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 529713836034; Thu, 19 Aug 2021 09:02:40 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 529713836034
From: "cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/101950] __builtin_clrsb is never inlined
Date: Thu, 19 Aug 2021 09:02:39 +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: 11.1.0
X-Bugzilla-Keywords: missed-optimization
X-Bugzilla-Severity: normal
X-Bugzilla-Who: cvs-commit at gcc dot gnu.org
X-Bugzilla-Status: ASSIGNED
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: jakub at gcc dot gnu.org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: 
Message-ID: <bug-101950-4-BnRqc2PQyD@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-101950-4@http.gcc.gnu.org/bugzilla/>
References: <bug-101950-4@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, 19 Aug 2021 09:02:40 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D101950

--- Comment #2 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jakub Jelinek <jakub@gcc.gnu.org>:

https://gcc.gnu.org/g:301dc6011cbceb7ea9debd86aaec7cadb37213c8

commit r12-3017-g301dc6011cbceb7ea9debd86aaec7cadb37213c8
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Thu Aug 19 11:00:27 2021 +0200

    expand: Add new clrsb fallback expansion [PR101950]

    As suggested in the PR, the following patch adds two new clrsb
    expansion possibilities if target doesn't have clrsb_optab for the
    requested nor wider modes, but does have clz_optab for the requested
    mode.
    One expansion is
    clrsb (op0)
    expands as
    clz (op0 ^ (((stype)op0) >> (prec-1))) - 1
    which is usable if CLZ_DEFINED_VALUE_AT_ZERO is 2 with value
    of prec, because the clz argument can be 0 and clrsb should give
    prec-1 in that case.
    The other expansion is
    clz (((op0 << 1) ^ (((stype)op0) >> (prec-1))) | 1)
    where the clz argument is never 0, but it is one operation longer.
    E.g. on x86_64-linux with -O2 -mno-lzcnt, this results for
    int foo (int x) { return __builtin_clrsb (x); }
    in
    -       subq    $8, %rsp
    -       movslq  %edi, %rdi
    -       call    __clrsbdi2
    -       addq    $8, %rsp
    -       subl    $32, %eax
    +       leal    (%rdi,%rdi), %eax
    +       sarl    $31, %edi
    +       xorl    %edi, %eax
    +       orl     $1, %eax
    +       bsrl    %eax, %eax
    +       xorl    $31, %eax
    and with -O2 -mlzcnt:
    +       movl    %edi, %eax
    +       sarl    $31, %eax
    +       xorl    %edi, %eax
    +       lzcntl  %eax, %eax
    +       subl    $1, %eax
    On armv7hl-linux-gnueabi with -O2:
    -       push    {r4, lr}
    -       bl      __clrsbsi2
    -       pop     {r4, pc}
    +       @ link register save eliminated.
    +       eor     r0, r0, r0, asr #31
    +       clz     r0, r0
    +       sub     r0, r0, #1
    +       bx      lr
    As it (at least usually) will make code larger, it is
    disabled for -Os or cold instructions.

    2021-08-19  Jakub Jelinek  <jakub@redhat.com>

            PR middle-end/101950
            * optabs.c (expand_clrsb_using_clz): New function.
            (expand_unop): Use it as another clrsb expansion fallback.

            * gcc.target/i386/pr101950-1.c: New test.
            * gcc.target/i386/pr101950-2.c: New test.=