RFR: 8355230: Crash in fuzzer tests: assert(n != nullptr) failed: must not be null

[Roland Westrelin]

On Tue, 20 May 2025 09:00:08 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

> How do we get to this case that the `phi->in(j) != nullptr` but `region->in(j) == nullptr`?

The `Region` is cleared by `RegionNode::Ideal` at parse time because it was initialized to `top`. When the crash occurs, the `Region` is enqueued for igvn but not yet processed. `RegionNode::Ideal` has logic to remove the null inputs and update the `Phi`s but it only runs during igvn.

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PR Comment: https://git.openjdk.org/jdk/pull/25268#issuecomment-2893726576