RFR: 8350960: RISC-V: Add riscv backend for Float16 operations - vectorization [v3]

[Hamlin Li]

On Wed, 14 May 2025 00:21:44 GMT, Fei Yang <fyang at openjdk.org> wrote:

>> No, it uses T_SHORT instead, in Float16.java it also uses a short as underlying payload.
>> And if you check the generated assembly code, you'll find some code like `vsetivli        t0,16,e16,m1,tu,mu`.
>> 
>> To avoid confusion, I will add an assertion here so that it can be understood later.
>
> Thanks for the answer. I see that is also reflected on the C2 source code [1].
> Why not save this `Matcher::vector_element_basic_type(this)` call then? I mean:
> 
> assert(Matcher::vector_element_basic_type(this) == T_SHORT, "must");
> __ vsetvli_helper(T_SHORT, Matcher::vector_length(this));
> 
> 
> [1] https://github.com/openjdk/jdk/blob/master/src/hotspot/share/opto/vectornode.cpp#L63

Make sense, fixed.

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PR Review Comment: https://git.openjdk.org/jdk/pull/25181#discussion_r2088371205