RFR: 8313406: nep_invoker_blob can be simplified more

[Jorn Vernee]

On Thu, 3 Aug 2023 04:07:27 GMT, Yasumasa Suenaga <ysuenaga at openjdk.org> wrote:

> then shuffling would remain somewhare even if we could eliminate them from NEP stub.

Since things on the Java side are visible to the JIT, it should be able to avoid the extra data motion.

> Thus this topic would be lower priority if my guessing is correct.

Yes, it is lower priority. It's relatively complex to solve, and also CPUs, in my experience, don't generally care that much about the shuffling. They probably just change their internal register allocation table instead of doing the actual moves.

Also, it will ultimately help more to implement C2 intrinsics for native calls, as that avoids going through the downcall stub altogether. I have an old POC for that which I will dust off.

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PR Comment: https://git.openjdk.org/jdk/pull/15089#issuecomment-1663298793