On 2013-10-23, at 19:33, robin wrote: > From: "Paul Gilmartin" <[email protected]> > Sent: Thursday, October 24, 2013 11:51 AM > >> On 2013-10-23 18:36, robin wrote: >>> >>> And anyway, how do you think that J > K is computed? >>> >>> The comparison is performed by subtracting K from J >>> (without changing either J or K, of course). >> >> Why not use the Compare instruction? (As in Assembler > > That IS what a compare is (in hardware). C compares > by subtracting one operand from the other. (without changing > either operand). > I'm skeptical:
o How does it set the condition code? o What happens if the values of J and K are so extreme that the subtraction would result in overflow? (I suppose I could imagine guard bits on the left.) o How is Compare done for non-numeric operands, as by CLC? -- gil
