Index: include/llvm/BinaryFormat/Dwarf.h
===================================================================
--- include/llvm/BinaryFormat/Dwarf.h
+++ include/llvm/BinaryFormat/Dwarf.h
@@ -24,6 +24,8 @@
 #include "llvm/Support/Compiler.h"
 #include "llvm/Support/DataTypes.h"
 #include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/Format.h"
+#include "llvm/Support/FormatVariadicDetails.h"
 
 namespace llvm {
 class StringRef;
@@ -405,8 +407,8 @@
 /// \defgroup DwarfConstantsDumping Dwarf constants dumping functions
 ///
 /// All these functions map their argument's value back to the
-/// corresponding enumerator name or return nullptr if the value isn't
-/// known.
+/// corresponding enumerator name or return an empty StringRef if the value
+/// isn't known.
 ///
 /// @{
 StringRef TagString(unsigned Tag);
@@ -573,8 +575,32 @@
   };
 };
 
+template <typename Enum> struct EnumTraits : public std::false_type {};
+template <> struct EnumTraits<Tag> : public std::true_type {
+  static constexpr char Type[] = "TAG";
+  static constexpr StringRef (*StringFn)(unsigned) = &TagString;
+};
+
 } // End of namespace dwarf
 
+/// Dwarf constants format_provider
+///
+/// Specialization of the format_provider template for dwarf enums. Unlike the
+/// dumping functions above, these format unknown enumerator values as
+/// DW_TYPE_Unknown_1234 (e.g. DW_TAG_Unknown_ffff).
+template <typename Enum>
+struct format_provider<
+    Enum, typename std::enable_if<dwarf::EnumTraits<Enum>::value>::type> {
+  static void format(const Enum &E, raw_ostream &OS, StringRef Style) {
+    StringRef Str = dwarf::EnumTraits<Enum>::StringFn(E);
+    if (Str.empty()) {
+      OS << "DW_" << dwarf::EnumTraits<Enum>::Type << "_Unknown_"
+         << llvm::format("%x", E);
+    } else
+      OS << Str;
+}
+};
+
 } // End of namespace llvm
 
 #endif
Index: lib/BinaryFormat/Dwarf.cpp
===================================================================
--- lib/BinaryFormat/Dwarf.cpp
+++ lib/BinaryFormat/Dwarf.cpp
@@ -675,3 +675,5 @@
   }
   return ExtensionsOk;
 }
+
+const char llvm::dwarf::EnumTraits<Tag>::Type[];
Index: lib/DebugInfo/DWARF/DWARFAbbreviationDeclaration.cpp
===================================================================
--- lib/DebugInfo/DWARF/DWARFAbbreviationDeclaration.cpp
+++ lib/DebugInfo/DWARF/DWARFAbbreviationDeclaration.cpp
@@ -16,6 +16,7 @@
 #include "llvm/DebugInfo/DWARF/DWARFUnit.h"
 #include "llvm/Support/DataExtractor.h"
 #include "llvm/Support/Format.h"
+#include "llvm/Support/FormatVariadic.h"
 #include "llvm/Support/raw_ostream.h"
 #include <cstddef>
 #include <cstdint>
@@ -126,12 +127,8 @@
 }
 
 void DWARFAbbreviationDeclaration::dump(raw_ostream &OS) const {
-  auto tagString = TagString(getTag());
   OS << '[' << getCode() << "] ";
-  if (!tagString.empty())
-    OS << tagString;
-  else
-    OS << format("DW_TAG_Unknown_%x", getTag());
+  OS << formatv("{0}", getTag());
   OS << "\tDW_CHILDREN_" << (hasChildren() ? "yes" : "no") << '\n';
   for (const AttributeSpec &Spec : AttributeSpecs) {
     OS << '\t';
Index: lib/DebugInfo/DWARF/DWARFAcceleratorTable.cpp
===================================================================
--- lib/DebugInfo/DWARF/DWARFAcceleratorTable.cpp
+++ lib/DebugInfo/DWARF/DWARFAcceleratorTable.cpp
@@ -15,6 +15,7 @@
 #include "llvm/Support/Compiler.h"
 #include "llvm/Support/DJB.h"
 #include "llvm/Support/Format.h"
+#include "llvm/Support/FormatVariadic.h"
 #include "llvm/Support/ScopedPrinter.h"
 #include "llvm/Support/raw_ostream.h"
 #include <cstddef>
@@ -38,10 +39,6 @@
 }
 } // namespace
 
-static DwarfConstant formatTag(unsigned Tag) {
-  return {dwarf::TagString, "TAG", Tag};
-}
-
 static DwarfConstant formatForm(unsigned Form) {
   return {dwarf::FormEncodingString, "FORM", Form};
 }
@@ -415,7 +412,7 @@
 
 void DWARFDebugNames::Abbrev::dump(ScopedPrinter &W) const {
   DictScope AbbrevScope(W, ("Abbreviation 0x" + Twine::utohexstr(Code)).str());
-  W.startLine() << "Tag: " << formatTag(Tag) << '\n';
+  W.startLine() << formatv("Tag: {0}\n", Tag);
 
   for (const auto &Attr : Attributes) {
     W.startLine() << formatIndex(Attr.Index) << ": " << formatForm(Attr.Form)
@@ -583,8 +580,7 @@
 
 void DWARFDebugNames::Entry::dump(ScopedPrinter &W) const {
   W.printHex("Abbrev", Abbr->Code);
-  W.startLine() << "Tag: " << formatTag(Abbr->Tag) << "\n";
-
+  W.startLine() << formatv("Tag: {0}\n", Abbr->Tag);
   assert(Abbr->Attributes.size() == Values.size());
   for (const auto &Tuple : zip_first(Abbr->Attributes, Values)) {
     W.startLine() << formatIndex(std::get<0>(Tuple).Index) << ": ";
Index: lib/DebugInfo/DWARF/DWARFDie.cpp
===================================================================
--- lib/DebugInfo/DWARF/DWARFDie.cpp
+++ lib/DebugInfo/DWARF/DWARFDie.cpp
@@ -21,6 +21,7 @@
 #include "llvm/Object/ObjectFile.h"
 #include "llvm/Support/DataExtractor.h"
 #include "llvm/Support/Format.h"
+#include "llvm/Support/FormatVariadic.h"
 #include "llvm/Support/MathExtras.h"
 #include "llvm/Support/WithColor.h"
 #include "llvm/Support/raw_ostream.h"
@@ -465,13 +466,8 @@
     if (abbrCode) {
       auto AbbrevDecl = getAbbreviationDeclarationPtr();
       if (AbbrevDecl) {
-        auto tagString = TagString(getTag());
-        if (!tagString.empty())
-          WithColor(OS, HighlightColor::Tag).get().indent(Indent) << tagString;
-        else
-          WithColor(OS, HighlightColor::Tag).get().indent(Indent)
-              << format("DW_TAG_Unknown_%x", getTag());
-
+        WithColor(OS, HighlightColor::Tag).get().indent(Indent)
+            << formatv("{0}", getTag());
         if (DumpOpts.Verbose)
           OS << format(" [%u] %c", abbrCode,
                        AbbrevDecl->hasChildren() ? '*' : ' ');
Index: unittests/BinaryFormat/DwarfTest.cpp
===================================================================
--- unittests/BinaryFormat/DwarfTest.cpp
+++ unittests/BinaryFormat/DwarfTest.cpp
@@ -9,6 +9,7 @@
 
 #include "llvm/BinaryFormat/Dwarf.h"
 #include "llvm/ADT/StringRef.h"
+#include "llvm/Support/FormatVariadic.h"
 #include "gtest/gtest.h"
 
 using namespace llvm;
@@ -192,4 +193,9 @@
   EXPECT_EQ(*RefSize, 8);
 }
 
+TEST(DwarfTest, format_provider) {
+  EXPECT_EQ("DW_TAG_compile_unit", formatv("{0}", DW_TAG_compile_unit).str());
+  EXPECT_EQ("DW_TAG_Unknown_ffff", formatv("{0}", DW_TAG_hi_user).str());
+}
+
 } // end namespace