RFR: 8342042: PPC64: compiler_fast_unlock_object flags failure instead of success [v2]

[Fredrik Bredberg]

On Wed, 16 Oct 2024 09:19:48 GMT, Richard Reingruber <rrich at openjdk.org> wrote:

>> This change inverts the `EQ` bit in `flag` with a condition register nand instruction in order to meet the post condition given at L2751-L2752:
>> 
>> 
>>   // flag == EQ indicates success, decrement held monitor count
>>   // flag == NE indicates failure
>> 
>> 
>> The fix passed our CI testing with LockingMode set to LM_LEGACY
>> Tier1-4 of hotspot and jdk. All of Langtools and jaxp. Renaissance Suite and SAP specific tests.
>> Testing was done on the main platforms and also on Linux/PPC64le and AIX.
>> 
>> The test runtime/logging/MonitorInflationTest.java failed on all platforms. Apparently it has issues with LM_LEGACY.
>
> Richard Reingruber has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Same enhancement for compiler_fast_unlock_lightweight_object as suggested by Axel

Marked as reviewed by fbredberg (Committer).

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PR Review: https://git.openjdk.org/jdk/pull/21496#pullrequestreview-2373071793