Index: head/sys/cddl/contrib/opensolaris/uts/common/sys/sysmacros.h
===================================================================
--- head/sys/cddl/contrib/opensolaris/uts/common/sys/sysmacros.h
+++ head/sys/cddl/contrib/opensolaris/uts/common/sys/sysmacros.h
@@ -32,6 +32,9 @@
 
 #include <sys/param.h>
 #include <sys/isa_defs.h>
+#if defined(__FreeBSD__) && defined(_KERNEL)
+#include <sys/libkern.h>
+#endif
 
 #ifdef	__cplusplus
 extern "C" {
@@ -382,6 +385,9 @@
 static __inline int
 highbit(ulong_t i)
 {
+#if defined(__FreeBSD__) && defined(_KERNEL) && defined(HAVE_INLINE_FLSL)
+	return (flsl(i));
+#else
 	register int h = 1;
 
 	if (i == 0)
@@ -407,6 +413,7 @@
 		h += 1;
 	}
 	return (h);
+#endif
 }
 
 /*
@@ -416,6 +423,9 @@
 static __inline int
 highbit64(uint64_t i)
 {
+#if defined(__FreeBSD__) && defined(_KERNEL) && defined(HAVE_INLINE_FLSLL)
+	return (flsll(i));
+#else
 	int h = 1;
 
 	if (i == 0)
@@ -439,6 +449,7 @@
 		h += 1;
 	}
 	return (h);
+#endif
 }
 
 #ifdef	__cplusplus