Re: RFC - VRP1 default mode

[Richard Biener <richard.guenther@gmail.com>]

On Wed, Oct 26, 2022 at 4:24 PM Andrew MacLeod <amacleod@redhat.com> wrote:
>
> Figured I would ask what you guys think of making ranger the default for
> the VRP1 pass now.
>
> With partial equivalences and the other bits I checked in the past few
> weeks I'm not aware of much that the legacy VRP pass gets that ranger
> doesn't.  The only exception to that which I am aware of is the trick
> played with the unreachable edges to set global ranges, but that is done
> in the DOM passes now anyway... so it just happens slightly later in the
> optimization cycle.

Note DOM should go away at some point.  Why can this not happen during
ranger driven VRP?

> There is one test case that needs adjustment for
> that which was just checking for a mask in DOM2
> (gcc.dg/tree-ssa/pr107009.c).   At this point I have not aware of
> anything that Id be concerned about, and the testsuite seems to run
> cleanly.

Did you enable Ada?  The only feature I don't see implemented is
symbolic range handling which boils down to general base + constant offset
range endpoints (that's what symbolic ranges allow).  That area was
specifically improved to optimize range checks emitted by the Ada frontend
but IIRC also applies to fortran -frange-check (not sure about test coverage
of that).

> We could change the default now and see if any issues show up, giving us
> a chance to address them. The code base has been well exercised for a
> while so risk should be low.  We could also reduce code size by
> stripping out unneeded code if we so desired.
>
> Or we could leave things as they are for one more cycle.  My preference
> would be to make the switch now and let it play out. Thoughts?
>
> Andrew
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