RFR: 8321122: Shenandoah: Remove ShenandoahLoopOptsAfterExpansion flag

[Roland Westrelin]

On Thu, 30 Nov 2023 16:00:17 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> More flags cleanup. `ShenandoahLoopOptsAfterExpansion` was added long time ago to gate more aggressive barrier optimizations in C2. It was default since then. There seem to be no reason to keep it as the flag. Just checking, @rwestrel -- you don't need it anymore, right?
> 
> Additional testing:
>  - [x] `hotspot_gc_shenandoah`

Marked as reviewed by roland (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/16908#pullrequestreview-1767912880