[Piglit] [PATCH] arb_shader_clock: add basic execution tests

[Ilia Mirkin]

On Fri, Mar 31, 2017 at 2:32 AM, Nicolai Hähnle <nhaehnle at gmail.com> wrote:
> On 30.03.2017 15:03, Ilia Mirkin wrote:
>>
>> On Thu, Mar 30, 2017 at 8:19 AM, Nicolai Hähnle <nhaehnle at gmail.com>
>> wrote:
>>>
>>> On 30.03.2017 14:07, Ilia Mirkin wrote:
>>>>
>>>>
>>>> Time could roll over... not sure what to do about that though. Maybe
>>>> check if the top 2 bits are set in the old value and are unset in the
>>>> new value, and hope that the counter precision > 2 bits? [It'd be
>>>> unfortunate for CIs to get occasional failures in these tests...]
>>>
>>>
>>>
>>> Shouldn't roll-over be covered by the cast to int followed by comparison
>>> with 0?
>>
>>
>> Let's say start_time == 0xfffffffffffffff, late_time = 0. Perhaps I'm
>> getting the math wrong here, but as far as I can see, that test will
>> fail.
>
>
> +       int64_t diff = int64_t(late_time - start_time);
> +
> +       if (diff <= 0l)
> +               atomicCounterIncrement(bad);
>
> In your example, we get late_time - start_time == 0 - uint64_t(-1) == 1, so
> the atomic increment of bad doesn't happen.

Right. So unless the counter goes REALLY fast (or is a single bit),
this should be pretty safe.

This series is

Reviewed-by: Ilia Mirkin <imirkin at alum.mit.edu>

>
> Cheers,
> Nicolai
>
>>
>>   -ilia
>>
>
>
> --
> Lerne, wie die Welt wirklich ist,
> Aber vergiss niemals, wie sie sein sollte.