When checking if a load can be folded, we check if there is any non-direct

When checking if a load can be folded, we check if there is any non-direct
way to reach the load via any nodes that would be folded. Start from the
root of the matched sub-tree.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@30956 91177308-0d34-0410-b5e6-96231b3b80d8