RFR: 8252505: C1/C2 compiler support for blackholes [v11]

[Vladimir Ivanov]

>> The only difference I see is receiver becomes treated as an ordinary
>> argument which is consumed by a blackhole while in the current
>> implementation you ignore receiver.
> 
> Actually, I don't think we need to ignore receiver in current code. It 
> is a left-over from my experiments that were only taking care of 
> primitive arguments. Since current code is much more simple, we can just 
> blackhole everything. Done in new commits.

Does it make more sense now to further limit the intrinsic to static 
methods only?

It won't simplify the implementation any futher, but will help reduce 
perceived complexity (need to reason about both virtual and static cases).

Best regards,
Vladimir Ivanov

>>>> If you want to keep instance method support, please, double-check that
>>>> null check stays there for correctness.
>>>
>>> OK, that looks empirically verifiable (i.e. with the jtreg test), 
>>> will od.
> 
> Added a new test, seems to pass fine.
>