subf : Subtract From

The Subtract From instructions subtract the second operand (RA) from the third (RB). Extended mnemonics are provided
that use the more “normal” order, in which the third operand is subtracted from the second. Both these mnemonics
can be coded with a final “o” and/or “.” to cause the OE and/or Rc bit to be set in the underlying instruction.
sub Rx,Ry,Rz (equivalent to: subf Rx,Rz,Ry)
subc Rx,Ry,Rz (equivalent to: subfc Rx,Rz,Ry)