On Wed, Jan 5, 2022 at 10:42 AM Jakub Jelinek <ja...@redhat.com> wrote:
>
> On Wed, Jan 05, 2022 at 10:38:53AM +0100, Richard Biener via Gcc-patches
> wrote:
> > On Wed, Jan 5, 2022 at 10:18 AM Zhao Wei Liew <zhaoweil...@gmail.com> wrote:
> > >
> > > > X >= -1 && X <= 1 is (hopefully?) going to be simplified
> > > > as (unsigned)X + 1 <= 2, it might be good to simplify it this way
> > > > here as well?
> > >
> > > Yup, GCC does simplify it that way in the end, so I didn't really bother
> > > to simplify it here. That said, I'm open to simplifying it here as well,
> > > but I'm not sure how to do the unsigned cast.
> >
> > You'd do sth like
> > (with
> > { tree utype = unsigned_type_for (type); }
> > (cond (le (plus (convert:utype @0) { build_one_cst (utype); }) {
> > build_int_cst (utype, 2); }) ...)
> >
> > extra tricky will be 1 bit integer types, I guess it might be easiest
> > to exclude them
> > and special case them separately - X / Y is always X for them I think,
>
> Note, we already have:
> /* X / bool_range_Y is X. */
> (simplify
> (div @0 SSA_NAME@1)
> (if (INTEGRAL_TYPE_P (type) && ssa_name_has_boolean_range (@1))
> @0))
> for those.
Ah, it might not handle the signed : 1 case though since -1 is not in the
bool range. We could generalize the above though.
Richard.
>
> Jakub
>
