Index: lib/Target/ARM/AsmParser/ARMAsmParser.cpp
===================================================================
--- lib/Target/ARM/AsmParser/ARMAsmParser.cpp
+++ lib/Target/ARM/AsmParser/ARMAsmParser.cpp
@@ -10212,8 +10212,13 @@
       } else {
         OS << "invalid operand for instruction";
         if (DevDiags) {
-          OS << " class" << I.getOperandClass() << ", error "
-             << I.getOperandError() << ", opcode "
+          OS << " class "
+#ifndef NDEBUG
+             << getMatchClassName((MatchClassKind)I.getOperandClass())
+#else
+             << I.getOperandClass()
+#endif
+             << ", error " << I.getOperandError() << ", opcode "
              << MII.getName(I.getOpcode());
         }
       }