RFR: 8260653: Unreachable nodes keep speculative types alive

[Nils Eliasson]

8260653: Unreachable nodes keep speculative types alive

-------------

Commit messages:
 - Remove useless nodes

Changes: https://git.openjdk.java.net/jdk/pull/2606/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=2606&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8260653
  Stats: 3 lines in 1 file changed: 3 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2606.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2606/head:pull/2606

PR: https://git.openjdk.java.net/jdk/pull/2606