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 the Dwarf line table for the specified section from the entries
122 // in the LineSection.
124 static inline void EmitDwarfLineTable(MCStreamer *MCOS,
125 const MCSection *Section,
126 const MCLineSection *LineSection,
127 const MCSection *DwarfLineSection) {
128 unsigned FileNum = 1;
129 unsigned LastLine = 1;
131 unsigned Flags = DWARF2_LINE_DEFAULT_IS_STMT ? DWARF2_FLAG_IS_STMT : 0;
133 MCSymbol *LastLabel = NULL;
135 // Loop through each MCLineEntry and encode the dwarf line number table.
136 for (MCLineSection::const_iterator
137 it = LineSection->getMCLineEntries()->begin(),
138 ie = LineSection->getMCLineEntries()->end(); it != ie; ++it) {
140 if (FileNum != it->getFileNum()) {
141 FileNum = it->getFileNum();
142 MCOS->EmitIntValue(dwarf::DW_LNS_set_file, 1);
143 MCOS->EmitULEB128IntValue(FileNum);
145 if (Column != it->getColumn()) {
146 Column = it->getColumn();
147 MCOS->EmitIntValue(dwarf::DW_LNS_set_column, 1);
148 MCOS->EmitULEB128IntValue(Column);
150 if (Isa != it->getIsa()) {
152 MCOS->EmitIntValue(dwarf::DW_LNS_set_isa, 1);
153 MCOS->EmitULEB128IntValue(Isa);
155 if ((it->getFlags() ^ Flags) & DWARF2_FLAG_IS_STMT) {
156 Flags = it->getFlags();
157 MCOS->EmitIntValue(dwarf::DW_LNS_negate_stmt, 1);
159 if (it->getFlags() & DWARF2_FLAG_BASIC_BLOCK)
160 MCOS->EmitIntValue(dwarf::DW_LNS_set_basic_block, 1);
161 if (it->getFlags() & DWARF2_FLAG_PROLOGUE_END)
162 MCOS->EmitIntValue(dwarf::DW_LNS_set_prologue_end, 1);
163 if (it->getFlags() & DWARF2_FLAG_EPILOGUE_BEGIN)
164 MCOS->EmitIntValue(dwarf::DW_LNS_set_epilogue_begin, 1);
166 int64_t LineDelta = static_cast<int64_t>(it->getLine()) - LastLine;
167 MCSymbol *Label = it->getLabel();
169 // At this point we want to emit/create the sequence to encode the delta in
170 // line numbers and the increment of the address from the previous Label
171 // and the current Label.
172 MCOS->EmitDwarfAdvanceLineAddr(LineDelta, LastLabel, Label);
174 LastLine = it->getLine();
178 // Emit a DW_LNE_end_sequence for the end of the section.
179 // Using the pointer Section create a temporary label at the end of the
180 // section and use that and the LastLabel to compute the address delta
181 // and use INT64_MAX as the line delta which is the signal that this is
182 // actually a DW_LNE_end_sequence.
184 // Switch to the section to be able to create a symbol at its end.
185 MCOS->SwitchSection(Section);
186 // Create a symbol at the end of the section.
187 MCSymbol *SectionEnd = MCOS->getContext().CreateTempSymbol();
188 // Set the value of the symbol, as we are at the end of the section.
189 MCOS->EmitLabel(SectionEnd);
191 // Switch back the the dwarf line section.
192 MCOS->SwitchSection(DwarfLineSection);
194 MCOS->EmitDwarfAdvanceLineAddr(INT64_MAX, LastLabel, SectionEnd);
198 // This emits the Dwarf file and the line tables.
200 void MCDwarfFileTable::Emit(MCStreamer *MCOS,
201 const MCSection *DwarfLineSection,
202 const MCSection *TextSection) {
203 // Switch to the section where the table will be emitted into.
204 MCOS->SwitchSection(DwarfLineSection);
206 // Create a symbol at the beginning of this section.
207 MCSymbol *LineStartSym = MCOS->getContext().CreateTempSymbol();
208 // Set the value of the symbol, as we are at the start of the section.
209 MCOS->EmitLabel(LineStartSym);
211 // Create a symbol for the end of the section (to be set when we get there).
212 MCSymbol *LineEndSym = MCOS->getContext().CreateTempSymbol();
214 // The first 4 bytes is the total length of the information for this
215 // compilation unit (not including these 4 bytes for the length).
216 MCOS->EmitValue(MakeStartMinusEndExpr(MCOS, LineStartSym, LineEndSym, 4),
217 4, 0, true /*UseSet*/);
219 // Next 2 bytes is the Version, which is Dwarf 2.
220 MCOS->EmitIntValue(2, 2);
222 // Create a symbol for the end of the prologue (to be set when we get there).
223 MCSymbol *ProEndSym = MCOS->getContext().CreateTempSymbol(); // Lprologue_end
225 // Length of the prologue, is the next 4 bytes. Which is the start of the
226 // section to the end of the prologue. Not including the 4 bytes for the
227 // total length, the 2 bytes for the version, and these 4 bytes for the
228 // length of the prologue.
229 MCOS->EmitValue(MakeStartMinusEndExpr(MCOS, LineStartSym, ProEndSym,
231 4, 0, true /*UseSet*/);
233 // Parameters of the state machine, are next.
234 MCOS->EmitIntValue(DWARF2_LINE_MIN_INSN_LENGTH, 1);
235 MCOS->EmitIntValue(DWARF2_LINE_DEFAULT_IS_STMT, 1);
236 MCOS->EmitIntValue(DWARF2_LINE_BASE, 1);
237 MCOS->EmitIntValue(DWARF2_LINE_RANGE, 1);
238 MCOS->EmitIntValue(DWARF2_LINE_OPCODE_BASE, 1);
240 // Standard opcode lengths
241 MCOS->EmitIntValue(0, 1); // length of DW_LNS_copy
242 MCOS->EmitIntValue(1, 1); // length of DW_LNS_advance_pc
243 MCOS->EmitIntValue(1, 1); // length of DW_LNS_advance_line
244 MCOS->EmitIntValue(1, 1); // length of DW_LNS_set_file
245 MCOS->EmitIntValue(1, 1); // length of DW_LNS_set_column
246 MCOS->EmitIntValue(0, 1); // length of DW_LNS_negate_stmt
247 MCOS->EmitIntValue(0, 1); // length of DW_LNS_set_basic_block
248 MCOS->EmitIntValue(0, 1); // length of DW_LNS_const_add_pc
249 MCOS->EmitIntValue(1, 1); // length of DW_LNS_fixed_advance_pc
250 MCOS->EmitIntValue(0, 1); // length of DW_LNS_set_prologue_end
251 MCOS->EmitIntValue(0, 1); // length of DW_LNS_set_epilogue_begin
252 MCOS->EmitIntValue(1, 1); // DW_LNS_set_isa
254 // Put out the directory and file tables.
256 // First the directory table.
257 const std::vector<StringRef> &MCDwarfDirs =
258 MCOS->getContext().getMCDwarfDirs();
259 for (unsigned i = 0; i < MCDwarfDirs.size(); i++) {
260 MCOS->EmitBytes(MCDwarfDirs[i], 0); // the DirectoryName
261 MCOS->EmitBytes(StringRef("\0", 1), 0); // the null term. of the string
263 MCOS->EmitIntValue(0, 1); // Terminate the directory list
265 // Second the file table.
266 const std::vector<MCDwarfFile *> &MCDwarfFiles =
267 MCOS->getContext().getMCDwarfFiles();
268 for (unsigned i = 1; i < MCDwarfFiles.size(); i++) {
269 MCOS->EmitBytes(MCDwarfFiles[i]->getName(), 0); // FileName
270 MCOS->EmitBytes(StringRef("\0", 1), 0); // the null term. of the string
272 MCOS->EmitULEB128IntValue(MCDwarfFiles[i]->getDirIndex());
273 MCOS->EmitIntValue(0, 1); // last modification timestamp (always 0)
274 MCOS->EmitIntValue(0, 1); // filesize (always 0)
276 MCOS->EmitIntValue(0, 1); // Terminate the file list
278 // This is the end of the prologue, so set the value of the symbol at the
279 // end of the prologue (that was used in a previous expression).
280 MCOS->EmitLabel(ProEndSym);
282 // Put out the line tables.
283 const DenseMap<const MCSection *, MCLineSection *> &MCLineSections =
284 MCOS->getContext().getMCLineSections();
285 const std::vector<const MCSection *> &MCLineSectionOrder =
286 MCOS->getContext().getMCLineSectionOrder();
287 for (std::vector<const MCSection*>::const_iterator it =
288 MCLineSectionOrder.begin(), ie = MCLineSectionOrder.end(); it != ie;
290 const MCSection *Sec = *it;
291 const MCLineSection *Line = MCLineSections.lookup(Sec);
292 EmitDwarfLineTable(MCOS, Sec, Line, DwarfLineSection);
294 // Now delete the MCLineSections that were created in MCLineEntry::Make()
295 // and used to emit the line table.
299 if (TextSection && MCLineSectionOrder.begin() == MCLineSectionOrder.end()) {
300 // Emit dummy entry if line table is empty.
302 MCOS->SwitchSection(TextSection);
303 MCSymbol *SectionEnd = MCOS->getContext().CreateTempSymbol();
304 // Set the value of the symbol, as we are at the end of the section.
305 MCOS->EmitLabel(SectionEnd);
307 // Switch back the the dwarf line section.
308 MCOS->SwitchSection(DwarfLineSection);
310 MCOS->EmitDwarfAdvanceLineAddr(INT64_MAX, NULL, SectionEnd);
313 // This is the end of the section, so set the value of the symbol at the end
314 // of this section (that was used in a previous expression).
315 MCOS->EmitLabel(LineEndSym);
318 /// Utility function to compute the size of the encoding.
319 uint64_t MCDwarfLineAddr::ComputeSize(int64_t LineDelta, uint64_t AddrDelta) {
320 SmallString<256> Tmp;
321 raw_svector_ostream OS(Tmp);
322 MCDwarfLineAddr::Encode(LineDelta, AddrDelta, OS);
323 return OS.GetNumBytesInBuffer();
326 /// Utility function to write the encoding to an object writer.
327 void MCDwarfLineAddr::Write(MCObjectWriter *OW, int64_t LineDelta,
328 uint64_t AddrDelta) {
329 SmallString<256> Tmp;
330 raw_svector_ostream OS(Tmp);
331 MCDwarfLineAddr::Encode(LineDelta, AddrDelta, OS);
332 OW->WriteBytes(OS.str());
335 /// Utility function to emit the encoding to a streamer.
336 void MCDwarfLineAddr::Emit(MCStreamer *MCOS, int64_t LineDelta,
337 uint64_t AddrDelta) {
338 SmallString<256> Tmp;
339 raw_svector_ostream OS(Tmp);
340 MCDwarfLineAddr::Encode(LineDelta, AddrDelta, OS);
341 MCOS->EmitBytes(OS.str(), /*AddrSpace=*/0);
344 /// Utility function to encode a Dwarf pair of LineDelta and AddrDeltas.
345 void MCDwarfLineAddr::Encode(int64_t LineDelta, uint64_t AddrDelta,
347 uint64_t Temp, Opcode;
348 bool NeedCopy = false;
350 // Scale the address delta by the minimum instruction length.
351 AddrDelta = ScaleAddrDelta(AddrDelta);
353 // A LineDelta of INT64_MAX is a signal that this is actually a
354 // DW_LNE_end_sequence. We cannot use special opcodes here, since we want the
355 // end_sequence to emit the matrix entry.
356 if (LineDelta == INT64_MAX) {
357 if (AddrDelta == MAX_SPECIAL_ADDR_DELTA)
358 OS << char(dwarf::DW_LNS_const_add_pc);
360 OS << char(dwarf::DW_LNS_advance_pc);
362 raw_svector_ostream OSE(Tmp);
363 MCObjectWriter::EncodeULEB128(AddrDelta, OSE);
366 OS << char(dwarf::DW_LNS_extended_op);
368 OS << char(dwarf::DW_LNE_end_sequence);
372 // Bias the line delta by the base.
373 Temp = LineDelta - DWARF2_LINE_BASE;
375 // If the line increment is out of range of a special opcode, we must encode
376 // it with DW_LNS_advance_line.
377 if (Temp >= DWARF2_LINE_RANGE) {
378 OS << char(dwarf::DW_LNS_advance_line);
380 raw_svector_ostream OSE(Tmp);
381 MCObjectWriter::EncodeSLEB128(LineDelta, OSE);
385 Temp = 0 - DWARF2_LINE_BASE;
389 // Use DW_LNS_copy instead of a "line +0, addr +0" special opcode.
390 if (LineDelta == 0 && AddrDelta == 0) {
391 OS << char(dwarf::DW_LNS_copy);
395 // Bias the opcode by the special opcode base.
396 Temp += DWARF2_LINE_OPCODE_BASE;
398 // Avoid overflow when addr_delta is large.
399 if (AddrDelta < 256 + MAX_SPECIAL_ADDR_DELTA) {
400 // Try using a special opcode.
401 Opcode = Temp + AddrDelta * DWARF2_LINE_RANGE;
407 // Try using DW_LNS_const_add_pc followed by special op.
408 Opcode = Temp + (AddrDelta - MAX_SPECIAL_ADDR_DELTA) * DWARF2_LINE_RANGE;
410 OS << char(dwarf::DW_LNS_const_add_pc);
416 // Otherwise use DW_LNS_advance_pc.
417 OS << char(dwarf::DW_LNS_advance_pc);
419 raw_svector_ostream OSE(Tmp);
420 MCObjectWriter::EncodeULEB128(AddrDelta, OSE);
424 OS << char(dwarf::DW_LNS_copy);
429 void MCDwarfFile::print(raw_ostream &OS) const {
430 OS << '"' << getName() << '"';
433 void MCDwarfFile::dump() const {