how to test which register is being used?

[Doug Evans]

Ben Elliston writes:
 >  > You should be able to access using the ifield operator to get the
 >  > value in the field that the operand is based on.
 > 
 > Given that ifield accesses the bit field, exactly as it appears in the
 > instruction encoding, wouldn't (index-of ..) be preferrable?  Slightly
 > confused,

For contexts where the bit field simplify specifies the register
number, and that is what's wanted,
this isn't something I would get anal over.  Whether that is the
context in question is something for Matthew to say.