On 06/15/2016 05:22 AM, Richard Biener wrote:
You look at TREE_TYPE of LOOP_VINFO_NITERS (loop_vinfo) - I don't think
this is meaningful (if then only by accident). I think you should look at the
control IV itself, possibly it's value-range, to determine the smallest possible
type to use.
Can we get an IV that's created after VRP? If so, then we have to be
prepared for the case where there's no range information on the IV. At
which point I think using type min/max of the IV is probably the right
fallback. But I do think we should be looking at range info much more
systematically.
I can't see how TREE_TYPE of the NITERS makes sense either.
Finally we have a related missed optimization opportunity, namely avoiding
peeling for gaps if we mask the last load of the group (profitability depends
on the overhead of such masking of course as it would be done in the main
vectorized loop).
I think that's a specific instance of a more general question -- what
transformations can be avoided by masking and can we generate costs to
select between those transformations and masking. Seems like a
follow-up item rather than a requirement for this work to go forward to me.
Jeff
