RFR: 8375010: C2 VectorAPI: assert(vbox->is_CheckCastPP()) failed: should be expanded [v2]

[Kerem Kat]

On Wed, 14 Jan 2026 17:03:01 GMT, Vladimir Ivanov <vlivanov at openjdk.org> wrote:

>> Kerem Kat has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Simplify expand_vbox_node_helper by merging VectorBox Phi handling
>
> src/hotspot/share/opto/vector.cpp line 357:
> 
>> 355:   // any of the inputs to VectorBoxNode are value-numbered they can only
>> 356:   // move up and are guaranteed to dominate.
>> 357:   if (vbox->is_Phi() && vect->bottom_type()->isa_vect()) {
> 
> Does `vect->bottom_type()->isa_vect()` check become redundant? In other words, is it possible to observe a non-vector value here? It seems like the important bit is whether `vect` is a `Phi` or not. 
> 
> Another observation: `vbox->is_Phi() && vect->is_Phi()` and `vbox->is_Phi() && !vect->is_Phi()` cases can be commoned.

It doesn't seem possible, I removed the redundant check and merged the if blocks to simplify.

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PR Review Comment: https://git.openjdk.org/jdk/pull/29200#discussion_r2694408683