svn commit: r223884 - head/sys/sys

[Konstantin Belousov]

Author: kib
Date: Sat Jul  9 14:29:23 2011
New Revision: 223884
URL: http://svn.freebsd.org/changeset/base/223884

Log:
  Implement bitcount16.
  
  Sponsored by:	The FreeBSD Foundation
  MFC after:	1 week

Modified:
  head/sys/sys/systm.h

Modified: head/sys/sys/systm.h
==============================================================================
--- head/sys/sys/systm.h	Sat Jul  9 12:20:15 2011	(r223883)
+++ head/sys/sys/systm.h	Sat Jul  9 14:29:23 2011	(r223884)
@@ -392,4 +392,15 @@ bitcount32(uint32_t x)
 	return (x);
 }
 
+static __inline uint16_t
+bitcount16(uint32_t x)
+{
+
+	x = (x & 0x5555) + ((x & 0xaaaa) >> 1);
+	x = (x & 0x3333) + ((x & 0xcccc) >> 2);
+	x = (x + (x >> 4)) & 0x0f0f;
+	x = (x + (x >> 8)) & 0x00ff;
+	return (x);
+}
+
 #endif /* !_SYS_SYSTM_H_ */