RFR: 8339643: Port JEP 404 to RISC-V [v4]

[Fei Yang]

On Wed, 18 Sep 2024 03:17:03 GMT, Fei Yang <fyang at openjdk.org> wrote:

>> The riscv64 implementation of [JDK-8337511](https://bugs.openjdk.org/browse/JDK-8337511) Implement JEP-404: Generational Shenandoah (Experimental).
>> This is mainly adapted from the changes in aarch64.
>> 
>> Testing
>> - [x] Gtest (release & fastdebug)
>> - [x] hotspot_gc_shenandoah (release & fastdebug)
>
> Fei Yang has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Improve ShenandoahBarrierSetAssembler::store_check

Thanks all for the review. Merged master and pushed one minor improvement for `ShenandoahBarrierSetAssembler::store_check`. This saves us one add instruction when doing address calculation under `UseCondCardMark`. `hotspot_gc_shenandoah` & `gtest` tested with release and fastdebug builds. I am going to integrate this change if no other opinions.

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PR Comment: https://git.openjdk.org/shenandoah/pull/493#issuecomment-2357443986