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Re: Inner-loop optimization regression from 3.3 to 3.4
- From: "Zack Weinberg" <zack at codesourcery dot com>
- To: Jan Hubicka <jh at suse dot cz>
- Cc: gcc at gcc dot gnu dot org, Jan Hubicka <hubicka at ucw dot cz>, rth at redhat dot com
- Date: Tue, 14 Oct 2003 19:53:04 -0700
- Subject: Re: Inner-loop optimization regression from 3.3 to 3.4
- References: <firstname.lastname@example.org><20031013130323.GY14005@kam.mff.cuni.cz>
Jan Hubicka <email@example.com> 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:
> 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.