RFR: 8371065: C2 SuperWord: VTransformLoopPhiNode::apply set wrong type, led to wrong constant folding of phi [v2]

[Emanuel Peter]

On Sat, 8 Nov 2025 11:41:15 GMT, Quan Anh Mai <qamai at openjdk.org> wrote:

>> Emanuel Peter has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   add diagnostic flag for product build
>
> Tbh I still feel a little uneasy with this, what if in the future we try to vectorize to a `long` sometimes, too? Is there anything stopping us from creating a new `Phi` for the `VTransformLoopPhiNode` instead?

@merykitty Would you prefer if I took the union of the entry edge and backedge type?

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PR Comment: https://git.openjdk.org/jdk/pull/28113#issuecomment-3506616584