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 447E5385843C; Mon,  4 Oct 2021 21:44:27 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 447E5385843C
From: "qinzhao at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/102285] New flag -ftrivial-auto-var-init=zero causes
 crash in pr82421.c
Date: Mon, 04 Oct 2021 21:44:26 +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: 12.0
X-Bugzilla-Keywords: ice-on-valid-code
X-Bugzilla-Severity: normal
X-Bugzilla-Who: qinzhao at gcc dot gnu.org
X-Bugzilla-Status: REOPENED
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: rguenth at gcc dot gnu.org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: 
Message-ID: <bug-102285-4-iNfAiKlwHg@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-102285-4@http.gcc.gnu.org/bugzilla/>
References: <bug-102285-4@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, 04 Oct 2021 21:44:27 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D102285

--- Comment #28 from qinzhao at gcc dot gnu.org ---
(In reply to Richard Biener from comment #21)
> Reduced testcase:
>=20
> int
> qy (void)
> {
>   int tw =3D 4;
>   int fb[tw];
>   return fb[2];
> }

For this reduced testing case, if compiled with=20
/home/opc/Install/latest/bin/gcc -c -O -ftrivial-auto-var-init=3Dzero
-fdump-tree-all t.c

******t.c.032t.cpp1:
int qy (int l9)
{
  unsigned char fb.3[16];
  int tw;
  int[0:D.1984] * fb.1;
  sizetype D.1984;
  void * saved_stack.2_16;
  int _27;

  <bb 2> :
  saved_stack.2_16 =3D __builtin_stack_save ();
  fb.1_25 =3D &fb.3;
  (*fb.1_25) =3D .DEFERRED_INIT (16, 2, 1);
  _27 =3D (*fb.1_25)[2];
  ..
}

******t.c.033t.forwprop1:
int qy (int l9)
{
  unsigned char fb.3[16];
  int tw;
  int[0:D.1984] * fb.1;
  sizetype D.1984;
  void * saved_stack.2_16;
  int _27;

  <bb 2> :
  saved_stack.2_16 =3D __builtin_stack_save ();
  MEM[(int[0:D.1984] *)&fb.3] =3D .DEFERRED_INIT (16, 2, 1);
  _27 =3D MEM[(int[0:D.1984] *)&fb.3][2];
  ..
}

the problem with the above IR for .DEFERRED_INIT expansion is:

for MEM[(int[0:D.1984] *)&fb.3] =3D .DEFERRED_INIT (16, 2, 1);

after the "ccp" and "forwprop", the original VLA *fb.1 is replaced with the=
 the
new fixed array &fb.3, however, the VAR_TYPE still is the old VLA type
int[0:D.1984]. if we can replace the var_type to the new "unsigned char [16=
]"
for both the LHS and the call to .DEFERRED_INIT. then expansion through
assign_expand should work.

We might need to special handling the LHS to get the new type for "fb.3"
instead of the old "var_type" for "assign_expand".=