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 DCC5F385840E; Mon, 20 Sep 2021 08:42:58 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org DCC5F385840E
From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/102391] Failure to optimize adjacent 8-bit
 loads into a single bigger load
Date: Mon, 20 Sep 2021 08:42:58 +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: enhancement
X-Bugzilla-Who: rguenth 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-102391-4-seTMHP0lD9@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-102391-4@http.gcc.gnu.org/bugzilla/>
References: <bug-102391-4@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: Mon, 20 Sep 2021 08:42:59 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D102391

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
the bswap pass is in principle able to handle these but it sees

  _1 =3D (sizetype) offset_12(D);
  _2 =3D RomHeader_13(D) + _1;
  _3 =3D *_2;
  _4 =3D (signed short) _3;
  _5 =3D _1 + 1;
  _6 =3D RomHeader_13(D) + _5;
  _7 =3D *_6;

so the constant offset is not forwarded to the MEM_REFs (int vs. size_t iss=
ue)
and the bswap pass doesn't perform any fancy dataref analysis to spot
constant offsetted same bases (it could simply use split_constant_offset
on the found base I guess or invoke DR analysis in BB mode).=