Date: Thu, 18 Feb 2010 12:51:55 +0100
From: Borislav Petkov <bp@amd64.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Michal Marek <mmarek@suse.cz>, "H. Peter Anvin" <hpa@zytor.com>,
       linux-kbuild <linux-kbuild@vger.kernel.org>,
       Borislav Petkov <petkovbb@googlemail.com>,
       Andrew Morton <akpm@linux-foundation.org>,
       Wu Fengguang <fengguang.wu@intel.com>,
       LKML <linux-kernel@vger.kernel.org>, Jamie Lokier <jamie@shareable.org>,
       Roland Dreier <rdreier@cisco.com>, Al Viro <viro@ZenIV.linux.org.uk>,
       "linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
       Ingo Molnar <mingo@elte.hu>, Brian Gerst <brgerst@gmail.com>
Subject: Re: [PATCH 2/5] bitops: compile time optimization for
 hweight_long(CONSTANT)
Message-ID: <20100218115155.GA20473@aftab>
References: <4B6FDAED.9060204@zytor.com>
 <20100208095945.GA14740@a1.tnic>
 <20100211172424.GB19779@aftab>
 <4B743F7D.3090605@zytor.com>
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 <4B75A66A.70005@zytor.com>
 <4B7BF5D6.3030701@suse.cz>
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On Thu, Feb 18, 2010 at 11:51:50AM +0100, Peter Zijlstra wrote:
> I guess one way to achieve that is to create a arch/x86/lib/hweight.c
> that includes lib/hweight.c and give the x86 one special compile flags
> and not build the lib on.

That's what I thought initially too but that won't fly because the
lib/hweight.c helpers have to be inlined into arch/x86/lib/hweight.c so
that gcc can take care of the clobbered registers. Otherwise, it just a
"call __sw_hweightXX" that gets issued into asm.


-- 
Regards/Gruss,
Boris.

-
Advanced Micro Devices, Inc.
Operating Systems Research Center
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