RFR: 8345178: RISC-V: Add gtests for narrow cmpxchg [v3]

[Robbin Ehn]

> Hi, please consider.
> 
> This adds tests of aligned narrow cmpxchg.
> 
> 
> Note: Google Test filter = *RiscV*
> [==========] Running 5 tests from 1 test suite.
> [----------] Global test environment set-up.
> [----------] 5 tests from RiscV
> ...
> [ RUN      ] RiscV.cmpxchg_int16_lr_sc_vm
> [       OK ] RiscV.cmpxchg_int16_lr_sc_vm (2 ms)
> [ RUN      ] RiscV.cmpxchg_int8_lr_sc_vm
> [       OK ] RiscV.cmpxchg_int8_lr_sc_vm (1 ms)
> [ RUN      ] RiscV.cmpxchg_int16_maybe_zacas_vm
> [       OK ] RiscV.cmpxchg_int16_maybe_zacas_vm (1 ms)
> [ RUN      ] RiscV.cmpxchg_int8_maybe_zacas_vm
> [       OK ] RiscV.cmpxchg_int8_maybe_zacas_vm (1 ms)
> [----------] 5 tests from RiscV (20831 ms total)
> 
> [----------] Global test environment tear-down
> [==========] 5 tests from 1 test suite ran. (20834 ms total)
> [  PASSED  ] 5 tests.
> 
> 
> Executed with -XX:+UnlockExperimentalVMOptions -XX:+UseZacas
> 
> Thanks, Robbin

Robbin Ehn has updated the pull request incrementally with one additional commit since the last revision:

  Review comment

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/22445/files
  - new: https://git.openjdk.org/jdk/pull/22445/files/b07b2c10..22e8c4e6

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=22445&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=22445&range=01-02

  Stats: 11 lines in 1 file changed: 0 ins; 5 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/22445.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22445/head:pull/22445

PR: https://git.openjdk.org/jdk/pull/22445