RFR: 8329764: G1: Handle null references during verification first [v2]

[Thomas Schatzl]

On Fri, 5 Apr 2024 12:09:35 GMT, Thomas Schatzl <tschatzl at openjdk.org> wrote:

>> Hi all,
>> 
>>   please review this change that suggests to move the null reference check in object iteration during heap verification first.
>> 
>> The reason is as stated, since null references are fairly common (not only in that test mentioned in https://bugs.openjdk.org/browse/JDK-8329314), it may make sense to put it first. Also, null references never fail anyway (and verification failure is supposed to be uncommon).
>> 
>> Improves total runtime of that test case from 3s (~3.9s cpu time) to 2.2s (~3.1s cpu time).
>> 
>> If you think it makes the code too ugly, I will retract it.
>> 
>> Testing: gha, local testing.
>
> Thomas Schatzl has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains two commits:
> 
>  - 8329764
>  - 8329570: G1: Excessive is_obj_dead_cond calls in verification

Still saving ~200ms (release build) verifying that large array.

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PR Comment: https://git.openjdk.org/jdk/pull/18650#issuecomment-2045429523