RFR: 8253566: clazz.isAssignableFrom will return false for interface implementors [v2]

[Roland Westrelin]

> The code pattern in the test case is optimized as a trichotomy which
> is wrong given SubTypeCheckNode is a special kind of CmpNode that's
> not commutative.

Roland Westrelin has updated the pull request with a new target base due to a merge or a rebase. The pull request now
contains three commits:

 - comment
 - test
 - trichotomy opt should not be applied to subtype check

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

Changes: https://git.openjdk.java.net/jdk/pull/422/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=422&range=01
  Stats: 71 lines in 2 files changed: 70 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/422.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/422/head:pull/422

PR: https://git.openjdk.java.net/jdk/pull/422