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

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@205831 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Pass.h

@@ -87,7 +87,8 @@ class Pass {
   Pass(const Pass &) LLVM_DELETED_FUNCTION;
 
 public:
-  explicit Pass(PassKind K, char &pid) : Resolver(0), PassID(&pid), Kind(K) { }
+  explicit Pass(PassKind K, char &pid)
+    : Resolver(nullptr), PassID(&pid), Kind(K) { }
   virtual ~Pass();