Index: docs/LangRef.rst
===================================================================
--- docs/LangRef.rst
+++ docs/LangRef.rst
@@ -1239,10 +1239,19 @@
     function call are also considered to be cold; and, thus, given low
     weight.
 ``convergent``
-    This attribute indicates that the callee is dependent on a convergent
+    This attribute indicates that the callee might depend on a convergent
     thread execution pattern under certain parallel execution models.
-    Transformations that are execution model agnostic may not make the execution
-    of a convergent operation control dependent on any additional values.
+
+    In these execution models, certain operations have the property that they
+    cannot be made control-dependent on any additional values.  We call these
+    operations ``convergent``.  For example, the ``llvm.cuda.syncthreads``
+    intrinsic is convergent, and so functions which (transitively) invoke it
+    must also be convergent.
+
+    Unless it can be proved that an operation does not transitively invoke any
+    convergent operations, transformations that are execution-model agnostic
+    may not make the execution of a convergent operation control-dependent on
+    any additional values.
 ``inaccessiblememonly``
     This attribute indicates that the function may only access memory that
     is not accessible by the module being compiled. This is a weaker form