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Date: Mon, 18 Apr 2005 16:12:05 +0200
From: Christian MICHON <christian.michon@gmail.com>
Subject: Re: [Qemu-devel] Profiling Qemu for speed?
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To: qemu-devel@nongnu.org

I did months ago gcc/FDO with a xp/lite installation as a "repetitive task"=
 :)
I did not improve the timings after all the effort.

Christian

On 4/18/05, Daniel Egger <de@axiros.com> wrote:
> On 18.04.2005, at 11:51, Ian Rogers wrote:
>=20
> > I'm not sure if you can get GCC to generate code sequences like this,
> > but you probably at least need to use the -fprofile-generate and
> > -fprofile-use options
> > http://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html
>=20
> Feedback optimisation (FDO) will not work for two reasons:
> a) qemu itself is something like a realtime compiler so FDO
>     will only speed up the compiler but not the generated code
> b) FDO will only provide speed boosts if the feedback phase
>     has a chance to analyse a representative work pattern that
>     is hopefully also repetitive
>=20
> After all FDO is mostly about making a tradeoff size/speed
> and rearranging code (mostly branches) to avoid branch
> mispredictions of the CPU.
>=20
> Servus,
>        Daniel
>=20
>=20
> _______________________________________________
> Qemu-devel mailing list
> Qemu-devel@nongnu.org
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>=20
>=20
>=20
>=20


--=20
Christian