Subject: Re: [PATCH v2 10/30] Add x86-specific parity functions
To: Andi Kleen <andi@firstfloor.org>, zengzhaoxiu@163.com
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From: Zeng Zhaoxiu <zhaoxiu.zeng@gmail.com>
Message-ID: <5705DA5C.9020503@gmail.com>
Date: Thu, 7 Apr 2016 11:56:12 +0800
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?? 2016??04??07?? 03:45, Andi Kleen д??:
> zengzhaoxiu@163.com writes:
>
>> From: Zhaoxiu Zeng <zhaoxiu.zeng@gmail.com>
>>
>> Use alternatives, lifted from arch_hweight
> Is there actually anything performance critical in the kernel that uses
> parity?
>
> FWIW the arch hweight custom calling convention is a problem for LTO
> because it needs different special flags, so I usually have to disable
> it. Likely other reasonable usages, such as automatic source code
> analysis, and other tool chain based usages have similar problems.
>
> As far as I can tell both for hweight and likely for parity it is
> badly overengineering and normal calling conventions would work as well,
> and cause much less problems.
>
> So if parity is really worth adding here (which I find doubtful,
> but you may have numbers), please add it without these magic
> calling hacks.
>
> -Andi
>

Thanks. I will instead use __arch_hweight.