RFR: 8268017: C2: assert(phi_type->isa_int() || phi_type->isa_ptr() || phi_type->isa_long()) failed: bad phi type

[Roland Westrelin]

PhiNode::Ideal() needs to support Cast nodes that were added recently.

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Commit messages:
 - test
 - fix

Changes: https://git.openjdk.java.net/jdk/pull/4409/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=4409&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8268017
  Stats: 131 lines in 5 files changed: 111 ins; 18 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4409.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4409/head:pull/4409

PR: https://git.openjdk.java.net/jdk/pull/4409