fix comment

There's no 'B3' in the example.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190167 91177308-0d34-0410-b5e6-96231b3b80d8
remove pointless assert

The if above it ensures the property anyway.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190168 91177308-0d34-0410-b5e6-96231b3b80d8
remove unused argument from LiveRanges::join()

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190169 91177308-0d34-0410-b5e6-96231b3b80d8
avoid unnecessary direct access to LiveInterval::ranges

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190170 91177308-0d34-0410-b5e6-96231b3b80d8