[PATCH] D85603: IR: Add convergence control operand bundle and intrinsics

[Sameer Sahasrabuddhe via Phabricator via llvm-commits]

sameerds added inline comments.


================
Comment at: llvm/docs/ConvergentOperations.rst:174-175
+
+The compiler frontend can emit IR that expresses the convergence constraints
+as follows:
+
----------------
But this use of the intrinsics does not add any new constraints, right? This specific optimization is already sufficiently constrained by control dependence.


================
Comment at: llvm/docs/ConvergentOperations.rst:743-744
+
+This problem goes away by inserting a loop heart intrinsic, which establishes
+a relationship between loop iterations across threads.
+
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The exhausted reader just begs to see the //corrected// version at this point! :) 


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Comment at: llvm/docs/ConvergentOperations.rst:807-809
+There is a cycle (closed walk in the CFG) that goes through both loop heart
+intrinsics using ``%anchor`` but not through the definition of ``%anchor``,
+so this code is invalid.
----------------
Following the structure of previous examples, it would be good to have a demonstration of how this can result in misinterpreted convergence. That would explain why this example //should be// illegal. This paragraph directly applies the rules to show how the example is //recognized// as illegal.


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https://reviews.llvm.org/D85603