From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760679AbYEMOfh (ORCPT ); Tue, 13 May 2008 10:35:37 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757565AbYEMOf3 (ORCPT ); Tue, 13 May 2008 10:35:29 -0400 Received: from mx1.suse.de ([195.135.220.2]:34783 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757356AbYEMOf2 (ORCPT ); Tue, 13 May 2008 10:35:28 -0400 From: Andreas Schwab To: Russell King Cc: Alexander van Heukelum , Nickolay Vinogradov , linux-kernel@vger.kernel.org, Andrew Morton Subject: Re: [PATCH] asm-generic/bitops/fls64.h References: <481E076A.8060302@protei.ru> <1210677433.22341.1252875863@webmail.messagingengine.com> <48298990.7040705@protei.ru> <1210685053.13437.1252892061@webmail.messagingengine.com> <20080513135839.GA19291@flint.arm.linux.org.uk> X-Yow: WHOA!! I'm having a RELIGIOUS EXPERIENCE right NOW!! Date: Tue, 13 May 2008 16:35:25 +0200 In-Reply-To: <20080513135839.GA19291@flint.arm.linux.org.uk> (Russell King's message of "Tue, 13 May 2008 14:58:39 +0100") Message-ID: User-Agent: Gnus/5.110009 (No Gnus v0.9) Emacs/22.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Russell King writes: > On Tue, May 13, 2008 at 03:24:13PM +0200, Alexander van Heukelum wrote: >> On Tue, 13 May 2008 16:29:04 +0400, "Nickolay Vinogradov" >> said: >> > Alexander van Heukelum пишет: >> > >> > > Hi Nickolay, >> > > >> > > The change is ok, I guess, but the cast should be a no-op (fls >> > > takes an int, which is always 32 bit in linux). What is the problem >> > > you are seeing? Does fls64() return a wrong value in some cases? If >> > > so, what cpu? Which values? >> > > >> > > Why would this be a bug on big endian systems only? There is no >> > > pointer magic involved, so the compiler should take care of the >> > > casts in a correct way. >> > > >> > > Maybe you see a compiler warning? Which compiler version? >> > > >> > > (also note that current (development) kernels now have separate >> > > versions for 32-bit and 64-bit environments.) >> > >> > Because fls() is a macro for asm-arm: >> > >> > #define fls(x) \ >> > ( __builtin_constant_p(x) ? constant_fls(x) : \ >> > ({ int __r; asm("clz\t%0, %1" : "=r"(__r) : "r"(x) : "cc"); >> > 32-__r; }) ) >> > >> > We can fix it right here: > > No. "fls" is for finding the last set bit in an _int_. It is not > supposed to have random crap passed to it, such as types longer than > sizeof(int). If you write fls as an (inline) function then the argument is implicitly converted. Andreas. -- Andreas Schwab, SuSE Labs, schwab@suse.de SuSE Linux Products GmbH, Maxfeldstraße 5, 90409 Nürnberg, Germany PGP key fingerprint = 58CA 54C7 6D53 942B 1756 01D3 44D5 214B 8276 4ED5 "And now for something completely different."