EarlyCSE: add tests

Summary: As a follow-up to rL255054 I wasn't able to convince myself that the code did what I thought, so I wrote more tests.

Reviewers: reames

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D15371

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@255295 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed