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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/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"
30 
31 using namespace llvm;
32 
ScaleAddrDelta(MCContext & Context,uint64_t AddrDelta)33 static inline uint64_t ScaleAddrDelta(MCContext &Context, uint64_t AddrDelta) {
34   unsigned MinInsnLength = Context.getAsmInfo()->getMinInstAlignment();
35   if (MinInsnLength == 1)
36     return AddrDelta;
37   if (AddrDelta % MinInsnLength != 0) {
38     // TODO: report this error, but really only once.
39     ;
40   }
41   return AddrDelta / MinInsnLength;
42 }
43 
44 //
45 // This is called when an instruction is assembled into the specified section
46 // and if there is information from the last .loc directive that has yet to have
47 // a line entry made for it is made.
48 //
Make(MCObjectStreamer * MCOS,MCSection * Section)49 void MCLineEntry::Make(MCObjectStreamer *MCOS, MCSection *Section) {
50   if (!MCOS->getContext().getDwarfLocSeen())
51     return;
52 
53   // Create a symbol at in the current section for use in the line entry.
54   MCSymbol *LineSym = MCOS->getContext().createTempSymbol();
55   // Set the value of the symbol to use for the MCLineEntry.
56   MCOS->EmitLabel(LineSym);
57 
58   // Get the current .loc info saved in the context.
59   const MCDwarfLoc &DwarfLoc = MCOS->getContext().getCurrentDwarfLoc();
60 
61   // Create a (local) line entry with the symbol and the current .loc info.
62   MCLineEntry LineEntry(LineSym, DwarfLoc);
63 
64   // clear DwarfLocSeen saying the current .loc info is now used.
65   MCOS->getContext().clearDwarfLocSeen();
66 
67   // Add the line entry to this section's entries.
68   MCOS->getContext()
69       .getMCDwarfLineTable(MCOS->getContext().getDwarfCompileUnitID())
70       .getMCLineSections()
71       .addLineEntry(LineEntry, Section);
72 }
73 
74 //
75 // This helper routine returns an expression of End - Start + IntVal .
76 //
MakeStartMinusEndExpr(const MCStreamer & MCOS,const MCSymbol & Start,const MCSymbol & End,int IntVal)77 static inline const MCExpr *MakeStartMinusEndExpr(const MCStreamer &MCOS,
78                                                   const MCSymbol &Start,
79                                                   const MCSymbol &End,
80                                                   int IntVal) {
81   MCSymbolRefExpr::VariantKind Variant = MCSymbolRefExpr::VK_None;
82   const MCExpr *Res =
83     MCSymbolRefExpr::create(&End, Variant, MCOS.getContext());
84   const MCExpr *RHS =
85     MCSymbolRefExpr::create(&Start, Variant, MCOS.getContext());
86   const MCExpr *Res1 =
87     MCBinaryExpr::create(MCBinaryExpr::Sub, Res, RHS, MCOS.getContext());
88   const MCExpr *Res2 =
89     MCConstantExpr::create(IntVal, MCOS.getContext());
90   const MCExpr *Res3 =
91     MCBinaryExpr::create(MCBinaryExpr::Sub, Res1, Res2, MCOS.getContext());
92   return Res3;
93 }
94 
95 //
96 // This emits the Dwarf line table for the specified section from the entries
97 // in the LineSection.
98 //
99 static inline void
EmitDwarfLineTable(MCObjectStreamer * MCOS,MCSection * Section,const MCLineSection::MCLineEntryCollection & LineEntries)100 EmitDwarfLineTable(MCObjectStreamer *MCOS, MCSection *Section,
101                    const MCLineSection::MCLineEntryCollection &LineEntries) {
102   unsigned FileNum = 1;
103   unsigned LastLine = 1;
104   unsigned Column = 0;
105   unsigned Flags = DWARF2_LINE_DEFAULT_IS_STMT ? DWARF2_FLAG_IS_STMT : 0;
106   unsigned Isa = 0;
107   unsigned Discriminator = 0;
108   MCSymbol *LastLabel = nullptr;
109 
110   // Loop through each MCLineEntry and encode the dwarf line number table.
111   for (auto it = LineEntries.begin(),
112             ie = LineEntries.end();
113        it != ie; ++it) {
114 
115     if (FileNum != it->getFileNum()) {
116       FileNum = it->getFileNum();
117       MCOS->EmitIntValue(dwarf::DW_LNS_set_file, 1);
118       MCOS->EmitULEB128IntValue(FileNum);
119     }
120     if (Column != it->getColumn()) {
121       Column = it->getColumn();
122       MCOS->EmitIntValue(dwarf::DW_LNS_set_column, 1);
123       MCOS->EmitULEB128IntValue(Column);
124     }
125     if (Discriminator != it->getDiscriminator()) {
126       Discriminator = it->getDiscriminator();
127       unsigned Size = getULEB128Size(Discriminator);
128       MCOS->EmitIntValue(dwarf::DW_LNS_extended_op, 1);
129       MCOS->EmitULEB128IntValue(Size + 1);
130       MCOS->EmitIntValue(dwarf::DW_LNE_set_discriminator, 1);
131       MCOS->EmitULEB128IntValue(Discriminator);
132     }
133     if (Isa != it->getIsa()) {
134       Isa = it->getIsa();
135       MCOS->EmitIntValue(dwarf::DW_LNS_set_isa, 1);
136       MCOS->EmitULEB128IntValue(Isa);
137     }
138     if ((it->getFlags() ^ Flags) & DWARF2_FLAG_IS_STMT) {
139       Flags = it->getFlags();
140       MCOS->EmitIntValue(dwarf::DW_LNS_negate_stmt, 1);
141     }
142     if (it->getFlags() & DWARF2_FLAG_BASIC_BLOCK)
143       MCOS->EmitIntValue(dwarf::DW_LNS_set_basic_block, 1);
144     if (it->getFlags() & DWARF2_FLAG_PROLOGUE_END)
145       MCOS->EmitIntValue(dwarf::DW_LNS_set_prologue_end, 1);
146     if (it->getFlags() & DWARF2_FLAG_EPILOGUE_BEGIN)
147       MCOS->EmitIntValue(dwarf::DW_LNS_set_epilogue_begin, 1);
148 
149     int64_t LineDelta = static_cast<int64_t>(it->getLine()) - LastLine;
150     MCSymbol *Label = it->getLabel();
151 
152     // At this point we want to emit/create the sequence to encode the delta in
153     // line numbers and the increment of the address from the previous Label
154     // and the current Label.
155     const MCAsmInfo *asmInfo = MCOS->getContext().getAsmInfo();
156     MCOS->EmitDwarfAdvanceLineAddr(LineDelta, LastLabel, Label,
157                                    asmInfo->getPointerSize());
158 
159     LastLine = it->getLine();
160     LastLabel = Label;
161   }
162 
163   // Emit a DW_LNE_end_sequence for the end of the section.
164   // Use the section end label to compute the address delta and use INT64_MAX
165   // as the line delta which is the signal that this is actually a
166   // DW_LNE_end_sequence.
167   MCSymbol *SectionEnd = MCOS->endSection(Section);
168 
169   // Switch back the dwarf line section, in case endSection had to switch the
170   // section.
171   MCContext &Ctx = MCOS->getContext();
172   MCOS->SwitchSection(Ctx.getObjectFileInfo()->getDwarfLineSection());
173 
174   const MCAsmInfo *AsmInfo = Ctx.getAsmInfo();
175   MCOS->EmitDwarfAdvanceLineAddr(INT64_MAX, LastLabel, SectionEnd,
176                                  AsmInfo->getPointerSize());
177 }
178 
179 //
180 // This emits the Dwarf file and the line tables.
181 //
Emit(MCObjectStreamer * MCOS,MCDwarfLineTableParams Params)182 void MCDwarfLineTable::Emit(MCObjectStreamer *MCOS,
183                             MCDwarfLineTableParams Params) {
184   MCContext &context = MCOS->getContext();
185 
186   auto &LineTables = context.getMCDwarfLineTables();
187 
188   // Bail out early so we don't switch to the debug_line section needlessly and
189   // in doing so create an unnecessary (if empty) section.
190   if (LineTables.empty())
191     return;
192 
193   // Switch to the section where the table will be emitted into.
194   MCOS->SwitchSection(context.getObjectFileInfo()->getDwarfLineSection());
195 
196   // Handle the rest of the Compile Units.
197   for (const auto &CUIDTablePair : LineTables)
198     CUIDTablePair.second.EmitCU(MCOS, Params);
199 }
200 
Emit(MCStreamer & MCOS,MCDwarfLineTableParams Params) const201 void MCDwarfDwoLineTable::Emit(MCStreamer &MCOS,
202                                MCDwarfLineTableParams Params) const {
203   MCOS.EmitLabel(Header.Emit(&MCOS, Params, None).second);
204 }
205 
206 std::pair<MCSymbol *, MCSymbol *>
Emit(MCStreamer * MCOS,MCDwarfLineTableParams Params) const207 MCDwarfLineTableHeader::Emit(MCStreamer *MCOS,
208                              MCDwarfLineTableParams Params) const {
209   static const char StandardOpcodeLengths[] = {
210       0, // length of DW_LNS_copy
211       1, // length of DW_LNS_advance_pc
212       1, // length of DW_LNS_advance_line
213       1, // length of DW_LNS_set_file
214       1, // length of DW_LNS_set_column
215       0, // length of DW_LNS_negate_stmt
216       0, // length of DW_LNS_set_basic_block
217       0, // length of DW_LNS_const_add_pc
218       1, // length of DW_LNS_fixed_advance_pc
219       0, // length of DW_LNS_set_prologue_end
220       0, // length of DW_LNS_set_epilogue_begin
221       1  // DW_LNS_set_isa
222   };
223   assert(array_lengthof(StandardOpcodeLengths) >=
224          (Params.DWARF2LineOpcodeBase - 1U));
225   return Emit(MCOS, Params, makeArrayRef(StandardOpcodeLengths,
226                                          Params.DWARF2LineOpcodeBase - 1));
227 }
228 
forceExpAbs(MCStreamer & OS,const MCExpr * Expr)229 static const MCExpr *forceExpAbs(MCStreamer &OS, const MCExpr* Expr) {
230   MCContext &Context = OS.getContext();
231   assert(!isa<MCSymbolRefExpr>(Expr));
232   if (Context.getAsmInfo()->hasAggressiveSymbolFolding())
233     return Expr;
234 
235   MCSymbol *ABS = Context.createTempSymbol();
236   OS.EmitAssignment(ABS, Expr);
237   return MCSymbolRefExpr::create(ABS, Context);
238 }
239 
emitAbsValue(MCStreamer & OS,const MCExpr * Value,unsigned Size)240 static void emitAbsValue(MCStreamer &OS, const MCExpr *Value, unsigned Size) {
241   const MCExpr *ABS = forceExpAbs(OS, Value);
242   OS.EmitValue(ABS, Size);
243 }
244 
245 std::pair<MCSymbol *, MCSymbol *>
Emit(MCStreamer * MCOS,MCDwarfLineTableParams Params,ArrayRef<char> StandardOpcodeLengths) const246 MCDwarfLineTableHeader::Emit(MCStreamer *MCOS, MCDwarfLineTableParams Params,
247                              ArrayRef<char> StandardOpcodeLengths) const {
248   MCContext &context = MCOS->getContext();
249 
250   // Create a symbol at the beginning of the line table.
251   MCSymbol *LineStartSym = Label;
252   if (!LineStartSym)
253     LineStartSym = context.createTempSymbol();
254   // Set the value of the symbol, as we are at the start of the line table.
255   MCOS->EmitLabel(LineStartSym);
256 
257   // Create a symbol for the end of the section (to be set when we get there).
258   MCSymbol *LineEndSym = context.createTempSymbol();
259 
260   // The first 4 bytes is the total length of the information for this
261   // compilation unit (not including these 4 bytes for the length).
262   emitAbsValue(*MCOS,
263                MakeStartMinusEndExpr(*MCOS, *LineStartSym, *LineEndSym, 4), 4);
264 
265   // Next 2 bytes is the Version, which is Dwarf 2.
266   MCOS->EmitIntValue(2, 2);
267 
268   // Create a symbol for the end of the prologue (to be set when we get there).
269   MCSymbol *ProEndSym = context.createTempSymbol(); // Lprologue_end
270 
271   // Length of the prologue, is the next 4 bytes.  Which is the start of the
272   // section to the end of the prologue.  Not including the 4 bytes for the
273   // total length, the 2 bytes for the version, and these 4 bytes for the
274   // length of the prologue.
275   emitAbsValue(
276       *MCOS,
277       MakeStartMinusEndExpr(*MCOS, *LineStartSym, *ProEndSym, (4 + 2 + 4)), 4);
278 
279   // Parameters of the state machine, are next.
280   MCOS->EmitIntValue(context.getAsmInfo()->getMinInstAlignment(), 1);
281   MCOS->EmitIntValue(DWARF2_LINE_DEFAULT_IS_STMT, 1);
282   MCOS->EmitIntValue(Params.DWARF2LineBase, 1);
283   MCOS->EmitIntValue(Params.DWARF2LineRange, 1);
284   MCOS->EmitIntValue(StandardOpcodeLengths.size() + 1, 1);
285 
286   // Standard opcode lengths
287   for (char Length : StandardOpcodeLengths)
288     MCOS->EmitIntValue(Length, 1);
289 
290   // Put out the directory and file tables.
291 
292   // First the directory table.
293   for (unsigned i = 0; i < MCDwarfDirs.size(); i++) {
294     MCOS->EmitBytes(MCDwarfDirs[i]); // the DirectoryName
295     MCOS->EmitBytes(StringRef("\0", 1)); // the null term. of the string
296   }
297   MCOS->EmitIntValue(0, 1); // Terminate the directory list
298 
299   // Second the file table.
300   for (unsigned i = 1; i < MCDwarfFiles.size(); i++) {
301     assert(!MCDwarfFiles[i].Name.empty());
302     MCOS->EmitBytes(MCDwarfFiles[i].Name); // FileName
303     MCOS->EmitBytes(StringRef("\0", 1)); // the null term. of the string
304     // the Directory num
305     MCOS->EmitULEB128IntValue(MCDwarfFiles[i].DirIndex);
306     MCOS->EmitIntValue(0, 1); // last modification timestamp (always 0)
307     MCOS->EmitIntValue(0, 1); // filesize (always 0)
308   }
309   MCOS->EmitIntValue(0, 1); // Terminate the file list
310 
311   // This is the end of the prologue, so set the value of the symbol at the
312   // end of the prologue (that was used in a previous expression).
313   MCOS->EmitLabel(ProEndSym);
314 
315   return std::make_pair(LineStartSym, LineEndSym);
316 }
317 
EmitCU(MCObjectStreamer * MCOS,MCDwarfLineTableParams Params) const318 void MCDwarfLineTable::EmitCU(MCObjectStreamer *MCOS,
319                               MCDwarfLineTableParams Params) const {
320   MCSymbol *LineEndSym = Header.Emit(MCOS, Params).second;
321 
322   // Put out the line tables.
323   for (const auto &LineSec : MCLineSections.getMCLineEntries())
324     EmitDwarfLineTable(MCOS, LineSec.first, LineSec.second);
325 
326   // This is the end of the section, so set the value of the symbol at the end
327   // of this section (that was used in a previous expression).
328   MCOS->EmitLabel(LineEndSym);
329 }
330 
getFile(StringRef & Directory,StringRef & FileName,unsigned FileNumber)331 unsigned MCDwarfLineTable::getFile(StringRef &Directory, StringRef &FileName,
332                                    unsigned FileNumber) {
333   return Header.getFile(Directory, FileName, FileNumber);
334 }
335 
getFile(StringRef & Directory,StringRef & FileName,unsigned FileNumber)336 unsigned MCDwarfLineTableHeader::getFile(StringRef &Directory,
337                                          StringRef &FileName,
338                                          unsigned FileNumber) {
339   if (Directory == CompilationDir)
340     Directory = "";
341   if (FileName.empty()) {
342     FileName = "<stdin>";
343     Directory = "";
344   }
345   assert(!FileName.empty());
346   if (FileNumber == 0) {
347     FileNumber = SourceIdMap.size() + 1;
348     assert((MCDwarfFiles.empty() || FileNumber == MCDwarfFiles.size()) &&
349            "Don't mix autonumbered and explicit numbered line table usage");
350     SmallString<256> Buffer;
351     auto IterBool = SourceIdMap.insert(
352         std::make_pair((Directory + Twine('\0') + FileName).toStringRef(Buffer),
353                        FileNumber));
354     if (!IterBool.second)
355       return IterBool.first->second;
356   }
357   // Make space for this FileNumber in the MCDwarfFiles vector if needed.
358   MCDwarfFiles.resize(FileNumber + 1);
359 
360   // Get the new MCDwarfFile slot for this FileNumber.
361   MCDwarfFile &File = MCDwarfFiles[FileNumber];
362 
363   // It is an error to use see the same number more than once.
364   if (!File.Name.empty())
365     return 0;
366 
367   if (Directory.empty()) {
368     // Separate the directory part from the basename of the FileName.
369     StringRef tFileName = sys::path::filename(FileName);
370     if (!tFileName.empty()) {
371       Directory = sys::path::parent_path(FileName);
372       if (!Directory.empty())
373         FileName = tFileName;
374     }
375   }
376 
377   // Find or make an entry in the MCDwarfDirs vector for this Directory.
378   // Capture directory name.
379   unsigned DirIndex;
380   if (Directory.empty()) {
381     // For FileNames with no directories a DirIndex of 0 is used.
382     DirIndex = 0;
383   } else {
384     DirIndex = 0;
385     for (unsigned End = MCDwarfDirs.size(); DirIndex < End; DirIndex++) {
386       if (Directory == MCDwarfDirs[DirIndex])
387         break;
388     }
389     if (DirIndex >= MCDwarfDirs.size())
390       MCDwarfDirs.push_back(Directory);
391     // The DirIndex is one based, as DirIndex of 0 is used for FileNames with
392     // no directories.  MCDwarfDirs[] is unlike MCDwarfFiles[] in that the
393     // directory names are stored at MCDwarfDirs[DirIndex-1] where FileNames
394     // are stored at MCDwarfFiles[FileNumber].Name .
395     DirIndex++;
396   }
397 
398   File.Name = FileName;
399   File.DirIndex = DirIndex;
400 
401   // return the allocated FileNumber.
402   return FileNumber;
403 }
404 
405 /// Utility function to emit the encoding to a streamer.
Emit(MCStreamer * MCOS,MCDwarfLineTableParams Params,int64_t LineDelta,uint64_t AddrDelta)406 void MCDwarfLineAddr::Emit(MCStreamer *MCOS, MCDwarfLineTableParams Params,
407                            int64_t LineDelta, uint64_t AddrDelta) {
408   MCContext &Context = MCOS->getContext();
409   SmallString<256> Tmp;
410   raw_svector_ostream OS(Tmp);
411   MCDwarfLineAddr::Encode(Context, Params, LineDelta, AddrDelta, OS);
412   MCOS->EmitBytes(OS.str());
413 }
414 
415 /// Given a special op, return the address skip amount (in units of
416 /// DWARF2_LINE_MIN_INSN_LENGTH).
SpecialAddr(MCDwarfLineTableParams Params,uint64_t op)417 static uint64_t SpecialAddr(MCDwarfLineTableParams Params, uint64_t op) {
418   return (op - Params.DWARF2LineOpcodeBase) / Params.DWARF2LineRange;
419 }
420 
421 /// Utility function to encode a Dwarf pair of LineDelta and AddrDeltas.
Encode(MCContext & Context,MCDwarfLineTableParams Params,int64_t LineDelta,uint64_t AddrDelta,raw_ostream & OS)422 void MCDwarfLineAddr::Encode(MCContext &Context, MCDwarfLineTableParams Params,
423                              int64_t LineDelta, uint64_t AddrDelta,
424                              raw_ostream &OS) {
425   uint64_t Temp, Opcode;
426   bool NeedCopy = false;
427 
428   // The maximum address skip amount that can be encoded with a special op.
429   uint64_t MaxSpecialAddrDelta = SpecialAddr(Params, 255);
430 
431   // Scale the address delta by the minimum instruction length.
432   AddrDelta = ScaleAddrDelta(Context, AddrDelta);
433 
434   // A LineDelta of INT64_MAX is a signal that this is actually a
435   // DW_LNE_end_sequence. We cannot use special opcodes here, since we want the
436   // end_sequence to emit the matrix entry.
437   if (LineDelta == INT64_MAX) {
438     if (AddrDelta == MaxSpecialAddrDelta)
439       OS << char(dwarf::DW_LNS_const_add_pc);
440     else if (AddrDelta) {
441       OS << char(dwarf::DW_LNS_advance_pc);
442       encodeULEB128(AddrDelta, OS);
443     }
444     OS << char(dwarf::DW_LNS_extended_op);
445     OS << char(1);
446     OS << char(dwarf::DW_LNE_end_sequence);
447     return;
448   }
449 
450   // Bias the line delta by the base.
451   Temp = LineDelta - Params.DWARF2LineBase;
452 
453   // If the line increment is out of range of a special opcode, we must encode
454   // it with DW_LNS_advance_line.
455   if (Temp >= Params.DWARF2LineRange) {
456     OS << char(dwarf::DW_LNS_advance_line);
457     encodeSLEB128(LineDelta, OS);
458 
459     LineDelta = 0;
460     Temp = 0 - Params.DWARF2LineBase;
461     NeedCopy = true;
462   }
463 
464   // Use DW_LNS_copy instead of a "line +0, addr +0" special opcode.
465   if (LineDelta == 0 && AddrDelta == 0) {
466     OS << char(dwarf::DW_LNS_copy);
467     return;
468   }
469 
470   // Bias the opcode by the special opcode base.
471   Temp += Params.DWARF2LineOpcodeBase;
472 
473   // Avoid overflow when addr_delta is large.
474   if (AddrDelta < 256 + MaxSpecialAddrDelta) {
475     // Try using a special opcode.
476     Opcode = Temp + AddrDelta * Params.DWARF2LineRange;
477     if (Opcode <= 255) {
478       OS << char(Opcode);
479       return;
480     }
481 
482     // Try using DW_LNS_const_add_pc followed by special op.
483     Opcode = Temp + (AddrDelta - MaxSpecialAddrDelta) * Params.DWARF2LineRange;
484     if (Opcode <= 255) {
485       OS << char(dwarf::DW_LNS_const_add_pc);
486       OS << char(Opcode);
487       return;
488     }
489   }
490 
491   // Otherwise use DW_LNS_advance_pc.
492   OS << char(dwarf::DW_LNS_advance_pc);
493   encodeULEB128(AddrDelta, OS);
494 
495   if (NeedCopy)
496     OS << char(dwarf::DW_LNS_copy);
497   else
498     OS << char(Temp);
499 }
500 
501 // Utility function to write a tuple for .debug_abbrev.
EmitAbbrev(MCStreamer * MCOS,uint64_t Name,uint64_t Form)502 static void EmitAbbrev(MCStreamer *MCOS, uint64_t Name, uint64_t Form) {
503   MCOS->EmitULEB128IntValue(Name);
504   MCOS->EmitULEB128IntValue(Form);
505 }
506 
507 // When generating dwarf for assembly source files this emits
508 // the data for .debug_abbrev section which contains three DIEs.
EmitGenDwarfAbbrev(MCStreamer * MCOS)509 static void EmitGenDwarfAbbrev(MCStreamer *MCOS) {
510   MCContext &context = MCOS->getContext();
511   MCOS->SwitchSection(context.getObjectFileInfo()->getDwarfAbbrevSection());
512 
513   // DW_TAG_compile_unit DIE abbrev (1).
514   MCOS->EmitULEB128IntValue(1);
515   MCOS->EmitULEB128IntValue(dwarf::DW_TAG_compile_unit);
516   MCOS->EmitIntValue(dwarf::DW_CHILDREN_yes, 1);
517   EmitAbbrev(MCOS, dwarf::DW_AT_stmt_list, dwarf::DW_FORM_data4);
518   if (MCOS->getContext().getGenDwarfSectionSyms().size() > 1 &&
519       MCOS->getContext().getDwarfVersion() >= 3) {
520     EmitAbbrev(MCOS, dwarf::DW_AT_ranges, dwarf::DW_FORM_data4);
521   } else {
522     EmitAbbrev(MCOS, dwarf::DW_AT_low_pc, dwarf::DW_FORM_addr);
523     EmitAbbrev(MCOS, dwarf::DW_AT_high_pc, dwarf::DW_FORM_addr);
524   }
525   EmitAbbrev(MCOS, dwarf::DW_AT_name, dwarf::DW_FORM_string);
526   if (!context.getCompilationDir().empty())
527     EmitAbbrev(MCOS, dwarf::DW_AT_comp_dir, dwarf::DW_FORM_string);
528   StringRef DwarfDebugFlags = context.getDwarfDebugFlags();
529   if (!DwarfDebugFlags.empty())
530     EmitAbbrev(MCOS, dwarf::DW_AT_APPLE_flags, dwarf::DW_FORM_string);
531   EmitAbbrev(MCOS, dwarf::DW_AT_producer, dwarf::DW_FORM_string);
532   EmitAbbrev(MCOS, dwarf::DW_AT_language, dwarf::DW_FORM_data2);
533   EmitAbbrev(MCOS, 0, 0);
534 
535   // DW_TAG_label DIE abbrev (2).
536   MCOS->EmitULEB128IntValue(2);
537   MCOS->EmitULEB128IntValue(dwarf::DW_TAG_label);
538   MCOS->EmitIntValue(dwarf::DW_CHILDREN_yes, 1);
539   EmitAbbrev(MCOS, dwarf::DW_AT_name, dwarf::DW_FORM_string);
540   EmitAbbrev(MCOS, dwarf::DW_AT_decl_file, dwarf::DW_FORM_data4);
541   EmitAbbrev(MCOS, dwarf::DW_AT_decl_line, dwarf::DW_FORM_data4);
542   EmitAbbrev(MCOS, dwarf::DW_AT_low_pc, dwarf::DW_FORM_addr);
543   EmitAbbrev(MCOS, dwarf::DW_AT_prototyped, dwarf::DW_FORM_flag);
544   EmitAbbrev(MCOS, 0, 0);
545 
546   // DW_TAG_unspecified_parameters DIE abbrev (3).
547   MCOS->EmitULEB128IntValue(3);
548   MCOS->EmitULEB128IntValue(dwarf::DW_TAG_unspecified_parameters);
549   MCOS->EmitIntValue(dwarf::DW_CHILDREN_no, 1);
550   EmitAbbrev(MCOS, 0, 0);
551 
552   // Terminate the abbreviations for this compilation unit.
553   MCOS->EmitIntValue(0, 1);
554 }
555 
556 // When generating dwarf for assembly source files this emits the data for
557 // .debug_aranges section. This section contains a header and a table of pairs
558 // of PointerSize'ed values for the address and size of section(s) with line
559 // table entries.
EmitGenDwarfAranges(MCStreamer * MCOS,const MCSymbol * InfoSectionSymbol)560 static void EmitGenDwarfAranges(MCStreamer *MCOS,
561                                 const MCSymbol *InfoSectionSymbol) {
562   MCContext &context = MCOS->getContext();
563 
564   auto &Sections = context.getGenDwarfSectionSyms();
565 
566   MCOS->SwitchSection(context.getObjectFileInfo()->getDwarfARangesSection());
567 
568   // This will be the length of the .debug_aranges section, first account for
569   // the size of each item in the header (see below where we emit these items).
570   int Length = 4 + 2 + 4 + 1 + 1;
571 
572   // Figure the padding after the header before the table of address and size
573   // pairs who's values are PointerSize'ed.
574   const MCAsmInfo *asmInfo = context.getAsmInfo();
575   int AddrSize = asmInfo->getPointerSize();
576   int Pad = 2 * AddrSize - (Length & (2 * AddrSize - 1));
577   if (Pad == 2 * AddrSize)
578     Pad = 0;
579   Length += Pad;
580 
581   // Add the size of the pair of PointerSize'ed values for the address and size
582   // of each section we have in the table.
583   Length += 2 * AddrSize * Sections.size();
584   // And the pair of terminating zeros.
585   Length += 2 * AddrSize;
586 
587 
588   // Emit the header for this section.
589   // The 4 byte length not including the 4 byte value for the length.
590   MCOS->EmitIntValue(Length - 4, 4);
591   // The 2 byte version, which is 2.
592   MCOS->EmitIntValue(2, 2);
593   // The 4 byte offset to the compile unit in the .debug_info from the start
594   // of the .debug_info.
595   if (InfoSectionSymbol)
596     MCOS->EmitSymbolValue(InfoSectionSymbol, 4,
597                           asmInfo->needsDwarfSectionOffsetDirective());
598   else
599     MCOS->EmitIntValue(0, 4);
600   // The 1 byte size of an address.
601   MCOS->EmitIntValue(AddrSize, 1);
602   // The 1 byte size of a segment descriptor, we use a value of zero.
603   MCOS->EmitIntValue(0, 1);
604   // Align the header with the padding if needed, before we put out the table.
605   for(int i = 0; i < Pad; i++)
606     MCOS->EmitIntValue(0, 1);
607 
608   // Now emit the table of pairs of PointerSize'ed values for the section
609   // addresses and sizes.
610   for (MCSection *Sec : Sections) {
611     const MCSymbol *StartSymbol = Sec->getBeginSymbol();
612     MCSymbol *EndSymbol = Sec->getEndSymbol(context);
613     assert(StartSymbol && "StartSymbol must not be NULL");
614     assert(EndSymbol && "EndSymbol must not be NULL");
615 
616     const MCExpr *Addr = MCSymbolRefExpr::create(
617       StartSymbol, MCSymbolRefExpr::VK_None, context);
618     const MCExpr *Size = MakeStartMinusEndExpr(*MCOS,
619       *StartSymbol, *EndSymbol, 0);
620     MCOS->EmitValue(Addr, AddrSize);
621     emitAbsValue(*MCOS, Size, AddrSize);
622   }
623 
624   // And finally the pair of terminating zeros.
625   MCOS->EmitIntValue(0, AddrSize);
626   MCOS->EmitIntValue(0, AddrSize);
627 }
628 
629 // When generating dwarf for assembly source files this emits the data for
630 // .debug_info section which contains three parts.  The header, the compile_unit
631 // DIE and a list of label DIEs.
EmitGenDwarfInfo(MCStreamer * MCOS,const MCSymbol * AbbrevSectionSymbol,const MCSymbol * LineSectionSymbol,const MCSymbol * RangesSectionSymbol)632 static void EmitGenDwarfInfo(MCStreamer *MCOS,
633                              const MCSymbol *AbbrevSectionSymbol,
634                              const MCSymbol *LineSectionSymbol,
635                              const MCSymbol *RangesSectionSymbol) {
636   MCContext &context = MCOS->getContext();
637 
638   MCOS->SwitchSection(context.getObjectFileInfo()->getDwarfInfoSection());
639 
640   // Create a symbol at the start and end of this section used in here for the
641   // expression to calculate the length in the header.
642   MCSymbol *InfoStart = context.createTempSymbol();
643   MCOS->EmitLabel(InfoStart);
644   MCSymbol *InfoEnd = context.createTempSymbol();
645 
646   // First part: the header.
647 
648   // The 4 byte total length of the information for this compilation unit, not
649   // including these 4 bytes.
650   const MCExpr *Length = MakeStartMinusEndExpr(*MCOS, *InfoStart, *InfoEnd, 4);
651   emitAbsValue(*MCOS, Length, 4);
652 
653   // The 2 byte DWARF version.
654   MCOS->EmitIntValue(context.getDwarfVersion(), 2);
655 
656   const MCAsmInfo &AsmInfo = *context.getAsmInfo();
657   // The 4 byte offset to the debug abbrevs from the start of the .debug_abbrev,
658   // it is at the start of that section so this is zero.
659   if (AbbrevSectionSymbol == nullptr)
660     MCOS->EmitIntValue(0, 4);
661   else
662     MCOS->EmitSymbolValue(AbbrevSectionSymbol, 4,
663                           AsmInfo.needsDwarfSectionOffsetDirective());
664 
665   const MCAsmInfo *asmInfo = context.getAsmInfo();
666   int AddrSize = asmInfo->getPointerSize();
667   // The 1 byte size of an address.
668   MCOS->EmitIntValue(AddrSize, 1);
669 
670   // Second part: the compile_unit DIE.
671 
672   // The DW_TAG_compile_unit DIE abbrev (1).
673   MCOS->EmitULEB128IntValue(1);
674 
675   // DW_AT_stmt_list, a 4 byte offset from the start of the .debug_line section,
676   // which is at the start of that section so this is zero.
677   if (LineSectionSymbol)
678     MCOS->EmitSymbolValue(LineSectionSymbol, 4,
679                           AsmInfo.needsDwarfSectionOffsetDirective());
680   else
681     MCOS->EmitIntValue(0, 4);
682 
683   if (RangesSectionSymbol) {
684     // There are multiple sections containing code, so we must use the
685     // .debug_ranges sections.
686 
687     // AT_ranges, the 4 byte offset from the start of the .debug_ranges section
688     // to the address range list for this compilation unit.
689     MCOS->EmitSymbolValue(RangesSectionSymbol, 4);
690   } else {
691     // If we only have one non-empty code section, we can use the simpler
692     // AT_low_pc and AT_high_pc attributes.
693 
694     // Find the first (and only) non-empty text section
695     auto &Sections = context.getGenDwarfSectionSyms();
696     const auto TextSection = Sections.begin();
697     assert(TextSection != Sections.end() && "No text section found");
698 
699     MCSymbol *StartSymbol = (*TextSection)->getBeginSymbol();
700     MCSymbol *EndSymbol = (*TextSection)->getEndSymbol(context);
701     assert(StartSymbol && "StartSymbol must not be NULL");
702     assert(EndSymbol && "EndSymbol must not be NULL");
703 
704     // AT_low_pc, the first address of the default .text section.
705     const MCExpr *Start = MCSymbolRefExpr::create(
706         StartSymbol, MCSymbolRefExpr::VK_None, context);
707     MCOS->EmitValue(Start, AddrSize);
708 
709     // AT_high_pc, the last address of the default .text section.
710     const MCExpr *End = MCSymbolRefExpr::create(
711       EndSymbol, MCSymbolRefExpr::VK_None, context);
712     MCOS->EmitValue(End, AddrSize);
713   }
714 
715   // AT_name, the name of the source file.  Reconstruct from the first directory
716   // and file table entries.
717   const SmallVectorImpl<std::string> &MCDwarfDirs = context.getMCDwarfDirs();
718   if (MCDwarfDirs.size() > 0) {
719     MCOS->EmitBytes(MCDwarfDirs[0]);
720     MCOS->EmitBytes(sys::path::get_separator());
721   }
722   const SmallVectorImpl<MCDwarfFile> &MCDwarfFiles =
723     MCOS->getContext().getMCDwarfFiles();
724   MCOS->EmitBytes(MCDwarfFiles[1].Name);
725   MCOS->EmitIntValue(0, 1); // NULL byte to terminate the string.
726 
727   // AT_comp_dir, the working directory the assembly was done in.
728   if (!context.getCompilationDir().empty()) {
729     MCOS->EmitBytes(context.getCompilationDir());
730     MCOS->EmitIntValue(0, 1); // NULL byte to terminate the string.
731   }
732 
733   // AT_APPLE_flags, the command line arguments of the assembler tool.
734   StringRef DwarfDebugFlags = context.getDwarfDebugFlags();
735   if (!DwarfDebugFlags.empty()){
736     MCOS->EmitBytes(DwarfDebugFlags);
737     MCOS->EmitIntValue(0, 1); // NULL byte to terminate the string.
738   }
739 
740   // AT_producer, the version of the assembler tool.
741   StringRef DwarfDebugProducer = context.getDwarfDebugProducer();
742   if (!DwarfDebugProducer.empty())
743     MCOS->EmitBytes(DwarfDebugProducer);
744   else
745     MCOS->EmitBytes(StringRef("llvm-mc (based on LLVM " PACKAGE_VERSION ")"));
746   MCOS->EmitIntValue(0, 1); // NULL byte to terminate the string.
747 
748   // AT_language, a 4 byte value.  We use DW_LANG_Mips_Assembler as the dwarf2
749   // draft has no standard code for assembler.
750   MCOS->EmitIntValue(dwarf::DW_LANG_Mips_Assembler, 2);
751 
752   // Third part: the list of label DIEs.
753 
754   // Loop on saved info for dwarf labels and create the DIEs for them.
755   const std::vector<MCGenDwarfLabelEntry> &Entries =
756       MCOS->getContext().getMCGenDwarfLabelEntries();
757   for (const auto &Entry : Entries) {
758     // The DW_TAG_label DIE abbrev (2).
759     MCOS->EmitULEB128IntValue(2);
760 
761     // AT_name, of the label without any leading underbar.
762     MCOS->EmitBytes(Entry.getName());
763     MCOS->EmitIntValue(0, 1); // NULL byte to terminate the string.
764 
765     // AT_decl_file, index into the file table.
766     MCOS->EmitIntValue(Entry.getFileNumber(), 4);
767 
768     // AT_decl_line, source line number.
769     MCOS->EmitIntValue(Entry.getLineNumber(), 4);
770 
771     // AT_low_pc, start address of the label.
772     const MCExpr *AT_low_pc = MCSymbolRefExpr::create(Entry.getLabel(),
773                                              MCSymbolRefExpr::VK_None, context);
774     MCOS->EmitValue(AT_low_pc, AddrSize);
775 
776     // DW_AT_prototyped, a one byte flag value of 0 saying we have no prototype.
777     MCOS->EmitIntValue(0, 1);
778 
779     // The DW_TAG_unspecified_parameters DIE abbrev (3).
780     MCOS->EmitULEB128IntValue(3);
781 
782     // Add the NULL DIE terminating the DW_TAG_unspecified_parameters DIE's.
783     MCOS->EmitIntValue(0, 1);
784   }
785 
786   // Add the NULL DIE terminating the Compile Unit DIE's.
787   MCOS->EmitIntValue(0, 1);
788 
789   // Now set the value of the symbol at the end of the info section.
790   MCOS->EmitLabel(InfoEnd);
791 }
792 
793 // When generating dwarf for assembly source files this emits the data for
794 // .debug_ranges section. We only emit one range list, which spans all of the
795 // executable sections of this file.
EmitGenDwarfRanges(MCStreamer * MCOS)796 static void EmitGenDwarfRanges(MCStreamer *MCOS) {
797   MCContext &context = MCOS->getContext();
798   auto &Sections = context.getGenDwarfSectionSyms();
799 
800   const MCAsmInfo *AsmInfo = context.getAsmInfo();
801   int AddrSize = AsmInfo->getPointerSize();
802 
803   MCOS->SwitchSection(context.getObjectFileInfo()->getDwarfRangesSection());
804 
805   for (MCSection *Sec : Sections) {
806     const MCSymbol *StartSymbol = Sec->getBeginSymbol();
807     MCSymbol *EndSymbol = Sec->getEndSymbol(context);
808     assert(StartSymbol && "StartSymbol must not be NULL");
809     assert(EndSymbol && "EndSymbol must not be NULL");
810 
811     // Emit a base address selection entry for the start of this section
812     const MCExpr *SectionStartAddr = MCSymbolRefExpr::create(
813       StartSymbol, MCSymbolRefExpr::VK_None, context);
814     MCOS->EmitFill(AddrSize, 0xFF);
815     MCOS->EmitValue(SectionStartAddr, AddrSize);
816 
817     // Emit a range list entry spanning this section
818     const MCExpr *SectionSize = MakeStartMinusEndExpr(*MCOS,
819       *StartSymbol, *EndSymbol, 0);
820     MCOS->EmitIntValue(0, AddrSize);
821     emitAbsValue(*MCOS, SectionSize, AddrSize);
822   }
823 
824   // Emit end of list entry
825   MCOS->EmitIntValue(0, AddrSize);
826   MCOS->EmitIntValue(0, AddrSize);
827 }
828 
829 //
830 // When generating dwarf for assembly source files this emits the Dwarf
831 // sections.
832 //
Emit(MCStreamer * MCOS)833 void MCGenDwarfInfo::Emit(MCStreamer *MCOS) {
834   MCContext &context = MCOS->getContext();
835 
836   // Create the dwarf sections in this order (.debug_line already created).
837   const MCAsmInfo *AsmInfo = context.getAsmInfo();
838   bool CreateDwarfSectionSymbols =
839       AsmInfo->doesDwarfUseRelocationsAcrossSections();
840   MCSymbol *LineSectionSymbol = nullptr;
841   if (CreateDwarfSectionSymbols)
842     LineSectionSymbol = MCOS->getDwarfLineTableSymbol(0);
843   MCSymbol *AbbrevSectionSymbol = nullptr;
844   MCSymbol *InfoSectionSymbol = nullptr;
845   MCSymbol *RangesSectionSymbol = nullptr;
846 
847   // Create end symbols for each section, and remove empty sections
848   MCOS->getContext().finalizeDwarfSections(*MCOS);
849 
850   // If there are no sections to generate debug info for, we don't need
851   // to do anything
852   if (MCOS->getContext().getGenDwarfSectionSyms().empty())
853     return;
854 
855   // We only use the .debug_ranges section if we have multiple code sections,
856   // and we are emitting a DWARF version which supports it.
857   const bool UseRangesSection =
858       MCOS->getContext().getGenDwarfSectionSyms().size() > 1 &&
859       MCOS->getContext().getDwarfVersion() >= 3;
860   CreateDwarfSectionSymbols |= UseRangesSection;
861 
862   MCOS->SwitchSection(context.getObjectFileInfo()->getDwarfInfoSection());
863   if (CreateDwarfSectionSymbols) {
864     InfoSectionSymbol = context.createTempSymbol();
865     MCOS->EmitLabel(InfoSectionSymbol);
866   }
867   MCOS->SwitchSection(context.getObjectFileInfo()->getDwarfAbbrevSection());
868   if (CreateDwarfSectionSymbols) {
869     AbbrevSectionSymbol = context.createTempSymbol();
870     MCOS->EmitLabel(AbbrevSectionSymbol);
871   }
872   if (UseRangesSection) {
873     MCOS->SwitchSection(context.getObjectFileInfo()->getDwarfRangesSection());
874     if (CreateDwarfSectionSymbols) {
875       RangesSectionSymbol = context.createTempSymbol();
876       MCOS->EmitLabel(RangesSectionSymbol);
877     }
878   }
879 
880   assert((RangesSectionSymbol != NULL) || !UseRangesSection);
881 
882   MCOS->SwitchSection(context.getObjectFileInfo()->getDwarfARangesSection());
883 
884   // Output the data for .debug_aranges section.
885   EmitGenDwarfAranges(MCOS, InfoSectionSymbol);
886 
887   if (UseRangesSection)
888     EmitGenDwarfRanges(MCOS);
889 
890   // Output the data for .debug_abbrev section.
891   EmitGenDwarfAbbrev(MCOS);
892 
893   // Output the data for .debug_info section.
894   EmitGenDwarfInfo(MCOS, AbbrevSectionSymbol, LineSectionSymbol,
895                    RangesSectionSymbol);
896 }
897 
898 //
899 // When generating dwarf for assembly source files this is called when symbol
900 // for a label is created.  If this symbol is not a temporary and is in the
901 // section that dwarf is being generated for, save the needed info to create
902 // a dwarf label.
903 //
Make(MCSymbol * Symbol,MCStreamer * MCOS,SourceMgr & SrcMgr,SMLoc & Loc)904 void MCGenDwarfLabelEntry::Make(MCSymbol *Symbol, MCStreamer *MCOS,
905                                      SourceMgr &SrcMgr, SMLoc &Loc) {
906   // We won't create dwarf labels for temporary symbols.
907   if (Symbol->isTemporary())
908     return;
909   MCContext &context = MCOS->getContext();
910   // We won't create dwarf labels for symbols in sections that we are not
911   // generating debug info for.
912   if (!context.getGenDwarfSectionSyms().count(MCOS->getCurrentSection().first))
913     return;
914 
915   // The dwarf label's name does not have the symbol name's leading
916   // underbar if any.
917   StringRef Name = Symbol->getName();
918   if (Name.startswith("_"))
919     Name = Name.substr(1, Name.size()-1);
920 
921   // Get the dwarf file number to be used for the dwarf label.
922   unsigned FileNumber = context.getGenDwarfFileNumber();
923 
924   // Finding the line number is the expensive part which is why we just don't
925   // pass it in as for some symbols we won't create a dwarf label.
926   unsigned CurBuffer = SrcMgr.FindBufferContainingLoc(Loc);
927   unsigned LineNumber = SrcMgr.FindLineNumber(Loc, CurBuffer);
928 
929   // We create a temporary symbol for use for the AT_high_pc and AT_low_pc
930   // values so that they don't have things like an ARM thumb bit from the
931   // original symbol. So when used they won't get a low bit set after
932   // relocation.
933   MCSymbol *Label = context.createTempSymbol();
934   MCOS->EmitLabel(Label);
935 
936   // Create and entry for the info and add it to the other entries.
937   MCOS->getContext().addMCGenDwarfLabelEntry(
938       MCGenDwarfLabelEntry(Name, FileNumber, LineNumber, Label));
939 }
940 
getDataAlignmentFactor(MCStreamer & streamer)941 static int getDataAlignmentFactor(MCStreamer &streamer) {
942   MCContext &context = streamer.getContext();
943   const MCAsmInfo *asmInfo = context.getAsmInfo();
944   int size = asmInfo->getCalleeSaveStackSlotSize();
945   if (asmInfo->isStackGrowthDirectionUp())
946     return size;
947   else
948     return -size;
949 }
950 
getSizeForEncoding(MCStreamer & streamer,unsigned symbolEncoding)951 static unsigned getSizeForEncoding(MCStreamer &streamer,
952                                    unsigned symbolEncoding) {
953   MCContext &context = streamer.getContext();
954   unsigned format = symbolEncoding & 0x0f;
955   switch (format) {
956   default: llvm_unreachable("Unknown Encoding");
957   case dwarf::DW_EH_PE_absptr:
958   case dwarf::DW_EH_PE_signed:
959     return context.getAsmInfo()->getPointerSize();
960   case dwarf::DW_EH_PE_udata2:
961   case dwarf::DW_EH_PE_sdata2:
962     return 2;
963   case dwarf::DW_EH_PE_udata4:
964   case dwarf::DW_EH_PE_sdata4:
965     return 4;
966   case dwarf::DW_EH_PE_udata8:
967   case dwarf::DW_EH_PE_sdata8:
968     return 8;
969   }
970 }
971 
emitFDESymbol(MCObjectStreamer & streamer,const MCSymbol & symbol,unsigned symbolEncoding,bool isEH)972 static void emitFDESymbol(MCObjectStreamer &streamer, const MCSymbol &symbol,
973                        unsigned symbolEncoding, bool isEH) {
974   MCContext &context = streamer.getContext();
975   const MCAsmInfo *asmInfo = context.getAsmInfo();
976   const MCExpr *v = asmInfo->getExprForFDESymbol(&symbol,
977                                                  symbolEncoding,
978                                                  streamer);
979   unsigned size = getSizeForEncoding(streamer, symbolEncoding);
980   if (asmInfo->doDwarfFDESymbolsUseAbsDiff() && isEH)
981     emitAbsValue(streamer, v, size);
982   else
983     streamer.EmitValue(v, size);
984 }
985 
EmitPersonality(MCStreamer & streamer,const MCSymbol & symbol,unsigned symbolEncoding)986 static void EmitPersonality(MCStreamer &streamer, const MCSymbol &symbol,
987                             unsigned symbolEncoding) {
988   MCContext &context = streamer.getContext();
989   const MCAsmInfo *asmInfo = context.getAsmInfo();
990   const MCExpr *v = asmInfo->getExprForPersonalitySymbol(&symbol,
991                                                          symbolEncoding,
992                                                          streamer);
993   unsigned size = getSizeForEncoding(streamer, symbolEncoding);
994   streamer.EmitValue(v, size);
995 }
996 
997 namespace {
998 class FrameEmitterImpl {
999   int CFAOffset = 0;
1000   int InitialCFAOffset = 0;
1001   bool IsEH;
1002   MCObjectStreamer &Streamer;
1003 
1004 public:
FrameEmitterImpl(bool IsEH,MCObjectStreamer & Streamer)1005   FrameEmitterImpl(bool IsEH, MCObjectStreamer &Streamer)
1006       : IsEH(IsEH), Streamer(Streamer) {}
1007 
1008   /// Emit the unwind information in a compact way.
1009   void EmitCompactUnwind(const MCDwarfFrameInfo &frame);
1010 
1011   const MCSymbol &EmitCIE(const MCSymbol *personality,
1012                           unsigned personalityEncoding, const MCSymbol *lsda,
1013                           bool IsSignalFrame, unsigned lsdaEncoding,
1014                           bool IsSimple);
1015   void EmitFDE(const MCSymbol &cieStart, const MCDwarfFrameInfo &frame,
1016                bool LastInSection, const MCSymbol &SectionStart);
1017   void EmitCFIInstructions(ArrayRef<MCCFIInstruction> Instrs,
1018                            MCSymbol *BaseLabel);
1019   void EmitCFIInstruction(const MCCFIInstruction &Instr);
1020 };
1021 
1022 } // end anonymous namespace
1023 
emitEncodingByte(MCObjectStreamer & Streamer,unsigned Encoding)1024 static void emitEncodingByte(MCObjectStreamer &Streamer, unsigned Encoding) {
1025   Streamer.EmitIntValue(Encoding, 1);
1026 }
1027 
EmitCFIInstruction(const MCCFIInstruction & Instr)1028 void FrameEmitterImpl::EmitCFIInstruction(const MCCFIInstruction &Instr) {
1029   int dataAlignmentFactor = getDataAlignmentFactor(Streamer);
1030   auto *MRI = Streamer.getContext().getRegisterInfo();
1031 
1032   switch (Instr.getOperation()) {
1033   case MCCFIInstruction::OpRegister: {
1034     unsigned Reg1 = Instr.getRegister();
1035     unsigned Reg2 = Instr.getRegister2();
1036     if (!IsEH) {
1037       Reg1 = MRI->getDwarfRegNum(MRI->getLLVMRegNum(Reg1, true), false);
1038       Reg2 = MRI->getDwarfRegNum(MRI->getLLVMRegNum(Reg2, true), false);
1039     }
1040     Streamer.EmitIntValue(dwarf::DW_CFA_register, 1);
1041     Streamer.EmitULEB128IntValue(Reg1);
1042     Streamer.EmitULEB128IntValue(Reg2);
1043     return;
1044   }
1045   case MCCFIInstruction::OpWindowSave: {
1046     Streamer.EmitIntValue(dwarf::DW_CFA_GNU_window_save, 1);
1047     return;
1048   }
1049   case MCCFIInstruction::OpUndefined: {
1050     unsigned Reg = Instr.getRegister();
1051     Streamer.EmitIntValue(dwarf::DW_CFA_undefined, 1);
1052     Streamer.EmitULEB128IntValue(Reg);
1053     return;
1054   }
1055   case MCCFIInstruction::OpAdjustCfaOffset:
1056   case MCCFIInstruction::OpDefCfaOffset: {
1057     const bool IsRelative =
1058       Instr.getOperation() == MCCFIInstruction::OpAdjustCfaOffset;
1059 
1060     Streamer.EmitIntValue(dwarf::DW_CFA_def_cfa_offset, 1);
1061 
1062     if (IsRelative)
1063       CFAOffset += Instr.getOffset();
1064     else
1065       CFAOffset = -Instr.getOffset();
1066 
1067     Streamer.EmitULEB128IntValue(CFAOffset);
1068 
1069     return;
1070   }
1071   case MCCFIInstruction::OpDefCfa: {
1072     unsigned Reg = Instr.getRegister();
1073     if (!IsEH)
1074       Reg = MRI->getDwarfRegNum(MRI->getLLVMRegNum(Reg, true), false);
1075     Streamer.EmitIntValue(dwarf::DW_CFA_def_cfa, 1);
1076     Streamer.EmitULEB128IntValue(Reg);
1077     CFAOffset = -Instr.getOffset();
1078     Streamer.EmitULEB128IntValue(CFAOffset);
1079 
1080     return;
1081   }
1082 
1083   case MCCFIInstruction::OpDefCfaRegister: {
1084     unsigned Reg = Instr.getRegister();
1085     if (!IsEH)
1086       Reg = MRI->getDwarfRegNum(MRI->getLLVMRegNum(Reg, true), false);
1087     Streamer.EmitIntValue(dwarf::DW_CFA_def_cfa_register, 1);
1088     Streamer.EmitULEB128IntValue(Reg);
1089 
1090     return;
1091   }
1092 
1093   case MCCFIInstruction::OpOffset:
1094   case MCCFIInstruction::OpRelOffset: {
1095     const bool IsRelative =
1096       Instr.getOperation() == MCCFIInstruction::OpRelOffset;
1097 
1098     unsigned Reg = Instr.getRegister();
1099     if (!IsEH)
1100       Reg = MRI->getDwarfRegNum(MRI->getLLVMRegNum(Reg, true), false);
1101 
1102     int Offset = Instr.getOffset();
1103     if (IsRelative)
1104       Offset -= CFAOffset;
1105     Offset = Offset / dataAlignmentFactor;
1106 
1107     if (Offset < 0) {
1108       Streamer.EmitIntValue(dwarf::DW_CFA_offset_extended_sf, 1);
1109       Streamer.EmitULEB128IntValue(Reg);
1110       Streamer.EmitSLEB128IntValue(Offset);
1111     } else if (Reg < 64) {
1112       Streamer.EmitIntValue(dwarf::DW_CFA_offset + Reg, 1);
1113       Streamer.EmitULEB128IntValue(Offset);
1114     } else {
1115       Streamer.EmitIntValue(dwarf::DW_CFA_offset_extended, 1);
1116       Streamer.EmitULEB128IntValue(Reg);
1117       Streamer.EmitULEB128IntValue(Offset);
1118     }
1119     return;
1120   }
1121   case MCCFIInstruction::OpRememberState:
1122     Streamer.EmitIntValue(dwarf::DW_CFA_remember_state, 1);
1123     return;
1124   case MCCFIInstruction::OpRestoreState:
1125     Streamer.EmitIntValue(dwarf::DW_CFA_restore_state, 1);
1126     return;
1127   case MCCFIInstruction::OpSameValue: {
1128     unsigned Reg = Instr.getRegister();
1129     Streamer.EmitIntValue(dwarf::DW_CFA_same_value, 1);
1130     Streamer.EmitULEB128IntValue(Reg);
1131     return;
1132   }
1133   case MCCFIInstruction::OpRestore: {
1134     unsigned Reg = Instr.getRegister();
1135     if (!IsEH)
1136       Reg = MRI->getDwarfRegNum(MRI->getLLVMRegNum(Reg, true), false);
1137     Streamer.EmitIntValue(dwarf::DW_CFA_restore | Reg, 1);
1138     return;
1139   }
1140   case MCCFIInstruction::OpGnuArgsSize: {
1141     Streamer.EmitIntValue(dwarf::DW_CFA_GNU_args_size, 1);
1142     Streamer.EmitULEB128IntValue(Instr.getOffset());
1143     return;
1144   }
1145   case MCCFIInstruction::OpEscape:
1146     Streamer.EmitBytes(Instr.getValues());
1147     return;
1148   }
1149   llvm_unreachable("Unhandled case in switch");
1150 }
1151 
1152 /// Emit frame instructions to describe the layout of the frame.
EmitCFIInstructions(ArrayRef<MCCFIInstruction> Instrs,MCSymbol * BaseLabel)1153 void FrameEmitterImpl::EmitCFIInstructions(ArrayRef<MCCFIInstruction> Instrs,
1154                                            MCSymbol *BaseLabel) {
1155   for (unsigned i = 0, N = Instrs.size(); i < N; ++i) {
1156     const MCCFIInstruction &Instr = Instrs[i];
1157     MCSymbol *Label = Instr.getLabel();
1158     // Throw out move if the label is invalid.
1159     if (Label && !Label->isDefined()) continue; // Not emitted, in dead code.
1160 
1161     // Advance row if new location.
1162     if (BaseLabel && Label) {
1163       MCSymbol *ThisSym = Label;
1164       if (ThisSym != BaseLabel) {
1165         Streamer.EmitDwarfAdvanceFrameAddr(BaseLabel, ThisSym);
1166         BaseLabel = ThisSym;
1167       }
1168     }
1169 
1170     EmitCFIInstruction(Instr);
1171   }
1172 }
1173 
1174 /// Emit the unwind information in a compact way.
EmitCompactUnwind(const MCDwarfFrameInfo & Frame)1175 void FrameEmitterImpl::EmitCompactUnwind(const MCDwarfFrameInfo &Frame) {
1176   MCContext &Context = Streamer.getContext();
1177   const MCObjectFileInfo *MOFI = Context.getObjectFileInfo();
1178 
1179   // range-start range-length  compact-unwind-enc personality-func   lsda
1180   //  _foo       LfooEnd-_foo  0x00000023          0                 0
1181   //  _bar       LbarEnd-_bar  0x00000025         __gxx_personality  except_tab1
1182   //
1183   //   .section __LD,__compact_unwind,regular,debug
1184   //
1185   //   # compact unwind for _foo
1186   //   .quad _foo
1187   //   .set L1,LfooEnd-_foo
1188   //   .long L1
1189   //   .long 0x01010001
1190   //   .quad 0
1191   //   .quad 0
1192   //
1193   //   # compact unwind for _bar
1194   //   .quad _bar
1195   //   .set L2,LbarEnd-_bar
1196   //   .long L2
1197   //   .long 0x01020011
1198   //   .quad __gxx_personality
1199   //   .quad except_tab1
1200 
1201   uint32_t Encoding = Frame.CompactUnwindEncoding;
1202   if (!Encoding) return;
1203   bool DwarfEHFrameOnly = (Encoding == MOFI->getCompactUnwindDwarfEHFrameOnly());
1204 
1205   // The encoding needs to know we have an LSDA.
1206   if (!DwarfEHFrameOnly && Frame.Lsda)
1207     Encoding |= 0x40000000;
1208 
1209   // Range Start
1210   unsigned FDEEncoding = MOFI->getFDEEncoding();
1211   unsigned Size = getSizeForEncoding(Streamer, FDEEncoding);
1212   Streamer.EmitSymbolValue(Frame.Begin, Size);
1213 
1214   // Range Length
1215   const MCExpr *Range = MakeStartMinusEndExpr(Streamer, *Frame.Begin,
1216                                               *Frame.End, 0);
1217   emitAbsValue(Streamer, Range, 4);
1218 
1219   // Compact Encoding
1220   Size = getSizeForEncoding(Streamer, dwarf::DW_EH_PE_udata4);
1221   Streamer.EmitIntValue(Encoding, Size);
1222 
1223   // Personality Function
1224   Size = getSizeForEncoding(Streamer, dwarf::DW_EH_PE_absptr);
1225   if (!DwarfEHFrameOnly && Frame.Personality)
1226     Streamer.EmitSymbolValue(Frame.Personality, Size);
1227   else
1228     Streamer.EmitIntValue(0, Size); // No personality fn
1229 
1230   // LSDA
1231   Size = getSizeForEncoding(Streamer, Frame.LsdaEncoding);
1232   if (!DwarfEHFrameOnly && Frame.Lsda)
1233     Streamer.EmitSymbolValue(Frame.Lsda, Size);
1234   else
1235     Streamer.EmitIntValue(0, Size); // No LSDA
1236 }
1237 
getCIEVersion(bool IsEH,unsigned DwarfVersion)1238 static unsigned getCIEVersion(bool IsEH, unsigned DwarfVersion) {
1239   if (IsEH)
1240     return 1;
1241   switch (DwarfVersion) {
1242   case 2:
1243     return 1;
1244   case 3:
1245     return 3;
1246   case 4:
1247     return 4;
1248   }
1249   llvm_unreachable("Unknown version");
1250 }
1251 
EmitCIE(const MCSymbol * personality,unsigned personalityEncoding,const MCSymbol * lsda,bool IsSignalFrame,unsigned lsdaEncoding,bool IsSimple)1252 const MCSymbol &FrameEmitterImpl::EmitCIE(const MCSymbol *personality,
1253                                           unsigned personalityEncoding,
1254                                           const MCSymbol *lsda,
1255                                           bool IsSignalFrame,
1256                                           unsigned lsdaEncoding,
1257                                           bool IsSimple) {
1258   MCContext &context = Streamer.getContext();
1259   const MCRegisterInfo *MRI = context.getRegisterInfo();
1260   const MCObjectFileInfo *MOFI = context.getObjectFileInfo();
1261 
1262   MCSymbol *sectionStart = context.createTempSymbol();
1263   Streamer.EmitLabel(sectionStart);
1264 
1265   MCSymbol *sectionEnd = context.createTempSymbol();
1266 
1267   // Length
1268   const MCExpr *Length =
1269       MakeStartMinusEndExpr(Streamer, *sectionStart, *sectionEnd, 4);
1270   emitAbsValue(Streamer, Length, 4);
1271 
1272   // CIE ID
1273   unsigned CIE_ID = IsEH ? 0 : -1;
1274   Streamer.EmitIntValue(CIE_ID, 4);
1275 
1276   // Version
1277   uint8_t CIEVersion = getCIEVersion(IsEH, context.getDwarfVersion());
1278   Streamer.EmitIntValue(CIEVersion, 1);
1279 
1280   // Augmentation String
1281   SmallString<8> Augmentation;
1282   if (IsEH) {
1283     Augmentation += "z";
1284     if (personality)
1285       Augmentation += "P";
1286     if (lsda)
1287       Augmentation += "L";
1288     Augmentation += "R";
1289     if (IsSignalFrame)
1290       Augmentation += "S";
1291     Streamer.EmitBytes(Augmentation);
1292   }
1293   Streamer.EmitIntValue(0, 1);
1294 
1295   if (CIEVersion >= 4) {
1296     // Address Size
1297     Streamer.EmitIntValue(context.getAsmInfo()->getPointerSize(), 1);
1298 
1299     // Segment Descriptor Size
1300     Streamer.EmitIntValue(0, 1);
1301   }
1302 
1303   // Code Alignment Factor
1304   Streamer.EmitULEB128IntValue(context.getAsmInfo()->getMinInstAlignment());
1305 
1306   // Data Alignment Factor
1307   Streamer.EmitSLEB128IntValue(getDataAlignmentFactor(Streamer));
1308 
1309   // Return Address Register
1310   if (CIEVersion == 1) {
1311     assert(MRI->getRARegister() <= 255 &&
1312            "DWARF 2 encodes return_address_register in one byte");
1313     Streamer.EmitIntValue(MRI->getDwarfRegNum(MRI->getRARegister(), IsEH), 1);
1314   } else {
1315     Streamer.EmitULEB128IntValue(
1316         MRI->getDwarfRegNum(MRI->getRARegister(), IsEH));
1317   }
1318 
1319   // Augmentation Data Length (optional)
1320 
1321   unsigned augmentationLength = 0;
1322   if (IsEH) {
1323     if (personality) {
1324       // Personality Encoding
1325       augmentationLength += 1;
1326       // Personality
1327       augmentationLength += getSizeForEncoding(Streamer, personalityEncoding);
1328     }
1329     if (lsda)
1330       augmentationLength += 1;
1331     // Encoding of the FDE pointers
1332     augmentationLength += 1;
1333 
1334     Streamer.EmitULEB128IntValue(augmentationLength);
1335 
1336     // Augmentation Data (optional)
1337     if (personality) {
1338       // Personality Encoding
1339       emitEncodingByte(Streamer, personalityEncoding);
1340       // Personality
1341       EmitPersonality(Streamer, *personality, personalityEncoding);
1342     }
1343 
1344     if (lsda)
1345       emitEncodingByte(Streamer, lsdaEncoding);
1346 
1347     // Encoding of the FDE pointers
1348     emitEncodingByte(Streamer, MOFI->getFDEEncoding());
1349   }
1350 
1351   // Initial Instructions
1352 
1353   const MCAsmInfo *MAI = context.getAsmInfo();
1354   if (!IsSimple) {
1355     const std::vector<MCCFIInstruction> &Instructions =
1356         MAI->getInitialFrameState();
1357     EmitCFIInstructions(Instructions, nullptr);
1358   }
1359 
1360   InitialCFAOffset = CFAOffset;
1361 
1362   // Padding
1363   Streamer.EmitValueToAlignment(IsEH ? 4 : MAI->getPointerSize());
1364 
1365   Streamer.EmitLabel(sectionEnd);
1366   return *sectionStart;
1367 }
1368 
EmitFDE(const MCSymbol & cieStart,const MCDwarfFrameInfo & frame,bool LastInSection,const MCSymbol & SectionStart)1369 void FrameEmitterImpl::EmitFDE(const MCSymbol &cieStart,
1370                                const MCDwarfFrameInfo &frame,
1371                                bool LastInSection,
1372                                const MCSymbol &SectionStart) {
1373   MCContext &context = Streamer.getContext();
1374   MCSymbol *fdeStart = context.createTempSymbol();
1375   MCSymbol *fdeEnd = context.createTempSymbol();
1376   const MCObjectFileInfo *MOFI = context.getObjectFileInfo();
1377 
1378   CFAOffset = InitialCFAOffset;
1379 
1380   // Length
1381   const MCExpr *Length = MakeStartMinusEndExpr(Streamer, *fdeStart, *fdeEnd, 0);
1382   emitAbsValue(Streamer, Length, 4);
1383 
1384   Streamer.EmitLabel(fdeStart);
1385 
1386   // CIE Pointer
1387   const MCAsmInfo *asmInfo = context.getAsmInfo();
1388   if (IsEH) {
1389     const MCExpr *offset =
1390         MakeStartMinusEndExpr(Streamer, cieStart, *fdeStart, 0);
1391     emitAbsValue(Streamer, offset, 4);
1392   } else if (!asmInfo->doesDwarfUseRelocationsAcrossSections()) {
1393     const MCExpr *offset =
1394         MakeStartMinusEndExpr(Streamer, SectionStart, cieStart, 0);
1395     emitAbsValue(Streamer, offset, 4);
1396   } else {
1397     Streamer.EmitSymbolValue(&cieStart, 4);
1398   }
1399 
1400   // PC Begin
1401   unsigned PCEncoding =
1402       IsEH ? MOFI->getFDEEncoding() : (unsigned)dwarf::DW_EH_PE_absptr;
1403   unsigned PCSize = getSizeForEncoding(Streamer, PCEncoding);
1404   emitFDESymbol(Streamer, *frame.Begin, PCEncoding, IsEH);
1405 
1406   // PC Range
1407   const MCExpr *Range =
1408       MakeStartMinusEndExpr(Streamer, *frame.Begin, *frame.End, 0);
1409   emitAbsValue(Streamer, Range, PCSize);
1410 
1411   if (IsEH) {
1412     // Augmentation Data Length
1413     unsigned augmentationLength = 0;
1414 
1415     if (frame.Lsda)
1416       augmentationLength += getSizeForEncoding(Streamer, frame.LsdaEncoding);
1417 
1418     Streamer.EmitULEB128IntValue(augmentationLength);
1419 
1420     // Augmentation Data
1421     if (frame.Lsda)
1422       emitFDESymbol(Streamer, *frame.Lsda, frame.LsdaEncoding, true);
1423   }
1424 
1425   // Call Frame Instructions
1426   EmitCFIInstructions(frame.Instructions, frame.Begin);
1427 
1428   // Padding
1429   // The size of a .eh_frame section has to be a multiple of the alignment
1430   // since a null CIE is interpreted as the end. Old systems overaligned
1431   // .eh_frame, so we do too and account for it in the last FDE.
1432   unsigned Align = LastInSection ? asmInfo->getPointerSize() : PCSize;
1433   Streamer.EmitValueToAlignment(Align);
1434 
1435   Streamer.EmitLabel(fdeEnd);
1436 }
1437 
1438 namespace {
1439 struct CIEKey {
getEmptyKey__anon19d5139a0211::CIEKey1440   static const CIEKey getEmptyKey() {
1441     return CIEKey(nullptr, 0, -1, false, false);
1442   }
getTombstoneKey__anon19d5139a0211::CIEKey1443   static const CIEKey getTombstoneKey() {
1444     return CIEKey(nullptr, -1, 0, false, false);
1445   }
1446 
CIEKey__anon19d5139a0211::CIEKey1447   CIEKey(const MCSymbol *Personality, unsigned PersonalityEncoding,
1448          unsigned LsdaEncoding, bool IsSignalFrame, bool IsSimple)
1449       : Personality(Personality), PersonalityEncoding(PersonalityEncoding),
1450         LsdaEncoding(LsdaEncoding), IsSignalFrame(IsSignalFrame),
1451         IsSimple(IsSimple) {}
1452   const MCSymbol *Personality;
1453   unsigned PersonalityEncoding;
1454   unsigned LsdaEncoding;
1455   bool IsSignalFrame;
1456   bool IsSimple;
1457 };
1458 } // anonymous namespace
1459 
1460 namespace llvm {
1461 template <> struct DenseMapInfo<CIEKey> {
getEmptyKeyllvm::DenseMapInfo1462   static CIEKey getEmptyKey() { return CIEKey::getEmptyKey(); }
getTombstoneKeyllvm::DenseMapInfo1463   static CIEKey getTombstoneKey() { return CIEKey::getTombstoneKey(); }
getHashValuellvm::DenseMapInfo1464   static unsigned getHashValue(const CIEKey &Key) {
1465     return static_cast<unsigned>(
1466         hash_combine(Key.Personality, Key.PersonalityEncoding, Key.LsdaEncoding,
1467                      Key.IsSignalFrame, Key.IsSimple));
1468   }
isEqualllvm::DenseMapInfo1469   static bool isEqual(const CIEKey &LHS, const CIEKey &RHS) {
1470     return LHS.Personality == RHS.Personality &&
1471            LHS.PersonalityEncoding == RHS.PersonalityEncoding &&
1472            LHS.LsdaEncoding == RHS.LsdaEncoding &&
1473            LHS.IsSignalFrame == RHS.IsSignalFrame &&
1474            LHS.IsSimple == RHS.IsSimple;
1475   }
1476 };
1477 } // namespace llvm
1478 
Emit(MCObjectStreamer & Streamer,MCAsmBackend * MAB,bool IsEH)1479 void MCDwarfFrameEmitter::Emit(MCObjectStreamer &Streamer, MCAsmBackend *MAB,
1480                                bool IsEH) {
1481   Streamer.generateCompactUnwindEncodings(MAB);
1482 
1483   MCContext &Context = Streamer.getContext();
1484   const MCObjectFileInfo *MOFI = Context.getObjectFileInfo();
1485   FrameEmitterImpl Emitter(IsEH, Streamer);
1486   ArrayRef<MCDwarfFrameInfo> FrameArray = Streamer.getDwarfFrameInfos();
1487 
1488   // Emit the compact unwind info if available.
1489   bool NeedsEHFrameSection = !MOFI->getSupportsCompactUnwindWithoutEHFrame();
1490   if (IsEH && MOFI->getCompactUnwindSection()) {
1491     bool SectionEmitted = false;
1492     for (unsigned i = 0, n = FrameArray.size(); i < n; ++i) {
1493       const MCDwarfFrameInfo &Frame = FrameArray[i];
1494       if (Frame.CompactUnwindEncoding == 0) continue;
1495       if (!SectionEmitted) {
1496         Streamer.SwitchSection(MOFI->getCompactUnwindSection());
1497         Streamer.EmitValueToAlignment(Context.getAsmInfo()->getPointerSize());
1498         SectionEmitted = true;
1499       }
1500       NeedsEHFrameSection |=
1501         Frame.CompactUnwindEncoding ==
1502           MOFI->getCompactUnwindDwarfEHFrameOnly();
1503       Emitter.EmitCompactUnwind(Frame);
1504     }
1505   }
1506 
1507   if (!NeedsEHFrameSection) return;
1508 
1509   MCSection &Section =
1510       IsEH ? *const_cast<MCObjectFileInfo *>(MOFI)->getEHFrameSection()
1511            : *MOFI->getDwarfFrameSection();
1512 
1513   Streamer.SwitchSection(&Section);
1514   MCSymbol *SectionStart = Context.createTempSymbol();
1515   Streamer.EmitLabel(SectionStart);
1516 
1517   DenseMap<CIEKey, const MCSymbol *> CIEStarts;
1518 
1519   const MCSymbol *DummyDebugKey = nullptr;
1520   bool CanOmitDwarf = MOFI->getOmitDwarfIfHaveCompactUnwind();
1521   for (auto I = FrameArray.begin(), E = FrameArray.end(); I != E;) {
1522     const MCDwarfFrameInfo &Frame = *I;
1523     ++I;
1524     if (CanOmitDwarf && Frame.CompactUnwindEncoding !=
1525           MOFI->getCompactUnwindDwarfEHFrameOnly())
1526       // Don't generate an EH frame if we don't need one. I.e., it's taken care
1527       // of by the compact unwind encoding.
1528       continue;
1529 
1530     CIEKey Key(Frame.Personality, Frame.PersonalityEncoding,
1531                Frame.LsdaEncoding, Frame.IsSignalFrame, Frame.IsSimple);
1532     const MCSymbol *&CIEStart = IsEH ? CIEStarts[Key] : DummyDebugKey;
1533     if (!CIEStart)
1534       CIEStart = &Emitter.EmitCIE(Frame.Personality, Frame.PersonalityEncoding,
1535                                   Frame.Lsda, Frame.IsSignalFrame,
1536                                   Frame.LsdaEncoding, Frame.IsSimple);
1537 
1538     Emitter.EmitFDE(*CIEStart, Frame, I == E, *SectionStart);
1539   }
1540 }
1541 
EmitAdvanceLoc(MCObjectStreamer & Streamer,uint64_t AddrDelta)1542 void MCDwarfFrameEmitter::EmitAdvanceLoc(MCObjectStreamer &Streamer,
1543                                          uint64_t AddrDelta) {
1544   MCContext &Context = Streamer.getContext();
1545   SmallString<256> Tmp;
1546   raw_svector_ostream OS(Tmp);
1547   MCDwarfFrameEmitter::EncodeAdvanceLoc(Context, AddrDelta, OS);
1548   Streamer.EmitBytes(OS.str());
1549 }
1550 
EncodeAdvanceLoc(MCContext & Context,uint64_t AddrDelta,raw_ostream & OS)1551 void MCDwarfFrameEmitter::EncodeAdvanceLoc(MCContext &Context,
1552                                            uint64_t AddrDelta,
1553                                            raw_ostream &OS) {
1554   // Scale the address delta by the minimum instruction length.
1555   AddrDelta = ScaleAddrDelta(Context, AddrDelta);
1556 
1557   if (AddrDelta == 0) {
1558   } else if (isUIntN(6, AddrDelta)) {
1559     uint8_t Opcode = dwarf::DW_CFA_advance_loc | AddrDelta;
1560     OS << Opcode;
1561   } else if (isUInt<8>(AddrDelta)) {
1562     OS << uint8_t(dwarf::DW_CFA_advance_loc1);
1563     OS << uint8_t(AddrDelta);
1564   } else if (isUInt<16>(AddrDelta)) {
1565     OS << uint8_t(dwarf::DW_CFA_advance_loc2);
1566     if (Context.getAsmInfo()->isLittleEndian())
1567       support::endian::Writer<support::little>(OS).write<uint16_t>(AddrDelta);
1568     else
1569       support::endian::Writer<support::big>(OS).write<uint16_t>(AddrDelta);
1570   } else {
1571     assert(isUInt<32>(AddrDelta));
1572     OS << uint8_t(dwarf::DW_CFA_advance_loc4);
1573     if (Context.getAsmInfo()->isLittleEndian())
1574       support::endian::Writer<support::little>(OS).write<uint32_t>(AddrDelta);
1575     else
1576       support::endian::Writer<support::big>(OS).write<uint32_t>(AddrDelta);
1577   }
1578 }
1579