RFR: 8334060: Implementation of Late Barrier Expansion for G1 [v2]

[Martin Doerr]

On Thu, 29 Aug 2024 08:37:24 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

>> Thanks, I prototyped the refactored version for both x64 and aarch64 [here](https://github.com/robcasloz/jdk/commit/c1ae871eadac0d44981b7892ac8f7b64e8734283). I do not have a strong opinion for or against this refactoring. @albertnetymk @kimbarrett what do you think about it? (asking since you have recently looked at this code).
>
> I find the use of default-arg-value `bool decode_new_val = false` a bit confusing. (I tend to think default-arg-value makes the code less readable in general.)
> 
> If not using default-arg-value, I suspect the diff will be larger, and I don't see the immediate benefit of this refactoring. Maybe this can be deferred to its own PR if it's really desirable?

@albertnetymk: FYI: The basic idea was to make compressed Oops optimizations easier. It allows using shorter decoding sequences and removing redundant null checks in the fast path. I've implemented it on PPC64: https://github.com/TheRealMDoerr/jdk/blob/ed9c0232f53a15d768804348e1d8a111fed9a19e/src/hotspot/cpu/ppc/gc/g1/g1BarrierSetAssembler_ppc.cpp#L471
But, I'm ok with postponing it.

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PR Review Comment: https://git.openjdk.org/jdk/pull/19746#discussion_r1741950634