RFR: 8348562: ZGC: segmentation fault due to missing node type check in barrier elision analysis

[Richard Reingruber]

On Mon, 27 Jan 2025 09:08:07 GMT, Roberto Castañeda Lozano <rcastanedalo at openjdk.org> wrote:

> > I guess it is pretty unlikely but I'd like to make sure that we don't miss an actual allocation because the pattern is a little bit different on ppc.
> 
> Hi Richard, note that `compiler/gcbarriers/TestG1BarrierGeneration.java` passes on PPC64 after applying [JDK-8346280](https://bugs.openjdk.org/browse/JDK-8346280) ([under review](https://github.com/openjdk/jdk/pull/23235)), implying that `is_allocation` is successful on PPC64 at least for the most common allocation scenarios. I also tried running the optimization tests in `compiler/gcbarriers/TestZGCBarrierElision.java` (currently only enabled for x64 and aarch64) on PPC64, and test cases that rely on `is_allocation` finding an allocation (such as `testAllocateThenStore`) pass. There are some failures, but I suspect they are due to other factors (e.g. ADL instruction naming mismatches). If you want to study the effectiveness of the barrier elision optimization on PPC64, I suggest to address these failures and enable `compiler/gcbarriers/TestZGCBarrierElision.java` for PPC64 as well.

Thanks for the explanation, Roberto. I wasn't aware that the code is trying to elide barriers and therefore missing one isn't that severe. Martin said he'll file an RFE to analyze the effectiveness on PPC64. I'm ok with that.

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PR Comment: https://git.openjdk.org/jdk/pull/23295#issuecomment-2615300955