389704cc60
We got some of the potential optimizations with D76727 and D76844. There are 2 likely enhancements that we could add to -vector-combine to get most of the remaining cases: 1. Allow bitcasted shuffle mask narrowing (widen the elements). 2. Combine shuffle-of-shuffle into a single shuffle. This is already partly handled by the x86 backend, but the tests here show that we still miss some of the potential combines.