Add basic verification of LiveIntervals.

We verify that the LiveInterval is live at uses and defs, and that all
instructions have a SlotIndex.

Stuff we don't check yet:

- Is the LiveInterval minimal?
- Do all defs correspond to instructions or phis?
- Do all defs dominate all their live ranges?
- Are all live ranges continually reachable from their def?

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@110386 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed