RFR: 8305637: Remove Opaque1 nodes for Parse Predicates and clean up useless predicate elimination [v2]

[Christian Hagedorn]

On Wed, 30 Aug 2023 14:54:37 GMT, Christian Hagedorn <chagedorn at openjdk.org> wrote:

>> src/hotspot/share/opto/multnode.cpp line 226:
>> 
>>> 224: 
>>> 225:   // we need a ParsePredicate node for predicate reasons
>>> 226:   if (reason != Deoptimization::Reason_none && !iff->is_ParsePredicate()) {
>> 
>> Unrelated to your change but this code doesn't seem to do what the comment says. `reason != Deoptimization::Reason_none` is not "predicate reasons". I think this needs to be cleaned up at some point.
>
> You're right. I've had a look at all the usages if `is_uncommon_trap_if_pattern()` and it seems that we only use this method for `Reason_none. So, I think I can simplify this method. I can do it in this PR as I'm touching this code here.

Okay, I've missed one usage which is not `Deoptimization::Reason` - but let me still have a look if I can clean this method up somehow.

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PR Review Comment: https://git.openjdk.org/jdk/pull/15449#discussion_r1310442185