TableGen: Use StringInit instead of std::string for DagInit arg names

llvm-svn: 288644
diff --git a/llvm/utils/TableGen/FixedLenDecoderEmitter.cpp b/llvm/utils/TableGen/FixedLenDecoderEmitter.cpp
index 010f415..e1aaecc 100644
--- a/llvm/utils/TableGen/FixedLenDecoderEmitter.cpp
+++ b/llvm/utils/TableGen/FixedLenDecoderEmitter.cpp
@@ -1759,13 +1759,15 @@
   // Gather the outputs/inputs of the instruction, so we can find their
   // positions in the encoding.  This assumes for now that they appear in the
   // MCInst in the order that they're listed.
-  std::vector<std::pair<Init*, std::string>> InOutOperands;
+  std::vector<std::pair<Init*, StringRef>> InOutOperands;
   DagInit *Out  = Def.getValueAsDag("OutOperandList");
   DagInit *In  = Def.getValueAsDag("InOperandList");
   for (unsigned i = 0; i < Out->getNumArgs(); ++i)
-    InOutOperands.push_back(std::make_pair(Out->getArg(i), Out->getArgName(i)));
+    InOutOperands.push_back(std::make_pair(Out->getArg(i),
+                                           Out->getArgNameStr(i)));
   for (unsigned i = 0; i < In->getNumArgs(); ++i)
-    InOutOperands.push_back(std::make_pair(In->getArg(i), In->getArgName(i)));
+    InOutOperands.push_back(std::make_pair(In->getArg(i),
+                                           In->getArgNameStr(i)));
 
   // Search for tied operands, so that we can correctly instantiate
   // operands that are not explicitly represented in the encoding.