From: Denis Chertykov <denisc@overta.ru>
To: Michael Matz <matz@suse.de>
Cc: Giovanni Bajo <giovannibajo@libero.it>, gcc@gcc.gnu.org
Subject: Re: [new-ra] Development status?
Date: Tue, 20 Jan 2004 16:35:00 -0000 [thread overview]
Message-ID: <n08i60kk.fsf@localhost.localdomain> (raw)
In-Reply-To: <Pine.LNX.4.58.0401191023350.3429@wotan.suse.de>
Michael Matz <matz@suse.de> writes:
> Hi,
>
> On Sun, 18 Jan 2004, Giovanni Bajo wrote:
>
> > what's the development status for new-ra?
>
> There is one big patch outstanding waiting review (and mayby design
> decisions), plus one smaller patch from Denis, which touches the remaining
> big problem:
>
> 1. For reload to become reducable (at least on sufficiently sane, probably
> on most platforms) we basically need to do something similar to
> regclass. This means figuring out the correct (i.e. possbile) register
> classes for each register reference. Due to GCCs design choosing a
> class for one reference might influence the possible classes for other
> references of the same register, or of other refs in the insn under
> consideration. Implementing this optimally would mean finding some
> minimal set of paths over a set of graphs (I'm not even yet sure how it
> would have to be structured). I haven't tried this but I think it
> would be too slow.
>
> Regclass.c does use some heuristics to find a good result, although
> it's also not exactly fast. Currently we can either use the results
> from regclass for new-ra, or use pre-reload to do that (which fixes the
> choice of one certain alternative for an insn, before choosing
> classes). Both result in suboptimal code, sometimes in horrible code.
>
> The above is something which needs to be implemented to make new-ra not
> regress compared to current ra.
>
> 2. Then, before considering new-ra done, pre-reload.c needs to be heavily
> massaged to not be an ugly clone of reload*.c . Cosmetic (it's more or
> less a black box), but still important.
>
> 3. Then, performance issues. Some passes in new-ra are only candidates
> for -O3 (or not even that), or have to be rewritten to be incremental.
> Web splitting in particular, which would ideally be integrated into the
> normal spilling process, which then also would mean we wouldn't have to
> disable interference region spilling when using it.
4. Then, allocator must have a support for register elimination.
>
> The first numbered item above is ugly. I believe at least, I haven't even
> starting implementing it, because I think it's so ugle ;-) I know that
> this is a vicious circle.
Michael ! I have completed the patch which calculate register classes
preferences as regclass (not as pre-reload).
Yes. I have converted regclass routines to work with webs.
I was interested in comparision of results given by pre-reload based
web_class and regclass based web_class.
Are you ready to look at patch and results ?
Denis.
next prev parent reply other threads:[~2004-01-20 16:35 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-01-18 3:13 Giovanni Bajo
2004-01-19 9:58 ` Michael Matz
2004-01-20 16:35 ` Denis Chertykov [this message]
2004-01-20 16:48 ` Michael Matz
2004-01-20 17:26 ` Denis Chertykov
2004-01-21 14:11 ` Michael Matz
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