[PATCH 8/12] generic hweight{32,16,8}()

[Akinobu Mita]

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);

HAVE_ARCH_HWEIGHT_BITOPS is defined when the architecture has its own
version of these functions.

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

Index: 2.6-git/include/asm-generic/bitops.h
===================================================================
--- 2.6-git.orig/include/asm-generic/bitops.h	2006-01-25 19:14:10.000000000 +0900
+++ 2.6-git/include/asm-generic/bitops.h	2006-01-25 19:14:11.000000000 +0900
@@ -458,14 +458,38 @@
 #endif /* HAVE_ARCH_FFS_BITOPS */
 
 
+#ifndef HAVE_ARCH_HWEIGHT_BITOPS
+
 /*
  * hweightN: returns the hamming weight (i.e. the number
  * of bits set) of a N-bit word
  */
 
-#define hweight32(x) generic_hweight32(x)
-#define hweight16(x) generic_hweight16(x)
-#define hweight8(x) generic_hweight8(x)
+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);
+}
+
+#endif /* HAVE_ARCH_HWEIGHT_BITOPS */
 
 #endif /* __KERNEL__ */
 
-
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