD);
2597 if (PreviousBaseLayout && PreviousBaseLayout->endsWithZeroSizedObject() &&
2598 BaseLayout.leadsWithZeroSizedBase() && !MDCUsesEBO)
2600 ElementInfo Info = getAdjustedElementInfo(BaseLayout);
2601 CharUnits BaseOffset;
2603 // Respect the external AST source base offset, if present.
2604 bool FoundBase = false;
2605 if (UseExternalLayout) {
2606 FoundBase = External.getExternalNVBaseOffset(BaseDecl, BaseOffset);
2608 assert(BaseOffset >= Size && "base offset already allocated");
2614 if (MDCUsesEBO && BaseDecl->isEmpty() &&
2615 BaseLayout.getNonVirtualSize() == CharUnits::Zero()) {
2616 BaseOffset = CharUnits::Zero();
2618 // Otherwise, lay the base out at the end of the MDC.
2619 BaseOffset = Size = Size.alignTo(Info.Alignment);
2622 Bases.insert(std::make_pair(BaseDecl, BaseOffset));
2623 Size += BaseLayout.getNonVirtualSize();
2624 PreviousBaseLayout = &BaseLayout;
2627 void MicrosoftRecordLayoutBuilder::layoutFields(const RecordDecl *RD) {
2628 LastFieldIsNonZeroWidthBitfield = false;
2629 for (const FieldDecl *Field : RD->fields())
2633 void MicrosoftRecordLayoutBuilder::layoutField(const FieldDecl *FD) {
2634 if (FD->isBitField()) {
2638 LastFieldIsNonZeroWidthBitfield = false;
2639 ElementInfo Info = getAdjustedElementInfo(FD);
2640 Alignment = std::max(Alignment, Info.Alignment);
2642 placeFieldAtOffset(CharUnits::Zero());
2643 Size = std::max(Size, Info.Size);
2645 CharUnits FieldOffset;
2646 if (UseExternalLayout) {
2648 Context.toCharUnitsFromBits(External.getExternalFieldOffset(FD));
2649 assert(FieldOffset >= Size && "field offset already allocated");
2651 FieldOffset = Size.alignTo(Info.Alignment);
2653 placeFieldAtOffset(FieldOffset);
2654 Size = FieldOffset + Info.Size;
2658 void MicrosoftRecordLayoutBuilder::layoutBitField(const FieldDecl *FD) {
2659 unsigned Width = FD->getBitWidthValue(Context);
2661 layoutZeroWidthBitField(FD);
2664 ElementInfo Info = getAdjustedElementInfo(FD);
2665 // Clamp the bitfield to a containable size for the sake of being able
2666 // to lay them out. Sema will throw an error.
2667 if (Width > Context.toBits(Info.Size))
2668 Width = Context.toBits(Info.Size);
2669 // Check to see if this bitfield fits into an existing allocation. Note:
2670 // MSVC refuses to pack bitfields of formal types with different sizes
2671 // into the same allocation.
2672 if (!IsUnion && LastFieldIsNonZeroWidthBitfield &&
2673 CurrentBitfieldSize == Info.Size && Width <= RemainingBitsInField) {
2674 placeFieldAtBitOffset(Context.toBits(Size) - RemainingBitsInField);
2675 RemainingBitsInField -= Width;
2678 LastFieldIsNonZeroWidthBitfield = true;
2679 CurrentBitfieldSize = Info.Size;
2681 placeFieldAtOffset(CharUnits::Zero());
2682 Size = std::max(Size, Info.Size);
2683 // TODO: Add a Sema warning that MS ignores bitfield alignment in unions.
2685 // Allocate a new block of memory and place the bitfield in it.
2686 CharUnits FieldOffset = Size.alignTo(Info.Alignment);
2687 placeFieldAtOffset(FieldOffset);
2688 Size = FieldOffset + Info.Size;
2689 Alignment = std::max(Alignment, Info.Alignment);
2690 RemainingBitsInField = Context.toBits(Info.Size) - Width;
2695 MicrosoftRecordLayoutBuilder::layoutZeroWidthBitField(const FieldDecl *FD) {
2696 // Zero-width bitfields are ignored unless they follow a non-zero-width
2698 if (!LastFieldIsNonZeroWidthBitfield) {
2699 placeFieldAtOffset(IsUnion ? CharUnits::Zero() : Size);
2700 // TODO: Add a Sema warning that MS ignores alignment for zero
2701 // sized bitfields that occur after zero-size bitfields or non-bitfields.
2704 LastFieldIsNonZeroWidthBitfield = false;
2705 ElementInfo Info = getAdjustedElementInfo(FD);
2707 placeFieldAtOffset(CharUnits::Zero());
2708 Size = std::max(Size, Info.Size);
2709 // TODO: Add a Sema warning that MS ignores bitfield alignment in unions.
2711 // Round up the current record size to the field's alignment boundary.
2712 CharUnits FieldOffset = Size.alignTo(Info.Alignment);
2713 placeFieldAtOffset(FieldOffset);
2715 Alignment = std::max(Alignment, Info.Alignment);
2719 void MicrosoftRecordLayoutBuilder::injectVBPtr(const CXXRecordDecl *RD) {
2720 if (!HasVBPtr || SharedVBPtrBase)
2722 // Inject the VBPointer at the injection site.
2723 CharUnits InjectionSite = VBPtrOffset;
2724 // But before we do, make sure it's properly aligned.
2725 VBPtrOffset = VBPtrOffset.alignTo(PointerInfo.Alignment);
2726 // Shift everything after the vbptr down, unless we're using an external
2728 if (UseExternalLayout)
2730 // Determine where the first field should be laid out after the vbptr.
2731 CharUnits FieldStart = VBPtrOffset + PointerInfo.Size;
2732 // Make sure that the amount we push the fields back by is a multiple of the
2734 CharUnits Offset = (FieldStart - InjectionSite)
2735 .alignTo(std::max(RequiredAlignment, Alignment));
2737 for (uint64_t &FieldOffset : FieldOffsets)
2738 FieldOffset += Context.toBits(Offset);
2739 for (BaseOffsetsMapTy::value_type &Base : Bases)
2740 if (Base.second >= InjectionSite)
2741 Base.second += Offset;
2744 void MicrosoftRecordLayoutBuilder::injectVFPtr(const CXXRecordDecl *RD) {
2747 // Make sure that the amount we push the struct back by is a multiple of the
2750 PointerInfo.Size.alignTo(std::max(RequiredAlignment, Alignment));
2751 // Push back the vbptr, but increase the size of the object and push back
2752 // regular fields by the offset only if not using external record layout.
2754 VBPtrOffset += Offset;
2756 if (UseExternalLayout)
2761 // If we're using an external layout, the fields offsets have already
2762 // accounted for this adjustment.
2763 for (uint64_t &FieldOffset : FieldOffsets)
2764 FieldOffset += Context.toBits(Offset);
2765 for (BaseOffsetsMapTy::value_type &Base : Bases)
2766 Base.second += Offset;
2769 void MicrosoftRecordLayoutBuilder::layoutVirtualBases(const CXXRecordDecl *RD) {
2772 // Vtordisps are always 4 bytes (even in 64-bit mode)
2773 CharUnits VtorDispSize = CharUnits::fromQuantity(4);
2774 CharUnits VtorDispAlignment = VtorDispSize;
2775 // vtordisps respect pragma pack.
2776 if (!MaxFieldAlignment.isZero())
2777 VtorDispAlignment = std::min(VtorDispAlignment, MaxFieldAlignment);
2778 // The alignment of the vtordisp is at least the required alignment of the
2779 // entire record. This requirement may be present to support vtordisp
2781 for (const CXXBaseSpecifier &VBase : RD->vbases()) {
2782 const CXXRecordDecl *BaseDecl = VBase.getType()->getAsCXXRecordDecl();
2783 const ASTRecordLayout &BaseLayout = Context.getASTRecordLayout(BaseDecl);
2785 std::max(RequiredAlignment, BaseLayout.getRequiredAlignment());
2787 VtorDispAlignment = std::max(VtorDispAlignment, RequiredAlignment);
2788 // Compute the vtordisp set.
2789 llvm::SmallPtrSet<const CXXRecordDecl *, 2> HasVtorDispSet;
2790 computeVtorDispSet(HasVtorDispSet, RD);
2791 // Iterate through the virtual bases and lay them out.
2792 const ASTRecordLayout *PreviousBaseLayout = nullptr;
2793 for (const CXXBaseSpecifier &VBase : RD->vbases()) {
2794 const CXXRecordDecl *BaseDecl = VBase.getType()->getAsCXXRecordDecl();
2795 const ASTRecordLayout &BaseLayout = Context.getASTRecordLayout(BaseDecl);
2796 bool HasVtordisp = HasVtorDispSet.count(BaseDecl) > 0;
2797 // Insert padding between two bases if the left first one is zero sized or
2798 // contains a zero sized subobject and the right is zero sized or one leads
2799 // with a zero sized base. The padding between virtual bases is 4
2800 // bytes (in both 32 and 64 bits modes) and always involves rounding up to
2801 // the required alignment, we don't know why.
2802 if ((PreviousBaseLayout && PreviousBaseLayout->endsWithZeroSizedObject() &&
2803 BaseLayout.leadsWithZeroSizedBase() && !recordUsesEBO(RD)) ||
2805 Size = Size.alignTo(VtorDispAlignment) + VtorDispSize;
2806 Alignment = std::max(VtorDispAlignment, Alignment);
2808 // Insert the virtual base.
2809 ElementInfo Info = getAdjustedElementInfo(BaseLayout);
2810 CharUnits BaseOffset;
2812 // Respect the external AST source base offset, if present.
2813 bool FoundBase = false;
2814 if (UseExternalLayout) {
2815 FoundBase = External.getExternalVBaseOffset(BaseDecl, BaseOffset);
2817 assert(BaseOffset >= Size && "base offset already allocated");
2820 BaseOffset = Size.alignTo(Info.Alignment);
2822 VBases.insert(std::make_pair(BaseDecl,
2823 ASTRecordLayout::VBaseInfo(BaseOffset, HasVtordisp)));
2824 Size = BaseOffset + BaseLayout.getNonVirtualSize();
2825 PreviousBaseLayout = &BaseLayout;
2829 void MicrosoftRecordLayoutBuilder::finalizeLayout(const RecordDecl *RD) {
2830 // Respect required alignment. Note that in 32-bit mode Required alignment
2831 // may be 0 and cause size not to be updated.
2833 if (!RequiredAlignment.isZero()) {
2834 Alignment = std::max(Alignment, RequiredAlignment);
2835 auto RoundingAlignment = Alignment;
2836 if (!MaxFieldAlignment.isZero())
2837 RoundingAlignment = std::min(RoundingAlignment, MaxFieldAlignment);
2838 RoundingAlignment = std::max(RoundingAlignment, RequiredAlignment);
2839 Size = Size.alignTo(RoundingAlignment);
2841 if (Size.isZero()) {
2842 if (!recordUsesEBO(RD) || !cast<CXXRecordDecl>(RD)->isEmpty()) {
2843 EndsWithZeroSizedObject = true;
2844 LeadsWithZeroSizedBase = true;
2846 // Zero-sized structures have size equal to their alignment if a
2847 // __declspec(align) came into play.
2848 if (RequiredAlignment >= MinEmptyStructSize)
2851 Size = MinEmptyStructSize;
2854 if (UseExternalLayout) {
2855 Size = Context.toCharUnitsFromBits(External.Size);
2857 Alignment = Context.toCharUnitsFromBits(External.Align);
2861 // Recursively walks the non-virtual bases of a class and determines if any of
2862 // them are in the bases with overridden methods set.
2864 RequiresVtordisp(const llvm::SmallPtrSetImpl<const CXXRecordDecl *> &
2865 BasesWithOverriddenMethods,
2866 const CXXRecordDecl *RD) {
2867 if (BasesWithOverriddenMethods.count(RD))
2869 // If any of a virtual bases non-virtual bases (recursively) requires a
2870 // vtordisp than so does this virtual base.
2871 for (const CXXBaseSpecifier &Base : RD->bases())
2872 if (!Base.isVirtual() &&
2873 RequiresVtordisp(BasesWithOverriddenMethods,
2874 Base.getType()->getAsCXXRecordDecl()))
2879 void MicrosoftRecordLayoutBuilder::computeVtorDispSet(
2880 llvm::SmallPtrSetImpl<const CXXRecordDecl *> &HasVtordispSet,
2881 const CXXRecordDecl *RD) const {
2882 // /vd2 or #pragma vtordisp(2): Always use vtordisps for virtual bases with
2884 if (RD->getMSVtorDispMode() == MSVtorDispAttr::ForVFTable) {
2885 for (const CXXBaseSpecifier &Base : RD->vbases()) {
2886 const CXXRecordDecl *BaseDecl = Base.getType()->getAsCXXRecordDecl();
2887 const ASTRecordLayout &Layout = Context.getASTRecordLayout(BaseDecl);
2888 if (Layout.hasExtendableVFPtr())
2889 HasVtordispSet.insert(BaseDecl);
2894 // If any of our bases need a vtordisp for this type, so do we. Check our
2895 // direct bases for vtordisp requirements.
2896 for (const CXXBaseSpecifier &Base : RD->bases()) {
2897 const CXXRecordDecl *BaseDecl = Base.getType()->getAsCXXRecordDecl();
2898 const ASTRecordLayout &Layout = Context.getASTRecordLayout(BaseDecl);
2899 for (const auto &bi : Layout.getVBaseOffsetsMap())
2900 if (bi.second.hasVtorDisp())
2901 HasVtordispSet.insert(bi.first);
2903 // We don't introduce any additional vtordisps if either:
2904 // * A user declared constructor or destructor aren't declared.
2905 // * #pragma vtordisp(0) or the /vd0 flag are in use.
2906 if ((!RD->hasUserDeclaredConstructor() && !RD->hasUserDeclaredDestructor()) ||
2907 RD->getMSVtorDispMode() == MSVtorDispAttr::Never)
2909 // /vd1 or #pragma vtordisp(1): Try to guess based on whether we think it's
2910 // possible for a partially constructed object with virtual base overrides to
2911 // escape a non-trivial constructor.
2912 assert(RD->getMSVtorDispMode() == MSVtorDispAttr::ForVBaseOverride);
2913 // Compute a set of base classes which define methods we override. A virtual
2914 // base in this set will require a vtordisp. A virtual base that transitively
2915 // contains one of these bases as a non-virtual base will also require a
2917 llvm::SmallPtrSet<const CXXMethodDecl *, 8> Work;
2918 llvm::SmallPtrSet<const CXXRecordDecl *, 2> BasesWithOverriddenMethods;
2919 // Seed the working set with our non-destructor, non-pure virtual methods.
2920 for (const CXXMethodDecl *MD : RD->methods())
2921 if (MD->isVirtual() && !isa<CXXDestructorDecl>(MD) && !MD->isPure())
2923 while (!Work.empty()) {
2924 const CXXMethodDecl *MD = *Work.begin();
2925 auto MethodRange = MD->overridden_methods();
2926 // If a virtual method has no-overrides it lives in its parent's vtable.
2927 if (MethodRange.begin() == MethodRange.end())
2928 BasesWithOverriddenMethods.insert(MD->getParent());
2930 Work.insert(MethodRange.begin(), MethodRange.end());
2931 // We've finished processing this element, remove it from the working set.
2934 // For each of our virtual bases, check if it is in the set of overridden
2935 // bases or if it transitively contains a non-virtual base that is.
2936 for (const CXXBaseSpecifier &Base : RD->vbases()) {
2937 const CXXRecordDecl *BaseDecl = Base.getType()->getAsCXXRecordDecl();
2938 if (!HasVtordispSet.count(BaseDecl) &&
2939 RequiresVtordisp(BasesWithOverriddenMethods, BaseDecl))
2940 HasVtordispSet.insert(BaseDecl);
2944 /// getASTRecordLayout - Get or compute information about the layout of the
2945 /// specified record (struct/union/class), which indicates its size and field
2946 /// position information.
2947 const ASTRecordLayout &
2948 ASTContext::getASTRecordLayout(const RecordDecl *D) const {
2949 // These asserts test different things. A record has a definition
2950 // as soon as we begin to parse the definition. That definition is
2951 // not a complete definition (which is what isDefinition() tests)
2952 // until we *finish* parsing the definition.
2954 if (D->hasExternalLexicalStorage() && !D->getDefinition())
2955 getExternalSource()->CompleteType(const_cast<RecordDecl*>(D));
2957 D = D->getDefinition();
2958 assert(D && "Cannot get layout of forward declarations!");
2959 assert(!D->isInvalidDecl() && "Cannot get layout of invalid decl!");
2960 assert(D->isCompleteDefinition() && "Cannot layout type before complete!");
2962 // Look up this layout, if already laid out, return what we have.
2963 // Note that we can't save a reference to the entry because this function
2965 const ASTRecordLayout *Entry = ASTRecordLayouts[D];
2966 if (Entry) return *Entry;
2968 const ASTRecordLayout *NewEntry = nullptr;
2970 if (isMsLayout(*this)) {
2971 MicrosoftRecordLayoutBuilder Builder(*this);
2972 if (const auto *RD = dyn_cast<CXXRecordDecl>(D)) {
2973 Builder.cxxLayout(RD);
2974 NewEntry = new (*this) ASTRecordLayout(
2975 *this, Builder.Size, Builder.Alignment, Builder.RequiredAlignment,
2976 Builder.HasOwnVFPtr, Builder.HasOwnVFPtr || Builder.PrimaryBase,
2977 Builder.VBPtrOffset, Builder.DataSize, Builder.FieldOffsets,
2978 Builder.NonVirtualSize, Builder.Alignment, CharUnits::Zero(),
2979 Builder.PrimaryBase, false, Builder.SharedVBPtrBase,
2980 Builder.EndsWithZeroSizedObject, Builder.LeadsWithZeroSizedBase,
2981 Builder.Bases, Builder.VBases);
2984 NewEntry = new (*this) ASTRecordLayout(
2985 *this, Builder.Size, Builder.Alignment, Builder.RequiredAlignment,
2986 Builder.Size, Builder.FieldOffsets);
2989 if (const auto *RD = dyn_cast<CXXRecordDecl>(D)) {
2990 EmptySubobjectMap EmptySubobjects(*this, RD);
2991 ItaniumRecordLayoutBuilder Builder(*this, &EmptySubobjects);
2994 // In certain situations, we are allowed to lay out objects in the
2995 // tail-padding of base classes. This is ABI-dependent.
2996 // FIXME: this should be stored in the record layout.
2997 bool skipTailPadding =
2998 mustSkipTailPadding(getTargetInfo().getCXXABI(), RD);
3000 // FIXME: This should be done in FinalizeLayout.
3001 CharUnits DataSize =
3002 skipTailPadding ? Builder.getSize() : Builder.getDataSize();
3003 CharUnits NonVirtualSize =
3004 skipTailPadding ? DataSize : Builder.NonVirtualSize;
3005 NewEntry = new (*this) ASTRecordLayout(
3006 *this, Builder.getSize(), Builder.Alignment,
3007 /*RequiredAlignment : used by MS-ABI)*/
3008 Builder.Alignment, Builder.HasOwnVFPtr, RD->isDynamicClass(),
3009 CharUnits::fromQuantity(-1), DataSize, Builder.FieldOffsets,
3010 NonVirtualSize, Builder.NonVirtualAlignment,
3011 EmptySubobjects.SizeOfLargestEmptySubobject, Builder.PrimaryBase,
3012 Builder.PrimaryBaseIsVirtual, nullptr, false, false, Builder.Bases,
3015 ItaniumRecordLayoutBuilder Builder(*this, /*EmptySubobjects=*/nullptr);
3018 NewEntry = new (*this) ASTRecordLayout(
3019 *this, Builder.getSize(), Builder.Alignment,
3020 /*RequiredAlignment : used by MS-ABI)*/
3021 Builder.Alignment, Builder.getSize(), Builder.FieldOffsets);
3025 ASTRecordLayouts[D] = NewEntry;
3027 if (getLangOpts().DumpRecordLayouts) {
3028 llvm::outs() << "\n*** Dumping AST Record Layout\n";
3029 DumpRecordLayout(D, llvm::outs(), getLangOpts().DumpRecordLayoutsSimple);
3035 const CXXMethodDecl *ASTContext::getCurrentKeyFunction(const CXXRecordDecl *RD) {
3036 if (!getTargetInfo().getCXXABI().hasKeyFunctions())
3039 assert(RD->getDefinition() && "Cannot get key function for forward decl!");
3040 RD = cast<CXXRecordDecl>(RD->getDefinition());
3043 // 1) computing the key function might trigger deserialization, which might
3044 // invalidate iterators into KeyFunctions
3045 // 2) 'get' on the LazyDeclPtr might also trigger deserialization and
3046 // invalidate the LazyDeclPtr within the map itself
3047 LazyDeclPtr Entry = KeyFunctions[RD];
3048 const Decl *Result =
3049 Entry ? Entry.get(getExternalSource()) : computeKeyFunction(*this, RD);
3051 // Store it back if it changed.
3052 if (Entry.isOffset() || Entry.isValid() != bool(Result))
3053 KeyFunctions[RD] = const_cast<Decl*>(Result);
3055 return cast_or_null<CXXMethodDecl>(Result);
3058 void ASTContext::setNonKeyFunction(const CXXMethodDecl *Method) {
3059 assert(Method == Method->getFirstDecl() &&
3060 "not working with method declaration from class definition");
3062 // Look up the cache entry. Since we're working with the first
3063 // declaration, its parent must be the class definition, which is
3064 // the correct key for the KeyFunctions hash.
3065 const auto &Map = KeyFunctions;
3066 auto I = Map.find(Method->getParent());
3068 // If it's not cached, there's nothing to do.
3069 if (I == Map.end()) return;
3071 // If it is cached, check whether it's the target method, and if so,
3072 // remove it from the cache. Note, the call to 'get' might invalidate
3073 // the iterator and the LazyDeclPtr object within the map.
3074 LazyDeclPtr Ptr = I->second;
3075 if (Ptr.get(getExternalSource()) == Method) {
3076 // FIXME: remember that we did this for module / chained PCH state?
3077 KeyFunctions.erase(Method->getParent());
3081 static uint64_t getFieldOffset(const ASTContext &C, const FieldDecl *FD) {
3082 const ASTRecordLayout &Layout = C.getASTRecordLayout(FD->getParent());
3083 return Layout.getFieldOffset(FD->getFieldIndex());
3086 uint64_t ASTContext::getFieldOffset(const ValueDecl *VD) const {
3087 uint64_t OffsetInBits;
3088 if (const FieldDecl *FD = dyn_cast<FieldDecl>(VD)) {
3089 OffsetInBits = ::getFieldOffset(*this, FD);
3091 const IndirectFieldDecl *IFD = cast<IndirectFieldDecl>(VD);
3094 for (const NamedDecl *ND : IFD->chain())
3095 OffsetInBits += ::getFieldOffset(*this, cast<FieldDecl>(ND));
3098 return OffsetInBits;
3101 uint64_t ASTContext::lookupFieldBitOffset(const ObjCInterfaceDecl *OID,
3102 const ObjCImplementationDecl *ID,
3103 const ObjCIvarDecl *Ivar) const {
3104 const ObjCInterfaceDecl *Container = Ivar->getContainingInterface();
3106 // FIXME: We should eliminate the need to have ObjCImplementationDecl passed
3107 // in here; it should never be necessary because that should be the lexical
3108 // decl context for the ivar.
3110 // If we know have an implementation (and the ivar is in it) then
3111 // look up in the implementation layout.
3112 const ASTRecordLayout *RL;
3113 if (ID && declaresSameEntity(ID->getClassInterface(), Container))
3114 RL = &getASTObjCImplementationLayout(ID);
3116 RL = &getASTObjCInterfaceLayout(Container);
3118 // Compute field index.
3120 // FIXME: The index here is closely tied to how ASTContext::getObjCLayout is
3121 // implemented. This should be fixed to get the information from the layout
3125 for (const ObjCIvarDecl *IVD = Container->all_declared_ivar_begin();
3126 IVD; IVD = IVD->getNextIvar()) {
3131 assert(Index < RL->getFieldCount() && "Ivar is not inside record layout!");
3133 return RL->getFieldOffset(Index);
3136 /// getObjCLayout - Get or compute information about the layout of the
3137 /// given interface.
3139 /// \param Impl - If given, also include the layout of the interface's
3140 /// implementation. This may differ by including synthesized ivars.
3141 const ASTRecordLayout &
3142 ASTContext::getObjCLayout(const ObjCInterfaceDecl *D,
3143 const ObjCImplementationDecl *Impl) const {
3144 // Retrieve the definition
3145 if (D->hasExternalLexicalStorage() && !D->getDefinition())
3146 getExternalSource()->CompleteType(const_cast<ObjCInterfaceDecl*>(D));
3147 D = D->getDefinition();
3148 assert(D && D->isThisDeclarationADefinition() && "Invalid interface decl!");
3150 // Look up this layout, if already laid out, return what we have.
3151 const ObjCContainerDecl *Key =
3152 Impl ? (const ObjCContainerDecl*) Impl : (const ObjCContainerDecl*) D;
3153 if (const ASTRecordLayout *Entry = ObjCLayouts[Key])
3156 // Add in synthesized ivar count if laying out an implementation.
3158 unsigned SynthCount = CountNonClassIvars(D);
3159 // If there aren't any synthesized ivars then reuse the interface
3160 // entry. Note we can't cache this because we simply free all
3161 // entries later; however we shouldn't look up implementations
3163 if (SynthCount == 0)
3164 return getObjCLayout(D, nullptr);
3167 ItaniumRecordLayoutBuilder Builder(*this, /*EmptySubobjects=*/nullptr);
3170 const ASTRecordLayout *NewEntry =
3171 new (*this) ASTRecordLayout(*this, Builder.getSize(),
3173 /*RequiredAlignment : used by MS-ABI)*/
3175 Builder.getDataSize(),
3176 Builder.FieldOffsets);
3178 ObjCLayouts[Key] = NewEntry;
3183 static void PrintOffset(raw_ostream &OS,
3184 CharUnits Offset, unsigned IndentLevel) {
3185 OS << llvm::format("%10" PRId64 " | ", (int64_t)Offset.getQuantity());
3186 OS.indent(IndentLevel * 2);
3189 static void PrintBitFieldOffset(raw_ostream &OS, CharUnits Offset,
3190 unsigned Begin, unsigned Width,
3191 unsigned IndentLevel) {
3192 llvm::SmallString<10> Buffer;
3194 llvm::raw_svector_ostream BufferOS(Buffer);
3195 BufferOS << Offset.getQuantity() << ':';
3199 BufferOS << Begin << '-' << (Begin + Width - 1);
3203 OS << llvm::right_justify(Buffer, 10) << " | ";
3204 OS.indent(IndentLevel * 2);
3207 static void PrintIndentNoOffset(raw_ostream &OS, unsigned IndentLevel) {
3209 OS.indent(IndentLevel * 2);
3212 static void DumpRecordLayout(raw_ostream &OS, const RecordDecl *RD,
3213 const ASTContext &C,
3215 unsigned IndentLevel,
3216 const char* Description,
3218 bool IncludeVirtualBases) {
3219 const ASTRecordLayout &Layout = C.getASTRecordLayout(RD);
3220 auto CXXRD = dyn_cast<CXXRecordDecl>(RD);
3222 PrintOffset(OS, Offset, IndentLevel);
3223 OS << C.getTypeDeclType(const_cast<RecordDecl*>(RD)).getAsString();
3225 OS << ' ' << Description;
3226 if (CXXRD && CXXRD->isEmpty())
3234 const CXXRecordDecl *PrimaryBase = Layout.getPrimaryBase();
3235 bool HasOwnVFPtr = Layout.hasOwnVFPtr();
3236 bool HasOwnVBPtr = Layout.hasOwnVBPtr();
3239 if (CXXRD->isDynamicClass() && !PrimaryBase && !isMsLayout(C)) {
3240 PrintOffset(OS, Offset, IndentLevel);
3241 OS << '(' << *RD << " vtable pointer)\n";
3242 } else if (HasOwnVFPtr) {
3243 PrintOffset(OS, Offset, IndentLevel);
3244 // vfptr (for Microsoft C++ ABI)
3245 OS << '(' << *RD << " vftable pointer)\n";
3249 SmallVector<const CXXRecordDecl *, 4> Bases;
3250 for (const CXXBaseSpecifier &Base : CXXRD->bases()) {
3251 assert(!Base.getType()->isDependentType() &&
3252 "Cannot layout class with dependent bases.");
3253 if (!Base.isVirtual())
3254 Bases.push_back(Base.getType()->getAsCXXRecordDecl());
3257 // Sort nvbases by offset.
3258 std::stable_sort(Bases.begin(), Bases.end(),
3259 [&](const CXXRecordDecl *L, const CXXRecordDecl *R) {
3260 return Layout.getBaseClassOffset(L) < Layout.getBaseClassOffset(R);
3263 // Dump (non-virtual) bases
3264 for (const CXXRecordDecl *Base : Bases) {
3265 CharUnits BaseOffset = Offset + Layout.getBaseClassOffset(Base);
3266 DumpRecordLayout(OS, Base, C, BaseOffset, IndentLevel,
3267 Base == PrimaryBase ? "(primary base)" : "(base)",
3268 /*PrintSizeInfo=*/false,
3269 /*IncludeVirtualBases=*/false);
3272 // vbptr (for Microsoft C++ ABI)
3274 PrintOffset(OS, Offset + Layout.getVBPtrOffset(), IndentLevel);
3275 OS << '(' << *RD << " vbtable pointer)\n";
3280 uint64_t FieldNo = 0;
3281 for (RecordDecl::field_iterator I = RD->field_begin(),
3282 E = RD->field_end(); I != E; ++I, ++FieldNo) {
3283 const FieldDecl &Field = **I;
3284 uint64_t LocalFieldOffsetInBits = Layout.getFieldOffset(FieldNo);
3285 CharUnits FieldOffset =
3286 Offset + C.toCharUnitsFromBits(LocalFieldOffsetInBits);
3288 // Recursively dump fields of record type.
3289 if (auto RT = Field.getType()->getAs<RecordType>()) {
3290 DumpRecordLayout(OS, RT->getDecl(), C, FieldOffset, IndentLevel,
3291 Field.getName().data(),
3292 /*PrintSizeInfo=*/false,
3293 /*IncludeVirtualBases=*/true);
3297 if (Field.isBitField()) {
3298 uint64_t LocalFieldByteOffsetInBits = C.toBits(FieldOffset - Offset);
3299 unsigned Begin = LocalFieldOffsetInBits - LocalFieldByteOffsetInBits;
3300 unsigned Width = Field.getBitWidthValue(C);
3301 PrintBitFieldOffset(OS, FieldOffset, Begin, Width, IndentLevel);
3303 PrintOffset(OS, FieldOffset, IndentLevel);
3305 OS << Field.getType().getAsString() << ' ' << Field << '\n';
3308 // Dump virtual bases.
3309 if (CXXRD && IncludeVirtualBases) {
3310 const ASTRecordLayout::VBaseOffsetsMapTy &VtorDisps =
3311 Layout.getVBaseOffsetsMap();
3313 for (const CXXBaseSpecifier &Base : CXXRD->vbases()) {
3314 assert(Base.isVirtual() && "Found non-virtual class!");
3315 const CXXRecordDecl *VBase = Base.getType()->getAsCXXRecordDecl();
3317 CharUnits VBaseOffset = Offset + Layout.getVBaseClassOffset(VBase);
3319 if (VtorDisps.find(VBase)->second.hasVtorDisp()) {
3320 PrintOffset(OS, VBaseOffset - CharUnits::fromQuantity(4), IndentLevel);
3321 OS << "(vtordisp for vbase " << *VBase << ")\n";
3324 DumpRecordLayout(OS, VBase, C, VBaseOffset, IndentLevel,
3325 VBase == Layout.getPrimaryBase() ?
3326 "(primary virtual base)" : "(virtual base)",
3327 /*PrintSizeInfo=*/false,
3328 /*IncludeVirtualBases=*/false);
3332 if (!PrintSizeInfo) return;
3334 PrintIndentNoOffset(OS, IndentLevel - 1);
3335 OS << "[sizeof=" << Layout.getSize().getQuantity();
3336 if (CXXRD && !isMsLayout(C))
3337 OS << ", dsize=" << Layout.getDataSize().getQuantity();
3338 OS << ", align=" << Layout.getAlignment().getQuantity();
3342 PrintIndentNoOffset(OS, IndentLevel - 1);
3343 OS << " nvsize=" << Layout.getNonVirtualSize().getQuantity();
3344 OS << ", nvalign=" << Layout.getNonVirtualAlignment().getQuantity();
3349 void ASTContext::DumpRecordLayout(const RecordDecl *RD,
3351 bool Simple) const {
3353 ::DumpRecordLayout(OS, RD, *this, CharUnits(), 0, nullptr,
3354 /*PrintSizeInfo*/true,
3355 /*IncludeVirtualBases=*/true);
3359 // The "simple" format is designed to be parsed by the
3360 // layout-override testing code. There shouldn't be any external
3361 // uses of this format --- when LLDB overrides a layout, it sets up
3362 // the data structures directly --- so feel free to adjust this as
3363 // you like as long as you also update the rudimentary parser for it
3366 const ASTRecordLayout &Info = getASTRecordLayout(RD);
3367 OS << "Type: " << getTypeDeclType(RD).getAsString() << "\n";
3369 OS << "<ASTRecordLayout\n";
3370 OS << " Size:" << toBits(Info.getSize()) << "\n";
3371 if (!isMsLayout(*this))
3372 OS << " DataSize:" << toBits(Info.getDataSize()) << "\n";
3373 OS << " Alignment:" << toBits(Info.getAlignment()) << "\n";
3374 OS << " FieldOffsets: [";
3375 for (unsigned i = 0, e = Info.getFieldCount(); i != e; ++i) {
3377 OS << Info.getFieldOffset(i);