__bitcount32
px_addr->plen = __bitcount32(mask.s_addr);
#define bitcount32(x) __bitcount32((uint32_t)(x))
return (__bitcount32(_x >> 32) + __bitcount32(_x));
#define __bitcountl(x) __bitcount32((unsigned long)(x))
#define __bitcount(x) __bitcount32((unsigned int)(x))
#define bitcount32(x) __bitcount32((uint32_t)(x))