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

[Roland Westrelin]

On Wed, 23 Aug 2023 07:23:56 GMT, Christian Hagedorn <chagedorn 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!

@chhagedorn @TobiHartmann thanks for the review.

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PR Comment: https://git.openjdk.org/jdk/pull/15380#issuecomment-1689560016