Assertion error in C2 on RISC-V

[wks]

As reported by @caizixian, when running on riscv64-linux-gnu, C2 will raise an assertion error when compiling write-barrier code. This error can still be reproduced on OpenJDK 21.

One workaround is removing the slot and target arguments of the MMTkBarrierSetRuntime::object_reference_write_slow_call(src, slot, target) function, leaving the src argument alone. While this is sufficient for the ObjectBarrier, it is not a general solution.

[caizixian]

This was a more detailed analysis of the problem when I debugged it https://mail.openjdk.org/pipermail/riscv-port-dev/2022-October/000663.html

[caizixian]

We might be able to ask some compiler experts on the hotspot mailing list