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 BE1A4385041E; Sun, 18 Jul 2021 17:04:57 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org BE1A4385041E
From: "uwe at netbsd dot org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/101469] wrong code with "-O2 -fPIE" for SH
Date: Sun, 18 Jul 2021 17:04:57 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: target
X-Bugzilla-Version: 10.3.0
X-Bugzilla-Keywords: wrong-code
X-Bugzilla-Severity: normal
X-Bugzilla-Who: uwe at netbsd dot org
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-101469-4-HHfZFCPMYM@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-101469-4@http.gcc.gnu.org/bugzilla/>
References: <bug-101469-4@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: Sun, 18 Jul 2021 17:04:57 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D101469

--- Comment #2 from Valeriy E. Ushakov <uwe at netbsd dot org> ---
I don't have the latest gcc handy, but I see this bug already in an old net=
bsd
tree from about an year ago with gcc 8.4.0

As hgutch@n.o pointed out, this seems to be a problem with this peephole2:

;;      mov     r12,r0
;;      add     #-48,r0     ->  add     #-48,r12
;;      mov.l   r0,@(4,r10)     mov.l   r12,@(4,r10)
;;      (r12 dead)
(define_peephole2
  [(set (match_operand:SI 0 "arith_reg_dest")
        (match_operand:SI 1 "arith_reg_dest"))
   (set (match_dup 0) (plus:SI (match_dup 0)
                               (match_operand:SI 2 "const_int_operand")))
   (set (match_operand:SI 3 "general_movdst_operand") (match_dup 0))]


as far as I can tell, it optimizes

  r0 =3D r2
  r0 +=3D 64
  *(r0+4) =3D r0

to

  r2 +=3D 64
  *(r0+4) =3D r2

failing to notice that the the destination uses r0 too.

Then in the cprop-registers step that r0 is replaced with r12 b/c of r0 =3D=
 r12
done a bit earlier.=