__arch_hweight16
unsigned int __arch_hweight16(unsigned int w);
unsigned int __arch_hweight16(unsigned int w);
#define hweight16(w) (__builtin_constant_p(w) ? __const_hweight16(w) : __arch_hweight16(w))
#define hweight16(w) (__builtin_constant_p(w) ? __const_hweight16(w) : __arch_hweight16(w))