LLVM  3.7.0
WinCodeViewLineTables.cpp
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1 //===-- llvm/lib/CodeGen/AsmPrinter/WinCodeViewLineTables.cpp --*- C++ -*--===//
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 // This file contains support for writing line tables info into COFF files.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "WinCodeViewLineTables.h"
15 #include "llvm/MC/MCExpr.h"
16 #include "llvm/MC/MCSymbol.h"
17 #include "llvm/Support/COFF.h"
18 
19 namespace llvm {
20 
21 StringRef WinCodeViewLineTables::getFullFilepath(const MDNode *S) {
22  assert(S);
23  assert((isa<DICompileUnit>(S) || isa<DIFile>(S) || isa<DISubprogram>(S) ||
24  isa<DILexicalBlockBase>(S)) &&
25  "Unexpected scope info");
26 
27  auto *Scope = cast<DIScope>(S);
28  StringRef Dir = Scope->getDirectory(),
29  Filename = Scope->getFilename();
30  char *&Result = DirAndFilenameToFilepathMap[std::make_pair(Dir, Filename)];
31  if (Result)
32  return Result;
33 
34  // Clang emits directory and relative filename info into the IR, but CodeView
35  // operates on full paths. We could change Clang to emit full paths too, but
36  // that would increase the IR size and probably not needed for other users.
37  // For now, just concatenate and canonicalize the path here.
38  std::string Filepath;
39  if (Filename.find(':') == 1)
40  Filepath = Filename;
41  else
42  Filepath = (Dir + "\\" + Filename).str();
43 
44  // Canonicalize the path. We have to do it textually because we may no longer
45  // have access the file in the filesystem.
46  // First, replace all slashes with backslashes.
47  std::replace(Filepath.begin(), Filepath.end(), '/', '\\');
48 
49  // Remove all "\.\" with "\".
50  size_t Cursor = 0;
51  while ((Cursor = Filepath.find("\\.\\", Cursor)) != std::string::npos)
52  Filepath.erase(Cursor, 2);
53 
54  // Replace all "\XXX\..\" with "\". Don't try too hard though as the original
55  // path should be well-formatted, e.g. start with a drive letter, etc.
56  Cursor = 0;
57  while ((Cursor = Filepath.find("\\..\\", Cursor)) != std::string::npos) {
58  // Something's wrong if the path starts with "\..\", abort.
59  if (Cursor == 0)
60  break;
61 
62  size_t PrevSlash = Filepath.rfind('\\', Cursor - 1);
63  if (PrevSlash == std::string::npos)
64  // Something's wrong, abort.
65  break;
66 
67  Filepath.erase(PrevSlash, Cursor + 3 - PrevSlash);
68  // The next ".." might be following the one we've just erased.
69  Cursor = PrevSlash;
70  }
71 
72  // Remove all duplicate backslashes.
73  Cursor = 0;
74  while ((Cursor = Filepath.find("\\\\", Cursor)) != std::string::npos)
75  Filepath.erase(Cursor, 1);
76 
77  Result = strdup(Filepath.c_str());
78  return StringRef(Result);
79 }
80 
81 void WinCodeViewLineTables::maybeRecordLocation(DebugLoc DL,
82  const MachineFunction *MF) {
83  const MDNode *Scope = DL.getScope();
84  if (!Scope)
85  return;
86  StringRef Filename = getFullFilepath(Scope);
87 
88  // Skip this instruction if it has the same file:line as the previous one.
89  assert(CurFn);
90  if (!CurFn->Instrs.empty()) {
91  const InstrInfoTy &LastInstr = InstrInfo[CurFn->Instrs.back()];
92  if (LastInstr.Filename == Filename && LastInstr.LineNumber == DL.getLine())
93  return;
94  }
95  FileNameRegistry.add(Filename);
96 
97  MCSymbol *MCL = Asm->MMI->getContext().createTempSymbol();
98  Asm->OutStreamer->EmitLabel(MCL);
99  CurFn->Instrs.push_back(MCL);
100  InstrInfo[MCL] = InstrInfoTy(Filename, DL.getLine(), DL.getCol());
101 }
102 
104  : Asm(nullptr), CurFn(nullptr) {
105  MachineModuleInfo *MMI = AP->MMI;
106 
107  // If module doesn't have named metadata anchors or COFF debug section
108  // is not available, skip any debug info related stuff.
109  if (!MMI->getModule()->getNamedMetadata("llvm.dbg.cu") ||
111  return;
112 
113  // Tell MMI that we have debug info.
114  MMI->setDebugInfoAvailability(true);
115  Asm = AP;
116 }
117 
119  if (FnDebugInfo.empty())
120  return;
121 
122  assert(Asm != nullptr);
123  Asm->OutStreamer->SwitchSection(
126 
127  // The COFF .debug$S section consists of several subsections, each starting
128  // with a 4-byte control code (e.g. 0xF1, 0xF2, etc) and then a 4-byte length
129  // of the payload followed by the payload itself. The subsections are 4-byte
130  // aligned.
131 
132  // Emit per-function debug information. This code is extracted into a
133  // separate function for readability.
134  for (size_t I = 0, E = VisitedFunctions.size(); I != E; ++I)
135  emitDebugInfoForFunction(VisitedFunctions[I]);
136 
137  // This subsection holds a file index to offset in string table table.
138  Asm->OutStreamer->AddComment("File index to string table offset subsection");
140  size_t NumFilenames = FileNameRegistry.Infos.size();
141  Asm->EmitInt32(8 * NumFilenames);
142  for (size_t I = 0, E = FileNameRegistry.Filenames.size(); I != E; ++I) {
143  StringRef Filename = FileNameRegistry.Filenames[I];
144  // For each unique filename, just write its offset in the string table.
145  Asm->EmitInt32(FileNameRegistry.Infos[Filename].StartOffset);
146  // The function name offset is not followed by any additional data.
147  Asm->EmitInt32(0);
148  }
149 
150  // This subsection holds the string table.
151  Asm->OutStreamer->AddComment("String table");
153  Asm->EmitInt32(FileNameRegistry.LastOffset);
154  // The payload starts with a null character.
155  Asm->EmitInt8(0);
156 
157  for (size_t I = 0, E = FileNameRegistry.Filenames.size(); I != E; ++I) {
158  // Just emit unique filenames one by one, separated by a null character.
159  Asm->OutStreamer->EmitBytes(FileNameRegistry.Filenames[I]);
160  Asm->EmitInt8(0);
161  }
162 
163  // No more subsections. Fill with zeros to align the end of the section by 4.
164  Asm->OutStreamer->EmitFill((-FileNameRegistry.LastOffset) % 4, 0);
165 
166  clear();
167 }
168 
169 static void EmitLabelDiff(MCStreamer &Streamer,
170  const MCSymbol *From, const MCSymbol *To,
171  unsigned int Size = 4) {
173  MCContext &Context = Streamer.getContext();
174  const MCExpr *FromRef = MCSymbolRefExpr::create(From, Variant, Context),
175  *ToRef = MCSymbolRefExpr::create(To, Variant, Context);
176  const MCExpr *AddrDelta =
177  MCBinaryExpr::create(MCBinaryExpr::Sub, ToRef, FromRef, Context);
178  Streamer.EmitValue(AddrDelta, Size);
179 }
180 
181 void WinCodeViewLineTables::emitDebugInfoForFunction(const Function *GV) {
182  // For each function there is a separate subsection
183  // which holds the PC to file:line table.
184  const MCSymbol *Fn = Asm->getSymbol(GV);
185  assert(Fn);
186 
187  const FunctionInfo &FI = FnDebugInfo[GV];
188  if (FI.Instrs.empty())
189  return;
190  assert(FI.End && "Don't know where the function ends?");
191 
192  StringRef GVName = GV->getName();
193  StringRef FuncName;
194  if (auto *SP = getDISubprogram(GV))
195  FuncName = SP->getDisplayName();
196 
197  // FIXME Clang currently sets DisplayName to "bar" for a C++
198  // "namespace_foo::bar" function, see PR21528. Luckily, dbghelp.dll is trying
199  // to demangle display names anyways, so let's just put a mangled name into
200  // the symbols subsection until Clang gives us what we need.
201  if (GVName.startswith("\01?"))
202  FuncName = GVName.substr(1);
203  // Emit a symbol subsection, required by VS2012+ to find function boundaries.
204  MCSymbol *SymbolsBegin = Asm->MMI->getContext().createTempSymbol(),
205  *SymbolsEnd = Asm->MMI->getContext().createTempSymbol();
206  Asm->OutStreamer->AddComment("Symbol subsection for " + Twine(FuncName));
208  EmitLabelDiff(*Asm->OutStreamer, SymbolsBegin, SymbolsEnd);
209  Asm->OutStreamer->EmitLabel(SymbolsBegin);
210  {
211  MCSymbol *ProcSegmentBegin = Asm->MMI->getContext().createTempSymbol(),
212  *ProcSegmentEnd = Asm->MMI->getContext().createTempSymbol();
213  EmitLabelDiff(*Asm->OutStreamer, ProcSegmentBegin, ProcSegmentEnd, 2);
214  Asm->OutStreamer->EmitLabel(ProcSegmentBegin);
215 
217  // Some bytes of this segment don't seem to be required for basic debugging,
218  // so just fill them with zeroes.
219  Asm->OutStreamer->EmitFill(12, 0);
220  // This is the important bit that tells the debugger where the function
221  // code is located and what's its size:
222  EmitLabelDiff(*Asm->OutStreamer, Fn, FI.End);
223  Asm->OutStreamer->EmitFill(12, 0);
224  Asm->OutStreamer->EmitCOFFSecRel32(Fn);
225  Asm->OutStreamer->EmitCOFFSectionIndex(Fn);
226  Asm->EmitInt8(0);
227  // Emit the function display name as a null-terminated string.
228  Asm->OutStreamer->EmitBytes(FuncName);
229  Asm->EmitInt8(0);
230  Asm->OutStreamer->EmitLabel(ProcSegmentEnd);
231 
232  // We're done with this function.
233  Asm->EmitInt16(0x0002);
235  }
236  Asm->OutStreamer->EmitLabel(SymbolsEnd);
237  // Every subsection must be aligned to a 4-byte boundary.
238  Asm->OutStreamer->EmitFill((-FuncName.size()) % 4, 0);
239 
240  // PCs/Instructions are grouped into segments sharing the same filename.
241  // Pre-calculate the lengths (in instructions) of these segments and store
242  // them in a map for convenience. Each index in the map is the sequential
243  // number of the respective instruction that starts a new segment.
244  DenseMap<size_t, size_t> FilenameSegmentLengths;
245  size_t LastSegmentEnd = 0;
246  StringRef PrevFilename = InstrInfo[FI.Instrs[0]].Filename;
247  for (size_t J = 1, F = FI.Instrs.size(); J != F; ++J) {
248  if (PrevFilename == InstrInfo[FI.Instrs[J]].Filename)
249  continue;
250  FilenameSegmentLengths[LastSegmentEnd] = J - LastSegmentEnd;
251  LastSegmentEnd = J;
252  PrevFilename = InstrInfo[FI.Instrs[J]].Filename;
253  }
254  FilenameSegmentLengths[LastSegmentEnd] = FI.Instrs.size() - LastSegmentEnd;
255 
256  // Emit a line table subsection, requred to do PC-to-file:line lookup.
257  Asm->OutStreamer->AddComment("Line table subsection for " + Twine(FuncName));
259  MCSymbol *LineTableBegin = Asm->MMI->getContext().createTempSymbol(),
260  *LineTableEnd = Asm->MMI->getContext().createTempSymbol();
261  EmitLabelDiff(*Asm->OutStreamer, LineTableBegin, LineTableEnd);
262  Asm->OutStreamer->EmitLabel(LineTableBegin);
263 
264  // Identify the function this subsection is for.
265  Asm->OutStreamer->EmitCOFFSecRel32(Fn);
266  Asm->OutStreamer->EmitCOFFSectionIndex(Fn);
267  // Insert flags after a 16-bit section index.
269 
270  // Length of the function's code, in bytes.
271  EmitLabelDiff(*Asm->OutStreamer, Fn, FI.End);
272 
273  // PC-to-linenumber lookup table:
274  MCSymbol *FileSegmentEnd = nullptr;
275 
276  // The start of the last segment:
277  size_t LastSegmentStart = 0;
278 
279  auto FinishPreviousChunk = [&] {
280  if (!FileSegmentEnd)
281  return;
282  for (size_t ColSegI = LastSegmentStart,
283  ColSegEnd = ColSegI + FilenameSegmentLengths[LastSegmentStart];
284  ColSegI != ColSegEnd; ++ColSegI) {
285  unsigned ColumnNumber = InstrInfo[FI.Instrs[ColSegI]].ColumnNumber;
286  Asm->EmitInt16(ColumnNumber); // Start column
287  Asm->EmitInt16(ColumnNumber); // End column
288  }
289  Asm->OutStreamer->EmitLabel(FileSegmentEnd);
290  };
291 
292  for (size_t J = 0, F = FI.Instrs.size(); J != F; ++J) {
293  MCSymbol *Instr = FI.Instrs[J];
294  assert(InstrInfo.count(Instr));
295 
296  if (FilenameSegmentLengths.count(J)) {
297  // We came to a beginning of a new filename segment.
298  FinishPreviousChunk();
299  StringRef CurFilename = InstrInfo[FI.Instrs[J]].Filename;
300  assert(FileNameRegistry.Infos.count(CurFilename));
301  size_t IndexInStringTable =
302  FileNameRegistry.Infos[CurFilename].FilenameID;
303  // Each segment starts with the offset of the filename
304  // in the string table.
305  Asm->OutStreamer->AddComment(
306  "Segment for file '" + Twine(CurFilename) + "' begins");
307  MCSymbol *FileSegmentBegin = Asm->MMI->getContext().createTempSymbol();
308  Asm->OutStreamer->EmitLabel(FileSegmentBegin);
309  Asm->EmitInt32(8 * IndexInStringTable);
310 
311  // Number of PC records in the lookup table.
312  size_t SegmentLength = FilenameSegmentLengths[J];
313  Asm->EmitInt32(SegmentLength);
314 
315  // Full size of the segment for this filename, including the prev two
316  // records.
317  FileSegmentEnd = Asm->MMI->getContext().createTempSymbol();
318  EmitLabelDiff(*Asm->OutStreamer, FileSegmentBegin, FileSegmentEnd);
319  LastSegmentStart = J;
320  }
321 
322  // The first PC with the given linenumber and the linenumber itself.
323  EmitLabelDiff(*Asm->OutStreamer, Fn, Instr);
324  Asm->EmitInt32(InstrInfo[Instr].LineNumber);
325  }
326 
327  FinishPreviousChunk();
328  Asm->OutStreamer->EmitLabel(LineTableEnd);
329 }
330 
332  assert(!CurFn && "Can't process two functions at once!");
333 
334  if (!Asm || !Asm->MMI->hasDebugInfo())
335  return;
336 
337  const Function *GV = MF->getFunction();
338  assert(FnDebugInfo.count(GV) == false);
339  VisitedFunctions.push_back(GV);
340  CurFn = &FnDebugInfo[GV];
341 
342  // Find the end of the function prolog.
343  // FIXME: is there a simpler a way to do this? Can we just search
344  // for the first instruction of the function, not the last of the prolog?
345  DebugLoc PrologEndLoc;
346  bool EmptyPrologue = true;
347  for (const auto &MBB : *MF) {
348  if (PrologEndLoc)
349  break;
350  for (const auto &MI : MBB) {
351  if (MI.isDebugValue())
352  continue;
353 
354  // First known non-DBG_VALUE and non-frame setup location marks
355  // the beginning of the function body.
356  // FIXME: do we need the first subcondition?
357  if (!MI.getFlag(MachineInstr::FrameSetup) && MI.getDebugLoc()) {
358  PrologEndLoc = MI.getDebugLoc();
359  break;
360  }
361  EmptyPrologue = false;
362  }
363  }
364  // Record beginning of function if we have a non-empty prologue.
365  if (PrologEndLoc && !EmptyPrologue) {
366  DebugLoc FnStartDL = PrologEndLoc.getFnDebugLoc();
367  maybeRecordLocation(FnStartDL, MF);
368  }
369 }
370 
372  if (!Asm || !CurFn) // We haven't created any debug info for this function.
373  return;
374 
375  const Function *GV = MF->getFunction();
376  assert(FnDebugInfo.count(GV));
377  assert(CurFn == &FnDebugInfo[GV]);
378 
379  if (CurFn->Instrs.empty()) {
380  FnDebugInfo.erase(GV);
381  VisitedFunctions.pop_back();
382  } else {
383  CurFn->End = Asm->getFunctionEnd();
384  }
385  CurFn = nullptr;
386 }
387 
389  // Ignore DBG_VALUE locations and function prologue.
390  if (!Asm || MI->isDebugValue() || MI->getFlag(MachineInstr::FrameSetup))
391  return;
392  DebugLoc DL = MI->getDebugLoc();
393  if (DL == PrevInstLoc || !DL)
394  return;
395  maybeRecordLocation(DL, Asm->MF);
396 }
397 }
std::unique_ptr< MCStreamer > OutStreamer
This is the MCStreamer object for the file we are generating.
Definition: AsmPrinter.h:83
MCSymbol * getSymbol(const GlobalValue *GV) const
Definition: AsmPrinter.cpp:339
static const MCSymbolRefExpr * create(const MCSymbol *Symbol, MCContext &Ctx)
Definition: MCExpr.h:315
void endFunction(const MachineFunction *) override
Gather post-function debug information.
MCSymbol - Instances of this class represent a symbol name in the MC file, and MCSymbols are created ...
Definition: MCSymbol.h:39
void EmitInt8(int Value) const
Emit a byte directive and value.
const MachineFunction * MF
The current machine function.
Definition: AsmPrinter.h:86
A debug info location.
Definition: DebugLoc.h:34
F(f)
void EmitInt32(int Value) const
Emit a long directive and value.
const Function * getFunction() const
getFunction - Return the LLVM function that this machine code represents
DebugLoc getFnDebugLoc() const
Find the debug info location for the start of the function.
Definition: DebugLoc.cpp:50
static const MCBinaryExpr * create(Opcode Op, const MCExpr *LHS, const MCExpr *RHS, MCContext &Ctx)
Definition: MCExpr.cpp:140
Base class for the full range of assembler expressions which are needed for parsing.
Definition: MCExpr.h:33
const Module * getModule() const
bool hasDebugInfo() const
hasDebugInfo - Returns true if valid debug info is present.
DISubprogram * getDISubprogram(const MDNode *Scope)
Find subprogram that is enclosing this scope.
Definition: DebugInfo.cpp:36
MCContext & getContext() const
Definition: MCStreamer.h:210
Context object for machine code objects.
Definition: MCContext.h:48
static cl::opt< std::string > FuncName("cppfname", cl::desc("Specify the name of the generated function"), cl::value_desc("function name"))
void EmitInt16(int Value) const
Emit a short directive and value.
MachineModuleInfo * MMI
This is a pointer to the current MachineModuleInfo.
Definition: AsmPrinter.h:89
bool isDebugValue() const
Definition: MachineInstr.h:748
bool erase(const KeyT &Val)
Definition: DenseMap.h:206
Streaming machine code generation interface.
Definition: MCStreamer.h:157
MCSymbol * createTempSymbol(bool CanBeUnnamed=true)
Create and return a new assembler temporary symbol with a unique but unspecified name.
Definition: MCContext.cpp:222
This class is intended to be used as a driving class for all asm writers.
Definition: AsmPrinter.h:66
bool getFlag(MIFlag Flag) const
Return whether an MI flag is set.
Definition: MachineInstr.h:150
void setDebugInfoAvailability(bool avail)
const MCContext & getContext() const
void beginInstruction(const MachineInstr *MI) override
Process beginning of an instruction.
size_type count(const KeyT &Val) const
Return 1 if the specified key is in the map, 0 otherwise.
Definition: DenseMap.h:119
void endModule() override
Emit the COFF section that holds the line table information.
const DebugLoc & getDebugLoc() const
Returns the debug location id of this MachineInstr.
Definition: MachineInstr.h:238
Representation of each machine instruction.
Definition: MachineInstr.h:51
NamedMDNode * getNamedMetadata(const Twine &Name) const
Return the first NamedMDNode in the module with the specified name.
Definition: Module.cpp:253
#define I(x, y, z)
Definition: MD5.cpp:54
MCSymbol * getFunctionEnd() const
Definition: AsmPrinter.h:159
void EmitValue(const MCExpr *Value, unsigned Size, const SMLoc &Loc=SMLoc())
Definition: MCStreamer.cpp:110
MCSection * getCOFFDebugSymbolsSection() const
bool LLVM_ATTRIBUTE_UNUSED_RESULT empty() const
Definition: DenseMap.h:79
const TargetLoweringObjectFile & getObjFileLowering() const
Return information about object file lowering.
Definition: AsmPrinter.cpp:134
void beginFunction(const MachineFunction *MF) override
Gather pre-function debug information.
Subtraction.
Definition: MCExpr.h:429
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:40
MachineModuleInfo - This class contains meta information specific to a module.
static void EmitLabelDiff(MCStreamer &Streamer, const MCSymbol *From, const MCSymbol *To, unsigned int Size=4)