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

[Eli Friedman via Phabricator via llvm-commits]

efriedma added a comment.

In https://reviews.llvm.org/D35267#950795, @alex-t wrote:

> In this case w/o bit propagation we're still correct but sub-optimal.


I'm worried that you're covering up bugs by accepting "sub-optimal" results.  Specifically, if you have a node which is marked divergent, but doesn't actually have any divergent operands, it will stay marked divergent in most cases... but if DAGCombine or legalization transforms it to some other equivalent operation, it'll erase the "divergent" marking.  So your markings will look mostly correct in simple cases, but break for more complicated cases.


https://reviews.llvm.org/D35267