linux-kernel - Re: [PATCH 2/3] lib: vsprintf: optimised put

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Message-id: <op.vg0do1xe7p4s8u@pikus>
Date:	Fri, 06 Aug 2010 10:54:27 +0200
From:	Michał Nazarewicz <m.nazarewicz@...sung.com>
To:	Michal Nazarewicz <mina86@...a86.com>,
	Denys Vlasenko <vda.linux@...glemail.com>
Cc:	linux-kernel@...r.kernel.org,
	"Douglas W. Jones" <jones@...uiowa.edu>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 2/3] lib: vsprintf: optimised put_dec() for 32-bit machines

On Fri, 06 Aug 2010 09:35:26 +0200, Denys Vlasenko <vda.linux@...glemail.com> wrote:

> On Friday 06 August 2010 09:08, Michal Nazarewicz wrote:
>> >> +static noinline_for_stack
>> >> +char *put_dec(char *buf, unsigned long long n)
>> >> +{
>> >> +	uint32_t d3, d2, d1, q;
>> >> +
>> >> +	if (!n) {
>> >> +		*buf++ = '0';
>> >> +		return buf;
>> >> +	}
>> >> +
>> >> +	d1  = (n >> 16) & 0xFFFF;
>> >> +	d2  = (n >> 32) & 0xFFFF;
>> >> +	d3  = (n >> 48) & 0xFFFF;
>> >
>> > Are you assuming that sizeof(long long) == 8, always?
>>
>> Well...  yes.  C requires long long to be at least 64-bit and I don't
>> see it being larger in any foreseeable feature.
>
> "640k will be enough for everybody"?
>
>> Wouldn't it be enough to put a static assert here?
>
> I'd prefer the code which works with arbitrarily wide long long.
> If needed, use
>
> if (sizeof(long long) == 8)
> 	64-bit code
> else
> 	generic code

Thanks.  That seems like a perfect solution.  I rearrange the code
and try to post updated version after the weekend.

-- 
Best regards,                                        _     _
| Humble Liege of Serenely Enlightened Majesty of  o' \,=./ `o
| Computer Science,  Michał "mina86" Nazarewicz       (o o)
+----[mina86*mina86.com]---[mina86*jabber.org]----ooO--(_)--Ooo--
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