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 833873950C79; Thu,  8 Jul 2021 17:16:16 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 833873950C79
From: "meissner at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/33699] [9/10/11/12 regression] missing optimization
 on const addr area store
Date: Thu, 08 Jul 2021 17:16:16 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: middle-end
X-Bugzilla-Version: 4.3.0
X-Bugzilla-Keywords: missed-optimization
X-Bugzilla-Severity: normal
X-Bugzilla-Who: meissner at gcc dot gnu.org
X-Bugzilla-Status: NEW
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P2
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: 9.5
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: cc
Message-ID: <bug-33699-4-pGxq5Vpyji@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-33699-4@http.gcc.gnu.org/bugzilla/>
References: <bug-33699-4@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, 08 Jul 2021 17:16:16 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D33699

Michael Meissner <meissner at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |meissner at gcc dot gnu.org

--- Comment #32 from Michael Meissner <meissner at gcc dot gnu.org> ---
I looked at adding the following powerpc patch that was proposed in March,
2021:
https://gcc.gnu.org/pipermail/gcc-patches/2021-March/566744.html

There are two parts to the patch, that are sort of unrelated.

The first part is to add minimum and maximum section anchor offset values a=
nd
use -fsection anchors.  I ran a spec 2017 benchmark on a pre-production pow=
er10
system, comparing my normal run times to run times with -fsection-anchors a=
nd
setting the minimum/maximum section anchor offsets.

Two benchmarks improved and two benchmarks regressed:

    xalancbmk_r: 1.75% regression
    cactuBSSN_r: 4.24% improvement
    blender_r: 1.92% regression
    roms_r: 1.05% improvement

I then built spec 2017 with just the part of setting const_anchor, but not =
the
section anchor minimum/maximum offsets.  Eight benchmarks did not build due=
 to
assertion failures in cse.c:

    gcc_r
    exchange2_r
    cactuBSSN_r
    wrf_r
    blender_r
    cam4_r
    fotonik3d_r
    roms_r

If I specify the section anchor minimum/maximum offsets, add -fsection-anch=
ors,
and set the const_anchor, all 23 INT+FP benchmarks build, but WRF_R does not
run correctly.  So without more debugging, I don't recommend setting
const_anchor.  It is probably useful to set the minimum/maximum section anc=
hor
offsets in case people use -fsection-anchors.

As an aside, if we wanted to accept using constant addresses in the PowerPC=
, we
would need to recognize a constant address as being legitimate.  This may be
useful in some embedded environments where you have devices at certain memo=
ry
locations.  But somebody would need to add the support.=