In <[EMAIL PROTECTED]>, on 10/23/2006
at 09:16 AM, Charles Mills <[EMAIL PROTECTED]> said:
>Do I recall correctly hearing that BCTR Rn,0 is no longer the favored
>way of decrementing a register, perhaps because the cache logic sees
>it as a potential branch, and that AHI Rn,-1 should be substituted?
It's not the cache logic, it's the I-fetch unit. If it tests for 0
then the BCTR should still be preferred.
>Similarly, that AHI is preferable to LA for adding a small increment
>to a register, perhaps because LA may invoke or "reserve" the
>address translation logic?
Again, it depends on how smart the I-fetch unit is.
On factor to take into consideration is the address mode. AHI has the
advantage that it is not sensitive to the address mode. AHI has the
disadvantage that it is not sensitive to the address mode.
--
Shmuel (Seymour J.) Metz, SysProg and JOAT
ISO position; see <http://patriot.net/~shmuel/resume/brief.html>
We don't care. We don't have to care, we're Congress.
(S877: The Shut up and Eat Your spam act of 2003)
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