The SelectionDAG scheduling preference now becomes source order
scheduling (machine scheduler generates better code -- even without
there being a machine model defined for LoongArch yet).
Most of the test changes are trivial instruction reorderings and
differing register allocations, without any obvious performance impact.
This is similar to commit: 3d0fbafd0bce43bb9106230a45d1130f7a40e5ec
a5c90e48b6