RFR: 8314233: C2: assert(assertion_predicate_has_loop_opaque_node(iff)) failed: unexpected

[Christian Hagedorn]

In the testcase, we try to initialize Assertion Predicates from the templates which have an `Opaque4` node. However, the code finds an unrelated `Opaque4` node added by an intrinsic. This, obviously, will not guard any `OpaqueLoop*` nodes required for Template Assertion Predicates and we fail with the assertion.

While splitting some changes away from the main fix of [JDK-8288981](https://bugs.openjdk.org/browse/JDK-8288981) for [JDK-8305636](https://bugs.openjdk.org/browse/JDK-8305636), I wrongly removed the check in loop peeling if an `Opaque4` node belongs to an `If` that also shares the uncommon trap with the Parse Predicate (this is not required in the main fix anymore because Template Assertion Predicates will always only have `HaltNodes` - but optimizing this here is wrong/too early).

The fix re-establishes the check for the uncommon trap.

Thanks,
Christian

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Commit messages:
 - Add new line at end of test
 - 8314233: C2: assert(assertion_predicate_has_loop_opaque_node(iff)) failed: unexpected

Changes: https://git.openjdk.org/jdk/pull/15290/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15290&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8314233
  Stats: 69 lines in 2 files changed: 68 ins; 1 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/15290.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15290/head:pull/15290

PR: https://git.openjdk.org/jdk/pull/15290