From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261204AbUBZWlb (ORCPT ); Thu, 26 Feb 2004 17:41:31 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261200AbUBZWla (ORCPT ); Thu, 26 Feb 2004 17:41:30 -0500 Received: from mx1.redhat.com ([66.187.233.31]:16523 "EHLO mx1.redhat.com") by vger.kernel.org with ESMTP id S261221AbUBZWkf (ORCPT ); Thu, 26 Feb 2004 17:40:35 -0500 To: Linus Torvalds Cc: Kernel Mailing List , Andrew Morton , arjanv@redhat.com, davej@redhat.com, Ingo Molnar Subject: Re: raid 5 with >= 5 members broken on x86 References: From: Alexandre Oliva Organization: Red Hat Global Engineering Services Compiler Team Date: 26 Feb 2004 19:40:21 -0300 In-Reply-To: Message-ID: User-Agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.3 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Feb 26, 2004, Linus Torvalds wrote: >> > There is nothing to say that gcc wouldn't do a re-load or something >> > in between, so you really need to tell the _first_ ask about it. >> The only other reload it could do is an input reload of p4 and p5, >> which, again, doesn't matter, because p4 and p5 are dead anyway. > Ok. That's the missing piece. The thing is wrong, but we don't care, > because even if gcc saves the old values for some silly reload, they're > dead and uninteresting. Yup. > Ok. I did the silly one-liner That's good enough for me. I tested that before trying this better approach, and it worked. > but if the "don't care" approach really improves code generation, > feel free to send one that fixes both the P5 and PII cases.. It's not the code generation that is improved, it's just that we can then refrain from pushing and popping something that nobody cares about. It would have worked to just assign a random value to p4 and p5 after the asm loop; it would be dead anyway. As long as we made sure p4 and p5 weren't shared with anything else before, that is. -- Alexandre Oliva Enjoy Guarana', see http://www.ic.unicamp.br/~oliva/ Happy GNU Year! oliva@{lsd.ic.unicamp.br, gnu.org} Red Hat GCC Developer aoliva@{redhat.com, gcc.gnu.org} Free Software Evangelist Professional serial bug killer