RFR: 8341293: Split field loads through Nested Phis [v7]

[Dhamoder Nalla]

On Fri, 7 Feb 2025 16:36:23 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

>>> @dhanalla Would you like this to be reviewed? We generally don't re-review until we get pinged again. The idea is that you are maybe still working on it, and so there is no point in reviewing half-processed code. So once you are happy, you can let us know ;)
>> Thanks, @eme64 for checking with me. Yes, it's ready for review.
>
> @dhanalla Testing failed for this test:
> `compiler/c2/irTests/scalarReplacement/AllocationMergesNestedPhiTests.java`
> With flags:
> - `-server -Xcomp`
> - `-ea -esa -XX:CompileThreshold=100 -XX:+UnlockExperimentalVMOptions -server -XX:-TieredCompilation`
> - `-XX:-TieredCompilation -XX:+AlwaysIncrementalInline`
> - `-XX:-TieredCompilation -XX:+StressReflectiveCode -XX:-ReduceInitialCardMarks -XX:-ReduceBulkZeroing -XX:-ReduceFieldZeroing`
> 
> We also have an internal test that is failing with the same assert:
> 
> `#  assert(jobj != nullptr && jobj != phantom_obj) failed: escaped allocation`

@eme64, Thanks for reviewing the PR.
I have addressed the CR comments, and it is now ready for review.

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PR Comment: https://git.openjdk.org/jdk/pull/21270#issuecomment-2787578996