summaryrefslogtreecommitdiff
path: root/lib/MC/MCDwarf.cpp
blob: 112d7d887a2d93ca23da1dbe5b8ec56419299602 (plain)
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
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
//===- lib/MC/MCDwarf.cpp - MCDwarf implementation ------------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#include "llvm/ADT/FoldingSet.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCDwarf.h"
#include "llvm/MC/MCAssembler.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCObjectWriter.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetAsmBackend.h"
#include "llvm/Target/TargetAsmInfo.h"
using namespace llvm;

// Given a special op, return the address skip amount (in units of
// DWARF2_LINE_MIN_INSN_LENGTH.
#define SPECIAL_ADDR(op) (((op) - DWARF2_LINE_OPCODE_BASE)/DWARF2_LINE_RANGE)

// The maximum address skip amount that can be encoded with a special op.
#define MAX_SPECIAL_ADDR_DELTA		SPECIAL_ADDR(255)

// First special line opcode - leave room for the standard opcodes.
// Note: If you want to change this, you'll have to update the
// "standard_opcode_lengths" table that is emitted in DwarfFileTable::Emit().  
#define DWARF2_LINE_OPCODE_BASE		13

// Minimum line offset in a special line info. opcode.  This value
// was chosen to give a reasonable range of values.
#define DWARF2_LINE_BASE		-5

// Range of line offsets in a special line info. opcode.
# define DWARF2_LINE_RANGE		14

// Define the architecture-dependent minimum instruction length (in bytes).
// This value should be rather too small than too big.
# define DWARF2_LINE_MIN_INSN_LENGTH	1

// Note: when DWARF2_LINE_MIN_INSN_LENGTH == 1 which is the current setting,
// this routine is a nop and will be optimized away.
static inline uint64_t ScaleAddrDelta(uint64_t AddrDelta)
{
  if (DWARF2_LINE_MIN_INSN_LENGTH == 1)
    return AddrDelta;
  if (AddrDelta % DWARF2_LINE_MIN_INSN_LENGTH != 0) {
    // TODO: report this error, but really only once.
    ;
  }
  return AddrDelta / DWARF2_LINE_MIN_INSN_LENGTH;
}

//
// This is called when an instruction is assembled into the specified section
// and if there is information from the last .loc directive that has yet to have
// a line entry made for it is made.
//
void MCLineEntry::Make(MCStreamer *MCOS, const MCSection *Section) {
  if (!MCOS->getContext().getDwarfLocSeen())
    return;

  // Create a symbol at in the current section for use in the line entry.
  MCSymbol *LineSym = MCOS->getContext().CreateTempSymbol();
  // Set the value of the symbol to use for the MCLineEntry.
  MCOS->EmitLabel(LineSym);

  // Get the current .loc info saved in the context.
  const MCDwarfLoc &DwarfLoc = MCOS->getContext().getCurrentDwarfLoc();

  // Create a (local) line entry with the symbol and the current .loc info.
  MCLineEntry LineEntry(LineSym, DwarfLoc);

  // clear DwarfLocSeen saying the current .loc info is now used.
  MCOS->getContext().ClearDwarfLocSeen();

  // Get the MCLineSection for this section, if one does not exist for this
  // section create it.
  const DenseMap<const MCSection *, MCLineSection *> &MCLineSections =
    MCOS->getContext().getMCLineSections();
  MCLineSection *LineSection = MCLineSections.lookup(Section);
  if (!LineSection) {
    // Create a new MCLineSection.  This will be deleted after the dwarf line
    // table is created using it by iterating through the MCLineSections
    // DenseMap.
    LineSection = new MCLineSection;
    // Save a pointer to the new LineSection into the MCLineSections DenseMap.
    MCOS->getContext().addMCLineSection(Section, LineSection);
  }

  // Add the line entry to this section's entries.
  LineSection->addLineEntry(LineEntry);
}

//
// This helper routine returns an expression of End - Start + IntVal .
// 
static inline const MCExpr *MakeStartMinusEndExpr(const MCStreamer &MCOS,
                                                  const MCSymbol &Start,
                                                  const MCSymbol &End,
                                                  int IntVal) {
  MCSymbolRefExpr::VariantKind Variant = MCSymbolRefExpr::VK_None;
  const MCExpr *Res =
    MCSymbolRefExpr::Create(&End, Variant, MCOS.getContext());
  const MCExpr *RHS =
    MCSymbolRefExpr::Create(&Start, Variant, MCOS.getContext());
  const MCExpr *Res1 =
    MCBinaryExpr::Create(MCBinaryExpr::Sub, Res, RHS, MCOS.getContext());
  const MCExpr *Res2 =
    MCConstantExpr::Create(IntVal, MCOS.getContext());
  const MCExpr *Res3 =
    MCBinaryExpr::Create(MCBinaryExpr::Sub, Res1, Res2, MCOS.getContext());
  return Res3;
}

//
// This emits the Dwarf line table for the specified section from the entries
// in the LineSection.
//
static inline void EmitDwarfLineTable(MCStreamer *MCOS,
                                      const MCSection *Section,
                                      const MCLineSection *LineSection) {
  unsigned FileNum = 1;
  unsigned LastLine = 1;
  unsigned Column = 0;
  unsigned Flags = DWARF2_LINE_DEFAULT_IS_STMT ? DWARF2_FLAG_IS_STMT : 0;
  unsigned Isa = 0;
  MCSymbol *LastLabel = NULL;

  // Loop through each MCLineEntry and encode the dwarf line number table.
  for (MCLineSection::const_iterator
         it = LineSection->getMCLineEntries()->begin(),
         ie = LineSection->getMCLineEntries()->end(); it != ie; ++it) {

    if (FileNum != it->getFileNum()) {
      FileNum = it->getFileNum();
      MCOS->EmitIntValue(dwarf::DW_LNS_set_file, 1);
      MCOS->EmitULEB128IntValue(FileNum);
    }
    if (Column != it->getColumn()) {
      Column = it->getColumn();
      MCOS->EmitIntValue(dwarf::DW_LNS_set_column, 1);
      MCOS->EmitULEB128IntValue(Column);
    }
    if (Isa != it->getIsa()) {
      Isa = it->getIsa();
      MCOS->EmitIntValue(dwarf::DW_LNS_set_isa, 1);
      MCOS->EmitULEB128IntValue(Isa);
    }
    if ((it->getFlags() ^ Flags) & DWARF2_FLAG_IS_STMT) {
      Flags = it->getFlags();
      MCOS->EmitIntValue(dwarf::DW_LNS_negate_stmt, 1);
    }
    if (it->getFlags() & DWARF2_FLAG_BASIC_BLOCK)
      MCOS->EmitIntValue(dwarf::DW_LNS_set_basic_block, 1);
    if (it->getFlags() & DWARF2_FLAG_PROLOGUE_END)
      MCOS->EmitIntValue(dwarf::DW_LNS_set_prologue_end, 1);
    if (it->getFlags() & DWARF2_FLAG_EPILOGUE_BEGIN)
      MCOS->EmitIntValue(dwarf::DW_LNS_set_epilogue_begin, 1);

    int64_t LineDelta = static_cast<int64_t>(it->getLine()) - LastLine;
    MCSymbol *Label = it->getLabel();

    // At this point we want to emit/create the sequence to encode the delta in
    // line numbers and the increment of the address from the previous Label
    // and the current Label.
    MCOS->EmitDwarfAdvanceLineAddr(LineDelta, LastLabel, Label);

    LastLine = it->getLine();
    LastLabel = Label;
  }

  // Emit a DW_LNE_end_sequence for the end of the section.
  // Using the pointer Section create a temporary label at the end of the
  // section and use that and the LastLabel to compute the address delta
  // and use INT64_MAX as the line delta which is the signal that this is
  // actually a DW_LNE_end_sequence.

  // Switch to the section to be able to create a symbol at its end.
  MCOS->SwitchSection(Section);

  MCContext &context = MCOS->getContext();
  // Create a symbol at the end of the section.
  MCSymbol *SectionEnd = context.CreateTempSymbol();
  // Set the value of the symbol, as we are at the end of the section.
  MCOS->EmitLabel(SectionEnd);

  // Switch back the the dwarf line section.
  MCOS->SwitchSection(context.getTargetAsmInfo().getDwarfLineSection());

  MCOS->EmitDwarfAdvanceLineAddr(INT64_MAX, LastLabel, SectionEnd);
}

//
// This emits the Dwarf file and the line tables.
//
void MCDwarfFileTable::Emit(MCStreamer *MCOS) {
  MCContext &context = MCOS->getContext();
  // Switch to the section where the table will be emitted into.
  MCOS->SwitchSection(context.getTargetAsmInfo().getDwarfLineSection());

  // Create a symbol at the beginning of this section.
  MCSymbol *LineStartSym = context.CreateTempSymbol();
  // Set the value of the symbol, as we are at the start of the section.
  MCOS->EmitLabel(LineStartSym);

  // Create a symbol for the end of the section (to be set when we get there).
  MCSymbol *LineEndSym = context.CreateTempSymbol();

  // The first 4 bytes is the total length of the information for this
  // compilation unit (not including these 4 bytes for the length).
  MCOS->EmitAbsValue(MakeStartMinusEndExpr(*MCOS, *LineStartSym, *LineEndSym,4),
                     4);

  // Next 2 bytes is the Version, which is Dwarf 2.
  MCOS->EmitIntValue(2, 2);

  // Create a symbol for the end of the prologue (to be set when we get there).
  MCSymbol *ProEndSym = context.CreateTempSymbol(); // Lprologue_end

  // Length of the prologue, is the next 4 bytes.  Which is the start of the
  // section to the end of the prologue.  Not including the 4 bytes for the
  // total length, the 2 bytes for the version, and these 4 bytes for the
  // length of the prologue.
  MCOS->EmitAbsValue(MakeStartMinusEndExpr(*MCOS, *LineStartSym, *ProEndSym,
                                        (4 + 2 + 4)),
                  4, 0);

  // Parameters of the state machine, are next.
  MCOS->EmitIntValue(DWARF2_LINE_MIN_INSN_LENGTH, 1);
  MCOS->EmitIntValue(DWARF2_LINE_DEFAULT_IS_STMT, 1);
  MCOS->EmitIntValue(DWARF2_LINE_BASE, 1);
  MCOS->EmitIntValue(DWARF2_LINE_RANGE, 1);
  MCOS->EmitIntValue(DWARF2_LINE_OPCODE_BASE, 1);

  // Standard opcode lengths
  MCOS->EmitIntValue(0, 1); // length of DW_LNS_copy
  MCOS->EmitIntValue(1, 1); // length of DW_LNS_advance_pc
  MCOS->EmitIntValue(1, 1); // length of DW_LNS_advance_line
  MCOS->EmitIntValue(1, 1); // length of DW_LNS_set_file
  MCOS->EmitIntValue(1, 1); // length of DW_LNS_set_column
  MCOS->EmitIntValue(0, 1); // length of DW_LNS_negate_stmt
  MCOS->EmitIntValue(0, 1); // length of DW_LNS_set_basic_block
  MCOS->EmitIntValue(0, 1); // length of DW_LNS_const_add_pc
  MCOS->EmitIntValue(1, 1); // length of DW_LNS_fixed_advance_pc
  MCOS->EmitIntValue(0, 1); // length of DW_LNS_set_prologue_end
  MCOS->EmitIntValue(0, 1); // length of DW_LNS_set_epilogue_begin
  MCOS->EmitIntValue(1, 1); // DW_LNS_set_isa

  // Put out the directory and file tables.

  // First the directory table.
  const std::vector<StringRef> &MCDwarfDirs =
    context.getMCDwarfDirs();
  for (unsigned i = 0; i < MCDwarfDirs.size(); i++) {
    MCOS->EmitBytes(MCDwarfDirs[i], 0); // the DirectoryName
    MCOS->EmitBytes(StringRef("\0", 1), 0); // the null term. of the string
  }
  MCOS->EmitIntValue(0, 1); // Terminate the directory list

  // Second the file table.
  const std::vector<MCDwarfFile *> &MCDwarfFiles =
    MCOS->getContext().getMCDwarfFiles();
  for (unsigned i = 1; i < MCDwarfFiles.size(); i++) {
    MCOS->EmitBytes(MCDwarfFiles[i]->getName(), 0); // FileName
    MCOS->EmitBytes(StringRef("\0", 1), 0); // the null term. of the string
    // the Directory num
    MCOS->EmitULEB128IntValue(MCDwarfFiles[i]->getDirIndex());
    MCOS->EmitIntValue(0, 1); // last modification timestamp (always 0)
    MCOS->EmitIntValue(0, 1); // filesize (always 0)
  }
  MCOS->EmitIntValue(0, 1); // Terminate the file list

  // This is the end of the prologue, so set the value of the symbol at the
  // end of the prologue (that was used in a previous expression).
  MCOS->EmitLabel(ProEndSym);

  // Put out the line tables.
  const DenseMap<const MCSection *, MCLineSection *> &MCLineSections =
    MCOS->getContext().getMCLineSections();
  const std::vector<const MCSection *> &MCLineSectionOrder =
    MCOS->getContext().getMCLineSectionOrder();
  for (std::vector<const MCSection*>::const_iterator it =
	MCLineSectionOrder.begin(), ie = MCLineSectionOrder.end(); it != ie;
       ++it) {
    const MCSection *Sec = *it;
    const MCLineSection *Line = MCLineSections.lookup(Sec);
    EmitDwarfLineTable(MCOS, Sec, Line);

    // Now delete the MCLineSections that were created in MCLineEntry::Make()
    // and used to emit the line table.
    delete Line;
  }

  if (MCOS->getContext().getAsmInfo().getLinkerRequiresNonEmptyDwarfLines()
      && MCLineSectionOrder.begin() == MCLineSectionOrder.end()) {
    // The darwin9 linker has a bug (see PR8715). For for 32-bit architectures
    // it requires:  
    // total_length >= prologue_length + 10
    // We are 4 bytes short, since we have total_length = 51 and
    // prologue_length = 45

    // The regular end_sequence should be sufficient.
    MCDwarfLineAddr::Emit(MCOS, INT64_MAX, 0);
  }

  // This is the end of the section, so set the value of the symbol at the end
  // of this section (that was used in a previous expression).
  MCOS->EmitLabel(LineEndSym);
}

/// Utility function to write the encoding to an object writer.
void MCDwarfLineAddr::Write(MCObjectWriter *OW, int64_t LineDelta,
                            uint64_t AddrDelta) {
  SmallString<256> Tmp;
  raw_svector_ostream OS(Tmp);
  MCDwarfLineAddr::Encode(LineDelta, AddrDelta, OS);
  OW->WriteBytes(OS.str());
}

/// Utility function to emit the encoding to a streamer.
void MCDwarfLineAddr::Emit(MCStreamer *MCOS, int64_t LineDelta,
                           uint64_t AddrDelta) {
  SmallString<256> Tmp;
  raw_svector_ostream OS(Tmp);
  MCDwarfLineAddr::Encode(LineDelta, AddrDelta, OS);
  MCOS->EmitBytes(OS.str(), /*AddrSpace=*/0);
}

/// Utility function to encode a Dwarf pair of LineDelta and AddrDeltas.
void MCDwarfLineAddr::Encode(int64_t LineDelta, uint64_t AddrDelta,
                             raw_ostream &OS) {
  uint64_t Temp, Opcode;
  bool NeedCopy = false;

  // Scale the address delta by the minimum instruction length.
  AddrDelta = ScaleAddrDelta(AddrDelta);

  // A LineDelta of INT64_MAX is a signal that this is actually a
  // DW_LNE_end_sequence. We cannot use special opcodes here, since we want the 
  // end_sequence to emit the matrix entry.
  if (LineDelta == INT64_MAX) {
    if (AddrDelta == MAX_SPECIAL_ADDR_DELTA)
      OS << char(dwarf::DW_LNS_const_add_pc);
    else {
      OS << char(dwarf::DW_LNS_advance_pc);
      SmallString<32> Tmp;
      raw_svector_ostream OSE(Tmp);
      MCObjectWriter::EncodeULEB128(AddrDelta, OSE);
      OS << OSE.str();
    }
    OS << char(dwarf::DW_LNS_extended_op);
    OS << char(1);
    OS << char(dwarf::DW_LNE_end_sequence);
    return;
  }

  // Bias the line delta by the base.
  Temp = LineDelta - DWARF2_LINE_BASE;

  // If the line increment is out of range of a special opcode, we must encode
  // it with DW_LNS_advance_line.
  if (Temp >= DWARF2_LINE_RANGE) {
    OS << char(dwarf::DW_LNS_advance_line);
    SmallString<32> Tmp;
    raw_svector_ostream OSE(Tmp);
    MCObjectWriter::EncodeSLEB128(LineDelta, OSE);
    OS << OSE.str();

    LineDelta = 0;
    Temp = 0 - DWARF2_LINE_BASE;
    NeedCopy = true;
  }

  // Use DW_LNS_copy instead of a "line +0, addr +0" special opcode.
  if (LineDelta == 0 && AddrDelta == 0) {
    OS << char(dwarf::DW_LNS_copy);
    return;
  }

  // Bias the opcode by the special opcode base.
  Temp += DWARF2_LINE_OPCODE_BASE;

  // Avoid overflow when addr_delta is large.
  if (AddrDelta < 256 + MAX_SPECIAL_ADDR_DELTA) {
    // Try using a special opcode.
    Opcode = Temp + AddrDelta * DWARF2_LINE_RANGE;
    if (Opcode <= 255) {
      OS << char(Opcode);
      return;
    }

    // Try using DW_LNS_const_add_pc followed by special op.
    Opcode = Temp + (AddrDelta - MAX_SPECIAL_ADDR_DELTA) * DWARF2_LINE_RANGE;
    if (Opcode <= 255) {
      OS << char(dwarf::DW_LNS_const_add_pc);
      OS << char(Opcode);
      return;
    }
  }

  // Otherwise use DW_LNS_advance_pc.
  OS << char(dwarf::DW_LNS_advance_pc);
  SmallString<32> Tmp;
  raw_svector_ostream OSE(Tmp);
  MCObjectWriter::EncodeULEB128(AddrDelta, OSE);
  OS << OSE.str();

  if (NeedCopy)
    OS << char(dwarf::DW_LNS_copy);
  else
    OS << char(Temp);
}

void MCDwarfFile::print(raw_ostream &OS) const {
  OS << '"' << getName() << '"';
}

void MCDwarfFile::dump() const {
  print(dbgs());
}

static int getDataAlignmentFactor(MCStreamer &streamer) {
  MCContext &context = streamer.getContext();
  const TargetAsmInfo &asmInfo = context.getTargetAsmInfo();
  int size = asmInfo.getPointerSize();
  if (asmInfo.getStackGrowthDirection() == TargetFrameLowering::StackGrowsUp)
    return size;
 else
   return -size;
}

static void EmitCFIInstruction(MCStreamer &Streamer,
                               const MCCFIInstruction &Instr) {
  int dataAlignmentFactor = getDataAlignmentFactor(Streamer);

  switch (Instr.getOperation()) {
  case MCCFIInstruction::Move: {
    const MachineLocation &Dst = Instr.getDestination();
    const MachineLocation &Src = Instr.getSource();

    // If advancing cfa.
    if (Dst.isReg() && Dst.getReg() == MachineLocation::VirtualFP) {
      assert(!Src.isReg() && "Machine move not supported yet.");

      if (Src.getReg() == MachineLocation::VirtualFP) {
        Streamer.EmitIntValue(dwarf::DW_CFA_def_cfa_offset, 1);
      } else {
        Streamer.EmitIntValue(dwarf::DW_CFA_def_cfa, 1);
        Streamer.EmitULEB128IntValue(Src.getReg());
      }

      Streamer.EmitULEB128IntValue(-Src.getOffset(), 1);
      return;
    }

    if (Src.isReg() && Src.getReg() == MachineLocation::VirtualFP) {
      assert(Dst.isReg() && "Machine move not supported yet.");
      Streamer.EmitIntValue(dwarf::DW_CFA_def_cfa_register, 1);
      Streamer.EmitULEB128IntValue(Dst.getReg());
      return;
    }

    unsigned Reg = Src.getReg();
    int Offset = Dst.getOffset() / dataAlignmentFactor;

    if (Offset < 0) {
      Streamer.EmitIntValue(dwarf::DW_CFA_offset_extended_sf, 1);
      Streamer.EmitULEB128IntValue(Reg);
      Streamer.EmitSLEB128IntValue(Offset);
    } else if (Reg < 64) {
      Streamer.EmitIntValue(dwarf::DW_CFA_offset + Reg, 1);
      Streamer.EmitULEB128IntValue(Offset, 1);
    } else {
      Streamer.EmitIntValue(dwarf::DW_CFA_offset_extended, 1);
      Streamer.EmitULEB128IntValue(Reg, 1);
      Streamer.EmitULEB128IntValue(Offset, 1);
    }
    return;
  }
  case MCCFIInstruction::Remember:
    Streamer.EmitIntValue(dwarf::DW_CFA_remember_state, 1);
    return;
  case MCCFIInstruction::Restore:
    Streamer.EmitIntValue(dwarf::DW_CFA_restore_state, 1);
    return;
  }
  llvm_unreachable("Unhandled case in switch");
}

/// EmitFrameMoves - Emit frame instructions to describe the layout of the
/// frame.
static void EmitCFIInstructions(MCStreamer &streamer,
                                const std::vector<MCCFIInstruction> &Instrs,
                                MCSymbol *BaseLabel) {
  for (unsigned i = 0, N = Instrs.size(); i < N; ++i) {
    const MCCFIInstruction &Instr = Instrs[i];
    MCSymbol *Label = Instr.getLabel();
    // Throw out move if the label is invalid.
    if (Label && !Label->isDefined()) continue; // Not emitted, in dead code.

    // Advance row if new location.
    if (BaseLabel && Label) {
      MCSymbol *ThisSym = Label;
      if (ThisSym != BaseLabel) {
        streamer.EmitDwarfAdvanceFrameAddr(BaseLabel, ThisSym);
        BaseLabel = ThisSym;
      }
    }

    EmitCFIInstruction(streamer, Instr);
  }
}

static void EmitSymbol(MCStreamer &streamer, const MCSymbol &symbol,
                       unsigned symbolEncoding) {
  MCContext &context = streamer.getContext();
  const TargetAsmInfo &asmInfo = context.getTargetAsmInfo();
  unsigned format = symbolEncoding & 0x0f;
  unsigned application = symbolEncoding & 0x70;
  unsigned size;
  switch (format) {
  default:
    assert(0 && "Unknown Encoding");
  case dwarf::DW_EH_PE_absptr:
  case dwarf::DW_EH_PE_signed:
    size = asmInfo.getPointerSize();
    break;
  case dwarf::DW_EH_PE_udata2:
  case dwarf::DW_EH_PE_sdata2:
    size = 2;
    break;
  case dwarf::DW_EH_PE_udata4:
  case dwarf::DW_EH_PE_sdata4:
    size = 4;
    break;
  case dwarf::DW_EH_PE_udata8:
  case dwarf::DW_EH_PE_sdata8:
    size = 8;
    break;
  }
  switch (application) {
  default:
    assert(0 && "Unknown Encoding");
    break;
  case 0:
    streamer.EmitSymbolValue(&symbol, size);
    break;
  case dwarf::DW_EH_PE_pcrel:
    streamer.EmitPCRelSymbolValue(&symbol, size);
    break;
  }
}

static const MachineLocation TranslateMachineLocation(
                                                  const TargetAsmInfo &AsmInfo,
                                                  const MachineLocation &Loc) {
  unsigned Reg = Loc.getReg() == MachineLocation::VirtualFP ?
    MachineLocation::VirtualFP :
    unsigned(AsmInfo.getDwarfRegNum(Loc.getReg(), true));
  const MachineLocation &NewLoc = Loc.isReg() ?
    MachineLocation(Reg) : MachineLocation(Reg, Loc.getOffset());
  return NewLoc;
}

static const MCSymbol &EmitCIE(MCStreamer &streamer,
                               const MCSymbol *personality,
                               unsigned personalityEncoding,
                               const MCSymbol *lsda,
                               unsigned lsdaEncoding) {
  MCContext &context = streamer.getContext();
  const TargetAsmInfo &asmInfo = context.getTargetAsmInfo();
  const MCSection &section = *asmInfo.getEHFrameSection();
  streamer.SwitchSection(&section);
  MCSymbol *sectionStart = streamer.getContext().CreateTempSymbol();
  MCSymbol *sectionEnd = streamer.getContext().CreateTempSymbol();

  // Length
  const MCExpr *Length = MakeStartMinusEndExpr(streamer, *sectionStart,
                                               *sectionEnd, 4);
  streamer.EmitLabel(sectionStart);
  streamer.EmitValue(Length, 4);

  // CIE ID
  streamer.EmitIntValue(0, 4);

  // Version
  streamer.EmitIntValue(dwarf::DW_CIE_VERSION, 1);

  // Augmentation String
  SmallString<8> Augmentation;
  Augmentation += "z";
  if (personality)
    Augmentation += "P";
  if (lsda)
    Augmentation += "L";
  Augmentation += "R";
  streamer.EmitBytes(Augmentation.str(), 0);
  streamer.EmitIntValue(0, 1);

  // Code Alignment Factor
  streamer.EmitULEB128IntValue(1);

  // Data Alignment Factor
  streamer.EmitSLEB128IntValue(getDataAlignmentFactor(streamer));

  // Return Address Register
  streamer.EmitULEB128IntValue(asmInfo.getDwarfRARegNum(true));

  // Augmentation Data Length (optional)
  MCSymbol *augmentationStart = streamer.getContext().CreateTempSymbol();
  MCSymbol *augmentationEnd = streamer.getContext().CreateTempSymbol();
  const MCExpr *augmentationLength = MakeStartMinusEndExpr(streamer,
                                                           *augmentationStart,
                                                           *augmentationEnd, 0);
  streamer.EmitULEB128Value(augmentationLength);

  // Augmentation Data (optional)
  streamer.EmitLabel(augmentationStart);
  if (personality) {
    // Personality Encoding
    streamer.EmitIntValue(personalityEncoding, 1);
    // Personality
    EmitSymbol(streamer, *personality, personalityEncoding);
  }
  if (lsda) {
    // LSDA Encoding
    streamer.EmitIntValue(lsdaEncoding, 1);
  }
  // Encoding of the FDE pointers
  streamer.EmitIntValue(dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4, 1);
  streamer.EmitLabel(augmentationEnd);

  // Initial Instructions

  const std::vector<MachineMove> Moves = asmInfo.getInitialFrameState();
  std::vector<MCCFIInstruction> Instructions;

  for (int i = 0, n = Moves.size(); i != n; ++i) {
    MCSymbol *Label = Moves[i].getLabel();
    const MachineLocation &Dst =
      TranslateMachineLocation(asmInfo, Moves[i].getDestination());
    const MachineLocation &Src =
      TranslateMachineLocation(asmInfo, Moves[i].getSource());
    MCCFIInstruction Inst(Label, Dst, Src);
    Instructions.push_back(Inst);
  }

  EmitCFIInstructions(streamer, Instructions, NULL);

  // Padding
  streamer.EmitValueToAlignment(4);

  streamer.EmitLabel(sectionEnd);
  return *sectionStart;
}

static MCSymbol *EmitFDE(MCStreamer &streamer,
                         const MCSymbol &cieStart,
                         const MCDwarfFrameInfo &frame) {
  MCContext &context = streamer.getContext();
  MCSymbol *fdeStart = context.CreateTempSymbol();
  MCSymbol *fdeEnd = context.CreateTempSymbol();

  // Length
  const MCExpr *Length = MakeStartMinusEndExpr(streamer, *fdeStart, *fdeEnd, 0);
  streamer.EmitValue(Length, 4);

  streamer.EmitLabel(fdeStart);
  // CIE Pointer
  const MCExpr *offset = MakeStartMinusEndExpr(streamer, cieStart, *fdeStart,
                                               0);
  streamer.EmitValue(offset, 4);

  // PC Begin
  streamer.EmitPCRelSymbolValue(frame.Begin, 4);

  // PC Range
  const MCExpr *Range = MakeStartMinusEndExpr(streamer, *frame.Begin,
                                              *frame.End, 0);
  streamer.EmitValue(Range, 4);

  // Augmentation Data Length
  MCSymbol *augmentationStart = streamer.getContext().CreateTempSymbol();
  MCSymbol *augmentationEnd = streamer.getContext().CreateTempSymbol();
  const MCExpr *augmentationLength = MakeStartMinusEndExpr(streamer,
                                                           *augmentationStart,
                                                           *augmentationEnd, 0);
  streamer.EmitULEB128Value(augmentationLength);

  // Augmentation Data
  streamer.EmitLabel(augmentationStart);
  if (frame.Lsda)
    EmitSymbol(streamer, *frame.Lsda, frame.LsdaEncoding);
  streamer.EmitLabel(augmentationEnd);
  // Call Frame Instructions

  EmitCFIInstructions(streamer, frame.Instructions, frame.Begin);

  // Padding
  streamer.EmitValueToAlignment(4);

  return fdeEnd;
}

namespace {
  struct CIEKey {
    static const CIEKey getEmptyKey() { return CIEKey(0, 0, -1); }
    static const CIEKey getTombstoneKey() { return CIEKey(0, -1, 0); }

    CIEKey(const MCSymbol* Personality_, unsigned PersonalityEncoding_,
           unsigned LsdaEncoding_) : Personality(Personality_),
                                     PersonalityEncoding(PersonalityEncoding_),
                                     LsdaEncoding(LsdaEncoding_) {
    }
    const MCSymbol* Personality;
    unsigned PersonalityEncoding;
    unsigned LsdaEncoding;
  };
}

namespace llvm {
  template <>
  struct DenseMapInfo<CIEKey> {
    static CIEKey getEmptyKey() {
      return CIEKey::getEmptyKey();
    }
    static CIEKey getTombstoneKey() {
      return CIEKey::getTombstoneKey();
    }
    static unsigned getHashValue(const CIEKey &Key) {
      FoldingSetNodeID ID;
      ID.AddPointer(Key.Personality);
      ID.AddInteger(Key.PersonalityEncoding);
      ID.AddInteger(Key.LsdaEncoding);
      return ID.ComputeHash();
    }
    static bool isEqual(const CIEKey &LHS,
                        const CIEKey &RHS) {
      return LHS.Personality == RHS.Personality &&
        LHS.PersonalityEncoding == RHS.PersonalityEncoding &&
        LHS.LsdaEncoding == RHS.LsdaEncoding;
    }
  };
}

void MCDwarfFrameEmitter::Emit(MCStreamer &streamer) {
  const MCContext &context = streamer.getContext();
  const TargetAsmInfo &asmInfo = context.getTargetAsmInfo();
  MCSymbol *fdeEnd = NULL;
  DenseMap<CIEKey, const MCSymbol*> CIEStarts;

  for (unsigned i = 0, n = streamer.getNumFrameInfos(); i < n; ++i) {
    const MCDwarfFrameInfo &frame = streamer.getFrameInfo(i);
    CIEKey key(frame.Personality, frame.PersonalityEncoding,
               frame.LsdaEncoding);
    const MCSymbol *&cieStart = CIEStarts[key];
    if (!cieStart)
      cieStart = &EmitCIE(streamer, frame.Personality,
                          frame.PersonalityEncoding, frame.Lsda,
                          frame.LsdaEncoding);
    fdeEnd = EmitFDE(streamer, *cieStart, frame);
    if (i != n - 1)
      streamer.EmitLabel(fdeEnd);
  }

  streamer.EmitValueToAlignment(asmInfo.getPointerSize());
  if (fdeEnd)
    streamer.EmitLabel(fdeEnd);
}

void MCDwarfFrameEmitter::EmitAdvanceLoc(MCStreamer &Streamer,
                                         uint64_t AddrDelta) {
  SmallString<256> Tmp;
  raw_svector_ostream OS(Tmp);
  MCDwarfFrameEmitter::EncodeAdvanceLoc(AddrDelta, OS);
  Streamer.EmitBytes(OS.str(), /*AddrSpace=*/0);
}

void MCDwarfFrameEmitter::EncodeAdvanceLoc(uint64_t AddrDelta,
                                           raw_ostream &OS) {
  // FIXME: Assumes the code alignment factor is 1.
  if (AddrDelta == 0) {
  } else if (isUIntN(6, AddrDelta)) {
    uint8_t Opcode = dwarf::DW_CFA_advance_loc | AddrDelta;
    OS << Opcode;
  } else if (isUInt<8>(AddrDelta)) {
    OS << uint8_t(dwarf::DW_CFA_advance_loc1);
    OS << uint8_t(AddrDelta);
  } else if (isUInt<16>(AddrDelta)) {
    // FIXME: check what is the correct behavior on a big endian machine.
    OS << uint8_t(dwarf::DW_CFA_advance_loc2);
    OS << uint8_t( AddrDelta       & 0xff);
    OS << uint8_t((AddrDelta >> 8) & 0xff);
  } else {
    // FIXME: check what is the correct behavior on a big endian machine.
    assert(isUInt<32>(AddrDelta));
    OS << uint8_t(dwarf::DW_CFA_advance_loc4);
    OS << uint8_t( AddrDelta        & 0xff);
    OS << uint8_t((AddrDelta >> 8)  & 0xff);
    OS << uint8_t((AddrDelta >> 16) & 0xff);
    OS << uint8_t((AddrDelta >> 24) & 0xff);

  }
}