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/Feature/metadata.ll
===================================================================
--- test/Feature/metadata.ll
+++ test/Feature/metadata.ll
@@ -1,11 +1,13 @@
-; RUN: llvm-as < %s | llvm-dis | llvm-as | llvm-dis
+; RUN: llvm-as < %s | llvm-dis | llvm-as | llvm-dis | FileCheck %s
 ; PR7105
 
 define void @foo(i32 %x) {
   call void @llvm.zonk(metadata i32 %x, i64 0, metadata !1)
   store i32 0, i32* null, !whatever !0, !whatever_else !{}, !more !{!"hello"}
   store i32 0, i32* null, !whatever !{!"hello", !1, !{}, !2}
-  ret void, !_1 !0
+  ;; \31 -> '1'. Make sure we emit the \ sequence when printing
+  ;; CHECK: !\31abc
+  ret void, !_1 !0, !\31abc !1
 }
 
 declare void @llvm.zonk(metadata, i64, metadata) nounwind readnone