[DAGCombiner] split trunc from extend in hoistLogicOpWithSameOpcodeHands; NFC

This duplicates several shared checks, but we need to split
this up to fix underlying bugs in smaller steps.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@348627 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed