RFR: 8338023: Support two vector selectFrom API [v10]

[Emanuel Peter]

On Mon, 16 Sep 2024 07:35:46 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

>> Jatin Bhateja has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Disabling VectorLoadShuffle bypassing optimization to comply with rearrange semantics at IR level.
>
> src/hotspot/share/opto/vectornode.hpp line 1625:
> 
>> 1623:   Node* Ideal(PhaseGVN* phase, bool can_reshape);
>> 1624:   virtual int Opcode() const;
>> 1625: };
> 
> `index` -> `indexes` because this is a vector, right? Otherwise I'll assume it is a scalar.
> Can you do some pseudo-code, that says how exactly the indices are interpreted? What if they are out of bounds? Does it wrap? Or assume they are in bounds? Undefined behaviour?

For me good comments here would be immendely valuable, because it helps with other C2 optimizations.

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PR Review Comment: https://git.openjdk.org/jdk/pull/20508#discussion_r1760667297