lib/MC/MCDwarf.cpp

   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/ADT/ArrayRef.h"
  12 #include "llvm/ADT/DenseMap.h"
  13 #include "llvm/ADT/Hashing.h"
  14 #include "llvm/ADT/Optional.h"
  15 #include "llvm/ADT/STLExtras.h"
  16 #include "llvm/ADT/SmallString.h"
  17 #include "llvm/ADT/SmallVector.h"
  18 #include "llvm/ADT/StringRef.h"
  19 #include "llvm/ADT/Twine.h"
  20 #include "llvm/BinaryFormat/Dwarf.h"
  21 #include "llvm/Config/config.h"
  22 #include "llvm/MC/MCAsmInfo.h"
  23 #include "llvm/MC/MCContext.h"
  24 #include "llvm/MC/MCExpr.h"
  25 #include "llvm/MC/MCObjectFileInfo.h"
  26 #include "llvm/MC/MCObjectStreamer.h"
  27 #include "llvm/MC/MCRegisterInfo.h"
  28 #include "llvm/MC/MCSection.h"
  29 #include "llvm/MC/MCStreamer.h"
  30 #include "llvm/MC/MCSymbol.h"
  31 #include "llvm/MC/StringTableBuilder.h"
  32 #include "llvm/Support/Casting.h"
  33 #include "llvm/Support/Endian.h"
  34 #include "llvm/Support/EndianStream.h"
  35 #include "llvm/Support/ErrorHandling.h"
  36 #include "llvm/Support/LEB128.h"
  37 #include "llvm/Support/MathExtras.h"
  38 #include "llvm/Support/Path.h"
  39 #include "llvm/Support/SourceMgr.h"
  40 #include "llvm/Support/raw_ostream.h"
  41 #include <cassert>
  42 #include <cstdint>
  43 #include <string>
  44 #include <utility>
  45 #include <vector>
  46
  47 using namespace llvm;
  48
  49 /// Manage the .debug_line_str section contents, if we use it.
  50 class llvm::MCDwarfLineStr {
  51   MCSymbol *LineStrLabel = nullptr;
  52   StringTableBuilder LineStrings{StringTableBuilder::DWARF};
  53   bool UseRelocs = false;
  54
  55 public:
  56   /// Construct an instance that can emit .debug_line_str (for use in a normal
  57   /// v5 line table).
  58   explicit MCDwarfLineStr(MCContext &Ctx) {
  59     UseRelocs = Ctx.getAsmInfo()->doesDwarfUseRelocationsAcrossSections();
  60     if (UseRelocs)
  61       LineStrLabel =
  62           Ctx.getObjectFileInfo()->getDwarfLineStrSection()->getBeginSymbol();
  63   }
  64
  65   /// Emit a reference to the string.
  66   void emitRef(MCStreamer *MCOS, StringRef Path);
  67
  68   /// Emit the .debug_line_str section if appropriate.
  69   void emitSection(MCStreamer *MCOS);
  70 };
  71
  72 static inline uint64_t ScaleAddrDelta(MCContext &Context, uint64_t AddrDelta) {
  73   unsigned MinInsnLength = Context.getAsmInfo()->getMinInstAlignment();
  74   if (MinInsnLength == 1)
  75     return AddrDelta;
  76   if (AddrDelta % MinInsnLength != 0) {
  77     // TODO: report this error, but really only once.
  78     ;
  79   }
  80   return AddrDelta / MinInsnLength;
  81 }
  82
  83 //
  84 // This is called when an instruction is assembled into the specified section
  85 // and if there is information from the last .loc directive that has yet to have
  86 // a line entry made for it is made.
  87 //
  88 void MCDwarfLineEntry::Make(MCObjectStreamer *MCOS, MCSection *Section) {
  89   if (!MCOS->getContext().getDwarfLocSeen())
  90     return;
  91
  92   // Create a symbol at in the current section for use in the line entry.
  93   MCSymbol *LineSym = MCOS->getContext().createTempSymbol();
  94   // Set the value of the symbol to use for the MCDwarfLineEntry.
  95   MCOS->EmitLabel(LineSym);
  96
  97   // Get the current .loc info saved in the context.
  98   const MCDwarfLoc &DwarfLoc = MCOS->getContext().getCurrentDwarfLoc();
  99
 100   // Create a (local) line entry with the symbol and the current .loc info.
 101   MCDwarfLineEntry LineEntry(LineSym, DwarfLoc);
 102
 103   // clear DwarfLocSeen saying the current .loc info is now used.
 104   MCOS->getContext().clearDwarfLocSeen();
 105
 106   // Add the line entry to this section's entries.
 107   MCOS->getContext()
 108       .getMCDwarfLineTable(MCOS->getContext().getDwarfCompileUnitID())
 109       .getMCLineSections()
 110       .addLineEntry(LineEntry, Section);
 111 }
 112
 113 //
 114 // This helper routine returns an expression of End - Start + IntVal .
 115 //
 116 static inline const MCExpr *MakeStartMinusEndExpr(const MCStreamer &MCOS,
 117                                                   const MCSymbol &Start,
 118                                                   const MCSymbol &End,
 119                                                   int IntVal) {
 120   MCSymbolRefExpr::VariantKind Variant = MCSymbolRefExpr::VK_None;
 121   const MCExpr *Res =
 122     MCSymbolRefExpr::create(&End, Variant, MCOS.getContext());
 123   const MCExpr *RHS =
 124     MCSymbolRefExpr::create(&Start, Variant, MCOS.getContext());
 125   const MCExpr *Res1 =
 126     MCBinaryExpr::create(MCBinaryExpr::Sub, Res, RHS, MCOS.getContext());
 127   const MCExpr *Res2 =
 128     MCConstantExpr::create(IntVal, MCOS.getContext());
 129   const MCExpr *Res3 =
 130     MCBinaryExpr::create(MCBinaryExpr::Sub, Res1, Res2, MCOS.getContext());
 131   return Res3;
 132 }
 133
 134 //
 135 // This helper routine returns an expression of Start + IntVal .
 136 //
 137 static inline const MCExpr *
 138 makeStartPlusIntExpr(MCContext &Ctx, const MCSymbol &Start, int IntVal) {
 139   MCSymbolRefExpr::VariantKind Variant = MCSymbolRefExpr::VK_None;
 140   const MCExpr *LHS = MCSymbolRefExpr::create(&Start, Variant, Ctx);
 141   const MCExpr *RHS = MCConstantExpr::create(IntVal, Ctx);
 142   const MCExpr *Res = MCBinaryExpr::create(MCBinaryExpr::Add, LHS, RHS, Ctx);
 143   return Res;
 144 }
 145
 146 //
 147 // This emits the Dwarf line table for the specified section from the entries
 148 // in the LineSection.
 149 //
 150 static inline void
 151 EmitDwarfLineTable(MCObjectStreamer *MCOS, MCSection *Section,
 152                    const MCLineSection::MCDwarfLineEntryCollection &LineEntries) {
 153   unsigned FileNum = 1;
 154   unsigned LastLine = 1;
 155   unsigned Column = 0;
 156   unsigned Flags = DWARF2_LINE_DEFAULT_IS_STMT ? DWARF2_FLAG_IS_STMT : 0;
 157   unsigned Isa = 0;
 158   unsigned Discriminator = 0;
 159   MCSymbol *LastLabel = nullptr;
 160
 161   // Loop through each MCDwarfLineEntry and encode the dwarf line number table.
 162   for (const MCDwarfLineEntry &LineEntry : LineEntries) {
 163     int64_t LineDelta = static_cast<int64_t>(LineEntry.getLine()) - LastLine;
 164
 165     if (FileNum != LineEntry.getFileNum()) {
 166       FileNum = LineEntry.getFileNum();
 167       MCOS->EmitIntValue(dwarf::DW_LNS_set_file, 1);
 168       MCOS->EmitULEB128IntValue(FileNum);
 169     }
 170     if (Column != LineEntry.getColumn()) {
 171       Column = LineEntry.getColumn();
 172       MCOS->EmitIntValue(dwarf::DW_LNS_set_column, 1);
 173       MCOS->EmitULEB128IntValue(Column);
 174     }
 175     if (Discriminator != LineEntry.getDiscriminator() &&
 176         MCOS->getContext().getDwarfVersion() >= 4) {
 177       Discriminator = LineEntry.getDiscriminator();
 178       unsigned Size = getULEB128Size(Discriminator);
 179       MCOS->EmitIntValue(dwarf::DW_LNS_extended_op, 1);
 180       MCOS->EmitULEB128IntValue(Size + 1);
 181       MCOS->EmitIntValue(dwarf::DW_LNE_set_discriminator, 1);
 182       MCOS->EmitULEB128IntValue(Discriminator);
 183     }
 184     if (Isa != LineEntry.getIsa()) {
 185       Isa = LineEntry.getIsa();
 186       MCOS->EmitIntValue(dwarf::DW_LNS_set_isa, 1);
 187       MCOS->EmitULEB128IntValue(Isa);
 188     }
 189     if ((LineEntry.getFlags() ^ Flags) & DWARF2_FLAG_IS_STMT) {
 190       Flags = LineEntry.getFlags();
 191       MCOS->EmitIntValue(dwarf::DW_LNS_negate_stmt, 1);
 192     }
 193     if (LineEntry.getFlags() & DWARF2_FLAG_BASIC_BLOCK)
 194       MCOS->EmitIntValue(dwarf::DW_LNS_set_basic_block, 1);
 195     if (LineEntry.getFlags() & DWARF2_FLAG_PROLOGUE_END)
 196       MCOS->EmitIntValue(dwarf::DW_LNS_set_prologue_end, 1);
 197     if (LineEntry.getFlags() & DWARF2_FLAG_EPILOGUE_BEGIN)
 198       MCOS->EmitIntValue(dwarf::DW_LNS_set_epilogue_begin, 1);
 199
 200     MCSymbol *Label = LineEntry.getLabel();
 201
 202     // At this point we want to emit/create the sequence to encode the delta in
 203     // line numbers and the increment of the address from the previous Label
 204     // and the current Label.
 205     const MCAsmInfo *asmInfo = MCOS->getContext().getAsmInfo();
 206     MCOS->EmitDwarfAdvanceLineAddr(LineDelta, LastLabel, Label,
 207                                    asmInfo->getCodePointerSize());
 208
 209     Discriminator = 0;
 210     LastLine = LineEntry.getLine();
 211     LastLabel = Label;
 212   }
 213
 214   // Emit a DW_LNE_end_sequence for the end of the section.
 215   // Use the section end label to compute the address delta and use INT64_MAX
 216   // as the line delta which is the signal that this is actually a
 217   // DW_LNE_end_sequence.
 218   MCSymbol *SectionEnd = MCOS->endSection(Section);
 219
 220   // Switch back the dwarf line section, in case endSection had to switch the
 221   // section.
 222   MCContext &Ctx = MCOS->getContext();
 223   MCOS->SwitchSection(Ctx.getObjectFileInfo()->getDwarfLineSection());
 224
 225   const MCAsmInfo *AsmInfo = Ctx.getAsmInfo();
 226   MCOS->EmitDwarfAdvanceLineAddr(INT64_MAX, LastLabel, SectionEnd,
 227                                  AsmInfo->getCodePointerSize());
 228 }
 229
 230 //
 231 // This emits the Dwarf file and the line tables.
 232 //
 233 void MCDwarfLineTable::Emit(MCObjectStreamer *MCOS,
 234                             MCDwarfLineTableParams Params) {
 235   MCContext &context = MCOS->getContext();
 236
 237   auto &LineTables = context.getMCDwarfLineTables();
 238
 239   // Bail out early so we don't switch to the debug_line section needlessly and
 240   // in doing so create an unnecessary (if empty) section.
 241   if (LineTables.empty())
 242     return;
 243
 244   // In a v5 non-split line table, put the strings in a separate section.
 245   Optional<MCDwarfLineStr> LineStr;
 246   if (context.getDwarfVersion() >= 5)
 247     LineStr = MCDwarfLineStr(context);
 248
 249   // Switch to the section where the table will be emitted into.
 250   MCOS->SwitchSection(context.getObjectFileInfo()->getDwarfLineSection());
 251
 252   // Handle the rest of the Compile Units.
 253   for (const auto &CUIDTablePair : LineTables) {
 254     CUIDTablePair.second.EmitCU(MCOS, Params, LineStr);
 255   }
 256
 257   if (LineStr)
 258     LineStr->emitSection(MCOS);
 259 }
 260
 261 void MCDwarfDwoLineTable::Emit(MCStreamer &MCOS, MCDwarfLineTableParams Params,
 262                                MCSection *Section) const {
 263   if (Header.MCDwarfFiles.empty())
 264     return;
 265   Optional<MCDwarfLineStr> NoLineStr(None);
 266   MCOS.SwitchSection(Section);
 267   MCOS.EmitLabel(Header.Emit(&MCOS, Params, None, NoLineStr).second);
 268 }
 269
 270 std::pair<MCSymbol *, MCSymbol *>
 271 MCDwarfLineTableHeader::Emit(MCStreamer *MCOS, MCDwarfLineTableParams Params,
 272                              Optional<MCDwarfLineStr> &LineStr) const {
 273   static const char StandardOpcodeLengths[] = {
 274       0, // length of DW_LNS_copy
 275       1, // length of DW_LNS_advance_pc
 276       1, // length of DW_LNS_advance_line
 277       1, // length of DW_LNS_set_file
 278       1, // length of DW_LNS_set_column
 279       0, // length of DW_LNS_negate_stmt
 280       0, // length of DW_LNS_set_basic_block
 281       0, // length of DW_LNS_const_add_pc
 282       1, // length of DW_LNS_fixed_advance_pc
 283       0, // length of DW_LNS_set_prologue_end
 284       0, // length of DW_LNS_set_epilogue_begin
 285       1  // DW_LNS_set_isa
 286   };
 287   assert(array_lengthof(StandardOpcodeLengths) >=
 288          (Params.DWARF2LineOpcodeBase - 1U));
 289   return Emit(
 290       MCOS, Params,
 291       makeArrayRef(StandardOpcodeLengths, Params.DWARF2LineOpcodeBase - 1),
 292       LineStr);
 293 }
 294
 295 static const MCExpr *forceExpAbs(MCStreamer &OS, const MCExpr* Expr) {
 296   MCContext &Context = OS.getContext();
 297   assert(!isa<MCSymbolRefExpr>(Expr));
 298   if (Context.getAsmInfo()->hasAggressiveSymbolFolding())
 299     return Expr;
 300
 301   MCSymbol *ABS = Context.createTempSymbol();
 302   OS.EmitAssignment(ABS, Expr);
 303   return MCSymbolRefExpr::create(ABS, Context);
 304 }
 305
 306 static void emitAbsValue(MCStreamer &OS, const MCExpr *Value, unsigned Size) {
 307   const MCExpr *ABS = forceExpAbs(OS, Value);
 308   OS.EmitValue(ABS, Size);
 309 }
 310
 311 void MCDwarfLineStr::emitSection(MCStreamer *MCOS) {
 312   // Switch to the .debug_line_str section.
 313   MCOS->SwitchSection(
 314       MCOS->getContext().getObjectFileInfo()->getDwarfLineStrSection());
 315   // Emit the strings without perturbing the offsets we used.
 316   LineStrings.finalizeInOrder();
 317   SmallString<0> Data;
 318   Data.resize(LineStrings.getSize());
 319   LineStrings.write((uint8_t *)Data.data());
 320   MCOS->EmitBinaryData(Data.str());
 321 }
 322
 323 void MCDwarfLineStr::emitRef(MCStreamer *MCOS, StringRef Path) {
 324   int RefSize = 4; // FIXME: Support DWARF-64
 325   size_t Offset = LineStrings.add(Path);
 326   if (UseRelocs) {
 327     MCContext &Ctx = MCOS->getContext();
 328     MCOS->EmitValue(makeStartPlusIntExpr(Ctx, *LineStrLabel, Offset), RefSize);
 329   } else
 330     MCOS->EmitIntValue(Offset, RefSize);
 331 }
 332
 333 void MCDwarfLineTableHeader::emitV2FileDirTables(MCStreamer *MCOS) const {
 334   // First the directory table.
 335   for (auto &Dir : MCDwarfDirs) {
 336     MCOS->EmitBytes(Dir);                // The DirectoryName, and...
 337     MCOS->EmitBytes(StringRef("\0", 1)); // its null terminator.
 338   }
 339   MCOS->EmitIntValue(0, 1); // Terminate the directory list.
 340
 341   // Second the file table.
 342   for (unsigned i = 1; i < MCDwarfFiles.size(); i++) {
 343     assert(!MCDwarfFiles[i].Name.empty());
 344     MCOS->EmitBytes(MCDwarfFiles[i].Name); // FileName and...
 345     MCOS->EmitBytes(StringRef("\0", 1));   // its null terminator.
 346     MCOS->EmitULEB128IntValue(MCDwarfFiles[i].DirIndex); // Directory number.
 347     MCOS->EmitIntValue(0, 1); // Last modification timestamp (always 0).
 348     MCOS->EmitIntValue(0, 1); // File size (always 0).
 349   }
 350   MCOS->EmitIntValue(0, 1); // Terminate the file list.
 351 }
 352
 353 static void emitOneV5FileEntry(MCStreamer *MCOS, const MCDwarfFile &DwarfFile,
 354                                bool EmitMD5, bool HasSource,
 355                                Optional<MCDwarfLineStr> &LineStr) {
 356   assert(!DwarfFile.Name.empty());
 357   if (LineStr)
 358     LineStr->emitRef(MCOS, DwarfFile.Name);
 359   else {
 360     MCOS->EmitBytes(DwarfFile.Name);     // FileName and...
 361     MCOS->EmitBytes(StringRef("\0", 1)); // its null terminator.
 362   }
 363   MCOS->EmitULEB128IntValue(DwarfFile.DirIndex); // Directory number.
 364   if (EmitMD5) {
 365     MD5::MD5Result *Cksum = DwarfFile.Checksum;
 366     MCOS->EmitBinaryData(
 367         StringRef(reinterpret_cast<const char *>(Cksum->Bytes.data()),
 368                   Cksum->Bytes.size()));
 369   }
 370   if (HasSource) {
 371     if (LineStr)
 372       LineStr->emitRef(MCOS, DwarfFile.Source.getValueOr(StringRef()));
 373     else {
 374       MCOS->EmitBytes(
 375           DwarfFile.Source.getValueOr(StringRef())); // Source and...
 376       MCOS->EmitBytes(StringRef("\0", 1));           // its null terminator.
 377     }
 378   }
 379 }
 380
 381 void MCDwarfLineTableHeader::emitV5FileDirTables(
 382     MCStreamer *MCOS, Optional<MCDwarfLineStr> &LineStr,
 383     StringRef CtxCompilationDir) const {
 384   // The directory format, which is just a list of the directory paths.  In a
 385   // non-split object, these are references to .debug_line_str; in a split
 386   // object, they are inline strings.
 387   MCOS->EmitIntValue(1, 1);
 388   MCOS->EmitULEB128IntValue(dwarf::DW_LNCT_path);
 389   MCOS->EmitULEB128IntValue(LineStr ? dwarf::DW_FORM_line_strp
 390                                     : dwarf::DW_FORM_string);
 391   MCOS->EmitULEB128IntValue(MCDwarfDirs.size() + 1);
 392   // Try not to emit an empty compilation directory.
 393   const StringRef CompDir =
 394       CompilationDir.empty() ? CtxCompilationDir : StringRef(CompilationDir);
 395   if (LineStr) {
 396     // Record path strings, emit references here.
 397     LineStr->emitRef(MCOS, CompDir);
 398     for (const auto &Dir : MCDwarfDirs)
 399       LineStr->emitRef(MCOS, Dir);
 400   } else {
 401     // The list of directory paths.  Compilation directory comes first.
 402     MCOS->EmitBytes(CompDir);
 403     MCOS->EmitBytes(StringRef("\0", 1));
 404     for (const auto &Dir : MCDwarfDirs) {
 405       MCOS->EmitBytes(Dir);                // The DirectoryName, and...
 406       MCOS->EmitBytes(StringRef("\0", 1)); // its null terminator.
 407     }
 408   }
 409
 410   // The file format, which is the inline null-terminated filename and a
 411   // directory index.  We don't track file size/timestamp so don't emit them
 412   // in the v5 table.  Emit MD5 checksums and source if we have them.
 413   uint64_t Entries = 2;
 414   if (HasAllMD5)
 415     Entries += 1;
 416   if (HasSource)
 417     Entries += 1;
 418   MCOS->EmitIntValue(Entries, 1);
 419   MCOS->EmitULEB128IntValue(dwarf::DW_LNCT_path);
 420   MCOS->EmitULEB128IntValue(LineStr ? dwarf::DW_FORM_line_strp
 421                                     : dwarf::DW_FORM_string);
 422   MCOS->EmitULEB128IntValue(dwarf::DW_LNCT_directory_index);
 423   MCOS->EmitULEB128IntValue(dwarf::DW_FORM_udata);
 424   if (HasAllMD5) {
 425     MCOS->EmitULEB128IntValue(dwarf::DW_LNCT_MD5);
 426     MCOS->EmitULEB128IntValue(dwarf::DW_FORM_data16);
 427   }
 428   if (HasSource) {
 429     MCOS->EmitULEB128IntValue(dwarf::DW_LNCT_LLVM_source);
 430     MCOS->EmitULEB128IntValue(LineStr ? dwarf::DW_FORM_line_strp
 431                                       : dwarf::DW_FORM_string);
 432   }
 433   // Then the counted list of files. The root file is file #0, then emit the
 434   // files as provide by .file directives.  To accommodate assembler source
 435   // written for DWARF v4 but trying to emit v5, if we didn't see a root file
 436   // explicitly, replicate file #1.
 437   MCOS->EmitULEB128IntValue(MCDwarfFiles.size());
 438   emitOneV5FileEntry(MCOS, RootFile.Name.empty() ? MCDwarfFiles[1] : RootFile,
 439                      HasAllMD5, HasSource, LineStr);
 440   for (unsigned i = 1; i < MCDwarfFiles.size(); ++i)
 441     emitOneV5FileEntry(MCOS, MCDwarfFiles[i], HasAllMD5, HasSource, LineStr);
 442 }
 443
 444 std::pair<MCSymbol *, MCSymbol *>
 445 MCDwarfLineTableHeader::Emit(MCStreamer *MCOS, MCDwarfLineTableParams Params,
 446                              ArrayRef<char> StandardOpcodeLengths,
 447                              Optional<MCDwarfLineStr> &LineStr) const {
 448   MCContext &context = MCOS->getContext();
 449
 450   // Create a symbol at the beginning of the line table.
 451   MCSymbol *LineStartSym = Label;
 452   if (!LineStartSym)
 453     LineStartSym = context.createTempSymbol();
 454   // Set the value of the symbol, as we are at the start of the line table.
 455   MCOS->EmitLabel(LineStartSym);
 456
 457   // Create a symbol for the end of the section (to be set when we get there).
 458   MCSymbol *LineEndSym = context.createTempSymbol();
 459
 460   // The first 4 bytes is the total length of the information for this
 461   // compilation unit (not including these 4 bytes for the length).
 462   emitAbsValue(*MCOS,
 463                MakeStartMinusEndExpr(*MCOS, *LineStartSym, *LineEndSym, 4), 4);
 464
 465   // Next 2 bytes is the Version.
 466   unsigned LineTableVersion = context.getDwarfVersion();
 467   MCOS->EmitIntValue(LineTableVersion, 2);
 468
 469   // Keep track of the bytes between the very start and where the header length
 470   // comes out.
 471   unsigned PreHeaderLengthBytes = 4 + 2;
 472
 473   // In v5, we get address info next.
 474   if (LineTableVersion >= 5) {
 475     MCOS->EmitIntValue(context.getAsmInfo()->getCodePointerSize(), 1);
 476     MCOS->EmitIntValue(0, 1); // Segment selector; same as EmitGenDwarfAranges.
 477     PreHeaderLengthBytes += 2;
 478   }
 479
 480   // Create a symbol for the end of the prologue (to be set when we get there).
 481   MCSymbol *ProEndSym = context.createTempSymbol(); // Lprologue_end
 482
 483   // Length of the prologue, is the next 4 bytes.  This is actually the length
 484   // from after the length word, to the end of the prologue.
 485   emitAbsValue(*MCOS,
 486                MakeStartMinusEndExpr(*MCOS, *LineStartSym, *ProEndSym,
 487                                      (PreHeaderLengthBytes + 4)),
 488                4);
 489
 490   // Parameters of the state machine, are next.
 491   MCOS->EmitIntValue(context.getAsmInfo()->getMinInstAlignment(), 1);
 492   // maximum_operations_per_instruction
 493   // For non-VLIW architectures this field is always 1.
 494   // FIXME: VLIW architectures need to update this field accordingly.
 495   if (LineTableVersion >= 4)
 496     MCOS->EmitIntValue(1, 1);
 497   MCOS->EmitIntValue(DWARF2_LINE_DEFAULT_IS_STMT, 1);
 498   MCOS->EmitIntValue(Params.DWARF2LineBase, 1);
 499   MCOS->EmitIntValue(Params.DWARF2LineRange, 1);
 500   MCOS->EmitIntValue(StandardOpcodeLengths.size() + 1, 1);
 501
 502   // Standard opcode lengths
 503   for (char Length : StandardOpcodeLengths)
 504     MCOS->EmitIntValue(Length, 1);
 505
 506   // Put out the directory and file tables.  The formats vary depending on
 507   // the version.
 508   if (LineTableVersion >= 5)
 509     emitV5FileDirTables(MCOS, LineStr, context.getCompilationDir());
 510   else
 511     emitV2FileDirTables(MCOS);
 512
 513   // This is the end of the prologue, so set the value of the symbol at the
 514   // end of the prologue (that was used in a previous expression).
 515   MCOS->EmitLabel(ProEndSym);
 516
 517   return std::make_pair(LineStartSym, LineEndSym);
 518 }
 519
 520 void MCDwarfLineTable::EmitCU(MCObjectStreamer *MCOS,
 521                               MCDwarfLineTableParams Params,
 522                               Optional<MCDwarfLineStr> &LineStr) const {
 523   MCSymbol *LineEndSym = Header.Emit(MCOS, Params, LineStr).second;
 524
 525   // Put out the line tables.
 526   for (const auto &LineSec : MCLineSections.getMCLineEntries())
 527     EmitDwarfLineTable(MCOS, LineSec.first, LineSec.second);
 528
 529   // This is the end of the section, so set the value of the symbol at the end
 530   // of this section (that was used in a previous expression).
 531   MCOS->EmitLabel(LineEndSym);
 532 }
 533
 534 Expected<unsigned> MCDwarfLineTable::tryGetFile(StringRef &Directory,
 535                                                 StringRef &FileName,
 536                                                 MD5::MD5Result *Checksum,
 537                                                 Optional<StringRef> Source,
 538                                                 unsigned FileNumber) {
 539   return Header.tryGetFile(Directory, FileName, Checksum, Source, FileNumber);
 540 }
 541
 542 Expected<unsigned>
 543 MCDwarfLineTableHeader::tryGetFile(StringRef &Directory,
 544                                    StringRef &FileName,
 545                                    MD5::MD5Result *Checksum,
 546                                    Optional<StringRef> &Source,
 547                                    unsigned FileNumber) {
 548   if (Directory == CompilationDir)
 549     Directory = "";
 550   if (FileName.empty()) {
 551     FileName = "<stdin>";
 552     Directory = "";
 553   }
 554   assert(!FileName.empty());
 555   // Keep track of whether any or all files have an MD5 checksum.
 556   // If any files have embedded source, they all must.
 557   if (MCDwarfFiles.empty()) {
 558     trackMD5Usage(Checksum);
 559     HasSource = (Source != None);
 560   }
 561   if (FileNumber == 0) {
 562     // File numbers start with 1 and/or after any file numbers
 563     // allocated by inline-assembler .file directives.
 564     FileNumber = MCDwarfFiles.empty() ? 1 : MCDwarfFiles.size();
 565     SmallString<256> Buffer;
 566     auto IterBool = SourceIdMap.insert(
 567         std::make_pair((Directory + Twine('\0') + FileName).toStringRef(Buffer),
 568                        FileNumber));
 569     if (!IterBool.second)
 570       return IterBool.first->second;
 571   }
 572   // Make space for this FileNumber in the MCDwarfFiles vector if needed.
 573   if (FileNumber >= MCDwarfFiles.size())
 574     MCDwarfFiles.resize(FileNumber + 1);
 575
 576   // Get the new MCDwarfFile slot for this FileNumber.
 577   MCDwarfFile &File = MCDwarfFiles[FileNumber];
 578
 579   // It is an error to see the same number more than once.
 580   if (!File.Name.empty())
 581     return make_error<StringError>("file number already allocated",
 582                                    inconvertibleErrorCode());
 583
 584   // If any files have embedded source, they all must.
 585   if (HasSource != (Source != None))
 586     return make_error<StringError>("inconsistent use of embedded source",
 587                                    inconvertibleErrorCode());
 588
 589   if (Directory.empty()) {
 590     // Separate the directory part from the basename of the FileName.
 591     StringRef tFileName = sys::path::filename(FileName);
 592     if (!tFileName.empty()) {
 593       Directory = sys::path::parent_path(FileName);
 594       if (!Directory.empty())
 595         FileName = tFileName;
 596     }
 597   }
 598
 599   // Find or make an entry in the MCDwarfDirs vector for this Directory.
 600   // Capture directory name.
 601   unsigned DirIndex;
 602   if (Directory.empty()) {
 603     // For FileNames with no directories a DirIndex of 0 is used.
 604     DirIndex = 0;
 605   } else {
 606     DirIndex = 0;
 607     for (unsigned End = MCDwarfDirs.size(); DirIndex < End; DirIndex++) {
 608       if (Directory == MCDwarfDirs[DirIndex])
 609         break;
 610     }
 611     if (DirIndex >= MCDwarfDirs.size())
 612       MCDwarfDirs.push_back(Directory);
 613     // The DirIndex is one based, as DirIndex of 0 is used for FileNames with
 614     // no directories.  MCDwarfDirs[] is unlike MCDwarfFiles[] in that the
 615     // directory names are stored at MCDwarfDirs[DirIndex-1] where FileNames
 616     // are stored at MCDwarfFiles[FileNumber].Name .
 617     DirIndex++;
 618   }
 619
 620   File.Name = FileName;
 621   File.DirIndex = DirIndex;
 622   File.Checksum = Checksum;
 623   trackMD5Usage(Checksum);
 624   File.Source = Source;
 625   if (Source)
 626     HasSource = true;
 627
 628   // return the allocated FileNumber.
 629   return FileNumber;
 630 }
 631
 632 /// Utility function to emit the encoding to a streamer.
 633 void MCDwarfLineAddr::Emit(MCStreamer *MCOS, MCDwarfLineTableParams Params,
 634                            int64_t LineDelta, uint64_t AddrDelta) {
 635   MCContext &Context = MCOS->getContext();
 636   SmallString<256> Tmp;
 637   raw_svector_ostream OS(Tmp);
 638   MCDwarfLineAddr::Encode(Context, Params, LineDelta, AddrDelta, OS);
 639   MCOS->EmitBytes(OS.str());
 640 }
 641
 642 /// Given a special op, return the address skip amount (in units of
 643 /// DWARF2_LINE_MIN_INSN_LENGTH).
 644 static uint64_t SpecialAddr(MCDwarfLineTableParams Params, uint64_t op) {
 645   return (op - Params.DWARF2LineOpcodeBase) / Params.DWARF2LineRange;
 646 }
 647
 648 /// Utility function to encode a Dwarf pair of LineDelta and AddrDeltas.
 649 void MCDwarfLineAddr::Encode(MCContext &Context, MCDwarfLineTableParams Params,
 650                              int64_t LineDelta, uint64_t AddrDelta,
 651                              raw_ostream &OS) {
 652   uint64_t Temp, Opcode;
 653   bool NeedCopy = false;
 654
 655   // The maximum address skip amount that can be encoded with a special op.
 656   uint64_t MaxSpecialAddrDelta = SpecialAddr(Params, 255);
 657
 658   // Scale the address delta by the minimum instruction length.
 659   AddrDelta = ScaleAddrDelta(Context, AddrDelta);
 660
 661   // A LineDelta of INT64_MAX is a signal that this is actually a
 662   // DW_LNE_end_sequence. We cannot use special opcodes here, since we want the
 663   // end_sequence to emit the matrix entry.
 664   if (LineDelta == INT64_MAX) {
 665     if (AddrDelta == MaxSpecialAddrDelta)
 666       OS << char(dwarf::DW_LNS_const_add_pc);
 667     else if (AddrDelta) {
 668       OS << char(dwarf::DW_LNS_advance_pc);
 669       encodeULEB128(AddrDelta, OS);
 670     }
 671     OS << char(dwarf::DW_LNS_extended_op);
 672     OS << char(1);
 673     OS << char(dwarf::DW_LNE_end_sequence);
 674     return;
 675   }
 676
 677   // Bias the line delta by the base.
 678   Temp = LineDelta - Params.DWARF2LineBase;
 679
 680   // If the line increment is out of range of a special opcode, we must encode
 681   // it with DW_LNS_advance_line.
 682   if (Temp >= Params.DWARF2LineRange ||
 683       Temp + Params.DWARF2LineOpcodeBase > 255) {
 684     OS << char(dwarf::DW_LNS_advance_line);
 685     encodeSLEB128(LineDelta, OS);
 686
 687     LineDelta = 0;
 688     Temp = 0 - Params.DWARF2LineBase;
 689     NeedCopy = true;
 690   }
 691
 692   // Use DW_LNS_copy instead of a "line +0, addr +0" special opcode.
 693   if (LineDelta == 0 && AddrDelta == 0) {
 694     OS << char(dwarf::DW_LNS_copy);
 695     return;
 696   }
 697
 698   // Bias the opcode by the special opcode base.
 699   Temp += Params.DWARF2LineOpcodeBase;
 700
 701   // Avoid overflow when addr_delta is large.
 702   if (AddrDelta < 256 + MaxSpecialAddrDelta) {
 703     // Try using a special opcode.
 704     Opcode = Temp + AddrDelta * Params.DWARF2LineRange;
 705     if (Opcode <= 255) {
 706       OS << char(Opcode);
 707       return;
 708     }
 709
 710     // Try using DW_LNS_const_add_pc followed by special op.
 711     Opcode = Temp + (AddrDelta - MaxSpecialAddrDelta) * Params.DWARF2LineRange;
 712     if (Opcode <= 255) {
 713       OS << char(dwarf::DW_LNS_const_add_pc);
 714       OS << char(Opcode);
 715       return;
 716     }
 717   }
 718
 719   // Otherwise use DW_LNS_advance_pc.
 720   OS << char(dwarf::DW_LNS_advance_pc);
 721   encodeULEB128(AddrDelta, OS);
 722
 723   if (NeedCopy)
 724     OS << char(dwarf::DW_LNS_copy);
 725   else {
 726     assert(Temp <= 255 && "Buggy special opcode encoding.");
 727     OS << char(Temp);
 728   }
 729 }
 730
 731 bool MCDwarfLineAddr::FixedEncode(MCContext &Context,
 732                                   MCDwarfLineTableParams Params,
 733                                   int64_t LineDelta, uint64_t AddrDelta,
 734                                   raw_ostream &OS,
 735                                   uint32_t *Offset, uint32_t *Size) {
 736   if (LineDelta != INT64_MAX) {
 737     OS << char(dwarf::DW_LNS_advance_line);
 738     encodeSLEB128(LineDelta, OS);
 739   }
 740
 741   // Use address delta to adjust address or use absolute address to adjust
 742   // address.
 743   bool SetDelta;
 744   // According to DWARF spec., the DW_LNS_fixed_advance_pc opcode takes a
 745   // single uhalf (unencoded) operand. So, the maximum value of AddrDelta
 746   // is 65535. We set a conservative upper bound for it for relaxation.
 747   if (AddrDelta > 60000) {
 748     const MCAsmInfo *asmInfo = Context.getAsmInfo();
 749     unsigned AddrSize = asmInfo->getCodePointerSize();
 750
 751     OS << char(dwarf::DW_LNS_extended_op);
 752     encodeULEB128(1 + AddrSize, OS);
 753     OS << char(dwarf::DW_LNE_set_address);
 754     // Generate fixup for the address.
 755     *Offset = OS.tell();
 756     *Size = AddrSize;
 757     SetDelta = false;
 758     std::vector<uint8_t> FillData;
 759     FillData.insert(FillData.begin(), AddrSize, 0);
 760     OS.write(reinterpret_cast<char *>(FillData.data()), AddrSize);
 761   } else {
 762     OS << char(dwarf::DW_LNS_fixed_advance_pc);
 763     // Generate fixup for 2-bytes address delta.
 764     *Offset = OS.tell();
 765     *Size = 2;
 766     SetDelta = true;
 767     OS << char(0);
 768     OS << char(0);
 769   }
 770
 771   if (LineDelta == INT64_MAX) {
 772     OS << char(dwarf::DW_LNS_extended_op);
 773     OS << char(1);
 774     OS << char(dwarf::DW_LNE_end_sequence);
 775   } else {
 776     OS << char(dwarf::DW_LNS_copy);
 777   }
 778
 779   return SetDelta;
 780 }
 781
 782 // Utility function to write a tuple for .debug_abbrev.
 783 static void EmitAbbrev(MCStreamer *MCOS, uint64_t Name, uint64_t Form) {
 784   MCOS->EmitULEB128IntValue(Name);
 785   MCOS->EmitULEB128IntValue(Form);
 786 }
 787
 788 // When generating dwarf for assembly source files this emits
 789 // the data for .debug_abbrev section which contains three DIEs.
 790 static void EmitGenDwarfAbbrev(MCStreamer *MCOS) {
 791   MCContext &context = MCOS->getContext();
 792   MCOS->SwitchSection(context.getObjectFileInfo()->getDwarfAbbrevSection());
 793
 794   // DW_TAG_compile_unit DIE abbrev (1).
 795   MCOS->EmitULEB128IntValue(1);
 796   MCOS->EmitULEB128IntValue(dwarf::DW_TAG_compile_unit);
 797   MCOS->EmitIntValue(dwarf::DW_CHILDREN_yes, 1);
 798   EmitAbbrev(MCOS, dwarf::DW_AT_stmt_list, context.getDwarfVersion() >= 4
 799                                                ? dwarf::DW_FORM_sec_offset
 800                                                : dwarf::DW_FORM_data4);
 801   if (context.getGenDwarfSectionSyms().size() > 1 &&
 802       context.getDwarfVersion() >= 3) {
 803     EmitAbbrev(MCOS, dwarf::DW_AT_ranges, context.getDwarfVersion() >= 4
 804                                               ? dwarf::DW_FORM_sec_offset
 805                                               : dwarf::DW_FORM_data4);
 806   } else {
 807     EmitAbbrev(MCOS, dwarf::DW_AT_low_pc, dwarf::DW_FORM_addr);
 808     EmitAbbrev(MCOS, dwarf::DW_AT_high_pc, dwarf::DW_FORM_addr);
 809   }
 810   EmitAbbrev(MCOS, dwarf::DW_AT_name, dwarf::DW_FORM_string);
 811   if (!context.getCompilationDir().empty())
 812     EmitAbbrev(MCOS, dwarf::DW_AT_comp_dir, dwarf::DW_FORM_string);
 813   StringRef DwarfDebugFlags = context.getDwarfDebugFlags();
 814   if (!DwarfDebugFlags.empty())
 815     EmitAbbrev(MCOS, dwarf::DW_AT_APPLE_flags, dwarf::DW_FORM_string);
 816   EmitAbbrev(MCOS, dwarf::DW_AT_producer, dwarf::DW_FORM_string);
 817   EmitAbbrev(MCOS, dwarf::DW_AT_language, dwarf::DW_FORM_data2);
 818   EmitAbbrev(MCOS, 0, 0);
 819
 820   // DW_TAG_label DIE abbrev (2).
 821   MCOS->EmitULEB128IntValue(2);
 822   MCOS->EmitULEB128IntValue(dwarf::DW_TAG_label);
 823   MCOS->EmitIntValue(dwarf::DW_CHILDREN_yes, 1);
 824   EmitAbbrev(MCOS, dwarf::DW_AT_name, dwarf::DW_FORM_string);
 825   EmitAbbrev(MCOS, dwarf::DW_AT_decl_file, dwarf::DW_FORM_data4);
 826   EmitAbbrev(MCOS, dwarf::DW_AT_decl_line, dwarf::DW_FORM_data4);
 827   EmitAbbrev(MCOS, dwarf::DW_AT_low_pc, dwarf::DW_FORM_addr);
 828   EmitAbbrev(MCOS, dwarf::DW_AT_prototyped, dwarf::DW_FORM_flag);
 829   EmitAbbrev(MCOS, 0, 0);
 830
 831   // DW_TAG_unspecified_parameters DIE abbrev (3).
 832   MCOS->EmitULEB128IntValue(3);
 833   MCOS->EmitULEB128IntValue(dwarf::DW_TAG_unspecified_parameters);
 834   MCOS->EmitIntValue(dwarf::DW_CHILDREN_no, 1);
 835   EmitAbbrev(MCOS, 0, 0);
 836
 837   // Terminate the abbreviations for this compilation unit.
 838   MCOS->EmitIntValue(0, 1);
 839 }
 840
 841 // When generating dwarf for assembly source files this emits the data for
 842 // .debug_aranges section. This section contains a header and a table of pairs
 843 // of PointerSize'ed values for the address and size of section(s) with line
 844 // table entries.
 845 static void EmitGenDwarfAranges(MCStreamer *MCOS,
 846                                 const MCSymbol *InfoSectionSymbol) {
 847   MCContext &context = MCOS->getContext();
 848
 849   auto &Sections = context.getGenDwarfSectionSyms();
 850
 851   MCOS->SwitchSection(context.getObjectFileInfo()->getDwarfARangesSection());
 852
 853   // This will be the length of the .debug_aranges section, first account for
 854   // the size of each item in the header (see below where we emit these items).
 855   int Length = 4 + 2 + 4 + 1 + 1;
 856
 857   // Figure the padding after the header before the table of address and size
 858   // pairs who's values are PointerSize'ed.
 859   const MCAsmInfo *asmInfo = context.getAsmInfo();
 860   int AddrSize = asmInfo->getCodePointerSize();
 861   int Pad = 2 * AddrSize - (Length & (2 * AddrSize - 1));
 862   if (Pad == 2 * AddrSize)
 863     Pad = 0;
 864   Length += Pad;
 865
 866   // Add the size of the pair of PointerSize'ed values for the address and size
 867   // of each section we have in the table.
 868   Length += 2 * AddrSize * Sections.size();
 869   // And the pair of terminating zeros.
 870   Length += 2 * AddrSize;
 871
 872   // Emit the header for this section.
 873   // The 4 byte length not including the 4 byte value for the length.
 874   MCOS->EmitIntValue(Length - 4, 4);
 875   // The 2 byte version, which is 2.
 876   MCOS->EmitIntValue(2, 2);
 877   // The 4 byte offset to the compile unit in the .debug_info from the start
 878   // of the .debug_info.
 879   if (InfoSectionSymbol)
 880     MCOS->EmitSymbolValue(InfoSectionSymbol, 4,
 881                           asmInfo->needsDwarfSectionOffsetDirective());
 882   else
 883     MCOS->EmitIntValue(0, 4);
 884   // The 1 byte size of an address.
 885   MCOS->EmitIntValue(AddrSize, 1);
 886   // The 1 byte size of a segment descriptor, we use a value of zero.
 887   MCOS->EmitIntValue(0, 1);
 888   // Align the header with the padding if needed, before we put out the table.
 889   for(int i = 0; i < Pad; i++)
 890     MCOS->EmitIntValue(0, 1);
 891
 892   // Now emit the table of pairs of PointerSize'ed values for the section
 893   // addresses and sizes.
 894   for (MCSection *Sec : Sections) {
 895     const MCSymbol *StartSymbol = Sec->getBeginSymbol();
 896     MCSymbol *EndSymbol = Sec->getEndSymbol(context);
 897     assert(StartSymbol && "StartSymbol must not be NULL");
 898     assert(EndSymbol && "EndSymbol must not be NULL");
 899
 900     const MCExpr *Addr = MCSymbolRefExpr::create(
 901       StartSymbol, MCSymbolRefExpr::VK_None, context);
 902     const MCExpr *Size = MakeStartMinusEndExpr(*MCOS,
 903       *StartSymbol, *EndSymbol, 0);
 904     MCOS->EmitValue(Addr, AddrSize);
 905     emitAbsValue(*MCOS, Size, AddrSize);
 906   }
 907
 908   // And finally the pair of terminating zeros.
 909   MCOS->EmitIntValue(0, AddrSize);
 910   MCOS->EmitIntValue(0, AddrSize);
 911 }
 912
 913 // When generating dwarf for assembly source files this emits the data for
 914 // .debug_info section which contains three parts.  The header, the compile_unit
 915 // DIE and a list of label DIEs.
 916 static void EmitGenDwarfInfo(MCStreamer *MCOS,
 917                              const MCSymbol *AbbrevSectionSymbol,
 918                              const MCSymbol *LineSectionSymbol,
 919                              const MCSymbol *RangesSectionSymbol) {
 920   MCContext &context = MCOS->getContext();
 921
 922   MCOS->SwitchSection(context.getObjectFileInfo()->getDwarfInfoSection());
 923
 924   // Create a symbol at the start and end of this section used in here for the
 925   // expression to calculate the length in the header.
 926   MCSymbol *InfoStart = context.createTempSymbol();
 927   MCOS->EmitLabel(InfoStart);
 928   MCSymbol *InfoEnd = context.createTempSymbol();
 929
 930   // First part: the header.
 931
 932   // The 4 byte total length of the information for this compilation unit, not
 933   // including these 4 bytes.
 934   const MCExpr *Length = MakeStartMinusEndExpr(*MCOS, *InfoStart, *InfoEnd, 4);
 935   emitAbsValue(*MCOS, Length, 4);
 936
 937   // The 2 byte DWARF version.
 938   MCOS->EmitIntValue(context.getDwarfVersion(), 2);
 939
 940   // The DWARF v5 header has unit type, address size, abbrev offset.
 941   // Earlier versions have abbrev offset, address size.
 942   const MCAsmInfo &AsmInfo = *context.getAsmInfo();
 943   int AddrSize = AsmInfo.getCodePointerSize();
 944   if (context.getDwarfVersion() >= 5) {
 945     MCOS->EmitIntValue(dwarf::DW_UT_compile, 1);
 946     MCOS->EmitIntValue(AddrSize, 1);
 947   }
 948   // The 4 byte offset to the debug abbrevs from the start of the .debug_abbrev,
 949   // it is at the start of that section so this is zero.
 950   if (AbbrevSectionSymbol == nullptr)
 951     MCOS->EmitIntValue(0, 4);
 952   else
 953     MCOS->EmitSymbolValue(AbbrevSectionSymbol, 4,
 954                           AsmInfo.needsDwarfSectionOffsetDirective());
 955   if (context.getDwarfVersion() <= 4)
 956     MCOS->EmitIntValue(AddrSize, 1);
 957
 958   // Second part: the compile_unit DIE.
 959
 960   // The DW_TAG_compile_unit DIE abbrev (1).
 961   MCOS->EmitULEB128IntValue(1);
 962
 963   // DW_AT_stmt_list, a 4 byte offset from the start of the .debug_line section,
 964   // which is at the start of that section so this is zero.
 965   if (LineSectionSymbol)
 966     MCOS->EmitSymbolValue(LineSectionSymbol, 4,
 967                           AsmInfo.needsDwarfSectionOffsetDirective());
 968   else
 969     MCOS->EmitIntValue(0, 4);
 970
 971   if (RangesSectionSymbol) {
 972     // There are multiple sections containing code, so we must use the
 973     // .debug_ranges sections.
 974
 975     // AT_ranges, the 4 byte offset from the start of the .debug_ranges section
 976     // to the address range list for this compilation unit.
 977     MCOS->EmitSymbolValue(RangesSectionSymbol, 4);
 978   } else {
 979     // If we only have one non-empty code section, we can use the simpler
 980     // AT_low_pc and AT_high_pc attributes.
 981
 982     // Find the first (and only) non-empty text section
 983     auto &Sections = context.getGenDwarfSectionSyms();
 984     const auto TextSection = Sections.begin();
 985     assert(TextSection != Sections.end() && "No text section found");
 986
 987     MCSymbol *StartSymbol = (*TextSection)->getBeginSymbol();
 988     MCSymbol *EndSymbol = (*TextSection)->getEndSymbol(context);
 989     assert(StartSymbol && "StartSymbol must not be NULL");
 990     assert(EndSymbol && "EndSymbol must not be NULL");
 991
 992     // AT_low_pc, the first address of the default .text section.
 993     const MCExpr *Start = MCSymbolRefExpr::create(
 994         StartSymbol, MCSymbolRefExpr::VK_None, context);
 995     MCOS->EmitValue(Start, AddrSize);
 996
 997     // AT_high_pc, the last address of the default .text section.
 998     const MCExpr *End = MCSymbolRefExpr::create(
 999       EndSymbol, MCSymbolRefExpr::VK_None, context);
1000     MCOS->EmitValue(End, AddrSize);
1001   }
1002
1003   // AT_name, the name of the source file.  Reconstruct from the first directory
1004   // and file table entries.
1005   const SmallVectorImpl<std::string> &MCDwarfDirs = context.getMCDwarfDirs();
1006   if (MCDwarfDirs.size() > 0) {
1007     MCOS->EmitBytes(MCDwarfDirs[0]);
1008     MCOS->EmitBytes(sys::path::get_separator());
1009   }
1010   const SmallVectorImpl<MCDwarfFile> &MCDwarfFiles =
1011     MCOS->getContext().getMCDwarfFiles();
1012   MCOS->EmitBytes(MCDwarfFiles[1].Name);
1013   MCOS->EmitIntValue(0, 1); // NULL byte to terminate the string.
1014
1015   // AT_comp_dir, the working directory the assembly was done in.
1016   if (!context.getCompilationDir().empty()) {
1017     MCOS->EmitBytes(context.getCompilationDir());
1018     MCOS->EmitIntValue(0, 1); // NULL byte to terminate the string.
1019   }
1020
1021   // AT_APPLE_flags, the command line arguments of the assembler tool.
1022   StringRef DwarfDebugFlags = context.getDwarfDebugFlags();
1023   if (!DwarfDebugFlags.empty()){
1024     MCOS->EmitBytes(DwarfDebugFlags);
1025     MCOS->EmitIntValue(0, 1); // NULL byte to terminate the string.
1026   }
1027
1028   // AT_producer, the version of the assembler tool.
1029   StringRef DwarfDebugProducer = context.getDwarfDebugProducer();
1030   if (!DwarfDebugProducer.empty())
1031     MCOS->EmitBytes(DwarfDebugProducer);
1032   else
1033     MCOS->EmitBytes(StringRef("llvm-mc (based on LLVM " PACKAGE_VERSION ")"));
1034   MCOS->EmitIntValue(0, 1); // NULL byte to terminate the string.
1035
1036   // AT_language, a 4 byte value.  We use DW_LANG_Mips_Assembler as the dwarf2
1037   // draft has no standard code for assembler.
1038   MCOS->EmitIntValue(dwarf::DW_LANG_Mips_Assembler, 2);
1039
1040   // Third part: the list of label DIEs.
1041
1042   // Loop on saved info for dwarf labels and create the DIEs for them.
1043   const std::vector<MCGenDwarfLabelEntry> &Entries =
1044       MCOS->getContext().getMCGenDwarfLabelEntries();
1045   for (const auto &Entry : Entries) {
1046     // The DW_TAG_label DIE abbrev (2).
1047     MCOS->EmitULEB128IntValue(2);
1048
1049     // AT_name, of the label without any leading underbar.
1050     MCOS->EmitBytes(Entry.getName());
1051     MCOS->EmitIntValue(0, 1); // NULL byte to terminate the string.
1052
1053     // AT_decl_file, index into the file table.
1054     MCOS->EmitIntValue(Entry.getFileNumber(), 4);
1055
1056     // AT_decl_line, source line number.
1057     MCOS->EmitIntValue(Entry.getLineNumber(), 4);
1058
1059     // AT_low_pc, start address of the label.
1060     const MCExpr *AT_low_pc = MCSymbolRefExpr::create(Entry.getLabel(),
1061                                              MCSymbolRefExpr::VK_None, context);
1062     MCOS->EmitValue(AT_low_pc, AddrSize);
1063
1064     // DW_AT_prototyped, a one byte flag value of 0 saying we have no prototype.
1065     MCOS->EmitIntValue(0, 1);
1066
1067     // The DW_TAG_unspecified_parameters DIE abbrev (3).
1068     MCOS->EmitULEB128IntValue(3);
1069
1070     // Add the NULL DIE terminating the DW_TAG_unspecified_parameters DIE's.
1071     MCOS->EmitIntValue(0, 1);
1072   }
1073
1074   // Add the NULL DIE terminating the Compile Unit DIE's.
1075   MCOS->EmitIntValue(0, 1);
1076
1077   // Now set the value of the symbol at the end of the info section.
1078   MCOS->EmitLabel(InfoEnd);
1079 }
1080
1081 // When generating dwarf for assembly source files this emits the data for
1082 // .debug_ranges section. We only emit one range list, which spans all of the
1083 // executable sections of this file.
1084 static void EmitGenDwarfRanges(MCStreamer *MCOS) {
1085   MCContext &context = MCOS->getContext();
1086   auto &Sections = context.getGenDwarfSectionSyms();
1087
1088   const MCAsmInfo *AsmInfo = context.getAsmInfo();
1089   int AddrSize = AsmInfo->getCodePointerSize();
1090
1091   MCOS->SwitchSection(context.getObjectFileInfo()->getDwarfRangesSection());
1092
1093   for (MCSection *Sec : Sections) {
1094     const MCSymbol *StartSymbol = Sec->getBeginSymbol();
1095     MCSymbol *EndSymbol = Sec->getEndSymbol(context);
1096     assert(StartSymbol && "StartSymbol must not be NULL");
1097     assert(EndSymbol && "EndSymbol must not be NULL");
1098
1099     // Emit a base address selection entry for the start of this section
1100     const MCExpr *SectionStartAddr = MCSymbolRefExpr::create(
1101       StartSymbol, MCSymbolRefExpr::VK_None, context);
1102     MCOS->emitFill(AddrSize, 0xFF);
1103     MCOS->EmitValue(SectionStartAddr, AddrSize);
1104
1105     // Emit a range list entry spanning this section
1106     const MCExpr *SectionSize = MakeStartMinusEndExpr(*MCOS,
1107       *StartSymbol, *EndSymbol, 0);
1108     MCOS->EmitIntValue(0, AddrSize);
1109     emitAbsValue(*MCOS, SectionSize, AddrSize);
1110   }
1111
1112   // Emit end of list entry
1113   MCOS->EmitIntValue(0, AddrSize);
1114   MCOS->EmitIntValue(0, AddrSize);
1115 }
1116
1117 //
1118 // When generating dwarf for assembly source files this emits the Dwarf
1119 // sections.
1120 //
1121 void MCGenDwarfInfo::Emit(MCStreamer *MCOS) {
1122   MCContext &context = MCOS->getContext();
1123
1124   // Create the dwarf sections in this order (.debug_line already created).
1125   const MCAsmInfo *AsmInfo = context.getAsmInfo();
1126   bool CreateDwarfSectionSymbols =
1127       AsmInfo->doesDwarfUseRelocationsAcrossSections();
1128   MCSymbol *LineSectionSymbol = nullptr;
1129   if (CreateDwarfSectionSymbols)
1130     LineSectionSymbol = MCOS->getDwarfLineTableSymbol(0);
1131   MCSymbol *AbbrevSectionSymbol = nullptr;
1132   MCSymbol *InfoSectionSymbol = nullptr;
1133   MCSymbol *RangesSectionSymbol = nullptr;
1134
1135   // Create end symbols for each section, and remove empty sections
1136   MCOS->getContext().finalizeDwarfSections(*MCOS);
1137
1138   // If there are no sections to generate debug info for, we don't need
1139   // to do anything
1140   if (MCOS->getContext().getGenDwarfSectionSyms().empty())
1141     return;
1142
1143   // We only use the .debug_ranges section if we have multiple code sections,
1144   // and we are emitting a DWARF version which supports it.
1145   const bool UseRangesSection =
1146       MCOS->getContext().getGenDwarfSectionSyms().size() > 1 &&
1147       MCOS->getContext().getDwarfVersion() >= 3;
1148   CreateDwarfSectionSymbols |= UseRangesSection;
1149
1150   MCOS->SwitchSection(context.getObjectFileInfo()->getDwarfInfoSection());
1151   if (CreateDwarfSectionSymbols) {
1152     InfoSectionSymbol = context.createTempSymbol();
1153     MCOS->EmitLabel(InfoSectionSymbol);
1154   }
1155   MCOS->SwitchSection(context.getObjectFileInfo()->getDwarfAbbrevSection());
1156   if (CreateDwarfSectionSymbols) {
1157     AbbrevSectionSymbol = context.createTempSymbol();
1158     MCOS->EmitLabel(AbbrevSectionSymbol);
1159   }
1160   if (UseRangesSection) {
1161     MCOS->SwitchSection(context.getObjectFileInfo()->getDwarfRangesSection());
1162     if (CreateDwarfSectionSymbols) {
1163       RangesSectionSymbol = context.createTempSymbol();
1164       MCOS->EmitLabel(RangesSectionSymbol);
1165     }
1166   }
1167
1168   assert((RangesSectionSymbol != nullptr) || !UseRangesSection);
1169
1170   MCOS->SwitchSection(context.getObjectFileInfo()->getDwarfARangesSection());
1171
1172   // Output the data for .debug_aranges section.
1173   EmitGenDwarfAranges(MCOS, InfoSectionSymbol);
1174
1175   if (UseRangesSection)
1176     EmitGenDwarfRanges(MCOS);
1177
1178   // Output the data for .debug_abbrev section.
1179   EmitGenDwarfAbbrev(MCOS);
1180
1181   // Output the data for .debug_info section.
1182   EmitGenDwarfInfo(MCOS, AbbrevSectionSymbol, LineSectionSymbol,
1183                    RangesSectionSymbol);
1184 }
1185
1186 //
1187 // When generating dwarf for assembly source files this is called when symbol
1188 // for a label is created.  If this symbol is not a temporary and is in the
1189 // section that dwarf is being generated for, save the needed info to create
1190 // a dwarf label.
1191 //
1192 void MCGenDwarfLabelEntry::Make(MCSymbol *Symbol, MCStreamer *MCOS,
1193                                      SourceMgr &SrcMgr, SMLoc &Loc) {
1194   // We won't create dwarf labels for temporary symbols.
1195   if (Symbol->isTemporary())
1196     return;
1197   MCContext &context = MCOS->getContext();
1198   // We won't create dwarf labels for symbols in sections that we are not
1199   // generating debug info for.
1200   if (!context.getGenDwarfSectionSyms().count(MCOS->getCurrentSectionOnly()))
1201     return;
1202
1203   // The dwarf label's name does not have the symbol name's leading
1204   // underbar if any.
1205   StringRef Name = Symbol->getName();
1206   if (Name.startswith("_"))
1207     Name = Name.substr(1, Name.size()-1);
1208
1209   // Get the dwarf file number to be used for the dwarf label.
1210   unsigned FileNumber = context.getGenDwarfFileNumber();
1211
1212   // Finding the line number is the expensive part which is why we just don't
1213   // pass it in as for some symbols we won't create a dwarf label.
1214   unsigned CurBuffer = SrcMgr.FindBufferContainingLoc(Loc);
1215   unsigned LineNumber = SrcMgr.FindLineNumber(Loc, CurBuffer);
1216
1217   // We create a temporary symbol for use for the AT_high_pc and AT_low_pc
1218   // values so that they don't have things like an ARM thumb bit from the
1219   // original symbol. So when used they won't get a low bit set after
1220   // relocation.
1221   MCSymbol *Label = context.createTempSymbol();
1222   MCOS->EmitLabel(Label);
1223
1224   // Create and entry for the info and add it to the other entries.
1225   MCOS->getContext().addMCGenDwarfLabelEntry(
1226       MCGenDwarfLabelEntry(Name, FileNumber, LineNumber, Label));
1227 }
1228
1229 static int getDataAlignmentFactor(MCStreamer &streamer) {
1230   MCContext &context = streamer.getContext();
1231   const MCAsmInfo *asmInfo = context.getAsmInfo();
1232   int size = asmInfo->getCalleeSaveStackSlotSize();
1233   if (asmInfo->isStackGrowthDirectionUp())
1234     return size;
1235   else
1236     return -size;
1237 }
1238
1239 static unsigned getSizeForEncoding(MCStreamer &streamer,
1240                                    unsigned symbolEncoding) {
1241   MCContext &context = streamer.getContext();
1242   unsigned format = symbolEncoding & 0x0f;
1243   switch (format) {
1244   default: llvm_unreachable("Unknown Encoding");
1245   case dwarf::DW_EH_PE_absptr:
1246   case dwarf::DW_EH_PE_signed:
1247     return context.getAsmInfo()->getCodePointerSize();
1248   case dwarf::DW_EH_PE_udata2:
1249   case dwarf::DW_EH_PE_sdata2:
1250     return 2;
1251   case dwarf::DW_EH_PE_udata4:
1252   case dwarf::DW_EH_PE_sdata4:
1253     return 4;
1254   case dwarf::DW_EH_PE_udata8:
1255   case dwarf::DW_EH_PE_sdata8:
1256     return 8;
1257   }
1258 }
1259
1260 static void emitFDESymbol(MCObjectStreamer &streamer, const MCSymbol &symbol,
1261                        unsigned symbolEncoding, bool isEH) {
1262   MCContext &context = streamer.getContext();
1263   const MCAsmInfo *asmInfo = context.getAsmInfo();
1264   const MCExpr *v = asmInfo->getExprForFDESymbol(&symbol,
1265                                                  symbolEncoding,
1266                                                  streamer);
1267   unsigned size = getSizeForEncoding(streamer, symbolEncoding);
1268   if (asmInfo->doDwarfFDESymbolsUseAbsDiff() && isEH)
1269     emitAbsValue(streamer, v, size);
1270   else
1271     streamer.EmitValue(v, size);
1272 }
1273
1274 static void EmitPersonality(MCStreamer &streamer, const MCSymbol &symbol,
1275                             unsigned symbolEncoding) {
1276   MCContext &context = streamer.getContext();
1277   const MCAsmInfo *asmInfo = context.getAsmInfo();
1278   const MCExpr *v = asmInfo->getExprForPersonalitySymbol(&symbol,
1279                                                          symbolEncoding,
1280                                                          streamer);
1281   unsigned size = getSizeForEncoding(streamer, symbolEncoding);
1282   streamer.EmitValue(v, size);
1283 }
1284
1285 namespace {
1286
1287 class FrameEmitterImpl {
1288   int CFAOffset = 0;
1289   int InitialCFAOffset = 0;
1290   bool IsEH;
1291   MCObjectStreamer &Streamer;
1292
1293 public:
1294   FrameEmitterImpl(bool IsEH, MCObjectStreamer &Streamer)
1295       : IsEH(IsEH), Streamer(Streamer) {}
1296
1297   /// Emit the unwind information in a compact way.
1298   void EmitCompactUnwind(const MCDwarfFrameInfo &frame);
1299
1300   const MCSymbol &EmitCIE(const MCDwarfFrameInfo &F);
1301   void EmitFDE(const MCSymbol &cieStart, const MCDwarfFrameInfo &frame,
1302                bool LastInSection, const MCSymbol &SectionStart);
1303   void EmitCFIInstructions(ArrayRef<MCCFIInstruction> Instrs,
1304                            MCSymbol *BaseLabel);
1305   void EmitCFIInstruction(const MCCFIInstruction &Instr);
1306 };
1307
1308 } // end anonymous namespace
1309
1310 static void emitEncodingByte(MCObjectStreamer &Streamer, unsigned Encoding) {
1311   Streamer.EmitIntValue(Encoding, 1);
1312 }
1313
1314 void FrameEmitterImpl::EmitCFIInstruction(const MCCFIInstruction &Instr) {
1315   int dataAlignmentFactor = getDataAlignmentFactor(Streamer);
1316   auto *MRI = Streamer.getContext().getRegisterInfo();
1317
1318   switch (Instr.getOperation()) {
1319   case MCCFIInstruction::OpRegister: {
1320     unsigned Reg1 = Instr.getRegister();
1321     unsigned Reg2 = Instr.getRegister2();
1322     if (!IsEH) {
1323       Reg1 = MRI->getDwarfRegNumFromDwarfEHRegNum(Reg1);
1324       Reg2 = MRI->getDwarfRegNumFromDwarfEHRegNum(Reg2);
1325     }
1326     Streamer.EmitIntValue(dwarf::DW_CFA_register, 1);
1327     Streamer.EmitULEB128IntValue(Reg1);
1328     Streamer.EmitULEB128IntValue(Reg2);
1329     return;
1330   }
1331   case MCCFIInstruction::OpWindowSave:
1332     Streamer.EmitIntValue(dwarf::DW_CFA_GNU_window_save, 1);
1333     return;
1334
1335   case MCCFIInstruction::OpUndefined: {
1336     unsigned Reg = Instr.getRegister();
1337     Streamer.EmitIntValue(dwarf::DW_CFA_undefined, 1);
1338     Streamer.EmitULEB128IntValue(Reg);
1339     return;
1340   }
1341   case MCCFIInstruction::OpAdjustCfaOffset:
1342   case MCCFIInstruction::OpDefCfaOffset: {
1343     const bool IsRelative =
1344       Instr.getOperation() == MCCFIInstruction::OpAdjustCfaOffset;
1345
1346     Streamer.EmitIntValue(dwarf::DW_CFA_def_cfa_offset, 1);
1347
1348     if (IsRelative)
1349       CFAOffset += Instr.getOffset();
1350     else
1351       CFAOffset = -Instr.getOffset();
1352
1353     Streamer.EmitULEB128IntValue(CFAOffset);
1354
1355     return;
1356   }
1357   case MCCFIInstruction::OpDefCfa: {
1358     unsigned Reg = Instr.getRegister();
1359     if (!IsEH)
1360       Reg = MRI->getDwarfRegNumFromDwarfEHRegNum(Reg);
1361     Streamer.EmitIntValue(dwarf::DW_CFA_def_cfa, 1);
1362     Streamer.EmitULEB128IntValue(Reg);
1363     CFAOffset = -Instr.getOffset();
1364     Streamer.EmitULEB128IntValue(CFAOffset);
1365
1366     return;
1367   }
1368   case MCCFIInstruction::OpDefCfaRegister: {
1369     unsigned Reg = Instr.getRegister();
1370     if (!IsEH)
1371       Reg = MRI->getDwarfRegNumFromDwarfEHRegNum(Reg);
1372     Streamer.EmitIntValue(dwarf::DW_CFA_def_cfa_register, 1);
1373     Streamer.EmitULEB128IntValue(Reg);
1374
1375     return;
1376   }
1377   case MCCFIInstruction::OpOffset:
1378   case MCCFIInstruction::OpRelOffset: {
1379     const bool IsRelative =
1380       Instr.getOperation() == MCCFIInstruction::OpRelOffset;
1381
1382     unsigned Reg = Instr.getRegister();
1383     if (!IsEH)
1384       Reg = MRI->getDwarfRegNumFromDwarfEHRegNum(Reg);
1385
1386     int Offset = Instr.getOffset();
1387     if (IsRelative)
1388       Offset -= CFAOffset;
1389     Offset = Offset / dataAlignmentFactor;
1390
1391     if (Offset < 0) {
1392       Streamer.EmitIntValue(dwarf::DW_CFA_offset_extended_sf, 1);
1393       Streamer.EmitULEB128IntValue(Reg);
1394       Streamer.EmitSLEB128IntValue(Offset);
1395     } else if (Reg < 64) {
1396       Streamer.EmitIntValue(dwarf::DW_CFA_offset + Reg, 1);
1397       Streamer.EmitULEB128IntValue(Offset);
1398     } else {
1399       Streamer.EmitIntValue(dwarf::DW_CFA_offset_extended, 1);
1400       Streamer.EmitULEB128IntValue(Reg);
1401       Streamer.EmitULEB128IntValue(Offset);
1402     }
1403     return;
1404   }
1405   case MCCFIInstruction::OpRememberState:
1406     Streamer.EmitIntValue(dwarf::DW_CFA_remember_state, 1);
1407     return;
1408   case MCCFIInstruction::OpRestoreState:
1409     Streamer.EmitIntValue(dwarf::DW_CFA_restore_state, 1);
1410     return;
1411   case MCCFIInstruction::OpSameValue: {
1412     unsigned Reg = Instr.getRegister();
1413     Streamer.EmitIntValue(dwarf::DW_CFA_same_value, 1);
1414     Streamer.EmitULEB128IntValue(Reg);
1415     return;
1416   }
1417   case MCCFIInstruction::OpRestore: {
1418     unsigned Reg = Instr.getRegister();
1419     if (!IsEH)
1420       Reg = MRI->getDwarfRegNumFromDwarfEHRegNum(Reg);
1421     Streamer.EmitIntValue(dwarf::DW_CFA_restore | Reg, 1);
1422     return;
1423   }
1424   case MCCFIInstruction::OpGnuArgsSize:
1425     Streamer.EmitIntValue(dwarf::DW_CFA_GNU_args_size, 1);
1426     Streamer.EmitULEB128IntValue(Instr.getOffset());
1427     return;
1428
1429   case MCCFIInstruction::OpEscape:
1430     Streamer.EmitBytes(Instr.getValues());
1431     return;
1432   }
1433   llvm_unreachable("Unhandled case in switch");
1434 }
1435
1436 /// Emit frame instructions to describe the layout of the frame.
1437 void FrameEmitterImpl::EmitCFIInstructions(ArrayRef<MCCFIInstruction> Instrs,
1438                                            MCSymbol *BaseLabel) {
1439   for (const MCCFIInstruction &Instr : Instrs) {
1440     MCSymbol *Label = Instr.getLabel();
1441     // Throw out move if the label is invalid.
1442     if (Label && !Label->isDefined()) continue; // Not emitted, in dead code.
1443
1444     // Advance row if new location.
1445     if (BaseLabel && Label) {
1446       MCSymbol *ThisSym = Label;
1447       if (ThisSym != BaseLabel) {
1448         Streamer.EmitDwarfAdvanceFrameAddr(BaseLabel, ThisSym);
1449         BaseLabel = ThisSym;
1450       }
1451     }
1452
1453     EmitCFIInstruction(Instr);
1454   }
1455 }
1456
1457 /// Emit the unwind information in a compact way.
1458 void FrameEmitterImpl::EmitCompactUnwind(const MCDwarfFrameInfo &Frame) {
1459   MCContext &Context = Streamer.getContext();
1460   const MCObjectFileInfo *MOFI = Context.getObjectFileInfo();
1461
1462   // range-start range-length  compact-unwind-enc personality-func   lsda
1463   //  _foo       LfooEnd-_foo  0x00000023          0                 0
1464   //  _bar       LbarEnd-_bar  0x00000025         __gxx_personality  except_tab1
1465   //
1466   //   .section __LD,__compact_unwind,regular,debug
1467   //
1468   //   # compact unwind for _foo
1469   //   .quad _foo
1470   //   .set L1,LfooEnd-_foo
1471   //   .long L1
1472   //   .long 0x01010001
1473   //   .quad 0
1474   //   .quad 0
1475   //
1476   //   # compact unwind for _bar
1477   //   .quad _bar
1478   //   .set L2,LbarEnd-_bar
1479   //   .long L2
1480   //   .long 0x01020011
1481   //   .quad __gxx_personality
1482   //   .quad except_tab1
1483
1484   uint32_t Encoding = Frame.CompactUnwindEncoding;
1485   if (!Encoding) return;
1486   bool DwarfEHFrameOnly = (Encoding == MOFI->getCompactUnwindDwarfEHFrameOnly());
1487
1488   // The encoding needs to know we have an LSDA.
1489   if (!DwarfEHFrameOnly && Frame.Lsda)
1490     Encoding |= 0x40000000;
1491
1492   // Range Start
1493   unsigned FDEEncoding = MOFI->getFDEEncoding();
1494   unsigned Size = getSizeForEncoding(Streamer, FDEEncoding);
1495   Streamer.EmitSymbolValue(Frame.Begin, Size);
1496
1497   // Range Length
1498   const MCExpr *Range = MakeStartMinusEndExpr(Streamer, *Frame.Begin,
1499                                               *Frame.End, 0);
1500   emitAbsValue(Streamer, Range, 4);
1501
1502   // Compact Encoding
1503   Size = getSizeForEncoding(Streamer, dwarf::DW_EH_PE_udata4);
1504   Streamer.EmitIntValue(Encoding, Size);
1505
1506   // Personality Function
1507   Size = getSizeForEncoding(Streamer, dwarf::DW_EH_PE_absptr);
1508   if (!DwarfEHFrameOnly && Frame.Personality)
1509     Streamer.EmitSymbolValue(Frame.Personality, Size);
1510   else
1511     Streamer.EmitIntValue(0, Size); // No personality fn
1512
1513   // LSDA
1514   Size = getSizeForEncoding(Streamer, Frame.LsdaEncoding);
1515   if (!DwarfEHFrameOnly && Frame.Lsda)
1516     Streamer.EmitSymbolValue(Frame.Lsda, Size);
1517   else
1518     Streamer.EmitIntValue(0, Size); // No LSDA
1519 }
1520
1521 static unsigned getCIEVersion(bool IsEH, unsigned DwarfVersion) {
1522   if (IsEH)
1523     return 1;
1524   switch (DwarfVersion) {
1525   case 2:
1526     return 1;
1527   case 3:
1528     return 3;
1529   case 4:
1530   case 5:
1531     return 4;
1532   }
1533   llvm_unreachable("Unknown version");
1534 }
1535
1536 const MCSymbol &FrameEmitterImpl::EmitCIE(const MCDwarfFrameInfo &Frame) {
1537   MCContext &context = Streamer.getContext();
1538   const MCRegisterInfo *MRI = context.getRegisterInfo();
1539   const MCObjectFileInfo *MOFI = context.getObjectFileInfo();
1540
1541   MCSymbol *sectionStart = context.createTempSymbol();
1542   Streamer.EmitLabel(sectionStart);
1543
1544   MCSymbol *sectionEnd = context.createTempSymbol();
1545
1546   // Length
1547   const MCExpr *Length =
1548       MakeStartMinusEndExpr(Streamer, *sectionStart, *sectionEnd, 4);
1549   emitAbsValue(Streamer, Length, 4);
1550
1551   // CIE ID
1552   unsigned CIE_ID = IsEH ? 0 : -1;
1553   Streamer.EmitIntValue(CIE_ID, 4);
1554
1555   // Version
1556   uint8_t CIEVersion = getCIEVersion(IsEH, context.getDwarfVersion());
1557   Streamer.EmitIntValue(CIEVersion, 1);
1558
1559   // Augmentation String
1560   SmallString<8> Augmentation;
1561   if (IsEH) {
1562     Augmentation += "z";
1563     if (Frame.Personality)
1564       Augmentation += "P";
1565     if (Frame.Lsda)
1566       Augmentation += "L";
1567     Augmentation += "R";
1568     if (Frame.IsSignalFrame)
1569       Augmentation += "S";
1570     Streamer.EmitBytes(Augmentation);
1571   }
1572   Streamer.EmitIntValue(0, 1);
1573
1574   if (CIEVersion >= 4) {
1575     // Address Size
1576     Streamer.EmitIntValue(context.getAsmInfo()->getCodePointerSize(), 1);
1577
1578     // Segment Descriptor Size
1579     Streamer.EmitIntValue(0, 1);
1580   }
1581
1582   // Code Alignment Factor
1583   Streamer.EmitULEB128IntValue(context.getAsmInfo()->getMinInstAlignment());
1584
1585   // Data Alignment Factor
1586   Streamer.EmitSLEB128IntValue(getDataAlignmentFactor(Streamer));
1587
1588   // Return Address Register
1589   unsigned RAReg = Frame.RAReg;
1590   if (RAReg == static_cast<unsigned>(INT_MAX))
1591     RAReg = MRI->getDwarfRegNum(MRI->getRARegister(), IsEH);
1592
1593   if (CIEVersion == 1) {
1594     assert(RAReg <= 255 &&
1595            "DWARF 2 encodes return_address_register in one byte");
1596     Streamer.EmitIntValue(RAReg, 1);
1597   } else {
1598     Streamer.EmitULEB128IntValue(RAReg);
1599   }
1600
1601   // Augmentation Data Length (optional)
1602   unsigned augmentationLength = 0;
1603   if (IsEH) {
1604     if (Frame.Personality) {
1605       // Personality Encoding
1606       augmentationLength += 1;
1607       // Personality
1608       augmentationLength +=
1609           getSizeForEncoding(Streamer, Frame.PersonalityEncoding);
1610     }
1611     if (Frame.Lsda)
1612       augmentationLength += 1;
1613     // Encoding of the FDE pointers
1614     augmentationLength += 1;
1615
1616     Streamer.EmitULEB128IntValue(augmentationLength);
1617
1618     // Augmentation Data (optional)
1619     if (Frame.Personality) {
1620       // Personality Encoding
1621       emitEncodingByte(Streamer, Frame.PersonalityEncoding);
1622       // Personality
1623       EmitPersonality(Streamer, *Frame.Personality, Frame.PersonalityEncoding);
1624     }
1625
1626     if (Frame.Lsda)
1627       emitEncodingByte(Streamer, Frame.LsdaEncoding);
1628
1629     // Encoding of the FDE pointers
1630     emitEncodingByte(Streamer, MOFI->getFDEEncoding());
1631   }
1632
1633   // Initial Instructions
1634
1635   const MCAsmInfo *MAI = context.getAsmInfo();
1636   if (!Frame.IsSimple) {
1637     const std::vector<MCCFIInstruction> &Instructions =
1638         MAI->getInitialFrameState();
1639     EmitCFIInstructions(Instructions, nullptr);
1640   }
1641
1642   InitialCFAOffset = CFAOffset;
1643
1644   // Padding
1645   Streamer.EmitValueToAlignment(IsEH ? 4 : MAI->getCodePointerSize());
1646
1647   Streamer.EmitLabel(sectionEnd);
1648   return *sectionStart;
1649 }
1650
1651 void FrameEmitterImpl::EmitFDE(const MCSymbol &cieStart,
1652                                const MCDwarfFrameInfo &frame,
1653                                bool LastInSection,
1654                                const MCSymbol &SectionStart) {
1655   MCContext &context = Streamer.getContext();
1656   MCSymbol *fdeStart = context.createTempSymbol();
1657   MCSymbol *fdeEnd = context.createTempSymbol();
1658   const MCObjectFileInfo *MOFI = context.getObjectFileInfo();
1659
1660   CFAOffset = InitialCFAOffset;
1661
1662   // Length
1663   const MCExpr *Length = MakeStartMinusEndExpr(Streamer, *fdeStart, *fdeEnd, 0);
1664   emitAbsValue(Streamer, Length, 4);
1665
1666   Streamer.EmitLabel(fdeStart);
1667
1668   // CIE Pointer
1669   const MCAsmInfo *asmInfo = context.getAsmInfo();
1670   if (IsEH) {
1671     const MCExpr *offset =
1672         MakeStartMinusEndExpr(Streamer, cieStart, *fdeStart, 0);
1673     emitAbsValue(Streamer, offset, 4);
1674   } else if (!asmInfo->doesDwarfUseRelocationsAcrossSections()) {
1675     const MCExpr *offset =
1676         MakeStartMinusEndExpr(Streamer, SectionStart, cieStart, 0);
1677     emitAbsValue(Streamer, offset, 4);
1678   } else {
1679     Streamer.EmitSymbolValue(&cieStart, 4);
1680   }
1681
1682   // PC Begin
1683   unsigned PCEncoding =
1684       IsEH ? MOFI->getFDEEncoding() : (unsigned)dwarf::DW_EH_PE_absptr;
1685   unsigned PCSize = getSizeForEncoding(Streamer, PCEncoding);
1686   emitFDESymbol(Streamer, *frame.Begin, PCEncoding, IsEH);
1687
1688   // PC Range
1689   const MCExpr *Range =
1690       MakeStartMinusEndExpr(Streamer, *frame.Begin, *frame.End, 0);
1691   emitAbsValue(Streamer, Range, PCSize);
1692
1693   if (IsEH) {
1694     // Augmentation Data Length
1695     unsigned augmentationLength = 0;
1696
1697     if (frame.Lsda)
1698       augmentationLength += getSizeForEncoding(Streamer, frame.LsdaEncoding);
1699
1700     Streamer.EmitULEB128IntValue(augmentationLength);
1701
1702     // Augmentation Data
1703     if (frame.Lsda)
1704       emitFDESymbol(Streamer, *frame.Lsda, frame.LsdaEncoding, true);
1705   }
1706
1707   // Call Frame Instructions
1708   EmitCFIInstructions(frame.Instructions, frame.Begin);
1709
1710   // Padding
1711   // The size of a .eh_frame section has to be a multiple of the alignment
1712   // since a null CIE is interpreted as the end. Old systems overaligned
1713   // .eh_frame, so we do too and account for it in the last FDE.
1714   unsigned Align = LastInSection ? asmInfo->getCodePointerSize() : PCSize;
1715   Streamer.EmitValueToAlignment(Align);
1716
1717   Streamer.EmitLabel(fdeEnd);
1718 }
1719
1720 namespace {
1721
1722 struct CIEKey {
1723   static const CIEKey getEmptyKey() {
1724     return CIEKey(nullptr, 0, -1, false, false, static_cast<unsigned>(INT_MAX));
1725   }
1726
1727   static const CIEKey getTombstoneKey() {
1728     return CIEKey(nullptr, -1, 0, false, false, static_cast<unsigned>(INT_MAX));
1729   }
1730
1731   CIEKey(const MCSymbol *Personality, unsigned PersonalityEncoding,
1732          unsigned LSDAEncoding, bool IsSignalFrame, bool IsSimple,
1733          unsigned RAReg)
1734       : Personality(Personality), PersonalityEncoding(PersonalityEncoding),
1735         LsdaEncoding(LSDAEncoding), IsSignalFrame(IsSignalFrame),
1736         IsSimple(IsSimple), RAReg(RAReg) {}
1737
1738   explicit CIEKey(const MCDwarfFrameInfo &Frame)
1739       : Personality(Frame.Personality),
1740         PersonalityEncoding(Frame.PersonalityEncoding),
1741         LsdaEncoding(Frame.LsdaEncoding), IsSignalFrame(Frame.IsSignalFrame),
1742         IsSimple(Frame.IsSimple), RAReg(Frame.RAReg) {}
1743
1744   const MCSymbol *Personality;
1745   unsigned PersonalityEncoding;
1746   unsigned LsdaEncoding;
1747   bool IsSignalFrame;
1748   bool IsSimple;
1749   unsigned RAReg;
1750 };
1751
1752 } // end anonymous namespace
1753
1754 namespace llvm {
1755
1756 template <> struct DenseMapInfo<CIEKey> {
1757   static CIEKey getEmptyKey() { return CIEKey::getEmptyKey(); }
1758   static CIEKey getTombstoneKey() { return CIEKey::getTombstoneKey(); }
1759
1760   static unsigned getHashValue(const CIEKey &Key) {
1761     return static_cast<unsigned>(
1762         hash_combine(Key.Personality, Key.PersonalityEncoding, Key.LsdaEncoding,
1763                      Key.IsSignalFrame, Key.IsSimple, Key.RAReg));
1764   }
1765
1766   static bool isEqual(const CIEKey &LHS, const CIEKey &RHS) {
1767     return LHS.Personality == RHS.Personality &&
1768            LHS.PersonalityEncoding == RHS.PersonalityEncoding &&
1769            LHS.LsdaEncoding == RHS.LsdaEncoding &&
1770            LHS.IsSignalFrame == RHS.IsSignalFrame &&
1771            LHS.IsSimple == RHS.IsSimple &&
1772            LHS.RAReg == RHS.RAReg;
1773   }
1774 };
1775
1776 } // end namespace llvm
1777
1778 void MCDwarfFrameEmitter::Emit(MCObjectStreamer &Streamer, MCAsmBackend *MAB,
1779                                bool IsEH) {
1780   Streamer.generateCompactUnwindEncodings(MAB);
1781
1782   MCContext &Context = Streamer.getContext();
1783   const MCObjectFileInfo *MOFI = Context.getObjectFileInfo();
1784   const MCAsmInfo *AsmInfo = Context.getAsmInfo();
1785   FrameEmitterImpl Emitter(IsEH, Streamer);
1786   ArrayRef<MCDwarfFrameInfo> FrameArray = Streamer.getDwarfFrameInfos();
1787
1788   // Emit the compact unwind info if available.
1789   bool NeedsEHFrameSection = !MOFI->getSupportsCompactUnwindWithoutEHFrame();
1790   if (IsEH && MOFI->getCompactUnwindSection()) {
1791     bool SectionEmitted = false;
1792     for (const MCDwarfFrameInfo &Frame : FrameArray) {
1793       if (Frame.CompactUnwindEncoding == 0) continue;
1794       if (!SectionEmitted) {
1795         Streamer.SwitchSection(MOFI->getCompactUnwindSection());
1796         Streamer.EmitValueToAlignment(AsmInfo->getCodePointerSize());
1797         SectionEmitted = true;
1798       }
1799       NeedsEHFrameSection |=
1800         Frame.CompactUnwindEncoding ==
1801           MOFI->getCompactUnwindDwarfEHFrameOnly();
1802       Emitter.EmitCompactUnwind(Frame);
1803     }
1804   }
1805
1806   if (!NeedsEHFrameSection) return;
1807
1808   MCSection &Section =
1809       IsEH ? *const_cast<MCObjectFileInfo *>(MOFI)->getEHFrameSection()
1810            : *MOFI->getDwarfFrameSection();
1811
1812   Streamer.SwitchSection(&Section);
1813   MCSymbol *SectionStart = Context.createTempSymbol();
1814   Streamer.EmitLabel(SectionStart);
1815
1816   DenseMap<CIEKey, const MCSymbol *> CIEStarts;
1817
1818   const MCSymbol *DummyDebugKey = nullptr;
1819   bool CanOmitDwarf = MOFI->getOmitDwarfIfHaveCompactUnwind();
1820   for (auto I = FrameArray.begin(), E = FrameArray.end(); I != E;) {
1821     const MCDwarfFrameInfo &Frame = *I;
1822     ++I;
1823     if (CanOmitDwarf && Frame.CompactUnwindEncoding !=
1824           MOFI->getCompactUnwindDwarfEHFrameOnly())
1825       // Don't generate an EH frame if we don't need one. I.e., it's taken care
1826       // of by the compact unwind encoding.
1827       continue;
1828
1829     CIEKey Key(Frame);
1830     const MCSymbol *&CIEStart = IsEH ? CIEStarts[Key] : DummyDebugKey;
1831     if (!CIEStart)
1832       CIEStart = &Emitter.EmitCIE(Frame);
1833
1834     Emitter.EmitFDE(*CIEStart, Frame, I == E, *SectionStart);
1835   }
1836 }
1837
1838 void MCDwarfFrameEmitter::EmitAdvanceLoc(MCObjectStreamer &Streamer,
1839                                          uint64_t AddrDelta) {
1840   MCContext &Context = Streamer.getContext();
1841   SmallString<256> Tmp;
1842   raw_svector_ostream OS(Tmp);
1843   MCDwarfFrameEmitter::EncodeAdvanceLoc(Context, AddrDelta, OS);
1844   Streamer.EmitBytes(OS.str());
1845 }
1846
1847 void MCDwarfFrameEmitter::EncodeAdvanceLoc(MCContext &Context,
1848                                            uint64_t AddrDelta,
1849                                            raw_ostream &OS) {
1850   // Scale the address delta by the minimum instruction length.
1851   AddrDelta = ScaleAddrDelta(Context, AddrDelta);
1852
1853   support::endianness E =
1854       Context.getAsmInfo()->isLittleEndian() ? support::little : support::big;
1855   if (AddrDelta == 0) {
1856   } else if (isUIntN(6, AddrDelta)) {
1857     uint8_t Opcode = dwarf::DW_CFA_advance_loc | AddrDelta;
1858     OS << Opcode;
1859   } else if (isUInt<8>(AddrDelta)) {
1860     OS << uint8_t(dwarf::DW_CFA_advance_loc1);
1861     OS << uint8_t(AddrDelta);
1862   } else if (isUInt<16>(AddrDelta)) {
1863     OS << uint8_t(dwarf::DW_CFA_advance_loc2);
1864     support::endian::write<uint16_t>(OS, AddrDelta, E);
1865   } else {
1866     assert(isUInt<32>(AddrDelta));
1867     OS << uint8_t(dwarf::DW_CFA_advance_loc4);
1868     support::endian::write<uint32_t>(OS, AddrDelta, E);
1869   }
1870 }