linux-kernel - Re: [PATCH 2/5] bitops: compile time optimization for hweight

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Message-ID: <20100217173411.GD13429@aftab>
Date:	Wed, 17 Feb 2010 18:34:11 +0100
From:	Borislav Petkov <bp@...64.org>
To:	Michal Marek <mmarek@...e.cz>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	linux-kbuild <linux-kbuild@...r.kernel.org>,
	Borislav Petkov <petkovbb@...glemail.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Wu Fengguang <fengguang.wu@...el.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Jamie Lokier <jamie@...reable.org>,
	Roland Dreier <rdreier@...co.com>,
	Al Viro <viro@...IV.linux.org.uk>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>, Brian Gerst <brgerst@...il.com>
Subject: Re: [PATCH 2/5] bitops: compile time optimization for
 hweight_long(CONSTANT)

On Wed, Feb 17, 2010 at 06:31:04PM +0100, Michal Marek wrote:
> On 17.2.2010 18:20, Borislav Petkov wrote:
> > On Wed, Feb 17, 2010 at 02:57:42PM +0100, Michal Marek wrote:
> >> On 12.2.2010 20:05, H. Peter Anvin wrote:
> >>> On 02/12/2010 09:47 AM, Borislav Petkov wrote:
> >>>>
> >>>> However, this is generic code and for the above to work we have to
> >>>> enforce x86-specific CFLAGS for it. What is the preferred way to do
> >>>> that?
> >>>>
> >>>
> >>> That's a question for Michal and the kbuild list.  Michal?
> >>
> >> (I was offline last week).
> >>
> >> The _preferred_ way probably is not to do it :), but otherwise you can
> >> set CFLAGS_hweight.o depending on CONFIG_X86(_32|_64), just like you do
> >> in arch/x86/lib/Makefile already.
> > 
> > Wouldn't it be better if we had something like ARCH_CFLAGS_hweight.o
> > which gets set in the arch Makefile instead?
> 
> We could, but is it worth it if there is only one potential user so far?
> IMO just put the condition to lib/Makefile now and if there turn out to
> be more cases like this, we can add support for ARCH_CFLAGS_foo.o then.

Ok, I'm fine with that too, thanks.

-- 
Regards/Gruss,
Boris.

--
Advanced Micro Devices, Inc.
Operating Systems Research Center
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