From: Andi Kleen <andi@firstfloor.org>
To: Alexander van Heukelum <heukelum@fastmail.fm>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>,
Alexander van Heukelum <heukelum@mailshack.com>,
Ingo Molnar <mingo@elte.hu>, Andi Kleen <andi@firstfloor.org>,
Thomas Gleixner <tglx@linutronix.de>,
"H. Peter Anvin" <hpa@zytor.com>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] x86: merge the simple bitops and move them to bitops.h
Date: Fri, 14 Mar 2008 20:55:20 +0100 [thread overview]
Message-ID: <20080314195520.GV2522@one.firstfloor.org> (raw)
In-Reply-To: <1205523826.7441.1242464129@webmail.messagingengine.com>
The CMOV define should probably be dependent on what CPU the kernel
is tuned for. It was originally written for when x86-64 was only
K8 which has fast CMOV, but e.g. on P4 CMOV is actually deprecated
over jumps.
> Both define fls64(), but i386 uses a generic one and x86_64 defines
> one all by itself. The generic one is currently not suitable for
> use by 64-bit archs... that can change.
It is very unlikely a generic one will ever be able to compete
with a single instruction.
> x86_64 defines ARCH_HAS_FAST_MULTIPLIER, i386 not. This affects a
> choice of generated code in the (generic) hweight function. It would
> be nice if that could move to some other file.
It depends on the CPU, but it can be probably safely set on pretty much
all modern x86 cores.
> x86_64 has a mysterious inline function set_bit_string, which is
> only used by pci-calgary_64.c and pci-gart_64.c. Not sure what to
> do with it.
It's generic and could really live in linux/bitops.h
-Andi
next prev parent reply other threads:[~2008-03-14 19:53 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-03-12 20:01 [PATCH] x86: merge the simple bitops and move them to bitops.h Alexander van Heukelum
2008-03-14 18:07 ` Jeremy Fitzhardinge
2008-03-14 19:43 ` Alexander van Heukelum
2008-03-14 19:55 ` Andi Kleen [this message]
2008-03-14 21:33 ` Alexander van Heukelum
2008-03-14 21:42 ` Andi Kleen
2008-03-14 22:01 ` Alexander van Heukelum
2008-03-14 22:18 ` Andi Kleen
2008-03-15 17:54 ` Alexander van Heukelum
2008-03-15 19:19 ` K8, EFFICEON and CORE2 support the cmovxx instructions Alexander van Heukelum
2008-03-15 20:18 ` H. Peter Anvin
2008-03-15 21:06 ` Alexander van Heukelum
2008-03-15 21:11 ` Willy Tarreau
2008-03-16 13:16 ` [PATCH] x86: K8, GEODE_LX, CRUSOE, " Alexander van Heukelum
2008-03-21 12:38 ` Ingo Molnar
2008-03-14 20:35 ` [PATCH v2] x86: merge the simple bitops and move them to bitops.h Alexander van Heukelum
2008-03-14 23:30 ` Randy Dunlap
2008-03-15 12:04 ` [PATCH v3] " Alexander van Heukelum
2008-03-21 12:35 ` Ingo Molnar
2008-03-14 21:15 ` [PATCH] " Jeremy Fitzhardinge
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