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Re: Inner-loop optimization regression from 3.3 to 3.4

Jan Hubicka <> 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.


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