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 775D43858405; Tue, 23 Nov 2021 18:21:17 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 775D43858405
From: "theodort at inf dot ethz.ch" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/103388] New: [12 Regression] missed
 optimization for dead code elimination at -O3 (vs. -O2)
Date: Tue, 23 Nov 2021 18:21:17 +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: 12.0
X-Bugzilla-Keywords: 
X-Bugzilla-Severity: normal
X-Bugzilla-Who: theodort at inf dot ethz.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
Message-ID: <bug-103388-4@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: Tue, 23 Nov 2021 18:21:17 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D103388

            Bug ID: 103388
           Summary: [12 Regression] missed optimization for dead code
                    elimination at -O3 (vs. -O2)
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: theodort at inf dot ethz.ch
  Target Milestone: ---

cat case.c
void foo(void);
void bar(void);

static int b, d, e, *c, *f =3D &d, *h =3D &b;

int main() {
  int **i =3D &c;
  if (e) {
    e =3D *f;
    bar();
    if (!(((i && d) + *h >=3D 1 ^ d & b) <=3D 4 | d))
      foo();
  }
}

trunk cannot eliminate the call to foo but 11.2.0 can:

gcc-11.2.0 -O3 -S -o /dev/stdout case.c
main:
.LFB0:
        .cfi_startproc
        movl    e(%rip), %ecx
        testl   %ecx, %ecx
        jne     .L8
        xorl    %eax, %eax
        ret
.L8:
        pushq   %rax
        .cfi_def_cfa_offset 16
        movl    d(%rip), %eax
        movl    %eax, e(%rip)
        call    bar
        xorl    %eax, %eax
        popq    %rdx
        .cfi_def_cfa_offset 8
        ret
        .cfi_endproc
.LFE0:

gcc-trunk -O3 -S -o /dev/stdout case.c
main:
.LFB0:
        .cfi_startproc
        movl    e(%rip), %esi
        testl   %esi, %esi
        jne     .L10
        xorl    %eax, %eax
        ret
.L10:
        pushq   %rcx
        .cfi_def_cfa_offset 16
        movl    d(%rip), %eax
        movl    %eax, e(%rip)
        call    bar
        movl    d(%rip), %edx
        movl    b(%rip), %eax
        cmpl    $1, %edx
        movl    %eax, %ecx
        sbbl    $-1, %ecx
        testl   %ecx, %ecx
        setg    %cl
        andl    %edx, %eax
        movzbl  %cl, %ecx
        xorl    %ecx, %eax
        cmpl    $4, %eax
        setle   %al
        movzbl  %al, %eax
        orl     %edx, %eax
        je      .L11
.L3:
        xorl    %eax, %eax
        popq    %rdx
        .cfi_remember_state
        .cfi_def_cfa_offset 8
        ret
.L11:
        .cfi_restore_state
        call    foo
        jmp     .L3
        .cfi_endproc
.LFE0:

gcc-trunk -v
Using built-in specs.
Supported LTO compression algorithms: zlib zstd
gcc version 12.0.0 20211123 (experimental) (GCC)

Started with
https://gcc.gnu.org/git/?p=3Dgcc.git;a=3Dcommit;h=3D4b3a325f07acebf47e82de2=
27ce1d5ba62f5bcae=