[RISCV] Use references to avoid unnecessary struct copies. NFC

Author: topperc

llvm/lib/Target/RISCV/AsmParser/RISCVAsmParser.cpp

@@ -2716,7 +2716,7 @@ ParseStatus RISCVAsmParser::parseDirective(AsmToken DirectiveID) {
 
 bool RISCVAsmParser::resetToArch(StringRef Arch, SMLoc Loc, std::string &Result,
                                  bool FromOptionDirective) {
-  for (auto Feature : RISCVFeatureKV)
+  for (auto &Feature : RISCVFeatureKV)
     if (llvm::RISCVISAInfo::isSupportedExtensionFeature(Feature.Key))
       clearFeatureBits(Feature.Value, Feature.Key);
 
@@ -2735,7 +2735,7 @@ bool RISCVAsmParser::resetToArch(StringRef Arch, SMLoc Loc, std::string &Result,
   }
   auto &ISAInfo = *ParseResult;
 
-  for (auto Feature : RISCVFeatureKV)
+  for (auto &Feature : RISCVFeatureKV)
     if (ISAInfo->hasExtension(Feature.Key))
       setFeatureBits(Feature.Value, Feature.Key);
 
@@ -2857,7 +2857,7 @@ bool RISCVAsmParser::parseDirectiveOption() {
         // It is invalid to disable an extension that there are other enabled
         // extensions depend on it.
         // TODO: Make use of RISCVISAInfo to handle this
-        for (auto Feature : RISCVFeatureKV) {
+        for (auto &Feature : RISCVFeatureKV) {
           if (getSTI().hasFeature(Feature.Value) &&
               Feature.Implies.test(Ext->Value))
             return Error(Loc,