From: Arnd Bergmann <arnd@arndb.de>
To: Anton Blanchard <anton@samba.org>
Cc: Andrew Morton <akpm@osdl.org>,
Tom Rini <trini@kernel.crashing.org>,
Linux Kernel list <linux-kernel@vger.kernel.org>,
linuxppc-dev list <linuxppc-dev@ozlabs.org>,
Paul Mackerras <paulus@samba.org>,
"H. Peter Anvin" <hpa@zytor.com>,
linuxppc64-dev <linuxppc64-dev@ozlabs.org>
Subject: Re: [PATCH] PPC/PPC64: Introduce CPU_HAS_FEATURE() macro
Date: Sat, 5 Feb 2005 12:04:34 +0100 [thread overview]
Message-ID: <200502051204.38965.arnd@arndb.de> (raw)
In-Reply-To: <20050205013426.GC11318@krispykreme.ozlabs.ibm.com>
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On Sünnavend 05 Februar 2005 02:34, Anton Blanchard wrote:
> Interesting :) However we already get bug reports with the current
> CONFIG_POWER4_ONLY option. I worry about adding more options that users
> could get wrong unless there is a noticeable improvement in performance.
>
The patch that I posted doesn't add any new user selectable options,
it only limits the supported CPUs to the ones that are available on
the supported platforms. If you select powermac or maple, the only
supported CPU will be PowerPC970, so the C compiler can optimize away
all runtime checks for CPU features.
I don't expect much noticeable performance advantage from the patch,
but it allows to make some of the source code nicer. E.g. you can
replace every instance of '#ifdef CONFIG_ALTIVEC' with 'if
(CPU_FTR_POSSIBLE & CPU_FTR_ALTIVEC)' or an inline function wrapping
that.
Arnd <><
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next prev parent reply other threads:[~2005-02-05 11:04 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-02-04 7:22 [PATCH] PPC/PPC64: Introduce CPU_HAS_FEATURE() macro Olof Johansson
2005-02-04 8:17 ` Pekka Enberg
2005-02-04 17:20 ` Olof Johansson
2005-02-05 7:48 ` Pekka Enberg
2005-02-05 9:08 ` Benjamin Herrenschmidt
2005-02-04 12:36 ` Arnd Bergmann
2005-02-04 18:35 ` Olof Johansson
2005-02-04 18:57 ` Arnd Bergmann
2005-02-04 23:50 ` Benjamin Herrenschmidt
2005-02-04 23:49 ` Benjamin Herrenschmidt
2005-02-05 0:22 ` Arnd Bergmann
2005-02-05 1:34 ` Anton Blanchard
2005-02-05 11:04 ` Arnd Bergmann [this message]
2005-02-05 1:47 ` Benjamin Herrenschmidt
2005-02-04 14:45 ` Tom Rini
2005-02-05 18:46 ` [PATCH] PPC/PPC64: Abstract cpu_feature checks Olof Johansson
2005-02-06 3:26 ` Olof Johansson
2005-02-06 11:57 ` Arnd Bergmann
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