linux-kernel - Re: [10 PATCHES] inline functions to avoid stack overflow

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Message-Id: <20080626.020621.45250426.davem@davemloft.net>
Date:	Thu, 26 Jun 2008 02:06:21 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	bart.vanassche@...il.com
Cc:	mpatocka@...hat.com, helge.hafting@...el.hist.no,
	sparclinux@...r.kernel.org, linux-kernel@...r.kernel.org,
	gcc@....gnu.org
Subject: Re: [10 PATCHES] inline functions to avoid stack overflow

From: "Bart Van Assche" <bart.vanassche@...il.com>
Date: Thu, 26 Jun 2008 08:32:35 +0200

> On Thu, Jun 26, 2008 at 12:09 AM, David Miller <davem@...emloft.net> wrote:
> > The extra 16 bytes of space allocated is so that GCC can perform a
> > secondary reload of a quad floating point value.  It always has to be
> > present, because we can't satisfy a secondary reload by emitting yet
> > another reload, it's the end of the possible level of recursions
> > allowed by the reload pass.
> 
> Is there any floating-point code present in the Linux kernel ?

Yes, but not coming from C compiled code.  Floating point is
used in most of the memcpy/memset implementations of the
sparc64 kernel.

> Would it be a good idea to add an option to gcc that tells gcc that
> the compiled code does not contain floating-point instructions, such
> that gcc knows that no space has to be provided for a quad floating
> point value ?

I think it exists already, it's called -mno-fpu :-)
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