bsd: add fls implementation

Because this is arch specific, I am adding it to a newly created file in
arch/x64. I am making it available to BSD through netport for the lack of a
better place

arch/x64/bitops.h

+#ifndef ARCH_BITOPS_H_
+#define ARCH_BITOPS_H_
+static inline unsigned int 
+bsrl(unsigned int mask)
+{
+    unsigned int result;
+    asm volatile("bsrl %1,%0" : "=r" (result) : "rm" (mask));
+    return result;
+}
+
+static inline int
+fls(int mask)
+{
+    return (mask == 0 ? mask : (int)bsrl((unsigned int)mask) + 1);
+}
+#endif

bsd/porting/netport.h

@@ -12,6 +12,7 @@
 #include <osv/debug.h>
 #define __NEED_socklen_t
 #include <bits/alltypes.h>
+#include "bitops.h"
 
 __BEGIN_DECLS