1//===- lib/MC/MCDwarf.cpp - MCDwarf implementation ------------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8
9#include "llvm/MC/MCDwarf.h"
10#include "llvm/ADT/ArrayRef.h"
11#include "llvm/ADT/DenseMap.h"
12#include "llvm/ADT/Hashing.h"
13#include "llvm/ADT/STLExtras.h"
14#include "llvm/ADT/SmallString.h"
15#include "llvm/ADT/SmallVector.h"
16#include "llvm/ADT/StringRef.h"
17#include "llvm/ADT/Twine.h"
18#include "llvm/BinaryFormat/Dwarf.h"
19#include "llvm/Config/config.h"
20#include "llvm/MC/MCAsmInfo.h"
21#include "llvm/MC/MCContext.h"
22#include "llvm/MC/MCExpr.h"
23#include "llvm/MC/MCObjectFileInfo.h"
24#include "llvm/MC/MCObjectStreamer.h"
25#include "llvm/MC/MCRegisterInfo.h"
26#include "llvm/MC/MCSection.h"
27#include "llvm/MC/MCStreamer.h"
28#include "llvm/MC/MCSymbol.h"
29#include "llvm/Support/Casting.h"
30#include "llvm/Support/Endian.h"
31#include "llvm/Support/EndianStream.h"
32#include "llvm/Support/ErrorHandling.h"
33#include "llvm/Support/LEB128.h"
34#include "llvm/Support/MathExtras.h"
35#include "llvm/Support/Path.h"
36#include "llvm/Support/SourceMgr.h"
37#include "llvm/Support/raw_ostream.h"
38#include <cassert>
39#include <cstdint>
40#include <optional>
41#include <string>
42#include <utility>
43#include <vector>
44
45using namespace llvm;
46
47MCSymbol *mcdwarf::emitListsTableHeaderStart(MCStreamer &S) {
48  MCSymbol *Start = S.getContext().createTempSymbol("debug_list_header_start");
49  MCSymbol *End = S.getContext().createTempSymbol("debug_list_header_end");
50  auto DwarfFormat = S.getContext().getDwarfFormat();
51  if (DwarfFormat == dwarf::DWARF64) {
52    S.AddComment("DWARF64 mark");
53    S.emitInt32(dwarf::DW_LENGTH_DWARF64);
54  }
55  S.AddComment("Length");
56  S.emitAbsoluteSymbolDiff(End, Start,
57                           dwarf::getDwarfOffsetByteSize(DwarfFormat));
58  S.emitLabel(Start);
59  S.AddComment("Version");
60  S.emitInt16(S.getContext().getDwarfVersion());
61  S.AddComment("Address size");
62  S.emitInt8(S.getContext().getAsmInfo()->getCodePointerSize());
63  S.AddComment("Segment selector size");
64  S.emitInt8(0);
65  return End;
66}
67
68static inline uint64_t ScaleAddrDelta(MCContext &Context, uint64_t AddrDelta) {
69  unsigned MinInsnLength = Context.getAsmInfo()->getMinInstAlignment();
70  if (MinInsnLength == 1)
71    return AddrDelta;
72  if (AddrDelta % MinInsnLength != 0) {
73    // TODO: report this error, but really only once.
74    ;
75  }
76  return AddrDelta / MinInsnLength;
77}
78
79MCDwarfLineStr::MCDwarfLineStr(MCContext &Ctx) {
80  UseRelocs = Ctx.getAsmInfo()->doesDwarfUseRelocationsAcrossSections();
81  if (UseRelocs) {
82    MCSection *DwarfLineStrSection =
83        Ctx.getObjectFileInfo()->getDwarfLineStrSection();
84    assert(DwarfLineStrSection && "DwarfLineStrSection must not be NULL");
85    LineStrLabel = DwarfLineStrSection->getBeginSymbol();
86  }
87}
88
89//
90// This is called when an instruction is assembled into the specified section
91// and if there is information from the last .loc directive that has yet to have
92// a line entry made for it is made.
93//
94void MCDwarfLineEntry::make(MCStreamer *MCOS, MCSection *Section) {
95  if (!MCOS->getContext().getDwarfLocSeen())
96    return;
97
98  // Create a symbol at in the current section for use in the line entry.
99  MCSymbol *LineSym = MCOS->getContext().createTempSymbol();
100  // Set the value of the symbol to use for the MCDwarfLineEntry.
101  MCOS->emitLabel(LineSym);
102
103  // Get the current .loc info saved in the context.
104  const MCDwarfLoc &DwarfLoc = MCOS->getContext().getCurrentDwarfLoc();
105
106  // Create a (local) line entry with the symbol and the current .loc info.
107  MCDwarfLineEntry LineEntry(LineSym, DwarfLoc);
108
109  // clear DwarfLocSeen saying the current .loc info is now used.
110  MCOS->getContext().clearDwarfLocSeen();
111
112  // Add the line entry to this section's entries.
113  MCOS->getContext()
114      .getMCDwarfLineTable(MCOS->getContext().getDwarfCompileUnitID())
115      .getMCLineSections()
116      .addLineEntry(LineEntry, Section);
117}
118
119//
120// This helper routine returns an expression of End - Start - IntVal .
121//
122static inline const MCExpr *makeEndMinusStartExpr(MCContext &Ctx,
123                                                  const MCSymbol &Start,
124                                                  const MCSymbol &End,
125                                                  int IntVal) {
126  MCSymbolRefExpr::VariantKind Variant = MCSymbolRefExpr::VK_None;
127  const MCExpr *Res = MCSymbolRefExpr::create(&End, Variant, Ctx);
128  const MCExpr *RHS = MCSymbolRefExpr::create(&Start, Variant, Ctx);
129  const MCExpr *Res1 = MCBinaryExpr::create(MCBinaryExpr::Sub, Res, RHS, Ctx);
130  const MCExpr *Res2 = MCConstantExpr::create(IntVal, Ctx);
131  const MCExpr *Res3 = MCBinaryExpr::create(MCBinaryExpr::Sub, Res1, Res2, Ctx);
132  return Res3;
133}
134
135//
136// This helper routine returns an expression of Start + IntVal .
137//
138static inline const MCExpr *
139makeStartPlusIntExpr(MCContext &Ctx, const MCSymbol &Start, int IntVal) {
140  MCSymbolRefExpr::VariantKind Variant = MCSymbolRefExpr::VK_None;
141  const MCExpr *LHS = MCSymbolRefExpr::create(&Start, Variant, Ctx);
142  const MCExpr *RHS = MCConstantExpr::create(IntVal, Ctx);
143  const MCExpr *Res = MCBinaryExpr::create(MCBinaryExpr::Add, LHS, RHS, Ctx);
144  return Res;
145}
146
147void MCLineSection::addEndEntry(MCSymbol *EndLabel) {
148  auto *Sec = &EndLabel->getSection();
149  // The line table may be empty, which we should skip adding an end entry.
150  // There are two cases:
151  // (1) MCAsmStreamer - emitDwarfLocDirective emits a location directive in
152  //     place instead of adding a line entry if the target has
153  //     usesDwarfFileAndLocDirectives.
154  // (2) MCObjectStreamer - if a function has incomplete debug info where
155  //     instructions don't have DILocations, the line entries are missing.
156  auto I = MCLineDivisions.find(Sec);
157  if (I != MCLineDivisions.end()) {
158    auto &Entries = I->second;
159    auto EndEntry = Entries.back();
160    EndEntry.setEndLabel(EndLabel);
161    Entries.push_back(EndEntry);
162  }
163}
164
165//
166// This emits the Dwarf line table for the specified section from the entries
167// in the LineSection.
168//
169void MCDwarfLineTable::emitOne(
170    MCStreamer *MCOS, MCSection *Section,
171    const MCLineSection::MCDwarfLineEntryCollection &LineEntries) {
172
173  unsigned FileNum, LastLine, Column, Flags, Isa, Discriminator;
174  MCSymbol *LastLabel;
175  auto init = [&]() {
176    FileNum = 1;
177    LastLine = 1;
178    Column = 0;
179    Flags = DWARF2_LINE_DEFAULT_IS_STMT ? DWARF2_FLAG_IS_STMT : 0;
180    Isa = 0;
181    Discriminator = 0;
182    LastLabel = nullptr;
183  };
184  init();
185
186  // Loop through each MCDwarfLineEntry and encode the dwarf line number table.
187  bool EndEntryEmitted = false;
188  for (const MCDwarfLineEntry &LineEntry : LineEntries) {
189    MCSymbol *Label = LineEntry.getLabel();
190    const MCAsmInfo *asmInfo = MCOS->getContext().getAsmInfo();
191    if (LineEntry.IsEndEntry) {
192      MCOS->emitDwarfAdvanceLineAddr(INT64_MAX, LastLabel, Label,
193                                     asmInfo->getCodePointerSize());
194      init();
195      EndEntryEmitted = true;
196      continue;
197    }
198
199    int64_t LineDelta = static_cast<int64_t>(LineEntry.getLine()) - LastLine;
200
201    if (FileNum != LineEntry.getFileNum()) {
202      FileNum = LineEntry.getFileNum();
203      MCOS->emitInt8(dwarf::DW_LNS_set_file);
204      MCOS->emitULEB128IntValue(FileNum);
205    }
206    if (Column != LineEntry.getColumn()) {
207      Column = LineEntry.getColumn();
208      MCOS->emitInt8(dwarf::DW_LNS_set_column);
209      MCOS->emitULEB128IntValue(Column);
210    }
211    if (Discriminator != LineEntry.getDiscriminator() &&
212        MCOS->getContext().getDwarfVersion() >= 4) {
213      Discriminator = LineEntry.getDiscriminator();
214      unsigned Size = getULEB128Size(Discriminator);
215      MCOS->emitInt8(dwarf::DW_LNS_extended_op);
216      MCOS->emitULEB128IntValue(Size + 1);
217      MCOS->emitInt8(dwarf::DW_LNE_set_discriminator);
218      MCOS->emitULEB128IntValue(Discriminator);
219    }
220    if (Isa != LineEntry.getIsa()) {
221      Isa = LineEntry.getIsa();
222      MCOS->emitInt8(dwarf::DW_LNS_set_isa);
223      MCOS->emitULEB128IntValue(Isa);
224    }
225    if ((LineEntry.getFlags() ^ Flags) & DWARF2_FLAG_IS_STMT) {
226      Flags = LineEntry.getFlags();
227      MCOS->emitInt8(dwarf::DW_LNS_negate_stmt);
228    }
229    if (LineEntry.getFlags() & DWARF2_FLAG_BASIC_BLOCK)
230      MCOS->emitInt8(dwarf::DW_LNS_set_basic_block);
231    if (LineEntry.getFlags() & DWARF2_FLAG_PROLOGUE_END)
232      MCOS->emitInt8(dwarf::DW_LNS_set_prologue_end);
233    if (LineEntry.getFlags() & DWARF2_FLAG_EPILOGUE_BEGIN)
234      MCOS->emitInt8(dwarf::DW_LNS_set_epilogue_begin);
235
236    // At this point we want to emit/create the sequence to encode the delta in
237    // line numbers and the increment of the address from the previous Label
238    // and the current Label.
239    MCOS->emitDwarfAdvanceLineAddr(LineDelta, LastLabel, Label,
240                                   asmInfo->getCodePointerSize());
241
242    Discriminator = 0;
243    LastLine = LineEntry.getLine();
244    LastLabel = Label;
245  }
246
247  // Generate DWARF line end entry.
248  // We do not need this for DwarfDebug that explicitly terminates the line
249  // table using ranges whenever CU or section changes. However, the MC path
250  // does not track ranges nor terminate the line table. In that case,
251  // conservatively use the section end symbol to end the line table.
252  if (!EndEntryEmitted)
253    MCOS->emitDwarfLineEndEntry(Section, LastLabel);
254}
255
256//
257// This emits the Dwarf file and the line tables.
258//
259void MCDwarfLineTable::emit(MCStreamer *MCOS, MCDwarfLineTableParams Params) {
260  MCContext &context = MCOS->getContext();
261
262  auto &LineTables = context.getMCDwarfLineTables();
263
264  // Bail out early so we don't switch to the debug_line section needlessly and
265  // in doing so create an unnecessary (if empty) section.
266  if (LineTables.empty())
267    return;
268
269  // In a v5 non-split line table, put the strings in a separate section.
270  std::optional<MCDwarfLineStr> LineStr;
271  if (context.getDwarfVersion() >= 5)
272    LineStr.emplace(context);
273
274  // Switch to the section where the table will be emitted into.
275  MCOS->switchSection(context.getObjectFileInfo()->getDwarfLineSection());
276
277  // Handle the rest of the Compile Units.
278  for (const auto &CUIDTablePair : LineTables) {
279    CUIDTablePair.second.emitCU(MCOS, Params, LineStr);
280  }
281
282  if (LineStr)
283    LineStr->emitSection(MCOS);
284}
285
286void MCDwarfDwoLineTable::Emit(MCStreamer &MCOS, MCDwarfLineTableParams Params,
287                               MCSection *Section) const {
288  if (!HasSplitLineTable)
289    return;
290  std::optional<MCDwarfLineStr> NoLineStr(std::nullopt);
291  MCOS.switchSection(Section);
292  MCOS.emitLabel(Header.Emit(&MCOS, Params, std::nullopt, NoLineStr).second);
293}
294
295std::pair<MCSymbol *, MCSymbol *>
296MCDwarfLineTableHeader::Emit(MCStreamer *MCOS, MCDwarfLineTableParams Params,
297                             std::optional<MCDwarfLineStr> &LineStr) const {
298  static const char StandardOpcodeLengths[] = {
299      0, // length of DW_LNS_copy
300      1, // length of DW_LNS_advance_pc
301      1, // length of DW_LNS_advance_line
302      1, // length of DW_LNS_set_file
303      1, // length of DW_LNS_set_column
304      0, // length of DW_LNS_negate_stmt
305      0, // length of DW_LNS_set_basic_block
306      0, // length of DW_LNS_const_add_pc
307      1, // length of DW_LNS_fixed_advance_pc
308      0, // length of DW_LNS_set_prologue_end
309      0, // length of DW_LNS_set_epilogue_begin
310      1  // DW_LNS_set_isa
311  };
312  assert(std::size(StandardOpcodeLengths) >=
313         (Params.DWARF2LineOpcodeBase - 1U));
314  return Emit(MCOS, Params,
315              ArrayRef(StandardOpcodeLengths, Params.DWARF2LineOpcodeBase - 1),
316              LineStr);
317}
318
319static const MCExpr *forceExpAbs(MCStreamer &OS, const MCExpr* Expr) {
320  MCContext &Context = OS.getContext();
321  assert(!isa<MCSymbolRefExpr>(Expr));
322  if (Context.getAsmInfo()->hasAggressiveSymbolFolding())
323    return Expr;
324
325  MCSymbol *ABS = Context.createTempSymbol();
326  OS.emitAssignment(ABS, Expr);
327  return MCSymbolRefExpr::create(ABS, Context);
328}
329
330static void emitAbsValue(MCStreamer &OS, const MCExpr *Value, unsigned Size) {
331  const MCExpr *ABS = forceExpAbs(OS, Value);
332  OS.emitValue(ABS, Size);
333}
334
335void MCDwarfLineStr::emitSection(MCStreamer *MCOS) {
336  // Switch to the .debug_line_str section.
337  MCOS->switchSection(
338      MCOS->getContext().getObjectFileInfo()->getDwarfLineStrSection());
339  SmallString<0> Data = getFinalizedData();
340  MCOS->emitBinaryData(Data.str());
341}
342
343SmallString<0> MCDwarfLineStr::getFinalizedData() {
344  // Emit the strings without perturbing the offsets we used.
345  if (!LineStrings.isFinalized())
346    LineStrings.finalizeInOrder();
347  SmallString<0> Data;
348  Data.resize(LineStrings.getSize());
349  LineStrings.write((uint8_t *)Data.data());
350  return Data;
351}
352
353size_t MCDwarfLineStr::addString(StringRef Path) {
354  return LineStrings.add(Path);
355}
356
357void MCDwarfLineStr::emitRef(MCStreamer *MCOS, StringRef Path) {
358  int RefSize =
359      dwarf::getDwarfOffsetByteSize(MCOS->getContext().getDwarfFormat());
360  size_t Offset = addString(Path);
361  if (UseRelocs) {
362    MCContext &Ctx = MCOS->getContext();
363    MCOS->emitValue(makeStartPlusIntExpr(Ctx, *LineStrLabel, Offset), RefSize);
364  } else
365    MCOS->emitIntValue(Offset, RefSize);
366}
367
368void MCDwarfLineTableHeader::emitV2FileDirTables(MCStreamer *MCOS) const {
369  // First the directory table.
370  for (auto &Dir : MCDwarfDirs) {
371    MCOS->emitBytes(Dir);                // The DirectoryName, and...
372    MCOS->emitBytes(StringRef("\0", 1)); // its null terminator.
373  }
374  MCOS->emitInt8(0); // Terminate the directory list.
375
376  // Second the file table.
377  for (unsigned i = 1; i < MCDwarfFiles.size(); i++) {
378    assert(!MCDwarfFiles[i].Name.empty());
379    MCOS->emitBytes(MCDwarfFiles[i].Name); // FileName and...
380    MCOS->emitBytes(StringRef("\0", 1));   // its null terminator.
381    MCOS->emitULEB128IntValue(MCDwarfFiles[i].DirIndex); // Directory number.
382    MCOS->emitInt8(0); // Last modification timestamp (always 0).
383    MCOS->emitInt8(0); // File size (always 0).
384  }
385  MCOS->emitInt8(0); // Terminate the file list.
386}
387
388static void emitOneV5FileEntry(MCStreamer *MCOS, const MCDwarfFile &DwarfFile,
389                               bool EmitMD5, bool HasAnySource,
390                               std::optional<MCDwarfLineStr> &LineStr) {
391  assert(!DwarfFile.Name.empty());
392  if (LineStr)
393    LineStr->emitRef(MCOS, DwarfFile.Name);
394  else {
395    MCOS->emitBytes(DwarfFile.Name);     // FileName and...
396    MCOS->emitBytes(StringRef("\0", 1)); // its null terminator.
397  }
398  MCOS->emitULEB128IntValue(DwarfFile.DirIndex); // Directory number.
399  if (EmitMD5) {
400    const MD5::MD5Result &Cksum = *DwarfFile.Checksum;
401    MCOS->emitBinaryData(
402        StringRef(reinterpret_cast<const char *>(Cksum.data()), Cksum.size()));
403  }
404  if (HasAnySource) {
405    if (LineStr)
406      LineStr->emitRef(MCOS, DwarfFile.Source.value_or(StringRef()));
407    else {
408      MCOS->emitBytes(DwarfFile.Source.value_or(StringRef())); // Source and...
409      MCOS->emitBytes(StringRef("\0", 1)); // its null terminator.
410    }
411  }
412}
413
414void MCDwarfLineTableHeader::emitV5FileDirTables(
415    MCStreamer *MCOS, std::optional<MCDwarfLineStr> &LineStr) const {
416  // The directory format, which is just a list of the directory paths.  In a
417  // non-split object, these are references to .debug_line_str; in a split
418  // object, they are inline strings.
419  MCOS->emitInt8(1);
420  MCOS->emitULEB128IntValue(dwarf::DW_LNCT_path);
421  MCOS->emitULEB128IntValue(LineStr ? dwarf::DW_FORM_line_strp
422                                    : dwarf::DW_FORM_string);
423  MCOS->emitULEB128IntValue(MCDwarfDirs.size() + 1);
424  // Try not to emit an empty compilation directory.
425  SmallString<256> Dir;
426  StringRef CompDir = MCOS->getContext().getCompilationDir();
427  if (!CompilationDir.empty()) {
428    Dir = CompilationDir;
429    MCOS->getContext().remapDebugPath(Dir);
430    CompDir = Dir.str();
431    if (LineStr)
432      CompDir = LineStr->getSaver().save(CompDir);
433  }
434  if (LineStr) {
435    // Record path strings, emit references here.
436    LineStr->emitRef(MCOS, CompDir);
437    for (const auto &Dir : MCDwarfDirs)
438      LineStr->emitRef(MCOS, Dir);
439  } else {
440    // The list of directory paths.  Compilation directory comes first.
441    MCOS->emitBytes(CompDir);
442    MCOS->emitBytes(StringRef("\0", 1));
443    for (const auto &Dir : MCDwarfDirs) {
444      MCOS->emitBytes(Dir);                // The DirectoryName, and...
445      MCOS->emitBytes(StringRef("\0", 1)); // its null terminator.
446    }
447  }
448
449  // The file format, which is the inline null-terminated filename and a
450  // directory index.  We don't track file size/timestamp so don't emit them
451  // in the v5 table.  Emit MD5 checksums and source if we have them.
452  uint64_t Entries = 2;
453  if (HasAllMD5)
454    Entries += 1;
455  if (HasAnySource)
456    Entries += 1;
457  MCOS->emitInt8(Entries);
458  MCOS->emitULEB128IntValue(dwarf::DW_LNCT_path);
459  MCOS->emitULEB128IntValue(LineStr ? dwarf::DW_FORM_line_strp
460                                    : dwarf::DW_FORM_string);
461  MCOS->emitULEB128IntValue(dwarf::DW_LNCT_directory_index);
462  MCOS->emitULEB128IntValue(dwarf::DW_FORM_udata);
463  if (HasAllMD5) {
464    MCOS->emitULEB128IntValue(dwarf::DW_LNCT_MD5);
465    MCOS->emitULEB128IntValue(dwarf::DW_FORM_data16);
466  }
467  if (HasAnySource) {
468    MCOS->emitULEB128IntValue(dwarf::DW_LNCT_LLVM_source);
469    MCOS->emitULEB128IntValue(LineStr ? dwarf::DW_FORM_line_strp
470                                      : dwarf::DW_FORM_string);
471  }
472  // Then the counted list of files. The root file is file #0, then emit the
473  // files as provide by .file directives.
474  // MCDwarfFiles has an unused element [0] so use size() not size()+1.
475  // But sometimes MCDwarfFiles is empty, in which case we still emit one file.
476  MCOS->emitULEB128IntValue(MCDwarfFiles.empty() ? 1 : MCDwarfFiles.size());
477  // To accommodate assembler source written for DWARF v4 but trying to emit
478  // v5: If we didn't see a root file explicitly, replicate file #1.
479  assert((!RootFile.Name.empty() || MCDwarfFiles.size() >= 1) &&
480         "No root file and no .file directives");
481  emitOneV5FileEntry(MCOS, RootFile.Name.empty() ? MCDwarfFiles[1] : RootFile,
482                     HasAllMD5, HasAnySource, LineStr);
483  for (unsigned i = 1; i < MCDwarfFiles.size(); ++i)
484    emitOneV5FileEntry(MCOS, MCDwarfFiles[i], HasAllMD5, HasAnySource, LineStr);
485}
486
487std::pair<MCSymbol *, MCSymbol *>
488MCDwarfLineTableHeader::Emit(MCStreamer *MCOS, MCDwarfLineTableParams Params,
489                             ArrayRef<char> StandardOpcodeLengths,
490                             std::optional<MCDwarfLineStr> &LineStr) const {
491  MCContext &context = MCOS->getContext();
492
493  // Create a symbol at the beginning of the line table.
494  MCSymbol *LineStartSym = Label;
495  if (!LineStartSym)
496    LineStartSym = context.createTempSymbol();
497
498  // Set the value of the symbol, as we are at the start of the line table.
499  MCOS->emitDwarfLineStartLabel(LineStartSym);
500
501  unsigned OffsetSize = dwarf::getDwarfOffsetByteSize(context.getDwarfFormat());
502
503  MCSymbol *LineEndSym = MCOS->emitDwarfUnitLength("debug_line", "unit length");
504
505  // Next 2 bytes is the Version.
506  unsigned LineTableVersion = context.getDwarfVersion();
507  MCOS->emitInt16(LineTableVersion);
508
509  // In v5, we get address info next.
510  if (LineTableVersion >= 5) {
511    MCOS->emitInt8(context.getAsmInfo()->getCodePointerSize());
512    MCOS->emitInt8(0); // Segment selector; same as EmitGenDwarfAranges.
513  }
514
515  // Create symbols for the start/end of the prologue.
516  MCSymbol *ProStartSym = context.createTempSymbol("prologue_start");
517  MCSymbol *ProEndSym = context.createTempSymbol("prologue_end");
518
519  // Length of the prologue, is the next 4 bytes (8 bytes for DWARF64). This is
520  // actually the length from after the length word, to the end of the prologue.
521  MCOS->emitAbsoluteSymbolDiff(ProEndSym, ProStartSym, OffsetSize);
522
523  MCOS->emitLabel(ProStartSym);
524
525  // Parameters of the state machine, are next.
526  MCOS->emitInt8(context.getAsmInfo()->getMinInstAlignment());
527  // maximum_operations_per_instruction
528  // For non-VLIW architectures this field is always 1.
529  // FIXME: VLIW architectures need to update this field accordingly.
530  if (LineTableVersion >= 4)
531    MCOS->emitInt8(1);
532  MCOS->emitInt8(DWARF2_LINE_DEFAULT_IS_STMT);
533  MCOS->emitInt8(Params.DWARF2LineBase);
534  MCOS->emitInt8(Params.DWARF2LineRange);
535  MCOS->emitInt8(StandardOpcodeLengths.size() + 1);
536
537  // Standard opcode lengths
538  for (char Length : StandardOpcodeLengths)
539    MCOS->emitInt8(Length);
540
541  // Put out the directory and file tables.  The formats vary depending on
542  // the version.
543  if (LineTableVersion >= 5)
544    emitV5FileDirTables(MCOS, LineStr);
545  else
546    emitV2FileDirTables(MCOS);
547
548  // This is the end of the prologue, so set the value of the symbol at the
549  // end of the prologue (that was used in a previous expression).
550  MCOS->emitLabel(ProEndSym);
551
552  return std::make_pair(LineStartSym, LineEndSym);
553}
554
555void MCDwarfLineTable::emitCU(MCStreamer *MCOS, MCDwarfLineTableParams Params,
556                              std::optional<MCDwarfLineStr> &LineStr) const {
557  MCSymbol *LineEndSym = Header.Emit(MCOS, Params, LineStr).second;
558
559  // Put out the line tables.
560  for (const auto &LineSec : MCLineSections.getMCLineEntries())
561    emitOne(MCOS, LineSec.first, LineSec.second);
562
563  // This is the end of the section, so set the value of the symbol at the end
564  // of this section (that was used in a previous expression).
565  MCOS->emitLabel(LineEndSym);
566}
567
568Expected<unsigned>
569MCDwarfLineTable::tryGetFile(StringRef &Directory, StringRef &FileName,
570                             std::optional<MD5::MD5Result> Checksum,
571                             std::optional<StringRef> Source,
572                             uint16_t DwarfVersion, unsigned FileNumber) {
573  return Header.tryGetFile(Directory, FileName, Checksum, Source, DwarfVersion,
574                           FileNumber);
575}
576
577static bool isRootFile(const MCDwarfFile &RootFile, StringRef &Directory,
578                       StringRef &FileName,
579                       std::optional<MD5::MD5Result> Checksum) {
580  if (RootFile.Name.empty() || StringRef(RootFile.Name) != FileName)
581    return false;
582  return RootFile.Checksum == Checksum;
583}
584
585Expected<unsigned>
586MCDwarfLineTableHeader::tryGetFile(StringRef &Directory, StringRef &FileName,
587                                   std::optional<MD5::MD5Result> Checksum,
588                                   std::optional<StringRef> Source,
589                                   uint16_t DwarfVersion, unsigned FileNumber) {
590  if (Directory == CompilationDir)
591    Directory = "";
592  if (FileName.empty()) {
593    FileName = "<stdin>";
594    Directory = "";
595  }
596  assert(!FileName.empty());
597  // Keep track of whether any or all files have an MD5 checksum.
598  // If any files have embedded source, they all must.
599  if (MCDwarfFiles.empty()) {
600    trackMD5Usage(Checksum.has_value());
601    HasAnySource |= Source.has_value();
602  }
603  if (DwarfVersion >= 5 && isRootFile(RootFile, Directory, FileName, Checksum))
604    return 0;
605  if (FileNumber == 0) {
606    // File numbers start with 1 and/or after any file numbers
607    // allocated by inline-assembler .file directives.
608    FileNumber = MCDwarfFiles.empty() ? 1 : MCDwarfFiles.size();
609    SmallString<256> Buffer;
610    auto IterBool = SourceIdMap.insert(
611        std::make_pair((Directory + Twine('\0') + FileName).toStringRef(Buffer),
612                       FileNumber));
613    if (!IterBool.second)
614      return IterBool.first->second;
615  }
616  // Make space for this FileNumber in the MCDwarfFiles vector if needed.
617  if (FileNumber >= MCDwarfFiles.size())
618    MCDwarfFiles.resize(FileNumber + 1);
619
620  // Get the new MCDwarfFile slot for this FileNumber.
621  MCDwarfFile &File = MCDwarfFiles[FileNumber];
622
623  // It is an error to see the same number more than once.
624  if (!File.Name.empty())
625    return make_error<StringError>("file number already allocated",
626                                   inconvertibleErrorCode());
627
628  if (Directory.empty()) {
629    // Separate the directory part from the basename of the FileName.
630    StringRef tFileName = sys::path::filename(FileName);
631    if (!tFileName.empty()) {
632      Directory = sys::path::parent_path(FileName);
633      if (!Directory.empty())
634        FileName = tFileName;
635    }
636  }
637
638  // Find or make an entry in the MCDwarfDirs vector for this Directory.
639  // Capture directory name.
640  unsigned DirIndex;
641  if (Directory.empty()) {
642    // For FileNames with no directories a DirIndex of 0 is used.
643    DirIndex = 0;
644  } else {
645    DirIndex = llvm::find(MCDwarfDirs, Directory) - MCDwarfDirs.begin();
646    if (DirIndex >= MCDwarfDirs.size())
647      MCDwarfDirs.push_back(std::string(Directory));
648    // The DirIndex is one based, as DirIndex of 0 is used for FileNames with
649    // no directories.  MCDwarfDirs[] is unlike MCDwarfFiles[] in that the
650    // directory names are stored at MCDwarfDirs[DirIndex-1] where FileNames
651    // are stored at MCDwarfFiles[FileNumber].Name .
652    DirIndex++;
653  }
654
655  File.Name = std::string(FileName);
656  File.DirIndex = DirIndex;
657  File.Checksum = Checksum;
658  trackMD5Usage(Checksum.has_value());
659  File.Source = Source;
660  if (Source.has_value())
661    HasAnySource = true;
662
663  // return the allocated FileNumber.
664  return FileNumber;
665}
666
667/// Utility function to emit the encoding to a streamer.
668void MCDwarfLineAddr::Emit(MCStreamer *MCOS, MCDwarfLineTableParams Params,
669                           int64_t LineDelta, uint64_t AddrDelta) {
670  MCContext &Context = MCOS->getContext();
671  SmallString<256> Tmp;
672  MCDwarfLineAddr::encode(Context, Params, LineDelta, AddrDelta, Tmp);
673  MCOS->emitBytes(Tmp);
674}
675
676/// Given a special op, return the address skip amount (in units of
677/// DWARF2_LINE_MIN_INSN_LENGTH).
678static uint64_t SpecialAddr(MCDwarfLineTableParams Params, uint64_t op) {
679  return (op - Params.DWARF2LineOpcodeBase) / Params.DWARF2LineRange;
680}
681
682/// Utility function to encode a Dwarf pair of LineDelta and AddrDeltas.
683void MCDwarfLineAddr::encode(MCContext &Context, MCDwarfLineTableParams Params,
684                             int64_t LineDelta, uint64_t AddrDelta,
685                             SmallVectorImpl<char> &Out) {
686  uint8_t Buf[16];
687  uint64_t Temp, Opcode;
688  bool NeedCopy = false;
689
690  // The maximum address skip amount that can be encoded with a special op.
691  uint64_t MaxSpecialAddrDelta = SpecialAddr(Params, 255);
692
693  // Scale the address delta by the minimum instruction length.
694  AddrDelta = ScaleAddrDelta(Context, AddrDelta);
695
696  // A LineDelta of INT64_MAX is a signal that this is actually a
697  // DW_LNE_end_sequence. We cannot use special opcodes here, since we want the
698  // end_sequence to emit the matrix entry.
699  if (LineDelta == INT64_MAX) {
700    if (AddrDelta == MaxSpecialAddrDelta)
701      Out.push_back(dwarf::DW_LNS_const_add_pc);
702    else if (AddrDelta) {
703      Out.push_back(dwarf::DW_LNS_advance_pc);
704      Out.append(Buf, Buf + encodeULEB128(AddrDelta, Buf));
705    }
706    Out.push_back(dwarf::DW_LNS_extended_op);
707    Out.push_back(1);
708    Out.push_back(dwarf::DW_LNE_end_sequence);
709    return;
710  }
711
712  // Bias the line delta by the base.
713  Temp = LineDelta - Params.DWARF2LineBase;
714
715  // If the line increment is out of range of a special opcode, we must encode
716  // it with DW_LNS_advance_line.
717  if (Temp >= Params.DWARF2LineRange ||
718      Temp + Params.DWARF2LineOpcodeBase > 255) {
719    Out.push_back(dwarf::DW_LNS_advance_line);
720    Out.append(Buf, Buf + encodeSLEB128(LineDelta, Buf));
721
722    LineDelta = 0;
723    Temp = 0 - Params.DWARF2LineBase;
724    NeedCopy = true;
725  }
726
727  // Use DW_LNS_copy instead of a "line +0, addr +0" special opcode.
728  if (LineDelta == 0 && AddrDelta == 0) {
729    Out.push_back(dwarf::DW_LNS_copy);
730    return;
731  }
732
733  // Bias the opcode by the special opcode base.
734  Temp += Params.DWARF2LineOpcodeBase;
735
736  // Avoid overflow when addr_delta is large.
737  if (AddrDelta < 256 + MaxSpecialAddrDelta) {
738    // Try using a special opcode.
739    Opcode = Temp + AddrDelta * Params.DWARF2LineRange;
740    if (Opcode <= 255) {
741      Out.push_back(Opcode);
742      return;
743    }
744
745    // Try using DW_LNS_const_add_pc followed by special op.
746    Opcode = Temp + (AddrDelta - MaxSpecialAddrDelta) * Params.DWARF2LineRange;
747    if (Opcode <= 255) {
748      Out.push_back(dwarf::DW_LNS_const_add_pc);
749      Out.push_back(Opcode);
750      return;
751    }
752  }
753
754  // Otherwise use DW_LNS_advance_pc.
755  Out.push_back(dwarf::DW_LNS_advance_pc);
756  Out.append(Buf, Buf + encodeULEB128(AddrDelta, Buf));
757
758  if (NeedCopy)
759    Out.push_back(dwarf::DW_LNS_copy);
760  else {
761    assert(Temp <= 255 && "Buggy special opcode encoding.");
762    Out.push_back(Temp);
763  }
764}
765
766// Utility function to write a tuple for .debug_abbrev.
767static void EmitAbbrev(MCStreamer *MCOS, uint64_t Name, uint64_t Form) {
768  MCOS->emitULEB128IntValue(Name);
769  MCOS->emitULEB128IntValue(Form);
770}
771
772// When generating dwarf for assembly source files this emits
773// the data for .debug_abbrev section which contains three DIEs.
774static void EmitGenDwarfAbbrev(MCStreamer *MCOS) {
775  MCContext &context = MCOS->getContext();
776  MCOS->switchSection(context.getObjectFileInfo()->getDwarfAbbrevSection());
777
778  // DW_TAG_compile_unit DIE abbrev (1).
779  MCOS->emitULEB128IntValue(1);
780  MCOS->emitULEB128IntValue(dwarf::DW_TAG_compile_unit);
781  MCOS->emitInt8(dwarf::DW_CHILDREN_yes);
782  dwarf::Form SecOffsetForm =
783      context.getDwarfVersion() >= 4
784          ? dwarf::DW_FORM_sec_offset
785          : (context.getDwarfFormat() == dwarf::DWARF64 ? dwarf::DW_FORM_data8
786                                                        : dwarf::DW_FORM_data4);
787  EmitAbbrev(MCOS, dwarf::DW_AT_stmt_list, SecOffsetForm);
788  if (context.getGenDwarfSectionSyms().size() > 1 &&
789      context.getDwarfVersion() >= 3) {
790    EmitAbbrev(MCOS, dwarf::DW_AT_ranges, SecOffsetForm);
791  } else {
792    EmitAbbrev(MCOS, dwarf::DW_AT_low_pc, dwarf::DW_FORM_addr);
793    EmitAbbrev(MCOS, dwarf::DW_AT_high_pc, dwarf::DW_FORM_addr);
794  }
795  EmitAbbrev(MCOS, dwarf::DW_AT_name, dwarf::DW_FORM_string);
796  if (!context.getCompilationDir().empty())
797    EmitAbbrev(MCOS, dwarf::DW_AT_comp_dir, dwarf::DW_FORM_string);
798  StringRef DwarfDebugFlags = context.getDwarfDebugFlags();
799  if (!DwarfDebugFlags.empty())
800    EmitAbbrev(MCOS, dwarf::DW_AT_APPLE_flags, dwarf::DW_FORM_string);
801  EmitAbbrev(MCOS, dwarf::DW_AT_producer, dwarf::DW_FORM_string);
802  EmitAbbrev(MCOS, dwarf::DW_AT_language, dwarf::DW_FORM_data2);
803  EmitAbbrev(MCOS, 0, 0);
804
805  // DW_TAG_label DIE abbrev (2).
806  MCOS->emitULEB128IntValue(2);
807  MCOS->emitULEB128IntValue(dwarf::DW_TAG_label);
808  MCOS->emitInt8(dwarf::DW_CHILDREN_no);
809  EmitAbbrev(MCOS, dwarf::DW_AT_name, dwarf::DW_FORM_string);
810  EmitAbbrev(MCOS, dwarf::DW_AT_decl_file, dwarf::DW_FORM_data4);
811  EmitAbbrev(MCOS, dwarf::DW_AT_decl_line, dwarf::DW_FORM_data4);
812  EmitAbbrev(MCOS, dwarf::DW_AT_low_pc, dwarf::DW_FORM_addr);
813  EmitAbbrev(MCOS, 0, 0);
814
815  // Terminate the abbreviations for this compilation unit.
816  MCOS->emitInt8(0);
817}
818
819// When generating dwarf for assembly source files this emits the data for
820// .debug_aranges section. This section contains a header and a table of pairs
821// of PointerSize'ed values for the address and size of section(s) with line
822// table entries.
823static void EmitGenDwarfAranges(MCStreamer *MCOS,
824                                const MCSymbol *InfoSectionSymbol) {
825  MCContext &context = MCOS->getContext();
826
827  auto &Sections = context.getGenDwarfSectionSyms();
828
829  MCOS->switchSection(context.getObjectFileInfo()->getDwarfARangesSection());
830
831  unsigned UnitLengthBytes =
832      dwarf::getUnitLengthFieldByteSize(context.getDwarfFormat());
833  unsigned OffsetSize = dwarf::getDwarfOffsetByteSize(context.getDwarfFormat());
834
835  // This will be the length of the .debug_aranges section, first account for
836  // the size of each item in the header (see below where we emit these items).
837  int Length = UnitLengthBytes + 2 + OffsetSize + 1 + 1;
838
839  // Figure the padding after the header before the table of address and size
840  // pairs who's values are PointerSize'ed.
841  const MCAsmInfo *asmInfo = context.getAsmInfo();
842  int AddrSize = asmInfo->getCodePointerSize();
843  int Pad = 2 * AddrSize - (Length & (2 * AddrSize - 1));
844  if (Pad == 2 * AddrSize)
845    Pad = 0;
846  Length += Pad;
847
848  // Add the size of the pair of PointerSize'ed values for the address and size
849  // of each section we have in the table.
850  Length += 2 * AddrSize * Sections.size();
851  // And the pair of terminating zeros.
852  Length += 2 * AddrSize;
853
854  // Emit the header for this section.
855  if (context.getDwarfFormat() == dwarf::DWARF64)
856    // The DWARF64 mark.
857    MCOS->emitInt32(dwarf::DW_LENGTH_DWARF64);
858  // The 4 (8 for DWARF64) byte length not including the length of the unit
859  // length field itself.
860  MCOS->emitIntValue(Length - UnitLengthBytes, OffsetSize);
861  // The 2 byte version, which is 2.
862  MCOS->emitInt16(2);
863  // The 4 (8 for DWARF64) byte offset to the compile unit in the .debug_info
864  // from the start of the .debug_info.
865  if (InfoSectionSymbol)
866    MCOS->emitSymbolValue(InfoSectionSymbol, OffsetSize,
867                          asmInfo->needsDwarfSectionOffsetDirective());
868  else
869    MCOS->emitIntValue(0, OffsetSize);
870  // The 1 byte size of an address.
871  MCOS->emitInt8(AddrSize);
872  // The 1 byte size of a segment descriptor, we use a value of zero.
873  MCOS->emitInt8(0);
874  // Align the header with the padding if needed, before we put out the table.
875  for(int i = 0; i < Pad; i++)
876    MCOS->emitInt8(0);
877
878  // Now emit the table of pairs of PointerSize'ed values for the section
879  // addresses and sizes.
880  for (MCSection *Sec : Sections) {
881    const MCSymbol *StartSymbol = Sec->getBeginSymbol();
882    MCSymbol *EndSymbol = Sec->getEndSymbol(context);
883    assert(StartSymbol && "StartSymbol must not be NULL");
884    assert(EndSymbol && "EndSymbol must not be NULL");
885
886    const MCExpr *Addr = MCSymbolRefExpr::create(
887      StartSymbol, MCSymbolRefExpr::VK_None, context);
888    const MCExpr *Size =
889        makeEndMinusStartExpr(context, *StartSymbol, *EndSymbol, 0);
890    MCOS->emitValue(Addr, AddrSize);
891    emitAbsValue(*MCOS, Size, AddrSize);
892  }
893
894  // And finally the pair of terminating zeros.
895  MCOS->emitIntValue(0, AddrSize);
896  MCOS->emitIntValue(0, AddrSize);
897}
898
899// When generating dwarf for assembly source files this emits the data for
900// .debug_info section which contains three parts.  The header, the compile_unit
901// DIE and a list of label DIEs.
902static void EmitGenDwarfInfo(MCStreamer *MCOS,
903                             const MCSymbol *AbbrevSectionSymbol,
904                             const MCSymbol *LineSectionSymbol,
905                             const MCSymbol *RangesSymbol) {
906  MCContext &context = MCOS->getContext();
907
908  MCOS->switchSection(context.getObjectFileInfo()->getDwarfInfoSection());
909
910  // Create a symbol at the start and end of this section used in here for the
911  // expression to calculate the length in the header.
912  MCSymbol *InfoStart = context.createTempSymbol();
913  MCOS->emitLabel(InfoStart);
914  MCSymbol *InfoEnd = context.createTempSymbol();
915
916  // First part: the header.
917
918  unsigned UnitLengthBytes =
919      dwarf::getUnitLengthFieldByteSize(context.getDwarfFormat());
920  unsigned OffsetSize = dwarf::getDwarfOffsetByteSize(context.getDwarfFormat());
921
922  if (context.getDwarfFormat() == dwarf::DWARF64)
923    // Emit DWARF64 mark.
924    MCOS->emitInt32(dwarf::DW_LENGTH_DWARF64);
925
926  // The 4 (8 for DWARF64) byte total length of the information for this
927  // compilation unit, not including the unit length field itself.
928  const MCExpr *Length =
929      makeEndMinusStartExpr(context, *InfoStart, *InfoEnd, UnitLengthBytes);
930  emitAbsValue(*MCOS, Length, OffsetSize);
931
932  // The 2 byte DWARF version.
933  MCOS->emitInt16(context.getDwarfVersion());
934
935  // The DWARF v5 header has unit type, address size, abbrev offset.
936  // Earlier versions have abbrev offset, address size.
937  const MCAsmInfo &AsmInfo = *context.getAsmInfo();
938  int AddrSize = AsmInfo.getCodePointerSize();
939  if (context.getDwarfVersion() >= 5) {
940    MCOS->emitInt8(dwarf::DW_UT_compile);
941    MCOS->emitInt8(AddrSize);
942  }
943  // The 4 (8 for DWARF64) byte offset to the debug abbrevs from the start of
944  // the .debug_abbrev.
945  if (AbbrevSectionSymbol)
946    MCOS->emitSymbolValue(AbbrevSectionSymbol, OffsetSize,
947                          AsmInfo.needsDwarfSectionOffsetDirective());
948  else
949    // Since the abbrevs are at the start of the section, the offset is zero.
950    MCOS->emitIntValue(0, OffsetSize);
951  if (context.getDwarfVersion() <= 4)
952    MCOS->emitInt8(AddrSize);
953
954  // Second part: the compile_unit DIE.
955
956  // The DW_TAG_compile_unit DIE abbrev (1).
957  MCOS->emitULEB128IntValue(1);
958
959  // DW_AT_stmt_list, a 4 (8 for DWARF64) byte offset from the start of the
960  // .debug_line section.
961  if (LineSectionSymbol)
962    MCOS->emitSymbolValue(LineSectionSymbol, OffsetSize,
963                          AsmInfo.needsDwarfSectionOffsetDirective());
964  else
965    // The line table is at the start of the section, so the offset is zero.
966    MCOS->emitIntValue(0, OffsetSize);
967
968  if (RangesSymbol) {
969    // There are multiple sections containing code, so we must use
970    // .debug_ranges/.debug_rnglists. AT_ranges, the 4/8 byte offset from the
971    // start of the .debug_ranges/.debug_rnglists.
972    MCOS->emitSymbolValue(RangesSymbol, OffsetSize);
973  } else {
974    // If we only have one non-empty code section, we can use the simpler
975    // AT_low_pc and AT_high_pc attributes.
976
977    // Find the first (and only) non-empty text section
978    auto &Sections = context.getGenDwarfSectionSyms();
979    const auto TextSection = Sections.begin();
980    assert(TextSection != Sections.end() && "No text section found");
981
982    MCSymbol *StartSymbol = (*TextSection)->getBeginSymbol();
983    MCSymbol *EndSymbol = (*TextSection)->getEndSymbol(context);
984    assert(StartSymbol && "StartSymbol must not be NULL");
985    assert(EndSymbol && "EndSymbol must not be NULL");
986
987    // AT_low_pc, the first address of the default .text section.
988    const MCExpr *Start = MCSymbolRefExpr::create(
989        StartSymbol, MCSymbolRefExpr::VK_None, context);
990    MCOS->emitValue(Start, AddrSize);
991
992    // AT_high_pc, the last address of the default .text section.
993    const MCExpr *End = MCSymbolRefExpr::create(
994      EndSymbol, MCSymbolRefExpr::VK_None, context);
995    MCOS->emitValue(End, AddrSize);
996  }
997
998  // AT_name, the name of the source file.  Reconstruct from the first directory
999  // and file table entries.
1000  const SmallVectorImpl<std::string> &MCDwarfDirs = context.getMCDwarfDirs();
1001  if (MCDwarfDirs.size() > 0) {
1002    MCOS->emitBytes(MCDwarfDirs[0]);
1003    MCOS->emitBytes(sys::path::get_separator());
1004  }
1005  const SmallVectorImpl<MCDwarfFile> &MCDwarfFiles = context.getMCDwarfFiles();
1006  // MCDwarfFiles might be empty if we have an empty source file.
1007  // If it's not empty, [0] is unused and [1] is the first actual file.
1008  assert(MCDwarfFiles.empty() || MCDwarfFiles.size() >= 2);
1009  const MCDwarfFile &RootFile =
1010      MCDwarfFiles.empty()
1011          ? context.getMCDwarfLineTable(/*CUID=*/0).getRootFile()
1012          : MCDwarfFiles[1];
1013  MCOS->emitBytes(RootFile.Name);
1014  MCOS->emitInt8(0); // NULL byte to terminate the string.
1015
1016  // AT_comp_dir, the working directory the assembly was done in.
1017  if (!context.getCompilationDir().empty()) {
1018    MCOS->emitBytes(context.getCompilationDir());
1019    MCOS->emitInt8(0); // NULL byte to terminate the string.
1020  }
1021
1022  // AT_APPLE_flags, the command line arguments of the assembler tool.
1023  StringRef DwarfDebugFlags = context.getDwarfDebugFlags();
1024  if (!DwarfDebugFlags.empty()){
1025    MCOS->emitBytes(DwarfDebugFlags);
1026    MCOS->emitInt8(0); // NULL byte to terminate the string.
1027  }
1028
1029  // AT_producer, the version of the assembler tool.
1030  StringRef DwarfDebugProducer = context.getDwarfDebugProducer();
1031  if (!DwarfDebugProducer.empty())
1032    MCOS->emitBytes(DwarfDebugProducer);
1033  else
1034    MCOS->emitBytes(StringRef("llvm-mc (based on LLVM " PACKAGE_VERSION ")"));
1035  MCOS->emitInt8(0); // NULL byte to terminate the string.
1036
1037  // AT_language, a 4 byte value.  We use DW_LANG_Mips_Assembler as the dwarf2
1038  // draft has no standard code for assembler.
1039  MCOS->emitInt16(dwarf::DW_LANG_Mips_Assembler);
1040
1041  // Third part: the list of label DIEs.
1042
1043  // Loop on saved info for dwarf labels and create the DIEs for them.
1044  const std::vector<MCGenDwarfLabelEntry> &Entries =
1045      MCOS->getContext().getMCGenDwarfLabelEntries();
1046  for (const auto &Entry : Entries) {
1047    // The DW_TAG_label DIE abbrev (2).
1048    MCOS->emitULEB128IntValue(2);
1049
1050    // AT_name, of the label without any leading underbar.
1051    MCOS->emitBytes(Entry.getName());
1052    MCOS->emitInt8(0); // NULL byte to terminate the string.
1053
1054    // AT_decl_file, index into the file table.
1055    MCOS->emitInt32(Entry.getFileNumber());
1056
1057    // AT_decl_line, source line number.
1058    MCOS->emitInt32(Entry.getLineNumber());
1059
1060    // AT_low_pc, start address of the label.
1061    const MCExpr *AT_low_pc = MCSymbolRefExpr::create(Entry.getLabel(),
1062                                             MCSymbolRefExpr::VK_None, context);
1063    MCOS->emitValue(AT_low_pc, AddrSize);
1064  }
1065
1066  // Add the NULL DIE terminating the Compile Unit DIE's.
1067  MCOS->emitInt8(0);
1068
1069  // Now set the value of the symbol at the end of the info section.
1070  MCOS->emitLabel(InfoEnd);
1071}
1072
1073// When generating dwarf for assembly source files this emits the data for
1074// .debug_ranges section. We only emit one range list, which spans all of the
1075// executable sections of this file.
1076static MCSymbol *emitGenDwarfRanges(MCStreamer *MCOS) {
1077  MCContext &context = MCOS->getContext();
1078  auto &Sections = context.getGenDwarfSectionSyms();
1079
1080  const MCAsmInfo *AsmInfo = context.getAsmInfo();
1081  int AddrSize = AsmInfo->getCodePointerSize();
1082  MCSymbol *RangesSymbol;
1083
1084  if (MCOS->getContext().getDwarfVersion() >= 5) {
1085    MCOS->switchSection(context.getObjectFileInfo()->getDwarfRnglistsSection());
1086    MCSymbol *EndSymbol = mcdwarf::emitListsTableHeaderStart(*MCOS);
1087    MCOS->AddComment("Offset entry count");
1088    MCOS->emitInt32(0);
1089    RangesSymbol = context.createTempSymbol("debug_rnglist0_start");
1090    MCOS->emitLabel(RangesSymbol);
1091    for (MCSection *Sec : Sections) {
1092      const MCSymbol *StartSymbol = Sec->getBeginSymbol();
1093      const MCSymbol *EndSymbol = Sec->getEndSymbol(context);
1094      const MCExpr *SectionStartAddr = MCSymbolRefExpr::create(
1095          StartSymbol, MCSymbolRefExpr::VK_None, context);
1096      const MCExpr *SectionSize =
1097          makeEndMinusStartExpr(context, *StartSymbol, *EndSymbol, 0);
1098      MCOS->emitInt8(dwarf::DW_RLE_start_length);
1099      MCOS->emitValue(SectionStartAddr, AddrSize);
1100      MCOS->emitULEB128Value(SectionSize);
1101    }
1102    MCOS->emitInt8(dwarf::DW_RLE_end_of_list);
1103    MCOS->emitLabel(EndSymbol);
1104  } else {
1105    MCOS->switchSection(context.getObjectFileInfo()->getDwarfRangesSection());
1106    RangesSymbol = context.createTempSymbol("debug_ranges_start");
1107    MCOS->emitLabel(RangesSymbol);
1108    for (MCSection *Sec : Sections) {
1109      const MCSymbol *StartSymbol = Sec->getBeginSymbol();
1110      const MCSymbol *EndSymbol = Sec->getEndSymbol(context);
1111
1112      // Emit a base address selection entry for the section start.
1113      const MCExpr *SectionStartAddr = MCSymbolRefExpr::create(
1114          StartSymbol, MCSymbolRefExpr::VK_None, context);
1115      MCOS->emitFill(AddrSize, 0xFF);
1116      MCOS->emitValue(SectionStartAddr, AddrSize);
1117
1118      // Emit a range list entry spanning this section.
1119      const MCExpr *SectionSize =
1120          makeEndMinusStartExpr(context, *StartSymbol, *EndSymbol, 0);
1121      MCOS->emitIntValue(0, AddrSize);
1122      emitAbsValue(*MCOS, SectionSize, AddrSize);
1123    }
1124
1125    // Emit end of list entry
1126    MCOS->emitIntValue(0, AddrSize);
1127    MCOS->emitIntValue(0, AddrSize);
1128  }
1129
1130  return RangesSymbol;
1131}
1132
1133//
1134// When generating dwarf for assembly source files this emits the Dwarf
1135// sections.
1136//
1137void MCGenDwarfInfo::Emit(MCStreamer *MCOS) {
1138  MCContext &context = MCOS->getContext();
1139
1140  // Create the dwarf sections in this order (.debug_line already created).
1141  const MCAsmInfo *AsmInfo = context.getAsmInfo();
1142  bool CreateDwarfSectionSymbols =
1143      AsmInfo->doesDwarfUseRelocationsAcrossSections();
1144  MCSymbol *LineSectionSymbol = nullptr;
1145  if (CreateDwarfSectionSymbols)
1146    LineSectionSymbol = MCOS->getDwarfLineTableSymbol(0);
1147  MCSymbol *AbbrevSectionSymbol = nullptr;
1148  MCSymbol *InfoSectionSymbol = nullptr;
1149  MCSymbol *RangesSymbol = nullptr;
1150
1151  // Create end symbols for each section, and remove empty sections
1152  MCOS->getContext().finalizeDwarfSections(*MCOS);
1153
1154  // If there are no sections to generate debug info for, we don't need
1155  // to do anything
1156  if (MCOS->getContext().getGenDwarfSectionSyms().empty())
1157    return;
1158
1159  // We only use the .debug_ranges section if we have multiple code sections,
1160  // and we are emitting a DWARF version which supports it.
1161  const bool UseRangesSection =
1162      MCOS->getContext().getGenDwarfSectionSyms().size() > 1 &&
1163      MCOS->getContext().getDwarfVersion() >= 3;
1164  CreateDwarfSectionSymbols |= UseRangesSection;
1165
1166  MCOS->switchSection(context.getObjectFileInfo()->getDwarfInfoSection());
1167  if (CreateDwarfSectionSymbols) {
1168    InfoSectionSymbol = context.createTempSymbol();
1169    MCOS->emitLabel(InfoSectionSymbol);
1170  }
1171  MCOS->switchSection(context.getObjectFileInfo()->getDwarfAbbrevSection());
1172  if (CreateDwarfSectionSymbols) {
1173    AbbrevSectionSymbol = context.createTempSymbol();
1174    MCOS->emitLabel(AbbrevSectionSymbol);
1175  }
1176
1177  MCOS->switchSection(context.getObjectFileInfo()->getDwarfARangesSection());
1178
1179  // Output the data for .debug_aranges section.
1180  EmitGenDwarfAranges(MCOS, InfoSectionSymbol);
1181
1182  if (UseRangesSection) {
1183    RangesSymbol = emitGenDwarfRanges(MCOS);
1184    assert(RangesSymbol);
1185  }
1186
1187  // Output the data for .debug_abbrev section.
1188  EmitGenDwarfAbbrev(MCOS);
1189
1190  // Output the data for .debug_info section.
1191  EmitGenDwarfInfo(MCOS, AbbrevSectionSymbol, LineSectionSymbol, RangesSymbol);
1192}
1193
1194//
1195// When generating dwarf for assembly source files this is called when symbol
1196// for a label is created.  If this symbol is not a temporary and is in the
1197// section that dwarf is being generated for, save the needed info to create
1198// a dwarf label.
1199//
1200void MCGenDwarfLabelEntry::Make(MCSymbol *Symbol, MCStreamer *MCOS,
1201                                     SourceMgr &SrcMgr, SMLoc &Loc) {
1202  // We won't create dwarf labels for temporary symbols.
1203  if (Symbol->isTemporary())
1204    return;
1205  MCContext &context = MCOS->getContext();
1206  // We won't create dwarf labels for symbols in sections that we are not
1207  // generating debug info for.
1208  if (!context.getGenDwarfSectionSyms().count(MCOS->getCurrentSectionOnly()))
1209    return;
1210
1211  // The dwarf label's name does not have the symbol name's leading
1212  // underbar if any.
1213  StringRef Name = Symbol->getName();
1214  if (Name.starts_with("_"))
1215    Name = Name.substr(1, Name.size()-1);
1216
1217  // Get the dwarf file number to be used for the dwarf label.
1218  unsigned FileNumber = context.getGenDwarfFileNumber();
1219
1220  // Finding the line number is the expensive part which is why we just don't
1221  // pass it in as for some symbols we won't create a dwarf label.
1222  unsigned CurBuffer = SrcMgr.FindBufferContainingLoc(Loc);
1223  unsigned LineNumber = SrcMgr.FindLineNumber(Loc, CurBuffer);
1224
1225  // We create a temporary symbol for use for the AT_high_pc and AT_low_pc
1226  // values so that they don't have things like an ARM thumb bit from the
1227  // original symbol. So when used they won't get a low bit set after
1228  // relocation.
1229  MCSymbol *Label = context.createTempSymbol();
1230  MCOS->emitLabel(Label);
1231
1232  // Create and entry for the info and add it to the other entries.
1233  MCOS->getContext().addMCGenDwarfLabelEntry(
1234      MCGenDwarfLabelEntry(Name, FileNumber, LineNumber, Label));
1235}
1236
1237static int getDataAlignmentFactor(MCStreamer &streamer) {
1238  MCContext &context = streamer.getContext();
1239  const MCAsmInfo *asmInfo = context.getAsmInfo();
1240  int size = asmInfo->getCalleeSaveStackSlotSize();
1241  if (asmInfo->isStackGrowthDirectionUp())
1242    return size;
1243  else
1244    return -size;
1245}
1246
1247static unsigned getSizeForEncoding(MCStreamer &streamer,
1248                                   unsigned symbolEncoding) {
1249  MCContext &context = streamer.getContext();
1250  unsigned format = symbolEncoding & 0x0f;
1251  switch (format) {
1252  default: llvm_unreachable("Unknown Encoding");
1253  case dwarf::DW_EH_PE_absptr:
1254  case dwarf::DW_EH_PE_signed:
1255    return context.getAsmInfo()->getCodePointerSize();
1256  case dwarf::DW_EH_PE_udata2:
1257  case dwarf::DW_EH_PE_sdata2:
1258    return 2;
1259  case dwarf::DW_EH_PE_udata4:
1260  case dwarf::DW_EH_PE_sdata4:
1261    return 4;
1262  case dwarf::DW_EH_PE_udata8:
1263  case dwarf::DW_EH_PE_sdata8:
1264    return 8;
1265  }
1266}
1267
1268static void emitFDESymbol(MCObjectStreamer &streamer, const MCSymbol &symbol,
1269                       unsigned symbolEncoding, bool isEH) {
1270  MCContext &context = streamer.getContext();
1271  const MCAsmInfo *asmInfo = context.getAsmInfo();
1272  const MCExpr *v = asmInfo->getExprForFDESymbol(&symbol,
1273                                                 symbolEncoding,
1274                                                 streamer);
1275  unsigned size = getSizeForEncoding(streamer, symbolEncoding);
1276  if (asmInfo->doDwarfFDESymbolsUseAbsDiff() && isEH)
1277    emitAbsValue(streamer, v, size);
1278  else
1279    streamer.emitValue(v, size);
1280}
1281
1282static void EmitPersonality(MCStreamer &streamer, const MCSymbol &symbol,
1283                            unsigned symbolEncoding) {
1284  MCContext &context = streamer.getContext();
1285  const MCAsmInfo *asmInfo = context.getAsmInfo();
1286  const MCExpr *v = asmInfo->getExprForPersonalitySymbol(&symbol,
1287                                                         symbolEncoding,
1288                                                         streamer);
1289  unsigned size = getSizeForEncoding(streamer, symbolEncoding);
1290  streamer.emitValue(v, size);
1291}
1292
1293namespace {
1294
1295class FrameEmitterImpl {
1296  int CFAOffset = 0;
1297  int InitialCFAOffset = 0;
1298  bool IsEH;
1299  MCObjectStreamer &Streamer;
1300
1301public:
1302  FrameEmitterImpl(bool IsEH, MCObjectStreamer &Streamer)
1303      : IsEH(IsEH), Streamer(Streamer) {}
1304
1305  /// Emit the unwind information in a compact way.
1306  void EmitCompactUnwind(const MCDwarfFrameInfo &frame);
1307
1308  const MCSymbol &EmitCIE(const MCDwarfFrameInfo &F);
1309  void EmitFDE(const MCSymbol &cieStart, const MCDwarfFrameInfo &frame,
1310               bool LastInSection, const MCSymbol &SectionStart);
1311  void emitCFIInstructions(ArrayRef<MCCFIInstruction> Instrs,
1312                           MCSymbol *BaseLabel);
1313  void emitCFIInstruction(const MCCFIInstruction &Instr);
1314};
1315
1316} // end anonymous namespace
1317
1318static void emitEncodingByte(MCObjectStreamer &Streamer, unsigned Encoding) {
1319  Streamer.emitInt8(Encoding);
1320}
1321
1322void FrameEmitterImpl::emitCFIInstruction(const MCCFIInstruction &Instr) {
1323  int dataAlignmentFactor = getDataAlignmentFactor(Streamer);
1324  auto *MRI = Streamer.getContext().getRegisterInfo();
1325
1326  switch (Instr.getOperation()) {
1327  case MCCFIInstruction::OpRegister: {
1328    unsigned Reg1 = Instr.getRegister();
1329    unsigned Reg2 = Instr.getRegister2();
1330    if (!IsEH) {
1331      Reg1 = MRI->getDwarfRegNumFromDwarfEHRegNum(Reg1);
1332      Reg2 = MRI->getDwarfRegNumFromDwarfEHRegNum(Reg2);
1333    }
1334    Streamer.emitInt8(dwarf::DW_CFA_register);
1335    Streamer.emitULEB128IntValue(Reg1);
1336    Streamer.emitULEB128IntValue(Reg2);
1337    return;
1338  }
1339  case MCCFIInstruction::OpWindowSave:
1340    Streamer.emitInt8(dwarf::DW_CFA_GNU_window_save);
1341    return;
1342
1343  case MCCFIInstruction::OpNegateRAState:
1344    Streamer.emitInt8(dwarf::DW_CFA_AARCH64_negate_ra_state);
1345    return;
1346
1347  case MCCFIInstruction::OpUndefined: {
1348    unsigned Reg = Instr.getRegister();
1349    Streamer.emitInt8(dwarf::DW_CFA_undefined);
1350    Streamer.emitULEB128IntValue(Reg);
1351    return;
1352  }
1353  case MCCFIInstruction::OpAdjustCfaOffset:
1354  case MCCFIInstruction::OpDefCfaOffset: {
1355    const bool IsRelative =
1356      Instr.getOperation() == MCCFIInstruction::OpAdjustCfaOffset;
1357
1358    Streamer.emitInt8(dwarf::DW_CFA_def_cfa_offset);
1359
1360    if (IsRelative)
1361      CFAOffset += Instr.getOffset();
1362    else
1363      CFAOffset = Instr.getOffset();
1364
1365    Streamer.emitULEB128IntValue(CFAOffset);
1366
1367    return;
1368  }
1369  case MCCFIInstruction::OpDefCfa: {
1370    unsigned Reg = Instr.getRegister();
1371    if (!IsEH)
1372      Reg = MRI->getDwarfRegNumFromDwarfEHRegNum(Reg);
1373    Streamer.emitInt8(dwarf::DW_CFA_def_cfa);
1374    Streamer.emitULEB128IntValue(Reg);
1375    CFAOffset = Instr.getOffset();
1376    Streamer.emitULEB128IntValue(CFAOffset);
1377
1378    return;
1379  }
1380  case MCCFIInstruction::OpDefCfaRegister: {
1381    unsigned Reg = Instr.getRegister();
1382    if (!IsEH)
1383      Reg = MRI->getDwarfRegNumFromDwarfEHRegNum(Reg);
1384    Streamer.emitInt8(dwarf::DW_CFA_def_cfa_register);
1385    Streamer.emitULEB128IntValue(Reg);
1386
1387    return;
1388  }
1389  // TODO: Implement `_sf` variants if/when they need to be emitted.
1390  case MCCFIInstruction::OpLLVMDefAspaceCfa: {
1391    unsigned Reg = Instr.getRegister();
1392    if (!IsEH)
1393      Reg = MRI->getDwarfRegNumFromDwarfEHRegNum(Reg);
1394    Streamer.emitIntValue(dwarf::DW_CFA_LLVM_def_aspace_cfa, 1);
1395    Streamer.emitULEB128IntValue(Reg);
1396    CFAOffset = Instr.getOffset();
1397    Streamer.emitULEB128IntValue(CFAOffset);
1398    Streamer.emitULEB128IntValue(Instr.getAddressSpace());
1399
1400    return;
1401  }
1402  case MCCFIInstruction::OpOffset:
1403  case MCCFIInstruction::OpRelOffset: {
1404    const bool IsRelative =
1405      Instr.getOperation() == MCCFIInstruction::OpRelOffset;
1406
1407    unsigned Reg = Instr.getRegister();
1408    if (!IsEH)
1409      Reg = MRI->getDwarfRegNumFromDwarfEHRegNum(Reg);
1410
1411    int Offset = Instr.getOffset();
1412    if (IsRelative)
1413      Offset -= CFAOffset;
1414    Offset = Offset / dataAlignmentFactor;
1415
1416    if (Offset < 0) {
1417      Streamer.emitInt8(dwarf::DW_CFA_offset_extended_sf);
1418      Streamer.emitULEB128IntValue(Reg);
1419      Streamer.emitSLEB128IntValue(Offset);
1420    } else if (Reg < 64) {
1421      Streamer.emitInt8(dwarf::DW_CFA_offset + Reg);
1422      Streamer.emitULEB128IntValue(Offset);
1423    } else {
1424      Streamer.emitInt8(dwarf::DW_CFA_offset_extended);
1425      Streamer.emitULEB128IntValue(Reg);
1426      Streamer.emitULEB128IntValue(Offset);
1427    }
1428    return;
1429  }
1430  case MCCFIInstruction::OpRememberState:
1431    Streamer.emitInt8(dwarf::DW_CFA_remember_state);
1432    return;
1433  case MCCFIInstruction::OpRestoreState:
1434    Streamer.emitInt8(dwarf::DW_CFA_restore_state);
1435    return;
1436  case MCCFIInstruction::OpSameValue: {
1437    unsigned Reg = Instr.getRegister();
1438    Streamer.emitInt8(dwarf::DW_CFA_same_value);
1439    Streamer.emitULEB128IntValue(Reg);
1440    return;
1441  }
1442  case MCCFIInstruction::OpRestore: {
1443    unsigned Reg = Instr.getRegister();
1444    if (!IsEH)
1445      Reg = MRI->getDwarfRegNumFromDwarfEHRegNum(Reg);
1446    if (Reg < 64) {
1447      Streamer.emitInt8(dwarf::DW_CFA_restore | Reg);
1448    } else {
1449      Streamer.emitInt8(dwarf::DW_CFA_restore_extended);
1450      Streamer.emitULEB128IntValue(Reg);
1451    }
1452    return;
1453  }
1454  case MCCFIInstruction::OpGnuArgsSize:
1455    Streamer.emitInt8(dwarf::DW_CFA_GNU_args_size);
1456    Streamer.emitULEB128IntValue(Instr.getOffset());
1457    return;
1458
1459  case MCCFIInstruction::OpEscape:
1460    Streamer.emitBytes(Instr.getValues());
1461    return;
1462  }
1463  llvm_unreachable("Unhandled case in switch");
1464}
1465
1466/// Emit frame instructions to describe the layout of the frame.
1467void FrameEmitterImpl::emitCFIInstructions(ArrayRef<MCCFIInstruction> Instrs,
1468                                           MCSymbol *BaseLabel) {
1469  for (const MCCFIInstruction &Instr : Instrs) {
1470    MCSymbol *Label = Instr.getLabel();
1471    // Throw out move if the label is invalid.
1472    if (Label && !Label->isDefined()) continue; // Not emitted, in dead code.
1473
1474    // Advance row if new location.
1475    if (BaseLabel && Label) {
1476      MCSymbol *ThisSym = Label;
1477      if (ThisSym != BaseLabel) {
1478        Streamer.emitDwarfAdvanceFrameAddr(BaseLabel, ThisSym, Instr.getLoc());
1479        BaseLabel = ThisSym;
1480      }
1481    }
1482
1483    emitCFIInstruction(Instr);
1484  }
1485}
1486
1487/// Emit the unwind information in a compact way.
1488void FrameEmitterImpl::EmitCompactUnwind(const MCDwarfFrameInfo &Frame) {
1489  MCContext &Context = Streamer.getContext();
1490  const MCObjectFileInfo *MOFI = Context.getObjectFileInfo();
1491
1492  // range-start range-length  compact-unwind-enc personality-func   lsda
1493  //  _foo       LfooEnd-_foo  0x00000023          0                 0
1494  //  _bar       LbarEnd-_bar  0x00000025         __gxx_personality  except_tab1
1495  //
1496  //   .section __LD,__compact_unwind,regular,debug
1497  //
1498  //   # compact unwind for _foo
1499  //   .quad _foo
1500  //   .set L1,LfooEnd-_foo
1501  //   .long L1
1502  //   .long 0x01010001
1503  //   .quad 0
1504  //   .quad 0
1505  //
1506  //   # compact unwind for _bar
1507  //   .quad _bar
1508  //   .set L2,LbarEnd-_bar
1509  //   .long L2
1510  //   .long 0x01020011
1511  //   .quad __gxx_personality
1512  //   .quad except_tab1
1513
1514  uint32_t Encoding = Frame.CompactUnwindEncoding;
1515  if (!Encoding) return;
1516  bool DwarfEHFrameOnly = (Encoding == MOFI->getCompactUnwindDwarfEHFrameOnly());
1517
1518  // The encoding needs to know we have an LSDA.
1519  if (!DwarfEHFrameOnly && Frame.Lsda)
1520    Encoding |= 0x40000000;
1521
1522  // Range Start
1523  unsigned FDEEncoding = MOFI->getFDEEncoding();
1524  unsigned Size = getSizeForEncoding(Streamer, FDEEncoding);
1525  Streamer.emitSymbolValue(Frame.Begin, Size);
1526
1527  // Range Length
1528  const MCExpr *Range =
1529      makeEndMinusStartExpr(Context, *Frame.Begin, *Frame.End, 0);
1530  emitAbsValue(Streamer, Range, 4);
1531
1532  // Compact Encoding
1533  Size = getSizeForEncoding(Streamer, dwarf::DW_EH_PE_udata4);
1534  Streamer.emitIntValue(Encoding, Size);
1535
1536  // Personality Function
1537  Size = getSizeForEncoding(Streamer, dwarf::DW_EH_PE_absptr);
1538  if (!DwarfEHFrameOnly && Frame.Personality)
1539    Streamer.emitSymbolValue(Frame.Personality, Size);
1540  else
1541    Streamer.emitIntValue(0, Size); // No personality fn
1542
1543  // LSDA
1544  Size = getSizeForEncoding(Streamer, Frame.LsdaEncoding);
1545  if (!DwarfEHFrameOnly && Frame.Lsda)
1546    Streamer.emitSymbolValue(Frame.Lsda, Size);
1547  else
1548    Streamer.emitIntValue(0, Size); // No LSDA
1549}
1550
1551static unsigned getCIEVersion(bool IsEH, unsigned DwarfVersion) {
1552  if (IsEH)
1553    return 1;
1554  switch (DwarfVersion) {
1555  case 2:
1556    return 1;
1557  case 3:
1558    return 3;
1559  case 4:
1560  case 5:
1561    return 4;
1562  }
1563  llvm_unreachable("Unknown version");
1564}
1565
1566const MCSymbol &FrameEmitterImpl::EmitCIE(const MCDwarfFrameInfo &Frame) {
1567  MCContext &context = Streamer.getContext();
1568  const MCRegisterInfo *MRI = context.getRegisterInfo();
1569  const MCObjectFileInfo *MOFI = context.getObjectFileInfo();
1570
1571  MCSymbol *sectionStart = context.createTempSymbol();
1572  Streamer.emitLabel(sectionStart);
1573
1574  MCSymbol *sectionEnd = context.createTempSymbol();
1575
1576  dwarf::DwarfFormat Format = IsEH ? dwarf::DWARF32 : context.getDwarfFormat();
1577  unsigned UnitLengthBytes = dwarf::getUnitLengthFieldByteSize(Format);
1578  unsigned OffsetSize = dwarf::getDwarfOffsetByteSize(Format);
1579  bool IsDwarf64 = Format == dwarf::DWARF64;
1580
1581  if (IsDwarf64)
1582    // DWARF64 mark
1583    Streamer.emitInt32(dwarf::DW_LENGTH_DWARF64);
1584
1585  // Length
1586  const MCExpr *Length = makeEndMinusStartExpr(context, *sectionStart,
1587                                               *sectionEnd, UnitLengthBytes);
1588  emitAbsValue(Streamer, Length, OffsetSize);
1589
1590  // CIE ID
1591  uint64_t CIE_ID =
1592      IsEH ? 0 : (IsDwarf64 ? dwarf::DW64_CIE_ID : dwarf::DW_CIE_ID);
1593  Streamer.emitIntValue(CIE_ID, OffsetSize);
1594
1595  // Version
1596  uint8_t CIEVersion = getCIEVersion(IsEH, context.getDwarfVersion());
1597  Streamer.emitInt8(CIEVersion);
1598
1599  if (IsEH) {
1600    SmallString<8> Augmentation;
1601    Augmentation += "z";
1602    if (Frame.Personality)
1603      Augmentation += "P";
1604    if (Frame.Lsda)
1605      Augmentation += "L";
1606    Augmentation += "R";
1607    if (Frame.IsSignalFrame)
1608      Augmentation += "S";
1609    if (Frame.IsBKeyFrame)
1610      Augmentation += "B";
1611    if (Frame.IsMTETaggedFrame)
1612      Augmentation += "G";
1613    Streamer.emitBytes(Augmentation);
1614  }
1615  Streamer.emitInt8(0);
1616
1617  if (CIEVersion >= 4) {
1618    // Address Size
1619    Streamer.emitInt8(context.getAsmInfo()->getCodePointerSize());
1620
1621    // Segment Descriptor Size
1622    Streamer.emitInt8(0);
1623  }
1624
1625  // Code Alignment Factor
1626  Streamer.emitULEB128IntValue(context.getAsmInfo()->getMinInstAlignment());
1627
1628  // Data Alignment Factor
1629  Streamer.emitSLEB128IntValue(getDataAlignmentFactor(Streamer));
1630
1631  // Return Address Register
1632  unsigned RAReg = Frame.RAReg;
1633  if (RAReg == static_cast<unsigned>(INT_MAX))
1634    RAReg = MRI->getDwarfRegNum(MRI->getRARegister(), IsEH);
1635
1636  if (CIEVersion == 1) {
1637    assert(RAReg <= 255 &&
1638           "DWARF 2 encodes return_address_register in one byte");
1639    Streamer.emitInt8(RAReg);
1640  } else {
1641    Streamer.emitULEB128IntValue(RAReg);
1642  }
1643
1644  // Augmentation Data Length (optional)
1645  unsigned augmentationLength = 0;
1646  if (IsEH) {
1647    if (Frame.Personality) {
1648      // Personality Encoding
1649      augmentationLength += 1;
1650      // Personality
1651      augmentationLength +=
1652          getSizeForEncoding(Streamer, Frame.PersonalityEncoding);
1653    }
1654    if (Frame.Lsda)
1655      augmentationLength += 1;
1656    // Encoding of the FDE pointers
1657    augmentationLength += 1;
1658
1659    Streamer.emitULEB128IntValue(augmentationLength);
1660
1661    // Augmentation Data (optional)
1662    if (Frame.Personality) {
1663      // Personality Encoding
1664      emitEncodingByte(Streamer, Frame.PersonalityEncoding);
1665      // Personality
1666      EmitPersonality(Streamer, *Frame.Personality, Frame.PersonalityEncoding);
1667    }
1668
1669    if (Frame.Lsda)
1670      emitEncodingByte(Streamer, Frame.LsdaEncoding);
1671
1672    // Encoding of the FDE pointers
1673    emitEncodingByte(Streamer, MOFI->getFDEEncoding());
1674  }
1675
1676  // Initial Instructions
1677
1678  const MCAsmInfo *MAI = context.getAsmInfo();
1679  if (!Frame.IsSimple) {
1680    const std::vector<MCCFIInstruction> &Instructions =
1681        MAI->getInitialFrameState();
1682    emitCFIInstructions(Instructions, nullptr);
1683  }
1684
1685  InitialCFAOffset = CFAOffset;
1686
1687  // Padding
1688  Streamer.emitValueToAlignment(Align(IsEH ? 4 : MAI->getCodePointerSize()));
1689
1690  Streamer.emitLabel(sectionEnd);
1691  return *sectionStart;
1692}
1693
1694void FrameEmitterImpl::EmitFDE(const MCSymbol &cieStart,
1695                               const MCDwarfFrameInfo &frame,
1696                               bool LastInSection,
1697                               const MCSymbol &SectionStart) {
1698  MCContext &context = Streamer.getContext();
1699  MCSymbol *fdeStart = context.createTempSymbol();
1700  MCSymbol *fdeEnd = context.createTempSymbol();
1701  const MCObjectFileInfo *MOFI = context.getObjectFileInfo();
1702
1703  CFAOffset = InitialCFAOffset;
1704
1705  dwarf::DwarfFormat Format = IsEH ? dwarf::DWARF32 : context.getDwarfFormat();
1706  unsigned OffsetSize = dwarf::getDwarfOffsetByteSize(Format);
1707
1708  if (Format == dwarf::DWARF64)
1709    // DWARF64 mark
1710    Streamer.emitInt32(dwarf::DW_LENGTH_DWARF64);
1711
1712  // Length
1713  const MCExpr *Length = makeEndMinusStartExpr(context, *fdeStart, *fdeEnd, 0);
1714  emitAbsValue(Streamer, Length, OffsetSize);
1715
1716  Streamer.emitLabel(fdeStart);
1717
1718  // CIE Pointer
1719  const MCAsmInfo *asmInfo = context.getAsmInfo();
1720  if (IsEH) {
1721    const MCExpr *offset =
1722        makeEndMinusStartExpr(context, cieStart, *fdeStart, 0);
1723    emitAbsValue(Streamer, offset, OffsetSize);
1724  } else if (!asmInfo->doesDwarfUseRelocationsAcrossSections()) {
1725    const MCExpr *offset =
1726        makeEndMinusStartExpr(context, SectionStart, cieStart, 0);
1727    emitAbsValue(Streamer, offset, OffsetSize);
1728  } else {
1729    Streamer.emitSymbolValue(&cieStart, OffsetSize,
1730                             asmInfo->needsDwarfSectionOffsetDirective());
1731  }
1732
1733  // PC Begin
1734  unsigned PCEncoding =
1735      IsEH ? MOFI->getFDEEncoding() : (unsigned)dwarf::DW_EH_PE_absptr;
1736  unsigned PCSize = getSizeForEncoding(Streamer, PCEncoding);
1737  emitFDESymbol(Streamer, *frame.Begin, PCEncoding, IsEH);
1738
1739  // PC Range
1740  const MCExpr *Range =
1741      makeEndMinusStartExpr(context, *frame.Begin, *frame.End, 0);
1742  emitAbsValue(Streamer, Range, PCSize);
1743
1744  if (IsEH) {
1745    // Augmentation Data Length
1746    unsigned augmentationLength = 0;
1747
1748    if (frame.Lsda)
1749      augmentationLength += getSizeForEncoding(Streamer, frame.LsdaEncoding);
1750
1751    Streamer.emitULEB128IntValue(augmentationLength);
1752
1753    // Augmentation Data
1754    if (frame.Lsda)
1755      emitFDESymbol(Streamer, *frame.Lsda, frame.LsdaEncoding, true);
1756  }
1757
1758  // Call Frame Instructions
1759  emitCFIInstructions(frame.Instructions, frame.Begin);
1760
1761  // Padding
1762  // The size of a .eh_frame section has to be a multiple of the alignment
1763  // since a null CIE is interpreted as the end. Old systems overaligned
1764  // .eh_frame, so we do too and account for it in the last FDE.
1765  unsigned Alignment = LastInSection ? asmInfo->getCodePointerSize() : PCSize;
1766  Streamer.emitValueToAlignment(Align(Alignment));
1767
1768  Streamer.emitLabel(fdeEnd);
1769}
1770
1771namespace {
1772
1773struct CIEKey {
1774  static const CIEKey getEmptyKey() {
1775    return CIEKey(nullptr, 0, -1, false, false, static_cast<unsigned>(INT_MAX),
1776                  false, false);
1777  }
1778
1779  static const CIEKey getTombstoneKey() {
1780    return CIEKey(nullptr, -1, 0, false, false, static_cast<unsigned>(INT_MAX),
1781                  false, false);
1782  }
1783
1784  CIEKey(const MCSymbol *Personality, unsigned PersonalityEncoding,
1785         unsigned LSDAEncoding, bool IsSignalFrame, bool IsSimple,
1786         unsigned RAReg, bool IsBKeyFrame, bool IsMTETaggedFrame)
1787      : Personality(Personality), PersonalityEncoding(PersonalityEncoding),
1788        LsdaEncoding(LSDAEncoding), IsSignalFrame(IsSignalFrame),
1789        IsSimple(IsSimple), RAReg(RAReg), IsBKeyFrame(IsBKeyFrame),
1790        IsMTETaggedFrame(IsMTETaggedFrame) {}
1791
1792  explicit CIEKey(const MCDwarfFrameInfo &Frame)
1793      : Personality(Frame.Personality),
1794        PersonalityEncoding(Frame.PersonalityEncoding),
1795        LsdaEncoding(Frame.LsdaEncoding), IsSignalFrame(Frame.IsSignalFrame),
1796        IsSimple(Frame.IsSimple), RAReg(Frame.RAReg),
1797        IsBKeyFrame(Frame.IsBKeyFrame),
1798        IsMTETaggedFrame(Frame.IsMTETaggedFrame) {}
1799
1800  StringRef PersonalityName() const {
1801    if (!Personality)
1802      return StringRef();
1803    return Personality->getName();
1804  }
1805
1806  bool operator<(const CIEKey &Other) const {
1807    return std::make_tuple(PersonalityName(), PersonalityEncoding, LsdaEncoding,
1808                           IsSignalFrame, IsSimple, RAReg, IsBKeyFrame,
1809                           IsMTETaggedFrame) <
1810           std::make_tuple(Other.PersonalityName(), Other.PersonalityEncoding,
1811                           Other.LsdaEncoding, Other.IsSignalFrame,
1812                           Other.IsSimple, Other.RAReg, Other.IsBKeyFrame,
1813                           Other.IsMTETaggedFrame);
1814  }
1815
1816  const MCSymbol *Personality;
1817  unsigned PersonalityEncoding;
1818  unsigned LsdaEncoding;
1819  bool IsSignalFrame;
1820  bool IsSimple;
1821  unsigned RAReg;
1822  bool IsBKeyFrame;
1823  bool IsMTETaggedFrame;
1824};
1825
1826} // end anonymous namespace
1827
1828namespace llvm {
1829
1830template <> struct DenseMapInfo<CIEKey> {
1831  static CIEKey getEmptyKey() { return CIEKey::getEmptyKey(); }
1832  static CIEKey getTombstoneKey() { return CIEKey::getTombstoneKey(); }
1833
1834  static unsigned getHashValue(const CIEKey &Key) {
1835    return static_cast<unsigned>(
1836        hash_combine(Key.Personality, Key.PersonalityEncoding, Key.LsdaEncoding,
1837                     Key.IsSignalFrame, Key.IsSimple, Key.RAReg,
1838                     Key.IsBKeyFrame, Key.IsMTETaggedFrame));
1839  }
1840
1841  static bool isEqual(const CIEKey &LHS, const CIEKey &RHS) {
1842    return LHS.Personality == RHS.Personality &&
1843           LHS.PersonalityEncoding == RHS.PersonalityEncoding &&
1844           LHS.LsdaEncoding == RHS.LsdaEncoding &&
1845           LHS.IsSignalFrame == RHS.IsSignalFrame &&
1846           LHS.IsSimple == RHS.IsSimple && LHS.RAReg == RHS.RAReg &&
1847           LHS.IsBKeyFrame == RHS.IsBKeyFrame &&
1848           LHS.IsMTETaggedFrame == RHS.IsMTETaggedFrame;
1849  }
1850};
1851
1852} // end namespace llvm
1853
1854void MCDwarfFrameEmitter::Emit(MCObjectStreamer &Streamer, MCAsmBackend *MAB,
1855                               bool IsEH) {
1856  MCContext &Context = Streamer.getContext();
1857  const MCObjectFileInfo *MOFI = Context.getObjectFileInfo();
1858  const MCAsmInfo *AsmInfo = Context.getAsmInfo();
1859  FrameEmitterImpl Emitter(IsEH, Streamer);
1860  ArrayRef<MCDwarfFrameInfo> FrameArray = Streamer.getDwarfFrameInfos();
1861
1862  // Emit the compact unwind info if available.
1863  bool NeedsEHFrameSection = !MOFI->getSupportsCompactUnwindWithoutEHFrame();
1864  if (IsEH && MOFI->getCompactUnwindSection()) {
1865    Streamer.generateCompactUnwindEncodings(MAB);
1866    bool SectionEmitted = false;
1867    for (const MCDwarfFrameInfo &Frame : FrameArray) {
1868      if (Frame.CompactUnwindEncoding == 0) continue;
1869      if (!SectionEmitted) {
1870        Streamer.switchSection(MOFI->getCompactUnwindSection());
1871        Streamer.emitValueToAlignment(Align(AsmInfo->getCodePointerSize()));
1872        SectionEmitted = true;
1873      }
1874      NeedsEHFrameSection |=
1875        Frame.CompactUnwindEncoding ==
1876          MOFI->getCompactUnwindDwarfEHFrameOnly();
1877      Emitter.EmitCompactUnwind(Frame);
1878    }
1879  }
1880
1881  // Compact unwind information can be emitted in the eh_frame section or the
1882  // debug_frame section. Skip emitting FDEs and CIEs when the compact unwind
1883  // doesn't need an eh_frame section and the emission location is the eh_frame
1884  // section.
1885  if (!NeedsEHFrameSection && IsEH) return;
1886
1887  MCSection &Section =
1888      IsEH ? *const_cast<MCObjectFileInfo *>(MOFI)->getEHFrameSection()
1889           : *MOFI->getDwarfFrameSection();
1890
1891  Streamer.switchSection(&Section);
1892  MCSymbol *SectionStart = Context.createTempSymbol();
1893  Streamer.emitLabel(SectionStart);
1894
1895  DenseMap<CIEKey, const MCSymbol *> CIEStarts;
1896
1897  const MCSymbol *DummyDebugKey = nullptr;
1898  bool CanOmitDwarf = MOFI->getOmitDwarfIfHaveCompactUnwind();
1899  // Sort the FDEs by their corresponding CIE before we emit them.
1900  // This isn't technically necessary according to the DWARF standard,
1901  // but the Android libunwindstack rejects eh_frame sections where
1902  // an FDE refers to a CIE other than the closest previous CIE.
1903  std::vector<MCDwarfFrameInfo> FrameArrayX(FrameArray.begin(), FrameArray.end());
1904  llvm::stable_sort(FrameArrayX,
1905                    [](const MCDwarfFrameInfo &X, const MCDwarfFrameInfo &Y) {
1906                      return CIEKey(X) < CIEKey(Y);
1907                    });
1908  for (auto I = FrameArrayX.begin(), E = FrameArrayX.end(); I != E;) {
1909    const MCDwarfFrameInfo &Frame = *I;
1910    ++I;
1911    if (CanOmitDwarf && Frame.CompactUnwindEncoding !=
1912          MOFI->getCompactUnwindDwarfEHFrameOnly() && IsEH)
1913      // CIEs and FDEs can be emitted in either the eh_frame section or the
1914      // debug_frame section, on some platforms (e.g. AArch64) the target object
1915      // file supports emitting a compact_unwind section without an associated
1916      // eh_frame section. If the eh_frame section is not needed, and the
1917      // location where the CIEs and FDEs are to be emitted is the eh_frame
1918      // section, do not emit anything.
1919      continue;
1920
1921    CIEKey Key(Frame);
1922    const MCSymbol *&CIEStart = IsEH ? CIEStarts[Key] : DummyDebugKey;
1923    if (!CIEStart)
1924      CIEStart = &Emitter.EmitCIE(Frame);
1925
1926    Emitter.EmitFDE(*CIEStart, Frame, I == E, *SectionStart);
1927  }
1928}
1929
1930void MCDwarfFrameEmitter::encodeAdvanceLoc(MCContext &Context,
1931                                           uint64_t AddrDelta,
1932                                           SmallVectorImpl<char> &Out) {
1933  // Scale the address delta by the minimum instruction length.
1934  AddrDelta = ScaleAddrDelta(Context, AddrDelta);
1935  if (AddrDelta == 0)
1936    return;
1937
1938  llvm::endianness E = Context.getAsmInfo()->isLittleEndian()
1939                           ? llvm::endianness::little
1940                           : llvm::endianness::big;
1941
1942  if (isUIntN(6, AddrDelta)) {
1943    uint8_t Opcode = dwarf::DW_CFA_advance_loc | AddrDelta;
1944    Out.push_back(Opcode);
1945  } else if (isUInt<8>(AddrDelta)) {
1946    Out.push_back(dwarf::DW_CFA_advance_loc1);
1947    Out.push_back(AddrDelta);
1948  } else if (isUInt<16>(AddrDelta)) {
1949    Out.push_back(dwarf::DW_CFA_advance_loc2);
1950    support::endian::write<uint16_t>(Out, AddrDelta, E);
1951  } else {
1952    assert(isUInt<32>(AddrDelta));
1953    Out.push_back(dwarf::DW_CFA_advance_loc4);
1954    support::endian::write<uint32_t>(Out, AddrDelta, E);
1955  }
1956}
1957