Index: utils/TableGen/AsmWriterEmitter.cpp
===================================================================
--- utils/TableGen/AsmWriterEmitter.cpp
+++ utils/TableGen/AsmWriterEmitter.cpp
@@ -586,6 +586,8 @@
   const auto &Registers = Target.getRegBank().getRegisters();
   std::vector<Record*> AltNameIndices = Target.getRegAltNameIndices();
   bool hasAltNames = AltNameIndices.size() > 1;
+  std::string Namespace =
+      Registers.front().TheDef->getValueAsString("Namespace");
 
   O <<
   "\n\n/// getRegisterName - This method is automatically generated by tblgen\n"
@@ -610,9 +612,9 @@
     O << "  switch(AltIdx) {\n"
       << "  default: llvm_unreachable(\"Invalid register alt name index!\");\n";
     for (unsigned i = 0, e = AltNameIndices.size(); i < e; ++i) {
-      std::string Namespace = AltNameIndices[1]->getValueAsString("Namespace");
       std::string AltName(AltNameIndices[i]->getName());
-      O << "  case " << Namespace << "::" << AltName << ":\n"
+      std::string Prefix = Namespace.empty() ? Namespace + "::" : "";
+      O << "  case " << Prefix << AltName << ":\n"
         << "    assert(*(AsmStrs" << AltName << "+RegAsmOffset"
         << AltName << "[RegNo-1]) &&\n"
         << "           \"Invalid alt name index for register!\");\n"