__uatomic_add_return

static inline __attribute__((always_inline))
unsigned long __uatomic_add_return(void *addr, unsigned long val,
                                 int len)
{
        switch (len) {
        case 1:
        {
                unsigned char result = val;

                __asm__ __volatile__(
                "lock; xaddb %1, %0"
                        : "+m"(*__hp(addr)), "+q" (result)
                        :
                        : "memory");
                return result + (unsigned char)val;
        }
        case 2:
        {
                unsigned short result = val;

                __asm__ __volatile__(
                "lock; xaddw %1, %0"
                        : "+m"(*__hp(addr)), "+r" (result)
                        :
                        : "memory");
                return result + (unsigned short)val;
        }
        case 4:
        {
                unsigned int result = val;

                __asm__ __volatile__(
                "lock; xaddl %1, %0"
                        : "+m"(*__hp(addr)), "+r" (result)
                        :
                        : "memory");
                return result + (unsigned int)val;
        }
#if (CAA_BITS_PER_LONG == 64)
        case 8:
        {
                unsigned long result = val;

                __asm__ __volatile__(
                "lock; xaddq %1, %0"
                        : "+m"(*__hp(addr)), "+r" (result)
                        :
                        : "memory");
                return result + (unsigned long)val;
        }
#endif
        }
        /*
         * generate an illegal instruction. Cannot catch this with
         * linker tricks when optimizations are disabled.
         */
        __asm__ __volatile__("ud2");
        return 0;
}