RFR: 8334060: Implementation of Late Barrier Expansion for G1 [v10]

[Roberto Castañeda Lozano]

On Wed, 28 Aug 2024 08:12:36 GMT, Kim Barrett <kbarrett at openjdk.org> wrote:

>> src/hotspot/share/gc/g1/c2/g1BarrierSetC2.cpp line 166:
>> 
>>> 164:  * post-barrier completely, if it is possible during compile time to prove the
>>> 165:  * object is newly allocated and that no safepoint exists between the allocation
>>> 166:  * and the store.
>> 
>> It might be worth saying explicitly that this is a compile-time version of the above mentioned young
>> generation filter.
>
> We can similarly elide the post-barrier if we can prove at compile-time that the value being written
> is null.  That case isn't handled here though.  Instead that's checked for in 
> `refine_barrier_by_new_val_type` and in `get_store_barrier`.  I'm not sure why it's structured
> that way.

> It might be worth saying explicitly that this is a compile-time version of the above mentioned young
generation filter.

Done (commit [72a04c4](https://github.com/openjdk/jdk/pull/19746/commits/72a04c4e8046256ee7e811d66934d5d9e24f4c7c)), thanks.

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PR Review Comment: https://git.openjdk.org/jdk/pull/19746#discussion_r1738184612