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Message-ID: <OF7904F8C7.4731B9DC-ON49257B5F.00055048-49257B5F.0005504A@lge.com>
Date: Thu, 2 May 2013 09:58:02 +0900
From: "¹ÎÂùÈ£" <chanho.min@....com>
To: Geert Uytterhoeven <geert@...ux-m68k.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
ÀÌ°æ½Ä <kyungsik.lee@....com>,
Yann Collet <yann.collet.73@...il.com>,
Bob Pearson <rpearson@...temfabricworks.com>,
Richard Weinberger <richard@....at>,
linux-kernel@...r.kernel.org,
sparclinux <sparclinux@...r.kernel.org>,
Linux/m68k <linux-m68k@...r.kernel.org>,
Linux-Next <linux-next@...r.kernel.org>
Subject: Re: [PATCH] lib: add weak __clzsi2()/__clzdi2() functions
>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
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