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

llvm-svn: 207197
diff --git a/llvm/lib/Target/NVPTX/NVPTXTargetMachine.cpp b/llvm/lib/Target/NVPTX/NVPTXTargetMachine.cpp
index 2226627..97dbde9 100644
--- a/llvm/lib/Target/NVPTX/NVPTXTargetMachine.cpp
+++ b/llvm/lib/Target/NVPTX/NVPTXTargetMachine.cpp
@@ -175,7 +175,7 @@
 }
 
 FunctionPass *NVPTXPassConfig::createTargetRegisterAllocator(bool) {
-  return 0; // No reg alloc
+  return nullptr; // No reg alloc
 }
 
 void NVPTXPassConfig::addFastRegAlloc(FunctionPass *RegAllocPass) {