RFR: 8321122: Shenandoah: Remove ShenandoahLoopOptsAfterExpansion flag

[Aleksey Shipilev]

On Fri, 1 Dec 2023 16:52:45 GMT, Roland Westrelin <roland 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?
> 
> It could be useful for diagnostic purposes. Say if a user reports a crash, one trouble shooting step could be to ask them to run with `ShenandoahLoopOptsAfterExpansion` off. This said, that never happened AFAIK. So I don't have a strong opinion. I'm also wondering if: they make an actual difference performance wise? with other changes that happened in the meantime, are they still doing anything useful?

I think we want to keep the flag list from growing, and this is one of the steps of culling the flags we do not need anymore. I cannot remember a case when this flag was useful either. I think long-term we want to switch to late barrier insertion anyway, which would render this flag obsolete. We can remove the flag when that happens, if you prefer.

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PR Comment: https://git.openjdk.org/jdk/pull/16908#issuecomment-1838046406