RFR: 8252696: Loop unswitching may cause out of bound array load to be executed

[Roland Westrelin]

Review thread so far: https://mail.openjdk.java.net/pipermail/hotspot-compiler-dev/2020-September/039853.html

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Commit messages:
 - Loop unswitching may cause out of bound array load to be executed

Changes: https://git.openjdk.java.net/jdk/pull/176/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=176&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8252696
  Stats: 24 lines in 3 files changed: 1 ins; 6 del; 17 mod
  Patch: https://git.openjdk.java.net/jdk/pull/176.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/176/head:pull/176

PR: https://git.openjdk.java.net/jdk/pull/176