RFR: 8341242: Shenandoah: LRB node is not matched as GC barrier after JDK-8340183

[Paul Hohensee]

On Mon, 30 Sep 2024 14:54:30 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> [JDK-8340183](https://bugs.openjdk.org/browse/JDK-8340183) introduced a regression: `ShenandoahBarrierSetC2::is_gc_barrier_node` is now answering `false` for the actual `ShenandoahLoadReferenceBarrierNode`. The fix reinstates the check for LRB node.
> 
> Additional testing:
>  - [ ] Linux x86_64 server fastdebug, `hotspot_gc_shenandoah`
>  - [x] Linux x86_64 server fastdebug, `jdk/jfr/api/consumer/ ` (100x) -- used to fail intermittently, now it does not

Marked as reviewed by phh (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/21266#pullrequestreview-2338076905