[C++11] Use nullptr

llvm-svn: 206361
diff --git a/polly/lib/Analysis/ScopDetection.cpp b/polly/lib/Analysis/ScopDetection.cpp
index c4935bf..e3ed267 100644
--- a/polly/lib/Analysis/ScopDetection.cpp
+++ b/polly/lib/Analysis/ScopDetection.cpp
@@ -468,7 +468,7 @@
 
 Region *ScopDetection::expandRegion(Region &R) {
   // Initial no valid region was found (greater than R)
-  Region *LastValidRegion = NULL;
+  Region *LastValidRegion = nullptr;
   Region *ExpandedRegion = R.getExpandedRegion();
 
   DEBUG(dbgs() << "\tExpanding " << R.getNameStr() << "\n");