--- Comment #12 from rsandifo at gcc dot gnu.org <rsandifo at gcc dot gnu.org>
(In reply to Jakub Jelinek from comment #11)
> (In reply to rsand...@gcc.gnu.org from comment #10)
> > I'd tried doing this in set_nonzero_bits first, before adding
> > intersect_range_with_nonzero_bits. See
> > https://gcc.gnu.org/ml/gcc-patches/2018-02/msg00095.html for why it didn't
> > work.
> IMHO that is a risk of all the VRP changes that some case will regress, the
> more important question is how much it will help in general, and I think it
Yeah I'd hoped so too, but...
> If it is only done in this special case, other passes can't benefit from the
> more accurate range info.
...when I did a comparison of the testsuite assembly output on a range
of targets, I didn't find any examples of things benefiting outside of
split_constant_offset, but quite a few regressions caused by trying
to interesect a VR_ANTI_RANGE with a reduced VR_RANGE.
The testsuite isn't the most representative codebase around, but still,
it suggests that we'd need to add some special cases elsewhere to