[llvm] [LLVM] New NoDivergenceSource function attribute (PR #111832)

[Nikita Popov via llvm-commits]

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@@ -2082,6 +2082,16 @@ example:
     function call, use of ``longjmp``, or other means. It is a compiler hint that
     is used at module level to improve dataflow analysis, dropped during linking,
     and has no effect on functions defined in the current module.
+``nodivergencesource``
+    A call to this function is not a source of divergence. In uniformity
+    analysis, a *source of divergence* is an instruction that generates
+    divergence even if its inputs are uniform. A call with no further information
+    would normally be considered a source of divergence; setting this attribute
+    on a function means that a call to it is not a source of divergence.
+
+    This is useful where known-name calls are being used as an extension
+    mechanism for instructions, as for example in `llvm-dialects
+    <https://github.com/GPUOpen-Drivers/llvm-dialects>`.
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nikic wrote:

Drop the last paragraph, it's more confusing than helpful, at least to me (what are known-name calls and what relation do they have to anything?)

https://github.com/llvm/llvm-project/pull/111832