[jdk11u-dev] RFR: 8279837: C2: assert(is_Loop()) failed: invalid node class: Region

[Martin Doerr]

Clean backport of JDK-8279837.

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Commit messages:
 - Backport 65eb066b630b892f22492457e0f86165e5ef4765

Changes: https://git.openjdk.java.net/jdk11u-dev/pull/862/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk11u-dev&pr=862&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8279837
  Stats: 87 lines in 2 files changed: 87 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk11u-dev/pull/862.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk11u-dev pull/862/head:pull/862

PR: https://git.openjdk.java.net/jdk11u-dev/pull/862