From: Dan Streetman Subject: Re: [PATCH] lib: fix 842 build on 32-bit architectures Date: Wed, 13 May 2015 19:52:24 -0400 Message-ID: <1431561144-29931-1-git-send-email-ddstreet@ieee.org> References: <2802721.Q9KnE9eNH4@wuerfel> Cc: Dan Streetman , Arnd Bergmann , Herbert Xu , linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org To: linux-arm-kernel@lists.infradead.org Return-path: Received: from mail-ie0-f181.google.com ([209.85.223.181]:35905 "EHLO mail-ie0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965675AbbEMXwy (ORCPT ); Wed, 13 May 2015 19:52:54 -0400 In-Reply-To: <2802721.Q9KnE9eNH4@wuerfel> Sender: linux-crypto-owner@vger.kernel.org List-ID: > Building the 842 code on 32-bit ARM currently results in this link > error: > > ERROR: "__aeabi_uldivmod" [lib/842/842_decompress.ko] undefined! Oops! Guess I should build/test on 32 bit more. > > 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. alternately, we know that fsize will always be less than 64 bits, at most it's 4<<9 or 8<<8 (both == 1<<11). So we could just change its type to u16. 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 int __do_index(struct sw842_param *p, u8 size, u8 bits, u16 fsize) { u64 index, offset, total = round_down(p->out - p->ostart, 8); int ret; Or, we could inline it and change the type to u16. In any case, Acked-by: Dan Streetman > > 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) > { > u64 index, offset, total = round_down(p->out - p->ostart, 8); > int ret; >