RFR: JDK-8316991: Reduce nullable allocation merges [v9]

[Cesar Soares Lucas]

On Tue, 26 Mar 2024 20:49:48 GMT, Vladimir Ivanov <vlivanov at openjdk.org> wrote:

>> Cesar Soares Lucas has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 13 commits:
>> 
>>  - Merge remote-tracking branch 'origin/master' into ram-nullables
>>  - Catching up with master
>>  - Fix broken build.
>>  - Merge with origin/master
>>  - Update test/micro/org/openjdk/bench/vm/compiler/AllocationMerges.java
>>    
>>    Co-authored-by: Andrey Turbanov <turbanoff at gmail.com>
>>  - Ammend previous fix & add repro tests.
>>  - Fix to prevent reducing already reduced Phi
>>  - Fix to prevent creating NULL ConNKlass constants.
>>  - Refrain from RAM of arrays and Phis controlled by Loop nodes.
>>  - Fix typo in test.
>>  - ... and 3 more: https://git.openjdk.org/jdk/compare/89e0889a...3129378f
>
> src/hotspot/share/opto/escape.cpp line 2976:
> 
>> 2974:     //
>> 2975:     if (field->base_count() > 1 && candidates.size() == 0) {
>> 2976:       bool further_validate = false;
> 
> A better name maybe? You can also extract its computation into a helper method (e.g. `has_non_reducible_merge(FieldNode* field)`.

Makes sense. Going up in next git push.

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PR Review Comment: https://git.openjdk.org/jdk/pull/15825#discussion_r1543572814