From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Dan Malek <dan@embeddededge.com>
Cc: linuxppc-dev@ozlabs.org
Subject: Re: [PATCH] Set cpu type explicitly, take 2
Date: Sat, 21 May 2005 08:27:32 +1000 [thread overview]
Message-ID: <1116628052.5153.123.camel@gaston> (raw)
In-Reply-To: <e9d0cf12aef70d985053ec7eafb0a9db@embeddededge.com>
On Fri, 2005-05-20 at 10:30 -0400, Dan Malek wrote:
> On May 20, 2005, at 3:45 AM, Benjamin Herrenschmidt wrote:
>
> > The problem is the same as ppc64 isn't it ?, -maltivec doesn't work
> > with
> > -mcpu=power4 on gcc 3.4 does it ? That would mean no RAID6...
>
> I don't understand "doesn't work." Does power4 imply altivec?
> Do we need to add -maltivec based on the configuration option?
No, -mcpu=970 is equivalent in a way to -mcpu=power4 and -maltivec,
howevever, there is a bug in gcc 3.4 which makes -maltivec cause an
error if you have -mcpu=power4. The RAID6 code needs -maltivec. So on
gcc 3.4, we need to use -mcpu=970 instead of -mcpu=power4. However, we
must _NOT_ do that on gcc-4.0 as that causes it to implicitely generate
altivec code all over the place. (Fortunately, the bug is also fixed
there, so with gcc-4.0, we just need -mcpu=power4 and -maltivec only on
the RAID6 code)
Messy ? Yeah !
Ben.
next prev parent reply other threads:[~2005-05-20 22:29 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-05-20 6:05 [PATCH] Set cpu type explicitly, take 2 Paul Mackerras
2005-05-20 7:45 ` Benjamin Herrenschmidt
2005-05-20 14:30 ` Dan Malek
2005-05-20 22:27 ` Benjamin Herrenschmidt [this message]
2005-05-20 14:28 ` Dan Malek
2005-05-21 0:55 ` Paul Mackerras
2005-05-20 14:59 ` Kumar Gala
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