On Wed, 4 Feb 2026 10:03:55 GMT, Paul Hübner <[email protected]> wrote:
> Hi all, > > The main ideas of this patch are to highlight and enforce the invariant we > enforce when it comes to value objects' identity hash code. > > The original JBS issues addresses the following points, which have been > addressed to various extents: > > 1. Adding assertions to the CAS-setting of the hash in the markWord. This is > vital to enforce the invariant and was added. > 2. Breaking the loop if the CAS results in a conflict. Putting the identity > hash in the markWord is an optimization, so one could break out of the loop > whenever. With the assertion, there's a good confidence that CAS will > eventually succeed, namely once other threads stop poking at the markWord > bits. **If there is demand, I can add a fixed upper bound.** > 3. SSA-ing the hash variable. Done. > 4. Possibly introducing a markWord::has_hash to improve legibility. I did not > do this as it would yield multiple `obj->mark()` calls in the fast path and > the current form is (in my opinion) sufficiently legible. > > Testing: tiers 1-3 on Linux (x64, AArch64), macOS (x64, AArch64), Windows > (x64). This pull request has now been integrated. Changeset: 69efed9b Author: Paul Hübner <[email protected]> URL: https://git.openjdk.org/valhalla/commit/69efed9b01b589564d344dfbd5de6e955d717997 Stats: 40 lines in 2 files changed: 26 ins; 1 del; 13 mod 8376566: [lworld] Runtime cleanups of markWord hashCode for inline types after JDK-8376171 Reviewed-by: coleenp, stefank, heidinga ------------- PR: https://git.openjdk.org/valhalla/pull/2029
