[X86][SSE] Add SimplifyDemandedBitsForTargetNode handling for MOVMSK

Moves existing SimplifyDemandedBits call out of combineMOVMSK and add SimplifyDemandedVectorElts call based on the sign bits we need.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@348282 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed