[PATCH] D62766: [Attributor] Deduce "nosync" function attribute.

[Nicolai Hähnle via Phabricator via llvm-commits]

nhaehnle added inline comments.


================
Comment at: llvm/docs/LangRef.rst:1481-1488
+``nosync``
+    This function attribute indicates that the function does not communicate
+    (synchronize) with another thread. By synchronization we mean that the function
+    does not access memory through non-relaxed atomic instructions or does not use
+    volatile acesses. This should be distinguished from cross-lane operations,
+    which could be interpreted as kind of synchronization is where threating it
+    as a memory dependence is not sufficient. If the function does ever synchronize
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Thanks, I think this is better, but there are still some problems:
* There are no relaxed atomics in LLVM, only unordered, monotonic, and stronger orderings.
* What about fences?

I would put the part about cross-lane operations at the end and rephrase it slightly for clarity. Suggestion:

> This attribute is only concerned with synchronization through memory operations and is therefore orthogonal to cross-lane and convergent operations. In particular, an operation such as a barrier can be `convergent` but also `nosync`.

Assuming we can agree about the actual statement of that last sentence...


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