RFR: 8294053: Unneeded local variable in handle_safefetch()

[Aleksey Shipilev]

On Thu, 22 Sep 2022 08:21:53 GMT, David Holmes <dholmes at openjdk.org> wrote:

> > and is initialized to the same value as is passed into the handle_safefetch() function by its callers.
> 
> Took me a bit to check that due to some confusing logic around SIGILL and SIGFPE handling. But I'm not clear about what will happen on Zero - it will always pass a pc of NULL where currently we will get it from `ucontext_get_pc(uc)`.

On Zero, `os::Posix::ucontext_get_pc(uc)` would fail with `ShouldNotReachHere()`, so this patch does not make it worse. `JVM_HANDLE_XXX_SIGNAL` makes a special provision for Zero by always taking `pc = NULL` route.  Zero signal handling fell victim to last years POSIX signal refactorings, and I still have it in my TODO to try and revive it. In fact, I am not even sure safefetch ever worked with Zero.

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PR: https://git.openjdk.org/jdk/pull/10373