[InstCombine] rearrange shuffle+binop fold; NFC

This code has a bug dealing with undefs, so we need
to add another escape hatch, so doing some cleanup
ahead of that.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@348175 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed