linux-kernel - Re: 2.6.32-rc3: floating-point build failure (undefined reference to `_

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Date:	Fri, 09 Oct 2009 09:32:13 -0700
From:	Arjan van de Ven <arjan@...ux.intel.com>
To:	Andreas Mohr <andi@...as.de>
CC:	Kyle McMartin <kyle@...artin.ca>, linux-kernel@...r.kernel.org,
	linux-acpi@...r.kernel.org
Subject: Re: 2.6.32-rc3: floating-point build failure (undefined reference
 to `__udivdi3' in menu governor)

Andreas Mohr wrote:
> Hi,
> 
> On Wed, Oct 07, 2009 at 01:45:54PM -0400, Kyle McMartin wrote:
>> On Wed, Oct 07, 2009 at 07:34:58PM +0200, Andreas Mohr wrote:
>>> Still happening.
>>> IOW it must be somewhere inside the DIV_ROUND_CLOSEST macro or so.
>>>
>> It's being a jerk and not realizing that RESOLUTION * DECAY is a power
>> of 2, so it can just do a shift...
>>
>> I don't recall if gcc 3 had these magic builtins, but if it does,
>> something like this might help since it's the u64 case that's
>> problematic.
> 
> Uh... nope:
> 
> In file included from kernel/sched.c:1818:
> kernel/sched_fair.c: In function `select_task_rq_fair':
> kernel/sched_fair.c:1366: implicit declaration of function `__builtin_popcountll'
> kernel/sched_fair.c:1366: implicit declaration of function `__builtin_ffsll'
> kernel/sched_fair.c:1366: warning: suggest parentheses around + or - inside shift
> kernel/sched.c: In function `update_sg_lb_stats':
> kernel/sched.c:3755: warning: suggest parentheses around + or - inside shift
> kernel/sched.c: In function `find_busiest_queue':
> kernel/sched.c:4050: warning: suggest parentheses around + or - inside shift
> make[1]: *** [kernel/sched.o] Error 1
> make: *** [kernel] Error 2
> 
> 
> Hmpf. Rather stuck now, ain'tcha, given that gcc 3.2.3 doesn't even have those?
> 

wonder if making a new define with the value of RESOLUTION * DECAY
(the actual value obviously) convinces your gcc that it really is a power of two ?
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