[jdk11u-dev] RFR: 8272570: C2: crash in PhaseCFG::global_code_motion

[Martin Doerr]

Clean backport of JDK-8272570.

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Commit messages:
 - Backport 0f428ca533627e758cdca599d4589f39c21e27b6

Changes: https://git.openjdk.java.net/jdk11u-dev/pull/462/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk11u-dev&pr=462&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8272570
  Stats: 55 lines in 2 files changed: 53 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk11u-dev/pull/462.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk11u-dev pull/462/head:pull/462

PR: https://git.openjdk.java.net/jdk11u-dev/pull/462