On 29/04/2016 11:55 PM, Tony Harminc wrote:
On 29 April 2016 at 11:50, Charles Mills <[email protected]> wrote:
What about substituting a branch relative for the branch on base register?
Trivial code change to make.
I was about to suggest that too. All the IBM published material I've
seen on this suggests that
It was a simple test case to exercise our legacy code base which issue
non-relative unconditional branches over eye-catchers. It's non-trivial
to change and test a huge code base and certainly you wouldn't want to
without understanding the problem. But there's certainly an issue as
our customers have reported.
-- all else being equal (heh), untaken branches are faster than taken
ones (even if the prediction is correct),
and
-- the penalty for misprediction is lower for relative branches than
register-based ones.
Tony H.
----------------------------------------------------------------------
For IBM-MAIN subscribe / signoff / archive access instructions,
send email to [email protected] with the message: INFO IBM-MAIN
----------------------------------------------------------------------
For IBM-MAIN subscribe / signoff / archive access instructions,
send email to [email protected] with the message: INFO IBM-MAIN
