RFR: Full region promotion

[William Kemper]

On Mon, 4 Oct 2021 16:50:53 GMT, Kelvin Nilsen <kdnilsen at openjdk.org> wrote:

>> Wouldn't we need to change how `end_of_range` is computed for humongous starts?
>
> That's a good catch.  I'm a bit inconsistent with this.  I think this is "harmless" because end_of_range does not limit the scanning within a single humongous object.  It only limits the search for the "next object" following an initially scanned object.  I agree I should fix this up to make the code less confusing.  (Do you agree that the error is "harmless as is"?   Would appreciate your careful eyes on this.)

`end_of_range` is used earlier to compute the `count` parameter (which is named `num_clusters` in the calling function). As I read it, this _does_ limit the number of cards scanned in the `process_clusters` call.

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PR: https://git.openjdk.java.net/shenandoah/pull/75