better handling of unknown operands

[Ben Elliston]

>>>>> "matthew" == matthew green <mrg@cygnus.com> writes:

  matthew> can't forget about those SEM-ONLY operands, but we do know that they
  matthew> exist.  i believe ben is onto a good diagnostic here, and we should
  matthew> try to make it work.  cgen's diagnostics are one of it's worst areas.
  matthew> if you change the assertion to be:

  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?

Ben