[PATCH] D35267: Pass Divergence Analysis data to selection DAG to drive divergence dependent instruction selection

Eli Friedman via Phabricator via llvm-commits llvm-commits at lists.llvm.org
Tue Dec 19 16:43:01 PST 2017

efriedma added a comment.

Actually, what I'd really like to see here is some sort of verifier for the divergent bit.  It should be possible to recompute the divergence of the SelectionDAG at any point from first principles. There's a small set of operations which are fundamentally divergent: CopyFromReg where the register contains a divergent value (you should be able to derive this from DivergenceAnalysis), divergent memory accesses, and some target-specific intrinsics.  (Not sure that's a complete list, but should be close.)  All other operations are divergent if and only if they have a divergent predecessor.


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