RFR: 8347422: Crash during safepoint handler execution with -XX:+UseAPX

[Jatin Bhateja]

On Mon, 13 Jan 2025 11:32:48 GMT, Tobias Hartmann <thartmann at openjdk.org> wrote:

> Thanks Jatin. In this case I would suggest that we should add a VM stress flag to give preference to EGPRs, or maybe [JDK-8343294](https://bugs.openjdk.org/browse/JDK-8343294) is good enough?
> 

Technically, randomizing allocation sequence from the same register class is not very useful, from the compiler standpoint it simply ensures that an LRG corresponding to the definition MachOper is never assigned the same register which is already assigned to its neighbors in the interference graph, so it simply picks the next available free register while choosing the color, a change in allocation order will not impact the spilling behavior either,  what I am doing is modifying the static allocation order so that we deterministically give preferences to EGPRs over GPRs, this will ensure that all our APX specific assembler support and special handling like the one extended by this patch as exercised throughly. 

> Do the existing tests trigger this even without `-XX:+SafepointALot`?

Yes, but with -XX:+SafepointALot crash hit early.

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PR Comment: https://git.openjdk.org/jdk/pull/23035#issuecomment-2586976104