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From: Andreas Schwab <schwab@suse.de>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
References: <20050715160115.GA22990@janus> <1121535588.14393.18.camel@gaston>
Date: Sat, 16 Jul 2005 20:02:18 +0200
In-Reply-To: <1121535588.14393.18.camel@gaston> (Benjamin Herrenschmidt's
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Cc: linuxppc-dev@ozlabs.org
Subject: Re: bug in arch/ppc/kernel/misc.S: __ashrdi3?
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Benjamin Herrenschmidt <benh@kernel.crashing.org> writes:

> On Fri, 2005-07-15 at 18:01 +0200, Frank van Maarseveen wrote:
>> I don't really grok the code but an operand seems to be missing and the
>> assembler makes something out of it I don't trust:
>> 
>> _GLOBAL(__ashrdi3)
>> 	...
>> 	rlwinm  r8,r7,0,32      # t3 = (count < 32) ? 32 : 0
>
> This is equivalent to r8 = r7 & 32. It will definitely not do what the
> comment says though. If (count < 64), however, it will do something
> like r8 = (r7 < 32) ? 0 : 32. Paul, maybe we should dbl check what's
> going in there ?

r7 is count + 32, and ((count + 32) & 32) is equivalent to the expression
above if count < 64.

Andreas.

-- 
Andreas Schwab, SuSE Labs, schwab@suse.de
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