From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 57E43C021A4 for ; Mon, 24 Feb 2025 22:17:35 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id B902910E049; Mon, 24 Feb 2025 22:17:34 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=gmail.com header.i=@gmail.com header.b="kZ/s8bUv"; dkim-atps=neutral Received: from mail-pl1-f174.google.com (mail-pl1-f174.google.com [209.85.214.174]) by gabe.freedesktop.org (Postfix) with ESMTPS id F210210E049 for ; Mon, 24 Feb 2025 22:17:33 +0000 (UTC) Received: by mail-pl1-f174.google.com with SMTP id d9443c01a7336-220bfdfb3f4so110041085ad.2 for ; Mon, 24 Feb 2025 14:17:33 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1740435453; x=1741040253; darn=lists.freedesktop.org; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date:from:to :cc:subject:date:message-id:reply-to; bh=MIAmGwREzfChZxhZrA3OzxmyUXhIuIWMIVivU3ALR/o=; b=kZ/s8bUvIP37211I73IBQT9Jsz/efLU9dIgjnITl52ME/9pOzFubmXV7IatnNfu0wm sROaWx5OCld6xl/QVlAnhzZqbF23JN96oyd8DQdPQm1fvS9ZZ4glN/yfnZwLhXo+fXAG IzwgDsDDN2dlop3364KShugHy5a+KlRoaTVGenbqToZQgycf5hkFfdPE+sYmdml6iaH8 8aZ3nTrZyE5mHw4OsCoQg3o3F+aj1e8zc2r+OptHkxoQ4Bw1itoliXA5vSxYxfSRBhMW vWy/cvnWCp+ADcL7lQ36Z5hvIbEt7qeN/7h6uwFOD6H31Tz+/lxD11oEsXNhBu12k77M +CdA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1740435453; x=1741040253; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=MIAmGwREzfChZxhZrA3OzxmyUXhIuIWMIVivU3ALR/o=; b=V0Jh8in8DjY0/+GvldviCflks+L+zGZXno+J9HTKGbAoR3Yhj2lY355hW5q621THB7 QOqqSECfdPcuEDGb61wmfuBug2DMXh1WhQOp4jiJMGtDXZg/zHsbHQa7nVwa72exdgjO 61BiJA7ws1/iPUOcltAt68/prtjhWKE7LJ5m0v8J/Fac2VahiVlr5kyg7gFZzxwCIWzF 26pAsbNE0FVt8NyFFHmCHgt4dsUbK4uinb4IYMW6JvU/PpvNiSVYGT+Mgm/SytPYBP5+ 7g0WBPMEKdxAUX6FAYXq4yZi+0r1MWzBeJKFBkjRB5WC4bfvwDCf8YaYJgWZrxOCxAfk zIAA== X-Forwarded-Encrypted: i=1; AJvYcCUhcOHXGmxhEAek10vLKdLDn3HYemSEJyuetWVI3VTgjIqnBqMAfTTs2Yy26ZWufq+1ABKTUCxEbys=@lists.freedesktop.org X-Gm-Message-State: AOJu0Yy4bIMv91idORV3ya0LvhfoAKkBS21EVXeO6pWbBqB/Y5nShewu zj+IXx/nILF6YIBOvAwHU7uPaf4C78UMpzB+l9bqqWKtMi0KiU6s X-Gm-Gg: ASbGncup1Fsh1v9oJy0NfQJxczgi9VuqpSmr0EnUUFB8rjgvOD1VS6bU6hsm1Es4VU5 8E9I0UN6I5v4xSW8wzTWsgHd2y3l0ODUyVVd3pYMItHvylcOnOJ7Z8odyz2UoBHonKWKAxgPAL2 uSEP/npzi0+TNccvfvHz3M8rVVXPTSg5hTRCZTnkyK81GNsJggBym4k03M32+AVHnLClQKRAlpj 6G4pu8KYgh5EO3tDHjUIKhd2lLwjc9CdLlalcuCh40o0/KF6n5YWv2gtcG/HIGJxV/A8JV7PCHN sEwON3lyu9eGm4gx4SNlpFawrU4454O3B4ycOaftSQr9A6jDMw== X-Google-Smtp-Source: AGHT+IHUNZzOI1ZFK/Wig2ECxEjG2LCeoTVF/IwXlP7H5EbtmMAu2d6RHqgduSyhdb+wHec1lfRRUA== X-Received: by 2002:a17:903:2a8d:b0:21f:6584:2085 with SMTP id d9443c01a7336-2219ffc4928mr267486635ad.42.1740435452344; Mon, 24 Feb 2025 14:17:32 -0800 (PST) Received: from localhost (maglev-oncall.nvidia.com. [216.228.125.128]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2230a01fe28sm1125415ad.100.2025.02.24.14.17.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 24 Feb 2025 14:17:31 -0800 (PST) Date: Mon, 24 Feb 2025 17:17:29 -0500 From: Yury Norov To: "H. Peter Anvin" Cc: Uros Bizjak , Kuan-Wei Chiu , tglx@linutronix.de, Ingo Molnar , bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, jk@ozlabs.org, joel@jms.id.au, eajames@linux.ibm.com, andrzej.hajda@intel.com, neil.armstrong@linaro.org, rfoss@kernel.org, maarten.lankhorst@linux.intel.com, mripard@kernel.org, tzimmermann@suse.de, airlied@gmail.com, simona@ffwll.ch, dmitry.torokhov@gmail.com, mchehab@kernel.org, awalls@md.metrocast.net, hverkuil@xs4all.nl, miquel.raynal@bootlin.com, richard@nod.at, vigneshr@ti.com, louis.peens@corigine.com, andrew+netdev@lunn.ch, davem@davemloft.net, edumazet@google.com, pabeni@redhat.com, parthiban.veerasooran@microchip.com, arend.vanspriel@broadcom.com, johannes@sipsolutions.net, gregkh@linuxfoundation.org, jirislaby@kernel.org, akpm@linux-foundation.org, mingo@kernel.org, alistair@popple.id.au, linux@rasmusvillemoes.dk, Laurent.pinchart@ideasonboard.com, jonas@kwiboo.se, jernej.skrabec@gmail.com, kuba@kernel.org, linux-kernel@vger.kernel.org, linux-fsi@lists.ozlabs.org, dri-devel@lists.freedesktop.org, linux-input@vger.kernel.org, linux-media@vger.kernel.org, linux-mtd@lists.infradead.org, oss-drivers@corigine.com, netdev@vger.kernel.org, linux-wireless@vger.kernel.org, brcm80211@lists.linux.dev, brcm80211-dev-list.pdl@broadcom.com, linux-serial@vger.kernel.org, bpf@vger.kernel.org, jserv@ccns.ncku.edu.tw, Yu-Chun Lin Subject: Re: [PATCH 03/17] x86: Replace open-coded parity calculation with parity8() Message-ID: References: <20250223164217.2139331-1-visitorckw@gmail.com> <20250223164217.2139331-4-visitorckw@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On Mon, Feb 24, 2025 at 01:55:28PM -0800, H. Peter Anvin wrote: > On 2/24/25 07:24, Uros Bizjak wrote: > > > > > > On 23. 02. 25 17:42, Kuan-Wei Chiu wrote: > > > Refactor parity calculations to use the standard parity8() helper. This > > > change eliminates redundant implementations and improves code > > > efficiency. > > > > The patch improves parity assembly code in bootflag.o from: > > > >   58:    89 de                    mov    %ebx,%esi > >   5a:    b9 08 00 00 00           mov    $0x8,%ecx > >   5f:    31 d2                    xor    %edx,%edx > >   61:    89 f0                    mov    %esi,%eax > >   63:    89 d7                    mov    %edx,%edi > >   65:    40 d0 ee                 shr    %sil > >   68:    83 e0 01                 and    $0x1,%eax > >   6b:    31 c2                    xor    %eax,%edx > >   6d:    83 e9 01                 sub    $0x1,%ecx > >   70:    75 ef                    jne    61 > >   72:    39 c7                    cmp    %eax,%edi > >   74:    74 7f                    je     f5 > >   76: > > > > to: > > > >   54:    89 d8                    mov    %ebx,%eax > >   56:    ba 96 69 00 00           mov    $0x6996,%edx > >   5b:    c0 e8 04                 shr    $0x4,%al > >   5e:    31 d8                    xor    %ebx,%eax > >   60:    83 e0 0f                 and    $0xf,%eax > >   63:    0f a3 c2                 bt     %eax,%edx > >   66:    73 64                    jae    cc > >   68: > > > > which is faster and smaller (-10 bytes) code. > > > > Of course, on x86, parity8() and parity16() can be implemented very simply: > > (Also, the parity functions really ought to return bool, and be flagged > __attribute_const__.) There was a discussion regarding return type when parity8() was added. The integer type was taken over bool with a sort of consideration that bool should be returned as an answer to some question, like parity_odd(). To me it's not a big deal. We can switch to boolean and describe in comment what the 'true' means for the parity() function.