RFR: 8292638: x86: Improve scratch register handling in VM stubs [v9]

[Vladimir Ivanov]

On Tue, 23 Aug 2022 16:12:01 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> is_reachable_from vs is_always_reachable: these look like siblings, so they probably should both either have _from, or both skip it.

Agree. Once I removed current location argument, `_from` doesn't make any sense anymore.

> I don't see why would we need to do tmp /* rscratch */ comments everywhere, looks like noise.

I prefer to keep it for documentary purposes. IMO it clearly points at rip-relative addressing being at play here and hints that the address is not always reachable (which can be acted upon to eliminate the usage).

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PR: https://git.openjdk.org/jdk/pull/9932