RFR: 8338341: GenShen: Cleanup headers, unreachable code and unintentional changes

[Kelvin Nilsen]

On Tue, 13 Aug 2024 23:49:12 GMT, William Kemper <wkemper at openjdk.org> wrote:

> This PR covers a number of small changes to address comments on https://github.com/openjdk/jdk/pull/20395

Marked as reviewed by kdnilsen (Committer).

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PR Review: https://git.openjdk.org/shenandoah/pull/468#pullrequestreview-2236870098