better handling of unknown operands

[Ben Elliston]

>>>>> "Doug" == Doug Evans <dje@transmeta.com> writes:

  matthew> every format op is either:
  matthew> - SEM-ONLY, or
  matthew> - has a matching syntax op, and
  matthew> every syntax op has matching format op.

  matthew> is there a case that this doesn't work with?  i looked at the current
  matthew> cgen input files and none of them appear to use the former currently,
  matthew> but it definately should be supported.  i can't think of a case for
  matthew> operands used for parsing purposes that don't have format ifields, but
  matthew> if there were, you could extend this with a (new? same?) attribute to
  matthew> indicate it was such.

  >> Anyone?  Anyone?

  Doug> I don't quite understand the question.

We're talking about improving the parsing of syntax strings and format
fields and validating their contents.  In this way, you'll be warned
if the operands appearing in the syntax string don't match what is
expected in the format field.  And we're just trying to discover all
of the corner cases before doing so.

Ben