RFR: 8367066: RISC-V: refine register selection in MacroAssembler:: decode_klass_not_null [v2]

[Hamlin Li]

> Hi,
> Can you help to review this patch?
> 
> Previously, the register selection in MacroAssembler:: decode_klass_not_null is misleading, better to refine it to improve the readability.
> 
> Thanks!
> 
> Running runtime test tier1/2/3...

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

  refine

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/27138/files
  - new: https://git.openjdk.org/jdk/pull/27138/files/7598f4d0..89ed8b85

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=27138&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=27138&range=00-01

  Stats: 11 lines in 2 files changed: 2 ins; 6 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/27138.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27138/head:pull/27138

PR: https://git.openjdk.org/jdk/pull/27138