RFR: 8283566: G1: Improve G1BarrierSet::enqueue performance [v2]

[Aleksey Shipilev]

On Mon, 28 Mar 2022 11:00:01 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> > > Thing is, it is not about nullity. It is about whether we have already loaded the oop or not. Maybe `enqueue_loaded`?
> > 
> > 
> > Okay.
> 
> After some back and forth, I settled on `enqueue_loc` for new method. This matches some of the related methods we have in Shenandoah. This also simplifies the patch.

Any opinions about this version?

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PR: https://git.openjdk.java.net/jdk/pull/7921