Fw: GSoC topic: Implement hot cold splitting at GIMPLE IR level

[Richard Biener]

On Tue, Mar 17, 2020 at 3:33 PM Aditya K via Gcc <gcc@gcc.gnu.org> wrote:
>
> As I understand the openmp outliner is also at the tree level. A region based outliner could be reused there. I’m not particular about the outliner being specific to ipa-split. A GSoC project can help us get the coding+testing done.  Any pass that needs a function splitting at tree level can reuse them.

There's a SESE region outliner (it also handles SEME regions with
alternate exits exiting the function), in move_sese_region_to_fn.
Probably exactly what would be needed for this.  It's also used by
OpenMP outlining (but not IPA split as Honza said).

Richard.

> -Aditya
> ________________________________
> From: Jakub Jelinek <jakub@redhat.com>
> Sent: Monday, March 16, 2020 5:19:16 PM
> To: Aditya K <hiraditya@msn.com>
> Cc: Jan Hubicka <hubicka@ucw.cz>; gcc@gcc.gnu.org <gcc@gcc.gnu.org>
> Subject: Re: Fw: GSoC topic: Implement hot cold splitting at GIMPLE IR level
>
> On Mon, Mar 16, 2020 at 11:11:14PM +0000, Aditya K via Gcc wrote:
> > >
> > > 2) ipa-split is very simplistic and only splits when there is no value
> > >    computed in header of function used in the tail.  We should support
> > >   adding extra parameters for values computed and do more general SESE
> > >    outlining
> > >  Note that we do SESE outlining for openMP but this code is not
> > >  interfaced very generically to be easilly used by ipa-split.
> >
> > This sounds like a good GSoC project to work on. We could have a SESE/SEME based ipa-split, that
> > could help with function splitting as well as openMP.
>
> No, OpenMP region outlining needs to be done where it is done currently,
> ipa-split is way too late for that.
>
>         Jakub
>