RFR: 8343148: C2: Refactor uses of "PhaseValue::*con*() + PhaseIdealLoop::set_ctrl()" into separate method

[theoweidmannoracle]

On Tue, 5 Nov 2024 18:20:58 GMT, Vladimir Kozlov <kvn at openjdk.org> wrote:

> Do we have other places (not new constant node) where we set Root as control? May be we can add `set_root_as_ctrl(n)` method in `loop node.hpp` in such case.

There's only three locations where control is set to the root in the loop files now (not counting the ones in the new methods I added). The main reason for this patch is bugs caused by people forgetting to set control for constants (e.g. https://bugs.openjdk.org/browse/JDK-8343137), which is now prevented if the new helper methods are used.

Do you think there would be any benefit from introducing `set_root_as_ctrl(n)` given there's only about three places where this pattern occurs now?

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PR Comment: https://git.openjdk.org/jdk/pull/21836#issuecomment-2461576384