CGRecordLayoutBuilder.cpp revision 263508 
11558Srgrimes//===--- CGRecordLayoutBuilder.cpp - CGRecordLayout builder  ----*- C++ -*-===//
274531Sru//
31558Srgrimes//                     The LLVM Compiler Infrastructure
41558Srgrimes//
5109725Sru// This file is distributed under the University of Illinois Open Source
6109597Sjmallett// License. See LICENSE.TXT for details.
774815Sru//
81558Srgrimes//===----------------------------------------------------------------------===//
9207145Sjeff//
10207145Sjeff// Builder implementation for CGRecordLayout objects.
111558Srgrimes//
12//===----------------------------------------------------------------------===//
13
14#include "CGRecordLayout.h"
15#include "CGCXXABI.h"
16#include "CodeGenTypes.h"
17#include "clang/AST/ASTContext.h"
18#include "clang/AST/Attr.h"
19#include "clang/AST/CXXInheritance.h"
20#include "clang/AST/DeclCXX.h"
21#include "clang/AST/Expr.h"
22#include "clang/AST/RecordLayout.h"
23#include "clang/Frontend/CodeGenOptions.h"
24#include "llvm/IR/DataLayout.h"
25#include "llvm/IR/DerivedTypes.h"
26#include "llvm/IR/Type.h"
27#include "llvm/Support/Debug.h"
28#include "llvm/Support/raw_ostream.h"
29using namespace clang;
30using namespace CodeGen;
31
32namespace {
33
34class CGRecordLayoutBuilder {
35public:
36  /// FieldTypes - Holds the LLVM types that the struct is created from.
37  ///
38  SmallVector<llvm::Type *, 16> FieldTypes;
39
40  /// BaseSubobjectType - Holds the LLVM type for the non-virtual part
41  /// of the struct. For example, consider:
42  ///
43  /// struct A { int i; };
44  /// struct B { void *v; };
45  /// struct C : virtual A, B { };
46  ///
47  /// The LLVM type of C will be
48  /// %struct.C = type { i32 (...)**, %struct.A, i32, %struct.B }
49  ///
50  /// And the LLVM type of the non-virtual base struct will be
51  /// %struct.C.base = type { i32 (...)**, %struct.A, i32 }
52  ///
53  /// This only gets initialized if the base subobject type is
54  /// different from the complete-object type.
55  llvm::StructType *BaseSubobjectType;
56
57  /// FieldInfo - Holds a field and its corresponding LLVM field number.
58  llvm::DenseMap<const FieldDecl *, unsigned> Fields;
59
60  /// BitFieldInfo - Holds location and size information about a bit field.
61  llvm::DenseMap<const FieldDecl *, CGBitFieldInfo> BitFields;
62
63  llvm::DenseMap<const CXXRecordDecl *, unsigned> NonVirtualBases;
64  llvm::DenseMap<const CXXRecordDecl *, unsigned> VirtualBases;
65
66  /// IndirectPrimaryBases - Virtual base classes, direct or indirect, that are
67  /// primary base classes for some other direct or indirect base class.
68  CXXIndirectPrimaryBaseSet IndirectPrimaryBases;
69
70  /// LaidOutVirtualBases - A set of all laid out virtual bases, used to avoid
71  /// avoid laying out virtual bases more than once.
72  llvm::SmallPtrSet<const CXXRecordDecl *, 4> LaidOutVirtualBases;
73
74  /// IsZeroInitializable - Whether this struct can be C++
75  /// zero-initialized with an LLVM zeroinitializer.
76  bool IsZeroInitializable;
77  bool IsZeroInitializableAsBase;
78
79  /// Packed - Whether the resulting LLVM struct will be packed or not.
80  bool Packed;
81
82private:
83  CodeGenTypes &Types;
84
85  /// LastLaidOutBaseInfo - Contains the offset and non-virtual size of the
86  /// last base laid out. Used so that we can replace the last laid out base
87  /// type with an i8 array if needed.
88  struct LastLaidOutBaseInfo {
89    CharUnits Offset;
90    CharUnits NonVirtualSize;
91
92    bool isValid() const { return !NonVirtualSize.isZero(); }
93    void invalidate() { NonVirtualSize = CharUnits::Zero(); }
94
95  } LastLaidOutBase;
96
97  /// Alignment - Contains the alignment of the RecordDecl.
98  CharUnits Alignment;
99
100  /// NextFieldOffset - Holds the next field offset.
101  CharUnits NextFieldOffset;
102
103  /// LayoutUnionField - Will layout a field in an union and return the type
104  /// that the field will have.
105  llvm::Type *LayoutUnionField(const FieldDecl *Field,
106                               const ASTRecordLayout &Layout);
107
108  /// LayoutUnion - Will layout a union RecordDecl.
109  void LayoutUnion(const RecordDecl *D);
110
111  /// Lay out a sequence of contiguous bitfields.
112  bool LayoutBitfields(const ASTRecordLayout &Layout,
113                       unsigned &FirstFieldNo,
114                       RecordDecl::field_iterator &FI,
115                       RecordDecl::field_iterator FE);
116
117  /// LayoutFields - try to layout all fields in the record decl.
118  /// Returns false if the operation failed because the struct is not packed.
119  bool LayoutFields(const RecordDecl *D);
120
121  /// Layout a single base, virtual or non-virtual
122  bool LayoutBase(const CXXRecordDecl *base,
123                  const CGRecordLayout &baseLayout,
124                  CharUnits baseOffset);
125
126  /// LayoutVirtualBase - layout a single virtual base.
127  bool LayoutVirtualBase(const CXXRecordDecl *base,
128                         CharUnits baseOffset);
129
130  /// LayoutVirtualBases - layout the virtual bases of a record decl.
131  bool LayoutVirtualBases(const CXXRecordDecl *RD,
132                          const ASTRecordLayout &Layout);
133
134  /// MSLayoutVirtualBases - layout the virtual bases of a record decl,
135  /// like MSVC.
136  bool MSLayoutVirtualBases(const CXXRecordDecl *RD,
137                            const ASTRecordLayout &Layout);
138
139  /// LayoutNonVirtualBase - layout a single non-virtual base.
140  bool LayoutNonVirtualBase(const CXXRecordDecl *base,
141                            CharUnits baseOffset);
142
143  /// LayoutNonVirtualBases - layout the virtual bases of a record decl.
144  bool LayoutNonVirtualBases(const CXXRecordDecl *RD,
145                             const ASTRecordLayout &Layout);
146
147  /// ComputeNonVirtualBaseType - Compute the non-virtual base field types.
148  bool ComputeNonVirtualBaseType(const CXXRecordDecl *RD);
149
150  /// LayoutField - layout a single field. Returns false if the operation failed
151  /// because the current struct is not packed.
152  bool LayoutField(const FieldDecl *D, uint64_t FieldOffset);
153
154  /// LayoutBitField - layout a single bit field.
155  void LayoutBitField(const FieldDecl *D, uint64_t FieldOffset);
156
157  /// AppendField - Appends a field with the given offset and type.
158  void AppendField(CharUnits fieldOffset, llvm::Type *FieldTy);
159
160  /// AppendPadding - Appends enough padding bytes so that the total
161  /// struct size is a multiple of the field alignment.
162  void AppendPadding(CharUnits fieldOffset, CharUnits fieldAlignment);
163
164  /// ResizeLastBaseFieldIfNecessary - Fields and bases can be laid out in the
165  /// tail padding of a previous base. If this happens, the type of the previous
166  /// base needs to be changed to an array of i8. Returns true if the last
167  /// laid out base was resized.
168  bool ResizeLastBaseFieldIfNecessary(CharUnits offset);
169
170  /// getByteArrayType - Returns a byte array type with the given number of
171  /// elements.
172  llvm::Type *getByteArrayType(CharUnits NumBytes);
173
174  /// AppendBytes - Append a given number of bytes to the record.
175  void AppendBytes(CharUnits numBytes);
176
177  /// AppendTailPadding - Append enough tail padding so that the type will have
178  /// the passed size.
179  void AppendTailPadding(CharUnits RecordSize);
180
181  CharUnits getTypeAlignment(llvm::Type *Ty) const;
182
183  /// getAlignmentAsLLVMStruct - Returns the maximum alignment of all the
184  /// LLVM element types.
185  CharUnits getAlignmentAsLLVMStruct() const;
186
187  /// CheckZeroInitializable - Check if the given type contains a pointer
188  /// to data member.
189  void CheckZeroInitializable(QualType T);
190
191public:
192  CGRecordLayoutBuilder(CodeGenTypes &Types)
193    : BaseSubobjectType(0),
194      IsZeroInitializable(true), IsZeroInitializableAsBase(true),
195      Packed(false), Types(Types) { }
196
197  /// Layout - Will layout a RecordDecl.
198  void Layout(const RecordDecl *D);
199};
200
201}
202
203void CGRecordLayoutBuilder::Layout(const RecordDecl *D) {
204  const ASTRecordLayout &Layout = Types.getContext().getASTRecordLayout(D);
205  Alignment = Layout.getAlignment();
206  Packed = D->hasAttr<PackedAttr>() || Layout.getSize() % Alignment != 0;
207
208  if (D->isUnion()) {
209    LayoutUnion(D);
210    return;
211  }
212
213  if (LayoutFields(D))
214    return;
215
216  // We weren't able to layout the struct. Try again with a packed struct
217  Packed = true;
218  LastLaidOutBase.invalidate();
219  NextFieldOffset = CharUnits::Zero();
220  FieldTypes.clear();
221  Fields.clear();
222  BitFields.clear();
223  NonVirtualBases.clear();
224  VirtualBases.clear();
225
226  LayoutFields(D);
227}
228
229CGBitFieldInfo CGBitFieldInfo::MakeInfo(CodeGenTypes &Types,
230                                        const FieldDecl *FD,
231                                        uint64_t Offset, uint64_t Size,
232                                        uint64_t StorageSize,
233                                        uint64_t StorageAlignment) {
234  llvm::Type *Ty = Types.ConvertTypeForMem(FD->getType());
235  CharUnits TypeSizeInBytes =
236    CharUnits::fromQuantity(Types.getDataLayout().getTypeAllocSize(Ty));
237  uint64_t TypeSizeInBits = Types.getContext().toBits(TypeSizeInBytes);
238
239  bool IsSigned = FD->getType()->isSignedIntegerOrEnumerationType();
240
241  if (Size > TypeSizeInBits) {
242    // We have a wide bit-field. The extra bits are only used for padding, so
243    // if we have a bitfield of type T, with size N:
244    //
245    // T t : N;
246    //
247    // We can just assume that it's:
248    //
249    // T t : sizeof(T);
250    //
251    Size = TypeSizeInBits;
252  }
253
254  // Reverse the bit offsets for big endian machines. Because we represent
255  // a bitfield as a single large integer load, we can imagine the bits
256  // counting from the most-significant-bit instead of the
257  // least-significant-bit.
258  if (Types.getDataLayout().isBigEndian()) {
259    Offset = StorageSize - (Offset + Size);
260  }
261
262  return CGBitFieldInfo(Offset, Size, IsSigned, StorageSize, StorageAlignment);
263}
264
265/// \brief Layout the range of bitfields from BFI to BFE as contiguous storage.
266bool CGRecordLayoutBuilder::LayoutBitfields(const ASTRecordLayout &Layout,
267                                            unsigned &FirstFieldNo,
268                                            RecordDecl::field_iterator &FI,
269                                            RecordDecl::field_iterator FE) {
270  assert(FI != FE);
271  uint64_t FirstFieldOffset = Layout.getFieldOffset(FirstFieldNo);
272  uint64_t NextFieldOffsetInBits = Types.getContext().toBits(NextFieldOffset);
273
274  unsigned CharAlign = Types.getTarget().getCharAlign();
275  assert(FirstFieldOffset % CharAlign == 0 &&
276         "First field offset is misaligned");
277  CharUnits FirstFieldOffsetInBytes
278    = Types.getContext().toCharUnitsFromBits(FirstFieldOffset);
279
280  unsigned StorageAlignment
281    = llvm::MinAlign(Alignment.getQuantity(),
282                     FirstFieldOffsetInBytes.getQuantity());
283
284  if (FirstFieldOffset < NextFieldOffsetInBits) {
285    CharUnits FieldOffsetInCharUnits =
286      Types.getContext().toCharUnitsFromBits(FirstFieldOffset);
287
288    // Try to resize the last base field.
289    if (!ResizeLastBaseFieldIfNecessary(FieldOffsetInCharUnits))
290      llvm_unreachable("We must be able to resize the last base if we need to "
291                       "pack bits into it.");
292
293    NextFieldOffsetInBits = Types.getContext().toBits(NextFieldOffset);
294    assert(FirstFieldOffset >= NextFieldOffsetInBits);
295  }
296
297  // Append padding if necessary.
298  AppendPadding(Types.getContext().toCharUnitsFromBits(FirstFieldOffset),
299                CharUnits::One());
300
301  // Find the last bitfield in a contiguous run of bitfields.
302  RecordDecl::field_iterator BFI = FI;
303  unsigned LastFieldNo = FirstFieldNo;
304  uint64_t NextContiguousFieldOffset = FirstFieldOffset;
305  for (RecordDecl::field_iterator FJ = FI;
306       (FJ != FE && (*FJ)->isBitField() &&
307        NextContiguousFieldOffset == Layout.getFieldOffset(LastFieldNo) &&
308        (*FJ)->getBitWidthValue(Types.getContext()) != 0); FI = FJ++) {
309    NextContiguousFieldOffset += (*FJ)->getBitWidthValue(Types.getContext());
310    ++LastFieldNo;
311
312    // We must use packed structs for packed fields, and also unnamed bit
313    // fields since they don't affect the struct alignment.
314    if (!Packed && ((*FJ)->hasAttr<PackedAttr>() || !(*FJ)->getDeclName()))
315      return false;
316  }
317  RecordDecl::field_iterator BFE = llvm::next(FI);
318  --LastFieldNo;
319  assert(LastFieldNo >= FirstFieldNo && "Empty run of contiguous bitfields");
320  FieldDecl *LastFD = *FI;
321
322  // Find the last bitfield's offset, add its size, and round it up to the
323  // character alignment to compute the storage required.
324  uint64_t LastFieldOffset = Layout.getFieldOffset(LastFieldNo);
325  uint64_t LastFieldSize = LastFD->getBitWidthValue(Types.getContext());
326  uint64_t TotalBits = (LastFieldOffset + LastFieldSize) - FirstFieldOffset;
327  CharUnits StorageBytes = Types.getContext().toCharUnitsFromBits(
328    llvm::RoundUpToAlignment(TotalBits, CharAlign));
329  uint64_t StorageBits = Types.getContext().toBits(StorageBytes);
330
331  // Grow the storage to encompass any known padding in the layout when doing
332  // so will make the storage a power-of-two. There are two cases when we can
333  // do this. The first is when we have a subsequent field and can widen up to
334  // its offset. The second is when the data size of the AST record layout is
335  // past the end of the current storage. The latter is true when there is tail
336  // padding on a struct and no members of a super class can be packed into it.
337  //
338  // Note that we widen the storage as much as possible here to express the
339  // maximum latitude the language provides, and rely on the backend to lower
340  // these in conjunction with shifts and masks to narrower operations where
341  // beneficial.
342  uint64_t EndOffset = Types.getContext().toBits(Layout.getDataSize());
343  if (BFE != FE)
344    // If there are more fields to be laid out, the offset at the end of the
345    // bitfield is the offset of the next field in the record.
346    EndOffset = Layout.getFieldOffset(LastFieldNo + 1);
347  assert(EndOffset >= (FirstFieldOffset + TotalBits) &&
348         "End offset is not past the end of the known storage bits.");
349  uint64_t SpaceBits = EndOffset - FirstFieldOffset;
350  uint64_t LongBits = Types.getTarget().getLongWidth();
351  uint64_t WidenedBits = (StorageBits / LongBits) * LongBits +
352                         llvm::NextPowerOf2(StorageBits % LongBits - 1);
353  assert(WidenedBits >= StorageBits && "Widening shrunk the bits!");
354  if (WidenedBits <= SpaceBits) {
355    StorageBits = WidenedBits;
356    StorageBytes = Types.getContext().toCharUnitsFromBits(StorageBits);
357    assert(StorageBits == (uint64_t)Types.getContext().toBits(StorageBytes));
358  }
359
360  unsigned FieldIndex = FieldTypes.size();
361  AppendBytes(StorageBytes);
362
363  // Now walk the bitfields associating them with this field of storage and
364  // building up the bitfield specific info.
365  unsigned FieldNo = FirstFieldNo;
366  for (; BFI != BFE; ++BFI, ++FieldNo) {
367    FieldDecl *FD = *BFI;
368    uint64_t FieldOffset = Layout.getFieldOffset(FieldNo) - FirstFieldOffset;
369    uint64_t FieldSize = FD->getBitWidthValue(Types.getContext());
370    Fields[FD] = FieldIndex;
371    BitFields[FD] = CGBitFieldInfo::MakeInfo(Types, FD, FieldOffset, FieldSize,
372                                             StorageBits, StorageAlignment);
373  }
374  FirstFieldNo = LastFieldNo;
375  return true;
376}
377
378bool CGRecordLayoutBuilder::LayoutField(const FieldDecl *D,
379                                        uint64_t fieldOffset) {
380  // If the field is packed, then we need a packed struct.
381  if (!Packed && D->hasAttr<PackedAttr>())
382    return false;
383
384  assert(!D->isBitField() && "Bitfields should be laid out seperately.");
385
386  CheckZeroInitializable(D->getType());
387
388  assert(fieldOffset % Types.getTarget().getCharWidth() == 0
389         && "field offset is not on a byte boundary!");
390  CharUnits fieldOffsetInBytes
391    = Types.getContext().toCharUnitsFromBits(fieldOffset);
392
393  llvm::Type *Ty = Types.ConvertTypeForMem(D->getType());
394  CharUnits typeAlignment = getTypeAlignment(Ty);
395
396  // If the type alignment is larger then the struct alignment, we must use
397  // a packed struct.
398  if (typeAlignment > Alignment) {
399    assert(!Packed && "Alignment is wrong even with packed struct!");
400    return false;
401  }
402
403  if (!Packed) {
404    if (const RecordType *RT = D->getType()->getAs<RecordType>()) {
405      const RecordDecl *RD = cast<RecordDecl>(RT->getDecl());
406      if (const MaxFieldAlignmentAttr *MFAA =
407            RD->getAttr<MaxFieldAlignmentAttr>()) {
408        if (MFAA->getAlignment() != Types.getContext().toBits(typeAlignment))
409          return false;
410      }
411    }
412  }
413
414  // Round up the field offset to the alignment of the field type.
415  CharUnits alignedNextFieldOffsetInBytes =
416    NextFieldOffset.RoundUpToAlignment(typeAlignment);
417
418  if (fieldOffsetInBytes < alignedNextFieldOffsetInBytes) {
419    // Try to resize the last base field.
420    if (ResizeLastBaseFieldIfNecessary(fieldOffsetInBytes)) {
421      alignedNextFieldOffsetInBytes =
422        NextFieldOffset.RoundUpToAlignment(typeAlignment);
423    }
424  }
425
426  if (fieldOffsetInBytes < alignedNextFieldOffsetInBytes) {
427    assert(!Packed && "Could not place field even with packed struct!");
428    return false;
429  }
430
431  AppendPadding(fieldOffsetInBytes, typeAlignment);
432
433  // Now append the field.
434  Fields[D] = FieldTypes.size();
435  AppendField(fieldOffsetInBytes, Ty);
436
437  LastLaidOutBase.invalidate();
438  return true;
439}
440
441llvm::Type *
442CGRecordLayoutBuilder::LayoutUnionField(const FieldDecl *Field,
443                                        const ASTRecordLayout &Layout) {
444  Fields[Field] = 0;
445  if (Field->isBitField()) {
446    uint64_t FieldSize = Field->getBitWidthValue(Types.getContext());
447
448    // Ignore zero sized bit fields.
449    if (FieldSize == 0)
450      return 0;
451
452    unsigned StorageBits = llvm::RoundUpToAlignment(
453      FieldSize, Types.getTarget().getCharAlign());
454    CharUnits NumBytesToAppend
455      = Types.getContext().toCharUnitsFromBits(StorageBits);
456
457    llvm::Type *FieldTy = llvm::Type::getInt8Ty(Types.getLLVMContext());
458    if (NumBytesToAppend > CharUnits::One())
459      FieldTy = llvm::ArrayType::get(FieldTy, NumBytesToAppend.getQuantity());
460
461    // Add the bit field info.
462    BitFields[Field] = CGBitFieldInfo::MakeInfo(Types, Field, 0, FieldSize,
463                                                StorageBits,
464                                                Alignment.getQuantity());
465    return FieldTy;
466  }
467
468  // This is a regular union field.
469  return Types.ConvertTypeForMem(Field->getType());
470}
471
472void CGRecordLayoutBuilder::LayoutUnion(const RecordDecl *D) {
473  assert(D->isUnion() && "Can't call LayoutUnion on a non-union record!");
474
475  const ASTRecordLayout &layout = Types.getContext().getASTRecordLayout(D);
476
477  llvm::Type *unionType = 0;
478  CharUnits unionSize = CharUnits::Zero();
479  CharUnits unionAlign = CharUnits::Zero();
480
481  bool hasOnlyZeroSizedBitFields = true;
482  bool checkedFirstFieldZeroInit = false;
483
484  unsigned fieldNo = 0;
485  for (RecordDecl::field_iterator field = D->field_begin(),
486       fieldEnd = D->field_end(); field != fieldEnd; ++field, ++fieldNo) {
487    assert(layout.getFieldOffset(fieldNo) == 0 &&
488          "Union field offset did not start at the beginning of record!");
489    llvm::Type *fieldType = LayoutUnionField(*field, layout);
490
491    if (!fieldType)
492      continue;
493
494    if (field->getDeclName() && !checkedFirstFieldZeroInit) {
495      CheckZeroInitializable(field->getType());
496      checkedFirstFieldZeroInit = true;
497    }
498
499    hasOnlyZeroSizedBitFields = false;
500
501    CharUnits fieldAlign = CharUnits::fromQuantity(
502                          Types.getDataLayout().getABITypeAlignment(fieldType));
503    CharUnits fieldSize = CharUnits::fromQuantity(
504                             Types.getDataLayout().getTypeAllocSize(fieldType));
505
506    if (fieldAlign < unionAlign)
507      continue;
508
509    if (fieldAlign > unionAlign || fieldSize > unionSize) {
510      unionType = fieldType;
511      unionAlign = fieldAlign;
512      unionSize = fieldSize;
513    }
514  }
515
516  // Now add our field.
517  if (unionType) {
518    AppendField(CharUnits::Zero(), unionType);
519
520    if (getTypeAlignment(unionType) > layout.getAlignment()) {
521      // We need a packed struct.
522      Packed = true;
523      unionAlign = CharUnits::One();
524    }
525  }
526  if (unionAlign.isZero()) {
527    (void)hasOnlyZeroSizedBitFields;
528    assert(hasOnlyZeroSizedBitFields &&
529           "0-align record did not have all zero-sized bit-fields!");
530    unionAlign = CharUnits::One();
531  }
532
533  // Append tail padding.
534  CharUnits recordSize = layout.getSize();
535  if (recordSize > unionSize)
536    AppendPadding(recordSize, unionAlign);
537}
538
539bool CGRecordLayoutBuilder::LayoutBase(const CXXRecordDecl *base,
540                                       const CGRecordLayout &baseLayout,
541                                       CharUnits baseOffset) {
542  ResizeLastBaseFieldIfNecessary(baseOffset);
543
544  AppendPadding(baseOffset, CharUnits::One());
545
546  const ASTRecordLayout &baseASTLayout
547    = Types.getContext().getASTRecordLayout(base);
548
549  LastLaidOutBase.Offset = NextFieldOffset;
550  LastLaidOutBase.NonVirtualSize = baseASTLayout.getNonVirtualSize();
551
552  llvm::StructType *subobjectType = baseLayout.getBaseSubobjectLLVMType();
553  if (getTypeAlignment(subobjectType) > Alignment)
554    return false;
555
556  AppendField(baseOffset, subobjectType);
557  return true;
558}
559
560bool CGRecordLayoutBuilder::LayoutNonVirtualBase(const CXXRecordDecl *base,
561                                                 CharUnits baseOffset) {
562  // Ignore empty bases.
563  if (base->isEmpty()) return true;
564
565  const CGRecordLayout &baseLayout = Types.getCGRecordLayout(base);
566  if (IsZeroInitializableAsBase) {
567    assert(IsZeroInitializable &&
568           "class zero-initializable as base but not as complete object");
569
570    IsZeroInitializable = IsZeroInitializableAsBase =
571      baseLayout.isZeroInitializableAsBase();
572  }
573
574  if (!LayoutBase(base, baseLayout, baseOffset))
575    return false;
576  NonVirtualBases[base] = (FieldTypes.size() - 1);
577  return true;
578}
579
580bool
581CGRecordLayoutBuilder::LayoutVirtualBase(const CXXRecordDecl *base,
582                                         CharUnits baseOffset) {
583  // Ignore empty bases.
584  if (base->isEmpty()) return true;
585
586  const CGRecordLayout &baseLayout = Types.getCGRecordLayout(base);
587  if (IsZeroInitializable)
588    IsZeroInitializable = baseLayout.isZeroInitializableAsBase();
589
590  if (!LayoutBase(base, baseLayout, baseOffset))
591    return false;
592  VirtualBases[base] = (FieldTypes.size() - 1);
593  return true;
594}
595
596bool
597CGRecordLayoutBuilder::MSLayoutVirtualBases(const CXXRecordDecl *RD,
598                                          const ASTRecordLayout &Layout) {
599  if (!RD->getNumVBases())
600    return true;
601
602  // The vbases list is uniqued and ordered by a depth-first
603  // traversal, which is what we need here.
604  for (CXXRecordDecl::base_class_const_iterator I = RD->vbases_begin(),
605        E = RD->vbases_end(); I != E; ++I) {
606
607    const CXXRecordDecl *BaseDecl =
608      cast<CXXRecordDecl>(I->getType()->castAs<RecordType>()->getDecl());
609
610    CharUnits vbaseOffset = Layout.getVBaseClassOffset(BaseDecl);
611    if (!LayoutVirtualBase(BaseDecl, vbaseOffset))
612      return false;
613  }
614  return true;
615}
616
617/// LayoutVirtualBases - layout the non-virtual bases of a record decl.
618bool
619CGRecordLayoutBuilder::LayoutVirtualBases(const CXXRecordDecl *RD,
620                                          const ASTRecordLayout &Layout) {
621  for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
622       E = RD->bases_end(); I != E; ++I) {
623    const CXXRecordDecl *BaseDecl =
624      cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
625
626    // We only want to lay out virtual bases that aren't indirect primary bases
627    // of some other base.
628    if (I->isVirtual() && !IndirectPrimaryBases.count(BaseDecl)) {
629      // Only lay out the base once.
630      if (!LaidOutVirtualBases.insert(BaseDecl))
631        continue;
632
633      CharUnits vbaseOffset = Layout.getVBaseClassOffset(BaseDecl);
634      if (!LayoutVirtualBase(BaseDecl, vbaseOffset))
635        return false;
636    }
637
638    if (!BaseDecl->getNumVBases()) {
639      // This base isn't interesting since it doesn't have any virtual bases.
640      continue;
641    }
642
643    if (!LayoutVirtualBases(BaseDecl, Layout))
644      return false;
645  }
646  return true;
647}
648
649bool
650CGRecordLayoutBuilder::LayoutNonVirtualBases(const CXXRecordDecl *RD,
651                                             const ASTRecordLayout &Layout) {
652  const CXXRecordDecl *PrimaryBase = Layout.getPrimaryBase();
653
654  // If we have a primary base, lay it out first.
655  if (PrimaryBase) {
656    if (!Layout.isPrimaryBaseVirtual()) {
657      if (!LayoutNonVirtualBase(PrimaryBase, CharUnits::Zero()))
658        return false;
659    } else {
660      if (!LayoutVirtualBase(PrimaryBase, CharUnits::Zero()))
661        return false;
662    }
663
664  // Otherwise, add a vtable / vf-table if the layout says to do so.
665  } else if (Layout.hasOwnVFPtr()) {
666    llvm::Type *FunctionType =
667      llvm::FunctionType::get(llvm::Type::getInt32Ty(Types.getLLVMContext()),
668                              /*isVarArg=*/true);
669    llvm::Type *VTableTy = FunctionType->getPointerTo();
670
671    if (getTypeAlignment(VTableTy) > Alignment) {
672      // FIXME: Should we allow this to happen in Sema?
673      assert(!Packed && "Alignment is wrong even with packed struct!");
674      return false;
675    }
676
677    assert(NextFieldOffset.isZero() &&
678           "VTable pointer must come first!");
679    AppendField(CharUnits::Zero(), VTableTy->getPointerTo());
680  }
681
682  // Layout the non-virtual bases.
683  for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
684       E = RD->bases_end(); I != E; ++I) {
685    if (I->isVirtual())
686      continue;
687
688    const CXXRecordDecl *BaseDecl =
689      cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
690
691    // We've already laid out the primary base.
692    if (BaseDecl == PrimaryBase && !Layout.isPrimaryBaseVirtual())
693      continue;
694
695    if (!LayoutNonVirtualBase(BaseDecl, Layout.getBaseClassOffset(BaseDecl)))
696      return false;
697  }
698
699  // Add a vb-table pointer if the layout insists.
700    if (Layout.hasOwnVBPtr()) {
701    CharUnits VBPtrOffset = Layout.getVBPtrOffset();
702    llvm::Type *Vbptr = llvm::Type::getInt32PtrTy(Types.getLLVMContext());
703    AppendPadding(VBPtrOffset, getTypeAlignment(Vbptr));
704    AppendField(VBPtrOffset, Vbptr);
705  }
706
707  return true;
708}
709
710bool
711CGRecordLayoutBuilder::ComputeNonVirtualBaseType(const CXXRecordDecl *RD) {
712  const ASTRecordLayout &Layout = Types.getContext().getASTRecordLayout(RD);
713
714  CharUnits NonVirtualSize  = Layout.getNonVirtualSize();
715  CharUnits NonVirtualAlign = Layout.getNonVirtualAlign();
716  CharUnits AlignedNonVirtualTypeSize =
717    NonVirtualSize.RoundUpToAlignment(NonVirtualAlign);
718
719  // First check if we can use the same fields as for the complete class.
720  CharUnits RecordSize = Layout.getSize();
721  if (AlignedNonVirtualTypeSize == RecordSize)
722    return true;
723
724  // Check if we need padding.
725  CharUnits AlignedNextFieldOffset =
726    NextFieldOffset.RoundUpToAlignment(getAlignmentAsLLVMStruct());
727
728  if (AlignedNextFieldOffset > AlignedNonVirtualTypeSize) {
729    assert(!Packed && "cannot layout even as packed struct");
730    return false; // Needs packing.
731  }
732
733  bool needsPadding = (AlignedNonVirtualTypeSize != AlignedNextFieldOffset);
734  if (needsPadding) {
735    CharUnits NumBytes = AlignedNonVirtualTypeSize - AlignedNextFieldOffset;
736    FieldTypes.push_back(getByteArrayType(NumBytes));
737  }
738
739  BaseSubobjectType = llvm::StructType::create(Types.getLLVMContext(),
740                                               FieldTypes, "", Packed);
741  Types.addRecordTypeName(RD, BaseSubobjectType, ".base");
742
743  // Pull the padding back off.
744  if (needsPadding)
745    FieldTypes.pop_back();
746
747  return true;
748}
749
750bool CGRecordLayoutBuilder::LayoutFields(const RecordDecl *D) {
751  assert(!D->isUnion() && "Can't call LayoutFields on a union!");
752  assert(!Alignment.isZero() && "Did not set alignment!");
753
754  const ASTRecordLayout &Layout = Types.getContext().getASTRecordLayout(D);
755
756  const CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(D);
757  if (RD)
758    if (!LayoutNonVirtualBases(RD, Layout))
759      return false;
760
761  unsigned FieldNo = 0;
762
763  for (RecordDecl::field_iterator FI = D->field_begin(), FE = D->field_end();
764       FI != FE; ++FI, ++FieldNo) {
765    FieldDecl *FD = *FI;
766
767    // If this field is a bitfield, layout all of the consecutive
768    // non-zero-length bitfields and the last zero-length bitfield; these will
769    // all share storage.
770    if (FD->isBitField()) {
771      // If all we have is a zero-width bitfield, skip it.
772      if (FD->getBitWidthValue(Types.getContext()) == 0)
773        continue;
774
775      // Layout this range of bitfields.
776      if (!LayoutBitfields(Layout, FieldNo, FI, FE)) {
777        assert(!Packed &&
778               "Could not layout bitfields even with a packed LLVM struct!");
779        return false;
780      }
781      assert(FI != FE && "Advanced past the last bitfield");
782      continue;
783    }
784
785    if (!LayoutField(FD, Layout.getFieldOffset(FieldNo))) {
786      assert(!Packed &&
787             "Could not layout fields even with a packed LLVM struct!");
788      return false;
789    }
790  }
791
792  if (RD) {
793    // We've laid out the non-virtual bases and the fields, now compute the
794    // non-virtual base field types.
795    if (!ComputeNonVirtualBaseType(RD)) {
796      assert(!Packed && "Could not layout even with a packed LLVM struct!");
797      return false;
798    }
799
800    // Lay out the virtual bases.  The MS ABI uses a different
801    // algorithm here due to the lack of primary virtual bases.
802    if (Types.getTarget().getCXXABI().hasPrimaryVBases()) {
803      RD->getIndirectPrimaryBases(IndirectPrimaryBases);
804      if (Layout.isPrimaryBaseVirtual())
805        IndirectPrimaryBases.insert(Layout.getPrimaryBase());
806
807      if (!LayoutVirtualBases(RD, Layout))
808        return false;
809    } else {
810      if (!MSLayoutVirtualBases(RD, Layout))
811        return false;
812    }
813  }
814
815  // Append tail padding if necessary.
816  AppendTailPadding(Layout.getSize());
817
818  return true;
819}
820
821void CGRecordLayoutBuilder::AppendTailPadding(CharUnits RecordSize) {
822  ResizeLastBaseFieldIfNecessary(RecordSize);
823
824  assert(NextFieldOffset <= RecordSize && "Size mismatch!");
825
826  CharUnits AlignedNextFieldOffset =
827    NextFieldOffset.RoundUpToAlignment(getAlignmentAsLLVMStruct());
828
829  if (AlignedNextFieldOffset == RecordSize) {
830    // We don't need any padding.
831    return;
832  }
833
834  CharUnits NumPadBytes = RecordSize - NextFieldOffset;
835  AppendBytes(NumPadBytes);
836}
837
838void CGRecordLayoutBuilder::AppendField(CharUnits fieldOffset,
839                                        llvm::Type *fieldType) {
840  CharUnits fieldSize =
841    CharUnits::fromQuantity(Types.getDataLayout().getTypeAllocSize(fieldType));
842
843  FieldTypes.push_back(fieldType);
844
845  NextFieldOffset = fieldOffset + fieldSize;
846}
847
848void CGRecordLayoutBuilder::AppendPadding(CharUnits fieldOffset,
849                                          CharUnits fieldAlignment) {
850  assert(NextFieldOffset <= fieldOffset &&
851         "Incorrect field layout!");
852
853  // Do nothing if we're already at the right offset.
854  if (fieldOffset == NextFieldOffset) return;
855
856  // If we're not emitting a packed LLVM type, try to avoid adding
857  // unnecessary padding fields.
858  if (!Packed) {
859    // Round up the field offset to the alignment of the field type.
860    CharUnits alignedNextFieldOffset =
861      NextFieldOffset.RoundUpToAlignment(fieldAlignment);
862    assert(alignedNextFieldOffset <= fieldOffset);
863
864    // If that's the right offset, we're done.
865    if (alignedNextFieldOffset == fieldOffset) return;
866  }
867
868  // Otherwise we need explicit padding.
869  CharUnits padding = fieldOffset - NextFieldOffset;
870  AppendBytes(padding);
871}
872
873bool CGRecordLayoutBuilder::ResizeLastBaseFieldIfNecessary(CharUnits offset) {
874  // Check if we have a base to resize.
875  if (!LastLaidOutBase.isValid())
876    return false;
877
878  // This offset does not overlap with the tail padding.
879  if (offset >= NextFieldOffset)
880    return false;
881
882  // Restore the field offset and append an i8 array instead.
883  FieldTypes.pop_back();
884  NextFieldOffset = LastLaidOutBase.Offset;
885  AppendBytes(LastLaidOutBase.NonVirtualSize);
886  LastLaidOutBase.invalidate();
887
888  return true;
889}
890
891llvm::Type *CGRecordLayoutBuilder::getByteArrayType(CharUnits numBytes) {
892  assert(!numBytes.isZero() && "Empty byte arrays aren't allowed.");
893
894  llvm::Type *Ty = llvm::Type::getInt8Ty(Types.getLLVMContext());
895  if (numBytes > CharUnits::One())
896    Ty = llvm::ArrayType::get(Ty, numBytes.getQuantity());
897
898  return Ty;
899}
900
901void CGRecordLayoutBuilder::AppendBytes(CharUnits numBytes) {
902  if (numBytes.isZero())
903    return;
904
905  // Append the padding field
906  AppendField(NextFieldOffset, getByteArrayType(numBytes));
907}
908
909CharUnits CGRecordLayoutBuilder::getTypeAlignment(llvm::Type *Ty) const {
910  if (Packed)
911    return CharUnits::One();
912
913  return CharUnits::fromQuantity(Types.getDataLayout().getABITypeAlignment(Ty));
914}
915
916CharUnits CGRecordLayoutBuilder::getAlignmentAsLLVMStruct() const {
917  if (Packed)
918    return CharUnits::One();
919
920  CharUnits maxAlignment = CharUnits::One();
921  for (size_t i = 0; i != FieldTypes.size(); ++i)
922    maxAlignment = std::max(maxAlignment, getTypeAlignment(FieldTypes[i]));
923
924  return maxAlignment;
925}
926
927/// Merge in whether a field of the given type is zero-initializable.
928void CGRecordLayoutBuilder::CheckZeroInitializable(QualType T) {
929  // This record already contains a member pointer.
930  if (!IsZeroInitializableAsBase)
931    return;
932
933  // Can only have member pointers if we're compiling C++.
934  if (!Types.getContext().getLangOpts().CPlusPlus)
935    return;
936
937  const Type *elementType = T->getBaseElementTypeUnsafe();
938
939  if (const MemberPointerType *MPT = elementType->getAs<MemberPointerType>()) {
940    if (!Types.getCXXABI().isZeroInitializable(MPT))
941      IsZeroInitializable = IsZeroInitializableAsBase = false;
942  } else if (const RecordType *RT = elementType->getAs<RecordType>()) {
943    const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
944    const CGRecordLayout &Layout = Types.getCGRecordLayout(RD);
945    if (!Layout.isZeroInitializable())
946      IsZeroInitializable = IsZeroInitializableAsBase = false;
947  }
948}
949
950CGRecordLayout *CodeGenTypes::ComputeRecordLayout(const RecordDecl *D,
951                                                  llvm::StructType *Ty) {
952  CGRecordLayoutBuilder Builder(*this);
953
954  Builder.Layout(D);
955
956  Ty->setBody(Builder.FieldTypes, Builder.Packed);
957
958  // If we're in C++, compute the base subobject type.
959  llvm::StructType *BaseTy = 0;
960  if (isa<CXXRecordDecl>(D) && !D->isUnion()) {
961    BaseTy = Builder.BaseSubobjectType;
962    if (!BaseTy) BaseTy = Ty;
963  }
964
965  CGRecordLayout *RL =
966    new CGRecordLayout(Ty, BaseTy, Builder.IsZeroInitializable,
967                       Builder.IsZeroInitializableAsBase);
968
969  RL->NonVirtualBases.swap(Builder.NonVirtualBases);
970  RL->CompleteObjectVirtualBases.swap(Builder.VirtualBases);
971
972  // Add all the field numbers.
973  RL->FieldInfo.swap(Builder.Fields);
974
975  // Add bitfield info.
976  RL->BitFields.swap(Builder.BitFields);
977
978  // Dump the layout, if requested.
979  if (getContext().getLangOpts().DumpRecordLayouts) {
980    llvm::outs() << "\n*** Dumping IRgen Record Layout\n";
981    llvm::outs() << "Record: ";
982    D->dump(llvm::outs());
983    llvm::outs() << "\nLayout: ";
984    RL->print(llvm::outs());
985  }
986
987#ifndef NDEBUG
988  // Verify that the computed LLVM struct size matches the AST layout size.
989  const ASTRecordLayout &Layout = getContext().getASTRecordLayout(D);
990
991  uint64_t TypeSizeInBits = getContext().toBits(Layout.getSize());
992  assert(TypeSizeInBits == getDataLayout().getTypeAllocSizeInBits(Ty) &&
993         "Type size mismatch!");
994
995  if (BaseTy) {
996    CharUnits NonVirtualSize  = Layout.getNonVirtualSize();
997    CharUnits NonVirtualAlign = Layout.getNonVirtualAlign();
998    CharUnits AlignedNonVirtualTypeSize =
999      NonVirtualSize.RoundUpToAlignment(NonVirtualAlign);
1000
1001    uint64_t AlignedNonVirtualTypeSizeInBits =
1002      getContext().toBits(AlignedNonVirtualTypeSize);
1003
1004    assert(AlignedNonVirtualTypeSizeInBits ==
1005           getDataLayout().getTypeAllocSizeInBits(BaseTy) &&
1006           "Type size mismatch!");
1007  }
1008
1009  // Verify that the LLVM and AST field offsets agree.
1010  llvm::StructType *ST =
1011    dyn_cast<llvm::StructType>(RL->getLLVMType());
1012  const llvm::StructLayout *SL = getDataLayout().getStructLayout(ST);
1013
1014  const ASTRecordLayout &AST_RL = getContext().getASTRecordLayout(D);
1015  RecordDecl::field_iterator it = D->field_begin();
1016  for (unsigned i = 0, e = AST_RL.getFieldCount(); i != e; ++i, ++it) {
1017    const FieldDecl *FD = *it;
1018
1019    // For non-bit-fields, just check that the LLVM struct offset matches the
1020    // AST offset.
1021    if (!FD->isBitField()) {
1022      unsigned FieldNo = RL->getLLVMFieldNo(FD);
1023      assert(AST_RL.getFieldOffset(i) == SL->getElementOffsetInBits(FieldNo) &&
1024             "Invalid field offset!");
1025      continue;
1026    }
1027
1028    // Ignore unnamed bit-fields.
1029    if (!FD->getDeclName())
1030      continue;
1031
1032    // Don't inspect zero-length bitfields.
1033    if (FD->getBitWidthValue(getContext()) == 0)
1034      continue;
1035
1036    const CGBitFieldInfo &Info = RL->getBitFieldInfo(FD);
1037    llvm::Type *ElementTy = ST->getTypeAtIndex(RL->getLLVMFieldNo(FD));
1038
1039    // Unions have overlapping elements dictating their layout, but for
1040    // non-unions we can verify that this section of the layout is the exact
1041    // expected size.
1042    if (D->isUnion()) {
1043      // For unions we verify that the start is zero and the size
1044      // is in-bounds. However, on BE systems, the offset may be non-zero, but
1045      // the size + offset should match the storage size in that case as it
1046      // "starts" at the back.
1047      if (getDataLayout().isBigEndian())
1048        assert(static_cast<unsigned>(Info.Offset + Info.Size) ==
1049               Info.StorageSize &&
1050               "Big endian union bitfield does not end at the back");
1051      else
1052        assert(Info.Offset == 0 &&
1053               "Little endian union bitfield with a non-zero offset");
1054      assert(Info.StorageSize <= SL->getSizeInBits() &&
1055             "Union not large enough for bitfield storage");
1056    } else {
1057      assert(Info.StorageSize ==
1058             getDataLayout().getTypeAllocSizeInBits(ElementTy) &&
1059             "Storage size does not match the element type size");
1060    }
1061    assert(Info.Size > 0 && "Empty bitfield!");
1062    assert(static_cast<unsigned>(Info.Offset) + Info.Size <= Info.StorageSize &&
1063           "Bitfield outside of its allocated storage");
1064  }
1065#endif
1066
1067  return RL;
1068}
1069
1070void CGRecordLayout::print(raw_ostream &OS) const {
1071  OS << "<CGRecordLayout\n";
1072  OS << "  LLVMType:" << *CompleteObjectType << "\n";
1073  if (BaseSubobjectType)
1074    OS << "  NonVirtualBaseLLVMType:" << *BaseSubobjectType << "\n";
1075  OS << "  IsZeroInitializable:" << IsZeroInitializable << "\n";
1076  OS << "  BitFields:[\n";
1077
1078  // Print bit-field infos in declaration order.
1079  std::vector<std::pair<unsigned, const CGBitFieldInfo*> > BFIs;
1080  for (llvm::DenseMap<const FieldDecl*, CGBitFieldInfo>::const_iterator
1081         it = BitFields.begin(), ie = BitFields.end();
1082       it != ie; ++it) {
1083    const RecordDecl *RD = it->first->getParent();
1084    unsigned Index = 0;
1085    for (RecordDecl::field_iterator
1086           it2 = RD->field_begin(); *it2 != it->first; ++it2)
1087      ++Index;
1088    BFIs.push_back(std::make_pair(Index, &it->second));
1089  }
1090  llvm::array_pod_sort(BFIs.begin(), BFIs.end());
1091  for (unsigned i = 0, e = BFIs.size(); i != e; ++i) {
1092    OS.indent(4);
1093    BFIs[i].second->print(OS);
1094    OS << "\n";
1095  }
1096
1097  OS << "]>\n";
1098}
1099
1100void CGRecordLayout::dump() const {
1101  print(llvm::errs());
1102}
1103
1104void CGBitFieldInfo::print(raw_ostream &OS) const {
1105  OS << "<CGBitFieldInfo"
1106     << " Offset:" << Offset
1107     << " Size:" << Size
1108     << " IsSigned:" << IsSigned
1109     << " StorageSize:" << StorageSize
1110     << " StorageAlignment:" << StorageAlignment << ">";
1111}
1112
1113void CGBitFieldInfo::dump() const {
1114  print(llvm::errs());
1115}
1116