Recommit r333268: [IPSCCP] Use PredicateInfo to propagate facts from cmp instructions.

r337828 resolves a PredicateInfo issue with unnamed types.

Original message:
This patch updates IPSCCP to use PredicateInfo to propagate
facts to true branches predicated by EQ and to false branches
predicated by NE.

As a follow up, we should be able to extend it to also propagate additional
facts about nonnull.

Reviewers: davide, mssimpso, dberlin, efriedma

Reviewed By: davide, dberlin

llvm-svn: 337904