Add test cases to prepare for the optimization that simplifies Add with

remainder expressions as operands.

Summary:
Add test cases to prepare for the new optimization that Simplifies integer add
expression X % C0 + (( X / C0 ) % C1) * C0 to X % (C0 * C1).

Patch by Bixia Zheng!

Reviewers: sanjoy

Reviewed By: sanjoy

Subscribers: jlebar, llvm-commits

Differential Revision: https://reviews.llvm.org/D46017

llvm-svn: 330991