[docs] Update DominatorTree docs to clarify expectations around unreachable blocks

[oota-llvm.git] / include / llvm / Support / GenericDomTree.h

diff --git a/include/llvm/Support/GenericDomTree.h b/include/llvm/Support/GenericDomTree.h
index 63678bb98bb10fc9b5253b4a94d37ef8b46ea63b..a790d754d207f0863baae5f0542e21148c69d285 100644 (file)
--- a/include/llvm/Support/GenericDomTree.h
+++ b/include/llvm/Support/GenericDomTree.h
@@ -371,8 +371,9 @@ public:
   void releaseMemory() { reset(); }
 
   /// getNode - return the (Post)DominatorTree node for the specified basic
-  /// block.  This is the same as using operator[] on this class.
-  ///
+  /// block.  This is the same as using operator[] on this class.  The result
+  /// may (but is not required to) be null for a forward (backwards)
+  /// statically unreachable block.
   DomTreeNodeBase<NodeT> *getNode(NodeT *BB) const {
     auto I = DomTreeNodes.find(BB);
     if (I != DomTreeNodes.end())
@@ -380,6 +381,7 @@ public:
     return nullptr;
   }
 
+  /// See getNode.
   DomTreeNodeBase<NodeT> *operator[](NodeT *BB) const { return getNode(BB); }
 
   /// getRootNode - This returns the entry node for the CFG of the function.  If