From: 민찬호 <chanho.min@lge.com>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: "Andrew Morton" <akpm@linux-foundation.org>,
이경식 <kyungsik.lee@lge.com>,
"Yann Collet" <yann.collet.73@gmail.com>,
"Bob Pearson" <rpearson@systemfabricworks.com>,
"Richard Weinberger" <richard@nod.at>,
linux-kernel@vger.kernel.org,
sparclinux <sparclinux@vger.kernel.org>,
Linux/m68k <linux-m68k@vger.kernel.org>,
Linux-Next <linux-next@vger.kernel.org>
Subject: Re: [PATCH] lib: add weak __clzsi2()/__clzdi2() functions
Date: Thu, 2 May 2013 09:58:02 +0900 [thread overview]
Message-ID: <OF7904F8C7.4731B9DC-ON49257B5F.00055048-49257B5F.0005504A@lge.com> (raw)
In-Reply-To: <20130430144605.1a99a7397702b332ee818fc8@linux-foundation.org>
>No, the link errors are for __ctzdi2, not __clzdi2.
>__ctzdi2 can be implemented using __ffs().
>> How's about we stop using __builtin_ctz[ll]() altogether? Use N-fls()?
>
>That was my first suggestion ;-)
>
Do we remove existing __builtin_ct[l]z?
Some architecture's __builtin_clz will be more optimized than N-fls
IMHO, This is not only about __builtin- but also supporting another
libgcc functions in kernel.
Some future user may need __clz[t]s[d]i2 symbol also.
>> btw, this:
>>
>> int __weak __clzsi2(int val)
>> {
>> return BITS_PER_LONG - fls(val);
>> }
>>
>> looks wrong. It will give a different result for 32- and 64-bit.
>
>Indeed. It should be hardcoded 32.
>
I will re-work this for 64-bit, and ctz also.
Thanks
Chanho Min
next prev parent reply other threads:[~2013-05-02 0:58 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-04-29 5:40 [PATCH] lib: add weak __clzsi2()/__clzdi2() functions Chanho Min
2013-04-29 7:20 ` Geert Uytterhoeven
2013-04-30 21:46 ` Andrew Morton
2013-05-01 7:35 ` Geert Uytterhoeven
2013-05-02 0:58 ` 민찬호 [this message]
2013-04-30 19:47 ` Andrew Morton
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