This patch removes function 'CommuteVectorShuffle' from X86ISelLowering.cpp
and moves its logic into SelectionDAG.cpp as method 'getCommutedVectorShuffles'.
This refactoring is in preperation of an upcoming change to the DAGCombiner.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213503 91177308-0d34-0410-b5e6-96231b3b80d8