diff --git a/include/llvm/CodeGen/SelectionDAGNodes.h b/include/llvm/CodeGen/SelectionDAGNodes.h
index 9f56e17..1ed4dc4 100644
--- a/include/llvm/CodeGen/SelectionDAGNodes.h
+++ b/include/llvm/CodeGen/SelectionDAGNodes.h
@@ -809,13 +809,18 @@
   /// operation.
   bool hasNUsesOfValue(unsigned NUses, unsigned Value) const;
 
-  // isOnlyUse - Return true if this node is the only use of N.
+  /// isOnlyUse - Return true if this node is the only use of N.
+  ///
   bool isOnlyUse(SDNode *N) const;
 
-  // isOperand - Return true if this node is an operand of N.
+  /// isOperand - Return true if this node is an operand of N.
+  ///
   bool isOperand(SDNode *N) const;
 
-  // isPredecessor - Return true if this node is a predecessor of N.
+  /// isPredecessor - Return true if this node is a predecessor of N. This node
+  /// is either an operand of N or it can be reached by recursively traversing
+  /// up the operands.
+  /// NOTE: this is an expensive method. Use it carefully.
   bool isPredecessor(SDNode *N) const;
 
   /// getNumOperands - Return the number of values used by this operation.
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index fe33ff5..4c21eff 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -2534,7 +2534,8 @@
 }
 
 
-// isOnlyUse - Return true if this node is the only use of N.
+/// isOnlyUse - Return true if this node is the only use of N.
+///
 bool SDNode::isOnlyUse(SDNode *N) const {
   bool Seen = false;
   for (SDNode::use_iterator I = N->use_begin(), E = N->use_end(); I != E; ++I) {
@@ -2548,7 +2549,8 @@
   return Seen;
 }
 
-// isOperand - Return true if this node is an operand of N.
+/// isOperand - Return true if this node is an operand of N.
+///
 bool SDOperand::isOperand(SDNode *N) const {
   for (unsigned i = 0, e = N->getNumOperands(); i != e; ++i)
     if (*this == N->getOperand(i))
@@ -2578,7 +2580,10 @@
   }
 }
 
-// isPredecessor - Return true if this node is a predecessor of N.
+/// isPredecessor - Return true if this node is a predecessor of N. This node
+/// is either an operand of N or it can be reached by recursively traversing
+/// up the operands.
+/// NOTE: this is an expensive method. Use it carefully.
 bool SDNode::isPredecessor(SDNode *N) const {
   std::set<SDNode *> Visited;
   bool found = false;