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Changed core cycle computations to use div_64x32 instead of full 64-bit

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divides. This involves tossing a few bits of resolution at divide time,
but should make no real difference in practice.
This commit is contained in:
Aaron Giles 2008-11-05 16:52:52 +00:00
parent 49452d9473
commit c0770e14ce
1 changed files with 28 additions and 6 deletions
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34
src/emu/cpuexec.c
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@ -76,6 +76,8 @@ struct _cpuexec_data
attotime localtime; /* local time, relative to the timer system's global time */
INT32 clock; /* current active clock */
double clockscale; /* current active clock scale factor */
INT32 divisor; /* 32-bit attoseconds_per_cycle divisor */
UINT8 divshift; /* right shift amount to fit the divisor into 32 bits */
emu_timer * timedint_timer; /* reference to this CPU's periodic interrupt timer */
@ -232,6 +234,7 @@ static void cpuexec_exit(running_machine *machine)
void cpuexec_timeslice(running_machine *machine)
{
int call_debugger = ((machine->debug_flags & DEBUG_FLAG_ENABLED) != 0);
attotime target = timer_next_fire_time();
attotime base = timer_get_time();
int cpunum, ran;
@ -258,7 +261,7 @@ void cpuexec_timeslice(running_machine *machine)
if (delta.seconds >= 0 && delta.attoseconds >= attoseconds_per_cycle[cpunum])
{
/* compute how long to run */
cycles_running = ATTOTIME_TO_CYCLES(cpunum, delta);
cycles_running = div_64x32(delta.attoseconds >> cpudata->divshift, cpudata->divisor);
LOG((" cpu %d: %d cycles\n", cpunum, cycles_running));
profiler_mark(PROFILER_CPU1 + cpunum);
@ -266,9 +269,14 @@ void cpuexec_timeslice(running_machine *machine)
/* note that this global variable cycles_stolen can be modified */
/* via the call to the cpunum_execute */
cycles_stolen = 0;
debugger_start_cpu_hook(machine, cpunum, target);
ran = cpunum_execute(cpunum, cycles_running);
debugger_stop_cpu_hook(machine, cpunum);
if (!call_debugger)
ran = cpunum_execute(cpunum, cycles_running);
else
{
debugger_start_cpu_hook(machine, cpunum, target);
ran = cpunum_execute(cpunum, cycles_running);
debugger_stop_cpu_hook(machine, cpunum);
}
#ifdef MAME_DEBUG
if (ran < cycles_stolen)
@ -301,12 +309,14 @@ void cpuexec_timeslice(running_machine *machine)
/* if we're suspended and counting, process */
if (cpudata->suspend != 0 && cpudata->eatcycles && attotime_compare(cpudata->localtime, target) < 0)
{
attotime delta = attotime_sub(target, cpudata->localtime);
/* compute how long to run */
cycles_running = ATTOTIME_TO_CYCLES(cpunum, attotime_sub(target, cpudata->localtime));
cycles_running = div_64x32(delta.attoseconds >> cpudata->divshift, cpudata->divisor);
LOG((" cpu %d: %d cycles (suspended)\n", cpunum, cycles_running));
cpudata->totalcycles += cycles_running;
cpudata->localtime = attotime_add(cpudata->localtime, ATTOTIME_IN_CYCLES(cycles_running, cpunum));
cpudata->localtime = attotime_add_attoseconds(cpudata->localtime, cycles_running * attoseconds_per_cycle[cpunum]);
LOG((" %d skipped, %d total, time = %s\n", cycles_running, (INT32)cpudata->totalcycles, attotime_string(cpudata->localtime, 9)));
}
}
@ -408,9 +418,21 @@ int cpunum_is_suspended(int cpunum, int reason)
static void update_clock_information(running_machine *machine, int cpunum)
{
INT64 attos;
/* recompute cps and spc */
cycles_per_second[cpunum] = (double)cpu[cpunum].clock * cpu[cpunum].clockscale;
attoseconds_per_cycle[cpunum] = ATTOSECONDS_PER_SECOND / ((double)cpu[cpunum].clock * cpu[cpunum].clockscale);
/* update the CPU's divisor */
attos = attoseconds_per_cycle[cpunum];
cpu[cpunum].divshift = 0;
while (attos >= (1UL << 31))
{
cpu[cpunum].divshift++;
attos >>= 1;
}
cpu[cpunum].divisor = attos;
/* re-compute the perfect interleave factor */
compute_perfect_interleave(machine);