For those of us who still have to use coal-fired 360s, it was good, at
last, to see Tony's contribution, standing out head-and-shoulders above
the rest.
But even Tony's is slightly overkill. NR sets the condition code, so you
don't need the Load-and-test:
* --------------------------------------------------------
LA R0,3 Mask for multiple of 4
NR R0,R15 Check multiple of 4
BNZ BAD_RC Not so: error
*
LA R0,BIG_RC Lowest invalid RC
CLR R0,R3 Check RC within limits
BL BAD_RC Not so: error
*
B RC_TREE(,R3) OK: go handle the RC
*
RC_TREE B RC0 No error
B RC4 Record not found (whatever)
B RC8 Zombie attack
B RC12 Gross security breach
BIG_RC EQU *-RC_TREE Bigger RCs are invalid
* --------------------------------------------------------
Brent Longborough
> -----Original Message -----
>
> Date: Mon, 27 Aug 2012 13:19:10 -0400
> From: Tony Thigpen <t...@vse2pdf.com>
> Subject: Re: which instructions should I use?
>
> Your code requires 2 scratch registers. The following uses just 1
> scratch register and does not require literal storage:
>
> LA R0,3
> NR R0,R15
> LTR R0,R0
> BNZ BAD_RC
>
> (I still have to use code that works on boxes without the jump
> instructions.)
>
> Tony Thigpen
