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Date: Wed, 30 Jan 2002 11:00:25 +0300
From: Andrey Panin <pazke@orbita1.ru>
To: Mark Hahn <hahn@physics.mcmaster.ca>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [ACPI] ACPI mentioned on lwn.net/kernel
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In-Reply-To: <Pine.LNX.4.33.0201291412590.18804-100000@coffee.psychology.mcmaster.ca>; from hahn@physics.mcmaster.ca on Tue, Jan 29, 2002 at 02:14:32PM -0500
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On Tue, Jan 29, 2002 at 02:14:32PM -0500, Mark Hahn wrote:
> > 	- what stop us from using -mregparm=3D3 gcc switch ?
>=20
> I dimly recall that it can generage bad code, perhaps only
> on old compilers.

Bad code, hmm ... slow code or wrong code ?
IIRC gcc 2.95.3 declared as minimal requirement for kernel compilation,
so may be it's not an issue anymore ?

>=20
> > 	- same with -Os -malign-loops=3D1 -malign-jumps=3D1 ?
>=20
> 2 is probably always the lowest you should go, and indeed,
> I think that's all the compiler permits.
>

gcc (at least 2.95.2) permits 1, but i didn't check generated code.

> > 	- any tool to measure perfomance gain/penalty of above ?
>=20
> lmbench.  it has to be a microbenchmark to measure this sort of thing,
> though a sanity check (kernel compile) would also be useful.

Thanks, i'll test these issues this weekend.=20

Best regards.

--=20
Andrey Panin            | Embedded systems software engineer
pazke@orbita1.ru        | PGP key: wwwkeys.eu.pgp.net
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