1 //===-- llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.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 Microsoft CodeView debug info.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "CodeViewDebug.h"
15 #include "llvm/DebugInfo/CodeView/CodeView.h"
16 #include "llvm/DebugInfo/CodeView/Line.h"
17 #include "llvm/DebugInfo/CodeView/SymbolRecord.h"
18 #include "llvm/DebugInfo/CodeView/TypeIndex.h"
19 #include "llvm/DebugInfo/CodeView/TypeRecord.h"
20 #include "llvm/MC/MCExpr.h"
21 #include "llvm/MC/MCSymbol.h"
22 #include "llvm/Support/COFF.h"
23 
24 using namespace llvm::codeview;
25 
26 namespace llvm {
27 
28 StringRef CodeViewDebug::getFullFilepath(const DIFile *File) {
29   std::string &Filepath = FileToFilepathMap[File];
30   if (!Filepath.empty())
31     return Filepath;
32 
33   StringRef Dir = File->getDirectory(), Filename = File->getFilename();
34 
35   // Clang emits directory and relative filename info into the IR, but CodeView
36   // operates on full paths.  We could change Clang to emit full paths too, but
37   // that would increase the IR size and probably not needed for other users.
38   // For now, just concatenate and canonicalize the path here.
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   return Filepath;
78 }
79 
80 unsigned CodeViewDebug::maybeRecordFile(const DIFile *F) {
81   unsigned NextId = FileIdMap.size() + 1;
82   auto Insertion = FileIdMap.insert(std::make_pair(F, NextId));
83   if (Insertion.second) {
84     // We have to compute the full filepath and emit a .cv_file directive.
85     StringRef FullPath = getFullFilepath(F);
86     NextId = Asm->OutStreamer->EmitCVFileDirective(NextId, FullPath);
87     assert(NextId == FileIdMap.size() && ".cv_file directive failed");
88   }
89   return Insertion.first->second;
90 }
91 
92 CodeViewDebug::InlineSite &CodeViewDebug::getInlineSite(const DILocation *Loc) {
93   const DILocation *InlinedAt = Loc->getInlinedAt();
94   auto Insertion = CurFn->InlineSites.insert({InlinedAt, InlineSite()});
95   if (Insertion.second) {
96     InlineSite &Site = Insertion.first->second;
97     Site.SiteFuncId = NextFuncId++;
98     Site.Inlinee = Loc->getScope()->getSubprogram();
99     InlinedSubprograms.insert(Loc->getScope()->getSubprogram());
100   }
101   return Insertion.first->second;
102 }
103 
104 void CodeViewDebug::maybeRecordLocation(DebugLoc DL,
105                                         const MachineFunction *MF) {
106   // Skip this instruction if it has the same location as the previous one.
107   if (DL == CurFn->LastLoc)
108     return;
109 
110   const DIScope *Scope = DL.get()->getScope();
111   if (!Scope)
112     return;
113 
114   // Skip this line if it is longer than the maximum we can record.
115   LineInfo LI(DL.getLine(), DL.getLine(), /*IsStatement=*/true);
116   if (LI.getStartLine() != DL.getLine() || LI.isAlwaysStepInto() ||
117       LI.isNeverStepInto())
118     return;
119 
120   ColumnInfo CI(DL.getCol(), /*EndColumn=*/0);
121   if (CI.getStartColumn() != DL.getCol())
122     return;
123 
124   if (!CurFn->HaveLineInfo)
125     CurFn->HaveLineInfo = true;
126   unsigned FileId = 0;
127   if (CurFn->LastLoc.get() && CurFn->LastLoc->getFile() == DL->getFile())
128     FileId = CurFn->LastFileId;
129   else
130     FileId = CurFn->LastFileId = maybeRecordFile(DL->getFile());
131   CurFn->LastLoc = DL;
132 
133   unsigned FuncId = CurFn->FuncId;
134   if (const DILocation *Loc = DL->getInlinedAt()) {
135     // If this location was actually inlined from somewhere else, give it the ID
136     // of the inline call site.
137     FuncId = getInlineSite(DL.get()).SiteFuncId;
138     // Ensure we have links in the tree of inline call sites.
139     const DILocation *ChildLoc = nullptr;
140     while (Loc->getInlinedAt()) {
141       InlineSite &Site = getInlineSite(Loc);
142       if (ChildLoc) {
143         // Record the child inline site if not already present.
144         auto B = Site.ChildSites.begin(), E = Site.ChildSites.end();
145         if (std::find(B, E, Loc) != E)
146           break;
147         Site.ChildSites.push_back(Loc);
148       }
149       ChildLoc = Loc;
150     }
151   }
152 
153   Asm->OutStreamer->EmitCVLocDirective(FuncId, FileId, DL.getLine(),
154                                        DL.getCol(), /*PrologueEnd=*/false,
155                                        /*IsStmt=*/false, DL->getFilename());
156 }
157 
158 CodeViewDebug::CodeViewDebug(AsmPrinter *AP)
159     : Asm(nullptr), CurFn(nullptr) {
160   MachineModuleInfo *MMI = AP->MMI;
161 
162   // If module doesn't have named metadata anchors or COFF debug section
163   // is not available, skip any debug info related stuff.
164   if (!MMI->getModule()->getNamedMetadata("llvm.dbg.cu") ||
165       !AP->getObjFileLowering().getCOFFDebugSymbolsSection())
166     return;
167 
168   // Tell MMI that we have debug info.
169   MMI->setDebugInfoAvailability(true);
170   Asm = AP;
171 }
172 
173 void CodeViewDebug::endModule() {
174   if (FnDebugInfo.empty())
175     return;
176 
177   emitTypeInformation();
178 
179   // FIXME: For functions that are comdat, we should emit separate .debug$S
180   // sections that are comdat associative with the main function instead of
181   // having one big .debug$S section.
182   assert(Asm != nullptr);
183   Asm->OutStreamer->SwitchSection(
184       Asm->getObjFileLowering().getCOFFDebugSymbolsSection());
185   Asm->OutStreamer->AddComment("Debug section magic");
186   Asm->EmitInt32(COFF::DEBUG_SECTION_MAGIC);
187 
188   // The COFF .debug$S section consists of several subsections, each starting
189   // with a 4-byte control code (e.g. 0xF1, 0xF2, etc) and then a 4-byte length
190   // of the payload followed by the payload itself.  The subsections are 4-byte
191   // aligned.
192 
193   // Make a subsection for all the inlined subprograms.
194   emitInlineeLinesSubsection();
195 
196   // Emit per-function debug information.
197   for (auto &P : FnDebugInfo)
198     emitDebugInfoForFunction(P.first, P.second);
199 
200   // This subsection holds a file index to offset in string table table.
201   Asm->OutStreamer->AddComment("File index to string table offset subsection");
202   Asm->OutStreamer->EmitCVFileChecksumsDirective();
203 
204   // This subsection holds the string table.
205   Asm->OutStreamer->AddComment("String table");
206   Asm->OutStreamer->EmitCVStringTableDirective();
207 
208   clear();
209 }
210 
211 void CodeViewDebug::emitTypeInformation() {
212   // Start the .debug$T section with 0x4.
213   Asm->OutStreamer->SwitchSection(
214       Asm->getObjFileLowering().getCOFFDebugTypesSection());
215   Asm->OutStreamer->AddComment("Debug section magic");
216   Asm->EmitInt32(COFF::DEBUG_SECTION_MAGIC);
217 
218   NamedMDNode *CU_Nodes =
219       Asm->MMI->getModule()->getNamedMetadata("llvm.dbg.cu");
220   if (!CU_Nodes)
221     return;
222 
223   // This type info currently only holds function ids for use with inline call
224   // frame info. All functions are assigned a simple 'void ()' type. Emit that
225   // type here.
226   TypeIndex ArgListIdx = getNextTypeIndex();
227   Asm->OutStreamer->AddComment("Type record length");
228   Asm->EmitInt16(2 + sizeof(ArgList));
229   Asm->OutStreamer->AddComment("Leaf type: LF_ARGLIST");
230   Asm->EmitInt16(LF_ARGLIST);
231   Asm->OutStreamer->AddComment("Number of arguments");
232   Asm->EmitInt32(0);
233 
234   TypeIndex VoidProcIdx = getNextTypeIndex();
235   Asm->OutStreamer->AddComment("Type record length");
236   Asm->EmitInt16(2 + sizeof(ProcedureType));
237   Asm->OutStreamer->AddComment("Leaf type: LF_PROCEDURE");
238   Asm->EmitInt16(LF_PROCEDURE);
239   Asm->OutStreamer->AddComment("Return type index");
240   Asm->EmitInt32(TypeIndex::Void().getIndex());
241   Asm->OutStreamer->AddComment("Calling convention");
242   Asm->EmitInt8(char(CallingConvention::NearC));
243   Asm->OutStreamer->AddComment("Function options");
244   Asm->EmitInt8(char(FunctionOptions::None));
245   Asm->OutStreamer->AddComment("# of parameters");
246   Asm->EmitInt16(0);
247   Asm->OutStreamer->AddComment("Argument list type index");
248   Asm->EmitInt32(ArgListIdx.getIndex());
249 
250   for (MDNode *N : CU_Nodes->operands()) {
251     auto *CUNode = cast<DICompileUnit>(N);
252     for (auto *SP : CUNode->getSubprograms()) {
253       StringRef DisplayName = SP->getDisplayName();
254       Asm->OutStreamer->AddComment("Type record length");
255       Asm->EmitInt16(2 + sizeof(FuncId) + DisplayName.size() + 1);
256       Asm->OutStreamer->AddComment("Leaf type: LF_FUNC_ID");
257       Asm->EmitInt16(LF_FUNC_ID);
258 
259       Asm->OutStreamer->AddComment("Scope type index");
260       Asm->EmitInt32(TypeIndex().getIndex());
261       Asm->OutStreamer->AddComment("Function type");
262       Asm->EmitInt32(VoidProcIdx.getIndex());
263       {
264         SmallString<32> NullTerminatedString(DisplayName);
265         if (NullTerminatedString.empty() || NullTerminatedString.back() != '\0')
266           NullTerminatedString.push_back('\0');
267         Asm->OutStreamer->AddComment("Function name");
268         Asm->OutStreamer->EmitBytes(NullTerminatedString);
269       }
270 
271       TypeIndex FuncIdIdx = getNextTypeIndex();
272       SubprogramToFuncId.insert(std::make_pair(SP, FuncIdIdx));
273     }
274   }
275 }
276 
277 void CodeViewDebug::emitInlineeLinesSubsection() {
278   if (InlinedSubprograms.empty())
279     return;
280 
281   MCStreamer &OS = *Asm->OutStreamer;
282   MCSymbol *InlineBegin = Asm->MMI->getContext().createTempSymbol(),
283            *InlineEnd = Asm->MMI->getContext().createTempSymbol();
284 
285   OS.AddComment("Inlinee lines subsection");
286   OS.EmitIntValue(unsigned(ModuleSubstreamKind::InlineeLines), 4);
287   OS.AddComment("Subsection size");
288   OS.emitAbsoluteSymbolDiff(InlineEnd, InlineBegin, 4);
289   OS.EmitLabel(InlineBegin);
290 
291   // We don't provide any extra file info.
292   // FIXME: Find out if debuggers use this info.
293   OS.AddComment("Inlinee lines signature");
294   OS.EmitIntValue(unsigned(InlineeLinesSignature::Normal), 4);
295 
296   for (const DISubprogram *SP : InlinedSubprograms) {
297     OS.AddBlankLine();
298     TypeIndex TypeId = SubprogramToFuncId[SP];
299     unsigned FileId = maybeRecordFile(SP->getFile());
300     OS.AddComment("Inlined function " + SP->getDisplayName() + " starts at " +
301                   SP->getFilename() + Twine(':') + Twine(SP->getLine()));
302     OS.AddBlankLine();
303     // The filechecksum table uses 8 byte entries for now, and file ids start at
304     // 1.
305     unsigned FileOffset = (FileId - 1) * 8;
306     OS.AddComment("Type index of inlined function");
307     OS.EmitIntValue(TypeId.getIndex(), 4);
308     OS.AddComment("Offset into filechecksum table");
309     OS.EmitIntValue(FileOffset, 4);
310     OS.AddComment("Starting line number");
311     OS.EmitIntValue(SP->getLine(), 4);
312   }
313 
314   OS.EmitLabel(InlineEnd);
315 }
316 
317 static void EmitLabelDiff(MCStreamer &Streamer,
318                           const MCSymbol *From, const MCSymbol *To,
319                           unsigned int Size = 4) {
320   MCSymbolRefExpr::VariantKind Variant = MCSymbolRefExpr::VK_None;
321   MCContext &Context = Streamer.getContext();
322   const MCExpr *FromRef = MCSymbolRefExpr::create(From, Variant, Context),
323                *ToRef   = MCSymbolRefExpr::create(To, Variant, Context);
324   const MCExpr *AddrDelta =
325       MCBinaryExpr::create(MCBinaryExpr::Sub, ToRef, FromRef, Context);
326   Streamer.EmitValue(AddrDelta, Size);
327 }
328 
329 void CodeViewDebug::collectInlineSiteChildren(
330     SmallVectorImpl<unsigned> &Children, const FunctionInfo &FI,
331     const InlineSite &Site) {
332   for (const DILocation *ChildSiteLoc : Site.ChildSites) {
333     auto I = FI.InlineSites.find(ChildSiteLoc);
334     assert(I != FI.InlineSites.end());
335     const InlineSite &ChildSite = I->second;
336     Children.push_back(ChildSite.SiteFuncId);
337     collectInlineSiteChildren(Children, FI, ChildSite);
338   }
339 }
340 
341 void CodeViewDebug::emitInlinedCallSite(const FunctionInfo &FI,
342                                         const DILocation *InlinedAt,
343                                         const InlineSite &Site) {
344   MCStreamer &OS = *Asm->OutStreamer;
345 
346   MCSymbol *InlineBegin = Asm->MMI->getContext().createTempSymbol(),
347            *InlineEnd = Asm->MMI->getContext().createTempSymbol();
348 
349   assert(SubprogramToFuncId.count(Site.Inlinee));
350   TypeIndex InlineeIdx = SubprogramToFuncId[Site.Inlinee];
351 
352   // SymbolRecord
353   Asm->OutStreamer->AddComment("Record length");
354   EmitLabelDiff(OS, InlineBegin, InlineEnd, 2);   // RecordLength
355   OS.EmitLabel(InlineBegin);
356   Asm->OutStreamer->AddComment("Record kind: S_INLINESITE");
357   Asm->EmitInt16(SymbolRecordKind::S_INLINESITE); // RecordKind
358 
359   Asm->OutStreamer->AddComment("PtrParent");
360   Asm->OutStreamer->EmitIntValue(0, 4);
361   Asm->OutStreamer->AddComment("PtrEnd");
362   Asm->OutStreamer->EmitIntValue(0, 4);
363   Asm->OutStreamer->AddComment("Inlinee type index");
364   Asm->EmitInt32(InlineeIdx.getIndex());
365 
366   unsigned FileId = maybeRecordFile(Site.Inlinee->getFile());
367   unsigned StartLineNum = Site.Inlinee->getLine();
368   SmallVector<unsigned, 3> SecondaryFuncIds;
369   collectInlineSiteChildren(SecondaryFuncIds, FI, Site);
370 
371   OS.EmitCVInlineLinetableDirective(Site.SiteFuncId, FileId, StartLineNum,
372                                     FI.Begin, FI.End, SecondaryFuncIds);
373 
374   OS.EmitLabel(InlineEnd);
375 
376   // Recurse on child inlined call sites before closing the scope.
377   for (const DILocation *ChildSite : Site.ChildSites) {
378     auto I = FI.InlineSites.find(ChildSite);
379     assert(I != FI.InlineSites.end() &&
380            "child site not in function inline site map");
381     emitInlinedCallSite(FI, ChildSite, I->second);
382   }
383 
384   // Close the scope.
385   Asm->OutStreamer->AddComment("Record length");
386   Asm->EmitInt16(2);                                  // RecordLength
387   Asm->OutStreamer->AddComment("Record kind: S_INLINESITE_END");
388   Asm->EmitInt16(SymbolRecordKind::S_INLINESITE_END); // RecordKind
389 }
390 
391 void CodeViewDebug::emitDebugInfoForFunction(const Function *GV,
392                                              FunctionInfo &FI) {
393   // For each function there is a separate subsection
394   // which holds the PC to file:line table.
395   const MCSymbol *Fn = Asm->getSymbol(GV);
396   assert(Fn);
397 
398   StringRef FuncName;
399   if (auto *SP = getDISubprogram(GV))
400     FuncName = SP->getDisplayName();
401 
402   // If our DISubprogram name is empty, use the mangled name.
403   if (FuncName.empty())
404     FuncName = GlobalValue::getRealLinkageName(GV->getName());
405 
406   // Emit a symbol subsection, required by VS2012+ to find function boundaries.
407   MCSymbol *SymbolsBegin = Asm->MMI->getContext().createTempSymbol(),
408            *SymbolsEnd = Asm->MMI->getContext().createTempSymbol();
409   Asm->OutStreamer->AddComment("Symbol subsection for " + Twine(FuncName));
410   Asm->EmitInt32(unsigned(ModuleSubstreamKind::Symbols));
411   Asm->OutStreamer->AddComment("Subsection size");
412   EmitLabelDiff(*Asm->OutStreamer, SymbolsBegin, SymbolsEnd);
413   Asm->OutStreamer->EmitLabel(SymbolsBegin);
414   {
415     MCSymbol *ProcRecordBegin = Asm->MMI->getContext().createTempSymbol(),
416              *ProcRecordEnd = Asm->MMI->getContext().createTempSymbol();
417     Asm->OutStreamer->AddComment("Record length");
418     EmitLabelDiff(*Asm->OutStreamer, ProcRecordBegin, ProcRecordEnd, 2);
419     Asm->OutStreamer->EmitLabel(ProcRecordBegin);
420 
421     Asm->OutStreamer->AddComment("Record kind: S_GPROC32_ID");
422     Asm->EmitInt16(unsigned(SymbolRecordKind::S_GPROC32_ID));
423 
424     // These fields are filled in by tools like CVPACK which run after the fact.
425     Asm->OutStreamer->AddComment("PtrParent");
426     Asm->OutStreamer->EmitIntValue(0, 4);
427     Asm->OutStreamer->AddComment("PtrEnd");
428     Asm->OutStreamer->EmitIntValue(0, 4);
429     Asm->OutStreamer->AddComment("PtrNext");
430     Asm->OutStreamer->EmitIntValue(0, 4);
431     // This is the important bit that tells the debugger where the function
432     // code is located and what's its size:
433     Asm->OutStreamer->AddComment("Code size");
434     EmitLabelDiff(*Asm->OutStreamer, Fn, FI.End);
435     Asm->OutStreamer->AddComment("Offset after prologue");
436     Asm->OutStreamer->EmitIntValue(0, 4);
437     Asm->OutStreamer->AddComment("Offset before epilogue");
438     Asm->OutStreamer->EmitIntValue(0, 4);
439     Asm->OutStreamer->AddComment("Function type index");
440     Asm->OutStreamer->EmitIntValue(0, 4);
441     Asm->OutStreamer->AddComment("Function section relative address");
442     Asm->OutStreamer->EmitCOFFSecRel32(Fn);
443     Asm->OutStreamer->AddComment("Function section index");
444     Asm->OutStreamer->EmitCOFFSectionIndex(Fn);
445     Asm->OutStreamer->AddComment("Flags");
446     Asm->EmitInt8(0);
447     // Emit the function display name as a null-terminated string.
448     Asm->OutStreamer->AddComment("Function name");
449     {
450       SmallString<32> NullTerminatedString(FuncName);
451       if (NullTerminatedString.empty() || NullTerminatedString.back() != '\0')
452         NullTerminatedString.push_back('\0');
453       Asm->OutStreamer->EmitBytes(NullTerminatedString);
454     }
455     Asm->OutStreamer->EmitLabel(ProcRecordEnd);
456 
457     // Emit inlined call site information. Only emit functions inlined directly
458     // into the parent function. We'll emit the other sites recursively as part
459     // of their parent inline site.
460     for (auto &KV : FI.InlineSites) {
461       const DILocation *InlinedAt = KV.first;
462       if (!InlinedAt->getInlinedAt())
463         emitInlinedCallSite(FI, InlinedAt, KV.second);
464     }
465 
466     // We're done with this function.
467     Asm->OutStreamer->AddComment("Record length");
468     Asm->EmitInt16(0x0002);
469     Asm->OutStreamer->AddComment("Record kind: S_PROC_ID_END");
470     Asm->EmitInt16(unsigned(SymbolRecordKind::S_PROC_ID_END));
471   }
472   Asm->OutStreamer->EmitLabel(SymbolsEnd);
473   // Every subsection must be aligned to a 4-byte boundary.
474   Asm->OutStreamer->EmitValueToAlignment(4);
475 
476   // We have an assembler directive that takes care of the whole line table.
477   Asm->OutStreamer->EmitCVLinetableDirective(FI.FuncId, Fn, FI.End);
478 }
479 
480 void CodeViewDebug::beginFunction(const MachineFunction *MF) {
481   assert(!CurFn && "Can't process two functions at once!");
482 
483   if (!Asm || !Asm->MMI->hasDebugInfo())
484     return;
485 
486   const Function *GV = MF->getFunction();
487   assert(FnDebugInfo.count(GV) == false);
488   CurFn = &FnDebugInfo[GV];
489   CurFn->FuncId = NextFuncId++;
490   CurFn->Begin = Asm->getFunctionBegin();
491 
492   // Find the end of the function prolog.
493   // FIXME: is there a simpler a way to do this? Can we just search
494   // for the first instruction of the function, not the last of the prolog?
495   DebugLoc PrologEndLoc;
496   bool EmptyPrologue = true;
497   for (const auto &MBB : *MF) {
498     if (PrologEndLoc)
499       break;
500     for (const auto &MI : MBB) {
501       if (MI.isDebugValue())
502         continue;
503 
504       // First known non-DBG_VALUE and non-frame setup location marks
505       // the beginning of the function body.
506       // FIXME: do we need the first subcondition?
507       if (!MI.getFlag(MachineInstr::FrameSetup) && MI.getDebugLoc()) {
508         PrologEndLoc = MI.getDebugLoc();
509         break;
510       }
511       EmptyPrologue = false;
512     }
513   }
514   // Record beginning of function if we have a non-empty prologue.
515   if (PrologEndLoc && !EmptyPrologue) {
516     DebugLoc FnStartDL = PrologEndLoc.getFnDebugLoc();
517     maybeRecordLocation(FnStartDL, MF);
518   }
519 }
520 
521 void CodeViewDebug::endFunction(const MachineFunction *MF) {
522   if (!Asm || !CurFn)  // We haven't created any debug info for this function.
523     return;
524 
525   const Function *GV = MF->getFunction();
526   assert(FnDebugInfo.count(GV));
527   assert(CurFn == &FnDebugInfo[GV]);
528 
529   // Don't emit anything if we don't have any line tables.
530   if (!CurFn->HaveLineInfo) {
531     FnDebugInfo.erase(GV);
532   } else {
533     CurFn->End = Asm->getFunctionEnd();
534   }
535   CurFn = nullptr;
536 }
537 
538 void CodeViewDebug::beginInstruction(const MachineInstr *MI) {
539   // Ignore DBG_VALUE locations and function prologue.
540   if (!Asm || MI->isDebugValue() || MI->getFlag(MachineInstr::FrameSetup))
541     return;
542   DebugLoc DL = MI->getDebugLoc();
543   if (DL == PrevInstLoc || !DL)
544     return;
545   maybeRecordLocation(DL, Asm->MF);
546 }
547 }
548