RFR: 8319801: Recursive lightweight locking: aarch64 implementation [v6]

[Axel Boldt-Christmas]

On Wed, 24 Jan 2024 11:27:25 GMT, Roman Kennke <rkennke at openjdk.org> wrote:

>> Axel Boldt-Christmas has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains 10 additional commits since the last revision:
>> 
>>  - Merge remote-tracking branch 'upstream_jdk/pr/16606' into JDK-8319801
>>  - Switch to CAS over LXSX
>>  - Fix missing $
>>  - Merge remote-tracking branch 'upstream_jdk/pr/16606' into JDK-8319801
>>  - Merge remote-tracking branch 'upstream_jdk/pr/16606' into JDK-8319801
>>  - Merge remote-tracking branch 'upstream_jdk/pr/16606' into JDK-8319801
>>  - Merge remote-tracking branch 'upstream_jdk/pr/16606' into JDK-8319801
>>  - Merge remote-tracking branch 'upstream_jdk/pr/16606' into JDK-8319801
>>  - 8319801: Recursive lightweight locking: aarch64 implementation
>>  - Cleanup: C2 fast_lock/fast_unlock aarch64
>
> src/hotspot/cpu/aarch64/c2_MacroAssembler_aarch64.cpp line 230:
> 
>> 228:                                               Register t2, Register t3) {
>> 229:   assert(LockingMode == LM_LIGHTWEIGHT, "must be");
>> 230:   // TODO: Current implementation does not use the box, consider removing.
> 
> If it's not used, then please remove it? Maybe it can help to allocate one less register, which may be useful performance-wise when register pressure is high?

Done.

> src/hotspot/cpu/aarch64/c2_MacroAssembler_aarch64.cpp line 339:
> 
>> 337:                                                 Register t2) {
>> 338:   assert(LockingMode == LM_LIGHTWEIGHT, "must be");
>> 339:   // TODO: Current implementation uses box only as a TEMP, consider renaming.
> 
> Yeah, please rename the register.

Done.

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

PR Review Comment: https://git.openjdk.org/jdk/pull/16608#discussion_r1464972254
PR Review Comment: https://git.openjdk.org/jdk/pull/16608#discussion_r1464972382