1//=== RecordLayoutBuilder.cpp - Helper class for building record layouts ---==//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9
10#include "clang/AST/ASTContext.h"
11#include "clang/AST/Attr.h"
12#include "clang/AST/CXXInheritance.h"
13#include "clang/AST/Decl.h"
14#include "clang/AST/DeclCXX.h"
15#include "clang/AST/DeclObjC.h"
16#include "clang/AST/Expr.h"
17#include "clang/AST/RecordLayout.h"
18#include "clang/Basic/TargetInfo.h"
19#include "clang/Sema/SemaDiagnostic.h"
20#include "llvm/Support/Format.h"
21#include "llvm/ADT/SmallSet.h"
22#include "llvm/Support/MathExtras.h"
23#include "llvm/Support/CrashRecoveryContext.h"
24
25using namespace clang;
26
27namespace {
28
29/// BaseSubobjectInfo - Represents a single base subobject in a complete class.
30/// For a class hierarchy like
31///
32/// class A { };
33/// class B : A { };
34/// class C : A, B { };
35///
36/// The BaseSubobjectInfo graph for C will have three BaseSubobjectInfo
37/// instances, one for B and two for A.
38///
39/// If a base is virtual, it will only have one BaseSubobjectInfo allocated.
40struct BaseSubobjectInfo {
41  /// Class - The class for this base info.
42  const CXXRecordDecl *Class;
43
44  /// IsVirtual - Whether the BaseInfo represents a virtual base or not.
45  bool IsVirtual;
46
47  /// Bases - Information about the base subobjects.
48  SmallVector<BaseSubobjectInfo*, 4> Bases;
49
50  /// PrimaryVirtualBaseInfo - Holds the base info for the primary virtual base
51  /// of this base info (if one exists).
52  BaseSubobjectInfo *PrimaryVirtualBaseInfo;
53
54  // FIXME: Document.
55  const BaseSubobjectInfo *Derived;
56};
57
58/// EmptySubobjectMap - Keeps track of which empty subobjects exist at different
59/// offsets while laying out a C++ class.
60class EmptySubobjectMap {
61  const ASTContext &Context;
62  uint64_t CharWidth;
63
64  /// Class - The class whose empty entries we're keeping track of.
65  const CXXRecordDecl *Class;
66
67  /// EmptyClassOffsets - A map from offsets to empty record decls.
68  typedef SmallVector<const CXXRecordDecl *, 1> ClassVectorTy;
69  typedef llvm::DenseMap<CharUnits, ClassVectorTy> EmptyClassOffsetsMapTy;
70  EmptyClassOffsetsMapTy EmptyClassOffsets;
71
72  /// MaxEmptyClassOffset - The highest offset known to contain an empty
73  /// base subobject.
74  CharUnits MaxEmptyClassOffset;
75
76  /// ComputeEmptySubobjectSizes - Compute the size of the largest base or
77  /// member subobject that is empty.
78  void ComputeEmptySubobjectSizes();
79
80  void AddSubobjectAtOffset(const CXXRecordDecl *RD, CharUnits Offset);
81
82  void UpdateEmptyBaseSubobjects(const BaseSubobjectInfo *Info,
83                                 CharUnits Offset, bool PlacingEmptyBase);
84
85  void UpdateEmptyFieldSubobjects(const CXXRecordDecl *RD,
86                                  const CXXRecordDecl *Class,
87                                  CharUnits Offset);
88  void UpdateEmptyFieldSubobjects(const FieldDecl *FD, CharUnits Offset);
89
90  /// AnyEmptySubobjectsBeyondOffset - Returns whether there are any empty
91  /// subobjects beyond the given offset.
92  bool AnyEmptySubobjectsBeyondOffset(CharUnits Offset) const {
93    return Offset <= MaxEmptyClassOffset;
94  }
95
96  CharUnits
97  getFieldOffset(const ASTRecordLayout &Layout, unsigned FieldNo) const {
98    uint64_t FieldOffset = Layout.getFieldOffset(FieldNo);
99    assert(FieldOffset % CharWidth == 0 &&
100           "Field offset not at char boundary!");
101
102    return Context.toCharUnitsFromBits(FieldOffset);
103  }
104
105protected:
106  bool CanPlaceSubobjectAtOffset(const CXXRecordDecl *RD,
107                                 CharUnits Offset) const;
108
109  bool CanPlaceBaseSubobjectAtOffset(const BaseSubobjectInfo *Info,
110                                     CharUnits Offset);
111
112  bool CanPlaceFieldSubobjectAtOffset(const CXXRecordDecl *RD,
113                                      const CXXRecordDecl *Class,
114                                      CharUnits Offset) const;
115  bool CanPlaceFieldSubobjectAtOffset(const FieldDecl *FD,
116                                      CharUnits Offset) const;
117
118public:
119  /// This holds the size of the largest empty subobject (either a base
120  /// or a member). Will be zero if the record being built doesn't contain
121  /// any empty classes.
122  CharUnits SizeOfLargestEmptySubobject;
123
124  EmptySubobjectMap(const ASTContext &Context, const CXXRecordDecl *Class)
125  : Context(Context), CharWidth(Context.getCharWidth()), Class(Class) {
126      ComputeEmptySubobjectSizes();
127  }
128
129  /// CanPlaceBaseAtOffset - Return whether the given base class can be placed
130  /// at the given offset.
131  /// Returns false if placing the record will result in two components
132  /// (direct or indirect) of the same type having the same offset.
133  bool CanPlaceBaseAtOffset(const BaseSubobjectInfo *Info,
134                            CharUnits Offset);
135
136  /// CanPlaceFieldAtOffset - Return whether a field can be placed at the given
137  /// offset.
138  bool CanPlaceFieldAtOffset(const FieldDecl *FD, CharUnits Offset);
139};
140
141void EmptySubobjectMap::ComputeEmptySubobjectSizes() {
142  // Check the bases.
143  for (CXXRecordDecl::base_class_const_iterator I = Class->bases_begin(),
144       E = Class->bases_end(); I != E; ++I) {
145    const CXXRecordDecl *BaseDecl =
146      cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
147
148    CharUnits EmptySize;
149    const ASTRecordLayout &Layout = Context.getASTRecordLayout(BaseDecl);
150    if (BaseDecl->isEmpty()) {
151      // If the class decl is empty, get its size.
152      EmptySize = Layout.getSize();
153    } else {
154      // Otherwise, we get the largest empty subobject for the decl.
155      EmptySize = Layout.getSizeOfLargestEmptySubobject();
156    }
157
158    if (EmptySize > SizeOfLargestEmptySubobject)
159      SizeOfLargestEmptySubobject = EmptySize;
160  }
161
162  // Check the fields.
163  for (CXXRecordDecl::field_iterator I = Class->field_begin(),
164       E = Class->field_end(); I != E; ++I) {
165
166    const RecordType *RT =
167      Context.getBaseElementType(I->getType())->getAs<RecordType>();
168
169    // We only care about record types.
170    if (!RT)
171      continue;
172
173    CharUnits EmptySize;
174    const CXXRecordDecl *MemberDecl = cast<CXXRecordDecl>(RT->getDecl());
175    const ASTRecordLayout &Layout = Context.getASTRecordLayout(MemberDecl);
176    if (MemberDecl->isEmpty()) {
177      // If the class decl is empty, get its size.
178      EmptySize = Layout.getSize();
179    } else {
180      // Otherwise, we get the largest empty subobject for the decl.
181      EmptySize = Layout.getSizeOfLargestEmptySubobject();
182    }
183
184    if (EmptySize > SizeOfLargestEmptySubobject)
185      SizeOfLargestEmptySubobject = EmptySize;
186  }
187}
188
189bool
190EmptySubobjectMap::CanPlaceSubobjectAtOffset(const CXXRecordDecl *RD,
191                                             CharUnits Offset) const {
192  // We only need to check empty bases.
193  if (!RD->isEmpty())
194    return true;
195
196  EmptyClassOffsetsMapTy::const_iterator I = EmptyClassOffsets.find(Offset);
197  if (I == EmptyClassOffsets.end())
198    return true;
199
200  const ClassVectorTy& Classes = I->second;
201  if (std::find(Classes.begin(), Classes.end(), RD) == Classes.end())
202    return true;
203
204  // There is already an empty class of the same type at this offset.
205  return false;
206}
207
208void EmptySubobjectMap::AddSubobjectAtOffset(const CXXRecordDecl *RD,
209                                             CharUnits Offset) {
210  // We only care about empty bases.
211  if (!RD->isEmpty())
212    return;
213
214  // If we have empty structures inside an union, we can assign both
215  // the same offset. Just avoid pushing them twice in the list.
216  ClassVectorTy& Classes = EmptyClassOffsets[Offset];
217  if (std::find(Classes.begin(), Classes.end(), RD) != Classes.end())
218    return;
219
220  Classes.push_back(RD);
221
222  // Update the empty class offset.
223  if (Offset > MaxEmptyClassOffset)
224    MaxEmptyClassOffset = Offset;
225}
226
227bool
228EmptySubobjectMap::CanPlaceBaseSubobjectAtOffset(const BaseSubobjectInfo *Info,
229                                                 CharUnits Offset) {
230  // We don't have to keep looking past the maximum offset that's known to
231  // contain an empty class.
232  if (!AnyEmptySubobjectsBeyondOffset(Offset))
233    return true;
234
235  if (!CanPlaceSubobjectAtOffset(Info->Class, Offset))
236    return false;
237
238  // Traverse all non-virtual bases.
239  const ASTRecordLayout &Layout = Context.getASTRecordLayout(Info->Class);
240  for (unsigned I = 0, E = Info->Bases.size(); I != E; ++I) {
241    BaseSubobjectInfo* Base = Info->Bases[I];
242    if (Base->IsVirtual)
243      continue;
244
245    CharUnits BaseOffset = Offset + Layout.getBaseClassOffset(Base->Class);
246
247    if (!CanPlaceBaseSubobjectAtOffset(Base, BaseOffset))
248      return false;
249  }
250
251  if (Info->PrimaryVirtualBaseInfo) {
252    BaseSubobjectInfo *PrimaryVirtualBaseInfo = Info->PrimaryVirtualBaseInfo;
253
254    if (Info == PrimaryVirtualBaseInfo->Derived) {
255      if (!CanPlaceBaseSubobjectAtOffset(PrimaryVirtualBaseInfo, Offset))
256        return false;
257    }
258  }
259
260  // Traverse all member variables.
261  unsigned FieldNo = 0;
262  for (CXXRecordDecl::field_iterator I = Info->Class->field_begin(),
263       E = Info->Class->field_end(); I != E; ++I, ++FieldNo) {
264    if (I->isBitField())
265      continue;
266
267    CharUnits FieldOffset = Offset + getFieldOffset(Layout, FieldNo);
268    if (!CanPlaceFieldSubobjectAtOffset(*I, FieldOffset))
269      return false;
270  }
271
272  return true;
273}
274
275void EmptySubobjectMap::UpdateEmptyBaseSubobjects(const BaseSubobjectInfo *Info,
276                                                  CharUnits Offset,
277                                                  bool PlacingEmptyBase) {
278  if (!PlacingEmptyBase && Offset >= SizeOfLargestEmptySubobject) {
279    // We know that the only empty subobjects that can conflict with empty
280    // subobject of non-empty bases, are empty bases that can be placed at
281    // offset zero. Because of this, we only need to keep track of empty base
282    // subobjects with offsets less than the size of the largest empty
283    // subobject for our class.
284    return;
285  }
286
287  AddSubobjectAtOffset(Info->Class, Offset);
288
289  // Traverse all non-virtual bases.
290  const ASTRecordLayout &Layout = Context.getASTRecordLayout(Info->Class);
291  for (unsigned I = 0, E = Info->Bases.size(); I != E; ++I) {
292    BaseSubobjectInfo* Base = Info->Bases[I];
293    if (Base->IsVirtual)
294      continue;
295
296    CharUnits BaseOffset = Offset + Layout.getBaseClassOffset(Base->Class);
297    UpdateEmptyBaseSubobjects(Base, BaseOffset, PlacingEmptyBase);
298  }
299
300  if (Info->PrimaryVirtualBaseInfo) {
301    BaseSubobjectInfo *PrimaryVirtualBaseInfo = Info->PrimaryVirtualBaseInfo;
302
303    if (Info == PrimaryVirtualBaseInfo->Derived)
304      UpdateEmptyBaseSubobjects(PrimaryVirtualBaseInfo, Offset,
305                                PlacingEmptyBase);
306  }
307
308  // Traverse all member variables.
309  unsigned FieldNo = 0;
310  for (CXXRecordDecl::field_iterator I = Info->Class->field_begin(),
311       E = Info->Class->field_end(); I != E; ++I, ++FieldNo) {
312    if (I->isBitField())
313      continue;
314
315    CharUnits FieldOffset = Offset + getFieldOffset(Layout, FieldNo);
316    UpdateEmptyFieldSubobjects(*I, FieldOffset);
317  }
318}
319
320bool EmptySubobjectMap::CanPlaceBaseAtOffset(const BaseSubobjectInfo *Info,
321                                             CharUnits Offset) {
322  // If we know this class doesn't have any empty subobjects we don't need to
323  // bother checking.
324  if (SizeOfLargestEmptySubobject.isZero())
325    return true;
326
327  if (!CanPlaceBaseSubobjectAtOffset(Info, Offset))
328    return false;
329
330  // We are able to place the base at this offset. Make sure to update the
331  // empty base subobject map.
332  UpdateEmptyBaseSubobjects(Info, Offset, Info->Class->isEmpty());
333  return true;
334}
335
336bool
337EmptySubobjectMap::CanPlaceFieldSubobjectAtOffset(const CXXRecordDecl *RD,
338                                                  const CXXRecordDecl *Class,
339                                                  CharUnits Offset) const {
340  // We don't have to keep looking past the maximum offset that's known to
341  // contain an empty class.
342  if (!AnyEmptySubobjectsBeyondOffset(Offset))
343    return true;
344
345  if (!CanPlaceSubobjectAtOffset(RD, Offset))
346    return false;
347
348  const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
349
350  // Traverse all non-virtual bases.
351  for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
352       E = RD->bases_end(); I != E; ++I) {
353    if (I->isVirtual())
354      continue;
355
356    const CXXRecordDecl *BaseDecl =
357      cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
358
359    CharUnits BaseOffset = Offset + Layout.getBaseClassOffset(BaseDecl);
360    if (!CanPlaceFieldSubobjectAtOffset(BaseDecl, Class, BaseOffset))
361      return false;
362  }
363
364  if (RD == Class) {
365    // This is the most derived class, traverse virtual bases as well.
366    for (CXXRecordDecl::base_class_const_iterator I = RD->vbases_begin(),
367         E = RD->vbases_end(); I != E; ++I) {
368      const CXXRecordDecl *VBaseDecl =
369        cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
370
371      CharUnits VBaseOffset = Offset + Layout.getVBaseClassOffset(VBaseDecl);
372      if (!CanPlaceFieldSubobjectAtOffset(VBaseDecl, Class, VBaseOffset))
373        return false;
374    }
375  }
376
377  // Traverse all member variables.
378  unsigned FieldNo = 0;
379  for (CXXRecordDecl::field_iterator I = RD->field_begin(), E = RD->field_end();
380       I != E; ++I, ++FieldNo) {
381    if (I->isBitField())
382      continue;
383
384    CharUnits FieldOffset = Offset + getFieldOffset(Layout, FieldNo);
385
386    if (!CanPlaceFieldSubobjectAtOffset(*I, FieldOffset))
387      return false;
388  }
389
390  return true;
391}
392
393bool
394EmptySubobjectMap::CanPlaceFieldSubobjectAtOffset(const FieldDecl *FD,
395                                                  CharUnits Offset) const {
396  // We don't have to keep looking past the maximum offset that's known to
397  // contain an empty class.
398  if (!AnyEmptySubobjectsBeyondOffset(Offset))
399    return true;
400
401  QualType T = FD->getType();
402  if (const RecordType *RT = T->getAs<RecordType>()) {
403    const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
404    return CanPlaceFieldSubobjectAtOffset(RD, RD, Offset);
405  }
406
407  // If we have an array type we need to look at every element.
408  if (const ConstantArrayType *AT = Context.getAsConstantArrayType(T)) {
409    QualType ElemTy = Context.getBaseElementType(AT);
410    const RecordType *RT = ElemTy->getAs<RecordType>();
411    if (!RT)
412      return true;
413
414    const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
415    const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
416
417    uint64_t NumElements = Context.getConstantArrayElementCount(AT);
418    CharUnits ElementOffset = Offset;
419    for (uint64_t I = 0; I != NumElements; ++I) {
420      // We don't have to keep looking past the maximum offset that's known to
421      // contain an empty class.
422      if (!AnyEmptySubobjectsBeyondOffset(ElementOffset))
423        return true;
424
425      if (!CanPlaceFieldSubobjectAtOffset(RD, RD, ElementOffset))
426        return false;
427
428      ElementOffset += Layout.getSize();
429    }
430  }
431
432  return true;
433}
434
435bool
436EmptySubobjectMap::CanPlaceFieldAtOffset(const FieldDecl *FD,
437                                         CharUnits Offset) {
438  if (!CanPlaceFieldSubobjectAtOffset(FD, Offset))
439    return false;
440
441  // We are able to place the member variable at this offset.
442  // Make sure to update the empty base subobject map.
443  UpdateEmptyFieldSubobjects(FD, Offset);
444  return true;
445}
446
447void EmptySubobjectMap::UpdateEmptyFieldSubobjects(const CXXRecordDecl *RD,
448                                                   const CXXRecordDecl *Class,
449                                                   CharUnits Offset) {
450  // We know that the only empty subobjects that can conflict with empty
451  // field subobjects are subobjects of empty bases that can be placed at offset
452  // zero. Because of this, we only need to keep track of empty field
453  // subobjects with offsets less than the size of the largest empty
454  // subobject for our class.
455  if (Offset >= SizeOfLargestEmptySubobject)
456    return;
457
458  AddSubobjectAtOffset(RD, Offset);
459
460  const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
461
462  // Traverse all non-virtual bases.
463  for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
464       E = RD->bases_end(); I != E; ++I) {
465    if (I->isVirtual())
466      continue;
467
468    const CXXRecordDecl *BaseDecl =
469      cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
470
471    CharUnits BaseOffset = Offset + Layout.getBaseClassOffset(BaseDecl);
472    UpdateEmptyFieldSubobjects(BaseDecl, Class, BaseOffset);
473  }
474
475  if (RD == Class) {
476    // This is the most derived class, traverse virtual bases as well.
477    for (CXXRecordDecl::base_class_const_iterator I = RD->vbases_begin(),
478         E = RD->vbases_end(); I != E; ++I) {
479      const CXXRecordDecl *VBaseDecl =
480      cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
481
482      CharUnits VBaseOffset = Offset + Layout.getVBaseClassOffset(VBaseDecl);
483      UpdateEmptyFieldSubobjects(VBaseDecl, Class, VBaseOffset);
484    }
485  }
486
487  // Traverse all member variables.
488  unsigned FieldNo = 0;
489  for (CXXRecordDecl::field_iterator I = RD->field_begin(), E = RD->field_end();
490       I != E; ++I, ++FieldNo) {
491    if (I->isBitField())
492      continue;
493
494    CharUnits FieldOffset = Offset + getFieldOffset(Layout, FieldNo);
495
496    UpdateEmptyFieldSubobjects(*I, FieldOffset);
497  }
498}
499
500void EmptySubobjectMap::UpdateEmptyFieldSubobjects(const FieldDecl *FD,
501                                                   CharUnits Offset) {
502  QualType T = FD->getType();
503  if (const RecordType *RT = T->getAs<RecordType>()) {
504    const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
505    UpdateEmptyFieldSubobjects(RD, RD, Offset);
506    return;
507  }
508
509  // If we have an array type we need to update every element.
510  if (const ConstantArrayType *AT = Context.getAsConstantArrayType(T)) {
511    QualType ElemTy = Context.getBaseElementType(AT);
512    const RecordType *RT = ElemTy->getAs<RecordType>();
513    if (!RT)
514      return;
515
516    const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
517    const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
518
519    uint64_t NumElements = Context.getConstantArrayElementCount(AT);
520    CharUnits ElementOffset = Offset;
521
522    for (uint64_t I = 0; I != NumElements; ++I) {
523      // We know that the only empty subobjects that can conflict with empty
524      // field subobjects are subobjects of empty bases that can be placed at
525      // offset zero. Because of this, we only need to keep track of empty field
526      // subobjects with offsets less than the size of the largest empty
527      // subobject for our class.
528      if (ElementOffset >= SizeOfLargestEmptySubobject)
529        return;
530
531      UpdateEmptyFieldSubobjects(RD, RD, ElementOffset);
532      ElementOffset += Layout.getSize();
533    }
534  }
535}
536
537typedef llvm::SmallPtrSet<const CXXRecordDecl*, 4> ClassSetTy;
538
539class RecordLayoutBuilder {
540protected:
541  // FIXME: Remove this and make the appropriate fields public.
542  friend class clang::ASTContext;
543
544  const ASTContext &Context;
545
546  EmptySubobjectMap *EmptySubobjects;
547
548  /// Size - The current size of the record layout.
549  uint64_t Size;
550
551  /// Alignment - The current alignment of the record layout.
552  CharUnits Alignment;
553
554  /// \brief The alignment if attribute packed is not used.
555  CharUnits UnpackedAlignment;
556
557  SmallVector<uint64_t, 16> FieldOffsets;
558
559  /// \brief Whether the external AST source has provided a layout for this
560  /// record.
561  unsigned ExternalLayout : 1;
562
563  /// \brief Whether we need to infer alignment, even when we have an
564  /// externally-provided layout.
565  unsigned InferAlignment : 1;
566
567  /// Packed - Whether the record is packed or not.
568  unsigned Packed : 1;
569
570  unsigned IsUnion : 1;
571
572  unsigned IsMac68kAlign : 1;
573
574  unsigned IsMsStruct : 1;
575
576  /// UnfilledBitsInLastByte - If the last field laid out was a bitfield,
577  /// this contains the number of bits in the last byte that can be used for
578  /// an adjacent bitfield if necessary.
579  unsigned char UnfilledBitsInLastByte;
580
581  /// MaxFieldAlignment - The maximum allowed field alignment. This is set by
582  /// #pragma pack.
583  CharUnits MaxFieldAlignment;
584
585  /// DataSize - The data size of the record being laid out.
586  uint64_t DataSize;
587
588  CharUnits NonVirtualSize;
589  CharUnits NonVirtualAlignment;
590
591  FieldDecl *ZeroLengthBitfield;
592
593  /// PrimaryBase - the primary base class (if one exists) of the class
594  /// we're laying out.
595  const CXXRecordDecl *PrimaryBase;
596
597  /// PrimaryBaseIsVirtual - Whether the primary base of the class we're laying
598  /// out is virtual.
599  bool PrimaryBaseIsVirtual;
600
601  /// HasOwnVFPtr - Whether the class provides its own vtable/vftbl
602  /// pointer, as opposed to inheriting one from a primary base class.
603  bool HasOwnVFPtr;
604
605  /// VBPtrOffset - Virtual base table offset. Only for MS layout.
606  CharUnits VBPtrOffset;
607
608  typedef llvm::DenseMap<const CXXRecordDecl *, CharUnits> BaseOffsetsMapTy;
609
610  /// Bases - base classes and their offsets in the record.
611  BaseOffsetsMapTy Bases;
612
613  // VBases - virtual base classes and their offsets in the record.
614  ASTRecordLayout::VBaseOffsetsMapTy VBases;
615
616  /// IndirectPrimaryBases - Virtual base classes, direct or indirect, that are
617  /// primary base classes for some other direct or indirect base class.
618  CXXIndirectPrimaryBaseSet IndirectPrimaryBases;
619
620  /// FirstNearlyEmptyVBase - The first nearly empty virtual base class in
621  /// inheritance graph order. Used for determining the primary base class.
622  const CXXRecordDecl *FirstNearlyEmptyVBase;
623
624  /// VisitedVirtualBases - A set of all the visited virtual bases, used to
625  /// avoid visiting virtual bases more than once.
626  llvm::SmallPtrSet<const CXXRecordDecl *, 4> VisitedVirtualBases;
627
628  /// \brief Externally-provided size.
629  uint64_t ExternalSize;
630
631  /// \brief Externally-provided alignment.
632  uint64_t ExternalAlign;
633
634  /// \brief Externally-provided field offsets.
635  llvm::DenseMap<const FieldDecl *, uint64_t> ExternalFieldOffsets;
636
637  /// \brief Externally-provided direct, non-virtual base offsets.
638  llvm::DenseMap<const CXXRecordDecl *, CharUnits> ExternalBaseOffsets;
639
640  /// \brief Externally-provided virtual base offsets.
641  llvm::DenseMap<const CXXRecordDecl *, CharUnits> ExternalVirtualBaseOffsets;
642
643  RecordLayoutBuilder(const ASTContext &Context,
644                      EmptySubobjectMap *EmptySubobjects)
645    : Context(Context), EmptySubobjects(EmptySubobjects), Size(0),
646      Alignment(CharUnits::One()), UnpackedAlignment(CharUnits::One()),
647      ExternalLayout(false), InferAlignment(false),
648      Packed(false), IsUnion(false), IsMac68kAlign(false), IsMsStruct(false),
649      UnfilledBitsInLastByte(0), MaxFieldAlignment(CharUnits::Zero()),
650      DataSize(0), NonVirtualSize(CharUnits::Zero()),
651      NonVirtualAlignment(CharUnits::One()),
652      ZeroLengthBitfield(0), PrimaryBase(0),
653      PrimaryBaseIsVirtual(false),
654      HasOwnVFPtr(false),
655      VBPtrOffset(CharUnits::fromQuantity(-1)),
656      FirstNearlyEmptyVBase(0) { }
657
658  /// Reset this RecordLayoutBuilder to a fresh state, using the given
659  /// alignment as the initial alignment.  This is used for the
660  /// correct layout of vb-table pointers in MSVC.
661  void resetWithTargetAlignment(CharUnits TargetAlignment) {
662    const ASTContext &Context = this->Context;
663    EmptySubobjectMap *EmptySubobjects = this->EmptySubobjects;
664    this->~RecordLayoutBuilder();
665    new (this) RecordLayoutBuilder(Context, EmptySubobjects);
666    Alignment = UnpackedAlignment = TargetAlignment;
667  }
668
669  void Layout(const RecordDecl *D);
670  void Layout(const CXXRecordDecl *D);
671  void Layout(const ObjCInterfaceDecl *D);
672
673  void LayoutFields(const RecordDecl *D);
674  void LayoutField(const FieldDecl *D);
675  void LayoutWideBitField(uint64_t FieldSize, uint64_t TypeSize,
676                          bool FieldPacked, const FieldDecl *D);
677  void LayoutBitField(const FieldDecl *D);
678
679  bool isMicrosoftCXXABI() const {
680    return Context.getTargetInfo().getCXXABI() == CXXABI_Microsoft;
681  }
682
683  void MSLayoutVirtualBases(const CXXRecordDecl *RD);
684
685  /// BaseSubobjectInfoAllocator - Allocator for BaseSubobjectInfo objects.
686  llvm::SpecificBumpPtrAllocator<BaseSubobjectInfo> BaseSubobjectInfoAllocator;
687
688  typedef llvm::DenseMap<const CXXRecordDecl *, BaseSubobjectInfo *>
689    BaseSubobjectInfoMapTy;
690
691  /// VirtualBaseInfo - Map from all the (direct or indirect) virtual bases
692  /// of the class we're laying out to their base subobject info.
693  BaseSubobjectInfoMapTy VirtualBaseInfo;
694
695  /// NonVirtualBaseInfo - Map from all the direct non-virtual bases of the
696  /// class we're laying out to their base subobject info.
697  BaseSubobjectInfoMapTy NonVirtualBaseInfo;
698
699  /// ComputeBaseSubobjectInfo - Compute the base subobject information for the
700  /// bases of the given class.
701  void ComputeBaseSubobjectInfo(const CXXRecordDecl *RD);
702
703  /// ComputeBaseSubobjectInfo - Compute the base subobject information for a
704  /// single class and all of its base classes.
705  BaseSubobjectInfo *ComputeBaseSubobjectInfo(const CXXRecordDecl *RD,
706                                              bool IsVirtual,
707                                              BaseSubobjectInfo *Derived);
708
709  /// DeterminePrimaryBase - Determine the primary base of the given class.
710  void DeterminePrimaryBase(const CXXRecordDecl *RD);
711
712  void SelectPrimaryVBase(const CXXRecordDecl *RD);
713
714  void EnsureVTablePointerAlignment(CharUnits UnpackedBaseAlign);
715
716  /// LayoutNonVirtualBases - Determines the primary base class (if any) and
717  /// lays it out. Will then proceed to lay out all non-virtual base clasess.
718  void LayoutNonVirtualBases(const CXXRecordDecl *RD);
719
720  /// LayoutNonVirtualBase - Lays out a single non-virtual base.
721  void LayoutNonVirtualBase(const BaseSubobjectInfo *Base);
722
723  void AddPrimaryVirtualBaseOffsets(const BaseSubobjectInfo *Info,
724                                    CharUnits Offset);
725
726  bool needsVFTable(const CXXRecordDecl *RD) const;
727  bool hasNewVirtualFunction(const CXXRecordDecl *RD,
728                             bool IgnoreDestructor = false) const;
729  bool isPossiblePrimaryBase(const CXXRecordDecl *Base) const;
730
731  void computeVtordisps(const CXXRecordDecl *RD,
732                        ClassSetTy &VtordispVBases);
733
734  /// LayoutVirtualBases - Lays out all the virtual bases.
735  void LayoutVirtualBases(const CXXRecordDecl *RD,
736                          const CXXRecordDecl *MostDerivedClass);
737
738  /// LayoutVirtualBase - Lays out a single virtual base.
739  void LayoutVirtualBase(const BaseSubobjectInfo *Base,
740                         bool IsVtordispNeed = false);
741
742  /// LayoutBase - Will lay out a base and return the offset where it was
743  /// placed, in chars.
744  CharUnits LayoutBase(const BaseSubobjectInfo *Base);
745
746  /// InitializeLayout - Initialize record layout for the given record decl.
747  void InitializeLayout(const Decl *D);
748
749  /// FinishLayout - Finalize record layout. Adjust record size based on the
750  /// alignment.
751  void FinishLayout(const NamedDecl *D);
752
753  void UpdateAlignment(CharUnits NewAlignment, CharUnits UnpackedNewAlignment);
754  void UpdateAlignment(CharUnits NewAlignment) {
755    UpdateAlignment(NewAlignment, NewAlignment);
756  }
757
758  /// \brief Retrieve the externally-supplied field offset for the given
759  /// field.
760  ///
761  /// \param Field The field whose offset is being queried.
762  /// \param ComputedOffset The offset that we've computed for this field.
763  uint64_t updateExternalFieldOffset(const FieldDecl *Field,
764                                     uint64_t ComputedOffset);
765
766  void CheckFieldPadding(uint64_t Offset, uint64_t UnpaddedOffset,
767                          uint64_t UnpackedOffset, unsigned UnpackedAlign,
768                          bool isPacked, const FieldDecl *D);
769
770  DiagnosticBuilder Diag(SourceLocation Loc, unsigned DiagID);
771
772  CharUnits getSize() const {
773    assert(Size % Context.getCharWidth() == 0);
774    return Context.toCharUnitsFromBits(Size);
775  }
776  uint64_t getSizeInBits() const { return Size; }
777
778  void setSize(CharUnits NewSize) { Size = Context.toBits(NewSize); }
779  void setSize(uint64_t NewSize) { Size = NewSize; }
780
781  CharUnits getAligment() const { return Alignment; }
782
783  CharUnits getDataSize() const {
784    assert(DataSize % Context.getCharWidth() == 0);
785    return Context.toCharUnitsFromBits(DataSize);
786  }
787  uint64_t getDataSizeInBits() const { return DataSize; }
788
789  void setDataSize(CharUnits NewSize) { DataSize = Context.toBits(NewSize); }
790  void setDataSize(uint64_t NewSize) { DataSize = NewSize; }
791
792  RecordLayoutBuilder(const RecordLayoutBuilder&);   // DO NOT IMPLEMENT
793  void operator=(const RecordLayoutBuilder&); // DO NOT IMPLEMENT
794public:
795  static const CXXMethodDecl *ComputeKeyFunction(const CXXRecordDecl *RD);
796};
797} // end anonymous namespace
798
799void
800RecordLayoutBuilder::SelectPrimaryVBase(const CXXRecordDecl *RD) {
801  for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
802         E = RD->bases_end(); I != E; ++I) {
803    assert(!I->getType()->isDependentType() &&
804           "Cannot layout class with dependent bases.");
805
806    const CXXRecordDecl *Base =
807      cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
808
809    // Check if this is a nearly empty virtual base.
810    if (I->isVirtual() && Context.isNearlyEmpty(Base)) {
811      // If it's not an indirect primary base, then we've found our primary
812      // base.
813      if (!IndirectPrimaryBases.count(Base)) {
814        PrimaryBase = Base;
815        PrimaryBaseIsVirtual = true;
816        return;
817      }
818
819      // Is this the first nearly empty virtual base?
820      if (!FirstNearlyEmptyVBase)
821        FirstNearlyEmptyVBase = Base;
822    }
823
824    SelectPrimaryVBase(Base);
825    if (PrimaryBase)
826      return;
827  }
828}
829
830/// DeterminePrimaryBase - Determine the primary base of the given class.
831void RecordLayoutBuilder::DeterminePrimaryBase(const CXXRecordDecl *RD) {
832  // If the class isn't dynamic, it won't have a primary base.
833  if (!RD->isDynamicClass())
834    return;
835
836  // Compute all the primary virtual bases for all of our direct and
837  // indirect bases, and record all their primary virtual base classes.
838  RD->getIndirectPrimaryBases(IndirectPrimaryBases);
839
840  // If the record has a dynamic base class, attempt to choose a primary base
841  // class. It is the first (in direct base class order) non-virtual dynamic
842  // base class, if one exists.
843  for (CXXRecordDecl::base_class_const_iterator i = RD->bases_begin(),
844         e = RD->bases_end(); i != e; ++i) {
845    // Ignore virtual bases.
846    if (i->isVirtual())
847      continue;
848
849    const CXXRecordDecl *Base =
850      cast<CXXRecordDecl>(i->getType()->getAs<RecordType>()->getDecl());
851
852    if (isPossiblePrimaryBase(Base)) {
853      // We found it.
854      PrimaryBase = Base;
855      PrimaryBaseIsVirtual = false;
856      return;
857    }
858  }
859
860  // The Microsoft ABI doesn't have primary virtual bases.
861  if (isMicrosoftCXXABI()) {
862    assert(!PrimaryBase && "Should not get here with a primary base!");
863    return;
864  }
865
866  // Under the Itanium ABI, if there is no non-virtual primary base class,
867  // try to compute the primary virtual base.  The primary virtual base is
868  // the first nearly empty virtual base that is not an indirect primary
869  // virtual base class, if one exists.
870  if (RD->getNumVBases() != 0) {
871    SelectPrimaryVBase(RD);
872    if (PrimaryBase)
873      return;
874  }
875
876  // Otherwise, it is the first indirect primary base class, if one exists.
877  if (FirstNearlyEmptyVBase) {
878    PrimaryBase = FirstNearlyEmptyVBase;
879    PrimaryBaseIsVirtual = true;
880    return;
881  }
882
883  assert(!PrimaryBase && "Should not get here with a primary base!");
884}
885
886BaseSubobjectInfo *
887RecordLayoutBuilder::ComputeBaseSubobjectInfo(const CXXRecordDecl *RD,
888                                              bool IsVirtual,
889                                              BaseSubobjectInfo *Derived) {
890  BaseSubobjectInfo *Info;
891
892  if (IsVirtual) {
893    // Check if we already have info about this virtual base.
894    BaseSubobjectInfo *&InfoSlot = VirtualBaseInfo[RD];
895    if (InfoSlot) {
896      assert(InfoSlot->Class == RD && "Wrong class for virtual base info!");
897      return InfoSlot;
898    }
899
900    // We don't, create it.
901    InfoSlot = new (BaseSubobjectInfoAllocator.Allocate()) BaseSubobjectInfo;
902    Info = InfoSlot;
903  } else {
904    Info = new (BaseSubobjectInfoAllocator.Allocate()) BaseSubobjectInfo;
905  }
906
907  Info->Class = RD;
908  Info->IsVirtual = IsVirtual;
909  Info->Derived = 0;
910  Info->PrimaryVirtualBaseInfo = 0;
911
912  const CXXRecordDecl *PrimaryVirtualBase = 0;
913  BaseSubobjectInfo *PrimaryVirtualBaseInfo = 0;
914
915  // Check if this base has a primary virtual base.
916  if (RD->getNumVBases()) {
917    const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
918    if (Layout.isPrimaryBaseVirtual()) {
919      // This base does have a primary virtual base.
920      PrimaryVirtualBase = Layout.getPrimaryBase();
921      assert(PrimaryVirtualBase && "Didn't have a primary virtual base!");
922
923      // Now check if we have base subobject info about this primary base.
924      PrimaryVirtualBaseInfo = VirtualBaseInfo.lookup(PrimaryVirtualBase);
925
926      if (PrimaryVirtualBaseInfo) {
927        if (PrimaryVirtualBaseInfo->Derived) {
928          // We did have info about this primary base, and it turns out that it
929          // has already been claimed as a primary virtual base for another
930          // base.
931          PrimaryVirtualBase = 0;
932        } else {
933          // We can claim this base as our primary base.
934          Info->PrimaryVirtualBaseInfo = PrimaryVirtualBaseInfo;
935          PrimaryVirtualBaseInfo->Derived = Info;
936        }
937      }
938    }
939  }
940
941  // Now go through all direct bases.
942  for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
943       E = RD->bases_end(); I != E; ++I) {
944    bool IsVirtual = I->isVirtual();
945
946    const CXXRecordDecl *BaseDecl =
947      cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
948
949    Info->Bases.push_back(ComputeBaseSubobjectInfo(BaseDecl, IsVirtual, Info));
950  }
951
952  if (PrimaryVirtualBase && !PrimaryVirtualBaseInfo) {
953    // Traversing the bases must have created the base info for our primary
954    // virtual base.
955    PrimaryVirtualBaseInfo = VirtualBaseInfo.lookup(PrimaryVirtualBase);
956    assert(PrimaryVirtualBaseInfo &&
957           "Did not create a primary virtual base!");
958
959    // Claim the primary virtual base as our primary virtual base.
960    Info->PrimaryVirtualBaseInfo = PrimaryVirtualBaseInfo;
961    PrimaryVirtualBaseInfo->Derived = Info;
962  }
963
964  return Info;
965}
966
967void RecordLayoutBuilder::ComputeBaseSubobjectInfo(const CXXRecordDecl *RD) {
968  for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
969       E = RD->bases_end(); I != E; ++I) {
970    bool IsVirtual = I->isVirtual();
971
972    const CXXRecordDecl *BaseDecl =
973      cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
974
975    // Compute the base subobject info for this base.
976    BaseSubobjectInfo *Info = ComputeBaseSubobjectInfo(BaseDecl, IsVirtual, 0);
977
978    if (IsVirtual) {
979      // ComputeBaseInfo has already added this base for us.
980      assert(VirtualBaseInfo.count(BaseDecl) &&
981             "Did not add virtual base!");
982    } else {
983      // Add the base info to the map of non-virtual bases.
984      assert(!NonVirtualBaseInfo.count(BaseDecl) &&
985             "Non-virtual base already exists!");
986      NonVirtualBaseInfo.insert(std::make_pair(BaseDecl, Info));
987    }
988  }
989}
990
991void
992RecordLayoutBuilder::EnsureVTablePointerAlignment(CharUnits UnpackedBaseAlign) {
993  CharUnits BaseAlign = (Packed) ? CharUnits::One() : UnpackedBaseAlign;
994
995  // The maximum field alignment overrides base align.
996  if (!MaxFieldAlignment.isZero()) {
997    BaseAlign = std::min(BaseAlign, MaxFieldAlignment);
998    UnpackedBaseAlign = std::min(UnpackedBaseAlign, MaxFieldAlignment);
999  }
1000
1001  // Round up the current record size to pointer alignment.
1002  setSize(getSize().RoundUpToAlignment(BaseAlign));
1003  setDataSize(getSize());
1004
1005  // Update the alignment.
1006  UpdateAlignment(BaseAlign, UnpackedBaseAlign);
1007}
1008
1009void
1010RecordLayoutBuilder::LayoutNonVirtualBases(const CXXRecordDecl *RD) {
1011  // Then, determine the primary base class.
1012  DeterminePrimaryBase(RD);
1013
1014  // Compute base subobject info.
1015  ComputeBaseSubobjectInfo(RD);
1016
1017  // If we have a primary base class, lay it out.
1018  if (PrimaryBase) {
1019    if (PrimaryBaseIsVirtual) {
1020      // If the primary virtual base was a primary virtual base of some other
1021      // base class we'll have to steal it.
1022      BaseSubobjectInfo *PrimaryBaseInfo = VirtualBaseInfo.lookup(PrimaryBase);
1023      PrimaryBaseInfo->Derived = 0;
1024
1025      // We have a virtual primary base, insert it as an indirect primary base.
1026      IndirectPrimaryBases.insert(PrimaryBase);
1027
1028      assert(!VisitedVirtualBases.count(PrimaryBase) &&
1029             "vbase already visited!");
1030      VisitedVirtualBases.insert(PrimaryBase);
1031
1032      LayoutVirtualBase(PrimaryBaseInfo);
1033    } else {
1034      BaseSubobjectInfo *PrimaryBaseInfo =
1035        NonVirtualBaseInfo.lookup(PrimaryBase);
1036      assert(PrimaryBaseInfo &&
1037             "Did not find base info for non-virtual primary base!");
1038
1039      LayoutNonVirtualBase(PrimaryBaseInfo);
1040    }
1041
1042  // If this class needs a vtable/vf-table and didn't get one from a
1043  // primary base, add it in now.
1044  } else if (needsVFTable(RD)) {
1045    assert(DataSize == 0 && "Vtable pointer must be at offset zero!");
1046    CharUnits PtrWidth =
1047      Context.toCharUnitsFromBits(Context.getTargetInfo().getPointerWidth(0));
1048    CharUnits PtrAlign =
1049      Context.toCharUnitsFromBits(Context.getTargetInfo().getPointerAlign(0));
1050    EnsureVTablePointerAlignment(PtrAlign);
1051    HasOwnVFPtr = true;
1052    setSize(getSize() + PtrWidth);
1053    setDataSize(getSize());
1054  }
1055
1056  bool HasDirectVirtualBases = false;
1057  bool HasNonVirtualBaseWithVBTable = false;
1058
1059  // Now lay out the non-virtual bases.
1060  for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
1061         E = RD->bases_end(); I != E; ++I) {
1062
1063    // Ignore virtual bases, but remember that we saw one.
1064    if (I->isVirtual()) {
1065      HasDirectVirtualBases = true;
1066      continue;
1067    }
1068
1069    const CXXRecordDecl *BaseDecl =
1070      cast<CXXRecordDecl>(I->getType()->castAs<RecordType>()->getDecl());
1071
1072    // Remember if this base has virtual bases itself.
1073    if (BaseDecl->getNumVBases())
1074      HasNonVirtualBaseWithVBTable = true;
1075
1076    // Skip the primary base, because we've already laid it out.  The
1077    // !PrimaryBaseIsVirtual check is required because we might have a
1078    // non-virtual base of the same type as a primary virtual base.
1079    if (BaseDecl == PrimaryBase && !PrimaryBaseIsVirtual)
1080      continue;
1081
1082    // Lay out the base.
1083    BaseSubobjectInfo *BaseInfo = NonVirtualBaseInfo.lookup(BaseDecl);
1084    assert(BaseInfo && "Did not find base info for non-virtual base!");
1085
1086    LayoutNonVirtualBase(BaseInfo);
1087  }
1088
1089  // In the MS ABI, add the vb-table pointer if we need one, which is
1090  // whenever we have a virtual base and we can't re-use a vb-table
1091  // pointer from a non-virtual base.
1092  if (isMicrosoftCXXABI() &&
1093      HasDirectVirtualBases && !HasNonVirtualBaseWithVBTable) {
1094    CharUnits PtrWidth =
1095      Context.toCharUnitsFromBits(Context.getTargetInfo().getPointerWidth(0));
1096    CharUnits PtrAlign =
1097      Context.toCharUnitsFromBits(Context.getTargetInfo().getPointerAlign(0));
1098
1099    // MSVC potentially over-aligns the vb-table pointer by giving it
1100    // the max alignment of all the non-virtual objects in the class.
1101    // This is completely unnecessary, but we're not here to pass
1102    // judgment.
1103    //
1104    // Note that we've only laid out the non-virtual bases, so on the
1105    // first pass Alignment won't be set correctly here, but if the
1106    // vb-table doesn't end up aligned correctly we'll come through
1107    // and redo the layout from scratch with the right alignment.
1108    //
1109    // TODO: Instead of doing this, just lay out the fields as if the
1110    // vb-table were at offset zero, then retroactively bump the field
1111    // offsets up.
1112    PtrAlign = std::max(PtrAlign, Alignment);
1113
1114    EnsureVTablePointerAlignment(PtrAlign);
1115    VBPtrOffset = getSize();
1116    setSize(getSize() + PtrWidth);
1117    setDataSize(getSize());
1118  }
1119}
1120
1121void RecordLayoutBuilder::LayoutNonVirtualBase(const BaseSubobjectInfo *Base) {
1122  // Layout the base.
1123  CharUnits Offset = LayoutBase(Base);
1124
1125  // Add its base class offset.
1126  assert(!Bases.count(Base->Class) && "base offset already exists!");
1127  Bases.insert(std::make_pair(Base->Class, Offset));
1128
1129  AddPrimaryVirtualBaseOffsets(Base, Offset);
1130}
1131
1132void
1133RecordLayoutBuilder::AddPrimaryVirtualBaseOffsets(const BaseSubobjectInfo *Info,
1134                                                  CharUnits Offset) {
1135  // This base isn't interesting, it has no virtual bases.
1136  if (!Info->Class->getNumVBases())
1137    return;
1138
1139  // First, check if we have a virtual primary base to add offsets for.
1140  if (Info->PrimaryVirtualBaseInfo) {
1141    assert(Info->PrimaryVirtualBaseInfo->IsVirtual &&
1142           "Primary virtual base is not virtual!");
1143    if (Info->PrimaryVirtualBaseInfo->Derived == Info) {
1144      // Add the offset.
1145      assert(!VBases.count(Info->PrimaryVirtualBaseInfo->Class) &&
1146             "primary vbase offset already exists!");
1147      VBases.insert(std::make_pair(Info->PrimaryVirtualBaseInfo->Class,
1148                                   ASTRecordLayout::VBaseInfo(Offset, false)));
1149
1150      // Traverse the primary virtual base.
1151      AddPrimaryVirtualBaseOffsets(Info->PrimaryVirtualBaseInfo, Offset);
1152    }
1153  }
1154
1155  // Now go through all direct non-virtual bases.
1156  const ASTRecordLayout &Layout = Context.getASTRecordLayout(Info->Class);
1157  for (unsigned I = 0, E = Info->Bases.size(); I != E; ++I) {
1158    const BaseSubobjectInfo *Base = Info->Bases[I];
1159    if (Base->IsVirtual)
1160      continue;
1161
1162    CharUnits BaseOffset = Offset + Layout.getBaseClassOffset(Base->Class);
1163    AddPrimaryVirtualBaseOffsets(Base, BaseOffset);
1164  }
1165}
1166
1167/// needsVFTable - Return true if this class needs a vtable or vf-table
1168/// when laid out as a base class.  These are treated the same because
1169/// they're both always laid out at offset zero.
1170///
1171/// This function assumes that the class has no primary base.
1172bool RecordLayoutBuilder::needsVFTable(const CXXRecordDecl *RD) const {
1173  assert(!PrimaryBase);
1174
1175  // In the Itanium ABI, every dynamic class needs a vtable: even if
1176  // this class has no virtual functions as a base class (i.e. it's
1177  // non-polymorphic or only has virtual functions from virtual
1178  // bases),x it still needs a vtable to locate its virtual bases.
1179  if (!isMicrosoftCXXABI())
1180    return RD->isDynamicClass();
1181
1182  // In the MS ABI, we need a vfptr if the class has virtual functions
1183  // other than those declared by its virtual bases.  The AST doesn't
1184  // tell us that directly, and checking manually for virtual
1185  // functions that aren't overrides is expensive, but there are
1186  // some important shortcuts:
1187
1188  //  - Non-polymorphic classes have no virtual functions at all.
1189  if (!RD->isPolymorphic()) return false;
1190
1191  //  - Polymorphic classes with no virtual bases must either declare
1192  //    virtual functions directly or inherit them, but in the latter
1193  //    case we would have a primary base.
1194  if (RD->getNumVBases() == 0) return true;
1195
1196  return hasNewVirtualFunction(RD);
1197}
1198
1199/// Does the given class inherit non-virtually from any of the classes
1200/// in the given set?
1201static bool hasNonVirtualBaseInSet(const CXXRecordDecl *RD,
1202                                   const ClassSetTy &set) {
1203  for (CXXRecordDecl::base_class_const_iterator
1204         I = RD->bases_begin(), E = RD->bases_end(); I != E; ++I) {
1205    // Ignore virtual links.
1206    if (I->isVirtual()) continue;
1207
1208    // Check whether the set contains the base.
1209    const CXXRecordDecl *base = I->getType()->getAsCXXRecordDecl();
1210    if (set.count(base))
1211      return true;
1212
1213    // Otherwise, recurse and propagate.
1214    if (hasNonVirtualBaseInSet(base, set))
1215      return true;
1216  }
1217
1218  return false;
1219}
1220
1221/// Does the given method (B::foo()) already override a method (A::foo())
1222/// such that A requires a vtordisp in B?  If so, we don't need to add a
1223/// new vtordisp for B in a yet-more-derived class C providing C::foo().
1224static bool overridesMethodRequiringVtorDisp(const ASTContext &Context,
1225                                             const CXXMethodDecl *M) {
1226  CXXMethodDecl::method_iterator
1227    I = M->begin_overridden_methods(), E = M->end_overridden_methods();
1228  if (I == E) return false;
1229
1230  const ASTRecordLayout::VBaseOffsetsMapTy &offsets =
1231    Context.getASTRecordLayout(M->getParent()).getVBaseOffsetsMap();
1232  do {
1233    const CXXMethodDecl *overridden = *I;
1234
1235    // If the overridden method's class isn't recognized as a virtual
1236    // base in the derived class, ignore it.
1237    ASTRecordLayout::VBaseOffsetsMapTy::const_iterator
1238      it = offsets.find(overridden->getParent());
1239    if (it == offsets.end()) continue;
1240
1241    // Otherwise, check if the overridden method's class needs a vtordisp.
1242    if (it->second.hasVtorDisp()) return true;
1243
1244  } while (++I != E);
1245  return false;
1246}
1247
1248/// In the Microsoft ABI, decide which of the virtual bases require a
1249/// vtordisp field.
1250void RecordLayoutBuilder::computeVtordisps(const CXXRecordDecl *RD,
1251                                           ClassSetTy &vtordispVBases) {
1252  // Bail out if we have no virtual bases.
1253  assert(RD->getNumVBases());
1254
1255  // Build up the set of virtual bases that we haven't decided yet.
1256  ClassSetTy undecidedVBases;
1257  for (CXXRecordDecl::base_class_const_iterator
1258         I = RD->vbases_begin(), E = RD->vbases_end(); I != E; ++I) {
1259    const CXXRecordDecl *vbase = I->getType()->getAsCXXRecordDecl();
1260    undecidedVBases.insert(vbase);
1261  }
1262  assert(!undecidedVBases.empty());
1263
1264  // A virtual base requires a vtordisp field in a derived class if it
1265  // requires a vtordisp field in a base class.  Walk all the direct
1266  // bases and collect this information.
1267  for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
1268       E = RD->bases_end(); I != E; ++I) {
1269    const CXXRecordDecl *base = I->getType()->getAsCXXRecordDecl();
1270    const ASTRecordLayout &baseLayout = Context.getASTRecordLayout(base);
1271
1272    // Iterate over the set of virtual bases provided by this class.
1273    for (ASTRecordLayout::VBaseOffsetsMapTy::const_iterator
1274           VI = baseLayout.getVBaseOffsetsMap().begin(),
1275           VE = baseLayout.getVBaseOffsetsMap().end(); VI != VE; ++VI) {
1276      // If it doesn't need a vtordisp in this base, ignore it.
1277      if (!VI->second.hasVtorDisp()) continue;
1278
1279      // If we've already seen it and decided it needs a vtordisp, ignore it.
1280      if (!undecidedVBases.erase(VI->first))
1281        continue;
1282
1283      // Add it.
1284      vtordispVBases.insert(VI->first);
1285
1286      // Quit as soon as we've decided everything.
1287      if (undecidedVBases.empty())
1288        return;
1289    }
1290  }
1291
1292  // Okay, we have virtual bases that we haven't yet decided about.  A
1293  // virtual base requires a vtordisp if any the non-destructor
1294  // virtual methods declared in this class directly override a method
1295  // provided by that virtual base.  (If so, we need to emit a thunk
1296  // for that method, to be used in the construction vftable, which
1297  // applies an additional 'vtordisp' this-adjustment.)
1298
1299  // Collect the set of bases directly overridden by any method in this class.
1300  // It's possible that some of these classes won't be virtual bases, or won't be
1301  // provided by virtual bases, or won't be virtual bases in the overridden
1302  // instance but are virtual bases elsewhere.  Only the last matters for what
1303  // we're doing, and we can ignore those:  if we don't directly override
1304  // a method provided by a virtual copy of a base class, but we do directly
1305  // override a method provided by a non-virtual copy of that base class,
1306  // then we must indirectly override the method provided by the virtual base,
1307  // and so we should already have collected it in the loop above.
1308  ClassSetTy overriddenBases;
1309  for (CXXRecordDecl::method_iterator
1310         M = RD->method_begin(), E = RD->method_end(); M != E; ++M) {
1311    // Ignore non-virtual methods and destructors.
1312    if (isa<CXXDestructorDecl>(*M) || !M->isVirtual())
1313      continue;
1314
1315    for (CXXMethodDecl::method_iterator I = M->begin_overridden_methods(),
1316          E = M->end_overridden_methods(); I != E; ++I) {
1317      const CXXMethodDecl *overriddenMethod = (*I);
1318
1319      // Ignore methods that override methods from vbases that require
1320      // require vtordisps.
1321      if (overridesMethodRequiringVtorDisp(Context, overriddenMethod))
1322        continue;
1323
1324      // As an optimization, check immediately whether we're overriding
1325      // something from the undecided set.
1326      const CXXRecordDecl *overriddenBase = overriddenMethod->getParent();
1327      if (undecidedVBases.erase(overriddenBase)) {
1328        vtordispVBases.insert(overriddenBase);
1329        if (undecidedVBases.empty()) return;
1330
1331        // We can't 'continue;' here because one of our undecided
1332        // vbases might non-virtually inherit from this base.
1333        // Consider:
1334        //   struct A { virtual void foo(); };
1335        //   struct B : A {};
1336        //   struct C : virtual A, virtual B { virtual void foo(); };
1337        // We need a vtordisp for B here.
1338      }
1339
1340      // Otherwise, just collect it.
1341      overriddenBases.insert(overriddenBase);
1342    }
1343  }
1344
1345  // Walk the undecided v-bases and check whether they (non-virtually)
1346  // provide any of the overridden bases.  We don't need to consider
1347  // virtual links because the vtordisp inheres to the layout
1348  // subobject containing the base.
1349  for (ClassSetTy::const_iterator
1350         I = undecidedVBases.begin(), E = undecidedVBases.end(); I != E; ++I) {
1351    if (hasNonVirtualBaseInSet(*I, overriddenBases))
1352      vtordispVBases.insert(*I);
1353  }
1354}
1355
1356/// hasNewVirtualFunction - Does the given polymorphic class declare a
1357/// virtual function that does not override a method from any of its
1358/// base classes?
1359bool
1360RecordLayoutBuilder::hasNewVirtualFunction(const CXXRecordDecl *RD,
1361                                           bool IgnoreDestructor) const {
1362  if (!RD->getNumBases())
1363    return true;
1364
1365  for (CXXRecordDecl::method_iterator method = RD->method_begin();
1366       method != RD->method_end();
1367       ++method) {
1368    if (method->isVirtual() && !method->size_overridden_methods() &&
1369        !(IgnoreDestructor && method->getKind() == Decl::CXXDestructor)) {
1370      return true;
1371    }
1372  }
1373  return false;
1374}
1375
1376/// isPossiblePrimaryBase - Is the given base class an acceptable
1377/// primary base class?
1378bool
1379RecordLayoutBuilder::isPossiblePrimaryBase(const CXXRecordDecl *base) const {
1380  // In the Itanium ABI, a class can be a primary base class if it has
1381  // a vtable for any reason.
1382  if (!isMicrosoftCXXABI())
1383    return base->isDynamicClass();
1384
1385  // In the MS ABI, a class can only be a primary base class if it
1386  // provides a vf-table at a static offset.  That means it has to be
1387  // non-virtual base.  The existence of a separate vb-table means
1388  // that it's possible to get virtual functions only from a virtual
1389  // base, which we have to guard against.
1390
1391  // First off, it has to have virtual functions.
1392  if (!base->isPolymorphic()) return false;
1393
1394  // If it has no virtual bases, then the vfptr must be at a static offset.
1395  if (!base->getNumVBases()) return true;
1396
1397  // Otherwise, the necessary information is cached in the layout.
1398  const ASTRecordLayout &layout = Context.getASTRecordLayout(base);
1399
1400  // If the base has its own vfptr, it can be a primary base.
1401  if (layout.hasOwnVFPtr()) return true;
1402
1403  // If the base has a primary base class, then it can be a primary base.
1404  if (layout.getPrimaryBase()) return true;
1405
1406  // Otherwise it can't.
1407  return false;
1408}
1409
1410void
1411RecordLayoutBuilder::LayoutVirtualBases(const CXXRecordDecl *RD,
1412                                        const CXXRecordDecl *MostDerivedClass) {
1413  const CXXRecordDecl *PrimaryBase;
1414  bool PrimaryBaseIsVirtual;
1415
1416  if (MostDerivedClass == RD) {
1417    PrimaryBase = this->PrimaryBase;
1418    PrimaryBaseIsVirtual = this->PrimaryBaseIsVirtual;
1419  } else {
1420    const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
1421    PrimaryBase = Layout.getPrimaryBase();
1422    PrimaryBaseIsVirtual = Layout.isPrimaryBaseVirtual();
1423  }
1424
1425  for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
1426         E = RD->bases_end(); I != E; ++I) {
1427    assert(!I->getType()->isDependentType() &&
1428           "Cannot layout class with dependent bases.");
1429
1430    const CXXRecordDecl *BaseDecl =
1431      cast<CXXRecordDecl>(I->getType()->castAs<RecordType>()->getDecl());
1432
1433    if (I->isVirtual()) {
1434      if (PrimaryBase != BaseDecl || !PrimaryBaseIsVirtual) {
1435        bool IndirectPrimaryBase = IndirectPrimaryBases.count(BaseDecl);
1436
1437        // Only lay out the virtual base if it's not an indirect primary base.
1438        if (!IndirectPrimaryBase) {
1439          // Only visit virtual bases once.
1440          if (!VisitedVirtualBases.insert(BaseDecl))
1441            continue;
1442
1443          const BaseSubobjectInfo *BaseInfo = VirtualBaseInfo.lookup(BaseDecl);
1444          assert(BaseInfo && "Did not find virtual base info!");
1445          LayoutVirtualBase(BaseInfo);
1446        }
1447      }
1448    }
1449
1450    if (!BaseDecl->getNumVBases()) {
1451      // This base isn't interesting since it doesn't have any virtual bases.
1452      continue;
1453    }
1454
1455    LayoutVirtualBases(BaseDecl, MostDerivedClass);
1456  }
1457}
1458
1459void RecordLayoutBuilder::MSLayoutVirtualBases(const CXXRecordDecl *RD) {
1460  if (!RD->getNumVBases())
1461    return;
1462
1463  ClassSetTy VtordispVBases;
1464  computeVtordisps(RD, VtordispVBases);
1465
1466  // This is substantially simplified because there are no virtual
1467  // primary bases.
1468  for (CXXRecordDecl::base_class_const_iterator I = RD->vbases_begin(),
1469       E = RD->vbases_end(); I != E; ++I) {
1470    const CXXRecordDecl *BaseDecl = I->getType()->getAsCXXRecordDecl();
1471    const BaseSubobjectInfo *BaseInfo = VirtualBaseInfo.lookup(BaseDecl);
1472    assert(BaseInfo && "Did not find virtual base info!");
1473
1474    // If this base requires a vtordisp, add enough space for an int field.
1475    // This is apparently always 32-bits, even on x64.
1476    bool vtordispNeeded = false;
1477    if (VtordispVBases.count(BaseDecl)) {
1478      CharUnits IntSize =
1479        CharUnits::fromQuantity(Context.getTargetInfo().getIntWidth() / 8);
1480
1481      setSize(getSize() + IntSize);
1482      setDataSize(getSize());
1483      vtordispNeeded = true;
1484    }
1485
1486    LayoutVirtualBase(BaseInfo, vtordispNeeded);
1487  }
1488}
1489
1490void RecordLayoutBuilder::LayoutVirtualBase(const BaseSubobjectInfo *Base,
1491                                            bool IsVtordispNeed) {
1492  assert(!Base->Derived && "Trying to lay out a primary virtual base!");
1493
1494  // Layout the base.
1495  CharUnits Offset = LayoutBase(Base);
1496
1497  // Add its base class offset.
1498  assert(!VBases.count(Base->Class) && "vbase offset already exists!");
1499  VBases.insert(std::make_pair(Base->Class,
1500                       ASTRecordLayout::VBaseInfo(Offset, IsVtordispNeed)));
1501
1502  if (!isMicrosoftCXXABI())
1503    AddPrimaryVirtualBaseOffsets(Base, Offset);
1504}
1505
1506CharUnits RecordLayoutBuilder::LayoutBase(const BaseSubobjectInfo *Base) {
1507  const ASTRecordLayout &Layout = Context.getASTRecordLayout(Base->Class);
1508
1509
1510  CharUnits Offset;
1511
1512  // Query the external layout to see if it provides an offset.
1513  bool HasExternalLayout = false;
1514  if (ExternalLayout) {
1515    llvm::DenseMap<const CXXRecordDecl *, CharUnits>::iterator Known;
1516    if (Base->IsVirtual) {
1517      Known = ExternalVirtualBaseOffsets.find(Base->Class);
1518      if (Known != ExternalVirtualBaseOffsets.end()) {
1519        Offset = Known->second;
1520        HasExternalLayout = true;
1521      }
1522    } else {
1523      Known = ExternalBaseOffsets.find(Base->Class);
1524      if (Known != ExternalBaseOffsets.end()) {
1525        Offset = Known->second;
1526        HasExternalLayout = true;
1527      }
1528    }
1529  }
1530
1531  // If we have an empty base class, try to place it at offset 0.
1532  if (Base->Class->isEmpty() &&
1533      (!HasExternalLayout || Offset == CharUnits::Zero()) &&
1534      EmptySubobjects->CanPlaceBaseAtOffset(Base, CharUnits::Zero())) {
1535    setSize(std::max(getSize(), Layout.getSize()));
1536
1537    return CharUnits::Zero();
1538  }
1539
1540  CharUnits UnpackedBaseAlign = Layout.getNonVirtualAlign();
1541  CharUnits BaseAlign = (Packed) ? CharUnits::One() : UnpackedBaseAlign;
1542
1543  // The maximum field alignment overrides base align.
1544  if (!MaxFieldAlignment.isZero()) {
1545    BaseAlign = std::min(BaseAlign, MaxFieldAlignment);
1546    UnpackedBaseAlign = std::min(UnpackedBaseAlign, MaxFieldAlignment);
1547  }
1548
1549  if (!HasExternalLayout) {
1550    // Round up the current record size to the base's alignment boundary.
1551    Offset = getDataSize().RoundUpToAlignment(BaseAlign);
1552
1553    // Try to place the base.
1554    while (!EmptySubobjects->CanPlaceBaseAtOffset(Base, Offset))
1555      Offset += BaseAlign;
1556  } else {
1557    bool Allowed = EmptySubobjects->CanPlaceBaseAtOffset(Base, Offset);
1558    (void)Allowed;
1559    assert(Allowed && "Base subobject externally placed at overlapping offset");
1560  }
1561
1562  if (!Base->Class->isEmpty()) {
1563    // Update the data size.
1564    setDataSize(Offset + Layout.getNonVirtualSize());
1565
1566    setSize(std::max(getSize(), getDataSize()));
1567  } else
1568    setSize(std::max(getSize(), Offset + Layout.getSize()));
1569
1570  // Remember max struct/class alignment.
1571  UpdateAlignment(BaseAlign, UnpackedBaseAlign);
1572
1573  return Offset;
1574}
1575
1576void RecordLayoutBuilder::InitializeLayout(const Decl *D) {
1577  if (const RecordDecl *RD = dyn_cast<RecordDecl>(D))
1578    IsUnion = RD->isUnion();
1579
1580  Packed = D->hasAttr<PackedAttr>();
1581
1582  IsMsStruct = D->hasAttr<MsStructAttr>();
1583
1584  // Honor the default struct packing maximum alignment flag.
1585  if (unsigned DefaultMaxFieldAlignment = Context.getLangOpts().PackStruct) {
1586    MaxFieldAlignment = CharUnits::fromQuantity(DefaultMaxFieldAlignment);
1587  }
1588
1589  // mac68k alignment supersedes maximum field alignment and attribute aligned,
1590  // and forces all structures to have 2-byte alignment. The IBM docs on it
1591  // allude to additional (more complicated) semantics, especially with regard
1592  // to bit-fields, but gcc appears not to follow that.
1593  if (D->hasAttr<AlignMac68kAttr>()) {
1594    IsMac68kAlign = true;
1595    MaxFieldAlignment = CharUnits::fromQuantity(2);
1596    Alignment = CharUnits::fromQuantity(2);
1597  } else {
1598    if (const MaxFieldAlignmentAttr *MFAA = D->getAttr<MaxFieldAlignmentAttr>())
1599      MaxFieldAlignment = Context.toCharUnitsFromBits(MFAA->getAlignment());
1600
1601    if (unsigned MaxAlign = D->getMaxAlignment())
1602      UpdateAlignment(Context.toCharUnitsFromBits(MaxAlign));
1603  }
1604
1605  // If there is an external AST source, ask it for the various offsets.
1606  if (const RecordDecl *RD = dyn_cast<RecordDecl>(D))
1607    if (ExternalASTSource *External = Context.getExternalSource()) {
1608      ExternalLayout = External->layoutRecordType(RD,
1609                                                  ExternalSize,
1610                                                  ExternalAlign,
1611                                                  ExternalFieldOffsets,
1612                                                  ExternalBaseOffsets,
1613                                                  ExternalVirtualBaseOffsets);
1614
1615      // Update based on external alignment.
1616      if (ExternalLayout) {
1617        if (ExternalAlign > 0) {
1618          Alignment = Context.toCharUnitsFromBits(ExternalAlign);
1619          UnpackedAlignment = Alignment;
1620        } else {
1621          // The external source didn't have alignment information; infer it.
1622          InferAlignment = true;
1623        }
1624      }
1625    }
1626}
1627
1628void RecordLayoutBuilder::Layout(const RecordDecl *D) {
1629  InitializeLayout(D);
1630  LayoutFields(D);
1631
1632  // Finally, round the size of the total struct up to the alignment of the
1633  // struct itself.
1634  FinishLayout(D);
1635}
1636
1637void RecordLayoutBuilder::Layout(const CXXRecordDecl *RD) {
1638  InitializeLayout(RD);
1639
1640  // Lay out the vtable and the non-virtual bases.
1641  LayoutNonVirtualBases(RD);
1642
1643  LayoutFields(RD);
1644
1645  NonVirtualSize = Context.toCharUnitsFromBits(
1646        llvm::RoundUpToAlignment(getSizeInBits(),
1647                                 Context.getTargetInfo().getCharAlign()));
1648  NonVirtualAlignment = Alignment;
1649
1650  if (isMicrosoftCXXABI()) {
1651    if (NonVirtualSize != NonVirtualSize.RoundUpToAlignment(Alignment)) {
1652    CharUnits AlignMember =
1653      NonVirtualSize.RoundUpToAlignment(Alignment) - NonVirtualSize;
1654
1655    setSize(getSize() + AlignMember);
1656    setDataSize(getSize());
1657
1658    NonVirtualSize = Context.toCharUnitsFromBits(
1659                             llvm::RoundUpToAlignment(getSizeInBits(),
1660                             Context.getTargetInfo().getCharAlign()));
1661    }
1662
1663    MSLayoutVirtualBases(RD);
1664  } else {
1665    // Lay out the virtual bases and add the primary virtual base offsets.
1666    LayoutVirtualBases(RD, RD);
1667  }
1668
1669  // Finally, round the size of the total struct up to the alignment
1670  // of the struct itself.
1671  FinishLayout(RD);
1672
1673#ifndef NDEBUG
1674  // Check that we have base offsets for all bases.
1675  for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
1676       E = RD->bases_end(); I != E; ++I) {
1677    if (I->isVirtual())
1678      continue;
1679
1680    const CXXRecordDecl *BaseDecl =
1681      cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
1682
1683    assert(Bases.count(BaseDecl) && "Did not find base offset!");
1684  }
1685
1686  // And all virtual bases.
1687  for (CXXRecordDecl::base_class_const_iterator I = RD->vbases_begin(),
1688       E = RD->vbases_end(); I != E; ++I) {
1689    const CXXRecordDecl *BaseDecl =
1690      cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
1691
1692    assert(VBases.count(BaseDecl) && "Did not find base offset!");
1693  }
1694#endif
1695}
1696
1697void RecordLayoutBuilder::Layout(const ObjCInterfaceDecl *D) {
1698  if (ObjCInterfaceDecl *SD = D->getSuperClass()) {
1699    const ASTRecordLayout &SL = Context.getASTObjCInterfaceLayout(SD);
1700
1701    UpdateAlignment(SL.getAlignment());
1702
1703    // We start laying out ivars not at the end of the superclass
1704    // structure, but at the next byte following the last field.
1705    setSize(SL.getDataSize());
1706    setDataSize(getSize());
1707  }
1708
1709  InitializeLayout(D);
1710  // Layout each ivar sequentially.
1711  for (const ObjCIvarDecl *IVD = D->all_declared_ivar_begin(); IVD;
1712       IVD = IVD->getNextIvar())
1713    LayoutField(IVD);
1714
1715  // Finally, round the size of the total struct up to the alignment of the
1716  // struct itself.
1717  FinishLayout(D);
1718}
1719
1720void RecordLayoutBuilder::LayoutFields(const RecordDecl *D) {
1721  // Layout each field, for now, just sequentially, respecting alignment.  In
1722  // the future, this will need to be tweakable by targets.
1723  const FieldDecl *LastFD = 0;
1724  ZeroLengthBitfield = 0;
1725  unsigned RemainingInAlignment = 0;
1726  for (RecordDecl::field_iterator Field = D->field_begin(),
1727       FieldEnd = D->field_end(); Field != FieldEnd; ++Field) {
1728    if (IsMsStruct) {
1729      FieldDecl *FD = *Field;
1730      if (Context.ZeroBitfieldFollowsBitfield(FD, LastFD))
1731        ZeroLengthBitfield = FD;
1732      // Zero-length bitfields following non-bitfield members are
1733      // ignored:
1734      else if (Context.ZeroBitfieldFollowsNonBitfield(FD, LastFD))
1735        continue;
1736      // FIXME. streamline these conditions into a simple one.
1737      else if (Context.BitfieldFollowsBitfield(FD, LastFD) ||
1738               Context.BitfieldFollowsNonBitfield(FD, LastFD) ||
1739               Context.NonBitfieldFollowsBitfield(FD, LastFD)) {
1740        // 1) Adjacent bit fields are packed into the same 1-, 2-, or
1741        // 4-byte allocation unit if the integral types are the same
1742        // size and if the next bit field fits into the current
1743        // allocation unit without crossing the boundary imposed by the
1744        // common alignment requirements of the bit fields.
1745        // 2) Establish a new alignment for a bitfield following
1746        // a non-bitfield if size of their types differ.
1747        // 3) Establish a new alignment for a non-bitfield following
1748        // a bitfield if size of their types differ.
1749        std::pair<uint64_t, unsigned> FieldInfo =
1750          Context.getTypeInfo(FD->getType());
1751        uint64_t TypeSize = FieldInfo.first;
1752        unsigned FieldAlign = FieldInfo.second;
1753        // This check is needed for 'long long' in -m32 mode.
1754        if (TypeSize > FieldAlign &&
1755            (Context.hasSameType(FD->getType(),
1756                                Context.UnsignedLongLongTy)
1757             ||Context.hasSameType(FD->getType(),
1758                                   Context.LongLongTy)))
1759          FieldAlign = TypeSize;
1760        FieldInfo = Context.getTypeInfo(LastFD->getType());
1761        uint64_t TypeSizeLastFD = FieldInfo.first;
1762        unsigned FieldAlignLastFD = FieldInfo.second;
1763        // This check is needed for 'long long' in -m32 mode.
1764        if (TypeSizeLastFD > FieldAlignLastFD &&
1765            (Context.hasSameType(LastFD->getType(),
1766                                Context.UnsignedLongLongTy)
1767             || Context.hasSameType(LastFD->getType(),
1768                                    Context.LongLongTy)))
1769          FieldAlignLastFD = TypeSizeLastFD;
1770
1771        if (TypeSizeLastFD != TypeSize) {
1772          if (RemainingInAlignment &&
1773              LastFD && LastFD->isBitField() &&
1774              LastFD->getBitWidthValue(Context)) {
1775            // If previous field was a bitfield with some remaining unfilled
1776            // bits, pad the field so current field starts on its type boundary.
1777            uint64_t FieldOffset =
1778            getDataSizeInBits() - UnfilledBitsInLastByte;
1779            uint64_t NewSizeInBits = RemainingInAlignment + FieldOffset;
1780            setDataSize(llvm::RoundUpToAlignment(NewSizeInBits,
1781                                                 Context.getTargetInfo().getCharAlign()));
1782            setSize(std::max(getSizeInBits(), getDataSizeInBits()));
1783            RemainingInAlignment = 0;
1784          }
1785
1786          uint64_t UnpaddedFieldOffset =
1787            getDataSizeInBits() - UnfilledBitsInLastByte;
1788          FieldAlign = std::max(FieldAlign, FieldAlignLastFD);
1789
1790          // The maximum field alignment overrides the aligned attribute.
1791          if (!MaxFieldAlignment.isZero()) {
1792            unsigned MaxFieldAlignmentInBits =
1793              Context.toBits(MaxFieldAlignment);
1794            FieldAlign = std::min(FieldAlign, MaxFieldAlignmentInBits);
1795          }
1796
1797          uint64_t NewSizeInBits =
1798            llvm::RoundUpToAlignment(UnpaddedFieldOffset, FieldAlign);
1799          setDataSize(llvm::RoundUpToAlignment(NewSizeInBits,
1800                                               Context.getTargetInfo().getCharAlign()));
1801          UnfilledBitsInLastByte = getDataSizeInBits() - NewSizeInBits;
1802          setSize(std::max(getSizeInBits(), getDataSizeInBits()));
1803        }
1804        if (FD->isBitField()) {
1805          uint64_t FieldSize = FD->getBitWidthValue(Context);
1806          assert (FieldSize > 0 && "LayoutFields - ms_struct layout");
1807          if (RemainingInAlignment < FieldSize)
1808            RemainingInAlignment = TypeSize - FieldSize;
1809          else
1810            RemainingInAlignment -= FieldSize;
1811        }
1812      }
1813      else if (FD->isBitField()) {
1814        uint64_t FieldSize = FD->getBitWidthValue(Context);
1815        std::pair<uint64_t, unsigned> FieldInfo =
1816          Context.getTypeInfo(FD->getType());
1817        uint64_t TypeSize = FieldInfo.first;
1818        RemainingInAlignment = TypeSize - FieldSize;
1819      }
1820      LastFD = FD;
1821    }
1822    else if (!Context.getTargetInfo().useBitFieldTypeAlignment() &&
1823             Context.getTargetInfo().useZeroLengthBitfieldAlignment()) {
1824      if (Field->isBitField() && Field->getBitWidthValue(Context) == 0)
1825        ZeroLengthBitfield = *Field;
1826    }
1827    LayoutField(*Field);
1828  }
1829  if (IsMsStruct && RemainingInAlignment &&
1830      LastFD && LastFD->isBitField() && LastFD->getBitWidthValue(Context)) {
1831    // If we ended a bitfield before the full length of the type then
1832    // pad the struct out to the full length of the last type.
1833    uint64_t FieldOffset =
1834      getDataSizeInBits() - UnfilledBitsInLastByte;
1835    uint64_t NewSizeInBits = RemainingInAlignment + FieldOffset;
1836    setDataSize(llvm::RoundUpToAlignment(NewSizeInBits,
1837                                         Context.getTargetInfo().getCharAlign()));
1838    setSize(std::max(getSizeInBits(), getDataSizeInBits()));
1839  }
1840}
1841
1842void RecordLayoutBuilder::LayoutWideBitField(uint64_t FieldSize,
1843                                             uint64_t TypeSize,
1844                                             bool FieldPacked,
1845                                             const FieldDecl *D) {
1846  assert(Context.getLangOpts().CPlusPlus &&
1847         "Can only have wide bit-fields in C++!");
1848
1849  // Itanium C++ ABI 2.4:
1850  //   If sizeof(T)*8 < n, let T' be the largest integral POD type with
1851  //   sizeof(T')*8 <= n.
1852
1853  QualType IntegralPODTypes[] = {
1854    Context.UnsignedCharTy, Context.UnsignedShortTy, Context.UnsignedIntTy,
1855    Context.UnsignedLongTy, Context.UnsignedLongLongTy
1856  };
1857
1858  QualType Type;
1859  for (unsigned I = 0, E = llvm::array_lengthof(IntegralPODTypes);
1860       I != E; ++I) {
1861    uint64_t Size = Context.getTypeSize(IntegralPODTypes[I]);
1862
1863    if (Size > FieldSize)
1864      break;
1865
1866    Type = IntegralPODTypes[I];
1867  }
1868  assert(!Type.isNull() && "Did not find a type!");
1869
1870  CharUnits TypeAlign = Context.getTypeAlignInChars(Type);
1871
1872  // We're not going to use any of the unfilled bits in the last byte.
1873  UnfilledBitsInLastByte = 0;
1874
1875  uint64_t FieldOffset;
1876  uint64_t UnpaddedFieldOffset = getDataSizeInBits() - UnfilledBitsInLastByte;
1877
1878  if (IsUnion) {
1879    setDataSize(std::max(getDataSizeInBits(), FieldSize));
1880    FieldOffset = 0;
1881  } else {
1882    // The bitfield is allocated starting at the next offset aligned
1883    // appropriately for T', with length n bits.
1884    FieldOffset = llvm::RoundUpToAlignment(getDataSizeInBits(),
1885                                           Context.toBits(TypeAlign));
1886
1887    uint64_t NewSizeInBits = FieldOffset + FieldSize;
1888
1889    setDataSize(llvm::RoundUpToAlignment(NewSizeInBits,
1890                                         Context.getTargetInfo().getCharAlign()));
1891    UnfilledBitsInLastByte = getDataSizeInBits() - NewSizeInBits;
1892  }
1893
1894  // Place this field at the current location.
1895  FieldOffsets.push_back(FieldOffset);
1896
1897  CheckFieldPadding(FieldOffset, UnpaddedFieldOffset, FieldOffset,
1898                    Context.toBits(TypeAlign), FieldPacked, D);
1899
1900  // Update the size.
1901  setSize(std::max(getSizeInBits(), getDataSizeInBits()));
1902
1903  // Remember max struct/class alignment.
1904  UpdateAlignment(TypeAlign);
1905}
1906
1907void RecordLayoutBuilder::LayoutBitField(const FieldDecl *D) {
1908  bool FieldPacked = Packed || D->hasAttr<PackedAttr>();
1909  uint64_t UnpaddedFieldOffset = getDataSizeInBits() - UnfilledBitsInLastByte;
1910  uint64_t FieldOffset = IsUnion ? 0 : UnpaddedFieldOffset;
1911  uint64_t FieldSize = D->getBitWidthValue(Context);
1912
1913  std::pair<uint64_t, unsigned> FieldInfo = Context.getTypeInfo(D->getType());
1914  uint64_t TypeSize = FieldInfo.first;
1915  unsigned FieldAlign = FieldInfo.second;
1916
1917  // This check is needed for 'long long' in -m32 mode.
1918  if (IsMsStruct && (TypeSize > FieldAlign) &&
1919      (Context.hasSameType(D->getType(),
1920                           Context.UnsignedLongLongTy)
1921       || Context.hasSameType(D->getType(), Context.LongLongTy)))
1922    FieldAlign = TypeSize;
1923
1924  if (ZeroLengthBitfield) {
1925    std::pair<uint64_t, unsigned> FieldInfo;
1926    unsigned ZeroLengthBitfieldAlignment;
1927    if (IsMsStruct) {
1928      // If a zero-length bitfield is inserted after a bitfield,
1929      // and the alignment of the zero-length bitfield is
1930      // greater than the member that follows it, `bar', `bar'
1931      // will be aligned as the type of the zero-length bitfield.
1932      if (ZeroLengthBitfield != D) {
1933        FieldInfo = Context.getTypeInfo(ZeroLengthBitfield->getType());
1934        ZeroLengthBitfieldAlignment = FieldInfo.second;
1935        // Ignore alignment of subsequent zero-length bitfields.
1936        if ((ZeroLengthBitfieldAlignment > FieldAlign) || (FieldSize == 0))
1937          FieldAlign = ZeroLengthBitfieldAlignment;
1938        if (FieldSize)
1939          ZeroLengthBitfield = 0;
1940      }
1941    } else {
1942      // The alignment of a zero-length bitfield affects the alignment
1943      // of the next member.  The alignment is the max of the zero
1944      // length bitfield's alignment and a target specific fixed value.
1945      unsigned ZeroLengthBitfieldBoundary =
1946        Context.getTargetInfo().getZeroLengthBitfieldBoundary();
1947      if (ZeroLengthBitfieldBoundary > FieldAlign)
1948        FieldAlign = ZeroLengthBitfieldBoundary;
1949    }
1950  }
1951
1952  if (FieldSize > TypeSize) {
1953    LayoutWideBitField(FieldSize, TypeSize, FieldPacked, D);
1954    return;
1955  }
1956
1957  // The align if the field is not packed. This is to check if the attribute
1958  // was unnecessary (-Wpacked).
1959  unsigned UnpackedFieldAlign = FieldAlign;
1960  uint64_t UnpackedFieldOffset = FieldOffset;
1961  if (!Context.getTargetInfo().useBitFieldTypeAlignment() && !ZeroLengthBitfield)
1962    UnpackedFieldAlign = 1;
1963
1964  if (FieldPacked ||
1965      (!Context.getTargetInfo().useBitFieldTypeAlignment() && !ZeroLengthBitfield))
1966    FieldAlign = 1;
1967  FieldAlign = std::max(FieldAlign, D->getMaxAlignment());
1968  UnpackedFieldAlign = std::max(UnpackedFieldAlign, D->getMaxAlignment());
1969
1970  // The maximum field alignment overrides the aligned attribute.
1971  if (!MaxFieldAlignment.isZero() && FieldSize != 0) {
1972    unsigned MaxFieldAlignmentInBits = Context.toBits(MaxFieldAlignment);
1973    FieldAlign = std::min(FieldAlign, MaxFieldAlignmentInBits);
1974    UnpackedFieldAlign = std::min(UnpackedFieldAlign, MaxFieldAlignmentInBits);
1975  }
1976
1977  // Check if we need to add padding to give the field the correct alignment.
1978  if (FieldSize == 0 ||
1979      (MaxFieldAlignment.isZero() &&
1980       (FieldOffset & (FieldAlign-1)) + FieldSize > TypeSize))
1981    FieldOffset = llvm::RoundUpToAlignment(FieldOffset, FieldAlign);
1982
1983  if (FieldSize == 0 ||
1984      (MaxFieldAlignment.isZero() &&
1985       (UnpackedFieldOffset & (UnpackedFieldAlign-1)) + FieldSize > TypeSize))
1986    UnpackedFieldOffset = llvm::RoundUpToAlignment(UnpackedFieldOffset,
1987                                                   UnpackedFieldAlign);
1988
1989  // Padding members don't affect overall alignment, unless zero length bitfield
1990  // alignment is enabled.
1991  if (!D->getIdentifier() && !Context.getTargetInfo().useZeroLengthBitfieldAlignment())
1992    FieldAlign = UnpackedFieldAlign = 1;
1993
1994  if (!IsMsStruct)
1995    ZeroLengthBitfield = 0;
1996
1997  if (ExternalLayout)
1998    FieldOffset = updateExternalFieldOffset(D, FieldOffset);
1999
2000  // Place this field at the current location.
2001  FieldOffsets.push_back(FieldOffset);
2002
2003  if (!ExternalLayout)
2004    CheckFieldPadding(FieldOffset, UnpaddedFieldOffset, UnpackedFieldOffset,
2005                      UnpackedFieldAlign, FieldPacked, D);
2006
2007  // Update DataSize to include the last byte containing (part of) the bitfield.
2008  if (IsUnion) {
2009    // FIXME: I think FieldSize should be TypeSize here.
2010    setDataSize(std::max(getDataSizeInBits(), FieldSize));
2011  } else {
2012    uint64_t NewSizeInBits = FieldOffset + FieldSize;
2013
2014    setDataSize(llvm::RoundUpToAlignment(NewSizeInBits,
2015                                         Context.getTargetInfo().getCharAlign()));
2016    UnfilledBitsInLastByte = getDataSizeInBits() - NewSizeInBits;
2017  }
2018
2019  // Update the size.
2020  setSize(std::max(getSizeInBits(), getDataSizeInBits()));
2021
2022  // Remember max struct/class alignment.
2023  UpdateAlignment(Context.toCharUnitsFromBits(FieldAlign),
2024                  Context.toCharUnitsFromBits(UnpackedFieldAlign));
2025}
2026
2027void RecordLayoutBuilder::LayoutField(const FieldDecl *D) {
2028  if (D->isBitField()) {
2029    LayoutBitField(D);
2030    return;
2031  }
2032
2033  uint64_t UnpaddedFieldOffset = getDataSizeInBits() - UnfilledBitsInLastByte;
2034
2035  // Reset the unfilled bits.
2036  UnfilledBitsInLastByte = 0;
2037
2038  bool FieldPacked = Packed || D->hasAttr<PackedAttr>();
2039  CharUnits FieldOffset =
2040    IsUnion ? CharUnits::Zero() : getDataSize();
2041  CharUnits FieldSize;
2042  CharUnits FieldAlign;
2043
2044  if (D->getType()->isIncompleteArrayType()) {
2045    // This is a flexible array member; we can't directly
2046    // query getTypeInfo about these, so we figure it out here.
2047    // Flexible array members don't have any size, but they
2048    // have to be aligned appropriately for their element type.
2049    FieldSize = CharUnits::Zero();
2050    const ArrayType* ATy = Context.getAsArrayType(D->getType());
2051    FieldAlign = Context.getTypeAlignInChars(ATy->getElementType());
2052  } else if (const ReferenceType *RT = D->getType()->getAs<ReferenceType>()) {
2053    unsigned AS = RT->getPointeeType().getAddressSpace();
2054    FieldSize =
2055      Context.toCharUnitsFromBits(Context.getTargetInfo().getPointerWidth(AS));
2056    FieldAlign =
2057      Context.toCharUnitsFromBits(Context.getTargetInfo().getPointerAlign(AS));
2058  } else {
2059    std::pair<CharUnits, CharUnits> FieldInfo =
2060      Context.getTypeInfoInChars(D->getType());
2061    FieldSize = FieldInfo.first;
2062    FieldAlign = FieldInfo.second;
2063
2064    if (ZeroLengthBitfield) {
2065      CharUnits ZeroLengthBitfieldBoundary =
2066        Context.toCharUnitsFromBits(
2067          Context.getTargetInfo().getZeroLengthBitfieldBoundary());
2068      if (ZeroLengthBitfieldBoundary == CharUnits::Zero()) {
2069        // If a zero-length bitfield is inserted after a bitfield,
2070        // and the alignment of the zero-length bitfield is
2071        // greater than the member that follows it, `bar', `bar'
2072        // will be aligned as the type of the zero-length bitfield.
2073        std::pair<CharUnits, CharUnits> FieldInfo =
2074          Context.getTypeInfoInChars(ZeroLengthBitfield->getType());
2075        CharUnits ZeroLengthBitfieldAlignment = FieldInfo.second;
2076        if (ZeroLengthBitfieldAlignment > FieldAlign)
2077          FieldAlign = ZeroLengthBitfieldAlignment;
2078      } else if (ZeroLengthBitfieldBoundary > FieldAlign) {
2079        // Align 'bar' based on a fixed alignment specified by the target.
2080        assert(Context.getTargetInfo().useZeroLengthBitfieldAlignment() &&
2081               "ZeroLengthBitfieldBoundary should only be used in conjunction"
2082               " with useZeroLengthBitfieldAlignment.");
2083        FieldAlign = ZeroLengthBitfieldBoundary;
2084      }
2085      ZeroLengthBitfield = 0;
2086    }
2087
2088    if (Context.getLangOpts().MSBitfields || IsMsStruct) {
2089      // If MS bitfield layout is required, figure out what type is being
2090      // laid out and align the field to the width of that type.
2091
2092      // Resolve all typedefs down to their base type and round up the field
2093      // alignment if necessary.
2094      QualType T = Context.getBaseElementType(D->getType());
2095      if (const BuiltinType *BTy = T->getAs<BuiltinType>()) {
2096        CharUnits TypeSize = Context.getTypeSizeInChars(BTy);
2097        if (TypeSize > FieldAlign)
2098          FieldAlign = TypeSize;
2099      }
2100    }
2101  }
2102
2103  // The align if the field is not packed. This is to check if the attribute
2104  // was unnecessary (-Wpacked).
2105  CharUnits UnpackedFieldAlign = FieldAlign;
2106  CharUnits UnpackedFieldOffset = FieldOffset;
2107
2108  if (FieldPacked)
2109    FieldAlign = CharUnits::One();
2110  CharUnits MaxAlignmentInChars =
2111    Context.toCharUnitsFromBits(D->getMaxAlignment());
2112  FieldAlign = std::max(FieldAlign, MaxAlignmentInChars);
2113  UnpackedFieldAlign = std::max(UnpackedFieldAlign, MaxAlignmentInChars);
2114
2115  // The maximum field alignment overrides the aligned attribute.
2116  if (!MaxFieldAlignment.isZero()) {
2117    FieldAlign = std::min(FieldAlign, MaxFieldAlignment);
2118    UnpackedFieldAlign = std::min(UnpackedFieldAlign, MaxFieldAlignment);
2119  }
2120
2121  // Round up the current record size to the field's alignment boundary.
2122  FieldOffset = FieldOffset.RoundUpToAlignment(FieldAlign);
2123  UnpackedFieldOffset =
2124    UnpackedFieldOffset.RoundUpToAlignment(UnpackedFieldAlign);
2125
2126  if (ExternalLayout) {
2127    FieldOffset = Context.toCharUnitsFromBits(
2128                    updateExternalFieldOffset(D, Context.toBits(FieldOffset)));
2129
2130    if (!IsUnion && EmptySubobjects) {
2131      // Record the fact that we're placing a field at this offset.
2132      bool Allowed = EmptySubobjects->CanPlaceFieldAtOffset(D, FieldOffset);
2133      (void)Allowed;
2134      assert(Allowed && "Externally-placed field cannot be placed here");
2135    }
2136  } else {
2137    if (!IsUnion && EmptySubobjects) {
2138      // Check if we can place the field at this offset.
2139      while (!EmptySubobjects->CanPlaceFieldAtOffset(D, FieldOffset)) {
2140        // We couldn't place the field at the offset. Try again at a new offset.
2141        FieldOffset += FieldAlign;
2142      }
2143    }
2144  }
2145
2146  // Place this field at the current location.
2147  FieldOffsets.push_back(Context.toBits(FieldOffset));
2148
2149  if (!ExternalLayout)
2150    CheckFieldPadding(Context.toBits(FieldOffset), UnpaddedFieldOffset,
2151                      Context.toBits(UnpackedFieldOffset),
2152                      Context.toBits(UnpackedFieldAlign), FieldPacked, D);
2153
2154  // Reserve space for this field.
2155  uint64_t FieldSizeInBits = Context.toBits(FieldSize);
2156  if (IsUnion)
2157    setDataSize(std::max(getDataSizeInBits(), FieldSizeInBits));
2158  else
2159    setDataSize(FieldOffset + FieldSize);
2160
2161  // Update the size.
2162  setSize(std::max(getSizeInBits(), getDataSizeInBits()));
2163
2164  // Remember max struct/class alignment.
2165  UpdateAlignment(FieldAlign, UnpackedFieldAlign);
2166}
2167
2168void RecordLayoutBuilder::FinishLayout(const NamedDecl *D) {
2169  if (ExternalLayout) {
2170    setSize(ExternalSize);
2171    return;
2172  }
2173
2174  // In C++, records cannot be of size 0.
2175  if (Context.getLangOpts().CPlusPlus && getSizeInBits() == 0) {
2176    if (const CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(D)) {
2177      // Compatibility with gcc requires a class (pod or non-pod)
2178      // which is not empty but of size 0; such as having fields of
2179      // array of zero-length, remains of Size 0
2180      if (RD->isEmpty())
2181        setSize(CharUnits::One());
2182    }
2183    else
2184      setSize(CharUnits::One());
2185  }
2186
2187  // MSVC doesn't round up to the alignment of the record with virtual bases.
2188  if (const CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(D)) {
2189    if (isMicrosoftCXXABI() && RD->getNumVBases())
2190      return;
2191  }
2192
2193  // Finally, round the size of the record up to the alignment of the
2194  // record itself.
2195  uint64_t UnpaddedSize = getSizeInBits() - UnfilledBitsInLastByte;
2196  uint64_t UnpackedSizeInBits =
2197    llvm::RoundUpToAlignment(getSizeInBits(),
2198                             Context.toBits(UnpackedAlignment));
2199  CharUnits UnpackedSize = Context.toCharUnitsFromBits(UnpackedSizeInBits);
2200  setSize(llvm::RoundUpToAlignment(getSizeInBits(), Context.toBits(Alignment)));
2201
2202  unsigned CharBitNum = Context.getTargetInfo().getCharWidth();
2203  if (const RecordDecl *RD = dyn_cast<RecordDecl>(D)) {
2204    // Warn if padding was introduced to the struct/class/union.
2205    if (getSizeInBits() > UnpaddedSize) {
2206      unsigned PadSize = getSizeInBits() - UnpaddedSize;
2207      bool InBits = true;
2208      if (PadSize % CharBitNum == 0) {
2209        PadSize = PadSize / CharBitNum;
2210        InBits = false;
2211      }
2212      Diag(RD->getLocation(), diag::warn_padded_struct_size)
2213          << Context.getTypeDeclType(RD)
2214          << PadSize
2215          << (InBits ? 1 : 0) /*(byte|bit)*/ << (PadSize > 1); // plural or not
2216    }
2217
2218    // Warn if we packed it unnecessarily. If the alignment is 1 byte don't
2219    // bother since there won't be alignment issues.
2220    if (Packed && UnpackedAlignment > CharUnits::One() &&
2221        getSize() == UnpackedSize)
2222      Diag(D->getLocation(), diag::warn_unnecessary_packed)
2223          << Context.getTypeDeclType(RD);
2224  }
2225}
2226
2227void RecordLayoutBuilder::UpdateAlignment(CharUnits NewAlignment,
2228                                          CharUnits UnpackedNewAlignment) {
2229  // The alignment is not modified when using 'mac68k' alignment or when
2230  // we have an externally-supplied layout that also provides overall alignment.
2231  if (IsMac68kAlign || (ExternalLayout && !InferAlignment))
2232    return;
2233
2234  if (NewAlignment > Alignment) {
2235    assert(llvm::isPowerOf2_32(NewAlignment.getQuantity() &&
2236           "Alignment not a power of 2"));
2237    Alignment = NewAlignment;
2238  }
2239
2240  if (UnpackedNewAlignment > UnpackedAlignment) {
2241    assert(llvm::isPowerOf2_32(UnpackedNewAlignment.getQuantity() &&
2242           "Alignment not a power of 2"));
2243    UnpackedAlignment = UnpackedNewAlignment;
2244  }
2245}
2246
2247uint64_t
2248RecordLayoutBuilder::updateExternalFieldOffset(const FieldDecl *Field,
2249                                               uint64_t ComputedOffset) {
2250  assert(ExternalFieldOffsets.find(Field) != ExternalFieldOffsets.end() &&
2251         "Field does not have an external offset");
2252
2253  uint64_t ExternalFieldOffset = ExternalFieldOffsets[Field];
2254
2255  if (InferAlignment && ExternalFieldOffset < ComputedOffset) {
2256    // The externally-supplied field offset is before the field offset we
2257    // computed. Assume that the structure is packed.
2258    Alignment = CharUnits::fromQuantity(1);
2259    InferAlignment = false;
2260  }
2261
2262  // Use the externally-supplied field offset.
2263  return ExternalFieldOffset;
2264}
2265
2266/// \brief Get diagnostic %select index for tag kind for
2267/// field padding diagnostic message.
2268/// WARNING: Indexes apply to particular diagnostics only!
2269///
2270/// \returns diagnostic %select index.
2271static unsigned getPaddingDiagFromTagKind(TagTypeKind Tag) {
2272  switch (Tag) {
2273  case TTK_Struct: return 0;
2274  case TTK_Interface: return 1;
2275  case TTK_Class: return 2;
2276  default: llvm_unreachable("Invalid tag kind for field padding diagnostic!");
2277  }
2278}
2279
2280void RecordLayoutBuilder::CheckFieldPadding(uint64_t Offset,
2281                                            uint64_t UnpaddedOffset,
2282                                            uint64_t UnpackedOffset,
2283                                            unsigned UnpackedAlign,
2284                                            bool isPacked,
2285                                            const FieldDecl *D) {
2286  // We let objc ivars without warning, objc interfaces generally are not used
2287  // for padding tricks.
2288  if (isa<ObjCIvarDecl>(D))
2289    return;
2290
2291  // Don't warn about structs created without a SourceLocation.  This can
2292  // be done by clients of the AST, such as codegen.
2293  if (D->getLocation().isInvalid())
2294    return;
2295
2296  unsigned CharBitNum = Context.getTargetInfo().getCharWidth();
2297
2298  // Warn if padding was introduced to the struct/class.
2299  if (!IsUnion && Offset > UnpaddedOffset) {
2300    unsigned PadSize = Offset - UnpaddedOffset;
2301    bool InBits = true;
2302    if (PadSize % CharBitNum == 0) {
2303      PadSize = PadSize / CharBitNum;
2304      InBits = false;
2305    }
2306    if (D->getIdentifier())
2307      Diag(D->getLocation(), diag::warn_padded_struct_field)
2308          << getPaddingDiagFromTagKind(D->getParent()->getTagKind())
2309          << Context.getTypeDeclType(D->getParent())
2310          << PadSize
2311          << (InBits ? 1 : 0) /*(byte|bit)*/ << (PadSize > 1) // plural or not
2312          << D->getIdentifier();
2313    else
2314      Diag(D->getLocation(), diag::warn_padded_struct_anon_field)
2315          << getPaddingDiagFromTagKind(D->getParent()->getTagKind())
2316          << Context.getTypeDeclType(D->getParent())
2317          << PadSize
2318          << (InBits ? 1 : 0) /*(byte|bit)*/ << (PadSize > 1); // plural or not
2319  }
2320
2321  // Warn if we packed it unnecessarily. If the alignment is 1 byte don't
2322  // bother since there won't be alignment issues.
2323  if (isPacked && UnpackedAlign > CharBitNum && Offset == UnpackedOffset)
2324    Diag(D->getLocation(), diag::warn_unnecessary_packed)
2325        << D->getIdentifier();
2326}
2327
2328const CXXMethodDecl *
2329RecordLayoutBuilder::ComputeKeyFunction(const CXXRecordDecl *RD) {
2330  // If a class isn't polymorphic it doesn't have a key function.
2331  if (!RD->isPolymorphic())
2332    return 0;
2333
2334  // A class that is not externally visible doesn't have a key function. (Or
2335  // at least, there's no point to assigning a key function to such a class;
2336  // this doesn't affect the ABI.)
2337  if (RD->getLinkage() != ExternalLinkage)
2338    return 0;
2339
2340  // Template instantiations don't have key functions,see Itanium C++ ABI 5.2.6.
2341  // Same behavior as GCC.
2342  TemplateSpecializationKind TSK = RD->getTemplateSpecializationKind();
2343  if (TSK == TSK_ImplicitInstantiation ||
2344      TSK == TSK_ExplicitInstantiationDefinition)
2345    return 0;
2346
2347  for (CXXRecordDecl::method_iterator I = RD->method_begin(),
2348         E = RD->method_end(); I != E; ++I) {
2349    const CXXMethodDecl *MD = *I;
2350
2351    if (!MD->isVirtual())
2352      continue;
2353
2354    if (MD->isPure())
2355      continue;
2356
2357    // Ignore implicit member functions, they are always marked as inline, but
2358    // they don't have a body until they're defined.
2359    if (MD->isImplicit())
2360      continue;
2361
2362    if (MD->isInlineSpecified())
2363      continue;
2364
2365    if (MD->hasInlineBody())
2366      continue;
2367
2368    // Ignore inline deleted or defaulted functions.
2369    if (!MD->isUserProvided())
2370      continue;
2371
2372    // We found it.
2373    return MD;
2374  }
2375
2376  return 0;
2377}
2378
2379DiagnosticBuilder
2380RecordLayoutBuilder::Diag(SourceLocation Loc, unsigned DiagID) {
2381  return Context.getDiagnostics().Report(Loc, DiagID);
2382}
2383
2384/// getASTRecordLayout - Get or compute information about the layout of the
2385/// specified record (struct/union/class), which indicates its size and field
2386/// position information.
2387const ASTRecordLayout &
2388ASTContext::getASTRecordLayout(const RecordDecl *D) const {
2389  // These asserts test different things.  A record has a definition
2390  // as soon as we begin to parse the definition.  That definition is
2391  // not a complete definition (which is what isDefinition() tests)
2392  // until we *finish* parsing the definition.
2393
2394  if (D->hasExternalLexicalStorage() && !D->getDefinition())
2395    getExternalSource()->CompleteType(const_cast<RecordDecl*>(D));
2396
2397  D = D->getDefinition();
2398  assert(D && "Cannot get layout of forward declarations!");
2399  assert(D->isCompleteDefinition() && "Cannot layout type before complete!");
2400
2401  // Look up this layout, if already laid out, return what we have.
2402  // Note that we can't save a reference to the entry because this function
2403  // is recursive.
2404  const ASTRecordLayout *Entry = ASTRecordLayouts[D];
2405  if (Entry) return *Entry;
2406
2407  const ASTRecordLayout *NewEntry;
2408
2409  if (const CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(D)) {
2410    EmptySubobjectMap EmptySubobjects(*this, RD);
2411    RecordLayoutBuilder Builder(*this, &EmptySubobjects);
2412    Builder.Layout(RD);
2413
2414    // MSVC gives the vb-table pointer an alignment equal to that of
2415    // the non-virtual part of the structure.  That's an inherently
2416    // multi-pass operation.  If our first pass doesn't give us
2417    // adequate alignment, try again with the specified minimum
2418    // alignment.  This is *much* more maintainable than computing the
2419    // alignment in advance in a separately-coded pass; it's also
2420    // significantly more efficient in the common case where the
2421    // vb-table doesn't need extra padding.
2422    if (Builder.VBPtrOffset != CharUnits::fromQuantity(-1) &&
2423        (Builder.VBPtrOffset % Builder.NonVirtualAlignment) != 0) {
2424      Builder.resetWithTargetAlignment(Builder.NonVirtualAlignment);
2425      Builder.Layout(RD);
2426    }
2427
2428    // FIXME: This is not always correct. See the part about bitfields at
2429    // http://www.codesourcery.com/public/cxx-abi/abi.html#POD for more info.
2430    // FIXME: IsPODForThePurposeOfLayout should be stored in the record layout.
2431    // This does not affect the calculations of MSVC layouts
2432    bool IsPODForThePurposeOfLayout =
2433      (!Builder.isMicrosoftCXXABI() && cast<CXXRecordDecl>(D)->isPOD());
2434
2435    // FIXME: This should be done in FinalizeLayout.
2436    CharUnits DataSize =
2437      IsPODForThePurposeOfLayout ? Builder.getSize() : Builder.getDataSize();
2438    CharUnits NonVirtualSize =
2439      IsPODForThePurposeOfLayout ? DataSize : Builder.NonVirtualSize;
2440
2441    NewEntry =
2442      new (*this) ASTRecordLayout(*this, Builder.getSize(),
2443                                  Builder.Alignment,
2444                                  Builder.HasOwnVFPtr,
2445                                  Builder.VBPtrOffset,
2446                                  DataSize,
2447                                  Builder.FieldOffsets.data(),
2448                                  Builder.FieldOffsets.size(),
2449                                  NonVirtualSize,
2450                                  Builder.NonVirtualAlignment,
2451                                  EmptySubobjects.SizeOfLargestEmptySubobject,
2452                                  Builder.PrimaryBase,
2453                                  Builder.PrimaryBaseIsVirtual,
2454                                  Builder.Bases, Builder.VBases);
2455  } else {
2456    RecordLayoutBuilder Builder(*this, /*EmptySubobjects=*/0);
2457    Builder.Layout(D);
2458
2459    NewEntry =
2460      new (*this) ASTRecordLayout(*this, Builder.getSize(),
2461                                  Builder.Alignment,
2462                                  Builder.getSize(),
2463                                  Builder.FieldOffsets.data(),
2464                                  Builder.FieldOffsets.size());
2465  }
2466
2467  ASTRecordLayouts[D] = NewEntry;
2468
2469  if (getLangOpts().DumpRecordLayouts) {
2470    llvm::errs() << "\n*** Dumping AST Record Layout\n";
2471    DumpRecordLayout(D, llvm::errs(), getLangOpts().DumpRecordLayoutsSimple);
2472  }
2473
2474  return *NewEntry;
2475}
2476
2477const CXXMethodDecl *ASTContext::getKeyFunction(const CXXRecordDecl *RD) {
2478  RD = cast<CXXRecordDecl>(RD->getDefinition());
2479  assert(RD && "Cannot get key function for forward declarations!");
2480
2481  const CXXMethodDecl *&Entry = KeyFunctions[RD];
2482  if (!Entry)
2483    Entry = RecordLayoutBuilder::ComputeKeyFunction(RD);
2484
2485  return Entry;
2486}
2487
2488static uint64_t getFieldOffset(const ASTContext &C, const FieldDecl *FD) {
2489  const ASTRecordLayout &Layout = C.getASTRecordLayout(FD->getParent());
2490  return Layout.getFieldOffset(FD->getFieldIndex());
2491}
2492
2493uint64_t ASTContext::getFieldOffset(const ValueDecl *VD) const {
2494  uint64_t OffsetInBits;
2495  if (const FieldDecl *FD = dyn_cast<FieldDecl>(VD)) {
2496    OffsetInBits = ::getFieldOffset(*this, FD);
2497  } else {
2498    const IndirectFieldDecl *IFD = cast<IndirectFieldDecl>(VD);
2499
2500    OffsetInBits = 0;
2501    for (IndirectFieldDecl::chain_iterator CI = IFD->chain_begin(),
2502                                           CE = IFD->chain_end();
2503         CI != CE; ++CI)
2504      OffsetInBits += ::getFieldOffset(*this, cast<FieldDecl>(*CI));
2505  }
2506
2507  return OffsetInBits;
2508}
2509
2510/// getObjCLayout - Get or compute information about the layout of the
2511/// given interface.
2512///
2513/// \param Impl - If given, also include the layout of the interface's
2514/// implementation. This may differ by including synthesized ivars.
2515const ASTRecordLayout &
2516ASTContext::getObjCLayout(const ObjCInterfaceDecl *D,
2517                          const ObjCImplementationDecl *Impl) const {
2518  // Retrieve the definition
2519  if (D->hasExternalLexicalStorage() && !D->getDefinition())
2520    getExternalSource()->CompleteType(const_cast<ObjCInterfaceDecl*>(D));
2521  D = D->getDefinition();
2522  assert(D && D->isThisDeclarationADefinition() && "Invalid interface decl!");
2523
2524  // Look up this layout, if already laid out, return what we have.
2525  const ObjCContainerDecl *Key =
2526    Impl ? (const ObjCContainerDecl*) Impl : (const ObjCContainerDecl*) D;
2527  if (const ASTRecordLayout *Entry = ObjCLayouts[Key])
2528    return *Entry;
2529
2530  // Add in synthesized ivar count if laying out an implementation.
2531  if (Impl) {
2532    unsigned SynthCount = CountNonClassIvars(D);
2533    // If there aren't any sythesized ivars then reuse the interface
2534    // entry. Note we can't cache this because we simply free all
2535    // entries later; however we shouldn't look up implementations
2536    // frequently.
2537    if (SynthCount == 0)
2538      return getObjCLayout(D, 0);
2539  }
2540
2541  RecordLayoutBuilder Builder(*this, /*EmptySubobjects=*/0);
2542  Builder.Layout(D);
2543
2544  const ASTRecordLayout *NewEntry =
2545    new (*this) ASTRecordLayout(*this, Builder.getSize(),
2546                                Builder.Alignment,
2547                                Builder.getDataSize(),
2548                                Builder.FieldOffsets.data(),
2549                                Builder.FieldOffsets.size());
2550
2551  ObjCLayouts[Key] = NewEntry;
2552
2553  return *NewEntry;
2554}
2555
2556static void PrintOffset(raw_ostream &OS,
2557                        CharUnits Offset, unsigned IndentLevel) {
2558  OS << llvm::format("%4" PRId64 " | ", (int64_t)Offset.getQuantity());
2559  OS.indent(IndentLevel * 2);
2560}
2561
2562static void DumpCXXRecordLayout(raw_ostream &OS,
2563                                const CXXRecordDecl *RD, const ASTContext &C,
2564                                CharUnits Offset,
2565                                unsigned IndentLevel,
2566                                const char* Description,
2567                                bool IncludeVirtualBases) {
2568  const ASTRecordLayout &Layout = C.getASTRecordLayout(RD);
2569
2570  PrintOffset(OS, Offset, IndentLevel);
2571  OS << C.getTypeDeclType(const_cast<CXXRecordDecl *>(RD)).getAsString();
2572  if (Description)
2573    OS << ' ' << Description;
2574  if (RD->isEmpty())
2575    OS << " (empty)";
2576  OS << '\n';
2577
2578  IndentLevel++;
2579
2580  const CXXRecordDecl *PrimaryBase = Layout.getPrimaryBase();
2581  bool HasVfptr = Layout.hasOwnVFPtr();
2582  bool HasVbptr = Layout.getVBPtrOffset() != CharUnits::fromQuantity(-1);
2583
2584  // Vtable pointer.
2585  if (RD->isDynamicClass() && !PrimaryBase &&
2586      C.getTargetInfo().getCXXABI() != CXXABI_Microsoft) {
2587    PrintOffset(OS, Offset, IndentLevel);
2588    OS << '(' << *RD << " vtable pointer)\n";
2589  }
2590
2591  // Dump (non-virtual) bases
2592  for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
2593         E = RD->bases_end(); I != E; ++I) {
2594    assert(!I->getType()->isDependentType() &&
2595           "Cannot layout class with dependent bases.");
2596    if (I->isVirtual())
2597      continue;
2598
2599    const CXXRecordDecl *Base =
2600      cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
2601
2602    CharUnits BaseOffset = Offset + Layout.getBaseClassOffset(Base);
2603
2604    DumpCXXRecordLayout(OS, Base, C, BaseOffset, IndentLevel,
2605                        Base == PrimaryBase ? "(primary base)" : "(base)",
2606                        /*IncludeVirtualBases=*/false);
2607  }
2608
2609  // vfptr and vbptr (for Microsoft C++ ABI)
2610  if (HasVfptr) {
2611    PrintOffset(OS, Offset, IndentLevel);
2612    OS << '(' << *RD << " vftable pointer)\n";
2613  }
2614  if (HasVbptr) {
2615    PrintOffset(OS, Offset + Layout.getVBPtrOffset(), IndentLevel);
2616    OS << '(' << *RD << " vbtable pointer)\n";
2617  }
2618
2619  // Dump fields.
2620  uint64_t FieldNo = 0;
2621  for (CXXRecordDecl::field_iterator I = RD->field_begin(),
2622         E = RD->field_end(); I != E; ++I, ++FieldNo) {
2623    const FieldDecl &Field = **I;
2624    CharUnits FieldOffset = Offset +
2625      C.toCharUnitsFromBits(Layout.getFieldOffset(FieldNo));
2626
2627    if (const RecordType *RT = Field.getType()->getAs<RecordType>()) {
2628      if (const CXXRecordDecl *D = dyn_cast<CXXRecordDecl>(RT->getDecl())) {
2629        DumpCXXRecordLayout(OS, D, C, FieldOffset, IndentLevel,
2630                            Field.getName().data(),
2631                            /*IncludeVirtualBases=*/true);
2632        continue;
2633      }
2634    }
2635
2636    PrintOffset(OS, FieldOffset, IndentLevel);
2637    OS << Field.getType().getAsString() << ' ' << Field << '\n';
2638  }
2639
2640  if (!IncludeVirtualBases)
2641    return;
2642
2643  // Dump virtual bases.
2644  const ASTRecordLayout::VBaseOffsetsMapTy &vtordisps =
2645    Layout.getVBaseOffsetsMap();
2646  for (CXXRecordDecl::base_class_const_iterator I = RD->vbases_begin(),
2647         E = RD->vbases_end(); I != E; ++I) {
2648    assert(I->isVirtual() && "Found non-virtual class!");
2649    const CXXRecordDecl *VBase =
2650      cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
2651
2652    CharUnits VBaseOffset = Offset + Layout.getVBaseClassOffset(VBase);
2653
2654    if (vtordisps.find(VBase)->second.hasVtorDisp()) {
2655      PrintOffset(OS, VBaseOffset - CharUnits::fromQuantity(4), IndentLevel);
2656      OS << "(vtordisp for vbase " << *VBase << ")\n";
2657    }
2658
2659    DumpCXXRecordLayout(OS, VBase, C, VBaseOffset, IndentLevel,
2660                        VBase == PrimaryBase ?
2661                        "(primary virtual base)" : "(virtual base)",
2662                        /*IncludeVirtualBases=*/false);
2663  }
2664
2665  OS << "  sizeof=" << Layout.getSize().getQuantity();
2666  OS << ", dsize=" << Layout.getDataSize().getQuantity();
2667  OS << ", align=" << Layout.getAlignment().getQuantity() << '\n';
2668  OS << "  nvsize=" << Layout.getNonVirtualSize().getQuantity();
2669  OS << ", nvalign=" << Layout.getNonVirtualAlign().getQuantity() << '\n';
2670  OS << '\n';
2671}
2672
2673void ASTContext::DumpRecordLayout(const RecordDecl *RD,
2674                                  raw_ostream &OS,
2675                                  bool Simple) const {
2676  const ASTRecordLayout &Info = getASTRecordLayout(RD);
2677
2678  if (const CXXRecordDecl *CXXRD = dyn_cast<CXXRecordDecl>(RD))
2679    if (!Simple)
2680      return DumpCXXRecordLayout(OS, CXXRD, *this, CharUnits(), 0, 0,
2681                                 /*IncludeVirtualBases=*/true);
2682
2683  OS << "Type: " << getTypeDeclType(RD).getAsString() << "\n";
2684  if (!Simple) {
2685    OS << "Record: ";
2686    RD->dump();
2687  }
2688  OS << "\nLayout: ";
2689  OS << "<ASTRecordLayout\n";
2690  OS << "  Size:" << toBits(Info.getSize()) << "\n";
2691  OS << "  DataSize:" << toBits(Info.getDataSize()) << "\n";
2692  OS << "  Alignment:" << toBits(Info.getAlignment()) << "\n";
2693  OS << "  FieldOffsets: [";
2694  for (unsigned i = 0, e = Info.getFieldCount(); i != e; ++i) {
2695    if (i) OS << ", ";
2696    OS << Info.getFieldOffset(i);
2697  }
2698  OS << "]>\n";
2699}
2700