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

llvm-svn: 93802

1 files changed, 2 insertions, 1 deletions

diff --git a/llvm/lib/VMCore/Metadata.cpp b/llvm/lib/VMCore/Metadata.cpp
index 8a40fed1cca..7d783958882 100644
--- a/llvm/lib/VMCore/Metadata.cpp
+++ b/llvm/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);