RFR: Move shenandoah_eliminate_wb_pre to ShenandoahBarrierSetC2

[Aleksey Shipilev]

On 09/11/2018 11:19 PM, Roman Kennke wrote:
> Compile::shenandoah_eliminate_wb_pre() can be moved into proper GC
> interface in ShenandoahBarrierSetC2.
> 
> It appears that this does an extra round of eliminate_gc_barrier() in
> PhaseMacroExpand::process_users_of_allocation(). It doesn't seem to
> hurt. Other than that, the code should be equivalent.
> 
> http://cr.openjdk.java.net/~rkennke/c2-move-eliminate/webrev.00/

Seems fine to me.

-Aleksey