From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Bavier Subject: Re: 01/03: gnu: Add QD. Date: Tue, 6 Feb 2018 08:27:32 -0600 Message-ID: <20180206082732.3659687a@centurylink.net> References: <20180202143848.26172.43250@vcs0.savannah.gnu.org> <20180202143849.080E924648@vcs0.savannah.gnu.org> <871si1z9v7.fsf@netris.org> <20180204220454.7eb68a5b@centurylink.net> <877erqap0i.fsf@netris.org> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: Received: from eggs.gnu.org ([2001:4830:134:3::10]:48300) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ej4Dj-0008P5-Mz for guix-devel@gnu.org; Tue, 06 Feb 2018 09:27:41 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ej4Dg-0006Ec-KA for guix-devel@gnu.org; Tue, 06 Feb 2018 09:27:39 -0500 Received: from mail.onyx.syn-alias.com ([206.152.134.66]:13730 helo=smtp.centurylink.net) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1ej4Dg-0006DT-D9 for guix-devel@gnu.org; Tue, 06 Feb 2018 09:27:36 -0500 In-Reply-To: <877erqap0i.fsf@netris.org> 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: Mark H Weaver Cc: guix-devel@gnu.org On Mon, 05 Feb 2018 20:24:45 -0500 Mark H Weaver wrote: > 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. Sorry about the confusion. I'll revise it to something more informative. I usually try to refrain from "witty" comments. > > >> 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. AMD also had a 4-argument FMA instruction much sooner. Thank you for the attention to this matter, `~Eric