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[patch 14/44] generic hweight{64,32,16,8}()

To: linux-kernel@vger.kernel.org
Subject: [patch 14/44] generic hweight{64,32,16,8}()
From: Akinobu Mita <mita@miraclelinux.com>
Date: Wed, 01 Feb 2006 18:02:38 +0900
Cc: Richard Henderson <rth@twiddle.net>, Ivan Kokshaysky <ink@jurassic.park.msu.ru>, Russell King <rmk@arm.linux.org.uk>, Ian Molton <spyro@f2s.com>, dev-etrax@axis.com, David Howells <dhowells@redhat.com>, Yoshinori Sato <ysato@users.sourceforge.jp>, Linus Torvalds <torvalds@osdl.org>, linux-ia64@vger.kernel.org, Hirokazu Takata <takata@linux-m32r.org>, linux-m68k@lists.linux-m68k.org, Greg Ungerer <gerg@uclinux.org>, linux-mips@linux-mips.org, parisc-linux@parisc-linux.org, linuxppc-dev@ozlabs.org, linux390@de.ibm.com, linuxsh-dev@lists.sourceforge.net, linuxsh-shmedia-dev@lists.sourceforge.net, sparclinux@vger.kernel.org, ultralinux@vger.kernel.org, Miles Bader <uclinux-v850@lsi.nec.co.jp>, Andi Kleen <ak@suse.de>, Chris Zankel <chris@zankel.net>, Akinobu Mita <mita@miraclelinux.com>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <20060201090224.536581000@localhost.localdomain>
Sender: linux-mips-bounce@linux-mips.org
This patch introduces the C-language equivalents of the functions below:

unsigned int hweight32(unsigned int w);
unsigned int hweight16(unsigned int w);
unsigned int hweight8(unsigned int w);
unsigned long hweight64(__u64 w);

In include/asm-generic/bitops/hweight.h

This code largely copied from:
include/linux/bitops.h

Signed-off-by: Akinobu Mita <mita@miraclelinux.com>
 include/asm-generic/bitops/hweight.h |   54 +++++++++++++++++++++++++++++++++++
 1 files changed, 54 insertions(+)

Index: 2.6-git/include/asm-generic/bitops/hweight.h
===================================================================
--- /dev/null
+++ 2.6-git/include/asm-generic/bitops/hweight.h
@@ -0,0 +1,54 @@
+#ifndef _ASM_GENERIC_BITOPS_HWEIGHT_H_
+#define _ASM_GENERIC_BITOPS_HWEIGHT_H_
+
+#include <asm/types.h>
+
+/**
+ * hweightN - returns the hamming weight of a N-bit word
+ * @x: the word to weigh
+ *
+ * The Hamming Weight of a number is the total number of bits set in it.
+ */
+
+static inline unsigned int hweight32(unsigned int w)
+{
+        unsigned int res = (w & 0x55555555) + ((w >> 1) & 0x55555555);
+        res = (res & 0x33333333) + ((res >> 2) & 0x33333333);
+        res = (res & 0x0F0F0F0F) + ((res >> 4) & 0x0F0F0F0F);
+        res = (res & 0x00FF00FF) + ((res >> 8) & 0x00FF00FF);
+        return (res & 0x0000FFFF) + ((res >> 16) & 0x0000FFFF);
+}
+
+static inline unsigned int hweight16(unsigned int w)
+{
+        unsigned int res = (w & 0x5555) + ((w >> 1) & 0x5555);
+        res = (res & 0x3333) + ((res >> 2) & 0x3333);
+        res = (res & 0x0F0F) + ((res >> 4) & 0x0F0F);
+        return (res & 0x00FF) + ((res >> 8) & 0x00FF);
+}
+
+static inline unsigned int hweight8(unsigned int w)
+{
+        unsigned int res = (w & 0x55) + ((w >> 1) & 0x55);
+        res = (res & 0x33) + ((res >> 2) & 0x33);
+        return (res & 0x0F) + ((res >> 4) & 0x0F);
+}
+
+static inline unsigned long hweight64(__u64 w)
+{
+#if BITS_PER_LONG == 32
+       return hweight32((unsigned int)(w >> 32)) + hweight32((unsigned int)w);
+#elif BITS_PER_LONG == 64
+       u64 res;
+       res = (w & 0x5555555555555555ul) + ((w >> 1) & 0x5555555555555555ul);
+       res = (res & 0x3333333333333333ul) + ((res >> 2) & 
0x3333333333333333ul);
+       res = (res & 0x0F0F0F0F0F0F0F0Ful) + ((res >> 4) & 
0x0F0F0F0F0F0F0F0Ful);
+       res = (res & 0x00FF00FF00FF00FFul) + ((res >> 8) & 
0x00FF00FF00FF00FFul);
+       res = (res & 0x0000FFFF0000FFFFul) + ((res >> 16) & 
0x0000FFFF0000FFFFul);
+       return (res & 0x00000000FFFFFFFFul) + ((res >> 32) & 
0x00000000FFFFFFFFul);
+#else
+#error BITS_PER_LONG not defined
+#endif
+}
+
+#endif /* _ASM_GENERIC_BITOPS_HWEIGHT_H_ */

--

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