[LLVM][TableGen] Use StringRef for CodeGenInstruction::AsmString (#144440)

Author: jurahul

llvm/utils/TableGen/Common/CodeGenInstruction.cpp

@@ -435,7 +435,7 @@ void CGIOperandList::ProcessDisableEncoding(StringRef DisableEncoding) {
 CodeGenInstruction::CodeGenInstruction(const Record *R)
     : TheDef(R), Operands(R), InferredFrom(nullptr) {
   Namespace = R->getValueAsString("Namespace");
-  AsmString = R->getValueAsString("AsmString").str();
+  AsmString = R->getValueAsString("AsmString");
 
   isPreISelOpcode = R->getValueAsBit("isPreISelOpcode");
   isReturn = R->getValueAsBit("isReturn");

llvm/utils/TableGen/Common/CodeGenInstruction.h

@@ -226,7 +226,7 @@ class CodeGenInstruction {
 
   /// AsmString - The format string used to emit a .s file for the
   /// instruction.
-  std::string AsmString;
+  StringRef AsmString;
 
   /// Operands - This is information about the (ins) and (outs) list specified
   /// to the instruction.