8388858: C2: Add UseLoopLimitCheckPredicate and UseParsePredicates flags

[chhagedorn]

We have flag switches for all predicates - except for Loop Limit Check Predicates. It is sometimes useful to also disable these for debugging or testing purposes to not create a Parse Predicate for them which means that we cannot create Loop Limit Check Predicates.

With that in place, it would also be useful to disable all Parse Predicates together. This is especially useful for debugging to simplify a graph. But it's also useful to simulate a situation where no Parse Predicates remain above a loop head. This could happen, for example, when partially peeling a loop (the Parse Predicates are above the partially peeled section and not above the loop head anymore and are thus removed) or when we trapped already and then no longer emit a Parse Predicate.

This patch proposes both flags:

• UseLoopLimitCheckPredicate: Disable Loop Limit Check Predicate creation.
• UseParsePredicates: Disables all Parse Predicates from being emitted.
  • When setting this flag to false, I automatically set all the other predicate enabling flags to false and emit a warning.
  • When setting all predicate enabling flags to false, I automatically set UseParsePredicates to false as well and emit a warning.

Testing:

• t1-4+hs-comp-stress, default
• t1-4+hs-comp-stress, -XX:-UseParsePredicates, --enable-preview
• t1-4+hs-comp-stress, -XX:-UseParsePredicates (found a reproducer for JDK-8388490)
• t1-4+hs-comp-stress, -XX:-UseLoopLimitCheckPredicate

Thanks,
Christian

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Issue

• JDK-8388858: C2: Add UseLoopLimitCheckPredicate and UseParsePredicates flags (Enhancement - P4)

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[bridgekeeper]

👋 Welcome back chagedorn! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

[chhagedorn]

Needed to update this test, otherwise, it takes forever and times out.

[chhagedorn]

Git wrongly did a remove + add here while it's just a rename.

[chhagedorn]

Added more variants here and strengthened the IR rules to check all parse predicates.

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