RFR: 8332249: Micro-optimize Method.hashCode [v2]

[Claes Redestad]

On Wed, 5 Jun 2024 13:45:46 GMT, Per Minborg <pminborg at openjdk.org> wrote:

>> As a note, If we would have access to the contemplated `StableValue` and `hash` was declared even as an _instance variable_ `StableValue<Integer>` in a regular class, then it would be trusted and would be eligible for constant folding due to the VM will have special rules for  fields of StableValue type.
>
> Ahh. There was a benchmark in the initial message. Sorry.

We think this is caused by the membars being conservatively emitted at method exit, and more precis membar control should help ARM. Filed: https://bugs.openjdk.org/browse/JDK-8333791

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PR Review Comment: https://git.openjdk.org/jdk/pull/19433#discussion_r1631071572