[PATCH] D31919: NewGVN: Don't propagate over phi backedges where undef causes us to have >1 value.

[Daniel Berlin via Phabricator via llvm-commits]

dberlin added a comment.

Unfortunately, as you can see, we lose optimization in a few cases where the phis *are* cycle-free.
I could just bite the bullet and build scc's to determine cycle-freeness.
I'll do some performance testing.


https://reviews.llvm.org/D31919