[PATCH] D61314: [SCCP] Remove forcedconstant, go to overdefined instead

[Eli Friedman via Phabricator via llvm-commits]

efriedma added a comment.

> I think we could however handle this directly in visitPhiNode: if some of the incoming values are unknown and some others are non-singleton constant ranges we have to go to overdefined.

If you treat unknown as if it were overdefined, you lose some of the nice properties of the sparse conditional propagation: in particular, that you get the same result regardless of the visitation order.  You'll get weird results in cases that don't actually involve any undef values.


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  https://reviews.llvm.org/D61314/new/

https://reviews.llvm.org/D61314