On Mon, 4 Jul 2011 17:06:54 +0200
Fabien Chouteau <chout...@adacore.com> wrote:
> On 01/07/2011 22:22, Scott Wood wrote:
> > On Fri, 1 Jul 2011 16:13:41 +0200
> > Fabien Chouteau <chout...@adacore.com> wrote:
> >> +static void booke_update_fixed_timer(CPUState *env,
> >> + uint8_t target_bit,
> >> + uint64_t *next,
> >> + struct QEMUTimer *timer)
> >> +{
> >> + ppc_tb_t *tb_env = env->tb_env;
> >> + uint64_t lapse;
> >> + uint64_t tb;
> >> + uint64_t period = 1 << (target_bit + 1);
> >> + uint64_t now;
> >> +
> >> + now = qemu_get_clock_ns(vm_clock);
> >> + tb = cpu_ppc_get_tb(tb_env, now, tb_env->tb_offset);
> >> +
> >> + if (tb <= (1 << target_bit)) {
> >> + lapse = (1 << target_bit) - tb;
> >> + } else {
> >> + lapse = period - ((tb - (1 << target_bit)) % period);
> >
> > We know period is a power of two, so just do "& (period - 1)".
> >
> > That should let you get rid of the special case for
> > "tb <= (1 << target_bit)" as well.
> >
>
> Do you mean "lapse = period - ((tb - (1 << target_bit)) & (period - 1));" ?
Yes.
Or more simply:
lapse = period - ((tb - period) & (period - 1));
> I don't see how this solves the "tb <= (1 << target_bit)" case.
Actually, since everything is unsigned the special case shouldn't be needed
regardless.
-Scott
