[jdk11u-dev] RFR: 8286177: C2: "failed: non-reduction loop contains reduction nodes" assert failure

[Goetz Lindenmaier]

I backport this for parity with 11.0.17-oracle.

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Commit messages:
 - Backport caceaba5594606023ea4eb8d99698243be5b76b8
 - Backport 47e478d6de40038d48290ac1b64a4957a77a397a

Changes: https://git.openjdk.org/jdk11u-dev/pull/1195/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=1195&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8286177
  Stats: 100 lines in 5 files changed: 100 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/1195.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev pull/1195/head:pull/1195

PR: https://git.openjdk.org/jdk11u-dev/pull/1195