Index: docs/LangRef.rst
===================================================================
--- docs/LangRef.rst
+++ docs/LangRef.rst
@@ -834,6 +834,11 @@
 nodes <metadata>` (but not metadata strings) are the only valid
 operands for a named metadata.
 
+#. Named metadata are represented as a string of characters with the
+   metadata prefix. The rules for metadata names are the same as for
+   identifiers, but quoted names are not allowed. ``"\xx"`` type escapes
+   are still valid, which allows any character to be part of a name.
+
 Syntax::
 
     ; Some unnamed metadata nodes, which are referenced by the named metadata.
Index: lib/IR/AsmWriter.cpp
===================================================================
--- lib/IR/AsmWriter.cpp
+++ lib/IR/AsmWriter.cpp
@@ -2215,15 +2215,13 @@
   }
 }
 
-void AssemblyWriter::printNamedMDNode(const NamedMDNode *NMD) {
-  Out << '!';
-  StringRef Name = NMD->getName();
+static void printMetadataIdentifier(StringRef Name,
+                                    formatted_raw_ostream &Out) {
   if (Name.empty()) {
     Out << "<empty name> ";
   } else {
-    if (isalpha(static_cast<unsigned char>(Name[0])) ||
-        Name[0] == '-' || Name[0] == '$' ||
-        Name[0] == '.' || Name[0] == '_')
+    if (isalpha(static_cast<unsigned char>(Name[0])) || Name[0] == '-' ||
+        Name[0] == '$' || Name[0] == '.' || Name[0] == '_')
       Out << Name[0];
     else
       Out << '\\' << hexdigit(Name[0] >> 4) << hexdigit(Name[0] & 0x0F);
@@ -2236,9 +2234,15 @@
         Out << '\\' << hexdigit(C >> 4) << hexdigit(C & 0x0F);
     }
   }
+}
+
+void AssemblyWriter::printNamedMDNode(const NamedMDNode *NMD) {
+  Out << '!';
+  printMetadataIdentifier(NMD->getName(), Out);
   Out << " = !{";
   for (unsigned i = 0, e = NMD->getNumOperands(); i != e; ++i) {
-    if (i) Out << ", ";
+    if (i)
+      Out << ", ";
     int Slot = Machine.getMetadataSlot(NMD->getOperand(i));
     if (Slot == -1)
       Out << "<badref>";
@@ -2248,7 +2252,6 @@
   Out << "}\n";
 }
 
-
 static void PrintLinkage(GlobalValue::LinkageTypes LT,
                          formatted_raw_ostream &Out) {
   switch (LT) {
@@ -2268,7 +2271,6 @@
   }
 }
 
-
 static void PrintVisibility(GlobalValue::VisibilityTypes Vis,
                             formatted_raw_ostream &Out) {
   switch (Vis) {
@@ -3008,9 +3010,10 @@
   for (const auto &I : MDs) {
     unsigned Kind = I.first;
     Out << Separator;
-    if (Kind < MDNames.size())
-      Out << "!" << MDNames[Kind];
-    else
+    if (Kind < MDNames.size()) {
+      Out << "!";
+      printMetadataIdentifier(MDNames[Kind], Out);
+    } else
       Out << "!<unknown kind #" << Kind << ">";
     Out << ' ';
     WriteAsOperandInternal(Out, I.second, &TypePrinter, &Machine, TheModule);
Index: lib/IR/LLVMContext.cpp
===================================================================
--- lib/IR/LLVMContext.cpp
+++ lib/IR/LLVMContext.cpp
@@ -240,15 +240,12 @@
 // Metadata Kind Uniquing
 //===----------------------------------------------------------------------===//
 
-/// getMDKindID - Return a unique non-zero ID for the specified metadata kind.
+/// Return a unique non-zero ID for the specified metadata kind.
 unsigned LLVMContext::getMDKindID(StringRef Name) const {
-  assert(!std::isdigit(Name.front()) &&
-         "Named metadata may not start with a digit");
-
   // If this is new, assign it its ID.
-  return pImpl->CustomMDKindNames.insert(std::make_pair(
-                                             Name,
-                                             pImpl->CustomMDKindNames.size()))
+  return pImpl->CustomMDKindNames.insert(
+                                     std::make_pair(
+                                         Name, pImpl->CustomMDKindNames.size()))
       .first->second;
 }
 
Index: test/Assembler/metadata.ll
===================================================================
--- test/Assembler/metadata.ll
+++ test/Assembler/metadata.ll
@@ -1,7 +1,7 @@
 ; RUN: llvm-as < %s | llvm-dis | llvm-as | llvm-dis | FileCheck %s
 ; RUN: verify-uselistorder %s
 
-; CHECK: @test
+; CHECK-LABEL: @test
 ; CHECK: ret void, !bar !1, !foo !0
 define void @test() {
   add i32 2, 1, !bar !0
@@ -11,17 +11,24 @@
   ret void, !foo !0, !bar !1
 }
 
-; CHECK: define void @test2() !foo !2 !baz !3
+; CHECK-LABEL: define void @test2() !foo !2 !baz !3
 define void @test2() !foo !2 !baz !3 {
   unreachable
 }
 
-; CHECK: define void @test3() !bar !3
+; CHECK-LABEL: define void @test3() !bar !3
 ; CHECK: unreachable, !bar !4
 define void @test3() !bar !3 {
   unreachable, !bar !4
 }
 
+; CHECK-LABEL: define void @test_attachment_name() {
+; CHECK:   unreachable, !\342abc !4
+define void @test_attachment_name() {
+  ;; Escape the first character when printing text IR, since it's a digit
+  unreachable, !\34\32abc !4
+}
+
 !0 = !DILocation(line: 662302, column: 26, scope: !1)
 !1 = !DISubprogram(name: "foo")
 !2 = distinct !{}