Index: llvm/docs/LangRef.rst
===================================================================
--- llvm/docs/LangRef.rst
+++ llvm/docs/LangRef.rst
@@ -1267,6 +1267,15 @@
     This indicates that callee does not free the pointer argument. This is not
     a valid attribute for return values.
 
+``noreadonunwind``
+    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 ``noreadonunwind``
+    argument unwinds, then the underlying object associated with the pointer
+    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``