PowerPC ftrace function trace optimisation
Alan Modra
amodra at gmail.com
Thu Apr 29 11:22:52 EST 2010
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
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