From: Andi Kleen <andi@firstfloor.org>
To: Stephan Diestelhorst <langer_mann@web.de>
Cc: Andi Kleen <andi@firstfloor.org>, Ingo Molnar <mingo@elte.hu>,
davej@codemonkey.org.uk, cpufreq@lists.linux.org.uk,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/1] Speedfreq-SMI call clobbers ECX
Date: Mon, 10 Mar 2008 22:51:45 +0100 [thread overview]
Message-ID: <20080310215145.GB9246@one.firstfloor.org> (raw)
In-Reply-To: <200803102226.39044.langer_mann@web.de>
> Please also note that these are not clobbers in the strict inline asm
> syntax, but rather dummy output values that correspond to actual
Outputs/Inputs are as bad as clobbers in triggering gcc reload ICEs.
> input parameters. I'd consider this a serious compiler flaw, if not
> bug, if these would not work. But let's not get into GCC vs.
It is, and it's (mostly) fixed in newer versions, but we're stuck with
supporting the older compiler versions unfortunately.
> > For asms with so many clobbers explicit push/pop is usually safer.
>
> Yes, but it is unneccessary overhead as the compiler can (should!)
> find more elegant ways to get those registers back if needed.
This code is not performance critical at all. Safer beats faster
any time in such cases.
-Andi
next prev parent reply other threads:[~2008-03-10 21:50 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-03-05 14:59 Stephan Diestelhorst
2008-03-05 15:35 ` Ingo Molnar
2008-03-05 16:02 ` H. Peter Anvin
2008-03-06 8:38 ` Stephan Diestelhorst
2008-03-06 8:51 ` Stephan Diestelhorst
2008-03-06 10:56 ` Ingo Molnar
2008-03-10 15:05 ` Stephan Diestelhorst
2008-03-10 16:46 ` Andi Kleen
2008-03-10 21:26 ` Stephan Diestelhorst
2008-03-10 21:51 ` Andi Kleen [this message]
2008-03-10 23:14 ` Stephan Diestelhorst
2008-03-11 9:39 ` Ingo Molnar
2008-03-12 15:04 ` Stephan Diestelhorst
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