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

[Vladimir Kozlov]

On Tue, 26 Mar 2024 20:51:33 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 472:
> 
>> 470: 
>> 471:       // Don't handle arrays.
>> 472:       if (alloc->Opcode() != Op_Allocate) {
> 
> Turn it into `alloc->Opcode() == Op_AllocateArray` or put `assert(alloc->Opcode() == Op_AllocateArray, "")` inside the branch.

I suggest to add assert inside branch to catch the case when we add an other Allocate subclass.

Also `ptn->ideal_node()->is_Allocate()` check at the line 468 is not needed because `as_Allocate()` has such assert check.

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PR Review Comment: https://git.openjdk.org/jdk/pull/15825#discussion_r1541592986