Add comment that MDNode::getFunction() is not to be used by performance-critical code (currently only used by AsmWriter)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@93802 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 4 insertions, 2 deletions

diff --git a/include/llvm/Metadata.h b/include/llvm/Metadata.h
index 179010b165..f64978cab4 100644
--- a/include/llvm/Metadata.h
+++ b/include/llvm/Metadata.h
@@ -154,7 +154,8 @@ public:
   
   // getFunction - If this metadata is function-local and recursively has a
   // function-local operand, return the first such operand's parent function.
-  // Otherwise, return null. 
+  // Otherwise, return null. getFunction() should not be used for performance-
+  // critical code because it recursively visits all the MDNode's operands.  
   Function *getFunction() const;
 
   // destroy - Delete this node.  Only when there are no uses.
diff --git a/lib/VMCore/Metadata.cpp b/lib/VMCore/Metadata.cpp
index 8a40fed1cc..7d78395888 100644
--- a/lib/VMCore/Metadata.cpp
+++ b/lib/VMCore/Metadata.cpp
@@ -154,7 +154,8 @@ static Function *assertLocalFunction(const MDNode *N) {
 
 // getFunction - If this metadata is function-local and recursively has a
 // function-local operand, return the first such operand's parent function.
-// Otherwise, return null. 
+// Otherwise, return null. getFunction() should not be used for performance-
+// critical code because it recursively visits all the MDNode's operands.  
 Function *MDNode::getFunction() const {
 #ifndef NDEBUG
   return assertLocalFunction(this);