[PDB] Copy inlinee lines records into the PDB

[rnk]

Summary

• Fixes inline call frame line table display in windbg.
• Improve llvm-pdbutil to dump extra file ids.
• Warn on unknown subsections so we don't have this kind of bug in the future.

[aganea]

I've noticed btw that obj2yaml/yaml2obj doesn't preserve the BinaryAnnotations if SectionData values are skimmed out of the .yaml (to reduce size). There's also something missing for S_FRAMEPROC in that regard:

lld/test/COFF/pdb-inlinees-extrafiles.s

6

Why not:

$ cl /Z7 /c /O2 t.c
$ obj2yaml t.obj >t.yaml

Which changes the test to:

# REQUIRES: x86
# RUN: yaml2obj %s -o=%t.obj
# RUN: lld-link -entry:main -nodefaultlib %t.obj -out:%t.exe -pdb:%t.pdb -debug
# RUN: llvm-pdbutil dump -il %t.pdb | FileCheck %s

I think it should be made clear/easy to re-generate the tests, if we want to change it, or if someone wants to duplicate it.

24

t1.h

lld/test/COFF/pdb-unknown-subsection.s

13

/s/verison/version (and the same below)

[rnk]

In D62701#1525151, @aganea wrote:

I've noticed btw that obj2yaml/yaml2obj doesn't preserve the BinaryAnnotations if SectionData values are skimmed out of the .yaml (to reduce size). There's also something missing for S_FRAMEPROC in that regard:

Hm. Going forward, I kind of feel like we should move towards writing tests in assembly and port some of the YAML ones to assembly. I think if we structure the assembly right, it can be more readable and more compact than YAML. It follows how things were done for ELF lld testing. I have an intern who is working on making LLVM generate more human-readable codeview record assembly, which is basically what I'm hacking on here.

[rnk]

lld/test/COFF/pdb-inlinees-extrafiles.s

6

Basically it boils down to, which do we think is a more useful test format, YAML or assembly? My preference is for assembly, and I'd like to replace a lot of the .test YAML inputs with .s inputs. Maybe that's unique to me, but it mirrors the direction the ELF linker took, where they moved away from YAML object input tests to assembly tests.

I can't generate assembly from MSVC, so I started with clang assembly output, and modified it to exercise the corner case in question.

[aganea]

lld/test/COFF/pdb-inlinees-extrafiles.s

6

Would there be a way to better represent "structured data" in the assembly below? Can you show a mock of what your intern is doing?

If you choose to go the ELF way for coherence, that is justified. Was the move in ELF because of file size concerns?

[aganea]

lld/test/COFF/pdb-inlinees-extrafiles.s

6

Oh I see, you want to represent both code and debug info in the same textual formal, and YAML doesn't offer that (only through raw SectionDatas. If the assembly below could offer structured representations (and named fields), in essence YAML readability, that would be a great!

[rnk]

lld/test/COFF/pdb-inlinees-extrafiles.s

6

Exactly, YAML doesn't do a very good job of representing machine code or relocations in a very human readable way. The code is just in hex SectionData, and the relocations are stored separately in an array, so it's not easily modifiable.

Here's an excerpt of the project proposal I wrote:

---

Currently, type info is emitted using CodeViewRecordIO as bytes, and then dumped as textual comments in the assembler output. It currently looks like this:

	# Struct (0x1003) {
	#   TypeLeafKind: LF_STRUCTURE (0x1505)
	#   MemberCount: 2
	#   Properties [ (0x200)
	#     HasUniqueName (0x200)
	#   ]
	#   FieldList: <field list> (0x1002)
	#   DerivedFrom: 0x0
	#   VShape: 0x0
	#   SizeOf: 16
	#   Name: Foo
	#   LinkageName: .?AUFoo@@
	# }
	.byte	0x22, 0x00, 0x05, 0x15
	.byte	0x02, 0x00, 0x00, 0x02
	.byte	0x02, 0x10, 0x00, 0x00
	.byte	0x00, 0x00, 0x00, 0x00
	.byte	0x00, 0x00, 0x00, 0x00
	.byte	0x10, 0x00, 0x46, 0x6f
	.byte	0x6f, 0x00, 0x2e, 0x3f
	.byte	0x41, 0x55, 0x46, 0x6f
	.byte	0x6f, 0x40, 0x40, 0x00

However, this is needlessly hard to read. It would be much nicer if we emitted assembly that looked like this:

.short 34       # RecordLen
.short 0x1505   # LF_STRUCTURE
.long 0x200     # Properties
.long 0x1002    # FieldList
.long 0x0       # DerivedFrom
.long 0x0       # VShape
.short 16       # SizeOf
.asciz "Foo"    # Name
.asciz ".?AUFoo@@"      # LinkageName

---

Nilanjana is still getting started and doesn't have a Phabricator account yet, but this is kind of the direction that I want to go. I figured we'd start with type records, then try to make symbol records more structured, and then move on to .cv_def_range, which is pretty gross right now.

[aganea]

LGTM! I'm less sure about the yaml->assembly change, but we could continue that offline :)
Maybe in a subsequent patch it'd be nice to fix obj2yaml IL part to avoid relying on SectionDatas.

lld/test/COFF/pdb-inlinees-extrafiles.s

6

What about a new .codeview directive which would include more structured data, and also solve .cv_def_range? You would get the best of both worlds, assembly code and readability for debug infos.

.codeview "
      - Kind:            LF_STRUCTURE
        Class:
          MemberCount:     0
          Options:         [ None, ForwardReference, HasUniqueName ]
          FieldList:       0
          Name:            Foo
          UniqueName:      '.?AUFoo@@'
          DerivationList:  0
          VTableShape:     0
          Size:            0
"

[aganea]

lld/test/COFF/pdb-inlinees-extrafiles.s

6

Nothing prevents from writing partial or entire sections with this:

.codeview "
sections:        
  - Name:            '.debug$S'
    Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_MEM_DISCARDABLE, IMAGE_SCN_MEM_READ ]
    Alignment:       1
    Subsections:     
      - !Symbols
        Records:         
          - Kind:            S_OBJNAME
            ObjNameSym:      
              Signature:       0
              ObjectName:      'F:\svn\test\t.obj'
          - Kind:            S_COMPILE3
            Compile3Sym:     
              Flags:           [ SecurityChecks, HotPatch ]
              Machine:         X64
              FrontendMajor:   19
              FrontendMinor:   16
              FrontendBuild:   27031
              FrontendQFE:     1
              BackendMajor:    19
              BackendMinor:    16
              BackendBuild:    27031
              BackendQFE:      1
              Version:         'Microsoft (R) Optimizing Compiler'

[rnk]

lld/test/COFF/pdb-inlinees-extrafiles.s

6

That's an interesting idea. Up until now, we haven't allowed llc, clang, or MC to have dependencies on ObjectYAML because we believed it was too large. We'd have to check that belief, and maybe optimize the code size of this feature, which will be seldomly used. But, it's not like we've been policing the size of the clang binary that much, and I'm sure there are other ways we could optimize its size.

One concern I have is that I want to be able to test feeding corrupt records to LLD. I think we can allow mixing YAML symbol records with today's assembler declared codeview records. If we do that, we won't lose any testing capabilities.

I'll have to think about it.

One other thing is, how do we get labels and relocations into and out of YAML? Today a lot of those things are only supported as offsets into sections and section indices. That's sort of the strong suit of assembly, which is really all about laying out code and finalizing offsets.

lld/COFF/PDB.cpp

class DebugSHandler {
   /// global PDB string table.
   DebugStringTableSubsectionRef CVStrTab;
 
   /// The DEBUG_S_FILECHKSMS subsection.  As above, these are referred to
   /// by other records in the .debug$S section and need to be merged into the
   /// PDB.
   DebugChecksumsSubsectionRef Checksums;
 
+  /// The DEBUG_S_INLINEELINES subsection. There can be only one of these per
+  /// object file.
+  DebugInlineeLinesSubsectionRef InlineeLines;
+
   /// The DEBUG_S_FRAMEDATA subsection(s).  There can be more than one of
   /// these and they need not appear in any specific order.  However, they
   /// contain string table references which need to be re-written, so we
   /// collect them all here and re-write them after all subsections have been
   /// discovered and processed.
   std::vector<DebugFrameDataSubsectionRef> NewFpoFrames;
 
   /// Pointers to raw memory that we determine have string table references
   /// that need to be re-written.  We first process all .debug$S subsections
   /// to ensure that we can handle subsections written in any order, building
   /// up this list as we go.  At the end, we use the string table (which must
   /// have been discovered by now else it is an error) to re-write these
   /// references.
   std::vector<ulittle32_t *> StringTableReferences;
 
 public:
   DebugSHandler(PDBLinker &Linker, ObjFile &File, const CVIndexMap &IndexMap)
       : Linker(Linker), File(File), IndexMap(IndexMap) {}
 
   void handleDebugS(lld::coff::SectionChunk &DebugS);
+
+  std::shared_ptr<DebugInlineeLinesSubsection>
+  mergeInlineeLines(DebugChecksumsSubsection *NewChecksums);
+
   void finish();
 };
 }
 
 // Visual Studio's debugger requires absolute paths in various places in the
 // PDB to work without additional configuration:
 // https://docs.microsoft.com/en-us/visualstudio/debugger/debug-source-files-common-properties-solution-property-pages-dialog-box
 static void pdbMakeAbsolute(SmallVectorImpl<char> &FileName) {
case DebugSubsectionKind::FileChecksums:
              "Encountered multiple checksum subsections!");
       ExitOnErr(Checksums.initialize(SS.getRecordData()));
       break;
     case DebugSubsectionKind::Lines:
       // We can add the relocated line table directly to the PDB without
       // modification because the file checksum offsets will stay the same.
       File.ModuleDBI->addDebugSubsection(SS);
       break;
+    case DebugSubsectionKind::InlineeLines:
+      assert(!InlineeLines.valid() &&
+             "Encountered multiple inlinee lines subsections!");
+      ExitOnErr(InlineeLines.initialize(SS.getRecordData()));
+      break;
     case DebugSubsectionKind::FrameData: {
       // We need to re-write string table indices here, so save off all
       // frame data subsections until we've processed the entire list of
       // subsections so that we can be sure we have the string table.
       DebugFrameDataSubsectionRef FDS;
       ExitOnErr(FDS.initialize(SS.getRecordData()));
       NewFpoFrames.push_back(std::move(FDS));
       break;
     }
     case DebugSubsectionKind::Symbols: {
       Linker.mergeSymbolRecords(&File, IndexMap, StringTableReferences,
                                 SS.getRecordData());
       break;
     }
+
+    case DebugSubsectionKind::CrossScopeImports:
+    case DebugSubsectionKind::CrossScopeExports:
+      // These appear to relate to cross-module optimization, so we might use
+      // these for ThinLTO.
+      break;
+
+    case DebugSubsectionKind::ILLines:
+    case DebugSubsectionKind::FuncMDTokenMap:
+    case DebugSubsectionKind::TypeMDTokenMap:
+    case DebugSubsectionKind::MergedAssemblyInput:
+      // These appear to relate to .Net assembly info.
+      break;
+
+    case DebugSubsectionKind::CoffSymbolRVA:
+      // Unclear what this is for.
+      break;
+
     default:
-      // FIXME: Process the rest of the subsections.
+      warn("ignoring unknown debug$S subsection kind 0x" +
+           utohexstr(uint32_t(SS.kind())));
       break;
     }
   }
 }
 
+static Expected<StringRef>
+getFileName(const DebugStringTableSubsectionRef &Strings,
+            const DebugChecksumsSubsectionRef &Checksums, uint32_t FileID) {
+  auto Iter = Checksums.getArray().at(FileID);
+  if (Iter == Checksums.getArray().end())
+    return make_error<CodeViewError>(cv_error_code::no_records);
+  uint32_t Offset = Iter->FileNameOffset;
+  return Strings.getString(Offset);
+}
+
+std::shared_ptr<DebugInlineeLinesSubsection>
+DebugSHandler::mergeInlineeLines(DebugChecksumsSubsection *NewChecksums) {
+  auto NewInlineeLines = std::make_shared<DebugInlineeLinesSubsection>(
+      *NewChecksums, InlineeLines.hasExtraFiles());
+
+  for (const InlineeSourceLine &Line : InlineeLines) {
+    TypeIndex Inlinee = Line.Header->Inlinee;
+    uint32_t FileID = Line.Header->FileID;
+    uint32_t SourceLine = Line.Header->SourceLineNum;
+
+    ArrayRef<TypeIndex> TypeOrItemMap =
+        IndexMap.IsTypeServerMap ? IndexMap.IPIMap : IndexMap.TPIMap;
+    if (!remapTypeIndex(Inlinee, TypeOrItemMap)) {
+      log("ignoring inlinee line record in " + File.getName() +
+          " with bad inlinee index 0x" + utohexstr(Inlinee.getIndex()));
+      continue;
+    }
+
+    SmallString<128> Filename =
+        ExitOnErr(getFileName(CVStrTab, Checksums, FileID));
+    pdbMakeAbsolute(Filename);
+    NewInlineeLines->addInlineSite(Inlinee, Filename, SourceLine);
+
+    if (InlineeLines.hasExtraFiles()) {
+      for (uint32_t ExtraFileId : Line.ExtraFiles) {
+        Filename = ExitOnErr(getFileName(CVStrTab, Checksums, ExtraFileId));
+        pdbMakeAbsolute(Filename);
+        NewInlineeLines->addExtraFile(Filename);
+      }
+    }
+  }
+
+  return NewInlineeLines;
+}
+
 void DebugSHandler::finish() {
   pdb::DbiStreamBuilder &DbiBuilder = Linker.Builder.getDbiBuilder();
 
   // We should have seen all debug subsections across the entire object file now
   // which means that if a StringTable subsection and Checksums subsection were
   // present, now is the time to handle them.
   if (!CVStrTab.valid()) {
     if (Checksums.valid())
for (ulittle32_t *Ref : StringTableReferences)
     *Ref = translateStringTableIndex(*Ref, CVStrTab, Linker.PDBStrTab);
 
   // Make a new file checksum table that refers to offsets in the PDB-wide
   // string table. Generally the string table subsection appears after the
   // checksum table, so we have to do this after looping over all the
   // subsections.
   auto NewChecksums = make_unique<DebugChecksumsSubsection>(Linker.PDBStrTab);
   for (FileChecksumEntry &FC : Checksums) {
-    SmallString<128> FileName =
+    SmallString<128> Filename =
         ExitOnErr(CVStrTab.getString(FC.FileNameOffset));
-    pdbMakeAbsolute(FileName);
-    ExitOnErr(Linker.Builder.getDbiBuilder().addModuleSourceFile(
-        *File.ModuleDBI, FileName));
-    NewChecksums->addChecksum(FileName, FC.Kind, FC.Checksum);
+    pdbMakeAbsolute(Filename);
+    ExitOnErr(DbiBuilder.addModuleSourceFile(*File.ModuleDBI, Filename));
+    NewChecksums->addChecksum(Filename, FC.Kind, FC.Checksum);
   }
+
+  // Rewrite inlinee item indices if present.
+  if (InlineeLines.valid())
+    File.ModuleDBI->addDebugSubsection(mergeInlineeLines(NewChecksums.get()));
+
   File.ModuleDBI->addDebugSubsection(std::move(NewChecksums));
 }
 
 void PDBLinker::addObjFile(ObjFile *File, CVIndexMap *ExternIndexMap) {
   if (File->MergedIntoPDB)
     return;
   File->MergedIntoPDB = true;
 
ExitOnErr(
       DbiBuilder.addDbgStream(pdb::DbgHeaderType::SectionHdr, SectionTable));
 }
 
 void PDBLinker::commit(codeview::GUID *Guid) {
   // Write to a file.
   ExitOnErr(Builder.commit(Config->PDBPath, Guid));
 }
 
-static Expected<StringRef>
-getFileName(const DebugStringTableSubsectionRef &Strings,
-            const DebugChecksumsSubsectionRef &Checksums, uint32_t FileID) {
-  auto Iter = Checksums.getArray().at(FileID);
-  if (Iter == Checksums.getArray().end())
-    return make_error<CodeViewError>(cv_error_code::no_records);
-  uint32_t Offset = Iter->FileNameOffset;
-  return Strings.getString(Offset);
-}
-
 static uint32_t getSecrelReloc() {
   switch (Config->Machine) {
   case AMD64:
     return COFF::IMAGE_REL_AMD64_SECREL;
   case I386:
     return COFF::IMAGE_REL_I386_SECREL;
   case ARMNT:
     return COFF::IMAGE_REL_ARM_SECREL;

lld/test/COFF/pdb-inlinees-extrafiles.s

+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj %s -o %t.obj -triple x86_64-windows-msvc
+# RUN: lld-link -entry:main -nodefaultlib %t.obj -out:%t.exe -pdb:%t.pdb -debug
+# RUN: llvm-pdbutil dump -il %t.pdb | FileCheck %s
+
+# The assembly was hand written to model the following C code. As of this
+# writing, clang does not emit extra files for inlinees, so it had to be hand
+# written.
+
+# // t1.h:
+# ++x;
+# #include "t2.h"
+# ++x;
+
+# // t2.h:
+# ++x;
+# __debugbreak();
+# ++x;
+
+# // t.c:
+# volatile int x;
+# static __forceinline void inlinee_1(void) {
+#   ++x;
+# #include "t1.inc"
+#   ++x;
+# }
+# int main() {
+#   ++x;
+#   inlinee_1();
+#   ++x;
+#   return x;
+# }
+
+# CHECK:                             Inlinee Lines
+# CHECK:      Mod 0000 | `{{.*}}pdb-inlinees-extrafiles.s.tmp.obj`:
+# CHECK-NEXT:  Inlinee |  Line | Source File
+# CHECK-NEXT:   0x1000 |     7 | C:\src\llvm-project\build\t.c (MD5: A79D837C976E9F0463A474D74E2EE9E7)
+# CHECK-NEXT:                    C:\src\llvm-project\build\t1.h (MD5: FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF)
+# CHECK-NEXT:                    C:\src\llvm-project\build\t2.h (MD5: FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF)
+
+  .text
+  .def   @feat.00;
+  .scl  3;
+  .type 0;
+  .endef
+  .globl  @feat.00
+.set @feat.00, 0
+  .intel_syntax noprefix
+  .file "t.c"
+  .def   main;
+  .scl  2;
+  .type 32;
+  .endef
+  .section  .text,"xr",one_only,main
+  .globl  main                    # -- Begin function main
+main:                                   # @main
+.Lfunc_begin0:
+  .cv_func_id 0
+# %bb.0:                                # %entry
+  .cv_file  1 "C:\\src\\llvm-project\\build\\t.c" "A79D837C976E9F0463A474D74E2EE9E7" 1
+  .cv_file  2 "C:\\src\\llvm-project\\build\\t1.h" "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF" 1
+  .cv_file  3 "C:\\src\\llvm-project\\build\\t2.h" "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF" 1
+  .cv_loc 0 1 13 0                # t.c:13:0
+  inc dword ptr [rip + x]
+.Ltmp0:
+  .cv_inline_site_id 1 within 0 inlined_at 1 14 0
+  .cv_loc 1 1 3 0                 # t.c:3:0
+  inc dword ptr [rip + x]
+.Ltmp1:
+  .cv_loc 1 2 1 0                 # t1.h:1:0
+  inc dword ptr [rip + x]
+  .cv_loc 1 3 1 0                 # t2.h:1:0
+  inc dword ptr [rip + x]
+  .cv_loc 1 3 2 0                 # t2.h:2:0
+  int3
+  .cv_loc 1 3 3 0                 # t2.h:3:0
+  inc dword ptr [rip + x]
+  .cv_loc 1 2 3 0                 # t1.h:3:0
+  inc dword ptr [rip + x]
+.Ltmp2:
+  .cv_loc 1 1 5 0                # t.c:5:0
+  inc dword ptr [rip + x]
+.Ltmp3:
+  .cv_loc 0 1 15 0                # t.c:15:0
+  inc dword ptr [rip + x]
+  .cv_loc 0 1 16 0                # t.c:16:0
+  mov  eax, dword ptr [rip + x]
+  ret
+.Ltmp4:
+.Lfunc_end0:
+                                        # -- End function
+  .comm x,4,2                   # @x
+  .section  .debug$S,"dr"
+  .p2align  2
+  .long 4                       # Debug section magic
+  .long 241
+  .long .Ltmp6-.Ltmp5           # Subsection size
+.Ltmp5:
+  .short  .Ltmp8-.Ltmp7           # Record length
+.Ltmp7:
+  .short  4412                    # Record kind: S_COMPILE3
+  .long 0                       # Flags and language
+  .short  208                     # CPUType
+  .short  9                       # Frontend version
+  .short  0
+  .short  0
+  .short  0
+  .short  9000                    # Backend version
+  .short  0
+  .short  0
+  .short  0
+  .asciz  "clang version 9.0.0 ([e-mail]:llvm/llvm-project.git aa762a56caf3ef2b0b41c501e66d3ef32903a2d0)" # Null-terminated compiler version string
+  .p2align  2
+.Ltmp8:
+.Ltmp6:
+  .p2align  2
+  .long 246                     # Inlinee lines subsection
+  .long .Ltmp10-.Ltmp9          # Subsection size
+.Ltmp9:
+  .long 1                       # Inlinee lines signature, extra files
+
+                                        # Inlined function inlinee_1 starts at t.c:7
+  .long 4098                    # Type index of inlined function
+  .cv_filechecksumoffset  1       # Offset into filechecksum table
+  .long 7                       # Starting line number
+  .long 2
+  .cv_filechecksumoffset  2       # Offset into filechecksum table
+  .cv_filechecksumoffset  3       # Offset into filechecksum table
+
+.Ltmp10:
+  .p2align  2
+  .section  .debug$S,"dr",associative,main
+  .p2align  2
+  .long 4                       # Debug section magic
+  .long 241                     # Symbol subsection for main
+  .long .Ltmp12-.Ltmp11         # Subsection size
+.Ltmp11:
+  .short  .Ltmp14-.Ltmp13         # Record length
+.Ltmp13:
+  .short  4423                    # Record kind: S_GPROC32_ID
+  .long 0                       # PtrParent
+  .long 0                       # PtrEnd
+  .long 0                       # PtrNext
+  .long .Lfunc_end0-main        # Code size
+  .long 0                       # Offset after prologue
+  .long 0                       # Offset before epilogue
+  .long 4101                    # Function type index
+  .secrel32 main            # Function section relative address
+  .secidx main                    # Function section index
+  .byte 0                       # Flags
+  .asciz  "main"                  # Function name
+  .p2align  2
+.Ltmp14:
+  .short  .Ltmp16-.Ltmp15         # Record length
+.Ltmp15:
+  .short  4114                    # Record kind: S_FRAMEPROC
+  .long 0                       # FrameSize
+  .long 0                       # Padding
+  .long 0                       # Offset of padding
+  .long 0                       # Bytes of callee saved registers
+  .long 0                       # Exception handler offset
+  .short  0                       # Exception handler section
+  .long 0                       # Flags (defines frame register)
+  .p2align  2
+.Ltmp16:
+  .short  .Ltmp18-.Ltmp17         # Record length
+.Ltmp17:
+  .short  4429                    # Record kind: S_INLINESITE
+  .long 0                       # PtrParent
+  .long 0                       # PtrEnd
+  .long 4098                    # Inlinee type index
+  .cv_inline_linetable  1 1 7 .Lfunc_begin0 .Lfunc_end0
+  .p2align  2
+.Ltmp18:
+  .short  2                       # Record length
+  .short  4430                    # Record kind: S_INLINESITE_END
+  .short  2                       # Record length
+  .short  4431                    # Record kind: S_PROC_ID_END
+.Ltmp12:
+  .p2align  2
+  .cv_linetable 0, main, .Lfunc_end0
+  .section  .debug$S,"dr"
+  .long 241                     # Symbol subsection for globals
+  .long .Ltmp22-.Ltmp21         # Subsection size
+.Ltmp21:
+  .short  .Ltmp24-.Ltmp23         # Record length
+.Ltmp23:
+  .short  4365                    # Record kind: S_GDATA32
+  .long 4102                    # Type
+  .secrel32 x               # DataOffset
+  .secidx x                       # Segment
+  .asciz  "x"                     # Name
+  .p2align  2
+.Ltmp24:
+.Ltmp22:
+  .p2align  2
+  .cv_filechecksums               # File index to string table offset subsection
+  .cv_stringtable                 # String table
+  .long 241
+  .long .Ltmp26-.Ltmp25         # Subsection size
+.Ltmp25:
+  .short  .Ltmp28-.Ltmp27         # Record length
+.Ltmp27:
+  .short  4428                    # Record kind: S_BUILDINFO
+  .long 4105                    # LF_BUILDINFO index
+  .p2align  2
+.Ltmp28:
+.Ltmp26:
+  .p2align  2
+  .section  .debug$T,"dr"
+  .p2align  2
+  .long 4                       # Debug section magic
+  # ArgList (0x1000) {
+  #   TypeLeafKind: LF_ARGLIST (0x1201)
+  #   NumArgs: 0
+  #   Arguments [
+  #   ]
+  # }
+  .byte 0x06, 0x00, 0x01, 0x12
+  .byte 0x00, 0x00, 0x00, 0x00
+  # Procedure (0x1001) {
+  #   TypeLeafKind: LF_PROCEDURE (0x1008)
+  #   ReturnType: void (0x3)
+  #   CallingConvention: NearC (0x0)
+  #   FunctionOptions [ (0x0)
+  #   ]
+  #   NumParameters: 0
+  #   ArgListType: () (0x1000)
+  # }
+  .byte 0x0e, 0x00, 0x08, 0x10
+  .byte 0x03, 0x00, 0x00, 0x00
+  .byte 0x00, 0x00, 0x00, 0x00
+  .byte 0x00, 0x10, 0x00, 0x00
+  # FuncId (0x1002) {
+  #   TypeLeafKind: LF_FUNC_ID (0x1601)
+  #   ParentScope: 0x0
+  #   FunctionType: void () (0x1001)
+  #   Name: inlinee_1
+  # }
+  .byte 0x16, 0x00, 0x01, 0x16
+  .byte 0x00, 0x00, 0x00, 0x00
+  .byte 0x01, 0x10, 0x00, 0x00
+  .byte 0x69, 0x6e, 0x6c, 0x69
+  .byte 0x6e, 0x65, 0x65, 0x5f
+  .byte 0x31, 0x00, 0xf2, 0xf1
+  # FuncId (0x1003) {
+  #   TypeLeafKind: LF_FUNC_ID (0x1601)
+  #   ParentScope: 0x0
+  #   FunctionType: void () (0x1001)
+  #   Name: inlinee_2
+  # }
+  .byte 0x16, 0x00, 0x01, 0x16
+  .byte 0x00, 0x00, 0x00, 0x00
+  .byte 0x01, 0x10, 0x00, 0x00
+  .byte 0x69, 0x6e, 0x6c, 0x69
+  .byte 0x6e, 0x65, 0x65, 0x5f
+  .byte 0x32, 0x00, 0xf2, 0xf1
+  # Procedure (0x1004) {
+  #   TypeLeafKind: LF_PROCEDURE (0x1008)
+  #   ReturnType: int (0x74)
+  #   CallingConvention: NearC (0x0)
+  #   FunctionOptions [ (0x0)
+  #   ]
+  #   NumParameters: 0
+  #   ArgListType: () (0x1000)
+  # }
+  .byte 0x0e, 0x00, 0x08, 0x10
+  .byte 0x74, 0x00, 0x00, 0x00
+  .byte 0x00, 0x00, 0x00, 0x00
+  .byte 0x00, 0x10, 0x00, 0x00
+  # FuncId (0x1005) {
+  #   TypeLeafKind: LF_FUNC_ID (0x1601)
+  #   ParentScope: 0x0
+  #   FunctionType: int () (0x1004)
+  #   Name: main
+  # }
+  .byte 0x12, 0x00, 0x01, 0x16
+  .byte 0x00, 0x00, 0x00, 0x00
+  .byte 0x04, 0x10, 0x00, 0x00
+  .byte 0x6d, 0x61, 0x69, 0x6e
+  .byte 0x00, 0xf3, 0xf2, 0xf1
+  # Modifier (0x1006) {
+  #   TypeLeafKind: LF_MODIFIER (0x1001)
+  #   ModifiedType: int (0x74)
+  #   Modifiers [ (0x2)
+  #     Volatile (0x2)
+  #   ]
+  # }
+  .byte 0x0a, 0x00, 0x01, 0x10
+  .byte 0x74, 0x00, 0x00, 0x00
+  .byte 0x02, 0x00, 0xf2, 0xf1
+  # StringId (0x1007) {
+  #   TypeLeafKind: LF_STRING_ID (0x1605)
+  #   Id: 0x0
+  #   StringData: C:\src\llvm-project\build
+  # }
+  .byte 0x22, 0x00, 0x05, 0x16
+  .byte 0x00, 0x00, 0x00, 0x00
+  .byte 0x43, 0x3a, 0x5c, 0x73
+  .byte 0x72, 0x63, 0x5c, 0x6c
+  .byte 0x6c, 0x76, 0x6d, 0x2d
+  .byte 0x70, 0x72, 0x6f, 0x6a
+  .byte 0x65, 0x63, 0x74, 0x5c
+  .byte 0x62, 0x75, 0x69, 0x6c
+  .byte 0x64, 0x00, 0xf2, 0xf1
+  # StringId (0x1008) {
+  #   TypeLeafKind: LF_STRING_ID (0x1605)
+  #   Id: 0x0
+  #   StringData: t.c
+  # }
+  .byte 0x0a, 0x00, 0x05, 0x16
+  .byte 0x00, 0x00, 0x00, 0x00
+  .byte 0x74, 0x2e, 0x63, 0x00
+  # BuildInfo (0x1009) {
+  #   TypeLeafKind: LF_BUILDINFO (0x1603)
+  #   NumArgs: 5
+  #   Arguments [
+  #     ArgType: C:\src\llvm-project\build (0x1007)
+  #     ArgType: 0x0
+  #     ArgType: t.c (0x1008)
+  #     ArgType: 0x0
+  #     ArgType: 0x0
+  #   ]
+  # }
+  .byte 0x1a, 0x00, 0x03, 0x16
+  .byte 0x05, 0x00, 0x07, 0x10
+  .byte 0x00, 0x00, 0x00, 0x00
+  .byte 0x00, 0x00, 0x08, 0x10
+  .byte 0x00, 0x00, 0x00, 0x00
+  .byte 0x00, 0x00, 0x00, 0x00
+  .byte 0x00, 0x00, 0xf2, 0xf1
+
+  .addrsig
+  .addrsig_sym x

lld/test/COFF/pdb-inlinees.s

+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj %s -o %t.obj -triple x86_64-windows-msvc
+# RUN: lld-link -entry:main -nodefaultlib %t.obj -out:%t.exe -pdb:%t.pdb -debug
+# RUN: llvm-pdbutil dump -il %t.pdb | FileCheck %s
+
+# Compiled from this C code, with modifications to test multiple file checksums:
+# volatile int x;
+# static __forceinline void inlinee_2(void) {
+#   ++x;
+#   __debugbreak();
+#   ++x;
+# }
+# static __forceinline void inlinee_1(void) {
+#   ++x;
+#   inlinee_2();
+#   ++x;
+# }
+# int main() {
+#   ++x;
+#   inlinee_1();
+#   ++x;
+#   return x;
+# }
+
+# CHECK:                             Inlinee Lines
+# CHECK:      Mod 0000 | `{{.*}}pdb-inlinees.s.tmp.obj`:
+# CHECK-NEXT:  Inlinee |  Line | Source File
+# CHECK-NEXT:   0x1000 |     7 | C:\src\llvm-project\build\t.c (MD5: A79D837C976E9F0463A474D74E2EE9E7)
+# CHECK-NEXT:   0x1001 |     2 | C:\src\llvm-project\build\file2.h (MD5: FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF)
+
+  .text
+  .def   @feat.00;
+  .scl  3;
+  .type 0;
+  .endef
+  .globl  @feat.00
+.set @feat.00, 0
+  .intel_syntax noprefix
+  .file "t.c"
+  .def   main;
+  .scl  2;
+  .type 32;
+  .endef
+  .section  .text,"xr",one_only,main
+  .globl  main                    # -- Begin function main
+main:                                   # @main
+.Lfunc_begin0:
+  .cv_func_id 0
+# %bb.0:                                # %entry
+  .cv_file  1 "C:\\src\\llvm-project\\build\\t.c" "A79D837C976E9F0463A474D74E2EE9E7" 1
+  .cv_file  2 "C:\\src\\llvm-project\\build\\file2.h" "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF" 1
+  .cv_loc 0 1 13 0                # t.c:13:0
+  inc dword ptr [rip + x]
+.Ltmp0:
+  .cv_inline_site_id 1 within 0 inlined_at 1 14 0
+  .cv_loc 1 1 8 0                 # t.c:8:0
+  inc dword ptr [rip + x]
+.Ltmp1:
+  .cv_inline_site_id 2 within 1 inlined_at 1 9 0
+  .cv_loc 2 2 3 0                 # file2.h:3:0
+  inc dword ptr [rip + x]
+  .cv_loc 2 2 4 0                 # file2.h:4:0
+  int3
+  .cv_loc 2 2 5 0                 # file2.h:5:0
+  inc dword ptr [rip + x]
+.Ltmp2:
+  .cv_loc 1 1 10 0                # t.c:10:0
+  inc dword ptr [rip + x]
+.Ltmp3:
+  .cv_loc 0 1 15 0                # t.c:15:0
+  inc dword ptr [rip + x]
+  .cv_loc 0 1 16 0                # t.c:16:0
+  mov  eax, dword ptr [rip + x]
+  ret
+.Ltmp4:
+.Lfunc_end0:
+                                        # -- End function
+  .comm x,4,2                   # @x
+  .section  .debug$S,"dr"
+  .p2align  2
+  .long 4                       # Debug section magic
+  .long 241
+  .long .Ltmp6-.Ltmp5           # Subsection size
+.Ltmp5:
+  .short  .Ltmp8-.Ltmp7           # Record length
+.Ltmp7:
+  .short  4412                    # Record kind: S_COMPILE3
+  .long 0                       # Flags and language
+  .short  208                     # CPUType
+  .short  9                       # Frontend version
+  .short  0
+  .short  0
+  .short  0
+  .short  9000                    # Backend version
+  .short  0
+  .short  0
+  .short  0
+  .asciz  "clang version 9.0.0 ([e-mail]:llvm/llvm-project.git aa762a56caf3ef2b0b41c501e66d3ef32903a2d0)" # Null-terminated compiler version string
+  .p2align  2
+.Ltmp8:
+.Ltmp6:
+  .p2align  2
+  .long 246                     # Inlinee lines subsection
+  .long .Ltmp10-.Ltmp9          # Subsection size
+.Ltmp9:
+  .long 0                       # Inlinee lines signature
+
+                                        # Inlined function inlinee_1 starts at t.c:7
+  .long 4098                    # Type index of inlined function
+  .cv_filechecksumoffset  1       # Offset into filechecksum table
+  .long 7                       # Starting line number
+
+                                        # Inlined function inlinee_2 starts at file2.h:2
+  .long 4099                    # Type index of inlined function
+  .cv_filechecksumoffset  2       # Offset into filechecksum table
+  .long 2                       # Starting line number
+.Ltmp10:
+  .p2align  2
+  .section  .debug$S,"dr",associative,main
+  .p2align  2
+  .long 4                       # Debug section magic
+  .long 241                     # Symbol subsection for main
+  .long .Ltmp12-.Ltmp11         # Subsection size
+.Ltmp11:
+  .short  .Ltmp14-.Ltmp13         # Record length
+.Ltmp13:
+  .short  4423                    # Record kind: S_GPROC32_ID
+  .long 0                       # PtrParent
+  .long 0                       # PtrEnd
+  .long 0                       # PtrNext
+  .long .Lfunc_end0-main        # Code size
+  .long 0                       # Offset after prologue
+  .long 0                       # Offset before epilogue
+  .long 4101                    # Function type index
+  .secrel32 main            # Function section relative address
+  .secidx main                    # Function section index
+  .byte 0                       # Flags
+  .asciz  "main"                  # Function name
+  .p2align  2
+.Ltmp14:
+  .short  .Ltmp16-.Ltmp15         # Record length
+.Ltmp15:
+  .short  4114                    # Record kind: S_FRAMEPROC
+  .long 0                       # FrameSize
+  .long 0                       # Padding
+  .long 0                       # Offset of padding
+  .long 0                       # Bytes of callee saved registers
+  .long 0                       # Exception handler offset
+  .short  0                       # Exception handler section
+  .long 0                       # Flags (defines frame register)
+  .p2align  2
+.Ltmp16:
+  .short  .Ltmp18-.Ltmp17         # Record length
+.Ltmp17:
+  .short  4429                    # Record kind: S_INLINESITE
+  .long 0                       # PtrParent
+  .long 0                       # PtrEnd
+  .long 4098                    # Inlinee type index
+  .cv_inline_linetable  1 1 7 .Lfunc_begin0 .Lfunc_end0
+  .p2align  2
+.Ltmp18:
+  .short  .Ltmp20-.Ltmp19         # Record length
+.Ltmp19:
+  .short  4429                    # Record kind: S_INLINESITE
+  .long 0                       # PtrParent
+  .long 0                       # PtrEnd
+  .long 4099                    # Inlinee type index
+  .cv_inline_linetable  2 2 2 .Lfunc_begin0 .Lfunc_end0
+  .p2align  2
+.Ltmp20:
+  .short  2                       # Record length
+  .short  4430                    # Record kind: S_INLINESITE_END
+  .short  2                       # Record length
+  .short  4430                    # Record kind: S_INLINESITE_END
+  .short  2                       # Record length
+  .short  4431                    # Record kind: S_PROC_ID_END
+.Ltmp12:
+  .p2align  2
+  .cv_linetable 0, main, .Lfunc_end0
+  .section  .debug$S,"dr"
+  .long 241                     # Symbol subsection for globals
+  .long .Ltmp22-.Ltmp21         # Subsection size
+.Ltmp21:
+  .short  .Ltmp24-.Ltmp23         # Record length
+.Ltmp23:
+  .short  4365                    # Record kind: S_GDATA32
+  .long 4102                    # Type
+  .secrel32 x               # DataOffset
+  .secidx x                       # Segment
+  .asciz  "x"                     # Name
+  .p2align  2
+.Ltmp24:
+.Ltmp22:
+  .p2align  2
+  .cv_filechecksums               # File index to string table offset subsection
+  .cv_stringtable                 # String table
+  .long 241
+  .long .Ltmp26-.Ltmp25         # Subsection size
+.Ltmp25:
+  .short  .Ltmp28-.Ltmp27         # Record length
+.Ltmp27:
+  .short  4428                    # Record kind: S_BUILDINFO
+  .long 4105                    # LF_BUILDINFO index
+  .p2align  2
+.Ltmp28:
+.Ltmp26:
+  .p2align  2
+  .section  .debug$T,"dr"
+  .p2align  2
+  .long 4                       # Debug section magic
+  # ArgList (0x1000) {
+  #   TypeLeafKind: LF_ARGLIST (0x1201)
+  #   NumArgs: 0
+  #   Arguments [
+  #   ]
+  # }
+  .byte 0x06, 0x00, 0x01, 0x12
+  .byte 0x00, 0x00, 0x00, 0x00
+  # Procedure (0x1001) {
+  #   TypeLeafKind: LF_PROCEDURE (0x1008)
+  #   ReturnType: void (0x3)
+  #   CallingConvention: NearC (0x0)
+  #   FunctionOptions [ (0x0)
+  #   ]
+  #   NumParameters: 0
+  #   ArgListType: () (0x1000)
+  # }
+  .byte 0x0e, 0x00, 0x08, 0x10
+  .byte 0x03, 0x00, 0x00, 0x00
+  .byte 0x00, 0x00, 0x00, 0x00
+  .byte 0x00, 0x10, 0x00, 0x00
+  # FuncId (0x1002) {
+  #   TypeLeafKind: LF_FUNC_ID (0x1601)
+  #   ParentScope: 0x0
+  #   FunctionType: void () (0x1001)
+  #   Name: inlinee_1
+  # }
+  .byte 0x16, 0x00, 0x01, 0x16
+  .byte 0x00, 0x00, 0x00, 0x00
+  .byte 0x01, 0x10, 0x00, 0x00
+  .byte 0x69, 0x6e, 0x6c, 0x69
+  .byte 0x6e, 0x65, 0x65, 0x5f
+  .byte 0x31, 0x00, 0xf2, 0xf1
+  # FuncId (0x1003) {
+  #   TypeLeafKind: LF_FUNC_ID (0x1601)
+  #   ParentScope: 0x0
+  #   FunctionType: void () (0x1001)
+  #   Name: inlinee_2
+  # }
+  .byte 0x16, 0x00, 0x01, 0x16
+  .byte 0x00, 0x00, 0x00, 0x00
+  .byte 0x01, 0x10, 0x00, 0x00
+  .byte 0x69, 0x6e, 0x6c, 0x69
+  .byte 0x6e, 0x65, 0x65, 0x5f
+  .byte 0x32, 0x00, 0xf2, 0xf1
+  # Procedure (0x1004) {
+  #   TypeLeafKind: LF_PROCEDURE (0x1008)
+  #   ReturnType: int (0x74)
+  #   CallingConvention: NearC (0x0)
+  #   FunctionOptions [ (0x0)
+  #   ]
+  #   NumParameters: 0
+  #   ArgListType: () (0x1000)
+  # }
+  .byte 0x0e, 0x00, 0x08, 0x10
+  .byte 0x74, 0x00, 0x00, 0x00
+  .byte 0x00, 0x00, 0x00, 0x00
+  .byte 0x00, 0x10, 0x00, 0x00
+  # FuncId (0x1005) {
+  #   TypeLeafKind: LF_FUNC_ID (0x1601)
+  #   ParentScope: 0x0
+  #   FunctionType: int () (0x1004)
+  #   Name: main
+  # }
+  .byte 0x12, 0x00, 0x01, 0x16
+  .byte 0x00, 0x00, 0x00, 0x00
+  .byte 0x04, 0x10, 0x00, 0x00
+  .byte 0x6d, 0x61, 0x69, 0x6e
+  .byte 0x00, 0xf3, 0xf2, 0xf1
+  # Modifier (0x1006) {
+  #   TypeLeafKind: LF_MODIFIER (0x1001)
+  #   ModifiedType: int (0x74)
+  #   Modifiers [ (0x2)
+  #     Volatile (0x2)
+  #   ]
+  # }
+  .byte 0x0a, 0x00, 0x01, 0x10
+  .byte 0x74, 0x00, 0x00, 0x00
+  .byte 0x02, 0x00, 0xf2, 0xf1
+  # StringId (0x1007) {
+  #   TypeLeafKind: LF_STRING_ID (0x1605)
+  #   Id: 0x0
+  #   StringData: C:\src\llvm-project\build
+  # }
+  .byte 0x22, 0x00, 0x05, 0x16
+  .byte 0x00, 0x00, 0x00, 0x00
+  .byte 0x43, 0x3a, 0x5c, 0x73
+  .byte 0x72, 0x63, 0x5c, 0x6c
+  .byte 0x6c, 0x76, 0x6d, 0x2d
+  .byte 0x70, 0x72, 0x6f, 0x6a
+  .byte 0x65, 0x63, 0x74, 0x5c
+  .byte 0x62, 0x75, 0x69, 0x6c
+  .byte 0x64, 0x00, 0xf2, 0xf1
+  # StringId (0x1008) {
+  #   TypeLeafKind: LF_STRING_ID (0x1605)
+  #   Id: 0x0
+  #   StringData: t.c
+  # }
+  .byte 0x0a, 0x00, 0x05, 0x16
+  .byte 0x00, 0x00, 0x00, 0x00
+  .byte 0x74, 0x2e, 0x63, 0x00
+  # BuildInfo (0x1009) {
+  #   TypeLeafKind: LF_BUILDINFO (0x1603)
+  #   NumArgs: 5
+  #   Arguments [
+  #     ArgType: C:\src\llvm-project\build (0x1007)
+  #     ArgType: 0x0
+  #     ArgType: t.c (0x1008)
+  #     ArgType: 0x0
+  #     ArgType: 0x0
+  #   ]
+  # }
+  .byte 0x1a, 0x00, 0x03, 0x16
+  .byte 0x05, 0x00, 0x07, 0x10
+  .byte 0x00, 0x00, 0x00, 0x00
+  .byte 0x00, 0x00, 0x08, 0x10
+  .byte 0x00, 0x00, 0x00, 0x00
+  .byte 0x00, 0x00, 0x00, 0x00
+  .byte 0x00, 0x00, 0xf2, 0xf1
+
+  .addrsig
+  .addrsig_sym x

lld/test/COFF/pdb-unknown-subsection.s

+# Check that unknown symbol subsections are ignored with a warning, and a PDB
+# is produced anyway.
+
+# REQUIRES: x86
+# RUN: llvm-mc -triple=i386-pc-win32 -filetype=obj -o %t.obj %s
+# RUN: lld-link -subsystem:console -debug -nodefaultlib -entry:foo -out:%t.exe -pdb:%t.pdb %t.obj 2>&1 | FileCheck %s --check-prefix=WARNING
+# RUN: llvm-pdbutil dump -symbols %t.pdb | FileCheck %s
+
+# WARNING: ignoring unknown debug$S subsection kind 0xFF
+
+# CHECK:                           Symbols
+# CHECK:        4 | S_COMPILE3 [size = 52]
+# CHECK:            machine = intel x86-x64, Ver = clang verison SENTINEL, language = c
+
+.text
+_foo:
+ret
+
+.global _foo
+
+.section .debug$S,"dr"
+  .p2align  2
+  .long 4                       # Debug section magic
+  .long 0xF1 # Symbol subsection
+  .long .Ltmp6-.Ltmp5           # Subsection size
+.Ltmp5:
+  .short  .Ltmp8-.Ltmp7           # Record length
+.Ltmp7:
+  .short  4412                    # Record kind: S_COMPILE3
+  .long 0                       # Flags and language
+  .short  208                     # CPUType
+  .short  9                       # Frontend version
+  .short  0
+  .short  0
+  .short  0
+  .short  9000                    # Backend version
+  .short  0
+  .short  0
+  .short  0
+  .asciz  "clang verison SENTINEL" # Null-terminated compiler version string
+  .p2align  2
+.Ltmp8:
+.Ltmp6:
+  .long 0xFF # Unknown subsection kind
+  .long 4           # Subsection size
+  .long  0

llvm/include/llvm/DebugInfo/CodeView/DebugInlineeLinesSubsection.h

 public:
   DebugInlineeLinesSubsectionRef();
 
   static bool classof(const DebugSubsectionRef *S) {
     return S->kind() == DebugSubsectionKind::InlineeLines;
   }
 
   Error initialize(BinaryStreamReader Reader);
+  Error initialize(BinaryStreamRef Section) {
+    return initialize(BinaryStreamReader(Section));
+  }
+
+  bool valid() const { return Lines.valid(); }
   bool hasExtraFiles() const;
 
   Iterator begin() const { return Lines.begin(); }
   Iterator end() const { return Lines.end(); }
 
 private:
   InlineeLinesSignature Signature;
-  VarStreamArray<InlineeSourceLine> Lines;
+  LinesArray Lines;
 };
 
 class DebugInlineeLinesSubsection final : public DebugSubsection {
 public:
   struct Entry {
     std::vector<support::ulittle32_t> ExtraFiles;
     InlineeSourceLineHeader Header;
   };

llvm/tools/llvm-pdbutil/DumpOutputStyle.cpp

iterateModuleSubsections<DebugInlineeLinesSubsectionRef>(
       File, PrintScope{P, 2},
       [this](uint32_t Modi, const SymbolGroup &Strings,
              DebugInlineeLinesSubsectionRef &Lines) {
         P.formatLine("{0,+8} | {1,+5} | {2}", "Inlinee", "Line", "Source File");
         for (const auto &Entry : Lines) {
           P.formatLine("{0,+8} | {1,+5} | ", Entry.Header->Inlinee,
                        fmtle(Entry.Header->SourceLineNum));
           Strings.formatFromChecksumsOffset(P, Entry.Header->FileID, true);
+          for (const auto &ExtraFileID : Entry.ExtraFiles) {
+            P.formatLine("                   ");
+            Strings.formatFromChecksumsOffset(P, ExtraFileID, true);
+          }
         }
         P.NewLine();
       });
 
   return Error::success();
 }
 
 Error DumpOutputStyle::dumpXmi() {