[EarlyCSE] Add debug counter for debugging mis-optimizations. NFC.

Reviewers: reames, spatel, davide, dberlin

Subscribers: mcrosier, llvm-commits

Differential Revision: https://reviews.llvm.org/D45162

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@329443 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed