From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mark H Weaver Subject: Re: Qt Date: Thu, 10 Oct 2013 18:19:09 -0400 Message-ID: <8738o8py5e.fsf@netris.org> References: <20131008190520.GA31264@debian> <87mwmjxym7.fsf@gnu.org> <20131010125952.GA32470@debian.bordeaux.inria.fr> <874n8pe0i2.fsf@gnu.org> <20131010200038.GA16170@debian> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Return-path: Received: from eggs.gnu.org ([2001:4830:134:3::10]:51407) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VUOaV-0006uI-Gb for guix-devel@gnu.org; Thu, 10 Oct 2013 18:20:13 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1VUOaP-0008SC-69 for guix-devel@gnu.org; Thu, 10 Oct 2013 18:20:07 -0400 In-Reply-To: <20131010200038.GA16170@debian> (Andreas Enge's message of "Thu, 10 Oct 2013 22:00:38 +0200") 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-bounces+gcggd-guix-devel=m.gmane.org@gnu.org To: Andreas Enge Cc: guix-devel@gnu.org Andreas Enge writes: > On Thu, Oct 10, 2013 at 03:09:09PM +0200, Ludovic Court=C3=A8s wrote: >> Andreas Enge skribis: >> > I do not know how much this slows down qt applications. According to w= ikipedia, >> > sse2 arrived in 2001. So one could argue that adding it would exclude = almost >> > no machines. >> Yes, you may be right for SSE2 (especially considering the fact that >> this kind of software is typically used on fairly recent machines.) > > Finally, I disabled everything special. You can assume SSE2 on x86_64, as _all_ x86_64 processors have it. In fact, the C function calling conventions of SysV x86_64 psABI (used by GNU/Linux) specify that the SSE2 registers are used for passing floating point values as arguments. > As this is not a number crunching library, I would like to be > convinced of the usefulness of SSE. Qt is not a number crunching library, but I suspect it _does_ have image rendering code, where SIMD instruction sets such as SSE2 can make a dramatic difference in performance. Regards, Mark