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 4A89F3858D20; Wed, 21 Feb 2024 00:03:12 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 4A89F3858D20
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
	s=default; t=1708473792;
	bh=6kW9CF8wQpnlFmfiWefNr3Yw8qSFKnYKO84j0Fl6Kf8=;
	h=From:To:Subject:Date:In-Reply-To:References:From;
	b=R/EencC91rk/WFNgC5OjOTyWsDHD3jPLkeRUe4mZ7q9BfrsOwtZTgDBpAcR9K4nzb
	 vnXWp7s83lzBueQNTER+aZMm/fweXkSoyCpz2/wUFoKgg2oJt86XBqQ2g6fHcC+7os
	 0+WK4yB/qvUQgOIqcJ05GJm4q+Tz9iTRvDaHOBOs=
From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/114009] [11/12/13/14 Regression] Missed
 optimization: (!a) * a => 0 when a=(a/2)*2
Date: Wed, 21 Feb 2024 00:03:12 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: tree-optimization
X-Bugzilla-Version: 14.0
X-Bugzilla-Keywords: missed-optimization
X-Bugzilla-Severity: normal
X-Bugzilla-Who: pinskia at gcc dot gnu.org
X-Bugzilla-Status: NEW
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: 11.5
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: bug_status cf_reconfirmed_on everconfirmed
Message-ID: <bug-114009-4-54ObKsH1Mg@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-114009-4@http.gcc.gnu.org/bugzilla/>
References: <bug-114009-4@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=3D114009

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2024-02-21
     Ever confirmed|0                           |1

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Confirmed.

What is happening is:
`(a/2)*2 =3D=3D 0` gets optimized to `((unsigned)a) + 1 <=3D 2` and then we=
 don't
handle:
`((unsigned)a) + 1 <=3D 2 ? (a/2) : 0` which is just 0. as a has the range =
of
[-1,1] for the truth side and divide that by 2 is always 0.=