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Subject: Re: [PATCH 02/17] x86, lto: Disable fancy hweight optimizations for LTO v2
From: "H. Peter Anvin" <hpa@zytor.com>
Date: Sat, 08 Feb 2014 13:43:29 -0800
To: Andi Kleen <ak@linux.intel.com>
CC: linux-kernel@vger.kernel.org, linux-kbuild@vger.kernel.org, x86@kernel.org
Message-ID: <bbf468ff-4a69-4e51-afc4-d894f459ded7@email.android.com>
Sender: linux-kernel-owner@vger.kernel.org

That's fine.

On February 8, 2014 12:21:24 PM PST, Andi Kleen <ak@linux.intel.com> wrote:
>On Sat, Feb 08, 2014 at 10:52:07AM -0800, H. Peter Anvin wrote:
>> On 02/08/2014 12:01 AM, Andi Kleen wrote:
>> > The fancy x86 hweight uses different compiler options for the
>> > hweight file. This does not work with LTO. Just disable the
>optimization
>> > with LTO
>> 
>> No, I'm going to NAK this.  This means not using the POPCNT
>instruction
>> if LTO is enabled, and that really isn't an acceptable option.
>
>I thought the use was obscure?
>
>Ok, suppose can just disable LTO for the file.
>The only drawback is that the functions will not be optimized away when
>not used, as they'll need to be __visible.
>
>-Andi

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