RFR: 8294729: [s390] Implement nmethod entry barriers [v16]

[Andrew Haley]

On Mon, 31 Oct 2022 15:10:44 GMT, Tyler Steele <tsteele at openjdk.org> wrote:

>> This draft PR implements native method barriers on s390. When complete, this will fix the build, and bring the other benefits of [JDK-8290025](https://bugs.openjdk.org/browse/JDK-8290025) to that platform.
>
> Tyler Steele has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Move nmethod_entry_barrier definition in hpp file

src/hotspot/cpu/s390/gc/shared/barrierSetAssembler_s390.cpp line 138:

> 136: 
> 137:     // Load value from current java object:
> 138:     __ z_lg(Z_R0_scratch, in_bytes(bs_nm->thread_disarmed_offset()), Z_thread); // 6 bytes

Isn't this loading from the current java Thread?

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PR: https://git.openjdk.org/jdk/pull/10558