[PDB] Add symbols to the PDB

Summary:
The main complexity in adding symbol records is that we need to
"relocate" all the type indices. Type indices do not have anything like
relocations, an opaque data structure describing where to find existing
type indices for fixups. The linker just has to "know" where the type
references are in the symbol records. I added an overload of
`discoverTypeIndices` that works on symbol records, and it seems to be
able to link the standard library.

Reviewers: zturner, ruiu

Subscribers: llvm-commits, hiraditya

Differential Revision: https://reviews.llvm.org/D34432

llvm-svn: 305933

6 files changed, 659 insertions, 10 deletions

diff --git a/lld/COFF/PDB.cpp b/lld/COFF/PDB.cpp
index 81ef6af6e1b..c9842cfd1b9 100644
--- a/lld/COFF/PDB.cpp
+++ b/lld/COFF/PDB.cpp
@@ -18,8 +18,8 @@
 #include "llvm/DebugInfo/CodeView/DebugSubsectionRecord.h"
 #include "llvm/DebugInfo/CodeView/DebugSubsectionVisitor.h"
 #include "llvm/DebugInfo/CodeView/LazyRandomTypeCollection.h"
-#include "llvm/DebugInfo/CodeView/SymbolDumper.h"
 #include "llvm/DebugInfo/CodeView/TypeDumpVisitor.h"
+#include "llvm/DebugInfo/CodeView/TypeIndexDiscovery.h"
 #include "llvm/DebugInfo/CodeView/TypeStreamMerger.h"
 #include "llvm/DebugInfo/CodeView/TypeTableBuilder.h"
 #include "llvm/DebugInfo/MSF/MSFBuilder.h"
@@ -115,6 +115,101 @@ static void mergeDebugT(ObjectFile *File,
     fatal(Err, "codeview::mergeTypeStreams failed");
 }
 
+static bool remapTypeIndex(TypeIndex &TI, ArrayRef<TypeIndex> TypeIndexMap) {
+  if (TI.isSimple())
+    return true;
+  if (TI.toArrayIndex() >= TypeIndexMap.size())
+    return false;
+  TI = TypeIndexMap[TI.toArrayIndex()];
+  return true;
+}
+
+static bool remapTypesInSymbolRecord(ObjectFile *File,
+                                     MutableArrayRef<uint8_t> Contents,
+                                     ArrayRef<TypeIndex> TypeIndexMap,
+                                     ArrayRef<TiReference> TypeRefs) {
+  for (const TiReference &Ref : TypeRefs) {
+    unsigned ByteSize = Ref.Count * sizeof(TypeIndex);
+    if (Contents.size() < Ref.Offset + ByteSize) {
+      log("ignoring short symbol record");
+      return false;
+    }
+    MutableArrayRef<TypeIndex> TIs(
+        reinterpret_cast<TypeIndex *>(Contents.data() + Ref.Offset), Ref.Count);
+    for (TypeIndex &TI : TIs)
+      if (!remapTypeIndex(TI, TypeIndexMap)) {
+        log("ignoring symbol record in " + File->getName() +
+            " with bad type index 0x" + utohexstr(TI.getIndex()));
+        return false;
+      }
+  }
+  return true;
+}
+
+/// MSVC translates S_PROC_ID_END to S_END.
+uint16_t canonicalizeSymbolKind(SymbolKind Kind) {
+  if (Kind == SymbolKind::S_PROC_ID_END)
+    return SymbolKind::S_END;
+  return Kind;
+}
+
+/// Copy the symbol record. In a PDB, symbol records must be 4 byte aligned.
+/// The object file may not be aligned.
+static MutableArrayRef<uint8_t> copySymbolForPdb(const CVSymbol &Sym,
+                                                 BumpPtrAllocator &Alloc) {
+  size_t Size = alignTo(Sym.length(), alignOf(CodeViewContainer::Pdb));
+  assert(Size >= 4 && "record too short");
+  assert(Size <= MaxRecordLength && "record too long");
+  void *Mem = Alloc.Allocate(Size, 4);
+
+  // Copy the symbol record and zero out any padding bytes.
+  MutableArrayRef<uint8_t> NewData(reinterpret_cast<uint8_t *>(Mem), Size);
+  memcpy(NewData.data(), Sym.data().data(), Sym.length());
+  memset(NewData.data() + Sym.length(), 0, Size - Sym.length());
+
+  // Update the record prefix length. It should point to the beginning of the
+  // next record. MSVC does some canonicalization of the record kind, so we do
+  // that as well.
+  auto *Prefix = reinterpret_cast<RecordPrefix *>(Mem);
+  Prefix->RecordKind = canonicalizeSymbolKind(Sym.kind());
+  Prefix->RecordLen = Size - 2;
+  return NewData;
+}
+
+static void mergeSymbolRecords(BumpPtrAllocator &Alloc, ObjectFile *File,
+                               ArrayRef<TypeIndex> TypeIndexMap,
+                               BinaryStreamRef SymData) {
+  // FIXME: Improve error recovery by warning and skipping records when
+  // possible.
+  CVSymbolArray Syms;
+  BinaryStreamReader Reader(SymData);
+  ExitOnErr(Reader.readArray(Syms, Reader.getLength()));
+  for (const CVSymbol &Sym : Syms) {
+    // Discover type index references in the record. Skip it if we don't know
+    // where they are.
+    SmallVector<TiReference, 32> TypeRefs;
+    if (!discoverTypeIndices(Sym, TypeRefs)) {
+      log("ignoring unknown symbol record with kind 0x" + utohexstr(Sym.kind()));
+      continue;
+    }
+
+    // Copy the symbol record so we can mutate it.
+    MutableArrayRef<uint8_t> NewData = copySymbolForPdb(Sym, Alloc);
+
+    // Re-map all the type index references.
+    MutableArrayRef<uint8_t> Contents =
+        NewData.drop_front(sizeof(RecordPrefix));
+    if (!remapTypesInSymbolRecord(File, Contents, TypeIndexMap, TypeRefs))
+      continue;
+
+    // FIXME: Fill in "Parent" and "End" fields by maintaining a stack of
+    // scopes.
+
+    // Add the symbol to the module.
+    File->ModuleDBI->addSymbol(CVSymbol(Sym.kind(), NewData));
+  }
+}
+
 // Allocate memory for a .debug$S section and relocate it.
 static ArrayRef<uint8_t> relocateDebugChunk(BumpPtrAllocator &Alloc,
                                             SectionChunk *DebugChunk) {
@@ -191,6 +286,9 @@ static void addObjectsToPDB(BumpPtrAllocator &Alloc, SymbolTable *Symtab,
           // modification because the file checksum offsets will stay the same.
           File->ModuleDBI->addDebugSubsection(SS);
           break;
+        case DebugSubsectionKind::Symbols:
+          mergeSymbolRecords(Alloc, File, TypeIndexMap, SS.getRecordData());
+          break;
         default:
           // FIXME: Process the rest of the subsections.
           break;
diff --git a/lld/test/COFF/pdb-comdat.test b/lld/test/COFF/pdb-comdat.test
index 0d036d350d0..1ccce3fefce 100644
--- a/lld/test/COFF/pdb-comdat.test
+++ b/lld/test/COFF/pdb-comdat.test
@@ -26,7 +26,7 @@ RUN: rm -rf %t && mkdir -p %t && cd %t
 RUN: yaml2obj %S/Inputs/pdb_comdat_main.yaml -o pdb_comdat_main.obj
 RUN: yaml2obj %S/Inputs/pdb_comdat_bar.yaml -o pdb_comdat_bar.obj
 RUN: lld-link pdb_comdat_main.obj pdb_comdat_bar.obj -out:t.exe -debug -pdb:t.pdb -nodefaultlib -entry:main
-RUN: llvm-pdbutil raw -l t.pdb | FileCheck %s
+RUN: llvm-pdbutil raw -l -symbols t.pdb | FileCheck %s
 
 CHECK:                            Lines
 CHECK: ============================================================
@@ -38,6 +38,54 @@ CHECK:       c:\src\llvm-project\build\pdb_comdat_bar.c (MD5: 365279DB4FCBEDD721
 CHECK-NOT:       c:\src\llvm-project\build\foo.h
 CHECK-LABEL:   Mod 0002 | `* Linker *`:
 
+CHECK:                           Symbols
+CHECK: ============================================================
+CHECK-LABEL:   Mod 0000 | `{{.*}}pdb_comdat_main.obj`:
+CHECK:   - S_OBJNAME [size = 56] sig=0, `C:\src\llvm-project\build\pdb_comdat_main.obj`
+CHECK:   - S_COMPILE3 [size = 60]
+CHECK:       machine = intel x86-x64, Ver = Microsoft (R) Optimizing Compiler, language = c
+CHECK:       frontend = 19.0.24215.1, backend = 19.0.24215.1
+CHECK:       flags = security checks | hot patchable
+CHECK:   - S_GPROC32_ID [size = 44] `main`
+    FIXME: We need to fill in "end".
+CHECK:       parent = 0, addr = 0002:0000, code size = 24, end = 0
+CHECK:       debug start = 4, debug end = 19, flags = none
+CHECK:   - S_FRAMEPROC [size = 32]
+CHECK:       size = 40, padding size = 0, offset to padding = 0
+CHECK:       bytes of callee saved registers = 0, exception handler addr = 0000:0000
+CHECK:       flags = has async eh | opt speed
+CHECK:   - S_END [size = 4]
+CHECK:   - S_GDATA32 [size = 24] `global`
+CHECK:       type = 0x0074 (int), addr = 0000:0000
+CHECK:   - S_BUILDINFO [size = 8] BuildId = `4106`
+CHECK:   - S_GPROC32_ID [size = 44] `foo`
+CHECK:       parent = 0, addr = 0002:0032, code size = 15, end = 0
+CHECK:       debug start = 0, debug end = 14, flags = none
+CHECK:   - S_FRAMEPROC [size = 32]
+CHECK:       size = 0, padding size = 0, offset to padding = 0
+CHECK:       bytes of callee saved registers = 0, exception handler addr = 0000:0000
+CHECK:       flags = marked inline | has async eh | opt speed
+CHECK:   - S_END [size = 4]
+CHECK-LABEL:   Mod 0001 | `{{.*}}pdb_comdat_bar.obj`:
+CHECK:   - S_OBJNAME [size = 56] sig=0, `C:\src\llvm-project\build\pdb_comdat_bar.obj`
+CHECK:   - S_COMPILE3 [size = 60]
+CHECK:       machine = intel x86-x64, Ver = Microsoft (R) Optimizing Compiler, language = c
+CHECK:       frontend = 19.0.24215.1, backend = 19.0.24215.1
+CHECK:       flags = security checks | hot patchable
+CHECK:   - S_GPROC32_ID [size = 44] `bar`
+CHECK:       parent = 0, addr = 0002:0048, code size = 14, end = 0
+CHECK:       debug start = 4, debug end = 9, flags = none
+CHECK:   - S_FRAMEPROC [size = 32]
+CHECK:       size = 40, padding size = 0, offset to padding = 0
+CHECK:       bytes of callee saved registers = 0, exception handler addr = 0000:0000
+CHECK:       flags = has async eh | opt speed
+CHECK:   - S_END [size = 4]
+CHECK:   - S_GDATA32 [size = 24] `global`
+CHECK:       type = 0x0074 (int), addr = 0000:0000
+CHECK:   - S_BUILDINFO [size = 8] BuildId = `4109`
+CHECK-NOT:   - S_GPROC32_ID {{.*}} `foo`
+CHECK-LABEL:   Mod 0002 | `* Linker *`:
+
 Reorder the object files and verify that the other table is selected.
 
 RUN: lld-link pdb_comdat_bar.obj pdb_comdat_main.obj -out:t.exe -debug -pdb:t.pdb -nodefaultlib -entry:main
diff --git a/lld/test/COFF/pdb-symbol-types.yaml b/lld/test/COFF/pdb-symbol-types.yaml
new file mode 100644
index 00000000000..590061953a3
--- /dev/null
+++ b/lld/test/COFF/pdb-symbol-types.yaml
@@ -0,0 +1,344 @@
+# RUN: yaml2obj %s -o %t.obj
+# RUN: lld-link %t.obj -nodefaultlib -entry:main -debug -out:%t.exe -pdb:%t.pdb
+# RUN: llvm-pdbutil raw -symbols %t.pdb | FileCheck %s
+
+# To regenerate the object file:
+# $ cat symbol-types.c
+# struct Foo { int x; };
+# typedef struct Foo UDT_Foo;
+# UDT_Foo global_foo = {42};
+# int main() { return global_foo.x; }
+# $ cl -c -Z7 symbol-types.c
+
+# Note that the type of 'global' goes from 0x1005 in the object file to 0x1004
+# in the PDB because the LF_FUNC_ID is moved to the id stream.
+
+# CHECK:                           Symbols
+# CHECK: ============================================================
+# CHECK-LABEL:   Mod 0000 | `C:\src\llvm-project\build\tools\lld\test\COFF\Output\pdb-symbol-types.yaml.tmp.obj`:
+# CHECK:   - S_OBJNAME [size = 52] sig=0, `C:\src\llvm-project\build\symbol-types.obj`
+# CHECK:   - S_COMPILE3 [size = 60]
+# CHECK:       machine = intel x86-x64, Ver = Microsoft (R) Optimizing Compiler, language = c
+# CHECK:       frontend = 19.0.24215.1, backend = 19.0.24215.1
+# CHECK:       flags = security checks | hot patchable
+# CHECK:   - S_GPROC32_ID [size = 44] `main`
+# CHECK:       parent = 0, addr = 0002:0000, code size = 7, end = 0
+# CHECK:       debug start = 0, debug end = 6, flags = none
+# CHECK:   - S_FRAMEPROC [size = 32]
+# CHECK:       size = 0, padding size = 0, offset to padding = 0
+# CHECK:       bytes of callee saved registers = 0, exception handler addr = 0000:0000
+# CHECK:       flags = has async eh | opt speed
+# CHECK:   - S_END [size = 4]
+# CHECK:   - S_GDATA32 [size = 28] `global_foo`
+# CHECK:       type = 0x1004 (Foo), addr = 0001:0000
+# CHECK:   - S_UDT [size = 16] `UDT_Foo`
+# CHECK:       original type = 0x1004
+# CHECK:   - S_UDT [size = 12] `Foo`
+# CHECK:       original type = 0x1004
+# CHECK:   - S_BUILDINFO [size = 8] BuildId = `4106`
+# CHECK-LABEL:   Mod 0001 | `* Linker *`:
+
+--- !COFF
+header:          
+  Machine:         IMAGE_FILE_MACHINE_AMD64
+  Characteristics: [  ]
+sections:        
+  - Name:            .drectve
+    Characteristics: [ IMAGE_SCN_LNK_INFO, IMAGE_SCN_LNK_REMOVE ]
+    Alignment:       1
+    SectionData:     2020202F44454641554C544C49423A224C4942434D5422202F44454641554C544C49423A224F4C444E414D45532220
+  - 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:      'C:\src\llvm-project\build\symbol-types.obj'
+          - Kind:            S_COMPILE3
+            Compile3Sym:     
+              Flags:           [ SecurityChecks, HotPatch ]
+              Machine:         X64
+              FrontendMajor:   19
+              FrontendMinor:   0
+              FrontendBuild:   24215
+              FrontendQFE:     1
+              BackendMajor:    19
+              BackendMinor:    0
+              BackendBuild:    24215
+              BackendQFE:      1
+              Version:         'Microsoft (R) Optimizing Compiler'
+      - !Symbols
+        Records:         
+          - Kind:            S_GPROC32_ID
+            ProcSym:         
+              CodeSize:        7
+              DbgStart:        0
+              DbgEnd:          6
+              FunctionType:    4098
+              Flags:           [  ]
+              DisplayName:     main
+          - Kind:            S_FRAMEPROC
+            FrameProcSym:    
+              TotalFrameBytes: 0
+              PaddingFrameBytes: 0
+              OffsetToPadding: 0
+              BytesOfCalleeSavedRegisters: 0
+              OffsetOfExceptionHandler: 0
+              SectionIdOfExceptionHandler: 0
+              Flags:           [ AsynchronousExceptionHandling, OptimizedForSpeed ]
+          - Kind:            S_PROC_ID_END
+            ScopeEndSym:     
+      - !Lines
+        CodeSize:        7
+        Flags:           [  ]
+        RelocOffset:     0
+        RelocSegment:    0
+        Blocks:          
+          - FileName:        'c:\src\llvm-project\build\symbol-types.c'
+            Lines:           
+              - Offset:          0
+                LineStart:       4
+                IsStatement:     true
+                EndDelta:        0
+              - Offset:          0
+                LineStart:       5
+                IsStatement:     true
+                EndDelta:        0
+              - Offset:          6
+                LineStart:       6
+                IsStatement:     true
+                EndDelta:        0
+            Columns:         
+      - !Symbols
+        Records:         
+          - Kind:            S_GDATA32
+            DataSym:         
+              Type:            4101
+              DisplayName:     global_foo
+          - Kind:            S_UDT
+            UDTSym:          
+              Type:            4101
+              UDTName:         UDT_Foo
+          - Kind:            S_UDT
+            UDTSym:          
+              Type:            4101
+              UDTName:         Foo
+      - !FileChecksums
+        Checksums:       
+          - FileName:        'c:\src\llvm-project\build\symbol-types.c'
+            Kind:            MD5
+            Checksum:        F833E1A4909FF6FEC5689A664F3BE725
+      - !StringTable
+        Strings:         
+          - 'c:\src\llvm-project\build\symbol-types.c'
+      - !Symbols
+        Records:         
+          - Kind:            S_BUILDINFO
+            BuildInfoSym:    
+              BuildId:         4111
+    Relocations:     
+      - VirtualAddress:  164
+        SymbolName:      main
+        Type:            IMAGE_REL_AMD64_SECREL
+      - VirtualAddress:  168
+        SymbolName:      main
+        Type:            IMAGE_REL_AMD64_SECTION
+      - VirtualAddress:  220
+        SymbolName:      main
+        Type:            IMAGE_REL_AMD64_SECREL
+      - VirtualAddress:  224
+        SymbolName:      main
+        Type:            IMAGE_REL_AMD64_SECTION
+      - VirtualAddress:  284
+        SymbolName:      global_foo
+        Type:            IMAGE_REL_AMD64_SECREL
+      - VirtualAddress:  288
+        SymbolName:      global_foo
+        Type:            IMAGE_REL_AMD64_SECTION
+  - Name:            '.debug$T'
+    Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_MEM_DISCARDABLE, IMAGE_SCN_MEM_READ ]
+    Alignment:       1
+    Types:           
+      - Kind:            LF_ARGLIST
+        ArgList:         
+          ArgIndices:      [ 0 ]
+      - Kind:            LF_PROCEDURE
+        Procedure:       
+          ReturnType:      116
+          CallConv:        NearC
+          Options:         [ None ]
+          ParameterCount:  0
+          ArgumentList:    4096
+      - Kind:            LF_FUNC_ID
+        FuncId:          
+          ParentScope:     0
+          FunctionType:    4097
+          Name:            main
+      - Kind:            LF_STRUCTURE
+        Class:           
+          MemberCount:     0
+          Options:         [ None, ForwardReference, HasUniqueName ]
+          FieldList:       0
+          Name:            Foo
+          UniqueName:      '.?AUFoo@@'
+          DerivationList:  0
+          VTableShape:     0
+          Size:            0
+      - Kind:            LF_FIELDLIST
+        FieldList:       
+          - Kind:            LF_MEMBER
+            DataMember:      
+              Attrs:           3
+              Type:            116
+              FieldOffset:     0
+              Name:            x
+      - Kind:            LF_STRUCTURE
+        Class:           
+          MemberCount:     1
+          Options:         [ None, HasUniqueName ]
+          FieldList:       4100
+          Name:            Foo
+          UniqueName:      '.?AUFoo@@'
+          DerivationList:  0
+          VTableShape:     0
+          Size:            4
+      - Kind:            LF_STRING_ID
+        StringId:        
+          Id:              0
+          String:          'c:\src\llvm-project\build\symbol-types.c'
+      - Kind:            LF_UDT_SRC_LINE
+        UdtSourceLine:   
+          UDT:             4101
+          SourceFile:      4102
+          LineNumber:      1
+      - Kind:            LF_STRING_ID
+        StringId:        
+          Id:              0
+          String:          'C:\src\llvm-project\build'
+      - Kind:            LF_STRING_ID
+        StringId:        
+          Id:              0
+          String:          'C:\PROGRA~2\MICROS~1.0\VC\Bin\amd64\cl.exe'
+      - Kind:            LF_STRING_ID
+        StringId:        
+          Id:              0
+          String:          '-c -Z7 -MT -IC:\PROGRA~2\MICROS~1.0\VC\include -IC:\PROGRA~2\MICROS~1.0\VC\atlmfc\include -IC:\PROGRA~2\WI3CF2~1\10\include\10.0.14393.0\ucrt -IC:\PROGRA~2\WI3CF2~1\10\include\10.0.14393.0\shared -IC:\PROGRA~2\WI3CF2~1\10\include\10.0.14393.0\um'
+      - Kind:            LF_SUBSTR_LIST
+        StringList:      
+          StringIndices:   [ 4106 ]
+      - Kind:            LF_STRING_ID
+        StringId:        
+          Id:              4107
+          String:          ' -IC:\PROGRA~2\WI3CF2~1\10\include\10.0.14393.0\winrt -TC -X'
+      - Kind:            LF_STRING_ID
+        StringId:        
+          Id:              0
+          String:          symbol-types.c
+      - Kind:            LF_STRING_ID
+        StringId:        
+          Id:              0
+          String:          'C:\src\llvm-project\build\vc140.pdb'
+      - Kind:            LF_BUILDINFO
+        BuildInfo:       
+          ArgIndices:      [ 4104, 4105, 4109, 4110, 4108 ]
+  - Name:            .data
+    Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_MEM_READ, IMAGE_SCN_MEM_WRITE ]
+    Alignment:       4
+    SectionData:     2A000000
+  - Name:            '.text$mn'
+    Characteristics: [ IMAGE_SCN_CNT_CODE, IMAGE_SCN_MEM_EXECUTE, IMAGE_SCN_MEM_READ ]
+    Alignment:       16
+    SectionData:     8B0500000000C3
+    Relocations:     
+      - VirtualAddress:  2
+        SymbolName:      global_foo
+        Type:            IMAGE_REL_AMD64_REL32
+symbols:         
+  - Name:            '@comp.id'
+    Value:           17063575
+    SectionNumber:   -1
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_STATIC
+  - Name:            '@feat.00'
+    Value:           2147484048
+    SectionNumber:   -1
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_STATIC
+  - Name:            .drectve
+    Value:           0
+    SectionNumber:   1
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_STATIC
+    SectionDefinition: 
+      Length:          47
+      NumberOfRelocations: 0
+      NumberOfLinenumbers: 0
+      CheckSum:        0
+      Number:          0
+  - Name:            '.debug$S'
+    Value:           0
+    SectionNumber:   2
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_STATIC
+    SectionDefinition: 
+      Length:          432
+      NumberOfRelocations: 6
+      NumberOfLinenumbers: 0
+      CheckSum:        0
+      Number:          0
+  - Name:            '.debug$T'
+    Value:           0
+    SectionNumber:   3
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_STATIC
+    SectionDefinition: 
+      Length:          732
+      NumberOfRelocations: 0
+      NumberOfLinenumbers: 0
+      CheckSum:        0
+      Number:          0
+  - Name:            .data
+    Value:           0
+    SectionNumber:   4
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_STATIC
+    SectionDefinition: 
+      Length:          4
+      NumberOfRelocations: 0
+      NumberOfLinenumbers: 0
+      CheckSum:        3482275674
+      Number:          0
+  - Name:            global_foo
+    Value:           0
+    SectionNumber:   4
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_EXTERNAL
+  - Name:            '.text$mn'
+    Value:           0
+    SectionNumber:   5
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_STATIC
+    SectionDefinition: 
+      Length:          7
+      NumberOfRelocations: 1
+      NumberOfLinenumbers: 0
+      CheckSum:        3635526833
+      Number:          0
+  - Name:            main
+    Value:           0
+    SectionNumber:   5
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_FUNCTION
+    StorageClass:    IMAGE_SYM_CLASS_EXTERNAL
+...
diff --git a/llvm/include/llvm/DebugInfo/CodeView/TypeIndexDiscovery.h b/llvm/include/llvm/DebugInfo/CodeView/TypeIndexDiscovery.h
index 82ceb503831..c393b42cd27 100644
--- a/llvm/include/llvm/DebugInfo/CodeView/TypeIndexDiscovery.h
+++ b/llvm/include/llvm/DebugInfo/CodeView/TypeIndexDiscovery.h
@@ -11,6 +11,7 @@
 #define LLVM_DEBUGINFO_CODEVIEW_TYPEINDEXDISCOVERY_H
 
 #include "llvm/ADT/SmallVector.h"
+#include "llvm/DebugInfo/CodeView/SymbolRecord.h"
 #include "llvm/DebugInfo/CodeView/TypeRecord.h"
 #include "llvm/Support/Error.h"
 
@@ -27,6 +28,11 @@ void discoverTypeIndices(ArrayRef<uint8_t> RecordData,
                          SmallVectorImpl<TiReference> &Refs);
 void discoverTypeIndices(const CVType &Type,
                          SmallVectorImpl<TiReference> &Refs);
+
+/// Discover type indices in symbol records. Returns false if this is an unknown
+/// record.
+bool discoverTypeIndices(const CVSymbol &Symbol,
+                         SmallVectorImpl<TiReference> &Refs);
 }
 }
 
diff --git a/llvm/lib/DebugInfo/CodeView/TypeIndexDiscovery.cpp b/llvm/lib/DebugInfo/CodeView/TypeIndexDiscovery.cpp
index 8704cea6078..1226d5be3f3 100644
--- a/llvm/lib/DebugInfo/CodeView/TypeIndexDiscovery.cpp
+++ b/llvm/lib/DebugInfo/CodeView/TypeIndexDiscovery.cpp
@@ -357,6 +357,82 @@ static void discoverTypeIndices(ArrayRef<uint8_t> Content, TypeLeafKind Kind,
   }
 }
 
+static bool discoverTypeIndices(ArrayRef<uint8_t> Content, SymbolKind Kind,
+                                SmallVectorImpl<TiReference> &Refs) {
+  uint32_t Count;
+  // FIXME: In the future it would be nice if we could avoid hardcoding these
+  // values.  One idea is to define some structures representing these types
+  // that would allow the use of offsetof().
+  switch (Kind) {
+  case SymbolKind::S_GPROC32:
+  case SymbolKind::S_LPROC32:
+  case SymbolKind::S_GPROC32_ID:
+  case SymbolKind::S_LPROC32_ID:
+  case SymbolKind::S_LPROC32_DPC:
+  case SymbolKind::S_LPROC32_DPC_ID:
+    Refs.push_back({TiRefKind::IndexRef, 24, 1}); // LF_FUNC_ID
+    break;
+  case SymbolKind::S_UDT:
+    Refs.push_back({TiRefKind::TypeRef, 0, 1}); // UDT
+    break;
+  case SymbolKind::S_GDATA32:
+  case SymbolKind::S_LDATA32:
+    Refs.push_back({TiRefKind::TypeRef, 0, 1}); // Type
+    break;
+  case SymbolKind::S_BUILDINFO:
+    Refs.push_back({TiRefKind::IndexRef, 0, 1}); // Compile flags
+    break;
+  case SymbolKind::S_LOCAL:
+    Refs.push_back({TiRefKind::TypeRef, 0, 1}); // Type
+    break;
+  case SymbolKind::S_CONSTANT:
+    Refs.push_back({TiRefKind::TypeRef, 0, 1}); // Type
+    break;
+  case SymbolKind::S_REGREL32:
+    Refs.push_back({TiRefKind::TypeRef, 4, 1}); // Type
+    break;
+  case SymbolKind::S_CALLSITEINFO:
+    Refs.push_back({TiRefKind::TypeRef, 8, 1}); // Call signature
+    break;
+  case SymbolKind::S_CALLERS:
+  case SymbolKind::S_CALLEES:
+    // The record is a count followed by an array of type indices.
+    Count = *reinterpret_cast<const ulittle32_t *>(Content.data());
+    Refs.push_back({TiRefKind::IndexRef, 4, Count}); // Callees
+    break;
+  case SymbolKind::S_INLINESITE:
+    Refs.push_back({TiRefKind::IndexRef, 8, 1}); // ID of inlinee
+    break;
+
+  // Defranges don't have types, just registers and code offsets.
+  case SymbolKind::S_DEFRANGE_REGISTER:
+  case SymbolKind::S_DEFRANGE_REGISTER_REL:
+  case SymbolKind::S_DEFRANGE_FRAMEPOINTER_REL:
+  case SymbolKind::S_DEFRANGE_FRAMEPOINTER_REL_FULL_SCOPE:
+  case SymbolKind::S_DEFRANGE_SUBFIELD_REGISTER:
+  case SymbolKind::S_DEFRANGE_SUBFIELD:
+    break;
+
+  // No type refernces.
+  case SymbolKind::S_LABEL32:
+  case SymbolKind::S_OBJNAME:
+  case SymbolKind::S_COMPILE:
+  case SymbolKind::S_COMPILE2:
+  case SymbolKind::S_COMPILE3:
+  case SymbolKind::S_BLOCK32:
+  case SymbolKind::S_FRAMEPROC:
+    break;
+  // Scope ending symbols.
+  case SymbolKind::S_END:
+  case SymbolKind::S_INLINESITE_END:
+  case SymbolKind::S_PROC_ID_END:
+    break;
+  default:
+    return false; // Unknown symbol.
+  }
+  return true;
+}
+
 void llvm::codeview::discoverTypeIndices(const CVType &Type,
                                          SmallVectorImpl<TiReference> &Refs) {
   ::discoverTypeIndices(Type.content(), Type.kind(), Refs);
@@ -369,3 +445,9 @@ void llvm::codeview::discoverTypeIndices(ArrayRef<uint8_t> RecordData,
   TypeLeafKind K = static_cast<TypeLeafKind>(uint16_t(P->RecordKind));
   ::discoverTypeIndices(RecordData.drop_front(sizeof(RecordPrefix)), K, Refs);
 }
+
+bool llvm::codeview::discoverTypeIndices(const CVSymbol &Sym,
+                                         SmallVectorImpl<TiReference> &Refs) {
+  SymbolKind K = Sym.kind();
+  return ::discoverTypeIndices(Sym.content(), K, Refs);
+}
diff --git a/llvm/unittests/DebugInfo/CodeView/TypeIndexDiscoveryTest.cpp b/llvm/unittests/DebugInfo/CodeView/TypeIndexDiscoveryTest.cpp
index 99c84906be9..fa9e9612318 100644
--- a/llvm/unittests/DebugInfo/CodeView/TypeIndexDiscoveryTest.cpp
+++ b/llvm/unittests/DebugInfo/CodeView/TypeIndexDiscoveryTest.cpp
@@ -10,6 +10,7 @@
 #include "llvm/DebugInfo/CodeView/TypeIndexDiscovery.h"
 
 #include "llvm/DebugInfo/CodeView/TypeTableBuilder.h"
+#include "llvm/DebugInfo/CodeView/SymbolSerializer.h"
 #include "llvm/Support/Allocator.h"
 
 #include "gmock/gmock.h"
@@ -26,6 +27,7 @@ public:
     Refs.clear();
     TTB = make_unique<TypeTableBuilder>(Storage);
     FLRB = make_unique<FieldListRecordBuilder>(*TTB);
+    Symbols.clear();
   }
 
   void TearDown() override {
@@ -37,7 +39,19 @@ protected:
   template <typename... Indices>
   bool checkTypeReferences(uint32_t RecordIndex, Indices &&... TIs) const {
     EXPECT_EQ(sizeof...(Indices), countRefs(RecordIndex));
-    return checkTypeReferencesImpl(RecordIndex, std::forward<Indices>(TIs)...);
+
+    // Choose between type or symbol records. The checking code doesn't care
+    // which we have.
+    std::vector<ArrayRef<uint8_t>> CVRecords;
+    if (Symbols.empty()) {
+      CVRecords = TTB->records();
+    } else {
+      for (const CVSymbol &S : Symbols)
+        CVRecords.push_back(S.data());
+    }
+
+    return checkTypeReferencesImpl(RecordIndex, CVRecords,
+                                   std::forward<Indices>(TIs)...);
   }
 
   template <typename... T> void writeFieldList(T &&... MemberRecords) {
@@ -54,6 +68,13 @@ protected:
     discoverAllTypeIndices();
   }
 
+  template <typename... T> void writeSymbolRecords(T &&... Records) {
+    writeSymbolRecordsImpl(std::forward<T>(Records)...);
+    ASSERT_EQ(sizeof...(T), Symbols.size());
+    discoverTypeIndicesInSymbols();
+  }
+
+
   std::unique_ptr<TypeTableBuilder> TTB;
 
 private:
@@ -83,18 +104,20 @@ private:
   }
 
   template <typename... Indices>
-  bool checkTypeReferencesImpl(uint32_t RecordIndex) const {
+  bool checkTypeReferencesImpl(uint32_t RecordIndex,
+                               ArrayRef<ArrayRef<uint8_t>> CVRecords) const {
     return true;
   }
 
   template <typename... Indices>
-  bool checkTypeReferencesImpl(uint32_t RecordIndex, TypeIndex TI,
-                               Indices &&... Rest) const {
-    ArrayRef<uint8_t> Record = TTB->records()[RecordIndex];
+  bool checkTypeReferencesImpl(uint32_t RecordIndex,
+                               ArrayRef<ArrayRef<uint8_t>> CVRecords,
+                               TypeIndex TI, Indices &&... Rest) const {
+    ArrayRef<uint8_t> Record = CVRecords[RecordIndex];
     bool Success = checkOneTypeReference(RecordIndex, Record, TI);
     EXPECT_TRUE(Success);
-    return Success &
-           checkTypeReferencesImpl(RecordIndex, std::forward<Indices>(Rest)...);
+    return Success & checkTypeReferencesImpl(RecordIndex, CVRecords,
+                                             std::forward<Indices>(Rest)...);
   }
 
   void discoverAllTypeIndices() {
@@ -105,6 +128,12 @@ private:
     }
   }
 
+  void discoverTypeIndicesInSymbols() {
+    Refs.resize(Symbols.size());
+    for (uint32_t I = 0; I < Symbols.size(); ++I)
+      discoverTypeIndices(Symbols[I], Refs[I]);
+  }
+
   // Helper function to write out a field list record with the given list
   // of member records.
   void writeFieldListImpl() {}
@@ -124,8 +153,19 @@ private:
     writeTypeRecordsImpl(std::forward<Rest>(Records)...);
   }
 
+  // Helper function to write out a list of symbol records.
+  void writeSymbolRecordsImpl() {}
+
+  template <typename RecType, typename... Rest>
+  void writeSymbolRecordsImpl(RecType &&Record, Rest &&... Records) {
+    Symbols.push_back(SymbolSerializer::writeOneSymbol(Record, Storage,
+                                                       CodeViewContainer::Pdb));
+    writeSymbolRecordsImpl(std::forward<Rest>(Records)...);
+  }
+
   std::vector<SmallVector<TiReference, 4>> Refs;
   std::unique_ptr<FieldListRecordBuilder> FLRB;
+  std::vector<CVSymbol> Symbols;
   BumpPtrAllocator Storage;
 };
 
@@ -492,4 +532,35 @@ TEST_F(TypeIndexIteratorTest, ManyMembers) {
       OneMethod.T1, OneMethod.T2, OneMethod.T3, OneMethod.T4, NestedType.Type,
       StaticDataMember.Type, VirtualBaseClass.BaseType,
       VirtualBaseClass.VBPtrType, VFPtr.Type, Continuation.ContinuationIndex);
-}
\ No newline at end of file
+}
+
+TEST_F(TypeIndexIteratorTest, ProcSym) {
+  ProcSym GS(SymbolRecordKind::GlobalProcSym);
+  GS.FunctionType = TypeIndex(0x40);
+  ProcSym LS(SymbolRecordKind::ProcSym);
+  LS.FunctionType = TypeIndex(0x41);
+  writeSymbolRecords(GS, LS);
+  checkTypeReferences(0, GS.FunctionType);
+  checkTypeReferences(1, LS.FunctionType);
+}
+
+TEST_F(TypeIndexIteratorTest, DataSym) {
+  DataSym DS(SymbolRecordKind::GlobalData);
+  DS.Type = TypeIndex(0x40);
+  writeSymbolRecords(DS);
+  checkTypeReferences(0, DS.Type);
+}
+
+TEST_F(TypeIndexIteratorTest, CallerSym) {
+  CallerSym Callees(SymbolRecordKind::CalleeSym);
+  Callees.Indices.push_back(TypeIndex(1));
+  Callees.Indices.push_back(TypeIndex(2));
+  Callees.Indices.push_back(TypeIndex(3));
+  CallerSym Callers(SymbolRecordKind::CallerSym);
+  Callers.Indices.push_back(TypeIndex(4));
+  Callers.Indices.push_back(TypeIndex(5));
+  Callers.Indices.push_back(TypeIndex(6));
+  writeSymbolRecords(Callees, Callers);
+  checkTypeReferences(0, TypeIndex(1), TypeIndex(2), TypeIndex(3));
+  checkTypeReferences(1, TypeIndex(4), TypeIndex(5), TypeIndex(6));
+}