RFR: 8376969: Shenandoah: GC state getters should be inlineable

[William Kemper]

On Mon, 2 Feb 2026 17:29:49 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> Noticed this when working on [JDK-8376749](https://bugs.openjdk.org/browse/JDK-8376749). Looks like some GC state checks we are using from the native barriers are not inlined into the fast-paths. This is very visible with smaller clones, for example. We should move GC state checks to appropriate .inline.hpp-s. Actually, I think these were inlineable before [JDK-8344055](https://bugs.openjdk.org/browse/JDK-8344055), so it is a minor regression in JDK 25.
> 
> This PR does a pretty simple move, so I expect no semantic change.
> 
> Additional testing:
>  - [x] Eye-balling barrier profiles on targeted microbenchmarks
>  - [x] Linux x86_64 server fastdebug, `hotspot_gc_shenandoah`

Looks good to me.

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Marked as reviewed by wkemper (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/29526#pullrequestreview-3741199164