RFR: 8313262: C2: Sinking node may cause required cast to be dropped

[Tobias Hartmann]

On Tue, 22 Aug 2023 07:29:13 GMT, Roland Westrelin <roland at openjdk.org> wrote:

> When a node is sunk out of a loop a cast node is created to pin the
> node out of the loop. When a chain of nodes is sunk, we don't want a
> cast node per node in the chain but rather one to pin the last of the
> chain. So the logic for sinking nodes looks for unneeded cast
> nodes. The test for what makes a cast unneeded is incorrect and causes
> a cast to not null to be wrongly removed.

Looks good to me too. All tests passed.

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Marked as reviewed by thartmann (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/15380#pullrequestreview-1590984275