Heads-up: sh/jdk CTW failure with Traversal

[Roman Kennke]

Testing looks good. Patch also looks good. Push it! :-)

Roman


> Fix is below. If one enqueue barrier feeds into another one, we only
> need to keep one.
> 
> Roland.
> 
> diff -r 6277fcfd1269 src/hotspot/share/gc/shenandoah/c2/shenandoahSupport.cpp
> --- a/src/hotspot/share/gc/shenandoah/c2/shenandoahSupport.cpp	Mon Mar 25 19:57:08 2019 +0100
> +++ b/src/hotspot/share/gc/shenandoah/c2/shenandoahSupport.cpp	Wed Mar 27 15:25:24 2019 +0100
> @@ -2101,6 +2101,7 @@
>   int ShenandoahEnqueueBarrierNode::needed(Node* n) {
>     if (n == NULL ||
>         n->is_Allocate() ||
> +      n->Opcode() == Op_ShenandoahEnqueueBarrier ||
>         n->bottom_type() == TypePtr::NULL_PTR ||
>         (n->bottom_type()->make_oopptr() != NULL && n->bottom_type()->make_oopptr()->const_oop() != NULL)) {
>       return NotNeeded;
>