Optimize checkAssignableTo to avoid clone when stackSize is 0, and use clone instead of Array.copyOf to avoid compression and then expansion
------------- Commit messages: - suggestion from @liach - optimize checkAssignableTo Changes: https://git.openjdk.org/jdk/pull/21121/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21121&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8340587 Stats: 7 lines in 1 file changed: 4 ins; 0 del; 3 mod Patch: https://git.openjdk.org/jdk/pull/21121.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/21121/head:pull/21121 PR: https://git.openjdk.org/jdk/pull/21121
