1//===--- CGRecordLayoutBuilder.cpp - CGRecordLayout builder  ----*- C++ -*-===//
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// Builder implementation for CGRecordLayout objects.
11//
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
82  /// IsMsStruct - Whether ms_struct is in effect or not
83  bool IsMsStruct;
84
85private:
86  CodeGenTypes &Types;
87
88  /// LastLaidOutBaseInfo - Contains the offset and non-virtual size of the
89  /// last base laid out. Used so that we can replace the last laid out base
90  /// type with an i8 array if needed.
91  struct LastLaidOutBaseInfo {
92    CharUnits Offset;
93    CharUnits NonVirtualSize;
94
95    bool isValid() const { return !NonVirtualSize.isZero(); }
96    void invalidate() { NonVirtualSize = CharUnits::Zero(); }
97
98  } LastLaidOutBase;
99
100  /// Alignment - Contains the alignment of the RecordDecl.
101  CharUnits Alignment;
102
103  /// NextFieldOffset - Holds the next field offset.
104  CharUnits NextFieldOffset;
105
106  /// LayoutUnionField - Will layout a field in an union and return the type
107  /// that the field will have.
108  llvm::Type *LayoutUnionField(const FieldDecl *Field,
109                               const ASTRecordLayout &Layout);
110
111  /// LayoutUnion - Will layout a union RecordDecl.
112  void LayoutUnion(const RecordDecl *D);
113
114  /// Lay out a sequence of contiguous bitfields.
115  bool LayoutBitfields(const ASTRecordLayout &Layout,
116                       unsigned &FirstFieldNo,
117                       RecordDecl::field_iterator &FI,
118                       RecordDecl::field_iterator FE);
119
120  /// LayoutField - try to layout all fields in the record decl.
121  /// Returns false if the operation failed because the struct is not packed.
122  bool LayoutFields(const RecordDecl *D);
123
124  /// Layout a single base, virtual or non-virtual
125  bool LayoutBase(const CXXRecordDecl *base,
126                  const CGRecordLayout &baseLayout,
127                  CharUnits baseOffset);
128
129  /// LayoutVirtualBase - layout a single virtual base.
130  bool LayoutVirtualBase(const CXXRecordDecl *base,
131                         CharUnits baseOffset);
132
133  /// LayoutVirtualBases - layout the virtual bases of a record decl.
134  bool LayoutVirtualBases(const CXXRecordDecl *RD,
135                          const ASTRecordLayout &Layout);
136
137  /// MSLayoutVirtualBases - layout the virtual bases of a record decl,
138  /// like MSVC.
139  bool MSLayoutVirtualBases(const CXXRecordDecl *RD,
140                            const ASTRecordLayout &Layout);
141
142  /// LayoutNonVirtualBase - layout a single non-virtual base.
143  bool LayoutNonVirtualBase(const CXXRecordDecl *base,
144                            CharUnits baseOffset);
145
146  /// LayoutNonVirtualBases - layout the virtual bases of a record decl.
147  bool LayoutNonVirtualBases(const CXXRecordDecl *RD,
148                             const ASTRecordLayout &Layout);
149
150  /// ComputeNonVirtualBaseType - Compute the non-virtual base field types.
151  bool ComputeNonVirtualBaseType(const CXXRecordDecl *RD);
152
153  /// LayoutField - layout a single field. Returns false if the operation failed
154  /// because the current struct is not packed.
155  bool LayoutField(const FieldDecl *D, uint64_t FieldOffset);
156
157  /// LayoutBitField - layout a single bit field.
158  void LayoutBitField(const FieldDecl *D, uint64_t FieldOffset);
159
160  /// AppendField - Appends a field with the given offset and type.
161  void AppendField(CharUnits fieldOffset, llvm::Type *FieldTy);
162
163  /// AppendPadding - Appends enough padding bytes so that the total
164  /// struct size is a multiple of the field alignment.
165  void AppendPadding(CharUnits fieldOffset, CharUnits fieldAlignment);
166
167  /// ResizeLastBaseFieldIfNecessary - Fields and bases can be laid out in the
168  /// tail padding of a previous base. If this happens, the type of the previous
169  /// base needs to be changed to an array of i8. Returns true if the last
170  /// laid out base was resized.
171  bool ResizeLastBaseFieldIfNecessary(CharUnits offset);
172
173  /// getByteArrayType - Returns a byte array type with the given number of
174  /// elements.
175  llvm::Type *getByteArrayType(CharUnits NumBytes);
176
177  /// AppendBytes - Append a given number of bytes to the record.
178  void AppendBytes(CharUnits numBytes);
179
180  /// AppendTailPadding - Append enough tail padding so that the type will have
181  /// the passed size.
182  void AppendTailPadding(CharUnits RecordSize);
183
184  CharUnits getTypeAlignment(llvm::Type *Ty) const;
185
186  /// getAlignmentAsLLVMStruct - Returns the maximum alignment of all the
187  /// LLVM element types.
188  CharUnits getAlignmentAsLLVMStruct() const;
189
190  /// CheckZeroInitializable - Check if the given type contains a pointer
191  /// to data member.
192  void CheckZeroInitializable(QualType T);
193
194public:
195  CGRecordLayoutBuilder(CodeGenTypes &Types)
196    : BaseSubobjectType(0),
197      IsZeroInitializable(true), IsZeroInitializableAsBase(true),
198      Packed(false), IsMsStruct(false),
199      Types(Types) { }
200
201  /// Layout - Will layout a RecordDecl.
202  void Layout(const RecordDecl *D);
203};
204
205}
206
207void CGRecordLayoutBuilder::Layout(const RecordDecl *D) {
208  Alignment = Types.getContext().getASTRecordLayout(D).getAlignment();
209  Packed = D->hasAttr<PackedAttr>();
210
211  IsMsStruct = D->isMsStruct(Types.getContext());
212
213  if (D->isUnion()) {
214    LayoutUnion(D);
215    return;
216  }
217
218  if (LayoutFields(D))
219    return;
220
221  // We weren't able to layout the struct. Try again with a packed struct
222  Packed = true;
223  LastLaidOutBase.invalidate();
224  NextFieldOffset = CharUnits::Zero();
225  FieldTypes.clear();
226  Fields.clear();
227  BitFields.clear();
228  NonVirtualBases.clear();
229  VirtualBases.clear();
230
231  LayoutFields(D);
232}
233
234CGBitFieldInfo CGBitFieldInfo::MakeInfo(CodeGenTypes &Types,
235                                        const FieldDecl *FD,
236                                        uint64_t Offset, uint64_t Size,
237                                        uint64_t StorageSize,
238                                        uint64_t StorageAlignment) {
239  llvm::Type *Ty = Types.ConvertTypeForMem(FD->getType());
240  CharUnits TypeSizeInBytes =
241    CharUnits::fromQuantity(Types.getDataLayout().getTypeAllocSize(Ty));
242  uint64_t TypeSizeInBits = Types.getContext().toBits(TypeSizeInBytes);
243
244  bool IsSigned = FD->getType()->isSignedIntegerOrEnumerationType();
245
246  if (Size > TypeSizeInBits) {
247    // We have a wide bit-field. The extra bits are only used for padding, so
248    // if we have a bitfield of type T, with size N:
249    //
250    // T t : N;
251    //
252    // We can just assume that it's:
253    //
254    // T t : sizeof(T);
255    //
256    Size = TypeSizeInBits;
257  }
258
259  // Reverse the bit offsets for big endian machines. Because we represent
260  // a bitfield as a single large integer load, we can imagine the bits
261  // counting from the most-significant-bit instead of the
262  // least-significant-bit.
263  if (Types.getDataLayout().isBigEndian()) {
264    Offset = StorageSize - (Offset + Size);
265  }
266
267  return CGBitFieldInfo(Offset, Size, IsSigned, StorageSize, StorageAlignment);
268}
269
270/// \brief Layout the range of bitfields from BFI to BFE as contiguous storage.
271bool CGRecordLayoutBuilder::LayoutBitfields(const ASTRecordLayout &Layout,
272                                            unsigned &FirstFieldNo,
273                                            RecordDecl::field_iterator &FI,
274                                            RecordDecl::field_iterator FE) {
275  assert(FI != FE);
276  uint64_t FirstFieldOffset = Layout.getFieldOffset(FirstFieldNo);
277  uint64_t NextFieldOffsetInBits = Types.getContext().toBits(NextFieldOffset);
278
279  unsigned CharAlign = Types.getContext().getTargetInfo().getCharAlign();
280  assert(FirstFieldOffset % CharAlign == 0 &&
281         "First field offset is misaligned");
282  CharUnits FirstFieldOffsetInBytes
283    = Types.getContext().toCharUnitsFromBits(FirstFieldOffset);
284
285  unsigned StorageAlignment
286    = llvm::MinAlign(Alignment.getQuantity(),
287                     FirstFieldOffsetInBytes.getQuantity());
288
289  if (FirstFieldOffset < NextFieldOffsetInBits) {
290    CharUnits FieldOffsetInCharUnits =
291      Types.getContext().toCharUnitsFromBits(FirstFieldOffset);
292
293    // Try to resize the last base field.
294    if (!ResizeLastBaseFieldIfNecessary(FieldOffsetInCharUnits))
295      llvm_unreachable("We must be able to resize the last base if we need to "
296                       "pack bits into it.");
297
298    NextFieldOffsetInBits = Types.getContext().toBits(NextFieldOffset);
299    assert(FirstFieldOffset >= NextFieldOffsetInBits);
300  }
301
302  // Append padding if necessary.
303  AppendPadding(Types.getContext().toCharUnitsFromBits(FirstFieldOffset),
304                CharUnits::One());
305
306  // Find the last bitfield in a contiguous run of bitfields.
307  RecordDecl::field_iterator BFI = FI;
308  unsigned LastFieldNo = FirstFieldNo;
309  uint64_t NextContiguousFieldOffset = FirstFieldOffset;
310  for (RecordDecl::field_iterator FJ = FI;
311       (FJ != FE && (*FJ)->isBitField() &&
312        NextContiguousFieldOffset == Layout.getFieldOffset(LastFieldNo) &&
313        (*FJ)->getBitWidthValue(Types.getContext()) != 0); FI = FJ++) {
314    NextContiguousFieldOffset += (*FJ)->getBitWidthValue(Types.getContext());
315    ++LastFieldNo;
316
317    // We must use packed structs for packed fields, and also unnamed bit
318    // fields since they don't affect the struct alignment.
319    if (!Packed && ((*FJ)->hasAttr<PackedAttr>() || !(*FJ)->getDeclName()))
320      return false;
321  }
322  RecordDecl::field_iterator BFE = llvm::next(FI);
323  --LastFieldNo;
324  assert(LastFieldNo >= FirstFieldNo && "Empty run of contiguous bitfields");
325  FieldDecl *LastFD = *FI;
326
327  // Find the last bitfield's offset, add its size, and round it up to the
328  // character alignment to compute the storage required.
329  uint64_t LastFieldOffset = Layout.getFieldOffset(LastFieldNo);
330  uint64_t LastFieldSize = LastFD->getBitWidthValue(Types.getContext());
331  uint64_t TotalBits = (LastFieldOffset + LastFieldSize) - FirstFieldOffset;
332  CharUnits StorageBytes = Types.getContext().toCharUnitsFromBits(
333    llvm::RoundUpToAlignment(TotalBits, CharAlign));
334  uint64_t StorageBits = Types.getContext().toBits(StorageBytes);
335
336  // Grow the storage to encompass any known padding in the layout when doing
337  // so will make the storage a power-of-two. There are two cases when we can
338  // do this. The first is when we have a subsequent field and can widen up to
339  // its offset. The second is when the data size of the AST record layout is
340  // past the end of the current storage. The latter is true when there is tail
341  // padding on a struct and no members of a super class can be packed into it.
342  //
343  // Note that we widen the storage as much as possible here to express the
344  // maximum latitude the language provides, and rely on the backend to lower
345  // these in conjunction with shifts and masks to narrower operations where
346  // beneficial.
347  uint64_t EndOffset = Types.getContext().toBits(Layout.getDataSize());
348  if (BFE != FE)
349    // If there are more fields to be laid out, the offset at the end of the
350    // bitfield is the offset of the next field in the record.
351    EndOffset = Layout.getFieldOffset(LastFieldNo + 1);
352  assert(EndOffset >= (FirstFieldOffset + TotalBits) &&
353         "End offset is not past the end of the known storage bits.");
354  uint64_t SpaceBits = EndOffset - FirstFieldOffset;
355  uint64_t LongBits = Types.getContext().getTargetInfo().getLongWidth();
356  uint64_t WidenedBits = (StorageBits / LongBits) * LongBits +
357                         llvm::NextPowerOf2(StorageBits % LongBits - 1);
358  assert(WidenedBits >= StorageBits && "Widening shrunk the bits!");
359  if (WidenedBits <= SpaceBits) {
360    StorageBits = WidenedBits;
361    StorageBytes = Types.getContext().toCharUnitsFromBits(StorageBits);
362    assert(StorageBits == (uint64_t)Types.getContext().toBits(StorageBytes));
363  }
364
365  unsigned FieldIndex = FieldTypes.size();
366  AppendBytes(StorageBytes);
367
368  // Now walk the bitfields associating them with this field of storage and
369  // building up the bitfield specific info.
370  unsigned FieldNo = FirstFieldNo;
371  for (; BFI != BFE; ++BFI, ++FieldNo) {
372    FieldDecl *FD = *BFI;
373    uint64_t FieldOffset = Layout.getFieldOffset(FieldNo) - FirstFieldOffset;
374    uint64_t FieldSize = FD->getBitWidthValue(Types.getContext());
375    Fields[FD] = FieldIndex;
376    BitFields[FD] = CGBitFieldInfo::MakeInfo(Types, FD, FieldOffset, FieldSize,
377                                             StorageBits, StorageAlignment);
378  }
379  FirstFieldNo = LastFieldNo;
380  return true;
381}
382
383bool CGRecordLayoutBuilder::LayoutField(const FieldDecl *D,
384                                        uint64_t fieldOffset) {
385  // If the field is packed, then we need a packed struct.
386  if (!Packed && D->hasAttr<PackedAttr>())
387    return false;
388
389  assert(!D->isBitField() && "Bitfields should be laid out seperately.");
390
391  CheckZeroInitializable(D->getType());
392
393  assert(fieldOffset % Types.getTarget().getCharWidth() == 0
394         && "field offset is not on a byte boundary!");
395  CharUnits fieldOffsetInBytes
396    = Types.getContext().toCharUnitsFromBits(fieldOffset);
397
398  llvm::Type *Ty = Types.ConvertTypeForMem(D->getType());
399  CharUnits typeAlignment = getTypeAlignment(Ty);
400
401  // If the type alignment is larger then the struct alignment, we must use
402  // a packed struct.
403  if (typeAlignment > Alignment) {
404    assert(!Packed && "Alignment is wrong even with packed struct!");
405    return false;
406  }
407
408  if (!Packed) {
409    if (const RecordType *RT = D->getType()->getAs<RecordType>()) {
410      const RecordDecl *RD = cast<RecordDecl>(RT->getDecl());
411      if (const MaxFieldAlignmentAttr *MFAA =
412            RD->getAttr<MaxFieldAlignmentAttr>()) {
413        if (MFAA->getAlignment() != Types.getContext().toBits(typeAlignment))
414          return false;
415      }
416    }
417  }
418
419  // Round up the field offset to the alignment of the field type.
420  CharUnits alignedNextFieldOffsetInBytes =
421    NextFieldOffset.RoundUpToAlignment(typeAlignment);
422
423  if (fieldOffsetInBytes < alignedNextFieldOffsetInBytes) {
424    // Try to resize the last base field.
425    if (ResizeLastBaseFieldIfNecessary(fieldOffsetInBytes)) {
426      alignedNextFieldOffsetInBytes =
427        NextFieldOffset.RoundUpToAlignment(typeAlignment);
428    }
429  }
430
431  if (fieldOffsetInBytes < alignedNextFieldOffsetInBytes) {
432    assert(!Packed && "Could not place field even with packed struct!");
433    return false;
434  }
435
436  AppendPadding(fieldOffsetInBytes, typeAlignment);
437
438  // Now append the field.
439  Fields[D] = FieldTypes.size();
440  AppendField(fieldOffsetInBytes, Ty);
441
442  LastLaidOutBase.invalidate();
443  return true;
444}
445
446llvm::Type *
447CGRecordLayoutBuilder::LayoutUnionField(const FieldDecl *Field,
448                                        const ASTRecordLayout &Layout) {
449  Fields[Field] = 0;
450  if (Field->isBitField()) {
451    uint64_t FieldSize = Field->getBitWidthValue(Types.getContext());
452
453    // Ignore zero sized bit fields.
454    if (FieldSize == 0)
455      return 0;
456
457    unsigned StorageBits = llvm::RoundUpToAlignment(
458      FieldSize, Types.getContext().getTargetInfo().getCharAlign());
459    CharUnits NumBytesToAppend
460      = Types.getContext().toCharUnitsFromBits(StorageBits);
461
462    llvm::Type *FieldTy = llvm::Type::getInt8Ty(Types.getLLVMContext());
463    if (NumBytesToAppend > CharUnits::One())
464      FieldTy = llvm::ArrayType::get(FieldTy, NumBytesToAppend.getQuantity());
465
466    // Add the bit field info.
467    BitFields[Field] = CGBitFieldInfo::MakeInfo(Types, Field, 0, FieldSize,
468                                                StorageBits,
469                                                Alignment.getQuantity());
470    return FieldTy;
471  }
472
473  // This is a regular union field.
474  return Types.ConvertTypeForMem(Field->getType());
475}
476
477void CGRecordLayoutBuilder::LayoutUnion(const RecordDecl *D) {
478  assert(D->isUnion() && "Can't call LayoutUnion on a non-union record!");
479
480  const ASTRecordLayout &layout = Types.getContext().getASTRecordLayout(D);
481
482  llvm::Type *unionType = 0;
483  CharUnits unionSize = CharUnits::Zero();
484  CharUnits unionAlign = CharUnits::Zero();
485
486  bool hasOnlyZeroSizedBitFields = true;
487  bool checkedFirstFieldZeroInit = false;
488
489  unsigned fieldNo = 0;
490  for (RecordDecl::field_iterator field = D->field_begin(),
491       fieldEnd = D->field_end(); field != fieldEnd; ++field, ++fieldNo) {
492    assert(layout.getFieldOffset(fieldNo) == 0 &&
493          "Union field offset did not start at the beginning of record!");
494    llvm::Type *fieldType = LayoutUnionField(*field, layout);
495
496    if (!fieldType)
497      continue;
498
499    if (field->getDeclName() && !checkedFirstFieldZeroInit) {
500      CheckZeroInitializable(field->getType());
501      checkedFirstFieldZeroInit = true;
502    }
503
504    hasOnlyZeroSizedBitFields = false;
505
506    CharUnits fieldAlign = CharUnits::fromQuantity(
507                          Types.getDataLayout().getABITypeAlignment(fieldType));
508    CharUnits fieldSize = CharUnits::fromQuantity(
509                             Types.getDataLayout().getTypeAllocSize(fieldType));
510
511    if (fieldAlign < unionAlign)
512      continue;
513
514    if (fieldAlign > unionAlign || fieldSize > unionSize) {
515      unionType = fieldType;
516      unionAlign = fieldAlign;
517      unionSize = fieldSize;
518    }
519  }
520
521  // Now add our field.
522  if (unionType) {
523    AppendField(CharUnits::Zero(), unionType);
524
525    if (getTypeAlignment(unionType) > layout.getAlignment()) {
526      // We need a packed struct.
527      Packed = true;
528      unionAlign = CharUnits::One();
529    }
530  }
531  if (unionAlign.isZero()) {
532    (void)hasOnlyZeroSizedBitFields;
533    assert(hasOnlyZeroSizedBitFields &&
534           "0-align record did not have all zero-sized bit-fields!");
535    unionAlign = CharUnits::One();
536  }
537
538  // Append tail padding.
539  CharUnits recordSize = layout.getSize();
540  if (recordSize > unionSize)
541    AppendPadding(recordSize, unionAlign);
542}
543
544bool CGRecordLayoutBuilder::LayoutBase(const CXXRecordDecl *base,
545                                       const CGRecordLayout &baseLayout,
546                                       CharUnits baseOffset) {
547  ResizeLastBaseFieldIfNecessary(baseOffset);
548
549  AppendPadding(baseOffset, CharUnits::One());
550
551  const ASTRecordLayout &baseASTLayout
552    = Types.getContext().getASTRecordLayout(base);
553
554  LastLaidOutBase.Offset = NextFieldOffset;
555  LastLaidOutBase.NonVirtualSize = baseASTLayout.getNonVirtualSize();
556
557  llvm::StructType *subobjectType = baseLayout.getBaseSubobjectLLVMType();
558  if (getTypeAlignment(subobjectType) > Alignment)
559    return false;
560
561  AppendField(baseOffset, subobjectType);
562  return true;
563}
564
565bool CGRecordLayoutBuilder::LayoutNonVirtualBase(const CXXRecordDecl *base,
566                                                 CharUnits baseOffset) {
567  // Ignore empty bases.
568  if (base->isEmpty()) return true;
569
570  const CGRecordLayout &baseLayout = Types.getCGRecordLayout(base);
571  if (IsZeroInitializableAsBase) {
572    assert(IsZeroInitializable &&
573           "class zero-initializable as base but not as complete object");
574
575    IsZeroInitializable = IsZeroInitializableAsBase =
576      baseLayout.isZeroInitializableAsBase();
577  }
578
579  if (!LayoutBase(base, baseLayout, baseOffset))
580    return false;
581  NonVirtualBases[base] = (FieldTypes.size() - 1);
582  return true;
583}
584
585bool
586CGRecordLayoutBuilder::LayoutVirtualBase(const CXXRecordDecl *base,
587                                         CharUnits baseOffset) {
588  // Ignore empty bases.
589  if (base->isEmpty()) return true;
590
591  const CGRecordLayout &baseLayout = Types.getCGRecordLayout(base);
592  if (IsZeroInitializable)
593    IsZeroInitializable = baseLayout.isZeroInitializableAsBase();
594
595  if (!LayoutBase(base, baseLayout, baseOffset))
596    return false;
597  VirtualBases[base] = (FieldTypes.size() - 1);
598  return true;
599}
600
601bool
602CGRecordLayoutBuilder::MSLayoutVirtualBases(const CXXRecordDecl *RD,
603                                          const ASTRecordLayout &Layout) {
604  if (!RD->getNumVBases())
605    return true;
606
607  // The vbases list is uniqued and ordered by a depth-first
608  // traversal, which is what we need here.
609  for (CXXRecordDecl::base_class_const_iterator I = RD->vbases_begin(),
610        E = RD->vbases_end(); I != E; ++I) {
611
612    const CXXRecordDecl *BaseDecl =
613      cast<CXXRecordDecl>(I->getType()->castAs<RecordType>()->getDecl());
614
615    CharUnits vbaseOffset = Layout.getVBaseClassOffset(BaseDecl);
616    if (!LayoutVirtualBase(BaseDecl, vbaseOffset))
617      return false;
618  }
619  return true;
620}
621
622/// LayoutVirtualBases - layout the non-virtual bases of a record decl.
623bool
624CGRecordLayoutBuilder::LayoutVirtualBases(const CXXRecordDecl *RD,
625                                          const ASTRecordLayout &Layout) {
626  for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
627       E = RD->bases_end(); I != E; ++I) {
628    const CXXRecordDecl *BaseDecl =
629      cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
630
631    // We only want to lay out virtual bases that aren't indirect primary bases
632    // of some other base.
633    if (I->isVirtual() && !IndirectPrimaryBases.count(BaseDecl)) {
634      // Only lay out the base once.
635      if (!LaidOutVirtualBases.insert(BaseDecl))
636        continue;
637
638      CharUnits vbaseOffset = Layout.getVBaseClassOffset(BaseDecl);
639      if (!LayoutVirtualBase(BaseDecl, vbaseOffset))
640        return false;
641    }
642
643    if (!BaseDecl->getNumVBases()) {
644      // This base isn't interesting since it doesn't have any virtual bases.
645      continue;
646    }
647
648    if (!LayoutVirtualBases(BaseDecl, Layout))
649      return false;
650  }
651  return true;
652}
653
654bool
655CGRecordLayoutBuilder::LayoutNonVirtualBases(const CXXRecordDecl *RD,
656                                             const ASTRecordLayout &Layout) {
657  const CXXRecordDecl *PrimaryBase = Layout.getPrimaryBase();
658
659  // If we have a primary base, lay it out first.
660  if (PrimaryBase) {
661    if (!Layout.isPrimaryBaseVirtual()) {
662      if (!LayoutNonVirtualBase(PrimaryBase, CharUnits::Zero()))
663        return false;
664    } else {
665      if (!LayoutVirtualBase(PrimaryBase, CharUnits::Zero()))
666        return false;
667    }
668
669  // Otherwise, add a vtable / vf-table if the layout says to do so.
670  } else if (Layout.hasOwnVFPtr()) {
671    llvm::Type *FunctionType =
672      llvm::FunctionType::get(llvm::Type::getInt32Ty(Types.getLLVMContext()),
673                              /*isVarArg=*/true);
674    llvm::Type *VTableTy = FunctionType->getPointerTo();
675
676    if (getTypeAlignment(VTableTy) > Alignment) {
677      // FIXME: Should we allow this to happen in Sema?
678      assert(!Packed && "Alignment is wrong even with packed struct!");
679      return false;
680    }
681
682    assert(NextFieldOffset.isZero() &&
683           "VTable pointer must come first!");
684    AppendField(CharUnits::Zero(), VTableTy->getPointerTo());
685  }
686
687  // Layout the non-virtual bases.
688  for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
689       E = RD->bases_end(); I != E; ++I) {
690    if (I->isVirtual())
691      continue;
692
693    const CXXRecordDecl *BaseDecl =
694      cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
695
696    // We've already laid out the primary base.
697    if (BaseDecl == PrimaryBase && !Layout.isPrimaryBaseVirtual())
698      continue;
699
700    if (!LayoutNonVirtualBase(BaseDecl, Layout.getBaseClassOffset(BaseDecl)))
701      return false;
702  }
703
704  // Add a vb-table pointer if the layout insists.
705  if (Layout.getVBPtrOffset() != CharUnits::fromQuantity(-1)) {
706    CharUnits VBPtrOffset = Layout.getVBPtrOffset();
707    llvm::Type *Vbptr = llvm::Type::getInt32PtrTy(Types.getLLVMContext());
708    AppendPadding(VBPtrOffset, getTypeAlignment(Vbptr));
709    AppendField(VBPtrOffset, Vbptr);
710  }
711
712  return true;
713}
714
715bool
716CGRecordLayoutBuilder::ComputeNonVirtualBaseType(const CXXRecordDecl *RD) {
717  const ASTRecordLayout &Layout = Types.getContext().getASTRecordLayout(RD);
718
719  CharUnits NonVirtualSize  = Layout.getNonVirtualSize();
720  CharUnits NonVirtualAlign = Layout.getNonVirtualAlign();
721  CharUnits AlignedNonVirtualTypeSize =
722    NonVirtualSize.RoundUpToAlignment(NonVirtualAlign);
723
724  // First check if we can use the same fields as for the complete class.
725  CharUnits RecordSize = Layout.getSize();
726  if (AlignedNonVirtualTypeSize == RecordSize)
727    return true;
728
729  // Check if we need padding.
730  CharUnits AlignedNextFieldOffset =
731    NextFieldOffset.RoundUpToAlignment(getAlignmentAsLLVMStruct());
732
733  if (AlignedNextFieldOffset > AlignedNonVirtualTypeSize) {
734    assert(!Packed && "cannot layout even as packed struct");
735    return false; // Needs packing.
736  }
737
738  bool needsPadding = (AlignedNonVirtualTypeSize != AlignedNextFieldOffset);
739  if (needsPadding) {
740    CharUnits NumBytes = AlignedNonVirtualTypeSize - AlignedNextFieldOffset;
741    FieldTypes.push_back(getByteArrayType(NumBytes));
742  }
743
744  BaseSubobjectType = llvm::StructType::create(Types.getLLVMContext(),
745                                               FieldTypes, "", Packed);
746  Types.addRecordTypeName(RD, BaseSubobjectType, ".base");
747
748  // Pull the padding back off.
749  if (needsPadding)
750    FieldTypes.pop_back();
751
752  return true;
753}
754
755bool CGRecordLayoutBuilder::LayoutFields(const RecordDecl *D) {
756  assert(!D->isUnion() && "Can't call LayoutFields on a union!");
757  assert(!Alignment.isZero() && "Did not set alignment!");
758
759  const ASTRecordLayout &Layout = Types.getContext().getASTRecordLayout(D);
760
761  const CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(D);
762  if (RD)
763    if (!LayoutNonVirtualBases(RD, Layout))
764      return false;
765
766  unsigned FieldNo = 0;
767  const FieldDecl *LastFD = 0;
768
769  for (RecordDecl::field_iterator FI = D->field_begin(), FE = D->field_end();
770       FI != FE; ++FI, ++FieldNo) {
771    FieldDecl *FD = *FI;
772    if (IsMsStruct) {
773      // Zero-length bitfields following non-bitfield members are
774      // ignored:
775      if (Types.getContext().ZeroBitfieldFollowsNonBitfield(FD, LastFD)) {
776        --FieldNo;
777        continue;
778      }
779      LastFD = FD;
780    }
781
782    // If this field is a bitfield, layout all of the consecutive
783    // non-zero-length bitfields and the last zero-length bitfield; these will
784    // all share storage.
785    if (FD->isBitField()) {
786      // If all we have is a zero-width bitfield, skip it.
787      if (FD->getBitWidthValue(Types.getContext()) == 0)
788        continue;
789
790      // Layout this range of bitfields.
791      if (!LayoutBitfields(Layout, FieldNo, FI, FE)) {
792        assert(!Packed &&
793               "Could not layout bitfields even with a packed LLVM struct!");
794        return false;
795      }
796      assert(FI != FE && "Advanced past the last bitfield");
797      continue;
798    }
799
800    if (!LayoutField(FD, Layout.getFieldOffset(FieldNo))) {
801      assert(!Packed &&
802             "Could not layout fields even with a packed LLVM struct!");
803      return false;
804    }
805  }
806
807  if (RD) {
808    // We've laid out the non-virtual bases and the fields, now compute the
809    // non-virtual base field types.
810    if (!ComputeNonVirtualBaseType(RD)) {
811      assert(!Packed && "Could not layout even with a packed LLVM struct!");
812      return false;
813    }
814
815    // Lay out the virtual bases.  The MS ABI uses a different
816    // algorithm here due to the lack of primary virtual bases.
817    if (Types.getContext().getTargetInfo().getCXXABI().hasPrimaryVBases()) {
818      RD->getIndirectPrimaryBases(IndirectPrimaryBases);
819      if (Layout.isPrimaryBaseVirtual())
820        IndirectPrimaryBases.insert(Layout.getPrimaryBase());
821
822      if (!LayoutVirtualBases(RD, Layout))
823        return false;
824    } else {
825      if (!MSLayoutVirtualBases(RD, Layout))
826        return false;
827    }
828  }
829
830  // Append tail padding if necessary.
831  AppendTailPadding(Layout.getSize());
832
833  return true;
834}
835
836void CGRecordLayoutBuilder::AppendTailPadding(CharUnits RecordSize) {
837  ResizeLastBaseFieldIfNecessary(RecordSize);
838
839  assert(NextFieldOffset <= RecordSize && "Size mismatch!");
840
841  CharUnits AlignedNextFieldOffset =
842    NextFieldOffset.RoundUpToAlignment(getAlignmentAsLLVMStruct());
843
844  if (AlignedNextFieldOffset == RecordSize) {
845    // We don't need any padding.
846    return;
847  }
848
849  CharUnits NumPadBytes = RecordSize - NextFieldOffset;
850  AppendBytes(NumPadBytes);
851}
852
853void CGRecordLayoutBuilder::AppendField(CharUnits fieldOffset,
854                                        llvm::Type *fieldType) {
855  CharUnits fieldSize =
856    CharUnits::fromQuantity(Types.getDataLayout().getTypeAllocSize(fieldType));
857
858  FieldTypes.push_back(fieldType);
859
860  NextFieldOffset = fieldOffset + fieldSize;
861}
862
863void CGRecordLayoutBuilder::AppendPadding(CharUnits fieldOffset,
864                                          CharUnits fieldAlignment) {
865  assert(NextFieldOffset <= fieldOffset &&
866         "Incorrect field layout!");
867
868  // Do nothing if we're already at the right offset.
869  if (fieldOffset == NextFieldOffset) return;
870
871  // If we're not emitting a packed LLVM type, try to avoid adding
872  // unnecessary padding fields.
873  if (!Packed) {
874    // Round up the field offset to the alignment of the field type.
875    CharUnits alignedNextFieldOffset =
876      NextFieldOffset.RoundUpToAlignment(fieldAlignment);
877    assert(alignedNextFieldOffset <= fieldOffset);
878
879    // If that's the right offset, we're done.
880    if (alignedNextFieldOffset == fieldOffset) return;
881  }
882
883  // Otherwise we need explicit padding.
884  CharUnits padding = fieldOffset - NextFieldOffset;
885  AppendBytes(padding);
886}
887
888bool CGRecordLayoutBuilder::ResizeLastBaseFieldIfNecessary(CharUnits offset) {
889  // Check if we have a base to resize.
890  if (!LastLaidOutBase.isValid())
891    return false;
892
893  // This offset does not overlap with the tail padding.
894  if (offset >= NextFieldOffset)
895    return false;
896
897  // Restore the field offset and append an i8 array instead.
898  FieldTypes.pop_back();
899  NextFieldOffset = LastLaidOutBase.Offset;
900  AppendBytes(LastLaidOutBase.NonVirtualSize);
901  LastLaidOutBase.invalidate();
902
903  return true;
904}
905
906llvm::Type *CGRecordLayoutBuilder::getByteArrayType(CharUnits numBytes) {
907  assert(!numBytes.isZero() && "Empty byte arrays aren't allowed.");
908
909  llvm::Type *Ty = llvm::Type::getInt8Ty(Types.getLLVMContext());
910  if (numBytes > CharUnits::One())
911    Ty = llvm::ArrayType::get(Ty, numBytes.getQuantity());
912
913  return Ty;
914}
915
916void CGRecordLayoutBuilder::AppendBytes(CharUnits numBytes) {
917  if (numBytes.isZero())
918    return;
919
920  // Append the padding field
921  AppendField(NextFieldOffset, getByteArrayType(numBytes));
922}
923
924CharUnits CGRecordLayoutBuilder::getTypeAlignment(llvm::Type *Ty) const {
925  if (Packed)
926    return CharUnits::One();
927
928  return CharUnits::fromQuantity(Types.getDataLayout().getABITypeAlignment(Ty));
929}
930
931CharUnits CGRecordLayoutBuilder::getAlignmentAsLLVMStruct() const {
932  if (Packed)
933    return CharUnits::One();
934
935  CharUnits maxAlignment = CharUnits::One();
936  for (size_t i = 0; i != FieldTypes.size(); ++i)
937    maxAlignment = std::max(maxAlignment, getTypeAlignment(FieldTypes[i]));
938
939  return maxAlignment;
940}
941
942/// Merge in whether a field of the given type is zero-initializable.
943void CGRecordLayoutBuilder::CheckZeroInitializable(QualType T) {
944  // This record already contains a member pointer.
945  if (!IsZeroInitializableAsBase)
946    return;
947
948  // Can only have member pointers if we're compiling C++.
949  if (!Types.getContext().getLangOpts().CPlusPlus)
950    return;
951
952  const Type *elementType = T->getBaseElementTypeUnsafe();
953
954  if (const MemberPointerType *MPT = elementType->getAs<MemberPointerType>()) {
955    if (!Types.getCXXABI().isZeroInitializable(MPT))
956      IsZeroInitializable = IsZeroInitializableAsBase = false;
957  } else if (const RecordType *RT = elementType->getAs<RecordType>()) {
958    const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
959    const CGRecordLayout &Layout = Types.getCGRecordLayout(RD);
960    if (!Layout.isZeroInitializable())
961      IsZeroInitializable = IsZeroInitializableAsBase = false;
962  }
963}
964
965CGRecordLayout *CodeGenTypes::ComputeRecordLayout(const RecordDecl *D,
966                                                  llvm::StructType *Ty) {
967  CGRecordLayoutBuilder Builder(*this);
968
969  Builder.Layout(D);
970
971  Ty->setBody(Builder.FieldTypes, Builder.Packed);
972
973  // If we're in C++, compute the base subobject type.
974  llvm::StructType *BaseTy = 0;
975  if (isa<CXXRecordDecl>(D) && !D->isUnion()) {
976    BaseTy = Builder.BaseSubobjectType;
977    if (!BaseTy) BaseTy = Ty;
978  }
979
980  CGRecordLayout *RL =
981    new CGRecordLayout(Ty, BaseTy, Builder.IsZeroInitializable,
982                       Builder.IsZeroInitializableAsBase);
983
984  RL->NonVirtualBases.swap(Builder.NonVirtualBases);
985  RL->CompleteObjectVirtualBases.swap(Builder.VirtualBases);
986
987  // Add all the field numbers.
988  RL->FieldInfo.swap(Builder.Fields);
989
990  // Add bitfield info.
991  RL->BitFields.swap(Builder.BitFields);
992
993  // Dump the layout, if requested.
994  if (getContext().getLangOpts().DumpRecordLayouts) {
995    llvm::errs() << "\n*** Dumping IRgen Record Layout\n";
996    llvm::errs() << "Record: ";
997    D->dump();
998    llvm::errs() << "\nLayout: ";
999    RL->dump();
1000  }
1001
1002#ifndef NDEBUG
1003  // Verify that the computed LLVM struct size matches the AST layout size.
1004  const ASTRecordLayout &Layout = getContext().getASTRecordLayout(D);
1005
1006  uint64_t TypeSizeInBits = getContext().toBits(Layout.getSize());
1007  assert(TypeSizeInBits == getDataLayout().getTypeAllocSizeInBits(Ty) &&
1008         "Type size mismatch!");
1009
1010  if (BaseTy) {
1011    CharUnits NonVirtualSize  = Layout.getNonVirtualSize();
1012    CharUnits NonVirtualAlign = Layout.getNonVirtualAlign();
1013    CharUnits AlignedNonVirtualTypeSize =
1014      NonVirtualSize.RoundUpToAlignment(NonVirtualAlign);
1015
1016    uint64_t AlignedNonVirtualTypeSizeInBits =
1017      getContext().toBits(AlignedNonVirtualTypeSize);
1018
1019    assert(AlignedNonVirtualTypeSizeInBits ==
1020           getDataLayout().getTypeAllocSizeInBits(BaseTy) &&
1021           "Type size mismatch!");
1022  }
1023
1024  // Verify that the LLVM and AST field offsets agree.
1025  llvm::StructType *ST =
1026    dyn_cast<llvm::StructType>(RL->getLLVMType());
1027  const llvm::StructLayout *SL = getDataLayout().getStructLayout(ST);
1028
1029  const ASTRecordLayout &AST_RL = getContext().getASTRecordLayout(D);
1030  RecordDecl::field_iterator it = D->field_begin();
1031  const FieldDecl *LastFD = 0;
1032  bool IsMsStruct = D->isMsStruct(getContext());
1033  for (unsigned i = 0, e = AST_RL.getFieldCount(); i != e; ++i, ++it) {
1034    const FieldDecl *FD = *it;
1035
1036    // For non-bit-fields, just check that the LLVM struct offset matches the
1037    // AST offset.
1038    if (!FD->isBitField()) {
1039      unsigned FieldNo = RL->getLLVMFieldNo(FD);
1040      assert(AST_RL.getFieldOffset(i) == SL->getElementOffsetInBits(FieldNo) &&
1041             "Invalid field offset!");
1042      LastFD = FD;
1043      continue;
1044    }
1045
1046    if (IsMsStruct) {
1047      // Zero-length bitfields following non-bitfield members are
1048      // ignored:
1049      if (getContext().ZeroBitfieldFollowsNonBitfield(FD, LastFD)) {
1050        --i;
1051        continue;
1052      }
1053      LastFD = FD;
1054    }
1055
1056    // Ignore unnamed bit-fields.
1057    if (!FD->getDeclName()) {
1058      LastFD = FD;
1059      continue;
1060    }
1061
1062    // Don't inspect zero-length bitfields.
1063    if (FD->getBitWidthValue(getContext()) == 0)
1064      continue;
1065
1066    const CGBitFieldInfo &Info = RL->getBitFieldInfo(FD);
1067    llvm::Type *ElementTy = ST->getTypeAtIndex(RL->getLLVMFieldNo(FD));
1068
1069    // Unions have overlapping elements dictating their layout, but for
1070    // non-unions we can verify that this section of the layout is the exact
1071    // expected size.
1072    if (D->isUnion()) {
1073      // For unions we verify that the start is zero and the size
1074      // is in-bounds. However, on BE systems, the offset may be non-zero, but
1075      // the size + offset should match the storage size in that case as it
1076      // "starts" at the back.
1077      if (getDataLayout().isBigEndian())
1078        assert(static_cast<unsigned>(Info.Offset + Info.Size) ==
1079               Info.StorageSize &&
1080               "Big endian union bitfield does not end at the back");
1081      else
1082        assert(Info.Offset == 0 &&
1083               "Little endian union bitfield with a non-zero offset");
1084      assert(Info.StorageSize <= SL->getSizeInBits() &&
1085             "Union not large enough for bitfield storage");
1086    } else {
1087      assert(Info.StorageSize ==
1088             getDataLayout().getTypeAllocSizeInBits(ElementTy) &&
1089             "Storage size does not match the element type size");
1090    }
1091    assert(Info.Size > 0 && "Empty bitfield!");
1092    assert(static_cast<unsigned>(Info.Offset) + Info.Size <= Info.StorageSize &&
1093           "Bitfield outside of its allocated storage");
1094  }
1095#endif
1096
1097  return RL;
1098}
1099
1100void CGRecordLayout::print(raw_ostream &OS) const {
1101  OS << "<CGRecordLayout\n";
1102  OS << "  LLVMType:" << *CompleteObjectType << "\n";
1103  if (BaseSubobjectType)
1104    OS << "  NonVirtualBaseLLVMType:" << *BaseSubobjectType << "\n";
1105  OS << "  IsZeroInitializable:" << IsZeroInitializable << "\n";
1106  OS << "  BitFields:[\n";
1107
1108  // Print bit-field infos in declaration order.
1109  std::vector<std::pair<unsigned, const CGBitFieldInfo*> > BFIs;
1110  for (llvm::DenseMap<const FieldDecl*, CGBitFieldInfo>::const_iterator
1111         it = BitFields.begin(), ie = BitFields.end();
1112       it != ie; ++it) {
1113    const RecordDecl *RD = it->first->getParent();
1114    unsigned Index = 0;
1115    for (RecordDecl::field_iterator
1116           it2 = RD->field_begin(); *it2 != it->first; ++it2)
1117      ++Index;
1118    BFIs.push_back(std::make_pair(Index, &it->second));
1119  }
1120  llvm::array_pod_sort(BFIs.begin(), BFIs.end());
1121  for (unsigned i = 0, e = BFIs.size(); i != e; ++i) {
1122    OS.indent(4);
1123    BFIs[i].second->print(OS);
1124    OS << "\n";
1125  }
1126
1127  OS << "]>\n";
1128}
1129
1130void CGRecordLayout::dump() const {
1131  print(llvm::errs());
1132}
1133
1134void CGBitFieldInfo::print(raw_ostream &OS) const {
1135  OS << "<CGBitFieldInfo"
1136     << " Offset:" << Offset
1137     << " Size:" << Size
1138     << " IsSigned:" << IsSigned
1139     << " StorageSize:" << StorageSize
1140     << " StorageAlignment:" << StorageAlignment << ">";
1141}
1142
1143void CGBitFieldInfo::dump() const {
1144  print(llvm::errs());
1145}
1146