Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S264547AbVBELQH (ORCPT ); Sat, 5 Feb 2005 06:16:07 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S264308AbVBELP7 (ORCPT ); Sat, 5 Feb 2005 06:15:59 -0500 Received: from natsmtp00.rzone.de ([81.169.145.165]:28322 "EHLO natsmtp00.rzone.de") by vger.kernel.org with ESMTP id S262705AbVBELPQ (ORCPT ); Sat, 5 Feb 2005 06:15:16 -0500 From: Arnd Bergmann To: Anton Blanchard Subject: Re: [PATCH] PPC/PPC64: Introduce CPU_HAS_FEATURE() macro Date: Sat, 5 Feb 2005 12:04:34 +0100 User-Agent: KMail/1.6.2 Cc: Benjamin Herrenschmidt , linuxppc64-dev , Andrew Morton , Tom Rini , Linux Kernel list , linuxppc-dev list , Paul Mackerras , "H. Peter Anvin" References: <20050204072254.GA17565@austin.ibm.com> <200502050122.27254.arnd@arndb.de> <20050205013426.GC11318@krispykreme.ozlabs.ibm.com> In-Reply-To: <20050205013426.GC11318@krispykreme.ozlabs.ibm.com> MIME-Version: 1.0 Content-Type: multipart/signed; protocol="application/pgp-signature"; micalg=pgp-sha1; boundary="Boundary-02=_GhKBCJkznSZL9xB"; charset="iso-8859-15" Content-Transfer-Encoding: 7bit Message-Id: <200502051204.38965.arnd@arndb.de> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1605 Lines: 44 --Boundary-02=_GhKBCJkznSZL9xB Content-Type: text/plain; charset="iso-8859-15" Content-Transfer-Encoding: quoted-printable Content-Disposition: inline On S=FCnnavend 05 Februar 2005 02:34, Anton Blanchard wrote: > Interesting :) However we already get bug reports with the current > CONFIG_POWER4_ONLY option. I worry about adding more options that users > could get wrong unless there is a noticeable improvement in performance. >=20 The patch that I posted doesn't add any new user selectable options, it only limits the supported CPUs to the ones that are available on the supported platforms. If you select powermac or maple, the only supported CPU will be PowerPC970, so the C compiler can optimize away all runtime checks for CPU features. I don't expect much noticeable performance advantage from the patch, but it allows to make some of the source code nicer. E.g. you can replace every instance of '#ifdef CONFIG_ALTIVEC' with 'if=20 (CPU_FTR_POSSIBLE & CPU_FTR_ALTIVEC)' or an inline function wrapping that. Arnd <>< --Boundary-02=_GhKBCJkznSZL9xB Content-Type: application/pgp-signature Content-Description: signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.4 (GNU/Linux) iD8DBQBCBKhG5t5GS2LDRf4RAkKbAKCXDT1IwF5F2WqcSsZl0FgZfgpTKACeL/gW J5uKZEdOgtvSb/m5klF+ZGQ= =iDSe -----END PGP SIGNATURE----- --Boundary-02=_GhKBCJkznSZL9xB-- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/