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

lib/CodeGen/LiveIntervalAnalysis.cpp

@@ -742,9 +742,6 @@ void LiveIntervals::extendToIndices(LiveInterval *LI,
 void LiveIntervals::pruneValue(LiveInterval *LI, SlotIndex Kill,
                                SmallVectorImpl<SlotIndex> *EndPoints) {
   LiveRangeQuery LRQ(*LI, Kill);
-  assert (!LRQ.valueDefined() && "Can't prune value at the defining instr");
-
-  // Also can't prune a value that isn't there.
   VNInfo *VNI = LRQ.valueOut();
   if (!VNI)
     return;