RFR: 8296440: Remove Method* handling from cleanup_inline_caches_impl

[Richard Reingruber]

On Wed, 1 Mar 2023 11:07:36 GMT, Richard Reingruber <rrich at openjdk.org> wrote:

> This PR replaces cleaning of static stubs in CompiledMethod::cleanup_inline_caches_impl() with a guarantee that it is actually not needed because the holder of the embedded target Method* is alive if the caller nmethod is not unloading.
> 
> The holder of the target Method* has to be alive because it is reachable from the caller nmethod's oop pool. This is checked by `check_path_to_callee()` when a statically bound call gets resolved.
> 
> C2i entry barriers can be removed for the same reason.
> 
> Testing:
> 
> Many rounds in our CI testing which includes most JCK and JTREG tests, Renaissance benchmark and SAP specific tests with fastdebug and release builds on the standard platforms plus PPC64.
> 
> I've also done tier1 and tier2 tests with -XX:-Inline and tier1 tests with ZGC.
> 
> I've started hotspot and jdk tier1 tests with -Xcomp. They were not finished when I stopped them after 24h.

Seems to be independen of `relocInfo::mustIterateImmediateOopsInCode()` then because on aarch64 it is false. Still this is a good point. The verification code should better use `nmethod::oops_do()`.

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PR: https://git.openjdk.org/jdk/pull/12802