convert the new matcher to check intermediate nodes for a single

convert the new matcher to check intermediate nodes for a single
use and only call IsProfitableToFold/IsLegalToFold on the load
being folded, like the old dagiselemitter does.  This
substantially simplifies the code and improves opportunities for
sharing.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@96368 91177308-0d34-0410-b5e6-96231b3b80d8