Date: Thu, 24 Jun 2004 08:05:34 -0400
From: Jakub Jelinek <jakub@redhat.com>
To: Arjan van de Ven <arjanv@redhat.com>
Cc: Andrew Morton <akpm@osdl.org>, linux-kernel@vger.kernel.org,
       torvalds@osdl.org
Subject: Re: using gcc built-ins for bitops?
Message-ID: <20040624120534.GW21264@devserv.devel.redhat.com>
Reply-To: Jakub Jelinek <jakub@redhat.com>
References: <20040624070936.GB30057@devserv.devel.redhat.com> <20040624020022.0601d4ae.akpm@osdl.org> <20040624113151.GA21376@devserv.devel.redhat.com>
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On Thu, Jun 24, 2004 at 01:31:51PM +0200, Arjan van de Ven wrote:
> On Thu, Jun 24, 2004 at 02:00:22AM -0700, Andrew Morton wrote:
> > For the implementation it would be nice to have the old-style
> > implementations in one header and the new-style ones in a separate header. 
> > That would create a bit of an all-or-nothing situation, but that should be
> > OK?
> 
> In addition I stuck those in asm-generic since they no longer are
> architecture specific....

This is not going to work.
Say on x86_64, __builtin_ctzl (~word) ends up __ctzdi2 (~word) call in GCC
3.4.x, which is not defined in the kernel (in 3.5 it will be bsfq).
On a bunch of arches which don't have an instruction for ffz operation
it will always result in a library call.

	Jakub
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