[8u] RFR: 8134739: compiler/loopopts/superword/TestVectorizationWithInvariant crashes in loop opts

[Roland Westrelin]

> Change does not apply cleanly to 8u but can be trivially adapted:
>
> http://cr.openjdk.java.net/~roland/8134739.8u/webrev.00/
>
> Initial change:
>
> https://bugs.openjdk.java.net/browse/JDK-8134739
> http://hg.openjdk.java.net/jdk9/jdk9/hotspot/rev/6d9d273e7f0d
>
> Tested with tier1.

Anyone for this review?

Roland.