[SelectionDAG] Add FSHL/FSHR support to computeKnownBits

Also exposes an issue in DAGCombiner::visitFunnelShift where we were assuming the shift amount had the result type (after legalization it'll have the targets shift amount type).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@349298 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed