[clang] Use StringRef in range-based for loops (NFC) (#144242)

When we iterate over std::vector<std::string>, we can directly assign
each element to StringRef.  We do not need to go through separate
statements.

Author: kazutakahirata

clang/lib/Basic/TargetInfo.cpp

@@ -555,8 +555,7 @@ void TargetInfo::adjust(DiagnosticsEngine &Diags, LangOptions &Opts) {
 bool TargetInfo::initFeatureMap(
     llvm::StringMap<bool> &Features, DiagnosticsEngine &Diags, StringRef CPU,
     const std::vector<std::string> &FeatureVec) const {
-  for (const auto &F : FeatureVec) {
-    StringRef Name = F;
+  for (StringRef Name : FeatureVec) {
     if (Name.empty())
       continue;
     // Apply the feature via the target.

clang/lib/Sema/SemaDeclAttr.cpp

@@ -3232,17 +3232,15 @@ bool Sema::checkTargetAttr(SourceLocation LiteralLoc, StringRef AttrStr) {
     if (ParsedAttrs.Duplicate != "")
       return Diag(LiteralLoc, diag::err_duplicate_target_attribute)
              << Duplicate << None << ParsedAttrs.Duplicate << Target;
-    for (const auto &Feature : ParsedAttrs.Features) {
-      StringRef CurFeature = Feature;
+    for (StringRef CurFeature : ParsedAttrs.Features) {
       if (!CurFeature.starts_with('+') && !CurFeature.starts_with('-'))
         return Diag(LiteralLoc, diag::warn_unsupported_target_attribute)
                << Unsupported << None << AttrStr << Target;
     }
   }
 
   if (Context.getTargetInfo().getTriple().isLoongArch()) {
-    for (const auto &Feature : ParsedAttrs.Features) {
-      StringRef CurFeature = Feature;
+    for (StringRef CurFeature : ParsedAttrs.Features) {
       if (CurFeature.starts_with("!arch=")) {
         StringRef ArchValue = CurFeature.split("=").second.trim();
         return Diag(LiteralLoc, diag::err_attribute_unsupported)

clang/lib/Tooling/ArgumentsAdjusters.cpp

@@ -22,8 +22,7 @@ namespace clang {
 namespace tooling {
 
 static StringRef getDriverMode(const CommandLineArguments &Args) {
-  for (const auto &Arg : Args) {
-    StringRef ArgRef = Arg;
+  for (StringRef ArgRef : Args) {
     if (ArgRef.consume_front("--driver-mode=")) {
       return ArgRef;
     }