RFR: 8355585: Aarch64: Add aarch64 backend for Float16 vector operations [v2]

[Hao Sun]

On Tue, 13 May 2025 12:49:32 GMT, Bhavana Kilambi <bkilambi at openjdk.org> wrote:

>> This patch adds aarch64 backend (both Neon and SVE) for FP16 vector operations - add, mul, sub, div, min, max, sqrt and fma.
>> 
>> Testing:
>> JTREG tests - hotspot_all, jdk (tier 1-3) and langtools (tier 1) pass on aarch64 which also includes the JTREG test to test the FP16 vector operations - `test/hotspot/jtreg/compiler/vectorization/TestFloat16VectorOperations.java`
>
> Bhavana Kilambi has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Address review comments

LGTM except one nit.

src/hotspot/cpu/aarch64/aarch64_vector_ad.m4 line 553:

> 551: 
> 552: // vector add - predicated
> 553: BINARY_OP_PREDICATE(vaddB,  AddVB,  sve_add,  B)

stylistic nit: remove the extra spaces.

In the initial commit, this extra space is added due to `vaddHF`. However, in the latest commit the predicated Float16 rules are removed.

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

PR Review: https://git.openjdk.org/jdk/pull/25096#pullrequestreview-2838450534
PR Review Comment: https://git.openjdk.org/jdk/pull/25096#discussion_r2087854380