Make the pattern matching work with modified memory accesses

Some optimizations (e.g., DeLICM) can modify memory accesses (e.g., change
their MemoryKind). Consequently, the pattern matching should take it into
the account.

Reviewed-by: Tobias Grosser <tobias@grosser.es&gt;,>
             Michael Kruse <llvm@meinersbur.de>

Differential Revision: https://reviews.llvm.org/D33138

llvm-svn: 308494