[PATCH] D43216: [Dominators] Ensure that every PostDomTree root is connected to the virtual node

[Dave Green via Phabricator via llvm-commits]

dmgreen added a comment.

Ah. Ok. Common forward dominators are not roots - of course they are not. That makes this harder.

After spending a day thinking about it, I have not come up with a sensible way to check this, that doesn't devolve into recalculating the tree (or worse). Especially as in this case we can't really trust the domtree to be "correct", with respects to the roots.

I was trying to come up with something where non-roots have non-virtual idoms or are reachable from 2+ roots. I'm not sure that can work though (or how slow it could be). I guess it may be simpler to just compare against a new tree, like we have already.


Repository:
  rL LLVM

https://reviews.llvm.org/D43216