8361702: C2: assert(is_dominator(compute_early_ctrl(limit, limit_ctrl), pre_end)) failed: node pinned on loop exit test?

[rwestrel]

A node in a pre loop only has uses out of the loop dominated by the
loop exit. PhaseIdealLoop::try_sink_out_of_loop() sets its control
to the loop exit projection. A range check in the main loop has this
node as input (through a chain of some other nodes). Range check
elimination needs to update the exit condition of the pre loop with an
expression that depends on the node pinned on its exit: that's
impossible and the assert fires. This is a variant of 8314024 (this
one was for a node with uses out of the pre loop on multiple paths). I
propose the same fix: leave the node with control in the pre loop in
this case.

---

Progress

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Issue

• JDK-8361702: C2: assert(is_dominator(compute_early_ctrl(limit, limit_ctrl), pre_end)) failed: node pinned on loop exit test? (Bug - P3)

Reviewers

• Christian Hagedorn (@chhagedorn - Reviewer) 🔄 Re-review required (review applies to 8abae076)

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[bridgekeeper]

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[openjdk]

@rwestrel This change is no longer ready for integration - check the PR body for details.

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[mlbridge]

Webrevs

• 01: Full - Incremental (2140c98d)
• 00: Full (8abae076)

[chhagedorn]

Some small comments, otherwise, looks good! I launched some testing.

Somehow forgot to submit my review from 2 days ago...