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

[Frederic Parain]

On Fri, 3 Oct 2025 14:16:17 GMT, Paul Hübner <phubner at openjdk.org> wrote:

>> This seems to pass multiple stressHierarchy test invocations with -XX:+UseParallelGC, and runtime/valhalla/inlinetypes tests. I think there's probably further investigation that needs to be done but hopefully this helps with the parallel GC test failures.
>> Testing with tier1-4.
>
> 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.

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PR Review Comment: https://git.openjdk.org/valhalla/pull/1655#discussion_r2402133078