RFR (S): JDK-8172434: CompareAndExchangeObject inserts two pre-barriers

[Vladimir Ivanov]

Looks good.

I'll sponsor the fix.

Best regards,
Vladimir Ivanov

On 2/14/17 12:46 PM, Roman Kennke wrote:
> Hi Vladimir,
>
> thanks!
>
> I think I need a sponsor now? Can you do that?
>
> Thanks,
> Roman
>
>
> Am Montag, den 13.02.2017, 16:41 -0800 schrieb Vladimir Kozlov:
>> Looks good.
>>
>> Thanks,
>> Vladimir
>>
>> On 2/13/17 1:11 PM, Roman Kennke wrote:
>>> in LibaryCallKit::inline_unsafe_access(), the pre_barrier() gets
>>> inserted twice for LS_cmp_exchange, in one case it is treated like
>>> the
>>> other CAS instructions, and at the end it is treated like
>>> get_and_set.
>>> It's not causing incorrect behaviour, but might impact performance.
>>>
>>> The fix is to leave out the 2nd pre-barrier for CAE by checking for
>>> get_and_set.
>>>
>>> Testing: jcstress
>>>
>>> http://cr.openjdk.java.net/~rkennke/fix-cae-prebarrier/webrev.01/
>>>
>>> Roman
>>>