[lworld] RFR: 8352727: [lworld] Remove or replace obsolete StressInlineTypeReturnedAsFields flag from tests

[Christian Hagedorn]

On Thu, 27 Mar 2025 14:23:21 GMT, Christian Hagedorn <chagedorn at openjdk.org> wrote:

> [JDK-8301007](https://bugs.openjdk.org/browse/JDK-8301007) renamed `StressInlineTypeReturnedAsFields` to `StressCallingConvention` and added some more stressing possibilities. However, it was forgotten to update the flag in tests in two locations:
> 
> ### Use in Default Scenario
> 
> One default scenario uses `-XX:+StressInlineTypeReturnedAsFields` for Valhalla IR tests. The tests still succeed because we have `-XX:+IgnoreUnrecognizedVMOptions` in place which ignores the now non-existing flag.
> 
> I tried to replace `StressInlineTypeReturnedAsFields` with the updated `StressCallingConvention` flag but it turns out that too many IR rules rely on a predictable calling convention such that we could verify that all allocations are removed. With `StressCallingConvention`, we could now randomly enforce allocations because we cannot pass a value object in scalarized form anymore because there is only a non-scalarized calling convention.
> 
> I therefore propose to simply drop `StressInlineTypeReturnedAsFields` from the default scenario without replacement. 
> 
> Note that we still have stress jobs in place that run with `StressCallingConvention` enabled to exercise different combinations of calling conventions.
> 
> 
> ### Use in `TestCallingConventionC1.java`
> The second use in `TestCallingConventionC1.java` can be replaced by `StressCallingConvention` because we do not have any IR rules that could be affected.
> 
> Thanks,
> Christian

Thanks Tobias for your review!

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PR Comment: https://git.openjdk.org/valhalla/pull/1412#issuecomment-2766169525