From: Alan Modra <amodra@gmail.com>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: linuxppc-dev@ozlabs.org, paulus@samba.org,
Anton Blanchard <anton@samba.org>,
rostedt@goodmis.org, imunsie@au1.ibm.com
Subject: Re: PowerPC ftrace function trace optimisation
Date: Thu, 29 Apr 2010 10:52:52 +0930 [thread overview]
Message-ID: <20100429012252.GC3510@bubble.grove.modra.org> (raw)
In-Reply-To: <1272502967.24542.137.camel@pasglop>
On Thu, Apr 29, 2010 at 11:02:47AM +1000, Benjamin Herrenschmidt wrote:
> From a quick test it appears that this only works with -m64, not -m32.
> Alan is that correct ?
Yes.
> Any chance you can fix that in future gcc versions ?
No need really. 32-bit _mcount calls happen before the prologue
anyway.
> > In fact if we are careful when switching to the new mcount ABI and don't
> > rely on the store of r0, we could probably optimise this even further in a
> > future gcc and remove the store completely. mcount would be 2 instructions:
> >
> > mflr r0
> > bl 8 <.foo+0x8>
Yeah. Also, I should have used a different name for this mcount from
the standard 64-bit mcount.
--
Alan Modra
Australia Development Lab, IBM
next prev parent reply other threads:[~2010-04-29 1:23 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-04-29 0:51 PowerPC ftrace function trace optimisation Anton Blanchard
2010-04-29 1:02 ` Benjamin Herrenschmidt
2010-04-29 1:08 ` Benjamin Herrenschmidt
2010-04-29 1:22 ` Alan Modra [this message]
2010-04-29 1:55 ` Steven Rostedt
2010-04-29 2:10 ` Benjamin Herrenschmidt
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