linux-kernel - Re: [PATCH v2 10/30] Add x86-specific parity functions

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Date:	Thu, 7 Apr 2016 11:56:12 +0800
From:	Zeng Zhaoxiu <zhaoxiu.zeng@...il.com>
To:	Andi Kleen <andi@...stfloor.org>, zengzhaoxiu@....com
Cc:	tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
	dvlasenk@...hat.com, bp@...e.de, akpm@...ux-foundation.org,
	dvyukov@...gle.com, keescook@...omium.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 10/30] Add x86-specific parity functions

在 2016年04月07日 03:45, Andi Kleen 写道:
> zengzhaoxiu@....com writes:
>
>> From: Zhaoxiu Zeng <zhaoxiu.zeng@...il.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.