RFR (XS) 8229350: Shenandoah does not need barriers before CreateEx

[Roman Kennke]

Ok! Thanks!

Roman


> Bug:
>   https://bugs.openjdk.java.net/browse/JDK-8229350
> 
> Fix:
> 
> diff -r 2e38a71e6038 src/hotspot/share/gc/shenandoah/c2/shenandoahSupport.cpp
> --- a/src/hotspot/share/gc/shenandoah/c2/shenandoahSupport.cpp  Fri Aug 09 03:51:20 2019 +0200
> +++ b/src/hotspot/share/gc/shenandoah/c2/shenandoahSupport.cpp  Fri Aug 09 12:18:09 2019 +0200
> @@ -3091,10 +3091,12 @@
>      case Op_CMoveP:
>        return needs_barrier_impl(phase, n->in(2), visited) ||
>               needs_barrier_impl(phase, n->in(3), visited);
>      case Op_ShenandoahEnqueueBarrier:
>        return needs_barrier_impl(phase, n->in(1), visited);
> +    case Op_CreateEx:
> +      return false;
>      default:
>        break;
>    }
>  #ifdef ASSERT
>    tty->print("need barrier on?: ");
> 
> 
> Testing: {x86_64, x86_32} x {hotspot_gc_shenandoah, vmTestbase_vm_mlvm}
>