[PATCH] D32990: [NewGVN] Take in account incoming edges computing congruent PhiExpression(s)

[Eli Friedman via Phabricator via llvm-commits]

efriedma added inline comments.


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Comment at: llvm/trunk/lib/Transforms/Scalar/NewGVN.cpp:742
+            [&](const Use *U1, const Use *U2) {
+              return PN->getIncomingBlock(*U1) < PN->getIncomingBlock(*U2);
+            });
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davide wrote:
> efriedma wrote:
> > Is there any possibility that sorting by pointer values here will give non-deterministic output?  If there isn't, please add a comment explaining why.
> I thought about this when writing the patch, and I think the answer is no (but I'm nervous when it comes to ordering based on pointers given I tracked down several non-determinism bugs because of these).
> As far as I can tell, we don't actually rely on the ordering for anything significant, e.g. we don't create new instructions based on that ordering.
> Does this make sense? If so, I'll add a comment. (and thanks for your feedback).
Yes, that makes sense.


Repository:
  rL LLVM

https://reviews.llvm.org/D32990