From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Geoff Levand <geoffrey.levand@am.sony.com>
Cc: Arnd Bergmann <arnd@arndb.de>,
linuxppc-dev@ozlabs.org, Paul Mackerras <paulus@samba.org>,
cbe-oss-dev@ozlabs.org
Subject: Re: [patch] powerpc: remove do-nothing cpu setup routines
Date: Tue, 09 May 2006 10:28:34 +1000 [thread overview]
Message-ID: <1147134514.4777.287.camel@localhost.localdomain> (raw)
In-Reply-To: <445FDF62.2030008@am.sony.com>
On Mon, 2006-05-08 at 17:16 -0700, Geoff Levand wrote:
> Segher Boessenkool wrote:
> >>> Removes the processor specific do-nothing routines
> >>> __setup_cpu_power3 and
> >>> __setup_cpu_power4 with the generic routine __setup_cpu_null.
> >>
> >> Why not just change the caller to test for NULL ?
>
> OK, I see the 32 bit version already does this, but I'm
> wondering if there is some restriction on the instruction
> sequence between the compare and the branch. Here's what's
> there:
>
> lwz r5,CPU_SPEC_SETUP(r4)
> cmpi 0,r5,0
> add r5,r5,r3
> beqlr
> mtctr r5
> bctr
>
> But, could this also be:
>
> lwz r5,CPU_SPEC_SETUP(r4)
> cmpi 0,r5,0
> beqlr
> add r5,r5,r3
> mtctr r5
> bctr
Just an optimisation for a code path that doesn't really need any :)
Blame habits...
Ben.
next prev parent reply other threads:[~2006-05-09 0:28 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-05-06 0:00 [patch] powerpc: remove do-nothing cpu setup routines Geoff Levand
2006-05-07 22:31 ` Benjamin Herrenschmidt
2006-05-08 0:12 ` Segher Boessenkool
2006-05-09 0:16 ` Geoff Levand
2006-05-09 0:28 ` Benjamin Herrenschmidt [this message]
2006-05-09 0:47 ` Segher Boessenkool
2006-05-09 2:36 ` Geoff Levand
2006-05-09 2:49 ` Geoff Levand
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