RE: Constraints between operands

["Will Newton" <will.newton@imgtec.com>]

 
> I was going to say have either a special "parse" or "insert" handler.
> I seem to recall other instances where I needed to validate 
> two operands against each other, but I can't find one at the moment.
> At any rate, you're right, the parse handler isn't passed 
> sufficient info.
> 
> If I can't find an existing example I think we need to extend cgen.
> e.g. pass the fields struct to either or both of the parse 
> and insert handlers.
> 
> Comments folks?

One thing that would seem useful is to be able to parse things easily
extending the existing infrastructure. I have come across two minor
instances where it could be useful to do this.

1. One of our addressing modes looks like this:

GETD  Reg1, [Reg2+#0x20++] ; Reg2+offset, post-increment Reg2

It is not possible to parse this using the builtin integer parser, it
barfs on the trailing ++. I implemented a parse handler for the integer
value and ended up using strtol, it would be nice if I could perhaps
pass an end pointer or length argument to cgen_parse_unsigned_integer to
tell it where to stop parsing and use that instead. Maybe this isn't
possible, it's not that big an issue.

2. To parse a register in a custom handler I ended up doing this:

  CGEN_OPERAND oper = meta_cgen_operand_table[opindex];
  int i;
  CGEN_KEYWORD *reg_names = NULL;

  for (i = 0; i < HW_MAX; i++)
    {
      if (meta_cgen_hw_table[i].type == oper.hw_type)
        {
          reg_names = (CGEN_KEYWORD *)meta_cgen_hw_table[i].asm_data;
        }
    }

  if (reg_names == NULL)
    return "internal error";

  errmsg = cgen_parse_keyword (cd, strp, reg_names, valuep);

Which is a little bit of a roundabout way to get something that perhaps
I should already have.