RFR: 8329661: Refactor ScavengableNMethods::verify_unlisted_nmethods

[Albert Mingkun Yang]

On Thu, 4 Apr 2024 11:28:17 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

> Simple removing redundant verification.

The real diff is in `ScavengableNMethods::verify_unlisted_nmethods`. The removed closure checks nmethods that are "not on-list" don't have old-to-young pointers. The same checking is already covered in `ScavengableNMethods::verify_nmethod`, which is invoked on all "live" (i.e. not unlinked) nmethods.

> I'm a little worried that this relies on the verify_nmethod call here:

In the Serial case, `ScavengableNMethods::prune_unlinked_nmethods` is used to cover the assert.

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PR Comment: https://git.openjdk.org/jdk/pull/18621#issuecomment-2037186304