RFR: 8291555: Implement alternative fast-locking scheme [v62]

[Thomas Stuefe]

On Mon, 24 Apr 2023 22:51:10 GMT, Daniel D. Daugherty <dcubed at openjdk.org> wrote:

>> Roman Kennke has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Remove unnecessary comments
>
> src/hotspot/cpu/arm/macroAssembler_arm.cpp line 1803:
> 
>> 1801: #ifdef ASSERT
>> 1802:   // Poison scratch regs
>> 1803:   POISON_REGS((~savemask), t1, t2, t3, 0x10000001);
> 
> Should this poison value be: 0x20000002

The poison values were something I used during development of the arm part, bug hunting wise. Though I think they make sense in general. I agree with @dcubed-ojdk, 0x2000002 would be the most logical value here. Either that or remove the poisening (though it had been useful).

> src/hotspot/cpu/arm/sharedRuntime_arm.cpp line 649:
> 
>> 647: 
>> 648:   __ flush();
>> 649:   return AdapterHandlerLibrary::new_entry(fingerprint, i2c_entry, c2i_entry, c2i_unverified_entry);
> 
> This change seems out of place... what's the story here?

This is a local revert of *8303154: Investigate and improve instruction cache flushing during compilation* - the missing flush caused random crashes, but I did not have time to investigate. I reverted the flush, crashes were gone.

If needed I may revisit this when there is time.

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PR Review Comment: https://git.openjdk.org/jdk/pull/10907#discussion_r1178250178
PR Review Comment: https://git.openjdk.org/jdk/pull/10907#discussion_r1178255706