linux-kernel - Re: [PATCH] __div64_32: implement division by multiplication for 32-bit arches

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Message-ID: <yw1xy4ekb68f.fsf@unicorn.mansr.com>
Date:	Fri, 30 Oct 2015 17:45:20 +0000
From:	Måns Rullgård <mans@...sr.com>
To:	Nicolas Pitre <nicolas.pitre@...aro.org>
Cc:	Alexey Brodkin <Alexey.Brodkin@...opsys.com>,
	"shemminger\@linux-foundation.org" <shemminger@...ux-foundation.org>,
	"linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>,
	"Vineet.Gupta1\@synopsys.com" <Vineet.Gupta1@...opsys.com>,
	"linux-snps-arc\@lists.infradead.org" 
	<linux-snps-arc@...ts.infradead.org>,
	"rmk+kernel\@arm.linux.org.uk" <rmk+kernel@....linux.org.uk>,
	"davem\@davemloft.net" <davem@...emloft.net>,
	"mingo\@elte.hu" <mingo@...e.hu>
Subject: Re: [PATCH] __div64_32: implement division by multiplication for 32-bit arches

Nicolas Pitre <nicolas.pitre@...aro.org> writes:

> On Fri, 30 Oct 2015, Alexey Brodkin wrote:
>
>> Hi Nicolas,
>> 
>> On Fri, 2015-10-30 at 11:17 -0400, Nicolas Pitre wrote:
>> > On Fri, 30 Oct 2015, Måns Rullgård wrote:
>> > 
>> > > Nicolas Pitre <nicolas.pitre@...aro.org> writes:
>> > > 
>> > > > OK... I was intrigued, so I adapted my ARM code to the generic case, 
>> > > > including the overflow avoidance optimizations.  Please have look and 
>> > > > tell me how this works for you.
>> > > > 
>> > > > If this patch is accepted upstream, then it could be possible to 
>> > > > abstract only the actual multiplication part with some architecture 
>> > > > specific assembly.
>> > > 
>> > > Good idea.
>> > 
>> > Could you please provide a reviewed-by or acked-by tag?
>> 
>> Sure!
>> 
>> Acked-by: Alexey Brodkin <abrodkin@...opsys.com>
>> 
>> BTW I thought about that optimization a bit more and now I think
>> we may even skip addition of arch-specific assembly insertions.
>
> I'm going to do it anyway given that I already have it for ARM.  It'll 
> be opt-in, so if your arch doesn't provide it then the current C 
> implementation will be used by default.

Great.  I'll try it out on MIPS once you've posted the patch.

-- 
Måns Rullgård
mans@...sr.com
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