On Fri, 19 Jun 2026 14:16:57 GMT, Christian Hagedorn <[email protected]> 
wrote:

>> The provided test cases fail when inlining the `Array.copyOf/copyOfRange()` 
>> intrinsics where the source array is flat and from an abstract value class.
>> 
>> The current code checks whether the source array or the destination array 
>> klass contain oops by assuming that a flat value class array is always 
>> concrete and thus an `InlineKlass` (i.e. can call `inline_klass()`). 
>> However, we could also have abstract value class arrays that are known to be 
>> flat (see test cases). This leads to a cast assertion failure because 
>> abstract value classes are represented by an `InstanceKlass` and not an 
>> `InlineKlass`.
>> 
>> To fix this, I added a simple bailout when detecting an abstract flat value 
>> class array. This is a conservative correctness fix and should be revisited 
>> again post-Valhalla-integration. We have 
>> [JDK-8251971](https://bugs.openjdk.org/browse/JDK-8251971) in place for that 
>> which should also tackle other issues around the arraycopy intrinsics and 
>> also address performance problems.
>> 
>> Thanks,
>> Christian
>> 
>> ---------
>> - [x] I confirm that I make this contribution in accordance with the 
>> [OpenJDK Interim AI Policy](https://openjdk.org/legal/ai).
>
> Christian Hagedorn has updated the pull request incrementally with one 
> additional commit since the last revision:
> 
>   fix tklass

src/hotspot/share/opto/library_call.cpp line 5215:

> 5213:                         (orig_t == nullptr || (!orig_t->is_not_flat() 
> && (!orig_t->is_flat() || orig_t->elem()->inline_klass()->contains_oops()))) 
> &&
> 5214:                         // Can dest array be flat and contain oops?
> 5215:                         can_dest_be_value_class_array && 
> (!tklass->is_flat() || 
> tklass->is_aryklassptr()->elem()->is_instklassptr()->instance_klass()->as_inline_klass()->contains_oops())));

This should also check for `tklass->is_not_flat()` instead.

-------------

PR Review Comment: 
https://git.openjdk.org/valhalla/pull/2569#discussion_r3443155265

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