RFR: 8316523: Relativize esp in interpreter frames (PowerPC only) [v2]

[Fredrik Bredberg]

On Mon, 2 Oct 2023 09:25:06 GMT, Fredrik Bredberg <fbredberg at openjdk.org> wrote:

>> Relativize esp (Expression Stack Pointer on PowerPC) in interpreter frames.
>> 
>> By changing the "esp" member in interpreter frames from being an absolute address into an offset that is relative to the frame pointer, we don't need to change the value as we freeze and thaw frames of virtual threads. This is since we might freeze and thaw from and to different worker threads, so the absolute address to locals might change, but the offset from the frame pointer will be constant.
>> 
>> This subtask only handles "esp" on PowerPC. The relativization of other interpreter frame members are handled in other subtasks to [JDK-8289296](https://bugs.openjdk.org/browse/JDK-8289296).
>> 
>> It has been sanity tested onr PowerPC using Qemu.
>
> Fredrik Bredberg has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Updated after review.

About taking care of PPC64. If I get something to work on x86 and aarch64, it's often not too much work to get it to run on the other platforms (like ppc), and by doing so I get a much better understanding of the general concepts, since the concepts may be more thoroughly described in some cpu port than in others. And, if you're new to a large code base, any method that makes you understand the concepts better, is a good thing. As usual, I still need a sponsor to get the show on the road.
Cheers guys, Fredrik

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PR Comment: https://git.openjdk.org/jdk/pull/15999#issuecomment-1748455026