[DAG] Move DAGCombiner::GetDemandedBits to SelectionDAG

This patch moves the DAGCombiner::GetDemandedBits function to SelectionDAG::GetDemandedBits as a first step towards making it easier for targets to get to the source of any demanded bits without the limitations of SimplifyDemandedBits.

Differential Revision: https://reviews.llvm.org/D35841

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@308983 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed