------- Comment #11 from rakdver at kam dot mff dot cuni dot cz 2010-02-09
08:30 -------
Subject: Re: [4.3/4.4/4.5 Regression] No loop
counter reversal for simple loops anymore
Hi,
> As suggested by Zdenek, here is a patch that lowers the cost of the IV when
> it is compared against zero in a condition. The fragile part of this patch is
> that it
> lowers the cost by a magical constant "10". Would there be a more appropriate
> way to compute the effect, or a better constant?
10 looks like way too much, forcing ivopts to prefer comparison with zero even
if other choice of induction variables would be better. The constant should be
target-dependent; but unless we already have this information somewhere, I
would
use 1, or even just change the complexity part of the cost (assuming that that
would
work),
Zdenek
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40886
