RFR: 8374889: C2 VectorAPI: must handle impossible combination of signed cast from float [v2]

[Emanuel Peter]

On Tue, 13 Jan 2026 08:24:52 GMT, Quan Anh Mai <qamai at openjdk.org> wrote:

>> Hmm, indeed, we could try to put a `Halt` node here, right?
>> @merykitty How exactly would you do that? Are there places we already do that?
>
> If you look at the end of `GraphKit::uncommon_trap`, the procedure would look like this:
> 
>     HaltNode* halt = new HaltNode(control(), frameptr(), "uncommon trap returned which should never happen"
>                                                          PRODUCT_ONLY(COMMA /*reachable*/false));
>     _gvn.set_type_bottom(halt);
>     root()->add_req(halt);
> 
>     stop_and_kill_map();

Nice idea! I applied it and tested it on the reproducer. Turns out the HaltNode is not in the final graph, so the path probably got folded away later. So we are able to prove that it is dead later on most likely.

Running testing again now...

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

PR Review Comment: https://git.openjdk.org/jdk/pull/29169#discussion_r2687142861