RFR: 8373513: C2: Move ProjNode::other_if_proj() to IfProjNode [v2]

[Emanuel Peter]

On Wed, 17 Dec 2025 09:40:07 GMT, Christian Hagedorn <chagedorn at openjdk.org> wrote:

>> This is a simple clean-up patch which moves `ProjNode::other_if_proj()` to `IfProjNode` and update its uses. It only makes sense to call `other_if_proj()` on actual `IfProjNodes`.
>> 
>> It also required to update more types from `ProjNode` to `IfProjNode` which is more type-safe and preciser. While touching the methods, I've also added some `const`/`static` where appropriate.
>> 
>> Thanks,
>> Christian
>
> Christian Hagedorn has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:
> 
>  - Fix nullptr
>  - Merge branch 'master' into JDK-8373513
>  - 8373513: C2: Move ProjNode::other_if_proj() to IfProjNode

Marked as reviewed by epeter (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/28785#pullrequestreview-3586840594