testing support loops with long (64b) trip counts

[Maurizio Cimadamore]

On 10/06/2020 12:43, Roland Westrelin wrote:
> Hi Maurizio,
>
> Thanks for giving the patch a try.
>
>> Overall, unless I did some mistake, it doesn't look like the patch is
>> changing much. The baseline + workaround for small segment remains the
>> fastest version around, which performs on par with unsafe. If we remove
>> the workaround, we get some 1.5-2x slower; but if we start looping on
>> longs (see the LoopOverNonConstantLong suite), then performances get
>> much, much worse.
>>
>> Am I missing something? Is our implementation doing something that is
>> confusing your optimization?
> I'll take a look at the benchmarks. With the current patch, elimination
> of range checks are unlikely to happen. That's follow up work. Could
> that be the problem?

Definitively :-)

Range checks are always the issue with performance potholes in the 
foreign memory API.

Maurizio

>
> Roland.
>