[InstCombine][AVX-512] Expand vector shift handling to work on the AVX-512 shift by immediate and shift by single value.

This does not include support for the AVX-512 variable shifts. That will be coming in a future patch.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@286739 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed