[lworld] RFR: 8376171: [lworld] Enable storing the hash code in the mark word of value objects [v2]

[Stefan Karlsson]

On Fri, 23 Jan 2026 15:55:13 GMT, Paul Hübner <phubner at openjdk.org> wrote:

> Thank you for doing this, and nice that we're not wasting the bits anymore :-).
> 
> I have left some smaller nit-ish comments, one open question I have myself is whether it's safe to `set_mark` when running with a concurrent GC. If anyone has any insights, it'd be good to hear.

Using non-casing setting of header bits is risky and even if it can be shown to be safe today it is limiting our possibilities poke around at the bits in the the future.

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PR Comment: https://git.openjdk.org/valhalla/pull/1954#issuecomment-3799011532