[14] RFR 8230765: Implement nmethod barrier for x86_32 platforms

[Zhengyu Gu]

Thanks, Roman.

-Zhengyu

On 11/25/19 4:07 PM, Roman Kennke wrote:
> It looks good to me, thanks!
> 
> Roman
> 
> 
>> Hi all,
>>
>> Please review this implementation of nmethod barrier for x86_32 platforms.
>>
>> x86_32 implementation mirrors x86_64's. The only difference is where it
>> reads nmethod disarmed value.
>>
>> Unlike 64-bits, 32-bits platform does not have a dedicated register for
>> current thread. So that it is cheaper to read disarmed value from global
>> location than from per-thread GC data.
>>
>> Currently, only Shenandoah GC uses the implementation for its concurrent
>> class unloading. This implementation, along with Shenandoah concurrent
>> class unloading, has been baked in shenandoah/jdk repo for some time
>> now,  they are ready for integration.
>>
>>
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8230765
>> Webrev: http://cr.openjdk.java.net/~zgu/JDK-8230765/webrev.01/
>>
>>
>> Test:
>>    hotspot_gc with x86_64 and x86_32 JVM on Linux
>>    Submit test.
>>
>> Thanks,
>>
>> -Zhengyu
>>
>