RFR: 8290432: C2 compilation fails with assert(node->_last_del == _last) failed: must have deleted the edge just produced [v6]

[Yi Yang]

On Thu, 1 Dec 2022 08:23:41 GMT, Christian Hagedorn <chagedorn at openjdk.org> wrote:

> it does not seem wrong to replace 125 Phi - the only problem is that 465 CastII also happens to have 432 CountedLoop as control input. 

If replacing Phi#125 is acceptable, we need to reach a consensus that the form of `Add->CastII->Phi` can be considered as parallel IV, which is not valid before [JDK-8273585](https://bugs.openjdk.org/browse/JDK-8273585). Prior to that, we only considered variables of the form `X += constant`(`Add->Phi`) to be IV. 

Do we have such a consensus that the form of `Add->CastII->Phi` is considered as parallel IV? A conservative approach would be a compilation bailout, as this patch does.

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PR: https://git.openjdk.org/jdk/pull/9695