1 //===- lib/MC/MCDwarf.cpp - MCDwarf implementation ------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 #include "llvm/MC/MCDwarf.h"
11 #include "llvm/ADT/Hashing.h"
12 #include "llvm/ADT/STLExtras.h"
13 #include "llvm/ADT/SmallString.h"
14 #include "llvm/ADT/Twine.h"
15 #include "llvm/Config/config.h"
16 #include "llvm/MC/MCAsmInfo.h"
17 #include "llvm/MC/MCContext.h"
18 #include "llvm/MC/MCExpr.h"
19 #include "llvm/MC/MCObjectFileInfo.h"
20 #include "llvm/MC/MCObjectStreamer.h"
21 #include "llvm/MC/MCRegisterInfo.h"
22 #include "llvm/MC/MCSection.h"
23 #include "llvm/MC/MCSymbol.h"
24 #include "llvm/Support/Debug.h"
25 #include "llvm/Support/ErrorHandling.h"
26 #include "llvm/Support/LEB128.h"
27 #include "llvm/Support/Path.h"
28 #include "llvm/Support/SourceMgr.h"
29 #include "llvm/Support/raw_ostream.h"
32 // Given a special op, return the address skip amount (in units of
33 // DWARF2_LINE_MIN_INSN_LENGTH.
34 #define SPECIAL_ADDR(op) (((op) - DWARF2_LINE_OPCODE_BASE)/DWARF2_LINE_RANGE)
36 // The maximum address skip amount that can be encoded with a special op.
37 #define MAX_SPECIAL_ADDR_DELTA SPECIAL_ADDR(255)
39 // First special line opcode - leave room for the standard opcodes.
40 // Note: If you want to change this, you'll have to update the
41 // "standard_opcode_lengths" table that is emitted in DwarfFileTable::Emit().
42 #define DWARF2_LINE_OPCODE_BASE 13
44 // Minimum line offset in a special line info. opcode. This value
45 // was chosen to give a reasonable range of values.
46 #define DWARF2_LINE_BASE -5
48 // Range of line offsets in a special line info. opcode.
49 #define DWARF2_LINE_RANGE 14
51 static inline uint64_t ScaleAddrDelta(MCContext &Context, uint64_t AddrDelta) {
52 unsigned MinInsnLength = Context.getAsmInfo()->getMinInstAlignment();
53 if (MinInsnLength == 1)
55 if (AddrDelta % MinInsnLength != 0) {
56 // TODO: report this error, but really only once.
59 return AddrDelta / MinInsnLength;
63 // This is called when an instruction is assembled into the specified section
64 // and if there is information from the last .loc directive that has yet to have
65 // a line entry made for it is made.
67 void MCLineEntry::Make(MCObjectStreamer *MCOS, const MCSection *Section) {
68 if (!MCOS->getContext().getDwarfLocSeen())
71 // Create a symbol at in the current section for use in the line entry.
72 MCSymbol *LineSym = MCOS->getContext().CreateTempSymbol();
73 // Set the value of the symbol to use for the MCLineEntry.
74 MCOS->EmitLabel(LineSym);
76 // Get the current .loc info saved in the context.
77 const MCDwarfLoc &DwarfLoc = MCOS->getContext().getCurrentDwarfLoc();
79 // Create a (local) line entry with the symbol and the current .loc info.
80 MCLineEntry LineEntry(LineSym, DwarfLoc);
82 // clear DwarfLocSeen saying the current .loc info is now used.
83 MCOS->getContext().ClearDwarfLocSeen();
85 // Add the line entry to this section's entries.
87 .getMCDwarfLineTable(MCOS->getContext().getDwarfCompileUnitID())
89 .addLineEntry(LineEntry, Section);
93 // This helper routine returns an expression of End - Start + IntVal .
95 static inline const MCExpr *MakeStartMinusEndExpr(const MCStreamer &MCOS,
96 const MCSymbol &Start,
99 MCSymbolRefExpr::VariantKind Variant = MCSymbolRefExpr::VK_None;
101 MCSymbolRefExpr::Create(&End, Variant, MCOS.getContext());
103 MCSymbolRefExpr::Create(&Start, Variant, MCOS.getContext());
105 MCBinaryExpr::Create(MCBinaryExpr::Sub, Res, RHS, MCOS.getContext());
107 MCConstantExpr::Create(IntVal, MCOS.getContext());
109 MCBinaryExpr::Create(MCBinaryExpr::Sub, Res1, Res2, MCOS.getContext());
114 // This emits the Dwarf line table for the specified section from the entries
115 // in the LineSection.
118 EmitDwarfLineTable(MCObjectStreamer *MCOS, const MCSection *Section,
119 const MCLineSection::MCLineEntryCollection &LineEntries) {
120 unsigned FileNum = 1;
121 unsigned LastLine = 1;
123 unsigned Flags = DWARF2_LINE_DEFAULT_IS_STMT ? DWARF2_FLAG_IS_STMT : 0;
125 unsigned Discriminator = 0;
126 MCSymbol *LastLabel = nullptr;
128 // Loop through each MCLineEntry and encode the dwarf line number table.
129 for (auto it = LineEntries.begin(),
130 ie = LineEntries.end();
133 if (FileNum != it->getFileNum()) {
134 FileNum = it->getFileNum();
135 MCOS->EmitIntValue(dwarf::DW_LNS_set_file, 1);
136 MCOS->EmitULEB128IntValue(FileNum);
138 if (Column != it->getColumn()) {
139 Column = it->getColumn();
140 MCOS->EmitIntValue(dwarf::DW_LNS_set_column, 1);
141 MCOS->EmitULEB128IntValue(Column);
143 if (Discriminator != it->getDiscriminator()) {
144 Discriminator = it->getDiscriminator();
145 unsigned Size = getULEB128Size(Discriminator);
146 MCOS->EmitIntValue(dwarf::DW_LNS_extended_op, 1);
147 MCOS->EmitULEB128IntValue(Size + 1);
148 MCOS->EmitIntValue(dwarf::DW_LNE_set_discriminator, 1);
149 MCOS->EmitULEB128IntValue(Discriminator);
151 if (Isa != it->getIsa()) {
153 MCOS->EmitIntValue(dwarf::DW_LNS_set_isa, 1);
154 MCOS->EmitULEB128IntValue(Isa);
156 if ((it->getFlags() ^ Flags) & DWARF2_FLAG_IS_STMT) {
157 Flags = it->getFlags();
158 MCOS->EmitIntValue(dwarf::DW_LNS_negate_stmt, 1);
160 if (it->getFlags() & DWARF2_FLAG_BASIC_BLOCK)
161 MCOS->EmitIntValue(dwarf::DW_LNS_set_basic_block, 1);
162 if (it->getFlags() & DWARF2_FLAG_PROLOGUE_END)
163 MCOS->EmitIntValue(dwarf::DW_LNS_set_prologue_end, 1);
164 if (it->getFlags() & DWARF2_FLAG_EPILOGUE_BEGIN)
165 MCOS->EmitIntValue(dwarf::DW_LNS_set_epilogue_begin, 1);
167 int64_t LineDelta = static_cast<int64_t>(it->getLine()) - LastLine;
168 MCSymbol *Label = it->getLabel();
170 // At this point we want to emit/create the sequence to encode the delta in
171 // line numbers and the increment of the address from the previous Label
172 // and the current Label.
173 const MCAsmInfo *asmInfo = MCOS->getContext().getAsmInfo();
174 MCOS->EmitDwarfAdvanceLineAddr(LineDelta, LastLabel, Label,
175 asmInfo->getPointerSize());
177 LastLine = it->getLine();
181 // Emit a DW_LNE_end_sequence for the end of the section.
182 // Using the pointer Section create a temporary label at the end of the
183 // section and use that and the LastLabel to compute the address delta
184 // and use INT64_MAX as the line delta which is the signal that this is
185 // actually a DW_LNE_end_sequence.
187 // Switch to the section to be able to create a symbol at its end.
188 // TODO: keep track of the last subsection so that this symbol appears in the
190 MCOS->SwitchSection(Section);
192 MCContext &context = MCOS->getContext();
193 // Create a symbol at the end of the section.
194 MCSymbol *SectionEnd = context.CreateTempSymbol();
195 // Set the value of the symbol, as we are at the end of the section.
196 MCOS->EmitLabel(SectionEnd);
198 // Switch back the dwarf line section.
199 MCOS->SwitchSection(context.getObjectFileInfo()->getDwarfLineSection());
201 const MCAsmInfo *asmInfo = MCOS->getContext().getAsmInfo();
202 MCOS->EmitDwarfAdvanceLineAddr(INT64_MAX, LastLabel, SectionEnd,
203 asmInfo->getPointerSize());
207 // This emits the Dwarf file and the line tables.
209 void MCDwarfLineTable::Emit(MCObjectStreamer *MCOS) {
210 MCContext &context = MCOS->getContext();
212 auto &LineTables = context.getMCDwarfLineTables();
214 // Bail out early so we don't switch to the debug_line section needlessly and
215 // in doing so create an unnecessary (if empty) section.
216 if (LineTables.empty())
219 // Switch to the section where the table will be emitted into.
220 MCOS->SwitchSection(context.getObjectFileInfo()->getDwarfLineSection());
222 // Handle the rest of the Compile Units.
223 for (const auto &CUIDTablePair : LineTables)
224 CUIDTablePair.second.EmitCU(MCOS);
227 void MCDwarfDwoLineTable::Emit(MCStreamer &MCOS) const {
228 MCOS.EmitLabel(Header.Emit(&MCOS, None).second);
231 std::pair<MCSymbol *, MCSymbol *> MCDwarfLineTableHeader::Emit(MCStreamer *MCOS) const {
232 static const char StandardOpcodeLengths[] = {
233 0, // length of DW_LNS_copy
234 1, // length of DW_LNS_advance_pc
235 1, // length of DW_LNS_advance_line
236 1, // length of DW_LNS_set_file
237 1, // length of DW_LNS_set_column
238 0, // length of DW_LNS_negate_stmt
239 0, // length of DW_LNS_set_basic_block
240 0, // length of DW_LNS_const_add_pc
241 1, // length of DW_LNS_fixed_advance_pc
242 0, // length of DW_LNS_set_prologue_end
243 0, // length of DW_LNS_set_epilogue_begin
246 static_assert(array_lengthof(StandardOpcodeLengths) ==
247 (DWARF2_LINE_OPCODE_BASE - 1),
249 return Emit(MCOS, StandardOpcodeLengths);
252 static const MCExpr *forceExpAbs(MCStreamer &OS, const MCExpr* Expr) {
253 MCContext &Context = OS.getContext();
254 assert(!isa<MCSymbolRefExpr>(Expr));
255 if (Context.getAsmInfo()->hasAggressiveSymbolFolding())
258 MCSymbol *ABS = Context.CreateTempSymbol();
259 OS.EmitAssignment(ABS, Expr);
260 return MCSymbolRefExpr::Create(ABS, Context);
263 static void emitAbsValue(MCStreamer &OS, const MCExpr *Value, unsigned Size) {
264 const MCExpr *ABS = forceExpAbs(OS, Value);
265 OS.EmitValue(ABS, Size);
268 std::pair<MCSymbol *, MCSymbol *>
269 MCDwarfLineTableHeader::Emit(MCStreamer *MCOS,
270 ArrayRef<char> StandardOpcodeLengths) const {
272 MCContext &context = MCOS->getContext();
274 // Create a symbol at the beginning of the line table.
275 MCSymbol *LineStartSym = Label;
277 LineStartSym = context.CreateTempSymbol();
278 // Set the value of the symbol, as we are at the start of the line table.
279 MCOS->EmitLabel(LineStartSym);
281 // Create a symbol for the end of the section (to be set when we get there).
282 MCSymbol *LineEndSym = context.CreateTempSymbol();
284 // The first 4 bytes is the total length of the information for this
285 // compilation unit (not including these 4 bytes for the length).
287 MakeStartMinusEndExpr(*MCOS, *LineStartSym, *LineEndSym, 4), 4);
289 // Next 2 bytes is the Version, which is Dwarf 2.
290 MCOS->EmitIntValue(2, 2);
292 // Create a symbol for the end of the prologue (to be set when we get there).
293 MCSymbol *ProEndSym = context.CreateTempSymbol(); // Lprologue_end
295 // Length of the prologue, is the next 4 bytes. Which is the start of the
296 // section to the end of the prologue. Not including the 4 bytes for the
297 // total length, the 2 bytes for the version, and these 4 bytes for the
298 // length of the prologue.
301 MakeStartMinusEndExpr(*MCOS, *LineStartSym, *ProEndSym, (4 + 2 + 4)), 4);
303 // Parameters of the state machine, are next.
304 MCOS->EmitIntValue(context.getAsmInfo()->getMinInstAlignment(), 1);
305 MCOS->EmitIntValue(DWARF2_LINE_DEFAULT_IS_STMT, 1);
306 MCOS->EmitIntValue(DWARF2_LINE_BASE, 1);
307 MCOS->EmitIntValue(DWARF2_LINE_RANGE, 1);
308 MCOS->EmitIntValue(StandardOpcodeLengths.size() + 1, 1);
310 // Standard opcode lengths
311 for (char Length : StandardOpcodeLengths)
312 MCOS->EmitIntValue(Length, 1);
314 // Put out the directory and file tables.
316 // First the directory table.
317 for (unsigned i = 0; i < MCDwarfDirs.size(); i++) {
318 MCOS->EmitBytes(MCDwarfDirs[i]); // the DirectoryName
319 MCOS->EmitBytes(StringRef("\0", 1)); // the null term. of the string
321 MCOS->EmitIntValue(0, 1); // Terminate the directory list
323 // Second the file table.
324 for (unsigned i = 1; i < MCDwarfFiles.size(); i++) {
325 assert(!MCDwarfFiles[i].Name.empty());
326 MCOS->EmitBytes(MCDwarfFiles[i].Name); // FileName
327 MCOS->EmitBytes(StringRef("\0", 1)); // the null term. of the string
329 MCOS->EmitULEB128IntValue(MCDwarfFiles[i].DirIndex);
330 MCOS->EmitIntValue(0, 1); // last modification timestamp (always 0)
331 MCOS->EmitIntValue(0, 1); // filesize (always 0)
333 MCOS->EmitIntValue(0, 1); // Terminate the file list
335 // This is the end of the prologue, so set the value of the symbol at the
336 // end of the prologue (that was used in a previous expression).
337 MCOS->EmitLabel(ProEndSym);
339 return std::make_pair(LineStartSym, LineEndSym);
342 void MCDwarfLineTable::EmitCU(MCObjectStreamer *MCOS) const {
343 MCSymbol *LineEndSym = Header.Emit(MCOS).second;
345 // Put out the line tables.
346 for (const auto &LineSec : MCLineSections.getMCLineEntries())
347 EmitDwarfLineTable(MCOS, LineSec.first, LineSec.second);
349 // This is the end of the section, so set the value of the symbol at the end
350 // of this section (that was used in a previous expression).
351 MCOS->EmitLabel(LineEndSym);
354 unsigned MCDwarfLineTable::getFile(StringRef &Directory, StringRef &FileName,
355 unsigned FileNumber) {
356 return Header.getFile(Directory, FileName, FileNumber);
359 unsigned MCDwarfLineTableHeader::getFile(StringRef &Directory,
361 unsigned FileNumber) {
362 if (Directory == CompilationDir)
364 if (FileName.empty()) {
365 FileName = "<stdin>";
368 assert(!FileName.empty());
369 if (FileNumber == 0) {
370 FileNumber = SourceIdMap.size() + 1;
371 assert((MCDwarfFiles.empty() || FileNumber == MCDwarfFiles.size()) &&
372 "Don't mix autonumbered and explicit numbered line table usage");
373 auto IterBool = SourceIdMap.insert(
374 std::make_pair((Directory + Twine('\0') + FileName).str(), FileNumber));
375 if (!IterBool.second)
376 return IterBool.first->second;
378 // Make space for this FileNumber in the MCDwarfFiles vector if needed.
379 MCDwarfFiles.resize(FileNumber + 1);
381 // Get the new MCDwarfFile slot for this FileNumber.
382 MCDwarfFile &File = MCDwarfFiles[FileNumber];
384 // It is an error to use see the same number more than once.
385 if (!File.Name.empty())
388 if (Directory.empty()) {
389 // Separate the directory part from the basename of the FileName.
390 StringRef tFileName = sys::path::filename(FileName);
391 if (!tFileName.empty()) {
392 Directory = sys::path::parent_path(FileName);
393 if (!Directory.empty())
394 FileName = tFileName;
398 // Find or make an entry in the MCDwarfDirs vector for this Directory.
399 // Capture directory name.
401 if (Directory.empty()) {
402 // For FileNames with no directories a DirIndex of 0 is used.
406 for (unsigned End = MCDwarfDirs.size(); DirIndex < End; DirIndex++) {
407 if (Directory == MCDwarfDirs[DirIndex])
410 if (DirIndex >= MCDwarfDirs.size())
411 MCDwarfDirs.push_back(Directory);
412 // The DirIndex is one based, as DirIndex of 0 is used for FileNames with
413 // no directories. MCDwarfDirs[] is unlike MCDwarfFiles[] in that the
414 // directory names are stored at MCDwarfDirs[DirIndex-1] where FileNames
415 // are stored at MCDwarfFiles[FileNumber].Name .
419 File.Name = FileName;
420 File.DirIndex = DirIndex;
422 // return the allocated FileNumber.
426 /// Utility function to emit the encoding to a streamer.
427 void MCDwarfLineAddr::Emit(MCStreamer *MCOS, int64_t LineDelta,
428 uint64_t AddrDelta) {
429 MCContext &Context = MCOS->getContext();
430 SmallString<256> Tmp;
431 raw_svector_ostream OS(Tmp);
432 MCDwarfLineAddr::Encode(Context, LineDelta, AddrDelta, OS);
433 MCOS->EmitBytes(OS.str());
436 /// Utility function to encode a Dwarf pair of LineDelta and AddrDeltas.
437 void MCDwarfLineAddr::Encode(MCContext &Context, int64_t LineDelta,
438 uint64_t AddrDelta, raw_ostream &OS) {
439 uint64_t Temp, Opcode;
440 bool NeedCopy = false;
442 // Scale the address delta by the minimum instruction length.
443 AddrDelta = ScaleAddrDelta(Context, AddrDelta);
445 // A LineDelta of INT64_MAX is a signal that this is actually a
446 // DW_LNE_end_sequence. We cannot use special opcodes here, since we want the
447 // end_sequence to emit the matrix entry.
448 if (LineDelta == INT64_MAX) {
449 if (AddrDelta == MAX_SPECIAL_ADDR_DELTA)
450 OS << char(dwarf::DW_LNS_const_add_pc);
451 else if (AddrDelta) {
452 OS << char(dwarf::DW_LNS_advance_pc);
453 encodeULEB128(AddrDelta, OS);
455 OS << char(dwarf::DW_LNS_extended_op);
457 OS << char(dwarf::DW_LNE_end_sequence);
461 // Bias the line delta by the base.
462 Temp = LineDelta - DWARF2_LINE_BASE;
464 // If the line increment is out of range of a special opcode, we must encode
465 // it with DW_LNS_advance_line.
466 if (Temp >= DWARF2_LINE_RANGE) {
467 OS << char(dwarf::DW_LNS_advance_line);
468 encodeSLEB128(LineDelta, OS);
471 Temp = 0 - DWARF2_LINE_BASE;
475 // Use DW_LNS_copy instead of a "line +0, addr +0" special opcode.
476 if (LineDelta == 0 && AddrDelta == 0) {
477 OS << char(dwarf::DW_LNS_copy);
481 // Bias the opcode by the special opcode base.
482 Temp += DWARF2_LINE_OPCODE_BASE;
484 // Avoid overflow when addr_delta is large.
485 if (AddrDelta < 256 + MAX_SPECIAL_ADDR_DELTA) {
486 // Try using a special opcode.
487 Opcode = Temp + AddrDelta * DWARF2_LINE_RANGE;
493 // Try using DW_LNS_const_add_pc followed by special op.
494 Opcode = Temp + (AddrDelta - MAX_SPECIAL_ADDR_DELTA) * DWARF2_LINE_RANGE;
496 OS << char(dwarf::DW_LNS_const_add_pc);
502 // Otherwise use DW_LNS_advance_pc.
503 OS << char(dwarf::DW_LNS_advance_pc);
504 encodeULEB128(AddrDelta, OS);
507 OS << char(dwarf::DW_LNS_copy);
512 // Utility function to write a tuple for .debug_abbrev.
513 static void EmitAbbrev(MCStreamer *MCOS, uint64_t Name, uint64_t Form) {
514 MCOS->EmitULEB128IntValue(Name);
515 MCOS->EmitULEB128IntValue(Form);
518 // When generating dwarf for assembly source files this emits
519 // the data for .debug_abbrev section which contains three DIEs.
520 static void EmitGenDwarfAbbrev(MCStreamer *MCOS) {
521 MCContext &context = MCOS->getContext();
522 MCOS->SwitchSection(context.getObjectFileInfo()->getDwarfAbbrevSection());
524 // DW_TAG_compile_unit DIE abbrev (1).
525 MCOS->EmitULEB128IntValue(1);
526 MCOS->EmitULEB128IntValue(dwarf::DW_TAG_compile_unit);
527 MCOS->EmitIntValue(dwarf::DW_CHILDREN_yes, 1);
528 EmitAbbrev(MCOS, dwarf::DW_AT_stmt_list, dwarf::DW_FORM_data4);
529 if (MCOS->getContext().getGenDwarfSectionSyms().size() > 1 &&
530 MCOS->getContext().getDwarfVersion() >= 3) {
531 EmitAbbrev(MCOS, dwarf::DW_AT_ranges, dwarf::DW_FORM_data4);
533 EmitAbbrev(MCOS, dwarf::DW_AT_low_pc, dwarf::DW_FORM_addr);
534 EmitAbbrev(MCOS, dwarf::DW_AT_high_pc, dwarf::DW_FORM_addr);
536 EmitAbbrev(MCOS, dwarf::DW_AT_name, dwarf::DW_FORM_string);
537 if (!context.getCompilationDir().empty())
538 EmitAbbrev(MCOS, dwarf::DW_AT_comp_dir, dwarf::DW_FORM_string);
539 StringRef DwarfDebugFlags = context.getDwarfDebugFlags();
540 if (!DwarfDebugFlags.empty())
541 EmitAbbrev(MCOS, dwarf::DW_AT_APPLE_flags, dwarf::DW_FORM_string);
542 EmitAbbrev(MCOS, dwarf::DW_AT_producer, dwarf::DW_FORM_string);
543 EmitAbbrev(MCOS, dwarf::DW_AT_language, dwarf::DW_FORM_data2);
544 EmitAbbrev(MCOS, 0, 0);
546 // DW_TAG_label DIE abbrev (2).
547 MCOS->EmitULEB128IntValue(2);
548 MCOS->EmitULEB128IntValue(dwarf::DW_TAG_label);
549 MCOS->EmitIntValue(dwarf::DW_CHILDREN_yes, 1);
550 EmitAbbrev(MCOS, dwarf::DW_AT_name, dwarf::DW_FORM_string);
551 EmitAbbrev(MCOS, dwarf::DW_AT_decl_file, dwarf::DW_FORM_data4);
552 EmitAbbrev(MCOS, dwarf::DW_AT_decl_line, dwarf::DW_FORM_data4);
553 EmitAbbrev(MCOS, dwarf::DW_AT_low_pc, dwarf::DW_FORM_addr);
554 EmitAbbrev(MCOS, dwarf::DW_AT_prototyped, dwarf::DW_FORM_flag);
555 EmitAbbrev(MCOS, 0, 0);
557 // DW_TAG_unspecified_parameters DIE abbrev (3).
558 MCOS->EmitULEB128IntValue(3);
559 MCOS->EmitULEB128IntValue(dwarf::DW_TAG_unspecified_parameters);
560 MCOS->EmitIntValue(dwarf::DW_CHILDREN_no, 1);
561 EmitAbbrev(MCOS, 0, 0);
563 // Terminate the abbreviations for this compilation unit.
564 MCOS->EmitIntValue(0, 1);
567 // When generating dwarf for assembly source files this emits the data for
568 // .debug_aranges section. This section contains a header and a table of pairs
569 // of PointerSize'ed values for the address and size of section(s) with line
571 static void EmitGenDwarfAranges(MCStreamer *MCOS,
572 const MCSymbol *InfoSectionSymbol) {
573 MCContext &context = MCOS->getContext();
575 auto &Sections = context.getGenDwarfSectionSyms();
577 MCOS->SwitchSection(context.getObjectFileInfo()->getDwarfARangesSection());
579 // This will be the length of the .debug_aranges section, first account for
580 // the size of each item in the header (see below where we emit these items).
581 int Length = 4 + 2 + 4 + 1 + 1;
583 // Figure the padding after the header before the table of address and size
584 // pairs who's values are PointerSize'ed.
585 const MCAsmInfo *asmInfo = context.getAsmInfo();
586 int AddrSize = asmInfo->getPointerSize();
587 int Pad = 2 * AddrSize - (Length & (2 * AddrSize - 1));
588 if (Pad == 2 * AddrSize)
592 // Add the size of the pair of PointerSize'ed values for the address and size
593 // of each section we have in the table.
594 Length += 2 * AddrSize * Sections.size();
595 // And the pair of terminating zeros.
596 Length += 2 * AddrSize;
599 // Emit the header for this section.
600 // The 4 byte length not including the 4 byte value for the length.
601 MCOS->EmitIntValue(Length - 4, 4);
602 // The 2 byte version, which is 2.
603 MCOS->EmitIntValue(2, 2);
604 // The 4 byte offset to the compile unit in the .debug_info from the start
605 // of the .debug_info.
606 if (InfoSectionSymbol)
607 MCOS->EmitSymbolValue(InfoSectionSymbol, 4,
608 asmInfo->needsDwarfSectionOffsetDirective());
610 MCOS->EmitIntValue(0, 4);
611 // The 1 byte size of an address.
612 MCOS->EmitIntValue(AddrSize, 1);
613 // The 1 byte size of a segment descriptor, we use a value of zero.
614 MCOS->EmitIntValue(0, 1);
615 // Align the header with the padding if needed, before we put out the table.
616 for(int i = 0; i < Pad; i++)
617 MCOS->EmitIntValue(0, 1);
619 // Now emit the table of pairs of PointerSize'ed values for the section
620 // addresses and sizes.
621 for (const auto &sec : Sections) {
622 MCSymbol *StartSymbol = sec.second.first;
623 MCSymbol *EndSymbol = sec.second.second;
624 assert(StartSymbol && "StartSymbol must not be NULL");
625 assert(EndSymbol && "EndSymbol must not be NULL");
627 const MCExpr *Addr = MCSymbolRefExpr::Create(
628 StartSymbol, MCSymbolRefExpr::VK_None, context);
629 const MCExpr *Size = MakeStartMinusEndExpr(*MCOS,
630 *StartSymbol, *EndSymbol, 0);
631 MCOS->EmitValue(Addr, AddrSize);
632 emitAbsValue(*MCOS, Size, AddrSize);
635 // And finally the pair of terminating zeros.
636 MCOS->EmitIntValue(0, AddrSize);
637 MCOS->EmitIntValue(0, AddrSize);
640 // When generating dwarf for assembly source files this emits the data for
641 // .debug_info section which contains three parts. The header, the compile_unit
642 // DIE and a list of label DIEs.
643 static void EmitGenDwarfInfo(MCStreamer *MCOS,
644 const MCSymbol *AbbrevSectionSymbol,
645 const MCSymbol *LineSectionSymbol,
646 const MCSymbol *RangesSectionSymbol) {
647 MCContext &context = MCOS->getContext();
649 MCOS->SwitchSection(context.getObjectFileInfo()->getDwarfInfoSection());
651 // Create a symbol at the start and end of this section used in here for the
652 // expression to calculate the length in the header.
653 MCSymbol *InfoStart = context.CreateTempSymbol();
654 MCOS->EmitLabel(InfoStart);
655 MCSymbol *InfoEnd = context.CreateTempSymbol();
657 // First part: the header.
659 // The 4 byte total length of the information for this compilation unit, not
660 // including these 4 bytes.
661 const MCExpr *Length = MakeStartMinusEndExpr(*MCOS, *InfoStart, *InfoEnd, 4);
662 emitAbsValue(*MCOS, Length, 4);
664 // The 2 byte DWARF version.
665 MCOS->EmitIntValue(context.getDwarfVersion(), 2);
667 const MCAsmInfo &AsmInfo = *context.getAsmInfo();
668 // The 4 byte offset to the debug abbrevs from the start of the .debug_abbrev,
669 // it is at the start of that section so this is zero.
670 if (AbbrevSectionSymbol == nullptr)
671 MCOS->EmitIntValue(0, 4);
673 MCOS->EmitSymbolValue(AbbrevSectionSymbol, 4,
674 AsmInfo.needsDwarfSectionOffsetDirective());
676 const MCAsmInfo *asmInfo = context.getAsmInfo();
677 int AddrSize = asmInfo->getPointerSize();
678 // The 1 byte size of an address.
679 MCOS->EmitIntValue(AddrSize, 1);
681 // Second part: the compile_unit DIE.
683 // The DW_TAG_compile_unit DIE abbrev (1).
684 MCOS->EmitULEB128IntValue(1);
686 // DW_AT_stmt_list, a 4 byte offset from the start of the .debug_line section,
687 // which is at the start of that section so this is zero.
688 if (LineSectionSymbol)
689 MCOS->EmitSymbolValue(LineSectionSymbol, 4,
690 AsmInfo.needsDwarfSectionOffsetDirective());
692 MCOS->EmitIntValue(0, 4);
694 if (RangesSectionSymbol) {
695 // There are multiple sections containing code, so we must use the
696 // .debug_ranges sections.
698 // AT_ranges, the 4 byte offset from the start of the .debug_ranges section
699 // to the address range list for this compilation unit.
700 MCOS->EmitSymbolValue(RangesSectionSymbol, 4);
702 // If we only have one non-empty code section, we can use the simpler
703 // AT_low_pc and AT_high_pc attributes.
705 // Find the first (and only) non-empty text section
706 auto &Sections = context.getGenDwarfSectionSyms();
707 const auto TextSection = Sections.begin();
708 assert(TextSection != Sections.end() && "No text section found");
710 MCSymbol *StartSymbol = TextSection->second.first;
711 MCSymbol *EndSymbol = TextSection->second.second;
712 assert(StartSymbol && "StartSymbol must not be NULL");
713 assert(EndSymbol && "EndSymbol must not be NULL");
715 // AT_low_pc, the first address of the default .text section.
716 const MCExpr *Start = MCSymbolRefExpr::Create(
717 StartSymbol, MCSymbolRefExpr::VK_None, context);
718 MCOS->EmitValue(Start, AddrSize);
720 // AT_high_pc, the last address of the default .text section.
721 const MCExpr *End = MCSymbolRefExpr::Create(
722 EndSymbol, MCSymbolRefExpr::VK_None, context);
723 MCOS->EmitValue(End, AddrSize);
726 // AT_name, the name of the source file. Reconstruct from the first directory
727 // and file table entries.
728 const SmallVectorImpl<std::string> &MCDwarfDirs = context.getMCDwarfDirs();
729 if (MCDwarfDirs.size() > 0) {
730 MCOS->EmitBytes(MCDwarfDirs[0]);
731 MCOS->EmitBytes(sys::path::get_separator());
733 const SmallVectorImpl<MCDwarfFile> &MCDwarfFiles =
734 MCOS->getContext().getMCDwarfFiles();
735 MCOS->EmitBytes(MCDwarfFiles[1].Name);
736 MCOS->EmitIntValue(0, 1); // NULL byte to terminate the string.
738 // AT_comp_dir, the working directory the assembly was done in.
739 if (!context.getCompilationDir().empty()) {
740 MCOS->EmitBytes(context.getCompilationDir());
741 MCOS->EmitIntValue(0, 1); // NULL byte to terminate the string.
744 // AT_APPLE_flags, the command line arguments of the assembler tool.
745 StringRef DwarfDebugFlags = context.getDwarfDebugFlags();
746 if (!DwarfDebugFlags.empty()){
747 MCOS->EmitBytes(DwarfDebugFlags);
748 MCOS->EmitIntValue(0, 1); // NULL byte to terminate the string.
751 // AT_producer, the version of the assembler tool.
752 StringRef DwarfDebugProducer = context.getDwarfDebugProducer();
753 if (!DwarfDebugProducer.empty())
754 MCOS->EmitBytes(DwarfDebugProducer);
756 MCOS->EmitBytes(StringRef("llvm-mc (based on LLVM " PACKAGE_VERSION ")"));
757 MCOS->EmitIntValue(0, 1); // NULL byte to terminate the string.
759 // AT_language, a 4 byte value. We use DW_LANG_Mips_Assembler as the dwarf2
760 // draft has no standard code for assembler.
761 MCOS->EmitIntValue(dwarf::DW_LANG_Mips_Assembler, 2);
763 // Third part: the list of label DIEs.
765 // Loop on saved info for dwarf labels and create the DIEs for them.
766 const std::vector<MCGenDwarfLabelEntry> &Entries =
767 MCOS->getContext().getMCGenDwarfLabelEntries();
768 for (const auto &Entry : Entries) {
769 // The DW_TAG_label DIE abbrev (2).
770 MCOS->EmitULEB128IntValue(2);
772 // AT_name, of the label without any leading underbar.
773 MCOS->EmitBytes(Entry.getName());
774 MCOS->EmitIntValue(0, 1); // NULL byte to terminate the string.
776 // AT_decl_file, index into the file table.
777 MCOS->EmitIntValue(Entry.getFileNumber(), 4);
779 // AT_decl_line, source line number.
780 MCOS->EmitIntValue(Entry.getLineNumber(), 4);
782 // AT_low_pc, start address of the label.
783 const MCExpr *AT_low_pc = MCSymbolRefExpr::Create(Entry.getLabel(),
784 MCSymbolRefExpr::VK_None, context);
785 MCOS->EmitValue(AT_low_pc, AddrSize);
787 // DW_AT_prototyped, a one byte flag value of 0 saying we have no prototype.
788 MCOS->EmitIntValue(0, 1);
790 // The DW_TAG_unspecified_parameters DIE abbrev (3).
791 MCOS->EmitULEB128IntValue(3);
793 // Add the NULL DIE terminating the DW_TAG_unspecified_parameters DIE's.
794 MCOS->EmitIntValue(0, 1);
797 // Add the NULL DIE terminating the Compile Unit DIE's.
798 MCOS->EmitIntValue(0, 1);
800 // Now set the value of the symbol at the end of the info section.
801 MCOS->EmitLabel(InfoEnd);
804 // When generating dwarf for assembly source files this emits the data for
805 // .debug_ranges section. We only emit one range list, which spans all of the
806 // executable sections of this file.
807 static void EmitGenDwarfRanges(MCStreamer *MCOS) {
808 MCContext &context = MCOS->getContext();
809 auto &Sections = context.getGenDwarfSectionSyms();
811 const MCAsmInfo *AsmInfo = context.getAsmInfo();
812 int AddrSize = AsmInfo->getPointerSize();
814 MCOS->SwitchSection(context.getObjectFileInfo()->getDwarfRangesSection());
816 for (const auto sec : Sections) {
818 MCSymbol *StartSymbol = sec.second.first;
819 MCSymbol *EndSymbol = sec.second.second;
820 assert(StartSymbol && "StartSymbol must not be NULL");
821 assert(EndSymbol && "EndSymbol must not be NULL");
823 // Emit a base address selection entry for the start of this section
824 const MCExpr *SectionStartAddr = MCSymbolRefExpr::Create(
825 StartSymbol, MCSymbolRefExpr::VK_None, context);
826 MCOS->EmitFill(AddrSize, 0xFF);
827 MCOS->EmitValue(SectionStartAddr, AddrSize);
829 // Emit a range list entry spanning this section
830 const MCExpr *SectionSize = MakeStartMinusEndExpr(*MCOS,
831 *StartSymbol, *EndSymbol, 0);
832 MCOS->EmitIntValue(0, AddrSize);
833 emitAbsValue(*MCOS, SectionSize, AddrSize);
836 // Emit end of list entry
837 MCOS->EmitIntValue(0, AddrSize);
838 MCOS->EmitIntValue(0, AddrSize);
842 // When generating dwarf for assembly source files this emits the Dwarf
845 void MCGenDwarfInfo::Emit(MCStreamer *MCOS) {
846 MCContext &context = MCOS->getContext();
848 // Create the dwarf sections in this order (.debug_line already created).
849 const MCAsmInfo *AsmInfo = context.getAsmInfo();
850 bool CreateDwarfSectionSymbols =
851 AsmInfo->doesDwarfUseRelocationsAcrossSections();
852 MCSymbol *LineSectionSymbol = nullptr;
853 if (CreateDwarfSectionSymbols)
854 LineSectionSymbol = MCOS->getDwarfLineTableSymbol(0);
855 MCSymbol *AbbrevSectionSymbol = nullptr;
856 MCSymbol *InfoSectionSymbol = nullptr;
857 MCSymbol *RangesSectionSymbol = NULL;
859 // Create end symbols for each section, and remove empty sections
860 MCOS->getContext().finalizeDwarfSections(*MCOS);
862 // If there are no sections to generate debug info for, we don't need
864 if (MCOS->getContext().getGenDwarfSectionSyms().empty())
867 // We only use the .debug_ranges section if we have multiple code sections,
868 // and we are emitting a DWARF version which supports it.
869 const bool UseRangesSection =
870 MCOS->getContext().getGenDwarfSectionSyms().size() > 1 &&
871 MCOS->getContext().getDwarfVersion() >= 3;
872 CreateDwarfSectionSymbols |= UseRangesSection;
874 MCOS->SwitchSection(context.getObjectFileInfo()->getDwarfInfoSection());
875 if (CreateDwarfSectionSymbols) {
876 InfoSectionSymbol = context.CreateTempSymbol();
877 MCOS->EmitLabel(InfoSectionSymbol);
879 MCOS->SwitchSection(context.getObjectFileInfo()->getDwarfAbbrevSection());
880 if (CreateDwarfSectionSymbols) {
881 AbbrevSectionSymbol = context.CreateTempSymbol();
882 MCOS->EmitLabel(AbbrevSectionSymbol);
884 if (UseRangesSection) {
885 MCOS->SwitchSection(context.getObjectFileInfo()->getDwarfRangesSection());
886 if (CreateDwarfSectionSymbols) {
887 RangesSectionSymbol = context.CreateTempSymbol();
888 MCOS->EmitLabel(RangesSectionSymbol);
892 assert((RangesSectionSymbol != NULL) || !UseRangesSection);
894 MCOS->SwitchSection(context.getObjectFileInfo()->getDwarfARangesSection());
896 // Output the data for .debug_aranges section.
897 EmitGenDwarfAranges(MCOS, InfoSectionSymbol);
899 if (UseRangesSection)
900 EmitGenDwarfRanges(MCOS);
902 // Output the data for .debug_abbrev section.
903 EmitGenDwarfAbbrev(MCOS);
905 // Output the data for .debug_info section.
906 EmitGenDwarfInfo(MCOS, AbbrevSectionSymbol, LineSectionSymbol,
907 RangesSectionSymbol);
911 // When generating dwarf for assembly source files this is called when symbol
912 // for a label is created. If this symbol is not a temporary and is in the
913 // section that dwarf is being generated for, save the needed info to create
916 void MCGenDwarfLabelEntry::Make(MCSymbol *Symbol, MCStreamer *MCOS,
917 SourceMgr &SrcMgr, SMLoc &Loc) {
918 // We won't create dwarf labels for temporary symbols.
919 if (Symbol->isTemporary())
921 MCContext &context = MCOS->getContext();
922 // We won't create dwarf labels for symbols in sections that we are not
923 // generating debug info for.
924 if (!context.getGenDwarfSectionSyms().count(MCOS->getCurrentSection().first))
927 // The dwarf label's name does not have the symbol name's leading
929 StringRef Name = Symbol->getName();
930 if (Name.startswith("_"))
931 Name = Name.substr(1, Name.size()-1);
933 // Get the dwarf file number to be used for the dwarf label.
934 unsigned FileNumber = context.getGenDwarfFileNumber();
936 // Finding the line number is the expensive part which is why we just don't
937 // pass it in as for some symbols we won't create a dwarf label.
938 unsigned CurBuffer = SrcMgr.FindBufferContainingLoc(Loc);
939 unsigned LineNumber = SrcMgr.FindLineNumber(Loc, CurBuffer);
941 // We create a temporary symbol for use for the AT_high_pc and AT_low_pc
942 // values so that they don't have things like an ARM thumb bit from the
943 // original symbol. So when used they won't get a low bit set after
945 MCSymbol *Label = context.CreateTempSymbol();
946 MCOS->EmitLabel(Label);
948 // Create and entry for the info and add it to the other entries.
949 MCOS->getContext().addMCGenDwarfLabelEntry(
950 MCGenDwarfLabelEntry(Name, FileNumber, LineNumber, Label));
953 static int getDataAlignmentFactor(MCStreamer &streamer) {
954 MCContext &context = streamer.getContext();
955 const MCAsmInfo *asmInfo = context.getAsmInfo();
956 int size = asmInfo->getCalleeSaveStackSlotSize();
957 if (asmInfo->isStackGrowthDirectionUp())
963 static unsigned getSizeForEncoding(MCStreamer &streamer,
964 unsigned symbolEncoding) {
965 MCContext &context = streamer.getContext();
966 unsigned format = symbolEncoding & 0x0f;
968 default: llvm_unreachable("Unknown Encoding");
969 case dwarf::DW_EH_PE_absptr:
970 case dwarf::DW_EH_PE_signed:
971 return context.getAsmInfo()->getPointerSize();
972 case dwarf::DW_EH_PE_udata2:
973 case dwarf::DW_EH_PE_sdata2:
975 case dwarf::DW_EH_PE_udata4:
976 case dwarf::DW_EH_PE_sdata4:
978 case dwarf::DW_EH_PE_udata8:
979 case dwarf::DW_EH_PE_sdata8:
984 static void emitFDESymbol(MCObjectStreamer &streamer, const MCSymbol &symbol,
985 unsigned symbolEncoding, bool isEH) {
986 MCContext &context = streamer.getContext();
987 const MCAsmInfo *asmInfo = context.getAsmInfo();
988 const MCExpr *v = asmInfo->getExprForFDESymbol(&symbol,
991 unsigned size = getSizeForEncoding(streamer, symbolEncoding);
992 if (asmInfo->doDwarfFDESymbolsUseAbsDiff() && isEH)
993 emitAbsValue(streamer, v, size);
995 streamer.EmitValue(v, size);
998 static void EmitPersonality(MCStreamer &streamer, const MCSymbol &symbol,
999 unsigned symbolEncoding) {
1000 MCContext &context = streamer.getContext();
1001 const MCAsmInfo *asmInfo = context.getAsmInfo();
1002 const MCExpr *v = asmInfo->getExprForPersonalitySymbol(&symbol,
1005 unsigned size = getSizeForEncoding(streamer, symbolEncoding);
1006 streamer.EmitValue(v, size);
1010 class FrameEmitterImpl {
1013 const MCSymbol *SectionStart;
1015 FrameEmitterImpl(bool isEH)
1016 : CFAOffset(0), IsEH(isEH), SectionStart(nullptr) {}
1018 void setSectionStart(const MCSymbol *Label) { SectionStart = Label; }
1020 /// Emit the unwind information in a compact way.
1021 void EmitCompactUnwind(MCObjectStreamer &streamer,
1022 const MCDwarfFrameInfo &frame);
1024 const MCSymbol &EmitCIE(MCObjectStreamer &streamer,
1025 const MCSymbol *personality,
1026 unsigned personalityEncoding,
1027 const MCSymbol *lsda,
1029 unsigned lsdaEncoding,
1031 MCSymbol *EmitFDE(MCObjectStreamer &streamer,
1032 const MCSymbol &cieStart,
1033 const MCDwarfFrameInfo &frame);
1034 void EmitCFIInstructions(MCObjectStreamer &streamer,
1035 ArrayRef<MCCFIInstruction> Instrs,
1036 MCSymbol *BaseLabel);
1037 void EmitCFIInstruction(MCObjectStreamer &Streamer,
1038 const MCCFIInstruction &Instr);
1041 } // end anonymous namespace
1043 static void emitEncodingByte(MCObjectStreamer &Streamer, unsigned Encoding) {
1044 Streamer.EmitIntValue(Encoding, 1);
1047 void FrameEmitterImpl::EmitCFIInstruction(MCObjectStreamer &Streamer,
1048 const MCCFIInstruction &Instr) {
1049 int dataAlignmentFactor = getDataAlignmentFactor(Streamer);
1050 auto *MRI = Streamer.getContext().getRegisterInfo();
1052 switch (Instr.getOperation()) {
1053 case MCCFIInstruction::OpRegister: {
1054 unsigned Reg1 = Instr.getRegister();
1055 unsigned Reg2 = Instr.getRegister2();
1057 Reg1 = MRI->getDwarfRegNum(MRI->getLLVMRegNum(Reg1, true), false);
1058 Reg2 = MRI->getDwarfRegNum(MRI->getLLVMRegNum(Reg2, true), false);
1060 Streamer.EmitIntValue(dwarf::DW_CFA_register, 1);
1061 Streamer.EmitULEB128IntValue(Reg1);
1062 Streamer.EmitULEB128IntValue(Reg2);
1065 case MCCFIInstruction::OpWindowSave: {
1066 Streamer.EmitIntValue(dwarf::DW_CFA_GNU_window_save, 1);
1069 case MCCFIInstruction::OpUndefined: {
1070 unsigned Reg = Instr.getRegister();
1071 Streamer.EmitIntValue(dwarf::DW_CFA_undefined, 1);
1072 Streamer.EmitULEB128IntValue(Reg);
1075 case MCCFIInstruction::OpAdjustCfaOffset:
1076 case MCCFIInstruction::OpDefCfaOffset: {
1077 const bool IsRelative =
1078 Instr.getOperation() == MCCFIInstruction::OpAdjustCfaOffset;
1080 Streamer.EmitIntValue(dwarf::DW_CFA_def_cfa_offset, 1);
1083 CFAOffset += Instr.getOffset();
1085 CFAOffset = -Instr.getOffset();
1087 Streamer.EmitULEB128IntValue(CFAOffset);
1091 case MCCFIInstruction::OpDefCfa: {
1092 unsigned Reg = Instr.getRegister();
1094 Reg = MRI->getDwarfRegNum(MRI->getLLVMRegNum(Reg, true), false);
1095 Streamer.EmitIntValue(dwarf::DW_CFA_def_cfa, 1);
1096 Streamer.EmitULEB128IntValue(Reg);
1097 CFAOffset = -Instr.getOffset();
1098 Streamer.EmitULEB128IntValue(CFAOffset);
1103 case MCCFIInstruction::OpDefCfaRegister: {
1104 unsigned Reg = Instr.getRegister();
1106 Reg = MRI->getDwarfRegNum(MRI->getLLVMRegNum(Reg, true), false);
1107 Streamer.EmitIntValue(dwarf::DW_CFA_def_cfa_register, 1);
1108 Streamer.EmitULEB128IntValue(Reg);
1113 case MCCFIInstruction::OpOffset:
1114 case MCCFIInstruction::OpRelOffset: {
1115 const bool IsRelative =
1116 Instr.getOperation() == MCCFIInstruction::OpRelOffset;
1118 unsigned Reg = Instr.getRegister();
1120 Reg = MRI->getDwarfRegNum(MRI->getLLVMRegNum(Reg, true), false);
1122 int Offset = Instr.getOffset();
1124 Offset -= CFAOffset;
1125 Offset = Offset / dataAlignmentFactor;
1128 Streamer.EmitIntValue(dwarf::DW_CFA_offset_extended_sf, 1);
1129 Streamer.EmitULEB128IntValue(Reg);
1130 Streamer.EmitSLEB128IntValue(Offset);
1131 } else if (Reg < 64) {
1132 Streamer.EmitIntValue(dwarf::DW_CFA_offset + Reg, 1);
1133 Streamer.EmitULEB128IntValue(Offset);
1135 Streamer.EmitIntValue(dwarf::DW_CFA_offset_extended, 1);
1136 Streamer.EmitULEB128IntValue(Reg);
1137 Streamer.EmitULEB128IntValue(Offset);
1141 case MCCFIInstruction::OpRememberState:
1142 Streamer.EmitIntValue(dwarf::DW_CFA_remember_state, 1);
1144 case MCCFIInstruction::OpRestoreState:
1145 Streamer.EmitIntValue(dwarf::DW_CFA_restore_state, 1);
1147 case MCCFIInstruction::OpSameValue: {
1148 unsigned Reg = Instr.getRegister();
1149 Streamer.EmitIntValue(dwarf::DW_CFA_same_value, 1);
1150 Streamer.EmitULEB128IntValue(Reg);
1153 case MCCFIInstruction::OpRestore: {
1154 unsigned Reg = Instr.getRegister();
1156 Reg = MRI->getDwarfRegNum(MRI->getLLVMRegNum(Reg, true), false);
1157 Streamer.EmitIntValue(dwarf::DW_CFA_restore | Reg, 1);
1160 case MCCFIInstruction::OpEscape:
1161 Streamer.EmitBytes(Instr.getValues());
1164 llvm_unreachable("Unhandled case in switch");
1167 /// Emit frame instructions to describe the layout of the frame.
1168 void FrameEmitterImpl::EmitCFIInstructions(MCObjectStreamer &streamer,
1169 ArrayRef<MCCFIInstruction> Instrs,
1170 MCSymbol *BaseLabel) {
1171 for (unsigned i = 0, N = Instrs.size(); i < N; ++i) {
1172 const MCCFIInstruction &Instr = Instrs[i];
1173 MCSymbol *Label = Instr.getLabel();
1174 // Throw out move if the label is invalid.
1175 if (Label && !Label->isDefined()) continue; // Not emitted, in dead code.
1177 // Advance row if new location.
1178 if (BaseLabel && Label) {
1179 MCSymbol *ThisSym = Label;
1180 if (ThisSym != BaseLabel) {
1181 streamer.EmitDwarfAdvanceFrameAddr(BaseLabel, ThisSym);
1182 BaseLabel = ThisSym;
1186 EmitCFIInstruction(streamer, Instr);
1190 /// Emit the unwind information in a compact way.
1191 void FrameEmitterImpl::EmitCompactUnwind(MCObjectStreamer &Streamer,
1192 const MCDwarfFrameInfo &Frame) {
1193 MCContext &Context = Streamer.getContext();
1194 const MCObjectFileInfo *MOFI = Context.getObjectFileInfo();
1196 // range-start range-length compact-unwind-enc personality-func lsda
1197 // _foo LfooEnd-_foo 0x00000023 0 0
1198 // _bar LbarEnd-_bar 0x00000025 __gxx_personality except_tab1
1200 // .section __LD,__compact_unwind,regular,debug
1202 // # compact unwind for _foo
1204 // .set L1,LfooEnd-_foo
1210 // # compact unwind for _bar
1212 // .set L2,LbarEnd-_bar
1215 // .quad __gxx_personality
1216 // .quad except_tab1
1218 uint32_t Encoding = Frame.CompactUnwindEncoding;
1219 if (!Encoding) return;
1220 bool DwarfEHFrameOnly = (Encoding == MOFI->getCompactUnwindDwarfEHFrameOnly());
1222 // The encoding needs to know we have an LSDA.
1223 if (!DwarfEHFrameOnly && Frame.Lsda)
1224 Encoding |= 0x40000000;
1227 unsigned FDEEncoding = MOFI->getFDEEncoding();
1228 unsigned Size = getSizeForEncoding(Streamer, FDEEncoding);
1229 Streamer.EmitSymbolValue(Frame.Begin, Size);
1232 const MCExpr *Range = MakeStartMinusEndExpr(Streamer, *Frame.Begin,
1234 emitAbsValue(Streamer, Range, 4);
1237 Size = getSizeForEncoding(Streamer, dwarf::DW_EH_PE_udata4);
1238 Streamer.EmitIntValue(Encoding, Size);
1240 // Personality Function
1241 Size = getSizeForEncoding(Streamer, dwarf::DW_EH_PE_absptr);
1242 if (!DwarfEHFrameOnly && Frame.Personality)
1243 Streamer.EmitSymbolValue(Frame.Personality, Size);
1245 Streamer.EmitIntValue(0, Size); // No personality fn
1248 Size = getSizeForEncoding(Streamer, Frame.LsdaEncoding);
1249 if (!DwarfEHFrameOnly && Frame.Lsda)
1250 Streamer.EmitSymbolValue(Frame.Lsda, Size);
1252 Streamer.EmitIntValue(0, Size); // No LSDA
1255 const MCSymbol &FrameEmitterImpl::EmitCIE(MCObjectStreamer &streamer,
1256 const MCSymbol *personality,
1257 unsigned personalityEncoding,
1258 const MCSymbol *lsda,
1260 unsigned lsdaEncoding,
1262 MCContext &context = streamer.getContext();
1263 const MCRegisterInfo *MRI = context.getRegisterInfo();
1264 const MCObjectFileInfo *MOFI = context.getObjectFileInfo();
1266 MCSymbol *sectionStart = context.CreateTempSymbol();
1267 streamer.EmitLabel(sectionStart);
1269 MCSymbol *sectionEnd = context.CreateTempSymbol();
1272 const MCExpr *Length = MakeStartMinusEndExpr(streamer, *sectionStart,
1274 emitAbsValue(streamer, Length, 4);
1277 unsigned CIE_ID = IsEH ? 0 : -1;
1278 streamer.EmitIntValue(CIE_ID, 4);
1281 // For DWARF2, we use CIE version 1
1282 // For DWARF3+, we use CIE version 3
1283 uint8_t CIEVersion = context.getDwarfVersion() <= 2 ? 1 : 3;
1284 streamer.EmitIntValue(CIEVersion, 1);
1286 // Augmentation String
1287 SmallString<8> Augmentation;
1289 Augmentation += "z";
1291 Augmentation += "P";
1293 Augmentation += "L";
1294 Augmentation += "R";
1296 Augmentation += "S";
1297 streamer.EmitBytes(Augmentation.str());
1299 streamer.EmitIntValue(0, 1);
1301 // Code Alignment Factor
1302 streamer.EmitULEB128IntValue(context.getAsmInfo()->getMinInstAlignment());
1304 // Data Alignment Factor
1305 streamer.EmitSLEB128IntValue(getDataAlignmentFactor(streamer));
1307 // Return Address Register
1308 if (CIEVersion == 1) {
1309 assert(MRI->getRARegister() <= 255 &&
1310 "DWARF 2 encodes return_address_register in one byte");
1311 streamer.EmitIntValue(MRI->getDwarfRegNum(MRI->getRARegister(), IsEH), 1);
1313 streamer.EmitULEB128IntValue(
1314 MRI->getDwarfRegNum(MRI->getRARegister(), IsEH));
1317 // Augmentation Data Length (optional)
1319 unsigned augmentationLength = 0;
1322 // Personality Encoding
1323 augmentationLength += 1;
1325 augmentationLength += getSizeForEncoding(streamer, personalityEncoding);
1328 augmentationLength += 1;
1329 // Encoding of the FDE pointers
1330 augmentationLength += 1;
1332 streamer.EmitULEB128IntValue(augmentationLength);
1334 // Augmentation Data (optional)
1336 // Personality Encoding
1337 emitEncodingByte(streamer, personalityEncoding);
1339 EmitPersonality(streamer, *personality, personalityEncoding);
1343 emitEncodingByte(streamer, lsdaEncoding);
1345 // Encoding of the FDE pointers
1346 emitEncodingByte(streamer, MOFI->getFDEEncoding());
1349 // Initial Instructions
1351 const MCAsmInfo *MAI = context.getAsmInfo();
1353 const std::vector<MCCFIInstruction> &Instructions =
1354 MAI->getInitialFrameState();
1355 EmitCFIInstructions(streamer, Instructions, nullptr);
1359 streamer.EmitValueToAlignment(IsEH ? 4 : MAI->getPointerSize());
1361 streamer.EmitLabel(sectionEnd);
1362 return *sectionStart;
1365 MCSymbol *FrameEmitterImpl::EmitFDE(MCObjectStreamer &streamer,
1366 const MCSymbol &cieStart,
1367 const MCDwarfFrameInfo &frame) {
1368 MCContext &context = streamer.getContext();
1369 MCSymbol *fdeStart = context.CreateTempSymbol();
1370 MCSymbol *fdeEnd = context.CreateTempSymbol();
1371 const MCObjectFileInfo *MOFI = context.getObjectFileInfo();
1374 const MCExpr *Length = MakeStartMinusEndExpr(streamer, *fdeStart, *fdeEnd, 0);
1375 emitAbsValue(streamer, Length, 4);
1377 streamer.EmitLabel(fdeStart);
1380 const MCAsmInfo *asmInfo = context.getAsmInfo();
1382 const MCExpr *offset = MakeStartMinusEndExpr(streamer, cieStart, *fdeStart,
1384 emitAbsValue(streamer, offset, 4);
1385 } else if (!asmInfo->doesDwarfUseRelocationsAcrossSections()) {
1386 const MCExpr *offset = MakeStartMinusEndExpr(streamer, *SectionStart,
1388 emitAbsValue(streamer, offset, 4);
1390 streamer.EmitSymbolValue(&cieStart, 4);
1394 unsigned PCEncoding =
1395 IsEH ? MOFI->getFDEEncoding() : (unsigned)dwarf::DW_EH_PE_absptr;
1396 unsigned PCSize = getSizeForEncoding(streamer, PCEncoding);
1397 emitFDESymbol(streamer, *frame.Begin, PCEncoding, IsEH);
1400 const MCExpr *Range = MakeStartMinusEndExpr(streamer, *frame.Begin,
1402 emitAbsValue(streamer, Range, PCSize);
1405 // Augmentation Data Length
1406 unsigned augmentationLength = 0;
1409 augmentationLength += getSizeForEncoding(streamer, frame.LsdaEncoding);
1411 streamer.EmitULEB128IntValue(augmentationLength);
1413 // Augmentation Data
1415 emitFDESymbol(streamer, *frame.Lsda, frame.LsdaEncoding, true);
1418 // Call Frame Instructions
1419 EmitCFIInstructions(streamer, frame.Instructions, frame.Begin);
1422 streamer.EmitValueToAlignment(PCSize);
1429 static const CIEKey getEmptyKey() {
1430 return CIEKey(nullptr, 0, -1, false, false);
1432 static const CIEKey getTombstoneKey() {
1433 return CIEKey(nullptr, -1, 0, false, false);
1436 CIEKey(const MCSymbol *Personality_, unsigned PersonalityEncoding_,
1437 unsigned LsdaEncoding_, bool IsSignalFrame_, bool IsSimple_)
1438 : Personality(Personality_), PersonalityEncoding(PersonalityEncoding_),
1439 LsdaEncoding(LsdaEncoding_), IsSignalFrame(IsSignalFrame_),
1440 IsSimple(IsSimple_) {}
1441 const MCSymbol *Personality;
1442 unsigned PersonalityEncoding;
1443 unsigned LsdaEncoding;
1451 struct DenseMapInfo<CIEKey> {
1452 static CIEKey getEmptyKey() {
1453 return CIEKey::getEmptyKey();
1455 static CIEKey getTombstoneKey() {
1456 return CIEKey::getTombstoneKey();
1458 static unsigned getHashValue(const CIEKey &Key) {
1459 return static_cast<unsigned>(hash_combine(Key.Personality,
1460 Key.PersonalityEncoding,
1465 static bool isEqual(const CIEKey &LHS,
1466 const CIEKey &RHS) {
1467 return LHS.Personality == RHS.Personality &&
1468 LHS.PersonalityEncoding == RHS.PersonalityEncoding &&
1469 LHS.LsdaEncoding == RHS.LsdaEncoding &&
1470 LHS.IsSignalFrame == RHS.IsSignalFrame &&
1471 LHS.IsSimple == RHS.IsSimple;
1476 void MCDwarfFrameEmitter::Emit(MCObjectStreamer &Streamer, MCAsmBackend *MAB,
1478 Streamer.generateCompactUnwindEncodings(MAB);
1480 MCContext &Context = Streamer.getContext();
1481 const MCObjectFileInfo *MOFI = Context.getObjectFileInfo();
1482 FrameEmitterImpl Emitter(IsEH);
1483 ArrayRef<MCDwarfFrameInfo> FrameArray = Streamer.getDwarfFrameInfos();
1485 // Emit the compact unwind info if available.
1486 bool NeedsEHFrameSection = !MOFI->getSupportsCompactUnwindWithoutEHFrame();
1487 if (IsEH && MOFI->getCompactUnwindSection()) {
1488 bool SectionEmitted = false;
1489 for (unsigned i = 0, n = FrameArray.size(); i < n; ++i) {
1490 const MCDwarfFrameInfo &Frame = FrameArray[i];
1491 if (Frame.CompactUnwindEncoding == 0) continue;
1492 if (!SectionEmitted) {
1493 Streamer.SwitchSection(MOFI->getCompactUnwindSection());
1494 Streamer.EmitValueToAlignment(Context.getAsmInfo()->getPointerSize());
1495 SectionEmitted = true;
1497 NeedsEHFrameSection |=
1498 Frame.CompactUnwindEncoding ==
1499 MOFI->getCompactUnwindDwarfEHFrameOnly();
1500 Emitter.EmitCompactUnwind(Streamer, Frame);
1504 if (!NeedsEHFrameSection) return;
1506 const MCSection &Section =
1507 IsEH ? *const_cast<MCObjectFileInfo*>(MOFI)->getEHFrameSection() :
1508 *MOFI->getDwarfFrameSection();
1510 Streamer.SwitchSection(&Section);
1511 MCSymbol *SectionStart = Context.CreateTempSymbol();
1512 Streamer.EmitLabel(SectionStart);
1513 Emitter.setSectionStart(SectionStart);
1515 MCSymbol *FDEEnd = nullptr;
1516 DenseMap<CIEKey, const MCSymbol *> CIEStarts;
1518 const MCSymbol *DummyDebugKey = nullptr;
1519 NeedsEHFrameSection = !MOFI->getSupportsCompactUnwindWithoutEHFrame();
1520 for (unsigned i = 0, n = FrameArray.size(); i < n; ++i) {
1521 const MCDwarfFrameInfo &Frame = FrameArray[i];
1523 // Emit the label from the previous iteration
1525 Streamer.EmitLabel(FDEEnd);
1529 if (!NeedsEHFrameSection && Frame.CompactUnwindEncoding !=
1530 MOFI->getCompactUnwindDwarfEHFrameOnly())
1531 // Don't generate an EH frame if we don't need one. I.e., it's taken care
1532 // of by the compact unwind encoding.
1535 CIEKey Key(Frame.Personality, Frame.PersonalityEncoding,
1536 Frame.LsdaEncoding, Frame.IsSignalFrame, Frame.IsSimple);
1537 const MCSymbol *&CIEStart = IsEH ? CIEStarts[Key] : DummyDebugKey;
1539 CIEStart = &Emitter.EmitCIE(Streamer, Frame.Personality,
1540 Frame.PersonalityEncoding, Frame.Lsda,
1541 Frame.IsSignalFrame,
1545 FDEEnd = Emitter.EmitFDE(Streamer, *CIEStart, Frame);
1548 Streamer.EmitValueToAlignment(Context.getAsmInfo()->getPointerSize());
1550 Streamer.EmitLabel(FDEEnd);
1553 void MCDwarfFrameEmitter::EmitAdvanceLoc(MCObjectStreamer &Streamer,
1554 uint64_t AddrDelta) {
1555 MCContext &Context = Streamer.getContext();
1556 SmallString<256> Tmp;
1557 raw_svector_ostream OS(Tmp);
1558 MCDwarfFrameEmitter::EncodeAdvanceLoc(Context, AddrDelta, OS);
1559 Streamer.EmitBytes(OS.str());
1562 void MCDwarfFrameEmitter::EncodeAdvanceLoc(MCContext &Context,
1565 // Scale the address delta by the minimum instruction length.
1566 AddrDelta = ScaleAddrDelta(Context, AddrDelta);
1568 if (AddrDelta == 0) {
1569 } else if (isUIntN(6, AddrDelta)) {
1570 uint8_t Opcode = dwarf::DW_CFA_advance_loc | AddrDelta;
1572 } else if (isUInt<8>(AddrDelta)) {
1573 OS << uint8_t(dwarf::DW_CFA_advance_loc1);
1574 OS << uint8_t(AddrDelta);
1575 } else if (isUInt<16>(AddrDelta)) {
1576 // FIXME: check what is the correct behavior on a big endian machine.
1577 OS << uint8_t(dwarf::DW_CFA_advance_loc2);
1578 OS << uint8_t( AddrDelta & 0xff);
1579 OS << uint8_t((AddrDelta >> 8) & 0xff);
1581 // FIXME: check what is the correct behavior on a big endian machine.
1582 assert(isUInt<32>(AddrDelta));
1583 OS << uint8_t(dwarf::DW_CFA_advance_loc4);
1584 OS << uint8_t( AddrDelta & 0xff);
1585 OS << uint8_t((AddrDelta >> 8) & 0xff);
1586 OS << uint8_t((AddrDelta >> 16) & 0xff);
1587 OS << uint8_t((AddrDelta >> 24) & 0xff);