llvm.org GIT mirror llvm / d0b2625 include / llvm / CodeGen / DIE.h
d0b2625

Tree @d0b2625 (Download .tar.gz)

DIE.h @d0b2625raw · history · blame

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
//===--- lib/CodeGen/DIE.h - DWARF Info Entries -----------------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// Data structures for DWARF info entries.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_LIB_CODEGEN_ASMPRINTER_DIE_H
#define LLVM_LIB_CODEGEN_ASMPRINTER_DIE_H

#include "llvm/ADT/FoldingSet.h"
#include "llvm/ADT/PointerIntPair.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/CodeGen/DwarfStringPoolEntry.h"
#include "llvm/Support/Dwarf.h"
#include <vector>

namespace llvm {
class AsmPrinter;
class MCExpr;
class MCSymbol;
class raw_ostream;
class DwarfTypeUnit;

//===--------------------------------------------------------------------===//
/// DIEAbbrevData - Dwarf abbreviation data, describes one attribute of a
/// Dwarf abbreviation.
class DIEAbbrevData {
  /// Attribute - Dwarf attribute code.
  ///
  dwarf::Attribute Attribute;

  /// Form - Dwarf form code.
  ///
  dwarf::Form Form;

public:
  DIEAbbrevData(dwarf::Attribute A, dwarf::Form F) : Attribute(A), Form(F) {}

  // Accessors.
  dwarf::Attribute getAttribute() const { return Attribute; }
  dwarf::Form getForm() const { return Form; }

  /// Profile - Used to gather unique data for the abbreviation folding set.
  ///
  void Profile(FoldingSetNodeID &ID) const;
};

//===--------------------------------------------------------------------===//
/// DIEAbbrev - Dwarf abbreviation, describes the organization of a debug
/// information object.
class DIEAbbrev : public FoldingSetNode {
  /// Unique number for node.
  ///
  unsigned Number;

  /// Tag - Dwarf tag code.
  ///
  dwarf::Tag Tag;

  /// Children - Whether or not this node has children.
  ///
  // This cheats a bit in all of the uses since the values in the standard
  // are 0 and 1 for no children and children respectively.
  bool Children;

  /// Data - Raw data bytes for abbreviation.
  ///
  SmallVector<DIEAbbrevData, 12> Data;

public:
  DIEAbbrev(dwarf::Tag T, bool C) : Tag(T), Children(C), Data() {}

  // Accessors.
  dwarf::Tag getTag() const { return Tag; }
  unsigned getNumber() const { return Number; }
  bool hasChildren() const { return Children; }
  const SmallVectorImpl<DIEAbbrevData> &getData() const { return Data; }
  void setChildrenFlag(bool hasChild) { Children = hasChild; }
  void setNumber(unsigned N) { Number = N; }

  /// AddAttribute - Adds another set of attribute information to the
  /// abbreviation.
  void AddAttribute(dwarf::Attribute Attribute, dwarf::Form Form) {
    Data.push_back(DIEAbbrevData(Attribute, Form));
  }

  /// Profile - Used to gather unique data for the abbreviation folding set.
  ///
  void Profile(FoldingSetNodeID &ID) const;

  /// Emit - Print the abbreviation using the specified asm printer.
  ///
  void Emit(const AsmPrinter *AP) const;

  void print(raw_ostream &O);
  void dump();
};

//===--------------------------------------------------------------------===//
/// DIEInteger - An integer value DIE.
///
class DIEInteger {
  uint64_t Integer;

public:
  explicit DIEInteger(uint64_t I) : Integer(I) {}

  /// BestForm - Choose the best form for integer.
  ///
  static dwarf::Form BestForm(bool IsSigned, uint64_t Int) {
    if (IsSigned) {
      const int64_t SignedInt = Int;
      if ((char)Int == SignedInt)
        return dwarf::DW_FORM_data1;
      if ((short)Int == SignedInt)
        return dwarf::DW_FORM_data2;
      if ((int)Int == SignedInt)
        return dwarf::DW_FORM_data4;
    } else {
      if ((unsigned char)Int == Int)
        return dwarf::DW_FORM_data1;
      if ((unsigned short)Int == Int)
        return dwarf::DW_FORM_data2;
      if ((unsigned int)Int == Int)
        return dwarf::DW_FORM_data4;
    }
    return dwarf::DW_FORM_data8;
  }

  uint64_t getValue() const { return Integer; }
  void setValue(uint64_t Val) { Integer = Val; }

  void EmitValue(const AsmPrinter *AP, dwarf::Form Form) const;
  unsigned SizeOf(const AsmPrinter *AP, dwarf::Form Form) const;

  void print(raw_ostream &O) const;
};

//===--------------------------------------------------------------------===//
/// DIEExpr - An expression DIE.
//
class DIEExpr {
  const MCExpr *Expr;

public:
  explicit DIEExpr(const MCExpr *E) : Expr(E) {}

  /// getValue - Get MCExpr.
  ///
  const MCExpr *getValue() const { return Expr; }

  void EmitValue(const AsmPrinter *AP, dwarf::Form Form) const;
  unsigned SizeOf(const AsmPrinter *AP, dwarf::Form Form) const;

  void print(raw_ostream &O) const;
};

//===--------------------------------------------------------------------===//
/// DIELabel - A label DIE.
//
class DIELabel {
  const MCSymbol *Label;

public:
  explicit DIELabel(const MCSymbol *L) : Label(L) {}

  /// getValue - Get MCSymbol.
  ///
  const MCSymbol *getValue() const { return Label; }

  void EmitValue(const AsmPrinter *AP, dwarf::Form Form) const;
  unsigned SizeOf(const AsmPrinter *AP, dwarf::Form Form) const;

  void print(raw_ostream &O) const;
};

//===--------------------------------------------------------------------===//
/// DIEDelta - A simple label difference DIE.
///
class DIEDelta {
  const MCSymbol *LabelHi;
  const MCSymbol *LabelLo;

public:
  DIEDelta(const MCSymbol *Hi, const MCSymbol *Lo) : LabelHi(Hi), LabelLo(Lo) {}

  void EmitValue(const AsmPrinter *AP, dwarf::Form Form) const;
  unsigned SizeOf(const AsmPrinter *AP, dwarf::Form Form) const;

  void print(raw_ostream &O) const;
};

//===--------------------------------------------------------------------===//
/// DIEString - A container for string values.
///
class DIEString {
  DwarfStringPoolEntryRef S;

public:
  DIEString(DwarfStringPoolEntryRef S) : S(S) {}

  /// getString - Grab the string out of the object.
  StringRef getString() const { return S.getString(); }

  void EmitValue(const AsmPrinter *AP, dwarf::Form Form) const;
  unsigned SizeOf(const AsmPrinter *AP, dwarf::Form Form) const;

  void print(raw_ostream &O) const;
};

//===--------------------------------------------------------------------===//
/// DIEEntry - A pointer to another debug information entry.  An instance of
/// this class can also be used as a proxy for a debug information entry not
/// yet defined (ie. types.)
class DIE;
class DIEEntry {
  DIE *Entry;

  DIEEntry() = delete;

public:
  explicit DIEEntry(DIE &E) : Entry(&E) {}

  DIE &getEntry() const { return *Entry; }

  /// Returns size of a ref_addr entry.
  static unsigned getRefAddrSize(const AsmPrinter *AP);

  void EmitValue(const AsmPrinter *AP, dwarf::Form Form) const;
  unsigned SizeOf(const AsmPrinter *AP, dwarf::Form Form) const {
    return Form == dwarf::DW_FORM_ref_addr ? getRefAddrSize(AP)
                                           : sizeof(int32_t);
  }

  void print(raw_ostream &O) const;
};

//===--------------------------------------------------------------------===//
/// \brief A signature reference to a type unit.
class DIETypeSignature {
  const DwarfTypeUnit *Unit;

  DIETypeSignature() = delete;

public:
  explicit DIETypeSignature(const DwarfTypeUnit &Unit) : Unit(&Unit) {}

  void EmitValue(const AsmPrinter *AP, dwarf::Form Form) const;
  unsigned SizeOf(const AsmPrinter *AP, dwarf::Form Form) const {
    assert(Form == dwarf::DW_FORM_ref_sig8);
    return 8;
  }

  void print(raw_ostream &O) const;
};

//===--------------------------------------------------------------------===//
/// DIELocList - Represents a pointer to a location list in the debug_loc
/// section.
//
class DIELocList {
  // Index into the .debug_loc vector.
  size_t Index;

public:
  DIELocList(size_t I) : Index(I) {}

  /// getValue - Grab the current index out.
  size_t getValue() const { return Index; }

  void EmitValue(const AsmPrinter *AP, dwarf::Form Form) const;
  unsigned SizeOf(const AsmPrinter *AP, dwarf::Form Form) const;

  void print(raw_ostream &O) const;
};

//===--------------------------------------------------------------------===//
/// DIEValue - A debug information entry value. Some of these roughly correlate
/// to DWARF attribute classes.
///
class DIEBlock;
class DIELoc;
class DIEValue {
public:
  enum Type {
    isNone,
#define HANDLE_DIEVALUE(T) is##T,
#include "llvm/CodeGen/DIEValue.def"
  };

private:
  /// Ty - Type of data stored in the value.
  ///
  Type Ty = isNone;
  dwarf::Attribute Attribute = (dwarf::Attribute)0;
  dwarf::Form Form = (dwarf::Form)0;

  /// Storage for the value.
  ///
  /// All values that aren't standard layout (or are larger than 8 bytes)
  /// should be stored by reference instead of by value.
  typedef AlignedCharArrayUnion<DIEInteger, DIEString, DIEExpr, DIELabel,
                                DIEDelta *, DIEEntry, DIETypeSignature,
                                DIEBlock *, DIELoc *, DIELocList> ValTy;
  static_assert(sizeof(ValTy) <= sizeof(uint64_t) ||
                    sizeof(ValTy) <= sizeof(void *),
                "Expected all large types to be stored via pointer");

  /// Underlying stored value.
  ValTy Val;

  template <class T> void construct(T V) {
    static_assert(std::is_standard_layout<T>::value ||
                      std::is_pointer<T>::value,
                  "Expected standard layout or pointer");
    new (reinterpret_cast<void *>(Val.buffer)) T(V);
  }

  template <class T> T *get() { return reinterpret_cast<T *>(Val.buffer); }
  template <class T> const T *get() const {
    return reinterpret_cast<const T *>(Val.buffer);
  }
  template <class T> void destruct() { get<T>()->~T(); }

  /// Destroy the underlying value.
  ///
  /// This should get optimized down to a no-op.  We could skip it if we could
  /// add a static assert on \a std::is_trivially_copyable(), but we currently
  /// support versions of GCC that don't understand that.
  void destroyVal() {
    switch (Ty) {
    case isNone:
      return;
#define HANDLE_DIEVALUE_SMALL(T)                                               \
  case is##T:                                                                  \
    destruct<DIE##T>();
    return;
#define HANDLE_DIEVALUE_LARGE(T)                                               \
  case is##T:                                                                  \
    destruct<const DIE##T *>();
    return;
#include "llvm/CodeGen/DIEValue.def"
    }
  }

  /// Copy the underlying value.
  ///
  /// This should get optimized down to a simple copy.  We need to actually
  /// construct the value, rather than calling memcpy, to satisfy strict
  /// aliasing rules.
  void copyVal(const DIEValue &X) {
    switch (Ty) {
    case isNone:
      return;
#define HANDLE_DIEVALUE_SMALL(T)                                               \
  case is##T:                                                                  \
    construct<DIE##T>(*X.get<DIE##T>());                                       \
    return;
#define HANDLE_DIEVALUE_LARGE(T)                                               \
  case is##T:                                                                  \
    construct<const DIE##T *>(*X.get<const DIE##T *>());                       \
    return;
#include "llvm/CodeGen/DIEValue.def"
    }
  }

public:
  DIEValue() = default;
  DIEValue(const DIEValue &X) : Ty(X.Ty), Attribute(X.Attribute), Form(X.Form) {
    copyVal(X);
  }
  DIEValue &operator=(const DIEValue &X) {
    destroyVal();
    Ty = X.Ty;
    Attribute = X.Attribute;
    Form = X.Form;
    copyVal(X);
    return *this;
  }
  ~DIEValue() { destroyVal(); }

#define HANDLE_DIEVALUE_SMALL(T)                                               \
  DIEValue(dwarf::Attribute Attribute, dwarf::Form Form, const DIE##T &V)      \
      : Ty(is##T), Attribute(Attribute), Form(Form) {                          \
    construct<DIE##T>(V);                                                      \
  }
#define HANDLE_DIEVALUE_LARGE(T)                                               \
  DIEValue(dwarf::Attribute Attribute, dwarf::Form Form, const DIE##T *V)      \
      : Ty(is##T), Attribute(Attribute), Form(Form) {                          \
    assert(V && "Expected valid value");                                       \
    construct<const DIE##T *>(V);                                              \
  }
#include "llvm/CodeGen/DIEValue.def"

  // Accessors
  Type getType() const { return Ty; }
  dwarf::Attribute getAttribute() const { return Attribute; }
  dwarf::Form getForm() const { return Form; }
  explicit operator bool() const { return Ty; }

#define HANDLE_DIEVALUE_SMALL(T)                                               \
  const DIE##T &getDIE##T() const {                                            \
    assert(getType() == is##T && "Expected " #T);                              \
    return *get<DIE##T>();                                                     \
  }
#define HANDLE_DIEVALUE_LARGE(T)                                               \
  const DIE##T &getDIE##T() const {                                            \
    assert(getType() == is##T && "Expected " #T);                              \
    return **get<const DIE##T *>();                                            \
  }
#include "llvm/CodeGen/DIEValue.def"

  /// EmitValue - Emit value via the Dwarf writer.
  ///
  void EmitValue(const AsmPrinter *AP) const;

  /// SizeOf - Return the size of a value in bytes.
  ///
  unsigned SizeOf(const AsmPrinter *AP) const;

  void print(raw_ostream &O) const;
  void dump() const;
};

struct IntrusiveBackListNode {
  PointerIntPair<IntrusiveBackListNode *, 1> Next;
  IntrusiveBackListNode() : Next(this, true) {}

  IntrusiveBackListNode *getNext() const {
    return Next.getInt() ? nullptr : Next.getPointer();
  }
};

struct IntrusiveBackListBase {
  typedef IntrusiveBackListNode Node;
  Node *Last = nullptr;

  bool empty() const { return !Last; }
  void push_back(Node &N) {
    assert(N.Next.getPointer() == &N && "Expected unlinked node");
    assert(N.Next.getInt() == true && "Expected unlinked node");

    if (Last) {
      N.Next = Last->Next;
      Last->Next.setPointerAndInt(&N, false);
    }
    Last = &N;
  }
};

template <class T> class IntrusiveBackList : IntrusiveBackListBase {
public:
  using IntrusiveBackListBase::empty;
  void push_back(T &N) { IntrusiveBackListBase::push_back(N); }
  T &back() { return *static_cast<T *>(Last); }
  const T &back() const { return *static_cast<T *>(Last); }

  class const_iterator;
  class iterator
      : public iterator_facade_base<iterator, std::forward_iterator_tag, T> {
    friend class const_iterator;
    Node *N = nullptr;

  public:
    iterator() = default;
    explicit iterator(T *N) : N(N) {}

    iterator &operator++() {
      N = N->getNext();
      return *this;
    }

    explicit operator bool() const { return N; }
    T &operator*() const { return *static_cast<T *>(N); }

    bool operator==(const iterator &X) const { return N == X.N; }
    bool operator!=(const iterator &X) const { return N != X.N; }
  };

  class const_iterator
      : public iterator_facade_base<const_iterator, std::forward_iterator_tag,
                                    const T> {
    const Node *N = nullptr;

  public:
    const_iterator() = default;
    // Placate MSVC by explicitly scoping 'iterator'.
    const_iterator(typename IntrusiveBackList<T>::iterator X) : N(X.N) {}
    explicit const_iterator(const T *N) : N(N) {}

    const_iterator &operator++() {
      N = N->getNext();
      return *this;
    }

    explicit operator bool() const { return N; }
    const T &operator*() const { return *static_cast<const T *>(N); }

    bool operator==(const const_iterator &X) const { return N == X.N; }
    bool operator!=(const const_iterator &X) const { return N != X.N; }
  };

  iterator begin() {
    return Last ? iterator(static_cast<T *>(Last->Next.getPointer())) : end();
  }
  const_iterator begin() const {
    return const_cast<IntrusiveBackList *>(this)->begin();
  }
  iterator end() { return iterator(); }
  const_iterator end() const { return const_iterator(); }

  static iterator toIterator(T &N) { return iterator(&N); }
  static const_iterator toIterator(const T &N) { return const_iterator(&N); }
};

/// A list of DIE values.
///
/// This is a singly-linked list, but instead of reversing the order of
/// insertion, we keep a pointer to the back of the list so we can push in
/// order.
///
/// There are two main reasons to choose a linked list over a customized
/// vector-like data structure.
///
///  1. For teardown efficiency, we want DIEs to be BumpPtrAllocated.  Using a
///     linked list here makes this way easier to accomplish.
///  2. Carrying an extra pointer per \a DIEValue isn't expensive.  45% of DIEs
///     have 2 or fewer values, and 90% have 5 or fewer.  A vector would be
///     over-allocated by 50% on average anyway, the same cost as the
///     linked-list node.
class DIEValueList {
  struct Node : IntrusiveBackListNode {
    DIEValue V;
    explicit Node(DIEValue V) : V(V) {}
  };

  typedef IntrusiveBackList<Node> ListTy;
  ListTy List;

public:
  class const_value_iterator;
  class value_iterator
      : public iterator_adaptor_base<value_iterator, ListTy::iterator,
                                     std::forward_iterator_tag, DIEValue> {
    friend class const_value_iterator;
    typedef iterator_adaptor_base<value_iterator, ListTy::iterator,
                                  std::forward_iterator_tag,
                                  DIEValue> iterator_adaptor;

  public:
    value_iterator() = default;
    explicit value_iterator(ListTy::iterator X) : iterator_adaptor(X) {}

    explicit operator bool() const { return bool(wrapped()); }
    DIEValue &operator*() const { return wrapped()->V; }
  };

  class const_value_iterator : public iterator_adaptor_base<
                                   const_value_iterator, ListTy::const_iterator,
                                   std::forward_iterator_tag, const DIEValue> {
    typedef iterator_adaptor_base<const_value_iterator, ListTy::const_iterator,
                                  std::forward_iterator_tag,
                                  const DIEValue> iterator_adaptor;

  public:
    const_value_iterator() = default;
    const_value_iterator(DIEValueList::value_iterator X)
        : iterator_adaptor(X.wrapped()) {}
    explicit const_value_iterator(ListTy::const_iterator X)
        : iterator_adaptor(X) {}

    explicit operator bool() const { return bool(wrapped()); }
    const DIEValue &operator*() const { return wrapped()->V; }
  };

  typedef iterator_range<value_iterator> value_range;
  typedef iterator_range<const_value_iterator> const_value_range;

  value_iterator addValue(BumpPtrAllocator &Alloc, DIEValue V) {
    List.push_back(*new (Alloc) Node(V));
    return value_iterator(ListTy::toIterator(List.back()));
  }
  template <class T>
  value_iterator addValue(BumpPtrAllocator &Alloc, dwarf::Attribute Attribute,
                    dwarf::Form Form, T &&Value) {
    return addValue(Alloc, DIEValue(Attribute, Form, std::forward<T>(Value)));
  }

  value_range values() {
    return llvm::make_range(value_iterator(List.begin()),
                            value_iterator(List.end()));
  }
  const_value_range values() const {
    return llvm::make_range(const_value_iterator(List.begin()),
                            const_value_iterator(List.end()));
  }
};

//===--------------------------------------------------------------------===//
/// DIE - A structured debug information entry.  Has an abbreviation which
/// describes its organization.
class DIE : IntrusiveBackListNode, public DIEValueList {
  friend class IntrusiveBackList<DIE>;

  /// Offset - Offset in debug info section.
  ///
  unsigned Offset;

  /// Size - Size of instance + children.
  ///
  unsigned Size;

  unsigned AbbrevNumber = ~0u;

  /// Tag - Dwarf tag code.
  ///
  dwarf::Tag Tag = (dwarf::Tag)0;

  /// Children DIEs.
  IntrusiveBackList<DIE> Children;

  DIE *Parent = nullptr;

  DIE() = delete;
  explicit DIE(dwarf::Tag Tag) : Offset(0), Size(0), Tag(Tag) {}

public:
  static DIE *get(BumpPtrAllocator &Alloc, dwarf::Tag Tag) {
    return new (Alloc) DIE(Tag);
  }

  // Accessors.
  unsigned getAbbrevNumber() const { return AbbrevNumber; }
  dwarf::Tag getTag() const { return Tag; }
  unsigned getOffset() const { return Offset; }
  unsigned getSize() const { return Size; }
  bool hasChildren() const { return !Children.empty(); }

  typedef IntrusiveBackList<DIE>::iterator child_iterator;
  typedef IntrusiveBackList<DIE>::const_iterator const_child_iterator;
  typedef iterator_range<child_iterator> child_range;
  typedef iterator_range<const_child_iterator> const_child_range;

  child_range children() {
    return llvm::make_range(Children.begin(), Children.end());
  }
  const_child_range children() const {
    return llvm::make_range(Children.begin(), Children.end());
  }

  DIE *getParent() const { return Parent; }

  /// Generate the abbreviation for this DIE.
  ///
  /// Calculate the abbreviation for this, which should be uniqued and
  /// eventually used to call \a setAbbrevNumber().
  DIEAbbrev generateAbbrev() const;

  /// Set the abbreviation number for this DIE.
  void setAbbrevNumber(unsigned I) { AbbrevNumber = I; }

  /// Climb up the parent chain to get the compile or type unit DIE this DIE
  /// belongs to.
  const DIE *getUnit() const;
  /// Similar to getUnit, returns null when DIE is not added to an
  /// owner yet.
  const DIE *getUnitOrNull() const;
  void setOffset(unsigned O) { Offset = O; }
  void setSize(unsigned S) { Size = S; }

  /// Add a child to the DIE.
  DIE &addChild(DIE *Child) {
    assert(!Child->getParent() && "Child should be orphaned");
    Child->Parent = this;
    Children.push_back(*Child);
    return Children.back();
  }

  /// Find a value in the DIE with the attribute given.
  ///
  /// Returns a default-constructed DIEValue (where \a DIEValue::getType()
  /// gives \a DIEValue::isNone) if no such attribute exists.
  DIEValue findAttribute(dwarf::Attribute Attribute) const;

  void print(raw_ostream &O, unsigned IndentCount = 0) const;
  void dump();
};

//===--------------------------------------------------------------------===//
/// DIELoc - Represents an expression location.
//
class DIELoc : public DIEValueList {
  mutable unsigned Size; // Size in bytes excluding size header.

public:
  DIELoc() : Size(0) {}

  /// ComputeSize - Calculate the size of the location expression.
  ///
  unsigned ComputeSize(const AsmPrinter *AP) const;

  /// BestForm - Choose the best form for data.
  ///
  dwarf::Form BestForm(unsigned DwarfVersion) const {
    if (DwarfVersion > 3)
      return dwarf::DW_FORM_exprloc;
    // Pre-DWARF4 location expressions were blocks and not exprloc.
    if ((unsigned char)Size == Size)
      return dwarf::DW_FORM_block1;
    if ((unsigned short)Size == Size)
      return dwarf::DW_FORM_block2;
    if ((unsigned int)Size == Size)
      return dwarf::DW_FORM_block4;
    return dwarf::DW_FORM_block;
  }

  void EmitValue(const AsmPrinter *AP, dwarf::Form Form) const;
  unsigned SizeOf(const AsmPrinter *AP, dwarf::Form Form) const;

  void print(raw_ostream &O) const;
};

//===--------------------------------------------------------------------===//
/// DIEBlock - Represents a block of values.
//
class DIEBlock : public DIEValueList {
  mutable unsigned Size; // Size in bytes excluding size header.

public:
  DIEBlock() : Size(0) {}

  /// ComputeSize - Calculate the size of the location expression.
  ///
  unsigned ComputeSize(const AsmPrinter *AP) const;

  /// BestForm - Choose the best form for data.
  ///
  dwarf::Form BestForm() const {
    if ((unsigned char)Size == Size)
      return dwarf::DW_FORM_block1;
    if ((unsigned short)Size == Size)
      return dwarf::DW_FORM_block2;
    if ((unsigned int)Size == Size)
      return dwarf::DW_FORM_block4;
    return dwarf::DW_FORM_block;
  }

  void EmitValue(const AsmPrinter *AP, dwarf::Form Form) const;
  unsigned SizeOf(const AsmPrinter *AP, dwarf::Form Form) const;

  void print(raw_ostream &O) const;
};

} // end llvm namespace

#endif