[codeview] Wire up the .cv_inline_linetable directive

This directive emits the binary annotations that describe line and code
deltas in inlined call sites. Single-stepping through inlined frames in
windbg now works.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@259535 91177308-0d34-0410-b5e6-96231b3b80d8

9 files changed, 215 insertions, 41 deletions

diff --git a/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp b/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
index e3c48296f34..de12fc38138 100644
--- a/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
+++ b/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
@@ -96,6 +96,7 @@ CodeViewDebug::InlineSite &CodeViewDebug::getInlineSite(const DILocation *Loc) {
     InlineSite &Site = Insertion.first->second;
     Site.SiteFuncId = NextFuncId++;
     Site.Inlinee = Loc->getScope()->getSubprogram();
+    InlinedSubprograms.insert(Loc->getScope()->getSubprogram());
   }
   return Insertion.first->second;
 }
@@ -188,6 +189,9 @@ void CodeViewDebug::endModule() {
   // of the payload followed by the payload itself.  The subsections are 4-byte
   // aligned.
 
+  // Make a subsection for all the inlined subprograms.
+  emitInlineeLinesSubsection();
+
   // Emit per-function debug information.
   for (auto &P : FnDebugInfo)
     emitDebugInfoForFunction(P.first, P.second);
@@ -257,6 +261,39 @@ void CodeViewDebug::emitTypeInformation() {
   }
 }
 
+void CodeViewDebug::emitInlineeLinesSubsection() {
+  if (InlinedSubprograms.empty())
+    return;
+
+  MCStreamer &OS = *Asm->OutStreamer;
+  MCSymbol *InlineBegin = Asm->MMI->getContext().createTempSymbol(),
+           *InlineEnd = Asm->MMI->getContext().createTempSymbol();
+
+  OS.AddComment("Inlinee lines subsection");
+  OS.EmitIntValue(unsigned(ModuleSubstreamKind::InlineeLines), 4);
+  OS.emitAbsoluteSymbolDiff(InlineEnd, InlineBegin, 4);
+  OS.EmitLabel(InlineBegin);
+
+  // We don't provide any extra file info.
+  // FIXME: Find out if debuggers use this info.
+  OS.EmitIntValue(unsigned(InlineeLinesSignature::Normal), 4);
+
+  for (const DISubprogram *SP : InlinedSubprograms) {
+    TypeIndex TypeId = SubprogramToFuncId[SP];
+    unsigned FileId = maybeRecordFile(SP->getFile());
+    OS.AddComment("Inlined function " + SP->getDisplayName() + " starts at " +
+                  SP->getFilename() + Twine(':') + Twine(SP->getLine()));
+    // The filechecksum table uses 8 byte entries for now, and file ids start at
+    // 1.
+    unsigned FileOffset = (FileId - 1) * 8;
+    OS.EmitIntValue(TypeId.getIndex(), 4);
+    OS.EmitIntValue(FileOffset, 4);
+    OS.EmitIntValue(SP->getLine(), 4);
+  }
+
+  OS.EmitLabel(InlineEnd);
+}
+
 static void EmitLabelDiff(MCStreamer &Streamer,
                           const MCSymbol *From, const MCSymbol *To,
                           unsigned int Size = 4) {
@@ -269,6 +306,18 @@ static void EmitLabelDiff(MCStreamer &Streamer,
   Streamer.EmitValue(AddrDelta, Size);
 }
 
+void CodeViewDebug::collectInlineSiteChildren(
+    SmallVectorImpl<unsigned> &Children, const FunctionInfo &FI,
+    const InlineSite &Site) {
+  for (const DILocation *ChildSiteLoc : Site.ChildSites) {
+    auto I = FI.InlineSites.find(ChildSiteLoc);
+    assert(I != FI.InlineSites.end());
+    const InlineSite &ChildSite = I->second;
+    Children.push_back(ChildSite.SiteFuncId);
+    collectInlineSiteChildren(Children, FI, ChildSite);
+  }
+}
+
 void CodeViewDebug::emitInlinedCallSite(const FunctionInfo &FI,
                                         const DILocation *InlinedAt,
                                         const InlineSite &Site) {
@@ -290,7 +339,13 @@ void CodeViewDebug::emitInlinedCallSite(const FunctionInfo &FI,
   Asm->OutStreamer->EmitBytes(
       StringRef(reinterpret_cast<const char *>(&SiteBytes), sizeof(SiteBytes)));
 
-  // FIXME: annotations
+  unsigned FileId = maybeRecordFile(Site.Inlinee->getFile());
+  unsigned StartLineNum = Site.Inlinee->getLine();
+  SmallVector<unsigned, 3> SecondaryFuncIds;
+  collectInlineSiteChildren(SecondaryFuncIds, FI, Site);
+
+  OS.EmitCVInlineLinetableDirective(Site.SiteFuncId, FileId, StartLineNum,
+                                    FI.Begin, SecondaryFuncIds);
 
   OS.EmitLabel(InlineEnd);
 
@@ -367,7 +422,7 @@ void CodeViewDebug::emitDebugInfoForFunction(const Function *GV,
   }
   Asm->OutStreamer->EmitLabel(SymbolsEnd);
   // Every subsection must be aligned to a 4-byte boundary.
-  Asm->OutStreamer->EmitFill((-FuncName.size()) % 4, 0);
+  Asm->OutStreamer->EmitValueToAlignment(4);
 
   // We have an assembler directive that takes care of the whole line table.
   Asm->OutStreamer->EmitCVLinetableDirective(FI.FuncId, Fn, FI.End);
@@ -383,6 +438,7 @@ void CodeViewDebug::beginFunction(const MachineFunction *MF) {
   assert(FnDebugInfo.count(GV) == false);
   CurFn = &FnDebugInfo[GV];
   CurFn->FuncId = NextFuncId++;
+  CurFn->Begin = Asm->getFunctionBegin();
 
   // Find the end of the function prolog.
   // FIXME: is there a simpler a way to do this? Can we just search
diff --git a/lib/CodeGen/AsmPrinter/CodeViewDebug.h b/lib/CodeGen/AsmPrinter/CodeViewDebug.h
index 4883905e907..d9f38f3eaf8 100644
--- a/lib/CodeGen/AsmPrinter/CodeViewDebug.h
+++ b/lib/CodeGen/AsmPrinter/CodeViewDebug.h
@@ -48,7 +48,8 @@ class LLVM_LIBRARY_VISIBILITY CodeViewDebug : public AsmPrinterHandler {
     MapVector<const DILocation *, InlineSite> InlineSites;
 
     DebugLoc LastLoc;
-    MCSymbol *End = nullptr;
+    const MCSymbol *Begin = nullptr;
+    const MCSymbol *End = nullptr;
     unsigned FuncId = 0;
     unsigned LastFileId = 0;
     bool HaveLineInfo = false;
@@ -59,6 +60,10 @@ class LLVM_LIBRARY_VISIBILITY CodeViewDebug : public AsmPrinterHandler {
 
   InlineSite &getInlineSite(const DILocation *Loc);
 
+  static void collectInlineSiteChildren(SmallVectorImpl<unsigned> &Children,
+                                        const FunctionInfo &FI,
+                                        const InlineSite &Site);
+
   /// Remember some debug info about each function. Keep it in a stable order to
   /// emit at the end of the TU.
   MapVector<const Function *, FunctionInfo> FnDebugInfo;
@@ -66,6 +71,8 @@ class LLVM_LIBRARY_VISIBILITY CodeViewDebug : public AsmPrinterHandler {
   /// Map from DIFile to .cv_file id.
   DenseMap<const DIFile *, unsigned> FileIdMap;
 
+  SmallSetVector<const DISubprogram *, 4> InlinedSubprograms;
+
   DenseMap<const DISubprogram *, codeview::TypeIndex> SubprogramToFuncId;
 
   unsigned TypeCount = 0;
@@ -93,6 +100,8 @@ class LLVM_LIBRARY_VISIBILITY CodeViewDebug : public AsmPrinterHandler {
 
   void emitTypeInformation();
 
+  void emitInlineeLinesSubsection();
+
   void emitDebugInfoForFunction(const Function *GV, FunctionInfo &FI);
 
   void emitInlinedCallSite(const FunctionInfo &FI, const DILocation *InlinedAt,
diff --git a/lib/MC/MCAsmStreamer.cpp b/lib/MC/MCAsmStreamer.cpp
index 1bac42a8d09..712b7a938be 100644
--- a/lib/MC/MCAsmStreamer.cpp
+++ b/lib/MC/MCAsmStreamer.cpp
@@ -207,6 +207,7 @@ public:
                                 const MCSymbol *FnEnd) override;
   void EmitCVInlineLinetableDirective(
       unsigned PrimaryFunctionId, unsigned SourceFileId, unsigned SourceLineNum,
+      const MCSymbol *FnStartSym,
       ArrayRef<unsigned> SecondaryFunctionIds) override;
   void EmitCVStringTableDirective() override;
   void EmitCVFileChecksumsDirective() override;
@@ -1019,9 +1020,10 @@ void MCAsmStreamer::EmitCVLinetableDirective(unsigned FunctionId,
 
 void MCAsmStreamer::EmitCVInlineLinetableDirective(
     unsigned PrimaryFunctionId, unsigned SourceFileId, unsigned SourceLineNum,
-    ArrayRef<unsigned> SecondaryFunctionIds) {
+    const MCSymbol *FnStartSym, ArrayRef<unsigned> SecondaryFunctionIds) {
   OS << "\t.cv_inline_linetable\t" << PrimaryFunctionId << ' ' << SourceFileId
-     << ' ' << SourceLineNum;
+     << ' ' << SourceLineNum << ' ';
+  FnStartSym->print(OS, MAI);
   if (!SecondaryFunctionIds.empty()) {
     OS << " contains";
     for (unsigned SecondaryFunctionId : SecondaryFunctionIds)
@@ -1029,7 +1031,8 @@ void MCAsmStreamer::EmitCVInlineLinetableDirective(
   }
   EmitEOL();
   this->MCStreamer::EmitCVInlineLinetableDirective(
-      PrimaryFunctionId, SourceFileId, SourceLineNum, SecondaryFunctionIds);
+      PrimaryFunctionId, SourceFileId, SourceLineNum, FnStartSym,
+      SecondaryFunctionIds);
 }
 
 void MCAsmStreamer::EmitCVStringTableDirective() {
diff --git a/lib/MC/MCAssembler.cpp b/lib/MC/MCAssembler.cpp
index 6965b1b037f..9a55ef3931e 100644
--- a/lib/MC/MCAssembler.cpp
+++ b/lib/MC/MCAssembler.cpp
@@ -15,6 +15,7 @@
 #include "llvm/MC/MCAsmInfo.h"
 #include "llvm/MC/MCAsmLayout.h"
 #include "llvm/MC/MCCodeEmitter.h"
+#include "llvm/MC/MCCodeView.h"
 #include "llvm/MC/MCContext.h"
 #include "llvm/MC/MCDwarf.h"
 #include "llvm/MC/MCExpr.h"
@@ -300,6 +301,8 @@ uint64_t MCAssembler::computeFragmentSize(const MCAsmLayout &Layout,
     return cast<MCDwarfLineAddrFragment>(F).getContents().size();
   case MCFragment::FT_DwarfFrame:
     return cast<MCDwarfCallFrameFragment>(F).getContents().size();
+  case MCFragment::FT_CVInlineLines:
+    return cast<MCCVInlineLineTableFragment>(F).getContents().size();
   case MCFragment::FT_Dummy:
     llvm_unreachable("Should not have been added");
   }
@@ -537,6 +540,11 @@ static void writeFragment(const MCAssembler &Asm, const MCAsmLayout &Layout,
     OW->writeBytes(CF.getContents());
     break;
   }
+  case MCFragment::FT_CVInlineLines: {
+    const auto &OF = cast<MCCVInlineLineTableFragment>(F);
+    OW->writeBytes(OF.getContents());
+    break;
+  }
   case MCFragment::FT_Dummy:
     llvm_unreachable("Should not have been added");
   }
@@ -813,6 +821,13 @@ bool MCAssembler::relaxDwarfCallFrameFragment(MCAsmLayout &Layout,
   return OldSize != Data.size();
 }
 
+bool MCAssembler::relaxCVInlineLineTable(MCAsmLayout &Layout,
+                                         MCCVInlineLineTableFragment &F) {
+  unsigned OldSize = F.getContents().size();
+  getContext().getCVContext().encodeInlineLineTable(Layout, F);
+  return OldSize != F.getContents().size();
+}
+
 bool MCAssembler::layoutSectionOnce(MCAsmLayout &Layout, MCSection &Sec) {
   // Holds the first fragment which needed relaxing during this layout. It will
   // remain NULL if none were relaxed.
@@ -844,6 +859,10 @@ bool MCAssembler::layoutSectionOnce(MCAsmLayout &Layout, MCSection &Sec) {
     case MCFragment::FT_LEB:
       RelaxedFrag = relaxLEB(Layout, *cast<MCLEBFragment>(I));
       break;
+    case MCFragment::FT_CVInlineLines:
+      RelaxedFrag =
+          relaxCVInlineLineTable(Layout, *cast<MCCVInlineLineTableFragment>(I));
+      break;
     }
     if (RelaxedFrag && !FirstRelaxedFragment)
       FirstRelaxedFragment = &*I;
diff --git a/lib/MC/MCCodeView.cpp b/lib/MC/MCCodeView.cpp
index a876470b826..ea226f7769e 100644
--- a/lib/MC/MCCodeView.cpp
+++ b/lib/MC/MCCodeView.cpp
@@ -12,6 +12,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/MC/MCCodeView.h"
+#include "llvm/MC/MCAsmLayout.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/DebugInfo/CodeView/CodeView.h"
 #include "llvm/DebugInfo/CodeView/Line.h"
@@ -226,40 +227,110 @@ static uint32_t encodeSignedNumber(uint32_t Data) {
 
 void CodeViewContext::emitInlineLineTableForFunction(
     MCObjectStreamer &OS, unsigned PrimaryFunctionId, unsigned SourceFileId,
-    unsigned SourceLineNum, ArrayRef<unsigned> SecondaryFunctionIds) {
-  std::vector<MCCVLineEntry> Locs = getFunctionLineEntries(PrimaryFunctionId);
-  std::vector<std::pair<BinaryAnnotationsOpCode, uint32_t>> Annotations;
+    unsigned SourceLineNum, const MCSymbol *FnStartSym,
+    ArrayRef<unsigned> SecondaryFunctionIds) {
+  // Create and insert a fragment into the current section that will be encoded
+  // later.
+  new MCCVInlineLineTableFragment(
+      PrimaryFunctionId, SourceFileId, SourceLineNum, FnStartSym,
+      SecondaryFunctionIds, OS.getCurrentSectionOnly());
+}
+
+unsigned computeLabelDiff(MCAsmLayout &Layout, const MCSymbol *Begin,
+                          const MCSymbol *End) {
+  MCContext &Ctx = Layout.getAssembler().getContext();
+  MCSymbolRefExpr::VariantKind Variant = MCSymbolRefExpr::VK_None;
+  const MCExpr *BeginRef = MCSymbolRefExpr::create(Begin, Variant, Ctx),
+               *EndRef = MCSymbolRefExpr::create(End, Variant, Ctx);
+  const MCExpr *AddrDelta =
+      MCBinaryExpr::create(MCBinaryExpr::Sub, EndRef, BeginRef, Ctx);
+  int64_t Result;
+  bool Success = AddrDelta->evaluateKnownAbsolute(Result, Layout);
+  assert(Success && "failed to evaluate label difference as absolute");
+  (void)Success;
+  assert(Result >= 0 && "negative label difference requested");
+  assert(Result < UINT_MAX && "label difference greater than 2GB");
+  return unsigned(Result);
+}
 
-  const MCCVLineEntry *LastLoc = nullptr;
-  unsigned LastFileId = SourceFileId;
-  unsigned LastLineNum = SourceLineNum;
+void CodeViewContext::encodeInlineLineTable(MCAsmLayout &Layout,
+                                            MCCVInlineLineTableFragment &Frag) {
+  size_t LocBegin;
+  size_t LocEnd;
+  std::tie(LocBegin, LocEnd) = getLineExtent(Frag.SiteFuncId);
+  for (unsigned SecondaryId : Frag.SecondaryFuncs) {
+    auto Extent = getLineExtent(SecondaryId);
+    LocBegin = std::min(LocBegin, Extent.first);
+    LocEnd = std::max(LocEnd, Extent.second);
+  }
+  if (LocBegin >= LocEnd)
+    return;
+  ArrayRef<MCCVLineEntry> Locs = getLinesForExtent(LocBegin, LocEnd + 1);
+  if (Locs.empty())
+    return;
 
+  SmallSet<unsigned, 8> InlinedFuncIds;
+  InlinedFuncIds.insert(Frag.SiteFuncId);
+  InlinedFuncIds.insert(Frag.SecondaryFuncs.begin(), Frag.SecondaryFuncs.end());
+
+  // Make an artificial start location using the function start and the inlinee
+  // lines start location information. All deltas start relative to this
+  // location.
+  MCCVLineEntry StartLoc(Frag.getFnStartSym(), MCCVLoc(Locs.front()));
+  StartLoc.setFileNum(Frag.StartFileId);
+  StartLoc.setLine(Frag.StartLineNum);
+  const MCCVLineEntry *LastLoc = &StartLoc;
+  bool WithinFunction = true;
+
+  SmallVectorImpl<char> &Buffer = Frag.getContents();
+  Buffer.clear(); // Clear old contents if we went through relaxation.
   for (const MCCVLineEntry &Loc : Locs) {
-    if (!LastLoc) {
-      // TODO ChangeCodeOffset
-      // TODO ChangeCodeLength
+    if (!InlinedFuncIds.count(Loc.getFunctionId())) {
+      // We've hit a cv_loc not attributed to this inline call site. Use this
+      // label to end the PC range.
+      if (WithinFunction) {
+        unsigned Length =
+            computeLabelDiff(Layout, LastLoc->getLabel(), Loc.getLabel());
+        compressAnnotation(ChangeCodeLength, Buffer);
+        compressAnnotation(Length, Buffer);
+      }
+      WithinFunction = false;
+      continue;
     }
+    WithinFunction = true;
 
-    if (Loc.getFileNum() != LastFileId)
-      Annotations.push_back({ChangeFile, Loc.getFileNum()});
+    if (Loc.getFileNum() != LastLoc->getFileNum()) {
+      compressAnnotation(ChangeFile, Buffer);
+      compressAnnotation(Loc.getFileNum(), Buffer);
+    }
 
-    if (Loc.getLine() != LastLineNum)
-      Annotations.push_back(
-          {ChangeLineOffset, encodeSignedNumber(Loc.getLine() - LastLineNum)});
+    int LineDelta = Loc.getLine() - LastLoc->getLine();
+    if (LineDelta == 0)
+      continue;
+
+    unsigned EncodedLineDelta = encodeSignedNumber(LineDelta);
+    unsigned CodeDelta =
+        computeLabelDiff(Layout, LastLoc->getLabel(), Loc.getLabel());
+    if (CodeDelta == 0) {
+      compressAnnotation(ChangeLineOffset, Buffer);
+      compressAnnotation(EncodedLineDelta, Buffer);
+    } else if (EncodedLineDelta < 0x8 && CodeDelta <= 0xf) {
+      // The ChangeCodeOffsetAndLineOffset combination opcode is used when the
+      // encoded line delta uses 3 or fewer set bits and the code offset fits
+      // in one nibble.
+      unsigned Operand = (EncodedLineDelta << 4) | CodeDelta;
+      compressAnnotation(ChangeCodeOffsetAndLineOffset, Buffer);
+      compressAnnotation(Operand, Buffer);
+    } else {
+      // Otherwise use the separate line and code deltas.
+      compressAnnotation(ChangeLineOffset, Buffer);
+      compressAnnotation(EncodedLineDelta, Buffer);
+      compressAnnotation(ChangeCodeOffset, Buffer);
+      compressAnnotation(CodeDelta, Buffer);
+    }
 
     LastLoc = &Loc;
-    LastFileId = Loc.getFileNum();
-    LastLineNum = Loc.getLine();
-  }
-
-  SmallString<32> Buffer;
-  for (auto Annotation : Annotations) {
-    BinaryAnnotationsOpCode Opcode = Annotation.first;
-    uint32_t Operand = Annotation.second;
-    compressAnnotation(Opcode, Buffer);
-    compressAnnotation(Operand, Buffer);
   }
-  OS.EmitBytes(Buffer);
 }
 
 //
diff --git a/lib/MC/MCFragment.cpp b/lib/MC/MCFragment.cpp
index 67f57a5c8fe..bfadfda47f2 100644
--- a/lib/MC/MCFragment.cpp
+++ b/lib/MC/MCFragment.cpp
@@ -289,6 +289,9 @@ void MCFragment::destroy() {
     case FT_SafeSEH:
       delete cast<MCSafeSEHFragment>(this);
       return;
+    case FT_CVInlineLines:
+      delete cast<MCCVInlineLineTableFragment>(this);
+      return;
     case FT_Dummy:
       delete cast<MCDummyFragment>(this);
       return;
@@ -327,9 +330,8 @@ LLVM_DUMP_METHOD void MCFragment::dump() {
   case MCFragment::FT_DwarfFrame: OS << "MCDwarfCallFrameFragment"; break;
   case MCFragment::FT_LEB:   OS << "MCLEBFragment"; break;
   case MCFragment::FT_SafeSEH:    OS << "MCSafeSEHFragment"; break;
-  case MCFragment::FT_Dummy:
-    OS << "MCDummyFragment";
-    break;
+  case MCFragment::FT_CVInlineLines: OS << "MCCVInlineLineTableFragment"; break;
+  case MCFragment::FT_Dummy: OS << "MCDummyFragment"; break;
   }
 
   OS << "<MCFragment " << (void*) this << " LayoutOrder:" << LayoutOrder
@@ -427,6 +429,12 @@ LLVM_DUMP_METHOD void MCFragment::dump() {
     OS << " Sym:" << F->getSymbol();
     break;
   }
+  case MCFragment::FT_CVInlineLines: {
+    const auto *F = cast<MCCVInlineLineTableFragment>(this);
+    OS << "\n       ";
+    OS << " Sym:" << *F->getFnStartSym();
+    break;
+  }
   case MCFragment::FT_Dummy:
     break;
   }
diff --git a/lib/MC/MCObjectStreamer.cpp b/lib/MC/MCObjectStreamer.cpp
index 4f0b597b434..4d849049f60 100644
--- a/lib/MC/MCObjectStreamer.cpp
+++ b/lib/MC/MCObjectStreamer.cpp
@@ -386,12 +386,13 @@ void MCObjectStreamer::EmitCVLinetableDirective(unsigned FunctionId,
 
 void MCObjectStreamer::EmitCVInlineLinetableDirective(
     unsigned PrimaryFunctionId, unsigned SourceFileId, unsigned SourceLineNum,
-    ArrayRef<unsigned> SecondaryFunctionIds) {
+    const MCSymbol *FnStartSym, ArrayRef<unsigned> SecondaryFunctionIds) {
   getContext().getCVContext().emitInlineLineTableForFunction(
-      *this, PrimaryFunctionId, SourceFileId, SourceLineNum,
+      *this, PrimaryFunctionId, SourceFileId, SourceLineNum, FnStartSym,
       SecondaryFunctionIds);
   this->MCStreamer::EmitCVInlineLinetableDirective(
-      PrimaryFunctionId, SourceFileId, SourceLineNum, SecondaryFunctionIds);
+      PrimaryFunctionId, SourceFileId, SourceLineNum, FnStartSym,
+      SecondaryFunctionIds);
 }
 
 void MCObjectStreamer::EmitCVStringTableDirective() {
diff --git a/lib/MC/MCParser/AsmParser.cpp b/lib/MC/MCParser/AsmParser.cpp
index 621618a5666..9f8027a381e 100644
--- a/lib/MC/MCParser/AsmParser.cpp
+++ b/lib/MC/MCParser/AsmParser.cpp
@@ -3229,7 +3229,7 @@ bool AsmParser::parseDirectiveCVLinetable() {
 }
 
 /// parseDirectiveCVInlineLinetable
-/// ::= .cv_inline_linetable PrimaryFunctionId FileId LineNum
+/// ::= .cv_inline_linetable PrimaryFunctionId FileId LineNum FnStart
 ///          ("contains" SecondaryFunctionId+)?
 bool AsmParser::parseDirectiveCVInlineLinetable() {
   int64_t PrimaryFunctionId = getTok().getIntVal();
@@ -3250,6 +3250,12 @@ bool AsmParser::parseDirectiveCVInlineLinetable() {
         "Line number less than zero in '.cv_inline_linetable' directive");
   Lex();
 
+  SMLoc Loc = getLexer().getLoc();
+  StringRef FnStartName;
+  if (parseIdentifier(FnStartName))
+    return Error(Loc, "expected identifier in directive");
+  MCSymbol *FnStartSym = getContext().getOrCreateSymbol(FnStartName);
+
   SmallVector<unsigned, 8> SecondaryFunctionIds;
   if (getLexer().is(AsmToken::Identifier)) {
     if (getTok().getIdentifier() != "contains")
@@ -3268,8 +3274,9 @@ bool AsmParser::parseDirectiveCVInlineLinetable() {
     }
   }
 
-  getStreamer().EmitCVInlineLinetableDirective(
-      PrimaryFunctionId, SourceFileId, SourceLineNum, SecondaryFunctionIds);
+  getStreamer().EmitCVInlineLinetableDirective(PrimaryFunctionId, SourceFileId,
+                                               SourceLineNum, FnStartSym,
+                                               SecondaryFunctionIds);
   return false;
 }
 
diff --git a/lib/MC/MCStreamer.cpp b/lib/MC/MCStreamer.cpp
index 1f445ca5893..dcb01b4d119 100644
--- a/lib/MC/MCStreamer.cpp
+++ b/lib/MC/MCStreamer.cpp
@@ -198,7 +198,7 @@ void MCStreamer::EmitCVLinetableDirective(unsigned FunctionId,
 
 void MCStreamer::EmitCVInlineLinetableDirective(
     unsigned PrimaryFunctionId, unsigned SourceFileId, unsigned SourceLineNum,
-    ArrayRef<unsigned> SecondaryFunctionIds) {}
+    const MCSymbol *FnStartSym, ArrayRef<unsigned> SecondaryFunctionIds) {}
 
 void MCStreamer::EmitEHSymAttributes(const MCSymbol *Symbol,
                                      MCSymbol *EHSymbol) {