[jdk11u-dev] RFR: 8277529: SIGSEGV in C2 CompilerThread Node::rematerialize() compiling Packet::readUnsignedTrint

[Vladimir Kempik]

Almost clean backport to jdk11u-dev.
only one piece of patch failed to apply cleanly in loopPredicate.cpp due to difference in context code
the included testcase fails before patch and passes after

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Commit messages:
 - 8277529: SIGSEGV in C2 CompilerThread Node::rematerialize() compiling Packet::readUnsignedTrint

Changes: https://git.openjdk.java.net/jdk11u-dev/pull/692/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk11u-dev&pr=692&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8277529
  Stats: 173 lines in 3 files changed: 161 ins; 7 del; 5 mod
  Patch: https://git.openjdk.java.net/jdk11u-dev/pull/692.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk11u-dev pull/692/head:pull/692

PR: https://git.openjdk.java.net/jdk11u-dev/pull/692