RFR: 8290965: PPC64: Implement post-call NOPs [v2]

[Richard Reingruber]

On Wed, 10 Jan 2024 15:19:38 GMT, Richard Reingruber <rrich at openjdk.org> wrote:

> Is this one performance critical?

This is a good question. Honestly I have difficulties understanding why PCNs should be performance critical at all. AFAIK  frames are only iterated on the slow path when freezing/thawing. Maybe the slow path is not that uncommen, e.g. if StackChunks are visited by GC.
I wanted to use `kind::nmethod` as default whenever possible in order not to miss a place that actually is performance critical.
See also https://github.com/openjdk/jdk/pull/8955#issuecomment-1142317441

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PR Review Comment: https://git.openjdk.org/jdk/pull/17171#discussion_r1447580465