[jdk11u-dev] RFR: 8223363: Bad node estimate assertion failure

[Martin Doerr]

Backport of [JDK-8223363](https://bugs.openjdk.java.net/browse/JDK-8223363) (including [JDK-8223502](https://bugs.openjdk.java.net/browse/JDK-8223502) and [JDK-8224648](https://bugs.openjdk.java.net/browse/JDK-8224648) as in original commit)
loopTransform.cpp (introduction of `policy_unswitching` and `policy_maximally_unroll`) and loopnode.hpp required manual integration. Rest applies cleanly.

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Commit messages:
 - Backport d222b01dee09f9963a3a0c7ae0088b64752b7809

Changes: https://git.openjdk.java.net/jdk11u-dev/pull/874/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk11u-dev&pr=874&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8223363
  Stats: 443 lines in 6 files changed: 310 ins; 37 del; 96 mod
  Patch: https://git.openjdk.java.net/jdk11u-dev/pull/874.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk11u-dev pull/874/head:pull/874

PR: https://git.openjdk.java.net/jdk11u-dev/pull/874