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/MC/MCAssembler.h"
12 #include "llvm/MC/MCStreamer.h"
13 #include "llvm/MC/MCSymbol.h"
14 #include "llvm/MC/MCExpr.h"
15 #include "llvm/MC/MCContext.h"
16 #include "llvm/MC/MCObjectWriter.h"
17 #include "llvm/ADT/SmallString.h"
18 #include "llvm/Support/Debug.h"
19 #include "llvm/Support/raw_ostream.h"
20 #include "llvm/Target/TargetAsmBackend.h"
23 // Given a special op, return the address skip amount (in units of
24 // DWARF2_LINE_MIN_INSN_LENGTH.
25 #define SPECIAL_ADDR(op) (((op) - DWARF2_LINE_OPCODE_BASE)/DWARF2_LINE_RANGE)
27 // The maximum address skip amount that can be encoded with a special op.
28 #define MAX_SPECIAL_ADDR_DELTA SPECIAL_ADDR(255)
30 // First special line opcode - leave room for the standard opcodes.
31 // Note: If you want to change this, you'll have to update the
32 // "standard_opcode_lengths" table that is emitted in DwarfFileTable::Emit().
33 #define DWARF2_LINE_OPCODE_BASE 13
35 // Minimum line offset in a special line info. opcode. This value
36 // was chosen to give a reasonable range of values.
37 #define DWARF2_LINE_BASE -5
39 // Range of line offsets in a special line info. opcode.
40 # define DWARF2_LINE_RANGE 14
42 // Define the architecture-dependent minimum instruction length (in bytes).
43 // This value should be rather too small than too big.
44 # define DWARF2_LINE_MIN_INSN_LENGTH 1
46 // Note: when DWARF2_LINE_MIN_INSN_LENGTH == 1 which is the current setting,
47 // this routine is a nop and will be optimized away.
48 static inline uint64_t ScaleAddrDelta(uint64_t AddrDelta)
50 if (DWARF2_LINE_MIN_INSN_LENGTH == 1)
52 if (AddrDelta % DWARF2_LINE_MIN_INSN_LENGTH != 0) {
53 // TODO: report this error, but really only once.
56 return AddrDelta / DWARF2_LINE_MIN_INSN_LENGTH;
60 // This is called when an instruction is assembled into the specified section
61 // and if there is information from the last .loc directive that has yet to have
62 // a line entry made for it is made.
64 void MCLineEntry::Make(MCStreamer *MCOS, const MCSection *Section) {
65 if (!MCOS->getContext().getDwarfLocSeen())
68 // Create a symbol at in the current section for use in the line entry.
69 MCSymbol *LineSym = MCOS->getContext().CreateTempSymbol();
70 // Set the value of the symbol to use for the MCLineEntry.
71 MCOS->EmitLabel(LineSym);
73 // Get the current .loc info saved in the context.
74 const MCDwarfLoc &DwarfLoc = MCOS->getContext().getCurrentDwarfLoc();
76 // Create a (local) line entry with the symbol and the current .loc info.
77 MCLineEntry LineEntry(LineSym, DwarfLoc);
79 // clear DwarfLocSeen saying the current .loc info is now used.
80 MCOS->getContext().ClearDwarfLocSeen();
82 // Get the MCLineSection for this section, if one does not exist for this
84 const DenseMap<const MCSection *, MCLineSection *> &MCLineSections =
85 MCOS->getContext().getMCLineSections();
86 MCLineSection *LineSection = MCLineSections.lookup(Section);
88 // Create a new MCLineSection. This will be deleted after the dwarf line
89 // table is created using it by iterating through the MCLineSections
91 LineSection = new MCLineSection;
92 // Save a pointer to the new LineSection into the MCLineSections DenseMap.
93 MCOS->getContext().addMCLineSection(Section, LineSection);
96 // Add the line entry to this section's entries.
97 LineSection->addLineEntry(LineEntry);
101 // This helper routine returns an expression of End - Start + IntVal .
103 static inline const MCExpr *MakeStartMinusEndExpr(MCStreamer *MCOS,
105 MCSymbol *End, int IntVal) {
106 MCSymbolRefExpr::VariantKind Variant = MCSymbolRefExpr::VK_None;
108 MCSymbolRefExpr::Create(End, Variant, MCOS->getContext());
110 MCSymbolRefExpr::Create(Start, Variant, MCOS->getContext());
112 MCBinaryExpr::Create(MCBinaryExpr::Sub, Res, RHS, MCOS->getContext());
114 MCConstantExpr::Create(IntVal, MCOS->getContext());
116 MCBinaryExpr::Create(MCBinaryExpr::Sub, Res1, Res2, MCOS->getContext());
121 // This emits an "absolute" address used in the start of a dwarf line number
122 // table. This will result in a relocatation entry for the address.
124 static inline void EmitDwarfSetAddress(MCStreamer *MCOS,
127 MCOS->EmitIntValue(dwarf::DW_LNS_extended_op, 1);
129 MCOS->EmitULEB128IntValue(PointerSize + 1);
131 MCOS->EmitIntValue(dwarf::DW_LNE_set_address, 1);
132 MCOS->EmitSymbolValue(Symbol, PointerSize);
136 // This emits the Dwarf line table for the specified section from the entries
137 // in the LineSection.
139 static inline void EmitDwarfLineTable(MCStreamer *MCOS,
140 const MCSection *Section,
141 const MCLineSection *LineSection,
142 const MCSection *DwarfLineSection,
145 unsigned FileNum = 1;
146 unsigned LastLine = 1;
148 unsigned Flags = DWARF2_LINE_DEFAULT_IS_STMT ? DWARF2_FLAG_IS_STMT : 0;
150 MCSymbol *LastLabel = NULL;
152 // Loop through each MCLineEntry and encode the dwarf line number table.
153 for (MCLineSection::const_iterator
154 it = LineSection->getMCLineEntries()->begin(),
155 ie = LineSection->getMCLineEntries()->end(); it != ie; ++it) {
157 if (FileNum != it->getFileNum()) {
158 FileNum = it->getFileNum();
159 MCOS->EmitIntValue(dwarf::DW_LNS_set_file, 1);
160 MCOS->EmitULEB128IntValue(FileNum);
162 if (Column != it->getColumn()) {
163 Column = it->getColumn();
164 MCOS->EmitIntValue(dwarf::DW_LNS_set_column, 1);
165 MCOS->EmitULEB128IntValue(Column);
167 if (Isa != it->getIsa()) {
169 MCOS->EmitIntValue(dwarf::DW_LNS_set_isa, 1);
170 MCOS->EmitULEB128IntValue(Isa);
172 if ((it->getFlags() ^ Flags) & DWARF2_FLAG_IS_STMT) {
173 Flags = it->getFlags();
174 MCOS->EmitIntValue(dwarf::DW_LNS_negate_stmt, 1);
176 if (it->getFlags() & DWARF2_FLAG_BASIC_BLOCK)
177 MCOS->EmitIntValue(dwarf::DW_LNS_set_basic_block, 1);
178 if (it->getFlags() & DWARF2_FLAG_PROLOGUE_END)
179 MCOS->EmitIntValue(dwarf::DW_LNS_set_prologue_end, 1);
180 if (it->getFlags() & DWARF2_FLAG_EPILOGUE_BEGIN)
181 MCOS->EmitIntValue(dwarf::DW_LNS_set_epilogue_begin, 1);
183 int64_t LineDelta = static_cast<int64_t>(it->getLine()) - LastLine;
184 MCSymbol *Label = it->getLabel();
186 // At this point we want to emit/create the sequence to encode the delta in
187 // line numbers and the increment of the address from the previous Label
188 // and the current Label.
189 if (LastLabel == NULL || DLS == NULL) {
190 // emit the sequence to set the address
191 EmitDwarfSetAddress(MCOS, Label, PointerSize);
192 // emit the sequence for the LineDelta (from 1) and a zero address delta.
193 MCDwarfLineAddr::Emit(MCOS, LineDelta, 0);
196 // Create an expression for the address delta from the LastLabel and
197 // this Label (plus 0).
198 const MCExpr *AddrDelta = MakeStartMinusEndExpr(MCOS, LastLabel, Label,0);
199 // Create a Dwarf Line fragment for the LineDelta and AddrDelta.
200 new MCDwarfLineAddrFragment(LineDelta, *AddrDelta, DLS);
203 LastLine = it->getLine();
207 // Emit a DW_LNE_end_sequence for the end of the section.
208 // Using the pointer Section create a temporary label at the end of the
209 // section and use that and the LastLabel to compute the address delta
210 // and use INT64_MAX as the line delta which is the signal that this is
211 // actually a DW_LNE_end_sequence.
213 // Switch to the section to be able to create a symbol at its end.
214 MCOS->SwitchSection(Section);
215 // Create a symbol at the end of the section.
216 MCSymbol *SectionEnd = MCOS->getContext().CreateTempSymbol();
217 // Set the value of the symbol, as we are at the end of the section.
218 MCOS->EmitLabel(SectionEnd);
220 // Switch back the the dwarf line section.
221 MCOS->SwitchSection(DwarfLineSection);
224 // emit the sequence to set the address
225 EmitDwarfSetAddress(MCOS, SectionEnd, PointerSize);
226 // emit the sequence for the LineDelta (from 1) and a zero address delta.
227 MCDwarfLineAddr::Emit(MCOS, INT64_MAX, 0);
229 // Create an expression for the address delta from the LastLabel and this
231 const MCExpr *AddrDelta = MakeStartMinusEndExpr(MCOS, LastLabel, SectionEnd,
233 // Create a Dwarf Line fragment for the LineDelta and AddrDelta.
234 new MCDwarfLineAddrFragment(INT64_MAX, *AddrDelta, DLS);
239 // This emits the Dwarf file and the line tables.
241 void MCDwarfFileTable::Emit(MCStreamer *MCOS,
242 const MCSection *DwarfLineSection,
245 const MCSection *TextSection) {
246 // Switch to the section where the table will be emitted into.
247 MCOS->SwitchSection(DwarfLineSection);
249 // Create a symbol at the beginning of this section.
250 MCSymbol *LineStartSym = MCOS->getContext().CreateTempSymbol();
251 // Set the value of the symbol, as we are at the start of the section.
252 MCOS->EmitLabel(LineStartSym);
254 // Create a symbol for the end of the section (to be set when we get there).
255 MCSymbol *LineEndSym = MCOS->getContext().CreateTempSymbol();
257 // The first 4 bytes is the total length of the information for this
258 // compilation unit (not including these 4 bytes for the length).
259 MCOS->EmitValue(MakeStartMinusEndExpr(MCOS, LineStartSym, LineEndSym, 4),
260 4, 0, true /*UseSet*/);
262 // Next 2 bytes is the Version, which is Dwarf 2.
263 MCOS->EmitIntValue(2, 2);
265 // Create a symbol for the end of the prologue (to be set when we get there).
266 MCSymbol *ProEndSym = MCOS->getContext().CreateTempSymbol(); // Lprologue_end
268 // Length of the prologue, is the next 4 bytes. Which is the start of the
269 // section to the end of the prologue. Not including the 4 bytes for the
270 // total length, the 2 bytes for the version, and these 4 bytes for the
271 // length of the prologue.
272 MCOS->EmitValue(MakeStartMinusEndExpr(MCOS, LineStartSym, ProEndSym,
274 4, 0, true /*UseSet*/);
276 // Parameters of the state machine, are next.
277 MCOS->EmitIntValue(DWARF2_LINE_MIN_INSN_LENGTH, 1);
278 MCOS->EmitIntValue(DWARF2_LINE_DEFAULT_IS_STMT, 1);
279 MCOS->EmitIntValue(DWARF2_LINE_BASE, 1);
280 MCOS->EmitIntValue(DWARF2_LINE_RANGE, 1);
281 MCOS->EmitIntValue(DWARF2_LINE_OPCODE_BASE, 1);
283 // Standard opcode lengths
284 MCOS->EmitIntValue(0, 1); // length of DW_LNS_copy
285 MCOS->EmitIntValue(1, 1); // length of DW_LNS_advance_pc
286 MCOS->EmitIntValue(1, 1); // length of DW_LNS_advance_line
287 MCOS->EmitIntValue(1, 1); // length of DW_LNS_set_file
288 MCOS->EmitIntValue(1, 1); // length of DW_LNS_set_column
289 MCOS->EmitIntValue(0, 1); // length of DW_LNS_negate_stmt
290 MCOS->EmitIntValue(0, 1); // length of DW_LNS_set_basic_block
291 MCOS->EmitIntValue(0, 1); // length of DW_LNS_const_add_pc
292 MCOS->EmitIntValue(1, 1); // length of DW_LNS_fixed_advance_pc
293 MCOS->EmitIntValue(0, 1); // length of DW_LNS_set_prologue_end
294 MCOS->EmitIntValue(0, 1); // length of DW_LNS_set_epilogue_begin
295 MCOS->EmitIntValue(1, 1); // DW_LNS_set_isa
297 // Put out the directory and file tables.
299 // First the directory table.
300 const std::vector<StringRef> &MCDwarfDirs =
301 MCOS->getContext().getMCDwarfDirs();
302 for (unsigned i = 0; i < MCDwarfDirs.size(); i++) {
303 MCOS->EmitBytes(MCDwarfDirs[i], 0); // the DirectoryName
304 MCOS->EmitBytes(StringRef("\0", 1), 0); // the null term. of the string
306 MCOS->EmitIntValue(0, 1); // Terminate the directory list
308 // Second the file table.
309 const std::vector<MCDwarfFile *> &MCDwarfFiles =
310 MCOS->getContext().getMCDwarfFiles();
311 for (unsigned i = 1; i < MCDwarfFiles.size(); i++) {
312 MCOS->EmitBytes(MCDwarfFiles[i]->getName(), 0); // FileName
313 MCOS->EmitBytes(StringRef("\0", 1), 0); // the null term. of the string
315 MCOS->EmitULEB128IntValue(MCDwarfFiles[i]->getDirIndex());
316 MCOS->EmitIntValue(0, 1); // last modification timestamp (always 0)
317 MCOS->EmitIntValue(0, 1); // filesize (always 0)
319 MCOS->EmitIntValue(0, 1); // Terminate the file list
321 // This is the end of the prologue, so set the value of the symbol at the
322 // end of the prologue (that was used in a previous expression).
323 MCOS->EmitLabel(ProEndSym);
325 // Put out the line tables.
326 const DenseMap<const MCSection *, MCLineSection *> &MCLineSections =
327 MCOS->getContext().getMCLineSections();
328 const std::vector<const MCSection *> &MCLineSectionOrder =
329 MCOS->getContext().getMCLineSectionOrder();
330 for (std::vector<const MCSection*>::const_iterator it =
331 MCLineSectionOrder.begin(), ie = MCLineSectionOrder.end(); it != ie;
333 const MCSection *Sec = *it;
334 const MCLineSection *Line = MCLineSections.lookup(Sec);
335 EmitDwarfLineTable(MCOS, Sec, Line, DwarfLineSection, DLS,
338 // Now delete the MCLineSections that were created in MCLineEntry::Make()
339 // and used to emit the line table.
343 if (TextSection && MCLineSectionOrder.begin() == MCLineSectionOrder.end()) {
344 // Emit dummy entry if line table is empty.
346 MCOS->SwitchSection(TextSection);
347 MCSymbol *SectionEnd = MCOS->getContext().CreateTempSymbol();
348 // Set the value of the symbol, as we are at the end of the section.
349 MCOS->EmitLabel(SectionEnd);
351 // Switch back the the dwarf line section.
352 MCOS->SwitchSection(DwarfLineSection);
354 // emit the sequence to set the address
355 EmitDwarfSetAddress(MCOS, SectionEnd, PointerSize);
356 // emit the sequence for the LineDelta (from 1) and a zero address delta.
357 MCDwarfLineAddr::Emit(MCOS, INT64_MAX, 0);
360 // This is the end of the section, so set the value of the symbol at the end
361 // of this section (that was used in a previous expression).
362 MCOS->EmitLabel(LineEndSym);
365 /// Utility function to compute the size of the encoding.
366 uint64_t MCDwarfLineAddr::ComputeSize(int64_t LineDelta, uint64_t AddrDelta) {
367 SmallString<256> Tmp;
368 raw_svector_ostream OS(Tmp);
369 MCDwarfLineAddr::Encode(LineDelta, AddrDelta, OS);
370 return OS.GetNumBytesInBuffer();
373 /// Utility function to write the encoding to an object writer.
374 void MCDwarfLineAddr::Write(MCObjectWriter *OW, int64_t LineDelta,
375 uint64_t AddrDelta) {
376 SmallString<256> Tmp;
377 raw_svector_ostream OS(Tmp);
378 MCDwarfLineAddr::Encode(LineDelta, AddrDelta, OS);
379 OW->WriteBytes(OS.str());
382 /// Utility function to emit the encoding to a streamer.
383 void MCDwarfLineAddr::Emit(MCStreamer *MCOS, int64_t LineDelta,
384 uint64_t AddrDelta) {
385 SmallString<256> Tmp;
386 raw_svector_ostream OS(Tmp);
387 MCDwarfLineAddr::Encode(LineDelta, AddrDelta, OS);
388 MCOS->EmitBytes(OS.str(), /*AddrSpace=*/0);
391 /// Utility function to encode a Dwarf pair of LineDelta and AddrDeltas.
392 void MCDwarfLineAddr::Encode(int64_t LineDelta, uint64_t AddrDelta,
394 uint64_t Temp, Opcode;
395 bool NeedCopy = false;
397 // Scale the address delta by the minimum instruction length.
398 AddrDelta = ScaleAddrDelta(AddrDelta);
400 // A LineDelta of INT64_MAX is a signal that this is actually a
401 // DW_LNE_end_sequence. We cannot use special opcodes here, since we want the
402 // end_sequence to emit the matrix entry.
403 if (LineDelta == INT64_MAX) {
404 if (AddrDelta == MAX_SPECIAL_ADDR_DELTA)
405 OS << char(dwarf::DW_LNS_const_add_pc);
407 OS << char(dwarf::DW_LNS_advance_pc);
409 raw_svector_ostream OSE(Tmp);
410 MCObjectWriter::EncodeULEB128(AddrDelta, OSE);
413 OS << char(dwarf::DW_LNS_extended_op);
415 OS << char(dwarf::DW_LNE_end_sequence);
419 // Bias the line delta by the base.
420 Temp = LineDelta - DWARF2_LINE_BASE;
422 // If the line increment is out of range of a special opcode, we must encode
423 // it with DW_LNS_advance_line.
424 if (Temp >= DWARF2_LINE_RANGE) {
425 OS << char(dwarf::DW_LNS_advance_line);
427 raw_svector_ostream OSE(Tmp);
428 MCObjectWriter::EncodeSLEB128(LineDelta, OSE);
432 Temp = 0 - DWARF2_LINE_BASE;
436 // Use DW_LNS_copy instead of a "line +0, addr +0" special opcode.
437 if (LineDelta == 0 && AddrDelta == 0) {
438 OS << char(dwarf::DW_LNS_copy);
442 // Bias the opcode by the special opcode base.
443 Temp += DWARF2_LINE_OPCODE_BASE;
445 // Avoid overflow when addr_delta is large.
446 if (AddrDelta < 256 + MAX_SPECIAL_ADDR_DELTA) {
447 // Try using a special opcode.
448 Opcode = Temp + AddrDelta * DWARF2_LINE_RANGE;
454 // Try using DW_LNS_const_add_pc followed by special op.
455 Opcode = Temp + (AddrDelta - MAX_SPECIAL_ADDR_DELTA) * DWARF2_LINE_RANGE;
457 OS << char(dwarf::DW_LNS_const_add_pc);
463 // Otherwise use DW_LNS_advance_pc.
464 OS << char(dwarf::DW_LNS_advance_pc);
466 raw_svector_ostream OSE(Tmp);
467 MCObjectWriter::EncodeULEB128(AddrDelta, OSE);
471 OS << char(dwarf::DW_LNS_copy);
476 void MCDwarfFile::print(raw_ostream &OS) const {
477 OS << '"' << getName() << '"';
480 void MCDwarfFile::dump() const {