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

[Roberto Castañeda Lozano]

On Fri, 30 Aug 2024 08:23:44 GMT, Roberto Castañeda Lozano <rcastanedalo at openjdk.org> wrote:

> I will study if the check in get_store_barrier is superseded by that in refine_barrier_by_new_val_type. If I can convince myself that this is the case I will consider removing the former.

This was indeed the case, so I have removed the compile-time null check from `G1BarrierSetC2::get_store_barrier` (commit deac05d7) and simplified the code around it (commit 6f4027bf). I also added a few extra test cases to exercise stores on newly-allocated objects with different nullness information (commit 1ea2862f).

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PR Review Comment: https://git.openjdk.org/jdk/pull/19746#discussion_r1741555725