From owner-svn-src-head@freebsd.org  Thu Jul 16 20:50:01 2020
Return-Path: <owner-svn-src-head@freebsd.org>
Delivered-To: svn-src-head@mailman.nyi.freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1])
 by mailman.nyi.freebsd.org (Postfix) with ESMTP id F255136D741;
 Thu, 16 Jul 2020 20:50:00 +0000 (UTC)
 (envelope-from mhorne@freebsd.org)
Received: from smtp.freebsd.org (smtp.freebsd.org
 [IPv6:2610:1c1:1:606c::24b:4])
 (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)
 key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256
 client-signature RSA-PSS (4096 bits) client-digest SHA256)
 (Client CN "smtp.freebsd.org",
 Issuer "Let's Encrypt Authority X3" (verified OK))
 by mx1.freebsd.org (Postfix) with ESMTPS id 4B75wm67Lrz452N;
 Thu, 16 Jul 2020 20:50:00 +0000 (UTC)
 (envelope-from mhorne@freebsd.org)
Received: from mail-yb1-f178.google.com (mail-yb1-f178.google.com
 [209.85.219.178])
 (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits))
 (Client CN "smtp.gmail.com", Issuer "GTS CA 1O1" (verified OK))
 (Authenticated sender: mhorne)
 by smtp.freebsd.org (Postfix) with ESMTPSA id ACFDE11938;
 Thu, 16 Jul 2020 20:50:00 +0000 (UTC)
 (envelope-from mhorne@freebsd.org)
Received: by mail-yb1-f178.google.com with SMTP id a15so3473648ybs.8;
 Thu, 16 Jul 2020 13:50:00 -0700 (PDT)
X-Gm-Message-State: AOAM532D/8SCLrjESdB1DOHE9qbVrm16h+ZBi8a7ODT1EkgonbhDKtcA
 80lF8Y09BEyvlCoWxt4G2U/PwDXDcZituaJdq2s=
X-Google-Smtp-Source: ABdhPJyqKThAxTFNvf68jjyZwMKGwNGllnwPig273+CYZy5iZVhHW2qpLD/nXTqNpHlD6ZaJ4p9Do6Uy1artqBU8EZY=
X-Received: by 2002:a25:5084:: with SMTP id e126mr9492004ybb.212.1594932600102; 
 Thu, 16 Jul 2020 13:50:00 -0700 (PDT)
MIME-Version: 1.0
References: <202007161128.06GBSPSB045345@repo.freebsd.org>
In-Reply-To: <202007161128.06GBSPSB045345@repo.freebsd.org>
From: Mitchell Horne <mhorne@freebsd.org>
Date: Thu, 16 Jul 2020 17:49:48 -0300
X-Gmail-Original-Message-ID: <CADeAsy1yY_CL5vSvvkgYSutN4gmJi4n1qrc_Duw2M44O+H-+4w@mail.gmail.com>
Message-ID: <CADeAsy1yY_CL5vSvvkgYSutN4gmJi4n1qrc_Duw2M44O+H-+4w@mail.gmail.com>
Subject: Re: svn commit: r363242 - head/sys/amd64/include
To: Mateusz Guzik <mjg@freebsd.org>
Cc: src-committers@freebsd.org, svn-src-all@freebsd.org, 
 svn-src-head@freebsd.org
Content-Type: text/plain; charset="UTF-8"
X-BeenThere: svn-src-head@freebsd.org
X-Mailman-Version: 2.1.33
Precedence: list
List-Id: SVN commit messages for the src tree for head/-current
 <svn-src-head.freebsd.org>
List-Unsubscribe: <https://lists.freebsd.org/mailman/options/svn-src-head>,
 <mailto:svn-src-head-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/svn-src-head/>
List-Post: <mailto:svn-src-head@freebsd.org>
List-Help: <mailto:svn-src-head-request@freebsd.org?subject=help>
List-Subscribe: <https://lists.freebsd.org/mailman/listinfo/svn-src-head>,
 <mailto:svn-src-head-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Thu, 16 Jul 2020 20:50:01 -0000

On Thu, Jul 16, 2020 at 8:28 AM Mateusz Guzik <mjg@freebsd.org> wrote:
>
> Author: mjg
> Date: Thu Jul 16 11:28:24 2020
> New Revision: 363242
> URL: https://svnweb.freebsd.org/changeset/base/363242
>
> Log:
>   amd64: patch ffsl to use the compiler builtin
>
>   This shortens fdalloc by over 60 bytes. Correctness verified by running both
>   variants at the same time and comparing the result of each call.
>
>   Note someone(tm) should make a pass at converting everything else feasible.
>

I have a local version of such a change. I'll see about getting it up
for review in the next little while.

Mitchell

> Modified:
>   head/sys/amd64/include/cpufunc.h
>
> Modified: head/sys/amd64/include/cpufunc.h
> ==============================================================================
> --- head/sys/amd64/include/cpufunc.h    Thu Jul 16 10:20:35 2020        (r363241)
> +++ head/sys/amd64/include/cpufunc.h    Thu Jul 16 11:28:24 2020        (r363242)
> @@ -167,7 +167,8 @@ enable_intr(void)
>  static __inline __pure2 int
>  ffsl(long mask)
>  {
> -       return (mask == 0 ? mask : (int)bsfq((u_long)mask) + 1);
> +
> +       return (__builtin_ffsl(mask));
>  }
>
>  #define        HAVE_INLINE_FFSLL