Re: Inner-loop optimization regression from 3.3 to 3.4

[Jan Hubicka <jh at suse dot cz>]

> Jan Hubicka <jh@suse.cz> writes:
> 
> > Overall I do believe that such things are very target specific and
> > require knowledge of branch probabilities and costs to be done properly,
> > so it belongs to backend.  I wrote ifcvt imporvement to deal with such a
> > testcases at:
> > http://gcc.gnu.org/ml/gcc-patches/2002-06/msg00026.html
> > It is able to combine || and && style tests (sequence of branches
> > targetting the same destination)
> >
> > It is used on hammer branch for a while and does not appear to cause any
> > problems now when RTL sharing issues are sorted out.  It causes small
> > but measurable SPEC imrovement (about 2points if I recall correctly).
> > I can update the patch easilly for current tree if it would be
> > considered for mainline.  There is small conflict with related IA-64
> > specific work for multiway branches.  ALso I was told that for IA-64 we
> > may extend the patch to deal with sequence of multiple branches, not
> > only combining two at a time.
> 
> This looks like a worthwhile thing to have, and since it addresses a
> regression I would say it could go in early in stage 3, if you were
> willing to update it and resolve the conflict with the IA-64.

OK, I will prepare updated version tomorrow and will try to make some
SPEC numbers too so we can decide what to do about that patch.

Honza
> 
> zw