[SystemZ][z/OS] RFC : Implementation for adding in HLASM Parsing support

[anirudhp]

Summary

• Opening a differential for an RFC posted here
• Not for any review or to be merged in - Just to gather opinions.
• The purpose of this patch is to garner opinions about adding HLASM parsing support for the 1st parameter of the inline asm block

llvm/lib/MC/MCParser/AsmParser.cpp

private:
   bool ParsingMSInlineAsm = false;
 
   /// Did we already inform the user about inconsistent MD5 usage?
   bool ReportedInconsistentMD5 = false;
 
   // Is alt macro mode enabled.
   bool AltMacroMode = false;
 
+protected:
+  virtual bool parseStatement(ParseStatementInfo &Info, MCAsmParserSemaCallback *SI);
+
 public:
   AsmParser(SourceMgr &SM, MCContext &Ctx, MCStreamer &Out,
             const MCAsmInfo &MAI, unsigned CB);
   AsmParser(const AsmParser &) = delete;
   AsmParser &operator=(const AsmParser &) = delete;
   ~AsmParser() override;
 
   bool Run(bool NoInitialTextSection, bool NoFinalize = false) override;
public:
   bool parseIdentifier(StringRef &Res) override;
   void eatToEndOfStatement() override;
 
   bool checkForValidSection() override;
 
   /// }
 
 private:
-  bool parseStatement(ParseStatementInfo &Info,
-                      MCAsmParserSemaCallback *SI);
   bool parseCurlyBlockScope(SmallVectorImpl<AsmRewrite>& AsmStrRewrites);
   bool parseCppHashLineFilenameComment(SMLoc L, bool SaveLocInfo = true);
 
   void checkForBadMacro(SMLoc DirectiveLoc, StringRef Name, StringRef Body,
                         ArrayRef<MCAsmMacroParameter> Parameters);
   bool expandMacro(raw_svector_ostream &OS, StringRef Body,
                    ArrayRef<MCAsmMacroParameter> Parameters,
                    ArrayRef<MCAsmMacroArgument> A, bool EnableAtPseudoVariable,
private:
   // Directives to support address-significance tables.
   bool parseDirectiveAddrsig();
   bool parseDirectiveAddrsigSym();
 
   void initializeDirectiveKindMap();
   void initializeCVDefRangeTypeMap();
 };
 
+class HLASMAsmParser : public AsmParser {
+private:
+  MCAsmLexer &Lexer;
+  const MCAsmInfo &MAI;
+  MCStreamer &Out;
+
+  enum HLASM_INSN_KIND {
+    DC,
+    COPY,
+    //...
+  };
+
+  // Initialize the hlasm assembler instruction map
+  void initializeHLASMInstructionKindMap() {
+    return;
+  }
+
+  bool parseAsHLASMLabel();
+  bool parseAsMachineInstruction();
+  bool parseAsHLASMInstruction();
+
+public:
+  HLASMAsmParser(SourceMgr &SM, MCContext &Ctx, MCStreamer &Out,
+                     const MCAsmInfo &MAI, unsigned CB = 0) : AsmParser(SM, Ctx, Out, MAI, 0 /*CB*/), Lexer(getLexer()), MAI(MAI),
+                     Out(Out) {
+    Lexer.setSkipSpace(false);
+    initializeHLASMInstructionKindMap();
+  }
+
+  ~HLASMAsmParser() {
+    Lexer.setSkipSpace(true);
+  }
+
+  bool parseStatement(ParseStatementInfo &Info, MCAsmParserSemaCallback *SI) override {
+    return false;
+  }
+};
+
 } // end anonymous namespace
 
 namespace llvm {
 
 extern MCAsmParserExtension *createDarwinAsmParser();
 extern MCAsmParserExtension *createELFAsmParser();
 extern MCAsmParserExtension *createCOFFAsmParser();
 extern MCAsmParserExtension *createWasmAsmParser();

 
 } // end namespace MCParserUtils
 } // end namespace llvm
 
 /// Create an MCAsmParser instance.
 MCAsmParser *llvm::createMCAsmParser(SourceMgr &SM, MCContext &C,
                                      MCStreamer &Out, const MCAsmInfo &MAI,
                                      unsigned CB) {
+  if (C.getObjectFileInfo()->getTargetTriple().isOSzOS() && MAI.getAssemblerDialect())
+    return new HLASMAsmParser(SM, C, Out, MAI, CB);
+
   return new AsmParser(SM, C, Out, MAI, CB);
 }