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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/101523] Huge number of combine attempts
Date: Thu, 21 Mar 2024 13:15:55 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D101523

--- Comment #40 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Segher Boessenkool from comment #39)
> (In reply to Richard Biener from comment #37)
> > Created attachment 57753 [details]
> > quick attempt at a limit
> >=20
> > So like this?
>=20
> Hrm.  It should be possible to not have the same test 28 times.  Just at =
one
> spot!

Not sure.  We loop over log-links multiple times.  You could argue we
should only call try_combine once ;)  But yeah, it's not very pretty,
agreed.  We could pass the counter to try_combine and have a special
return value, (void *)-1 for the failed-and-exhausted case, handling
that in retry: like

retry:
  if (next =3D=3D NULL || next =3D=3D (void *)-1)
    attempts =3D 0;

then only the last case where we mangle 'set' and have to restore it on
failure would need special casing (and of course try_combine itself).
But in a way that's also ugly so I guess I stay with my proposal.

At least until somebody actually tried if and how much it helps (and for wh=
ich
values of the --param).=