[SystemZ][z/OS] Introduce dialect querying helper functions

[anirudhp]

Summary

• In the SystemZAsmParser, there will be a few queries to the type of dialect it is (AD_ATT, AD_HLASM) in future patches.
• It would be nice to have two small helper functions isParsingATT() and isParsingHLASM()
• Putting this as a separate smaller patch allows us to remove its definitions from other dependent patches.

[abhina.sreeskantharajan]

LGTM

[anirudhp]

Ping :)

[uweigand]

LGTM.

llvm/lib/Target/SystemZ/AsmParser/SystemZAsmParser.cpp

private:
   // or from 'a' through 'z', or '$', '_','#', or '@'.
   inline bool isHLASMAlpha(char C) {
     return isAlpha(C) || llvm::is_contained("_@#$", C);
   }
 
   // A digit in HLASM is a number from 0 to 9.
   inline bool isHLASMAlnum(char C) { return isHLASMAlpha(C) || isDigit(C); }
 
+  // Are we parsing using the AD_HLASM dialect?
+  inline bool isParsingHLASM() { return getMAIAssemblerDialect() == AD_HLASM; }
+
+  // Are we parsing using the AD_ATT dialect?
+  inline bool isParsingATT() { return getMAIAssemblerDialect() == AD_ATT; }
+
 public:
   SystemZAsmParser(const MCSubtargetInfo &sti, MCAsmParser &parser,
                    const MCInstrInfo &MII,
                    const MCTargetOptions &Options)
     : MCTargetAsmParser(Options, sti, MII), Parser(parser) {
     MCAsmParserExtension::Initialize(Parser);
 
     // Alias the .word directive to .short.
Operands.push_back(SystemZOperand::createImmTLS(Expr, Sym,
                                                     StartLoc, EndLoc));
   else
     Operands.push_back(SystemZOperand::createImm(Expr, StartLoc, EndLoc));
 
   return MatchOperand_Success;
 }
 
 bool SystemZAsmParser::isLabel(AsmToken &Token) {
-  if (getMAIAssemblerDialect() == AD_ATT)
+  if (isParsingATT())
     return true;
 
   // HLASM labels are ordinary symbols.
   // An HLASM label always starts at column 1.
   // An ordinary symbol syntax is laid out as follows:
   // Rules:
   // 1. Has to start with an "alphabetic character". Can be followed by up to
   //    62 alphanumeric characters. An "alphabetic character", in this scenario,