Re: [PATCH] Add a late-combine pass [PR106594]

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

On Mon, Jun 24, 2024 at 9:38 PM Segher Boessenkool
<segher@kernel.crashing.org> wrote:
>
> I didn't see this before.   Sigh.
>
> On Tue, Jan 02, 2024 at 09:47:11AM +0000, Richard Sandiford wrote:
> > Segher Boessenkool <segher@kernel.crashing.org> writes:
> > > On Tue, Oct 24, 2023 at 07:49:10PM +0100, Richard Sandiford wrote:
> > >> This patch adds a combine pass that runs late in the pipeline.
> > >
> > > But it is not.  It is a completely new thing, and much closer to
> > > fwprop than to combine, too.
> >
> > Well, it is a combine pass.
>
> No, it is not.  In the context of GCC combine is the instruction
> combiner.  Which does something else than this does.
>
> So use a different name.  Please.  It will be NAKked by the combine
> maintainer otherwise.
>
> > It's not a new instance of the pass in
> > combine.cc, but I don't think that's the implication.  We already have
> > two combine passes: the combine.cc one and the postreload one.
>
> There is no postreload-combine pass.  There is a postreload pass that
> does various trivial things.  One of those is reload_combine, which is
> nothing like combine.  It is a kind of limited fwprop for memory
> addressing.
>
> > > Could you rename it to something else, please?  Something less confusing
> > > to both users and maintainers :-)
> >
> > Do you have any suggestions?
>
> Since it is something like fwprop, maybe something like that?  Or maybe
> put "addressing" in the name, if that is the point here.
>
> > >> The pass currently has a single objective: remove definitions by
> > >> substituting into all uses.
> > >
> > > The easy case ;-)
> >
> > And the yet a case that no existing pass handles. :)  That's why I'm
> > trying to add something that does.
>
> So, fwprop.

fullprop

Richard.

>
> Segher