[clang] Use StringRef::ltrim (NFC)

Author: kazutakahirata

clang/lib/ASTMatchers/Dynamic/Parser.cpp

@@ -299,10 +299,8 @@ class Parser::CodeTokenizer {
 
   /// Consume all leading whitespace from \c Code.
   void consumeWhitespace() {
-    Code = Code.drop_while([](char c) {
-      // Don't trim newlines.
-      return StringRef(" \t\v\f\r").contains(c);
-    });
+    // Don't trim newlines.
+    Code = Code.ltrim(" \t\v\f\r");
   }
 
   SourceLocation currentLocation() {

clang/lib/Basic/IdentifierTable.cpp

@@ -628,8 +628,7 @@ ObjCMethodFamily Selector::getMethodFamilyImpl(Selector sel) {
     return OMF_performSelector;
 
   // The other method families may begin with a prefix of underscores.
-  while (!name.empty() && name.front() == '_')
-    name = name.substr(1);
+  name = name.ltrim('_');
 
   if (name.empty()) return OMF_None;
   switch (name.front()) {

clang/lib/Basic/Targets/AArch64.cpp

@@ -1365,8 +1365,7 @@ bool AArch64TargetInfo::validateConstraintModifier(
     StringRef Constraint, char Modifier, unsigned Size,
     std::string &SuggestedModifier) const {
   // Strip off constraint modifiers.
-  while (Constraint[0] == '=' || Constraint[0] == '+' || Constraint[0] == '&')
-    Constraint = Constraint.substr(1);
+  Constraint = Constraint.ltrim("=+&");
 
   switch (Constraint[0]) {
   default:

clang/lib/Basic/Targets/ARM.cpp

@@ -1230,8 +1230,7 @@ bool ARMTargetInfo::validateConstraintModifier(
   bool isInOut = (Constraint[0] == '+');
 
   // Strip off constraint modifiers.
-  while (Constraint[0] == '=' || Constraint[0] == '+' || Constraint[0] == '&')
-    Constraint = Constraint.substr(1);
+  Constraint = Constraint.ltrim("=+&");
 
   switch (Constraint[0]) {
   default:

clang/lib/Basic/Targets/X86.cpp

@@ -1613,8 +1613,7 @@ bool X86TargetInfo::validateOutputSize(const llvm::StringMap<bool> &FeatureMap,
                                        StringRef Constraint,
                                        unsigned Size) const {
   // Strip off constraint modifiers.
-  while (Constraint[0] == '=' || Constraint[0] == '+' || Constraint[0] == '&')
-    Constraint = Constraint.substr(1);
+  Constraint = Constraint.ltrim("=+&");
 
   return validateOperandSize(FeatureMap, Constraint, Size);
 }