MCDwarf.cpp revision 203576aa0cb9d8bf2d2e4d910ebab4b7a63262ae 
1//===- lib/MC/MCDwarf.cpp - MCDwarf implementation ------------------------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9
10#include "llvm/MC/MCDwarf.h"
11#include "llvm/MC/MCAsmInfo.h"
12#include "llvm/MC/MCContext.h"
13#include "llvm/MC/MCObjectFileInfo.h"
14#include "llvm/MC/MCObjectWriter.h"
15#include "llvm/MC/MCRegisterInfo.h"
16#include "llvm/MC/MCStreamer.h"
17#include "llvm/MC/MCSymbol.h"
18#include "llvm/MC/MCExpr.h"
19#include "llvm/Support/Debug.h"
20#include "llvm/Support/ErrorHandling.h"
21#include "llvm/Support/raw_ostream.h"
22#include "llvm/ADT/FoldingSet.h"
23#include "llvm/ADT/SmallString.h"
24#include "llvm/ADT/StringExtras.h"
25#include "llvm/ADT/Twine.h"
26using namespace llvm;
27
28// Given a special op, return the address skip amount (in units of
29// DWARF2_LINE_MIN_INSN_LENGTH.
30#define SPECIAL_ADDR(op) (((op) - DWARF2_LINE_OPCODE_BASE)/DWARF2_LINE_RANGE)
31
32// The maximum address skip amount that can be encoded with a special op.
33#define MAX_SPECIAL_ADDR_DELTA         SPECIAL_ADDR(255)
34
35// First special line opcode - leave room for the standard opcodes.
36// Note: If you want to change this, you'll have to update the
37// "standard_opcode_lengths" table that is emitted in DwarfFileTable::Emit().
38#define DWARF2_LINE_OPCODE_BASE         13
39
40// Minimum line offset in a special line info. opcode.  This value
41// was chosen to give a reasonable range of values.
42#define DWARF2_LINE_BASE                -5
43
44// Range of line offsets in a special line info. opcode.
45#define DWARF2_LINE_RANGE               14
46
47// Define the architecture-dependent minimum instruction length (in bytes).
48// This value should be rather too small than too big.
49#define DWARF2_LINE_MIN_INSN_LENGTH     1
50
51// Note: when DWARF2_LINE_MIN_INSN_LENGTH == 1 which is the current setting,
52// this routine is a nop and will be optimized away.
53static inline uint64_t ScaleAddrDelta(uint64_t AddrDelta) {
54  if (DWARF2_LINE_MIN_INSN_LENGTH == 1)
55    return AddrDelta;
56  if (AddrDelta % DWARF2_LINE_MIN_INSN_LENGTH != 0) {
57    // TODO: report this error, but really only once.
58    ;
59  }
60  return AddrDelta / DWARF2_LINE_MIN_INSN_LENGTH;
61}
62
63//
64// This is called when an instruction is assembled into the specified section
65// and if there is information from the last .loc directive that has yet to have
66// a line entry made for it is made.
67//
68void MCLineEntry::Make(MCStreamer *MCOS, const MCSection *Section) {
69  if (!MCOS->getContext().getDwarfLocSeen())
70    return;
71
72  // Create a symbol at in the current section for use in the line entry.
73  MCSymbol *LineSym = MCOS->getContext().CreateTempSymbol();
74  // Set the value of the symbol to use for the MCLineEntry.
75  MCOS->EmitLabel(LineSym);
76
77  // Get the current .loc info saved in the context.
78  const MCDwarfLoc &DwarfLoc = MCOS->getContext().getCurrentDwarfLoc();
79
80  // Create a (local) line entry with the symbol and the current .loc info.
81  MCLineEntry LineEntry(LineSym, DwarfLoc);
82
83  // clear DwarfLocSeen saying the current .loc info is now used.
84  MCOS->getContext().ClearDwarfLocSeen();
85
86  // Get the MCLineSection for this section, if one does not exist for this
87  // section create it.
88  const DenseMap<const MCSection *, MCLineSection *> &MCLineSections =
89    MCOS->getContext().getMCLineSections();
90  MCLineSection *LineSection = MCLineSections.lookup(Section);
91  if (!LineSection) {
92    // Create a new MCLineSection.  This will be deleted after the dwarf line
93    // table is created using it by iterating through the MCLineSections
94    // DenseMap.
95    LineSection = new MCLineSection;
96    // Save a pointer to the new LineSection into the MCLineSections DenseMap.
97    MCOS->getContext().addMCLineSection(Section, LineSection);
98  }
99
100  // Add the line entry to this section's entries.
101  LineSection->addLineEntry(LineEntry);
102}
103
104//
105// This helper routine returns an expression of End - Start + IntVal .
106//
107static inline const MCExpr *MakeStartMinusEndExpr(const MCStreamer &MCOS,
108                                                  const MCSymbol &Start,
109                                                  const MCSymbol &End,
110                                                  int IntVal) {
111  MCSymbolRefExpr::VariantKind Variant = MCSymbolRefExpr::VK_None;
112  const MCExpr *Res =
113    MCSymbolRefExpr::Create(&End, Variant, MCOS.getContext());
114  const MCExpr *RHS =
115    MCSymbolRefExpr::Create(&Start, Variant, MCOS.getContext());
116  const MCExpr *Res1 =
117    MCBinaryExpr::Create(MCBinaryExpr::Sub, Res, RHS, MCOS.getContext());
118  const MCExpr *Res2 =
119    MCConstantExpr::Create(IntVal, MCOS.getContext());
120  const MCExpr *Res3 =
121    MCBinaryExpr::Create(MCBinaryExpr::Sub, Res1, Res2, MCOS.getContext());
122  return Res3;
123}
124
125//
126// This emits the Dwarf line table for the specified section from the entries
127// in the LineSection.
128//
129static inline void EmitDwarfLineTable(MCStreamer *MCOS,
130                                      const MCSection *Section,
131                                      const MCLineSection *LineSection) {
132  unsigned FileNum = 1;
133  unsigned LastLine = 1;
134  unsigned Column = 0;
135  unsigned Flags = DWARF2_LINE_DEFAULT_IS_STMT ? DWARF2_FLAG_IS_STMT : 0;
136  unsigned Isa = 0;
137  MCSymbol *LastLabel = NULL;
138
139  // Loop through each MCLineEntry and encode the dwarf line number table.
140  for (MCLineSection::const_iterator
141         it = LineSection->getMCLineEntries()->begin(),
142         ie = LineSection->getMCLineEntries()->end(); it != ie; ++it) {
143
144    if (FileNum != it->getFileNum()) {
145      FileNum = it->getFileNum();
146      MCOS->EmitIntValue(dwarf::DW_LNS_set_file, 1);
147      MCOS->EmitULEB128IntValue(FileNum);
148    }
149    if (Column != it->getColumn()) {
150      Column = it->getColumn();
151      MCOS->EmitIntValue(dwarf::DW_LNS_set_column, 1);
152      MCOS->EmitULEB128IntValue(Column);
153    }
154    if (Isa != it->getIsa()) {
155      Isa = it->getIsa();
156      MCOS->EmitIntValue(dwarf::DW_LNS_set_isa, 1);
157      MCOS->EmitULEB128IntValue(Isa);
158    }
159    if ((it->getFlags() ^ Flags) & DWARF2_FLAG_IS_STMT) {
160      Flags = it->getFlags();
161      MCOS->EmitIntValue(dwarf::DW_LNS_negate_stmt, 1);
162    }
163    if (it->getFlags() & DWARF2_FLAG_BASIC_BLOCK)
164      MCOS->EmitIntValue(dwarf::DW_LNS_set_basic_block, 1);
165    if (it->getFlags() & DWARF2_FLAG_PROLOGUE_END)
166      MCOS->EmitIntValue(dwarf::DW_LNS_set_prologue_end, 1);
167    if (it->getFlags() & DWARF2_FLAG_EPILOGUE_BEGIN)
168      MCOS->EmitIntValue(dwarf::DW_LNS_set_epilogue_begin, 1);
169
170    int64_t LineDelta = static_cast<int64_t>(it->getLine()) - LastLine;
171    MCSymbol *Label = it->getLabel();
172
173    // At this point we want to emit/create the sequence to encode the delta in
174    // line numbers and the increment of the address from the previous Label
175    // and the current Label.
176    const MCAsmInfo &asmInfo = MCOS->getContext().getAsmInfo();
177    MCOS->EmitDwarfAdvanceLineAddr(LineDelta, LastLabel, Label,
178                                   asmInfo.getPointerSize());
179
180    LastLine = it->getLine();
181    LastLabel = Label;
182  }
183
184  // Emit a DW_LNE_end_sequence for the end of the section.
185  // Using the pointer Section create a temporary label at the end of the
186  // section and use that and the LastLabel to compute the address delta
187  // and use INT64_MAX as the line delta which is the signal that this is
188  // actually a DW_LNE_end_sequence.
189
190  // Switch to the section to be able to create a symbol at its end.
191  MCOS->SwitchSection(Section);
192
193  MCContext &context = MCOS->getContext();
194  // Create a symbol at the end of the section.
195  MCSymbol *SectionEnd = context.CreateTempSymbol();
196  // Set the value of the symbol, as we are at the end of the section.
197  MCOS->EmitLabel(SectionEnd);
198
199  // Switch back the the dwarf line section.
200  MCOS->SwitchSection(context.getObjectFileInfo()->getDwarfLineSection());
201
202  const MCAsmInfo &asmInfo = MCOS->getContext().getAsmInfo();
203  MCOS->EmitDwarfAdvanceLineAddr(INT64_MAX, LastLabel, SectionEnd,
204                                 asmInfo.getPointerSize());
205}
206
207//
208// This emits the Dwarf file and the line tables.
209//
210void MCDwarfFileTable::Emit(MCStreamer *MCOS) {
211  MCContext &context = MCOS->getContext();
212  // Switch to the section where the table will be emitted into.
213  MCOS->SwitchSection(context.getObjectFileInfo()->getDwarfLineSection());
214
215  // Create a symbol at the beginning of this section.
216  MCSymbol *LineStartSym = context.CreateTempSymbol();
217  // Set the value of the symbol, as we are at the start of the section.
218  MCOS->EmitLabel(LineStartSym);
219
220  // Create a symbol for the end of the section (to be set when we get there).
221  MCSymbol *LineEndSym = context.CreateTempSymbol();
222
223  // The first 4 bytes is the total length of the information for this
224  // compilation unit (not including these 4 bytes for the length).
225  MCOS->EmitAbsValue(MakeStartMinusEndExpr(*MCOS, *LineStartSym, *LineEndSym,4),
226                     4);
227
228  // Next 2 bytes is the Version, which is Dwarf 2.
229  MCOS->EmitIntValue(2, 2);
230
231  // Create a symbol for the end of the prologue (to be set when we get there).
232  MCSymbol *ProEndSym = context.CreateTempSymbol(); // Lprologue_end
233
234  // Length of the prologue, is the next 4 bytes.  Which is the start of the
235  // section to the end of the prologue.  Not including the 4 bytes for the
236  // total length, the 2 bytes for the version, and these 4 bytes for the
237  // length of the prologue.
238  MCOS->EmitAbsValue(MakeStartMinusEndExpr(*MCOS, *LineStartSym, *ProEndSym,
239                                        (4 + 2 + 4)),
240                  4, 0);
241
242  // Parameters of the state machine, are next.
243  MCOS->EmitIntValue(DWARF2_LINE_MIN_INSN_LENGTH, 1);
244  MCOS->EmitIntValue(DWARF2_LINE_DEFAULT_IS_STMT, 1);
245  MCOS->EmitIntValue(DWARF2_LINE_BASE, 1);
246  MCOS->EmitIntValue(DWARF2_LINE_RANGE, 1);
247  MCOS->EmitIntValue(DWARF2_LINE_OPCODE_BASE, 1);
248
249  // Standard opcode lengths
250  MCOS->EmitIntValue(0, 1); // length of DW_LNS_copy
251  MCOS->EmitIntValue(1, 1); // length of DW_LNS_advance_pc
252  MCOS->EmitIntValue(1, 1); // length of DW_LNS_advance_line
253  MCOS->EmitIntValue(1, 1); // length of DW_LNS_set_file
254  MCOS->EmitIntValue(1, 1); // length of DW_LNS_set_column
255  MCOS->EmitIntValue(0, 1); // length of DW_LNS_negate_stmt
256  MCOS->EmitIntValue(0, 1); // length of DW_LNS_set_basic_block
257  MCOS->EmitIntValue(0, 1); // length of DW_LNS_const_add_pc
258  MCOS->EmitIntValue(1, 1); // length of DW_LNS_fixed_advance_pc
259  MCOS->EmitIntValue(0, 1); // length of DW_LNS_set_prologue_end
260  MCOS->EmitIntValue(0, 1); // length of DW_LNS_set_epilogue_begin
261  MCOS->EmitIntValue(1, 1); // DW_LNS_set_isa
262
263  // Put out the directory and file tables.
264
265  // First the directory table.
266  const std::vector<StringRef> &MCDwarfDirs =
267    context.getMCDwarfDirs();
268  for (unsigned i = 0; i < MCDwarfDirs.size(); i++) {
269    MCOS->EmitBytes(MCDwarfDirs[i], 0); // the DirectoryName
270    MCOS->EmitBytes(StringRef("\0", 1), 0); // the null term. of the string
271  }
272  MCOS->EmitIntValue(0, 1); // Terminate the directory list
273
274  // Second the file table.
275  const std::vector<MCDwarfFile *> &MCDwarfFiles =
276    MCOS->getContext().getMCDwarfFiles();
277  for (unsigned i = 1; i < MCDwarfFiles.size(); i++) {
278    MCOS->EmitBytes(MCDwarfFiles[i]->getName(), 0); // FileName
279    MCOS->EmitBytes(StringRef("\0", 1), 0); // the null term. of the string
280    // the Directory num
281    MCOS->EmitULEB128IntValue(MCDwarfFiles[i]->getDirIndex());
282    MCOS->EmitIntValue(0, 1); // last modification timestamp (always 0)
283    MCOS->EmitIntValue(0, 1); // filesize (always 0)
284  }
285  MCOS->EmitIntValue(0, 1); // Terminate the file list
286
287  // This is the end of the prologue, so set the value of the symbol at the
288  // end of the prologue (that was used in a previous expression).
289  MCOS->EmitLabel(ProEndSym);
290
291  // Put out the line tables.
292  const DenseMap<const MCSection *, MCLineSection *> &MCLineSections =
293    MCOS->getContext().getMCLineSections();
294  const std::vector<const MCSection *> &MCLineSectionOrder =
295    MCOS->getContext().getMCLineSectionOrder();
296  for (std::vector<const MCSection*>::const_iterator it =
297         MCLineSectionOrder.begin(), ie = MCLineSectionOrder.end(); it != ie;
298       ++it) {
299    const MCSection *Sec = *it;
300    const MCLineSection *Line = MCLineSections.lookup(Sec);
301    EmitDwarfLineTable(MCOS, Sec, Line);
302
303    // Now delete the MCLineSections that were created in MCLineEntry::Make()
304    // and used to emit the line table.
305    delete Line;
306  }
307
308  if (MCOS->getContext().getAsmInfo().getLinkerRequiresNonEmptyDwarfLines()
309      && MCLineSectionOrder.begin() == MCLineSectionOrder.end()) {
310    // The darwin9 linker has a bug (see PR8715). For for 32-bit architectures
311    // it requires:
312    // total_length >= prologue_length + 10
313    // We are 4 bytes short, since we have total_length = 51 and
314    // prologue_length = 45
315
316    // The regular end_sequence should be sufficient.
317    MCDwarfLineAddr::Emit(MCOS, INT64_MAX, 0);
318  }
319
320  // This is the end of the section, so set the value of the symbol at the end
321  // of this section (that was used in a previous expression).
322  MCOS->EmitLabel(LineEndSym);
323}
324
325/// Utility function to write the encoding to an object writer.
326void MCDwarfLineAddr::Write(MCObjectWriter *OW, int64_t LineDelta,
327                            uint64_t AddrDelta) {
328  SmallString<256> Tmp;
329  raw_svector_ostream OS(Tmp);
330  MCDwarfLineAddr::Encode(LineDelta, AddrDelta, OS);
331  OW->WriteBytes(OS.str());
332}
333
334/// Utility function to emit the encoding to a streamer.
335void MCDwarfLineAddr::Emit(MCStreamer *MCOS, int64_t LineDelta,
336                           uint64_t AddrDelta) {
337  SmallString<256> Tmp;
338  raw_svector_ostream OS(Tmp);
339  MCDwarfLineAddr::Encode(LineDelta, AddrDelta, OS);
340  MCOS->EmitBytes(OS.str(), /*AddrSpace=*/0);
341}
342
343/// Utility function to encode a Dwarf pair of LineDelta and AddrDeltas.
344void MCDwarfLineAddr::Encode(int64_t LineDelta, uint64_t AddrDelta,
345                             raw_ostream &OS) {
346  uint64_t Temp, Opcode;
347  bool NeedCopy = false;
348
349  // Scale the address delta by the minimum instruction length.
350  AddrDelta = ScaleAddrDelta(AddrDelta);
351
352  // A LineDelta of INT64_MAX is a signal that this is actually a
353  // DW_LNE_end_sequence. We cannot use special opcodes here, since we want the
354  // end_sequence to emit the matrix entry.
355  if (LineDelta == INT64_MAX) {
356    if (AddrDelta == MAX_SPECIAL_ADDR_DELTA)
357      OS << char(dwarf::DW_LNS_const_add_pc);
358    else {
359      OS << char(dwarf::DW_LNS_advance_pc);
360      MCObjectWriter::EncodeULEB128(AddrDelta, OS);
361    }
362    OS << char(dwarf::DW_LNS_extended_op);
363    OS << char(1);
364    OS << char(dwarf::DW_LNE_end_sequence);
365    return;
366  }
367
368  // Bias the line delta by the base.
369  Temp = LineDelta - DWARF2_LINE_BASE;
370
371  // If the line increment is out of range of a special opcode, we must encode
372  // it with DW_LNS_advance_line.
373  if (Temp >= DWARF2_LINE_RANGE) {
374    OS << char(dwarf::DW_LNS_advance_line);
375    SmallString<32> Tmp;
376    raw_svector_ostream OSE(Tmp);
377    MCObjectWriter::EncodeSLEB128(LineDelta, OSE);
378    OS << OSE.str();
379
380    LineDelta = 0;
381    Temp = 0 - DWARF2_LINE_BASE;
382    NeedCopy = true;
383  }
384
385  // Use DW_LNS_copy instead of a "line +0, addr +0" special opcode.
386  if (LineDelta == 0 && AddrDelta == 0) {
387    OS << char(dwarf::DW_LNS_copy);
388    return;
389  }
390
391  // Bias the opcode by the special opcode base.
392  Temp += DWARF2_LINE_OPCODE_BASE;
393
394  // Avoid overflow when addr_delta is large.
395  if (AddrDelta < 256 + MAX_SPECIAL_ADDR_DELTA) {
396    // Try using a special opcode.
397    Opcode = Temp + AddrDelta * DWARF2_LINE_RANGE;
398    if (Opcode <= 255) {
399      OS << char(Opcode);
400      return;
401    }
402
403    // Try using DW_LNS_const_add_pc followed by special op.
404    Opcode = Temp + (AddrDelta - MAX_SPECIAL_ADDR_DELTA) * DWARF2_LINE_RANGE;
405    if (Opcode <= 255) {
406      OS << char(dwarf::DW_LNS_const_add_pc);
407      OS << char(Opcode);
408      return;
409    }
410  }
411
412  // Otherwise use DW_LNS_advance_pc.
413  OS << char(dwarf::DW_LNS_advance_pc);
414  SmallString<32> Tmp;
415  raw_svector_ostream OSE(Tmp);
416  MCObjectWriter::EncodeULEB128(AddrDelta, OSE);
417  OS << OSE.str();
418
419  if (NeedCopy)
420    OS << char(dwarf::DW_LNS_copy);
421  else
422    OS << char(Temp);
423}
424
425void MCDwarfFile::print(raw_ostream &OS) const {
426  OS << '"' << getName() << '"';
427}
428
429void MCDwarfFile::dump() const {
430  print(dbgs());
431}
432
433static int getDataAlignmentFactor(MCStreamer &streamer) {
434  MCContext &context = streamer.getContext();
435  const MCAsmInfo &asmInfo = context.getAsmInfo();
436  int size = asmInfo.getPointerSize();
437  if (asmInfo.isStackGrowthDirectionUp())
438    return size;
439  else
440    return -size;
441}
442
443static unsigned getSizeForEncoding(MCStreamer &streamer,
444                                   unsigned symbolEncoding) {
445  MCContext &context = streamer.getContext();
446  unsigned format = symbolEncoding & 0x0f;
447  switch (format) {
448  default:
449    assert(0 && "Unknown Encoding");
450  case dwarf::DW_EH_PE_absptr:
451  case dwarf::DW_EH_PE_signed:
452    return context.getAsmInfo().getPointerSize();
453  case dwarf::DW_EH_PE_udata2:
454  case dwarf::DW_EH_PE_sdata2:
455    return 2;
456  case dwarf::DW_EH_PE_udata4:
457  case dwarf::DW_EH_PE_sdata4:
458    return 4;
459  case dwarf::DW_EH_PE_udata8:
460  case dwarf::DW_EH_PE_sdata8:
461    return 8;
462  }
463}
464
465static void EmitSymbol(MCStreamer &streamer, const MCSymbol &symbol,
466                       unsigned symbolEncoding, const char *comment = 0) {
467  MCContext &context = streamer.getContext();
468  const MCAsmInfo &asmInfo = context.getAsmInfo();
469  const MCExpr *v = asmInfo.getExprForFDESymbol(&symbol,
470                                                symbolEncoding,
471                                                streamer);
472  unsigned size = getSizeForEncoding(streamer, symbolEncoding);
473  if (streamer.isVerboseAsm() && comment) streamer.AddComment(comment);
474  streamer.EmitAbsValue(v, size);
475}
476
477static void EmitPersonality(MCStreamer &streamer, const MCSymbol &symbol,
478                            unsigned symbolEncoding) {
479  MCContext &context = streamer.getContext();
480  const MCAsmInfo &asmInfo = context.getAsmInfo();
481  const MCExpr *v = asmInfo.getExprForPersonalitySymbol(&symbol,
482                                                        symbolEncoding,
483                                                        streamer);
484  unsigned size = getSizeForEncoding(streamer, symbolEncoding);
485  streamer.EmitValue(v, size);
486}
487
488static const MachineLocation TranslateMachineLocation(
489                                                  const MCRegisterInfo &MRI,
490                                                  const MachineLocation &Loc) {
491  unsigned Reg = Loc.getReg() == MachineLocation::VirtualFP ?
492    MachineLocation::VirtualFP :
493    unsigned(MRI.getDwarfRegNum(Loc.getReg(), true));
494  const MachineLocation &NewLoc = Loc.isReg() ?
495    MachineLocation(Reg) : MachineLocation(Reg, Loc.getOffset());
496  return NewLoc;
497}
498
499namespace {
500  class FrameEmitterImpl {
501    int CFAOffset;
502    int CIENum;
503    bool UsingCFI;
504    bool IsEH;
505    const MCSymbol *SectionStart;
506  public:
507    FrameEmitterImpl(bool usingCFI, bool isEH, const MCSymbol *sectionStart) :
508      CFAOffset(0), CIENum(0), UsingCFI(usingCFI), IsEH(isEH),
509      SectionStart(sectionStart) {
510    }
511
512    /// EmitCompactUnwind - Emit the unwind information in a compact way. If
513    /// we're successful, return 'true'. Otherwise, return 'false' and it will
514    /// emit the normal CIE and FDE.
515    bool EmitCompactUnwind(MCStreamer &streamer,
516                           const MCDwarfFrameInfo &frame);
517
518    const MCSymbol &EmitCIE(MCStreamer &streamer,
519                            const MCSymbol *personality,
520                            unsigned personalityEncoding,
521                            const MCSymbol *lsda,
522                            unsigned lsdaEncoding);
523    MCSymbol *EmitFDE(MCStreamer &streamer,
524                      const MCSymbol &cieStart,
525                      const MCDwarfFrameInfo &frame);
526    void EmitCFIInstructions(MCStreamer &streamer,
527                             const std::vector<MCCFIInstruction> &Instrs,
528                             MCSymbol *BaseLabel);
529    void EmitCFIInstruction(MCStreamer &Streamer,
530                            const MCCFIInstruction &Instr);
531  };
532
533} // end anonymous namespace
534
535static void EmitEncodingByte(MCStreamer &Streamer, unsigned Encoding,
536                             StringRef Prefix) {
537  if (Streamer.isVerboseAsm()) {
538    const char *EncStr = 0;
539    switch (Encoding) {
540    default: EncStr = "<unknown encoding>";
541    case dwarf::DW_EH_PE_absptr: EncStr = "absptr";
542    case dwarf::DW_EH_PE_omit:   EncStr = "omit";
543    case dwarf::DW_EH_PE_pcrel:  EncStr = "pcrel";
544    case dwarf::DW_EH_PE_udata4: EncStr = "udata4";
545    case dwarf::DW_EH_PE_udata8: EncStr = "udata8";
546    case dwarf::DW_EH_PE_sdata4: EncStr = "sdata4";
547    case dwarf::DW_EH_PE_sdata8: EncStr = "sdata8";
548    case dwarf::DW_EH_PE_pcrel |dwarf::DW_EH_PE_udata4: EncStr = "pcrel udata4";
549    case dwarf::DW_EH_PE_pcrel |dwarf::DW_EH_PE_sdata4: EncStr = "pcrel sdata4";
550    case dwarf::DW_EH_PE_pcrel |dwarf::DW_EH_PE_udata8: EncStr = "pcrel udata8";
551    case dwarf::DW_EH_PE_pcrel |dwarf::DW_EH_PE_sdata8: EncStr = "pcrel sdata8";
552    case dwarf::DW_EH_PE_indirect |dwarf::DW_EH_PE_pcrel|dwarf::DW_EH_PE_udata4:
553      EncStr = "indirect pcrel udata4";
554    case dwarf::DW_EH_PE_indirect |dwarf::DW_EH_PE_pcrel|dwarf::DW_EH_PE_sdata4:
555      EncStr = "indirect pcrel sdata4";
556    case dwarf::DW_EH_PE_indirect |dwarf::DW_EH_PE_pcrel|dwarf::DW_EH_PE_udata8:
557      EncStr = "indirect pcrel udata8";
558    case dwarf::DW_EH_PE_indirect |dwarf::DW_EH_PE_pcrel|dwarf::DW_EH_PE_sdata8:
559      EncStr = "indirect pcrel sdata8";
560    }
561
562    Streamer.AddComment(Twine(Prefix) + " = " + EncStr);
563  }
564
565  Streamer.EmitIntValue(Encoding, 1);
566}
567
568void FrameEmitterImpl::EmitCFIInstruction(MCStreamer &Streamer,
569                                          const MCCFIInstruction &Instr) {
570  int dataAlignmentFactor = getDataAlignmentFactor(Streamer);
571  bool VerboseAsm = Streamer.isVerboseAsm();
572
573  switch (Instr.getOperation()) {
574  case MCCFIInstruction::Move:
575  case MCCFIInstruction::RelMove: {
576    const MachineLocation &Dst = Instr.getDestination();
577    const MachineLocation &Src = Instr.getSource();
578    const bool IsRelative = Instr.getOperation() == MCCFIInstruction::RelMove;
579
580    // If advancing cfa.
581    if (Dst.isReg() && Dst.getReg() == MachineLocation::VirtualFP) {
582      if (Src.getReg() == MachineLocation::VirtualFP) {
583        if (VerboseAsm) Streamer.AddComment("DW_CFA_def_cfa_offset");
584        Streamer.EmitIntValue(dwarf::DW_CFA_def_cfa_offset, 1);
585      } else {
586        if (VerboseAsm) Streamer.AddComment("DW_CFA_def_cfa");
587        Streamer.EmitIntValue(dwarf::DW_CFA_def_cfa, 1);
588        if (VerboseAsm) Streamer.AddComment(Twine("Reg ") +
589                                            Twine(Src.getReg()));
590        Streamer.EmitULEB128IntValue(Src.getReg());
591      }
592
593      if (IsRelative)
594        CFAOffset += Src.getOffset();
595      else
596        CFAOffset = -Src.getOffset();
597
598      if (VerboseAsm) Streamer.AddComment(Twine("Offset " + Twine(CFAOffset)));
599      Streamer.EmitULEB128IntValue(CFAOffset);
600      return;
601    }
602
603    if (Src.isReg() && Src.getReg() == MachineLocation::VirtualFP) {
604      assert(Dst.isReg() && "Machine move not supported yet.");
605      if (VerboseAsm) Streamer.AddComment("DW_CFA_def_cfa_register");
606      Streamer.EmitIntValue(dwarf::DW_CFA_def_cfa_register, 1);
607      if (VerboseAsm) Streamer.AddComment(Twine("Reg ") + Twine(Dst.getReg()));
608      Streamer.EmitULEB128IntValue(Dst.getReg());
609      return;
610    }
611
612    unsigned Reg = Src.getReg();
613    int Offset = Dst.getOffset();
614    if (IsRelative)
615      Offset -= CFAOffset;
616    Offset = Offset / dataAlignmentFactor;
617
618    if (Offset < 0) {
619      if (VerboseAsm) Streamer.AddComment("DW_CFA_offset_extended_sf");
620      Streamer.EmitIntValue(dwarf::DW_CFA_offset_extended_sf, 1);
621      if (VerboseAsm) Streamer.AddComment(Twine("Reg ") + Twine(Reg));
622      Streamer.EmitULEB128IntValue(Reg);
623      if (VerboseAsm) Streamer.AddComment(Twine("Offset ") + Twine(Offset));
624      Streamer.EmitSLEB128IntValue(Offset);
625    } else if (Reg < 64) {
626      if (VerboseAsm) Streamer.AddComment(Twine("DW_CFA_offset + Reg(") +
627                                          Twine(Reg) + ")");
628      Streamer.EmitIntValue(dwarf::DW_CFA_offset + Reg, 1);
629      if (VerboseAsm) Streamer.AddComment(Twine("Offset ") + Twine(Offset));
630      Streamer.EmitULEB128IntValue(Offset);
631    } else {
632      if (VerboseAsm) Streamer.AddComment("DW_CFA_offset_extended");
633      Streamer.EmitIntValue(dwarf::DW_CFA_offset_extended, 1);
634      if (VerboseAsm) Streamer.AddComment(Twine("Reg ") + Twine(Reg));
635      Streamer.EmitULEB128IntValue(Reg);
636      if (VerboseAsm) Streamer.AddComment(Twine("Offset ") + Twine(Offset));
637      Streamer.EmitULEB128IntValue(Offset);
638    }
639    return;
640  }
641  case MCCFIInstruction::Remember:
642    if (VerboseAsm) Streamer.AddComment("DW_CFA_remember_state");
643    Streamer.EmitIntValue(dwarf::DW_CFA_remember_state, 1);
644    return;
645  case MCCFIInstruction::Restore:
646    if (VerboseAsm) Streamer.AddComment("DW_CFA_restore_state");
647    Streamer.EmitIntValue(dwarf::DW_CFA_restore_state, 1);
648    return;
649  case MCCFIInstruction::SameValue: {
650    unsigned Reg = Instr.getDestination().getReg();
651    if (VerboseAsm) Streamer.AddComment("DW_CFA_same_value");
652    Streamer.EmitIntValue(dwarf::DW_CFA_same_value, 1);
653    if (VerboseAsm) Streamer.AddComment(Twine("Reg ") + Twine(Reg));
654    Streamer.EmitULEB128IntValue(Reg);
655    return;
656  }
657  }
658  llvm_unreachable("Unhandled case in switch");
659}
660
661/// EmitFrameMoves - Emit frame instructions to describe the layout of the
662/// frame.
663void FrameEmitterImpl::EmitCFIInstructions(MCStreamer &streamer,
664                                    const std::vector<MCCFIInstruction> &Instrs,
665                                           MCSymbol *BaseLabel) {
666  for (unsigned i = 0, N = Instrs.size(); i < N; ++i) {
667    const MCCFIInstruction &Instr = Instrs[i];
668    MCSymbol *Label = Instr.getLabel();
669    // Throw out move if the label is invalid.
670    if (Label && !Label->isDefined()) continue; // Not emitted, in dead code.
671
672    // Advance row if new location.
673    if (BaseLabel && Label) {
674      MCSymbol *ThisSym = Label;
675      if (ThisSym != BaseLabel) {
676        if (streamer.isVerboseAsm()) streamer.AddComment("DW_CFA_advance_loc4");
677        streamer.EmitDwarfAdvanceFrameAddr(BaseLabel, ThisSym);
678        BaseLabel = ThisSym;
679      }
680    }
681
682    EmitCFIInstruction(streamer, Instr);
683  }
684}
685
686/// EmitCompactUnwind - Emit the unwind information in a compact way. If we're
687/// successful, return 'true'. Otherwise, return 'false' and it will emit the
688/// normal CIE and FDE.
689bool FrameEmitterImpl::EmitCompactUnwind(MCStreamer &Streamer,
690                                         const MCDwarfFrameInfo &Frame) {
691  MCContext &Context = Streamer.getContext();
692  const MCObjectFileInfo *MOFI = Context.getObjectFileInfo();
693  bool VerboseAsm = Streamer.isVerboseAsm();
694
695  // range-start range-length  compact-unwind-enc personality-func   lsda
696  //  _foo       LfooEnd-_foo  0x00000023          0                 0
697  //  _bar       LbarEnd-_bar  0x00000025         __gxx_personality  except_tab1
698  //
699  //   .section __LD,__compact_unwind,regular,debug
700  //
701  //   # compact unwind for _foo
702  //   .quad _foo
703  //   .set L1,LfooEnd-_foo
704  //   .long L1
705  //   .long 0x01010001
706  //   .quad 0
707  //   .quad 0
708  //
709  //   # compact unwind for _bar
710  //   .quad _bar
711  //   .set L2,LbarEnd-_bar
712  //   .long L2
713  //   .long 0x01020011
714  //   .quad __gxx_personality
715  //   .quad except_tab1
716
717  uint32_t Encoding = Frame.CompactUnwindEncoding;
718  if (!Encoding) return false;
719
720  // The encoding needs to know we have an LSDA.
721  if (Frame.Lsda)
722    Encoding |= 0x40000000;
723
724  Streamer.SwitchSection(MOFI->getCompactUnwindSection());
725
726  // Range Start
727  unsigned FDEEncoding = MOFI->getFDEEncoding(UsingCFI);
728  unsigned Size = getSizeForEncoding(Streamer, FDEEncoding);
729  if (VerboseAsm) Streamer.AddComment("Range Start");
730  Streamer.EmitSymbolValue(Frame.Function, Size);
731
732  // Range Length
733  const MCExpr *Range = MakeStartMinusEndExpr(Streamer, *Frame.Begin,
734                                              *Frame.End, 0);
735  if (VerboseAsm) Streamer.AddComment("Range Length");
736  Streamer.EmitAbsValue(Range, 4);
737
738  // Compact Encoding
739  Size = getSizeForEncoding(Streamer, dwarf::DW_EH_PE_udata4);
740  if (VerboseAsm) Streamer.AddComment(Twine("Compact Unwind Encoding: 0x") +
741                                      Twine(llvm::utohexstr(Encoding)));
742  Streamer.EmitIntValue(Encoding, Size);
743
744
745  // Personality Function
746  Size = getSizeForEncoding(Streamer, dwarf::DW_EH_PE_absptr);
747  if (VerboseAsm) Streamer.AddComment("Personality Function");
748  if (Frame.Personality)
749    Streamer.EmitSymbolValue(Frame.Personality, Size);
750  else
751    Streamer.EmitIntValue(0, Size); // No personality fn
752
753  // LSDA
754  Size = getSizeForEncoding(Streamer, Frame.LsdaEncoding);
755  if (VerboseAsm) Streamer.AddComment("LSDA");
756  if (Frame.Lsda)
757    Streamer.EmitSymbolValue(Frame.Lsda, Size);
758  else
759    Streamer.EmitIntValue(0, Size); // No LSDA
760
761  return true;
762}
763
764const MCSymbol &FrameEmitterImpl::EmitCIE(MCStreamer &streamer,
765                                          const MCSymbol *personality,
766                                          unsigned personalityEncoding,
767                                          const MCSymbol *lsda,
768                                          unsigned lsdaEncoding) {
769  MCContext &context = streamer.getContext();
770  const MCRegisterInfo &MRI = context.getRegisterInfo();
771  const MCObjectFileInfo *MOFI = context.getObjectFileInfo();
772  bool verboseAsm = streamer.isVerboseAsm();
773
774  MCSymbol *sectionStart;
775  if (MOFI->isFunctionEHFrameSymbolPrivate() || !IsEH)
776    sectionStart = context.CreateTempSymbol();
777  else
778    sectionStart = context.GetOrCreateSymbol(Twine("EH_frame") + Twine(CIENum));
779
780  streamer.EmitLabel(sectionStart);
781  CIENum++;
782
783  MCSymbol *sectionEnd = context.CreateTempSymbol();
784
785  // Length
786  const MCExpr *Length = MakeStartMinusEndExpr(streamer, *sectionStart,
787                                               *sectionEnd, 4);
788  if (verboseAsm) streamer.AddComment("CIE Length");
789  streamer.EmitAbsValue(Length, 4);
790
791  // CIE ID
792  unsigned CIE_ID = IsEH ? 0 : -1;
793  if (verboseAsm) streamer.AddComment("CIE ID Tag");
794  streamer.EmitIntValue(CIE_ID, 4);
795
796  // Version
797  if (verboseAsm) streamer.AddComment("DW_CIE_VERSION");
798  streamer.EmitIntValue(dwarf::DW_CIE_VERSION, 1);
799
800  // Augmentation String
801  SmallString<8> Augmentation;
802  if (IsEH) {
803    if (verboseAsm) streamer.AddComment("CIE Augmentation");
804    Augmentation += "z";
805    if (personality)
806      Augmentation += "P";
807    if (lsda)
808      Augmentation += "L";
809    Augmentation += "R";
810    streamer.EmitBytes(Augmentation.str(), 0);
811  }
812  streamer.EmitIntValue(0, 1);
813
814  // Code Alignment Factor
815  if (verboseAsm) streamer.AddComment("CIE Code Alignment Factor");
816  streamer.EmitULEB128IntValue(1);
817
818  // Data Alignment Factor
819  if (verboseAsm) streamer.AddComment("CIE Data Alignment Factor");
820  streamer.EmitSLEB128IntValue(getDataAlignmentFactor(streamer));
821
822  // Return Address Register
823  if (verboseAsm) streamer.AddComment("CIE Return Address Column");
824  streamer.EmitULEB128IntValue(MRI.getDwarfRegNum(MRI.getRARegister(), true));
825
826  // Augmentation Data Length (optional)
827
828  unsigned augmentationLength = 0;
829  if (IsEH) {
830    if (personality) {
831      // Personality Encoding
832      augmentationLength += 1;
833      // Personality
834      augmentationLength += getSizeForEncoding(streamer, personalityEncoding);
835    }
836    if (lsda)
837      augmentationLength += 1;
838    // Encoding of the FDE pointers
839    augmentationLength += 1;
840
841    if (verboseAsm) streamer.AddComment("Augmentation Size");
842    streamer.EmitULEB128IntValue(augmentationLength);
843
844    // Augmentation Data (optional)
845    if (personality) {
846      // Personality Encoding
847      EmitEncodingByte(streamer, personalityEncoding,
848                       "Personality Encoding");
849      // Personality
850      if (verboseAsm) streamer.AddComment("Personality");
851      EmitPersonality(streamer, *personality, personalityEncoding);
852    }
853
854    if (lsda)
855      EmitEncodingByte(streamer, lsdaEncoding, "LSDA Encoding");
856
857    // Encoding of the FDE pointers
858    EmitEncodingByte(streamer, MOFI->getFDEEncoding(UsingCFI),
859                     "FDE Encoding");
860  }
861
862  // Initial Instructions
863
864  const MCAsmInfo &MAI = context.getAsmInfo();
865  const std::vector<MachineMove> &Moves = MAI.getInitialFrameState();
866  std::vector<MCCFIInstruction> Instructions;
867
868  for (int i = 0, n = Moves.size(); i != n; ++i) {
869    MCSymbol *Label = Moves[i].getLabel();
870    const MachineLocation &Dst =
871      TranslateMachineLocation(MRI, Moves[i].getDestination());
872    const MachineLocation &Src =
873      TranslateMachineLocation(MRI, Moves[i].getSource());
874    MCCFIInstruction Inst(Label, Dst, Src);
875    Instructions.push_back(Inst);
876  }
877
878  EmitCFIInstructions(streamer, Instructions, NULL);
879
880  // Padding
881  streamer.EmitValueToAlignment(IsEH
882                                ? 4 : context.getAsmInfo().getPointerSize());
883
884  streamer.EmitLabel(sectionEnd);
885  return *sectionStart;
886}
887
888MCSymbol *FrameEmitterImpl::EmitFDE(MCStreamer &streamer,
889                                    const MCSymbol &cieStart,
890                                    const MCDwarfFrameInfo &frame) {
891  MCContext &context = streamer.getContext();
892  MCSymbol *fdeStart = context.CreateTempSymbol();
893  MCSymbol *fdeEnd = context.CreateTempSymbol();
894  const MCObjectFileInfo *MOFI = context.getObjectFileInfo();
895  bool verboseAsm = streamer.isVerboseAsm();
896
897  if (!MOFI->isFunctionEHFrameSymbolPrivate() && IsEH) {
898    MCSymbol *EHSym =
899      context.GetOrCreateSymbol(frame.Function->getName() + Twine(".eh"));
900    streamer.EmitEHSymAttributes(frame.Function, EHSym);
901    streamer.EmitLabel(EHSym);
902  }
903
904  // Length
905  const MCExpr *Length = MakeStartMinusEndExpr(streamer, *fdeStart, *fdeEnd, 0);
906  if (verboseAsm) streamer.AddComment("FDE Length");
907  streamer.EmitAbsValue(Length, 4);
908
909  streamer.EmitLabel(fdeStart);
910
911  // CIE Pointer
912  const MCAsmInfo &asmInfo = context.getAsmInfo();
913  if (IsEH) {
914    const MCExpr *offset = MakeStartMinusEndExpr(streamer, cieStart, *fdeStart,
915                                                 0);
916    if (verboseAsm) streamer.AddComment("FDE CIE Offset");
917    streamer.EmitAbsValue(offset, 4);
918  } else if (!asmInfo.doesDwarfRequireRelocationForSectionOffset()) {
919    const MCExpr *offset = MakeStartMinusEndExpr(streamer, *SectionStart,
920                                                 cieStart, 0);
921    streamer.EmitAbsValue(offset, 4);
922  } else {
923    streamer.EmitSymbolValue(&cieStart, 4);
924  }
925
926  unsigned fdeEncoding = MOFI->getFDEEncoding(UsingCFI);
927  unsigned size = getSizeForEncoding(streamer, fdeEncoding);
928
929  // PC Begin
930  unsigned PCBeginEncoding = IsEH ? fdeEncoding :
931    (unsigned)dwarf::DW_EH_PE_absptr;
932  unsigned PCBeginSize = getSizeForEncoding(streamer, PCBeginEncoding);
933  EmitSymbol(streamer, *frame.Begin, PCBeginEncoding, "FDE initial location");
934
935  // PC Range
936  const MCExpr *Range = MakeStartMinusEndExpr(streamer, *frame.Begin,
937                                              *frame.End, 0);
938  if (verboseAsm) streamer.AddComment("FDE address range");
939  streamer.EmitAbsValue(Range, size);
940
941  if (IsEH) {
942    // Augmentation Data Length
943    unsigned augmentationLength = 0;
944
945    if (frame.Lsda)
946      augmentationLength += getSizeForEncoding(streamer, frame.LsdaEncoding);
947
948    if (verboseAsm) streamer.AddComment("Augmentation size");
949    streamer.EmitULEB128IntValue(augmentationLength);
950
951    // Augmentation Data
952    if (frame.Lsda)
953      EmitSymbol(streamer, *frame.Lsda, frame.LsdaEncoding,
954                 "Language Specific Data Area");
955  }
956
957  // Call Frame Instructions
958
959  EmitCFIInstructions(streamer, frame.Instructions, frame.Begin);
960
961  // Padding
962  streamer.EmitValueToAlignment(PCBeginSize);
963
964  return fdeEnd;
965}
966
967namespace {
968  struct CIEKey {
969    static const CIEKey getEmptyKey() { return CIEKey(0, 0, -1); }
970    static const CIEKey getTombstoneKey() { return CIEKey(0, -1, 0); }
971
972    CIEKey(const MCSymbol* Personality_, unsigned PersonalityEncoding_,
973           unsigned LsdaEncoding_) : Personality(Personality_),
974                                     PersonalityEncoding(PersonalityEncoding_),
975                                     LsdaEncoding(LsdaEncoding_) {
976    }
977    const MCSymbol* Personality;
978    unsigned PersonalityEncoding;
979    unsigned LsdaEncoding;
980  };
981}
982
983namespace llvm {
984  template <>
985  struct DenseMapInfo<CIEKey> {
986    static CIEKey getEmptyKey() {
987      return CIEKey::getEmptyKey();
988    }
989    static CIEKey getTombstoneKey() {
990      return CIEKey::getTombstoneKey();
991    }
992    static unsigned getHashValue(const CIEKey &Key) {
993      FoldingSetNodeID ID;
994      ID.AddPointer(Key.Personality);
995      ID.AddInteger(Key.PersonalityEncoding);
996      ID.AddInteger(Key.LsdaEncoding);
997      return ID.ComputeHash();
998    }
999    static bool isEqual(const CIEKey &LHS,
1000                        const CIEKey &RHS) {
1001      return LHS.Personality == RHS.Personality &&
1002        LHS.PersonalityEncoding == RHS.PersonalityEncoding &&
1003        LHS.LsdaEncoding == RHS.LsdaEncoding;
1004    }
1005  };
1006}
1007
1008void MCDwarfFrameEmitter::Emit(MCStreamer &Streamer,
1009                               bool UsingCFI,
1010                               bool IsEH) {
1011  MCContext &Context = Streamer.getContext();
1012  MCObjectFileInfo *MOFI =
1013    const_cast<MCObjectFileInfo*>(Context.getObjectFileInfo());
1014  const MCSection &Section = IsEH ? *MOFI->getEHFrameSection() :
1015                                    *MOFI->getDwarfFrameSection();
1016  Streamer.SwitchSection(&Section);
1017  MCSymbol *SectionStart = Context.CreateTempSymbol();
1018  Streamer.EmitLabel(SectionStart);
1019
1020  MCSymbol *FDEEnd = NULL;
1021  DenseMap<CIEKey, const MCSymbol*> CIEStarts;
1022  FrameEmitterImpl Emitter(UsingCFI, IsEH, SectionStart);
1023
1024  const MCSymbol *DummyDebugKey = NULL;
1025  for (unsigned i = 0, n = Streamer.getNumFrameInfos(); i < n; ++i) {
1026    const MCDwarfFrameInfo &Frame = Streamer.getFrameInfo(i);
1027    if (IsEH && MOFI->getCompactUnwindSection() &&
1028        Frame.CompactUnwindEncoding &&
1029        Emitter.EmitCompactUnwind(Streamer, Frame)) {
1030      FDEEnd = NULL;
1031      continue;
1032    }
1033
1034    CIEKey Key(Frame.Personality, Frame.PersonalityEncoding,
1035               Frame.LsdaEncoding);
1036    const MCSymbol *&CIEStart = IsEH ? CIEStarts[Key] : DummyDebugKey;
1037    if (!CIEStart)
1038      CIEStart = &Emitter.EmitCIE(Streamer, Frame.Personality,
1039                                  Frame.PersonalityEncoding, Frame.Lsda,
1040                                  Frame.LsdaEncoding);
1041
1042    FDEEnd = Emitter.EmitFDE(Streamer, *CIEStart, Frame);
1043
1044    if (i != n - 1)
1045      Streamer.EmitLabel(FDEEnd);
1046  }
1047
1048  Streamer.EmitValueToAlignment(Context.getAsmInfo().getPointerSize());
1049  if (FDEEnd)
1050    Streamer.EmitLabel(FDEEnd);
1051}
1052
1053void MCDwarfFrameEmitter::EmitAdvanceLoc(MCStreamer &Streamer,
1054                                         uint64_t AddrDelta) {
1055  SmallString<256> Tmp;
1056  raw_svector_ostream OS(Tmp);
1057  MCDwarfFrameEmitter::EncodeAdvanceLoc(AddrDelta, OS);
1058  Streamer.EmitBytes(OS.str(), /*AddrSpace=*/0);
1059}
1060
1061void MCDwarfFrameEmitter::EncodeAdvanceLoc(uint64_t AddrDelta,
1062                                           raw_ostream &OS) {
1063  // FIXME: Assumes the code alignment factor is 1.
1064  if (AddrDelta == 0) {
1065  } else if (isUIntN(6, AddrDelta)) {
1066    uint8_t Opcode = dwarf::DW_CFA_advance_loc | AddrDelta;
1067    OS << Opcode;
1068  } else if (isUInt<8>(AddrDelta)) {
1069    OS << uint8_t(dwarf::DW_CFA_advance_loc1);
1070    OS << uint8_t(AddrDelta);
1071  } else if (isUInt<16>(AddrDelta)) {
1072    // FIXME: check what is the correct behavior on a big endian machine.
1073    OS << uint8_t(dwarf::DW_CFA_advance_loc2);
1074    OS << uint8_t( AddrDelta       & 0xff);
1075    OS << uint8_t((AddrDelta >> 8) & 0xff);
1076  } else {
1077    // FIXME: check what is the correct behavior on a big endian machine.
1078    assert(isUInt<32>(AddrDelta));
1079    OS << uint8_t(dwarf::DW_CFA_advance_loc4);
1080    OS << uint8_t( AddrDelta        & 0xff);
1081    OS << uint8_t((AddrDelta >> 8)  & 0xff);
1082    OS << uint8_t((AddrDelta >> 16) & 0xff);
1083    OS << uint8_t((AddrDelta >> 24) & 0xff);
1084
1085  }
1086}
1087