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

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206142 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/SpillPlacement.cpp

@@ -218,7 +218,7 @@ bool SpillPlacement::runOnMachineFunction(MachineFunction &mf) {
 
 void SpillPlacement::releaseMemory() {
   delete[] nodes;
-  nodes = 0;
+  nodes = nullptr;
 }
 
 /// activate - mark node n as active if it wasn't already.
@@ -393,6 +393,6 @@ SpillPlacement::finish() {
       ActiveNodes->reset(n);
       Perfect = false;
     }
-  ActiveNodes = 0;
+  ActiveNodes = nullptr;
   return Perfect;
 }