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 1FCCE3858D37; Thu, 21 Apr 2022 17:47:23 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 1FCCE3858D37
From: "denis.campredon at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug rtl-optimization/105338] New: Regression: jump or cmove
 generated for pattern (x ? CST : 0)
Date: Thu, 21 Apr 2022 17:47:22 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: new
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: rtl-optimization
X-Bugzilla-Version: 12.0
X-Bugzilla-Keywords: 
X-Bugzilla-Severity: normal
X-Bugzilla-Who: denis.campredon at gmail dot com
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-105338-4@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, 21 Apr 2022 17:47:23 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D105338

            Bug ID: 105338
           Summary: Regression: jump or cmove generated for pattern (x ?
                    CST : 0)
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: rtl-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: denis.campredon at gmail dot com
  Target Milestone: ---

int f(int i) {
    return i ? 5 : 0;
}

int g(int i) {
    return i ? -2 : 0;
}

int h(int b) {
    return !!b * -2;
}

int i(int b) {
    return !!b * 5;
}

int j(int b) {
    if (!b) return 0;
    return -2;
}
-------------
With -02 gcc 11.2 the five functions above output branchless code like:

f(int):
        neg     edi
        sbb     eax, eax
        and     eax, 5
        ret
g(int):
        neg     edi
        sbb     eax, eax
        and     eax, -2
        ret
...
--------------

Whereas -02 gcc 12 now outputs a cmov or jump depending of sign of the
constant:
f(int):
        mov     eax, edi
        test    edi, edi
        mov     edx, 5
        cmovne  eax, edx
        ret

g(int):
        mov     eax, edi
        test    edi, edi
        jne     .L11
        ret
.L11:
        mov     eax, -2
        ret

h(int):
        mov     eax, edi
        test    edi, edi
        jne     .L17
        ret
.L17:
        mov     eax, -2
        ret

i(int):
        mov     eax, edi
        test    edi, edi
        mov     edx, 5
        cmovne  eax, edx
        ret

j(int):
        mov     eax, edi
        test    edi, edi
        mov     edx, -2
        cmovne  eax, edx
        ret
---------------------------

Alternatively, with the following code

int k(int b) {
    bool b2 =3D b;
    return b2 * 5;
}
----------------

Both gcc 12 and 11.2 are outputing
k(int):
        xor     eax, eax
        test    edi, edi
        setne   al
        lea     eax, [rax+rax*4]
        ret=