RFR: 8257498: Remove useless skeleton predicates

[Roland Westrelin]

On Thu, 14 Jan 2021 08:14:18 GMT, Christian Hagedorn <chagedorn at openjdk.org> wrote:

> This enhancement removes useless skeleton predicates in the same way as we already remove normal useless predicates in `PhaseIdealLoop::eliminate_useless_predicates()`.
> 
> Thanks,
> Christian

Changes requested by roland (Reviewer).

src/hotspot/share/opto/loopnode.cpp line 3560:

> 3558: 
> 3559:     if (UseLoopPredicate) {
> 3560:       predicate = find_predicate_insertion_point(entry, Deoptimization::Reason_predicate);

Don't we need to do this for Deoptimization::Reason_profile_predicate as well?

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PR: https://git.openjdk.java.net/jdk/pull/2075