From: Joe Perches <joe@perches.com>
To: zengzhaoxiu@163.com, linux-kernel@vger.kernel.org
Cc: Zeng Zhaoxiu <zhaoxiu.zeng@gmail.com>,
Steven Miao <realmz6@gmail.com>,
adi-buildroot-devel@lists.sourceforge.net
Subject: Re: [PATCH V3] blackfin: optimize ffz, __ffs, ffs, __fls, and fls functions
Date: Fri, 15 Apr 2016 09:08:34 -0700 [thread overview]
Message-ID: <1460736514.19090.32.camel@perches.com> (raw)
In-Reply-To: <1460733645-77406-1-git-send-email-zengzhaoxiu@163.com>
On Fri, 2016-04-15 at 23:20 +0800, zengzhaoxiu@163.com wrote:
> From: Zeng Zhaoxiu <zhaoxiu.zeng@gmail.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));
next prev parent reply other threads:[~2016-04-15 16:08 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-15 7:52 [PATCH] blackfin: optimize ffz, __ffs, ffs, __fls, and fls functions zengzhaoxiu
2016-04-15 8:23 ` [PATCH V2] " zengzhaoxiu
2016-04-15 9:16 ` [PATCH] " kbuild test robot
2016-04-15 15:20 ` [PATCH V3] " zengzhaoxiu
2016-04-15 16:08 ` Joe Perches [this message]
2016-04-15 16:18 ` Zhaoxiu Zeng
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