Use StringRef::starts_with (NFC) (llvm#94112)

Author: kazutakahirata

lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp

@@ -152,7 +152,7 @@ static bool IsTrivialBasename(const llvm::StringRef &basename) {
   // because it is significantly more efficient then using the general purpose
   // regular expression library.
   size_t idx = 0;
-  if (basename.size() > 0 && basename[0] == '~')
+  if (basename.starts_with('~'))
     idx = 1;
 
   if (basename.size() <= idx)

lldb/source/Utility/UriParser.cpp

@@ -47,7 +47,7 @@ std::optional<URI> URI::Parse(llvm::StringRef uri) {
       ((path_pos != std::string::npos) ? path_pos : uri.size()) - host_pos);
 
   // Extract hostname
-  if (!host_port.empty() && host_port[0] == '[') {
+  if (host_port.starts_with('[')) {
     // hostname is enclosed with square brackets.
     pos = host_port.rfind(']');
     if (pos == std::string::npos)

llvm/lib/MC/MCExpr.cpp

@@ -76,7 +76,7 @@ void MCExpr::print(raw_ostream &OS, const MCAsmInfo *MAI, bool InParens) const {
     // Parenthesize names that start with $ so that they don't look like
     // absolute names.
     bool UseParens = MAI && MAI->useParensForDollarSignNames() && !InParens &&
-                     !Sym.getName().empty() && Sym.getName()[0] == '$';
+                     Sym.getName().starts_with('$');
 
     if (UseParens) {
       OS << '(';