------- Comment #4 from dberlin at gcc dot gnu dot org 2006-03-30 14:04 ------- (In reply to comment #2) > You can see that PRE makes a mess out of it because of the copied loop header > of the inner loop. So maybe Zdeneks patch to move the loop header copy > outside > of the first loop helps here. Though I'd prefer to prevent PRE from doing the > transformation here. Danny, any ideas? >
Errr, why can't we just improve SCEV to handle this case if we can detect it? :) Either that, or stop mucking up the inner loop in the first place by copying it's header (which, BTW, also screws up other transformations). Zdenek has said that loop header copying is there, in part, to increase the effectiveness of code motion. This is the increased code motion you get :). -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26939
