Use getVNInfoBefore() when it makes sense.

llvm-svn: 144517
diff --git a/llvm/lib/CodeGen/SplitKit.cpp b/llvm/lib/CodeGen/SplitKit.cpp
index 6c46d53..751d604 100644
--- a/llvm/lib/CodeGen/SplitKit.cpp
+++ b/llvm/lib/CodeGen/SplitKit.cpp
@@ -586,7 +586,7 @@
 void SplitEditor::overlapIntv(SlotIndex Start, SlotIndex End) {
   assert(OpenIdx && "openIntv not called before overlapIntv");
   const VNInfo *ParentVNI = Edit->getParent().getVNInfoAt(Start);
-  assert(ParentVNI == Edit->getParent().getVNInfoAt(End.getPrevSlot()) &&
+  assert(ParentVNI == Edit->getParent().getVNInfoBefore(End) &&
          "Parent changes value in extended range");
   assert(LIS.getMBBFromIndex(Start) == LIS.getMBBFromIndex(End) &&
          "Range cannot span basic blocks");