From: "H. Peter Anvin" <hpa@zytor.com>
To: Jan Beulich <jbeulich@novell.com>
Cc: Chuck Ebbert <cebbert@redhat.com>,
mingo@elte.hu, tglx@linutronix.de, linux-kernel@vger.kernel.org
Subject: Re: [RFC] x86: bitops asm constraint fixes
Date: Wed, 19 Mar 2008 06:19:03 -0700 [thread overview]
Message-ID: <47E112C7.8020406@zytor.com> (raw)
In-Reply-To: <47DE44F6.76E4.0078.0@novell.com>
Jan Beulich wrote:
>
> That's not very desirable: For one part, because there are uses of
> bitops on arrays of ints (and casting these up isn't fully correct on
> x86-64 because of the same reason that using the bitops on char
> arrays isn't correct (see the other response I sent to Jeremy's reply),
> but also because operating on longs requires REX prefixes n x86-64,
> hence making the code bigger for no good reason.
>
It might be worthwhile to find out if 64-bit bitops are faster.
Bitops are normally defined only on longs, but since x86 is a
littleendian architecture we sometimes fudge that in arch-specific code.
-hpa
next prev parent reply other threads:[~2008-03-19 19:25 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-03-13 9:08 [RFC] x86: bitops asm constraint fixes Jan Beulich
2008-03-14 7:51 ` H. Peter Anvin
2008-03-14 8:09 ` Jan Beulich
2008-03-14 18:56 ` Jeremy Fitzhardinge
2008-03-17 9:08 ` Jan Beulich
2008-03-14 21:07 ` Chuck Ebbert
2008-03-17 9:16 ` Jan Beulich
2008-03-19 13:19 ` H. Peter Anvin [this message]
2008-03-21 13:54 ` Ingo Molnar
-- strict thread matches above, loose matches on Subject: below --
2008-03-27 8:12 Jan Beulich
2008-03-27 8:41 ` Ingo Molnar
2008-04-14 12:53 ` Jan Beulich
2008-03-28 19:55 Jan Beulich
2008-04-14 13:31 Jan Beulich
2008-04-14 16:21 ` Jeremy Fitzhardinge
2008-04-15 7:03 ` Jan Beulich
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