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Message-ID: <je3aocdqxh.fsf@sykes.suse.de>
Date: Wed, 21 May 2008 10:03:54 +0200
From: Andreas Schwab <schwab@...e.de>
To: Trent Piepho <tpiepho@...escale.com>
Cc: linuxppc-dev@...abs.org, Scott Wood <scottwood@...escale.com>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code
Trent Piepho <tpiepho@...escale.com> writes:
> On Wed, 21 May 2008, Andreas Schwab wrote:
>> Trent Piepho <tpiepho@...escale.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@...e.de
SuSE Linux Products GmbH, Maxfeldstraße 5, 90409 Nürnberg, Germany
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"And now for something completely different."
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