Regunit live ranges are computed on demand, so when mi-sched calls
handleMove, some regunits may not have live ranges yet.
That makes updating them easier: Just skip the non-existing ranges. They
will be computed correctly from the rescheduled machine code when they
are needed.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@158831 91177308-0d34-0410-b5e6-96231b3b80d8