…out I

*really need* output-register-is-equal-to-input-register constraints for this.

…sters.

…more

subtle than it looks; because the RHS is allocated before the LHS, if the LHS
is same-reg then there's the chance of the RHS allocating the required
register, leading to deadlock. So, blacklist the required register in the RHS.

… not

newgen's forté: you end up with huge numbers of rules for every combination of
address modes.