The machine scheduler (before register allocation) is enabled by default for
SystemZ.
The SelectionDAG scheduling preference now becomes source order scheduling
(was regpressure).
Review: Ulrich Weigand
https://reviews.llvm.org/D37977
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@315063 91177308-0d34-0410-b5e6-96231b3b80d8