Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code
From: Andreas Schwab
Date: Wed May 21 2008 - 04:04:21 EST
Trent Piepho <tpiepho@xxxxxxxxxxxxx> writes:
> On Wed, 21 May 2008, Andreas Schwab wrote:
>> Trent Piepho <tpiepho@xxxxxxxxxxxxx> 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 Schwab, SuSE Labs, schwab@xxxxxxx
SuSE Linux Products GmbH, Maxfeldstraße 5, 90409 Nürnberg, Germany
PGP key fingerprint = 58CA 54C7 6D53 942B 1756 01D3 44D5 214B 8276 4ED5
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