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

[Hamlin Li]

> Hi,
> Can you help to review this patch?
> It's a follow-up of https://github.com/openjdk/jdk/commit/9a3f9997b68a1f64e53b9711b878fb073c3c9b90.
> Thanks!
> 
> ## Test
> 
> Performance data
> <google-sheets-html-origin style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;">
> Benchmark | (vectorDim) | Mode | Cnt | Score - patch | Score - master | Improvement (master/patch) | Error | Units
> -- | -- | -- | -- | -- | -- | -- | -- | --
> Float16OperationsBenchmark.addBenchmark | 256 | avgt | 10 | 382.123 | 2595.718 | 6.793 | 0.631 | ns/op
> Float16OperationsBenchmark.addBenchmark | 512 | avgt | 10 | 563.726 | 5167.687 | 9.167 | 0.063 | ns/op
> Float16OperationsBenchmark.addBenchmark | 1024 | avgt | 10 | 888.455 | 9468.714 | 10.658 | 0.147 | ns/op
> Float16OperationsBenchmark.addBenchmark | 2048 | avgt | 10 | 1540.255 | 18879.796 | 12.258 | 0.396 | ns/op
> Float16OperationsBenchmark.divBenchmark | 256 | avgt | 10 | 579.959 | 4028.335 | 6.946 | 0.008 | ns/op
> Float16OperationsBenchmark.divBenchmark | 512 | avgt | 10 | 914.634 | 8034.234 | 8.784 | 0.027 | ns/op
> Float16OperationsBenchmark.divBenchmark | 1024 | avgt | 10 | 1494.017 | 15125.924 | 10.124 | 0.292 | ns/op
> Float16OperationsBenchmark.divBenchmark | 2048 | avgt | 10 | 2728.517 | 30197.97 | 11.068 | 32.869 | ns/op
> Float16OperationsBenchmark.fmaBenchmark | 256 | avgt | 10 | 476.764 | 2817.035 | 5.909 | 0.012 | ns/op
> Float16OperationsBenchmark.fmaBenchmark | 512 | avgt | 10 | 707.035 | 5239.438 | 7.41 | 0.129 | ns/op
> Float16OperationsBenchmark.fmaBenchmark | 1024 | avgt | 10 | 1114.29 | 7361.105 | 6.606 | 0.024 | ns/op
> Float16OperationsBenchmark.fmaBenchmark | 2048 | avgt | 10 | 1931.713 | 14465.602 | 7.488 | 1.852 | ns/op
> Float16OperationsBenchmark.maxBenchmark | 256 | avgt | 10 | 501.892 | 3754.563 | 7.481 | 0.408 | ns/op
> Float16OperationsBenchmark.maxBenchmark | 512 | avgt | 10 | 738.148 | 7450.666 | 10.094 | 1.206 | ns/op
> Float16OperationsBenchmark.maxBenchmark | 1024 | avgt | 10 | 1195.262 | 15463.892 | 12.938 | 8.889 | ns/op
> Float16OperationsBenchmark.maxBenchmark | 2048 | avgt | 10 | 2253.656 | 30649.239 | 13.6 | 6.154 | ns/op
> Float16OperationsBenchmark.minBenchmark | 256 | avgt | 10 | 501.873 | 3753.9 | 7.48 | 0.298 | ns/op
> Float16OperationsBenchmark.minBenchmark ...

Hamlin Li has updated the pull request incrementally with one additional commit since the last revision:

  minor

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/25181/files
  - new: https://git.openjdk.org/jdk/pull/25181/files/0ad3b5a9..0e165958

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=25181&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=25181&range=01-02

  Stats: 24 lines in 1 file changed: 0 ins; 8 del; 16 mod
  Patch: https://git.openjdk.org/jdk/pull/25181.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25181/head:pull/25181

PR: https://git.openjdk.org/jdk/pull/25181