RFR: 8320646: RISC-V: C2 VectorCastHF2F [v3]

[Hamlin Li]

> Hi,
> Can you review this patch to add instrinsics for VectorCastHF2F/VectorCastF2HF?
> Thanks!
> 
> ## Test
> 
> test/jdk/java/lang/Float/Binary16ConversionNaN.java
> test/jdk/java/lang/Float/Binary16Conversion.java
> 
> hotspot/jtreg/compiler/intrinsics/float16
> hotspot/jtreg/compiler/vectorization/TestFloatConversionsVectorjava
> hotspot/jtreg/compiler/vectorization/TestFloatConversionsVectorNaN.java

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

  make UseZvfh experimatal; clean code

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/17698/files
  - new: https://git.openjdk.org/jdk/pull/17698/files/5964bb60..0dce1573

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=17698&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=17698&range=01-02

  Stats: 5 lines in 2 files changed: 0 ins; 2 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/17698.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17698/head:pull/17698

PR: https://git.openjdk.org/jdk/pull/17698