[DAG] Fix condition on overlapping store check.

Prevent overlapping store elision when overlapping store is
pre-inc/dec as analysis is wrong in these cases.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@321204 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed