RFR: 8318218: RISC-V: C2 CompressBits [v6]

[Hamlin Li]

> Hi,
> Can you review the change to add intrinsic for CompressBits for Long & Integer?
> Thanks!
> 
> ## Test
> pass jtreg test:
> test/jdk/java/lang/CompressExpand*.java

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

  reserve all used v register; use t0 directly

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/16481/files
  - new: https://git.openjdk.org/jdk/pull/16481/files/dc6dedbf..b6456d79

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=16481&range=05
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=16481&range=04-05

  Stats: 26 lines in 3 files changed: 3 ins; 0 del; 23 mod
  Patch: https://git.openjdk.org/jdk/pull/16481.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16481/head:pull/16481

PR: https://git.openjdk.org/jdk/pull/16481