[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/ADT/ArrayRef.h

@@ -49,7 +49,7 @@ namespace llvm {
     /// @{
 
     /// Construct an empty ArrayRef.
-    /*implicit*/ ArrayRef() : Data(0), Length(0) {}
+    /*implicit*/ ArrayRef() : Data(nullptr), Length(0) {}
 
     /// Construct an empty ArrayRef from None.
     /*implicit*/ ArrayRef(NoneType) : Data(nullptr), Length(0) {}

include/llvm/ADT/DenseMap.h

@@ -985,7 +985,7 @@ public:
 private:
   pointer Ptr, End;
 public:
-  DenseMapIterator() : Ptr(0), End(0) {}
+  DenseMapIterator() : Ptr(nullptr), End(nullptr) {}
 
   DenseMapIterator(pointer Pos, pointer E, bool NoAdvance = false)
     : Ptr(Pos), End(E) {

include/llvm/ADT/ilist.h

@@ -494,9 +494,9 @@ private:
       // Note: we have to be careful about the case when we move the first node
       // in the list.  This node is the list sentinel node and we can't move it.
       NodeTy *ThisSentinel = getTail();
-      setTail(0);
+      setTail(nullptr);
       NodeTy *L2Sentinel = L2.getTail();
-      L2.setTail(0);
+      L2.setTail(nullptr);
 
       // Remove [first, last) from its old position.
       NodeTy *First = &*first, *Prev = this->getPrev(First);
@@ -537,7 +537,7 @@ public:
   //
 
   size_type LLVM_ATTRIBUTE_UNUSED_RESULT size() const {
-    if (Head == 0) return 0; // Don't require construction of sentinel if empty.
+    if (!Head) return 0; // Don't require construction of sentinel if empty.
     return std::distance(begin(), end());
   }