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 75953385800A; Fri,  5 Mar 2021 03:18:18 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 75953385800A
From: "unlvsur at live dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/99396] std::rotl and std::rotr Does not
 convert into ROTATE on the gimple level
Date: Fri, 05 Mar 2021 03:18:18 +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: 11.0
X-Bugzilla-Keywords: missed-optimization
X-Bugzilla-Severity: enhancement
X-Bugzilla-Who: unlvsur at live dot com
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-99396-4-2HWlgzmZMr@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-99396-4@http.gcc.gnu.org/bugzilla/>
References: <bug-99396-4@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: Fri, 05 Mar 2021 03:18:18 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D99396

--- Comment #4 from cqwrteur <unlvsur at live dot com> ---
(In reply to Andrew Pinski from comment #3)
> (In reply to cqwrteur from comment #2)
> > I would like to see __builtin_cpp_rotl and __builtin_cpp_rotr to allow =
more
> > aggressive optimizations since rotl and rotr are so important for
> > cryptography.
>=20
> You don't need them.
> The following code will already produce the rotate instruction:
> auto f3(std::size_t v, int t)
> {
>   return (v<<t) | (v>>(sizeof(v)*8 - t));
> }
>=20
> Note std::rotl/std::rotr has specific behavior dealing with 0 and negative
> values and all.

but if it is constant, it would get optimized to just ror or rol=