Use SmallVectorImpl& instead of SmallVector to avoid repeating small vector size.

llvm-svn: 186098
diff --git a/llvm/lib/CodeGen/LiveInterval.cpp b/llvm/lib/CodeGen/LiveInterval.cpp
index 861e99b..6be6bf3 100644
--- a/llvm/lib/CodeGen/LiveInterval.cpp
+++ b/llvm/lib/CodeGen/LiveInterval.cpp
@@ -415,7 +415,7 @@
 void LiveInterval::join(LiveInterval &Other,
                         const int *LHSValNoAssignments,
                         const int *RHSValNoAssignments,
-                        SmallVector<VNInfo*, 16> &NewVNInfo,
+                        SmallVectorImpl<VNInfo *> &NewVNInfo,
                         MachineRegisterInfo *MRI) {
   verify();