From: Akinobu Mita <akinobu.mita@gmail.com>
Date: Tue, 22 Dec 2009 00:20:16 +0000 (-0800)
Subject: x86, core: Optimize hweight32()
X-Git-Tag: v2.6.34-rc1~252^2~14
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=39d997b514e12d5aff0dca206eb8996b3957927e;p=pandora-kernel.git

x86, core: Optimize hweight32()

Optimize hweight32 by using the same technique in hweight64.

The proof of this technique can be found in the commit log for
f9b4192923fa6e38331e88214b1fe5fc21583fcc ("bitops: hweight()
speedup").

The userspace benchmark on x86_32 showed 20% speedup with
bitmap_weight() which uses hweight32 to count bits for each
unsigned long on 32bit architectures.

 int main(void)
 {
	#define SZ (1024 * 1024 * 512)

	static DECLARE_BITMAP(bitmap, SZ) = {
	        [0 ... 100] = 1,
	};

	return bitmap_weight(bitmap, SZ);
 }

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
LKML-Reference: <1258603932-4590-1-git-send-email-akinobu.mita@gmail.com>
[ only x86 sets ARCH_HAS_FAST_MULTIPLIER so we do this via the x86 tree]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---

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