Index: lib/Bitcode/Reader/BitcodeReader.cpp
===================================================================
--- lib/Bitcode/Reader/BitcodeReader.cpp
+++ lib/Bitcode/Reader/BitcodeReader.cpp
@@ -6382,6 +6382,7 @@
 }
 
 namespace {
+// FIXME: Use llvm::Error instead of std::error_code.
 class BitcodeErrorCategoryType : public std::error_category {
   const char *name() const LLVM_NOEXCEPT override {
     return "llvm.bitcode";
Index: lib/DebugInfo/PDB/DIA/DIAError.cpp
===================================================================
--- lib/DebugInfo/PDB/DIA/DIAError.cpp
+++ lib/DebugInfo/PDB/DIA/DIAError.cpp
@@ -5,6 +5,7 @@
 using namespace llvm;
 using namespace llvm::pdb;
 
+// FIXME: Use llvm::Error instead of std::error_code.
 class DIAErrorCategory : public std::error_category {
 public:
   const char *name() const LLVM_NOEXCEPT override { return "llvm.pdb.dia"; }
Index: lib/DebugInfo/PDB/GenericError.cpp
===================================================================
--- lib/DebugInfo/PDB/GenericError.cpp
+++ lib/DebugInfo/PDB/GenericError.cpp
@@ -15,6 +15,7 @@
 using namespace llvm::pdb;
 
 namespace {
+// FIXME: Use llvm::Error instead of std::error_code.
 class GenericErrorCategory : public std::error_category {
 public:
   const char *name() const LLVM_NOEXCEPT override { return "llvm.pdb"; }
Index: lib/DebugInfo/PDB/Raw/RawError.cpp
===================================================================
--- lib/DebugInfo/PDB/Raw/RawError.cpp
+++ lib/DebugInfo/PDB/Raw/RawError.cpp
@@ -6,6 +6,7 @@
 using namespace llvm::pdb;
 
 namespace {
+// FIXME: Use llvm::Error instead of std::error_code.
 class RawErrorCategory : public std::error_category {
 public:
   const char *name() const LLVM_NOEXCEPT override { return "llvm.pdb.raw"; }
Index: lib/ExecutionEngine/Orc/OrcError.cpp
===================================================================
--- lib/ExecutionEngine/Orc/OrcError.cpp
+++ lib/ExecutionEngine/Orc/OrcError.cpp
@@ -20,6 +20,7 @@
 
 namespace {
 
+// FIXME: Use llvm::Error instead of std::error_code.
 class OrcErrorCategory : public std::error_category {
 public:
   const char *name() const LLVM_NOEXCEPT override { return "orc"; }
Index: lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp
===================================================================
--- lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp
+++ lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp
@@ -34,6 +34,7 @@
   GenericRTDyldError = 1
 };
 
+// FIXME: Use llvm::Error instead of std::error_code.
 class RuntimeDyldErrorCategory : public std::error_category {
 public:
   const char *name() const LLVM_NOEXCEPT override { return "runtimedyld"; }
Index: lib/Object/Error.cpp
===================================================================
--- lib/Object/Error.cpp
+++ lib/Object/Error.cpp
@@ -19,6 +19,7 @@
 using namespace object;
 
 namespace {
+// FIXME: Use llvm::Error instead of std::error_code.
 class _object_error_category : public std::error_category {
 public:
   const char* name() const LLVM_NOEXCEPT override;
Index: lib/ProfileData/Coverage/CoverageMapping.cpp
===================================================================
--- lib/ProfileData/Coverage/CoverageMapping.cpp
+++ lib/ProfileData/Coverage/CoverageMapping.cpp
@@ -556,6 +556,7 @@
   llvm_unreachable("A value of coveragemap_error has no message.");
 }
 
+// FIXME: Use llvm::Error instead of std::error_code.
 class CoverageMappingErrorCategoryType : public std::error_category {
   const char *name() const LLVM_NOEXCEPT override { return "llvm.coveragemap"; }
   std::string message(int IE) const override {
Index: lib/ProfileData/InstrProf.cpp
===================================================================
--- lib/ProfileData/InstrProf.cpp
+++ lib/ProfileData/InstrProf.cpp
@@ -67,6 +67,7 @@
   llvm_unreachable("A value of instrprof_error has no message.");
 }
 
+// FIXME: Use llvm::Error instead of std::error_code.
 class InstrProfErrorCategoryType : public std::error_category {
   const char *name() const LLVM_NOEXCEPT override { return "llvm.instrprof"; }
   std::string message(int IE) const override {
Index: lib/ProfileData/SampleProf.cpp
===================================================================
--- lib/ProfileData/SampleProf.cpp
+++ lib/ProfileData/SampleProf.cpp
@@ -20,6 +20,7 @@
 using namespace llvm;
 
 namespace {
+// FIXME: Use llvm::Error instead of std::error_code.
 class SampleProfErrorCategoryType : public std::error_category {
   const char *name() const LLVM_NOEXCEPT override { return "llvm.sampleprof"; }
   std::string message(int IE) const override {
Index: lib/Support/Error.cpp
===================================================================
--- lib/Support/Error.cpp
+++ lib/Support/Error.cpp
@@ -19,6 +19,7 @@
     MultipleErrors
   };
 
+  // FIXME: Use llvm::Error instead of std::error_code.
   class ErrorErrorCategory : public std::error_category {
   public:
     const char *name() const LLVM_NOEXCEPT override { return "Error"; }
Index: tools/llvm-cxxdump/Error.cpp
===================================================================
--- tools/llvm-cxxdump/Error.cpp
+++ tools/llvm-cxxdump/Error.cpp
@@ -17,6 +17,7 @@
 using namespace llvm;
 
 namespace {
+// FIXME: Use llvm::Error instead of std::error_code.
 class cxxdump_error_category : public std::error_category {
 public:
   const char *name() const LLVM_NOEXCEPT override { return "llvm.cxxdump"; }
Index: tools/llvm-readobj/Error.cpp
===================================================================
--- tools/llvm-readobj/Error.cpp
+++ tools/llvm-readobj/Error.cpp
@@ -17,6 +17,7 @@
 using namespace llvm;
 
 namespace {
+// FIXME: Use llvm::Error instead of std::error_code.
 class _readobj_error_category : public std::error_category {
 public:
   const char* name() const LLVM_NOEXCEPT override;
Index: tools/obj2yaml/Error.cpp
===================================================================
--- tools/obj2yaml/Error.cpp
+++ tools/obj2yaml/Error.cpp
@@ -13,6 +13,7 @@
 using namespace llvm;
 
 namespace {
+// FIXME: Use llvm::Error instead of std::error_code.
 class _obj2yaml_error_category : public std::error_category {
 public:
   const char *name() const LLVM_NOEXCEPT override;