RFR: 8269476: Skip nmethod entry barrier if there is no oops in the jit code [v2]

[Zhengyu Gu]

On Mon, 28 Jun 2021 11:17:11 GMT, 王超 <github.com+25214855+casparcwang at openjdk.org> wrote:

>> src/hotspot/cpu/aarch64/gc/shared/barrierSetNMethod_aarch64.cpp line 166:
>> 
>>> 164: 
>>> 165: void BarrierSetNMethod::fix_entry_barrier(nmethod*, bool) {
>>> 166:   // not implement yet
>> 
>> Shall we use `Unimplemented();` here?
>
> refactor to x86 only

I think there is a simpler way to accomplish this by playing with disarmed_value, e.g. setting nmethod's disarmed_value to certain pattern to indicate it is always disarmed.

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PR: https://git.openjdk.java.net/jdk/pull/4610