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

llvm-svn: 206252

llvm/lib/IR/BasicBlock.cpp

@@ -81,7 +81,7 @@ BasicBlock::~BasicBlock() {
     }
   }
 
-  assert(getParent() == 0 && "BasicBlock still linked into the program!");
+  assert(getParent() == nullptr && "BasicBlock still linked into the program!");
   dropAllReferences();
   InstList.clear();
 }