[X86] Add support for zeroed shuffle elements to getShuffleScalarElt

Enable handling of SM_SentinelZero shuffle elements to getShuffleScalarElt. Improves VZEXT_LOAD matches in EltsFromConsecutiveLoads.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@258865 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed