8388361: [lworld] C2 hits node limit during scalarization in safepoints

[TobiHartmann]

This PR replaces the Valhalla draft PR 2652, which was already reviewed by @marc-chevalier and @fparain but was not integrated due to the code freeze immediately before the Valhalla mainline integration.

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During scalarization of an inline type in a large number of safepoints, we hit the node limit. This only happens in extreme cases where the test generates a large number of live locals and safepoints + -XX:+DeoptimizeALot which marks every local live at every safepoint. In the regression test, we have 60 safepoints, each one with 100 live Integers, and end up creating 6000 new SafePointScalarObjectNode.

The fix is to check the node budget and bail out from compilation if it's exceeded. Alternatively, we could fall back to use_oop = true if allow_oop is set and the inline type is allocated. However, I don't think that's worth it for this edge case.

Thanks,
Tobias

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Issue

• JDK-8388361: [lworld] C2 hits node limit during scalarization in safepoints (Bug - P4)

Reviewers

• Marc Chevalier (@marc-chevalier - Committer)

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[TobiHartmann]

Thanks again for the review Marc!