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 747D7385841C; Fri, 12 Apr 2024 10:15:07 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 747D7385841C
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
	s=default; t=1712916907;
	bh=9lPWFtrX0kWoX8WJdL7ex9qpdFK4nAYJaStwcuK0Pxs=;
	h=From:To:Subject:Date:In-Reply-To:References:From;
	b=GZ1sc/d7DTutinSHkhriX19ugukLGHwUu16cc7QT5gSFwCllWZelbkp9cXbzRIFTt
	 MmxMVT2Ejhj5/O5s4iNab/+ztMzLtWOou3pbjHI9gcEZ8UTyFJXpedTGhEmaC30RBe
	 xt8aOWuL5GMou7zAdz1tQB2uHq5lBvbIMXpefB4E=
From: "tnfchris at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/114403] [14 regression] LLVM miscompiled with
 -O3 -march=znver2 -fno-vect-cost-model since r14-6822-g01f4251b8775c8
Date: Fri, 12 Apr 2024 10:15:06 +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: wrong-code
X-Bugzilla-Severity: normal
X-Bugzilla-Who: tnfchris at gcc dot gnu.org
X-Bugzilla-Status: ASSIGNED
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P1
X-Bugzilla-Assigned-To: tnfchris at gcc dot gnu.org
X-Bugzilla-Target-Milestone: 14.0
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: 
Message-ID: <bug-114403-4-Iig9r9jd2o@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-114403-4@http.gcc.gnu.org/bugzilla/>
References: <bug-114403-4@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=3D114403

--- Comment #24 from Tamar Christina <tnfchris at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #23)
> Maybe easier to understand testcase:
>=20
> with -O3 -msse4.1 -fno-vect-cost-model we return 20 instead of 8.  Adding
> -fdisable-tree-cunroll avoids the issue.  The upper bound we set on the
> vector loop causes us to force taking the IV exit which continues
> with i =3D=3D (niter - 1) / VF * VF, but 'niter' is 20 here.

yes,indeed, that's what my patch was arguing last time, but I didn't explai=
n it
well enough.

I'm about to send out v2 (waiting for regtest to finish) which hopefully
articulates this better.=