RFR: fix aarch64 membar elision with shenandoah

[Roman Kennke]

Am 12.07.2018 um 17:09 schrieb Aleksey Shipilev:
> On 07/12/2018 05:05 PM, Roman Kennke wrote:
>> Am 12.07.2018 um 15:51 schrieb Roland Westrelin:
>>>
>>> http://cr.openjdk.java.net/~roland/shenandoah/aarch64-membars-elision/webrev.02/
>>>
>>> This fixes membar elision on aarch64 with shenandoah. Thanks to Andrew
>>> Dinn for verifying the change and fixing the traversal gc case.
>>>
>>> Roland.
>>>
>>
>>
>> The patch looks good.
>>
>> I verified that it builds + passes tests.
>>
>> I'll check the predicates in x86. They should be equivalent.
> 
> If there are predicate changes that make sense on their own, they should be pushed as separate
> changesets, so they arrive to backports.
> 
> -Aleksey
> 

Oh wait, I just got this from a test:

#  Internal Error
(/home/rkennke/src/shenandoah-jdk/src/hotspot/cpu/aarch64/aarch64.ad:2873),
pid=27969, tid=28271
#  guarantee(mbar != NULL) failed: CAS not embedded in normal graph!


Hmmmmmm.