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 E3E5D3857036; Wed, 16 Dec 2020 11:30:35 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org E3E5D3857036
From: "danielhanchen at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/98317] New: Vector Extensions aligned(1) not generating
 unaligned loads/stores
Date: Wed, 16 Dec 2020 11:30:35 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: new
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: c++
X-Bugzilla-Version: 10.2.0
X-Bugzilla-Keywords: 
X-Bugzilla-Severity: normal
X-Bugzilla-Who: danielhanchen at gmail dot com
X-Bugzilla-Status: UNCONFIRMED
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: bug_id short_desc product version bug_status
 bug_severity priority component assigned_to reporter target_milestone
Message-ID: <bug-98317-4@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: Wed, 16 Dec 2020 11:30:36 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D98317

            Bug ID: 98317
           Summary: Vector Extensions aligned(1) not generating unaligned
                    loads/stores
           Product: gcc
           Version: 10.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: danielhanchen at gmail dot com
  Target Milestone: ---

The ordering of aligned(1) causes GCC to generate movaps / movups.

typedef float   float128_tv1    __attribute__ ((aligned(1), vector_size(16)=
));
typedef float   float128_tv2    __attribute__ ((vector_size(16), aligned(1)=
));

float128_tv1 provides MOVAPS
float128_tv2 provides MOVUPS

It seems like the ordering of the arguments changes the assembly.

https://gcc.godbolt.org/z/5qs7e7

It seems like GCC 10.2 and 9.2 all have this issue.
Unless if this was already documentated, this issue can cause massive issue=
s if
memory is unaligned and an aligned load/store is used instead.=