[PredicateInfo] Fix non-determinism in codegen uncovered by reverse iterating SmallPtrSet

Summary:
Sort OpsToRename before iterating to make iteration order deterministic.

Thanks to Daniel Berlin for the sorting logic.

Reviewers: dberlin, RKSimon, efriedma, davide

Reviewed By: dberlin, davide

Subscribers: sanjoy, davide, llvm-commits

Differential Revision: https://reviews.llvm.org/D33265

llvm-svn: 304447