RecordLayoutBuilder.cpp revision 52bbe7a1133c3cb57e9246f1b96c12940ea3821a 
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/Attr.h"
11#include "clang/AST/CXXInheritance.h"
12#include "clang/AST/Decl.h"
13#include "clang/AST/DeclCXX.h"
14#include "clang/AST/DeclObjC.h"
15#include "clang/AST/Expr.h"
16#include "clang/AST/RecordLayout.h"
17#include "clang/Basic/TargetInfo.h"
18#include "clang/Sema/SemaDiagnostic.h"
19#include "llvm/Support/Format.h"
20#include "llvm/ADT/SmallSet.h"
21#include "llvm/Support/MathExtras.h"
22#include "llvm/Support/CrashRecoveryContext.h"
23
24using namespace clang;
25
26namespace {
27
28/// BaseSubobjectInfo - Represents a single base subobject in a complete class.
29/// For a class hierarchy like
30///
31/// class A { };
32/// class B : A { };
33/// class C : A, B { };
34///
35/// The BaseSubobjectInfo graph for C will have three BaseSubobjectInfo
36/// instances, one for B and two for A.
37///
38/// If a base is virtual, it will only have one BaseSubobjectInfo allocated.
39struct BaseSubobjectInfo {
40  /// Class - The class for this base info.
41  const CXXRecordDecl *Class;
42
43  /// IsVirtual - Whether the BaseInfo represents a virtual base or not.
44  bool IsVirtual;
45
46  /// Bases - Information about the base subobjects.
47  llvm::SmallVector<BaseSubobjectInfo*, 4> Bases;
48
49  /// PrimaryVirtualBaseInfo - Holds the base info for the primary virtual base
50  /// of this base info (if one exists).
51  BaseSubobjectInfo *PrimaryVirtualBaseInfo;
52
53  // FIXME: Document.
54  const BaseSubobjectInfo *Derived;
55};
56
57/// EmptySubobjectMap - Keeps track of which empty subobjects exist at different
58/// offsets while laying out a C++ class.
59class EmptySubobjectMap {
60  const ASTContext &Context;
61  uint64_t CharWidth;
62
63  /// Class - The class whose empty entries we're keeping track of.
64  const CXXRecordDecl *Class;
65
66  /// EmptyClassOffsets - A map from offsets to empty record decls.
67  typedef llvm::SmallVector<const CXXRecordDecl *, 1> ClassVectorTy;
68  typedef llvm::DenseMap<CharUnits, ClassVectorTy> EmptyClassOffsetsMapTy;
69  EmptyClassOffsetsMapTy EmptyClassOffsets;
70
71  /// MaxEmptyClassOffset - The highest offset known to contain an empty
72  /// base subobject.
73  CharUnits MaxEmptyClassOffset;
74
75  /// ComputeEmptySubobjectSizes - Compute the size of the largest base or
76  /// member subobject that is empty.
77  void ComputeEmptySubobjectSizes();
78
79  void AddSubobjectAtOffset(const CXXRecordDecl *RD, CharUnits Offset);
80
81  void UpdateEmptyBaseSubobjects(const BaseSubobjectInfo *Info,
82                                 CharUnits Offset, bool PlacingEmptyBase);
83
84  void UpdateEmptyFieldSubobjects(const CXXRecordDecl *RD,
85                                  const CXXRecordDecl *Class,
86                                  CharUnits Offset);
87  void UpdateEmptyFieldSubobjects(const FieldDecl *FD, CharUnits Offset);
88
89  /// AnyEmptySubobjectsBeyondOffset - Returns whether there are any empty
90  /// subobjects beyond the given offset.
91  bool AnyEmptySubobjectsBeyondOffset(CharUnits Offset) const {
92    return Offset <= MaxEmptyClassOffset;
93  }
94
95  CharUnits
96  getFieldOffset(const ASTRecordLayout &Layout, unsigned FieldNo) const {
97    uint64_t FieldOffset = Layout.getFieldOffset(FieldNo);
98    assert(FieldOffset % CharWidth == 0 &&
99           "Field offset not at char boundary!");
100
101    return Context.toCharUnitsFromBits(FieldOffset);
102  }
103
104protected:
105  bool CanPlaceSubobjectAtOffset(const CXXRecordDecl *RD,
106                                 CharUnits Offset) const;
107
108  bool CanPlaceBaseSubobjectAtOffset(const BaseSubobjectInfo *Info,
109                                     CharUnits Offset);
110
111  bool CanPlaceFieldSubobjectAtOffset(const CXXRecordDecl *RD,
112                                      const CXXRecordDecl *Class,
113                                      CharUnits Offset) const;
114  bool CanPlaceFieldSubobjectAtOffset(const FieldDecl *FD,
115                                      CharUnits Offset) const;
116
117public:
118  /// This holds the size of the largest empty subobject (either a base
119  /// or a member). Will be zero if the record being built doesn't contain
120  /// any empty classes.
121  CharUnits SizeOfLargestEmptySubobject;
122
123  EmptySubobjectMap(const ASTContext &Context, const CXXRecordDecl *Class)
124  : Context(Context), CharWidth(Context.getCharWidth()), Class(Class) {
125      ComputeEmptySubobjectSizes();
126  }
127
128  /// CanPlaceBaseAtOffset - Return whether the given base class can be placed
129  /// at the given offset.
130  /// Returns false if placing the record will result in two components
131  /// (direct or indirect) of the same type having the same offset.
132  bool CanPlaceBaseAtOffset(const BaseSubobjectInfo *Info,
133                            CharUnits Offset);
134
135  /// CanPlaceFieldAtOffset - Return whether a field can be placed at the given
136  /// offset.
137  bool CanPlaceFieldAtOffset(const FieldDecl *FD, CharUnits Offset);
138};
139
140void EmptySubobjectMap::ComputeEmptySubobjectSizes() {
141  // Check the bases.
142  for (CXXRecordDecl::base_class_const_iterator I = Class->bases_begin(),
143       E = Class->bases_end(); I != E; ++I) {
144    const CXXRecordDecl *BaseDecl =
145      cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
146
147    CharUnits EmptySize;
148    const ASTRecordLayout &Layout = Context.getASTRecordLayout(BaseDecl);
149    if (BaseDecl->isEmpty()) {
150      // If the class decl is empty, get its size.
151      EmptySize = Layout.getSize();
152    } else {
153      // Otherwise, we get the largest empty subobject for the decl.
154      EmptySize = Layout.getSizeOfLargestEmptySubobject();
155    }
156
157    if (EmptySize > SizeOfLargestEmptySubobject)
158      SizeOfLargestEmptySubobject = EmptySize;
159  }
160
161  // Check the fields.
162  for (CXXRecordDecl::field_iterator I = Class->field_begin(),
163       E = Class->field_end(); I != E; ++I) {
164    const FieldDecl *FD = *I;
165
166    const RecordType *RT =
167      Context.getBaseElementType(FD->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    const FieldDecl *FD = *I;
265    if (FD->isBitField())
266      continue;
267
268    CharUnits FieldOffset = Offset + getFieldOffset(Layout, FieldNo);
269    if (!CanPlaceFieldSubobjectAtOffset(FD, FieldOffset))
270      return false;
271  }
272
273  return true;
274}
275
276void EmptySubobjectMap::UpdateEmptyBaseSubobjects(const BaseSubobjectInfo *Info,
277                                                  CharUnits Offset,
278                                                  bool PlacingEmptyBase) {
279  if (!PlacingEmptyBase && Offset >= SizeOfLargestEmptySubobject) {
280    // We know that the only empty subobjects that can conflict with empty
281    // subobject of non-empty bases, are empty bases that can be placed at
282    // offset zero. Because of this, we only need to keep track of empty base
283    // subobjects with offsets less than the size of the largest empty
284    // subobject for our class.
285    return;
286  }
287
288  AddSubobjectAtOffset(Info->Class, Offset);
289
290  // Traverse all non-virtual bases.
291  const ASTRecordLayout &Layout = Context.getASTRecordLayout(Info->Class);
292  for (unsigned I = 0, E = Info->Bases.size(); I != E; ++I) {
293    BaseSubobjectInfo* Base = Info->Bases[I];
294    if (Base->IsVirtual)
295      continue;
296
297    CharUnits BaseOffset = Offset + Layout.getBaseClassOffset(Base->Class);
298    UpdateEmptyBaseSubobjects(Base, BaseOffset, PlacingEmptyBase);
299  }
300
301  if (Info->PrimaryVirtualBaseInfo) {
302    BaseSubobjectInfo *PrimaryVirtualBaseInfo = Info->PrimaryVirtualBaseInfo;
303
304    if (Info == PrimaryVirtualBaseInfo->Derived)
305      UpdateEmptyBaseSubobjects(PrimaryVirtualBaseInfo, Offset,
306                                PlacingEmptyBase);
307  }
308
309  // Traverse all member variables.
310  unsigned FieldNo = 0;
311  for (CXXRecordDecl::field_iterator I = Info->Class->field_begin(),
312       E = Info->Class->field_end(); I != E; ++I, ++FieldNo) {
313    const FieldDecl *FD = *I;
314    if (FD->isBitField())
315      continue;
316
317    CharUnits FieldOffset = Offset + getFieldOffset(Layout, FieldNo);
318    UpdateEmptyFieldSubobjects(FD, FieldOffset);
319  }
320}
321
322bool EmptySubobjectMap::CanPlaceBaseAtOffset(const BaseSubobjectInfo *Info,
323                                             CharUnits Offset) {
324  // If we know this class doesn't have any empty subobjects we don't need to
325  // bother checking.
326  if (SizeOfLargestEmptySubobject.isZero())
327    return true;
328
329  if (!CanPlaceBaseSubobjectAtOffset(Info, Offset))
330    return false;
331
332  // We are able to place the base at this offset. Make sure to update the
333  // empty base subobject map.
334  UpdateEmptyBaseSubobjects(Info, Offset, Info->Class->isEmpty());
335  return true;
336}
337
338bool
339EmptySubobjectMap::CanPlaceFieldSubobjectAtOffset(const CXXRecordDecl *RD,
340                                                  const CXXRecordDecl *Class,
341                                                  CharUnits Offset) const {
342  // We don't have to keep looking past the maximum offset that's known to
343  // contain an empty class.
344  if (!AnyEmptySubobjectsBeyondOffset(Offset))
345    return true;
346
347  if (!CanPlaceSubobjectAtOffset(RD, Offset))
348    return false;
349
350  const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
351
352  // Traverse all non-virtual bases.
353  for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
354       E = RD->bases_end(); I != E; ++I) {
355    if (I->isVirtual())
356      continue;
357
358    const CXXRecordDecl *BaseDecl =
359      cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
360
361    CharUnits BaseOffset = Offset + Layout.getBaseClassOffset(BaseDecl);
362    if (!CanPlaceFieldSubobjectAtOffset(BaseDecl, Class, BaseOffset))
363      return false;
364  }
365
366  if (RD == Class) {
367    // This is the most derived class, traverse virtual bases as well.
368    for (CXXRecordDecl::base_class_const_iterator I = RD->vbases_begin(),
369         E = RD->vbases_end(); I != E; ++I) {
370      const CXXRecordDecl *VBaseDecl =
371        cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
372
373      CharUnits VBaseOffset = Offset + Layout.getVBaseClassOffset(VBaseDecl);
374      if (!CanPlaceFieldSubobjectAtOffset(VBaseDecl, Class, VBaseOffset))
375        return false;
376    }
377  }
378
379  // Traverse all member variables.
380  unsigned FieldNo = 0;
381  for (CXXRecordDecl::field_iterator I = RD->field_begin(), E = RD->field_end();
382       I != E; ++I, ++FieldNo) {
383    const FieldDecl *FD = *I;
384    if (FD->isBitField())
385      continue;
386
387    CharUnits FieldOffset = Offset + getFieldOffset(Layout, FieldNo);
388
389    if (!CanPlaceFieldSubobjectAtOffset(FD, FieldOffset))
390      return false;
391  }
392
393  return true;
394}
395
396bool
397EmptySubobjectMap::CanPlaceFieldSubobjectAtOffset(const FieldDecl *FD,
398                                                  CharUnits Offset) const {
399  // We don't have to keep looking past the maximum offset that's known to
400  // contain an empty class.
401  if (!AnyEmptySubobjectsBeyondOffset(Offset))
402    return true;
403
404  QualType T = FD->getType();
405  if (const RecordType *RT = T->getAs<RecordType>()) {
406    const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
407    return CanPlaceFieldSubobjectAtOffset(RD, RD, Offset);
408  }
409
410  // If we have an array type we need to look at every element.
411  if (const ConstantArrayType *AT = Context.getAsConstantArrayType(T)) {
412    QualType ElemTy = Context.getBaseElementType(AT);
413    const RecordType *RT = ElemTy->getAs<RecordType>();
414    if (!RT)
415      return true;
416
417    const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
418    const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
419
420    uint64_t NumElements = Context.getConstantArrayElementCount(AT);
421    CharUnits ElementOffset = Offset;
422    for (uint64_t I = 0; I != NumElements; ++I) {
423      // We don't have to keep looking past the maximum offset that's known to
424      // contain an empty class.
425      if (!AnyEmptySubobjectsBeyondOffset(ElementOffset))
426        return true;
427
428      if (!CanPlaceFieldSubobjectAtOffset(RD, RD, ElementOffset))
429        return false;
430
431      ElementOffset += Layout.getSize();
432    }
433  }
434
435  return true;
436}
437
438bool
439EmptySubobjectMap::CanPlaceFieldAtOffset(const FieldDecl *FD,
440                                         CharUnits Offset) {
441  if (!CanPlaceFieldSubobjectAtOffset(FD, Offset))
442    return false;
443
444  // We are able to place the member variable at this offset.
445  // Make sure to update the empty base subobject map.
446  UpdateEmptyFieldSubobjects(FD, Offset);
447  return true;
448}
449
450void EmptySubobjectMap::UpdateEmptyFieldSubobjects(const CXXRecordDecl *RD,
451                                                   const CXXRecordDecl *Class,
452                                                   CharUnits Offset) {
453  // We know that the only empty subobjects that can conflict with empty
454  // field subobjects are subobjects of empty bases that can be placed at offset
455  // zero. Because of this, we only need to keep track of empty field
456  // subobjects with offsets less than the size of the largest empty
457  // subobject for our class.
458  if (Offset >= SizeOfLargestEmptySubobject)
459    return;
460
461  AddSubobjectAtOffset(RD, Offset);
462
463  const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
464
465  // Traverse all non-virtual bases.
466  for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
467       E = RD->bases_end(); I != E; ++I) {
468    if (I->isVirtual())
469      continue;
470
471    const CXXRecordDecl *BaseDecl =
472      cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
473
474    CharUnits BaseOffset = Offset + Layout.getBaseClassOffset(BaseDecl);
475    UpdateEmptyFieldSubobjects(BaseDecl, Class, BaseOffset);
476  }
477
478  if (RD == Class) {
479    // This is the most derived class, traverse virtual bases as well.
480    for (CXXRecordDecl::base_class_const_iterator I = RD->vbases_begin(),
481         E = RD->vbases_end(); I != E; ++I) {
482      const CXXRecordDecl *VBaseDecl =
483      cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
484
485      CharUnits VBaseOffset = Offset + Layout.getVBaseClassOffset(VBaseDecl);
486      UpdateEmptyFieldSubobjects(VBaseDecl, Class, VBaseOffset);
487    }
488  }
489
490  // Traverse all member variables.
491  unsigned FieldNo = 0;
492  for (CXXRecordDecl::field_iterator I = RD->field_begin(), E = RD->field_end();
493       I != E; ++I, ++FieldNo) {
494    const FieldDecl *FD = *I;
495    if (FD->isBitField())
496      continue;
497
498    CharUnits FieldOffset = Offset + getFieldOffset(Layout, FieldNo);
499
500    UpdateEmptyFieldSubobjects(FD, FieldOffset);
501  }
502}
503
504void EmptySubobjectMap::UpdateEmptyFieldSubobjects(const FieldDecl *FD,
505                                                   CharUnits Offset) {
506  QualType T = FD->getType();
507  if (const RecordType *RT = T->getAs<RecordType>()) {
508    const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
509    UpdateEmptyFieldSubobjects(RD, RD, Offset);
510    return;
511  }
512
513  // If we have an array type we need to update every element.
514  if (const ConstantArrayType *AT = Context.getAsConstantArrayType(T)) {
515    QualType ElemTy = Context.getBaseElementType(AT);
516    const RecordType *RT = ElemTy->getAs<RecordType>();
517    if (!RT)
518      return;
519
520    const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
521    const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
522
523    uint64_t NumElements = Context.getConstantArrayElementCount(AT);
524    CharUnits ElementOffset = Offset;
525
526    for (uint64_t I = 0; I != NumElements; ++I) {
527      // We know that the only empty subobjects that can conflict with empty
528      // field subobjects are subobjects of empty bases that can be placed at
529      // offset zero. Because of this, we only need to keep track of empty field
530      // subobjects with offsets less than the size of the largest empty
531      // subobject for our class.
532      if (ElementOffset >= SizeOfLargestEmptySubobject)
533        return;
534
535      UpdateEmptyFieldSubobjects(RD, RD, ElementOffset);
536      ElementOffset += Layout.getSize();
537    }
538  }
539}
540
541class RecordLayoutBuilder {
542protected:
543  // FIXME: Remove this and make the appropriate fields public.
544  friend class clang::ASTContext;
545
546  const ASTContext &Context;
547
548  EmptySubobjectMap *EmptySubobjects;
549
550  /// Size - The current size of the record layout.
551  uint64_t Size;
552
553  /// Alignment - The current alignment of the record layout.
554  CharUnits Alignment;
555
556  /// \brief The alignment if attribute packed is not used.
557  CharUnits UnpackedAlignment;
558
559  llvm::SmallVector<uint64_t, 16> FieldOffsets;
560
561  /// Packed - Whether the record is packed or not.
562  unsigned Packed : 1;
563
564  unsigned IsUnion : 1;
565
566  unsigned IsMac68kAlign : 1;
567
568  unsigned IsMsStruct : 1;
569
570  /// UnfilledBitsInLastByte - If the last field laid out was a bitfield,
571  /// this contains the number of bits in the last byte that can be used for
572  /// an adjacent bitfield if necessary.
573  unsigned char UnfilledBitsInLastByte;
574
575  /// MaxFieldAlignment - The maximum allowed field alignment. This is set by
576  /// #pragma pack.
577  CharUnits MaxFieldAlignment;
578
579  /// DataSize - The data size of the record being laid out.
580  uint64_t DataSize;
581
582  CharUnits NonVirtualSize;
583  CharUnits NonVirtualAlignment;
584
585  FieldDecl *ZeroLengthBitfield;
586
587  /// PrimaryBase - the primary base class (if one exists) of the class
588  /// we're laying out.
589  const CXXRecordDecl *PrimaryBase;
590
591  /// PrimaryBaseIsVirtual - Whether the primary base of the class we're laying
592  /// out is virtual.
593  bool PrimaryBaseIsVirtual;
594
595  typedef llvm::DenseMap<const CXXRecordDecl *, CharUnits> BaseOffsetsMapTy;
596
597  /// Bases - base classes and their offsets in the record.
598  BaseOffsetsMapTy Bases;
599
600  // VBases - virtual base classes and their offsets in the record.
601  BaseOffsetsMapTy VBases;
602
603  /// IndirectPrimaryBases - Virtual base classes, direct or indirect, that are
604  /// primary base classes for some other direct or indirect base class.
605  CXXIndirectPrimaryBaseSet IndirectPrimaryBases;
606
607  /// FirstNearlyEmptyVBase - The first nearly empty virtual base class in
608  /// inheritance graph order. Used for determining the primary base class.
609  const CXXRecordDecl *FirstNearlyEmptyVBase;
610
611  /// VisitedVirtualBases - A set of all the visited virtual bases, used to
612  /// avoid visiting virtual bases more than once.
613  llvm::SmallPtrSet<const CXXRecordDecl *, 4> VisitedVirtualBases;
614
615  RecordLayoutBuilder(const ASTContext &Context, EmptySubobjectMap
616                      *EmptySubobjects)
617    : Context(Context), EmptySubobjects(EmptySubobjects), Size(0),
618      Alignment(CharUnits::One()), UnpackedAlignment(Alignment),
619      Packed(false), IsUnion(false),
620      IsMac68kAlign(false), IsMsStruct(false),
621      UnfilledBitsInLastByte(0), MaxFieldAlignment(CharUnits::Zero()),
622      DataSize(0), NonVirtualSize(CharUnits::Zero()),
623      NonVirtualAlignment(CharUnits::One()),
624      ZeroLengthBitfield(0), PrimaryBase(0),
625      PrimaryBaseIsVirtual(false), FirstNearlyEmptyVBase(0) { }
626
627  void Layout(const RecordDecl *D);
628  void Layout(const CXXRecordDecl *D);
629  void Layout(const ObjCInterfaceDecl *D);
630
631  void LayoutFields(const RecordDecl *D);
632  void LayoutField(const FieldDecl *D);
633  void LayoutWideBitField(uint64_t FieldSize, uint64_t TypeSize,
634                          bool FieldPacked, const FieldDecl *D);
635  void LayoutBitField(const FieldDecl *D);
636
637  /// BaseSubobjectInfoAllocator - Allocator for BaseSubobjectInfo objects.
638  llvm::SpecificBumpPtrAllocator<BaseSubobjectInfo> BaseSubobjectInfoAllocator;
639
640  typedef llvm::DenseMap<const CXXRecordDecl *, BaseSubobjectInfo *>
641    BaseSubobjectInfoMapTy;
642
643  /// VirtualBaseInfo - Map from all the (direct or indirect) virtual bases
644  /// of the class we're laying out to their base subobject info.
645  BaseSubobjectInfoMapTy VirtualBaseInfo;
646
647  /// NonVirtualBaseInfo - Map from all the direct non-virtual bases of the
648  /// class we're laying out to their base subobject info.
649  BaseSubobjectInfoMapTy NonVirtualBaseInfo;
650
651  /// ComputeBaseSubobjectInfo - Compute the base subobject information for the
652  /// bases of the given class.
653  void ComputeBaseSubobjectInfo(const CXXRecordDecl *RD);
654
655  /// ComputeBaseSubobjectInfo - Compute the base subobject information for a
656  /// single class and all of its base classes.
657  BaseSubobjectInfo *ComputeBaseSubobjectInfo(const CXXRecordDecl *RD,
658                                              bool IsVirtual,
659                                              BaseSubobjectInfo *Derived);
660
661  /// DeterminePrimaryBase - Determine the primary base of the given class.
662  void DeterminePrimaryBase(const CXXRecordDecl *RD);
663
664  void SelectPrimaryVBase(const CXXRecordDecl *RD);
665
666  virtual CharUnits GetVirtualPointersSize(const CXXRecordDecl *RD) const;
667
668  /// LayoutNonVirtualBases - Determines the primary base class (if any) and
669  /// lays it out. Will then proceed to lay out all non-virtual base clasess.
670  void LayoutNonVirtualBases(const CXXRecordDecl *RD);
671
672  /// LayoutNonVirtualBase - Lays out a single non-virtual base.
673  void LayoutNonVirtualBase(const BaseSubobjectInfo *Base);
674
675  void AddPrimaryVirtualBaseOffsets(const BaseSubobjectInfo *Info,
676                                    CharUnits Offset);
677
678  /// LayoutVirtualBases - Lays out all the virtual bases.
679  void LayoutVirtualBases(const CXXRecordDecl *RD,
680                          const CXXRecordDecl *MostDerivedClass);
681
682  /// LayoutVirtualBase - Lays out a single virtual base.
683  void LayoutVirtualBase(const BaseSubobjectInfo *Base);
684
685  /// LayoutBase - Will lay out a base and return the offset where it was
686  /// placed, in chars.
687  CharUnits LayoutBase(const BaseSubobjectInfo *Base);
688
689  /// InitializeLayout - Initialize record layout for the given record decl.
690  void InitializeLayout(const Decl *D);
691
692  /// FinishLayout - Finalize record layout. Adjust record size based on the
693  /// alignment.
694  void FinishLayout(const NamedDecl *D);
695
696  void UpdateAlignment(CharUnits NewAlignment, CharUnits UnpackedNewAlignment);
697  void UpdateAlignment(CharUnits NewAlignment) {
698    UpdateAlignment(NewAlignment, NewAlignment);
699  }
700
701  void CheckFieldPadding(uint64_t Offset, uint64_t UnpaddedOffset,
702                          uint64_t UnpackedOffset, unsigned UnpackedAlign,
703                          bool isPacked, const FieldDecl *D);
704
705  DiagnosticBuilder Diag(SourceLocation Loc, unsigned DiagID);
706
707  CharUnits getSize() const {
708    assert(Size % Context.getCharWidth() == 0);
709    return Context.toCharUnitsFromBits(Size);
710  }
711  uint64_t getSizeInBits() const { return Size; }
712
713  void setSize(CharUnits NewSize) { Size = Context.toBits(NewSize); }
714  void setSize(uint64_t NewSize) { Size = NewSize; }
715
716  CharUnits getDataSize() const {
717    assert(DataSize % Context.getCharWidth() == 0);
718    return Context.toCharUnitsFromBits(DataSize);
719  }
720  uint64_t getDataSizeInBits() const { return DataSize; }
721
722  void setDataSize(CharUnits NewSize) { DataSize = Context.toBits(NewSize); }
723  void setDataSize(uint64_t NewSize) { DataSize = NewSize; }
724
725
726  RecordLayoutBuilder(const RecordLayoutBuilder&);   // DO NOT IMPLEMENT
727  void operator=(const RecordLayoutBuilder&); // DO NOT IMPLEMENT
728public:
729  static const CXXMethodDecl *ComputeKeyFunction(const CXXRecordDecl *RD);
730
731  virtual ~RecordLayoutBuilder() { }
732};
733} // end anonymous namespace
734
735void
736RecordLayoutBuilder::SelectPrimaryVBase(const CXXRecordDecl *RD) {
737  for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
738         E = RD->bases_end(); I != E; ++I) {
739    assert(!I->getType()->isDependentType() &&
740           "Cannot layout class with dependent bases.");
741
742    const CXXRecordDecl *Base =
743      cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
744
745    // Check if this is a nearly empty virtual base.
746    if (I->isVirtual() && Context.isNearlyEmpty(Base)) {
747      // If it's not an indirect primary base, then we've found our primary
748      // base.
749      if (!IndirectPrimaryBases.count(Base)) {
750        PrimaryBase = Base;
751        PrimaryBaseIsVirtual = true;
752        return;
753      }
754
755      // Is this the first nearly empty virtual base?
756      if (!FirstNearlyEmptyVBase)
757        FirstNearlyEmptyVBase = Base;
758    }
759
760    SelectPrimaryVBase(Base);
761    if (PrimaryBase)
762      return;
763  }
764}
765
766CharUnits
767RecordLayoutBuilder::GetVirtualPointersSize(const CXXRecordDecl *RD) const {
768  return Context.toCharUnitsFromBits(Context.Target.getPointerWidth(0));
769}
770
771/// DeterminePrimaryBase - Determine the primary base of the given class.
772void RecordLayoutBuilder::DeterminePrimaryBase(const CXXRecordDecl *RD) {
773  // If the class isn't dynamic, it won't have a primary base.
774  if (!RD->isDynamicClass())
775    return;
776
777  // Compute all the primary virtual bases for all of our direct and
778  // indirect bases, and record all their primary virtual base classes.
779  RD->getIndirectPrimaryBases(IndirectPrimaryBases);
780
781  // If the record has a dynamic base class, attempt to choose a primary base
782  // class. It is the first (in direct base class order) non-virtual dynamic
783  // base class, if one exists.
784  for (CXXRecordDecl::base_class_const_iterator i = RD->bases_begin(),
785         e = RD->bases_end(); i != e; ++i) {
786    // Ignore virtual bases.
787    if (i->isVirtual())
788      continue;
789
790    const CXXRecordDecl *Base =
791      cast<CXXRecordDecl>(i->getType()->getAs<RecordType>()->getDecl());
792
793    if (Base->isDynamicClass()) {
794      // We found it.
795      PrimaryBase = Base;
796      PrimaryBaseIsVirtual = false;
797      return;
798    }
799  }
800
801  // Otherwise, it is the first nearly empty virtual base that is not an
802  // indirect primary virtual base class, if one exists.
803  if (RD->getNumVBases() != 0) {
804    SelectPrimaryVBase(RD);
805    if (PrimaryBase)
806      return;
807  }
808
809  // Otherwise, it is the first nearly empty virtual base that is not an
810  // indirect primary virtual base class, if one exists.
811  if (FirstNearlyEmptyVBase) {
812    PrimaryBase = FirstNearlyEmptyVBase;
813    PrimaryBaseIsVirtual = true;
814    return;
815  }
816
817  // Otherwise there is no primary base class.
818  assert(!PrimaryBase && "Should not get here with a primary base!");
819
820  // Allocate the virtual table pointer at offset zero.
821  assert(DataSize == 0 && "Vtable pointer must be at offset zero!");
822
823  // Update the size.
824  setSize(getSize() + GetVirtualPointersSize(RD));
825  setDataSize(getSize());
826
827  CharUnits UnpackedBaseAlign =
828    Context.toCharUnitsFromBits(Context.Target.getPointerAlign(0));
829  CharUnits BaseAlign = (Packed) ? CharUnits::One() : UnpackedBaseAlign;
830
831  // The maximum field alignment overrides base align.
832  if (!MaxFieldAlignment.isZero()) {
833    BaseAlign = std::min(BaseAlign, MaxFieldAlignment);
834    UnpackedBaseAlign = std::min(UnpackedBaseAlign, MaxFieldAlignment);
835  }
836
837  // Update the alignment.
838  UpdateAlignment(BaseAlign, UnpackedBaseAlign);
839}
840
841BaseSubobjectInfo *
842RecordLayoutBuilder::ComputeBaseSubobjectInfo(const CXXRecordDecl *RD,
843                                              bool IsVirtual,
844                                              BaseSubobjectInfo *Derived) {
845  BaseSubobjectInfo *Info;
846
847  if (IsVirtual) {
848    // Check if we already have info about this virtual base.
849    BaseSubobjectInfo *&InfoSlot = VirtualBaseInfo[RD];
850    if (InfoSlot) {
851      assert(InfoSlot->Class == RD && "Wrong class for virtual base info!");
852      return InfoSlot;
853    }
854
855    // We don't, create it.
856    InfoSlot = new (BaseSubobjectInfoAllocator.Allocate()) BaseSubobjectInfo;
857    Info = InfoSlot;
858  } else {
859    Info = new (BaseSubobjectInfoAllocator.Allocate()) BaseSubobjectInfo;
860  }
861
862  Info->Class = RD;
863  Info->IsVirtual = IsVirtual;
864  Info->Derived = 0;
865  Info->PrimaryVirtualBaseInfo = 0;
866
867  const CXXRecordDecl *PrimaryVirtualBase = 0;
868  BaseSubobjectInfo *PrimaryVirtualBaseInfo = 0;
869
870  // Check if this base has a primary virtual base.
871  if (RD->getNumVBases()) {
872    const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
873    if (Layout.isPrimaryBaseVirtual()) {
874      // This base does have a primary virtual base.
875      PrimaryVirtualBase = Layout.getPrimaryBase();
876      assert(PrimaryVirtualBase && "Didn't have a primary virtual base!");
877
878      // Now check if we have base subobject info about this primary base.
879      PrimaryVirtualBaseInfo = VirtualBaseInfo.lookup(PrimaryVirtualBase);
880
881      if (PrimaryVirtualBaseInfo) {
882        if (PrimaryVirtualBaseInfo->Derived) {
883          // We did have info about this primary base, and it turns out that it
884          // has already been claimed as a primary virtual base for another
885          // base.
886          PrimaryVirtualBase = 0;
887        } else {
888          // We can claim this base as our primary base.
889          Info->PrimaryVirtualBaseInfo = PrimaryVirtualBaseInfo;
890          PrimaryVirtualBaseInfo->Derived = Info;
891        }
892      }
893    }
894  }
895
896  // Now go through all direct bases.
897  for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
898       E = RD->bases_end(); I != E; ++I) {
899    bool IsVirtual = I->isVirtual();
900
901    const CXXRecordDecl *BaseDecl =
902      cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
903
904    Info->Bases.push_back(ComputeBaseSubobjectInfo(BaseDecl, IsVirtual, Info));
905  }
906
907  if (PrimaryVirtualBase && !PrimaryVirtualBaseInfo) {
908    // Traversing the bases must have created the base info for our primary
909    // virtual base.
910    PrimaryVirtualBaseInfo = VirtualBaseInfo.lookup(PrimaryVirtualBase);
911    assert(PrimaryVirtualBaseInfo &&
912           "Did not create a primary virtual base!");
913
914    // Claim the primary virtual base as our primary virtual base.
915    Info->PrimaryVirtualBaseInfo = PrimaryVirtualBaseInfo;
916    PrimaryVirtualBaseInfo->Derived = Info;
917  }
918
919  return Info;
920}
921
922void RecordLayoutBuilder::ComputeBaseSubobjectInfo(const CXXRecordDecl *RD) {
923  for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
924       E = RD->bases_end(); I != E; ++I) {
925    bool IsVirtual = I->isVirtual();
926
927    const CXXRecordDecl *BaseDecl =
928      cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
929
930    // Compute the base subobject info for this base.
931    BaseSubobjectInfo *Info = ComputeBaseSubobjectInfo(BaseDecl, IsVirtual, 0);
932
933    if (IsVirtual) {
934      // ComputeBaseInfo has already added this base for us.
935      assert(VirtualBaseInfo.count(BaseDecl) &&
936             "Did not add virtual base!");
937    } else {
938      // Add the base info to the map of non-virtual bases.
939      assert(!NonVirtualBaseInfo.count(BaseDecl) &&
940             "Non-virtual base already exists!");
941      NonVirtualBaseInfo.insert(std::make_pair(BaseDecl, Info));
942    }
943  }
944}
945
946void
947RecordLayoutBuilder::LayoutNonVirtualBases(const CXXRecordDecl *RD) {
948  // Then, determine the primary base class.
949  DeterminePrimaryBase(RD);
950
951  // Compute base subobject info.
952  ComputeBaseSubobjectInfo(RD);
953
954  // If we have a primary base class, lay it out.
955  if (PrimaryBase) {
956    if (PrimaryBaseIsVirtual) {
957      // If the primary virtual base was a primary virtual base of some other
958      // base class we'll have to steal it.
959      BaseSubobjectInfo *PrimaryBaseInfo = VirtualBaseInfo.lookup(PrimaryBase);
960      PrimaryBaseInfo->Derived = 0;
961
962      // We have a virtual primary base, insert it as an indirect primary base.
963      IndirectPrimaryBases.insert(PrimaryBase);
964
965      assert(!VisitedVirtualBases.count(PrimaryBase) &&
966             "vbase already visited!");
967      VisitedVirtualBases.insert(PrimaryBase);
968
969      LayoutVirtualBase(PrimaryBaseInfo);
970    } else {
971      BaseSubobjectInfo *PrimaryBaseInfo =
972        NonVirtualBaseInfo.lookup(PrimaryBase);
973      assert(PrimaryBaseInfo &&
974             "Did not find base info for non-virtual primary base!");
975
976      LayoutNonVirtualBase(PrimaryBaseInfo);
977    }
978  }
979
980  // Now lay out the non-virtual bases.
981  for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
982         E = RD->bases_end(); I != E; ++I) {
983
984    // Ignore virtual bases.
985    if (I->isVirtual())
986      continue;
987
988    const CXXRecordDecl *BaseDecl =
989      cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
990
991    // Skip the primary base.
992    if (BaseDecl == PrimaryBase && !PrimaryBaseIsVirtual)
993      continue;
994
995    // Lay out the base.
996    BaseSubobjectInfo *BaseInfo = NonVirtualBaseInfo.lookup(BaseDecl);
997    assert(BaseInfo && "Did not find base info for non-virtual base!");
998
999    LayoutNonVirtualBase(BaseInfo);
1000  }
1001}
1002
1003void RecordLayoutBuilder::LayoutNonVirtualBase(const BaseSubobjectInfo *Base) {
1004  // Layout the base.
1005  CharUnits Offset = LayoutBase(Base);
1006
1007  // Add its base class offset.
1008  assert(!Bases.count(Base->Class) && "base offset already exists!");
1009  Bases.insert(std::make_pair(Base->Class, Offset));
1010
1011  AddPrimaryVirtualBaseOffsets(Base, Offset);
1012}
1013
1014void
1015RecordLayoutBuilder::AddPrimaryVirtualBaseOffsets(const BaseSubobjectInfo *Info,
1016                                                  CharUnits Offset) {
1017  // This base isn't interesting, it has no virtual bases.
1018  if (!Info->Class->getNumVBases())
1019    return;
1020
1021  // First, check if we have a virtual primary base to add offsets for.
1022  if (Info->PrimaryVirtualBaseInfo) {
1023    assert(Info->PrimaryVirtualBaseInfo->IsVirtual &&
1024           "Primary virtual base is not virtual!");
1025    if (Info->PrimaryVirtualBaseInfo->Derived == Info) {
1026      // Add the offset.
1027      assert(!VBases.count(Info->PrimaryVirtualBaseInfo->Class) &&
1028             "primary vbase offset already exists!");
1029      VBases.insert(std::make_pair(Info->PrimaryVirtualBaseInfo->Class,
1030                                   Offset));
1031
1032      // Traverse the primary virtual base.
1033      AddPrimaryVirtualBaseOffsets(Info->PrimaryVirtualBaseInfo, Offset);
1034    }
1035  }
1036
1037  // Now go through all direct non-virtual bases.
1038  const ASTRecordLayout &Layout = Context.getASTRecordLayout(Info->Class);
1039  for (unsigned I = 0, E = Info->Bases.size(); I != E; ++I) {
1040    const BaseSubobjectInfo *Base = Info->Bases[I];
1041    if (Base->IsVirtual)
1042      continue;
1043
1044    CharUnits BaseOffset = Offset + Layout.getBaseClassOffset(Base->Class);
1045    AddPrimaryVirtualBaseOffsets(Base, BaseOffset);
1046  }
1047}
1048
1049void
1050RecordLayoutBuilder::LayoutVirtualBases(const CXXRecordDecl *RD,
1051                                        const CXXRecordDecl *MostDerivedClass) {
1052  const CXXRecordDecl *PrimaryBase;
1053  bool PrimaryBaseIsVirtual;
1054
1055  if (MostDerivedClass == RD) {
1056    PrimaryBase = this->PrimaryBase;
1057    PrimaryBaseIsVirtual = this->PrimaryBaseIsVirtual;
1058  } else {
1059    const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
1060    PrimaryBase = Layout.getPrimaryBase();
1061    PrimaryBaseIsVirtual = Layout.isPrimaryBaseVirtual();
1062  }
1063
1064  for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
1065         E = RD->bases_end(); I != E; ++I) {
1066    assert(!I->getType()->isDependentType() &&
1067           "Cannot layout class with dependent bases.");
1068
1069    const CXXRecordDecl *BaseDecl =
1070      cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
1071
1072    if (I->isVirtual()) {
1073      if (PrimaryBase != BaseDecl || !PrimaryBaseIsVirtual) {
1074        bool IndirectPrimaryBase = IndirectPrimaryBases.count(BaseDecl);
1075
1076        // Only lay out the virtual base if it's not an indirect primary base.
1077        if (!IndirectPrimaryBase) {
1078          // Only visit virtual bases once.
1079          if (!VisitedVirtualBases.insert(BaseDecl))
1080            continue;
1081
1082          const BaseSubobjectInfo *BaseInfo = VirtualBaseInfo.lookup(BaseDecl);
1083          assert(BaseInfo && "Did not find virtual base info!");
1084          LayoutVirtualBase(BaseInfo);
1085        }
1086      }
1087    }
1088
1089    if (!BaseDecl->getNumVBases()) {
1090      // This base isn't interesting since it doesn't have any virtual bases.
1091      continue;
1092    }
1093
1094    LayoutVirtualBases(BaseDecl, MostDerivedClass);
1095  }
1096}
1097
1098void RecordLayoutBuilder::LayoutVirtualBase(const BaseSubobjectInfo *Base) {
1099  assert(!Base->Derived && "Trying to lay out a primary virtual base!");
1100
1101  // Layout the base.
1102  CharUnits Offset = LayoutBase(Base);
1103
1104  // Add its base class offset.
1105  assert(!VBases.count(Base->Class) && "vbase offset already exists!");
1106  VBases.insert(std::make_pair(Base->Class, Offset));
1107
1108  AddPrimaryVirtualBaseOffsets(Base, Offset);
1109}
1110
1111CharUnits RecordLayoutBuilder::LayoutBase(const BaseSubobjectInfo *Base) {
1112  const ASTRecordLayout &Layout = Context.getASTRecordLayout(Base->Class);
1113
1114  // If we have an empty base class, try to place it at offset 0.
1115  if (Base->Class->isEmpty() &&
1116      EmptySubobjects->CanPlaceBaseAtOffset(Base, CharUnits::Zero())) {
1117    setSize(std::max(getSize(), Layout.getSize()));
1118
1119    return CharUnits::Zero();
1120  }
1121
1122  CharUnits UnpackedBaseAlign = Layout.getNonVirtualAlign();
1123  CharUnits BaseAlign = (Packed) ? CharUnits::One() : UnpackedBaseAlign;
1124
1125  // The maximum field alignment overrides base align.
1126  if (!MaxFieldAlignment.isZero()) {
1127    BaseAlign = std::min(BaseAlign, MaxFieldAlignment);
1128    UnpackedBaseAlign = std::min(UnpackedBaseAlign, MaxFieldAlignment);
1129  }
1130
1131  // Round up the current record size to the base's alignment boundary.
1132  CharUnits Offset = getDataSize().RoundUpToAlignment(BaseAlign);
1133
1134  // Try to place the base.
1135  while (!EmptySubobjects->CanPlaceBaseAtOffset(Base, Offset))
1136    Offset += BaseAlign;
1137
1138  if (!Base->Class->isEmpty()) {
1139    // Update the data size.
1140    setDataSize(Offset + Layout.getNonVirtualSize());
1141
1142    setSize(std::max(getSize(), getDataSize()));
1143  } else
1144    setSize(std::max(getSize(), Offset + Layout.getSize()));
1145
1146  // Remember max struct/class alignment.
1147  UpdateAlignment(BaseAlign, UnpackedBaseAlign);
1148
1149  return Offset;
1150}
1151
1152void RecordLayoutBuilder::InitializeLayout(const Decl *D) {
1153  if (const RecordDecl *RD = dyn_cast<RecordDecl>(D))
1154    IsUnion = RD->isUnion();
1155
1156  Packed = D->hasAttr<PackedAttr>();
1157
1158  IsMsStruct = D->hasAttr<MsStructAttr>();
1159
1160  // mac68k alignment supersedes maximum field alignment and attribute aligned,
1161  // and forces all structures to have 2-byte alignment. The IBM docs on it
1162  // allude to additional (more complicated) semantics, especially with regard
1163  // to bit-fields, but gcc appears not to follow that.
1164  if (D->hasAttr<AlignMac68kAttr>()) {
1165    IsMac68kAlign = true;
1166    MaxFieldAlignment = CharUnits::fromQuantity(2);
1167    Alignment = CharUnits::fromQuantity(2);
1168  } else {
1169    if (const MaxFieldAlignmentAttr *MFAA = D->getAttr<MaxFieldAlignmentAttr>())
1170      MaxFieldAlignment = Context.toCharUnitsFromBits(MFAA->getAlignment());
1171
1172    if (unsigned MaxAlign = D->getMaxAlignment())
1173      UpdateAlignment(Context.toCharUnitsFromBits(MaxAlign));
1174  }
1175}
1176
1177void RecordLayoutBuilder::Layout(const RecordDecl *D) {
1178  InitializeLayout(D);
1179  LayoutFields(D);
1180
1181  // Finally, round the size of the total struct up to the alignment of the
1182  // struct itself.
1183  FinishLayout(D);
1184}
1185
1186void RecordLayoutBuilder::Layout(const CXXRecordDecl *RD) {
1187  InitializeLayout(RD);
1188
1189  // Lay out the vtable and the non-virtual bases.
1190  LayoutNonVirtualBases(RD);
1191
1192  LayoutFields(RD);
1193
1194  NonVirtualSize = Context.toCharUnitsFromBits(
1195        llvm::RoundUpToAlignment(getSizeInBits(),
1196                                 Context.Target.getCharAlign()));
1197  NonVirtualAlignment = Alignment;
1198
1199  // Lay out the virtual bases and add the primary virtual base offsets.
1200  LayoutVirtualBases(RD, RD);
1201
1202  VisitedVirtualBases.clear();
1203
1204  // Finally, round the size of the total struct up to the alignment of the
1205  // struct itself.
1206  FinishLayout(RD);
1207
1208#ifndef NDEBUG
1209  // Check that we have base offsets for all bases.
1210  for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
1211       E = RD->bases_end(); I != E; ++I) {
1212    if (I->isVirtual())
1213      continue;
1214
1215    const CXXRecordDecl *BaseDecl =
1216      cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
1217
1218    assert(Bases.count(BaseDecl) && "Did not find base offset!");
1219  }
1220
1221  // And all virtual bases.
1222  for (CXXRecordDecl::base_class_const_iterator I = RD->vbases_begin(),
1223       E = RD->vbases_end(); I != E; ++I) {
1224    const CXXRecordDecl *BaseDecl =
1225      cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
1226
1227    assert(VBases.count(BaseDecl) && "Did not find base offset!");
1228  }
1229#endif
1230}
1231
1232void RecordLayoutBuilder::Layout(const ObjCInterfaceDecl *D) {
1233  if (ObjCInterfaceDecl *SD = D->getSuperClass()) {
1234    const ASTRecordLayout &SL = Context.getASTObjCInterfaceLayout(SD);
1235
1236    UpdateAlignment(SL.getAlignment());
1237
1238    // We start laying out ivars not at the end of the superclass
1239    // structure, but at the next byte following the last field.
1240    setSize(SL.getDataSize());
1241    setDataSize(getSize());
1242  }
1243
1244  InitializeLayout(D);
1245
1246  // Layout each ivar sequentially.
1247  llvm::SmallVector<ObjCIvarDecl*, 16> Ivars;
1248  Context.ShallowCollectObjCIvars(D, Ivars);
1249  for (unsigned i = 0, e = Ivars.size(); i != e; ++i)
1250    LayoutField(Ivars[i]);
1251
1252  // Finally, round the size of the total struct up to the alignment of the
1253  // struct itself.
1254  FinishLayout(D);
1255}
1256
1257void RecordLayoutBuilder::LayoutFields(const RecordDecl *D) {
1258  // Layout each field, for now, just sequentially, respecting alignment.  In
1259  // the future, this will need to be tweakable by targets.
1260  const FieldDecl *LastFD = 0;
1261  ZeroLengthBitfield = 0;
1262  for (RecordDecl::field_iterator Field = D->field_begin(),
1263       FieldEnd = D->field_end(); Field != FieldEnd; ++Field) {
1264    if (IsMsStruct) {
1265      FieldDecl *FD =  (*Field);
1266      if (Context.ZeroBitfieldFollowsBitfield(FD, LastFD))
1267        ZeroLengthBitfield = FD;
1268      // Zero-length bitfields following non-bitfield members are
1269      // ignored:
1270      else if (Context.ZeroBitfieldFollowsNonBitfield(FD, LastFD))
1271        continue;
1272      else if (Context.BitfieldFollowsBitfield(FD, LastFD) ||
1273               Context.BitfieldFollowsNoneBitfield(FD, LastFD)) {
1274        // Adjacent bit fields are packed into the same 1-, 2-, or
1275        // 4-byte allocation unit if the integral types are the same
1276        // size and if the next bit field fits into the current
1277        // allocation unit without crossing the boundary imposed by the
1278        // common alignment requirements of the bit fields.
1279        // Also, establish a new alignment for a bitfield following
1280        // a non-bitfield if size of their types differ.
1281        std::pair<uint64_t, unsigned> FieldInfo =
1282          Context.getTypeInfo(FD->getType());
1283        uint64_t TypeSize = FieldInfo.first;
1284        unsigned FieldAlign = FieldInfo.second;
1285        FieldInfo = Context.getTypeInfo(LastFD->getType());
1286        uint64_t TypeSizeLastFD = FieldInfo.first;
1287        unsigned FieldAlignLastFD = FieldInfo.second;
1288        if (TypeSizeLastFD != TypeSize) {
1289          uint64_t UnpaddedFieldOffset =
1290            getDataSizeInBits() - UnfilledBitsInLastByte;
1291          FieldAlign = std::max(FieldAlign, FieldAlignLastFD);
1292          uint64_t NewSizeInBits =
1293            llvm::RoundUpToAlignment(UnpaddedFieldOffset, FieldAlign);
1294          setDataSize(llvm::RoundUpToAlignment(NewSizeInBits,
1295                                               Context.Target.getCharAlign()));
1296          UnfilledBitsInLastByte = getDataSizeInBits() - NewSizeInBits;
1297          setSize(std::max(getSizeInBits(), getDataSizeInBits()));
1298        }
1299      }
1300      LastFD = FD;
1301    }
1302    LayoutField(*Field);
1303  }
1304}
1305
1306void RecordLayoutBuilder::LayoutWideBitField(uint64_t FieldSize,
1307                                             uint64_t TypeSize,
1308                                             bool FieldPacked,
1309                                             const FieldDecl *D) {
1310  assert(Context.getLangOptions().CPlusPlus &&
1311         "Can only have wide bit-fields in C++!");
1312
1313  // Itanium C++ ABI 2.4:
1314  //   If sizeof(T)*8 < n, let T' be the largest integral POD type with
1315  //   sizeof(T')*8 <= n.
1316
1317  QualType IntegralPODTypes[] = {
1318    Context.UnsignedCharTy, Context.UnsignedShortTy, Context.UnsignedIntTy,
1319    Context.UnsignedLongTy, Context.UnsignedLongLongTy
1320  };
1321
1322  QualType Type;
1323  for (unsigned I = 0, E = llvm::array_lengthof(IntegralPODTypes);
1324       I != E; ++I) {
1325    uint64_t Size = Context.getTypeSize(IntegralPODTypes[I]);
1326
1327    if (Size > FieldSize)
1328      break;
1329
1330    Type = IntegralPODTypes[I];
1331  }
1332  assert(!Type.isNull() && "Did not find a type!");
1333
1334  CharUnits TypeAlign = Context.getTypeAlignInChars(Type);
1335
1336  // We're not going to use any of the unfilled bits in the last byte.
1337  UnfilledBitsInLastByte = 0;
1338
1339  uint64_t FieldOffset;
1340  uint64_t UnpaddedFieldOffset = getDataSizeInBits() - UnfilledBitsInLastByte;
1341
1342  if (IsUnion) {
1343    setDataSize(std::max(getDataSizeInBits(), FieldSize));
1344    FieldOffset = 0;
1345  } else {
1346    // The bitfield is allocated starting at the next offset aligned appropriately
1347    // for T', with length n bits.
1348    FieldOffset = llvm::RoundUpToAlignment(getDataSizeInBits(),
1349                                           Context.toBits(TypeAlign));
1350
1351    uint64_t NewSizeInBits = FieldOffset + FieldSize;
1352
1353    setDataSize(llvm::RoundUpToAlignment(NewSizeInBits,
1354                                         Context.Target.getCharAlign()));
1355    UnfilledBitsInLastByte = getDataSizeInBits() - NewSizeInBits;
1356  }
1357
1358  // Place this field at the current location.
1359  FieldOffsets.push_back(FieldOffset);
1360
1361  CheckFieldPadding(FieldOffset, UnpaddedFieldOffset, FieldOffset,
1362                    Context.toBits(TypeAlign), FieldPacked, D);
1363
1364  // Update the size.
1365  setSize(std::max(getSizeInBits(), getDataSizeInBits()));
1366
1367  // Remember max struct/class alignment.
1368  UpdateAlignment(TypeAlign);
1369}
1370
1371void RecordLayoutBuilder::LayoutBitField(const FieldDecl *D) {
1372  bool FieldPacked = Packed || D->hasAttr<PackedAttr>();
1373  uint64_t UnpaddedFieldOffset = getDataSizeInBits() - UnfilledBitsInLastByte;
1374  uint64_t FieldOffset = IsUnion ? 0 : UnpaddedFieldOffset;
1375  uint64_t FieldSize = D->getBitWidth()->EvaluateAsInt(Context).getZExtValue();
1376
1377  std::pair<uint64_t, unsigned> FieldInfo = Context.getTypeInfo(D->getType());
1378  uint64_t TypeSize = FieldInfo.first;
1379  unsigned FieldAlign = FieldInfo.second;
1380
1381  if (ZeroLengthBitfield) {
1382    // If a zero-length bitfield is inserted after a bitfield,
1383    // and the alignment of the zero-length bitfield is
1384    // greater than the member that follows it, `bar', `bar'
1385    // will be aligned as the type of the zero-length bitfield.
1386    if (ZeroLengthBitfield != D) {
1387      std::pair<uint64_t, unsigned> FieldInfo =
1388        Context.getTypeInfo(ZeroLengthBitfield->getType());
1389      unsigned ZeroLengthBitfieldAlignment = FieldInfo.second;
1390      // Ignore alignment of subsequent zero-length bitfields.
1391      if ((ZeroLengthBitfieldAlignment > FieldAlign) || (FieldSize == 0))
1392        FieldAlign = ZeroLengthBitfieldAlignment;
1393      if (FieldSize)
1394        ZeroLengthBitfield = 0;
1395    }
1396  }
1397
1398  if (FieldSize > TypeSize) {
1399    LayoutWideBitField(FieldSize, TypeSize, FieldPacked, D);
1400    return;
1401  }
1402
1403  // The align if the field is not packed. This is to check if the attribute
1404  // was unnecessary (-Wpacked).
1405  unsigned UnpackedFieldAlign = FieldAlign;
1406  uint64_t UnpackedFieldOffset = FieldOffset;
1407  if (!Context.Target.useBitFieldTypeAlignment())
1408    UnpackedFieldAlign = 1;
1409
1410  if (FieldPacked || !Context.Target.useBitFieldTypeAlignment())
1411    FieldAlign = 1;
1412  FieldAlign = std::max(FieldAlign, D->getMaxAlignment());
1413  UnpackedFieldAlign = std::max(UnpackedFieldAlign, D->getMaxAlignment());
1414
1415  // The maximum field alignment overrides the aligned attribute.
1416  if (!MaxFieldAlignment.isZero()) {
1417    unsigned MaxFieldAlignmentInBits = Context.toBits(MaxFieldAlignment);
1418    FieldAlign = std::min(FieldAlign, MaxFieldAlignmentInBits);
1419    UnpackedFieldAlign = std::min(UnpackedFieldAlign, MaxFieldAlignmentInBits);
1420  }
1421
1422  // Check if we need to add padding to give the field the correct alignment.
1423  if (FieldSize == 0 || (FieldOffset & (FieldAlign-1)) + FieldSize > TypeSize)
1424    FieldOffset = llvm::RoundUpToAlignment(FieldOffset, FieldAlign);
1425
1426  if (FieldSize == 0 ||
1427      (UnpackedFieldOffset & (UnpackedFieldAlign-1)) + FieldSize > TypeSize)
1428    UnpackedFieldOffset = llvm::RoundUpToAlignment(UnpackedFieldOffset,
1429                                                   UnpackedFieldAlign);
1430
1431  // Padding members don't affect overall alignment.
1432  if (!D->getIdentifier())
1433    FieldAlign = UnpackedFieldAlign = 1;
1434
1435  // Place this field at the current location.
1436  FieldOffsets.push_back(FieldOffset);
1437
1438  CheckFieldPadding(FieldOffset, UnpaddedFieldOffset, UnpackedFieldOffset,
1439                    UnpackedFieldAlign, FieldPacked, D);
1440
1441  // Update DataSize to include the last byte containing (part of) the bitfield.
1442  if (IsUnion) {
1443    // FIXME: I think FieldSize should be TypeSize here.
1444    setDataSize(std::max(getDataSizeInBits(), FieldSize));
1445  } else {
1446    uint64_t NewSizeInBits = FieldOffset + FieldSize;
1447
1448    setDataSize(llvm::RoundUpToAlignment(NewSizeInBits,
1449                                         Context.Target.getCharAlign()));
1450    UnfilledBitsInLastByte = getDataSizeInBits() - NewSizeInBits;
1451  }
1452
1453  // Update the size.
1454  setSize(std::max(getSizeInBits(), getDataSizeInBits()));
1455
1456  // Remember max struct/class alignment.
1457  UpdateAlignment(Context.toCharUnitsFromBits(FieldAlign),
1458                  Context.toCharUnitsFromBits(UnpackedFieldAlign));
1459}
1460
1461void RecordLayoutBuilder::LayoutField(const FieldDecl *D) {
1462  if (D->isBitField()) {
1463    LayoutBitField(D);
1464    return;
1465  }
1466
1467  uint64_t UnpaddedFieldOffset = getDataSizeInBits() - UnfilledBitsInLastByte;
1468
1469  // Reset the unfilled bits.
1470  UnfilledBitsInLastByte = 0;
1471
1472  bool FieldPacked = Packed || D->hasAttr<PackedAttr>();
1473  CharUnits FieldOffset =
1474    IsUnion ? CharUnits::Zero() : getDataSize();
1475  CharUnits FieldSize;
1476  CharUnits FieldAlign;
1477
1478  if (D->getType()->isIncompleteArrayType()) {
1479    // This is a flexible array member; we can't directly
1480    // query getTypeInfo about these, so we figure it out here.
1481    // Flexible array members don't have any size, but they
1482    // have to be aligned appropriately for their element type.
1483    FieldSize = CharUnits::Zero();
1484    const ArrayType* ATy = Context.getAsArrayType(D->getType());
1485    FieldAlign = Context.getTypeAlignInChars(ATy->getElementType());
1486  } else if (const ReferenceType *RT = D->getType()->getAs<ReferenceType>()) {
1487    unsigned AS = RT->getPointeeType().getAddressSpace();
1488    FieldSize =
1489      Context.toCharUnitsFromBits(Context.Target.getPointerWidth(AS));
1490    FieldAlign =
1491      Context.toCharUnitsFromBits(Context.Target.getPointerAlign(AS));
1492  } else {
1493    std::pair<CharUnits, CharUnits> FieldInfo =
1494      Context.getTypeInfoInChars(D->getType());
1495    FieldSize = FieldInfo.first;
1496    FieldAlign = FieldInfo.second;
1497
1498    if (ZeroLengthBitfield) {
1499      // If a zero-length bitfield is inserted after a bitfield,
1500      // and the alignment of the zero-length bitfield is
1501      // greater than the member that follows it, `bar', `bar'
1502      // will be aligned as the type of the zero-length bitfield.
1503      std::pair<CharUnits, CharUnits> FieldInfo =
1504        Context.getTypeInfoInChars(ZeroLengthBitfield->getType());
1505      CharUnits ZeroLengthBitfieldAlignment = FieldInfo.second;
1506      if (ZeroLengthBitfieldAlignment > FieldAlign)
1507        FieldAlign = ZeroLengthBitfieldAlignment;
1508      ZeroLengthBitfield = 0;
1509    }
1510
1511    if (Context.getLangOptions().MSBitfields || IsMsStruct) {
1512      // If MS bitfield layout is required, figure out what type is being
1513      // laid out and align the field to the width of that type.
1514
1515      // Resolve all typedefs down to their base type and round up the field
1516      // alignment if necessary.
1517      QualType T = Context.getBaseElementType(D->getType());
1518      if (const BuiltinType *BTy = T->getAs<BuiltinType>()) {
1519        CharUnits TypeSize = Context.getTypeSizeInChars(BTy);
1520        if (TypeSize > FieldAlign)
1521          FieldAlign = TypeSize;
1522      }
1523    }
1524  }
1525
1526  // The align if the field is not packed. This is to check if the attribute
1527  // was unnecessary (-Wpacked).
1528  CharUnits UnpackedFieldAlign = FieldAlign;
1529  CharUnits UnpackedFieldOffset = FieldOffset;
1530
1531  if (FieldPacked)
1532    FieldAlign = CharUnits::One();
1533  CharUnits MaxAlignmentInChars =
1534    Context.toCharUnitsFromBits(D->getMaxAlignment());
1535  FieldAlign = std::max(FieldAlign, MaxAlignmentInChars);
1536  UnpackedFieldAlign = std::max(UnpackedFieldAlign, MaxAlignmentInChars);
1537
1538  // The maximum field alignment overrides the aligned attribute.
1539  if (!MaxFieldAlignment.isZero()) {
1540    FieldAlign = std::min(FieldAlign, MaxFieldAlignment);
1541    UnpackedFieldAlign = std::min(UnpackedFieldAlign, MaxFieldAlignment);
1542  }
1543
1544  // Round up the current record size to the field's alignment boundary.
1545  FieldOffset = FieldOffset.RoundUpToAlignment(FieldAlign);
1546  UnpackedFieldOffset =
1547    UnpackedFieldOffset.RoundUpToAlignment(UnpackedFieldAlign);
1548
1549  if (!IsUnion && EmptySubobjects) {
1550    // Check if we can place the field at this offset.
1551    while (!EmptySubobjects->CanPlaceFieldAtOffset(D, FieldOffset)) {
1552      // We couldn't place the field at the offset. Try again at a new offset.
1553      FieldOffset += FieldAlign;
1554    }
1555  }
1556
1557  // Place this field at the current location.
1558  FieldOffsets.push_back(Context.toBits(FieldOffset));
1559
1560  CheckFieldPadding(Context.toBits(FieldOffset), UnpaddedFieldOffset,
1561                    Context.toBits(UnpackedFieldOffset),
1562                    Context.toBits(UnpackedFieldAlign), FieldPacked, D);
1563
1564  // Reserve space for this field.
1565  uint64_t FieldSizeInBits = Context.toBits(FieldSize);
1566  if (IsUnion)
1567    setSize(std::max(getSizeInBits(), FieldSizeInBits));
1568  else
1569    setSize(FieldOffset + FieldSize);
1570
1571  // Update the data size.
1572  setDataSize(getSizeInBits());
1573
1574  // Remember max struct/class alignment.
1575  UpdateAlignment(FieldAlign, UnpackedFieldAlign);
1576}
1577
1578void RecordLayoutBuilder::FinishLayout(const NamedDecl *D) {
1579  // In C++, records cannot be of size 0.
1580  if (Context.getLangOptions().CPlusPlus && getSizeInBits() == 0) {
1581    if (const CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(D)) {
1582      // Compatibility with gcc requires a class (pod or non-pod)
1583      // which is not empty but of size 0; such as having fields of
1584      // array of zero-length, remains of Size 0
1585      if (RD->isEmpty())
1586        setSize(CharUnits::One());
1587    }
1588    else
1589      setSize(CharUnits::One());
1590  }
1591  // Finally, round the size of the record up to the alignment of the
1592  // record itself.
1593  uint64_t UnpaddedSize = getSizeInBits() - UnfilledBitsInLastByte;
1594  uint64_t UnpackedSizeInBits =
1595    llvm::RoundUpToAlignment(getSizeInBits(),
1596                             Context.toBits(UnpackedAlignment));
1597  CharUnits UnpackedSize = Context.toCharUnitsFromBits(UnpackedSizeInBits);
1598  setSize(llvm::RoundUpToAlignment(getSizeInBits(), Context.toBits(Alignment)));
1599
1600  unsigned CharBitNum = Context.Target.getCharWidth();
1601  if (const RecordDecl *RD = dyn_cast<RecordDecl>(D)) {
1602    // Warn if padding was introduced to the struct/class/union.
1603    if (getSizeInBits() > UnpaddedSize) {
1604      unsigned PadSize = getSizeInBits() - UnpaddedSize;
1605      bool InBits = true;
1606      if (PadSize % CharBitNum == 0) {
1607        PadSize = PadSize / CharBitNum;
1608        InBits = false;
1609      }
1610      Diag(RD->getLocation(), diag::warn_padded_struct_size)
1611          << Context.getTypeDeclType(RD)
1612          << PadSize
1613          << (InBits ? 1 : 0) /*(byte|bit)*/ << (PadSize > 1); // plural or not
1614    }
1615
1616    // Warn if we packed it unnecessarily. If the alignment is 1 byte don't
1617    // bother since there won't be alignment issues.
1618    if (Packed && UnpackedAlignment > CharUnits::One() &&
1619        getSize() == UnpackedSize)
1620      Diag(D->getLocation(), diag::warn_unnecessary_packed)
1621          << Context.getTypeDeclType(RD);
1622  }
1623}
1624
1625void RecordLayoutBuilder::UpdateAlignment(CharUnits NewAlignment,
1626                                          CharUnits UnpackedNewAlignment) {
1627  // The alignment is not modified when using 'mac68k' alignment.
1628  if (IsMac68kAlign)
1629    return;
1630
1631  if (NewAlignment > Alignment) {
1632    assert(llvm::isPowerOf2_32(NewAlignment.getQuantity() &&
1633           "Alignment not a power of 2"));
1634    Alignment = NewAlignment;
1635  }
1636
1637  if (UnpackedNewAlignment > UnpackedAlignment) {
1638    assert(llvm::isPowerOf2_32(UnpackedNewAlignment.getQuantity() &&
1639           "Alignment not a power of 2"));
1640    UnpackedAlignment = UnpackedNewAlignment;
1641  }
1642}
1643
1644void RecordLayoutBuilder::CheckFieldPadding(uint64_t Offset,
1645                                            uint64_t UnpaddedOffset,
1646                                            uint64_t UnpackedOffset,
1647                                            unsigned UnpackedAlign,
1648                                            bool isPacked,
1649                                            const FieldDecl *D) {
1650  // We let objc ivars without warning, objc interfaces generally are not used
1651  // for padding tricks.
1652  if (isa<ObjCIvarDecl>(D))
1653    return;
1654
1655  unsigned CharBitNum = Context.Target.getCharWidth();
1656
1657  // Warn if padding was introduced to the struct/class.
1658  if (!IsUnion && Offset > UnpaddedOffset) {
1659    unsigned PadSize = Offset - UnpaddedOffset;
1660    bool InBits = true;
1661    if (PadSize % CharBitNum == 0) {
1662      PadSize = PadSize / CharBitNum;
1663      InBits = false;
1664    }
1665    if (D->getIdentifier())
1666      Diag(D->getLocation(), diag::warn_padded_struct_field)
1667          << (D->getParent()->isStruct() ? 0 : 1) // struct|class
1668          << Context.getTypeDeclType(D->getParent())
1669          << PadSize
1670          << (InBits ? 1 : 0) /*(byte|bit)*/ << (PadSize > 1) // plural or not
1671          << D->getIdentifier();
1672    else
1673      Diag(D->getLocation(), diag::warn_padded_struct_anon_field)
1674          << (D->getParent()->isStruct() ? 0 : 1) // struct|class
1675          << Context.getTypeDeclType(D->getParent())
1676          << PadSize
1677          << (InBits ? 1 : 0) /*(byte|bit)*/ << (PadSize > 1); // plural or not
1678  }
1679
1680  // Warn if we packed it unnecessarily. If the alignment is 1 byte don't
1681  // bother since there won't be alignment issues.
1682  if (isPacked && UnpackedAlign > CharBitNum && Offset == UnpackedOffset)
1683    Diag(D->getLocation(), diag::warn_unnecessary_packed)
1684        << D->getIdentifier();
1685}
1686
1687const CXXMethodDecl *
1688RecordLayoutBuilder::ComputeKeyFunction(const CXXRecordDecl *RD) {
1689  // If a class isn't polymorphic it doesn't have a key function.
1690  if (!RD->isPolymorphic())
1691    return 0;
1692
1693  // A class inside an anonymous namespace doesn't have a key function.  (Or
1694  // at least, there's no point to assigning a key function to such a class;
1695  // this doesn't affect the ABI.)
1696  if (RD->isInAnonymousNamespace())
1697    return 0;
1698
1699  // Template instantiations don't have key functions,see Itanium C++ ABI 5.2.6.
1700  // Same behavior as GCC.
1701  TemplateSpecializationKind TSK = RD->getTemplateSpecializationKind();
1702  if (TSK == TSK_ImplicitInstantiation ||
1703      TSK == TSK_ExplicitInstantiationDefinition)
1704    return 0;
1705
1706  for (CXXRecordDecl::method_iterator I = RD->method_begin(),
1707         E = RD->method_end(); I != E; ++I) {
1708    const CXXMethodDecl *MD = *I;
1709
1710    if (!MD->isVirtual())
1711      continue;
1712
1713    if (MD->isPure())
1714      continue;
1715
1716    // Ignore implicit member functions, they are always marked as inline, but
1717    // they don't have a body until they're defined.
1718    if (MD->isImplicit())
1719      continue;
1720
1721    if (MD->isInlineSpecified())
1722      continue;
1723
1724    if (MD->hasInlineBody())
1725      continue;
1726
1727    // We found it.
1728    return MD;
1729  }
1730
1731  return 0;
1732}
1733
1734DiagnosticBuilder
1735RecordLayoutBuilder::Diag(SourceLocation Loc, unsigned DiagID) {
1736  return Context.getDiagnostics().Report(Loc, DiagID);
1737}
1738
1739namespace {
1740  // This class implements layout specific to the Microsoft ABI.
1741  class MSRecordLayoutBuilder : public RecordLayoutBuilder {
1742  public:
1743    MSRecordLayoutBuilder(const ASTContext& Ctx,
1744                          EmptySubobjectMap *EmptySubobjects) :
1745      RecordLayoutBuilder(Ctx, EmptySubobjects) {}
1746
1747    virtual CharUnits GetVirtualPointersSize(const CXXRecordDecl *RD) const;
1748  };
1749}
1750
1751CharUnits
1752MSRecordLayoutBuilder::GetVirtualPointersSize(const CXXRecordDecl *RD) const {
1753  // We should reserve space for two pointers if the class has both
1754  // virtual functions and virtual bases.
1755  CharUnits PointerWidth =
1756    Context.toCharUnitsFromBits(Context.Target.getPointerWidth(0));
1757  if (RD->isPolymorphic() && RD->getNumVBases() > 0)
1758    return 2 * PointerWidth;
1759  return PointerWidth;
1760}
1761
1762/// getASTRecordLayout - Get or compute information about the layout of the
1763/// specified record (struct/union/class), which indicates its size and field
1764/// position information.
1765const ASTRecordLayout &
1766ASTContext::getASTRecordLayout(const RecordDecl *D) const {
1767  D = D->getDefinition();
1768  assert(D && "Cannot get layout of forward declarations!");
1769
1770  // Look up this layout, if already laid out, return what we have.
1771  // Note that we can't save a reference to the entry because this function
1772  // is recursive.
1773  const ASTRecordLayout *Entry = ASTRecordLayouts[D];
1774  if (Entry) return *Entry;
1775
1776  const ASTRecordLayout *NewEntry;
1777
1778  if (const CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(D)) {
1779    EmptySubobjectMap EmptySubobjects(*this, RD);
1780
1781    // When compiling for Microsoft, use the special MS builder.
1782    llvm::OwningPtr<RecordLayoutBuilder> Builder;
1783    switch (Target.getCXXABI()) {
1784    default:
1785      Builder.reset(new RecordLayoutBuilder(*this, &EmptySubobjects));
1786      break;
1787    case CXXABI_Microsoft:
1788      Builder.reset(new MSRecordLayoutBuilder(*this, &EmptySubobjects));
1789    }
1790    // Recover resources if we crash before exiting this method.
1791    llvm::CrashRecoveryContextCleanupRegistrar<RecordLayoutBuilder>
1792      RecordBuilderCleanup(Builder.get());
1793
1794    Builder->Layout(RD);
1795
1796    // FIXME: This is not always correct. See the part about bitfields at
1797    // http://www.codesourcery.com/public/cxx-abi/abi.html#POD for more info.
1798    // FIXME: IsPODForThePurposeOfLayout should be stored in the record layout.
1799    bool IsPODForThePurposeOfLayout = cast<CXXRecordDecl>(D)->isPOD();
1800
1801    // FIXME: This should be done in FinalizeLayout.
1802    CharUnits DataSize =
1803      IsPODForThePurposeOfLayout ? Builder->getSize() : Builder->getDataSize();
1804    CharUnits NonVirtualSize =
1805      IsPODForThePurposeOfLayout ? DataSize : Builder->NonVirtualSize;
1806
1807    NewEntry =
1808      new (*this) ASTRecordLayout(*this, Builder->getSize(),
1809                                  Builder->Alignment,
1810                                  DataSize,
1811                                  Builder->FieldOffsets.data(),
1812                                  Builder->FieldOffsets.size(),
1813                                  NonVirtualSize,
1814                                  Builder->NonVirtualAlignment,
1815                                  EmptySubobjects.SizeOfLargestEmptySubobject,
1816                                  Builder->PrimaryBase,
1817                                  Builder->PrimaryBaseIsVirtual,
1818                                  Builder->Bases, Builder->VBases);
1819  } else {
1820    RecordLayoutBuilder Builder(*this, /*EmptySubobjects=*/0);
1821    Builder.Layout(D);
1822
1823    NewEntry =
1824      new (*this) ASTRecordLayout(*this, Builder.getSize(),
1825                                  Builder.Alignment,
1826                                  Builder.getSize(),
1827                                  Builder.FieldOffsets.data(),
1828                                  Builder.FieldOffsets.size());
1829  }
1830
1831  ASTRecordLayouts[D] = NewEntry;
1832
1833  if (getLangOptions().DumpRecordLayouts) {
1834    llvm::errs() << "\n*** Dumping AST Record Layout\n";
1835    DumpRecordLayout(D, llvm::errs());
1836  }
1837
1838  return *NewEntry;
1839}
1840
1841const CXXMethodDecl *ASTContext::getKeyFunction(const CXXRecordDecl *RD) {
1842  RD = cast<CXXRecordDecl>(RD->getDefinition());
1843  assert(RD && "Cannot get key function for forward declarations!");
1844
1845  const CXXMethodDecl *&Entry = KeyFunctions[RD];
1846  if (!Entry)
1847    Entry = RecordLayoutBuilder::ComputeKeyFunction(RD);
1848
1849  return Entry;
1850}
1851
1852/// getInterfaceLayoutImpl - Get or compute information about the
1853/// layout of the given interface.
1854///
1855/// \param Impl - If given, also include the layout of the interface's
1856/// implementation. This may differ by including synthesized ivars.
1857const ASTRecordLayout &
1858ASTContext::getObjCLayout(const ObjCInterfaceDecl *D,
1859                          const ObjCImplementationDecl *Impl) const {
1860  assert(!D->isForwardDecl() && "Invalid interface decl!");
1861
1862  // Look up this layout, if already laid out, return what we have.
1863  ObjCContainerDecl *Key =
1864    Impl ? (ObjCContainerDecl*) Impl : (ObjCContainerDecl*) D;
1865  if (const ASTRecordLayout *Entry = ObjCLayouts[Key])
1866    return *Entry;
1867
1868  // Add in synthesized ivar count if laying out an implementation.
1869  if (Impl) {
1870    unsigned SynthCount = CountNonClassIvars(D);
1871    // If there aren't any sythesized ivars then reuse the interface
1872    // entry. Note we can't cache this because we simply free all
1873    // entries later; however we shouldn't look up implementations
1874    // frequently.
1875    if (SynthCount == 0)
1876      return getObjCLayout(D, 0);
1877  }
1878
1879  RecordLayoutBuilder Builder(*this, /*EmptySubobjects=*/0);
1880  Builder.Layout(D);
1881
1882  const ASTRecordLayout *NewEntry =
1883    new (*this) ASTRecordLayout(*this, Builder.getSize(),
1884                                Builder.Alignment,
1885                                Builder.getDataSize(),
1886                                Builder.FieldOffsets.data(),
1887                                Builder.FieldOffsets.size());
1888
1889  ObjCLayouts[Key] = NewEntry;
1890
1891  return *NewEntry;
1892}
1893
1894static void PrintOffset(llvm::raw_ostream &OS,
1895                        CharUnits Offset, unsigned IndentLevel) {
1896  OS << llvm::format("%4d | ", Offset.getQuantity());
1897  OS.indent(IndentLevel * 2);
1898}
1899
1900static void DumpCXXRecordLayout(llvm::raw_ostream &OS,
1901                                const CXXRecordDecl *RD, const ASTContext &C,
1902                                CharUnits Offset,
1903                                unsigned IndentLevel,
1904                                const char* Description,
1905                                bool IncludeVirtualBases) {
1906  const ASTRecordLayout &Layout = C.getASTRecordLayout(RD);
1907
1908  PrintOffset(OS, Offset, IndentLevel);
1909  OS << C.getTypeDeclType(const_cast<CXXRecordDecl *>(RD)).getAsString();
1910  if (Description)
1911    OS << ' ' << Description;
1912  if (RD->isEmpty())
1913    OS << " (empty)";
1914  OS << '\n';
1915
1916  IndentLevel++;
1917
1918  const CXXRecordDecl *PrimaryBase = Layout.getPrimaryBase();
1919
1920  // Vtable pointer.
1921  if (RD->isDynamicClass() && !PrimaryBase) {
1922    PrintOffset(OS, Offset, IndentLevel);
1923    OS << '(' << RD << " vtable pointer)\n";
1924  }
1925  // Dump (non-virtual) bases
1926  for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
1927         E = RD->bases_end(); I != E; ++I) {
1928    assert(!I->getType()->isDependentType() &&
1929           "Cannot layout class with dependent bases.");
1930    if (I->isVirtual())
1931      continue;
1932
1933    const CXXRecordDecl *Base =
1934      cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
1935
1936    CharUnits BaseOffset = Offset + Layout.getBaseClassOffset(Base);
1937
1938    DumpCXXRecordLayout(OS, Base, C, BaseOffset, IndentLevel,
1939                        Base == PrimaryBase ? "(primary base)" : "(base)",
1940                        /*IncludeVirtualBases=*/false);
1941  }
1942
1943  // Dump fields.
1944  uint64_t FieldNo = 0;
1945  for (CXXRecordDecl::field_iterator I = RD->field_begin(),
1946         E = RD->field_end(); I != E; ++I, ++FieldNo) {
1947    const FieldDecl *Field = *I;
1948    CharUnits FieldOffset = Offset +
1949      C.toCharUnitsFromBits(Layout.getFieldOffset(FieldNo));
1950
1951    if (const RecordType *RT = Field->getType()->getAs<RecordType>()) {
1952      if (const CXXRecordDecl *D = dyn_cast<CXXRecordDecl>(RT->getDecl())) {
1953        DumpCXXRecordLayout(OS, D, C, FieldOffset, IndentLevel,
1954                            Field->getName().data(),
1955                            /*IncludeVirtualBases=*/true);
1956        continue;
1957      }
1958    }
1959
1960    PrintOffset(OS, FieldOffset, IndentLevel);
1961    OS << Field->getType().getAsString() << ' ' << Field << '\n';
1962  }
1963
1964  if (!IncludeVirtualBases)
1965    return;
1966
1967  // Dump virtual bases.
1968  for (CXXRecordDecl::base_class_const_iterator I = RD->vbases_begin(),
1969         E = RD->vbases_end(); I != E; ++I) {
1970    assert(I->isVirtual() && "Found non-virtual class!");
1971    const CXXRecordDecl *VBase =
1972      cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
1973
1974    CharUnits VBaseOffset = Offset + Layout.getVBaseClassOffset(VBase);
1975    DumpCXXRecordLayout(OS, VBase, C, VBaseOffset, IndentLevel,
1976                        VBase == PrimaryBase ?
1977                        "(primary virtual base)" : "(virtual base)",
1978                        /*IncludeVirtualBases=*/false);
1979  }
1980
1981  OS << "  sizeof=" << Layout.getSize().getQuantity();
1982  OS << ", dsize=" << Layout.getDataSize().getQuantity();
1983  OS << ", align=" << Layout.getAlignment().getQuantity() << '\n';
1984  OS << "  nvsize=" << Layout.getNonVirtualSize().getQuantity();
1985  OS << ", nvalign=" << Layout.getNonVirtualAlign().getQuantity() << '\n';
1986  OS << '\n';
1987}
1988
1989void ASTContext::DumpRecordLayout(const RecordDecl *RD,
1990                                  llvm::raw_ostream &OS) const {
1991  const ASTRecordLayout &Info = getASTRecordLayout(RD);
1992
1993  if (const CXXRecordDecl *CXXRD = dyn_cast<CXXRecordDecl>(RD))
1994    return DumpCXXRecordLayout(OS, CXXRD, *this, CharUnits(), 0, 0,
1995                               /*IncludeVirtualBases=*/true);
1996
1997  OS << "Type: " << getTypeDeclType(RD).getAsString() << "\n";
1998  OS << "Record: ";
1999  RD->dump();
2000  OS << "\nLayout: ";
2001  OS << "<ASTRecordLayout\n";
2002  OS << "  Size:" << toBits(Info.getSize()) << "\n";
2003  OS << "  DataSize:" << toBits(Info.getDataSize()) << "\n";
2004  OS << "  Alignment:" << toBits(Info.getAlignment()) << "\n";
2005  OS << "  FieldOffsets: [";
2006  for (unsigned i = 0, e = Info.getFieldCount(); i != e; ++i) {
2007    if (i) OS << ", ";
2008    OS << Info.getFieldOffset(i);
2009  }
2010  OS << "]>\n";
2011}
2012