[llvm] Prevent duplicate files in debug line header in dwarf 5.

[tamur]

Summary

Motivation: In previous dwarf versions, file name indexes started from 1, and
the primary source file was not explicit. Dwarf 5 standard (6.2.4) prescribes
the primary source file to be explicitly given an entry with an index number 0.

The current implementation honors the specification by just duplicating the
main source file, once with index number 0, and later maybe with another
index number. While this is compliant with the letter of the standard, the
duplication causes problems for consumers of this information such as lldb.
(Some files are duplicated, where only some of them have a line table although
all refer to the same file)

With this change, dwarf 5 debug line section files always start from 0, and
the zeroth entry is not duplicated whenever possible. This requires different
handling of dwarf 4 and dwarf 5 during generation (e.g. when a function returns
an index zero for a file name, it signals an error in dwarf 4, but not in dwarf 5)
However, I think the minor complication is worth it, because it enables all
consumers (lldb, gdb, dwarfdump, objdump, and so on) to treat all files in the
file name list homogenously.

[probinson]

Thanks for working on this! I knew I had left duplications behind, but the task to take care of them hadn't ever gotten to the top of the list.
Mostly style things to start with.

llvm/include/llvm/MC/MCContext.h

528 ↗

(On Diff #191187)

You could constify as a separate NFC preliminary.

llvm/include/llvm/MC/MCDwarf.h

221 ↗

(On Diff #191187)

Because the only constructor requires a DwarfVersion parameter, you don't need to initialize here?

224 ↗

(On Diff #191187)

explicit ? Don't want this to be a converting constructor.

llvm/lib/MC/MCAsmStreamer.cpp

1914 ↗

(On Diff #191187)

You could constify as a separate NFC preliminary.

llvm/lib/MC/MCDwarf.cpp

545 ↗

(On Diff #191187)

Current style is lowerCamelCase for methods, so isRootFile here.
I know MC is inconsistent on this point, but new code should use the new style.

llvm/test/CodeGen/AMDGPU/flat-error-unsupported-gpu-hsa.ll

11 ↗

(On Diff #191187)

This looks unrelated, please rebase.

llvm/test/tools/llvm-objdump/X86/function-sections-line-numbers.s

33 ↗

(On Diff #191187)

Curious why this .file 1 is still present, it looks redundant now.

[tamur]

I moved nfc changes to a separate patch.

llvm/test/tools/llvm-objdump/X86/function-sections-line-numbers.s

33 ↗

(On Diff #191187)

(sorry, it was an oversight)

[probinson]

A couple more style nits and LGTM.

llvm/lib/DebugInfo/DWARF/DWARFDebugLine.cpp

1024 ↗

(On Diff #191781)

No 'else' after a 'return'

1033 ↗

(On Diff #191781)

No 'else' after a 'return'

[dblaikie]

llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.h

104 ↗

(On Diff #191781)

accessor probably could/should be a const member function

llvm/lib/DebugInfo/DWARF/DWARFDebugLine.cpp

1034 ↗

(On Diff #191781)

Perhaps in v4 we could keep Index == array index, and leave FileNames[0] unused? (I guess then it might need a special case when being emitted to skip over FileNames[0]?)

llvm/lib/MC/MCDwarf.cpp

549–550 ↗

(On Diff #191781)

Probably more common to write a nullptr check as "!X" in LLVM code.

[tamur]

llvm/lib/DebugInfo/DWARF/DWARFDebugLine.cpp

1034 ↗

(On Diff #191781)

I'd prefer not to change dwarf4 behavior as much as possible, if that's ok with you?

[dblaikie]

llvm/lib/DebugInfo/DWARF/DWARFDebugLine.cpp

1034 ↗

(On Diff #191781)

Within this change, that makes sense - but if you have time to make this change as a separate patch, it'd be worth trying (to see if it's a good simplification, etc) as a follow-up to this.

LLVM's testing is pretty robust such that we can usually make changes like this (especially to existing functionality like DWARFv4 support that's been directly and indirectly tested by lots of test cases over the years) with pretty high confidence that if the tests pass, the change is OK & ideally the chaneg I suggesting wouldn't change the overall behavior, but be a refactoring/change in implementation only.

llvm/trunk/include/llvm/DebugInfo/DWARF/DWARFDebugLine.h

struct LineTable {
     using SequenceVector = std::vector<Sequence>;
     using SequenceIter = SequenceVector::const_iterator;
 
     struct Prologue Prologue;
     RowVector Rows;
     SequenceVector Sequences;
 
   private:
+    const llvm::DWARFDebugLine::FileNameEntry &
+    getFileNameEntry(uint64_t Index) const;
     uint32_t findRowInSeq(const DWARFDebugLine::Sequence &Seq,
                           object::SectionedAddress Address) const;
     Optional<StringRef>
     getSourceByIndex(uint64_t FileIndex,
                      DILineInfoSpecifier::FileLineInfoKind Kind) const;
 
     uint32_t lookupAddressImpl(object::SectionedAddress Address) const;
 

llvm/trunk/include/llvm/MC/MCContext.h

public:
 
     bool isValidDwarfFileNumber(unsigned FileNumber, unsigned CUID = 0);
 
     const std::map<unsigned, MCDwarfLineTable> &getMCDwarfLineTables() const {
       return MCDwarfLineTablesCUMap;
     }
 
     MCDwarfLineTable &getMCDwarfLineTable(unsigned CUID) {
-      return MCDwarfLineTablesCUMap[CUID];
+      return MCDwarfLineTablesCUMap.emplace(CUID, DwarfVersion).first->second;
     }
 
     const MCDwarfLineTable &getMCDwarfLineTable(unsigned CUID) const {
       auto I = MCDwarfLineTablesCUMap.find(CUID);
       assert(I != MCDwarfLineTablesCUMap.end());
       return I->second;
     }
 

llvm/trunk/include/llvm/MC/MCDwarf.h

struct MCDwarfLineTableHeader {
   SmallVector<MCDwarfFile, 3> MCDwarfFiles;
   StringMap<unsigned> SourceIdMap;
   std::string CompilationDir;
   MCDwarfFile RootFile;
   bool HasSource = false;
 private:
   bool HasAllMD5 = true;
   bool HasAnyMD5 = false;
+  unsigned DwarfVersion;
 
 public:
-  MCDwarfLineTableHeader() = default;
+  explicit MCDwarfLineTableHeader(unsigned DwarfVersion) :
+    DwarfVersion(DwarfVersion) {}
 
   Expected<unsigned> tryGetFile(StringRef &Directory, StringRef &FileName,
                                 MD5::MD5Result *Checksum,
                                 Optional<StringRef> &Source,
                                 unsigned FileNumber = 0);
   std::pair<MCSymbol *, MCSymbol *>
   Emit(MCStreamer *MCOS, MCDwarfLineTableParams Params,
        Optional<MCDwarfLineStr> &LineStr) const;
   std::pair<MCSymbol *, MCSymbol *>
   Emit(MCStreamer *MCOS, MCDwarfLineTableParams Params,
        ArrayRef<char> SpecialOpcodeLengths,
        Optional<MCDwarfLineStr> &LineStr) const;
   void resetMD5Usage() {
     HasAllMD5 = true;
     HasAnyMD5 = false;
   }
   void trackMD5Usage(bool MD5Used) {
     HasAllMD5 &= MD5Used;
     HasAnyMD5 |= MD5Used;
   }
   bool isMD5UsageConsistent() const {
     return MCDwarfFiles.empty() || (HasAllMD5 == HasAnyMD5);
   }
 
+  void setRootFile(StringRef Directory, StringRef FileName,
+                   MD5::MD5Result *Checksum, Optional<StringRef> Source) {
+    CompilationDir = Directory;
+    RootFile.Name = FileName;
+    RootFile.DirIndex = 0;
+    RootFile.Checksum = Checksum;
+    RootFile.Source = Source;
+    trackMD5Usage(Checksum);
+    HasSource = Source.hasValue();
+  }
+
 private:
   void emitV2FileDirTables(MCStreamer *MCOS) const;
   void emitV5FileDirTables(MCStreamer *MCOS, Optional<MCDwarfLineStr> &LineStr,
                            StringRef CtxCompilationDir) const;
 };
 
 class MCDwarfDwoLineTable {
   MCDwarfLineTableHeader Header;
 
 public:
+  MCDwarfDwoLineTable(unsigned DwarfVersion) : Header(DwarfVersion) {}
+
   void maybeSetRootFile(StringRef Directory, StringRef FileName,
                         MD5::MD5Result *Checksum, Optional<StringRef> Source) {
     if (!Header.RootFile.Name.empty())
       return;
     Header.CompilationDir = Directory;
     Header.RootFile.Name = FileName;
     Header.RootFile.DirIndex = 0;
     Header.RootFile.Checksum = Checksum;
void Emit(MCStreamer &MCOS, MCDwarfLineTableParams Params,
             MCSection *Section) const;
 };
 
 class MCDwarfLineTable {
   MCDwarfLineTableHeader Header;
   MCLineSection MCLineSections;
 
 public:
+  MCDwarfLineTable(unsigned DwarfVersion) : Header(DwarfVersion) {}
   // This emits the Dwarf file and the line tables for all Compile Units.
   static void Emit(MCObjectStreamer *MCOS, MCDwarfLineTableParams Params);
 
   // This emits the Dwarf file and the line tables for a given Compile Unit.
   void EmitCU(MCObjectStreamer *MCOS, MCDwarfLineTableParams Params,
               Optional<MCDwarfLineStr> &LineStr) const;
 
   Expected<unsigned> tryGetFile(StringRef &Directory, StringRef &FileName,

llvm/trunk/lib/CodeGen/AsmPrinter/DwarfCompileUnit.h

class DwarfCompileUnit final : public DwarfUnit {
 
   DenseMap<const DINode *, std::unique_ptr<DbgEntity>> &getAbstractEntities() {
     if (isDwoUnit() && !DD->shareAcrossDWOCUs())
       return AbstractEntities;
     return DU->getAbstractEntities();
   }
 
 public:
+  unsigned getDwarfVersion() const { return DD->getDwarfVersion(); }
   DwarfCompileUnit(unsigned UID, const DICompileUnit *Node, AsmPrinter *A,
                    DwarfDebug *DW, DwarfFile *DWU);
 
   bool hasRangeLists() const { return HasRangeLists; }
   unsigned getUniqueID() const { return UniqueID; }
 
   DwarfCompileUnit *getSkeleton() const {
     return Skeleton;

llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp

return TT.isOSBinFormatMachO() ? AccelTableKind::Apple
                                    : AccelTableKind::Dwarf;
   return AccelTableKind::None;
 }
 
 DwarfDebug::DwarfDebug(AsmPrinter *A, Module *M)
     : DebugHandlerBase(A), DebugLocs(A->OutStreamer->isVerboseAsm()),
       InfoHolder(A, "info_string", DIEValueAllocator),
       SkeletonHolder(A, "skel_string", DIEValueAllocator),
+      SplitTypeUnitFileTable(A->getDwarfVersion()),
       IsDarwin(A->TM.getTargetTriple().isOSDarwin()) {
   const Triple &TT = Asm->TM.getTargetTriple();
 
   // Make sure we know our "debugger tuning".  The target option takes
   // precedence; fall back to triple-based defaults.
   if (Asm->TM.Options.DebuggerTuning != DebuggerKind::Default)
     DebuggerTuning = Asm->TM.Options.DebuggerTuning;
   else if (IsDarwin)

llvm/trunk/lib/CodeGen/AsmPrinter/DwarfUnit.cpp

void DwarfUnit::addBlock(DIE &Die, dwarf::Attribute Attribute,
   Die.addValue(DIEValueAllocator, Attribute, Block->BestForm(), Block);
 }
 
 void DwarfUnit::addSourceLine(DIE &Die, unsigned Line, const DIFile *File) {
   if (Line == 0)
     return;
 
   unsigned FileID = getOrCreateSourceID(File);
-  assert(FileID && "Invalid file id");
   addUInt(Die, dwarf::DW_AT_decl_file, None, FileID);
   addUInt(Die, dwarf::DW_AT_decl_line, None, Line);
 }
 
 void DwarfUnit::addSourceLine(DIE &Die, const DILocalVariable *V) {
   assert(V);
 
   addSourceLine(Die, V->getLine(), V->getFile());

llvm/trunk/lib/DebugInfo/DWARF/DWARFDebugLine.cpp

while (SeqPos != LastSeq && SeqPos->LowPC < EndAddr) {
 
     ++SeqPos;
   }
 
   return true;
 }
 
 bool DWARFDebugLine::LineTable::hasFileAtIndex(uint64_t FileIndex) const {
+  uint16_t DwarfVersion = Prologue.getVersion();
+  assert(DwarfVersion != 0 && "LineTable has no dwarf version information");
+  if (DwarfVersion >= 5)
+    return FileIndex < Prologue.FileNames.size();
+  else
     return FileIndex != 0 && FileIndex <= Prologue.FileNames.size();
 }
+const llvm::DWARFDebugLine::FileNameEntry &
+DWARFDebugLine::LineTable::getFileNameEntry(uint64_t Index) const {
+  uint16_t DwarfVersion = Prologue.getVersion();
+  assert(DwarfVersion != 0 && "LineTable has no dwarf version information");
+  if (DwarfVersion >= 5)
+    return Prologue.FileNames[Index];
+  else
+    return Prologue.FileNames[Index - 1];
+}
 
 Optional<StringRef> DWARFDebugLine::LineTable::getSourceByIndex(uint64_t FileIndex,
                                                                 FileLineInfoKind Kind) const {
   if (Kind == FileLineInfoKind::None || !hasFileAtIndex(FileIndex))
     return None;
-  const FileNameEntry &Entry = Prologue.FileNames[FileIndex - 1];
+  const FileNameEntry &Entry = getFileNameEntry(FileIndex);
   if (Optional<const char *> source = Entry.Source.getAsCString())
     return StringRef(*source);
   return None;
 }
 
 static bool isPathAbsoluteOnWindowsOrPosix(const Twine &Path) {
   // Debug info can contain paths from any OS, not necessarily
   // an OS we're currently running on. Moreover different compilation units can
   // be compiled on different operating systems and linked together later.
   return sys::path::is_absolute(Path, sys::path::Style::posix) ||
          sys::path::is_absolute(Path, sys::path::Style::windows);
 }
 
 bool DWARFDebugLine::LineTable::getFileNameByIndex(uint64_t FileIndex,
                                                    const char *CompDir,
                                                    FileLineInfoKind Kind,
                                                    std::string &Result) const {
   if (Kind == FileLineInfoKind::None || !hasFileAtIndex(FileIndex))
     return false;
-  const FileNameEntry &Entry = Prologue.FileNames[FileIndex - 1];
+  const FileNameEntry &Entry = getFileNameEntry(FileIndex);
   StringRef FileName = Entry.Name.getAsCString().getValue();
   if (Kind != FileLineInfoKind::AbsoluteFilePath ||
       isPathAbsoluteOnWindowsOrPosix(FileName)) {
     Result = FileName;
     return true;
   }
 
   SmallString<16> FilePath;

llvm/trunk/lib/MC/MCContext.cpp

 /// error and zero is returned and the client reports the error, else the
 /// allocated file number is returned.  The file numbers may be in any order.
 Expected<unsigned> MCContext::getDwarfFile(StringRef Directory,
                                            StringRef FileName,
                                            unsigned FileNumber,
                                            MD5::MD5Result *Checksum,
                                            Optional<StringRef> Source,
                                            unsigned CUID) {
-  MCDwarfLineTable &Table = MCDwarfLineTablesCUMap[CUID];
+  MCDwarfLineTable &Table =
+      MCDwarfLineTablesCUMap.emplace(CUID, DwarfVersion).first->second;
   return Table.tryGetFile(Directory, FileName, Checksum, Source, FileNumber);
 }
 
 /// isValidDwarfFileNumber - takes a dwarf file number and returns true if it
 /// currently is assigned and false otherwise.
 bool MCContext::isValidDwarfFileNumber(unsigned FileNumber, unsigned CUID) {
   const MCDwarfLineTable &LineTable = getMCDwarfLineTable(CUID);
   if (FileNumber == 0)
-    return getDwarfVersion() >= 5 && LineTable.hasRootFile();
+    return getDwarfVersion() >= 5;
   if (FileNumber >= LineTable.getMCDwarfFiles().size())
     return false;
 
   return !LineTable.getMCDwarfFiles()[FileNumber].Name.empty();
 }
 
 /// Remove empty sections from SectionsForRanges, to avoid generating
 /// useless debug info for them.

llvm/trunk/lib/MC/MCDwarf.cpp

 Expected<unsigned> MCDwarfLineTable::tryGetFile(StringRef &Directory,
                                                 StringRef &FileName,
                                                 MD5::MD5Result *Checksum,
                                                 Optional<StringRef> Source,
                                                 unsigned FileNumber) {
   return Header.tryGetFile(Directory, FileName, Checksum, Source, FileNumber);
 }
 
+bool isRootFile(const MCDwarfFile &RootFile, StringRef &Directory,
+                StringRef &FileName, MD5::MD5Result *Checksum) {
+  if (RootFile.Name.empty() || RootFile.Name != FileName.data())
+    return false;
+  if (!RootFile.Checksum)
+    return !Checksum;
+  return *RootFile.Checksum == *Checksum;
+}
+
 Expected<unsigned>
 MCDwarfLineTableHeader::tryGetFile(StringRef &Directory,
                                    StringRef &FileName,
                                    MD5::MD5Result *Checksum,
                                    Optional<StringRef> &Source,
                                    unsigned FileNumber) {
   if (Directory == CompilationDir)
     Directory = "";
   if (FileName.empty()) {
     FileName = "<stdin>";
     Directory = "";
   }
   assert(!FileName.empty());
   // Keep track of whether any or all files have an MD5 checksum.
   // If any files have embedded source, they all must.
   if (MCDwarfFiles.empty()) {
     trackMD5Usage(Checksum);
     HasSource = (Source != None);
   }
+  if (isRootFile(RootFile, Directory, FileName, Checksum) && DwarfVersion >= 5)
+    return 0;
   if (FileNumber == 0) {
     // File numbers start with 1 and/or after any file numbers
     // allocated by inline-assembler .file directives.
     FileNumber = MCDwarfFiles.empty() ? 1 : MCDwarfFiles.size();
     SmallString<256> Buffer;
     auto IterBool = SourceIdMap.insert(
         std::make_pair((Directory + Twine('\0') + FileName).toStringRef(Buffer),
                        FileNumber));

llvm/trunk/test/MC/ARM/dwarf-asm-multiple-sections.s

 // RUN: llvm-mc < %s -triple=armv7-linux-gnueabi -filetype=obj -o %t -g -dwarf-version 5 -fdebug-compilation-dir=/tmp
 // RUN: llvm-dwarfdump -v %t | FileCheck -check-prefix DWARF -check-prefix DWARF45 %s
 // RUN: llvm-dwarfdump --debug-line %t | FileCheck -check-prefix DWARF-DL -check-prefix DWARF-DL-5 -DDWVER=5 -DDWFILE=0 %s
 // RUN: llvm-objdump -r %t | FileCheck -check-prefix RELOC -check-prefix RELOC5 %s
-// RUN: llvm-mc < %s -triple=armv7-linux-gnueabi -filetype=obj -o %t -g -fdebug-compilation-dir=/tmp
+// RUN: llvm-mc < %s -triple=armv7-linux-gnueabi -filetype=obj -o %t -g -dwarf-version 4 -fdebug-compilation-dir=/tmp
 // RUN: llvm-dwarfdump -v %t | FileCheck -check-prefix DWARF -check-prefix DWARF45 %s
-// RUN: llvm-dwarfdump --debug-line %t | FileCheck -check-prefix DWARF-DL -DDWVER=4 -DDWFILE=1 %s
+// RUN: llvm-dwarfdump --debug-line %t | FileCheck -check-prefix DWARF-DL -check-prefix DWARF-DL-4 -DDWVER=4 -DDWFILE=1 %s
 // RUN: llvm-objdump -r %t | FileCheck -check-prefix RELOC -check-prefix RELOC4 %s
 // RUN: llvm-mc < %s -triple=armv7-linux-gnueabi -filetype=obj -o %t -g -dwarf-version 3 -fdebug-compilation-dir=/tmp
 // RUN: llvm-dwarfdump -v %t | FileCheck -check-prefix DWARF -check-prefix DWARF3 %s
 // RUN: llvm-dwarfdump --debug-line %t | FileCheck -check-prefix DWARF-DL -DDWVER=3 -DDWFILE=1 %s
 // RUN: llvm-mc < %s -triple=armv7-linux-gnueabi -filetype=obj -o %t -g -dwarf-version 2 2>&1 | FileCheck -check-prefix VERSION %s
 // RUN: not llvm-mc < %s -triple=armv7-linux-gnueabi -filetype=obj -o %t -g -dwarf-version 1 2>&1 | FileCheck -check-prefix DWARF1 %s
 // RUN: not llvm-mc < %s -triple=armv7-linux-gnueabi -filetype=obj -o %t -g -dwarf-version 6 2>&1 | FileCheck -check-prefix DWARF6 %s
   .section .text, "ax"

 
 
 // DWARF-DL: .debug_line contents:
 // DWARF-DL: version: [[DWVER]]
 // DWARF-DL-5:    address_size: 4
 // DWARF-DL-5:    include_directories[  0] = "/tmp"
 // DWARF-DL:      file_names[  [[DWFILE]]]:
 // DWARF-DL:      name: "{{(<stdin>|-)}}"
-// DWARF-DL:      0x0000000000000000     17      0      1   0   0  is_stmt
-// DWARF-DL-NEXT: 0x0000000000000004     17      0      1   0   0  is_stmt end_sequence
-// DWARF-DL-NEXT: 0x0000000000000000     21      0      1   0   0  is_stmt
-// DWARF-DL-NEXT: 0x0000000000000004     21      0      1   0   0  is_stmt end_sequence
-
+// DWARF-DL-5:      0x0000000000000000     17      0      0   0   0  is_stmt
+// DWARF-DL-5-NEXT: 0x0000000000000004     17      0      0   0   0  is_stmt end_sequence
+// DWARF-DL-5-NEXT: 0x0000000000000000     21      0      0   0   0  is_stmt
+// DWARF-DL-5-NEXT: 0x0000000000000004     21      0      0   0   0  is_stmt end_sequence
+// DWARF-DL-4:      0x0000000000000000     17      0      1   0   0  is_stmt
+// DWARF-DL-4-NEXT: 0x0000000000000004     17      0      1   0   0  is_stmt end_sequence
+// DWARF-DL-4-NEXT: 0x0000000000000000     21      0      1   0   0  is_stmt
+// DWARF-DL-4-NEXT: 0x0000000000000004     21      0      1   0   0  is_stmt end_sequence
 
 // DWARF: .debug_ranges contents:
 // DWARF: 00000000 ffffffff 00000000
 // DWARF: 00000000 00000000 00000004
 // DWARF: 00000000 ffffffff 00000000
 // DWARF: 00000000 00000000 00000004
 // DWARF: 00000000 <End of list>
 

llvm/trunk/test/MC/ELF/debug-mixed-md5.ll

 ; RUN: %llc_dwarf -filetype=asm -dwarf-version=5 %s -o - | FileCheck %s -check-prefix=ASM
 ; RUN: %llc_dwarf -filetype=obj -dwarf-version=5 %s -o - | llvm-dwarfdump -debug-line - | FileCheck %s -check-prefix=OBJ
 ; ASM: .file 0 "{{.+}}" md5
-; ASM: .file 1 "{{.+}}" md5
-; ASM: .file 2 "t1.cpp"
+; ASM: .file 1 "t1.cpp"
 ; ASM-NOT: md5
 ; OBJ: file_names[ 0]:
 ; OBJ-NOT: md5
 ;
 ; Generated from this source (see PR37623):
 ;
 ; #define a(...) template __VA_ARGS__;
 ; template <class> class b {};

llvm/trunk/test/MC/ELF/dwarf-file0.s

 # CHECK-NOT:   include_directories
 # CHECK-4-NOT: file_names[ 0]
 # CHECK-5:     file_names[ 0]:
 # CHECK-5-NEXT: name: "root.cpp"
 # CHECK-5-NEXT: dir_index: 0
 # CHECK:       file_names[ 1]:
 # CHECK-NEXT:  name: "header.h"
 # CHECK-NEXT:  dir_index: 1
-# CHECK:       file_names[ 2]:
-# CHECK-NEXT:  name: "root.cpp"
+# CHECK-4:     file_names[ 2]:
+# CHECK-4-NEXT: name: "root.cpp"
 # CHECK-4-NEXT: dir_index: 2
-# CHECK-5-NEXT: dir_index: 0
 
 # ASM-NOT: .file
 # ASM-5:   .file 0 "/test" "root.cpp"
 # ASM:     .file 1 "/include" "header.h"
 # ASM-4:   .file 2 "/test" "root.cpp"
-# ASM-5:   .file 2 "root.cpp"
 # ASM-NOT: .file
 
 # WARN:      file 0 not supported prior to DWARF-5
 # WARN-NEXT: .file 0
 # WARN-NEXT: ^

llvm/trunk/test/tools/llvm-objdump/X86/function-sections-line-numbers.s

# CHECK-NOT: test.cpp:1
   .file "test.cpp"
   .section  .text._Z2f1v,"ax",@progbits
   .globl  _Z2f1v                  # -- Begin function _Z2f1v
   .p2align  4, 0x90
   .type _Z2f1v,@function
 _Z2f1v:                                 # @_Z2f1v
 .Lfunc_begin0:
   .file 0 "/home/avl" "test.cpp" md5 0xefae234cc05b45384d782316d3a5d338
-  .file  1 "test.cpp" md5 0xefae234cc05b45384d782316d3a5d338
-  .loc  1 1 0                   # test.cpp:1:0
+  .loc  0 1 0                   # test.cpp:1:0
   .cfi_startproc
 # %bb.0:                                # %entry
   pushq %rbp
   .cfi_def_cfa_offset 16
   .cfi_offset %rbp, -16
   movq  %rsp, %rbp
   .cfi_def_cfa_register %rbp
 .Ltmp0:
-  .loc  1 1 12 prologue_end     # test.cpp:1:12
+  .loc  0 1 12 prologue_end     # test.cpp:1:12
   popq  %rbp
   .cfi_def_cfa %rsp, 8
   retq
 .Ltmp1:
 .Lfunc_end0:
   .size _Z2f1v, .Lfunc_end0-_Z2f1v
   .cfi_endproc
                                         # -- End function
   .section  .text._Z2f2v,"ax",@progbits
   .globl  _Z2f2v                  # -- Begin function _Z2f2v
   .p2align  4, 0x90
   .type _Z2f2v,@function
 _Z2f2v:                                 # @_Z2f2v
 .Lfunc_begin1:
-  .loc  1 2 0                   # test.cpp:2:0
+  .loc  0 2 0                   # test.cpp:2:0
   .cfi_startproc
 # %bb.0:                                # %entry
   pushq %rbp
   .cfi_def_cfa_offset 16
   .cfi_offset %rbp, -16
   movq  %rsp, %rbp
   .cfi_def_cfa_register %rbp
 .Ltmp2:
-  .loc  1 2 12 prologue_end     # test.cpp:2:12
+  .loc  0 2 12 prologue_end     # test.cpp:2:12
   popq  %rbp
   .cfi_def_cfa %rsp, 8
   retq
 .Ltmp3:
 .Lfunc_end1:
   .size _Z2f2v, .Lfunc_end1-_Z2f2v
   .cfi_endproc
                                         # -- End function