Date: Mon, 28 Mar 2016 11:29:15 -0400 (EDT)
Message-Id: <20160328.112915.1286498398436148099.davem@davemloft.net>
To: zhaoxiu.zeng@gmail.com
Cc: linux-kernel@vger.kernel.org, sparclinux@vger.kernel.org
Subject: Re: [PATCH 10/31] Add sparc-specific parity functions
From: David Miller <davem@davemloft.net>
In-Reply-To: <56F8C4A3.1070808@gmail.com>
References: <56F780FE.7000600@gmail.com>
	<20160327.224308.220596078048860811.davem@davemloft.net>
	<56F8C4A3.1070808@gmail.com>
Mime-Version: 1.0
Content-Type: Text/Plain; charset=iso-2022-jp
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 971
Lines: 25

From: Zeng Zhaoxiu <zhaoxiu.zeng@gmail.com>
Date: Mon, 28 Mar 2016 13:44:03 +0800

> 在 2016年03月28日 10:43, David Miller 写道:
>> From: "zhaoxiu.zeng" <zhaoxiu.zeng@gmail.com>
>> Date: Sun, 27 Mar 2016 14:43:10 +0800
>>
>>> +
>>> +/*
>>> + * parityN: returns the parity of a N-bit word,
>>> + * i.e. the number of 1-bits in x modulo 2.
>>> + */
>>> +
>>> +#define __arch_parity4(w)	(__arch_hweight8((w) & 0xf) & 1)
>>> +#define __arch_parity8(w)	(__arch_hweight8(w) & 1)
>>> +#define __arch_parity16(w)	(__arch_hweight16(w) & 1)
>>> +#define __arch_parity32(w)	(__arch_hweight32(w) & 1)
>>> +#define __arch_parity64(w)	((unsigned int)__arch_hweight64(w) & 1)
>> This looks like asm-generic/ material to me.
> 
> This is generic for the architectures which have popcount instruction,
> but more higher costs than asm-generic/ for others.

Which is why said stanza's in the asm-generic header should be triggered
by a CPP define or similar.