Go back to comparing spill weights when deciding if interference can be evicted.

Go back to comparing spill weights when deciding if interference can be evicted.

It gives better results. Sometimes, a live range can be large and still have
high spill weight. Such a range should not be spilled.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@127036 91177308-0d34-0410-b5e6-96231b3b80d8