RFR: 8315884: New Object to ObjectMonitor mapping [v20]

[Axel Boldt-Christmas]

On Thu, 15 Aug 2024 13:45:11 GMT, Yudi Zheng <yzheng at openjdk.org> wrote:

>> Axel Boldt-Christmas has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Remove newline
>
> src/hotspot/cpu/x86/c2_MacroAssembler_x86.cpp line 677:
> 
>> 675: 
>> 676:       // Check for match.
>> 677:       cmpptr(obj, Address(t));
> 
> `Address(t)` can be cached (in rax?) and reused in the subsequent `comptr`

It can. Just a quick test with `LockUnlock.testInflated` µbenchmarks shows a ~5% regression when using a mov of [T] into rax and then using rax for cmp. (On my current AMD machine). But worth pursuing in a more extensive followup. 

I'll note this in the followup RFEs.

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PR Review Comment: https://git.openjdk.org/jdk/pull/20067#discussion_r1718488820