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 67D5A385C400; Wed,  1 Sep 2021 20:52:03 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 67D5A385C400
From: "deller at gmx dot de" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/102162] Byte-wise access optimized away at
 -O1 and above
Date: Wed, 01 Sep 2021 20:52:03 +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: unknown
X-Bugzilla-Keywords: 
X-Bugzilla-Severity: normal
X-Bugzilla-Who: deller at gmx dot de
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: 
Message-ID: <bug-102162-4-kuKic4z2kW@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-102162-4@http.gcc.gnu.org/bugzilla/>
References: <bug-102162-4@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, 01 Sep 2021 20:52:03 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D102162

--- Comment #3 from deller at gmx dot de ---
Hi Arnd,

I think the problem with your testcase is, that the compiler doesn't know t=
he=20
alignment of the parameter "p" in your f_unaligned() function.
So it will generate byte-accesses.

If you modify your testcase by adding this and compiling with -O1 (or highe=
r)
you see the problem:

int evil;
int f_unaligned2(void)
{
     return get_unaligned(&evil);
}

00000000 <f_unaligned2>:
   0:   2b 60 00 00     addil L%0,dp,r1
   4:   34 21 00 00     ldo 0(r1),r1
   8:   e8 40 c0 00     bv r0(rp)
   c:   0c 20 10 9c     ldw 0(r1),ret0=