[PATCH] D33731: Prevent RemoveDeadNodes from deleted already deleted node.

Nirav Dave via Phabricator via llvm-commits llvm-commits at lists.llvm.org
Wed Jun 7 11:49:23 PDT 2017

niravd added a comment.

> Is there still a way to expose the bug?

I'm reasonably there's a sequence that could trigger the bug in some backend, but I don't think I can generate it. The failing test was dealing with a net of TokenFactors fusedin a single instruction which wasn't being simplified.

> If not, can we just assert that no deleted node can get this far?

Unfortunately no. The original bug is that we're triggering on a deleted_node a bit further down in deallocation. the caller of the changed function is builds up a list of nodes to delete after having moved some of the the users of the added nodes' values. But it's possible that moving those values will cause a previously added node to be deleted. I could filter the node vector on the caller side and prune there, but that's just a un-loopfused version of this.


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