JDK-8251994 changes excluded optimization added by JDK-8076284. It is incomplete and buggy in current state.

Using unrolling and cloning information to vectorize is interesting idea but as I see it is not complete. Even if pack_parallel() method is able create packs, they are all removed by filter_packs() method. And additionally the cases listed in RFR are vectorized without hoisting loads and pack_parallel - I verified it:
https://mail.openjdk.java.net/pipermail/hotspot-compiler-dev/2015-April/017645.html

This code should be revisited to be useful or removed.