RFR: Factor out storeval barrier from read barriers

[Aleksey Shipilev]

On 08/30/2017 11:51 PM, Roman Kennke wrote:
> Alright. I separated them by introducing _impl() methods that actually
> implement the barriers (or, in the case of c2 and runtime, reuse
> existing _impls), and have the entry points only check their flags and
> then call _impl. This means we can now turn off read-barriers and still
> get storeval barriers, or turn off storeval barriers and still get read
> barriers.
> 
> Tested by: hotspot_gc_shenandoah.
> 
> http://cr.openjdk.java.net/~rkennke/storevalbarrier/webrev.01/

Looks good to me.

-Aleksey