Re: [RFC][PATCH] NTP shiftR cleanup

[Roman Zippel <zippel@linux-m68k.org>]

Hi,

On Fri, 9 Sep 2005, john stultz wrote:

> +/* Required to safely shift negative values */
> +#define shiftR(x, s) ({ __typeof__(x) __x = x;\
> +		__typeof__(s) __s = s; \
> +		(__x < 0) ? (-((-__x) >> (__s))) : ((__x) >> (__s));})
> +

Some parenthesis are missing and some are redundant. Formatting it so it 
looks more like normal function makes it more readable:

#define shiftR(x, s) ({				\
	__typeof__(x) __x = (x);		\
	__typeof__(s) __s = (s);		\
	__x < 0 ? -(-__x >> __s) : __x >> __s;	\
})

> @@ -792,13 +769,8 @@ static void update_wall_time_one_tick(vo
>  	 * advance the tick more.
>  	 */
>  	time_phase += time_adj;
> -	if (time_phase <= -FINENSEC) {
> -		long ltemp = -time_phase >> (SHIFT_SCALE - 10);
> -		time_phase += ltemp << (SHIFT_SCALE - 10);
> -		delta_nsec -= ltemp;
> -	}
> -	else if (time_phase >= FINENSEC) {
> -		long ltemp = time_phase >> (SHIFT_SCALE - 10);
> +	if (abs(time_phase) >= FINENSEC) {
> +		long ltemp = shiftR(time_phase, (SHIFT_SCALE - 10));
>  		time_phase -= ltemp << (SHIFT_SCALE - 10);
>  		delta_nsec += ltemp;
>  	}

It would be interesting to check, whether gcc produces the same code here.

bye, Roman