linux-kernel - Re: [PATCH V3] blackfin: optimize ffz, __ffs, ffs, _

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Message-ID: <57111463.9090109@163.com>
Date:	Sat, 16 Apr 2016 00:18:43 +0800
From:	Zhaoxiu Zeng <zengzhaoxiu@....com>
To:	Joe Perches <joe@...ches.com>, linux-kernel@...r.kernel.org
Cc:	Zeng Zhaoxiu <zhaoxiu.zeng@...il.com>,
	Steven Miao <realmz6@...il.com>,
	adi-buildroot-devel@...ts.sourceforge.net
Subject: Re: [PATCH V3] blackfin: optimize ffz, __ffs, ffs, __fls, and fls
 functions

在 2016/4/16 0:08, Joe Perches 写道:
> On Fri, 2016-04-15 at 23:20 +0800, zengzhaoxiu@....com wrote:
>> From: Zeng Zhaoxiu <zhaoxiu.zeng@...il.com>
>>
>> blackfin has popcount instruction (ONES), we can do the efficient
>> computing (ffz, __ffs, ffs, __fls, and fls) use this instruction.
> []
>> diff --git a/arch/blackfin/include/asm/bitops.h b/arch/blackfin/include/asm/bitops.h
> []
>> +static inline unsigned int __arch_hweight64(__u64 w)
>> +{
>> +	return __arch_hweight32((unsigned int)(w >> 32)) +
>> +	       __arch_hweight32((unsigned int)w);
>> +}
> trivia:  perhaps this is more readable as:
>
> 	return __arch_hweight32(upper_32_bits(w)) +
> 	       __arch_hweight32(lower_32_bits(w));
>
>

Yes.
I just moved these codes from the bottom of  bitops.h, didn't change anything.