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 2FF77389801B; Thu, 24 Jun 2021 15:39:53 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 2FF77389801B
From: "amker at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/101145] niter analysis fails for until-wrap
 condition
Date: Thu, 24 Jun 2021 15:39:52 +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: 12.0
X-Bugzilla-Keywords: missed-optimization
X-Bugzilla-Severity: normal
X-Bugzilla-Who: amker 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: ---
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: 
Message-ID: <bug-101145-4-YImGvicmBa@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-101145-4@http.gcc.gnu.org/bugzilla/>
References: <bug-101145-4@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
X-BeenThere: gcc-bugs@gcc.gnu.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Gcc-bugs mailing list <gcc-bugs.gcc.gnu.org>
List-Unsubscribe: <https://gcc.gnu.org/mailman/options/gcc-bugs>,
 <mailto:gcc-bugs-request@gcc.gnu.org?subject=unsubscribe>
List-Archive: <https://gcc.gnu.org/pipermail/gcc-bugs/>
List-Post: <mailto:gcc-bugs@gcc.gnu.org>
List-Help: <mailto:gcc-bugs-request@gcc.gnu.org?subject=help>
List-Subscribe: <https://gcc.gnu.org/mailman/listinfo/gcc-bugs>,
 <mailto:gcc-bugs-request@gcc.gnu.org?subject=subscribe>
X-List-Received-Date: Thu, 24 Jun 2021 15:39:53 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D101145

--- Comment #2 from bin cheng <amker at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #1)
> This comes up with a pending patch to split loops like
>=20
> void
> foo (int *a, int *b, unsigned l, unsigned n)
> {
>   while (++l !=3D n)
>     a[l] =3D b[l] + 1;
> }
>=20
> into
>=20
>   while (++l > n)
>     a[l] =3D b[l] + 1;
>   while (++l < n)
>     a[l] =3D b[l] + 1;
>=20
> since for the second loop (the "usual" case involving no wrapping of the =
IV)
> this results in affine IVs and thus analyzable data dependence.

Special case like "i++ > constant" are handled in function
adjust_cond_for_loop_until_wrap, however, it only handles constant invarian=
t on
the other side right now.

Will see how to cover simple cases as reported here.=