From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262482AbTDQCKl (ORCPT ); Wed, 16 Apr 2003 22:10:41 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262507AbTDQCKl (ORCPT ); Wed, 16 Apr 2003 22:10:41 -0400 Received: from fmr01.intel.com ([192.55.52.18]:57812 "EHLO hermes.fm.intel.com") by vger.kernel.org with ESMTP id S262482AbTDQCKk convert rfc822-to-8bit (ORCPT ); Wed, 16 Apr 2003 22:10:40 -0400 content-class: urn:content-classes:message MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT X-MimeOLE: Produced By Microsoft Exchange V6.0.6375.0 Subject: RE: [BK+PATCH] remove __constant_memcpy Date: Wed, 16 Apr 2003 19:22:33 -0700 Message-ID: <3014AAAC8E0930438FD38EBF6DCEB56401A45522@fmsmsx407.fm.intel.com> X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: [BK+PATCH] remove __constant_memcpy Thread-Index: AcMEhhozhBTbGgesTyOBOjitMlP2AwAAGyew From: "Nakajima, Jun" To: "Linus Torvalds" , "Jeff Garzik" Cc: "LKML" X-OriginalArrivalTime: 17 Apr 2003 02:22:33.0430 (UTC) FILETIME=[34329760:01C30488] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org I think the fear is valid. Intel compiler, for example, uses FP if it's required to optimize the code with a particular option. And the option is not necessary obvious when telling if it uses FP or not (and it does not matter for most users). This could happen with gcc. I think we can do it better than the compiler does, because we know the usage better, e.g. alignment, typical size, etc. Thanks, Jun > -----Original Message----- > From: Linus Torvalds [mailto:torvalds@transmeta.com] > Sent: Wednesday, April 16, 2003 7:06 PM > To: Jeff Garzik > Cc: LKML > Subject: Re: [BK+PATCH] remove __constant_memcpy > > > On Wed, 16 Apr 2003, Jeff Garzik wrote: > > > > gcc's __builtin_memcpy performs the same function (and more) as the > > kernel's __constant_memcpy. So, let's remove __constant_memcpy, and let > > the compiler do it. > > Please don't. > > There's no way gcc will EVER get the SSE2 cases right. It just cannot do > it. In fact, I live in fear that we will have to turn off the compiler > intrisics entirely some day just because there is always the worry that > gcc will start using FP. > > So the advantage of doing our own memcpy() is not that it's necessarily > faster than the gcc built-in, but simply because I do not believe that the > gcc people care enough about the kernel to let them make the choice. > > Linus > > - > 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/