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?
Date: Thu, 24 Jun 2004 08:05:34 -0400 [thread overview]
Message-ID: <20040624120534.GW21264@devserv.devel.redhat.com> (raw)
In-Reply-To: <20040624113151.GA21376@devserv.devel.redhat.com>
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
next prev parent reply other threads:[~2004-06-24 12:06 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-06-24 7:09 using gcc built-ins for bitops? Arjan van de Ven
2004-06-24 9:00 ` Andrew Morton
2004-06-24 9:06 ` Arjan van de Ven
2004-06-24 13:41 ` Ben Collins
2004-06-24 9:17 ` Arjan van de Ven
2004-06-24 11:31 ` Arjan van de Ven
2004-06-24 12:05 ` Jakub Jelinek [this message]
2004-06-24 12:35 ` Arjan van de Ven
2004-06-24 15:30 ` Linus Torvalds
2004-06-24 9:31 ` Paul Jackson
2004-06-24 10:36 ` Jakub Jelinek
2004-06-24 15:25 ` Linus Torvalds
2004-06-24 11:51 ` Gabriel Paubert
2004-06-24 12:21 ` Arjan van de Ven
[not found] <2awGH-DF-17@gated-at.bofh.it>
2004-06-24 13:46 ` Pascal Schmidt
2004-06-24 13:49 ` Arjan van de Ven
2004-06-24 13:51 ` Pascal Schmidt
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