RFR: Factor out storeval barrier from read barriers

[Zhengyu Gu]

May I ask why it calls "StoreValBarrier"? while it seems to only deal 
with read.

Thanks,

-Zhengyu

On 08/27/2017 03:20 AM, Aleksey Shipilev wrote:
> On 08/25/2017 08:37 PM, Roman Kennke wrote:
>> I also added a flag ShenandoahStoreValBarriers that does the same as the
>> other ShenandoahXXXBarriers flag, turn generation of the barriers off on
>> request. The way it's currently done, the storeval barrier is also
>> controlled by ShenandoahReadBarriers, dunno if we want to change that?
>> I.e. -ShReadBarrier not affect ShStoreValBarrier ?
> 
> Making a separate ShStoreValBarrier is good with me. Having it separate from ShReadBarrier is good
> with me too, because I wondered what the impact on storeval barriers was.
> 
>> http://cr.openjdk.java.net/~rkennke/storevalbarrier/webrev.00/
> 
> This looks good.
> 
> Thanks,
> -Aleksey
> 
>