[RegBankSelect] Use frequency and probability information to compute
more precise cost in Greedy mode.

In Fast mode the cost is irrelevant so do not bother requiring that
those passes get scheduled.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@270244 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed