On 06/22/2016 09:03 AM, Ilya Enkovich wrote:
2016-06-16 9:26 GMT+03:00 Jeff Law <l...@redhat.com>:
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.
I need to build a vector {niters, ..., niters} and compare to it. Why doesn't
it make sense to choose the same type for IV? I agree that choosing a smaller
type may be beneficial. Shouldn't I look at nb_iterations_upper_bound then
to check if NITERS can be casted to a smaller type?
Isn't TREE_TYPE (LOOP_VINFO_NITERS (loop_vinfo)) the type of the
constant being used to represent the number of iterations? That is
independent of the type of the IV.
Though I guess your argument is that since you're building a vector of
niters, that indeed what you want is the type of that constant, not the
type of the IV. That might be worth a comment in the code :-)
jeff
