RFR: 8255936: "parsing found no loops but there are some" assertion failure with Shenandoah

[Roland Westrelin]

On Tue, 17 Nov 2020 13:47:25 GMT, Roland Westrelin <roland at openjdk.org> wrote:

>> hi, @rwestrel  
>> 
>> Can we have an assertion to make this loop invariant more prominent? 
>> `I think the cleaner fix is to preserve the invariant that the never branch is always right after the loop head in an infinite loop. `
>
>> Can we have an assertion to make this loop invariant more prominent?
>> `I think the cleaner fix is to preserve the invariant that the never branch is always right after the loop head in an infinite loop. `
> 
> Thanks for the suggestion. Actually I reworked the fix so it has nothing to do with the previous one.

I pushed a new fix that's different from the previous one. I realized that NeverBranchNode::Ideal() should remove the NeverBranch once the barrier is expanded but we don't run igvn after barrier expansion which is a mistake.

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PR: https://git.openjdk.java.net/jdk/pull/1073