Track IR ordering of SelectionDAG nodes 3/4.

Remove the old IR ordering mechanism and switch to new one.  Fix unit
test failures.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@182704 91177308-0d34-0410-b5e6-96231b3b80d8
Track IR ordering of SelectionDAG nodes 4/4.

Unit test cases for -pre-RA-sched=source.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@182706 91177308-0d34-0410-b5e6-96231b3b80d8