Index: llvm/docs/LangRef.rst
===================================================================
--- llvm/docs/LangRef.rst
+++ llvm/docs/LangRef.rst
@@ -1183,11 +1183,16 @@
     structure that is the return value of the function in the source
     program. This pointer must be guaranteed by the caller to be valid:
     loads and stores to the structure may be assumed by the callee not
-    to trap and to be properly aligned. This is not a valid attribute
-    for return values.
+    to trap and to be properly aligned.
+
+    If the call unwinds, then the underlying object associated with the
+    argument is overwritten with a :ref:`poison value <poisonvalue>`.
+    As such, subsequent reads cannot depend on the object containing any
+    particular value.
 
     The sret type argument specifies the in memory type, which must be
-    the same as the pointee type of the argument.
+    the same as the pointee type of the argument. This is not a valid
+    attribute for return values.
 
 .. _attr_elementtype: