[C++] Use 'nullptr'. Target edition.

llvm-svn: 207197
diff --git a/llvm/lib/Target/SystemZ/SystemZElimCompare.cpp b/llvm/lib/Target/SystemZ/SystemZElimCompare.cpp
index 8f3eef1..cb17897 100644
--- a/llvm/lib/Target/SystemZ/SystemZElimCompare.cpp
+++ b/llvm/lib/Target/SystemZ/SystemZElimCompare.cpp
@@ -64,7 +64,7 @@
 public:
   static char ID;
   SystemZElimCompare(const SystemZTargetMachine &tm)
-    : MachineFunctionPass(ID), TII(0), TRI(0) {}
+    : MachineFunctionPass(ID), TII(nullptr), TRI(nullptr) {}
 
   const char *getPassName() const override {
     return "SystemZ Comparison Elimination";