[master] RFR: OMWorld: Cleanups [v2]

[Axel Boldt-Christmas]

On Thu, 23 May 2024 19:46:58 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

>> Axel Boldt-Christmas has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   LockStackInflateContendedLocks only used for current thread
>
> src/hotspot/cpu/aarch64/c2_MacroAssembler_aarch64.cpp line 502:
> 
>> 500:       ldr(t1_monitor, Address(box, BasicLock::object_monitor_cache_offset_in_bytes()));
>> 501:       // null check with Flags == NE, no valid pointer below alignof(ObjectMonitor*)
>> 502:       cmp(t1_monitor, checked_cast<uint8_t>(alignof(ObjectMonitor*)));
> 
> I don't know what this means.

Maybe I should say `valid ObjectMonitor* check` instead of `null check`. 

The reason that the check used to be against `2` is because some iterations of the code have signalled information in the lowest bit. 

Currently it could just be a check agains `1` which would check for `nullptr` while also setting Flags to NE. 

The check is simply that based on the fact that no valid ObjectMonitor* except nullptr can exist below `alignof(ObjectMonitor*)`.

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PR Review Comment: https://git.openjdk.org/lilliput/pull/178#discussion_r1613627124