On Wed, 17 Jul 2024 18:46:11 GMT, Vladimir Ivanov <vliva...@openjdk.org> wrote:
>> This is because the C++ runtime does secondary super cache lookups even
>> before the bitmap has been calculated and the hash table sorted. In this
>> case the bitmap is zero, so teh search thinks there are no secondary supers.
>> Setting _bitmap to SECONDARY_SUPERS_BITMAP_FULL forces a linear search.
>>
>> I guess there might be a better way to do this. Perhaps a comment is needed?
>>
>> I agree about `_secondary_supers_bitmap` name.
>
> Now it starts to sound concerning... `Klass::set_secondary_supers()`
> initializes both `_secondary_supers` and `_bitmap` which implies that
> `Klass::is_subtype_of()` may be called on not yet initialized Klass. It
> that's the case, it does look like a bug on its own. How is it expected to
> work when `_secondary_supers` hasn't been set yet?
On a second thought the following setter may be the culprit:
void Klass::set_secondary_supers(Array<Klass*>* secondaries) {
assert(!UseSecondarySupersTable || secondaries == nullptr, "");
set_secondary_supers(secondaries, SECONDARY_SUPERS_BITMAP_EMPTY);
}
It should be adjusted to set `SECONDARY_SUPERS_BITMAP_FULL` instead.
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PR Review Comment: https://git.openjdk.org/jdk/pull/19989#discussion_r1681581587
