On Wed, 26 Aug 2026 11:46:42 GMT, Axel Boldt-Christmas <[email protected]> wrote:
> Historically we have had displaced markWord's because locking (stack locks, > and inflated monitors). > > After the `UseObjectMonitorTable` removal there are no more need to protect > against displaced markWords. > > I suggest we simplify this logic and clean up the interface w.r.t. > `identity_hash`. > > Changes the `fast_no_hash_check` and `has_no_hash` into `has_identity_hash` > and `has_hash` checks. > As before it is invalid to read the hash on marked objects, added asserts to > ensure this. > Rewrote `oopDesc::slow_identity_hash` to not regenerate a new hash every time > it transiently fails to install the hash in the markWord due to some other > header change. > > There are a few places which right now calls `identity_hash` from develop > logging / introspection printing `InstanceStackChunkKlass::print_chunk` and > `Continuation::print`. It is a bit unfortunate that we have these > side-effects in debug VMs. But think we should handle these in a future RFE. > > Testing (in progress): > * Tier 1-3 Oracle supported platforms > * GHA > > --------- > - [x] I confirm that I make this contribution in accordance with the [OpenJDK > Interim AI Policy](https://openjdk.org/legal/ai). This pull request has now been integrated. Changeset: 1d173df7 Author: Axel Boldt-Christmas <[email protected]> URL: https://git.openjdk.org/jdk/commit/1d173df7c110c3750a52a09146a5d05ef0fa2938 Stats: 137 lines in 14 files changed: 36 ins; 53 del; 48 mod 8391174: Simplify `identity_hash` after UseObjectMonitorTable removal Reviewed-by: stefank, jsjolen, iklam ------------- PR: https://git.openjdk.org/jdk/pull/32535
