Re: [PATCH] rs6000: Add a builtin to read the time base register on PowerPC

[Segher Boessenkool]

Point being, for simulator environments, you may not want the
loop that was suggested later.  On the other hand, that might
not be an observable period, either.

I don't think looping a million times would be too slow for the
testsuite: there are many tests that do a lot more work than that,
already.

The worst case for hardware that I know of can take about 100
clock cycles for one timebase tick.

But how about this then, which only iterates much if the test
fails:


int
main (void)
{
        uint64_t t = __builtin_ppc_get_timebase ();
        int j;

        for (j = 0; j < 1000000; j++)
                if (t != __builtin_ppc_get_timebase ())
                        break;

        return (j == 1000000);
}


Segher