Index: docs/LangRef.rst
===================================================================
--- docs/LangRef.rst
+++ docs/LangRef.rst
@@ -10860,6 +10860,15 @@
 
 LLVM provides intrinsics for some arithmetic with overflow operations.
 
+Each of these intrinsics returns a two-element struct. If no overflow
+occurs, the first element of the returned struct will be equal to the
+mathematically correct result and the second element will be
+0. Otherwise, the first element of the returned struct will be the
+unique value that is equivalent to the mathematically correct result
+modulo two raised to the k power, where k is the number of bits in the
+operand type, and the second element will be 1. The behavior of these
+intrinsics is well-defined for all argument values.
+
 '``llvm.sadd.with.overflow.*``' Intrinsics
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^