TableGen: Use StringRef instead of const std::string& in return vals.

This will allow to switch to a different string storage in an upcoming
commit.

llvm-svn: 288612
diff --git a/llvm/utils/TableGen/CodeEmitterGen.cpp b/llvm/utils/TableGen/CodeEmitterGen.cpp
index fc2e5aa..f34c0de 100644
--- a/llvm/utils/TableGen/CodeEmitterGen.cpp
+++ b/llvm/utils/TableGen/CodeEmitterGen.cpp
@@ -279,7 +279,7 @@
         R->getValueAsBit("isPseudo"))
       continue;
     const std::string &InstName = R->getValueAsString("Namespace") + "::"
-      + R->getName();
+      + R->getName().str();
     std::string Case = getInstructionCase(R, Target);
 
     CaseMap[Case].push_back(InstName);