RFR: 8294197: Zero: JVM_handle_linux_signal should not assume deopt NOPs

[Coleen Phillimore]

On Thu, 22 Sep 2022 09:45:22 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> This is a simple regression from Loom added code. In `JVM_handle_linux_signal` there is a new block that handles deopt NOPs. Zero does not have them, and so it currently encounters `ShouldNotReachHere()` when entering the block and doing either `os::Posix::ucontext_get_pc(uc)` or `NativeDeoptInstruction::is_deopt_at(pc)`.
> 
> This block should not be entered with Zero at all. 
> 
> Additional testing:
>  - [x] Artificially crashing Linux x86_64 Zero fastdebug now produces a sensible hs_err

Looks good plus trivial.

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Marked as reviewed by coleenp (Reviewer).

PR: https://git.openjdk.org/jdk/pull/10389