A value that is live in to a basic block should be returned by valueIn()
in LiveRangeQuery(getMBBStartIdx(MBB)), unless it is a PHI-def which
should be returned by valueDefined() instead.
Current code isn't using this functionality. Future code will.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@163990 91177308-0d34-0410-b5e6-96231b3b80d8