From: Russell King - ARM Linux Subject: Re: [PATCH] lib: fix 842 build on 32-bit architectures Date: Thu, 14 May 2015 11:03:30 +0100 Message-ID: <20150514100330.GV2067@n2100.arm.linux.org.uk> References: <2802721.Q9KnE9eNH4@wuerfel> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Herbert Xu , Dan Streetman , linux-crypto@vger.kernel.org To: Arnd Bergmann Return-path: Received: from pandora.arm.linux.org.uk ([78.32.30.218]:44963 "EHLO pandora.arm.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932475AbbENKDl (ORCPT ); Thu, 14 May 2015 06:03:41 -0400 Content-Disposition: inline In-Reply-To: <2802721.Q9KnE9eNH4@wuerfel> Sender: linux-crypto-owner@vger.kernel.org List-ID: On Wed, May 13, 2015 at 10:56:39PM +0200, Arnd Bergmann wrote: > Building the 842 code on 32-bit ARM currently results in this link > error: > > ERROR: "__aeabi_uldivmod" [lib/842/842_decompress.ko] undefined! > > The reason is that the __do_index function performs a 64-bit > division by a power-of-two number, but it has no insight into > the function arguments. > > By marking that function inline, the fsize argument is always > known at the time that do_index is called, and the compiler is > able to replace the extremely expensive 64-bit division with > a cheap constant shift operation. > > Aside from fixing that link error, this approach should also improve > both code size and performance on 32-bit architectures significantly. > > Signed-off-by: Arnd Bergmann > --- > Found while building arm32 allmodconfig with gcc-5.0 > > diff --git a/lib/842/842_decompress.c b/lib/842/842_decompress.c > index 6b2b45aecde3..285bf6b6959c 100644 > --- a/lib/842/842_decompress.c > +++ b/lib/842/842_decompress.c > @@ -169,7 +169,7 @@ static int do_data(struct sw842_param *p, u8 n) > return 0; > } > > -static int __do_index(struct sw842_param *p, u8 size, u8 bits, u64 fsize) > +static inline int __do_index(struct sw842_param *p, u8 size, u8 bits, u64 fsize) This had better get a comment to say why this is done, to stop the "don't do static inline in a .c" brigade reverting this change. -- FTTC broadband for 0.8mile line: currently at 10.5Mbps down 400kbps up according to speedtest.net.