linux-kernel - Re: [PATCH] arch: metag: lib: add "umoddi3.S" file for _

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Date:	Fri, 20 Dec 2013 19:51:31 +0800
From:	Chen Gang <gang.chen.5i5j@...il.com>
To:	James Hogan <james.hogan@...tec.com>
CC:	rostedt@...dmis.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-metag@...r.kernel.org
Subject: Re: [PATCH] arch: metag: lib: add "umoddi3.S" file for __umoddi3()

On 12/20/2013 06:48 PM, James Hogan wrote:
> On 20/12/13 10:20, Chen Gang wrote:
>> Hmm... but do you know why we need some 64-bit functions which are
>> implemented under "arch/metag/lib/*.S"? can we use <linux/math64.h>
>> instead of them? (e.g 64-bit '/').
> 
> If you look at linux/math64.h you'll see it only implements division
> operations. The other 64 bit operations like shift, compare, and
> multiply are relatively cheap so are implemented as intrinsics instead.
> 

OK, thanks. tomorrow, I will send related patch: use 'div64_u64_rem'
instead of umoddi3 ('%').  :-)

And I guess, in kernel wide, we need remove all 'umoddi3' and 'udivdi3'.

  umoddi3 ('%'): frv, ia64, parisc, tile, xtensa
  udivdi3 ('/'): frv, ia64, parisc, tile, xtensa, sh, sparc.
  especially, sh and sparc only provide '/', do not provide '%'.


BTW: originally, I make a mistake -- treat 'udevsi3' as 'udevdi3'.


Thanks.
-- 
Chen Gang

Open, share and attitude like air, water and life which God blessed
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