From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugzilla@gcc.gnu.org>
Received: by sourceware.org (Postfix, from userid 48)
	id 5103D3858C53; Thu,  2 Mar 2023 11:39:00 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 5103D3858C53
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
	s=default; t=1677757140;
	bh=ihDkPS0sFN5jap1Foag5BoOh75q2Q90uztcPSJYM4j8=;
	h=From:To:Subject:Date:In-Reply-To:References:From;
	b=P2OwI4NiNWwf2ZOOVA0z0yThqk38htm1lxl62mD87FhNowRHQDzVCcHdmmIwCj8AH
	 d2JGxO3Wk54D68KzoQ4d3/jUUvAKGFLbTc11jHV6D0MVOhYESlmSsn9H1kqmaXdv1i
	 iGiviAL8pFpvMHQ4LyILN69TDwT8TO7KxFWL1CuE=
From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/108738] compile-time and memory-hog in mdreorg
Date: Thu, 02 Mar 2023 11:38:59 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: target
X-Bugzilla-Version: 13.0
X-Bugzilla-Keywords: 
X-Bugzilla-Severity: normal
X-Bugzilla-Who: rguenth at gcc dot gnu.org
X-Bugzilla-Status: ASSIGNED
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: rguenth at gcc dot gnu.org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: 
Message-ID: <bug-108738-4-SjeFNJsAl9@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-108738-4@http.gcc.gnu.org/bugzilla/>
References: <bug-108738-4@http.gcc.gnu.org/bugzilla/>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/
Auto-Submitted: auto-generated
MIME-Version: 1.0
List-Id: <gcc-bugs.sourceware.org>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D108738

--- Comment #7 from Richard Biener <rguenth at gcc dot gnu.org> ---
So it's now better than before but still quadratic.

Finding a strathegic place to limit the search with some --param might be a
solution, but there's no easy
point to hook that into.  You'd not want to disable the whole pass but
terminate the greedy search and axe the candidates sofar processed (to not =
run
into the same ones again), which might then result in "odd" STV decisions if
the remains are picked up.  To avoid this maybe maintain a "too big" set of
candidates
and if a further greedy search lands at a insn in that set, axe that search=
 as
well.  Note it's not the size of the set but the complexity of the search t=
hat
needs limiting, so count the number of ref visits through
analyze_register_chain
for an invocation of scalar_chain::build and limit that to some --param.

I'm trying to prototype that.=