RFR: 8366444: Add support for add/mul reduction operations for Float16 [v5]

[Emanuel Peter]

On Mon, 12 Jan 2026 08:47:07 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

>> If I remember correctly, I tried doing that initially but the loop did not get vectorized. The Ideal graph showed there were a lot of nodes related to object creation (probably for the intermediate `Float16` result) which bloated the size of the loop resulting in the loop not getting unrolled (and eventually not vectorized). I also tried a standalone loop where I do not return the intermediate result hoping that escape analysis could help in avoiding the object creation but did not help either.
>
> Hmm, I see. That sounds like a deficiency in the auto unboxing of Float16.
> 
> Suggestion: You should create both variants of the IR tests. And then file an RFE for the one that does not yet vectorize because of the boxing issues.
> 
> Because the way things are now, it's not a huge win, to be honest. Which user is supposed to write their code in such a convoluted way, having to cast back and forth? Would they not expect they could just use Float16 all the way through?

@jatin-bhateja What do you think?

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PR Review Comment: https://git.openjdk.org/jdk/pull/27526#discussion_r2681319220