Extend -new-coalescer SSA update to handle mapped values as well.
The old-fashioned many-to-one value mapping doesn't always work when
merging vector lanes. A value can map to multiple different values, and
it can even be necessary to insert new PHIs.
When a value number is defined by a copy from a value number that
required SSa update, include the live range of the copied value number
in the SSA update as well. It is not necessarily a copy of the original
value number any longer.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@164329
91177308-0d34-0410-b5e6-
96231b3b80d8