RFR: 8337753: Target class of upcall stub may be unloaded [v3]

[Martin Doerr]

On Wed, 4 Sep 2024 16:45:38 GMT, Amit Kumar <amitkumar at openjdk.org> wrote:

>> I looked into it, but couldn't find out. But I remove the `save_return_pc` & `restore_return_pc` and everything seems fine. So maybe we can remove it.
>
> Tier1 test are fine with/without "saving & restoring" return_pc;

I found it: https://github.com/openjdk/jdk/blob/433f6d8a0643b59663bf76c0f3a2af27a6cc56b7/src/hotspot/cpu/s390/gc/g1/g1BarrierSetAssembler_s390.cpp#L238
Called here:
https://github.com/openjdk/jdk/blob/433f6d8a0643b59663bf76c0f3a2af27a6cc56b7/src/hotspot/cpu/s390/gc/g1/g1BarrierSetAssembler_s390.cpp#L115
Other GCs with load barriers are not implemented, so the save&restore code is redundant.
The stub is frameless and only needs the save&restore code when calling C.

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PR Review Comment: https://git.openjdk.org/jdk/pull/20479#discussion_r1744140160