[CGP] Fix the crash caused by enable of complex addr mode

We must collect all AddModes even if they are the same.
This is due to Original value is different but we need all original
values collected as they are used as anchors in common phi finding.

Reviewers: john.brawn, reames
Reviewed By: john.brawn
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D40166

llvm-svn: 318638