RFR: 8342884: RISC-V: verify float <--> float16 conversion [v2]

[Hamlin Li]

> Hi,
> Can you help to review this simple patch? it removes the `Experimental` of the `UseZvfh`.
> Thanks
> 
> Currently, only float <--> float16 conversions use Zvfh extension, I've run the jmh tests on bananapi, the performance result shows it's good.
> <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-XX:+UseZfh -XX:+UnlockExperimentalVMOptions -XX:+/-UseZvfh | (size) | Mode | Cnt | Score -intrinsic | Score +intrinsic | Error | Units | Improvement
> -- | -- | -- | -- | -- | -- | -- | -- | --
> Fp16ConversionBenchmark.float16ToFloat | 2048 | avgt | 10 | 8129.72 | 4729.125 | 71.937 | ns/op | 1.719
> Fp16ConversionBenchmark.float16ToFloatMemory | 2048 | avgt | 10 | 16.9 | 16.894 | 0.002 | ns/op | 1
> Fp16ConversionBenchmark.floatToFloat16 | 2048 | avgt | 10 | 12561.962 | 3767.944 | 12.652 | ns/op | 3.334
> Fp16ConversionBenchmark.floatToFloat16Memory | 2048 | avgt | 10 | 18.146 | 18.147 | 0.003 | ns/op | 1
> 
> </google-sheets-html-origin>

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

  hw probe

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/21664/files
  - new: https://git.openjdk.org/jdk/pull/21664/files/580d3879..944dacdd

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=21664&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=21664&range=00-01

  Stats: 5 lines in 2 files changed: 4 ins; 1 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/21664.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21664/head:pull/21664

PR: https://git.openjdk.org/jdk/pull/21664