RFR: 8320649: C2: Optimize scoped values [v7]

[Roland Westrelin]

On Thu, 8 Feb 2024 06:53:31 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

>> Roland Westrelin has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains ten commits:
>> 
>>  - review comment
>>  - Merge branch 'master' into JDK-8320649
>>  - Update src/hotspot/share/opto/callGenerator.cpp
>>    
>>    Co-authored-by: Emanuel Peter <emanuel.peter at oracle.com>
>>  - Update test/hotspot/jtreg/compiler/c2/irTests/TestScopedValue.java
>>    
>>    Co-authored-by: Andrey Turbanov <turbanoff at gmail.com>
>>  - merge fix
>>  - Merge branch 'master' into JDK-8320649
>>  - test failures
>>  - white spaces + bug id in test
>>  - test & fix
>
> src/hotspot/share/gc/shared/c2/barrierSetC2.hpp line 190:
> 
>> 188: class C2OptAccess: public C2Access {
>> 189:   PhaseGVN& _gvn;
>> 190:   Node* _mem;
> 
> Hmm. It is a little strange to have a `_mem` node that is not even a `MemNode*`. What types are expected here?

`_mem` is some node that carry memory state. `MemNode` is not the super type of all nodes that modify memory state. It's not even a super type of some of the nodes that modify memory state (`LoadNode` doesn't). Such a super type doesn't exist.

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PR Review Comment: https://git.openjdk.org/jdk/pull/16966#discussion_r1482668384