[jdk11u-dev] RFR: 8293996: C2: fix and simplify IdealLoopTree::do_remove_empty_loop [v3]

[Goetz Lindenmaier]

> I backport this for parity with 11.0.19-oracle.
> 
> Resolved Copyright in test file, will mark as clean.

Goetz Lindenmaier has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains two additional commits since the last revision:

 - Merge branch 'openjdk:master' into goetz_backport_8293996
 - Backport dd51f7e0b75d3a16403608d89cd206ac0bedf882

-------------

Changes:
  - all: https://git.openjdk.org/jdk11u-dev/pull/1628/files
  - new: https://git.openjdk.org/jdk11u-dev/pull/1628/files/3cfeeb57..6bc61143

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=1628&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=1628&range=01-02

  Stats: 80 lines in 9 files changed: 68 ins; 0 del; 12 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/1628.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev pull/1628/head:pull/1628

PR: https://git.openjdk.org/jdk11u-dev/pull/1628