reimplement the second half of the or/add optimization. We should now

reimplement the second half of the or/add optimization.  We should now
only end up emitting LEA instead of OR.  If we aren't able to promote
something into an LEA, we should never be emitting it as an ADD.

Add some testcases that we emit "or" in cases where we used to produce
an "add".

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@116026 91177308-0d34-0410-b5e6-96231b3b80d8