/*      $OpenBSD: ctzdi2.c,v 1.1 2022/12/14 23:50:31 jsg Exp $  */

/*
 * Public domain.
 * Written by Dale Rahn.
 */

#include <lib/libkern/libkern.h>

/*
 * ffsl -- vax ffs instruction with long arg
 */

#ifdef __LP64__
static int
ffsl(long mask)
{
        int bit;
        unsigned long r = mask;
        static const signed char t[16] = {
                -60, 1, 2, 1,
                  3, 1, 2, 1,
                  4, 1, 2, 1,
                  3, 1, 2, 1
        };

        bit = 0;
        if (!(r & 0xffffffff)) {
                bit += 32;
                r >>= 32;
        }
        if (!(r & 0xffff)) {
                bit += 16;
                r >>= 16;
        }
        if (!(r & 0xff)) {
                bit += 8;
                r >>= 8;
        }
        if (!(r & 0xf)) {
                bit += 4;
                r >>= 4;
        }

        return (bit + t[ r & 0xf ]);
}
#else
static int
ffsl(long mask)
{
        return ffs(mask);
}
#endif

int
__ctzdi2(long mask)
{
        if (mask == 0)
                return 0;
        return ffsl(mask) - 1;
}