[PATCH] D150976: [LangRef] Document the de facto meaning of convergent

[Jay Foad via Phabricator via llvm-commits]

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The "convergent" attribute was originally documented as "cannot be made
control-dependent on any *additional* values", but in practice it now
prevents any change in control dependence.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D150976

Files:
  llvm/docs/LangRef.rst


Index: llvm/docs/LangRef.rst
===================================================================
--- llvm/docs/LangRef.rst
+++ llvm/docs/LangRef.rst
@@ -1746,16 +1746,16 @@
     function call are also considered to be cold; and, thus, given low
     weight.
 ``convergent``
-    In some parallel execution models, there exist operations that cannot be
-    made control-dependent on any additional values.  We call such operations
-    ``convergent``, and mark them with this attribute.
+    In some parallel execution models, there exist operations that implicitly
+    depend on the set of values upon which they are control-dependent.  We call
+    such operations ``convergent``, and mark them with this attribute.
 
     The ``convergent`` attribute may appear on functions or call/invoke
     instructions.  When it appears on a function, it indicates that calls to
-    this function should not be made control-dependent on additional values.
-    For example, the intrinsic ``llvm.nvvm.barrier0`` is ``convergent``, so
-    calls to this intrinsic cannot be made control-dependent on additional
-    values.
+    this function should not be made control-dependent on a different set of
+    values. For example, the intrinsic ``llvm.nvvm.barrier0`` is
+    ``convergent``, so calls to this intrinsic cannot be made control-dependent
+    on additional values.
 
     When it appears on a call/invoke, the ``convergent`` attribute indicates
     that we should treat the call as though we're calling a convergent


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