[C++11] More 'nullptr' conversion. In some cases just using a boolean check instead of comparing to nullptr.

llvm-svn: 206243
diff --git a/llvm/lib/Analysis/LoopPass.cpp b/llvm/lib/Analysis/LoopPass.cpp
index 38e753f..addff3e 100644
--- a/llvm/lib/Analysis/LoopPass.cpp
+++ b/llvm/lib/Analysis/LoopPass.cpp
@@ -61,8 +61,8 @@
   : FunctionPass(ID), PMDataManager() {
   skipThisLoop = false;
   redoThisLoop = false;
-  LI = NULL;
-  CurrentLoop = NULL;
+  LI = nullptr;
+  CurrentLoop = nullptr;
 }
 
 /// Delete loop from the loop queue and loop hierarchy (LoopInfo).