RFR: JDK-8272574: Crashes in PhaseIdealLoop::build_loop_late_post_work [v2]

[Dean Long]

On Tue, 17 Aug 2021 12:42:49 GMT, 王超 <github.com+25214855+casparcwang at openjdk.org> wrote:

>> Current loop predication will promote nodes(with a dependency on a later control node) to the insertion point which dominates the later control node.
>> 
>> In the following example, loopPrediction will promote node 434 to the outer loop(predicted insert point is right after node 424), and it depends on control node 207.  But node 424 dominates node 207, which means after the promotion, the cloned nodes have a control dependency on a later control node, which leads to a bad graph.
>> 
>> ![image](https://user-images.githubusercontent.com/25214855/129720970-ff65b8f4-8bef-401d-8590-54aca6de470e.png)
>> 
>> ![image](https://user-images.githubusercontent.com/25214855/129721369-4c61222b-7305-4522-9a37-e3e6e2138aa9.png)
>
> 王超 has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Fix version

We have two other bugs failing with the same assert: JDK-8272562 and JDK-8271954.  Could they be related?

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PR: https://git.openjdk.java.net/jdk/pull/5142