[jdk8u-dev] RFR: 8071996: split_if accesses NULL region of ConstraintCast

[Roland Westrelin]

Applies cleanly. Tested with tier1.

A customer reported a crash that's likely this bug. The fix is low risk. I propose we backport it.

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Commit messages:
 - Backport d4d8ef4585c1c6192fe35524faa6c6961d1e7a64

Changes: https://git.openjdk.org/jdk8u-dev/pull/649/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk8u-dev&pr=649&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8071996
  Stats: 12 lines in 1 file changed: 8 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk8u-dev/pull/649.diff
  Fetch: git fetch https://git.openjdk.org/jdk8u-dev.git pull/649/head:pull/649

PR: https://git.openjdk.org/jdk8u-dev/pull/649