From: Mikael Pettersson <mikpe@csd.uu.se>
To: <cutaway@bellsouth.net>
Cc: <linux-kernel@vger.kernel.org>
Subject: Re: 387 emulator hack - mutant AAD trick - any objections?
Date: Fri, 27 May 2005 09:25:26 +0200 [thread overview]
Message-ID: <17046.52070.257018.186057@alkaid.it.uu.se> (raw)
In-Reply-To: <000701c5628b$583f8060$2800000a@pc365dualp2>
cutaway@bellsouth.net writes:
> Will there be any objections to using a quasi-documented mutation of the
> x86's AAD instruction in the 387 emulator? Every CPU around has to do this
> mutation correctly or a LOT of existing code will break...
>
> The performance of storing to user space of BCD numbers in the 387 emulator
> code could be improved significantly by using the mutant AAD instruction
> trick (i.e. alter its implicit base from 10 to 16). See reg_ld_str.c, in
> function FPU_store_bcd()
What do you mean by "quasi-documented" and "mutant"?
Intel certainly documents the "D5 ib" form as being a
valid way to change the base from the default 10.
The only issue AFAIK is that assemblers may only
recognise the plain base-10 AAD syntax. No biggie.
/Mikael
next prev parent reply other threads:[~2005-05-27 7:45 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-05-27 7:11 cutaway
2005-05-27 7:25 ` Mikael Pettersson [this message]
2005-05-27 12:17 ` Maciej W. Rozycki
2005-05-27 7:44 cutaway
2005-05-27 9:35 ` Denis Vlasenko
2005-05-27 11:43 ` cutaway
2005-05-27 12:24 ` Maciej W. Rozycki
2005-05-27 13:47 ` cutaway
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