RFR: 8296771: RISC-V: C2: assert(false) failed: bad AD file

[Aleksey Shipilev]

On Thu, 10 Nov 2022 09:35:52 GMT, Xiaolin Zheng <xlinzheng at openjdk.org> wrote:

> The backend encounters the same assertion failure as [JDK-8295414](https://bugs.openjdk.org/browse/JDK-8295414). This patch is a similar fix.
> 
> Same, `partialSubtypeCheck` uses `iRegP_R15` as a result while its use `iRegP`  doesn't match the `iRegP_R15`, causing this failure.
> 
> The details are in the JBS issue [JDK-8296771](https://bugs.openjdk.org/browse/JDK-8296771).
> 
> Tested the failed `compiler/types/TestSubTypeCheckMacroTrichotomy.java`, and a hotspot tier1 is running now.
> 
> Thanks,
> Xiaolin

Looks fine to me. I do wonder if there are similar lurking bugs with other `iRegP_*` that should probably also be part of `operand iRegP`; this limited fix is okay, though, as `riscv.ad` only has `iRegP_R15` and `iRegP_R10` as result registers in existing match rules.

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Marked as reviewed by shade (Reviewer).

PR: https://git.openjdk.org/jdk/pull/11085