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 C8113385843A; Wed, 27 Mar 2024 16:10:21 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org C8113385843A
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
	s=default; t=1711555821;
	bh=U8IhafjuAdgShN6OnGx8Kmj2YT/tc6UhumVKoNf2qi4=;
	h=From:To:Subject:Date:In-Reply-To:References:From;
	b=s+dv3PELARr6KvIz4Hklsa+JpFYXp0cqOCXgpncrb9ncQcx+3qxhqAbesk35t2Lco
	 Ya+5x3JACr3yxyhYXZdueHS9Qs8O0k0ZQqFj7DzgeJuW9tuDwUzI+5ZFw11rmC3DHa
	 s9R41h/U0E9ZP8jnxAA+PQOQwa2RsbXJHhcbdzhk=
From: "cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug rtl-optimization/101523] Huge number of combine attempts
Date: Wed, 27 Mar 2024 16:10:21 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: rtl-optimization
X-Bugzilla-Version: 12.0
X-Bugzilla-Keywords: compile-time-hog, memory-hog
X-Bugzilla-Severity: normal
X-Bugzilla-Who: cvs-commit at gcc dot gnu.org
X-Bugzilla-Status: NEW
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: segher at gcc dot gnu.org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: 
Message-ID: <bug-101523-4-USFYV2outZ@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-101523-4@http.gcc.gnu.org/bugzilla/>
References: <bug-101523-4@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=3D101523

--- Comment #50 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Segher Boessenkool <segher@gcc.gnu.or=
g>:

https://gcc.gnu.org/g:839bc42772ba7af66af3bd16efed4a69511312ae

commit r14-9692-g839bc42772ba7af66af3bd16efed4a69511312ae
Author: Segher Boessenkool <segher@kernel.crashing.org>
Date:   Wed Mar 27 14:09:52 2024 +0000

    combine: Don't combine if I2 does not change

    In some cases combine will "combine" an I2 and I3, but end up putting
    exactly the same thing back as I2 as was there before.  This is never
    progress, so we shouldn't do it, it will lead to oscillating behaviour
    and the like.

    If we want to canonicalise things, that's fine, but this is not the
    way to do it.

    2024-03-27  Segher Boessenkool  <segher@kernel.crashing.org>

            PR rtl-optimization/101523
            * combine.cc (try_combine): Don't do a 2-insn combination if
            it does not in fact change I2.=