Index: llvm/docs/LangRef.rst
===================================================================
--- llvm/docs/LangRef.rst
+++ llvm/docs/LangRef.rst
@@ -1269,6 +1269,16 @@
     This indicates that callee does not free the pointer argument. This is not
     a valid attribute for return values.
 
+``noreadafterunwind``
+    This indicates that the underlying object of a pointer argument is not read
+    on the unwind path in the following sense: If a call with a
+    ``noreadafterunwind`` argument unwinds, then the underlying object
+    associated with the argument is overwritten with a :ref:`poison value
+    <poisonvalue>`. As such, reads from this object do not result in immediate
+    undefined behavior, but program behavior cannot depend on the object
+    containing any specific value.  This attribute cannot be applied to return
+    values.
+
 .. _nest:
 
 ``nest``