From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mark H Weaver Subject: Re: 01/03: gnu: Add QD. Date: Mon, 05 Feb 2018 20:24:45 -0500 Message-ID: <877erqap0i.fsf@netris.org> References: <20180202143848.26172.43250@vcs0.savannah.gnu.org> <20180202143849.080E924648@vcs0.savannah.gnu.org> <871si1z9v7.fsf@netris.org> <20180204220454.7eb68a5b@centurylink.net> Mime-Version: 1.0 Content-Type: text/plain Return-path: Received: from eggs.gnu.org ([2001:4830:134:3::10]:56172) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eis0j-0002QZ-R9 for guix-devel@gnu.org; Mon, 05 Feb 2018 20:25:26 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eis0e-0000gx-FG for guix-devel@gnu.org; Mon, 05 Feb 2018 20:25:25 -0500 Received: from world.peace.net ([50.252.239.5]:34658) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1eis0e-0000ge-AP for guix-devel@gnu.org; Mon, 05 Feb 2018 20:25:20 -0500 In-Reply-To: <20180204220454.7eb68a5b@centurylink.net> (Eric Bavier's message of "Sun, 4 Feb 2018 22:04:54 -0600") List-Id: "Development of GNU Guix and the GNU System distribution." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: guix-devel-bounces+gcggd-guix-devel=m.gmane.org@gnu.org Sender: "Guix-devel" To: Eric Bavier Cc: guix-devel@gnu.org Hi Eric, Eric Bavier writes: > On Sat, 03 Feb 2018 22:55:56 -0500 > Mark H Weaver wrote: > >> ericbavier@centurylink.net (Eric Bavier) writes: >> > + `(#:configure-flags `("--disable-enable_fma" ;weird :/ >> >> "weird :/" is not a very useful comment. > > Sorry. I thought it was obvious it was in reference to the > "disable-enable" bit. I thought that might be the case, but I was still curious why you were disabling FMA support, and the comment didn't help. >> Can you change it to explain >> why you added this flag? It seems unfortunate to disable fused >> multiply-add for this kind of library. > > The library does not support runtime ISA detection. I thought FMAs are > something we don't support in our baseline x86-64 builds? Indeed. I was surprised to learn that FMAs are only supported in very recent Intel processors. My Yeeloong with MIPS-based Loongson 2F processor from 2008 includes support for FMA instructions, and I guessed that Intel had them long before, but actually Intel didn't add them until several years later. Mark