3.7. Parsing Instructions

The final function which needs defining is ParseInstruction, which parses the instruction mnemonic, followed by all the operands until the end of the statement is reached, called by MatchInstructionImpl to identify all operands for matching.

The instruction mnemonic is parsed by a TableGen generated function, but is first split into sections separated by the dots in the mnemonic, with each part being added to the instructions operand list.

For example the mnemonic l.add would become [l, .add], lf.add.s would become [lf, .add, .s], etc.

Once the mnemonic has been split up and added to the operand list, the ParseOperand function defined above is repeatedly called to parse the next operand until the end of the statement is reached (AsmToken::EndOfStatement), with commas being consumed between operands.

bool OR1KAsmParser::
ParseInstruction(StringRef Name, SMLoc NameLoc,
                 SmallVectorImpl<MCParsedAsmOperand*> &Operands) {
  // First operand is token for instruction
  size_t dotLoc = Name.find('.');
  Operands.push_back(OR1KOperand::CreateToken(Name.substr(0,dotLoc),NameLoc));
  if (dotLoc < Name.size()) {
    size_t dotLoc2 = Name.rfind('.');
    if (dotLoc == dotLoc2)
      Operands.push_back(OR1KOperand::CreateToken(Name.substr(dotLoc),NameLoc));
    else {
      Operands.push_back(OR1KOperand::CreateToken(Name.substr
                                        (dotLoc, dotLoc2-dotLoc), NameLoc));
      Operands.push_back(OR1KOperand::CreateToken(Name.substr
                                        (dotLoc2), NameLoc));
    }
  }

  // If there are no more operands, then finish
  if (getLexer().is(AsmToken::EndOfStatement))
    return false;

  // Parse first operand
  if (ParseOperand(Operands))
    return true;

  // Parse until end of statement, consuming commas between operands
  while (getLexer().isNot(AsmToken::EndOfStatement) &&
        getLexer().is(AsmToken::Comma)) {
    // Consume comma token
    getLexer().Lex();

    // Parse next operand
    if(ParseOperand(Operands))
      return true;
  }

  return false;
}