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From: Andreas Schwab <schwab@suse.de>
To: Trent Piepho <tpiepho@freescale.com>
Cc: linuxppc-dev@ozlabs.org, Scott Wood <scottwood@freescale.com>,
       linux-kernel@vger.kernel.org
Subject: Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code
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X-Yow: Is this "BOOZE"?
Date: Wed, 21 May 2008 10:03:54 +0200
In-Reply-To: <Pine.LNX.4.64.0805201612240.7453@t2.domain.actdsltmp> (Trent
	Piepho's message of "Tue, 20 May 2008 16:14:49 -0700 (PDT)")
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Trent Piepho <tpiepho@freescale.com> writes:

> On Wed, 21 May 2008, Andreas Schwab wrote:
>> Trent Piepho <tpiepho@freescale.com> writes:
>>
>>> It's the _le versions that have a problem, since we can't get gcc to just use
>>> the register indexed mode.  It seems like an obvious thing to have a
>>> constraint for, but I guess there weren't enough instructions that only come
>>> in 'x' versions to bother with it.  There is a 'Z' constraint, "Memory operand
>>> that is an indexed or indirect from a register", but I tried it and it can use
>>> both "rb,ri" and "disp(rb)" forms.  Actually, I'm not sure how 'Z' is any
>>> different than "m"?
>>
>> 'Z' will never emit a non-zero constant displacement.
>
> It's too bad gas doesn't appear to be smart enough to turn:
>         stwbrx 0, 0(3)   -or-   stwbr 0, 0(3)

Use the %y modifier when substituting the operand.

Andreas.

-- 
Andreas Schwab, SuSE Labs, schwab@suse.de
SuSE Linux Products GmbH, Maxfeldstraße 5, 90409 Nürnberg, Germany
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"And now for something completely different."