[PATCH] critical-anti-dependency breaker: don't use reg def info from kill insts (PR20308)

[Sanjay Patel]

Added willschm as reviewer because Abbott & Costello aren't available.

On 2nd reading of bug 18863, I see that it was left open to track the issue in MachineCopyPropagation. I'll add what I'm seeing in my test case there.

http://reviews.llvm.org/D4977