[Bug tree-optimization/100499] Different results with -fpeel-loops -ftree-loop-vectorize options

["aldyh at redhat dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100499

--- Comment #20 from Aldy Hernandez <aldyh at redhat dot com> ---
On Wed, May 19, 2021 at 8:31 AM rguenth at gcc dot gnu.org
<gcc-bugzilla@gcc.gnu.org> wrote:
>
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100499
>
> --- Comment #17 from Richard Biener <rguenth at gcc dot gnu.org> ---
> (In reply to Andrew Macleod from comment #16)

> > We could add an expression evaluator that can walk that expression, invoking
> > range-ops on each expression, and calling a ranger instance to evaluate a
> > range for any ssa_name it finds.
> >
> > It would bail if there are unknown tree-codes to range-ops.
>
> Yeah, it would be similar to the existing determine_value_range () function
> which does exactly do this (but not using ranger).

determine_value_range() has been calling range-ops under the covers
for quite a while, so it's half-way there.  It would require some
minor tweaks:

a) Use irange instead of value_range so as to not throw away the
higher precision range-ops calculates.

b) If we want context-aware ranges, pass it a gimple statement / edge
/ etc, and a range_query/ranger.

Oh yeah, and return a proper range, not this value_range_kind +
wide_int + wide_int business (determine_value_range_1 does this
already).