Re: [RFC][PATCH] NTP shift_right cleanup (v. A1)

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

Hi,

On Wed, 14 Sep 2005, john stultz wrote:

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

Still too much/little parenthesis.

> @@ -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 = shift_right(time_phase, (SHIFT_SCALE - 10));
>  		time_phase -= ltemp << (SHIFT_SCALE - 10);
>  		delta_nsec += ltemp;
>  	}

I checked and this actually generates worse code.

bye, Roman
-
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