Fix a couple more implicit conversions that Clang doesn't diagnose.
diff --git a/llvm/utils/TableGen/CodeGenDAGPatterns.cpp b/llvm/utils/TableGen/CodeGenDAGPatterns.cpp
index 043cb38..703cd51 100644
--- a/llvm/utils/TableGen/CodeGenDAGPatterns.cpp
+++ b/llvm/utils/TableGen/CodeGenDAGPatterns.cpp
@@ -3108,7 +3108,8 @@
     Record *XFormNode = Xforms.back();
     Record *SDNode = XFormNode->getValueAsDef("Opcode");
     StringRef Code = XFormNode->getValueAsString("XFormFunction");
-    SDNodeXForms.insert(std::make_pair(XFormNode, NodeXForm(SDNode, Code)));
+    SDNodeXForms.insert(
+        std::make_pair(XFormNode, NodeXForm(SDNode, std::string(Code))));
 
     Xforms.pop_back();
   }