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

[Zhengyu Gu]

On 11/26/19 1:43 PM, Erik Österlund wrote:
> Hi Zhengyu,
> 
> Looks good; ship it.

Pushed.

Thanks,

-Zhengyu

> 
> Thanks
> /Erik
> 
>> On 26 Nov 2019, at 19:07, Zhengyu Gu <zgu at redhat.com> wrote:
>>
>> Hi Erik,
>>
>> On 11/26/19 8:24 AM, Zhengyu Gu wrote:
>>>> Here is a patch with my proposed cleanup:
>>>> http://cr.openjdk.java.net/~eosterlund/8230765/webrev.02/
>>>>
>>>> Incremental:
>>>> http://cr.openjdk.java.net/~eosterlund/8230765/webrev.01_02/
>>>>
>>> Yes, this indeed a much cleaner approach. I will take your proposed cleanup and run through submit.
>>
>> I took your patch. There is just one little hiccup: compiler expects intptr_t instead of int* on x86_32, the fix is straightforward.
>>
>>    __ push(tmp);
>> -  __ movptr(tmp, bs_nm->disarmed_value_address());
>> +  __ movptr(tmp, (intptr_t)bs_nm->disarmed_value_address());
>>    Address disarmed_addr(tmp, 0);
>>    __ align(4);
>>    __ cmpl(disarmed_addr, 0);
>>
>>
>> Full webrev: http://cr.openjdk.java.net/~zgu/JDK-8230765/webrev.02/
>>
>> and patch passed submit tests.
>>
>> Okay to push?
>>
>> Thanks,
>>
>> -Zhengyu
>>
>>
>>> -Zhengyu
>>>> Thanks,
>>>> /Erik
>>>>
>>>>> On 11/25/19 9:35 PM, Zhengyu Gu wrote:
>>>>>> 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
>>>>>>
>>>>
>>
>