[NewGVN] Check for congruency of memory accesses.

This is fine as nothing in the code relies on leader and memory
leader being the same for a given congruency class. Ack'ed by
Dan.

Fixes PR33720.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@307699 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed