[lworld] RFR: 8368875: [lworld] UseParallelGC fails null narrow klass assertion failure

[Paul Hübner]

On Fri, 3 Oct 2025 14:22:23 GMT, Frederic Parain <fparain at openjdk.org> wrote:

>> src/hotspot/share/oops/markWord.hpp line 310:
>> 
>>> 308:   bool must_be_preserved() const {
>>> 309:     return (!is_unlocked() || !has_no_hash() ||
>>> 310:       (EnableValhalla && (is_larval_state() || is_inline_type() || is_flat_array() || is_null_free_array())));
>> 
>> Doesn't `is_inline_type` imply `is_larval_state`?  (edit: other way around)
>
> The other way around, `is_larval_state` implies `is_inline_type` because only value classes instances can be in a larval state.

Thanks @fparain, I mixed it up when writing it down. I knew that, I promise 😅.  

I think it would be good to introduce an `is_valhalla_concept` (naming may vary) which ORs the larval, inline type, flat array and null free array bit masks into a single mask. That way we can check it in just one call, which is imo easier to read. Thoughts?

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PR Review Comment: https://git.openjdk.org/valhalla/pull/1655#discussion_r2402155434