Archipelago » qemu

#include "host-utils.h"

            uint32_t frac;

            int clz1, clz2;

            int shift;

            /* We need to divide time by period, where time is stored in

               rem (64-bit integer) and period is stored in period/period_frac

               (64.32 fixed point).

               Doing full precision division is hard, so scale values and

               do a 64-bit division.  The result should be rounded down,

               so that the rounding error never causes the timer to go

               backwards.

            */

            clz1 = clz64(rem);

            clz2 = clz64(div);

            shift = clz1 < clz2 ? clz1 : clz2;

            rem <<= shift;

            div <<= shift;

            if (shift >= 32) {

                div |= ((uint64_t)s->period_frac << (shift - 32));

            } else {

                if (shift != 0)

                    div |= (s->period_frac >> (32 - shift));

                /* Look at remaining bits of period_frac and round div up if 

                   necessary.  */

                if ((uint32_t)(s->period_frac << shift))

                    div += 1;

            }