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 90D753858CDA; Tue, 10 Jan 2023 12:41:27 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 90D753858CDA
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
	s=default; t=1673354487;
	bh=d4E7hlXq8VwRYVFvIQ1DWFqLsCkBmm7NscZOTOgaIUA=;
	h=From:To:Subject:Date:From;
	b=LkY9otMJE+Pu/6B+vXCp+6MULzHANtCWOH5e/Z7/C0lVrbTFJyTAAJrrsJervGN5k
	 StqZvS10VVF2nKjc3dT5giB1I39ftsgYRUoAdXWFz4lzeE3d2SHji3Ed9+GdzoCvxj
	 t1oRLx2V7qRVAU2FIY6vsMfvBYC1a0b25cc3CfdI=
From: "yann at ywg dot ch" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/108354] New: Dead Code Elimination Regression
 at -O2 (trunk vs. 12.2.0)
Date: Tue, 10 Jan 2023 12:41:27 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: new
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: tree-optimization
X-Bugzilla-Version: 13.0
X-Bugzilla-Keywords: 
X-Bugzilla-Severity: normal
X-Bugzilla-Who: yann at ywg dot ch
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: bug_id short_desc product version bug_status
 bug_severity priority component assigned_to reporter target_milestone
 attachments.created
Message-ID: <bug-108354-4@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
List-Id: <gcc-bugs.sourceware.org>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D108354

            Bug ID: 108354
           Summary: Dead Code Elimination Regression at -O2 (trunk vs.
                    12.2.0)
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: yann at ywg dot ch
  Target Milestone: ---

Created attachment 54229
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=3D54229&action=3Dedit
presented code as file

cat case.c #617
int b;
int *c;
int e;
static int *f =3D &e;
int g;
void foo();
short(a)(short h, short i) { return h - i; }
int(d)(int h) { return h =3D=3D 83647 ? 0 : -h; }
int main() {
  short j;
  int *k =3D &e, *l =3D &b;
  *f =3D 0 =3D=3D c;
  j =3D a(0 !=3D 2, *k);
  if (d(j ^ (0 =3D=3D l || *k)) !=3D *k)
    ;
  else
    foo();
  c =3D &g;
}

`gcc-cb93c5f8008b95743b741d6f1842f9be50c6985c (trunk) -O2` can not eliminate
`foo` but `gcc-releases/gcc-12.2.0 -O2` can.

`gcc-cb93c5f8008b95743b741d6f1842f9be50c6985c (trunk) -O2 -S -o /dev/stdout
case.c`
--------- OUTPUT ---------
main:
.LFB2:
        .cfi_startproc
        xorl    %eax, %eax
        cmpq    $0, c(%rip)
        setne   %dl
        sete    %al
        movzbl  %dl, %edx
        movl    %eax, e(%rip)
        orl     %eax, %edx
        je      .L12
        movq    $g, c(%rip)
        xorl    %eax, %eax
        ret
.L12:
        pushq   %rax
        .cfi_def_cfa_offset 16
        xorl    %eax, %eax
        call    foo
        xorl    %eax, %eax
        movq    $g, c(%rip)
        popq    %rdx
        .cfi_def_cfa_offset 8
        ret
---------- END OUTPUT ---------


`gcc-releases/gcc-12.2.0 -O2 -S -o /dev/stdout case.c`
--------- OUTPUT ---------
main:
.LFB2:
        .cfi_startproc
        xorl    %eax, %eax
        cmpq    $0, c(%rip)
        movq    $g, c(%rip)
        sete    %al
        movl    %eax, e(%rip)
        xorl    %eax, %eax
        ret
---------- END OUTPUT ---------


Bisects to:
https://gcc.gnu.org/git/?p=3Dgcc.git;a=3Dcommit;h=3Db3e98eb3396e16ae8b20c94=
916bc2bd7862d2c97=