RFR: Don't generate arraycopy pre-barrier calls for traversal GC

[Aleksey Shipilev]

On 06/18/2018 06:41 PM, Roman Kennke wrote:
> the arraycopy-pre-barrier is a no-op for traversal GC. There's no need
> to generate the pointless runtime call and the gc state check.
> 
> http://cr.openjdk.java.net/~rkennke/no-array-prebarrier-traversal/webrev.00/
> 
> Test: tier3_gc_shenandoah (in progress)

OK.

-Aleksey