RFR: 8265132 : C2 compilation fails with assert "missing precedence edge"

[Jamsheed Mohammed C M]

Issue is similar to https://bugs.openjdk.java.net/browse/JDK-8261730
but happens at next https://github.com/jamsheedcm/jdk/blob/master/src/hotspot/share/opto/gcm.cpp#L830

Request for review

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Commit messages:
 - fix for C2 compilation fails with assert missing precedence edge
 - Merge branch 'openjdk:master' into master
 - Merge pull request #5 from openjdk/master
 - Merge branch 'master' of https://github.com/jamsheedcm/jdk
 - Merge pull request #4 from openjdk/master
 - Merge branch 'master' of https://github.com/jamsheedcm/jdk
 - Merge pull request #3 from openjdk/master
 - Merge branch 'master' of https://github.com/jamsheedcm/jdk
 - Merge pull request #2 from openjdk/master
 - Merge branch 'master' of https://github.com/jamsheedcm/jdk
 - ... and 1 more: https://git.openjdk.java.net/jdk/compare/9eaa4afc...5a857f86

Changes: https://git.openjdk.java.net/jdk/pull/4200/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=4200&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8265132
  Stats: 59 lines in 3 files changed: 38 ins; 16 del; 5 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4200.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4200/head:pull/4200

PR: https://git.openjdk.java.net/jdk/pull/4200