RFR (XS) 8223448: Shenandoah disabled barriers blocks omit LRB

[Roman Kennke]

Looks good.

Roman


> Bug:
>    https://bugs.openjdk.java.net/browse/JDK-8223448
> 
> This looks like a trivial omission, but it breaks x86_32 (when specifically enabled), which does not
> have all the barriers implemented yet.
> 
> Fix:
> 
> diff -r 3a75a903a488 src/hotspot/share/gc/shenandoah/shenandoahArguments.cpp
> --- a/src/hotspot/share/gc/shenandoah/shenandoahArguments.cpp Mon May 06 19:20:26 2019 +0200
> +++ b/src/hotspot/share/gc/shenandoah/shenandoahArguments.cpp Mon May 06 19:25:02 2019 +0200
> @@ -45,6 +45,7 @@
>     FLAG_SET_DEFAULT(ShenandoahGCHeuristics, "passive");
> 
>     FLAG_SET_DEFAULT(ShenandoahSATBBarrier, false);
> +  FLAG_SET_DEFAULT(ShenandoahLoadRefBarrier, false);
>     FLAG_SET_DEFAULT(ShenandoahKeepAliveBarrier, false);
>     FLAG_SET_DEFAULT(ShenandoahStoreValEnqueueBarrier, false);
>     FLAG_SET_DEFAULT(ShenandoahCASBarrier, false);
> @@ -106,6 +107,7 @@
>     // C2 barrier verification is only reliable when all default barriers are enabled
>     if (ShenandoahVerifyOptoBarriers &&
>             (!FLAG_IS_DEFAULT(ShenandoahSATBBarrier) ||
> +           !FLAG_IS_DEFAULT(ShenandoahLoadRefBarrier) ||
>              !FLAG_IS_DEFAULT(ShenandoahKeepAliveBarrier) ||
>              !FLAG_IS_DEFAULT(ShenandoahStoreValEnqueueBarrier) ||
>              !FLAG_IS_DEFAULT(ShenandoahCASBarrier) ||
> 
> Testing: hotspot_gc_shenandoah
>