Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261323AbUKBSwR (ORCPT ); Tue, 2 Nov 2004 13:52:17 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261325AbUKBSwR (ORCPT ); Tue, 2 Nov 2004 13:52:17 -0500 Received: from twinlark.arctic.org ([168.75.98.6]:60364 "EHLO twinlark.arctic.org") by vger.kernel.org with ESMTP id S261323AbUKBSwN (ORCPT ); Tue, 2 Nov 2004 13:52:13 -0500 Date: Tue, 2 Nov 2004 10:52:12 -0800 (PST) From: dean gaudet To: Denis Vlasenko cc: Marc Bevand , linux-kernel@vger.kernel.org Subject: Re: [rc4-amd64] RC4 optimized for AMD64 In-Reply-To: <200411020854.21629.vda@port.imtp.ilyichevsk.odessa.ua> Message-ID: References: <200411020854.21629.vda@port.imtp.ilyichevsk.odessa.ua> 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 Content-Length: 1002 Lines: 28 On Tue, 2 Nov 2004, Denis Vlasenko wrote: > On Monday 01 November 2004 22:44, dean gaudet wrote: > > note that > > p4 would prefer "sub $1, %r11b" here instead of dec... but the difference > > is likely minimal. > > p4 is not the only x86 CPU on the planet. Why should I use > longer instruction then? you're asking about spending one byte? one byte extra for code which could perform better on more CPUs? i could equally well say "k8 is not the only x86-64 cpu on the planet". i really don't care whether this change is made or not, i only mentioned a general perf rule. go ahead and use -Os for the rest of the kernel if you're worried about size, it'll likely go faster. but spending 1 byte in code which is perf critical is nothing. -dean - 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/