Index: llvm/include/llvm/DebugInfo/CodeView/CodeViewRecordIO.h
===================================================================
--- llvm/include/llvm/DebugInfo/CodeView/CodeViewRecordIO.h
+++ llvm/include/llvm/DebugInfo/CodeView/CodeViewRecordIO.h
@@ -32,6 +32,7 @@
   virtual void EmitBytes(StringRef Data) = 0;
   virtual void EmitIntValue(uint64_t Value, unsigned Size) = 0;
   virtual void EmitBinaryData(StringRef Data) = 0;
+  virtual void AddComment(const Twine &T) = 0;
   virtual ~CodeViewRecordStreamer() = default;
 };
 
@@ -59,7 +60,7 @@
   Error beginRecord(Optional<uint32_t> MaxLength);
   Error endRecord();
 
-  Error mapInteger(TypeIndex &TypeInd);
+  Error mapInteger(TypeIndex &TypeInd, const char* Comment = nullptr);
 
   bool isStreaming() const {
     return (Streamer != nullptr) && (Reader == nullptr) && (Writer == nullptr);
@@ -92,8 +93,9 @@
     return Error::success();
   }
 
-  template <typename T> Error mapInteger(T &Value) {
+  template <typename T> Error mapInteger(T &Value, const char* Comment = nullptr) {
     if (isStreaming()) {
+      emitComment(Comment);
       Streamer->EmitIntValue((int)Value, sizeof(T));
       incrStreamedLen(sizeof(T));
       return Error::success();
@@ -105,7 +107,7 @@
     return Reader->readInteger(Value);
   }
 
-  template <typename T> Error mapEnum(T &Value) {
+  template <typename T> Error mapEnum(T &Value, const char* Comment = nullptr) {
     if (!isStreaming() && sizeof(Value) > maxFieldLength())
       return make_error<CodeViewError>(cv_error_code::insufficient_buffer);
 
@@ -115,7 +117,7 @@
     if (isWriting() || isStreaming())
       X = static_cast<U>(Value);
 
-    if (auto EC = mapInteger(X))
+    if (auto EC = mapInteger(X, Comment))
       return EC;
 
     if (isReading())
@@ -124,19 +126,20 @@
     return Error::success();
   }
 
-  Error mapEncodedInteger(int64_t &Value);
-  Error mapEncodedInteger(uint64_t &Value);
-  Error mapEncodedInteger(APSInt &Value);
-  Error mapStringZ(StringRef &Value);
-  Error mapGuid(GUID &Guid);
+  Error mapEncodedInteger(int64_t &Value, const char* Comment = nullptr);
+  Error mapEncodedInteger(uint64_t &Value, const char* Comment = nullptr);
+  Error mapEncodedInteger(APSInt &Value, const char* Comment = nullptr);
+  Error mapStringZ(StringRef &Value, const char* Comment = nullptr);
+  Error mapGuid(GUID &Guid, const char* Comment = nullptr);
 
-  Error mapStringZVectorZ(std::vector<StringRef> &Value);
+  Error mapStringZVectorZ(std::vector<StringRef> &Value, const char* Comment = nullptr);
 
   template <typename SizeType, typename T, typename ElementMapper>
-  Error mapVectorN(T &Items, const ElementMapper &Mapper) {
+  Error mapVectorN(T &Items, const ElementMapper &Mapper, const char* Comment = nullptr) {
     SizeType Size;
     if (isStreaming()) {
       Size = static_cast<SizeType>(Items.size());
+      emitComment(Comment);
       Streamer->EmitIntValue(Size, sizeof(Size));
       incrStreamedLen(sizeof(Size)); // add 1 for the delimiter
 
@@ -168,7 +171,8 @@
   }
 
   template <typename T, typename ElementMapper>
-  Error mapVectorTail(T &Items, const ElementMapper &Mapper) {
+  Error mapVectorTail(T &Items, const ElementMapper &Mapper, const char* Comment = nullptr) {
+    emitComment(Comment);
     if (isStreaming() || isWriting()) {
       for (auto &Item : Items) {
         if (auto EC = Mapper(*this, Item))
@@ -186,8 +190,8 @@
     return Error::success();
   }
 
-  Error mapByteVectorTail(ArrayRef<uint8_t> &Bytes);
-  Error mapByteVectorTail(std::vector<uint8_t> &Bytes);
+  Error mapByteVectorTail(ArrayRef<uint8_t> &Bytes, const char* Comment = nullptr);
+  Error mapByteVectorTail(std::vector<uint8_t> &Bytes, const char* Comment = nullptr);
 
   Error padToAlignment(uint32_t Align);
   Error skipPadding();
@@ -199,8 +203,8 @@
   }
 
 private:
-  void emitEncodedSignedInteger(const int64_t &Value);
-  void emitEncodedUnsignedInteger(const uint64_t &Value);
+  void emitEncodedSignedInteger(const int64_t &Value, const char* Comment = nullptr);
+  void emitEncodedUnsignedInteger(const uint64_t &Value, const char* Comment = nullptr);
   Error writeEncodedSignedInteger(const int64_t &Value);
   Error writeEncodedUnsignedInteger(const uint64_t &Value);
 
@@ -214,6 +218,13 @@
       StreamedLen = 4; // The record prefix is 4 bytes long
   }
 
+  void emitComment(const char* Comment) {
+    if (isStreaming() && (Comment != nullptr)) {
+      Twine TComment(Comment);
+      Streamer->AddComment(TComment);
+    }
+  }
+
   struct RecordLimit {
     uint32_t BeginOffset;
     Optional<uint32_t> MaxLength;
Index: llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
===================================================================
--- llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
+++ llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
@@ -108,6 +108,10 @@
 
   void EmitBinaryData(StringRef Data) { OS->EmitBinaryData(Data); }
 
+  void AddComment(const Twine &T) {
+    OS->AddComment(T);
+  }
+
 private:
   MCStreamer *OS = nullptr;
 };
Index: llvm/lib/DebugInfo/CodeView/CodeViewRecordIO.cpp
===================================================================
--- llvm/lib/DebugInfo/CodeView/CodeViewRecordIO.cpp
+++ llvm/lib/DebugInfo/CodeView/CodeViewRecordIO.cpp
@@ -97,8 +97,9 @@
   return Reader->skip(BytesToAdvance);
 }
 
-Error CodeViewRecordIO::mapByteVectorTail(ArrayRef<uint8_t> &Bytes) {
+Error CodeViewRecordIO::mapByteVectorTail(ArrayRef<uint8_t> &Bytes, const char* Comment) {
   if (isStreaming()) {
+    emitComment(Comment);
     Streamer->EmitBinaryData(toStringRef(Bytes));
     incrStreamedLen(Bytes.size());
   } else if (isWriting()) {
@@ -111,9 +112,9 @@
   return Error::success();
 }
 
-Error CodeViewRecordIO::mapByteVectorTail(std::vector<uint8_t> &Bytes) {
+Error CodeViewRecordIO::mapByteVectorTail(std::vector<uint8_t> &Bytes, const char* Comment) {
   ArrayRef<uint8_t> BytesRef(Bytes);
-  if (auto EC = mapByteVectorTail(BytesRef))
+  if (auto EC = mapByteVectorTail(BytesRef, Comment))
     return EC;
   if (!isWriting())
     Bytes.assign(BytesRef.begin(), BytesRef.end());
@@ -121,8 +122,9 @@
   return Error::success();
 }
 
-Error CodeViewRecordIO::mapInteger(TypeIndex &TypeInd) {
+Error CodeViewRecordIO::mapInteger(TypeIndex &TypeInd, const char* Comment) {
   if (isStreaming()) {
+    emitComment(Comment);
     Streamer->EmitIntValue(TypeInd.getIndex(), sizeof(TypeInd.getIndex()));
     incrStreamedLen(sizeof(TypeInd.getIndex()));
   } else if (isWriting()) {
@@ -137,12 +139,12 @@
   return Error::success();
 }
 
-Error CodeViewRecordIO::mapEncodedInteger(int64_t &Value) {
+Error CodeViewRecordIO::mapEncodedInteger(int64_t &Value, const char* Comment) {
   if (isStreaming()) {
     if (Value >= 0)
-      emitEncodedUnsignedInteger(static_cast<uint64_t>(Value));
+      emitEncodedUnsignedInteger(static_cast<uint64_t>(Value), Comment);
     else
-      emitEncodedSignedInteger(Value);
+      emitEncodedSignedInteger(Value, Comment);
   } else if (isWriting()) {
     if (Value >= 0) {
       if (auto EC = writeEncodedUnsignedInteger(static_cast<uint64_t>(Value)))
@@ -161,9 +163,9 @@
   return Error::success();
 }
 
-Error CodeViewRecordIO::mapEncodedInteger(uint64_t &Value) {
+Error CodeViewRecordIO::mapEncodedInteger(uint64_t &Value, const char* Comment) {
   if (isStreaming())
-    emitEncodedUnsignedInteger(Value);
+    emitEncodedUnsignedInteger(Value, Comment);
   else if (isWriting()) {
     if (auto EC = writeEncodedUnsignedInteger(Value))
       return EC;
@@ -176,12 +178,12 @@
   return Error::success();
 }
 
-Error CodeViewRecordIO::mapEncodedInteger(APSInt &Value) {
+Error CodeViewRecordIO::mapEncodedInteger(APSInt &Value, const char* Comment) {
   if (isStreaming()) {
     if (Value.isSigned())
-      emitEncodedSignedInteger(Value.getSExtValue());
+      emitEncodedSignedInteger(Value.getSExtValue(), Comment);
     else
-      emitEncodedUnsignedInteger(Value.getZExtValue());
+      emitEncodedUnsignedInteger(Value.getZExtValue(), Comment);
   } else if (isWriting()) {
     if (Value.isSigned())
       return writeEncodedSignedInteger(Value.getSExtValue());
@@ -191,9 +193,10 @@
   return Error::success();
 }
 
-Error CodeViewRecordIO::mapStringZ(StringRef &Value) {
+Error CodeViewRecordIO::mapStringZ(StringRef &Value, const char* Comment) {
   if (isStreaming()) {
     auto NullTerminatedString = StringRef(Value.data(), Value.size() + 1);
+    emitComment(Comment);
     Streamer->EmitBytes(NullTerminatedString);
     incrStreamedLen(NullTerminatedString.size());
   } else if (isWriting()) {
@@ -208,12 +211,13 @@
   return Error::success();
 }
 
-Error CodeViewRecordIO::mapGuid(GUID &Guid) {
+Error CodeViewRecordIO::mapGuid(GUID &Guid, const char* Comment) {
   constexpr uint32_t GuidSize = 16;
 
   if (isStreaming()) {
     StringRef GuidSR =
         StringRef((reinterpret_cast<const char *>(&Guid)), GuidSize);
+    emitComment(Comment);
     Streamer->EmitBytes(GuidSR);
     incrStreamedLen(GuidSize);
     return Error::success();
@@ -234,9 +238,10 @@
   return Error::success();
 }
 
-Error CodeViewRecordIO::mapStringZVectorZ(std::vector<StringRef> &Value) {
+Error CodeViewRecordIO::mapStringZVectorZ(std::vector<StringRef> &Value, const char* Comment) {
 
   if (!isReading()) {
+    emitComment(Comment);
     for (auto V : Value) {
       if (auto EC = mapStringZ(V))
         return EC;
@@ -257,41 +262,49 @@
   return Error::success();
 }
 
-void CodeViewRecordIO::emitEncodedSignedInteger(const int64_t &Value) {
+void CodeViewRecordIO::emitEncodedSignedInteger(const int64_t &Value, const char* Comment) {
   assert(Value < 0 && "Encoded integer is not signed!");
   if (Value >= std::numeric_limits<int8_t>::min()) {
     Streamer->EmitIntValue(LF_CHAR, 2);
+    emitComment(Comment);
     Streamer->EmitIntValue(Value, 1);
     incrStreamedLen(3);
   } else if (Value >= std::numeric_limits<int16_t>::min()) {
     Streamer->EmitIntValue(LF_SHORT, 2);
+    emitComment(Comment);
     Streamer->EmitIntValue(Value, 2);
     incrStreamedLen(4);
   } else if (Value >= std::numeric_limits<int32_t>::min()) {
     Streamer->EmitIntValue(LF_LONG, 2);
+    emitComment(Comment);
     Streamer->EmitIntValue(Value, 4);
     incrStreamedLen(6);
   } else {
     Streamer->EmitIntValue(LF_QUADWORD, 2);
+    emitComment(Comment);
     Streamer->EmitIntValue(Value, 4);
     incrStreamedLen(6);
   }
 }
 
-void CodeViewRecordIO::emitEncodedUnsignedInteger(const uint64_t &Value) {
+void CodeViewRecordIO::emitEncodedUnsignedInteger(const uint64_t &Value, const char* Comment) {
   if (Value < LF_NUMERIC) {
+    emitComment(Comment);
     Streamer->EmitIntValue(Value, 2);
     incrStreamedLen(2);
   } else if (Value <= std::numeric_limits<uint16_t>::max()) {
     Streamer->EmitIntValue(LF_USHORT, 2);
+    emitComment(Comment);
     Streamer->EmitIntValue(Value, 2);
     incrStreamedLen(4);
   } else if (Value <= std::numeric_limits<uint32_t>::max()) {
     Streamer->EmitIntValue(LF_ULONG, 2);
+    emitComment(Comment);
     Streamer->EmitIntValue(Value, 4);
     incrStreamedLen(6);
   } else {
     Streamer->EmitIntValue(LF_UQUADWORD, 2);
+    emitComment(Comment);
     Streamer->EmitIntValue(Value, 8);
     incrStreamedLen(6);
   }
Index: llvm/lib/DebugInfo/CodeView/TypeRecordMapping.cpp
===================================================================
--- llvm/lib/DebugInfo/CodeView/TypeRecordMapping.cpp
+++ llvm/lib/DebugInfo/CodeView/TypeRecordMapping.cpp
@@ -21,19 +21,19 @@
       : IsFromOverloadList(IsFromOverloadList) {}
 
   Error operator()(CodeViewRecordIO &IO, OneMethodRecord &Method) const {
-    error(IO.mapInteger(Method.Attrs.Attrs));
+    error(IO.mapInteger(Method.Attrs.Attrs, "NumAttributes"));
     if (IsFromOverloadList) {
       uint16_t Padding = 0;
-      error(IO.mapInteger(Padding));
+      error(IO.mapInteger(Padding, "Padding"));
     }
-    error(IO.mapInteger(Method.Type));
+    error(IO.mapInteger(Method.Type, "Type"));
     if (Method.isIntroducingVirtual()) {
-      error(IO.mapInteger(Method.VFTableOffset));
+      error(IO.mapInteger(Method.VFTableOffset, "VFTableOffset"));
     } else if (IO.isReading())
       Method.VFTableOffset = -1;
 
     if (!IsFromOverloadList)
-      error(IO.mapStringZ(Method.Name));
+      error(IO.mapStringZ(Method.Name, "Name"));
 
     return Error::success();
   }
@@ -75,9 +75,9 @@
     // Reading & Streaming mode come after writing mode is executed for each
     // record. Truncating large names are done during writing, so its not
     // necessary to do it while reading or streaming.
-    error(IO.mapStringZ(Name));
+    error(IO.mapStringZ(Name, "Name"));
     if (HasUniqueName)
-      error(IO.mapStringZ(UniqueName));
+      error(IO.mapStringZ(UniqueName, "LinkageName"));
   }
 
   return Error::success();
@@ -144,32 +144,32 @@
 }
 
 Error TypeRecordMapping::visitKnownRecord(CVType &CVR, ModifierRecord &Record) {
-  error(IO.mapInteger(Record.ModifiedType));
-  error(IO.mapEnum(Record.Modifiers));
+  error(IO.mapInteger(Record.ModifiedType, "ModifiedType"));
+  error(IO.mapEnum(Record.Modifiers, "Modifiers"));
   return Error::success();
 }
 
 Error TypeRecordMapping::visitKnownRecord(CVType &CVR,
                                           ProcedureRecord &Record) {
-  error(IO.mapInteger(Record.ReturnType));
-  error(IO.mapEnum(Record.CallConv));
-  error(IO.mapEnum(Record.Options));
-  error(IO.mapInteger(Record.ParameterCount));
-  error(IO.mapInteger(Record.ArgumentList));
+  error(IO.mapInteger(Record.ReturnType, "ReturnType"));
+  error(IO.mapEnum(Record.CallConv, "CallingConvention"));
+  error(IO.mapEnum(Record.Options, "FunctionOptions"));
+  error(IO.mapInteger(Record.ParameterCount, "NumParameters"));
+  error(IO.mapInteger(Record.ArgumentList, "ArgListType"));
 
   return Error::success();
 }
 
 Error TypeRecordMapping::visitKnownRecord(CVType &CVR,
                                           MemberFunctionRecord &Record) {
-  error(IO.mapInteger(Record.ReturnType));
-  error(IO.mapInteger(Record.ClassType));
-  error(IO.mapInteger(Record.ThisType));
-  error(IO.mapEnum(Record.CallConv));
-  error(IO.mapEnum(Record.Options));
-  error(IO.mapInteger(Record.ParameterCount));
-  error(IO.mapInteger(Record.ArgumentList));
-  error(IO.mapInteger(Record.ThisPointerAdjustment));
+  error(IO.mapInteger(Record.ReturnType, "ReturnType"));
+  error(IO.mapInteger(Record.ClassType, "ClassType"));
+  error(IO.mapInteger(Record.ThisType, "ThisType"));
+  error(IO.mapEnum(Record.CallConv, "CallingConvention"));
+  error(IO.mapEnum(Record.Options, "FunctionOptions"));
+  error(IO.mapInteger(Record.ParameterCount, "NumParameters"));
+  error(IO.mapInteger(Record.ArgumentList, "ArgListType"));
+  error(IO.mapInteger(Record.ThisPointerAdjustment, "ThisAdjustment"));
 
   return Error::success();
 }
@@ -177,7 +177,8 @@
 Error TypeRecordMapping::visitKnownRecord(CVType &CVR, ArgListRecord &Record) {
   error(IO.mapVectorN<uint32_t>(
       Record.ArgIndices,
-      [](CodeViewRecordIO &IO, TypeIndex &N) { return IO.mapInteger(N); }));
+      [](CodeViewRecordIO &IO, TypeIndex &N) { return IO.mapInteger(N, "Argument"); },
+      "NumArgs"));
   return Error::success();
 }
 
@@ -185,32 +186,33 @@
                                           StringListRecord &Record) {
   error(IO.mapVectorN<uint32_t>(
       Record.StringIndices,
-      [](CodeViewRecordIO &IO, TypeIndex &N) { return IO.mapInteger(N); }));
+      [](CodeViewRecordIO &IO, TypeIndex &N) { return IO.mapInteger(N, "Strings"); },
+      "NumStrings"));
 
   return Error::success();
 }
 
 Error TypeRecordMapping::visitKnownRecord(CVType &CVR, PointerRecord &Record) {
-  error(IO.mapInteger(Record.ReferentType));
-  error(IO.mapInteger(Record.Attrs));
+  error(IO.mapInteger(Record.ReferentType, "PointeeType"));
+  error(IO.mapInteger(Record.Attrs, "Attributes"));
 
   if (Record.isPointerToMember()) {
     if (IO.isReading())
       Record.MemberInfo.emplace();
 
     MemberPointerInfo &M = *Record.MemberInfo;
-    error(IO.mapInteger(M.ContainingType));
-    error(IO.mapEnum(M.Representation));
+    error(IO.mapInteger(M.ContainingType, "ClassType"));
+    error(IO.mapEnum(M.Representation, "Representation"));
   }
 
   return Error::success();
 }
 
 Error TypeRecordMapping::visitKnownRecord(CVType &CVR, ArrayRecord &Record) {
-  error(IO.mapInteger(Record.ElementType));
-  error(IO.mapInteger(Record.IndexType));
-  error(IO.mapEncodedInteger(Record.Size));
-  error(IO.mapStringZ(Record.Name));
+  error(IO.mapInteger(Record.ElementType, "ElementType"));
+  error(IO.mapInteger(Record.IndexType, "IndexType"));
+  error(IO.mapEncodedInteger(Record.Size, "SizeOf"));
+  error(IO.mapStringZ(Record.Name, "Name"));
 
   return Error::success();
 }
@@ -220,12 +222,12 @@
          (CVR.kind() == TypeLeafKind::LF_CLASS) ||
          (CVR.kind() == TypeLeafKind::LF_INTERFACE));
 
-  error(IO.mapInteger(Record.MemberCount));
-  error(IO.mapEnum(Record.Options));
-  error(IO.mapInteger(Record.FieldList));
-  error(IO.mapInteger(Record.DerivationList));
-  error(IO.mapInteger(Record.VTableShape));
-  error(IO.mapEncodedInteger(Record.Size));
+  error(IO.mapInteger(Record.MemberCount, "MemberCount"));
+  error(IO.mapEnum(Record.Options, "Properties"));
+  error(IO.mapInteger(Record.FieldList, "FieldList"));
+  error(IO.mapInteger(Record.DerivationList, "DerivedFrom"));
+  error(IO.mapInteger(Record.VTableShape, "VShape"));
+  error(IO.mapEncodedInteger(Record.Size, "SizeOf"));
   error(mapNameAndUniqueName(IO, Record.Name, Record.UniqueName,
                              Record.hasUniqueName()));
 
@@ -233,10 +235,10 @@
 }
 
 Error TypeRecordMapping::visitKnownRecord(CVType &CVR, UnionRecord &Record) {
-  error(IO.mapInteger(Record.MemberCount));
-  error(IO.mapEnum(Record.Options));
-  error(IO.mapInteger(Record.FieldList));
-  error(IO.mapEncodedInteger(Record.Size));
+  error(IO.mapInteger(Record.MemberCount, "MemberCount"));
+  error(IO.mapEnum(Record.Options, "Properties"));
+  error(IO.mapInteger(Record.FieldList, "FieldList"));
+  error(IO.mapEncodedInteger(Record.Size, "SizeOf"));
   error(mapNameAndUniqueName(IO, Record.Name, Record.UniqueName,
                              Record.hasUniqueName()));
 
@@ -244,10 +246,10 @@
 }
 
 Error TypeRecordMapping::visitKnownRecord(CVType &CVR, EnumRecord &Record) {
-  error(IO.mapInteger(Record.MemberCount));
-  error(IO.mapEnum(Record.Options));
-  error(IO.mapInteger(Record.UnderlyingType));
-  error(IO.mapInteger(Record.FieldList));
+  error(IO.mapInteger(Record.MemberCount, "NumEnumerators"));
+  error(IO.mapEnum(Record.Options, "Properties"));
+  error(IO.mapInteger(Record.UnderlyingType, "UnderlyingType"));
+  error(IO.mapInteger(Record.FieldList, "FieldListType"));
   error(mapNameAndUniqueName(IO, Record.Name, Record.UniqueName,
                              Record.hasUniqueName()));
 
@@ -255,9 +257,9 @@
 }
 
 Error TypeRecordMapping::visitKnownRecord(CVType &CVR, BitFieldRecord &Record) {
-  error(IO.mapInteger(Record.Type));
-  error(IO.mapInteger(Record.BitSize));
-  error(IO.mapInteger(Record.BitOffset));
+  error(IO.mapInteger(Record.Type, "Type"));
+  error(IO.mapInteger(Record.BitSize, "BitSize"));
+  error(IO.mapInteger(Record.BitOffset, "BitOffset"));
 
   return Error::success();
 }
@@ -268,7 +270,7 @@
   if (!IO.isReading()) {
     ArrayRef<VFTableSlotKind> Slots = Record.getSlots();
     Size = Slots.size();
-    error(IO.mapInteger(Size));
+    error(IO.mapInteger(Size, "VFEntryCount"));
 
     for (size_t SlotIndex = 0; SlotIndex < Slots.size(); SlotIndex += 2) {
       uint8_t Byte = static_cast<uint8_t>(Slots[SlotIndex]) << 4;
@@ -292,61 +294,62 @@
 }
 
 Error TypeRecordMapping::visitKnownRecord(CVType &CVR, VFTableRecord &Record) {
-  error(IO.mapInteger(Record.CompleteClass));
-  error(IO.mapInteger(Record.OverriddenVFTable));
-  error(IO.mapInteger(Record.VFPtrOffset));
+  error(IO.mapInteger(Record.CompleteClass, "CompleteClass"));
+  error(IO.mapInteger(Record.OverriddenVFTable, "OverriddenVFTable"));
+  error(IO.mapInteger(Record.VFPtrOffset, "VFPtrOffset"));
   uint32_t NamesLen = 0;
   if (!IO.isReading()) {
     for (auto Name : Record.MethodNames)
       NamesLen += Name.size() + 1;
   }
-  error(IO.mapInteger(NamesLen));
+  error(IO.mapInteger(NamesLen, ""));
   error(IO.mapVectorTail(
       Record.MethodNames,
-      [](CodeViewRecordIO &IO, StringRef &S) { return IO.mapStringZ(S); }));
+      [](CodeViewRecordIO &IO, StringRef &S) { return IO.mapStringZ(S, "MethodName"); },
+      "VFTableName"));
 
   return Error::success();
 }
 
 Error TypeRecordMapping::visitKnownRecord(CVType &CVR, StringIdRecord &Record) {
-  error(IO.mapInteger(Record.Id));
-  error(IO.mapStringZ(Record.String));
+  error(IO.mapInteger(Record.Id, "Id"));
+  error(IO.mapStringZ(Record.String, "StringData"));
 
   return Error::success();
 }
 
 Error TypeRecordMapping::visitKnownRecord(CVType &CVR,
                                           UdtSourceLineRecord &Record) {
-  error(IO.mapInteger(Record.UDT));
-  error(IO.mapInteger(Record.SourceFile));
-  error(IO.mapInteger(Record.LineNumber));
+  error(IO.mapInteger(Record.UDT, "UDT"));
+  error(IO.mapInteger(Record.SourceFile, "SourceFile"));
+  error(IO.mapInteger(Record.LineNumber, "LineNumber"));
 
   return Error::success();
 }
 
 Error TypeRecordMapping::visitKnownRecord(CVType &CVR,
                                           UdtModSourceLineRecord &Record) {
-  error(IO.mapInteger(Record.UDT));
-  error(IO.mapInteger(Record.SourceFile));
-  error(IO.mapInteger(Record.LineNumber));
-  error(IO.mapInteger(Record.Module));
+  error(IO.mapInteger(Record.UDT, "UDT"));
+  error(IO.mapInteger(Record.SourceFile, "SourceFile"));
+  error(IO.mapInteger(Record.LineNumber, "LineNumber"));
+  error(IO.mapInteger(Record.Module, "Module"));
 
   return Error::success();
 }
 
 Error TypeRecordMapping::visitKnownRecord(CVType &CVR, FuncIdRecord &Record) {
-  error(IO.mapInteger(Record.ParentScope));
-  error(IO.mapInteger(Record.FunctionType));
-  error(IO.mapStringZ(Record.Name));
+  error(IO.mapInteger(Record.ParentScope, "ParentScope"));
+  error(IO.mapInteger(Record.FunctionType, "FunctionType"));
+  error(IO.mapStringZ(Record.Name, "Name"));
 
   return Error::success();
 }
 
 Error TypeRecordMapping::visitKnownRecord(CVType &CVR,
                                           MemberFuncIdRecord &Record) {
-  error(IO.mapInteger(Record.ClassType));
-  error(IO.mapInteger(Record.FunctionType));
-  error(IO.mapStringZ(Record.Name));
+  error(IO.mapInteger(Record.ClassType, "ClassType"));
+  error(IO.mapInteger(Record.FunctionType, "FunctionType"));
+  error(IO.mapStringZ(Record.Name, "Name"));
 
   return Error::success();
 }
@@ -355,7 +358,8 @@
                                           BuildInfoRecord &Record) {
   error(IO.mapVectorN<uint16_t>(
       Record.ArgIndices,
-      [](CodeViewRecordIO &IO, TypeIndex &N) { return IO.mapInteger(N); }));
+      [](CodeViewRecordIO &IO, TypeIndex &N) { return IO.mapInteger(N, "Argument"); },
+      "NumArgs"));
 
   return Error::success();
 }
@@ -364,7 +368,7 @@
                                           MethodOverloadListRecord &Record) {
   // TODO: Split the list into multiple records if it's longer than 64KB, using
   // a subrecord of TypeRecordKind::Index to chain the records together.
-  error(IO.mapVectorTail(Record.Methods, MapOneMethodRecord(true)));
+  error(IO.mapVectorTail(Record.Methods, MapOneMethodRecord(true), "Method"));
 
   return Error::success();
 }
@@ -378,22 +382,22 @@
 
 Error TypeRecordMapping::visitKnownRecord(CVType &CVR,
                                           TypeServer2Record &Record) {
-  error(IO.mapGuid(Record.Guid));
-  error(IO.mapInteger(Record.Age));
-  error(IO.mapStringZ(Record.Name));
+  error(IO.mapGuid(Record.Guid, "Guid"));
+  error(IO.mapInteger(Record.Age, "Age"));
+  error(IO.mapStringZ(Record.Name, "Name"));
   return Error::success();
 }
 
 Error TypeRecordMapping::visitKnownRecord(CVType &CVR, LabelRecord &Record) {
-  error(IO.mapEnum(Record.Mode));
+  error(IO.mapEnum(Record.Mode, "Mode"));
   return Error::success();
 }
 
 Error TypeRecordMapping::visitKnownMember(CVMemberRecord &CVR,
                                           BaseClassRecord &Record) {
-  error(IO.mapInteger(Record.Attrs.Attrs));
-  error(IO.mapInteger(Record.Type));
-  error(IO.mapEncodedInteger(Record.Offset));
+  error(IO.mapInteger(Record.Attrs.Attrs, "NumAttributes"));
+  error(IO.mapInteger(Record.Type, "BaseType"));
+  error(IO.mapEncodedInteger(Record.Offset, "BaseOffset"));
 
   return Error::success();
 }
@@ -403,27 +407,27 @@
   error(IO.mapInteger(Record.Attrs.Attrs));
 
   // FIXME: Handle full APInt such as __int128.
-  error(IO.mapEncodedInteger(Record.Value));
-  error(IO.mapStringZ(Record.Name));
+  error(IO.mapEncodedInteger(Record.Value, "EnumValue"));
+  error(IO.mapStringZ(Record.Name, "Name"));
 
   return Error::success();
 }
 
 Error TypeRecordMapping::visitKnownMember(CVMemberRecord &CVR,
                                           DataMemberRecord &Record) {
-  error(IO.mapInteger(Record.Attrs.Attrs));
-  error(IO.mapInteger(Record.Type));
-  error(IO.mapEncodedInteger(Record.FieldOffset));
-  error(IO.mapStringZ(Record.Name));
+  error(IO.mapInteger(Record.Attrs.Attrs, "NumAttributes"));
+  error(IO.mapInteger(Record.Type, "Type"));
+  error(IO.mapEncodedInteger(Record.FieldOffset, "FieldOffset"));
+  error(IO.mapStringZ(Record.Name, "Name"));
 
   return Error::success();
 }
 
 Error TypeRecordMapping::visitKnownMember(CVMemberRecord &CVR,
                                           OverloadedMethodRecord &Record) {
-  error(IO.mapInteger(Record.NumOverloads));
-  error(IO.mapInteger(Record.MethodList));
-  error(IO.mapStringZ(Record.Name));
+  error(IO.mapInteger(Record.NumOverloads, "MethodCount"));
+  error(IO.mapInteger(Record.MethodList, "MethodListIndex"));
+  error(IO.mapStringZ(Record.Name, "Name"));
 
   return Error::success();
 }
@@ -438,9 +442,9 @@
 Error TypeRecordMapping::visitKnownMember(CVMemberRecord &CVR,
                                           NestedTypeRecord &Record) {
   uint16_t Padding = 0;
-  error(IO.mapInteger(Padding));
-  error(IO.mapInteger(Record.Type));
-  error(IO.mapStringZ(Record.Name));
+  error(IO.mapInteger(Padding, "Padding"));
+  error(IO.mapInteger(Record.Type, "Type"));
+  error(IO.mapStringZ(Record.Name, "Name"));
 
   return Error::success();
 }
@@ -448,9 +452,9 @@
 Error TypeRecordMapping::visitKnownMember(CVMemberRecord &CVR,
                                           StaticDataMemberRecord &Record) {
 
-  error(IO.mapInteger(Record.Attrs.Attrs));
-  error(IO.mapInteger(Record.Type));
-  error(IO.mapStringZ(Record.Name));
+  error(IO.mapInteger(Record.Attrs.Attrs, "NumAttributes"));
+  error(IO.mapInteger(Record.Type, "Type"));
+  error(IO.mapStringZ(Record.Name, "Name"));
 
   return Error::success();
 }
@@ -458,11 +462,11 @@
 Error TypeRecordMapping::visitKnownMember(CVMemberRecord &CVR,
                                           VirtualBaseClassRecord &Record) {
 
-  error(IO.mapInteger(Record.Attrs.Attrs));
-  error(IO.mapInteger(Record.BaseType));
-  error(IO.mapInteger(Record.VBPtrType));
-  error(IO.mapEncodedInteger(Record.VBPtrOffset));
-  error(IO.mapEncodedInteger(Record.VTableIndex));
+  error(IO.mapInteger(Record.Attrs.Attrs, "NumAttributes"));
+  error(IO.mapInteger(Record.BaseType, "BaseType"));
+  error(IO.mapInteger(Record.VBPtrType, "VBPtrType"));
+  error(IO.mapEncodedInteger(Record.VBPtrOffset, "VBPtrOffset"));
+  error(IO.mapEncodedInteger(Record.VTableIndex, "VBTableIndex"));
 
   return Error::success();
 }
@@ -470,8 +474,8 @@
 Error TypeRecordMapping::visitKnownMember(CVMemberRecord &CVR,
                                           VFPtrRecord &Record) {
   uint16_t Padding = 0;
-  error(IO.mapInteger(Padding));
-  error(IO.mapInteger(Record.Type));
+  error(IO.mapInteger(Padding, "Padding"));
+  error(IO.mapInteger(Record.Type, "Type"));
 
   return Error::success();
 }
@@ -479,23 +483,23 @@
 Error TypeRecordMapping::visitKnownMember(CVMemberRecord &CVR,
                                           ListContinuationRecord &Record) {
   uint16_t Padding = 0;
-  error(IO.mapInteger(Padding));
-  error(IO.mapInteger(Record.ContinuationIndex));
+  error(IO.mapInteger(Padding, "Padding"));
+  error(IO.mapInteger(Record.ContinuationIndex, "ContinuationIndex"));
 
   return Error::success();
 }
 
 Error TypeRecordMapping::visitKnownRecord(CVType &CVR,
                                           PrecompRecord &Precomp) {
-  error(IO.mapInteger(Precomp.StartTypeIndex));
-  error(IO.mapInteger(Precomp.TypesCount));
-  error(IO.mapInteger(Precomp.Signature));
-  error(IO.mapStringZ(Precomp.PrecompFilePath));
+  error(IO.mapInteger(Precomp.StartTypeIndex, "StartIndex"));
+  error(IO.mapInteger(Precomp.TypesCount, "Count"));
+  error(IO.mapInteger(Precomp.Signature, "Signature"));
+  error(IO.mapStringZ(Precomp.PrecompFilePath, "PrecompFile"));
   return Error::success();
 }
 
 Error TypeRecordMapping::visitKnownRecord(CVType &CVR,
                                           EndPrecompRecord &EndPrecomp) {
-  error(IO.mapInteger(EndPrecomp.Signature));
+  error(IO.mapInteger(EndPrecomp.Signature, "Signature"));
   return Error::success();
 }
Index: llvm/test/DebugInfo/COFF/types-basic.ll
===================================================================
--- llvm/test/DebugInfo/COFF/types-basic.ll
+++ llvm/test/DebugInfo/COFF/types-basic.ll
@@ -347,17 +347,15 @@
 ; CHECK:   ]
 ; CHECK: ]
 
-
-
 ; ASM: .section	.debug$T,"dr"
 ; ASM: .p2align	2
 ; ASM: .long	4                       # Debug section magic
 ; ASM: .short	18
 ; ASM: .short	4609
-; ASM: .long	3
-; ASM: .long	64
-; ASM: .long	65
-; ASM: .long	19
+; ASM: .long	3                       # NumArgs
+; ASM: .long	64                      # Argument
+; ASM: .long	65                      # Argument
+; ASM: .long	19                      # Argument
 ; ASM: # ArgList (0x1000) {
 ; ASM: #   TypeLeafKind: LF_ARGLIST (0x1201)
 ; ASM: #   NumArgs: 3
@@ -369,11 +367,11 @@
 ; ASM: # }
 ; ASM: .short	14
 ; ASM: .short	4104
-; ASM: .long	3
-; ASM: .byte	0
-; ASM: .byte	0
-; ASM: .short	3
-; ASM: .long	4096
+; ASM: .long	3                       # ReturnType
+; ASM: .byte	0                       # CallingConvention
+; ASM: .byte	0                       # FunctionOptions
+; ASM: .short	3                       # NumParameters
+; ASM: .long	4096                    # ArgListType
 ; ASM: # Procedure (0x1001) {
 ; ASM: #   TypeLeafKind: LF_PROCEDURE (0x1008)
 ; ASM: #   ReturnType: void (0x3)
@@ -385,9 +383,9 @@
 ; ASM: # }
 ; ASM: .short	14
 ; ASM: .short	5633
-; ASM: .long	0
-; ASM: .long	4097
-; ASM: .asciz	"f"
+; ASM: .long	0                       # ParentScope
+; ASM: .long	4097                    # FunctionType
+; ASM: .asciz	"f"                     # Name
 ; ASM: .byte	242
 ; ASM: .byte	241
 ; ASM: # FuncId (0x1002) {
@@ -398,8 +396,8 @@
 ; ASM: # }
 ; ASM: .short	10
 ; ASM: .short	4097
-; ASM: .long	116
-; ASM: .short	1
+; ASM: .long	116                     # ModifiedType
+; ASM: .short	1                       # Modifiers
 ; ASM: .byte	242
 ; ASM: .byte	241
 ; ASM: # Modifier (0x1003) {
@@ -411,8 +409,8 @@
 ; ASM: # }
 ; ASM: .short	10
 ; ASM: .short	4098
-; ASM: .long	4099
-; ASM: .long	65548
+; ASM: .long	4099                    # PointeeType
+; ASM: .long	65548                   # Attributes
 ; ASM: # Pointer (0x1004) {
 ; ASM: #   TypeLeafKind: LF_POINTER (0x1002)
 ; ASM: #   PointeeType: const int (0x1003)
@@ -429,13 +427,13 @@
 ; ASM: # }
 ; ASM: .short	22
 ; ASM: .short	5381
-; ASM: .short	0
-; ASM: .short	128
-; ASM: .long	0
-; ASM: .long	0
-; ASM: .long	0
-; ASM: .short	0
-; ASM: .asciz	"A"
+; ASM: .short	0                       # MemberCount
+; ASM: .short	128                     # Properties
+; ASM: .long	0                       # FieldList
+; ASM: .long	0                       # DerivedFrom
+; ASM: .long	0                       # VShape
+; ASM: .short	0                       # SizeOf
+; ASM: .asciz	"A"                     # Name
 ; ASM: # Struct (0x1005) {
 ; ASM: #   TypeLeafKind: LF_STRUCTURE (0x1505)
 ; ASM: #   MemberCount: 0
@@ -450,10 +448,10 @@
 ; ASM: # }
 ; ASM: .short	18
 ; ASM: .short	4098
-; ASM: .long	116
-; ASM: .long	32844
-; ASM: .long	4101
-; ASM: .short	4
+; ASM: .long	116                     # PointeeType
+; ASM: .long	32844                   # Attributes
+; ASM: .long	4101                    # ClassType
+; ASM: .short	4                       # Representation
 ; ASM: .byte	242
 ; ASM: .byte	241
 ; ASM: # Pointer (0x1006) {
@@ -474,8 +472,8 @@
 ; ASM: # }
 ; ASM: .short	10
 ; ASM: .short	4098
-; ASM: .long	4101
-; ASM: .long	66572
+; ASM: .long	4101                    # PointeeType
+; ASM: .long	66572                   # Attributes
 ; ASM: # Pointer (0x1007) {
 ; ASM: #   TypeLeafKind: LF_POINTER (0x1002)
 ; ASM: #   PointeeType: A (0x1005)
@@ -492,7 +490,7 @@
 ; ASM: # }
 ; ASM: .short	6
 ; ASM: .short	4609
-; ASM: .long	0
+; ASM: .long	0                       # NumArgs
 ; ASM: # ArgList (0x1008) {
 ; ASM: #   TypeLeafKind: LF_ARGLIST (0x1201)
 ; ASM: #   NumArgs: 0
@@ -501,14 +499,14 @@
 ; ASM: # }
 ; ASM: .short	26
 ; ASM: .short	4105
-; ASM: .long	3
-; ASM: .long	4101
-; ASM: .long	4103
-; ASM: .byte	0
-; ASM: .byte	0
-; ASM: .short	0
-; ASM: .long	4104
-; ASM: .long	0
+; ASM: .long	3                       # ReturnType
+; ASM: .long	4101                    # ClassType
+; ASM: .long	4103                    # ThisType
+; ASM: .byte	0                       # CallingConvention
+; ASM: .byte	0                       # FunctionOptions
+; ASM: .short	0                       # NumParameters
+; ASM: .long	4104                    # ArgListType
+; ASM: .long	0                       # ThisAdjustment
 ; ASM: # MemberFunction (0x1009) {
 ; ASM: #   TypeLeafKind: LF_MFUNCTION (0x1009)
 ; ASM: #   ReturnType: void (0x3)
@@ -548,13 +546,13 @@
 ; ASM: # }
 ; ASM: .short	22
 ; ASM: .short	5381
-; ASM: .short	2
-; ASM: .short	0
-; ASM: .long	4106
-; ASM: .long	0
-; ASM: .long	0
-; ASM: .short	4
-; ASM: .asciz	"A"
+; ASM: .short	2                       # MemberCount
+; ASM: .short	0                       # Properties
+; ASM: .long	4106                    # FieldList
+; ASM: .long	0                       # DerivedFrom
+; ASM: .long	0                       # VShape
+; ASM: .short	4                       # SizeOf
+; ASM: .asciz	"A"                     # Name
 ; ASM: # Struct (0x100B) {
 ; ASM: #   TypeLeafKind: LF_STRUCTURE (0x1505)
 ; ASM: #   MemberCount: 2
@@ -568,8 +566,8 @@
 ; ASM: # }
 ; ASM: .short	30
 ; ASM: .short	5637
-; ASM: .long	0
-; ASM: .asciz	"D:\\src\\llvm\\build\\t.cpp"
+; ASM: .long	0                       # Id
+; ASM: .asciz	"D:\\src\\llvm\\build\\t.cpp" # StringData
 ; ASM: # StringId (0x100C) {
 ; ASM: #   TypeLeafKind: LF_STRING_ID (0x1605)
 ; ASM: #   Id: 0x0
@@ -577,9 +575,9 @@
 ; ASM: # }
 ; ASM: .short	14
 ; ASM: .short	5638
-; ASM: .long	4107
-; ASM: .long	4108
-; ASM: .long	1
+; ASM: .long	4107                    # UDT
+; ASM: .long	4108                    # SourceFile
+; ASM: .long	1                       # LineNumber
 ; ASM: # UdtSourceLine (0x100D) {
 ; ASM: #   TypeLeafKind: LF_UDT_SRC_LINE (0x1606)
 ; ASM: #   UDT: A (0x100B)
@@ -588,10 +586,10 @@
 ; ASM: # }
 ; ASM: .short	18
 ; ASM: .short	4098
-; ASM: .long	4105
-; ASM: .long	65644
-; ASM: .long	4101
-; ASM: .short	8
+; ASM: .long	4105                    # PointeeType
+; ASM: .long	65644                   # Attributes
+; ASM: .long	4101                    # ClassType
+; ASM: .short	8                       # Representation
 ; ASM: .byte	242
 ; ASM: .byte	241
 ; ASM: # Pointer (0x100E) {
@@ -612,8 +610,8 @@
 ; ASM: # }
 ; ASM: .short	10
 ; ASM: .short	4097
-; ASM: .long	3
-; ASM: .short	1
+; ASM: .long	3                       # ModifiedType
+; ASM: .short	1                       # Modifiers
 ; ASM: .byte	242
 ; ASM: .byte	241
 ; ASM: # Modifier (0x100F) {
@@ -625,8 +623,8 @@
 ; ASM: # }
 ; ASM: .short	10
 ; ASM: .short	4098
-; ASM: .long	4111
-; ASM: .long	65548
+; ASM: .long	4111                    # PointeeType
+; ASM: .long	65548                   # Attributes
 ; ASM: # Pointer (0x1010) {
 ; ASM: #   TypeLeafKind: LF_POINTER (0x1002)
 ; ASM: #   PointeeType: const void (0x100F)
@@ -643,11 +641,11 @@
 ; ASM: # }
 ; ASM: .short	14
 ; ASM: .short	4104
-; ASM: .long	3
-; ASM: .byte	0
-; ASM: .byte	0
-; ASM: .short	0
-; ASM: .long	4104
+; ASM: .long	3                       # ReturnType
+; ASM: .byte	0                       # CallingConvention
+; ASM: .byte	0                       # FunctionOptions
+; ASM: .short	0                       # NumParameters
+; ASM: .long	4104                    # ArgListType
 ; ASM: # Procedure (0x1011) {
 ; ASM: #   TypeLeafKind: LF_PROCEDURE (0x1008)
 ; ASM: #   ReturnType: void (0x3)
@@ -659,9 +657,9 @@
 ; ASM: # }
 ; ASM: .short	22
 ; ASM: .short	5633
-; ASM: .long	0
-; ASM: .long	4113
-; ASM: .asciz	"CharTypes"
+; ASM: .long	0                       # ParentScope
+; ASM: .long	4113                    # FunctionType
+; ASM: .asciz	"CharTypes"             # Name
 ; ASM: .byte	242
 ; ASM: .byte	241
 ; ASM: # FuncId (0x1012) {
@@ -672,8 +670,8 @@
 ; ASM: # }
 ; ASM: .short	26
 ; ASM: .short	5637
-; ASM: .long	0
-; ASM: .asciz	"D:\\src\\llvm\\build"
+; ASM: .long	0                       # Id
+; ASM: .asciz	"D:\\src\\llvm\\build"  # StringData
 ; ASM: .byte	242
 ; ASM: .byte	241
 ; ASM: # StringId (0x1013) {
@@ -683,8 +681,8 @@
 ; ASM: # }
 ; ASM: .short	14
 ; ASM: .short	5637
-; ASM: .long	0
-; ASM: .asciz	"t.cpp"
+; ASM: .long	0                       # Id
+; ASM: .asciz	"t.cpp"                 # StringData
 ; ASM: .byte	242
 ; ASM: .byte	241
 ; ASM: # StringId (0x1014) {
@@ -694,12 +692,12 @@
 ; ASM: # }
 ; ASM: .short	26
 ; ASM: .short	5635
-; ASM: .short	5
-; ASM: .long	4115
-; ASM: .long	0
-; ASM: .long	4116
-; ASM: .long	0
-; ASM: .long	0
+; ASM: .short	5                       # NumArgs
+; ASM: .long	4115                    # Argument
+; ASM: .long	0                       # Argument
+; ASM: .long	4116                    # Argument
+; ASM: .long	0                       # Argument
+; ASM: .long	0                       # Argument
 ; ASM: .byte	242
 ; ASM: .byte	241
 ; ASM: # BuildInfo (0x1015) {