RFR: 8258192: Obsolete the CriticalJNINatives flag

[Coleen Phillimore]

On Thu, 11 Nov 2021 07:16:27 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> This change removes the disabled CriticalJNINatives code, and the flag now gives an obsolete message.
>> Tested with tier1 on cpus x64, aarch64, and builds on linux-x86-open,linux-s390x-open,linux-arm32-debug,linux-ppc64le-debug.
>
> src/hotspot/cpu/ppc/sharedRuntime_ppc.cpp line 1746:
> 
>> 1744:   // NW     [ABI_REG_ARGS]             <-- 1) R1_SP
>> 1745:   //        [outgoing arguments]       <-- 2) R1_SP + out_arg_slot_offset
>> 1746:   //        [oopHandle area]           <-- 3) R1_SP + oop_handle_offset (save area for critical natives) ?
> 
> `?`. The comment `(save area for critical natives)` must be redundant now.

I didn't know if the save area is still needed for something else, which is why I left the ?.  I can remove the comment but haven't made any  substantial changes here.  I'm not sure if they're needed or not, but I can't test them if I made them.

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PR: https://git.openjdk.java.net/jdk/pull/6343