[jdk20u] RFR: 8302976: C2 intrinsification of Float.floatToFloat16 and Float.float16ToFloat yields different result than the interpreter

Tue Mar 21 21:54:05 UTC 2023

Backport [JDK-8302976](https://bugs.openjdk.org/browse/JDK-8302976) "C2 intrinsification of Float.floatToFloat16 and Float.float16ToFloat yields different result than the interpreter".

Backport did not apply cleanly because of `NULL` to `nullptr` changes in JDK 21. And because these intrinsics were implemented for RISC-V port only in JDK 21 and I have to exclude corresponding changes from backport.

The fix was pushed into JDK 21 two weeks ago. No issues were found since then.

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

Commit messages:
 - Backport 8cfd74f76afc9e5d50c52104fef9974784718dd4

Changes: https://git.openjdk.org/jdk20u/pull/21/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk20u&pr=21&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8302976
  Stats: 1358 lines in 43 files changed: 1213 ins; 104 del; 41 mod
  Patch: https://git.openjdk.org/jdk20u/pull/21.diff
  Fetch: git fetch https://git.openjdk.org/jdk20u.git pull/21/head:pull/21

PR: https://git.openjdk.org/jdk20u/pull/21